New Trees: Recent Introductions to Cultivation 9781842465998, 9781842461730

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New Trees Recent Introductions to Cultivation John Grimshaw Ross Bayton Line drawings by Hazel Wilks

Commissioned and produced by the

International Dendrology Society Kew Publishing Royal Botanic Gardens, Kew

© The Board of Trustees of the Royal Botanic Gardens, Kew 2009 Text © The International Dendrology Society 2009 Line drawings © Hazel Wilks Photographs © the photographers, as stated in captions John Grimshaw and Ross Bayton have asserted their rights to be identified as the authors of this work, in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording or otherwise, without written permission of the publisher, unless in accordance with the provisions of the Copyright Designs and Patents Act 1988. Great care has been taken to maintain the accuracy of the information contained in this work. However, neither the publisher, the editors nor the authors can be held responsible for any consequences arising from use of the information contained herein. The views expressed in the work are those of the individual authors and do not necessarily reflect those of the publisher or of the Board of Trustees of the Royal Botanic Gardens, Kew. First published in 2009 by Royal Botanic Gardens, Kew Richmond, Surrey, TW9 3AB, UK Website www.kew.org Published in association with the International Dendrology Society Hergest Estate Office, Kington, Herefordshire, HR5 3EG, UK Correspondence may be sent to [email protected] ISBN 978 1 84246 173 0 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Production editor: Sarah Cannon Typesetting and page layout by Sarah Cannon Publishing Services, Oxford, UK Cover design by Jeff Eden, Publishing, Design & Photography, Royal Botanic Gardens, Kew Print production: Lloyd Kirton, Publishing, Design & Photography, Royal Botanic Gardens, Kew Reprographics by Saxon Photolitho, Norwich, UK Printed and bound in Germany by APPL For information or to purchase Kew titles, please visit www.kewbooks.com, or email [email protected]. Kew’s mission is to inspire and deliver science-based plant conservation worldwide, enhancing the quality of life.

The paper used in this book contains wood from well-managed forests, certified in accordance with the strict environmental, social and economic standards of the Forest Stewardship Council (FSC).

Contents Sponsors ........................................................................................................... v Forewords – Giles Coode-Adams, Tony Kirkham .............................................. vi Authors’ Preface, Acknowledgements ............................................................ viii Section I. Introduction Chapter 1. Introducing New Trees ............................................................. 1 Chapter 2. Conservation ......................................................................... 17 Chapter 3. Cultivation ............................................................................. 29 Section II. Species Accounts Abies – Zelkova ....................................................................................... 40 Section III. Appendices Appendix 1. Focus Arboreta .................................................................. 909 Appendix 2. Collectors’ References ....................................................... 917 Appendix 3. Sources of Material for Line Drawings ............................... 919 Glossary and Abbreviations .......................................................................... 923 Bibliography ................................................................................................. 931 Index of Tree Names ..................................................................................... 959

Plate 1. Fallen leaves of Acer pycnanthum reveal their autumn colours and glaucous undersides. Image P. de Spoelberch.

Sponsors The research, writing and preparation for press of New Trees has been made possible by the generous support of the donors listed below. The International Dendrology Society and the Dendrology Charitable Company thank them all very much indeed for their contributions.

29th May 1961 Charitable Trust

Micky Ingall

The American Fund for Charities

The Jordan Charitable Foundation

Anonymous

Roy Lancaster

Lawrence Banks

Arabella Lennox-Boyd

Ian Bond

Longwood Gardens

Giles and Sonia Coode-Adams

LSA Charitable Trust

The Ernest Cook Trust

The Mercers’ Charitable Foundation

Vicomte Philippe de Spoelberch

The Normanby Charitable Trust

The Viscount Devonport

Susanna Peake Charitable Trust

The Duke of Devonshire’s Charitable Trust

P F Charitable Trust

The Dulverton Trust

The Viscount Ridley

Rupert and Sara Eley

Rothschild Foundation

The Englefield Charitable Trust

The Coral Samuel Charitable Trust

The Lord Faringdon Charitable Trust Carol Gurney

The Samuel Storey Family Charitable Trust

Michael Heathcoat Amory

The John Swire 1989 Charitable Trust

Robin Herbert

The Trusthouse Charitable Foundation

The Lord Heseltine

Major Simon Whitbread Charitable Trust

The Earl of Home

Colonel W.H. Whitbread Charitable Trust

The Idlewild Trust

The Wynkcoombe Trust

John and Elizabeth Ravenscroft

The International Dendrology Society President Mr F.C. Rauwenhoff Chairman The Hon. Sir Richard Storey Bt.

Hergest Estate Office, Kington, Herefordshire HR5 3EG, UK Telephone (+44) 1544 232045 E-mail [email protected] Website www.dendrology.org

Plate 2 (opposite). Liquidambar acalycina SABE 1950, photographed at Kew. Image T. Kirkham.

Forewords When I worked at the Royal Botanic Gardens, Kew, in the mid 1990s, I used to be given surplus trees and shrubs. A high proportion of these gifts had been introduced into cultivation through expeditions going out from Kew and collecting in the wild. Imagine my frustration when I failed to find these species covered in the most comprehensive tree books – Bean and Krüssmann. My chance came when I became Chairman of the Scientific and Education Committee of the International Dendrology Society in 2002. I rather timidly suggested that we ought to do something about all the taxa that had been introduced into cultivation since 1970. To my astonishment there was universal agreement and even enthusiasm. We costed the project and raised the money, through the great generosity of many donors. Then came the hard part. We wanted a lead author who had an easy writing style, was a good taxonomist, and understood the difficulties of growing trees. In John Grimshaw we found a winner, who has driven the project forward with enormous energy and skill. He was soon joined by Ross Bayton, whose main task was to write up the descriptions of the individual species – a boring task you might think, but essential if the project was to be authoritative. He did this with a sure touch, as well as working on the glossary and index. The third member of the team was botanical artist Hazel Wilks, who has produced superlative line drawings, beautiful in themselves and an essential element in helping to identify different species. One of the extraordinary things about this book is the way the dendrological world has come together. People have given so much in so many different ways, whether by measuring a tree, providing field notes, a photograph specially taken, or perhaps most important of all, reviewing the account of a particular genus. Given that 180 genera and over 800 species are described in full, with notes on hundreds more, the help that was received from experts in their various fields from all over the world was fundamental to the book. This coming together of dendrologists was brought home to me when a group of international amateurs and experts gathered at Colesbourne Park in January 2007 to review the different generic accounts. One of the experts said to me that it was the most exciting thing he had ever done in his life. The project has been assisted by many botanic gardens throughout the world, a great many individual experts and many arboreta. The members of the Scientific and Education Committee have been stalwart in their support, sometimes speaking forthrightly, sometimes critically, but always with the aim of making a better book. The journey has been a long one, with a subject that has continued to grow during the process. It has been a huge achievement for all those who have taken part, and has been not only fun, but enormously worthwhile. Giles Coode-Adams, October 2008

Acer oblongum var. itoanum

As Head of the Arboretum at the Royal Botanic Gardens, Kew it is my job to maintain and increase the diversity of the hardy woody plant collections, to meet the scientific research and educational needs of Kew. This is the role that William Jackson Bean played when he was the Assistant Curator of the Arboretum, between 1900 and 1922, when many of the trees that he was planting were new to cultivation, though they now form the backbone of the treescape we know at Kew today. Just as then, many of the trees we are currently planting have been acquired from fieldwork and expeditions, made by myself and other collectors, from Kew and similar organisations across the world – although with improved communications and transport such work is somewhat easier than in the past. Climate change, too, coupled with a deeper appreciation of the value of a good provenance, has broadened the boundaries of plant exploration, and we are able to find hardy plant material from countries over a much wider area, including Taiwan, Vietnam, China, Chile and Mexico. As a result we can now experiment with tree selection with confidence and push the parameters of hardiness, by planting species that we wouldn’t have dared to try in previous years. The consequence is that gardeners all round the world now succeed with many plants never before grown outdoors without protection. When looking at young trees recently established in the gardens my mind often takes me back to the actual parent tree and the very find spot in the wild from where the original seed was collected, pleasurably reliving memories of conditions endured or the many international friendships made, on expeditions whose goal was to establish such trees in cultivation for all to enjoy. Dendrologists and arboriculturists are always keen to have the best specimens of their trees and find out how other growers have fared with the establishment of new introductions, comparing growth rates and first-flowerings – sometimes in a spirit of friendly competition, but principally as an international body of enthusiasts freely exchanging plant material, disseminating information and sharing our observations with others. I am often given specimens for Kew by friends and curators of other arboreta, or find myself with collections of my own in the nursery, with only the field notes to go on for cultural information. Similarly, on my walks through the Arboretum I often come across notable specimens in the heritage landscape and feel the need to know more about their history and background, perhaps questioning why they were planted in that location, or wanting to check their recorded historical size against more recent measurements. In such cases, the first book I turn to is W.J. Bean’s Trees and Shrubs Hardy in the British Isles, that reliable and informative classic reference. However, in the last few decades, as new taxa have arrived in our gardens from locations around the globe, and established collections are renamed by taxonomists, the number of species missing from this monumental work has increased. Recently I needed more information on Acer pictum subsp. okamotoanum, a tree that I collected in South Korea in 1989, but found it missing from Bean’s work. To address this and many other such omissions, the International Dendrology Society commissioned New Trees, to complement Bean’s great work, and I have been fortunate to have been working on the fringes of this publication with John Grimshaw and Ross Bayton, providing information and material from the collections in the Arboretum at Kew. I am greatly looking forward to using the book, and am confident that dendrologists and horticulturists around the world will find it both a pleasure to read and a valued reference.

Tony Kirkham, October 2008

Authors’ Preface

Plate 3. Since the days of Sir Joseph Banks, collectors from Kew have been responsible for introducing new plants to cultivation – so it is appropriate that Banksia integrifolia subsp. monticola, gathered recently in New South Wales (ETAZ 4), should now grow outside the Temperate House there. Image J. Grimshaw.

Throughout the modern era, travellers have been bringing home trees and other plants to beautify gardens or the wider landscape, or for commercial use. Some were brought home by opportunistic sailors or merchants, but plant-hunting as a profession – and perhaps also a passion – became established early on. We can think of John Tradescant the Elder signing up as a soldier to get himself abroad to find new plants in the early 1600s, and his son, John the Younger, travelling to Virginia for the same purpose. The line continued, through the likes of John and William Bartram to Robert Fortune, David Douglas, Philipp von Siebold, and into the twentieth century with names such as Ernest Wilson, George Forrest and David Fairchild. These professionals were assisted by the many botanists (institutional and amateur) travelling in the wilds who, in addition to their herbarium collections, often sent home seeds or plants. By these means the gardens of the wider world were stocked with an ever-increasing diversity of plants. Plant-hunting as a profession reached its crescendo with the intensive exploration of the interior of China during the first four decades of the twentieth century. It is one of the myths of horticulture that it never revived after the Second World War, though it is true that the glory days were over, terminated as much by austerity at home as by political changes abroad. The closure of China to western travellers from 1949 to 1980 was a particular blow. At no time did the introduction of new plant material ever cease, however. Frank Kingdon-Ward, ‘last of the great plant-hunters’, undertook his final expedition to Burma in 1956. In the same year a member of the next generation, John L. Creech, was collecting in Japan on behalf of the US Department of Agriculture and Longwood Gardens. It was on this expedition that Lagerstroemia fauriei, one of the most significant of ‘new’ trees, was collected. The baton had passed on. Exploration for new ornamental plants continues apace today, and there are those who call this, not without justification, the ‘second Golden Age’ of plant-hunting, with scientific institutions, corporations and private individuals all taking part. The new era of collecting, however, going on so actively around us, has yet to attract the attention of the wider public, still captivated by the exploits of earlier generations. Perhaps the modern collectors’ experiences are not exciting enough, their three-week jaunts no substitute for many months of hard trek – and there have as yet been no deaths in bull-pits to attract morbid interest (and be repeated every time the term ‘plant-hunter’ appears in the press). For narrative appeal, confiscation of seeds by customs does not match their loss from a capsized canoe, though equally galling to the collector. Bobby Ward (2004) has made a valuable start, but a full synthesis of present-day plant-collecting is still needed. There are episodes enough to enliven it, kidnap by Colombian rebels, run-over feet, the karaoke bar directly below the hotel room and the inevitable horror stories of primitive sanitation being just a few.

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The result of all this activity is that more plants than ever before are available to gardeners. Two particularly important factors are at play. The first is ease of access to the world’s remotest places: it has never previously been possible to travel so freely in almost every part of the world, and to get there (and back) so quickly. Secondly, rising global temperatures are steadily bringing to an ever-widening area the possibility of cultivating more and more species. These factors, coupled with gardeners’ natural instincts to try out new plants, are leading to a burgeoning garden flora – and hence contributed, in no small part, to the girth of this book. (For its size and solidity we make no apologies. There is a lot to record.) The book is principally concerned with the trees introduced to cultivation in the last four or five decades: probably only a small proportion of the total plant diversity that has been introduced, but of huge significance. Trees, unlike most other groups of plants, have an impact on the landscape that can extend over decades and centuries, to form a living continuum through history. It is a privilege to stand in front of a Sequoiadendron, whether in California or in Scotland, and muse on its longevity and magnificence, or on the time when it too was a ‘new’ tree and seedlings of it were items of great worth. So too may a future generation ponder a Wollemia. It was in order to bring the dendrological literature up to date that the International Dendrology Society first conceived, then commissioned the project that was to become known as New Trees. The process by which it was determined whether a given species qualified for inclusion is described elsewhere (see pp. 1–2) but essentially, from its germination, the concept was that New Trees should be a complementary volume to ‘Bean’. By this monosyllable is meant the set of five squat books occupying almost a foot of the bookshelves of most serious gardeners – the four volumes of W.J. Bean’s Trees and Shrubs Hardy in the British Isles, and its subsequent Supplement. During his career at Kew, where he ended up as Curator, William Jackson Bean (1863–1947) had an unrivalled opportunity to observe

Plate 4. Pinus yunnanensis Wilson 1369, collected on an expedition to Sichuan in 1908, and probably planted here at Kew by W.J. Bean himself. Image J. Grimshaw.

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Plate 5. By 2008 Tony Avent’s tree of Cathaya argyrophylla, planted in 2001, had reached 2.5 m (see p. 224). Other specimens of a similar age are now coning in the Australian Bicentennial Arboretum (C. Callaghan, pers. comm. 2008) – the first outside China to do so. Image J. Grimshaw.

New Trees

the multitudes of plants that arrived in the great wave of plant-hunting endeavour of the early-twentieth century, as well as having access to a first-class collection of established species. The first edition of his magnum opus appeared in two volumes in 1914. Although a follow-up was soon required, it did not appear until 1933. Thereafter regular new editions were published until the seventh, issued in 1950, which was the last to which Bean himself contributed directly. Then there was a gap of some 20 years until the eighth edition appeared, during the course of the 1970s, to which corrections were added until the early 1980s. Desmond Clarke was the Chief Editor and Sir George Taylor the General Editor, assisted by a team of specialists, but the core and spirit of the work have remained Bean’s own. A Supplement prepared by Clarke appeared in 1988. Inevitably, after 30 years of active change in climate and cultivated plant inventory, even the eighth edition of Bean is showing its age, and a completely new edition is urgently needed. There are numerous other works dealing comprehensively with a large range of woody plants. Alfred Rehder’s Manual of Cultivated Trees and Shrubs Hardy in North America (1927, revised 1940) was a long-standing essential in North America – now, however, largely superseded by Michael Dirr’s Manual of Woody Landscape Plants (1998) and, to a slightly lesser extent, by Arthur Lee Jacobson’s North American Landscape Trees (1996). In Europe another monumental work appeared during the 1970s in the shape of Gerd Krüssmann’s series of books describing a very large number of woody plants (the three-volume Manual of Broad-leaved Trees and Shrubs, and the Manual of Cultivated Conifers). Translated from the original German into English and made widely available during the 1980s, these four volumes remain the most comprehensive source of technical descriptions of species and cultivars known up until the late 1970s. Thumbnail descriptions and histories in a compact volume are the foundation of the lasting success and popularity of the Hillier Manual of Trees & Shrubs (1972, seventh edition 2002), the first point of reference for many. With the exception of Dirr’s work, however, none of these combine full botanical descriptions with the information on growing plants that makes Bean so interesting and instructive to the gardener. The conscious decision was therefore taken that New Trees should match Bean in style, combining accurate, substantial botanical descriptions with readable commentary on the horticultural values of the species covered and details of their intro-

Authors’ Preface

duction. There are two major differences. First, our book covers only trees (a difficult distinction, discussed on p. 2), and secondly, it attempts to cover northern Europe and North America as well as the British Isles (for the boundaries of this, ‘our area’, see p. 3). These stipulations had the effect of both narrowing and widening the scope of the book, and must be taken into account when its merits and failings are considered. One of the failings we readily acknowledge is that, despite its international intentions, it is, inevitably, somewhat Anglocentric – a situation we can identify, but do not apologise for. In a way, New Trees can be seen as a stop-gap until the challenge posed by replacing Bean is taken up, but we hope that it will be a useful one. For a gardening botanist (and there are two of us) it is difficult to imagine a more exciting project than that on which we embarked in 2004 and 2005, respectively. It has brought us into contact with huge numbers of delightful and interesting people, all with a passion for trees, taken us to wonderful gardens and arboreta, and, above all, given us the opportunity to see and enjoy the fabulous diversity of material that is new to cultivation. The vast majority of the species described have been observed and studied in the growing state especially for this book. Some are represented in cultivation by no more than a few small saplings. Sometimes only one or two representatives of a species were traced, over the two continents. Others have become familiar in the nursery trade and are freely available. A lot more should be! One of the challenges of writing about newly introduced species is that they are inevitably still young trees, and their size and effect in maturity, and long-term prospects in cultivation, are as yet unknown quantities. Our technical descriptions give an idea of mature stature but this may or may not be achieved (or exceeded) in cultivation. In many cases too, the plants’ environmental tolerances in cultivation have not yet been worked out, and a path must be steered between pessimism and the optimism of nursery catalogues. Planting a ‘new tree’ will often lead to a voyage of discovery – as it always has – but this should not deter gardeners from trying. It is disappointing to see how few recent introductions are being planted in so-called ‘great gardens’, where once it was de rigueur to have the latest Rhododendron or Magnolia, but which now can find no space for a Schefflera or Schima. A book such as New Trees is never complete. It is impossible to track down every specimen of every species. Observations and measurements are also soon superseded – though in almost all cases the observations we cite are dated, which at least adds a time reference point. In addition, further taxa come into cultivation, or into our ken, with every passing month. In some cases it was possible to add an account, or insert a note, but other information came too late for inclusion, arriving after the relevant section was in page layout. There are many unidentified or uncertain taxa in private collections that have been omitted pending identification, or their demonstration of more than temporary persistence. All these we have airily thought of as ‘second edition species’. We believe

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Plate 6. Early beginnings. Mass germination of Abies magnifica var. shastensis as the snow retreats on Mount Shasta, California, July 2004. Image J. Grimshaw.

Plate 7. Protected by a cage, the first Wollemia planted outside at Kew (Plate 575) has so far done extremely well. Image T. Kirkham.

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Plate 8. Acer kweilinense W.P. Fang & M.Y. Fang – an elegant maple, recently introduced by Maurice Foster but coming to our attention too late for inclusion in the text. Image J. Grimshaw.

New Trees

the identification of most cited specimens to be correct, but it has not been possible to check every one, and some have yet to have their identity confirmed, following flowering and fruiting. Please let us know if you have a good specimen of any species mentioned in the book, that you think should be recorded, or if you have a challenge on or re-identification for any species or individual, or know of additional species in cultivation. Pending the putative second edition, it is planned that a New Trees ’updates‘ column will be provided within the pages of the International Dendrology Society Yearbook. Please make contact with us via the permanent e-mail address (ids.newtrees@googlemail. com), or by letter sent to the IDS secretariat. It is worth recording here how New Trees has been compiled. John Grimshaw, working from his home at Colesbourne in Gloucestershire, has been the leader of the project and was responsible for preparing the narrative text. He travelled extensively throughout the course of the project to observe trees in arboreta and gardens, and discuss their requirements with their growers. Ross Bayton, based for the project at the Royal Botanic Gardens, Kew, compiled the botanical descriptions for genera and species, in all but a handful of cases. In addition he guided our botanical artist, Hazel Wilks, in her work on the line drawings, which were also done at Kew. Hazel’s contribution should not be overlooked, as the book is so much enhanced by her beautiful drawings. The individual accounts for most genera were read and commented on by specialists as they were prepared, and the text was read in its entirety by Susyn Andrews and Allen Coombes, who made many valuable contributions thereby. The copy-editing and page layout were done with meticulous attention and endless patience by Sarah Cannon in Oxford, and for general proof-reading we benefited from the eagle eyes of Margaret Okole. At the stage of page proofs Eric Hsu brought a fresh pair of eyes to the work, and Christine Battle undertook the enormous task of compiling the index. We are extremely grateful to all of them for their time and the care they have given to ensuring that the text is as error-free as possible. At Kew Publishing we have been encouraged and supported by Gina Fullerlove, John Harris, Lloyd Kirton and Lydia White, whom we thank most sincerely for their input. New Trees has been a team effort ranging far beyond its authors, artist, editors and publishers. We have been helped by an incredible array of people, many of whom were previously unknown to us, providing information, images, specimens, food, a bed, or just friendship and support, during the course of the project, for which we have been most grateful. A list of their names may be found in the acknowledgements section below (pp. xiv–xv). We thank them all for all their help, in whatever form it took, and we have attempted to ensure that their contributions of information are properly credited in the text, as for all other sources and authorities. We would particularly like to thank our partners, Adrian Hallowes and Nick Foy, for their support and tolerance during the preparation of ‘the book’. We are grateful too to the directors, curators and owners of the many gardens and nurseries that we have visited, whether officially or as members of the public, gaining views of their trees. The New Trees project has been strongly supported by

Authors’ Preface

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the Royal Botanic Gardens, Kew, and we thank the Directors, Sir Peter Crane and Prof. Steven Hopper, and the Keepers of the Herbarium, Prof. Simon Owens and Prof. David Mabberley, for their hospitality in allowing us use of their facilities, as well as the many staff members in the Herbarium and Library who have given us assistance. In the gardens, Tony Kirkham, Head of the Arboretum, has been a great ally and source of images and information, as well as contributing a thoughtful Foreword. A particularly rich source of information has been records from the Tree Register of the British Isles (TROBI), kindly extracted for us by its Assistant Registrar Dr Owen Johnson (who also provided many personal comments and images, and an advance copy of his forthcoming report on half-hardy trees in the United Kingdom). From his personal materials, including notes and herbarium specimens, Jan De Langhe, botanist at the Arboretum Het Leen Eeklo in Belgium, extracted records of trees observed by him in arboreta across Europe – counterbalancing to some extent the otherwise Anglophonic bias – for which hard labour we are very grateful. Peter Wharton, of the University of British Columbia Botanic Garden, and creator of its David C. Lam Asian Garden, was one of our most valued correspondents, until his untimely death in June 2008 deprived us of his wisdom and a great friendship. Sean Hogan of Cistus Nursery in Portland, Oregon, and Tom Hudson of Tregrehan in Cornwall, both with exceptional plant collections, have been most generous with their time and allowed their brains to be picked on species throughout the alphabet. Very many others have also supplied information used in the book, and we thank them all. The preparation of New Trees has been an important episode in the history of the International Dendrology Society, from whose Scientific and Education Committee the idea sprang. This committee, with its off-shoot the New Trees Editorial Subcommittee, has overseen and guided the project from the outset. All members are thanked, but particularly the Editorial Subcommittee, comprising Susyn Andrews, Lawrence Banks, Allen Coombes, Bill McNamara and Philippe de Spoelberch, who have not stinted in their support, and the Chairman, Giles Coode-Adams. Giles has been godfather to the whole project, never wavering in his support and optimism, and we thank him most deeply for this. He was supported in turn by three successive Chairmen of the IDS, Lawrence Banks, Carol Gurney and Sir Richard Storey, the Treasurer, Micky Ingall, and indeed by the whole Council of the Society. James Greenfield, the Secretary of the IDS, and his assistant Sharon Scott, have borne the brunt of much boring correspondence and administration on behalf of the Society and the Dendrology Charitable Company. It has been a pleasure and privilege to work for and with this great Society. Without the support of the sponsors (see p. v) this book could not have happened, and we add our own sincere thanks to those expressed elsewhere.

John Grimshaw, Ross Bayton December 2008

Plate 9. Researching New Trees has been a wonderful experience (even when work went on into the night). Nothaphoebe cavaleriei, observed in Aiken, South Carolina. Image J. Grimshaw.

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New Trees

Acknowledgements A huge number of people have contributed in some way to the New Trees project and we thank them all most sincerely for their assistance in whatever form it took. They are the following, and we trust there are no omissions from this list; our apologies if so.

Pterocarya macroptera (top) Prunus sogdiana (opposite)

Anthony (Tony) Aiello, Morris Arboretum, Pennsylvania; Tim Alderton, JC Raulston Arboretum, North Carolina; Michael Heathcoat Amory, Chevithorne Barton, Devon; Kathy and Marvin Andersen, Donald Andersen and Kathy Meyer, Phoenixville, Pennsylvania; Susyn Andrews, Kew, Surrey; Hugh Angus, National Arboretum, Westonbirt, Gloucestershire; Kenneth Ashburner, Stone Lane Gardens, Devon; Tony Avent, Plant Delights Nursery and Juniper Level Botanical Garden, Raleigh, North Carolina; Kris Bachtell, Morton Arboretum, Illinois; Chris Bailes, RHS Garden Rosemoor, Devon; Dr Bill Baker, Royal Botanic Gardens, Kew; Piotr Banaszczak, Rogów Arboretum, Poland; Lawrence and Elizabeth Banks, Hergest Croft, Herefordshire; Mark Barratt, Hergest Croft, Herefordshire; Paul Bartlett, Stone Lane Gardens, Devon; Christine Battle, Upton Cheyney, Gloucestershire; Dr John Beaman, Royal Botanic Gardens, Kew; Matt Bishop and John Colton, Buckland Monachorum, Devon; Jimi Blake, Hunting Brook Gardens, Co. Wicklow; Jo Bömer, Zundert, the Netherlands; Ian and Caroline Bond, Upton Wold, Gloucestershire; Wolfgang Bopp, Sir Harold Hillier Gardens, Hampshire; Graham Blunt, Plantbase Nursery, Wadhurst, East Sussex; Dave and Laura Brastow, Tumwater, Washington; Chris Brickell, Nutbourne, West Sussex; Andrew Brookes, University of Portsmouth/Butterfly Conservation, Hampshire and Isle of Wight Branch; H. Brown, Sir Harold Hillier Gardens; Andrew Bunting, Scott Arboretum, Pennsylvania; Chris Callaghan, Australian Bicentennial Arboretum, New South Wales; Frank Callahan, Medford, Oregon; Koen Camelbeke, Arboretum Wespelaar, Belgium; Peter Catt, Liss Forest Nursery, Hampshire; Glyn Church, New Plymouth, New Zealand; Dr James Compton, Tisbury, Wiltshire; Allen Coombes and Maricela Rodriguez-Coombes, Sir Harold Hillier Gardens, Hampshire; Geoff Cooper, Witney, Oxfordshire; Norbert Cordeiro and Anna Kessler-Cordeiro, Chicago; Kenneth Cox, Glendoick, Perthshire; Tom Cox, Cox Arboretum, Georgia; Dr David L. Creech, SFA Mast Arboretum, Nacogdoches, Texas; Veronica Cross, Stoke Lacy, Herefordshire; Dr John David, RHS Garden Wisley, Surrey; Jan De Langhe, Arboretum Het Leen Eeklo, Belgium; Dr Peter Del Tredici, Arnold Arboretum, Massachusetts; Vicomte Philippe de Spoelberch and Daphne Lippitt, Herkenrode, Belgium; Dr Michael Dosmann, Arnold Arboretum, Massachusetts; Graham Duncan, Kirstenbosch Botanical Garden, Cape Town; Nick Dunn, Frank P. Matthews Ltd., Tenbury Wells, Worcestershire; Linda Eirhart, Winterthur, Delaware; Dr Thomas S. Elias, US National Arboretum, Washington DC; Henry and Carolyn Elwes, Colesbourne Park, Gloucestershire; Aljos Farjon, Royal Botanic Gardens, Kew; Dr Roger Farrow, Canberra, Australia; David and Colleen Fenwick, Plymouth, Devon; Richard (Dick) Figlar, Magnolian Grove Arboretum, South Carolina; Mark Fillan, Tuckermarsh, Devon; Joyce Fingerut, Stonington, Connecticut; Mark Flanagan, Keeper of the Gardens, Windsor Great Park; Charles and Lara Foley, Arusha, Tanzania; Gert Fortgens, Arboretum Trompenburg, Rotterdam; Maurice Foster, Ivy Hatch, Kent; Michael Frankis, Newcastle upon Tyne; David Franklin, Oxford; Dr Peter W. Fritsch, California Academy of Sciences, San Francisco; Dr David Frodin, Chelsea Physic Garden, London; John Gallagher, Verwood, Dorset; Jim Gardiner, RHS Garden Wisley, Surrey; Martin Gardner, Royal Botanic Garden Edinburgh; Martin Gibbons, Richmond, Surrey; Ken Gillanders, Longley, Tasmania; Dustin Gimbel, Seal Beach, California; Christopher T. Glen, JC Raulston Arboretum, North Carolina; Mike Glover, Barcham Trees plc, Cambridgeshire; Mike Grant, The Plantsman, RHS Publications, Peterborough; Peter Gregory, Cirencester, Gloucestershire; Dr Christopher Grey-Wilson, Kenninghall, Norfolk; Peter and Susan Grimshaw, Maidenhead, Berkshire; Phyllis and Dick Gustafson, Central Point, Oregon; Capt. Shaun Haddock, Arboretum de la Bergerette, Dept. Tarn et Garonne, France; Dr Clement W. Hamilton, Morton Arboretum, Illinois; David Hardman, Wakehurst Place, West Sussex; James Harris, Mallet Court, Somerset; Tom Hart Dyke, Lullingstone Castle, Kent; Laurence J. Hatch, New Ornamentals Society, North Carolina; Harry Hay, Lower Kingswood, Surrey; The Lord Heseltine, Thenford, Oxfordshire; Howard Higson, Quarryhill Botanical Garden, Glen Ellen, California; John Hillier, Hillier Nurseries, Hampshire; Dr Nicolas Hind, Royal Botanic Gardens, Kew; Dan Hinkley and Robert Jones, Indianola,

Authors’ Preface

Washington; Dr Andrew L. Hipp, Morton Arboretum, Illinois; Randall Hitchin, Washington Park Arboretum, Seattle; Sean Hogan and the late Parker Sanderson, Cistus Nursery, Portland, Oregon; Stan C. Hokanson, Minnesota Landscape Arboretum, Minneapolis; The Lord Howick of Glendale (Charles), Howick, Northumberland; Eric Hsu, University of Tasmania, Hobart; Tom and Jo Hudson, Tregrehan, Cornwall; Kevin Hughes, Heale Gardens, Wiltshire; Ed Ikin, Nymans Garden, West Sussex; Eike Jablonski, LTA Arboretum, Ettelbruck, Luxembourg; Andrew Jackson, Wakehurst Place, West Sussex; Dr Richard Jinks, Forest Research, Alice Holt Lodge, Farnham, Surrey; Dr Owen Johnson, St Leonards-on-Sea, East Sussex; Dr Barrie Juniper, Department of Plant Sciences, University of Oxford; Douglas Justice, University of British Columbia Botanic Garden, Vancouver; Kunso Kim, Morton Arboretum, Illinois; Tony Kirkham, Royal Botanic Gardens, Kew; Thierry Lamant, Orléans, France; Roy Lancaster, Chandlers Ford, Hampshire; Sven Landrein, Royal Botanic Gardens, Kew; Dr F. Todd Lasseigne, Paul J. Ciener Botanical Garden, North Carolina; Janette Latta, Royal Botanic Garden Edinburgh; Dr Gwilym Lewis, Royal Botanic Gardens, Kew; Geoff Locke, Mount Pleasant Trees, Gloucestershire, Dan Luscombe, National Pinetum, Bedgebury, Kent; Prof. David Mabberley, Royal Botanic Gardens, Kew; Nick Macer, Pan Global Plants, Frampton, Gloucestershire; Paul Maher, National Botanic Garden, Glasnevin, Dublin; Skip March, Alexandria, Virginia; Dr Hugh McAllister, University of Liverpool; Josh McCullough, Portland, Oregon; Dr David McDonald, Cape Town; Sharon McDonald, Royal Botanic Gardens, Kew (now of the RHS Garden Wisley); Jim McKenney, Montgomery Co., Maryland; Bill McNamara, Quarryhill Botanical Garden, Glen Ellen, California; Thomas Methuen-Campbell, Penrice Castle, Swansea; Terry and Maria Milton, Woking, Surrey; Daniel Moeller, Hoyt Arboretum, Portland, Oregon; Jette D. Møller, Botanical Garden and Museum, Natural History Museum of Denmark, Copenhagen; Jenni Navratil, Oxford; Piers Newth, Harcourt Arboretum, University of Oxford; Rob Nicholson, Smith College, Massachusetts; Andrew Norfield, White Cloud Seeds, Nelson, New Zealand; Seamus O’Brien, Kilmacurragh Arboretum, Co. Wicklow; Mikinori Ogisu, Osaka, Japan; Sara Oldfield, Botanic Gardens Conservation International, Kew; Dr Richard T. Olsen, US National Arboretum, Washington DC; Drs Hans Persoon, University Botanic Garden, Utrecht, the Netherlands; Prof. James B. Phipps, University of Western Ontario, Ontario; Franklin Picard, Arboretum Segrez, Seine et Oise, France; Dr Donald Pigott, Cartmel, Cumbria; Stuart Priest, Batsford Arboretum, Gloucestershire; John Purse, Faversham, Kent; Jan Ravensberg, Ballyboughlin, Co. Offaly; The Viscount Ridley (Matthew) and the late Viscountess Ridley, Blagdon, Northumberland; Dr Mike Robinson, Forest Row, East Sussex; Keith Rushforth, Ashill, Devon; Dr John Ruter, University of Georgia; Chris Sanders, Eccleshall, Staffordshire; Daniel Sanford, Ipswich, Suffolk; Celia Sawyer, University of Oxford Botanic Garden; Tony Schilling, Ullapool, Ross-shire; Dr Brian Schrire, Royal Botanic Gardens, Kew; James Shiffer and Kirsten Delegard, Minneapolis, Minnesota; Dr Doug Smith, Wickham, Hampshire; Dr Jason A. Smith, School of Forest Resources and Conservation, University of Florida, Gainesville; Dave Stephenson, Minnesota Landscape Arboretum, Minneapolis; Guy and Edie Sternberg, Starhill Forest Arboretum, Illinois; Boyce Tankersley, Chicago Botanical Garden, Illinois; Philip Thomas, Royal Botanic Garden Edinburgh; Simon Toomer, National Arboretum, Westonbirt, Gloucestershire; Jennifer Trehane, Wimborne, Dorset; Val Tyson, JC Raulston Arboretum, North Carolina; Barry Unwin, Stranraer, Dumfries & Galloway; Robert Unwin, Royal Botanic Garden Edinburgh; Paulus van den Berk, Sint-Oedenrode, the Netherlands; Dick and Rita van Hoey Smith, Arboretum Trompenburg, Rotterdam; Jef Van Meulder, Arboretum Bokrijk, Belgium; Steve Verge, Wallingford, Oxfordshire; James Waddick, Kansas City, Missouri; Eva Wallander, Nature Conservancy, Jönköping, Sweden; Dr Bobby J. Ward and Roy Dicks, Raleigh, North Carolina; Dr George Ware, Morton Arboretum, Illinois; Mark Weathington, JC Raulston Arboretum, North Carolina; Dr Dennis Werner, JC Raulston Arboretum, North Carolina; the late Peter Wharton, University of British Columbia Botanic Garden, Vancouver; Tim Whiteley, Evenley Wood, Northamptonshire; Michael Wickenden, Cally Gardens, Dumfries & Galloway; Edward Wilson, Worcester College, Oxford; Nicholas Wray, University of Bristol Botanic Garden, Bristol; Steve Wright, Hergest Croft, Herefordshire; Bleddyn and Sue Wynn-Jones, Crûg Farm, Gwynedd; Michiel Zwaan and Maritgen Doelman, Maasland, the Netherlands.

xv

C A

B

F E

D

1 cm

J H

G

K L

M

N

Chapter 1. Introducing New Trees What is a New Tree? ‘New’ As explained elsewhere (p. ix), the foundation of New Trees is the encyclopaedia known fondly to gardeners as ‘Bean’ but more correctly as W.J. Bean’s Trees and Shrubs Hardy in the British Isles, in its eighth edition, together with the Supplement by D.L. Clarke (1988). Our basic aim was to provide descriptions and horticultural commentary, comparable to those of Bean, on tree species established in cultivation but not covered in this work. Bean’s coverage of his species is not uniform. Some well known taxa receive a full entry, others merely a note. Those accorded a full entry in Bean, with description and horticultural notes, were not considered for further discussion in New Trees, even in cases where recent introductions have made a species much more widely known and better understood than previously. An example of this is Liriodendron chinense, which has become widely planted and greatly valued in recent years, but for Bean was a rare tree. For many such species updating of information is needed, to cover new cultivars and current understanding of cultural conditions, but this is beyond our remit. Other species are mentioned by Bean only as a brief note, and where these have since become more widely grown they have been included here (with a crossreference to Bean: see p. 15). Most of the species described in New Trees, however, were not covered by Bean, and represent recent introductions to cultivation, for which no comparable source of information is available. A handful have been in and out of cultivation for centuries but somehow slipped past Bean and his successors: Pinus taeda and Quercus muehlenbergii are examples of this. Others, such as Maddenia wilsonii, have completely evaded the literature since they were introduced. The majority have been known to science for many years and only a few are recent discoveries. Our coverage list was derived by going through the collection records of major botanic gardens and private collections in the United Kingdom, Europe and North America (see p. 3 for discussion of our geographical scope), comparing their holdings against Bean’s accounts. Many names on the list turned out to be synonyms of taxa covered in Bean and could therefore be discarded. Other species were kept on the list even though they are grown in only one or two gardens; it was felt to be important that our coverage be inclusive rather than exclusive, as plants can suddenly be made widely available through the nursery trade. Species that have not been attempted in the open ground, or are as yet represented only by very recently planted out saplings, have not been included

Figure 1 (opposite). Rosaceous fruits. Pyrus communis subsp. mamorensis (A); P. elaeagnifolia (K); P. phaeocarpa (N). Malus toringo (B); M. coronaria var. platycarpa (H); M. rockii (L). Sorbus sp. sect. Discolores (C); S. tamamschjanae (F). Aria aronioides (D); A. hemsleyi (E). Crataegus pseudoheterophylla (G); C. meyeri (J); C. mexicana (M).

Plate 10. Many ‘new trees’ – only recently established in cultivation – have long been known to science. Joseph Rock took this photograph of Juniperus tibetica in 1926. Image Harvard University.

2

Plate 11. The hybrid ×Gordlinia grandiflora is an exciting new tree, bred in North Carolina (p. 785). Image T. Ranney.

New Trees

unless of particular significance (as, for example, Xanthocyparis vietnamensis). It is worth noting that there are probably hundreds more tree taxa in this category (‘second edition species’). Some of these are mentioned in the introduction to their genus, or in the accounts of related species. Among the species we describe there are also some in the ‘botanical interest only’ category: these often achieve surprisingly wide distribution. In general, cultivars have been described or discussed only in cases where they are selections made from recently introduced material, and hybrids that have arisen in cultivation have usually also been omitted. Exceptional new cultivars are referred to, however, usually in the introduction to their genus, and there is more extended coverage of cultivars in our accounts of the genera Malus, Prunus and Ulmus, in which they are of particular importance.

‘Trees’

Plate 12. In the right conditions, Osmanthus fragrans makes a small tree. Its scent, wrote Reginald Farrer (1909), is ‘a glimpse through the gate of Paradise’. Image J. Grimshaw.

The great encyclopaedic works of woody plants have usually included both trees and shrubs. Early in the New Trees project, however, it was decided that this book should describe only trees, requiring the making of some difficult decisions. The definition applied is that a ‘tree’ should be a woody plant, normally with a single trunk reaching or exceeding 5 m in height, at least in its native habitat. A ‘shrub’ would normally have multiple woody stems emerging from the base or close to the ground, and would seldom exceed 5 m in height. This definition is generally satisfactory, but inevitably leaves a very broad grey area of exceptions and difficulties. Genera such as Berberis and Cotoneaster, in which true trees are very rare, were easy to exclude, but there are more difficult, borderline cases. Heptacodium miconioides Rehder is one example: indubitably multistemmed, and usually small – but specimens of 10 m have been seen in the United States (it was not included). There are several monopodial trees in Euonymus and Viburnum, but these genera have been excluded because the majority of species are shrubs. We are not completely consistent, however, having been persuaded to include one Buddleja; and in some cases, especially genera such as Lindera and Styrax that are less well covered in the literature, a number of shrubby species are described alongside the trees. We have also excluded Rhododendron in its entirety, not only because most are shrubby, in the sense of being multistemmed, even when large, but because they are well covered already in an excellent literature. Palms and other monocotyledons have also been excluded.

Section I. Introduction

Chapter 1. Introducing New Trees

3

Geographical Scope – ‘Our area’ Our second departure from Bean is that New Trees is international in scope, covering trees growing in cultivation in Europe and North America as well as the British Isles. Nevertheless, Bean’s principle that the species described should be ‘hardy in the British Isles’ is sound guidance, since it provides a focus for what could otherwise be a boundless task. The exceptional climate of the British Isles also means that it is possible to grow here any tree that can be grown in northern Europe, and the same is true for most of North America. They may not grow very well, but they will grow somewhere in the diverse conditions of the British Isles. To curtail the potentially vast scope of the work, boundaries had to be set to reflect this concept of fundamental hardiness, by excluding species that grow only in conditions unknown in the mainland British Isles – in the climate of the coastal fringes of the Mediterranean basin, for example, or the heat and humidity of the American South, or the deserts of its Southwest, where the garden floras are fundamentally different. To avoid distraction by their wonderful possibilities, species growing only on the Isles of Scilly were also discounted. No northward limits were set. The boundary of ‘our area’ in continental Europe was taken as that between Zones 8 and 9 (on the USDA Plant Hardiness scale). South of this line the natural vegetation is recognisably Mediterranean in character, and the excluded area coincides with remarkable precision with that in which olives are grown as a regular crop – in French, the zone olivier. This boundary neatly excises all the tender plants that decorate the gardens of the Mediterranean littoral. The inclusion of Ficus elastica – so fine a park tree in southern Spain – would not be appropriate here, for example. (We will probably be promptly informed of a beauty in central London.) Plotting a boundary over the vastness of North America and its diverse conditions was less easy. The area of southern California with a Mediterranean climate and associated garden flora was excluded, on the same grounds as in Europe, and this extends through the arid southwestern states. The East Coast’s summer heat and humidity are unknown in Europe, yet very many cultivated trees have come from this area. Our boundary was set, perhaps slightly arbitrarily, at the North Carolina – South Carolina state line. This enabled the inclusion of many southern species growing in North Carolina, but excluded the impossibilities of the Gulf Coast and Florida. Our line then heads boldly if somewhat undefinedly westwards across the horticulturally semi-desert central states, and ends with determination at San Francisco. Delimitation in California is difficult, since climatic zones there are particularly complicated. We chose the San Francisco Bay Area as the cut-off point between the warmer south and cooler north. There could be no justification for taking a more northerly point when so many of our finest garden trees come from this latitude (Sequoia, for example, and Sequoiadendron), but the Bay Area is very temperate and many plants can be grown there that would struggle further inland or to the north (Corymbia ficifolia, for example, which is used as a street tree in San Francisco). We therefore did not add to our list new species from the great collections in the Bay Area – notably the University of California Botanical Garden at Berkeley, and the San Francisco Botanical

Plate 13. Rhus wallichii, from Nepal, growing at Quarryhill Botanical Garden, California. The list of species described in New Trees was determined by presence in cultivation rather than place of origin. Image H. Higson.

4

New Trees

Garden (formerly the Strybing Arboretum) – though if a tree grown elsewhere is also cultivated in these gardens, the record has been considered for mention. For logistical reasons, the arboreta of Australia, New Zealand and temperate Asia have generally not been taken into account. New Trees will, however, have relevance to all these extralimital areas, as there is much climatic and horticultural overlap.

Origins of Recent Tree Introductions Plate 14 (below). The forests of Asia are the main source of new tree introductions. Acer wardii, Arunachal Pradesh, India. Image M. Wickenden.

The trees described in this work have mostly been introduced from the temperate regions of the world, but increasing numbers derive from the subtropics and even the tropics, their cultivation made possible by the effects of climate change. Some of our species have vast ranges – the widest being that of Alangium chinTable 1. Recent tree introductions by area of origin ense, found from Angola to the Philippines – while others are island or local endemics, or are currently confined to very few sites by the China, Sino-Himalaya 46.8 % effects of habitat destruction. Table 1 records, at very coarse scale, Australia 11.1 % the places of origin of recently introduced species, grouped into Mexico, Central America 10.8 % Eastern North America 5.5 % broad geographical areas. As always, the mountains of China and Middle East, Central Asia 4.4 % the Himalaya are a principal source of temperate trees. Within this Japan 3.9 % area, it should be noted, the closed country of Myanmar (Burma) Manchuria (northeast China, N. Korea, east Siberia) 3.2 % remains both temptation and frustration to plant hunters, and no Western North America 3.1 % recently introduced taxa that are principally Burmese are recorded New Zealand 3.1 % here. The high proportion of Australian records is mainly due to the Temperate South America 3.0 % Sub-Saharan Africa 1.7 % large numbers of Eucalyptus introduced from that continent, but Rest of the world 1.3 % there are also many new species of other Australian genera in culNorth Africa 1.2 % tivation. From no other region do the trees so dramatically demonWestern Europe 1.2 % strate how global warming has widened options for gardeners.

Section I. Introduction

Chapter 1. Introducing New Trees

5

Hardiness Hardiness – the ability of a plant to survive in the ground all year round – is an issue that concerns all gardeners. It is frequently imagined to be a simple reflection of a plant’s tolerance of a certain number of degrees of frost, and is most often defined in these terms. This may be a useful, though crude, guide, but the complexities of hardiness go far beyond it. Many factors, including planting site, the maturity of the plant and its provenance, may confound predictions of hardiness based only on climatic parameters. In so many cases we do not yet know what the ultimate tolerances of a particular species are, and growing many of those we describe will be a journey of discovery. Please keep records! Many attempts have been made to categorise hardiness for horticultural purposes, Plate 15. Juglans neotropica is currently maintained in a and an admirable review has been published (Brady 2008), comparing the various pot in Ian Bond’s collection schemes in use in the northern hemisphere. Hardiness zone maps are based on climatic of walnuts at Upton Wold, parameters, usually mean winter isotherms, so that areas sharing similar climates are Gloucestershire. An Andean banded together. They are inevitably broad-brush in format, and microclimates are species, its hardiness is so far usually obscured. At best, they are useful guidelines to areas with similar climates. unknown. Image J. Grimshaw. The most widely used map of hardiness zones is that produced by the US Department of Agriculture (USDA), currently used in the 1990 version (Cathey 1990; for the online version, see USDA 2003), though in the process of being updated. It is based on a very simple system, using mean annual minima separated into isotherms of 10 ° Fahrenheit, sometimes subdivided into intervals Table 2. USDA Hardines Zones of 5 °F, labelled ‘a’ for the cooler half and ‘b’ for the warmer half Zone 1 Below –50 °F Below –45.6 °C (see Table 2). The USDA Hardiness Zone Map is a fundamental Zone 2a –50 to –45 °F –45.5 to –42.8 °C part of American horticulture, and every gardener in the United Zone 2b –45 to –40 °F –42.7 to –40.0 °C – – –39.9 to –37.3 °C Zone 3a 40 to 35 °F States knows his or her zone. For much of North America east of –35 to –30 °F –37.2 to –34.5 °C Zone 3b the Rocky Mountains, where the zones form fairly regular bands –30 to –25 °F –34.4 to –31.7 °C Zone 4a across the continent from north to south, it can be assumed that the Zone 4b –25 to –20 °F –31.6 to –28.9 °C –20 to –15 °F –28.8 to –26.2 °C winter climate throughout a zone will be much the same – hence Zone 5a –15 to –10 °F –26.1 to –23.4 °C Zone 5b the easy acceptance of such categories. –10 to –5 °F –23.3 to –20.6 °C Zone 6a To the west of the Rockies, the diversity of the landscape makes Zone 6b –5 to 0 °F –20.5 to –17.8 °C the application of this system more patchy and less valued. Espe- Zone 7a –17.7 to –15.0 °C 0 to 5 °F –14.9 to –12.3 °C 5 to 10 °F cially in California, and to a certain extent elsewhere on the West Zone 7b –12.2 to –9.5 °C 10 to 15 °F Zone 8a Coast, the zonation published by Sunset magazine, which uses –9.4 to –6.7 °C Zone 8b 15 to 20 °F a more complex set of parameters, is widely used. The zonation Zone 9a –6.6 to –3.9 °C 20 to 25 °F –3.8 to –1.2 °C 25 to 30 °F scale of the USDA map is, however, applicable to winter minima Zone 9b –1.1 to 1.6 °C Zone 10a 30 to 35 °F anywhere, enabling the generation of similar maps for Europe Zone 10b 35 to 40 °F 1.7 to 4.4 °C and China, for example. What it does not do is consider any other Zone 11 Above 40 °F Above 4.5 °C climatic variables, such as summer temperatures.

6

New Trees

In Europe the pattern is more complicated, as complexities of coastline and topography modify the climate. Thanks especially to the effect of the Atlantic Ocean, the western edge of Europe is much milder than its latitude would suggest it ought to be, with a corresponding effect on zonation: in Europe, coldness increases not only northwards but eastwards. The British Isles (the islands of Great Britain, Ireland and their satellites), insulated by the sea, enjoy a uniquely mild climate for their latitude, such that a vast array of plant species may be grown outdoors somewhere in the archipelago. A similar climate is experienced in the western extremities of continental Europe, especially in Brittany, but not far inland the continental climate begins to take effect, with hotter summers and colder winters than experienced in the truly maritime areas, changing the range of species that can be grown. According to the delimitations of the USDA Zones, most of the British Isles experience a Zone 8 winter (–12.2 to –6.7 °C), but in fact most areas are Zone 8b (–9.4 to –6.7 °C), and southern and coastal areas are Zone 9 (–6.6 to –1.2 °C); only the highest mountains experience Zone 7 conditions (of –17.7 to –12.3 °C). Comparing this to similar zones in the United States immediately reveals the flaws in a hardiness rating system that uses only one parameter: there is no comparison between the climate experienced in Raleigh, North Carolina (Zone 7b) and that in the Cairngorms of Scotland (also 7b), nor between the Zone 9 of Texas and that of the Thames Valley. Despite these considerable limitations, the advantage of the USDA map is that it is widely understood, and the simple zonation scale can easily be used to map winter minima anywhere else in the world. For this reason it has been adopted for New Trees in preference to any other scheme, but hardiness ratings given should be taken only as a guideline to winter minima that species are known or believed to tolerate. They take no account of any other climatic factors such as summer heat (see below) and rainfall, that are also essential elements governing the growth of a plant. The danger with attributions to hardiness zones using any scheme is prescriptiveness. Too often, especially in North America, the standard attribution is used as a reason for not attempting to grow a plant beyond its supposed zone, especially in

Plate 16 (near right). Pyrus elaeagnifolia, photographed here during an International Dendrology Society tour to Turkey, is rated hardy to USDA Zone 5. Image J.R.P van Hoey Smith. Plate 17 (far right). Afrocarpus gracilior could be worth trying in mild parts of our area. This beautiful specimen is in Ethiopia, where such trees are often spared during forest clearance. Image J. Grimshaw.

Section I. Introduction

Chapter 1. Introducing New Trees

mainstream horticulture. More free-thinking establishments and individuals who disregard these strictures are sometimes said to be in ‘zonal denial’ – and thank goodness they are, or horticulture would never progress. On the other hand, a certain caution is wise. The nursery trade is often optimistic, and estimates of hardiness in catalogues may need to be regarded with a degree of scepticism unless backed up by extended experience of a plant in local conditions. The survival of a new introduction for a year or so does not constitute a valid trial; as in other aspects of life, prognostications based on brief acquaintance can result in disappointments. Some of these plants will turn out to be what may be termed ‘kiss me hardy’, dependent on unusually favourable seasons for survival, while others will prove more reliable. Experimentation is the only way to establish these facts, and gardeners should never be afraid to push the boundaries – especially during the current period of climate change.

7

Plate 18. Acacia dealbata subsp. subalpina, assessed hardy in USDA Zones 8–9, in dramatic foliage combination with a purple Phormium at Cistus Nursery, Oregon. Image Phytophoto.

Summer heat A generally very poorly understood factor is the effect of summer heat on plant performance. Heat can have obvious direct effects such as sun-scorch and desiccation, but its physiological effects are much more stealthy. When a plant is affected by cold, it is often relatively easy to identify the point at which damage or death occurs, but the effect of heat is slow and cumulative and may be either deleterious or beneficial. In some plants, notably those from cool climates, extended periods of high temperatures can be very damaging and lead to death, as the plant’s physiology becomes unable to function and fails. Others, on the other hand, require heat to ripen their wood and mature, or simply need hot conditions to grow away. Such plants do not perform well where summer mean temperatures are on the cool side. As with winter temperatures, it is possible to plot heat isotherms to create a map of areas sharing similar summer temperatures. Such a map of the United States was prepared for the American Horticultural Society (AHS) by the plant physiologist H. Marc Cathey (who as Director of the US National Arboretum was also responsible for the 1990 USDA Hardiness Zone Map). Published in 1998 (American Horticultural Society 1998–2008), the AHS map uses the number of days in each year when the temperature reaches 30 °C or more to plot twelve Heat Zones, ranging from 1 (with one or fewer such hot days per year – as, for example, in Alaska) to 12 (more than 210 such days per year – in small areas of Florida and Texas). The AHS map was intended to help gardeners choose plants that would survive the summers in their location, and as such has the same element of prescriptiveness as the USDA map. It is, however, invaluable in demonstrating vividly differences in summer temperatures between, say, Richmond in Virginia and Richmond in Greater London. Where Virginia experiences 60 to 90 days per year when temperatures reach 30 °C (Heat Zone 7), London has no more than a handful – and this is in the warmest part of the United Kingdom. Moving southwards from Virginia the contrast increases, until the

Plate 19. Quercus hemisphaerica in South Carolina. Many trees from the southeastern United States need high summer temperatures to thrive, and do not do well in cooler European conditions. Image J. Grimshaw.

8

Plate 20. Now flourishing and fruiting annually at the Chelsea Physic Garden, London, this grapefruit (Citrus ×aurantium Grapefruit Group) has grown outdoors here since the 1950s. It is known as ‘Aunt Queenie’, after the lady who grew it from a post-War pip. Image J. Grimshaw.

New Trees

steamy heat of the Deep South is reached, where most areas experience in excess of 90 days with temperatures of 30 °C (Heat Zones 8 and over). On the USDA hardiness scale, however, these same areas (eastern North Carolina southwards) are rated as Zone 8, comparable to most of England – where a 30 °C day is an extreme rarity and cause for much complaint (not to mention the exposure of far too much flesh). The effect of warm summers on the growth in Britain of eastern North American trees has long been noted. Juglans nigra is a classic example, doing best in southern and eastern England but struggling further north (Mitchell 1996). Others, including almost all the American white oaks, and some of the pines, grow very poorly in the British climate, while some species such as Acer rubrum and Quercus rubra (and most other North American red oaks) thrive. All are equally frost-hardy: it is their need for summer heat that makes the difference. A similar situation is found in Japan and eastern and southern China, where summers are hot and humid, and winters cold: among plants from these areas there is a similar mixture of responses to cooler summers. No such hot and humid conditions occur anywhere in Europe, but the effect of increased summer warmth is often visible in North American trees growing as close to England as Belgium, for example, where they benefit from the hotter summers of the Continent. Increasing temperatures may lead to greater success with such species.

Global Warming and Climate Change The global climate has always varied, with changes occurring over relatively short periods of time. The very recent ice ages, with their glacial and interglacial periods and rapid onset and termination, are the most familiar example of this. Species distributions and ecosystems have responded by contracting or expanding, and in so doing have created the current biogeographic pattern. The difference today is the extent to which humans dominate the planet and have modified the environment, making adaptation to climate change by species and their ecosystems much less feasible. Catastrophic loss of biodiversity and immense human suffering seem to be inevitable if the world’s climate does change markedly in the next few decades, as most climatologists believe it will. The orthodox view, accepted by the Intergovernmental Panel on Climate Change (IPCC) and the vast majority of scientists around the world, is that the mean surface temperature of the earth is rising as a result of human activity, especially from the release of greenhouse gases. Over the past century global mean temperatures have risen by 0.74 °C, with 0.4 °C of that increase having come since 1970, and the rise continues at accelerating pace. Predictions vary, but it seems most likely that by 2100 global temperatures will be 1.8 to 4 °C higher than they were in 1990, or possibly a little higher or lower than these values (Defra 2008). (The full range of current predictions is 1.1 to 6.8 °C higher.) The local and global effects of the current trend of global warming, and the scale of the disaster it unleashes, will become apparent only with time. Predictions of consequences vary, but the general view seems to be that most places will become warmer and drier,

Section I. Introduction

Chapter 1. Introducing New Trees

and that unpredictable weather events will become more frequent. Sea-levels will certainly rise, resulting in coastal and estuarine flooding. In observing the progress of climate change it is critical to watch trends, not data points. For example, according to the Royal Horticultural Society’s webpage on climate change (Royal Horticultural Society Learning 2008), one consequence of climate change for the United Kingdom will be ‘hotter, drier summers, increasing risk of drought’. Such predictions caused much mirth during the atrocious cold wet ‘summers’ of 2007 and 2008, but are nonetheless valid as statements of a trend over time. There can be no doubt that a warming climate will have huge consequences for the cultivation of trees and other horticultural subjects. Up to the present the effects have most frequently been perceived to be beneficial, since rising temperatures have undoubtedly enabled a far wider range of species to be cultivated outdoors in our area than ever before, as testified in part by the diversity of taxa in this book. The effect is most noticeable on the milder fringes of both continents, because it is here that a slight increase in temperature makes the greatest difference to plant growth: an increase in mean winter minima from –1 °C to 0 °C is much more significant than an increase from –10 ° to –9 °C if a plant is not able to tolerate much frost. An increased interval between hard winters is in itself beneficial for many species, as the older and more mature a specimen is, the more it may be able to tolerate low temperatures. A shift of zones northwards is already mooted for the forthcoming revised USDA Hardiness Zone Map, and a rival, the hardiness map released in 2006 by the Arbor Day Foundation, has already anticipated such a move with an update that places many areas in a zone at least one higher than in the original 1990 map. On the other hand, rising temperatures, especially if coupled with drier conditions, are likely to make the cultivation of some species much more difficult. This includes some of our most familiar and best-loved trees, including natives. In the United Kingdom the Beech Fagus sylvatica is assumed to be one of the species most likely to be affected, as it frequently grows on shallow soils prone to drying out. Recent dry summers have already demonstrated how stressed drought-stricken Beeches become, and hotter, drier conditions will not only exacerbate the stress on mature trees (of this and many other species), but also reduce the opportunities for successful establishment of seedlings (Indicators of Climate Change UK 2003). Across most of our area winters will probably become milder, but are likely also to be wetter and stormier, with the concomitant effects of waterlogging and wind damage, while the likelihood of earlier bud-break will put many plants at risk from spring frosts. The evidence from phenological records is remarkable proof of this trend: for example, the famous tree of Aesculus indica ‘Sydney Pearce’ at Kew is now flowering on average nine days earlier than it did in the 1980s (Royal Botanic Gardens, Kew 2008). A long-term phenology monitoring project is now in place at Kew. More insidious perhaps is the probability that many plants will not receive the period of vernalisation required for effective

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Plate 21. Ficus aff. heterophylla DJHS 4307 at Juniper Level Botanic Garden in North Carolina. As global temperatures rise, more species of Ficus are likely to become growable in our area. Image J. Grimshaw.

Plate 22. Hardy trees such as this Quercus ellipsoidalis may suffer in climate change, if rising temperatures reduce vernalisation periods and encourage early bud-break. Image J. Grimshaw.

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Bucking the trend of a warming climate, the 2008–2009 winter has been unusually testing across much of our area. Commentary on tree survival will be gratefully received (e-mail address [email protected]).

New Trees

regulation of their internal clock. Further, pests and diseases may also be able to take advantage of less rigorous winter conditions to cause increased trouble. Against the effects of warming induced by greenhouse gases may be set a number of natural phenomena, including variations in sunspot activity and effects of oceanic oscillation patterns, while a major volcanic eruption could produce a temporary cooling effect through the reflection of heat from atmospheric particulates. One of the more alarming predicted effects of global warming, widely reported in the media, is that the Gulf Stream and the associated North Atlantic Drift, carrying warm water across the Atlantic to bathe the shores of Europe, could be ‘turned off’ by increased volumes of fresh water entering the North Atlantic from melting polar ice, plunging northwestern Europe into the freezer. There is evidence that the transatlantic flow has weakened significantly in recent decades (Bryden et al. 2005), but any effect from this is most likely to be seen off northern Norway, where the Norwegian current may be weakened and the heat exchange that occurs there could possibly be reduced. The myth of the balmy Gulf Stream waters keeping western Europe mild has effectively been exploded by Seager (2006, 2008), who has shown that the 15 to 20 °C difference in winter minima between equivalent latitudes on each side of the Atlantic can be accounted for by the innate heat-storage capacity of the ocean (without any form of heat transport by currents) and the effect of the massive stationary wave of air formed by the west–east flow over the Rocky Mountains – bringing cold air southwards across North America but warm air across Europe. Each of these phenomena accounts for about half the winter temperature difference between North America and Europe; were the Gulf Stream to be removed altogether the difference to winter minima on both shores of the Atlantic would be no more than 3 °C, and the proportionate difference would be maintained. In consequence, even if the flow does weaken, winter minima in northwestern Europe will not fall so dramatically as to cause an ice age, and predicted atmospheric temperature increases would even out the difference (Seager 2008). Whatever happens in the next few years, the climatic future looks distinctly unsettled. There are innumerable websites and publications on the subject of global warming and climate change, offering various points of view and opinions. Their perusal will be instructive, if potentially terrifying, but it is well to remember that the bottom line is this: there are too many humans, using too many of the world’s resources and doing too much damage to the world’s ecosystems.

Nomenclature

Plate 23. Magnolia laevifolia, formerly Michelia yunnanensis. The inclusion of Michelia in Magnolia better reflects evolutionary relationships of the family. Image K. Camelbeke.

Taxonomy (the process of naming plants) and systematics (the study of their relationships) are ever-changing. New discoveries and scientific innovations improve our understanding of how different plants are related to one another, and taxonomy evolves to reflect these relationships. This book incorporates many advances in taxonomy at family, genus and species level. Utilising a modern taxonomic scheme can, however, leave experienced horticulturists at a loss, as familiar names are relegated to synonymy. We believe that the names used here are the most appropriate for each species, reflecting contemporary botanical opinion in published sources. In this approach we do not always agree with some references, such as the often conservative RHS Plant Finder (Lord 2008, for example), frequently recommended as a source of reliable names; but where nomenclature is contentious, discussion of our sources and

Section I. Introduction

Chapter 1. Introducing New Trees

reasoning for adopting the new name is included, often headlined as a ‘Taxonomic note’, following the description of the plant. Historically, plant names have often not reflected their true relationships, unrelated taxa being grouped together on the basis of apparent similarities. The advent in recent years of sophisticated techniques, especially in DNA analysis, has made it possible to examine relationships at the genetic level and look beyond morphological features that may unwarrantedly suggest a relationship. The value of DNA for phylogenetic research is that it is much less likely to be affected by environmental factors than are morphological characters, changing only slowly through mutations recorded in the genetic ‘annals’. Despite this, molecular information remains only part of the suite of characters that make up the defining points of any taxon, and should always be combined with a full assessment of morphology in the delimitation of taxa at all ranks. Modern systematics makes substantial use of the principles of cladistics, which utilises a wide set of data to generate tree-like branching diagrams or ‘cladograms’ that summarise hypotheses of relationship among the species under consideration, derived analytically from the data (Kitching et al. 1998, Skelton & Smith 2002). A cladogram is made up of pairs of ‘sister groups’, each containing one or more species hypothesised to have diverged from a single ancestor. It thus resembles a family tree. Each lineage derived from a single ancestor in the evolutionary sequence is known as a ‘clade’, and should contain both the ancestor and all its surviving descendant species. Such a clade is termed ‘monophyletic’ – having only one evolutionary origin (though subsequent divergence may have occurred in the descendants), and thus truly ‘natural’. Monophyletic groups of this kind are now used as the basis for classification, as they are believed to reflect the course of evolution most accurately. Traditional taxonomy has often grouped together taxa that derive from several ancestors in their evolutionary past, and are therefore held together only by superficial morphological similarities, a state known as ‘polyphyly’. Two examples of polyphyletic genera are Acacia and Sorbus in their traditional senses – each containing several lineages with different ancestry. Another important concept is that of ‘paraphyly’, in which analysis shows that a group of taxa are descended from a common ancestor, but some of them are excluded by the systematist on account of perceived differences. For example, to keep some genera of Magnoliaceae segregated (Michelia, Manglietia) would be to accept a paraphyletic state; united within Magnolia, they complete a neat monophyletic clade. Neither paraphyletic nor polyphyletic groups are recognised by cladistic analysis. They are artificial systematic constructs that hinder evolutionary studies and natural classification, so should not continue to be recognised, however familiar they may have become (Bateman 2001). An important consequence of this revolution in botanical thought is that relationships within and between flowering plant (angiosperm) families are being intensively scrutinised, and their boundaries redefined where necessary to reflect true monophyletic relationships. This work is led by the Angiosperm Phylogeny Group (APG 1998, 2003). The APG is an international group of botanists who have published

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Plate 24. Young leaves of Acer sikkimense, shining as if they had been polished. The work of the Angiosperm Phylogeny Group has led to Acer being placed in the largely tropical family Sapindaceae. Image J. Grimshaw.

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Plate 25. Quercus affinis, flourishing at Kew. Oak taxonomy has been clarified by the World Checklist of Fagales. Image J. Grimshaw.

New Trees

a consensus classification of the angiosperms, based on phylogenetic analysis of DNA. This classification (recognising monophyletic families only), while necessarily incomplete, has become a standard reference, and is adhered to in New Trees. Thus a number of well-known family names have disappeared, after amalgamation with other families (Aceraceae is now included in Sapindaceae, for example, and Tiliaceae in Malvaceae). Other families (including Hamamelidaceae, Scrophulariaceae) have been divided, resulting in unfamiliar segregates (Altingiaceae, Stilbaceae). In some cases the APG classification amalgamates families which, if kept separate, would remain monophyletic (for example, Proteaceae + Platanaceae). In these cases we have retained the familiar name, but the optional family name is also noted, in brackets. Below the family level, each genus is treated using the most recently available taxonomic account. The standard format begins with the generic name and authority (author names abbreviated according to Brummitt & Powell 1992; available online, www.ipni.org). This is followed by generic synonyms. For the most part, only significant synonyms have been cited, though in cases of major taxonomic change (Magnolia, for example) all synonyms are listed. Species accounts follow the same format. Where possible, names have been checked against the World Checklist of Selected Plant Families (produced at the Royal Botanic Gardens, Kew; most available online). Though this so far takes in only a small number of families, these include important ‘tree families’ such as Betulaceae, Fagaceae, Magnoliaceae and Myrtaceae. The exception to their general availability online, as of September 2008, is the World Checklist and Bibliography of Conifers (Farjon 2001). The advantage of the World Checklist series, and the excellent USDA Germplasm Resources Information Network (USDA/ARS, National Genetic Resources Program 2008), is that they attempt to identify the valid name for any taxon and provide its synonymy, thus differing from the International Plant Names Index (IPNI) website. IPNI is the standard source for plant names and associated information, but gives no indication of current validity. Although the World Checklist series is invaluable, we dissent occasionally from its authors’ opinions, and from a horticultural viewpoint it can sometimes be problematic in its tendency to subsume into the undifferentiated species minor variants of garden interest, whose names have been published under the International Code of Botanical Nomenclature (usually referred to as the Botanical Code: McNeill et al. 2006). Recognition of these taxa as cultivars or Cultivar Groups would be the appropriate action here. Hybrids of garden origin with nothospecific names are also often dismissed in the Checklists, or unwarrantedly transmogrified into cultivars.

Section I. Introduction

Chapter 1. Introducing New Trees

In discussing plants of garden origin, the conventions of the International Code of Nomenclature for Cultivated Plants (usually abbreviated to the Cultivated Plant Code: Brickell et al. 2004) are followed. The Cultivar Group concept is rightly gaining widespread acceptance and use, for its convenience in uniting plants with similar characteristics but which are not sufficiently distinct to warrant individual cultivar names. A confusing and somewhat irritating area in horticultural taxonomy is the frequent application of trade designations or selling names that are different to the accepted cultivar name, and may vary between countries. These names are applied to promote sales: for example, the Japanese Cherry Prunus ‘Matsumae-fuki’ is sold in the United Kingdom as Chocolate Ice, as this is supposedly easier to remember and enunciate. In written material selling names are conventionally given in a different typeface (Helvetica is used here), and lack the single quotation marks that indicate a cultivar name. The correct cultivar name is supposed to be given alongside a selling name, but in practice this is not always done. Vernacular names are often a difficult area, especially in a book with international scope. The validity of usage of common names is unquestionable, when in application by local people – Ash in England, Raulí in Chile, Putaputaweta in New Zealand – and there is no reason why vernacular names in other languages should not be accepted into botanical English as proper nouns. Our view is that the scientific name is always preferable for accurate communication, but many gardeners, especially in North America, like to use an English name, and many names have been invented to fit this perceived need (selling names are often co-opted as part of a vernacular name, as in the case of the Accolade Elm). Where such vernacular names are established in the literature we have provided them (though we jibbed at adopting ‘worm-head’ as the English name for Meliosma), but generally we have not coined new names here. We have adopted the excellent convention, recommended by the Botanical Society of the British Isles, of capitalising initial letters of common names where these are proper nouns referable to a single species – for example, Black Sallee for Eucalyptus stellulata. This practice enables them to be recognised at once and attributed to a single species, and its use could be advantageously adopted throughout horticulture.

Sources Information for New Trees has been gathered from many sources. The initial selection of species for coverage was obtained by comparing the collection lists of our focus gardens and arboreta, where available, against the list of taxa described by Bean. A list of these focus collections is given in Appendix 1 (p. 909), including catalogue and database references, so these sources have generally not been referenced individually in the text. Our botanical descriptions are in most cases adapted from published literature, and these sources are indicated as references at the end of each description, but many details were also checked on living trees, or herbarium specimens at Kew, to supplement published information. Generally, most published botanical descriptions are drawn up from herbarium material, and their quality depends on the information available from the specimens and their accompanying notes. Often much detail is

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Plate 26. The correct name for this cherry cultivar is Prunus ‘Matsumae-fuki’ but in the United Kingdom it may also be found under the trade designation (selling name) Chocolate Ice. Image Frank P. Matthews, Trees for Life.

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Plate 27. A group of Podocarpus matudae at Tregrehan, flourishing in the mild Cornish climate enjoyed by this exceptional garden. Image J. Grimshaw.

New Trees

missing, and especially for rarer taxa this is not always easily supplied from other sources – ultimate tree height, for example! It should also be borne in mind that a plant’s performance in cultivation is not necessarily the same as in the wild, and its parts may be larger or smaller than dimensions cited. Our horticultural commentaries are derived in large part from John Grimshaw’s own observation of trees growing in arboreta across our area, and most unreferenced information is drawn from this research. Notes were taken using a standardised check sheet when possible, but observations were also recorded in a series of notebooks. Further information has been obtained from personal communications with growers (referenced in the text as ‘pers. comm.’) or from published sources (referenced through the bibliography in the usual way). Much valuable information was derived from the New Trees workshop held at Colesbourne Park in January 2007, when an international group gathered to talk about recently introduced species. Records of the presence of a tree in an arboretum may also be taken from database sources (usually not specifically referenced each time). Tree heights may be derived from personal observation, from contributors, from the records of the Tree Register of the British Isles (TROBI) and the Tree Register of Ireland (TROI), and in some cases from arboretum online databases. Most notably these are available for specimens at the JC Raulston Arboretum and the Sir Harold Hillier Gardens, and information given on the stature of trees from these institutions is mostly from this source. Many measurements for specimens at the Hillier Gardens were made particularly for New Trees by H. Brown, to whom we are very grateful. Comments on a tree’s commercial availability have usually been made on the authority of the RHS Plant Finder in its annual printed editions and online, and for western North America we found The Plant Locator, Western Region was invaluable (Hill & Narizny 2004). The comprehensive selection offered by Firma C. Esveld of Boskoop in the Netherlands, in their published and online catalogues (Plantentuin Esveld 2006-2008), has often been taken as evidence of a species’ availability in continental Europe. Other catalogues were also consulted, and are acknowledged. Internet sources have been used cautiously, traditionally published sources having been preferred when available. In many cases these now overlap, when printed material is made available online as well. Good examples include the invaluable free access online to the floras of Australia, China and North America, even though these are only partly complete. Many journals are also hosted on pay-for-use sites. Inevitably, as online catalogues and personal websites proliferate, much information is available only on the internet. The ease with which this material can be updated or deleted makes online sources potentially transient, though not necessarily incorrect. All websites from which information has been used are referenced fully in the bibliography, including URL and the date on which the site was last accessed by us. In most cases this was during the proof-reading stage of the book in 2008, when almost all sites referenced earlier in the work were found to be still current. Geographical names are generally given as in The Times Comprehensive Atlas of the World (1999 edition), but other authoritative sources have also been consulted. It should be noted that ortho-

Section I. Introduction

Chapter 1. Introducing New Trees

15

graphic variants abound in the literature, especially where transliteration is necessary. The highest mountain in Vietnam, for example, is given in our accounts as ‘Fan Si Pan’, as in The Times Atlas, but elsewhere may be found as ‘Phan Xi Pan’, ‘Fansipan’ and so on.

Cross-references and Synonyms The species described in New Trees are for the most part only a sample of the diversity of their genus, from which there may be many well-established species (‘old trees’) in cultivation, described in previous reference works. To facilitate comparisons we provide cross-references to the descriptions of such trees in the encyclopaedic works of Bean and Krüssmann, using the abbreviation of a key letter and a page number. For example, among our accounts for Abies (p. 46), the line: A[bies] alba Mill. B144, S17, K29 indicates that there are descriptions or discussions of Abies alba on page 144 of Bean’s Trees and Shrubs (Volume I), page 17 of Clarke’s Supplement (Clarke 1988), and page 29 of Krüssmann’s Manual of Cultivated Conifers (Krüssmann 1985b). A summary of the volumes comprising these sources is presented in Table 3. Individual volume numbers are not given in our abbreviated cross-references, as they are clearly discernible from the initial of the genus in question or, in the case of Krüssmann’s works, by whether the tree is broadleaved or coniferous. In cases where we quote a point of view or snippet of information from these sources, however, the reference is given in the text in the usual way (‘Bean 1976a’, etc.), as for any other bibliographic reference. The dates of publication given for volumes of ‘Bean’ have been taken from John Grimshaw’s working set and may vary from those in other sets, as a result of revised impressions having been issued, after the first appearance of the eighth edition. So far as we can determine, however, the revisions do not affect pagination for cross-referencing purposes. Table 3. Sources for cross-references Key

Volumes referred to

B

W.J. Bean. Trees and Shrubs Hardy in the British Isles, Eighth Edition. Volume I. A–C (referenced in bibliography as Bean 1976a) Volume II. D–M (Bean 1981a) Volume III. N–Rh (Bean 1976b) Volume IV. Ri–Z (Bean 1981b)

S

D.L. Clarke (1988). W.J. Bean. Trees and Shrubs Hardy in the British Isles. Supplement.

K

G. Krüssmann. Manual of Cultivated Broad-leaved Trees and Shrubs, English translation. Volume I. A–D (referenced in bibliography as Krüssmann 1984) Volume II. E–Pro (Krüssmann 1985a) Volume III. Pru–Z (Krüssmann 1986) G. Krüssmann (1985b). Manual of Cultivated Conifers.

NT

J.M. Grimshaw & R.P. Bayton (2009). New Trees. Recent Introductions to Cultivation (this work).

Plate 28. The tropicallooking leaf of Cornus chinensis. The first introductions of this plant from Assam, noted by Bean (B706), were tender, but hardier Chinese material is now in cultivation. Image J. Grimshaw.

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New Trees

As part of our cross-referencing we have endeavoured to show where names have changed from those used by Bean, Clarke and Krüssmann, and give current, correct names, signalled by the word ‘NOW’. Thus the cross-reference: A[bies] bornmuelleriana (NOW A. nordmanniana subsp. equi-trojani (Asch. & Sint. ex Boiss.) Coode & Cullen, NT56) B161, S28, K31 indicates that the name Abies bornmuelleriana (as used by the three authorities, on the pages noted) is now considered to be synonymous with A. nordmanniana subsp. equi-trojani, and the tree is described under this name on page 56 of New Trees. For convenience of reference, some species with new names in different genera have been cross-referenced using the word ‘WAS’. For example, the cross-reference: M[agnolia] doltsopa (Buch.-Ham. ex DC.) Figlar (WAS Michelia doltsopa B738, K307) indicates that this tree, which should be referred to as a Magnolia, was described by Bean and Krüssmann under the now discarded generic name Michelia. Very occasionally we have employed the word ‘OR’, where in cases of competing names of apparently equal validity we equivocate by not firmly choosing one over the other. For example, the cross-reference: U[lmus] procera Salisb. (OR U. minor Mill. var. vulgaris Richens) B653, K412 indicates that this distinct taxon, described by Bean and Krüssmann as Ulmus procera, can be regarded either as a full species in this way, or as a variant of U. minor conceived more broadly, and may be found in contemporary literature under either name. The index contains many further names, and should always be consulted.

Illustrations Most of the technical paragraphs in our accounts include a short section headed ‘Illustration’ where we give references (in normal bibliographic format) to works where an illustration of that tree has been found during our research. For example, the account for Pterocarya macroptera var. insignis (p. 678) includes the line: Illustration Lu et al. 1999, Rix 2007; NT675

1 cm

Figure 2. Nothofagus ×leonii: cupule with seeds.

indicating that this variety is illustrated in two external references, and in New Trees also, on page 675. Information on the whereabouts of illustrations is not comprehensive, as works not used in our research have not been checked. Where a genus has been the subject of an important illustrated monograph (Acer, Magnolia, Pinus and Quercus, for example), repetitious referencing of illustrations is avoided by mentioning this source in the introductory discussion of the genus. Our line drawings were made by Hazel Wilks, working with both dry and living specimens, principally from the Royal Botanic Gardens, Kew. These were supplemented with material supplied by growers around the United Kingdom, to whom we are very grateful. The specimens used are cited in Appendix 3 (pp. 919–222). Our photographs were taken in gardens and wild habitats around the world by a diversity of photographers, credited in each case in the caption beside the image, and have been selected to show attractive or interesting features of the trees.

Chapter 2. Conservation Trees around the world are under threat from a variety of factors, most seriously from the effects of logging and forest clearance for agriculture and plantations, but also from many other causes, including disease and the failure to regenerate, that can whittle away at populations. At this time of rapid change in the world’s economies, political situations, fuel sources, climate, and above all, human population, effective conservation of its resources and biodiversity is more than ever essential – yet these are under more pressure than ever before. HRH The Prince of Wales has spoken of the ‘insane biocide’ currently taking place on this planet. Gardeners may not be able to prevent this, but we have a capacity to mitigate it in some small way through the application of conservation principles in our collections. The cause of plant and habitat conservation is championed by many governmental and non-governmental organisations and agencies, including the collaborative Botanic Gardens Conservation International (BGCI). The BGCI website (www.bgci.org) is a very useful starting point for information relating to plant conservation, both in the wild and in horticulture.

Plate 29. The fate of many forests: clearance for timber and subsistence agriculture. Quercus lamellosa is the dominant tree in this case. Image E. Jablonski.

IUCN Red List Categories Under the heading ‘Conservation’, the description for each species in New Trees gives the current assessment of its conservation status by the World Conservation Union (IUCN), as recorded in the online IUCN Red List 2008 – a very important component of each entry. The current IUCN categories are defined in Table 4 (overleaf), but full details of the criteria used in the assessment of a taxon should be sought in the printed and online publications of IUCN Red List Categories and Criteria, Version 3.1 (IUCN 2001). Gardeners should take it upon themselves to be aware of the conservation status of all the plants they grow, and take particular care of those that are threatened. The coverage of the Red List is patchy, reflecting individual areas of expertise and effort, and many tree families or genera have so far received almost no attention. However, the IUCN/SSC Conifer Specialist Group, led by Aljos Farjon of Kew, has assessed the conservation status of the vast majority of conifer taxa, while the IUCN/ SSC Global Tree Specialist Group, under the auspices of the Global Trees Campaign, has recently undertaken surveys of Magnolia (Cicuzza et al. 2007), Quercus (Oldfield

Plate 30. Regeneration is always a problem where grazing pressure is heavy. This is Cedrus libani subsp. stenocoma in southern Turkey. Image D. Luscombe.

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Table 4. IUCN Red List categories, and numbers of New Trees species in each

New Trees

& Eastwood 2007) and Acer (Gibbs and Oldfield, in press; when available, this will supersede the somewhat scanty conservaRed List category Definition In NT tion notes for Acer presented here). RhodoExtinct No living specimens known to survive anywhere. 0 dendron is currently under review (BGCI Extinct in Wild Survives only in cultivation, in captivity, or as a 0 2007–2008). Regional assessments have naturalised population outside its natural range. also been undertaken by the Group, and Critically Facing an extremely high risk of extinction in the 18 can be downloaded from the Global Trees Endangered wild, based on various assessment criteria (see IUCN 2001). Considered threatened. Campaign website (www.globaltrees.org). Occasionally there are differences of Endangered Facing a very high risk of extinction in the wild, 32 based on various assessment criteria opinion between categories assigned in the (IUCN 2001). Considered threatened. IUCN Red List and assessments published Vulnerable Facing a high risk of extinction in the wild, based 47 elsewhere. These are mostly due to time lags on various assessment criteria (IUCN 2001). involved in getting botanical assessments Considered threatened. onto the Red List. Several instances of this Near Threatened Has been evaluated against the assessment criteria 7 and does not currently qualify for any of the are to be found among species covered in threatened categories, but is believed to be likely the publication Threatened Plants of Cento qualify for threatened status in the near future. tral and South Chile (Gardner et al. 2006). Least Concern Has been evaluated against the assessment criteria 117 The specialist authors of this work regard (or ‘Lower Risk’) and does not currently qualify for any of the threatened categories, or as Near Threatened. Legrandia concinna as ‘critically endanThese taxa are mostly widespread and abundant. gered’, for example, but it has not yet been The preceding version of the Red List (1994) used ‘Lower Risk’ for this category. Most assessments evaluated by the IUCN. Some countries, of trees were made under its categories and have including China, operate their own systems not been updated in the current Red List (2008) for assessing conservation status, again Data Deficient Inadequate information available to evaluate this 6 resulting in some divergences of view. In taxon using the assessment crieria: more data required. This assessment is often an indication such cases we give both opinions. IUCN that its status is giving some cause for concern. assessments usually cover the taxon over its Not Evaluated No IUCN Red List evaluation has yet been made. 547 entire range, but in national conservation assessments smaller populations may be assigned a separate category. Definitions abbreviated from IUCN (2001). Number of New Trees species in each category, according to IUCN Red List 2008. Taxonomic change can affect the conservation category of a taxon. For example, the birch often called Betula uber was assessed by the IUCN as being ‘Critically Endangered’ as a species, but as it has now been shown to be no more than a variety, Plate 31. Prumnopitys occurring occasionally in a population of the typical Betula lenta, such an assessment, ferruginea has been placed together with the associated conservation obligations, seems less necessary. in the category Least ConIt is interesting to consider the proportions of New Trees species in each catcern (IUCN), as it is relatively egory. Self-evidently, there are no ‘Extinct’ species in cultivation, and no recently abundant in the wild in New introduced hardy trees are in the category ‘Extinct in Wild’. An obvious example Zealand. Image A. Farjon. of a tree that is extinct in the wild is Franklinia alatamaha Marshall, which has been maintained in cultivation since shortly after its discovery in 1765, though extirpated as a wild species in 1803. The international community of botanic gardens is currently working with several species of trees to reintroduce them to their original habitats. Two island taxa, for example, are each being propagated as descendants of single individuals – Sophora toromiro Skottsb. from Easter Island, and Trochetiopsis erythroxylon (Forst. f.) Marais from Saint Helena (Marinelli 2004).

Section I. Introduction

Chapter 2. Conservation

Similarly, in mainland China, efforts are underway to conserve some of the threatened Magnolia species (Cicuzza et al. 2007). Such attempts are last-ditch and can be expensive, but unfortunately may well become necessary more frequently in future. Nearly 100 of the taxa described in New Trees (12.5% of the total) are in one of the three categories that mark a plant as threatened. The assessments ‘Vulnerable’, ‘Endangered’ and ‘Critically Endangered’ indicate to the international community that special measures are needed to protect these taxa. Many countries have statutory requirements to undertake national conservation action for threatened species, though these may or may not be triggered effectively. In horticulture, particular attention must be given to such plants, as cultivated material may be the key to their survival in the future, in the way that it has been for Franklinia. ‘Not Evaluated’ is both the largest and the most worrying category, and its inhabitants should not be assumed to be of no conservation concern. Many of the species it shelters are abundant and unlikely to become threatened, but it throws a treacherous veil of obscurity over many others whose situation may be far from secure. Once a taxon has been classified into a threatened category it can be monitored and steps taken to conserve it and its habitats, but a taxon that is ‘Not Evaluated’ may be invisible to the eyes of the international conservation community. Within the Magnoliaceae – a family of 245 taxa – Cicuzza et al. (2007) assessed 112 as being threatened (31 of these ‘Critically Endangered’), and another nine as ‘Near Threatened’; only 20 could be considered to be of ‘Least Concern’. Ninety-four taxa, however, were not evaluated at all, leaving their status entirely in doubt, although proportionally it must be expected that at least some are threatened in the wild.

Conservation Legislation International conservation measures are enshrined in two important conventions, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on Biological Diversity (CBD), discussed below. Individual countries also have their own national legislation on conservation issues, establishing protected areas, regulating the use of their biological resources and providing penalties for infringements. Travellers and collectors should be take care to be aware of and respect these laws. The Convention on International Trade in Endangered Species regulates commerce and transactions involving species (sometimes defined by populations) deemed by the international community to be at risk, so included on one of its appendices (see the CITES website: www.cites.org). Those on Appendix I are the most threatened and at risk from exploitation, and include, for example, big cats, great apes, elephants, parrots, sharks, and plants such as some orchids and cacti, populations of which are often at risk from overexploitation for the

19

Plate 32. Abies nebrodensis is Critically Endangered in the wild in Sicily (IUCN), but regeneration is being encouraged by fencing out livestock. Image D. Luscombe.

Plate 33. A team of botanists from Chile and Edinburgh collect seeds of Beilschmiedia miersii in Chile. Such collaboration and resource sharing is implicit in the Convention on Biological Diversity. Image M. Gardner.

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Plate 34. Wollemia nobilis being propagated for sale in Australia, prior to its worldwide commercial release. Sales revenue from these plants directly aids conservation of the species. Image T. Kirkham.

New Trees

horticultural trade. A few timber trees are listed on Appendix I, including the temperate species Abies guatemalensis (see p. 53), Araucaria araucana, Fitzroya cupressoides, Pilgerodendron uviferum and Podocarpus parlatorei. Trade in wild-origin specimens of species listed on Appendix I is permitted only in exceptional circumstances, but trade in artificially propagated individuals is permitted under licence. Appendix II species are not necessarily endangered but could be put at risk by overexploitation if trade in them were not controlled. Trade is permitted, under licences issued by the CITES management authority for each country, but is sometimes subject to a quota system. Species listed on Appendix II may be ornamentals, or may be used for medicinal purposes and subject to overharvesting, as in the case of the temperate trees included: Prunus africana (see p. 659) and Asian species of Taxus (with certain exemptions for artificially propagated T. cuspidata) (see p. 839). Appendix III covers species with local conservation concerns for which CITES-controlled trade would be beneficial. In signatory countries there are stiff penalties for the contravention of CITES by traffic in listed species. As an international trade regulator, however, CITES does not have any bearing on in-country conservation of species or their habitats. The Convention on Biological Diversity (CBD), also sometimes known as the Rio Treaty or the Biodiversity Convention, was signed by representatives of the majority of the world’s countries following the UNEP-organised Earth Summit in Rio de Janeiro in June 1992, and came into force on 29 December 1993 (see the CBD website for full information on the treaty text and the secretariat that oversees its implementation: www.cbd.int). The CBD is a milestone in the international effort to conserve the biodiversity of the planet equitably and sustainably, and has been effective in the initiation and support of conservation activity worldwide, as signatories are required to develop national strategies and action plans to conserve, protect and enhance biological diversity within their territories. One of the most significant features of the CBD is its assertion that all nations have sovereign rights over their own biological resources, but are also responsible for their conservation and sustainable use. Article 15 of the Convention states that national governments are entitled to determine who may have access to the biological diversity of their countries, and that any such access must be with ‘Informed Prior Consent’, on mutually agreed terms that promote the fair and equitable sharing of benefits. The implications of this so-called ‘grand bargain’ for botanic gardens (and in fact horticulture and botanical science in general) are detailed in an important document produced by the Royal Botanic Gardens, Kew entitled The CBD for Botanists: An Introduction to the Convention on Biological Diversity for People Working with Botanical Collections

Section I. Introduction

Chapter 2. Conservation

(Williams et al. 2006), which is available as a presentation to download from the Kew website. The publication A CBD Manual for Botanic Gardens (Davis 2008) is available from BGCI on request or can be downloaded from their website. These documents stress the necessity for obtaining full and correct permissions before undertaking any collecting work, and the obligation to stick to the terms under which material is collected (especially in regard to further distribution), and discuss the ways in which benefits resulting from such collected materials (and associated intellectual property) can be shared with the source country. They are important reading for anyone involved with the collection and distribution of wild-origin material – although the rigour with which their recommendations are adhered to varies widely between source countries and institutions. The use of biological resources obtained before 1993, often known as ‘pre-CBD material’, is not covered by the Convention, but some institutions have adopted a policy of treating such accessions as if they dated from after 1993. Most countries have accepted the principles of the CBD in relation to their own conservation activities and control of their own biological resources, but hold no brief to monitor the use of such material on behalf of other parties. The result is that, unlike with CITES, there are no penalties for the ownership of material imported without the agreement of national authorities under the terms of Article 15 (although the importer could be in contravention of national legislation on the importation of seeds or plants). There are very few gardens where such material is not being grown. Observance of the ethics of the CBD implies that gardeners should attempt to return a benefit to the source country for their use of such material. The Convention does not define the term ‘benefits’, and individuals or institutions may choose to make return in various ways – whether in the form of royalties, where material is commercially exploited, or through support of research or conservation efforts in the source country, or perhaps by charitable donations to assist local facilities such as schools or hospitals. Very few ornamental plants derived directly from wild-collected material have any individual long-term commercial significance, but altogether the trade in horticultural plants is vast, estimated at up to approximately twenty billion US dollars each year (Williams et al. 2006). Almost nothing of this is at present returned to source countries. In a persuasive article, the Canadian horticulturist Dave Demers (2007) has argued the case for the application of ‘fair trade’ principles to all horticultural plants, through the imposition of a small surcharge on their price when they are sold by collaborating, certified nurseries. A controlling organisation would be required, but the returns could be potentially very substantial, enabling horticulturists to support the conservation of wild habitat and wild plants in a way that would acknowledge the debt they owe to the source countries for the pleasure they gain from their hobby. This is a concept that should be very carefully considered by the horticultural community. The United States is a signatory to the CBD, but has not ratified the Treaty, preventing its full implementation. Most American botanic gardens have nevertheless adopted its principles for their acquisitions and collecting policies. In an interesting development, a 2008 amendment to the United States’ Lacey Act (originally dating from 1900, when it was passed to prevent trafficking in illegally taken animal products) has become the first legislation worldwide to regulate trade in illegally acquired plant products, from within the United States or from another country – illegality of harvest being defined by the laws of the countries or states concerned. The aim of the legislation was to control trade in illegal timber and its derivative products, but the wording is ‘plants

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Plate 35. Amentotaxus formosana, assessed as Critically Endangered (IUCN), is maintained in cultivation in a few collections. This photograph was taken at the Royal Botanic Garden Edinburgh. Image R. Unwin.

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New Trees

Plate 36. Araucaria angustifolia in southern Brazil, where it is Critically Endangered (IUCN) due to logging and forest clearance for agriculture. Image A. Farjon.

and plant products’ and it may therefore have application to at least some horticultural material. The burden of proof that products have been legally acquired has been shifted to the importer, who must declare the country of origin and specific name of all species contributing to all elements of a shipment, including products such as paper, and furniture containing wooden parts. How the amendment relates to horticultural material is unclear, however, as live trees and other plants ‘intended for replanting’ are apparently excluded (unless on a CITES Appendix or covered by the United States’ own Endangered Species Act) (EIA 2008, USDA-APHIS 2008). The 2008 amendment is seen by environmental organisations as a great advance in the fight against illegal logging, and superior to voluntary codes of practice in place in the European Union, for example, but how it can be effectively policed remains to be seen.

Conservation in Cultivation One of the principal justifications for their activity advanced by botanic gardens (as it is by their zoological equivalents) is their role as reservoirs of genetic material in case of disaster overtaking wild populations. For the many tree species reduced to a handful of individuals in the wild, this insurance policy is essential to prevent extinction and allow restoration of wild populations. The ‘conservation in cultivation’ concept has flaws as well as plus points, however. The most serious objection is that it is, at the least, very difficult to preserve a fully representational sample of the gene pool in a cultivated or captive population. There can be no doubt that the best method of conserving a species is to maintain its wild habitat in as natural a state as possible, whatever that may be. Having introduced a species to cultivation, however, there is a clear responsibility to ensure that it is protected there in as viable a population as possible. Maintaining the maximum gene pool of authentic wild-origin material is extremely important.

Section I. Introduction

Chapter 2. Conservation

Second- and later-generation plants, raised from seed in cultivation, always carry the risk of being hybrids (see below). Genetic drift also occurs with each narrowing of the gene pool: in their day-to-day actions as they grow their plants, gardeners are unconsciously responsible for a great deal of selection for favourable characters, and this drift continues in successive generations. Maximum information should also remain associated with the plants. Specimens of known wild origin with accurate records have much greater scientific and conservation value than individuals of the same taxon without this information attached. Detailed locality records and field notes should always be made, and when possible the original collection should be backed up with a herbarium specimen. Every collection of wild material represents a small sample of genetic material referable to a wild population, and the more detailed the associated information is, the more useful the material could potentially be. It could be used in scientific research into the relationships of plants, providing, for example, a sample of DNA without the need to mount a special expedition to obtain it, or for conservation schemes, whether programmes of reintroduction or controlled reproduction in cultivation – with the confidence that it represents a true (if sometimes limited) record of the species’ variation in the wild. Horticulturists, both professional and amateur, have not always been very good at this. An exceptionally interesting analysis of the success (or otherwise) of the material introduced by the Sino-American Botanical Expedition (SABE) of 1980 has been published by Michael Dosmann and Peter Del Tredici of the Arnold Arboretum (Dosmann & Del Tredici 2003), and should be required reading for all involved in dealing with collections of wild-origin material. The SABE expedition was important as the first collecting trip to China by western botanists since 1949. In addition to herbarium specimens, 689 collections of seed or vegetative propagules were made, from 462 taxa, during the expedition and afterwards by individual team members. Among the trees introduced by SABE to western gardens were Aria yuana, Liquidambar acalycina, Magnolia zenii and Pittosporum brevicalyx ‘Golden Temple’, whose stories are recorded here in New Trees. Seed was distributed principally to four American institutions, but material was also given to other gardens and collections in North America and Europe. Later, in 2001, Dosmann and Del Tredici began a survey of results from the expedition, noting that although most collections are well documented at the time they are made, there are very few follow-up reports for ornamental plant introductions. Their results showed that of the 689 collections made, 279 (40.5%) were still in cultivation in gardens in North America and Europe, but 130 of these (46.6%) were represented only by a single accession, and often by a single plant. After adjustments to allow for material that was questionably viable at the time of introduction, Dosmann & Del Tredici were led to the conclusion that only about 60 per cent of the potentially extant taxa were still in cultivation. Unfortunately there are no corresponding figures from other similar expeditions against which to compare these survival rates. Wide distribution of collected seed, and secondary distribution of germinated seedlings, are extremely important because as all practical gardeners know, and Dosmann and Del Tredici

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Plate 37. Quercus pseudosemecarpifolia SICH 2254. With wild-origin material, retaining the collection number with the plant is essential to preserving its scientific and conservation value. Image T. Kirkham.

Plate 38. Successfully introduced in 1980, Tetradium ruticarpum SABE 1947 (seen here at Kew) has since become quite widely planted. Image T. Kirkham.

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Plate 39. A young Pyrenaria spectabilis. Collections from which only a few seedlings germinate need particular care and attention, to ensure their survival in cultivation. Image J. Grimshaw.

New Trees

enunciated, ‘differential survival may result from cultural practices in the greenhouse, environmental conditions in the outdoor nursery, or just plain luck’. SABE seed was mainly shared between four botanic gardens in the United States (the University of California Botanical Garden, the US National Arboretum, the Arnold Arboretum, and the New York Botanical Garden/Cary Arboretum), but excess seed from 240 collections was also distributed to other institutions and individuals. Following germination, and retention of material for their own collections, the Arnold Arboretum and the US National Arboretum undertook controlled distribution of surplus seedlings to other institutions. Less organised was a mass dispersal of material (principally grown at the Cary Arboretum) during a free-for-all at the annual meeting of the American Association of Botanical Gardens and Arboreta in 1982. While this had the effect of finding homes for quantities of plants, many were taken away without their collection number, or any other supporting data. Much detective work was needed on the part of Dosmann and Del Tredici to untangle the traces of where material had gone, underlining the need for accurate records of where plants have been distributed to, as well as where they came from. This is particularly important in cases where material transfer agreements are in place through arrangements with source countries, but it is critical that records are maintained even for specimens that have slipped the CBD net. It may prove to be essential for reintroduction schemes in the future! A plant that goes undocumented has immediately lost much of its scientific and conservation value. Another of the findings of the SABE study was that survival rates were generally poorest when the number of seeds that germinated from the original batch was low. Where few seeds germinate there are fewer plants to distribute, and the chances of failure under a single set of conditions is greater. As the study showed, the process of introduction can be a delicate one. It is probable that the figure of 60 per cent survival after 22 years is rather high, and attributable to the wide distribution of many collections either as seed or as young plants. What is particularly worrying, however, is the high proportion of surviving collections represented by a single plant. In the absence of in-depth study such as that undertaken by Dosmann and Del Tredici it is not easy for institutions or private gardeners to detect rarities in their collections, though the growing use of the botanic garden records system BG-BASE is making the process somewhat easier. Conservation in cultivation is not confined to species that are threatened in the wild. Plants can be rare in gardens too, and in need of management to ensure their persistence in horticulture, especially as it is no longer possible to assume that new stock can be freely introduced from the wild. This applies not only to recent introductions but to earlier ones, equally or in even greater degree. The case of Picea farreri, which survives in cultivation as propagations from the solitary original tree, is an important example of rescue work, and the fact that Hugh McAllister was able to describe several new Sorbus microspecies from survivors of collections made by George Forrest is another demonstration of the importance of maintaining trees of known wild origin. The conservation status of a plant in the wild is easily checked by reference to the IUCN Red List, and a policy of care can be adopted accordingly, but there is nothing comparable for plants once they are in cultivation. In some countries there are systems similar to the National Plant Collections scheme organised in the United Kingdom

Section I. Introduction

Chapter 2. Conservation

by Plant Heritage (formerly the National Council for the Conservation of Plants and Gardens, NCCPG), whereby enthusiastic individuals bring together a collection of all possible representatives of their chosen group. Such organisations have done great work in gathering together information and material, but many taxa are still outside the system – and single collections are not necessarily the answer. An example of effective gathering of data on a cultivated species across many locations is the Franklinia census, conducted by Bartram’s Garden in Pennsylvania, which has revealed the whereabouts of more than 2000 individuals of this species (Bartram’s Garden 2004). More such registers could usefully be maintained, especially by specialist societies or the holders of National Plant Collections, for species that are rare either in the wild or in cultivation, much as zoological institutions maintain stud books for their taxa of particular conservation importance. An obvious starting point would be the 18 IUCN Critically Endangered taxa described in this book, including Cupressus dupreziana var. dupreziana, Magnolia grandis and Ulmus gaussenii. For these rare taxa, which are only ever likely to feature in specialist collections, such an approach is feasible. It would probably not be worthwhile in the case of the also Critically Endangered but mass-propagated Wollemia nobilis (although a register of the locations of specimens known to have been clonally propagated from wild trees would be very useful). In many cases a realistic evaluation of the gene pool in cultivation is required. For example, it is probable that all material of Magnolia grandis in cultivation is derived from a single importation, and that most individuals have been propagated from one clone of this: not a good situation for a species swimming in the shallow end of the gene pool, both in the wild and in horticulture. The normal nursery practice of propagating from a single stock specimen is a serious problem in terms of the maintenance of genetic diversity in cultivated plants. From a commercial viewpoint it is understandable, but it would be useful if the clone in question could at least be made recognisable by the application of a cultivar name. The rare Chinese Parrotia subaequalis, for example, has entered cultivation by various routes and is being distributed privately and commercially. At present there are perhaps five clones of it in cultivation, and these certainly ought to be identified in some formal way, to enable conservation groves of the species to be established and avoid the mass planting of a limited number of clones. The stamp-collecting mentality – that one representative of a taxon in a collection is sufficient – is a too-frequent obstacle to effective conservation in cultivation. A self-satisfied ‘we’ve got that’ is not good enough when it comes to rare species or material of wild

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Plate 40. Sorbus coxii was described in 2005 from trees grown from seeds collected by George Forrest in 1910. Image P. Williams.

Plate 41. Tilia endochrysea was introduced from Guangdong by D. & S. Pigott in 1993 – but only one clone survived. Image J. Grimshaw

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New Trees

origin. Those who introduce wild-origin material should try to ensure that somewhere a small group of specimens of each accession are planted together, to supply diverse propagation material for the future or for study. In this regard the groups of Betula and Alnus trees planted by Kenneth Ashburner at Stone Lane Gardens in Devon, as part of his National Plant Collections of these genera, are an excellent example to follow. Space can, of course, be an issue, but such conservation groves do not necessarily need to be planted so as to provide perfect specimens for the future, and could be placed along boundaries or in other places relatively out of the way. Several of the tree growers mentioned in these pages have successfully persuaded local authorities to allow them to plant specimens in local parks, and this may be another option for the space-restricted enthusiast to pursue.

Plate 42. Planting in groups of specimens from the same provenance is the ideal way to develop a scientifically useful collection, but it rarely happens. The plantings at Stone Lane Gardens are a model. Shown here, a group of Alnus sieboldiana originating from Honshu in 1980. Image Stone Lane Gardens.

Section I. Introduction

Chapter 2. Conservation

27

An insidious threat to the maintenance of taxa in cultivation is the risk of hybridisation. Species in many tree genera are freely interfertile, and in arboretum conditions the risk of their crossing with another species may be optimised. Where hybridity is known to be an issue, progeny from cultivated trees should be viewed with circumspection, and seed should not be distributed without a strong warning attached. In many cases vegetative propagation will be necessary, to maintain the true species.

Invasive aliens Many species of plant, including trees, introduced to different parts of the world for ornamental purposes, have become invasive pests, causing serious damage to natural ecosystems. Invasives are usually only a tiny fraction of the diversity of alien species introduced to any given country but their impact can be devastating, as documented in a vast array of books, articles and websites. The species involved vary from region to region, as do their effects, and an Australian Table 5. Conservation guidelines for dendrologists Acacia that could be invasive in South Africa may currently be a hard-to-grow rarity in the British Isles. The onus is on those who • When collecting wild material, observe the laws of the country concerned. introduce and grow new ornamental plants to ensure that they do not ‘take off’ and become invasive. If they do, or show signs of so • Adhere to any material transfer agreements that have been made with the source country. doing, growers must take all steps possible to remove the plant and caution others to do likewise. It is also worth recalling that, • Ensure that all importations comply with phytosanitary and import regulations. with climate change, regeneration niches may become available to plants in areas formerly inhospitable to them, so established • Support conservation organisations or development agencies that encourage sustainable use of natural species should be monitored as well. resources, thus returning a benefit to source countries Some countries and regions have lists of proscribed invasive for their biological resources that you enjoy at home. The Global Trees Campaign – a joint initiative of BGCI plants, that may not be imported, or grown or sold within their and Fauna & Flora International – may be of interest. boundaries, and where such regulations are in force they must be followed. Regulations of this kind are likely to become more • Treat wild-origin material with great respect. It may be of conservation and scientific value in future. widespread in future. In the United States, for example, the Animal • Maintain detailed records of the source of material and Plant Health Inspection Service (APHIS) is currently preparing grown, and of specimens passed on to other gardens. a regulation proposing a new category of imported plants: ‘Not • Label each individual carefully and permanently with Authorized Pending Pest Risk Assessment’ (NAPPRA). Once added its collection number and accession details. as a Proposed Rule on the Federal Register this regulation will be • Distribute material as widely as possible, passing on subject to comment and modifications, but its first application is collection details with the plants. Take particular care with collections from which few seeds germinate. likely to be in the establishment of a list of plants that are weedy elsewhere in the world and are deemed to have great potential • Plant wild-origin material in groups whenever possible. to become noxious weeds in the United States. Further down the • Avoid propagation of single clones. If it is unavoidable, attach an identifying name or collection number. line, APHIS plans to require a ‘pest risk assessment’ (PRA), before importation, for any plants that are not already present (Lehtonen • Repropagate older specimens vegetatively, or by seed if hybridisation is not a problem. & Tschanz 2008; J. Fingerut, pers. comm. 2008), and protocols for screening plants for potential invasiveness before importation • Avoid distributing potentially hybrid seed or seedlings from arboreta under the name of a wild species. are already in place (NAPPO 2008). The prospect of a register of this kind – a so-called ‘white list’ – has been mooted for several • Identify plants of particular conservation significance, both by use of the IUCN Red List and in terms of their years, and has aroused much resentment in the American horticulabundance in horticulture. Treat them accordingly. tural community (see, for example, the website of the No White • Observe your plants (including established species) List Coalition: 2006). for indications that they might be invasive. Take steps As part of their follow-up of collections made by SABE in 1980, to remove such species and prevent their wider spread. Dosmann and Del Tredici (2003) examined the data for evidence

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New Trees

of potential for weediness in these plants. In line with the generally accepted view that only a very small proportion of exotic plants ever become weedy, none of the SABE collections was found to have given any cause for concern, and the authors commented wryly that ‘the larger problem for many botanical institutions seems to be keeping the plants alive rather than preventing them from escaping’. They argue that there is a continuing need for plants to be introduced for research purposes, and that botanic gardens are ideally placed to evaluate potential weediness, through their capacity for long-term monitoring of species within a relatively confined area.

A

1 cm

1 cm

Figure 3. Styrax formosanus: single flower (A); habit with flowers (B); infructescence (C); calyx and persistent style after the corolla has fallen (D).

B

1 cm

C 1 cm

D

Chapter 3. Cultivation Planting a tree is an investment for the future, and it makes sense to maximise the chances of long-term success – measured by healthy growth, permanence and stability. Most gardeners have tried and tested methods of tree growing and planting that work for them. In recent years, however, there have been some important developments in techniques, notably in methods to encourage healthy root growth and establishment, focusing attention on this critical but usually invisible aspect of a tree’s life. Some notes on these and other aspects of tree cultivation are offered here. A very useful review has been produced by Mark Flanagan and Tony Kirkham (1995), based on their experiences at Wakehurst Place and Kew. More recently, Tony Kirkham (2006) has developed a protocol for successful tree planting, which we reproduce here with his permission (Table 6, overleaf). Some of the points made are amplified in the notes below.

Nursery Techniques Propagation The principles of tree propagation by seed and by vegetative techniques are covered in many sources, and these subjects will not be discussed further here. Most gardeners have trusted techniques for propagation, especially from seed, that they find effective. There are indications, however, that climate change may force a rethink for species needing cold winter stratification. In his work on Sorbus, for example, Hugh McAllister has found that the average British winter is now insufficiently cold to provide the chilling required for the germination of many Sorbus taxa that have traditionally been sown in pots and exposed to outside ambient temperatures. In consequence he now prefers to sow on filter paper in petri dishes kept in a refrigerator, from which germinating seedlings can be removed and potted up (McAllister 2005a). The adoption of such techniques may be useful in other genera where a prolonged winter chill period is required.

Container-growing The horticultural trade standard, at least for retail sales, is to supply containerised trees that can (supposedly) be planted at any time of year, and the majority of amateur gardeners also grow their specimens in pots until planting. Usually, the container used is a classically shaped plant pot made of rigid black plastic. Research and practice is showing clearly, however, that such pots are far from ideal, as they encourage the spiralling of roots at their base, from which it can be very difficult for a stable root system to develop when the specimen is planted out. The ‘old-fashioned’ technique of growing plants in an open-ground nursery has many advantages for producing a

Plate 43. A tray of Juniperus procera seedlings germinating well. Image J. Grimshaw.

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New Trees

Table 6. Tony Kirkham’s guide to successful tree planting

1. Grow or obtain plants with healthy, unspiralled root systems, either from open-ground nursery beds or grown in modern, air-pruning pots. 2. Protect nursery stock between lifting and planting, to avoid damage to the roots and root hairs from sun, wind or frost. 3. Prepare a shallow, wide planting pit, to enable the roots to spread freely into the adjacent soil. Square pits seem to be best, and avoid the risk of root circling. 4. Do not add soil ameliorants or fertilisers to the backfill. 5. Apply mycorrhizae to tree roots at planting. This greatly increases the chance and rate of successful establishment. 6. Planting depth is critical. Do not plant too deeply. 7. Staking should be avoided. It can damage trees, and may slow the rate at which they establish and become stable. Plant young trees, that will not require staking, or use short stakes, with appropriate tree ties, and remove the stakes within 18 months. 8. Use suitable guards for protection against rodents and other pests. 9. Mulch the surface of the planting area, to reduce competition from weeds and the need for irrigation. 10. Irrigate during the early years of the tree’s life, to avoid dessication and stress.

Plate 44. Seedlings growing well from acorns distributed as Quercus liboensis (their identity will be confirmed as the trees grow up: see p. 695). Sowing large seeds in deep plug cells of this type is ideal – but keep the mice away! Image J. MacEwen.

good tree (see below), but the commercial imperative is for containerisation. Fortunately there are a number of useful innovations that are beginning to be more widely adopted. It is to be hoped that this will put an end to the prevalent root abuse that renders it a waste of time, currently, planting most containerised trees. The use of pots is unavoidable while seedlings are small, but diligence is required to ensure that their roots remain unconstrained and, above all, unspiralled by confinement. An excellent development for the sowing of large seeds is the availability of trays of long narrow plug cells with ribbed sides into which single seeds can be inserted, and which allow the tap root to grow straight down, until it is ‘air pruned’ (see below) on reaching the aperture at the base. In the United Kingdom a particularly successful system is offered under the name Rootrainers®, in which the rows of cells can be opened neatly like a book, allowing undamaged root systems to be removed (for more information see the website www. rootrainers.co.uk). The problem of spiralled roots at the base of pots has also spurred development of a number of revolutionary container designs, for which their manufacturers claim great benefits – and the fact that some are increasingly being taken up by commercial growers and botanic gardens suggests that such claims are justified. The principle on which they work is again that of ‘air pruning’: that when roots reach freely circulating air, or are exposed to light, they die back at their tips and tend to make a mass of fibrous roots rather than relatively few major

Section I. Introduction

Chapter 3. Cultivation

branches, that in a conventional pot would quickly delve to the bottom and spiral round into a knot. The leading system is exemplified by the product range known as Air-Pots™, developed and patented by Australian horticulturist Jamie Single, and now in use worldwide (see the website www. superoots.com). The containers are formed by the folding of a sheet of plastic into a cylinder around a perforated base, clamped into shape with simple screws. The plastic is moulded into a dense pattern of cones, some of which point inwards, others outwards – the effect somewhat reminiscent of the projections and hollows of an egg-box. The outward-pointing cones have a circular aperture at their apex. The result is that a growing root never meets a smooth straight surface that would encourage it to grow downwards and spiral, but instead is guided into one of the outward-projecting cones. Here it eventually reaches the open air and dies back, stimulating the development of more root fibres behind the tip. The result is a remarkably dense and vigorous mass of roots, with neither tap root nor spirals to cause problems at planting or later. The container is easily released from the rootball by undoing the screws that hold it together. An alternative system, patented by Europe’s largest growers of containerised trees, Barcham Trees in Cambridgeshire, is known as the Barcham Light Pot ™ (see www. barcham.co.uk). Manufactured in various sizes, these white-coloured ‘pots’ are designed principally with the needs of growers and suppliers of commercial nursery stock in mind, and look rather like the large bags in which aggregates are delivered, even to the extent of having handles for ease of conveyance by fork-lift truck. The concept was developed from the discovery by Australian growers that roots of Eucalyptus growing in traditional black pots were being scorched. On the principle that white reflects heat and keeps things cooler, they began to use white pots. The change of colour reduced the scorch but some light penetrated, and the natural phototropic response to this caused the roots to grow straight down rather than spiralling and becoming tangled. Barcham Light Pots function by the same process, and are used for some 450 taxa of trees, successfully finished for sales on the nursery (having been potted as lifted, field-grown stock). The pot is usually removed on planting, although the upper half may be left on to act as a root barrier – in paved areas, for example. The pot also incorporates an integral permeable and degradable mulch mat, to reduce weed growth and irrigation requirements (Glover 2006; M. Glover, pers. comm. 2008). In both cases, growth in the container seems to be faster and sturdier, and production times are greatly reduced – a significant advantage to commercial growers. Most importantly, perhaps, the mass of fibrous roots is poised to grow quickly once the tree is planted, leading to extremely rapid establishment and great stability. Left in the pot for long enough the roots do eventually become tangled, of course, in both systems, and the benefit is lost. Barcham Trees have in place a system of ‘use-by’ dates, usually 18 to 24 months on from containerisation, after which surplus trees are discarded (M. Glover, pers. comm. 2008). It is to be hoped that such systems will be adopted rapidly by growers at all levels, and demanded by customers at nurseries. The slightly greater cost should be seen as an investment that will pay dividends in the form of vigorous stable root systems.

31

Plate 45. Air-Pots™ prevent roots spiralling to the bottom of the pot, and encourage a container-grown plant to establish quickly and stably. This is Tetradium ruticarpum, being planted at Colesbourne Park. Image J. Grimshaw.

32

New Trees

Open-ground production The traditional method of growing trees in the open ground prior to transplanting them remains an important alternative to containerisation. The aim is a fibrous rootball without circling or spiralled roots – achievable as long as the seedling was planted out before these developed in a pot. Although growing trees in the ground requires a certain amount of care and attention, particularly in the undercutting of the rootball to avoid the development of tap roots, they are not nearly so dependent on artificial irrigation as container-grown specimens, nor do they need to be kept stable as pots do. Transplanting from the nursery requires some forward planning, however, as the bare roots are prone to damage through desiccation or frost, so they should only be lifted once the planting site has been prepared, and must then be dealt with promptly. With broadleaved evergreens and conifers it can be advantageous to spray plants with an anti-desiccant before transplanting and for a short while afterwards, to minimise damage.

Planting Techniques Choice of site Plate 46. Many species from northeastern Asia and Siberia break bud too early in areas with mild winters, and are apt to be caught by late frosts. Abies sachalinensis var. mayriana is one such. Image J. Grimshaw.

Several factors are important in determining a planting site. Availability of space is one, and harmony with the garden’s planting scheme is another. These are particularly important in smaller gardens, where it may be possible to grow only a limited number of trees, and great care needs to be taken over their selection and placing. In the context of a larger arboretum or park the best possible site for a species should be chosen on the basis of what is known of its ecological requirements. It is extraordinary how much ecologically inappropriate planting one sees, with species that require full sun tucked away in shade, and shade-lovers baking in the open. Gardeners have much to learn about the ecological needs of their plants, especially their regeneration and establishment niches – though so too do ecologists. The tendency in botanic gardens to plant in areas with related species is unfortunate in several ways. It may prevent a tree being placed in really optimal conditions, and can also be conducive to the rapid spread of pests or diseases. Availability of space is often the deciding factor, but the characteristics of a site should inform the choice of the tree that will occupy it.

Preparation of the pit The aim of modern planting pits is to enable the roots to penetrate easily from the prepared ground into the surrounding soil, thereby encouraging long-term stability. The traditional method, of digging a nice big hole and filling it with goodies, tends to result in the construction of something very like a large plant pot filled with rich soil. In such holes the roots have no incentive to quest elsewhere and can form a tight, compacted or even girdled mass within its confines, rather than spreading out freely through the surrounding

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soil. Puddling of the sides is particularly to be avoided in clay-rich soil, as this is likely to exacerbate the effect of containerising the roots, and the pit may act as a sump. At Kew, wide, square and rather shallow pits are favoured, because on their sandy soil tree roots spread out rather than delve (Flanagan & Kirkham 1995), but elsewhere, and especially where the ground is stony, it might be worth digging somewhat deeper. The pit should be backfilled only with the excavated soil, and then left for a few weeks, to avoid excessive settling after the tree has been planted. Mound planting is an option sometimes advocated if the soil is poorly drained or compacted – only the lower portion of the rootball being buried below the existing ground level, and soil being brought up to normal planting level at the base of the stem to form a wide, shallow mound. From this position developing roots can access the upper levels of the soil and spread out naturally. In all cases care should be taken to ensure that trees are not planted too deep. Avoiding the addition of soil ameliorants or fertilisers goes very much against the grain of most gardeners’ thoughts and practice in tree planting, but seen in the context of the philosophy of this technique it makes sense not to do so, especially if mycorrhizal activity is to be encouraged.

Mycorrhizae Translated from its Latin and Greek origins, mycorrhizae literally means ‘fungus root’, and refers to the complex interaction that occurs between fungal strands and the roots of the majority of the world’s plants. In practice, however, the word is usually taken to refer only to the fungal partner in the interaction. Mycorrhizal associations are known to have functioned since the first land plants emerged, and their prevalence is clear evidence of their importance to both partners. The fungus benefits by access to carbohydrates produced by the plant’s photosynthesis, while the plant benefits from both inorganic and organic nutrients extracted and concentrated by the fungus, especially where these are scarce. It may also use the fungal network to extract water from the soil. Mycorrhizal associations have two principal forms: ‘endomycorrhizal’, where the fungus penetrates the root cells, and ‘ectomycorrhizal’, in which there is a close association between root and fungus but no penetration of the cell wall. Both forms are found in tree roots, but temperate trees are most likely to have ectomycorrhizal associations – often formed with such familiar fungi as Amanita muscaria, the poisonous red and white Fly Agaric, but potentially involving a huge diversity of fungus species.

Plate 47. A difficult tree to establish in cultivation, Arbutus xalapensis is almost certainly strongly dependent on mycorrhizae, like most other members of the Ericaceae. Image N. Macer.

34

Plate 48. Even trees from familiar genera benefit from mycorrhizal associations. Acer pseudosieboldianum subsp. takesimense in flower. Image P. de Spoelberch.

New Trees

The study of mycorrhizae and their effects is a vast and technical field, but a useful horticultural summary has been provided by Spence Gunn (2006), and the Australian mycologist Mark Brundrett hosts an informative and accessible ‘online textbook’ entitled Mycorrhizal Associations (Brundrett 2008). Mycorrhizal fungi are usually absent from frequently cultivated soil, and their absence can lead to poor performance of species that would normally benefit from such an association. In undisturbed soils or woodlands they are ubiquitous, and artificial inoculation would be superfluous. Increasingly, however, growers are coming to the view that inoculating a garden tree with mycorrhizal fungi prior to planting can be extremely beneficial. A number of preparations containing mycorrhizal inoculants are now available, for both commercial and amateur growers, and they are coming into wider use, proponents claiming increased root health and vigour for treated specimens, and thus better plant health generally. In fertile soils the additional benefit conveyed by mycorrhizae will be relatively little, but in poorer conditions they can be of great significance, and for gardeners avoiding the use of inorganic compounds they offer a useful method of encouraging good growth.

Staking The movement of air over a plant has a very important effect in encouraging it to grow steadily and stoutly: the technical term is ‘seismomorphogenesis’. Without the effects of movement the plant will grow spindly and be much less robust, as may be seen where tree saplings are grown under glass. It is possible to get a sapling to put on long extension growth that way, but the result will be a poor plant until it has had a chance to thicken up on exposure to freely moving air. Traditional heavy staking for trees reduces their movement in the wind and thereby the effects of seismomorphogenesis. A persistent problem in horticulture is that trees are generally planted when too large, as well as frequently coming out of inappropriate, root-restricting pots. Such top-heavy specimens require some sort of staking, and for this a short stake is recommended, securing the base of the stem, using a suitable tree tie – but after 18 months or so it should be removed. A bamboo cane lightly fastened to the stem may also be used to guide weak-stemmed specimens for a season or two. Much better, however, is to avoid the need for staking altogether by planting trees young and with a good rootball. If planted young, support will not be necessary, establishment will be faster and the resulting root system more stable, and growth will soon catch up.

Aftercare Following planting the tree should be surrounded with a mulched area to reduce weed growth and the need for excessive irrigation. It is important that young trees are supplied with sufficient water during their first few years, to get them established without stress, and the time and effort that this takes should not be overlooked when grand planting schemes are being conceived. Water is most usefully applied directly to the roots, and it is helpful to insert a flexible pipe in the vicinity of the rootball

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at planting time, down which it can easily be poured. Installing these pipes also increases gaseous exchange, which is beneficial to successful tree establishment. The use of water-holding polymers, mixed with the backfill before planting, can be an effective way of reducing the interval between waterings, especially on droughty sites (Flanagan & Kirkham 1995). Young trees need protection against a range of pests, from mice and rabbits to deer and tractor drivers, and appropriate guards should be employed. Deer fencing is becoming almost essential across much of North America and Europe, where deer populations are increasing very rapidly, often in the shelter of suburbia. Not only do the animals cause damage by browsing, but the habit of thrashing their antlers clear of velvet can be devastating to young saplings. Several North American arboreta have taken to placing a ring of rigid stakes around young trees (see Plate 405, p. 603), to prevent a buck’s head from coming into contact with the branches or trunk. For many growers, however, the Grey Squirrel is the biggest threat to tree growth, stripping bark in spring as the sap rises and frequently killing or deforming the crown. It is impossible to use barrier methods of protection against squirrels, and the only remedy is a vigorous culling campaign.

Tender species The complex issue of hardiness has been discussed elsewhere (see p. 5). Mitigation of the effects of winter cold can often be achieved by selecting a favourable site with shelter and good drainage, and summer heat can be maximised in similar ways if this is a necessary factor for success (as it very often is). Shade should not be mistaken for shelter, however. Where a tree is suspected of being tender there is a very good case to be made for growing it in a pot under glass until it has reached a reasonable size and formed a framework of hard wood. Such a plant may be able to withstand frost better than a younger seedling. The danger of root girdling in the pot is high though, and there is little doubt that seedlings of rapidly growing taxa such as Acacia and Eucalyptus are best planted as young as possible to avoid this problem.

Planting time This is a contentious subject, many having firm opinions on one season over another. Much depends on local circumstances of soil condition and climate, not to mention how the normal garden work schedule is planned. Most planting is done between late autumn and early spring, and bare-rooted deciduous species tend to be planted earlier than conifers or broadleaved evergreens. Root activity is usually at its greatest, however, when the soil is both warm and moist, as may be seen by inspecting the roots of potted specimens. Bud break in deciduous species is often well in advance of any development of new roots. My personal preference (JMG) is to plant vigorously growing young specimens from containers in May, June or even July, when both top growth and roots are active – but this is only feasible where there is a guaranteed supply of water, as, for example, in a closely worked and

Plate 49. Quercus insignis from Central America is too tender for cultivation outside in northern Europe. Here shoots are seen regenerating from a frost-killed main stem. Image P. de Spoelberch.

36

New Trees

observed domestic garden. Late planting in warm soil is certainly very advantageous for getting tender or warmth-loving species off to a good start, encouraging rapid penetration of the soil by the roots and establishment before the winter.

Pruning In recent years there have been many advances in the art and craft of pruning trees and shrubs, particularly in the understanding of where best to place the cut for rapid and healthy healing. An excellent guide to this often botched, but essential element of tree care can be found in George Brown’s classic work The Pruning of Trees, Shrubs and Conifers, revised by Tony Kirkham (Brown & Kirkham 2004). Gardeners, and garden policies, vary in the extent to which they aim to train young trees into desired shapes. For many a neat standard is the aspiration, for which careful formative pruning is usually necessary, in the nursery and while the tree is young. Others prefer to allow their trees to assume their natural shape, and minimise such early pruning. Much depends on the formality of the setting, and other uses of and constraints on the available garden space.

Labelling

* There are no mulberries in New Trees.

Plate 50. Stamped aluminium tags secured using plasticcoated wire, as at Kew, are a reliable form of labelling. Image J. Grimshaw.

During the research for New Trees the difficulties and deficiencies of arboretum labelling became very apparent, and there was much muttering of ‘here we go round the xxxxxxxx * bush’ during the hunt for labels that were obscure or, not infrequently, entirely absent. An unlabelled tree has lost most of its scientific and conservation value, not to mention any benefit to members of the public who may wish to find out what it is. Opinions differ greatly on types of labels to use, and the choice is often dictated mainly by the budget available. Whatever decision is made, it is essential that the lettering should deteriorate less rapidly than the label itself: a blank label, however firmly secured, is not much use. Engraved white on black labels are attractive and easy to read for the visitor to an arboretum, but all plastics eventually become brittle, and regular checking and replacement is needed. Embossed aluminium labels such as are used at Kew, containing all relevant information about the specimen and its accession, are excellent. At Hergest Croft, successive generations of the Banks family have used a system of notches clipped into the edge of metal labels and recorded on index cards for each tree, enabling identification even if the acid-etched lettering on the label were to become illegible. A more modern form of this approach is the bar code, which can be adopted for tree-labelling as for anything else, providing a unique identifier from which all collection data can be read using a hand-held scanner. For security, secondary labels on each tree are always a very good idea. Whatever type of label is used, it must be firmly attached to the tree, or to an adjacent stake if necessary. Nailing labels to older specimens is a traditional and practical option (though not suitable for Eucalyptus where the bark is regularly sloughed); otherwise they must be hung from an appropriate branch using plastic-coated wire. The tubular plastic filament sold in the United Kingdom as FlexiTie™ may also be a viable option, as it seems to have a very long life and will expand as stems grow, avoiding constriction.

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Finding the label, as mentioned above, can be a frustrating challenge. The best labelling seen during the course of our research was at the Morton Arboretum, where it is the policy to affix the label on the south side of each specimen, and where disciplined regular checks ensure that every one is in its place. Labels are principally useful for casual identification, and should be supported by a detailed map (and record system) covering all plantings, updated whenever necessary. With the general availability of GPS plotting technology and associated software such maps are not difficult to produce – but even a sketch map is better than nothing.

Cataloguing A detailed and consistently maintained catalogue of the collection is essential. As a minimum this should record the name of the tree, an accession number, the source of the tree, and its location in the arboretum. If it is of known wild origin this must also be stated, together with as much information on its provenance as possible, and the catalogue should also record its conservation category. Growing wild-origin material imposes a duty of care on the gardener which includes the responsibility to maintain it with information attached. Records should also be kept of where propagation material has been distributed to. The catalogue can record additional information of interest to the grower, such as percentage germination rates, the reasons for any failures, if known (at least one contains entries such as ‘knocked over by football’), and notes on heights of specimens at planting and at subsequent measurements. This can be a fun part of record-keeping. Records can be maintained in various ways, usually now electronically using simple database or spreadsheet programmes (remember to make a back-up copy!), or, for public gardens and research institutes, more complex database systems. Ideally, the catalogue for a public garden should be accessible online, and in this era there is no acceptable reason why it could not be. Information deemed to be sensitive, such as collecting locality, can be obscured and revealed only to bona fide researchers, but evidence of the existence of a plant and its location in the collection should be available to all.

Pests and Diseases Pests and diseases are a constant problem with all classes of garden plants, but in the case of trees their impact is particularly significant as they can have serious consequences for the landscape and the ecosystem – Dutch elm disease and sudden oak death being classic examples of this, joined recently by the devastating Emerald Ash Borer and disfiguring Horse Chestnut Leaf Miner, among many others. Neither is it easy to treat a tree or forest against pathogens or pests without the undesirable release of massive quantities of pesticides into the environment.

Plate 51. Growing a diverse collection of trees imposes a certain responsibility for labelling and record-keeping but this need not be a chore, especially when the progress of specimens is recorded. Image J. Grimshaw.

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New Trees

In the case of a serious and sudden outbreak of disease, affecting many plants, or the rapid advance of an insect pest – the unwelcome news, for example, that the Emerald Ash Borer is well established in the Moscow area, poised to devastate the ashes of Europe (Baranchikov et al. 2008), or the discovery of the previously unknown pathogen Phytophthora kernoviae in historic Cornish gardens (Defra n.d.) – effective coordination of governmental agencies may be the only way to limit the impact of the attack, but compliance with plant health regulations is essential to reduce the likelihood of problems spreading. Gardeners must ensure that any material they import complies with phytosanitary regulations for both the exporting and the importing countries, and be ruthless in destroying any infected material, however precious it might seem to be. ‘His importation of “Phytovora destructans” led to the eradication of trees in this country’ would not make for happy obituary reading. It is essential to be always on the alert for unusual symptoms, especially on recently acquired material. We have not laboured the issue of pests and diseases in New Trees, not least because in most cases little is known about potential problems. There are many excellent government and academic websites (easily located via internet searches), regularly updated, that deal with specific problems and local outbreaks far better than would be possible in a general work of this kind, and the reader is referred to these. The simplest solution to serious problems in any genus or locality is to sidestep the issue by avoiding planting those species that are affected. Monocultures or heavy concentrations of specimens from a single genus are the most vulnerable, and the effects of an outbreak will be greatest in such collections. A diversely planted arboretum will always be best placed to weather the attack of any genus-specific pest or disease, lessening the total impact it might have.

Plate 52. An importation of Juglans sigillata arrives on the doorstep. The seeds of many tree species are commercially available, but their provenance may not be known. Image J. Grimshaw.

Availability of New Trees New plant introductions come into cultivation by a number of routes, and the diversity of the garden flora continues to increase. Some material is collected on expeditions mounted by botanic gardens as a part of their institutional research programmes or acquisition policies. Such material is often hedged about with non-commercialisation and material transfer agreements with the source country and is effectively off-limits to the average gardener, unless it ‘leaks’ from a botanic garden by illicit means. Much of the unusual material in wider circulation has been collected in the wild by amateur enthusiasts or professional horticulturists (or their agents), with or without official sanction. Such material may be passed between friends within the horticultural community or sold commercially. The majority of such plants have a very limited distribution, however, and it is extremely rare for any species to become a great commercial success in this way. In addition to these ‘official’ and ‘unofficial’ collections, there is a very extensive global trade in tree seed made available by parastatal organisations and in-country collectors, supplying both the wholesale and retail markets. The rise of the internet marketplace has meant that it is now possible for small enterprises to sell locally gathered seed worldwide, with transactions processed in seconds.

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There are many such sources, locatable via the internet. Material of this kind is much harder to document and trace, as it is usually supplied without a collection number or any information on provenance, and it is of much less scientific and conservation value than a documented wild-origin collection would be. Identifications may also be less than certain – but this problem is not confined to commercially collected seed. The result is that it is possible to find commercial sources for most of the species described in New Trees, though they are scattered around the world and obtaining some will require considerable determination. Many of the species covered are available through the retail nursery trade in Europe and North America. For example, the RHS Plant Finder 2008–2009 indicates that 266 ‘new trees’ are available from British nurseries, which is slightly over one quarter of the species described. Many of these are available from only a single source, and it is likely that for some the number of specimens available in any one year will be small. This figure is, however, an understatement of availability, as not all nurseries are included in the book, stocks come and go, and many nurseries do not list species they have in short supply. It is probable that the diligent collector could find at least 400 ‘new’ species in the retail nurseries of Europe, and many more could be obtained by importing from North America or New Zealand (or vice versa), with due regard to phytosanitary regulations.

Plate 53. A collection in the making. A Taiwanese botanist assists in gathering seed of Carpinus rankanensis (ETOT 122) in the Taipingshan, Taiwan in 1992 (see p. 210). Image T. Kirkham.

Section II. Species Accounts Anatomy of a Species Account Author(s) of the name Accepted binomial name

Genus name Synonym(s) Superseded name(s) for all or part of the variation of the species

Botanical description Derived from published sources (see p. 13); measurements/flowering times given usually refer to wild plants; technical terms are defined in the glossary (see p. 923) Horticultural commentary Based on observations, personal communications with growers and published sources (see p. 14 for sources of information)

Cross-reference(s) Pages on which descriptions of the species will be found in standard texts: B = Bean’s Trees and Shrubs Hardy in the British Isles (Eighth Edn.); S = Clarke’s Supplement to Bean; K = Krüssmann’s Manuals (see p. 15)

Infrageneric classification For large genera only Vernacular name(s) (see p. 13)

Specific epithet

Pinus yunnanensis Franch.

Yunnan Pine

(Subgen. Pinus, Sect. Pinus)

Syn. P. yunnanensis var. tenuifolia W.C. Cheng & Y.W. Law Tree to 30 m, trunk straight and erect, stately, 1 m dbh. Bark scaly, greyish or reddish brown, breaking into plates separated by longitudinal fissures. Crown dense, forming a dome. Branchlets reddish brown, thick; vegetative buds not resinous. Leaves in fascicles of three or sometimes in pairs, not or slightly pendulous, greyish green or bright green, triangular in cross-section, 10–30 × 0.12 cm, apex acute. Fascicle sheaths persistent. Cataphylls dark brown to black, gradually eroding. Male strobili yellowish to yellowish brown, ovoid, 1.5 × 0.5 cm. Female cones lateral, in whorls of two to five, with short, stout peduncles; cones 5–10 cm long, green then yellow-brown to chestnut-brown, mature cones ovoid-conical, mature in about 20 months and opening in the following summer. Scales 3 × 1.5 cm, oblong-ellipsoid, hard, stiff, woody; apophysis swollen and rounded; umbo dorsal, slightly sunken or slightly protruding, with a minute prickle. Seeds brown, 5–6 mm; wings 1.2–1.4 cm long. Fu et al. 1999a, Farjon 2005c. Distribution CHINA: eastern Guangxi, eastern Guizhou, southern Sichuan, Yunnan. Habitat Mountains, high plateaus and river valleys between 400 and 3100 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Fu et al. 1999a, Farjon 2005c. Cross-references B246, S381, K248. Taxonomic note Var. tenuifolia from river valleys in Guangxi and Guizhou was placed in synonymy by Farjon (2001). It has pendulous leaves less than 0.1 cm wide.

Although it was introduced by Wilson, Pinus yunnanensis did not achieve wide cultivation until recently and was given only cursory treatment by Bean (1976b). It may not be the most spectacular pine in the world, but its frequent reintroductions in recent years are grounds for it receiving a fuller treatment here. The three old trees of P. yunnanensis surviving at Kew are from Wilson’s collections in Sichuan in November 1908 (Wilson 1396, 1399), sent from the Arnold Arboretum (where no examples of this species are currently grown). They have made good, though relatively short trees of 15–17 m, with dense crowns containing many long-persistent cones. The bark is thick and dark, though the ridges are reddish. A grafted young tree from Wilson 1399 grows with them. As noted above, recent reintroductions have been numerous; the 2001 catalogue of the Royal Botanic Garden Edinburgh lists accessions from six different sources, from the Sino-British Cangshan Expedition, 1981 (SBEC 109, 1043) through to Jennifer Bute’s gathering (no. 16) in 1997. The species seems to do well in most parts of the British Isles, and is grown in a few collections in continental Europe. In North America it is found in West Coast arboreta and nurseries, but seems to be absent from collections further east.

Habitat Conditions in which the species grows in the wild

USDA Hardiness Zone Estimated or observed frost tolerance of the species, using the USDA hardiness scale (see p. 5)

Conservation status IUCN Red List assessment, and other such assessments (see p. 18)

Reference(s) Source material for the botanical description, or further reading Distribution The area(s) over which the species occurs in the wild or as naturalised populations Illustration Illustration(s) of the species in other works, referenced via the bibliography (and see p. 15); NT indicates an image in New Trees (by page reference)

Bibliographic reference (see p. 931)

Collectors’ references Identifying collectors or collecting teams (see p. 919); name or abbreviation is in italics

Taxonomic note Discussion of divergent views on nomenclature and systematics

Genera in which New Trees are described

Abies

Cathaya

Halleria

Nothotsuga

Sophora

Acacia

Cedrus

Halocarpus

Nyssa

Sorbus

Acer

Celtis

Hedycarya

Olea

Styrax

Ackama

Cephalotaxus

Huodendron

Osmanthus

×Taxodiomeria

Adinandra

Ceratonia

Hymenosporum

Parrotia

Taxus

Aesculus

Ceratopetalum

Ilex

Paulownia

Telopea

Aextoxicon

Cercis

Illicium

Pennantia

Ternstroemia

Afrocarpus

Chamaecyparis

Itoa

Persea

Tetraclinis

Agathis

×Chitalpa

Juglans

Peumus

Tetradium

Ailanthus

Choerospondias

Juniperus

Phoebe

Thuja

Alangium

Cinnamomum

Keteleeria

Picconia

Tilia

Albizia

Citrus

Knightia

Picea

Torreya

Alectryon

Clethra

Koelreuteria

Pinus

Tsuga

Allocasuarina

Cornus

Lagerstroemia

Pitavia

Ulmus

Alniphyllum

Corylus

Larix

Pittosporum

Weinmannia

Alnus

Corymbia

Laurelia

Platanus

Widdringtonia

Amentotaxus

Corynocarpus

Legrandia

Podocarpus

Wollemia

Amomyrtus

Craibiodendron

Lepidothamnus

Polylepis

Xanthocyparis

Aralia

Crataegus

Leucaena

Polyspora

Zelkova

Araucaria

Cryptocarya

Libocedrus

Populus

Arbutus

Cupressus

Lindera

Prumnopitys

Aria (in Sorbus)

×Cuprocyparis

Liquidambar

Prunus

Banksia

Dalbergia

Lithocarpus

Pseudopanax

Beilschmiedia

Daphniphyllum

Lithraea

Pseudotsuga

Betula

Diospyros

Litsea

Pterocarya

Bischofia

Dipentodon

Maddenia

Pterostyrax

Blepharocalyx

Drimys

Maesa

Pyrenaria

Bretschneidera

Elaeocarpus

Magnolia

Pyrus

Buddleja

Engelhardtia

Mallotus

Quercus

Callistemon

Eriobotrya

Malus

Quillaja

Callitris

Eucalyptus

Maytenus

Rehdero-

Calocedrus

Eucryphia

Meliosma

Camellia

Exbucklandia

Melliodendron

Rhus

Camptotheca

Fagus

Metrosideros

Salix

Carpinus

Ficus

Myoporum

Sassafras

Carpodetus

Fraxinus

Myrceugenia

Schefflera

Carya

Glochidion

Neopanax

Schima

Castanea

Grevillea

Nestegis

×Schimlinia

Castanopsis

Hagenia

Nothaphoebe

Schinus

Casuarina

Halesia

Nothofagus

Sloanea

dendron

1 cm 5 mm

Figure 4. Betula insignis: seed cone (A); single fruit (B).

PINACEAE

ABIES

Mill.

Silver Firs Abies is a genus of 48 species (Farjon 2001), distributed across the northern hemisphere. The genus extends southwards as far as Honduras in Central America, and Vietnam in Asia. There are also a number of taxa in Mediterranean Africa. One remarkable feature of the genus is the preponderance of relict taxa with restricted distributions. Silver firs are tall, evergreen trees with straight, columnar trunks. The bark is generally smooth and pale in colour, though older trees can develop scales and longitudinal fissures. Primary branches are produced in regular whorls and spread horizontally, often curving downwards at maturity. The leader shoot is rigid and upright. Immature growth is often soft and bright green, contrasting with the darker mature foliage. These fresh shoots are particularly susceptible to late frosts. There are one to five buds, and these are often large and resinous. The needle-like leaves are arranged in two ranks (pectinate), each consisting of several rows. Usually, there is a V-shaped partition between the two main ranks, though this is absent in A. koreana and A. pinsapo. The leaves are attached to a shallow depression in the stem, which is clearly visible when the leaf is detached, and are twisted at the base so that the stomatal surface faces downwards. Stomata are arranged in two grey-white rows separated by the midrib, though they are also present on the upper surface of the leaf in some species. Most Abies species have two resin canals in each leaf, and the relative positions of these within the leaf can be informative. The male strobili are catkin-like and relatively undifferentiated, though in section Pseudopicea (for example, A. delavayi, A. fabri, A. forrestii, A. fargesii) the strobili are long and slender with red or purple microsporophylls. The strobili are generally pendulous, and occur in the upper half of the crown. They are produced from lateral axillary buds, and are often crowded towards the tips of the previous year’s shoots. The cones are erect and restricted to the upper part of the crown in most taxa. They mature in one year, during which time their colour changes from purple (or rarely green) to brown. The cone scales are spirally arranged around a central rachis, and at maturity they fall leaving only the rachis attached to the tree. Immature cones have colourful bracts that cover the scales, and these may be hidden (included) or exserted from the mature cone. There are two seeds on each scale, and they are partially enclosed in a membranous cup, which extends to form a persistent triangular wing. When identifying Abies species, the most important characters are those of the branchlets (colour, pubescence, presence of resin on buds), leaves (size, arrangement, stomata distribution, resin ducts) and cones (size, shape, colour, shape of seed scale, bract size and position) (Farjon 1990). To bring the taxonomy of cultivated trees up to date we here provide keys to subspecific taxa and indicate important synonymy, following the taxonomic views of Aljos Farjon (1990, 2001). The Flora of China treatment (Fu et al. 1999c) and other authorities do not always agree with these. It is clear that a thorough modern revision of the genus is urgently needed, which might reduce the excessive number of names for local forms and enable the firs to be seen in a more focused way than is apparent at present. With changing taxonomic concepts and nomenclature, coupled with

Plate 54. Mount Shasta in northern California supports a healthy forest of Abies magnifica var. shastensis. Image J. Grimshaw.

44

Abies

New Trees

Q

R

1 cm

P

1 cm

N

M

1 cm

A

1 cm

B

1 cm 1 cm

1 cm

C

1 cm

D E J F

G

H

K

L

Section II. Species Accounts

occasional misidentifications, the naming of many (especially older) trees in collections has become confused. In consequence the identification of older champions is not always reliable, and these are only cited here where identification is certain. A number of Mexican Abies are poorly known, with disputed taxonomy, and are represented in cultivation by no more than a handful of specimens. Abies colimensis Rushforth & Narave, from the upper reaches of the Nevado de Colima in Jalisco, was included in A. religiosa by Farjon (2001) but differs in its much larger, barrel-shaped cone with reflexed scales (looking somewhat similar to cones of A. magnifica and A. procera). It is rare in horticulture. Abies flinckii Rushforth comprises the two entities named by Martínez as A. religiosa var. emarginata Martínez and A. guatemalensis var. jaliscana Martínez, differing from typical A. religiosa and A. guatemalensis in its longer, narrower cones and longer foliage. Farjon (2001) included it in A. guatemalensis var. jaliscana. It is found in western Mexico, north of the range of A. guatemalensis and west of that of A. religiosa. Material collected by Keith Rushforth (KR 0621, the type collection) at 2350 m at Nevado de Colima, Jalisco in 1984 did well for Mike Hudson in New Zealand until it died suddenly, having reached 9 m, and a grafted specimen reached 3.5 m for Tom Hudson in Cornwall but was killed by Armillaria (T. Hudson, pers. comm. 2007). It is however listed as growing in the San Francisco Botanical Garden (formerly known as the Strybing Arboretum). Abies mexicana Martínez (see Krüssmann (1985b) and Clarke (1988): K46, S31) is related to A. durangensis, rather than to A. vejarii in which it has been placed as a subspecies (A. vejarii subsp. mexicana (Martínez) Liu), differing from A. vejarii in its ‘foliage arrangement, cones, bark and ecology’ (Rushforth 1987a). It is found in the same general area as A. vejarii, in the Sierra Madre Oriental in Coahuila and Nuevo León, but at lower elevations. Abies mexicana has a sparse presence in cultivation from collections by Keith Rushforth (KR 479), Jim Priest (JP 109), and Rob Nicholson, Carl Schoenfeld, John Fairey and Mel Shemluck (Nicholson et al. B1), all from 1 km south of San José de la Hoya, near Galeana, Nuevo León and just to the north of Cerro Potosí, where there are trees to 20 m that bear green-brown cones with included bracts, growing with Pseudotsuga on a northwest aspect at the bottom of a canyon (K. Rushforth, pers. comm. 2008). Two trees grown from Nicholson et al. B1 are thriving at Arboretum Wespelaar (P. de Spoelberch, pers. comm. 2008). The firs are among the most beautiful of conifers, being distinguished by their attractive branching pattern, often handsome foliage and sometimes enormous stature. This beauty can become marred by irregularities in shape as they age, but a group of young, vigorous trees is a lovely sight. Their horticultural use, however, is constrained by several factors. First, they tend to be potentially very large (with the exception of the bijou A. koreana), so gardeners with small plots avoid them – although against this may be set the fact that they often produce their outstanding cones at an early age. Secondly, many species do not do best in areas that are hot and dry, or hot and humid, so the finest specimens tend to be in cooler, moister areas, a pattern that holds good not only for the British Isles, where the genus is well known, but also in continental Europe and North America. A danger point in the cultivation of Abies is the period of shoot extension in spring, when new shoots can be nipped by frost. This can be a serious problem for some species, particularly those

Abies

45

Figure 5 (opposite). Abies morphology. Abies homolepis: habit with cone (A). A. pinsapo var. marocana: branchlet (B); leaf underside (H). A. borisiiregis: branchlet (C); leaf underside (G). A. forrestii: cone rachis (D); branchlet with male strobili (E); seed (R). A. chensiensis: leaf underside (F). A. durangensis: leaf underside (J). A. sibirica: leaf underside (K). A. forrestii var. georgei: leaf underside (L). A. cilicica: seed scale, upper surface without seeds (M), upper surface with two seeds (N), lower surface with bract scale (P); seed (Q).

Plate 55. Abies pinsapo var. marocana from Jebel Lakraa, Morocco, showing neat elongated cones and, in this case (see p. 57), short, densely placed leaves. Image M. Gardner.

46

Abies

New Trees

from very cold places, which can be fooled by warm early spring temperatures so that they are consistently frozen back each year. These are often best in cool areas where the new shoots do not break quite so early as in warmer situations. Happily there are plenty of other species from suitable habitats from which to make a selection for cultivation where summers are warmer and drier. A beautiful example is A. vejarii, which seems capable of equalling in loveliness all the classic firs of Europe and western America, even in situations where firs might not be expected to thrive. Most Abies find the combination of heat and humidity intolerable, however, and in the southeastern United States only A. firma will thrive (T. Cox, J. Ruter, pers. comms. 2007; Dirr 1998). Adelgid aphids can be a very serious problem on Abies and have caused great losses to A. alba in Europe and A. balsamea and A. fraseri in eastern North America, but they seem to be less serious in horticultural settings.

Plate 56. Abies borisiiregis is conspicuous in the limestone mountains of Macedonia, northern Greece. Image J. Grimshaw.

A. alba Mill. B144, S17, K29 A. alba f. flabellata (NOW A. alba Mill.) K29 A. alba f. microcarpa (NOW A. alba Mill.) K29 A. alba f. pendula (NOW A. alba Mill.) B145 A. alba f. pyramidalis (NOW A. alba Mill.) B145 A. alba f. recurva (NOW A. alba Mill.) K29

A. amabilis Douglas ex J. Forbes B145, S17, K30 A. ×arnoldiana Nitz. K30 A. balsamea (L.) Mill. B146, S17, K30 A. balsamea f. hudsonia (NOW A. balsamea Hudsonia Group) B147, S18, K31 A. balsamea var. phanerolepis Fernald K31

Abies borisii-regis Mattf.

King Boris Fir, Bulgarian Fir, Macedonian Fir

The taxonomic revision of Liu (1971) treated A. borisii-regis as a natural hybrid between A. alba Mill. and A. cephalonica Loudon, and this was also suggested by the analysis of Mitsopoulos & Panetsos (1987). Morphology is intermediate between the two purported parent taxa, although unlike in A. cephalonica the young shoots are pubescent, and the leaves differ from A. alba in that the leaf apices are entire and there are a few stomata on the upper leaf surface. The bands of stomata on the underside of the leaf are grey-green, rather than white as in A. alba (Warren & Johnson 1988), and cones are very rarely produced (Anon. 1964). Rushforth (1987a) suggested that it is not a recent hybrid, and should be considered as a member of a group of species including A. alba, A. cephalonica and A. nordmanniana. Farjon (2001) treats it as a full species. Anon. 1964, Warren & Johnson 1988, Farjon 1990. Distribution ALBANIA; BULGARIA: Pirin and Rhodope Mts.; GREECE: Macedonia; MACEDONIA (Former Yugoslav Republic). Habitat Between 700 and 1800 m asl in mountainous areas. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Liu 1971; NT44, NT46. Cross-reference K31.

The King Boris Fir is abundant in the mountains of Macedonia, and in places forms quite a dense forest of vigorous young trees. It is not easily distinguishable from other European silver firs, and like A. alba it can make a big tree in the right conditions, but it is in general much more adaptable and useful for horticulture than that species (Rushforth 1987a). The Tree Register of the British Isles (TROBI) has 14 records of specimens over 30 m tall, and 26 over

Section II. Species Accounts

Abies

20 m, the tallest noted being 38.5 m (109 cm dbh), at Rossylongan, Co. Donegal, in 2000 (Tree Register of Ireland, TROI) – although the identity of this individual is not certain. On the British mainland the largest recorded was 36 m (dbh 155 cm), at Stonefield Castle Hotel, Argyll, measured in 1992 by Alan Mitchell (TROBI). Most of these big trees are in areas particularly known to favour A. alba, namely the damper, cooler north and west, but not all of them are, and A. borisii-regis would seem to be a good candidate to attempt where a silver fir is desired in drier areas. At the Royal Botanic Garden Edinburgh there is a very fine specimen planted in 1968 (22 m in 2004, TROBI) that is the best-looking fir in the collection, well furnished with densely leafy branches. Rather slower-growing, having been planted in 1911, is a large example at Wakehurst Place, measured at 27 m in 1991 (Kew records). It is also in cultivation in many European collections and generally thrives, with specimens at Rogów Arboretum being described as ‘fast-growing, tall and healthy’ (P. Banaszczak, pers. comm. 2007). A. bornmuelleriana (NOW A. nordmanniana subsp. equitrojani (Asch. & Sint. ex Boiss.) Coode & Cullen, NT56) B161, S28, K31 A. bracteata (D. Don) A. Poit. B147, S18, K31

A. cephalonica Loudon B148, S18, K32 A. cephalonica var. apollinis (NOW A. cephalonica Loudon) B148, S19, K32 A. ×chengii Rushforth S19

Abies chensiensis Tiegh.

Shensi Fir

This species was described by Bean (B149, S19) and Krüssmann (K33). Two subspecies have since been recognised, however, and a key to these is provided below.

1a. Longest leaves of sterile branches to 7.5 cm, occasionally longer; China (northeast Yunnan, southeast Xizang), India (Arunachal Pradesh) ........... subsp. salouenensis 1b. Longest leaves of sterile branches < 4.5 cm ..................................................................................... 2 2a. Resin canals in leaves of coning shoots medial; cones 8–10 cm long; China (southeast Gansu, Henan, west Hubei, south Shaanxi, west Sichuan) ...... subsp. chensiensis 2b. Resin canals in leaves of coning shoots marginal; cones 10–14 cm long; China (Yunnan: Lijiang Shan Massif) ..................................................... subsp. yulongxueshanensis

Abies chensiensis subsp. salouenensis

Salween Fir

(Bordères & Gaussen) Rushforth Subsp. salouenensis differs from the type subspecies mainly in that the leaves are longer (up to 7.5 cm vs. 2–4 cm in subsp. chensiensis). The resin canals of leaves in coning shoots of subsp. salouenensis are marginal, while those of subsp. chensiensis are medial. Rushforth 1984a, Farjon 1990, Fu et al. 1999c. Distribution CHINA: northwest Yunnan, southeast Xizang; INDIA: northeast Arunachal Pradesh. Habitat Montane forest, between 2000 and 3200 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration NT48. Taxonomic note Flora of China treats both these taxa as synonyms of A. ernestii var. salouenensis (Bordères & Gaussen) W.C. Cheng & L.K. Fu. Abies ×chengii Rushforth is now considered to be A. forrestii × A. chensiensis subsp. salouenensis (K. Rushforth, pers. comm. 2007).

The Salween Fir was first introduced to cultivation before World War II by George Forrest (for example, F 30668) and Frank Kingdon-Ward (for example, KW 10412), and trees from these early introductions are still to be found in collections in the

47

48

Abies

Plate 57. A promising young Abies chensiensis subsp. salouenensis at Arboretum Wespelaar, with characteristic long leaves. Image P. de Spoelberch.

New Trees

United Kingdom. These older trees (and propagations from them) are now being joined by trees from the new generation of collectors. Several trees assumed to be grown from F 30668 and planted out at Borde Hill, West Sussex, c. 1940, have achieved 14–16 m (the largest with dbh 40 cm), and Alan Mitchell measured one of unknown origin at Burnside, Forfar, Angus in 1990 that was 16 m tall with a dbh of 25 cm. Growth is steady rather than fast, a tree grown by Keith Rushforth (pers. comm. 2007) achieving 12–15 m in 25 years. When doing well, subsp. salouenensis is an attractive tree, with long dark needles slightly drooping from the twigs, and in maturity its bluish cones are another feature. It is said to require a sheltered damp site to do well (Rushforth 1987a), but a young tree at Thenford House, Northamptonshire is growing happily in a comparatively open site, and produces an abundant crop of big blue-black cones that drip copious resin.

Abies chensiensis subsp. yulongxueshanensis Rushforth Subsp. yulongxueshanensis differs from the type subspecies in the length of the female cones, which range from 10 to 14 cm (female cones of subsp. chensiensis are typically 8–11 cm long, though they can reach 12 cm). Like subsp. salouenensis, the resin canals in the leaves of coning shoots are marginal. Rushforth 1984a, Farjon 1990, Fu et al. 1999c. Distribution CHINA: northern Yunnan, Yulong Xue Shan massif in the Lijiang Shan. Habitat Montane forest between 2600 and 3200 m asl. USDA Hardiness Zone 6. Conservation status Vulnerable. Restricted to a small area of forest.

Abies chensiensis subsp. yulongxueshanensis is extremely rare in cultivation, which is perhaps just as well considering that its name is difficult both to write and to say, but with it also being rare in the wild this is somewhat worrying. It appears to be known only from a collection made by T.T. Yu (15050) growing at Benmore. A. cilicica (Ant. & Kotschy) Carrière B149, S20, K33 A. cilicica subsp. isaurica Coode & Cullen S20 A. concolor (Gordon) Lindl. ex Hildebr. B150, S20, K33 A. concolor f. violacea (NOW A. concolor Violacea Group) B150 A. concolor var. lowiana (NOW A. concolor Lowiana Group) B150, S20, K33

Abies delavayi Franch.

Delavay Fir

Abies delavayi was described by Bean (B151), who used a broad species concept, including a number of other taxa as varieties. All of these have subsequently been recognised separately by Farjon (2001): var. fabri (= Abies fabri), var. faxoniana (= A. fargesii var. faxoniana), var. forrestii (= A. forrestii) and var. georgei (= A. forrestii var. georgei). Abies delavayi sensu Farjon includes two varieties: var. motuoensis W.C. Cheng & L.K. Fu, from Tibet, and var. nukiangensis (W.C. Cheng & L.K. Fu) Farjon & Silba, from northwest Yunnan. Neither variety has apparently been introduced into cultivation. In addition, A. fansipanensis Q.P. Xiang was reduced to a subspecies of A. delavayi. See also Krüssmann (1985b: K34) and Clarke (1988: S21).

1a. Crown conical; branchlets slender; leaves less densely arranged; cone rachis slender; China (south Gansu, Shaanxi, west Hubei, northwest Sichuan) ...................................... A. fargesii 1b. Crown broad, flat-topped in mature trees; branchlets stiff and robust; leaves densely arranged; cone rachis robust ....................................................................................................... 2

Section II. Species Accounts

Abies

2a. Young branchlets yellowish brown; China (west Sichuan: on Mt. Emei and surrounding ranges) ............................................................................................................ A. fabri 2b. Young shoots usually purple, red or dark orange-brown .................................................................. 3 3a. Bract scales with long, narrow cusps, 1–2 cm long; China (southeast Xizang, west Yunnan), India (Arunachal Pradesh), Myanmar (north), Vietnam (north) ................ A. delavayi 3b. Bract scales with broad cusps, to 1 cm long; China (northwest Yunnan, southeast Xizang, southwest Sichuan) ............................................................................ A. forrestii

A. delavayi var. fabri (NOW A. fabri (Mast.) Craib subsp. fabri) B151, S21

Abies delavayi subsp. fansipanensis (Q.P. Xiang) Rushforth Subsp. fansipanensis differs from the type subspecies in that the bract scales are half the length of the seed scales, rather than the same length. Subsp. delavayi has elongated cusps that are partially exserted, but subsp. fansipanensis has short cusps which are barely visible in the mature cone. In this respect, subsp. fansipanensis resembles A. delavayi var. nukiangensis, but unlike the latter its leaves are narrow and strongly revolute, as in the type subspecies. Farjon 1990, Rushforth 1999. Distribution VIETNAM: Lao Cai (Fan Si Pan). Habitat Montane forest, between 2600 and 2800 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable, with limited distribution and subject to timber extraction.

This taxon seems to be an isolate with a narrow altitudinal range on Fan Si Pan and perhaps adjacent mountains, where it is greatly reduced in numbers by deforestation (T. Hudson, pers. comm. 2005). Trees of up to 18 m tall and 1.2 m dbh have been recorded on the mountain, usually growing on steep, cooler eastern or northeastern slopes or ridges (P. Wharton, pers. comm. 2007). The silhouette of old trees on the ridge tops reminded the late Peter Wharton of ancient Araucaria araucana trees in Chile. Unfortunately natural regeneration seems to be infrequent. It has been collected on several occasions by recent visitors to northern Vietnam, but it remains extremely rare in cultivation and the only plants seen are youngsters growing steadily at Tregrehan. For Keith Rushforth (pers. comm. 2007) it has achieved 2 m in 12 years. The curled foliage is distinctive, and the bright silver stomatal lines on the underside contrast well with the dark green upper surface of the needles. A. delavayi var. faxoniana (NOW A. fargesii var faxoniana (Rehder & E.H. Wilson) Tang S. Liu) B152, S23, K35 A. delavayi var. forrestii (NOW A. forrestii Coltm.-Rog. var forrestii) B152, S24, K35 A. delavayi var. georgei (NOW A. forrestii var. georgei (Orr) Farjon) B153, S24, K35

Abies densa Griff.

Sikkim Fir

Tree to 60 m, 2.5 m dbh. Bark smooth, grey, breaking into large plates in older trees. Crown broad or columnar, becoming flat-topped in mature trees. Branchlets yellowish brown, becoming grey with age; conspicuously grooved, leaf scars circular; vegetative buds slightly resinous. Leaves spirally arranged, mostly on two planes, (1.5–)2–4(–5) × 0.2–0.25 cm, straight or slightly curved, margins revolute, apex emarginate. Male strobili arranged radially around the shoot, 2–4.5 cm long, yellow with purple microsporophylls. Cones erect, sessile or short-pedunculate, cylindrical, apex obtuse, 8–12 × 4–5.5 cm, purple-blue when immature, darkening later. Seed scales flabellate to cuneate, 1.5–2 × 2–2.5 cm. Bract scales ligulate to spathulate, 2–2.5 cm long, usually not exserted. Seeds brown, cuneate, with cuneate wings, 1 × 0.5 cm. Farjon 1990, Fu et al. 1999c. Distribution BHUTAN; CHINA: southeast Xizang; INDIA: Arunachal Pradesh, Assam, Sikkim; NEPAL. Habitat High mountain cloud forest between 2450 and 4000 m asl. Pronounced seasonality, with hot, wet summers and very cold winters; annual precipitation over 2000 mm. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Farjon 1990; NT50.

49

50

Abies

New Trees

Abies densa has never been a common tree in arboreta, but its presence has probably been masked by misidentifications and confusion with other Himalayan firs. This is discussed by Clarke (1988) under his entry for A. spectabilis; he concluded that A. densa was probably first introduced by Joseph Hooker from his famous Sikkim expedition of 1849–1850. With the confusion surrounding the identification of these taxa it is perhaps wisest to disregard old records and concentrate on more recent introductions, of which there have been several from Nepal and Bhutan in recent decades. The finest specimen known (said to have been collected by Ludlow & Sherriff, though of unknown origin) is at Benmore, and was 26 m tall (69 cm dbh) when measured in 1991 by Alan Mitchell (TROBI). It will be succeeded there by numerous young trees planted in the Bhutanese Glade, derived from collections made by expeditions from the Royal Botanic Garden Edinburgh during the 1980s and 1990s. In Charles Howick’s experience (pers. comm. 2005) A. densa is prone to die young, which may explain its general scarcity, but at Howick he has several young specimens of about 8 m. They are slightly untidy-looking trees, with mid-green needles (flushing bright green), but their abundantly produced young cones are a spectacular deep Prussian blue (with some resin on the top). As for most Himalayan firs, a cool wet site would seem to be the most appropriate for successful cultivation. Plate 58. The striking blueblack immature cone of the Sikkim Fir, Abies densa. Image J. Grimshaw.

Abies durangensis Martínez

Durango Fir

Tree to 40 m, 1–1.5 m dbh. Bark smooth, grey or reddish brown, becoming deeply fissured and dark brown to black in older trees. Crown narrow and pyramidical or rounded, often above a long, clear bole. Branchlets dark purple-red or reddish brown, becoming brown with age; conspicuously grooved between the leaves; leaf scars circular or ovate; vegetative buds very resinous, yellow. Leaves spirally arranged, mostly on two planes, (1.4–)2–3.5(–4.5) × 0.1–0.16 cm, curved slightly backwards or forwards, apex sharp and acuminate. Male strobili lateral and in leaf axils, 1–2 cm long, perular scales resinous, microsporophylls red. Female cones erect, short-pedunculate, cylindrical, apex obtuse, 5.5–10 × 3–4.5 cm, pale brown to yellow. Seed scales flabellate, 1.5–2 × 2–2.8 cm. Bract scales spathulate, 1–1.5 cm long with short cusps, not exserted. Seeds yellowish brown and cuneate, wings rounded or cuneate, 0.9 × 0.7 cm. Farjon 1990. Distribution MEXICO: Chihuahua, Coahuila, Durango, Jalisco, Sinaloa. Habitat High mountain valleys and steep canyons between 1600 and 2900 m asl. Climate cool and moist. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Farjon 1990; NT44, NT51. Cross-reference K35.

Abies durangensis is part of the group of western North American firs that includes A. grandis and A. concolor and extends southwards through Mexico to reach Guatemala (Rushforth 1987a). It is most closely related to A. concolor Lowiana Group but, unlike that generally amenable taxon, has not flourished in cultivation in the United Kingdom. Keith Rushforth has one of 5–6 m after 12 years, and at Kew there is a scrawny 4 m specimen that was planted in 1992. Both were grown from seed collected at 3050 m in the Sierra Madre Occidental by an expedition from the Royal Veterinary & Agricultural University, Horsholm, Denmark. Trees from this provenance are also in cultivation at Herkenrode and Arboretum Wespelaar, where they do well (K. Camelbeke, pers. comm. 2007). Trees of Chihuahuan origin from a 1988 collection by J. Hjerting and S. Ødum (no. 8) are also growing slowly at the Sir Harold Hillier Gardens, where the

Section II. Species Accounts

Abies

51

D B A 1 cm 1 cm

C 1 cm

larger one was 5 m when measured in 2006 (Sir Harold Hillier Gardens database). It is also grown at Benmore. Full sun is said to be essential for this species to succeed (K. Rushforth, pers. comm. 2007).

Abies durangensis var. coahuilensis (I.M. Johnst.) Martínez Var. coahuilensis differs from the type variety in that the branchlets are more pubescent and there are few or no stomata on the upper side of the leaves, which are also shorter than in var. durangensis. The midrib of var. coahuilensis is wider and more conspicuous than in the type variety. Farjon 1990. Distribution MEXICO: Coahuila. Habitat Restricted to a few valleys at altitudes of between 2200 and 2300 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable, due to small population size. Cross-reference K35.

This taxon is known to be in cultivation only at Benmore, where there is a tree from a wild collection in Coahuila in 1987.

Figure 6. Abies durangensis: habit with seed cones (A); seed scale, lower surface with bract scale (B), upper surface with two seeds (C); winged seed (D).

52

Abies

New Trees

A. equi-trojani (NOW A. nordmanniana subsp. equi-trojani (Asch. & Sint. ex Boiss.) Coode & Cullen, NT56) K35 A. fabri (Mast.) Craib (WAS A. delavayi var. fabri B151, S21) A. fabri subsp. minensis (BordèresRey & Gaussen) Rushforth S22

A. fargesii Franch. B153, S23, K35 A. fargesii var. faxoniana (Rehder & E.H. Wilson) Tang S. Liu (WAS A. delavayi var. faxoniana B152, S23, K35) A. firma Siebold & Zucc. B154, S23, K35

Abies forrestii Coltm.-Rog.

Forrest Fir

This species was described by Bean (B152, S24) and Krüssmann (K35) under the name Abies delavayi var. forrestii. Abies forrestii var. georgei (Orr) Farjon was also described by them (B153, S24, K35), under the name A. delavayi var. georgei (Orr) Melville. Two additional varieties have since been recognised, and a key to these is provided below. Var. smithii Viguié & Gaussen is not known in cultivation.

1a. Cones large, 7–10(–14) cm long; young shoots glabrous and shiny; China (southwest Sichuan, northwest Yunnan, southeast Xizang) ................................. var. forrestii 1b. Cones (usually) < 8 cm long; young shoots densely rusty brown-pubescent ..................................... 2 2a. Leaf resin canals medial; China (northwest Yunnan, southeast Xizang) ............................ var. ferreana 2b. Leaf resin canals marginal ............................................................................................................... 3 3a. Bract scales conspicuously longer than seed scales, apex acuminate with lanceolate cusp; China (southwest Sichuan, northwest Yunnan, southeast Xizang) ....... var. georgei 3b. Bract scales equal to, or only slightly longer than seed scales, apex rounded with short, central cusp; China (northwest Yunnan) ....................................................... var. smithii

Abies forrestii var. ferreana (Bordères & Gaussen) Farjon & Silba Syn. A. chayuensis W.C. Cheng & L.K. Fu, A. rolii Bordères & Gaussen, A. yuana Bordères & Gaussen Var. ferreana differs from the type variety in that the branchlets are strongly pubescent and the cones are smaller. In addition, the resin canals are medial rather than marginal. Farjon 1990. Distribution CHINA: northwest Yunnan, southeast Xizang. Habitat Montane forest, between 2400 and 4300 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated.

The minor characters separating these so-called varieties should perhaps not be taken too seriously, despite the plethora of synonyms they have generated (see Farjon 2001). According to Rushforth (1987a), seed of var. ferreana was collected by Forrest and Kingdon Ward, but authenticated specimens are scarce. A recent collection was that made by the Kunming–Gothenburg Expedition (KGB 503) in 1993, from which a specimen is growing at Edinburgh. Material under this name has recently been offered by a nursery in Northern Ireland.

A. fraseri (Pursh) Poir. B154, S24, K36 A. grandis (Douglas ex D. Don) Lindl. B155, S25, K36

Section II. Species Accounts

Abies guatemalensis Rehder

Abies

53

Guatemalan Fir

Syn. A. tacanensis Lundell, A. zapotekensis Debreczy, Racz & Ramírez Tree to 40 m, trunk columnar, 1–1.5 m dbh. Bark smooth, greyish brown in young trees, becoming scaly in older trees. Crown broad and conical or dome-shaped. Branchlets slender, purplish or brownish red, becoming dark purple then grey with age, conspicuously grooved between the leaves; leaf scars circular or ovate; vegetative buds resinous. Leaves spirally arranged, in two lateral rows at right angles to the shoot, (1.2–)1.5–4(–5.5) × 0.1–0.2 cm, apex obtuse. Male strobili lateral, 2–2.5 cm long, yellowish. Cones erect, subsessile, cylindrical with an obtuse apex, 8–12 × 4–5.5 cm, purple when immature, dark brown when mature. Seed scales reniform, 2–2.5 × 3 cm. Bract scales cuneate, 1.2–1.7 cm long with short triangular cusps, only slightly exserted. Seeds light brown, with broad egg-shaped wings, 1–1.5 cm long. Farjon 1990. Distribution EL SALVADOR; GUATEMALA; HONDURAS; MEXICO: Chiapas, Colima, Guerrero, Jalisco, Michoacán, Nayarit, Oaxaca, Tamaulipas. Habitat Pacific side of the Sierra Madre del Sur mountain chain, between 1800 and 3700 m asl. Climate cool and moist, with most precipitation occurring in winter. USDA Hardiness Zone 9. Conservation status Vulnerable. Illustration Liu 1971, Farjon 1990; NT53. Cross-reference K36. Taxonomic note A number of varieties of A. guatemalensis have been described (var. longibracteata Debreczy & Racz, var. ixtepejiensis Silba, var. rushforthii Silba and var. tamaulipensis Silba) and these names appear in the literature, occasionally at specific rank. However, Farjon (2001) recognises only var. jaliscana.

Abies guatemalensis has the distinction of being the only ‘new tree’ on CITES Appendix I, given maximum possible protection in international trade. The only other hardy trees on Appendix I are Araucaria araucana, Fitzroya cupressoides, Pilgerodendron uviferum and Podocarpus parlatorei. Abies guatemalensis has become threatened by forest clearance, timber harvesting and the use of juveniles as Christmas trees. The latter problem is being addressed by collecting seed and encouraging farmers to grow crops of the tree as a commercial venture (De Macvean 2003, Córdova 2007). It is rare in cultivation, but surprisingly hardy. A specimen at Wakehurst Place is doing well, being 8 m tall when seen in 2005, with a rather un-Abies-like appearance caused by its very dense mass of ascending branches. The foliage is dark green and conspicuously flattened to the side of the shoots. This tree derives from a collection made at San Carlos in the Sierra Madre Oriental, Tamaulipas in 1993, at the surprisingly low altitude of 1070 m. Rushforth (1987a) predicted that high-altitude provenances offered the best chance of successful establishment in horticulture, and this would indeed seem wise for further gatherings. It is established in the Berkeley Botanic Garden, and probably elsewhere in the milder parts of the United States, from collections in Tamaulipas in the early 1990s. Material of unknown origin has also been circulated by Arboretum Waasland, Belgium, and it has been offered in the past in western North America. A. hickelii Flous & Gaussen S31, K36 A. holophylla Maxim. B155, S25, K36

Abies homolepis Siebold & Zucc.

Nikko Fir

This species was described by Bean (B156, S26) and Krüssmann (K36). A. homolepis f. tomomi (NOW A. homolepis Siebold & Zucc. var. homolepis) K37

Abies homolepis var. umbellata (Mayr) E.H. Wilson This variety differs from the type in several characters of the cones. Immature cones are green rather than purple, and the apex is umbilicate rather than obtuse. The cones are usually larger than those of the type. Farjon 1990. Distribution JAPAN: central Honshu, Kyushu, Shikoku. Habitat Montane forest between 700 and 2000 m asl. Var. umbellata grows in mesic soils, in a cool, humid climate. USDA Hardiness Zone 5.

Plate 59. Abies guatemalensis var. jaliscana has a much less tidy growth habit than most firs. Image N. Macer.

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Conservation status Not evaluated. Illustration Liu 1971. Cross-reference K37. Taxonomic note This variety is often sympatric with both the type variety and A. firma Siebold & Zucc., and may be a hybrid (Liu 1971).

Abies homolepis var. umbellata is generally more written about than grown, and is probably of limited horticultural difference to the type. Trees from seed collected by E.H. Wilson (Wilson 4078) are still growing in some collections, including one particularly large specimen at Dawyck, planted in 1924 (an adjacent plaque informs visitors that it was measured at 24.5 m, 71 cm dbh, in 2001). This remains densely clad with branches and foliage, and although a fine tree, is decidedly sombre. There are also some younger specimens in the Scottish botanical gardens from cultivated origins. In the Rogów Arboretum there is a forest plot with 30 specimens, planted in 1959, that are healthy and fully hardy in the continental conditions experienced in Poland (P. Banaszczak, pers. comm. 2007).

A. ×insignis Carrière ex Bailly B161, K37 A. kawakamii (Hayata) T. Itô B157, S26, K38 A. koreana E.H. Wilson B157, S26, K38

A. koreana f. sikokiana (NOW A. veitchii var. sikokiana (Nakai) Kusaka, NT60) K39 A. lasiocarpa (Hook.) Nutt. B158, S26, K39 A. lasiocarpa var. arizonica (Merriam) Lemmon B158, S26, K40

Abies magnifica A. Murray

California Red Fir

This species was described by Bean (B158, S27) and Krüssmann (K40). Var. shastensis was also recognised and described by Bean (B159, S27), but a more detailed description is provided below.

Abies magnifica var. shastensis Lemmon

Shasta Red Fir

Syn. A. magnifica var. xanthocarpa Lemmon Var. shastensis has smaller cones than the type variety (10–13 × 5–8 cm vs. 18–25 × 7–10 cm) and the bract scales are exserted and reflexed. Farjon 1990, Thieret 1993. Distribution USA: from Lassen Peak, California to Crater Lake, Oregon. Habitat Montane forest between 1400 and 2700 m asl. Soils are thin and the climate extreme, with short, warm summers and long, cold winters. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Liu 1971; NTxi, NT42. Cross-references B159, S27, K40. Taxonomic note Var. shastensis occurs in an area of overlap between the distributions of A. magnifica and A. procera Rehder, and may be of hybrid origin (Liu 1971, Silba 1986).

The volcanic cone of Mount Shasta is one of the most beautiful sights on a journey along the California I5 freeway, which runs in the valley between it and the Siskiyou mountains to the west. The discerning botanist will turn to the Siskiyous and their fabulous botanical diversity; in contrast Mount Shasta is extremely depauperate, no doubt in consequence of its recent volcanic origin. Its slopes, however, support a fine forest of Abies magnifica var. shastensis, growing as large trees to the timberline, and a detour was made to visit these trees when I (JMG) was in western North America in June 2004. With the snow-capped peak behind them they are a magnificent sight. The snow was only just melting at treeline, and as it receded it revealed thousands of Abies seedlings emerging through the otherwise barren pumice gravel, as densely as Sycamore (Acer pseudoplatanus) seedlings in an English lawn. The foliage characteristics vary considerably between the trees, and this population is probably best considered to be an unstable genetic mix between A. magnifica and A. procera (Hunt 1993b).

Section II. Species Accounts

Abies

55

Despite the prolificacy of its seed set, the Shasta Red Fir is rare in cultivation. A tree at Bedgebury National Pinetum in Kent was reported to be 17 m in 1968, but others in cultivation at this time were observed to be ‘miserable grafted specimens’ (Mitchell 1972). There is a tree of about 10 m at Mount Usher, planted in 1957, said to be var. shastensis, and at Howick there is a young tree from Warner & Howick 269, collected on Mount Shasta in 1986. This is only 2 m tall, and very slow-growing, but has a good shape. Material from several collections is grown at Benmore and Dawyck, and it seems probable that it will thrive best in cool moist sites such as these. Three trees from D.S. Paterson & S. Clarke 85, collected in California in 1991, are thriving at Dawyck.

A. magnifica var. xanthocarpa (NOW A. magnifica var. shastensis Lemmon, NT54) K40 A. mariesii Mast. B159, S27, K40

A. marocana (NOW A. pinsapo var. marocana (Trab.) Ceballos & Bolaño, NT57) B164, S29, K40 A. mexicana Martínez S31; NT45

Abies nebrodensis (Lojac.) Mattei

Sicilian Fir

Tree to 15 m, 0.4–0.6 m dbh; trees in cultivation may grow larger than the few, stunted wild specimens. Bark smooth, light grey in young trees, becoming scaly in older trees. Crown broad and conical. Branchlets robust, stiff, shiny, yellowish green, turning grey with age; conspicuous ridges between the rows of leaves; leaf scars circular or ovate with a pale central area; vegetative buds slightly resinous. Leaves spirally arranged, 1.5–2.2 × 0.2–0.4 cm, apex acute or mucronate. Male strobili lateral, 1.5–2 cm long, greenish yellow. Female cones erect, short-pedunculate, cylindrical, apex conical, 8–10 × 3–4 cm, yellowish green when immature, greenish brown when mature. Seed scales cuneate, 2–2.5 cm long. Bract scales linear to spathulate, 2.5–3 cm long, reflexed and exserted. Seeds reddish brown and conical, wings broad-cuneate, 1–1.5 cm long. Ostl 1989, Farjon 1990. Distribution ITALY: Madonie Mts. of northern Sicily. Habitat Restricted to secondary maquis at between 1400 and 1650 m asl. Typical Mediterranean climate. USDA Hardiness Zone 5. Conservation status Critically Endangered. The wild population comprises approximately 30 trees in an area of less than 1.5 km2. Illustration Liu 1971, Farjon 1990; NT19, NT55. Cross-reference K41. Taxonomic note Ostl (1989) suggested that A. nebrodensis is an ancient hybrid with A. alba as one of the parents. Fossil evidence indicates that A. alba was present in Sicily in the past, though it is now absent.

Abies nebrodensis is clinging to survival as a wild tree on degraded hillsides in Sicily, reduced from forests to the double handful of mature trees left today, rediscovered only in 1957. As one of the rarest trees in the world it is subject to an intensive conservation effort featuring natural habitat protection and ex situ cultivation in Sicily and elsewhere (IUCN 1995–2006). It is therefore important that specimens in cultivation are kept well documented, especially if they are of known Sicilian origin, as they may be an important part of the genetic reservoir of this beleaguered species. Hybridisation is a problem, however, so seed should not be supplied as A. nebrodensis if grown in proximity to other firs. Regardless of its rarity, the Sicilian Fir is worth cultivating as a beautiful tree, with sweeping branches well clad in mid-green leaves. Coming from dry limestone hills it is adapted to hotter, drier conditions than most Abies enjoy, and it does well even in the south of England. It will grow fast when happy, one handsome specimen at Bedgebury planted in 1983 being 11 m when measured by Owen Johnson in 2001, and somewhat taller when seen in 2005. The current UK

Plate 60. The cones of Abies are both ornamental and important for identification. In Abies nebrodensis the bract scales are exserted and reflexed. Image A. Farjon.

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New Trees

champion is 20 m (49 cm dbh), at Leonardslee, West Sussex (in 2003, TROBI). A cultivar with yellow new growth is marketed in North America as ‘Sicilian Gold’. A. nephrolepis (Trautv. ex Maxim.) Maxim. B159, S27, K41

A. nephrolepis f. chlorocarpa (NOW A. nephrolepis (Trautv. ex Maxim.) Maxim.) B159, K41

Abies nordmanniana (Steven) Spach

Caucasian Fir, Nordmann Fir

This species was described by Bean (B160, S27) and Krüssmann (K41), but it has now gained a subspecies.

Abies nordmanniana subsp. equi-trojani

Trojan Horse Fir

(Asch. & Sint. ex Boiss.) Coode & Cullen Syn. A. bornmuelleriana Mattf., A. equi-trojani (Asch. & Sint. ex Boiss.) Mattf. The vegetative morphology of this subspecies is somewhat intermediate between A. nordmanniana and A. cephalonica. The branchlets are glabrous and the leaves are small with an acute apex. Subsp. nordmanniana has pubescent branchlets and leaves with an emarginate apex. The cones are very similar to those of the type subspecies, though the bract scales and associated cusps may be smaller. Davis et al. 1965, Farjon 1990. Distribution TURKEY: western mountains, Kaz Dag, Ulu Dag. Habitat North-facing mountain slopes between 900 and 2100 m asl. Soils calcareous. USDA Hardiness Zone 5. Conservation status Lower Risk. Illustration NT56. Taxonomic note Abies bornmuelleriana (placed in synonymy with A. nordmanniana subsp. equi-trojani by Farjon 2001) is a puzzling taxon, as it shares characters with both subspecies. As in the nominate subspecies, the leaves have an emarginate apex, yet like subsp. equi-trojani, the branchlets are glabrous. Unlike either subspecies, the buds of A. bornmuelleriana are resinous (Davis et al. 1965). The distribution of A. bornmuelleriana is intermediate between those of the two subspecies of A. nordmanniana, and it may be the product of hybridisation. Bean (1976a) suggested a hybrid origin for A. bornmuelleriana, but with A. cephalonica as one of the parents.

Plate 61. The Trojan Horse Fir Abies nordmanniana subsp. equi-trojani (here at Kew) quickly forms an attractive tree. Image J. Grimshaw.

The Trojan Horse Fir has inveigled itself into numerous collections over the years and seems to be as tolerant as the familiar subsp. nordmanniana, and just as magnificent. In the wild it can become a very large tree, field notes from the Flanagan & Pitman expedition to Turkey in 1990 reporting specimens of 35 m growing with Fagus orientalis at 1650 m on the southern slopes of Ulu Dag in Bursa Province. Specimens from this provenance (TURX 20) are in cultivation at Wakehurst Place where they are growing steadily into tidy young trees, of about 5 m in 2005. The largest known in cultivation in the British Isles is a 22.5 m tall tree (dbh 60 cm) at Rowallane, Co. Down, measured in 2000 (TROI). It does well at Rogów Arboretum, but would seem to be a bit slower-growing there than in England, as although trees of Turkish origin planted in 1981 are dense and well shaped they are still only 5 m tall (P. Banaszczak, pers. comm. 2007). On the other side of the Atlantic, there is a beautiful specimen of approximately 15 m at the Morris Arboretum, accessioned as wild-origin seed in 1956 and now looking impressive, with branches sweeping to the ground. A. nordmanniana f. macrolepis Viguié & Gaussen K42 A. numidica de Lannoy ex Carrière B161, S28, K42 A. oaxacana (NOW A. hickelii var. oaxacana (Martínez) Farjon & Silba) K43

Section II. Species Accounts

A. pardei (NOW A. alba Mill.) B162, K43 A. pindrow (Royle ex D. Don) Royle B162, S29, K43

Abies

57

A. pindrow var. brevifolia Dallim. & A.B. Jacks. B163, S29, K43 A. pindrow var. intermedia Henry B163, S29, K43

Abies pinsapo Boiss.

Pinsapo, Spanish Fir

This species was described by Bean (B163, S29) and Krüssmann (K43). A key to the varieties is provided below. 1a. Vegetative buds not resinous; Morocco (Mt. Tazaot) .................................................... var. tazaotana 1b. Vegetative buds very resinous or slightly resinous ............................................................................ 2 2a. Leaf arrangement pectinate, flat; leaves with faint groove, and fewer stomata on the upper surface, apex acuminate; cones large, 10–18 cm long; Morocco (Rif Mts.) ..................................................... var. marocana 2b. Leaf arrangement perpendicular from shoots, bristly; leaves without groove, several rows of stomata on the upper surface, apex obtuse; cones smaller, 9–14 cm long; Spain (Andalucía) .................................... var. pinsapo

A. pinsapo f. glauca (Carrière) Beissn. B164

Abies pinsapo var. marocana (Trab.) Ceballos & Bolaño Syn. A. marocana Trab. Compared with var. pinsapo, var. marocana has larger, less resinous buds, the leaf arrangement is slightly flatter and pectinate, the leaf apices more acute or acuminate, and there are fewer stomata on the upper surface. The distinctive spiky texture of the leaves is very different from that in the type variety (Laver 2003). The cones are slightly larger (10–18 × 3.5–5 cm vs. 9–14 × 3–4 cm in var. pinsapo) and the bract scales are subulate rather than oblong. Farjon 1990. Distribution MOROCCO: western Rif Mts. (Mts. Tissouka, Mago, Kraa and Bab Rouida). Habitat North-facing slopes between 1400 and 2100 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk, though vulnerable to overgrazing. Illustration Liu 1971, Farjon 1990; NT44, NT45.

Abies pinsapo var. tazaotana (Côzar ex Villar) Pourtet This variety differs from the type in that the vegetative buds are not resinous, and the bract scales are subulate. Farjon 1990. Distribution MOROCCO: Mt. Tazaot. Habitat North-facing slopes between 1600 and 2000 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable. While common locally, this variety has a restricted distribution. Illustration Liu 1971; NT57.

All three varieties are cultivated at Wakehurst Place, where they can be usefully compared. As seen there, var. pinsapo with its short, densely spaced needles is the most distinct, the other two being much closer in appearance to each other than to var. pinsapo. The Wakehurst specimen of var. tazaotana, a conical young tree 3.5 m tall in 2005, was raised from seed collected by B. Valdes (no. 2063) in 1992 at 1600 m on Jebel Lakraa, on the way to the type locality on Jebel Tassaot. Also growing at Wakehurst Place are plants labelled var. marocana, grown from collections again made by Valdes (no. 2228) on Jebel Lakraa, but on a different part of the mountain. These have leaves intermediate in length and density of placement between those of var. pinsapo and of the single specimen of var. tazaotana (which has the longest and least closely spaced of the three, radiating from all round the stem like the quills of an angry porcupine). At Kew, however, there is a specimen of var. marocana with short, densely packed leaves, closely resembling those of var. pinsapo. This has an equally

Plate 62. Long, sharp leaves of Abies pinsapo var. tazaotana (B. Valdes 2228). Leaf length is not, however, a reliable character to separate the varieties of this species. Image J. Grimshaw.

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authentic provenance, having been collected on Mount Tisouka, near Chechaouen in 1982, by an Arnold Arboretum expedition. It is making a good tree. There is clearly considerable variation in wild populations in Morocco, and names should perhaps be regarded with some suspicion. An old tree of unknown origin but considered to be var. marocana in the Hillier Gardens was measured at 15.5 m (47 cm dbh) in 2002 (Sir Harold Hillier Gardens database). As might be expected of a species from Spain and the Atlas, it will do well in drier conditions than most firs, but though it will grow on chalk, good soil will give the best results (Horsman 1984, Rushforth 1987a). A. procera Rehder B164, S30, K43 A. recurvata Mast. B165, S30, K44 A. recurvata var. ernestii (Rehder) C.T. Kuan S31 A. religiosa (Kunth) Schltdl. & Cham. B166, S31, K44

A. religiosa var. glaucescens (NOW A. religiosa (Kunth) Schltdl. & Cham.) K44 A. rolii (NOW A. forrestii var. ferreana (Bordères & Gaussen) Farjon & Silba, NT52) K44

Abies sachalinensis (F. Schmidt) Mast.

Sakhalin Fir

This species was described by Bean (B166, S32) and Krüssmann (K44), but three varieties have since been described. A key to these is provided below. 1a. Bract scales included; Japan (Hokkaido), Russian Federation (Sakhalin) ..................... var. nemorensis 1b. Bract scales exserted ....................................................................................................................... 2 2a. Resin canals marginal; Russian Federation (Kamchatka) ................................................... var. gracilis 2b. Resin canals medial ......................................................................................................................... 3 3a. Bark smooth, whitish grey; cones pale purple with strongly exserted bracts, bracts pale green when immature, turning pale brown at maturity; Japan (Hokkaido), Russian Federation (Sakhalin) ...................................................... var. mayriana 3b. Bark with resin blisters, grey-brown; cones dark purple with partially exserted bracts, bracts reddish when immature, turning dark brown at maturity; Japan (Hokkaido), Russian Federation (Kuril Is., Sakhalin) ..................... var. sachalinensis

Abies sachalinensis var. gracilis (Kom.) Farjon This variety has flatter leaves than the type, and marginal (not medial) resin canals. Farjon 1990. Distribution RUSSIAN FEDERATION: eastern Kamchatka, Semyachik valley. Habitat Between 0 and 1650 m asl. Soils are well drained, but with year-round moistness. USDA Hardiness Zone 5. Conservation status Vulnerable. It has an extremely limited distribution.

Abies sachalinensis var. mayriana Miyabe & Kudô Var. mayriana has whitish grey (rather than grey-brown) bark and the cones are lighter in colour than the typical dark purple. The bract scales are green initially, but mature to pale brown, and are exserted to a greater degree than in the type. Farjon 1990. Distribution JAPAN: Hokkaido; RUSSIAN FEDERATION: Sakhalin. Habitat As for var. gracilis. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Liu 1971, Farjon 1990; NT32. Cross-reference K44.

Abies sachalinensis var. nemorensis Mayr The only character that distinguishes this variety from the type and from var. mayriana is the bract scales, which are included. Farjon 1990. Distribution JAPAN: Hokkaido; RUSSIAN FEDERATION: Kuril Is., Sakhalin. Habitat As for var. gracilis. USDA Hardiness Zone 5. Conservation status Not evaluated. Cross-reference K44.

Section II. Species Accounts

Abies

59

The rather trivial technical characters that distinguish the various subspecies of Abies sachalinensis are probably much less important to horticulturists than the provenance of the material they are trying to grow. In habitat on Hokkaido, A. sachalinensis is described as a ‘grand’ tree (Flanagan & Kirkham 2005), but this is not the general experience in cultivation. The species as a whole has the unfortunate habit of flushing early and suffering frost damage to the new shoots in most years, with the consequence that young trees seldom seem to ‘get away’, even in conditions that might be assumed to be favourable for them. As an example, two specimens of var. gracilis growing at Dawyck are both under 50 cm, despite having been accessioned in 1992 and 1993 from wild-collected material. At Howick, even though frost damage has been slight, var. gracilis was very slow to get going after planting in 1997, but has now achieved 1.2 m (C. Howick, pers. comm. 2007). The situation is similar in most places where A. sachalinensis is grown, with the exception of Benmore where it seems to grow better than elsewhere. Eventually, however, enough growth is put on to produce a young tree of sufficient height to escape the effects of ground frosts and begin to grow away more satisfactorily. This has been observed in var. mayriana both at Dawyck (from Sakhalin, ESUS 210, collected in 1996, 1.2 m in 2006) and at Thenford House (of unknown origin, 2 m in 2006), where young trees have succeeded in making a good leader and are beginning to grow strongly – although their history of false starts is clearly visible. Where this has not happened, as with plants of ESUS 210 at Kew, they remain very small and stunted. Even in a continental climate, as at Rogów, frost damage occurs to new shoots and the trees (of var. mayriana) are very slow-growing (P. Banaszczak, pers. comm. 2007).

Abies sibirica Ledeb.

Siberian Fir

Tree to 40 m, to 1 m dbh. Bark smooth, grey-brown with numerous resin blisters in young trees, breaking into plates in older trees. Crown narrow, pyramidical or conical. Branchlets slender, firm, yellowish grey or pale brown, then grey with age; densely pubescent though glabrous later; leaf scars small, circular; vegetative buds densely resinous. Leaves spirally arranged, 1.3–3 cm × 0.15 cm, apex emarginate to acute. Male strobili lateral and crowded on the underside of the shoot, 1.5 cm long, yellow with red microsporophylls. Female cones erect, nearly sessile, cylindrical, apex obtuse, 5–7.5 × 2.5–3.5 cm, purple-blue when immature, blue-brown or greenish brown when mature. Seed scales flabellate, 1–1.2 cm long. Bract scales included, short and rounded, 0.8 cm long with a tiny cusp. Seeds brown and cuneate, wings broad-cuneate, 1–1.2 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Xinjiang; RUSSIAN FEDERATION: Amur, Buryatiya, Chita, Irkutsk, Itay, Khabarovsk, Krasnoyarsk, Tuva, West Siberia, Yakutiya. Habitat One of the characteristic tree species of the taiga, together with Picea obovata and Larix gmelinii. Occurs between 0 and 2000 m asl, on alluvial (and calcareous) soils. USDA Hardiness Zone 2. Conservation status Lower Risk. Illustration Liu 1971, Farjon 1990, Fu et al. 1999c; NT44, NT59. Cross-references B160, K44.

Bean’s rather cursory note on Abies sibirica (1976a) was probably appropriate, as this species does not do well in the British Isles and needs a colder climate to thrive. The new growth is very prone to spring frosts, which cripple the tree early in life. In the British Isles a few specimens have straggled up to 10 m and some even beyond this, the largest recorded being a 14 m (30 cm dbh)

Plate 63. Abies sibirica, dressed appropriately, at Rogów Arboretum, Poland. Image P. Banaszczak.

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tree at Abbeyleix, Co. Laois, although this was in a poor state when measured in 2000 (TROI). The species may be worth trying in the United States in the upper Midwest, or in Canada, but the experience at Rogów is that although it can be fast-growing it is weak and short-lived, with damage to new shoots from spring frosts (P. Banaszczak, pers. comm. 2007).

Abies sibirica subsp. semenovii (B. Fedtsch.) Farjon This subspecies has yellow-brown branchlets with prominent ridges and grooves, and the buds are less resinous than in the type. The resin canals are marginal (medial in subsp. sibirica) and the cones are yellowish brown, with broader bract scales. Farjon 1990. Distribution KYRGYZSTAN: western Tien Shan. Habitat North slopes of mountains or steep valleys between 1300 and 2850 m asl. USDA Hardiness Zone 2. Conservation status Vulnerable. Illustration Liu 1971.

Seed of subsp. semenovii collected by John Silba in the Tien Shan in 1989 is the only introduction of this taxon that we can trace, but material seems to have been disseminated quite widely. For Keith Rushforth (pers. comm. 2007) in Devon it has proved hardier than subsp. sibirica, which has died out for him, subsp. semenovii by contrast having grown, slowly, to almost 2 m (in 15 years). At Howick two specimens planted in 1992 are about 2.5 m tall, and although not damaged by frost, have been reluctant to form good leaders (C. Howick, pers. comm. 2007). There is also a small tree at Wakehurst Place. A. spectabilis (D. Don) Spach B167, S32, K45 A. spectabilis var. brevifolia (NOW A. spectabilis (D. Don) Spach) S33, K45 A. squamata Mast. B167, S33, K45

A. sutchuenensis (NOW A. fargesii var. sutchuenensis Franch.) B168, K45 A. tacanensis (NOW A. guatemalensis Rehder var. guatemalensis, NT53) K45 A. ×vasconcellosiana Franco K45

Abies veitchii Lindl. Plate 64. Conspicuous resin blisters on the stem of Abies veitchii var. sikokiana at Wakehurst Place. Image J. Grimshaw.

Veitch Fir

Abies veitchii was described by Bean (B169, S33) and Krüssmann (K45). A. veitchii var. nikkoensis (NOW A. veitchii Lindl. var. veitchii) K45 A. veitchii var. olivacea (NOW A. veitchii Lindl. var. veitchii) K45

Abies veitchii var. sikokiana (Nakai) Kusaka This variety has shorter leaves (0.5–2 cm) than typical (3 cm), and smaller cones (3–4 × 1.5–2 cm, vs. 6–8 cm). The cones are ellipsoidal, and only the cusps of the bracts are exserted. Farjon 1990. Distribution JAPAN: Shikoku. Habitat Subalpine forest, between 800 and 2000 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk. While common locally, distribution restricted. Illustration Liu 1971; NT60.

Abies veitchii is a widely successful species and there seems to be no reason why var. sikokiana should not also thrive in many different conditions. It is not common in cultivation, but there are specimens in some of the major collections in Europe and North America. In May 2006 a slightly leaning tree of 10 m in the University of Minnesota Landscape Arboretum was in fully fertile mode, bearing a lot of small pendulous female cones coloured reddish maroon, overcast with blue, while the male cones were

Section II. Species Accounts

Abies

61

simultaneously shedding their pollen. With the new light green shoots emerging, the tree looked very attractive in this state. At Wakehurst Place a tree of cultivated origin has grown to 8 m since accession in 1989. Its trunk bears many resin blisters, so numerous towards its base that it seems to be wearing wrinkled stockings. The short leaves are distinctly upward-pointing.

Abies vejarii Martínez

Vejar Fir

Tree to 40 m, 0.8–1 m dbh. Bark smooth, thin, grey, becoming rough, scaly and grey-brown in older trees. Crown broadly conical or pyramidical, old trees having a somewhat open crown. Branchlets slender, firm, purplish red, becoming reddish or orange-brown with age, leaf scars circular, vegetative buds very resinous. Leaves glaucous-green, spirally arranged, 1–2 × 0.1–0.2 cm, slightly grooved, apex acute. Male strobili lateral, crowded, short (~0.5 cm), almost globular, with reddish microsporophylls. Female cones erect, shortpedunculate, barrel-shaped, apex obtuse or truncate, 6–12 × 4–6 cm, dark purple when immature, purple or blue with a hint of brown when mature, resinous. Seed scales fan-shaped to cuneate, 1.5–2 cm long. Bract scales spathulate, 0.8–1 cm long, with triangular cusp, exserted. Seeds brown, cuneate, wings cuneate or triangular, 1.5 × 1.2 cm, purplish brown. Farjon 1990. Distribution MEXICO: Coahuila, Nuevo León, Tamaulipas. Habitat Steep mountain slopes between 2000 and 2200 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Liu 1971, Farjon 1990; NT61. Crossreferences B166, S31, K45. Taxonomic note Abies vejarii var. macrocarpa Martínez has larger cones, but only the nominate variety is in cultivation.

Abies vejarii is perhaps the most impressive of the recently introduced firs, with good trees to be found in several British arboreta. The finest is that at Thenford House, where it has been growing alongside an excellent Quercus semecarpifolia since both were presented by Keith Rushforth in 1986 (M. Heseltine, pers. comm. 2006). The Abies is growing incredibly well, and had reached approximately 20 m (43 cm dbh) by 2006, forming a magnificent cylindrical column of deep-green growth to its base. The unripe cones are light green, borne only at the top of the tree. There is another good specimen at Kew (15 m, 25 cm dbh), grown from KR 515 in 1985 and also thriving. Rushforth’s collection was made in 1984 in the Coahuila–Nuevo León part of its range (Clarke 1988), but the first introduction was made in 1962, according to Mitchell (1972), although no details are provided. It was also collected by Michael Frankis (no. 151) at 3180 m on Cerro Potosí in 1991, trees from which source are growing at the Hillier Gardens and Tregrehan. A good specimen of A. vejarii has also been seen at Mount Usher, and the distribution of specimens over 10 m recorded by TROBI suggests that this is a very adaptable and fast-growing species. Its tolerance of the comparatively warm, dry conditions of southern and south-central England is particularly useful. It is also cultivated in the United States: for example, at the Washington Park Arboretum, where a tree planted in 1970 (from a commercial source) is now a shapely 18 m tall, although has yet to fruit. This specimen has not suffered any winter damage, and appears to be very well suited to the Seattle climate (R. Hitchin, pers. comm. 2007).

A. vejarii var. mexicana (NOW A. mexicana Martínez OR A. vejarii subsp. mexicana (Martínez) Farjon; NT45) K46

A. ×vilmorinii Masters B164, K46 A. yuana (NOW A. forrestii var. ferreana (Bordères & Gaussen) Farjon & Silba, NT52) K46

Plate 65. The foliage of Abies vejarii can vary from greyish, as here, to dark green. Image R. Hitchin.

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Acacia

New Trees

1 cm 1 cm

B

A 1 cm

C

D

1 cm

Section II. Species Accounts

Acacia

63

LEGUMINOSAE (MIMOSOIDEAE)

ACACIA

Mill.

Syn. Acaciella Britton & Rose, Racosperma Mart., Senegalia Raf., Vachellia Wight & Arn.

Acacias, Blackwoods, Wattles In its traditional sense, Acacia is a huge genus of over 1500 species, found throughout the warmer parts of the world. The greatest diversity is in Australia which has over 950 species, making it the largest genus of vascular plants in that country. However, Acacia is also abundant in Africa (> 130 spp.), Madagascar (c.100 spp.), the Americas (c. 270 spp.) and the Asia–Pacific region (> 55 spp.). Acacia species are primarily trees and shrubs, but also, rarely, lianas or herbs. The branches are slender or thick and contorted, rarely winged, armed or unarmed; Acacia spines may be prickles (curved and distributed along the stems) or modified stipules (usually straight and restricted to the nodes). The leaves are alternate, bipinnate or reduced to phyllodes; rarely scalelike or completely absent. Phyllodes have the appearance of simple entire leaves, but are actually derived from the petiole; they may be foliose or reduced to spines. Foliar glands are present on the petiole (and sometimes on the rachis also) in most species. The inflorescences are axillary, simple or racemose, and rarely paniculate. The flowers are arranged into globular heads or cylindrical spikes and are typically yellow, cream or white, rarely red; they may be unisexual or hermaphrodite, and 4- or 5-merous. The petals are greatly reduced or absent and have been largely replaced in the role of attractant by the numerous stamens. The fruit is a legume (pod) and these are extremely variable across the genus; they may be dehiscent or indehiscent (Chapman et al. 2001a, 2001b, Lewis et al. 2005). Many Acacia species have symbiotic relationships with ants, which protect the plants from herbivory. The ants are rewarded with the provision of food (for example, extrafloral nectaries, protein packages on leaflet tips) and shelter (swollen thorns in which the ants can nest). It is generally accepted that Acacia in its current format is an assemblage of disparate groups that should be split into several segregate genera. However, the various solutions suggested for its dismemberment have caused major disagreements. One proposal, submitted to the International Botanical Congress in Vienna (2005), is that the name Acacia be conserved for all species in subgenus Phyllodineae, which would include all but nine of the Australian species (Orchard & Maslin 2003) – but not the type species of the genus, namely the African A. nilotica (L.) Delile. This proposal greatly reduces the number of name changes in prospect (as most species are Australian), but would mean that all African Acacia species would fall into either Vachellia (about half the species) or Senegalia – a move not popular with African botanists, who consider this to be an unwarranted reversal of the

Figure 7 (opposite). Acacia pataczekii: habit with flowers (A); fruit (B). A. spectabilis: habit with flowers (C); fruit (D).

Plate 66. Acacia pods and seeds are an important food resource for many large African mammals. This is Acacia karroo. Image G. Lewis.

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New Trees

normal rules of botany wherein the type species has precedence (Moll 2005). American species would fall into Vachellia, Senegalia, Acaciella and one other as yet unnamed genus. The proposal was accepted by the Congress, but it remains to be seen whether the new names enter into common usage. Acacias are iconic trees for many parts of the world, hence the passions aroused by the Australian name grab. The Australian national flower is the Golden Wattle Acacia pycnantha, while in Africa thorn trees epitomise the bush: brutal, but beautiful. Sadly the African species are mostly too tender for outdoor cultivation in our area, although they flourish along the Mediterranean coast and in southern California. For horticultural purposes the Australian wattles fall into two groups: those with leaflike phyllodes, of which A. melanoxylon R. Br. is probably the best known, and those with pinnate leaves, exemplified by A. baileyana F. v. Muell. and A. dealbata Link. The generality with which A. baileyana is now grown in England (with an Award of Garden Merit from the Royal Horticultural Society) is in extraordinary contrast with the notes in the last edition of Bean (1976a), where a specimen that ‘once grew’ in Cornwall is the only one cited outside Ireland. Rising temperatures and generally milder winters have undoubtedly played a part in this, but perhaps some thought should also be given to the possibility that seed is now imported from colder locations in Australia, and that home-grown seed from surviving plants favours the hardier individuals. One of the most beautiful small trees that has become freely available recently is A. baileyana ‘Purpurea’, a stunner in which deep-purple pigmentation combines with the bluish colour of the leaves to great effect. It fully deserves its Award of Garden Merit. It is probable that other Acacia species will become available from time to time as seed is imported and crops are raised by nurseries. There are also a few shrubby species, already in cultivation, that are not covered here. For such plants the Mimosaceae volume of Flora of Australia (Chapman et al. 2001a, 2001b) should be consulted, and there is extensive coverage in the New RHS Dictionary of Gardening (Huxley et al. 1992). The website of the WorldWideWattle project (www.worldwidewattle.com) is also very comprehensive and well illustrated. Several wattle species are weedy and invasive – causing massive problems in South Africa, for example – and this should be borne in mind, even if this scenario is improbable in most of our area. In general Acacia prefers a lime-free soil, and good drainage and full sun are essential. Seed provides the best method of propagation, although semi-ripe cuttings can be taken and rooted with bottom heat. Seeds should be scarified or soaked before sowing in warm conditions. Transplant with care and plant in their final positions when quite young; pot-bound plants should be avoided.

A. acinacea Lindl. B173 A. alata R. Br. K55

A. armata (NOW A. paradoxa DC.) B172, K55 A. baileyana F. Muell. B173, K55

Acacia caven (Molina) Molina

Aromo, Caven, Espinal

Syn. Vachellia caven (Molina) Seigler & Ebinger Tree or shrub to 5 m, densely branched. Branchlets with white stipular spines, 1–3 cm long. Leaves bipinnate, often in fascicles, bright green; pinnae 3–8(–10) pairs; pinnules 12–30 pairs, linear, 0.1–0.4 × 0.1 cm; rachis with distinct gland at point of attachment of first pinnae. Inflorescence simple, axillary, with two to three heads per node; heads globular, 1–2 cm diameter, bright yellow, fragrant. Flowers densely packed,

Section II. Species Accounts

Acacia

5-merous, petals larger than sepals, stamens numerous. Legume cylindrical, 3–7 × 1.2–2.5 cm, leathery, dark brown or black. Flowering in spring, before the foliage emerges. Cialdella 1984, 1997. Distribution ARGENTINA; BOLIVIA; CHILE; PARAGUAY. Habitat Tolerant of a variety of habitats, though often found in coastal areas. Resistant to desertification; often invasive and difficult to eradicate (in humid areas). USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT65, NT908.

Acacia caven is a fast-growing small tree which soon takes on a characterful appearance, its somewhat contorted trunks supporting a rounded canopy of thorny branches. The thorns are whitish and very sharp. The pinnate leaves are semi-deciduous to a degree that is probably dependent on water availability, but are fewest by early spring when the tree comes into flower. The deep-yellow flowers are produced in great abundance and are very fragrant, scenting the air around the tree. Although recommended for desert or semi-arid conditions in southern parts of the United States (Arid Zone Trees 2000–2008), A. caven is adaptable and grows successfully at Kew. The tree there is from a collection made by Watson & Pern (WAPE 6325) in low Andean foothills near Chillán, Bío-Bío, Chile, in 1988. Trees from the same collection also grow at the University of California Botanical Garden at Berkeley. A. cultriformis G. Don B176, K55

Acacia dealbata Link

Silver Wattle

Syn. Racosperma dealbatum (Link) Pedley

This species was described by Bean (B173) and Krüssmann (K55).

Acacia dealbata subsp. subalpina Tindale & Kodela This subspecies differs from the type in having shorter leaves (1.5–8.5 vs. 5–12 cm), and shorter pinnae (0.5–2.5 vs. 1.5–5.5 cm) and pinnules (0.1–0.4 vs. 0.15–0.6 cm). The flowering heads have fewer flowers (13–24 vs. 22–42) and the plant has a smaller stature, being a shrub or small tree to 5 m, rarely 10 m (vs. 30 m in subsp. dealbata). Chapman et al. 2001a, 2001b, Kodela & Harden 2001. Distribution AUSTRALIA: Australian Capital Territory, New South Wales, Victoria. Habitat Tall, open forest or woodland on mountain ridges, slopes and in gullies with streams. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT7.

Described only in 2001, Acacia dealbata subsp. subalpina is of great interest to gardeners in temperate areas, as it represents the highest-altitude provenance of the species. For most practical horticultural purposes it is very similar to typical A. dealbata in physical appearance, although subsp. subalpina is supposed to be shorter and smaller in its parts, but the fact that its range is principally above 700 m in the mountains of southeastern Australia (Kodela & Tindale 2001) is highly significant in terms of its potential extra hardiness. Subsp. subalpina has become widely cultivated, and is freely available in commerce, but in the United Kingdom at least its supposed advantage has yet to be put to the test, and Hogan (2008) has found that other high-altitude forms from mainland Australia are hardier. Its supposedly more compact stature may also be an advantage in smaller gardens, although a specimen in the Oxford Botanic Garden had reached 6 m before it was removed in 2007 (S. Andrews, pers. comm. 2007).

Plate 67. Masses of deepyellow flower clusters appear on the branches of Acacia caven in spring. Image M. Gardner.

65

66

Acacia

New Trees

A. decipiens (NOW A. truncata (Burm. f.) Hort. ex Hoffmanns.) K56 A. decurrens Willd. B174, K56 A. diffusa (NOW A. genistifolia Link) B174, K56 A. farnesiana (L.) Willd. K56 A. horrida (L.) Willd. K56 A. juniperina (NOW A. ulicifolia (Salisb.) Court) B174

Acacia karroo Hayne

Sweet Thorn

Syn. A. natalitia E. Mey., Vachellia karroo (Hayne) Banfi & Galasso Tree to 15 m. Bark rough, dark reddish brown to black. Branchlets glabrous, with inconspicuous reddish glands, epidermis peeling off to reveal rusty red underbark; stipular spines straight, stout, white with dark tips, to 7(–17) cm long; other prickles absent. Leaves bipinnate, small or large gland present at the junction of each pinnae-pair; pinnae (1–)2–7(–9) pairs; pinnules 5–15(–27) pairs, 0.4–0.7 × 0.1–0.3 cm, oblong, glabrous or with minutely ciliate margins, apex obtuse to subacute. Inflorescence heads globular, 0.8– 1.2 cm diameter, bright golden-yellow and fragrant; individual globes are borne in the axils of the current season’s growth; but are occasionally clustered along leafless stems, giving the appearance of a terminal raceme. Flowers densely packed, 5-merous, petals larger than sepals, stamens numerous. Legume dehiscent, linear, ± falcate, 6–16 × 0.6–1 cm, thinly woody, slightly constricted between seeds. Flowering October to February, fruits ripening from January onwards (South Africa). Brenan 1970, Coates Palgrave 1990. Distribution ANGOLA; BOTSWANA; LESOTHO; MALAWI; MOZAMBIQUE; NAMIBIA; SOUTH AFRICA; SWAZILAND; ZAMBIA; ZIMBABWE. Habitat Woodland, wooded grassland, coastal scrub between 0 and 1520 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT66.

Plate 68. Vicious spines reduce browsing on young plants of the classic African savanna tree Acacia karroo. Image J.R.P. van Hoey Smith.

One of the quintessential trees of the African savannas and veld, Acacia karroo is considered in South Africa to be an indicator of fertile conditions and good grazing, and the supplier of many useful products (Coates Palgrave 1990). In Australia, on the other hand, it is classed as a ‘noxious weed’ – just as many Australian wattles are in South Africa. The occurrence of A. karroo on the South African Highveld exposes it in the wild to frost and this hardiness is persistent in at least some provenances. It is growing happily in front of the Curvilinear Range at Glasnevin, showing its characteristic reddish bark and gleaming white spines very well. It is available from several UK nurseries, but curiously no significant specimens have been traced in Britain in research for the current work. It is cultivated in California, and naturalised in southern Spain. A. longifolia (Andrews) Willd. B174, K56 A. longifolia var. sophorae (Labill.) Court B175 A. longifolia var. floribunda (NOW A. floribunda (Vent.) Willd.) B175 A. melanoxylon R. Br. B175, K56 A. mucronata H.L. Wendl. B175, S34, K56

Acacia obliquinervia Tindale

Mountain Hickory Wattle

Shrub or tree 1–15 m. Branchlets glabrous, glaucous. Leaves reduced to phyllodes; phyllodes obovate to narrowly oblanceolate, narrowed and often recurved at the base, 5–17 × 1.5–5 cm, glabrous, greyish green to glaucous, penninerved. Inflorescence axillary, racemose to paniculate, main axes 2–10 cm long; heads

Section II. Species Accounts

Acacia

67

globular, with 20–35 flowers, bright golden- or lemon-yellow. Flowers densely packed, 5-merous. Legume oblong, flat, slightly raised over seeds, 4–15 × 1.2–2.5 cm, papery to thinly leathery, slightly glaucous. Seeds shiny black, with aril. Flowering in spring. Chapman et al. 2001a, 2001b. Distribution AUSTRALIA: Australian Capital Territory, New South Wales, Victoria. Habitat Montane forest and woodland between 500 and 1700 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Ross & Irons 1997.

Acacia obliquinervia is one of the most attractive of phyllodic wattles, forming a neatly shaped tree that is densely clad in broad phyllodes. These are often greyish green but some trees are an excellent glaucous-blue. Leaves on young shoots are reddish at first. The bright yellow flowers appear in spring and contrast well with the foliage. Though not yet well known in cultivation, A. obliquinervia is one of the most hardy of the genus. In the wild it has been known to survive –16 ºC and in cultivation it seems to be able to cope with similar temperatures, though young trees have been cut to the ground by –13.5 ºC in Germany (Ross & Irons 1997). It is in cultivation throughout Europe and in North America wherever climatic conditions are appropriate, and is rated by enthusiasts as a superb new species to try (S. Hogan, pers. comm. 2007), but every effort should be made to obtain or select the best glaucous forms from batches of seedlings. Germination is sporadic after the standard boiling water treatment, and a cold stratification period may be necessary to achieve good germination rates (Ross & Irons 1997). It is very sensitive to over-watering (Wrigley & Fagg 1996).

Acacia pataczekii D.I. Morris

Pataczek’s Wattle, Wally’s Wattle

Shrub or tree to 6 m, freely suckering when disturbed. Branchlets angular to terete, glabrous, dark red and slightly glaucous. Leaves reduced to phyllodes; phyllodes extremely variable, oblong to elliptic to oblanceolate, rarely obovate, 2–6 × 0.8–2 cm, thin and leathery, glabrous, lateral veins obscure, margins entire, apex rounded to acute; phyllodes attached to a stem projection. Inflorescence racemose and axillary, 1.5–10 cm long and flexuous; heads globular with 10–15 lemon-yellow flowers. Flowers densely packed, 5-merous, petals absent, stamens numerous. Legume narrowly oblong, 2.5–4.5 × 0.7–1.1 cm, purplish brown, hard and elastic. Seeds with aril. Flowering in spring. Chapman et al. 2001a, 2001b. Distribution AUSTRALIA: northeast Tasmania. Habitat Understorey tree in eucalypt forests at about 1400 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT62, NT67.

This Tasmanian endemic is well established in the northern hemisphere, even being produced by Dutch wholesale nurseries and thus easily available in Europe (though less so in the United States). States) It is grown in several British gardens, but for many years the best-known specimen in the United Kingdom was one of 6 m that grew behind the former Alpine House at Kew, forming a lovely small tree with dark reddish bark and a compact crown of greyish phyllodes, flowering and fruiting freely. Unfortunately this has been lost under the extension of the Jodrell Laboratory. Another fine tree still grows at Kew, near King William’s Temple. It should be possible to grow A. pataczekii throughout the maritime and milder parts of our area, given a well-drained sunny site.

A. podalyriifolia G. Don B176, K56 A. pravissima F. Muell. B176, S35, K56 A. pulchella R. Br. B176, K56

A. pycnantha Benth. B177, K56 A. retinodes Schltdl. B177, S35, K56 A. riceana Hensl. B177, S35, K56

Plate 69. Acacia pataczekii has acquired the common name Wally’s Wattle, ensuring the double commemoration of its discoverer, Tasmanian Forest Ranger Wally Pataczek. Image K. Gillanders.

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New Trees

Acacia rubida A. Cunn.

Red-stem Wattle

Shrub or tree to 5 m. Branchlets red or reddish brown, glabrous. Leaves reduced to phyllodes, though juvenile bipinnate leaves often present; phyllodes narrowly elliptic to oblanceolate, falcate or straight, 5–20 × 5–25 cm, thin, green to glaucous, though drying to a reddish colour, one prominent longitudinal vein, margins entire or indented at the gland, apex acute or with a hooked tip. Inflorescence racemose and axillary, 2–7 cm long; heads globular with 10–20 light golden flowers. Flowers densely packed, 5-merous, petals absent, stamens numerous. Legume 5–12 × 0.5–0.8 cm, thin and papery or hard and flexible, somewhat glaucous. Seeds with aril. Flowering late spring. Chapman et al. 2001a, 2001b, Kodela & Harden 2001. Distribution AUSTRALIA: Australian Capital Territory, New South Wales, Queensland, Victoria. Habitat Typically near watercourses on a variety of soils including clay and sand, especially in upland areas. USDA Hardiness Zone 9. Conservation status Not evaluated. Taxonomic note Acacia rubida is a variable species. Though usually a small tree, it reaches 13 m or more in some parts of Victoria. A dwarf variant (reaching only 1.5 m) with small phyllodes (4–5 cm long) and spreading hairs on its branchlets occurs in parts of New South Wales (Chapman et al. 2001a, 2001b).

A comparatively small and slow-growing tree, Acacia rubida would seem to be an ideal choice for warm gardens where space is limited but an interesting and architectural plant is needed. Its long shoots carry the leaves more or less perpendicularly to the stem, and the bright yellow flowers appear amongst them. The stems are always reddish, but this coloration intensifies in winter and may also spread to the leaves. It is widely grown in southern Britain, at least, and in the western United States. States

Acacia spectabilis A. Cunn. ex Benth.

Glory Wattle, Mudgee Wattle

Syn. Racosperma spectabile (A. Cunn. ex Benth.) Pedley Shrub or tree to 6 m. Branchlets terete or with indistinct ridges, with short hairs or glabrous; young shoots pale, glabrous or shortly pubescent, rarely glaucous-purple. Leaves bipinnate, blue-green and glaucous, 2–8 cm long; pinnae 2–6(–7) pairs, (0.5–)1–3.5 cm long, narrowing towards the base; pinnules (2–)4–8 pairs, narrowly obovate or oblong, 0.7–1.6 × 0.2–0.7 cm, glabrous, with two to three obscure veins, apex rounded or emarginate; petiole distinct, 0.5–1.2 cm long, terete, often with a gland at its apex, glabrous or hairy; rachis glabrous or hairy, usually without glands. Inflorescence elongated axillary racemes, or terminal/axillary panicles; heads globular with 12–20 light golden flowers. Flowers densely packed, 5-merous, petals glaucous, stamens numerous. Legume straight-sided, 4–10(–17) × 1–1.5 cm, thin and leathery, purplish- or blue-brown and glaucous. Flowering July to November, fruiting November to June (Australia). Chapman et al. 2001a, 2001b, Kodela & Harden 2001. Distribution AUSTRALIA: New South Wales, Queensland. Habitat Open forest, scrub or heath with well-drained soils. Often associated with Callitris spp. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT62, NT68.

Plate 70. Acacia spectabilis in full glory. Image Royal Botanic Gardens, Kew.

With its large inflorescences, glaucous foliage and silvery bark, Acacia spectabilis is much appreciated as a garden tree in Australia (Elliot & Jones 1982) and in southern California, but is rare in our region. It is regarded as moderately frost-resistant in Australia (Australian National Botanic Gardens 1972) and should survive in the mildest parts of western Europe and the Pacific Coast. It is grown in Cornwall, and a tree at Tregrehan planted in 1996 is now 3 m tall, after snow damage to the brittle wood (T. Hudson, pers. comm. 2006). It is tolerant of a range of conditions, from quite dry to moist (Elliot & Jones 1982).

A. verticillata (L’Hér.) Willd. B178, K56

Section II. Species Accounts

Acer

69

SAPINDACEAE (formerly ACERACEAE)

ACER

L.

Maples Acer is one of the most significant tree genera of the northern hemisphere. The 156 species occur in North America south to Mexico, in Europe and North Africa, and from the Middle East through the Himalaya to southeastern Asia (de Jong 2002). Though it is primarily a temperate genus, species of Acer occur in tropical Asia, crossing the equator on Java. They are trees or shrubs, grown primarily for their leaves, which display an array of shapes, sizes and colours. Bark is extremely variable and often diagnostic; it may be smooth, ridged or flaky, seldom rough or forming plates, an exception being the coarse exfoliating plates of A. yui. Bud scales are often large and foliose with 2–15 pairs, eventually caducous. The leaves are deciduous or evergreen, opposite and typically palmate with five lobes, although they may be entire or with 3–13 lobes, or they may be pinnate with three, five or rarely seven leaflets. Hairs are

Plate 71. ‘It is a truth universally acknowledged …’ This male Acer sinopurpurascens at Arboretum Trompenburg is certainly in need of a wife (see p. 110). It is easy to forget how attractive the flowers of maples can be. Image J.R.P. van Hoey Smith.

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Acer

New Trees

usually present in the vein axils of the leaf undersides and often elsewhere. Stipules are absent (present in A. saccharum subsp. nigrum). Inflorescences are extremely variable in form – compound or simple, corymbose, paniculate, racemose or umbellate – and are produced in terminal and/or lateral positions. Flowering occurs before or as the leaves emerge. The flowers are hermaphrodite or unisexual (trees sometimes dioecious). They have (four to) five (to six) sepals, (four to) five (to six) petals (rarely none), the sepals and petals sometimes fused together, usually yellowish or green, though some species have contrasting white petals and green or red sepals; (4–)8(–13) stamens, nectaries forming a fleshy disc or ring in the centre of the flower; the stamens may be inserted inside or outside the ring or, more commonly, emerge from the ring itself. The fruit is a two-seeded schizocarp, a dry indehiscent structure that breaks up at maturity into single-seeded sections. These sections each have a single wing and are known as samaras (van Gelderen et al. 1994, de Jong 2002). Development of the samara proceeds directly after flowering, and large but immature fruits are often a conspicuous feature of the trees through the summer. In the following account the entries for fruiting time refer to ripening. Despite the interest of horticulturists, Acer has not been a subject for recent academic botanical study, and a modern revision is urgently needed to clarify the systematic position of many taxa. The taxonomy in this account is generally based on Piet de Jong’s classification in the current standard reference Maples of the World (van Gelderen et al. 1994), although this differs in some respects from other major authorities such as the recently available Flora of China account (Xu et al. 2008); some modifications have been included in the present work on the advice of Peter Gregory, in advance of his own forthcoming book on maples (Gregory, in prep.). A summary table of the infrageneric classification of Acer is provided below, which helps place unfamiliar species with better-known relatives, but for more detail Maples of the World should be consulted. A number of familiar species with multiple subspecific taxa are included, as some of the names are unfamiliar and represent recent collections. For these species simple keys covering the important characters are provided. Almost all species mentioned in this account are illustrated (mostly by colour photographs) in Maples of the World, its companion volume Maples for Gardens (van Gelderen & van Gelderen 1999), and An Illustrated Guide to Maples (le Hardÿ de Beaulieu 2003).

ACER

L.

A guide to the infrageneric classification of Acer (derived from van Gelderen et al. 1994)

Section Parviflora Leaves 3- (sometimes 5- or 7-) lobed, or simple Bud scales 2- (sometimes 3-) paired Inflorescence a large corymb Flower 5-merous

Series Parviflora (e.g. A. nipponicum) Leaves 3- or 5-lobed Inflorescence paniculate-corymbose, with 35–400 flowers Series Distyla (e.g. A. distylum) Leaves simple Inflorescence erect, with 35–70 flowers Series Caudata (e.g. A. caudatum) Leaves 3-, 5- or 7-lobed Inflorescence erect, with 50–200 flowers

Section II. Species Accounts

Section Palmata

Acer

Series Palmata (e.g. A. palmatum, A. japonicum)

Deciduous to evergreen

Leaves 5- to 9- (to 13-) lobed

Leaves 3- to 13-lobed, or simple Bud scales 4-paired

Inflorescence with 5–25 flowers

Inflorescence a terminal or occasionally

71

Series Sinensia (e.g. A. campbellii)

axillary corymb

Leaves 3- to 7-lobed

Flower 5-merous

Inflorescence large, elongated, 20–250 flowers Series Penninervia (e.g. A. laevigatum) Often almost evergreen Leaves simple, leathery in texture Inflorescence large, elongated, 20–250 flowers

Section Wardiana (e.g. A. wardii) Leaves 3-lobed Bud scales 2-paired Inflorescence an upright corymb Section Macrantha (e.g. A. pensylvanicum, A. davidii) Bark often longitudinally striated (‘snakebark’) Leaves simple or 3- to 7-lobed Bud scales 2-paired Inflorescence a terminal or occasionally axillary raceme or corymb Flower 5-merous Section Glabra Leaves simple or 3- to 5-lobed Bud scales 2- to 4-paired Inflorescence a terminal or axillary raceme or corymb, small Flower 4- or 5-merous

Series Glabra (e.g. A. glabrum) Monoecious Leaves 3- to 5-lobed or partially trifoliolate Flower 5-merous

Section Negundo Leaves compound, with 5–7 leaflets Bud scales 2- to 3-paired Inflorescence a raceme or compound raceme, with 15–50 dioecious flowers Flower 4-merous

Series Negundo (e.g. A. negundo) Leaves pinnate Bud scales (2- to) 3-paired Flowers apetalous, on long, pendulous peduncles, appearing before leaves

Series Arguta (e.g. A. stachyophyllum) Dioecious Flower 4-merous

Series Cissifolia (e.g. A. cissifolium) Leaves trifoliolate Bud scales 2-paired Flowers with petals, on long racemes, appearing with leaves Section Indivisa (e.g. A. carpinifolium) Leaves simple, with strongly parallel lateral veins Bud scales 9- to 13-paired Inflorescence terminal or axillary, with 10–20 flowers Flower 4-merous

Plate 72. Acer ceriferum (section Palmata, series Palmata), showing hairs in the axils of the veins on the underside of the leaves. Image P. Banaszczak.

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Acer

New Trees

Section Acer

Series Acer (e.g. A. pseudoplatanus)

Leaves 3- to 5-lobed

Leaves usually 5-lobed

Bud scales 5- to 13-paired Inflorescences terminal or axillary corymbs

Bud scales 5- to 10-paired Inflorescence with 25–150 flowers

Flower 5-merous, but stamens usually 8 Series Monspessulana (e.g. A. monspessulanum) Leaves usually 3-lobed, sometimes simple or 5-lobed Bud scales 8- to 12-paired Inflorescence with 10–50 flowers on pendulous pedicels Series Saccharodendron (e.g. A. saccharum) Leaves 3- to 5- (to 7-) lobed Bud scales 6- to 9-paired Inflorescences terminal, or axillary from leafless buds, 10–60 flowers on pendulous pedicels Section Pentaphylla Series Pentaphylla (e.g. A. pentaphyllum) Often evergreen, sometimes deciduous Leaves 5- to 7-lobed Leaves simple or 3-lobed, sometimes compound Bud scales 4- to 8-paired Inflorescence a terminal or axillary Series Trifida (e.g. A. buergerianum) corymb, with 25–75 flowers Leaves usually more or less evergreen, Flower 5-merous simple to 3-lobed Section Trifoliata Leaves 3-foliolate Bud scales 11- to 15-paired Inflorescence terminal or axillary, usually with 3 flowers, sometimes up to 25, in racemes or corymbs Flower 5- or 6-merous

Series Grisea (e.g. A. griseum) Often with peeling bark

Section Lithocarpa Leaves large, 3- to 5-lobed Bud scales 5- to 12-paired Inflorescence axillary from leafless buds, racemose or corymbose with 10–20 flowers Flower 5-merous

Series Lithocarpa (e.g. A. sterculiaceum) Petioles sometimes lactiferous Bud scales 8- to 12-paired Inflorescences axillary from leafless buds, racemose or corymbose with 10–20 flowers

Series Mandschurica (e.g. A. mandschuricum) Bark not peeling

Series Macrophylla (e.g. A. macrophyllum) Leaves deeply 5-lobed, with lactiferous petioles Bud scales 5- to 8-paired Inflorescences large, with 30–80 flowers in a corymbose panicle Section Platanoidea (e.g. A. platanoides) Leaves 3- to 7-lobed, occasionally simple, petioles lactiferous Bud scales 5- to 8-paired or 6- to 10-paired Inflorescence a terminal or axillary corymb Flower 5-merous Section Pubescentia (e.g. A. pilosum) Leaves 3-lobed, glaucous below Bud scales 6- to 10-paired Inflorescence a terminal or axillary corymb Flower 5-merous

Section II. Species Accounts

Acer

73

Section Ginnala (e.g. A. ginnala) Leaves simple or 3-lobed Bud scales 5- to 10-paired Inflorescence a terminal or axillary corymb Flower 5-merous Section Rubra (e.g. A. rubrum) Leaves 3- to 5-lobed, glaucous below Bud scales 4- to 7-paired Inflorescence a cluster of 5 flowers from axillary buds Flower 5-merous Section Hyptiocarpa (e.g. A. laurinum) Evergreen Leaves simple, margins entire, glaucous below Bud scales 7- to 11-paired Inflorescence an axillary corymb or raceme Flower 5-merous

One of the most important genera of ornamental trees for temperate climates, Acer is deservedly popular and widely grown. As with Quercus there is a huge array of different forms, sizes and adaptations: from the majestic Sycamore A. pseudoplatanus and other temperate giants such as A. saccharinum and A. macrophyllum, to xeri-adapted shrubs such A. hyrcanum subsp. reginae-amaliae, and species like A. laurinum with the classic rain-forest adaptations of leathery evergreen, simple leaves with a long drip-tip. Throughout this diversity the pairs of opposite leaves are a valuable clue in avoiding embarrassing errors of identification. With a few exceptions it is the foliage that provides the principal attraction to gardeners, as maple leaves provide a broad palette of colours throughout the year. The first flush of spring leaves may be red or pink; during the summer there is an impressive range of green shades, and cultivated maples add red, yellow and variegated forms. However, as landscape trees, it is for their often spectacular autumn colours that the maples are most renowned. Enthusiasm for the genus is perhaps most apparent in the popularity of the ‘Japanese maples’, of which the majority of cultivars, selected for their foliage characteristics, are derived from A. palmatum, with some derivatives of A. japonicum and A. shirasawanum. They are sold in huge numbers worldwide, often to be planted in unsuitable sites where they scorch and shrivel, or get frosted shortly after shoot emergence, rather than in the sheltered, rather humid sites they favour. There are, however, more resilient species within section Palmata, such as A. pseudosieboldianum and A. sieboldianum, that have many of the same qualities and deserve more attention than they seem to receive. Another group receiving much attention are the ‘snakebark’ maples of section Macrantha, popular both for the beautiful patterns and colours of their bark, especially in young trees, and their often good autumn colours. Well-known examples include A. davidii and A. pensylvanicum, which in its cultivar ‘Erythrocladum’ has

Plate 73. Autumnal colours in Acer sieboldianum are as good as in any other maple, making it a most desirable small tree. Image J.R.P. van Hoey Smith.

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Acer

Plate 74. Many of the snakebark maple cultivars that have arisen in cultivation are unattributable to species, as in the case of the superb ‘White Tigress’, seen here at the Royal Horticultural Society’s Wisley Garden. Image K. Camelbeke.

Figure 8 (opposite). Acer, branchlets with fruit. Acer cordatum (A); A. oblongum var. itoanum (B); A. laevigatum var. salweenense (C); A. fabri (D); A. calcaratum (E).

New Trees

strikingly red young stems in winter. These two have hybridised in cultivation to give the hybrid group A. ×conspicuum (described in more detail below), selections from which are now amongst the most popular of garden maples, especially in Europe. In recent years a number of snakebark maple cultivars have been selected and named for distinct characteristics of habit, bark pattern, leaf shape or colouring. Some are attributed to A. davidii, but may well be garden hybrids. Two such, distinguished by the Royal Horticultural Society’s Award of Garden Merit, are the George Forrest Group, with green and white bark and simple leaves, and ‘Serpentine’, a small, rather stiff tree with a somewhat sinuous appearance, purplish-tinged bark and rather dark foliage – its red samaras a mark of possible hybridity (L. Banks, pers. comm. 2007). ‘Karmen’ has chocolate-coloured leaves on emergence and darkish green bark. Acer pectinatum subsp. forrestii ‘Sirene’ has dark, purplish-tinged bark with pinkish striations, and the leaves emerge with purple flush before turning dark green. Both of these may also be hybrids. In the United States A. tegmentosum ‘Joe Witt’, selected from a tree in the Washington Park Arboretum, is highly valued for its very ‘white’ stems and yellow autumn colour; it seems to be unknown in Europe. ‘White Tigress’ is another American selection, probably derived in part from A. tegmentosum, but now prowling the world and proving to be a most beautiful tree, with crisp white striations on dark green stems. Members of this section are particularly promiscuous, and as the ‘new’ species described below – such as A. morifolium and A. rubescens – become better known and more widely grown, it seems probable that their genes will become more frequent in the mixing pot and further hybrids will arise. In the absence of wild-origin seed it would seem wisest to propagate individuals of known provenance by cuttings, most of which root readily. The snakebarks are tough, hardy trees in much of western Europe, and in the cooler parts of North America, although they do not flourish in hot and humid or dry conditions, which excludes them from much of the United States. On the American East Coast in particular they are susceptible to a canker (R. Olsen, pers. comm. 2007). In all areas their bark is prone to being scorched in hot sun, and it is therefore advisable to plant them in a situation where they are not exposed to the hottest part of the day. It should be noted that although sometimes described in catalogues as ‘small’ trees, and undeniably charming when young, they are capable of becoming quite large, quite quickly. The evergreen maples with simple leaves are an interesting group for the gardener in milder areas to explore. While most are indubitably tropical or subtropical and decidedly tender, some are surprisingly hardy, even in the eastern United States States. Careful collection from the coldest provenances will be particularly important. Found over a vast tract of southeastern Asia, from Nepal to Laos and Vietnam, and including much of western China, are members of the Acer campbellii complex. This remains poorly understood, both in the wild and in cultivation, although the authors of Maples of the World recognise five separate subspecies of A. campbellii (van Gelderen et al. 1994). It requires a focused study. They are attractive small trees, usually with greenish stems and somewhat leathery three- to seven-pointed leaves, but they have a reputation for not being very hardy. In recent years the group has

Section II. Species Accounts

Acer

75

B A

C

E

D

1 cm

76

Acer

Plate 75. Acer tonkinense probably needs a mild, sheltered garden to thrive, or to be maintained under glass. This young plant was photographed at the Esveld nursery, Boskoop. Image J.R.P. van Hoey Smith.

New Trees

been joined by material from northern Vietnam, distributed quite widely through specialist nurseries in both the United States and Europe as A. campbellii var. fansipanense Gagnep. There is some uncertainty over the validity of this name (it is not listed by IPNI), and the exact status of the material it represents has not been thoroughly investigated. It is said to differ in having narrower leaf lobes and smaller fruits than subsp. campbellii (Ho 2000). This area of northern Vietnam has an extraordinary diversity of series Sinensia, with A. campbellii subsp. campbellii, subsp. flabellatum (and its var. yunnanense) and subsp. wilsonii all growing in the Hoang Lien Son Range, and in the same general region also are found A. chapaense, A. fenzelianum, A. oliverianum and A. tonkinense (P. Wharton, pers. comm. 2007). It would seem wise to attempt the identification of any maple from northern Vietnam with a flexible mind! Probably the majority of specimens labelled var. fansipanense in cultivation derive from collections made by Sue and Bleddyn Wynn-Jones, and sometimes Dan Hinkley as well, from a single tree growing near a campsite at 2710 m on Fan Si Pan (for example, BSWJ 8270, HWJ 569 – although this was sold through Heronswood Nursery as subsp. campbellii) (B. Wynn-Jones, pers. comm. 2007; Crûg Farm Plants 2007–2008, Heronswood Nursery catalogue 2004). Saplings from this provenance have been observed at Hergest Croft and elsewhere, and are certainly attractive and worth cultivating, apparently being reasonably hardy in western Britain and in the Pacific Northwest. They have firm, three- or five-lobed leaves carried on conspicuously red petioles, and as young trees at least the stems remain green to the ground. The leaves flush in various shades of red and brown, and turn a good colour in autumn (Crûg Farm Plants 2007–2008). At Hergest Croft there is one in which the stem is golden-yellow, that deserves propagation (L. Banks, pers. comm. 2007). At lower altitudes (1400–1500 m) the trees can be up to 20 m tall in riparian situations, bearing ‘remarkably large’ leaves with three large forward-pointing lobes and two smaller side lobes (P. Wharton, pers. comm. 2007). Acer is hugely popular in the horticultural world and it is certain that the genus will remain an important target for collectors. Among very recent introductions is A. yui, with unique bark characteristics, collected in Gansu in 2005 by a NACPEC expedition (Aiello 2006). Germination of the seed collected was poor, but a few seedlings are growing steadily at the Morris Arboretum and elsewhere (A. Aiello, pers. comm. 2007). Hybrid maples are relatively rare, but seedlings raised from cultivated material should always be observed carefully for hybrid characters. In addition to those described here a few good garden hybrids are in circulation, among these being A. ×hillieri (A. miyabei × A. cappadocicum), with cultivars ‘West Hill’ and ‘Summergold’. Dirr (1998) mentions the promising development of hybrids of A. maximowiczianum and A. griseum with some excitement, as potentially offering very ornamental trees with good heat tolerance for the southern United States. The cultivars ‘Cinnamon Flake’, ‘Ginzam’ (Gingerbread) and ‘Girard’ are available in the United States, but are not common. It is probable that they originated in the Highland Park Arboretum in Rochester, New York, where there are plants of both parents that date to the beginning of the twentieth century. Young hybrid plants exfoliate in varying degrees, with some approaching the extent seen in A. griseum, but this feature does not develop at such an early age (on seedlings from a controlled cross made at the US National Arboretum, exfoliation started at age 10) and they are therefore less popular with the

Section II. Species Accounts

Acer

nursery trade, despite their greater heat tolerance than A. griseum. At age 19 the USNA seedlings are showing very good bark, but with age it tends to become greyer, with exfoliation confined to smaller patches (R. Olsen, pers. comm. 2007). Maple collections abound, and many arboreta have an excellent range of the species. In the Netherlands the ‘Aceretum’ at the nursery of Firma C. Esveld in Boskoop, owned by the van Gelderen family, has an extremely comprehensive collection, although limited space means that many taxa are not able to grow to full size. Less hardy species are maintained under glass. In Belgium, Herkenrode and Arboretum Wespelaar hold a good range, as does the de Belder property of Hemelrijk. In the United Kingdom, the National Arboretum at Westonbirt holds the National Plant Collection of Japanese maples, but also has a good range of other species. National Plant Collections of ‘other’ maples are held at Hergest Croft, Herefordshire, and at Blagdon, Northumberland, where many species thrive in the cooler conditions of northern England. Over many years a good number of maples have been attempted at the Rogów Arboretum in central Poland, and useful information about their success and hardiness is available (Tumilowicz 2002, Banaszczak 2007). In North America there are good collections of maples at the David C. Lam Asian Garden in Vancouver (mostly of documented wild origin), the Washington Park Arboretum in Seattle and the Arnold Arboretum in Boston, but according to Richard Olsen perhaps the most outstanding collection of hardy maples in the United States is at the Dawes Arboretum in Newark, Ohio – information that unfortunately came too late for it to be used as a source of data for this book. With such diversity in the genus it is difficult to give a simple summary of cultivation requirements, but it is clear that maples do better in cooler, moister sites than in hot or dry localities. Lime tolerance is an issue sometimes discussed, but it may be that a well-prepared, moisture-retaining soil is more important for success than the presence of lime is for failure (although certain species remain firmly calcifuge). Diseases are relatively few, and often superficial without lasting effect (for example, powdery mildew on foliage in late summer), but Verticillium wilt can be troublesome, especially on Japanese maples, and there is usually no option but to remove the affected specimen. Armillaria can be a serious problem in ground already infected with it. Insect pests are more numerous, especially in North America, where several species of moth and sawfly cause serious damage to foliage, and borers penetrate shoots, causing dieback. Aphids can be a problem, often producing large volumes of honeydew that may be a nuisance to objects below the trees, especially when it develops sooty mould. Scale insects also affect Acer, but healthy specimens are usually able to tolerate moderate infestations. Vine Weevil is damaging to potted maples but less significant for specimens already in the ground. Where they are present Grey Squirrels can be a terrible nuisance, often seriously damaging the bark and sometimes girdling the tree in the process. A. acuminatum Wall. ex D. Don B186, S37, K68 A. aidzuense (NOW A. tataricum subsp. aidzuense (Franch.) P.C. de Jong) S41 A. albopurpurascens Hayata S49, K68

A. amplum Rehder (OR A. longipes subsp. amplum (Rehder) P.C. de Jong, NT89) B192, S39, K68 A. amplum subsp. tientaiense (C.K. Schneid.) Y.S. Chen (OR A. longipes subsp. amplum (Rehder) P.C. de Jong, NT89) B192, K68

77

78

Acer

New Trees

A. argutum Maxim. B186, K68 A. barbatum (NOW A. saccharum subsp. floridanum (Chapman) Desmarais) B232 A. barbinerve Maxim. B187, K68

Acer ×bornmuelleri Borbás Shrub or small tree to 8 m, densely branched. Branchlets glabrous, greyish brown. Leaves deciduous, palmately three-lobed, sometimes five-lobed, 2.5–5 × ~8 cm, rather thin and glossy, glabrous or with some sparse hairs; autumn colour limited. Inflorescence terminal, corymbose, lax. Flowers sterile. Samaras similar to those of A. campestre. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution ALBANIA; BOSNIA-HERZEGOVINA; BULGARIA; CROATIA; GREECE; ITALY; MACEDONIA; ROMANIA; SERBIA & MONTENEGRO; SLOVENIA; TURKEY. Habitat As for the parent species. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Cross-reference K68. Taxonomic note This taxon is supposed to be a hybrid between A. campestre and A. monspessulanum – interesting as an example of a hybrid between members of two sections (Platanoidea and Acer, respectively) (van Gelderen et al. 1994) – but the theory that it is a form of A. ×coriaceum has recently been advanced (le Hardÿ de Beaulieu 2003). The story becomes even more complicated since the parentage of A. ×coriaceum is most likely to be A. opalus × A. monspessulanum, rather than A. pseudoplatanus × A. monspessulanum as usually stated (P. Gregory, pers. comm. 2007).

Admitted even by enthusiasts to be of interest to collectors only (van Gelderen & van Gelderen 1999), Acer ×bornmuelleri is a small tree with features tending towards A. monspessulanum. It flowers abundantly in spring (le Hardÿ de Beaulieu 2003). The finest specimen known is that at the Sir Harold Hillier Gardens, 12.3 m tall, 37.8 cm dbh, in 2004. It is only occasionally available but young plants are sometimes encountered, as for example at Thenford House. A. ×boscii Spach K68 A. buergerianum Miq. B187, S37, K68 A. buergerianum var. formosanum (Hayata) Sasaki K69 A. buergerianum var. ningpoense (Hance) Rehder K69 A. buergerianum var. trinerve (NOW A. buergerianum Miq.) B188, K69 A. caesium Wall. ex Brandis B201, S42, K69 A. caesium subsp. giraldii (Pax) A.E. Murray K69

Acer calcaratum Gagnep.

(Sect. Palmata, Ser. Sinensia)

Syn. A. craibianum Delendick, A. osmastonii Gamble Tree 8–10 m, though usually smaller in cultivation. Branchlets glabrous, fresh green and very vigorous. Leaves deciduous, 20–25 × 7.5–11 cm, palmately three-lobed, divided to half or one-third of the length, upper surface dark green and glabrous, lower surface pale green, margins coarsely lobed to entire, apex acute to acuminate; petiole 2–4 cm long. Inflorescence terminal, corymbose. Flowers 5-merous, cream to yellow. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution INDIA: Sikkim; MYANMAR; THAILAND. Habitat Moist forest. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Delendick 1978, van Gelderen & van Gelderen 1999; NT75.

This tender tree was introduced from Thailand to Sydney by the Australian botanist and horticulturist Peter Valder, and from there scions reached Firma C. Esveld in Boskoop, from which source material was distributed to other maple enthusiasts in Europe (J. Harris, pers. comm. 2006). The species survived for a decade at Esveld but was eventually killed by frost, and A. calcaratum was feared lost from cultivation (van Gelderen & van Gelderen 1999). Fortunately this is not the case, as it is grown by James Harris at Mallet Court Nursery, in a polytunnel, where it seeds freely and breeds true, enabling it to be made commercially available – and it is also now grow-

Section II. Species Accounts

Acer

79

ing again at Esveld. Young plants are therefore occasional in cultivation, but require a warm, sheltered position to prosper. The evergreen leaves are rather elegant, and borne on green stems. A. campbellii Hook. f. B188, S37, K70 A. campestre L. B189, S37, K70 A. campestre var. austriacum (NOW A. campestre L.) B189, K70 A. campestre var. hebecarpum DC. K71 A. campestre var. leiocarpum Wallr. K71 A. campestre var. tauricum (Kirchn.) Pax K71 A. capillipes Maxim. B190, S38, K71 A. cappadocicum Gled. B191, S38, K71 A. cappadocicum var. cultratum (NOW A. cappadocicum subsp. sinicum (Rehder) Hand.-Mazz.) B192, S39, K71

Acer caudatifolium Hayata

A. cappadocicum var. indicum (NOW A. cappadocicum Gled. subsp. cappadocicum) K72 A. cappadocicum var. sinicum (NOW A. cappadocicum subsp. sinicum (Rehder) Hand.-Mazz.) B192, S39, K72 A. cappadocicum f. tricaudatum (NOW A. cappadocicum subsp. sinicum var. tricaudatum (Veitch ex Rehder) Rehder) B192, K72 A. carpinifolium Siebold & Zucc. B192, S39, K72 A. catalpifolium (NOW A. longipes subsp. catalpifolium (Rehder) P.C. de Jong, NT89) B192, K72

(Sect. Macrantha)

Kawakami Maple

Syn. A. insulare Makino, A. kawakamii Koidz., A. morrisonense Hayata non H.L. Li Tree to 12 m, though perhaps as tall as 20 m in the wild; densely branched. Bark smooth, green to reddish green with faint white ‘snakebark’ striping. Branchlets slender, glabrous, light green to reddish green. Leaves deciduous, 6–10 × 2.5–5 cm, unlobed or three-lobed (rarely five-lobed), upper surface dark green and glabrous, lower surface pale green and glabrous, but for the tufts of hair in the vein axils, five to eight lateral veins on each side of the midrib, margins double-serrate, apex long-acuminate; petiole 2.5–7 cm long, yellowish green; autumn colour yellow to russet. Inflorescence lateral, racemose, pendulous, 5–7 cm long with 7–15 flowers, unisexual. Flowers 5-merous, 1 cm diameter; sepals purplish, oblong to obovate, shorter than petals; petals white, rhomboidal, inward-curved; stamens eight, inserted outside the nectar disc. Fruiting raceme with 7–17 pairs of samaras; samaras 1.8–2.5 cm long, wing strongly keeled and veined, spreading obtusely or rarely horizontally, reddish, turning straw-coloured when ripe. Fruiting September (Taiwan). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008; Gregory, in prep. Distribution TAIWAN. Habitat Montane forest between 650 and 2500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT79, NT80, NT108. Cross-reference K72.

Acer caudatifolium forms a small tree that, like so many of the snakebark group, retains green stems almost to the ground. It varies somewhat in habit, some trees being upright and rather twiggy, while others are much laxer. An 8 m tree at Tregrehan has an almost weeping shape. The young leaves, which appear very early in the year, are bronzed on emergence, becoming mid-green during the summer and usually fading yellow in autumn. Autumn coloration can be much more interesting, however, Dan Hinkley noting it as ‘one of the most spectacular [maples] in autumn finery’, with red and orange colours in north-central Taiwan (Heronswood Nursery catalogue 2003). The first introductions to Europe were made by James Harris in 1971 (van Gelderen et al. 1994) but these have been supplemented by later introductions, including ETOT 21, 54, 158 from 1992, distributions from Chollipo Arboretum and private collections (for example, BSWJ 3114, DJHT 99018, 99057). It is a frequent species in mixed forest in Taiwan, and variation in appearance and hardiness should be expected.

Plate 76. A fruiting shoot of Acer caudatifolium at Kew, grown from ETOT 54. Image T. Kirkham.

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Acer

Plate 77. The bark of Acer caudatifolium has a sinuous pattern in shades of green, interspersed with many pale lenticels. Image R. Hitchin.

New Trees

Unfortunately A. caudatifolium is rather tender when young, at least in its most familiar form: at Colesbourne Park, Gloucestershire a young plant of 1 m was killed outright by a November frost of –9 ºC in 2005, after two years in the ground. In the United Kingdom it seems to increase in hardiness when established (Flanagan & Kirkham 2005), but in harsher continental climates it is not successful, as a series of casualties at Rogów Arboretum has demonstrated (P. Banaszczak, pers. comm. 2007). In consequence it is rather rare, except in mild maritime climates. There are good specimens at Hergest Croft, one of Chollipo provenance being c. 8 m tall in 2006 and forming a nice straight tree, bearing fruit when seen in October of that year. A certain amount of variation in leaf shape is apparent among the Hergest specimens, but all have the long-pointed leaf that gives the species its name. It is likely to thrive best in mild, moist conditions – no doubt the reason for the success of an 8 m specimen at Mount Congreve, Co. Waterford (Johnson 2007), and it flourishes in the milder parts of the Pacific Northwest, with good specimens at both the Washington Park Arboretum and the David C. Lam Asian Garden. It can be planted as an understorey tree where there is a high canopy. A young tree is growing well at the JC Raulston Arboretum (1.8 m in 2006, from seed sown in 2001), but suffers annual dieback to the long unripened summer growths, even though planted in a sheltered site (T. Alderton, pers. comm. 2007). At the same arboretum, growing with the protection of a lath house, is a plant labelled A. caudatifolium ‘Variegatum’ (almost certainly an illegitimate name). Obtained from Heronswood Nursery in 2000 but ultimately originating from Japan, this has flourished in these conditions, now being over 2 m in height, and tolerating both summer heat and winter cold (T. Lasseigne, T. Alderton, pers. comms. 2007); at Heronswood it also did well, providing structure and colour in the woodland garden (Heronswood Nursery catalogue 2000). The only problem is the identity of the plant, both correspondents suggesting that its leaves seem rather large for A. caudatifolium and that it differs in other ways as well. A. caudatum Wall. S39, K72 A. caudatum var. prattii Rehder K73

Acer ceriferum Rehder

(Sect. Palmata, Ser. Palmata)

Syn. A. robustum Pax Shrub or tree 5–10 m. Branchlets purple to brown, slender and glabrous. Leaves deciduous, papery or membranous, 4–13 × 4–14 cm, palmately seven-lobed to nine-lobed, divided to one-quarter or one-third of the length, shiny green on both surfaces, largely glabrous, but with some silky hairs below, margins irregularly serrate, apex caudate to acuminate; petiole 4–5 cm long, glabrous; autumn colour red. Inflorescence terminal, corymbose with four to eight flowers. Flowers 5-merous, staminate or hermaphrodite; sepals ovateoblong, purple, petals oblong to obovate, stamens eight, inserted outside the nectar disc. Samaras 2.2–6 cm long, yellowish green, wings spreading horizontally or obtusely. Flowering May, fruiting September (China). Van Gelderen et al. 1994, Xu et al. 2008. Distribution CHINA: Anhui, southern Gansu, Henan, western Hubei, southern Shaanxi, Shanxi, Sichuan, Zhejiang. Habitat Forests between 700 and 2000 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT71. Cross-reference K100. Taxonomic note Acer robustum Pax is a later homonym of A. robustum Opiz and must be replaced by the unfamiliar A. ceriferum (Xu et al. 2008).

Section II. Species Accounts

Acer

Although Acer ceriferum was collected by Wilson in 1907 (no. 339), the oldest known specimen in cultivation seems to be a 35-year-old tree at Rogów, grown from Beijing Botanical Garden seed. Although hardy in these Zone 6 conditions it is very slow-growing (4 m) and has never flowered (Tumilowicz 2002). More recently it has become commercially available both in Europe and in North America. Plants are young and in consequence all rather small, but gardeners are likely to find this an interesting addition to the A. palmatum group. In the United Kingdom the best is probably a nice specimen at Blagdon (P. Gregory, pers. comm. 2007). The species differs from A. palmatum in having silky hairs on the undersides of its leaves, and more conspicuously in its much larger samaras. The leaves turn a purplish red in autumn, and flush yellowish red in spring.

Acer chapaense Gagnep.

(Sect. Platanoidea)

Tree 20–25 m. Bark brown. Branchlets glabrous, remaining green for several years. Leaves deciduous, 5–15 cm across, orbicular, palmately three- to five-lobed, lobes shallow, both surfaces glabrous, margins subentire to sinuate; petiole 1–4 cm long, slender, exudes milky sap when broken. Inflorescence not seen. Samaras ~4 cm long, wings diverging at 45º; nutlets striped or veined. Van Gelderen et al. 1994, Rushforth 1995. Distribution VIETNAM. Habitat Broadleaved, mesic forest between 1600 and 1800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Rushforth 1995. Taxonomic note Xu et al. (2008) treat this taxon as a synonym of A. amplum subsp. bodinieri (H. Lév.) Y.S. Chen.

Acer chapaense seems first to have been collected by Bob Cherry and Keith Rushforth during an expedition to Vietnam in 1992. It became established in Bob Cherry’s arboretum at Kulnura, New South Wales, whence seed from the cultivated trees has been distributed. Young plants from this source are growing well at Hergest Croft, and are now over 2 m tall, having survived the 2005–2006 winter without damage. The whole plant (at least when young) has a resemblance to members of the A. campbellii group, but has milky sap and lacks serrated leaf margins. The leaves are leathery, with a faint velvety feel to the underside, and flush red-bronze. They persist on the tree for much of the winter, falling in January, not long before the new shoots break. In Vietnam it grows in wet forest with a number of broadleaved trees that are generally considered to be hardy, in the United Kingdom at least (Rushforth 1995), but it should probably be given a sheltered site in a moist fertile situation. A. cinnamomifolium (NOW A. coriaceifolium H. Lév., NT82) S49 A. circinatum Pursh B193, S39, K73 A. cissifolium (Siebold & Zucc.) K. Koch B193, K73

Acer ×conspicuum van Gelderen & Oterdoom

(Sect. Macrantha)

This taxon is the result of a cross between A. davidii and A. pensylvanicum, although the name seems to be being applied somewhat casually to other crosses as well. Shrub or tree to 10 m, sparsely branched. Bark blue-green or reddish with conspicuous white stripes. Leaves deciduous, 5–20 × 5–15 cm, palmately threeor five-lobed, the lobes long-acuminate, glabrous or sparsely pubescent below, margins serrate; petiole 2–10 cm long, reddish; autumn colour golden- or orange-yellow. Inflorescence terminal, pendulous racemes, 4–15 cm long. Flowers small. Samaras similar to those of A. davidii, usually short. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution In cultivation only. USDA Hardiness Zone 5–7 (dependent on cultivar). Illustration NT82.

This artificial hybrid is of such importance to horticulture that it is included here for completeness, together with a number of other important snakebark maple selections that have come to recent prominence. These are extremely popular garden trees,

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Plate 78. One of the most striking snakebark maples is Acer ×conspicuum ‘Elephant’s Ear’, raised and introduced by R. Bulk, Boskoop, the Netherlands. Image K. Camelbeke.

New Trees

although it should be noted that many can reach at least 10 m in height, with a rounded crown. A. ×conspicuum has occurred on several occasions where the parents grow together, and can be expected to reappear in seedlings of cultivated origin. The first was ‘Silver Vein’, the result of a deliberate cross made in 1961 by Peter Douwsma in 1961 and introduced by Hillier Nurseries in 1975 (Hillier & Coombes 2002). This is now acclaimed as one of the best snakebark maples, retaining the excellent bark coloration for many years (van Gelderen & van Gelderen 1999). It is the parent of ‘Phoenix’, with striking coral-pink winter stems that are highly effective in the winter landscape. Other cultivars include ‘Candy Stripe’ (which may be A. capillipes × A. pensylvanicum) with very strongly striated bark, and ‘Elephant’s Ear’ with big leaves and purplish bark. Brightly variegated leaves on red stems are borne by ‘Silver Cardinal’, attributed to this hybrid but possibly involving A. rubescens (Hillier & Coombes 2002); it is not hardy at Rogów Arboretum (P. Banaszczak, pers. comm. 2007). A similar, but even brighter selection, ‘Red Flamingo’, is almost certainly a derivative of A. rubescens (P. Gregory, pers. comm. 2007).

Acer cordatum Pax

(Sect. Palmata, Ser. Penninervia)

Shrub or tree to 13 m, though smaller in cultivation; often multistemmed. Bark smooth and grey. Branchlets grey and glabrous. Leaves evergreen, leathery or papery, 6–8 × 3–4 cm, entire, ovate, upper surface bright green, lower surface glaucous-green, three to five lateral veins on each side of the midrib, margins serrate towards the apex, apex acuminate; petiole 1–1.5 cm long. Inflorescence terminal, corymbose, with three to five flowers. Flowers staminate or hermaphrodite, 5-merous; sepals green, petals yellowish green, stamens eight. Samaras 1.4–2(–3.5) cm long, yellowish brown when mature, wings spreading variously. Flowering April, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang. Habitat Forest in valleys between 200 and 1200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT75. Cross-reference K73. Taxonomic note Flora of China (Xu et al. 2008) also recognises var. dimorphifolium (Metcalf) Y.S. Chen, with two- or three-lobed leaves. In Maples of the World (van Gelderen et al. 1994), it is treated as a variety of A. laevigatum.

This tender species with entire evergreen leaves has a toe-hold in cultivation in the mildest parts of our area, and under cover in specialist collections where winters are too severe for it to survive outside (the Esveld Aceretum, for example). A specimen at Bodnant, Conwy was killed in the severe 1981–1982 winter (van Gelderen et al. 1994). A very sheltered site is clearly indicated, but collections from its highest sites would be interesting. No large specimens are recorded by TROBI, but it is grown at Tregrehan, where it was 2 m tall in 2005, retaining green bark along its trunk. The foliage is glossy dark green, flushing reddish after a short period when the tree is deciduous (T. Hudson, pers. comm. 2007)

Acer coriaceifolium H. Lév.

(Sect. Pentaphylla, Ser. Trifida)

Syn. A. cinnamomifolium Hayata Tree to 15 m, though often a shrub in cultivation. Bark grey to blackish brown. Branchlets pubescent to tomentose. Leaves evergreen, leathery, 7–12 × 2.5–5 cm, entire, ovate to oblong or rarely lanceolate, upper surface dark green and glabrous, lower surface pale green and tomentose, three to six lateral veins on each side of the midrib, margins entire, apex apiculate; petiole 1.5–3 cm long, reddish and tomentose. Inflorescence terminal, corymbose, tomentose. Flowers 5-merous; sepals pale green and oblong, petals light yellow

Section II. Species Accounts

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and obovate, stamens eight, inserted inside disc. Samaras 2.8–3.5 cm long, yellowish brown when mature, wings spreading obtusely or acutely. Flowering March, fruiting August (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: southern Anhui, Fujian, Guangdong, northern Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, southeast Sichuan, Zhejiang. Habitat Forest between 1500 and 2500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT83. Cross-reference K73.

Acer coriaceifolium is another evergreen entire-leaved maple with a marginal existence in Europe, surviving in mild coastal gardens and greenhouse collections – although one sapling at Furzey Gardens, Hampshire survived –12 ºC in 2006 (Johnson 2007). Seed from the Shanghai Botanic Garden in 1983 (distributed as A. cinnamomifolium) was the first recorded introduction to the West (van Gelderen et al. 1994). It is not known if there have been later reintroductions; its altitude range suggests that collections from its highest locations would be useful. There are trees up to 4 m tall at Tregrehan, but no larger specimens have been located. In North America it has been distributed by Heronswood Nursery, and a young plant obtained from there in 2000 by the JC Raulston Arboretum is doing remarkably well, surviving at least –10 ºC most winters to reach 1.5 m by May 2006. The leaves are sometimes damaged, and the plant may become partly defoliated, but it is surprisingly happy in the North Carolina Piedmont area (as also are A. fabri and A. laevigatum) (T. Lasseigne, pers. comm. 2007). In North Carolina the buds break in very early spring (T. Alderton, pers. comm. 2007), which may be a problem where late frosts are regular. The foliage is a dull pale green (darker when grown in shade), with distinct tomentum below when young, although this seems to disappear as the leaf matures, to leave a grey underside. A. ×coriaceum Tausch B194, K74 A. craibianum (NOW A. calcaratum Gagnep., NT78) S37 A. crataegifolium Siebold & Zucc. B194, K74 A. davidii Franch. B195, S39, K74 A. diabolicum K. Koch B196, S40, K75 A. diabolicum f. purpurascens (NOW A. diabolicum Blume ex K. Koch) B196, S40, K75

Acer duplicatoserratum Hayata

A. ×dieckii (Pax) Pax B196, K75 A. distylum Siebold & Zucc. B197, S40, K75 A. divergens (NOW A. cappadocicum subsp. divergens (Pax) A.E. Murray) B190, S38, K75 A. divergens var. trilobum (NOW A. cappadocicum subsp. sinicum var. tricaudatum (Veitch ex Rehder) Rehder) S38

(Sect. Palmata, Ser. Palmata)

Syn. A. palmatum var. pubescens Li Small tree, ultimate height unknown. Branchlets covered with white pubescence, later glabrous. Leaves deciduous, 2.3–5.5 × 3–8 cm, palmately five-lobed to nine-lobed up to half-way to the base, both surfaces covered with rough, white hairs, margins sharply double-serrate, lobe apex acuminate; petiole 1.5–5 cm long, pubescent. Inflorescence corymbose, densely pubescent. Flowers small, staminate or hermaphrodite;

Plate 79. The evergreen Acer coriaceifolium is marginally hardy in much of our area, but flourishes at Hackfalls, New Zealand, where this picture was taken. Image J.R.P. van Hoey Smith.

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sepals five, purplish, ovate to lanceolate, petals four, white, ovate to orbicular, stamens four. Samaras 2–3 cm long, yellowish brown when mature, wings spreading obtusely. Flowering April, fruiting September (Taiwan). Van Gelderen et al. 1994, Xu et al. 2008. Distribution TAIWAN. Habitat Deciduous forest between 1000 and 2000 m asl. USDA Hardiness Zone 6. Conservation status Vulnerable, due to overharvesting and poor regeneration. Cross-reference K90 (as A. palmatum var. pubescens). Taxonomic note Acer duplicatoserratum var. chinense C.S. Chang occurs in mainland China (Anhui, Fujian, Guizhou, southern Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shandong, Zhejiang); the petioles are pubescent when young, but later become glabrous (van Gelderen et al. 1994, Xu et al. 2008).

A member of the Acer palmatum complex, A. duplicatoserratum is distinguished from its relatives by its pubescent shoots and leaves, but otherwise looks very similar to A. palmatum. It is rare both in the wild and in cultivation, although it ought not to be particularly challenging to grow. Trees from both Taiwan (from Edward Needham’s 1998 collection EN 0036) and Zhejiang in mainland China (SBG 303, 1996) are cultivated at Tregrehan, where they have been slow-growing (T. Hudson, pers. comm. 2007). There are some differences between these two stocks, but this needs investigation as the trees mature.

A. ×durettii (NOW A. ×coriaceum Tausch) B197, K75

Acer elegantulum W.P. Fang & P.L. Chiu

(Sect. Palmata, Ser. Sinensia)

Syn. A. olivaceum W.P. Fang & P.L. Chiu

Plate 80. The new growth of many maples flushes reddish or bronze, as here on a young Acer elegantulum at Plantentuin Esveld. Image J.R.P. van Hoey Smith.

Tree to 15 m, though often not exceeding 5 m in cultivation; densely branched. Bark brown and scabrous. Branchlets green. Leaves deciduous, thin and papery, 5–13 × 7–16 cm, palmately five-lobed (rarely sevenlobed), largely glabrous, but for the tufts of hair in the vein axils of the lower surface, margins minutely serrate, lobe apex acute to acuminate or mucronate; petiole 2.8–6 cm long, glabrous. Inflorescence terminal, paniculate. Flowers 5-merous, staminate or hermaphrodite; sepals light green, ovate to oblong, petals light green, obovate to oblong, stamens eight, inserted outside nectar disc. Samaras 2–2.5 cm long, pale yellow when mature, wings spreading obtusely. Flowering May, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: southern Anhui, Fujian, Guangxi, Guizhou, Hunan, Jiangxi, Zhejiang. Habitat Montane forest between 200 and 1400 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT84. Taxonomic note Acer elegantulum var. macrurum W.P. Fang & P.L. Chiu has smaller samaras (1–1.5 cm long) (van Gelderen et al. 1994).

Acer elegantulum has a distinct resemblance to A. campbellii, from which it is separated in the Flora of China key only by having a glabrous instead of a pubescent disc within the flower. A rigorous phylogenetic study of this series is urgently needed. As seen at Hergest Croft, the posture of the leaves is slightly different, those of A. elegantulum being slightly drooping whereas those of the A. campbellii group are held flat. The leaves of A. elegantulum are also smaller and, in the specimens seen, more deeply lobed, giving a shape suggestive of that of Cannabis sativa. The leaves flush with shiny bronze to deep purple-brown, but become green when mature, with the stems remaining green. The whole plant has a very pendulous habit like other members of series Sinensia. Acer elegantulum is represented in the major English and European collections, where it seems to grow well, flowering and fruiting well after 12–15 years, and it is also cultivated in the milder parts of North America. The first introduction seems to have been made in about 1985 from Shanghai Botanic Garden (van Gelderen

Section II. Species Accounts

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85

et al. 1994), while a flourishing tree of over 3 m at Westonbirt derives from a 1986 introduction from Hangzhou Botanical Garden (le Hardÿ de Beaulieu 2003). It soon became available to collectors through the nursery trade. A tree at Tregrehan planted in 1989 is still only a couple of metres tall, but this may be due to its situation in a rather shaded place (T. Hudson, pers. comm. 2007). A specimen at Sandling Park, Kent was 3 m tall in 2006 (TROBI). A. erianthum Schwer. B197, S40, K75 A. fabri Hance S45, K75 A. fargesii (NOW A. fabri Hance) B198, K75 A. flabellatum (NOW A. campbellii subsp. flabellatum (Rehder) A.E. Murray) B188, K75 A. flabellatum var. yunnanense (NOW A. campbellii subsp. flabellatum var. yunnanense (Rehder) W.P. Fang) B188, K75 A. forrestii (NOW A. pectinatum subsp. forrestii (Diels) A.E. Murray) B198, S41, K75 A. franchetii (NOW A. sterculiaceum subsp. franchetii (Pax) A.E. Murray) B199, S41, K75

Acer ×freemanii A.E. Murray

(Sect. Rubra)

This important maple is the result of a cross between A. rubrum and A. saccharinum. Tree 20–25 m; branches upright, forming rounded or oval crown. Bark silvery grey. Leaves smaller and less deeply lobed than those of A. saccharinum; deeply dissected, sinuses rounded to acute; autumn colour red and yellow on the same leaf. Samaras 3–6 cm long, striated. Flowering February to March (USA). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution USA: occasional where the parents overlap. This hybrid was also produced artificially at the US National Arboretum by Oliver Freeman in 1933. Habitat As for parent species. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT85. Cross-reference K76.

Acer ×freemanii is an increasingly important tree, especially in North America, selected clones combining the best features of the two much-loved parents: the flaming reds of the autumn coloration of A. rubrum, with greater tolerance of cold and drier conditions inherited from A. saccharinum. In addition, the hybrid has stronger branches than the notoriously brittle A. saccharinum and is thus more suitable to use as a street tree in its stead (Dirr 1998, van den Berk 2002). In Europe the best-known clone is ‘Jeffersred’ (sold as Autumn Blaze), capable of fabulous autumn colour, as is ‘DTR102’ (Autumn Fantasy), which also colours well in warmer areas. ‘Marmo’ was selected from a male tree in the Morton Arboretum for both its superb and long-lasting autumn colour and its seedlessness. ‘Celzam’ (Celebration) is rather narrow in outline and thus particularly suited for use as a street tree. Other clones are ‘Armstrong’ and ‘Elegant’, once thought to be selections of A. rubrum and A. saccharinum, respectively, but now considered hybrids. All are capable of becoming large trees. A. fulvescens Rehder B212, S47 A. garrettii Craib K76 A. ginnala (NOW A. tataricum subsp. ginnala (Maxim.) Wesm.) B200, S41, K76

A. ginnala var. aidzuense (NOW A. tataricum subsp. aidzuense (Franch.) P.C. de Jong) K76 A. giraldii (NOW A. caesium subsp. giraldii (Pax) A.E. Murray) B200, S41, K76

Plate 81. Occuring both in the wild and in gardens, Acer ×freemanii combines the best features of both parents. This somewhat fastigiate clone is ‘Armstrong’. Image K. Camelbeke.

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A. glabrum Torr. B201, S42, K76 A. glabrum var. douglasii (NOW A. glabrum subsp. douglasii (Hook.) Wesm.) S42, K76 A. glabrum f. rhodocarpum Schwer. K76 A. glabrum var. tripartitum (NOW A. glabrum Torr. subsp. glabrum) S42 A. grandidentatum (NOW A. saccharum subsp. grandidentatum (Nutt. ex Torr. & Gray) Desmarais) B201 A. griseum (Franch.) Pax B202, S42, K77 A. grosseri (NOW A. davidii subsp. grosseri (Pax) P.C. de Jong) B202, S42, K77

A. grosseri var. hersii (NOW A. davidii subsp. grosseri (Pax) P.C. de Jong) B203, S42, K77 A. heldreichii Boiss. B203, S43, K77 A. henryi Pax B203, S43, K77 A. henryi var. intermedium (NOW A. henryi Pax) K77 A. ×hillieri Lancaster S43, K77 A. hookeri (NOW A. sikkimense Miq. subsp. sikkimense, NT109) B204, S44, K77 A. hookeri var. majus Pax K77 A. ×hybridum Bosc. B204, K77 A. hypoleucum Hayata K78

Acer hyrcanum

Balkan Maple

Fisch. & C.A. Mey. (Sect. Acer, Ser. Monspessulana)

This species was described by Bean (B205, S44) and Krüssmann (K78). Seven subspecies are now recognised, though these are imperfectly known and future investigations may relegate some names into synonymy. A key to the subspecies, several of which appear to be in cultivation, is provided below.

1a. Tree or shrub to 4–12 m tall; leaves 3–10 cm across, margins flat .................................................... 2 1b. Shrub to 2–3 m tall; leaves 0.5–1.5 cm across, margins undulate; Greece, western Turkey ............... subsp. reginae-amaliae (Orph. ex Boiss.) A.E. Murray 2a. Leaves five-lobed, margins coarsely serrate; samaras 3–4 cm long ................................................... 3 2b. Leaves three-lobed or with two additional poorly developed basal lobes, margins entire; samaras not over 1 cm long; southern Turkey .............. subsp. sphaerocarpum Yalt. 3a. Leaves with petioles to 10 cm long .................................................................................................. 4 3b. Leaves almost sessile; Lebanon, western Turkey ...................................... subsp. keckianum (Pax) Yalt. 4a. Leaves dark bluish green above ....................................................................................................... 5 4b. Leaves green above ......................................................................................................................... 6 5a. Leaves tomentose below, lobes abruptly acuminate; Ukraine (Crimea) .................................................................... subsp. stevenii (Pojark.) A.E. Murray 5b. Leaves glabrous, lobes acute to rounded; Albania, BosniaHerzegovina, Bulgaria, Croatia, Greece, Macedonia, Serbia & Montenegro ............................................................ subsp. intermedium (Pancˇic´) Bornm.

Section II. Species Accounts

6a. Small tree or shrub, to 5–6 m tall; leaves slightly tomentose below, deeply incised; Lebanon, western Syria, southern Turkey ............................................................... subsp. tauricola (Boiss. & Blanche) Yalt. 6b. Tree or rarely shrub, to 10–12 m tall; leaves glabrous, shallowly incised; Asia (Lebanon, western Iran, Turkey), Europe (Croatia, Bosnia-Herzegovina, Serbia & Montenegro) .............................. subsp. hyrcanum

Acer hyrcanum is one of the rather unexciting maples from eastern Europe and the Middle East that can really only justify their space in a specialist collection. Even the nominate subspecies seems to be very scarce. It can be relatively large, but in many situations it is often rather small and scrubby. All the subspecies prefer a warm site. Most are in cultivation, and are occasionally offered for sale by specialists such as Firma C. Esveld, but notable specimens are rare. At Wakehurst Place there is a tree of subsp. tauricola grown from seed from the Flanagan & Pitman expedition to Turkey in 1990 (TURX 99), collected at 1670 m in the Amanus Mountains, Hatay Province, where the parent trees were up to 25 m tall. A specimen from the same collection at the Hillier Gardens was 3.6 m in 2005. At the Rogów Arboretum subsp. stevenii from the Crimea has formed a slow-growing small tree (P. Banaszczak, pers. comm. 2007). While the leaves of some of these subspecies can be quite large and coarse, the distinction of having the smallest leaves in the genus goes to subsp. reginae-amaliae, from arid places in Greece and Turkey (van Gelderen & van Gelderen 1999), which would make an interesting shrub for a dry bank. A specimen of it is doing very well at Blagdon, Northumberland. Amalia of Oldenburg (1818–1875) was Queen Consort of King Otto of Greece until they were deposed in 1862. She is recorded to have been interested in horticulture, agriculture and viticulture, and was responsible for laying out the gardens of the royal palace in Athens (Wikipedia 2007). Her successor, Queen Olga, is commemorated by the autumn-flowering snowdrop Galanthus reginae-olgae – which would grow well on the same dry bank as the maple. A curious observation noted at Hergest Croft is that A. hyrcanum seedlings make a strong root before the cotyledons emerge – apparently an adaptation to drier habitats. The slow-growing tree there is derived from seed collected on Kop Dag in northeastern Turkey, by R.L. Banks in 1982, outside the known range of any of the subspecies, and has not been identified to subspecific level (L. Banks, pers. comm. 2006). A. hyrcanum var. keckianum (NOW A. hyrcanum subsp. keckianum (Pax) Yalt.) K78 A. hyrcanum subsp. stevenii (Pojark.) A.E. Murray K78 A. hyrcanum subsp. tauricolum (Boiss. & Blanche) Yalt. K78 A. japonicum Thunb. B205, S44, K78 A. laevigatum Veitch B198, S45, K78 A. laevigatum var. salweenense (W.W. Sm.) Cowan ex W.P. Fang K79 A. lanceolatum (NOW A. oblongum Wall. ex DC.) S49

Acer laurinum Hassk.

(Sect. Hyptiocarpa)

Tree to 30 m. Bark grey. Branchlets green to glaucous or purplish, glabrous. Leaves evergreen, 9–15 × 3–8 cm, oblong to elliptic or lanceolate, upper surface dark glossy green, lower surface glaucous, white or bluish grey, five to six lateral veins on each side of the midrib, margins entire or remotely serrate, apex short-acuminate to obtuse; petiole 3–6 cm long, glabrous green. Inflorescence lateral, corymbose, on two-year-old branches,

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Acer

New Trees

2.5–10 cm long, glabrous or pubescent. Flowers yellowish, 5-merous, staminate or hermaphrodite flowers on separate plants; sepals ovate, 0.2–0.3 cm long, petals shorter, stamens 8–12, inserted into the nectar disc. Samaras 3–7 cm long, yellowish brown when mature, wing heavily veined, spreading acutely. Flowering June to September, fruiting September to December (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CAMBODIA; CHINA: southwest Guangxi, Hainan, southeast Xizang, Yunnan; INDIA; INDONESIA: the only Acer to cross the Equator, ranging through Sumatra and Java to reach Flores; LAOS; MALAYSIA; MYANMAR; PHILIPPINES; THAILAND; VIETNAM. Habitat Evergreen forest between 700 and 2500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note See also Acer pinnatinervium.

In the wild Acer laurinum is a magnificent tree, of true ‘tropical forest’ appearance, given by its glossy evergreen leaves with a long drip-tip. It is indeed a constituent of the Asian tropical forests over a huge range, so it is not surprising that it is extremely tender. It was grown in the Netherlands for some years, but all stock perished in the 1991–1992 winter, so that its extinction in cultivation was bemoaned (van Gelderen & van Gelderen 1999). However, in 1990 seed was collected by Keith Rushforth (KR 1983) in northern Vietnam, and specimens from this source are now established in southwestern England. One at Tregrehan, planted in 1995, has made a very beautiful tree of 5–6 m, that has flowered and fruited since it was only 3 m tall (Hudson 2004), the flowers appearing in autumn. This individual has quite broad leaves, dark glossy green above with a bluish glaucous underside, and so far has retained a greenish stem. Acer laurinum is also in cultivation at the San Francisco Botanical Garden. It is clear that provenance makes a great deal of difference to the survival chances of this species in cultivation, but a very sheltered, favourable site will always be needed. If this is not available it would make a lovely conservatory specimen. Plate 82. The spring flush of a most un-maple-like maple. Grown and photographed as Acer laurinum, this is in fact A. pinnatinervium (see p. 100). Image J. Grimshaw.

A. laxiflorum Pax (OR A. pectinatum subsp. laxiflorum (Pax) A.E. Murray) B206, S46, K79 A. leucoderme (NOW A. saccharum subsp. leucoderme (Small) Desmarais) B232, K79

Acer longipes Franch. ex Rehder

A. litseifolium Hayata K79 A. lobelii (NOW A. cappadocicum subsp. lobelii (Ten.) A.E. Murray) B207, S46, K79

(Sect. Platanoidea)

Syn. A. fulvescens Rehder Tree to 18 m, crown umbellate. Bark grey to olive-brown. Branchlets initially smooth and dark brown; later rough and silvery. Leaves deciduous, papery, 8–15 × 7–15 cm, palmately three-lobed or rarely entire or fivelobed, upper surface glabrous, lower surface persistently grey- or yellow-pubescent, especially along the veins, margins entire, lobe apex acuminate or aristate; petiole 5–9 cm long, slender, glabrous, exudes milky sap when broken; autumn colour clear yellow. Inflorescence terminal, racemose. Flowers yellowish, 5-merous, staminate or hermaphrodite; sepals elliptic to oblong, ~0.4 cm long, petals oblong to obovate, same length as sepals, stamens eight, inserted into the nectar disc. Samaras 1–1.3 cm long, yellowish brown when mature, wings spreading acutely or erectly. Flowering April, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: northern Guangxi, southern Henan, Hunan, western Hubei, Jiangxi, southern Shaanxi, Sichuan. Habitat Mixed forest in valleys between 300 and 1650 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT89. Crossreferences B212, S47 (as A. fulvescens); K80. Taxonomic note The persistent hairs on the undersides of the leaves distinguish A. longipes subsp. longipes from all other members of section Platanoidea.

Section II. Species Accounts

Acer

Van Gelderen et al. (1994) recognised four subspecies of A. longipes, and a key to these is provided below. Xu et al. (2008) recognise A. longipes Franch. ex Rehder and A. amplum Rehder as separate species, with A. amplum having the following subspecies: subsp. amplum (including A. longipes subsp. firmianioides), subsp. bodinieri (H. Lév.) Y.S. Chen, subsp. catalpifolium (Rehder) Y.S. Chen, subsp. tientaiense (C.K. Schneid.) Y.S. Chen. Acer fulvescens Rehder is regarded as a full species.

1a. Leaves pubescent on the lower surface; China (northern Guangxi, southern Henan, western Hubei, Hunan, Jiangxi, southern Shaanxi, Sichuan) ..................... subsp. longipes 1b. Leaves glabrous

........................................................................................................................... 2

2a. Leaves large, 20 × 28 cm; China (Hubei) .......................... subsp. firmianioides (W.C. Cheng) de Jong 2b. Leaves smaller, 8–25 × 5–15 cm ...................................................................................................... 3 3a. Leaf blade entire and unlobed, or rarely with two- or three-lobed leaves on the same branchlet; samara 5–5.5 cm long; China (northeastern Guangxi, northern Guizhou, Sichuan) ............. subsp. catalpifolium (Rehder) de Jong 3b. Leaf blade three- to five-lobed; samara 2.5–4.5 cm long; China (southern Anhui, Fujian, northwestern Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang) ..... subsp. amplum (Rehder) de Jong

Acer longipes is closely related to, and rather resembles the more familiar A. cappadocicum and A. platanoides and can at times match them for size, although in cultivation it seems to be less vigorous. As a common tree in Sichuan (van Gelderen et al. 1994) it is not surprising that it was collected by earlier travellers there, but few trees resulted. One planted at Borde Hill in 1932, possibly derived from Wilson’s collections of 1908 (Wilson 1004, 1162) (Bean 1976a), was grown as A. fulvescens for many years, and provided seed for more recent plantings (van Gelderen et al. 1994). In 1995 it was 13 m, 50 cm dbh (Johnson 2003). A tree planted in 1976 in Park Wood, Hergest Croft, is now approximately 10 m in height, but shows signs of squirrel damage. The name fulvescens appears to refer to the ‘fulvous’ or yellowish brown pubescence that covers the young leaves of this taxon, and persists on the undersides of the mature leaves. More recently A. longipes subsp. longipes has been collected by the various SICH expeditions (SICH 0629, 0731, 1329, 1814, 2087, 2226), and young plants from these gatherings are growing in several collections in the United Kingdom Kingdom, at Quarryhill, and in Vancouver where they are up to 8 m tall (from SICH 2087, 2226) (P. Wharton, pers. comm. 2007). In Poland it suffers from winter damage and frozen young shoots (P. Banaszczak, pers. comm. 2007). Attractive features of the species are the rich red of the petioles, and its clear yellow autumn colour. Subsp. amplum was introduced by both Wilson and Forrest, and a few notable specimens are mentioned by Bean (1976a). A Forrest introduction planted in 1937 at

Plate 83. Mature trunks of Acer longipes subsp. longipes in Sichuan, showing its rugged bark. Image T. Kirkham.

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New Trees

Borde Hill was 13 m in 1995 (Johnson 2003). It remains uncommon in cultivation but is represented in major collections. A yellow-leaved selection has been named ‘Gold Coin’ and distributed by Firma C. Esveld, in whose Aceretum the original plant grows as a large shrub. Subsp. catalpifolium is also in cultivation and available in the nursery trade. Wilson 1359, collected in 1908, and his collection 4208 of 1910, are referrable to subsp. catalpifolium and may be the source of some of this material (P. Gregory, pers. comm. 2007). It has large leaves, especially when young, and (as with subsp. firmianioides) these can be weakly lobed. There is a particularly fine one growing at Chevithorne Barton, Devon, 10–11 m tall and c. 30 cm dbh in 2006. Subsp. firmianioides, if truly distinct, is apparently not in cultivation.

A. macrophyllum Pursh B208, S46, K80 A. mandschuricum Maxim. B209, K80 A. ×martinii Jord. K80

Acer metcalfii Rehder

A. maximowiczii (NOW A. pectinatum subsp. maximowiczii (Pax) A.E. Murray) B209, K80

(Sect. Macrantha)

Syn. A. sikkimense subsp. metcalfii (Rehder) P.C. de Jong Tree to 10 m. Bark smooth, snakebark-patterned. Leaves deciduous, thick, 10–14 × 7–11 cm, dark green above, three-lobed, lobes acuminate, margins coarsely serrate; petiole 2–3(–5) cm long. Inflorescence terminal, racemose, with c.15 flowers; flower details unrecorded, but similar to those of A. davidii subsp. grosseri. Samaras 2–2.5 cm long, brownish yellow, wings spreading obtusely. Xu et al. 2008. Distribution CHINA: northern Guangdong, northeast Guangxi, southeast Guizhou, southern Hunan. Habitat Mixed forests between 800 and 1500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note The relationships of A. metcalfii are disputed. It was treated as a subsp. of A. sikkimense by de Jong (in van Gelderen et al. 1994), but this view was never entirely satisfactory. It seems to be related to the A. davidii group, differing in its acuminate lobes and serrate margins, and is closest to A. davidii subsp. grosseri according to Chin-sung Chang (in Xu et. al. 2008). The authors of the Flora of China account disagree among themselves, however, as to how these taxa should be recognised.

Acer metcalfii is not well understood, either as a wild tree, where its relationship to the other snakebark species needs resolution, or in cultivation, where trees grown under this name may be wrongly identified. Living material was not known to the authors of Maples of the World, but they commented that it was described by Rehder as being close to A. davidii subsp. grosseri (van Gelderen et al. 1994), and this is how it is now treated in the Flora of China account. There is little material indubitably of A. metcalfii in cultivation, but at Tregrehan there is a 4 m specimen (TROBI), grown as a graft (onto A. davidii) from a seedling collected in southern Hunan by Bob Cherry (K. Rushforth, pers. comm. 2008). Trees at Hergest Croft grown from Lancaster 962, collected as A. davidii at 3800 m in the Pi River valley in western Sichuan in 1981 (R. Lancaster, pers. comm. 2007), were identified as A. sikkimense subsp. metcalfii by Stephen Spongberg (L. Banks, pers. comm. 2006), but western Sichuan is outside the area in which A. metcalfii is normally considered to occur and the identification should be revisited. Trees from the same gathering also grow at Wakehurst Place. The finest Lancaster 962 at Hergest Croft is approximately 8 m tall (2006) and forms an elegant small tree, most striking in its retention of green bark all the way to the ground. The bark has good pale striations. The leaves are mid-green with a red petiole, but are disappointing in autumn, falling with no significant colour change (unlike A. davidii subsp. grosseri). On the

Section II. Species Accounts

Acer

young trees the leaves were quite large, but they have diminished in size with greater maturity. Whatever its real affinity this attractive tree, which can be readily propagated from cuttings, deserves wider distribution (see Figure 10, p. 108).

A. micranthum Siebold & Zucc. B210, S47, K81 A. miyabei Maxim. B210, S47, K81 A. mono (NOW A. pictum Thunb.) B211, S47, K81 A. mono f. ambiguum (NOW A. pictum subsp. pictum f. ambiguum (Pax) H. Ohashi) B212, K81 A. mono f. connivens (NOW A. pictum subsp. dissectum f. connivens (G. Nicholson) H. Ohashi) B211

A. mono f. dissectum (NOW A. pictum subsp. dissectum (Wesmael) H. Ohashi) K82 A. mono var. latilobum Koidz. K82 A. mono var. mayrii (NOW A. pictum subsp. mayrii (Schwer.) H. Ohashi) B212, K82 A. mono var. savatieri (NOW A. pictum subsp. pictum) K82 A. mono var. tricuspis (NOW A. pictum subsp. tricuspis (Rehder) H. Ohashi) B212, K82

Acer monspessulanum

Montpellier Maple

L. (Sect. Acer, Ser. Monspessulana)

This species was described by Bean (B212, S47) and Krüssmann (K82). Eight subspecies, five varieties and one form are recognised by van Gelderen et al. (1994), but only subsp. monspessulanum, subsp. ibericum and subsp. turcomanicum appear to be in cultivation. Acer monspessulanum is a charming small tree that deserves wider planting. A. monspessulanum subsp. cinerascens (Boiss.) Yalt. K82 A. monspessulanum subsp. cinerascens var. boissieri Schwer. K82 A. monspessulanum subsp. cinerascens var. bornmuelleri Schwer. K82 A. monspessulanum subsp. cinerascens f. commutatum (J. Presl) Borb. K82 A. monspessulanum subsp. cinerascens f. hispanicum Schwer. K82 A. monspessulanum subsp. cinerascens f. ibericum (Willd.) K82 A. monspessulanum subsp. cinerascens f. liburnicum Pax K82 A. monspessulanum subsp. cinerascens f. maroccanum Schwer. K83 A. monspessulanum subsp. cinerascens var. paxii Schwer. K82

Acer monspessulanum subsp. ibericum (Bieb.) Yalt. Subsp. ibericum forms a small tree of 8 m. It differs from typical A. monspessulanum, which can form a tree 6–12 m tall, in that leaves are glaucous-green above with dense web-like hairs beneath. The leaves are also somewhat larger, 7 × 9 cm vs. 3–5 × 3–5 cm in subsp. monspessulanum. Van Gelderen et al. 1994. Distribution ARMENIA; AZERBAIJAN; IRAN; TURKEY. Habitat Woods and thickets, mountain slopes. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Taxonomic note Confusingly, the classical name ‘Iberia’ refers both to Spain and Portugal (the modern Iberia) and to a region of the Caucasus centred on modern Georgia (Stearn 1983).

This eastern variant was introduced from Iran, by Ann Ala and Roy Lancaster in 1972, where it grew as a small 6 m tree in rich woody vegetation on the northern slope of the Elburz mountains (R. Lancaster, pers. comm. 2007). Several specimens from this

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New Trees

collection (Lancaster & Ala 8) are growing slowly at the Sir Harold Hillier Gardens, ranging in height between 3 m and 4 m by 2006, but no others have been traced. It has good yellow autumn colour (R. Lancaster, pers. comm. 2007).

Acer monspessulanum subsp. turcomanicum (Pojark.) A.E. Murray Subsp. turcomanicum forms a large, densely branched shrub of 4–5 m. It differs from typical A. monspessulanum in that the flowers are whitish (vs. yellow-green) and the samaras are bright red at maturity (vs. yellowgreen). In addition, the leathery leaves are almost evergreen in some locations, and have rusty hairs on the lower surface. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution IRAN; TURKMENISTAN. Habitat Montane forest. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT92. Cross-reference K83.

Although rather shrubby, Acer monspessulanum subsp. turcomanicum earns its place by the effective contrast of its red samaras against the green foliage. It would be ideal for a well-drained sunny bank. It is not common but is commercially available in Europe, and there are a few notable specimens in collections. At the Hillier Gardens a tree planted in 1988 was 5 m in 2005. It has been very slow-growing at the Rogów Arboretum, where one planted in 1959 is still only 2–3 m tall, although perfectly hardy there (P. Banaszczak, pers. comm. 2007). Plate 84. Attractive glossy foliage is produced by the slow-growing Acer monspessulanum subsp. turcomanicum. Image P. Banaszczak.

Figure 9 (opposite). Acer morifolium: habit with inflorescences (A), habit with fruits (B); lobed leaf (C).

Acer morifolium Koidz.

(Sect. Macrantha)

Mulberry-leaf Maple, Yaku Maple

Shrub or tree 10–12(–15) m; usually multistemmed. Bark green with white longitudinal stripes. Branchlets shiny red or purplish red, tinged with green on the undersides, with scattered lenticels. Leaves deciduous, 5–9 × 2–4 cm, unlobed and ovate to cordate, or remotely three- or five-lobed, upper surface lustrous dark green and often bronzed, lower surface pale green with slight rusty pubescence, later almost glabrous, six to eight lateral veins on each side of the midrib, margins conspicuously double-serrate, apex acuminate or acute; petiole 3–8 cm long, bright red and grooved; autumn colour golden-yellow with hints of red. Inflorescence terminal, racemose, 6–10 cm long. Flowers yellowish green, 5-merous, usually dioecious; sepals narrowly oblong, ~0.15 cm long, petals narrowly obovate and same size as sepals, perianth segments partially fused, stamens eight, inserted outside the nectar disc. Samaras 1.5–2 cm long, yellowish brown when mature, wings spreading horizontally. Flowering April, fruiting September to October (Japan). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999; Gregory, in prep. Distribution JAPAN: Ryukyu Is., Tanega-shima, Yakushima. Habitat Warm, temperate forest. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Wharton et al. 2005; NT93.

Acer morifolium is a very pleasant addition to the snakebark maples in cultivation and is likely to become popular as stocks are multiplied (ideally by cuttings rather than as grafts). It is closely allied to A. capillipes, which it rather resembles, but can be differentiated by the brownish (rather than white) hairs on its leaves. Young trees (at least) show good patterning on the bark, with reddish and white streaks on the dark green background. This coloration dulls and darkens somewhat with age. The leaves flush a good red, and pass through bronzed stages to become a dark green above, duller below, with very strong venation, but they are variable in their degree of lobing. This seems particularly to be associated with youth and vigour, as those on the more vigorous new shoots tend to have more pronounced lobing (up to five being visible occasionally). On mature shoots a simple outline, or very weak lobation, is the norm. The autumn colour is good, in shades between soft orange and red. Despite the low altitude and southerly latitude of its origin, A. morifolium is surprisingly hardy. There are vigorous trees of this species at Westonbirt, and at Hergest

Section II. Species Accounts

Acer

93

1 cm

A

B

C

94

Acer

New Trees

Croft (from BSWJ 6037, collected at 100 m on Yaku-shima in 1998) (B. Wynn-Jones, pers. comm. 2007), and it is also reported to be thriving very well at the David C. Lam Asian Garden in Vancouver (Wharton et al. 2005). The Vancouver material was collected at 180 m on Yaku-shima by Dr M. Tsukada of the Forest Experimental Station (University of Tokyo), Hokkaido (P. Wharton, pers. comm. 2007). The species arrived in the Netherlands from Japan in the early 1990s, since when it has been introduced on several occasions via different routes, some material in the United States being received from Chollipo Arboretum, for example (Heronswood Nursery catalogue 2000). Several variegated clones are known in Japan (Yano 2003). A. multiserratum (NOW A. caudatum Wall.) B239, K83

Acer negundo L.

Plate 85. The contrast between the glaucous stems and bright red petioles of Acer negundo subsp. mexicanum adds a new twist to a familiar species. Image N. Macer.

(Sect. Negundo, Ser. Negundo)

Ash-leaved Maple, Box Elder

It may seem very odd to include so familiar a species in a book on recent introductions, but the resolution of the taxonomy of Acer negundo has resulted in the description of several subspecific taxa whose names are appearing only now in catalogues and the literature, although the plants they cover may have been cultivated for some time. The great advantage of A. negundo is its adaptability, it being tolerant in one form or another of great heat and/or great cold, although it is often unattractively shaped and sometimes weedy. The abundant fruits it produces can be a pleasing feature in themselves, hanging on the tree long after the leaves have fallen. A recent collection from Pico de Orizaba, Puebla, Mexico of subsp. mexicanum (F&M 48) may be the first introduction of this taxon to cultivation. It is too soon to make a judgement on its hardiness or garden-worthiness, but young plants have survived lengthy periods of being frozen solid in their pots. The stems are violet with a white bloom and produce red-flushed new leaves with red petiole and rachis (Pan Global Plants catalogue 2006). In the wild the trees were 7–9 m tall. Acer negundo was described by Bean (B213, S48) and Krüssmann (K85). In this book, rather than giving separate descriptions for individual subspecific taxa of this distinctive species, we provide a key to the subspecies and varieties, below.

1a. Branchlets glabrous or almost so ..................................................................................................... 2 1b. Branchlets pubescent ...................................................................................................................... 3 2a. Leaflets three to seven (to nine), olive-green to fresh green, 5–10 × 3–5 cm, glabrous; Canada (Ontario), USA (Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Vermont, West Virginia, Wisconsin) ............................ subsp. negundo 2b. Leaflets three, dark green, but paler beneath, 6–8 × 2.5–3 cm, densely tomentose beneath; Guatemala, Mexico (Chiapas, Hidalgo, Jalisco, México, Michoacán, Nuevo León, Oaxaca, Puebla, San Luis Potosí, Tlaxcala, Veracruz) ............................................................................ subsp. mexicanum (DC.) Wesm.

Section II. Species Accounts

Acer

3a. Leaflets glabrous beneath or slightly hairy on the midrib; Canada (Alberta, Manitoba, Ontario, Saskatchewan), USA (Colorado, Montana, Nebraska, New Mexico, North Dakota, South Dakota, Utah, Wisconsin, Wyoming) .................................................. subsp. interius (Britton) Á. Löve & D. Löve 3b. Leaflets thickly tomentose to puberulent .......................................................................................... 4 4a. Leaflets three to seven, ovate, tomentose when immature, covered in white hairs at maturity; USA (California) ........................................................ subsp. californicum (Torr. & A. Gray) Wesm. 4b. Leaflets three, broadly elliptic, puberulent beneath; USA (Arizona, Missouri, Texas) ............................................. subsp. californicum var. texanum Pax

A. negundo var. californicum (NOW A. negundo subsp. californicum (Torr. & A. Gray) Wesm.) B213, K84 A. negundo var. interius (NOW A. negundo subsp. interius (Britton) Á. Löve & D. Löve) K84 A. negundo var. mexicanum (NOW A. negundo subsp. mexicanum (DC.) Wesm., NT94) K84 A. negundo var. pseudo-californicum (NOW A. negundo ‘Pseudocalifornicum’) K84 A. negundo var. texanum (NOW A. negundo subsp. californicum var. texanum Pax) K85

Acer oblongum DC.

A. negundo var. violaceum (NOW A. negundo ‘Violaceum’) B214, S48 A. nigrum (NOW A. saccharum subsp. nigrum (F. Michx.) Desmarais) B232 A. nikoense (NOW A. maximowiczianum Miq.) B214, S48, K85 A. nikoense var. megalocarpum Rehder K85 A. nipponicum Hara B239, K85

(Sect. Palmata, Ser. Penninervia)

Flying Moth Maple

This species was described by Bean (B215, S49) and Krüssmann (K86). It is in general rather tender, but is valued as a street tree in Mediterranean Europe and southern California (le Hardÿ de Beaulieu 2003). Six varieties are recognised in addition to var. oblongum; of these, two (var. concolor and var. latialatum) were discussed by Bean, and a third, var. itoanum, has recently come into cultivation. Seedlings attributed to A. oblongum var. concolor Pax (see Bean: B215) have been offered commercially, from a collection made in Vietnam in 2003 (HWJ 3869). The parent trees had a very striking white glaucous underside to their leaves (Heronswood Nursery catalogue 2005), which should make these very interesting specimens to watch. Dan Hinkley (pers. comm. 2007) reported that individuals in his garden in coastal Washington had been defoliated by frosts of –8 ºC in the winter of 2006– 2007, but that they were budding out in the spring. Young plants seen at Crûg Farm, Gwynedd in 2007 had rather large leaves, and their identification should perhaps be revisited in future. A. oblongum var. concolor Pax B215, K86

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Acer oblongum var. itoanum (Hayata) H.L. Li Var. itoanum differs from typical A. oblongum in its slightly smaller leaves (4.5–10 × 2–5 cm) with wavy margins, and its somewhat isolated distribution. Van Gelderen et al. 1994. Distribution JAPAN: Ryukyu Is. Habitat Subtropical evergreen forests between 1000 and 1700 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT75.

The only large specimen of Acer oblongum var. itoanum seen in the research for the current work grows at Quarryhill, where it was 3.5 m in 2004. The leaves of this individual vary from simple to trilobed or irregular in shape, and are dull dark green in colour. Perhaps because it is planted in a comparatively open spot, its foliage is apt to be sun-scorched, and the shoot tips can be damaged by frost; a site under a high canopy might be more favourable. This tree is a survivor from a batch of seedlings raised from the 1992 Index Seminum of Chiba University, Japan, the rest having succumbed to Armillaria (W. McNamara, pers. comm. 2004; H. Higson, pers. comm. 2007). There is a young plant still in the nursery at Kew, donated by Makino Botanical Garden, Japan. A. oblongum var. latialatum Pax B215, K86 A. okamotoanum (NOW A. pictum subsp. okamotoanum (Nakai) H. Ohashi, NT99) S47, K86

Acer oliverianum Pax

(Sect. Palmata, Ser. Sinensia)

Oliver’s Maple

This species was described by Bean (B216) and Krüssmann (K86).

Acer oliverianum subsp. formosanum (Koidz.) A.E. Murray Syn. A. serrulatum Hayata

Plate 86. The elegant foliage of Acer oliverianum subsp. formosanum emerges very early in the season. Image P. de Spoelberch.

Subsp. formosanum forms a tree to 20 m tall; leaves deeply five-lobed, with central lobe longest, not leathery in texture; samaras ~2.5 cm long, wings spreading obtusely. Typical A. oliverianum forms a small tree or shrub 8–10 m tall; leaves regularly five-lobed, leathery in texture; samaras 3–3.5 cm long, wings spreading almost horizontally. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution TAIWAN. Habitat Forests between 1000 and 2000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT96. Cross-references B216, S49 (as A. serrulatum), K86. Taxonomic note Flora of China (Xu et al. 2008) treats this as A. serrulatum, stating that it differs from A. oliverianum in the number of flowers and different flavonoid patterns, but P. Gregory (pers. comm. 2008) maintains the status quo.

Acer oliverianum subsp. formosanum is potentially a rather large and magnificent tree, but as yet all specimens in cultivation are still young. An early introduction was made by Kirkham & Flanagan, who collected seed at 2210 m in Nantou Co., Taiwan in 1992 (ETOT 64). Material from this source has been widely distributed and trees are generally doing very well, including one specimen at the Hillier Gardens that was 5.1 m tall in 2006, and a flourishing grove at the University of British Columbia Botanical Garden in Vancouver (Flanagan & Kirkham 2005). Other introductions include those by Bleddyn and Sue Wynn-Jones (BSWJ 1891) and Dan Hinkley (DJHT 99081) from more recent trips to Taiwan.

Section II. Species Accounts

Acer

The specimens seen for New Trees all have a distinct elegance, with attractive dark olive-green foliage and greenish stems: the trunk colour when mature is described by Dan Hinkley (Heronswood Nursery catalogue 2005) as ‘a pleasing frosted light green’. The new growth emerges alarmingly early in the year, and can be damaged by light frosts, but usually recovers. The species has a reputation for tenderness (van Gelderen et al. 1994), which may be accurate in continental Europe but is not borne out by experience in the United Kingdom or western North America, when trees have been carefully sited. Growth at the shoot tip continues all summer, the new leaves having a reddish or purple-bronze tinge that can persist on the undersides. In autumn it turns a good yellow, orange or red and holds its leaves late (L. Banks, pers. comm. 2006). A. opalus Mill. B216, S49, K86 A. opalus var. obtusatum (Willd.) Henry B217, S49, K86 A. opalus subsp. hispanicum (Pourr.) A.E. Murray K86 A. opalus var. microphyllum (NOW A. opalus subsp. hispanicum (Pourr.) A.E. Murray) K86

Acer palmatum Thunb.

A. opalus var. tomentosum (NOW A. opalus var. obtusatum (Willd.) Henry) B217, S49, K86 A. orientale (NOW A. obtusifolium Sibth. & Sm.) K86 A. osmastonii (NOW A. calcaratum Gagnep., NT78) B189, K87

(Sect. Palmata, Ser. Palmata)

Smooth Japanese Maple

This well-loved species was described by Bean (B217, S50) and Krüssmann (K87), and is given extensive coverage in all works that deal with maples. Over the years its variation has caused a great deal of confusion to both botanists and gardeners, but the situation has now been clarified by the recognition of three subspecies. Familiar cultivars are derived from all three, having been selected for centuries in Japan before being further developed in modern horticulture. The key below is provided as a guide to unfamiliar nomenclature and to enable the attribution of wild-origin material to its correct subspecies. Wild-collected material of any of the three is very scarce in cultivation – unfortunately, as it would be interesting to see the true natural variation present in these trees. Intermediates occur in the wild and have been named by Japanese botanists (P. Gregory, pers. comm. 2007). 1a. Leaves 5–10 cm long, with seven (to nine) lobes, divided more than three-quarters to the base, margins coarsely toothed; Japan .................. subsp. matsumurae Koidz. 1b. Leaves with five to seven lobes, divided to about half the diameter of the leaf ................................. 2 2a. Tree or shrub to 10 m tall, usually taller than wide; leaves 5–10(–15) cm long, with five to seven lobes, divided up to two-thirds to the base, margins very finely serrate; samaras 3–5 cm long; China, Japan, Korea .... subsp. amoenum (Carrière) Hara 2b. Tree or shrub to 10 m tall, usually wider than tall; leaves 4–6 cm long, 5–10 cm across, with five to seven lobes, divided two-thirds to three-quarters to the base, margins coarsely double-serrate; samaras 1–1.5 cm long; China, Japan, Korea, Taiwan .... subsp. palmatum

A. palmatum var. amoenum (NOW A. palmatum subsp. amoenum (Carrière) Hara) K88

A. palmatum var. heptalobum (NOW A. palmatum subsp. amoenum (Carrière) Hara) B218

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A. palmatum var. pubescens (NOW A. duplicatoserratum Hayata, NT83) K90 A. papilio (NOW A. caudatum Wall.) B219

Acer pauciflorum W.P. Fang

(Sect. Palmata, Ser. Palmata)

Syn. A. pubipalmatum W.P. Fang Small, upright tree 10–12 m; usually smaller in cultivation. Bark grey and slightly fissured. Branchlets green, slender and covered with short hairs. Leaves deciduous, membranous, 4–7.5 × 5–9 cm, palmately five- to seven-lobed, divided to half or three-quarters of their length, upper surface dark green and glabrous or with short light-coloured hairs, lower surface light green, densely covered with white hairs, margins double-serrate, apex acuminate; petiole 2–5 cm long, densely pubescent; autumn colour yellow or orange to maroon. Inflorescence terminal, corymbose with five to nine flowers. Flowers 5-merous, staminate or hermaphrodite; sepals ovate, reddish purple, petals white to cream, broadly ovate, same size as sepals, stamens eight, inserted on the surface of the nectar disc. Samaras 0.9–2 cm long, purplish brown, wings spreading obtusely. Flowering May, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008; Gregory, in prep. Distribution CHINA: southern Anhui, Zhejiang. Habitat Forests between 600 and 1000 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Cross-reference K99.

Hairy palms are more often associated with schoolboy jokes than with maples, but the whitish hairs on the leaf undersides help distinguish this species from Acer palmatum, which it otherwise rather resembles. It is a small, rather shrubby tree, but seems to be hardier and more versatile than A. palmatum (although its full potential is still unknown), which may give it a bright future in cultivation (P. Gregory, pers. comm. 2007). Like A. palmatum it has excellent autumn colour, ranging through yellow, orange and scarlet. It was introduced to Europe in the mid-1990s (van Gelderen & van Gelderen 1999) as scionwood from the Japanese collector Masato Yokoi. At the Esveld Aceretum it has achieved 2 m after ten years (Plantentuin Esveld Collections 2006–2008). It had reached North America somewhat earlier, seed having been received at the JC Raulston Arboretum in 1988 from a Chinese source (records are incomplete), growing to 3 m there before being destroyed during the erection of a new building in 2001 (T. Lasseigne, V. Tyson, pers. comms. 2007). A nice young specimen from a 1994 accession was observed at the Arnold Arboretum in May 2006. It has also done very well at the David C. Lam Asian Garden in Vancouver, where it has been growing since seed was received from Hangzhou Botanical Garden in 1993. These trees show an upright habit and are currently about 6 m tall (P. Wharton, pers. comm. 2007). It has displayed only ‘moderate frost resistance’ at Rogów Arboretum (P. Banaszczak, pers. comm. 2007), so should probably be avoided in areas with severe winters. A. paxii Franch. B215, K91 A. pectinatum Wall. ex Pax B220, S57, K91 A. pensylvanicum L. B221, S57, K91 A. pentaphyllum Diels B222, S57, K91 A. pentapotamicum J.L. Stewart B222, S58, K91

Acer pictum Thunb.

(Sect. Platanoidea)

Painted Maple

Syn. A. mono Maxim.

This relatively well-known species was described by Bean (B211, S47) and Krüssmann (K82) under the name Acer mono. After considerable debate as to the nomenclature of this taxon, Ohashi (1993b) demonstrated that A. pictum is the correct name, and

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he recognised 11 subspecies with numerous forms. The following two taxa appear to be distinct and have been recently introduced, but it is possible that others of Ohashi’s rather poorly differentiated subspecies are present in cultivation.

Acer pictum subsp. macropterum (W.P. Fang) H. Ohashi Subsp. macropterum has three- to five-lobed leaves that are pubescent beneath. The samaras are 3–4 cm long with wings spreading horizontally. Xu et al. 2008. Distribution CHINA: southeast Gansu, western Sichuan, southeast Xizang, Yunnan. Habitat Mixed forests between 1900 and 3300 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated.

The only known introduction to cultivation of this taxon was a collection of seed under the number SICH 1107 made at c. 2660 m near Muli, Yunnan, by the Sichuan Expedition of 1992. The parent tree was a fine 15 m with a trunk of 90 cm dbh, growing in mixed deciduous forest. Seedlings did not become established at Kew, and although one grew at Quarryhill for 12 years this has now been killed by Armillaria (H. Higson, pers. comm. 2007). No others have been traced.

Acer pictum subsp. okamotoanum (Nakai) H. Ohashi This subspecies has five- to seven-lobed leaves, 12–15 cm across with entire margins, and samaras 3.5–4.5 cm long with converging wings. Van Gelderen et al. 1994. Distribution SOUTH KOREA: Ullung-do. Habitat Forest remnants. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT99, NT100.

Rarity has added piquancy to the interest in this taxon, but fortunately it would seem that the report of only 15 surviving specimens (van Gelderen et al. 1994) is an underestimate, as Kirkham & Flanagan (2005) record it as a principal constituent of woodland they visited in South Korea in 1989. There, on the island of Ullung-do, it is a large tree up to 20 m tall, with wide-spreading branches. Seed from this expedition (KFBX 168) has given rise to a very vigorous specimen at Kew, 8 m tall in 2005 (Flanagan & Kirkham 2005), but there are several other large specimens in the United Kingdom as well, including one that was 9 m tall when measured by Owen Johnson for TROBI in 2003, at Batsford Park, Gloucestershire, and one that has reached 10 m at Hergest Croft (planted in 1985). The Hergest Croft tree is a fine individual with ascending branches, although it is prone to depredations by squirrels. Another large specimen (9–10 m) grows at Chevithorne Barton in Devon. Both of the latter trees are derived from a collection made in 1982 by James Harris and Joe Witt, from which only two seeds germinated (J. Harris, pers. comm. 2006). Viable seed is now produced in cultivation. In North America it is growing at the Arnold Arboretum and elsewhere. At the David C. Lam Asian Garden, a 12 m tall tree, grown from seed collected by Ferris Miller in 1980, has an 18 m spread of branches; Peter Wharton commented that it is ‘very, very vigorous’ (pers. comm. 2007). It is not fully hardy in Poland (P. Banaszczak, pers. comm. 2007). The leaves of all the A. pictum subsp. okamotoanum seen have had an elegant poise with upturned lobe tips, enhanced by

Plate 87. Acer pictum subsp. okamotoanum dominates in this woodland on the Korean island of Ullung-do, where it is endemic. Image T. Kirkham.

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a slightly undulate margin. They emerge light red and turn a good yellow in autumn. It grows very well on alkaline soils (J. Harris, pers. comm. 2007).

Acer pilosum Maxim.

(Sect. Pubescentia)

This species was described by Bean (B222) and Krüssmann (K91), but it seems probable that var. pilosum is not in cultivation.

Acer pilosum var. stenolobum (Rehder) W.P. Fang Syn. A. stenolobum var. megalophyllum W.P. Fang & Y.T. Wu The leaves of var. stenolobum have shorter lobes than in var. pilosum, which are only 0.5 cm wide (2.5 cm in the type variety). The samaras are 2–2.5 cm long with wings spreading at an obtuse or right angle. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: northeast Gansu, southwest Nei Mongol, southeast Ningxia, northern Shaanxi. Habitat Forests between 1000 and

Plate 88. Broad leaves with long-tipped lobes are characteristic of Acer pictum subsp. okamotoanum. Image R. Hitchin.

1500 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated.

Acer pilosum var. stenolobum is regarded as one of the rarest maples in cultivation, all stock being said to be derived from a tree at the Arnold Arboretum introduced by William Purdom in 1911 (van Gelderen et al. 1994, van Gelderen & van Gelderen 1999). It makes a small tree of no great beauty, although the angular leaves turn a good red in autumn. It is now cultivated in the major maple collections in Europe as well as North America, where it is fully hardy, but it would seem to need reintroduction. A wider sample of material would be helpful, to establish whether var. stenolobum really is distinct.

Acer pinnatinervium Merr.

(Sect. Hyptiocarpa)

Syn. A. jingdongense T.Z. Hsu This species is considered by van Gelderen et al. (1994) to be synonymous with A. laurinum, but is recognised as distinct by Xu et al. 2008. It forms a tree to 10 m with rough, grey or greyish brown bark. It has glabrous, pinnatinerved leaves with 8–12 pairs of lateral veins, with purplish petioles 2–3.5 cm long, and samaras 2–4 cm long. In comparison, A. laurinum has trinerved leaves with five to six pairs of lateral veins, a pubescent underside, and samaras 4–7 cm long. Xu et al. 2008. Distribution CHINA: southwest Xizang, Yunnan; INDIA; THAILAND. Habitat Mixed forest between 500 and 2400 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT88.

One of the simple-leaved evergreen maples from the warmer parts of Asia, Acer pinnatinervium is potentially a large tree. It is known in cultivation only as a few young plants growing at Tregrehan, from a collection made in Yunnan, but these seem to be doing very well. The relationship to A. laurinum is evident, but this material differs in having reddish stems and petioles and larger leaves. The leaves are handsome, glossy green above, shining white below. As with all this group, it will need a mild, sheltered situation, or to be grown as a potted plant under cover. A. platanoides L. B223, S58, K91

Acer ×pseudoheldreichii Fukarek & Celjo

(Sect. Acer, Ser. Acer)

This taxon is the result of a cross between A. pseudoplatanus and A. heldreichii, and occurs both in the wild and freely in horticulture. It is a large tree, with habit similar to that of the parents. Leaves deciduous, palmately five-lobed, 10–15 cm across, divided to half of the blade length, upper surface green with deeper green veins, lower surface glaucous or light green; autumn colour yellow. Samaras on long, pendulous racemes; samaras 3–5 cm long. Van Gelderen et al. 1994. Distribution Primarily in the Balkans, where the

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distributions of the parent species overlap. Habitat As for the parent species. USDA Hardiness Zone 5. Conservation status Not evaluated.

A Sycamore look-alike will perhaps not often be the first choice for planting, but in a large arboretum the mass of dark foliage provided by Acer ×pseudoheldreichii could be a useful foil to other trees. It is very hardy, and large specimens are recorded from the Belmont Arboretum, Wageningen, the Netherlands (van Gelderen et al. 1994), Rogów Arboretum (P. Banaszczak, pers. comm. 2007), and Kew, where it was 14 m, 37 cm dbh in 2001 (TROBI). Much more interesting is a dark-leaved clone of this hybrid raised from A. heldreichii seeds by Matthew Ridley at Blagdon, Northumberland, and named ‘Blagdon’. It is assumed that the other parent was A. pseudoplatanus ‘Atropurpureum’. The attractively shaped, deeply lobed leaves of the resultant hybrid remain purple-tinged all summer. The original tree is now approximately 8 m tall (M. Ridley, pers. comm. 2007). Grafted plants have been widely distributed from Blagdon, though it is not yet in commerce. A. pseudoplatanus L. B225, S58, K96 A. pseudoplatanus f. erythrocarpum (Carrière) Pax B227, S59, K97 A. pseudoplatanus var. tomentosum Tausch B227, K97 A. pseudoplatanus f. variegatum (West.) Rehder B227, S59

Acer pseudosieboldianum

Keijo Maple, Korean Maple

(Pax) Kom. (Sect. Palmata, Ser. Palmata) Syn. A. microsieboldianum Nakai Shrub or tree 8–10 m; crown rather open, often wider than tall. Branchlets sticky, long and slender with a whitish bloom. Leaves deciduous, papery, 10–15 cm wide, palmately 9- to 11-lobed, divided to half or twothirds of the length, upper surface dark green, lower surface densely white pubescent, margins double-serrate, apex acuminate; petiole 3.5–4 cm long, densely pubescent when young; autumn colour yellow, orange or red. Inflorescence terminal, corymbose, pubescent. Flowers 5-merous, staminate or hermaphrodite; sepals lanceolate, reddish purple, petals white to cream, obovate, stamens eight. Samaras ~3 cm long, purplish yellow, wings strongly veined, spreading obtusely. Flowering May to June, fruiting September to October (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: Heilongjiang, southeast Jilin, eastern Liaoning; NORTH KOREA; RUSSIAN FEDERATION. Habitat Forests between 700 and 900 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration NT101. Crossreference B206, K99. Taxonomic note A number of segregates were named by Nakai but are disregarded by van Gelderen et al. (1994); they occasionally appear in catalogues.

Despite being widely grown in maple collections throughout our area, Acer pseudosieboldianum is rather overshadowed by its close relatives A. japonicum and A. palmatum and other members of series Palmata, which surpass it in foliage qualities, although not in hardiness. Dirr (1998) evaluates A. palmatum as suitable for Zones 5 and 6–8, but recommends A. pseudosieboldianum as a substitute in Zones 4–5, as being better able to tolerate low winter temperatures. This is borne out by experience at Rogów in Poland (Zone 6), where it flourishes and is hardier than both A. palmatum and A. japonicum (Tumilowicz 2002, Banaszczak 2007). The trees there, planted in 1974, are now reaching 8–9 m tall (P. Banaszczak, pers. comm. 2007). Acer pseudosieboldianum subsp. pseudosieboldianum has leaves that are rounded, with short divisions, and thus lack the

Plate 89. Acer pseudosieboldianum subsp. pseudosieboldianum is a good choice for those seeking striking autumnal colour in areas too cold for A. palmatum. Image P. Banaszczak.

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elegance associated with the Japanese maples. It was not recommended by van Gelderen et al. (1994) on account of a poor, ‘floppy and loose’ shape, and the habit of retaining dull brown leaves on the twigs for some time before they fall. This, however, contrasts with travellers’ descriptions of it (for example, E.H. Wilson, quoted in Bean 1976a; Flanagan & Kirkham 2005) as a brilliant autumn feature of its native forests, with yellow to scarlet colours – and the persistence of the leaves is seen by others as an advantage! Although its date of introduction is cited as 1903 (Krüssmann 1984, Johnson 2003), the details seem to be obscure. The largest specimen in the United Kingdom is in the Bute Park Arboretum, Cardiff, where it was 11 m tall in 2005 (TROBI).

Acer pseudosieboldianum subsp. takesimense (Nakai) P.C. de Jong Subsp. takesimense is a heavily branched shrub or small tree, often with smaller (5–10 cm across), typically 9- or 11-lobed leaves. Fruits small, wings spreading horizontally. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution SOUTH KOREA: Ullung-do. Habitat Forests. USDA Hardiness Zone 6– 7. Conservation status Not evaluated. Illustration NT34, NT102, NT108. Taxonomic note Some authorities maintain this as a separate species, A. takesimense Nakai.

Plate 90. Of exceptional foliar beauty, Acer pseudosieboldianum subsp. takesimense is the second endemic maple of Ullung-do, once known as Takeshima Island. Image P. Banaszczak.

This beautiful maple is the second endemic Acer on Ullung-do, but rather scarce there (Flanagan & Kirkham 2005). It was introduced to cultivation in 1982 by James Harris and Stephen Spongberg, at the same time as A. pictum var. okamotoanum, and has been collected by other expeditions since (though not by Flanagan and Kirkham). It is an exceptionally attractive tree and, unlike the nominate subspecies, can hold its own amongst the familiar Japanese species, with leaves that are almost circular if traced around the points of their numerous lobes. The leaves somewhat resemble those of A. shirasawanum, but are much larger. In summer they are dark green, and in autumn turn orange or yellow. Although now represented in collections across our area and in commerce, A. pseudosieboldianum subsp. takesimense cannot be described as a common plant. At Hergest Croft a specimen received as seed from Chollipo Arboretum and planted in Park Wood in 1990 is currently 4–5 m tall, and there is a similar-sized one at the Arnold Arboretum. At Rogów in Poland it has grown well and has suffered no winter damage since planting in 1994, achieving 2.5 m after seven years (Tumilowicz 2002, Banaszczak 2007). Its habit is typically rather upright, and it is best considered to be a small tree with several erect branches arising from above the base.

Acer pubinerve Rehder

(Sect. Palmata, Ser. Sinensia)

Syn. A. wuyuanense W.P. Fang & Y.T. Wu Tree 5–7 m. Bark dark grey, brown or purple. Branchlets pale green or purplish green, slender and glabrous. Leaves deciduous, 7–9 cm across, palmately five-lobed, lobes one-third to half of the length, dark green and largely glabrous, margins slightly serrate, apex caudate; petiole 4–5 cm long. Inflorescence paniculate to racemose, few-flowered. Flowers 5-merous, staminate or hermaphrodite; sepals purplish green, petals white,

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stamens 8–10, inserted outside the nectar disc. Samaras ~3 cm long, yellowish, wings spreading horizontally. Flowering April, fruiting October (China). Van Gelderen et al. 1994. Distribution CHINA: Jiangxi. Habitat Forests. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT103.

In North American collections as disparate as the David C. Lam Asian Garden in Vancouver and the US National Arboretum in Washington DC, Acer pubinerve (labelled A. wuyuanense) has won high praise as a beautiful small tree with great garden potential. In both these locations it is grown from seed collected by the 1988 NACPEC expedition to Huangshan, Anhui Province, China, near the Chi Guang Ge Temple at 640 m. As observed in May 2006, two specimens at the US National Arboretum had made rounded trees, approximately 2.5 m tall and equally wide. A notable feature was the abundance of pale green samaras nestling among the leaves. For Douglas Justice in Vancouver, however, it is the emerging foliage that draws attention. Memorably, he describes it as being like ‘oily, dark brown chicken feet’ (D. Justice, in Wharton et al. 2005), although his suggested English name Chocolate Maple is a more pleasing descriptor! This dark spring growth emerges from dark twigs, but becomes a rich green. In Vancouver, ‘A. wuyuanense’ has made trees 5 m tall by 3 m wide. This is evidently an exceptionally interesting species, of great value for smaller gardens, but it is not yet commercially available. Except for some young seedlings at Westonbirt (P. Gregory, pers. comm. 2007), it seems to be unknown in Europe at the present time; some trees from the Huangshan were distributed from Castle Howard by James Russell in the late 1980s, but none grow there now (T. Kirkham, pers. comm. 2007). One donated to Philippe de Spoelberch was dead by 1992 (K. Camelbeke, pers. comm. 2007).

Acer pycnanthum K. Koch

(Sect. Rubra)

Japanese Red Maple, Hananoki

Tree to 15 m; usually smaller in cultivation. Bark grey and longitudinally fissured, becoming rather shaggy. Branchlets reddish brown to grey-brown, glabrous. Leaves deciduous, papery or leathery, 6–8(–12) × 2.5–7(–11) cm, palmately three-lobed, lobing very shallow, upper surface shiny green and glabrous, lower surface glaucous and largely glabrous, margins irregularly serrate, apex acute; petiole 3–9 cm long, reddish; autumn colour yellow to orange-red. Inflorescence terminal and lateral, umbellate with 4–10 flowers. Flowers 5-merous, dioecious; sepals oblong, red, petals none to five, smaller than sepals, stamens five to six, inserted outside the nectar disc. Samaras 2–3 cm long, wings spreading acutely. Flowering April, fruiting May to June (Japan). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution JAPAN: central Honshu. Habitat Wet, lowland sites. USDA Hardiness Zone 5. Conservation status Not evaluated (but restricted distribution). Illustration NTiii, NT104. Cross-reference K100. Taxonomic note This species is very similar to the closely related A. rubrum, though it has slightly smaller leaves and stature.

Acer pycnanthum was said by Bean (1976a) to be probably not in cultivation in the United Kingdom, but over 25 specimens are currently on the TROBI list of notable individuals, the tallest in England being two male trees of over 14 m at the Sir Harold Hillier Gardens. An important source of seed in the early 1970s was the Japanese nurseryman Seyo Yamaguchi, who gave material to Peter Barnes and Roy Lancaster (R. Lancaster, pers. comm. 2007), from which some of the largest specimens today are derived (including the Irish champion at Dunloe Castle Hotel, Co. Kerry, 15 m tall when measured in 2000, TROI); but the first introduction to the West is credited to James Harris in 1971 by van Gelderen et al. (1994). The species can make shapely

Plate 91. Acer pubinerve (syn. A. wuyuanense) is forming attractive small trees in those gardens fortunate enough to possess it. This one is in the US National Arboretum. Image J. Grimshaw.

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pyramidal specimens with considerable presence, several being designated National Monuments in Japan, and in cultivation many look set to exceed the 15 m quoted for wild trees. A smaller stature is said to be a distinguishing feature from its close relative, the North American A. rubrum, but the difference may become blurred in cultivation if these trees continue to grow strongly. Other horticultural distinctions are its slightly glossier leaves and less reliable autumn colour – at Hergest Croft it is ‘sometimes a good red’ (L. Banks, pers. comm. 2006), although in the wild it can be a brilliant scarlet. The young foliage can also be tinted red, and as in A. rubrum the flowers and reddish young fruit can be spectacular. Several variegated cultivars are known (van Gelderen & van Gelderen 1999).

A. ×ramosum Schwer. K100 A. reginae-amaliae (NOW A. hyrcanum subsp. reginae-amaliae (Orph. ex Boiss.) A.E. Murray, NT86) K100 A. ×rotundilobum Schwer. B228, K100

Plate 92. Acer pycnanthum at Herkenrode. The autumnal colour is not as intense in cultivation as it is in the wild. Image P. de Spoelberch.

Acer rubescens Hayata

(Sect. Macrantha)

Syn. A. morrisonense H.L. Li non Hayata Tree 10–20 m. Bark smooth, green with irregular white longitudinal stripes. Branchlets somewhat glossy, with whitish stripes. Leaves deciduous, papery, 8–10 × 6–8 cm, palmately five-lobed (rarely seven-lobed), divided to one-fifth of the length, upper surface shiny bronze-green to dark green with caducous rusty hairs on the midrib, lower surface lighter green, dull with persistent rusty hairs, margins coarsely serrate, apex acute to acuminate; petiole 4–8 cm long, red and glabrous; autumn colour bronze to red-orange, finally yellow. Inflorescence terminal and lateral, racemose with 10–30 flowers. Flowers 5-merous, 3–4 cm diameter, dioecious; sepals triangular-ovate, dark green, petals oblong, yellow, stamens eight, inserted outside the nectar disc. Samaras 1.8–2.3 cm long, yellowish brown, wings distinctly veined and spreading almost horizontally. Flowering March to April, fruiting October (Taiwan). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008; Gregory, in prep. Distribution TAIWAN. Habitat Montane forest between 1800 and 2200 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT105, NT108.

In horticulture, Acer rubescens has been somewhat confused with A. caudatifolium, principally because the two species share the synonym A. morrisonense, and material of A. rubescens has been distributed as A. morrisonense through the nursery trade in England. There should, however, be little risk of mistake, as (besides the botanical distinctions) A. rubescens often has a strong red flush to all its parts (as its name suggests), with dark olive-green leaves, while A. caudatifolium is rather green in appearance, with mid-green leaves. Much of the cultivated stock of A. rubescens has come from a tree at Trewithen, Cornwall, 19 m tall (67 cm dbh) in 2004 (TROBI), for long the only specimen known in cultivation. This was planted in 1912, from a seed collection (Yashiroda 109) made in Taiwan (van Gelderen et al. 1994, Johnson 2003). Scions of it are being grown throughout the British Isles, and many have become fine trees. One observed at Hergest Croft is c. 12 m tall (dbh 56 cm), with stiffly ascending branches. The bark is extremely attractive, being a mixture of dark green and brown, with paler lines and

Section II. Species Accounts

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large lenticels, the pattern retained to the ground. The younger growth is deep red, as are the petioles and the expanding leaves. When mature the leaves are glossy dark green, and vary greatly in the degree of lobing. Seedlings are very variable, however, and recent introductions have revealed further variation. A specimen grown from BSWJ 1744 at Hergest Croft is rather gaunt, with wide-spreading limbs, and has green stems with white stripes. The species is extremely fast-growing (A. Norfield, pers. comm. 2006), but is said to require a sheltered site (van Gelderen & van Gelderen 1999), and in Poland it is damaged by frost (P. Banaszczak, pers. comm. 2007). At Kew it is susceptible to frost until well established (Flanagan & Kirkham 2005), possibly because the leaves tend to emerge rather early – although at Hergest Croft it has not been affected by frost (L. Banks, pers. comm. 2006). The leaves also remain on the tree rather late into the autumn, turning a dull red. It is well established from ETOT 158 (1993) at the David C. Lam Asian Garden at the University of British Columbia (Justice 2002), but seems not to be widely cultivated in North America. Several variegated clones are known, having white mottling and marbling of varying extent; with the red stems this can give a rather striking effect.

A. rubrum L. B228, S59, K101 A. rubrum var. barbatum (NOW A. rubrum L.) K101 A. rubrum var. drummondii (Nutt.) A.E. Murray K101 A. rubrum var. tomentosum Pax K101 A. rubrum var. trilobum Torr. & A. Gray ex Koch K101

Acer saccharum Marshall

A. rufinerve Siebold & Zucc. B229, K101 A. rufinerve f. albolimbatum (NOW A. rufinerve ‘Albo-limbatum’) B229 A. saccharinum L. B230, S59, K101 A. saccharinum f. laciniatum (NOW A. saccharinum ‘Laciniatum’) B230

(Sect. Acer, Ser. Saccharodendron)

Sugar Maple

This species was described by Bean (B231, S60) and Krüssmann (K104), and is an important maple in temperate tree collections and landscapes. Authorities recognise variable numbers of subspecific taxa. Desmarais (1952) constructed a key to six subspecies, though additional taxa are recognised by van Gelderen et al. (1994). Presented below is a key to seven subspecies (devised by Peter Gregory and used with his kind permission), with an indication of the distribution of each from van Gelderen et al. (1994). However, the delimitation of the various subspecies and varieties is complex, as morphological characters vary continuously across the vast range. Most of the A. saccharum subspecies are well known in cultivation, and were described by Bean (1976a) under different names (A. barbatum, A. grandidentatum, A. leucoderme, A. nigrum). Material from the southernmost population, recognised as subsp. skutchii, is new to cultivation and is described below. Numerous cultivars of A. saccharum have been named, with varying characters useful for different sites and conditions. A summary guide is provided by Dirr (1998).

105

Plate 93. The generally reddish tint seen in Acer rubescens does not appear in the bark, but is apparent here in the petioles of the leaves in the background. Image R. Hitchin.

106

Acer

New Trees

1a. Leaf underside pale green to glaucous ............................................................................................. 2 1b. Leaf underside yellow-green, lobes shallow, central lobe with divergent margins ............................ 6 2a. Leaves large (≥ 10–15 cm) ............................................................................................................... 3 2b. Leaves small (5–10 cm) ................................................................................................................... 5 3a. Leaves deeply lobed, margins of central lobe parallel to inwardly angled ........................................ 4 3b. Leaves shallowly lobed, margins of central lobe slightly divergent; USA (Illinois, Indiana, Missouri) ........................................................................... subsp. schneckii 4a. Lobe tips acute, leaf undersides glabrous to pubescent with silky appressed hairs; widespread in eastern North America (Canada, Mexico, USA) ................. subsp. saccharum 4b. Lobe tips bluntly pointed, leaf undersides pubescent and glaucous; Guatemala, Mexico (southern) ............................................................................... subsp. skutchii 5a. Margins of central lobe parallel to slightly divergent, lobe tips bluntly pointed; Mexico, USA (Florida, Texas) .......... subsp. floridanum (Chapman) Desmarais 5b. Margins of central lobe inwardly angled, lobe tips rounded; USA (Oklahoma and Texas to Arizona and Montana, especially Rocky Mts.) ................................................................ subsp. grandidentatum 6a. Leaves small (5–10 cm), undersides with soft appressed hairs, bark smooth, pale grey to chalky white; USA (Alabama, Arkansas, Florida, Georgia, Louisiana, N. Carolina, S. Carolina) ......... subsp. leucoderme (Small) Desmarais 6b. Leaves large (≥ 10–15 cm), undersides with stiff, short, erect hairs, bark rough, dark grey-brown to black; Canada (Ontario, Quebec), USA (northeast, south to Kentucky, west to Michigan, Iowa, Kansas) ....................... subsp. nigrum

Plate 94. The pale glaucous leaf undersides of the Mexican Acer saccharum subsp. skutchii are distinctive. It is almost evergreen where winters are not severe. Image M. Foster.

A. saccharum subsp. grandidentatum (Nutt. ex Torr. & A. Gray) Desmarais K104 A. saccharum subsp. nigrum (F. Michx.) Desmarais K104 A. saccharum var. rugelii (Pax) Rehder B231, K104 A. saccharum subsp. schneckii (Rehder) Desmarais K104

Acer saccharum subsp. skutchii (Rehder) A.E. Murray Subsp. skutchii forms a tree to 20 m tall. Branchlets glabrous. Leaves 12–16 × 14–20 cm, lower surface glaucous with dense tomentum on the veins. Samaras 2.5–4.5 cm long. Van Gelderen et al. 1994. Distribution GUATEMALA; MEXICO. Habitat Cloud forest over limestone. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT106.

This is the southernmost variant of the sugar maples, but its precise delimitation in the western Mexican mountains is not entirely clear (S. Hogan, pers. comm. 2007), as subspp. floridanum, grandidentatum and saccharum also penetrate Mexico (van Gelderen et al. 1994). Material from Tamaulipas in cultivation in the western United States appears to fit subsp. skutchii, and has large leathery leaves that persist into the New Year, when they colour red and fall slightly before or as the new leaves emerge, thus making the tree almost evergreen. At Tregrehan at least it has attractive pinkish spring growth (T. Hudson, pers. comm. 2007). There is a good specimen in the Hogan–Sanderson plantings in Northeast 11th Avenue, Portland, Oregon, and it is grown in the southeastern states from collections made by Yucca Do Nursery. It is rare

Section II. Species Accounts

Acer

in Europe, but a few examples are known. Tom Hudson (pers. comm. 2007) planted one in 1995 at Tregrehan but, in the belief that it was tender, put it in a sheltered site where competition from other trees has suppressed it, and it is still only 2 m in 2007. This taxon in fact appears to be extremely hardy, reported to tolerate at least –18 ºC, and to grow well in heavy clay soils (Raulston 1996), although leaves will be lost if temperatures fall below this (Hogan 2008).

Acer schneiderianum Pax & K. Hoffm.

(Sect. Palmata, Ser. Sinensia)

Small tree, 6–8 m. Bark smooth, grey or greyish brown. Branchlets slender, glabrous and green with some bronzing on the upper surfaces. Leaves deciduous, 6–8 × 8–11 cm, palmately five-lobed, divided to half of the length, upper surface dark green with a tuft of silvery hairs at the junction of the petiole and lamina, lower surface pale or greyish green with silky hairs along the veins, margins minutely serrate, apex acute to acuminate; petiole to 6 cm long, red and extremely slender. Inflorescence terminal, paniculate, 3–4 cm long. Flowers 5-merous, 0.3–0.4 cm diameter, staminate or hermaphrodite; sepals oblong, green, petals ovate-oblong, pale yellow, stamens eight, inserted inside the nectar disc. Samaras ~2 cm long, purplish red to pale yellow, wings spreading almost horizontally. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999; Gregory, in prep. Distribution CHINA: western Sichuan, northern Yunnan. Habitat Montane forest. USDA Hardiness Zone 6. Conservation status Not evaluated. Cross-reference K105. Taxonomic note Flora of China (Xu et al. 2008) treats this species as a synonym of A. oliverianum subsp. oliverianum.

Reported in Maples of the World (van Gelderen et al. 1994) to be unknown in cultivation at that time, Acer schneiderianum has since been introduced on several occasions. Priority appears to belong to SICH 1214, collected in November 1992 at 2390 m in Zhaojue Co., Sichuan. Here the parent trees of up to 8 m in height grew in a rich community of broadleaved trees on a north-facing slope. Good specimens are established at Wakehurst Place and in Giles Coode-Adams’ arboretum at Feeringbury Manor, Essex, the latter being the larger tree, at 6 m in 2006 (TROBI). A 1995 introduction by Mikinori Ogisu (Ogisu 95089) from Xichang, Sichuan was widely distributed, and is established in many British collections. There have also been more recent commercial introductions, and the species is offered by specialist nurseries in Europe. In North America it remains little known, but it is growing well in Vancouver (Wharton et al. 2005) from SICH 1214 and has reached 6 m there too, resisting the heavy snow of the 2006–2007 winter without branch breakage (P. Wharton, pers. comm. 2007). Acer schneiderianum resembles members of the A. campbellii group, but has somewhat finer branching and less leathery leaves, which flush red or bronzed and become a good orange in autumn (Wharton et al. 2005). A young plant observed at Hergest Croft has an attractive ‘pewtered’ cast to the mature leaves in summer. This plant originated as seed imported from China by Andrew Norfield – one of several Chinese species introduced to a wider market by his nursery. It appears to be hardy and to flourish in the conditions usually enjoyed by members of Acer section Palmata.

A. semenovii (NOW A. tataricum subsp. semenovii (Regel & Herder) A.E. Murray) B200, K105 A. sempervirens L. B232, S60, K105 A. ×senecaense Slavin K105 A. ×sericeum Schwer. K105

A. serrulatum (NOW A. oliverianum subsp. formosanum (Koidz.) A.E. Murray, NT96) B216, S49 A. shirasawanum Koidz. S44, K105 A. shirasawanum f. aureum (NOW A. shirasawanum ‘Aureum’) B205, S45, K78

107

108

Acer

New Trees

B C

A

D

E

1 cm

Section II. Species Accounts

Acer sieboldianum Miq.

(Sect. Palmata, Ser. Palmata)

Acer

109

Siebold’s Maple

Shrub or small tree, 8–10 m. Bark grey and smooth. Branchlets greenish brown, pubescent to tomentose, somewhat sticky when young. Leaves deciduous, papery, 5–7 × 6–9 cm, palmately lobed with (7–)9(–11) lobes, divided to half of the length, upper surface dark green, lower surface pale green with dense white hairs that persist along the veins, margins double-serrate, apex acuminate; petiole 3–6 cm long, pubescent; autumn colour coppery red. Inflorescence terminal, corymbose, 3–5 cm long with 15–20 flowers. Flowers 5-merous, staminate or hermaphrodite; sepals narrowly ovate, pale purple, petals ovate, greenish yellow, shorter than sepals, stamens eight, inserted inside the nectar disc. Samaras 1.5–2 cm long, greenish yellow, wings spreading at an angle of 130º–160º. Flowering April to June (Japan). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999. Distribution JAPAN: Honshu, Shikoku, Kyushu. Habitat Montane forest in southern Japan; in northern Japan, between 0 and 900 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration NT73, NT108. Cross-reference B206, K105.

Acer sieboldianum is anything but a ‘new tree’, but given its curious treatment in a very short paragraph by Bean (1976a), and minimal coverage elsewhere (for example, Hillier & Coombes 2002), a fuller account is desirable here. Introduced by Philipp von Siebold in the nineteenth century, it has remained overshadowed by its allies A. japonicum, A. palmatum and A. shirasawanum but is deserving of greater attention, not least for its exceptional and reliable autumn colour and much greater hardiness (although it can show some damage after a severe Polish winter: P. Banaszczak, pers. comm. 2007). According to van Gelderen et al. (1994) it flourishes in Scandinavia where A. palmatum is not hardy, and this would suggest a wide applicability in North America, where it is freely available. There are good specimens in many European collections, mostly making small trees of up to 10 m or so and, where there is room, forming wide-spreading rounded crowns, although sometimes the branches are more upright. The leaves are a fresh green in summer, with late shoots emerging bright red (L. Banks, pers. comm. 2006) before the tree becomes clad in superb autumn colour of scarlet and gold.

Acer sikkimense Miq.

(Sect. Macrantha)

Sikkim Maple

Syn. A. hookeri Miq. Tree to 12 m, though often a shrub in cultivation. Bark greyish black, slightly white-striped. Branchlets red or brown, glabrous. Leaves deciduous to semi-evergreen, papery to leathery, 10–14 × 5–8 cm, entire or rarely three-lobed, upper surface dark green, lower surface pale green with barbed hairs in the vein axils, margins entire to serrulate, apex caudate; petiole 2–4 cm long, glabrous; autumn colour rather limited. Inflorescence terminal, racemose, with 40–50 flowers. Flowers rather small, 5-merous, staminate or hermaphrodite; sepals ~0.3 cm long, oblong-ovate, petals greenish yellow, same length as sepals, stamens eight, inserted inside the nectar disc. Samaras 2–2.5 cm long, brown, wings spreading obtusely, rarely horizontally. Flowering March, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution BHUTAN; CHINA: southeast Xizang, Yunnan; INDIA: Assam, Sikkim; MYANMAR; NEPAL. Habitat Mixed forest between 1700 and 3000 m asl. May grow as an epiphyte. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT11. Cross-references B204 (as A. hookeri), K106.

Despite having a vast range Acer sikkimense is not very well known in cultivation, probably because it often occurs at rather low altitudes at lower latitudes. It was described by Bean (1976a), as A. hookeri, and stated by him to be tender in the British Isles, a view that seems to be borne out by the general dearth of specimens growing outside here. It is in cultivation at Tregrehan, from Chinese and Vietnamese origins. Except on the mildest fringes of western Europe or the Pacific Coast, however, it is probably too tender for outdoor use. Beyond our area it is grown in California and Australia. Described by Peter Wharton (pers. comm. 2007) as an ‘intriguing’ species, it is clearly very variable, and Wharton noted that in northern Vietnam, at least, it occurs

Figure 10 (opposite). Acer, branchlets with fruit. Acer caudatifolium (A); A. rubescens (B); A. pseudosieboldianum subsp. takesimense (C); A. Lancaster 962, Hergest Croft, grown as A. sikkimense var. metcalfii (D); A. sieboldianum (E).

110

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New Trees

in populations that vary from evergreen to deciduous. This suggests that there is much variation to experiment with in cultivation. A. sinense Pax (OR A. campbellii subsp. sinense (Pax) P.C. de Jong) B233, S61, K106 A. sinense var. concolor (NOW A. sinense Pax) B233, K106 A. sino-oblongum Metcalf K106

Acer sinopurpurascens W.C. Cheng

(Sect. Lithocarpa, Ser. Lithocarpa)

Tree 8–10 m, though often smaller in cultivation. Bark greyish brown, almost smooth. Branchlets green initially, later grey-brown. Leaves deciduous, deeply five-lobed or rarely three-lobed, upper surface dull green, lower surface pale green, both surfaces pilose along the veins when young, margins entire or rarely dentate, apex acute or acuminate; petiole 4–8.5 cm long, slender, pubescent when young, exudes milky sap when broken; autumn colour yellow. Inflorescence lateral, pendulous or corymbose racemes with three to seven flowers, dioecious. Flowers 5-merous; sepals (three to) five (to six), ~0.5 cm long though unequal in size, purplish red, petals five (absent in staminate flowers), same length as sepals, stamens eight, inserted inside nectar disc. Samaras 3–6 cm long, pale yellow, bristly, wings spreading obtusely. Flowering April, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: southern Anhui, northeast Hubei, northern Jiangxi, northwest Zhejiang. Habitat Mixed forest between 700 and 1000 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT69, NT110. Cross-reference K106.

Plate 95. The solitary female specimen of Acer sinopurpurascens at Rogów never sets viable fruit. Image P. Banaszczak.

Although an attractive and elegant tree that deserves widespread cultivation, Acer sinopurpurascens is extremely rare in horticulture due to difficulties in its propagation, possibilities for grafting being limited by the absence of related species with latex (van Gelderen & van Gelderen 1999). Neither is seed a useful alternative as it is a dioecious species and specimens are widely separated. A few arranged marriages might be useful. The red flowers, appearing early in the year and on young plants, are spectacular (le Hardÿ de Beaulieu 2003). The male tree is at Arboretum Trompenburg, growing by the canal running through the garden. When observed in 2005 it was c. 10 m tall (25 cm dbh) with two more or less equal main stems from a fork at 3.5 m. The branches are spreading and slightly pendulous, bearing the dark green, three-pointed leaves as a light canopy. This specimen was obtained from Dr Illa Martin from Germany in 1964, as part of a dispersal of stock following the death of her husband, but its ultimate origin is unknown (van Hoey Smith 2001). In England a female tree at the Valley Gardens is mentioned and illustrated by van Gelderen & van Gelderen (1999), but this specimen is not recorded by TROBI. That database does however record two further good specimens, a 5 m tree at Batsford Park, Gloucestershire in 2003, and a 7.3 m male individual at the Sir Harold Hillier Gardens in 2002. A few plants propagated from the Trompenburg specimen have been distributed by Esveld, but overall this is a good example of a case where a concerted conservation attempt is needed to propagate a rare and recalcitrant species. In Poland, a female tree derived from Shanghai Botanic Garden seed has been hardy

Section II. Species Accounts

Acer

since 1981 at Rogów and has reached over 7 m – but again, being a solitary specimen, it does not set viable seed (Tumilowicz 2002). The species appears to be unknown in North American collections, but its hardiness should be useful there. A. spicatum Lam. B233, K107

Acer stachyophyllum Hiern

(Sect. Glabra, Ser. Arguta)

This species was described briefly by Bean (B237), who also described A. tetramerum Pax, now synonymous with A. stachyophyllum. See also Krüssmann (K107).

Acer stachyophyllum subsp. betulifolium

Birch-leaf Maple

(Maxim.) P.C. de Jong Subsp. betulifolium is said to be a multistemmed tree or shrub that suckers freely from the base once established, unlike subsp. stachyophyllum which, while multistemmed, does not produce suckers (van Gelderen et al. 1994, van Gelderen & van Gelderen 1999), but this seems not to be a very reliable distinction (P. Gregory, L. Banks, pers. comms. 2007). The leaves of subsp. betulifolium (3–5 × 2–3 cm) are somewhat smaller than those of subsp. stachyophyllum (4–8 × 3–5 cm). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution CHINA: southern Gansu, western Henan, western Hubei, Ningxia, southern Shaanxi, Sichuan, Yunnan; MYANMAR. Habitat Alpine forests between 1400 and 3300 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated.

Accounts of the early introductions of Acer stachyophyllum and its varieties are somewhat confused by the former use of the name A. tetramerum. It seems, however, that it was first introduced by Ernest Wilson (Wilson 4102) from Sichuan in 1910, with later collections by George Forrest (Bean 1976a). There are numerous mature specimens from these early collections in British and Irish arboreta, the largest recorded being 15.5 m at Hergest Croft in 1995 (TROBI), an old tree planted prior to 1930 and possibly an original Wilson collection (L. Banks, pers. comm. 2007). A large plant (perhaps best described as a thicket) of this taxon also grows in the Esveld Aceretum in Boskoop, from where it has been abundantly propagated and distributed. It has also been collected in Sichuan on several occasions through the SICH expeditions between 1988 and 2003 (for example, SICH 207, 1119, 1457, 1740, 2310), at altitudes between 1580 and 3050 m. It is frequently a component of regenerating or secondary forest. Although a snakebark, this is not one of the more attractive members of the group, and with its suckering habit needs ample space to develop. The mid-green leaves turn yellow in autumn.

A. sterculiaceum Wall. (WAS A. villosum B200) A. sterculiaceum subsp. sterculiaceum K107 A. sterculiaceum subsp. franchetii (Pax) A.E. Murray K107 (WAS A. franchetii B199, S41, K75) A. sutchuenense Franch. B204, S43, K107 A. syriacum (NOW A. obtusifolium Sibth. & Sm.) B234, S61

A. takesimense (NOW A. pseudosieboldianum subsp. takesimense (Nakai) P.C. de Jong, NT102) S44 A. taronense (NOW A. pectinatum subsp. taronense (Hand.-Mazz.) A.E. Murray) B234, S61, K107 A. tataricum L. B235, K107 A. tataricum var. incumbens Pax K107 A. tegmentosum Maxim. B235, K107

111

112

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New Trees

Acer tenellum Pax

(Sect. Platanoidea)

Shrub or tree to 8 m, or more in cultivation. Bark pale or dark grey, smooth. Branchlets yellowish green to olive-brown, slender, glabrous and with round, raised lenticels. Leaves deciduous, thin and papery, tremulous, 4–6 × 3–6 cm, palmately three- to five-lobed, rarely entire, lobes shallow, upper surface dull dark green and glabrous, lower surface pale green with some caducous hairs along the veins, margins entire, apex acute or rarely acuminate; petiole 3–8 cm long, slender, pale green or reddish, exudes milky sap when broken; autumn colour yellow. Inflorescence terminal, corymbose, 1.5–2 cm long. Flowers 5-merous, staminate or hermaphrodite; sepals oblong to ovate, pale green, petals oblong-obovate, yellowish green, stamens 8–10, inserted outside the nectar disc. Samaras 2–2.2 cm long, purple when young, wings spreading nearly horizontally. Flowering May, fruiting September (China). Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008; Gregory, in prep. Distribution CHINA: western Hubei, Jiangxi, Sichuan, Yunnan. Habitat Mixed forest between 1200 and 1800 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated.

Acer tenellum is rare in cultivation, and dismissed by van Gelderen & van Gelderen (1999) as being of ‘botanical interest only’. Despite this it is represented in a number of British and European collections, the largest verified specimen being in the United Kingdom (11 m, dbh 36 cm, TROBI), at Borde Hill, West Sussex, probably grown from seed collected by Wilson in 1901 (van Gelderen et al. 1994). A taller tree (16 m) at Glasnevin is the subject of discussion over its identity. There is also some doubt over the authenticity of material offered commercially in the United States (Hill & Narizny 2004). Vegetative propagation is difficult (van Gelderen & van Gelderen 1999), but it is available from nurseries specialising in Acer. Its charm lies in its small, rather rounded leaves, said to quiver in the breeze like those of an Aspen (Populus tremula) (van Gelderen & van Gelderen 1999).

A. tenuifolium (NOW A. shirasawanum subsp. tenuifolium Koidz.) S45 A. tetramerum (NOW A. stachyophyllum Hiern) B236, S61

Acer tonkinense Lecomte

A. thomsonii Miq. (OR A. sterculiaceum subsp. thomsonii (Miq.) A.E. Murray) B200, K107 A. tibetense W.P. Fang K107 A. tibetense var. slendzinskii Racib. K108 A. tibetense var. torminaloides Pax K108

(Sect. Palmata, Ser. Sinensia)

Tonkin Maple

Shrub or tree 8–12 m. Bark dark brown, smooth. Branchlets purplish green to olive-brown, glabrous and waxy. Leaves deciduous, somewhat leathery, 10–15 × 7–5 cm, palmately three- to five-lobed, lobes shallow, upper surface glabrous, lower surface glabrous but for the tufts of hair in the vein axils, margins entire in subsp. tonkinense and subsp. liquidambarifolium (serrate in young leaves and with remote teeth in subsp. kwangsiense), apex acute; petiole 2–3.5 cm long, purplish green; autumn colour orange-yellow to red. Inflorescence terminal, paniculate, 8–10 cm long with numerous flowers. Flowers 5-merous, staminate or hermaphrodite; sepals triangular, purplish green, petals yellowish, stamens 8–10, inserted outside the nectar disc. Samaras 1.8–3 cm long, yellowish, wings spreading horizontally. Flowering April to May, fruiting September (China). Van Gelderen et al. 1994, Xu et al. 2008. Distribution CHINA: Guangxi, southern Guizhou, southeast Xizang, southeast Yunnan; MYANMAR; THAILAND; VIETNAM. Habitat Mixed forest between 300 and 1800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT76. Crossreference K108. Taxonomic note Van Gelderen et al. (1994) recognised two subspecies with somewhat larger leaves: subsp. kwangsiense (W.P. Fang & M.Y. Fang) W.P. Fang, with leaves 12–17 cm across with sparse teeth on the margin (cultivated by Firma C. Esveld under glass in the Netherlands); and subsp. liquidambarifolium (H.H. Hu & W.C. Cheng) W.P. Fang, with evenly lobed leaves 8–14 cm across. The latter is said to be extremely beautiful in the wild in Vietnam (D. Hinkley, pers. comm. 2007), but grows at rather low altitudes. These subspecies are not accepted by Xu et al. 2008.

Section II. Species Accounts

Acer

113

Acer tonkinense is extremely rare in cultivation and has not been seen in any collections visited in the research for New Trees. Such little information as can be gleaned suggests that it is not hardy in most of our area and must be maintained under glass. It has, however, recently been offered commercially, most notably by Heronswood Nursery in their 2002 catalogue. The plants offered were grown from seed supplied by James Waddick of Kansas City, Missouri, obtained from Shanghai Botanic Garden, and were described as having thick leathery leaves, each of the five lobes terminating in a long-acuminate point. At Heronswood it proved ‘very hardy’ and formed a notable feature with ‘ashen lime’ stems in winter (Heronswood Nursery catalogue 2002). It comes into growth early in the year (D. Hinkley, pers. comm. 2007). A. trautvetteri (NOW A. heldreichii subsp. trautvetteri (Medw.) A.E. Murray) B237, K108 A. triflorum Kom. B237, K108 A. truncatum Bunge B238, S61, K108 A. tschonoskii Maxim. B238, K108 A. tschonoskii var. rubripes (NOW A. tschonoskii subsp. koreanum A.E. Murray) B238, K108 A. turcomanicum (NOW A. monspessulanum subsp. turcomanicum (Pojark.) A.E. Murray, NT92) S48 A. turkestanicum (NOW A. platanoides subsp. turkestanicum (Pax) P.C. de Jong) S62, K108

Acer wardii W.W. Sm.

A. tutcheri Duthie K108 A. ukurunduense (NOW A. caudatum subsp. ukurunduense (Trautv. & C.A. Mey.) A.E. Murray) B238, K108 A. ×veitchii (NOW A. ×schwerinii Pax) B194, K108 A. velutinum Boiss. B239, S62, K108 A. velutinum f. glabrescens (Boiss. & Buhse) Rehder K109 A. velutinum var. vanvolxemii (Mast.) Rehder B239, K109 A. velutinum f. wolfii (Schwer.) Rehder K109 A. villosum (NOW A. sterculiaceum Wall.) B200

(Sect. Wardiana)

Shrub or tree 5–10 m. Bark light or dark grey, somewhat rough with inconspicuous stripes. Branchlets reddish purple, slender, glabrous. Leaves deciduous, papery, 7–9 × 6–8 cm, palmately three-lobed, lobes half to two-thirds of the length, upper surface shiny and glabrous, lower surface usually glabrous, margins serrulate, apex elongated, caudate to acuminate; petiole 3–5 cm long, slender, glabrous. Inflorescence terminal (and lateral), paniculate to racemose, slender with conspicuous bracts. Flowers 5-merous, staminate or hermaphrodite; sepals reflexed, linear to oblong, petals linear to oblong, purple, stamens 8–10, inserted in centre of nectar disc. Samaras 2.2–2.5 cm long, purplish yellow, wings spreading obtusely. Flowering May, fruiting September (China). Van Gelderen et al. 1994, Xu et al. 2008. Distribution CHINA: eastern Xizang, northwest Yunnan; INDIA: Arunachal Pradesh, Assam (?); MYANMAR. Habitat Alpine forest between 2400 and 3600 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT4, NT113. Cross-references B199, K109.

Discovered by Frank Kingdon-Ward in 1914, but introduced by George Forrest, this interesting species was placed in its own section by de Jong (van Gelderen et al. 1994). For decades it was represented in cultivation by a single tree at Trewithen in

Plate 96. Long drip-tips give an indication of the dampness of the natural habitat of Acer wardii, seen here in the Gongshan, Yunnan. Image M. Foster.

114

Ackama

New Trees

C 1 cm

1 mm

1 mm

B A

Section II. Species Accounts

Acer

115

Cornwall, but this was killed in the famously cold winter of 1962–1963, and although a cutting was reported to have been rooted from it (Bean 1976a), no specimens seem to have persisted. In recent years it has been reintroduced from western Yunnan, and young plants are now in cultivation at Tregrehan. It is evidently well adapted to its extremely wet native habitat, having long drip-tips on each of the three lobes of the leaves. The young plants have red shoots and a green main stem, and the mature tree is said to have a very ornamental weeping habit (Hudson 2004). How hardy these plants will be remains to be seen. In the Mishmi Hills of Arunachal Pradesh it forms thickets of shoots arising as suckers from the roots of older trees (M. Wickenden, pers. comm. 2007). A. wilsonii (NOW A. campbellii subsp. wilsonii (Rehder) P.C. de Jong) B240, S62, K109

A. yui W.P. Fang K109 A. ×zoeschense Pax B240, S62, K109

CUNONIACEAE

ACKAMA

A. Cunn.

The genus Ackama includes four species, two in Australia and two in New Zealand (de Lange et al. 2002). Ackama was placed in synonymy with Caldcluvia D. Don by Hoogland (1979). Later studies of the seeds and fruits suggested that its continued recognition as a separate genus was warranted (Godley 1983, Webb & Simpson 1991), but modern DNA-based studies have confirmed the close relationship with Caldcluvia. Both genera provide domatia (refuges) for ants in tufts of hair along the leaf midvein. However, Ackama is easily identified by its lack of floral pedicels and its round seeds with long hairs (Bradford & Barnes 2001). Ackama species are evergreen trees or shrubs with imparipinnate, stipulate leaves. The inflorescences are compound panicles with unisexual (or hermaphrodite), 5-merous flowers. The fruits are dehiscent, leathery capsules and are red, pink or cream at maturity (Allan 1961, de Lange et al. 2002).

Ackama rosifolia A. Cunn.

Makamaka

Tree to 12 m, dbh 0.6 m. Branchlets, petioles, immature leaves and inflorescence branches covered in dense, brown pubescence. Leaves evergreen, 4–12 × 2–7.5 cm, imparipinnate, leaflets (3–)6(–20), elliptic to oblong, terminal leaflet 4–6 × 1.6–4 cm, subsequent leaflets diminishing to 1 cm long, upper surface glabrous, lower surface with conspicuous deep pouches, entrances of which fringed with hair, margins serrate, apex obtuse to acute; rachis not winged, with dense ferruginous pubescence; petiole to 2 cm long, pubescent; stipules foliose, caducous, 1.1 × 0.5 cm, green with red veins, margins toothed. Inflorescence paniculate, to 15 cm long. Monoecious; flowers unisexual or hermaphrodite, sessile, 0.3 cm across. Fruit a pink capsule, globose to cylindrical, splitting longitudinally to quarter or half of its length; fruit with conspicuous, persistent style. Flowering August to November, fruiting January to March (New Zealand). Allan 1961, de Lange et al. 2002. Distribution NEW ZEALAND: North Is., Northland Peninsula. Habitat Lowland forest, particularly forest margins and along streams. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT114.

Figure 11 (opposite). Ackama rosifolia: flowering shoot (A); single flower (B); pair of fruits (C).

116

Ackama

New Trees

In its native New Zealand, the Makamaka is recommended for planting in sheltered and even shady sites (Native Garden Nursery 2005). It comes from the Kauri forests of the northern part of the North Island and therefore requires a comparatively warm situation (Hudson 2004). When mature it is an attractive small tree, with slightly yellowish green leaves tinged reddish below. The small cream flowers are followed by red fruits. It grew for a few years at Tregrehan but has now died (T. Hudson, pers. comm. 2006), which suggests that it prefers warmer conditions than coastal Cornwall enjoys.

TERNSTROEMIACEAE (or PENTAPHYLACACEAE)

ADINANDRA

Jack

There are approximately 90 species of Adinandra, distributed across southern and eastern Asia, of which only A. millettii is in cultivation. They are evergreen trees or shrubs with alternate, petiolate, entire or serrulate leaves. Adinandra flowers are solitary or in pairs, and hermaphrodite; the pedicel is recurved (usually) or erect (rarely). The flowers are subtended by two bracteoles at the base of the pedicel; these are persistent or caducous. The flowers are 5-merous; the sepals are thick, imbricate, persistent; the petals imbricate, glabrous or with silky hairs on the outsides; the stamens, 15–60, are in one to five whorls, filaments free or fused together; the ovary pubescent or glabrous. The fruit is a many-seeded berry with a persistent style (Kobuski 1947, Ming & Bartholomew 2007).

Adinandra millettii Benth. & Hook. f. ex Hance Syn. A. drakeana Franch., A. hemsleyi Hand.-Mazz. ex Metcalf Plate 97. Adinandra millettii will eventually form a small tree, but remains very rare in cultivation. Image B. Ward.

Shrub or tree 2–10(–16) m. Bark smooth, brown. Branchlets greyish brown with appressed pubescence; terminal buds pubescent. Leaves leathery, 4.5–9 × 2–3 cm, oblong to elliptic, upper surface shiny green and glabrous, lower surface pale to yellowish green with appressed pubescence, 10–12 secondary veins on each side of the midrib, margins entire or sparsely serrate towards the apex, apex short-acuminate; petiole 0.3–0.5 cm long, pubescent or glabrous, reddish towards base. Flowers axillary and solitary; pedicel ~2 cm long, slender, pubescent or glabrous. Bracteoles 0.2–0.3 cm long, caducous; sepals ovate-lanceolate to triangular, 0.7–0.8 cm long, sparsely pubescent outside; petals white, ovate to oblong, ~0.9 cm long; stamens ~25. Fruit black, globose, ~1 cm diameter. Flowering May to July, fruiting August to October (China). Kobuski 1947, Ming & Bartholomew 2007. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, eastern Guizhou, southeastern Hubei, southern Hunan, Jiangxi, southwestern Zhejiang; VIETNAM. Habitat Evergreen forests and thickets on mountain slopes between 100 and 1300 (1800) m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT116.

Adinandra millettii is apparently extremely rare in cultivation, the only plants traced for the current work being two in Vancouver and two in North Carolina, the latter vegetative propagations from the former. The University of British Columbia accession was made in 1988, from seed collected by Peter Wharton, Peter Bristol and Lawrence Lee (no collection number) at 840 m near Huangshan

Section II. Species Accounts

Adinandra

117

City, Anhui. Cuttings were obtained from this by J.C. Raulston in 1991 and at least one specimen was planted in his arboretum (the second growing there now is a cutting from this original). This is now c. 3 m tall and apparently happy, although somewhat shaded. It resembles a small-leaved laurel (Prunus laurocerasus), with attractive, very glossy evergreen leaves, and was in abundant bud when seen in May 2006. The flowers, however, are insignificant. The trees in Vancouver are almost 3 m tall, and seem to be totally hardy there (P. Wharton, pers. comm. 2007). Although the sample is limited, A. millettii appears to be an adaptable and perhaps useful small evergreen tree.

SAPINDACEAE (formerly HIPPOCASTANACEAE)

AESCULUS

L.

Buckeyes, Horse Chestnuts Aesculus comprises 13–15 species, most of which occur in eastern North America and eastern Asia, with a single species in Europe and two in the greater California region (Forest et al. 2001). They are small shrubs to large trees with grey to brown, smooth or scaly bark. Winter buds are large and often sticky and resinous. The leaves are deciduous, opposite and palmate with 5–11 leaflets. The leaflets are thin or somewhat leathery, with crenate to serrate (rarely entire) margins, and may be glabrous or tomentose. Inflorescences are terminal panicles of varying size and shape. The flowers have pedicels 0.2–1.5 cm long; the campanulate or tubular calyx is white, yellow or red, with five lobes, though the depth of the lobing varies considerably; there are four to five petals, white or yellow to red; (five to) six to eight stamens, that are exserted or included, anthers yellow, orange or reddish, filaments white. The fruit is a dehiscent capsule with a smooth, scaly or spiny surface; the seeds, one to three (to six), are brown with a pale-coloured hilum of varying size (Hardin 1957a, 1957c). Hybridisation is common in Aesculus (Hardin 1957b) and particular care should therefore be taken when identifying seed-grown trees. Aesculus are greatly appreciated as flowering trees and shrubs, and A. hippocastanum is an essential feature of the European treescape. Sadly though, in the past few years it has been simultaneously ravaged by two scourges. Most widespread is the Horse Chestnut Leaf Miner Cameraria ohridella, a moth whose larvae feed within the leaf tissue, causing extensive damage and early defoliation of the trees. While unsightly, the damage seems principally to occur late enough in the season not to affect the growth of the tree too greatly. The moth has spread through Europe at a rate of 40–60 km per year since appearing in Austria in 1989. It was first noted in the United Kingdom in 2002, but is now well established across much of England. It seems (at present) that A. hippocastanum and A. turbinata are worst affected, with the large eastern North American species being also susceptible. The Asian species, and A. californica and A. parviflora, are apparently resistant (Forest Research 2008a). The frequency of bleeding cankers on A. hippocastanum caused by Pseudomonas syringae pathovar. aesculi has also increased rapidly in recent years in Europe, caus-

Plate 98. The unfolding leaves of a remarkable horse-chestnut from Vietnam. With its fine inflorescences and huge fruits it probably deserves formal distinction from the related Aesculus assamica, but the name A. wangii (see p. 118) has never been validly published. Image J. Grimshaw.

118

Aesculus

New Trees

ing crown dieback in severely affected trees, and unsightly weeping from the trunk. There is no known cure, beyond pruning out infected areas if this is feasible. Webber (2008) provides useful online information. The extent to which other species are affected is not yet known. The genus is promiscuous and numerous hybrids are known – two are described below – although many of these are collector’s items only. A commercially important recent introduction is Aesculus ‘Autumn Splendor’, selected at the University of Minnesota Landscape Arboretum in 1980. This has been assigned to A. ×arnoldiana, but Dirr (1998) suggests that it is a selection of A. glabra. As the name implies it has excellent dark red autumn coloration, but also good yellow inflorescences. An Aesculus has been introduced to both Europe and North America from northern Vietnam, under the name A. wangii. This name has never been validly published, and the taxon may be only a variant of A. assamica (Turland & Xia 2005). It is said to be very ornamental, with large narrow candle-like inflorescences (P. Wharton, pers. comm. 2007, Wynn-Jones 2008). At present it is represented in cultivation only by young trees, but it seems to be flourishing in a range of gardens. The best specimen noted is at Ness Botanic Gardens, where it is a vigorous, well-branched 3–4 m tall. A. arguta (NOW A. glabra var. arguta (Buckley) B.L. Rob.) B250, S64, K120

A. ×arnoldiana Sarg. K118 A. assamica Griff. S66, K118

Aesculus ×bushii C.K. Schneid. This taxon, together with A. ×mississippiensis Sarg., is a naturally occurring hybrid with A. glabra and A. pavia as the parent species. Such hybrids typically have yellow, pink or red flowers (different coloured flowers can occur within the same inflorescence) with exserted stamens, petals of unequal size with glandular margins, and capsules with an irregularly spiny surface. They form small, low-spreading trees to 8–10 m tall. The morphology is rather variable and depends on the exact parentage of the hybrid. F1 hybrids are intermediate, but backcrossing of hybrids with either of the parental species results in a variety of forms that are more similar to that parent. Hardin 1957b, Wright 1985. Distribution USA: Alabama, Arkansas, Louisiana, Mississippi, Missouri, Oklahoma, Texas. Habitat As for the parent species. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT118. Crossreference K118. Taxonomic note The differences between A. ×bushii and A. ×mississippiensis are uncertain and the names may be synonymous.

Aesculus ×bushii is quite widely cultivated and freely available in commerce. It forms a small tree (9 m at Kew, 9.7 m at the Hillier Gardens, TROBI) and is noted for its multi-coloured inflorescences: the flowers start yellow and fade through pink to red. Plate 99. A large tree of Aesculus ×bushii in flower in Worlitz, Germany. Image K. Camelbeke.

A. californica (Spach) Nutt. B250, S64, K118 A. ×carnea Zeyher B252, S64, K118 A. chinensis Bunge B253, S64, K119 A. +dallimorei Sealy B253, K119 A. discolor Pursh B262

A. ×dupontii Sarg. K119 A. ×dupontii var. hessei Sarg. K118 A. flava Aiton B254, S65, K119 A. flava f. vestita (NOW A. flava Aiton) B255, K119 A. flava f. virginica (NOW A. flava Aiton) S65, K119

Section II. Species Accounts

A. georgiana (NOW A. sylvatica Bartram) S67 A. glabra Willd. B255, S65, K119 A. glabra var. arguta (Buckley) Buckley K120 A. glabra var. leucodermis Sarg. B256, K120 A. glabra var. monticola Sarg. B256, K120 A. glabra f. pallida (Willd.) Schelle B256, K120 A. glabra var. sargentii Rehder B256, K120

Aesculus

119

A. glaucescens Sarg. B256, K120 A. hippocastanum L. B256, S66, K120 A. hippocastanum f. laciniata (Jacques) Schelle B257 A. ×hybrida DC. B255, S65, K120 A. ×hybrida var. purpurascens A. Gray K122 A. indica Coleb. ex Wall. B258, S66, K122

Aesculus ×marylandica Booth ex Kirchner This taxon is the result of a cross between A. glabra and A. flava. Such hybrids typically have exserted stamens, stipitate glands on the pedicels and perianth surfaces, and greater differences of size and shape between the upper and lateral petals than in the parents. The capsule walls usually have some spines, though large areas may be spine-free. Hardin 1957b. Distribution USA: Alabama, Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, Tennessee. Habitat As for the parent species. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT119. Cross-reference K122.

Aesculus ×marylandica is another collector’s tree, and apparently rather rare, although it is commercially available from European and British nurseries. The only large specimen noted by TROBI is an old 8 m tree at Kew whose origin is unrecorded. At Herkenrode and Arboretum Wespelaar it grows vigorously (K. Camelbeke, pers. comm. 2007). The flowers are soft yellow, and in autumn the leaves can turn an excellent gold.

A. ×mississippiensis (NOW A. ×bushii C.K. Schneid., NT118) S65, K122 A. ×mutabilis (Spach) Schelle B260, S67, K122 A. neglecta (NOW A. ×neglecta Lindl.) B260, S67, K122 A. parryi A. Gray K122 A. parviflora Walter B261, K122 A. parviflora f. serotina Rehder K122 A. pavia L. B261, S68, K122 A. pavia var. discolor (Pursh) Torr. & A. Gray K123 A. pavia var. flavescens (Sarg.) Correll K123

A. ×plantierensis (NOW A. ×carnea ‘Plantierensis’) B262, S68, K123 A. splendens (NOW A. pavia L.) B262, S68, K123 A. sylvatica Bartam S67, K123 A. sylvatica var. lanceolata (Sarg.) Sarg. K123 A. sylvatica var. pubescens (Sarg.) Sarg. K123 A. sylvatica var. tomentosa Sarg. K123 A. turbinata Blume B263, S68, K123 A. wilsonii Rehder B253, S64, K123 A. woerlitzensis Koehne K124 A. woerlitzensis var. ellwangeri Rehder K124

Plate 100. The greenish white and pink flowers of Aesculus ×marylandica are produced in late spring. Image P. de Spoelberch.

120

Aextoxicon

New Trees

AEXTOXICACEAE

AEXTOXICON

Ruíz & Pav.

Aextoxicon is the only genus in the Aextoxicaceae, a family that has been associated previously with the Aquifoliaceae, Celastraceae, Elaeagnaceae, Euphorbiaceae and Icacinaceae, although DNA and wood anatomy both link it to the Berberidopsidaceae (APG 2003, Carlquist 2003). Aextoxicon is monospecific, comprising only the species A. punctatum (Govaerts 2000a).

Aextoxicon punctatum Ruíz & Pav.

Olivillo

Large shrub or tree to 20 m, trunk to 1 m dbh. Bark thick and smooth. Crown rounded and compact, often densely branched. Major branches rather thick and ascending. Leaves evergreen, 3.5–9 × 1.5–3 cm, opposite to alternate and with a distinct petiole, oblong to elliptical, leathery, with contrasting surface colours; upper surface dull green, lower surface grey or ferruginous with a layer of peltate scales, scales also prominent on new shoots and buds, margins entire and revolute, apex acute. Dioecious; flowers yellowish and in short axillary racemes, flower buds globose and densely covered in scales. Male and female flowers similar, 0.1–0.5 cm wide, rather insignificant. Fruit an ellipsoidal drupe, 1 × 0.7 cm, pedunculate, smooth, hard and purple to black. Rodríguez R. et al. 1983. Distribution ARGENTINA: between Lago Puelo in Chubut Province and El Bolsón in Río Negro Province; CHILE: from the Limarí River in Coquimbo Province to Chiloé Is. in Los Lagos Province. Habitat Aextoxicon is endemic to the sub-Antarctic forests of the southern Andes, between 15 and 1000 m asl. It prefers a humid atmosphere, and forms pure forests or mixes with Eucryphia, Drimys and several Myrtaceae. USDA Hardiness Zone 8. Conservation status Data Deficient. Illustration Rodríguez R. et al. 1983; NT120, NT515.

Plate 101. The black fruits of Aextoxicon punctatum gave rise to the local name Olivillo in its native Chile. Seen here at Los Molinos, Valdivia in May 2007. Image S. O’Brien.

This curious plant bears an extraordinary resemblance to one of the larger-leaved evergreen Elaeagnus, with its shoots and leathery leaves covered in a dense, almost metallic-seeming scatter of peltate scales, and the incautious will easily be fooled by a young specimen. The scales become sparser with age. The flowers are small and rather insignificant but are followed by black berries that give rise to its Spanish name, Olivillo or ‘little olive’. Now grown in a number of collections throughout the United Kingdom and in the western United States, and commercially available, this species was first introduced by Harold Comber in the 1920s (Lancaster 2005), but most individuals are from recent introductions. An expedition to Chile in 1998 resulted in the specimen now growing at the Royal Botanic Garden Edinburgh, derived from UCEXC 544. This plant was 3 m high when seen in 2005, which suggests that it can grow relatively rapidly in suitable conditions. Although it seems quite hardy in the British Isles, its habitat implies that it will favour milder, wetter rather than hotter and drier conditions. In the wild Aextoxicon punctatum forms dense stands of tall trees (Chilebosque 1999–2008a). The chestnutcoloured wood is popular for furnituremaking and interior carpentry.

Section II. Species Accounts

Afrocarpus

121

PODOCARPACEAE

AFROCARPUS

(Buchh. & E. Gray) C.N. Page

The six species of Afrocarpus occur in the montane forests of eastern, central and southern Africa, from Ethiopia south to the Cape. There is also one species in Madagascar (A. gaussenii (Woltz) C.N. Page) and one on the islands of the Gulf of Guinea (A. mannii (Hook. f.) C.N. Page). Afrocarpus species are large, dioecious, columnar, evergreen conifers. The branchlets are often square in section and deeply ridged. The leaves are flattened, narrowly lanceolate to elliptic, amphistomatic, and with a single midrib. They are spirally arranged, leathery with hard, acute to acuminate apices, and range in size from 2.5–15 cm long. Male strobili are solitary or rarely in groups of two to three, on short, naked, axillary peduncles. Female cones are solitary, terminal on short, naked or leafy axillary branchlets, subglobose to obovoid, enclosed in a fleshy, yellowish green to purplish black epimatium. The outer layers of the seed coat form a hard, woody shell, giving the cone a drupe-like structure (Page 1988). Afrocarpus was formerly subsumed in Podocarpus, but differs in its large drupe-like fruit, lacking the arillate structure found in Podocarpus. It is rare in cultivation outside in our area, but is seen under glass in botanical gardens or in interior landscaping.

Afrocarpus falcatus (Thunb.) C.N. Page

Outeniqua Yellowwood

Syn. Podocarpus falcatus (Thunb.) Endl. Tree 20–60 m. Trunk usually straight, 1–2 m dbh, sometimes with massive spreading limbs. Bark flaking irregularly, greyish brown to dark brown. Branches spreading to ascending. Leaves opposite or loosely spiralled, 3–5 × 0.3–0.5 cm, linear to slightly falcate, sharply acute, tapering to base, hard and leathery, pale to dark green. Male cones axillary in small clusters, 10 × 3 mm. Female cones solitary, green when young, maturing to a ± globose single seed c. 1.5 cm diameter, with thin yellowish flesh externally. Coates Palgrave 1990. Distribution MOZAMBIQUE: southern area; SOUTH AFRICA: Western Cape to Limpopo Province. Habitat Moist montane forests. USDA Hardiness Zone 9. Conservation status Lower Risk, but many forest areas now destroyed or with large trees having been selectively extracted. Illustration NT121, NT122. Cross-reference K255 (as Podocarpus falcatus). Taxonomic note Afrocarpus falcatus has frequently been conflated with A. gracilior (Pilg.) C.N. Page, from montane forests in tropical East and Northeast Africa, and the two are confused in the literature and probably in cultivation as well (both names are in circulation in the North American nursery trade). They are very similar, but A. gracilior has longer, more falcate leaves. As a juvenile plant A. gracilior is very tolerant of deep shade, and young specimens are sometimes used for interior decoration (as, for example, in the terminal buildings of Schiphol Airport, Amsterdam). It is conceivable that it might survive outside, if planted in sheltered places (see p. 6).

One of the most important timber species in South Africa, yielding a fine yellowish wood, Afrocarpus falcatus can be a large tree and dominant within the forest ecosystem. Its ecology has been extensively studied in the Knysna forest, South Africa by C.J. Geldenhuys (1993); he demonstrated that the seeds are largely dispersed by fruit bats, and that the seedlings germinate and establish in shade. The most magnificent specimen seen in research for the current work is a venerable tree with wide-spreading branches in the Old Company’s Garden in the heart of Cape Town, but there are good younger ones at Kirstenbosch. In the northern hemisphere there is a fine tree in the University of California Botanical Garden, Berkeley, and it is growing successfully both in Oregon and in southwestern England, where it seems to be hardier than might be

Plate 102. The plum-like fruit of Afrocarpus falcatus is dispersed by fruit bats, which eat the flesh covering the large hard seed. Image D. Luscombe.

122

Afrocarpus

New Trees

B

A

1 cm

D

C

Figure 12. Branchlets with fruit: Afrocarpus falcatus (A), Podocarpus latifolius (C). With male strobili: A. falcatus (B), P. latifolius (D).

1 cm

imagined. Nicholas Wray (pers. comm. 2008) reports that at the University of Bristol Botanic Garden it has withstood being frozen in pots at –9 ºC for several days, and suffers damage to new growth only below –5 ºC. He believes that the best chance of success is to plant out specimens that are 4–5 years old and at least 1.5 m tall, when they will have attained a certain toughness. A warm site is indicated, however.

Section II. Species Accounts

Agathis

123

ARAUCARIACEAE

AGATHIS

Salisb.

Kauris, Kauri Pines Agathis is an important genus of about 20 species of large timber trees from southeastern Asia, Australasia and the Pacific islands, with one species in New Zealand that is described below. Trees may be 45–60 m in height with columnar trunks, with a single leader when young, forking when older. The bark contains resin canals, as do the leaves, which makes them brittle and easily snapped. The opposite or subopposite leaves have short petioles and are usually lanceolate to ovate or elliptic, leathery, and often glaucous; both within an individual tree and at the species level, however, the leaves can be very variable in shape. Agathis are monoecious, but produce female cones before the males. The male strobili are more or less sessile, cylindrical, composed of a number of bracts that produce the microsporophylls. The female cones are massively globose and borne on shoot tips, with tightly appressed scales, each with a single ovule. The cones shatter at maturity. The seed is a flattened ovoid, with one large wing and sometimes a second smaller wing (Whitmore 1980). Agathis is almost entirely unknown to temperate gardeners, being a typical rainforest genus. In New Zealand the indigenous Kauri, Agathis australis, which used to be an important forest species, has been extensively logged, reducing an original extent of perhaps 1.2 million hectares to just 140 hectares. Regeneration is very slow, and would naturally occur after severe disturbance that removes competition. The species is now grown elsewhere for timber (Marinelli 2004). A number of other Agathis species are described by Krüssmann (1985b), but are not known to have been cultivated outside in our area. A fascinating account of early introductions of Agathis to horticulture has been given by Mabberley (2002).

Agathis australis (Lambert) Steud.

Kauri

Tree 30–40(–50 m), usually with a massive trunk, 3–7 m dbh in largest specimens, with a clear bole for 10–20 m, becoming hollow with age. Bark bluish grey, falling in large thick flakes. When young the crown is narrow, conical and unbranched, but the tree develops massive spreading branches with age. Leaves sessile, alternate to subopposite, larger when juvenile, 5–10 cm long, adult leaves 1.5–6 × 1.0–1.5 cm, glaucous to mid-green. Male strobili stout, 2–5 × 1 cm. Female cones 6 × 6–8 cm wide, glaucous-green, scales 1.8 cm long with short mucronate umbo. Seeds mature 19–20 months after pollination and are compressed ovoid in shape, with a wing. Whitmore 1980. Distribution NEW ZEALAND: northern peninsula of North Is. Habitat Warm temperate lowland forest with subtropical affinities. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Van Gelderen & van Hoey Smith 1996, Marinelli 2004; NT123. Cross-reference K48.

Agathis australis is one of those species that is grown in the mildest parts of our area, for its inherent interest as an important and magnificent tree in its native New Zealand, but has never reached its potential here. It first reached Europe in 1823, with a further importation to Kew in 1838 (Dallimore et al. 1966). Successive generations

Plate 103. In its native New Zealand the bulky trunk of Agathis australis develops attractive bark. Image J.R.P. van Hoey Smith.

124

Agathis

New Trees

have tried to grow it, and there are sparse records of trees around the western fringes of the British Isles. The largest known to have grown in the northern hemisphere was a specimen at Tresco Abbey, Isles of Scilly, that attained 19.5 m, dbh 31 cm, while the current surviving champion is one of 16 m at Ilnacullin, Co. Cork, a garden where four specimens over 10 m were measured in 2002, by Aubrey Fennell (Johnson 2007). There are attractive, fruiting specimens of about 8 m at Mount Usher. A slow-growing specimen at Tregrehan recorded to be only 4 m after 40 years in 1931 (Dallimore et al. 1966) has disappeared and been replaced by a group of young trees that appear (so far) to be doing better than their predecessor. On these specimens the new growth is brownish bronze. Agathis australis will, it seems certain, remain a curiosity for those in our mildest areas.

SIMAROUBACEAE

AILANTHUS

Desf.

Trees of Heaven There are about five species of Ailanthus, distributed from central Asia to Australia, though one (A. altissima) is widely naturalised outside this area. Ailanthus species are large, deciduous or evergreen trees, often emitting a strong smell from the leaves and staminate flowers. The leaves are alternate, imparipinnate and crowded at the tips of the branches; they can grow to over a metre in length. The leaflets are more or less opposite, with glands on the undersides. Ailanthus is primarily dioecious, though some hermaphrodite flowers usually occur; the flowers are borne in terminal or axillary panicles and are rather small. Each staminate flower has five (to six) sepals, five (to six) greenish yellow petals, and 10(–12) stamens, which are inserted at the base of a 10-lobed nectar disc. The fruit is a samara with a single seed in the centre of an elliptic wing; these occur in clusters of two to five within the larger fruiting panicle (Brizicky 1962, Li 1993, Harden 2002). Ailanthus like a rich, well-drained soil but will tolerate much poorer sites. As well as sowing themselves (too freely), they will also sprout from suckers at some distance from the base of the trunk. Seed or root cuttings are the usual methods of propagation.

Ailanthus altissima (Mill.) Swingle This species was described by Bean (B265, S69) and Krüssmann (K126). Although it makes a handsome tree, it has become well known as an invasive plant in many parts of the world. A. altissima f. erythrocarpa (NOW A. altissima ‘Erythrocarpa’) K126 A. altissima var. sutchuenensis (Dode) Rehder & E.H. Wilson B266, K126

Ailanthus altissima var. tanakae (Hayata) Kaneh. & Sasaki This variety appears to differ from typical A. altissima only in the colour of the bark (yellowish grey rather than grey) and the shape of the leaflets (falcate rather than straight). It is the only Ailanthus taxon to occur naturally

Section II. Species Accounts

Ailanthus

125

on Taiwan. Li 1993, Zheng et al. 2004. Distribution TAIWAN. Habitat Medium- to high-altitude forest in the north. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT125. Taxonomic note The characters used to differentiate var. tanakae and var. sutchuenensis (red branchlets) from typical A. altissima are rather minor, and further study of this widely occurring species may lead to their reduction into synonymy.

Introducing new stock of a species considered to be a dangerous invasive alien in many parts of the world may seem foolhardy, but Ailanthus altissima var. tanakae has been collected several times in recent years. One of its principal distinctions from the type appears to be that it occurs in Taiwan, not mainland China – so often an important taxonomic character, it seems! Dan Hinkley (pers. comm. 2006) says that it is indistinguishable from any other A. altissima when seen in the wild. Nevertheless, in the young plants seen under this name there is a difference – difficult to pin down, but perhaps it is a combination of the red rachis, darker lamina and poise of the leaflets that gives it that slight air of distinction. Most notable, however, is its habit of retaining its leaves well into winter. When observed at Kew in mid-December 2006, two trees from ETOT 51 (collected in 1996) were in full dark green leaf, when all surrounding Ailanthus were completely bare. After a period of strong winds, as this was, this is remarkable, especially as many of the leaves are up to 1 m in length with 15 pairs of leaflets. These trees are doing well, up to 10 m, and fruiting freely. There is no evidence to suggest that var. tanakae is potentially less of a problem tree than the normal A. altissima, so it should only be planted after careful consideration for its potential impact, or used as a foliage feature, coppiced to prevent it from flowering. A. giraldii (NOW A. altissima (Mill.) Swingle) B266, S69, K126 A. giraldii var. duclouxii (Dode) Rehder K127 A. vilmoriniana Dode B266, K127

CORNACEAE (formerly ALANGIACEAE)

ALANGIUM

Lam.

Alangium comprises 26 species, ranging from tropical Africa to the southwest Pacific (Govaerts 2000b). Until recently the genus was generally placed in its own family, Alangiaceae, but molecular studies have indicated a closer relationship with Cornaceae, and the two have now been merged (APG 2003). Alangium species are typically trees or rarely shrubs or woody climbers; the habit can vary within a species. The stems are unarmed and grow horizontally or are pendulous. The leaves are evergreen or deciduous, alternate and simple or lobed. Stipules are absent and the petiole is

Plate 104. The Taiwanese Ailanthus altissima var. tanakae differs only slightly from trees on the mainland, but the red rachis is one point of distinction. Image J. Grimshaw.

126

Alangium

Figure 13 (opposite). Alangium chinense: habit with flower buds (A); lobed leaf (B); flowers opening (C); fruits (D).

New Trees

often articulated at the base and apex. Alangium is monoecious; inflorescences are axillary and corymbose, with all branches ending in flowers; the inflorescence may be sessile or pedunculate. The flowers are hermaphrodite, with floral parts in whorls of 4–10. The fruit is a drupe with a fleshy or spongy mesocarp and a hard endocarp containing one to two seeds (Bloembergen 1939). Alangium platanifolium, stated by Bean (1976a) to be rather tender, is now quite widely grown in collections throughout our area, usually forming a small shrubby tree with deciduous, plane-like pale green leaves. Plants labelled A. platanifolium ‘Macrophyllum’ are grown in western North America – presumably the var. macrophyllum mentioned by Krüssmann. The leaves of these plants are perhaps slightly larger than average for the species and should be less deeply lobed (Krüssmann 1984).

Alangium chinense (Lour.) Harms

Plate 105. At the Scott Arboretum of Swarthmore College, Pennsylvania, Alangium chinense is forming a shapely young tree, apparently appreciating the hot East Coast summers. Image R. Maurer.

Shrub or tree to 15 m, dbh 0.3 m; branches horizontal. Branchlets pubescent when young, later glabrous or rarely hirsute; internodes 2–10 cm long. Leaves evergreen or deciduous, 5–30 × 3–28 cm, basically ovate though rarely almost palmate, upper surface glabrous, lower surface glabrous or with tufts of hair in the vein axils, three to six secondary veins on each side of the midvein, margins entire or with shallow lobes or teeth, apex acuminate; petiole 1.5–7 cm long, pubescent. Inflorescence with one to four branches, pedunculate and pubescent, 2.2–8.5 cm long. Monoecious; flowers hermaphrodite and fragrant; corolla campanulate, ranging in colour from white to orange, usually 7-merous (typically between 5- and 8-merous) and 0.8–1.2 cm long; petals papillose or glabrous. Fruit an ellipsoidal drupe with an acute apex and an apical disc, 0.5–1.3 × 0.5–0.7 cm and dark violet in colour; the endocarp has one to two compartments, each bearing a single seed. This species is very widespread and its flowering period depends on location. Bloembergen 1939, Lu 1993b. Distribution ANGOLA; BANGLADESH; BHUTAN; CAMBODIA; CAMEROON; CHINA; DEM. REP. CONGO; EQUATORIAL GUINEA: Bioko; INDIA: Assam, Himalaya; INDONESIA: Java, Lesser Sunda Is.; JAPAN: Kyushu, Ryukyu Is.; KENYA; LAOS; MALAWI; MYANMAR; NEPAL; PHILIPPINES; TAIWAN; TANZANIA; UGANDA; VIETNAM. Habitat Open areas of forest or forest margins between 20 and 3300 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Lu 1993b; NT126, NT127. Cross-reference K128. Taxonomic note Alangium chinense varies considerably across its range. African specimens typically have entire leaves and one compartment in the ovary and fruit, while Asian specimens have lobed or dentate leaves and two compartments in the ovary and fruit (Bloembergen 1939).

Alangium chinense is rare in cultivation, although offered by several nurseries in the United Kingdom and United States. At Tregrehan, where it has been grown since 1994, it is shrubby, the young growth failing to ripen (Hudson 2004), but at the Scott Arboretum (where winters are much colder but summers much warmer) a five-year-old plant was 4 m tall when seen in 2006, forming a good trunk and apparently thriving. The leaves are a bright fresh green, making it an attractive specimen. It flowers in Pennsylvania in early summer. With such a wide-ranging species provenance is particularly important, but in general a warm site with ample summer moisture is indicated. In less than ideal situations it is most likely to form a low shrubby specimen.

A. platanifolium (Siebold & Zucc.) Harms B270, S69, K128 A. platanifolium var. genuinum Wang K129 A. platanifolium var. macrophyllum (Siebold & Zucc.) Wang K129

Section II. Species Accounts

Alangium

127

A

B

1 cm

1 cm

1 cm

D

1 cm

C

128

Albizia

New Trees

LEGUMINOSAE (MIMOSOIDEAE)

ALBIZIA

Durazz.

Silk Trees Albizia is a genus of about 150 species, with a cosmopolitan distribution across tropical and subtropical areas. They are trees, shrubs or rarely climbers, typically unarmed, though the climbing species have recurved prickles by the leaf scars. Leaves are alternate, bipinnate; foliar glands are present on the petiole and sometimes between or below the junctions of pairs of pinnae and/or pinnules; pinnules are opposite, petiolulate or sessile, small to large, often asymmetric, few to numerous; stipules small and caducous or, rarely, conspicuous and leaf-like (for example, A. chinensis Merr.). The inflorescences are axillary or terminal, heads or corymbs, which may be arranged in fascicles, panicles or rarely spikes or racemes; heads or corymbs may be dimorphic, with a single large central flower and adjacent smaller flowers. The flowers are hermaphrodite, sessile or pedicellate and (4–)5-merous. The calyx and corolla are often greatly reduced and have been largely replaced in the role of attractant by the numerous stamens. The fruit is a strap-shaped legume (pod), which may be dehiscent or indehiscent (Nielsen 1981, Chakrabarty & Gangopadhyay 1996). Of all the numerous Albizia species, only A. julibrissin has become familiar in temperate gardens. It is a notable beneficiary of the currently warming climate and is now being grown over a much wider area than was previously thought possible. Provenance and selection for cold-hardiness are undoubtedly also factors in this, but warmer summers enable new wood to ripen more thoroughly and this in turn confers extra tolerance to frost. A notable new selection made in Japan is ‘Summer Chocolate’, with amazing dark purplish foliage. Its comparative hardiness is not yet known. In the southern United States the yellow-flowered A. lebbeck (L.) Benth. has become naturalised and is rather invasive in Florida, but is not hardy further north (Cook 2006). A. julibrissin Durazz. B270, S69, K129 A. julibrissin var. rosea Mouill. K129

Albizia kalkora (Roxb.) Prain

Kalkora Mimosa

Syn. A. coreana Nakai Shrub or tree 3–8(–20) m. Bark rough, greyish brown. Branchlets brown, sparsely covered with white pubescence when young. Leaves bipinnate; pinnae three to six pairs, each 10–20 cm long with secondary stipules at the base; pinnules 7–15 pairs, opposite, oblong to obovate, 1.5–4 × 0.5–1.5 cm, pubescent on both surfaces; petiole 4–8 cm long; stipules inconspicuous. Heads two to seven, arranged in axillary or terminal panicles; peduncles 4–7 cm long. Flowers 25–30 per head, white, turning yellow, dimorphic; terminal flower sessile, 2–2.5 cm long; lateral flowers pedicellate. Legume linear to narrowly oblong, 7–16 × 1.5–3.5 cm, dark brown, obtuse to acute at both ends; dehiscent, with 4–12 seeds. Flowering after leaves have emerged and fully opened; June (USA). Nielsen 1981. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Shanxi, Sichuan, Zhejiang; INDIA; JAPAN: southern Kyushu; MYANMAR; NORTH KOREA; SOUTH KOREA; TAIWAN; VIETNAM. Habitat

Section II. Species Accounts

Albizia

129

Thickets and sparse forest between 500 and 2000 m asl. USDA Hardiness Zone 7a/8b. Conservation status Not evaluated. Cross-reference K129. Illustration NT129. Taxonomic note Chakrabarty & Gangopadhyay (1996) place A. kalkora in synonymy with A. garrettii I.C. Nielsen, but list Mimosa kalkora as a synonym of A. julibrissin. This approach does not appear to have been widely accepted (see, for example, Ohashi & Endo 2001, Wu & Nielsen 2006). The Korean Albizia coreana is considered synonymous with A. kalkora by Lee (2002) and IPNI (2005).

Albizia kalkora is in limited cultivation in the United States at the present time, often labelled A. coreana. It can form big trees, with spreading umbrageous crowns, covering themselves with white powder-puff inflorescences. The foliage of A. kalkora is much coarser and less attractive than that of the familiar A. julibrissin. Its introduction to the United States is attributed to Frank N. Meyer of the US Department of Agriculture’s Foreign Seed and Plant Division. Meyer collected seed near Boshan, Shantung, China in September 1907 (PI 21969), and from Pangshan, Chihli (PI 22618) in November 1907 – where, he states, the ‘species is quite distinct from Albizia julibrissin, which is much more floriferous and of which the leaves, though much finer pinnated, are much smaller’ (USDA 1909). There is still a notable specimen at the old USDA Plant Introduction Station in Savannah, Georgia, presumably from these collections, and it would seem that it is from this source that the species has achieved a limited commercial distribution in the southern United States (R. Olsen, pers. comm. 2007). As an example, a seedling of A. kalkora purchased from Woodlanders Nursery, South Carolina in 1989 had developed into a fine tree of 12 m at the JC Raulston Arboretum, before it was removed not long ago (V. Tyson, pers. comm. 2007). More recent introductions have come from NACPEC expeditions, including seedlings still under glass at the Morris Arboretum from a collection made in Shanxi Province, China in 2002. It is anticipated that these will be hardy in the Philadelphia area (A. Aiello, pers. comm. 2007). Concerns have recently been raised over the potential for self-sowing of A. kalkora, one naturalised population being known from the campus of Duke University in Durham, North Carolina. In this area hybrids with A. julibrissin have also been found (Cook 2006), confirming suspicions long held by J.C. Raulston, R. Olsen and others. Trees labelled Albizia coreana are growing at the US National Arboretum Woody Landscape Plant Crop Germplasm Repository at Glenn Dale, Maryland, from collections made at Chollipo Arboretum and at Mount Yudal, South Korea, in 1984 and 1985, respectively. It is probable that all material of ‘A. coreana’ in the United States is derived from these two collections (R. Olsen, pers. comm. 2006). At the JC Raulston Arboretum one such specimen received from the National Arboretum in 1988 (NA 55290) had reached nearly 12 m in 2006, and is an attractive tree. The species is in cultivation in New Zealand (for example, at Eastwoodhill, as A. coreana) but no specimens have been traced in Europe, or in western North America. It would seem to need hot and humid summers to thrive.

A. lebbeck (L.) Benth. K129 A. lophantha (NOW Paraserianthes lophantha (Willd.) I.C. Nielsen) K129 A. procera (Roxb.) Benth. K129

Plate 106. The white powder-puff inflorescences of Albizia kalkora are freely produced, but it needs hot summers to thrive. Image JC Raulston Arboretum.

130

Alectryon

New Trees

SAPINDACEAE

ALECTRYON

Gaertn.

The 25 species of Alectryon occur in the Philippines, eastern Indonesia, New Guinea, Australia, New Caledonia, and in the Pacific from New Zealand to Hawaii (Edwards & Gadek 2001); only A. excelsus from New Zealand is known to be cultivated in our area. They are trees or shrubs with terete branchlets and evergreen paripinnate leaves. The leaflets are in one to eight pairs, opposite to alternate, pubescent to glabrous, with margins entire to dentate, serrate or crenate. Inflorescences are axillary, paniculate, racemose or thyrsoid. The flowers are unisexual or rarely hermaphrodite; the calyx has four to six lobes, the lobes pubescent on both surfaces; the petals, four to five (sometimes absent), are as long as or shorter than the calyx lobes; the (five to) eight stamens have hairy filaments. The fruit is a dehiscent capsule with a smooth or slightly warty surface; in several species, the capsule is brightly coloured. The single seed is black and partially covered by a bright red aril (Leenhouts 1988).

Alectryon excelsus Gaertn.

Plate 107. The red aril surrounding the black seed of Alectryon excelsus forms a striking advertisement to the birds that disperse them. Image R. Lucas.

New Zealand Oak, Titoki

Tree to 20 m, 0.6 m dbh; single- or multistemmed. Bark brown to black, mottled with white, lenticellate. Branchlets winged, densely covered in ferruginous hairs. Leaves alternate, imparipinnate, 8–26 × 10–17 cm; leaflets (three to) five (to seven) pairs, smooth not puckered, ovate to oblong or lanceolate, 5–10 × 2–5 cm, matt or shiny green with short hairs on the midrib and veins, margins entire to serrate or dentate, apex obtuse to acuminate; petiolules ~0.5 cm long; petiole ~8 cm long; newly emerging leaves rosy pink. Inflorescences paniculate, 9–30 cm long, densely pubescent. Flowers hermaphrodite or unisexual, 0.3–0.4 cm diameter, pedicels ~0.5 cm long; calyx lobes five, covered in silky hairs, petals absent, stamens five to eight, anthers purple, filaments hairy. Capsules sessile, woody, 1.5–2 × 1–1.4 cm, dehiscent, containing a single seed. Seed 0.7–0.9 × 0.6–0.8 cm, globose, partially enclosed in a scarlet, fleshy aril. Flowering November, fruiting December (New Zealand). Salmon 1980, de Lange et al. 1999. Distribution NEW ZEALAND: North Is. (usually within 100 km of coast) and South Is. (northeast coast). Habitat Lowland forest between 0 and 600 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT130. Cross-reference K129.

In New Zealand Alectryon excelsus is an important landscape tree, widely planted for the sake of its broad evergreen crown of handsome pinnate leaves, large inflorescences of purplish flowers, and bright red and black seeds. The leaves flush rosy pink and turn to mid-green, retaining some of the silky hairs found in many parts of the tree. Titoki has been cultivated in the San Francisco Bay Area since at least 1893, when one was planted on the Stanford University campus by Dr David Starr Jordan (this tree has since been removed, but there are several descendants or replacements on the campus at the present time) (Bracewell 2005). It is also grown in other Bay Area gardens. Beyond this favourable enclave, it appears to be frequently grown only in Cornwall, where it is available from nurseries, with occasional appearances elsewhere, such as the 1.2 m specimen reported from Southend, Essex (Johnson 2007). No large specimens are known. Tom Hudson (pers. comm. 2006) reports that it is

Section II. Species Accounts

Alectryon

131

slow-growing and needs a certain maturity to be hardy. He recommends growing young plants on in warmth for some time before planting out. In New Zealand A. excelsus is a lowland plant, preferring fertile alluvial soils, but also growing on volcanic substrata (New Zealand Plant Conservation Network 2005a). In cultivation a fertile warm site is indicated.

CASUARINACEAE

ALLOCASUARINA

L.A.S. Johnson

She-oaks There are about 60 species of Allocasuarina, all of which are endemic to Australia. They are typical of nutrient-impoverished soils and are most abundant in southern Australia. Allocasuarina species are shrubs or trees with distinctive articulated stems and reduced tooth-like leaves. The leaves (teeth) occur in whorls and the portion of branchlet between each whorl is termed an ‘article’. The articles have several longitudinal ridges (‘phyllichnia’) which are separated by deep furrows. The number of ridges matches the number of teeth. Branchlets may be persistent or deciduous. The leaves are in whorls of 4–14. Allocasuarina species are monoecious or dioecious, with separate staminate and pistillate inflorescences. Inflorescences are composed of alternating whorls of tooth-like bracts, each of which bears a single flower with two bracteoles. The staminate inflorescences resemble catkins, with the flowers arranged along the branchlets, while the pistillate inflorescences are globose, with the flowers clustered at the tips of lateral branches. The pistillate inflorescences may also be sessile. The individual flowers are insignificant. Fruits are borne inside the pistillate inflorescence, which becomes woody at maturity and is often described as a ‘cone’. The floral bracteoles extend only slightly from the cone and typically have a divided or spiny dorsal protuberance (absent in Casuarina, in which the bracteoles extend well beyond the cone). The fruit is a shiny, reddish brown or black samara (Wilson & Johnson 1989, 1990). Allocasuarina, together with Gymnostoma L.A.S. Johnson and Ceuthostoma L.A.S. Johnson, was split from the genus Casuarina (Johnson 1980, 1982, 1988). As with the more familiar Casuarina, the members of Allocasuarina have fine, equisetoid growth that gives the trees a very

Plate 108. The intricate ‘cones’ of Allocasuarina duncanii. Image R. Unwin.

132

Allocasuarina

New Trees

distinctive appearance. Allocasuarina littoralis (Salisb.) L.A.S. Johnson and A. verticillata (Lam.) L.A.S. Johnson are not infrequently cultivated in Australia, where they are recommended as suitable small trees for gardens and landscapes, being tolerant of a range of ‘difficult’ conditions ranging from hot, dry sites to clay soil and the shoreline (Metro Trees 2007). Senior (2004) mentions that a few species of ‘Casuarina’ have been attempted in Cornwall in recent years, including Allocasuarina littoralis, but gives no indication of their success, while Johnson (2007) mentions that A. littoralis, A. torulosa (Ait.) L.A.S. Johnson and A. verticillata are in cultivation in the British Isles, the latter two recorded from Tresco Abbey, Isles of Scilly.

Allocasuarina duncanii L.A.S. Johnson & D. Morris

Duncan’s She-oak

Tree to 8 m. Branchlets up to 20 cm long, articles 0.4–1.7 cm long, smooth and glabrous, dull mid-green; phyllichnia flat, rounded or angled. Leaves tooth-like; teeth seven to nine, apressed or spreading, 0.08–0.15 cm long or to 0.35 cm long in juvenile growth. Dioecious; staminate inflorescences spicate, 0.75–1.3 cm long with six to eight whorls, early deciduous; pistillate inflorescences on lateral branchlets 0.4–1 cm long; cone 1.5–6 × 1.2–2.5 cm, bracteoles triangular and protruding. Fruit a samara, 0.6–1 cm long, dark brown or black. Johnson & Morris 1994. Distribution AUSTRALIA: Tasmania, Snug Plains (only known from one location). Habitat Dry, sclerophyllous Eucalyptus forest at c. 600 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated (IUCN), but this species has a restricted distribution and might be threatened if the protected status of its only habitat was changed. Illustration Johnson & Morris 1994; NT131. Taxonomic note This species is very similar to A. monilifera (L.A.S. Johnson) L.A.S. Johnson, though the staminate inflorescences are shorter.

Discovered only a few years previously, Allocasuarina duncanii was first introduced to cultivation by Barry Unwin of Logan Botanic Garden from collections made (B. Unwin 160) during his visit to Tasmania in 1996. Several young plants are now established at Logan, the tallest having reached 2.4 m in 2006 and apparently growing steadily. They have already flowered and fruited, producing beautifully ornate cones. It is a great surprise to see a plant so redolent of tropical beaches growing in Galloway, but A. duncanii is also cultivated in Cornwall and should be tried elsewhere.

STYRACACEAE

ALNIPHYLLUM

Matsum.

Alniphyllum comprises three species in China, India, Myanmar, Laos, Taiwan and Vietnam. They are deciduous trees, the leaves alternate with serrate margins; stipules absent. Inflorescences are terminal or axillary, paniculate or racemose. The flowers are hermaphrodite and 5-merous; the calyx cup-shaped, the corolla campanulate, with 10 stamens, five long and five short. The fruit is a slightly fleshy capsule, dehiscing via five valves; the seeds have membranous wings at each end (Hwang & Grimes 1996). Alniphyllum is little known in cultivation, although the widely distributed A. fortunei (described below) was discovered in the mid-nineteenth century. Alniphyllum

Section II. Species Accounts

Alniphyllum

133

pterospermum Matsum. has also been described, by Huxley et al. (1992), but the only specimen traced is in the University of California Botanical Garden at Berkeley.

Alniphyllum fortunei (Hemsl.) Makino Tree to 20 m. Bark greyish brown. Branchlets covered with brown, stellate tomentum. Leaves papery, 5–15(–20) × 4–7(–11) cm, elliptic to obovate, both surfaces covered with brown stellate tomentum, to a greater or lesser degree, 7–12 secondary veins on each side of the midrib, margins remotely serrate, apex acute to acuminate; petiole 1–2 cm long. Inflorescences terminal or axillary, racemose or paniculate; pedicels 0.4–0.8 cm long. Flowers 1.5–2 cm long; calyx densely grey-pubescent, corolla lobes elliptic, 1–1.5 cm long, white. Capsule oblong to ellipsoid, 1–2.5 cm long, sparsely white-pubescent. Flowering April to July, fruiting August to October (China). Hwang & Grimes 1996. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; INDIA; LAOS; MYANMAR; VIETNAM. Habitat Mixed forest between 200 and 2200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT133. Cross-reference K131.

Alniphyllum fortunei is scarce in cultivation – unaccountably, as it has many good qualities. If the problem is that it is tender, hardier provenances should be sought from within its vast range. The trunk is pale yellowish brown or whitish, showing up well in winter. The shape of the leaves is aptly described by their comparison to an Alnus; they are quite thick and borne on red-tinted twigs. The big white flowers are produced in large showy panicles in spring (Hudson 2004). The largest specimen known in cultivation is at Abbotsbury Subtropical Gardens, Dorset, 10 m tall from planting in 1990 (Johnson 2007). Plants grown from Shanghai Botanic Garden seed have been in cultivation at Tregrehan since 1993, planted out in 1995 and growing steadily ever since. These are now over 5 m tall, but they are a favourite of squirrels, which chew the bark (T. Hudson, pers. comm. 2006). The species is also grown under glass in some European collections (for example, at Arboretum Freiburg-Günterstal in Germany), and there is a coppicing specimen at the JC Raulston Arboretum.

Plate 109. Alniphyllum fortunei is seldom grown, probably requiring very mild conditions, but its beautiful flowers make it worth the effort. Image Q. Cronk.

134

Alnus

New Trees

1 cm

A

B

C

1 cm

1 cm

D

Section II. Species Accounts

ALNUS

Alnus

135

BETULACEAE

Mill.

Alders Thirty-five species of Alnus are recognised, distributed across the northern hemisphere, though with an extension through Central America into the Andes (Govaerts & Frodin 1998). Two subgenera (Alnus and Alnobetula) are recognised within the genus, and some important distinctions are summarised in the table below (p. 136). Alders are deciduous or occasionally evergreen trees or shrubs with distinctive root nodules, which contain nitrogen-fixing mycorrhizae. The bark is typically smooth, though in mature specimens it can be furrowed, corky or broken into flat plates. The Latin American species (A. acuminata, A. jorullensis) have prominent constrictions in the stem. Winter buds form at the apex of short branches and are usually protected by two bud scales (some species have no bud scales, merely reduced leaves: for example, A. acuminata, A. formosana, A. ferdinandi-coburgii). These are pubescent, glandular, and covered in a resinous secretion. Initially, the expanding leaves are plicate (folded), though they flatten later. The leaves are simple, petiolate and with double-serrated margins (rarely entire). They are typically ovate, pubescent and deeply grooved. All alders have glandular leaves, the glands concentrated on the lower surface and petiole. Stipules are present in most species and range in size between 0.5 and 15 mm long. Alnus is monoecious; the staminate inflorescences (catkins) are cylindrical and pendent, with numerous inconspicuous flowers, the pistillate inflorescences erect, solitary or in groups, with numerous, persistent, fivelobed woody bracts, overlapping to form cone-like structures (referred to as ‘cones’ in the account below). This contrasts with Betula, where the pistillate inflorescences are catkin-like. The pistillate flowers are also inconspicuous. Most alders have a twoyear flowering strategy, whereby inflorescences are initiated in summer and remain dormant over winter, flowering in spring the following year. However, a few species initiate flowering in spring and flower in autumn of the same year. The fruit is a tiny samara, with papery or leathery wings, although these are reduced in some species (Furlow 1979a, 1979b, 1982, Ashburner 1986, Li & Skvortsov 1999). Alnus is an often overlooked genus, its members forming part of the backdrop of trees in many places but seldom receiving much attention except as useful, fast-growing temporary fillers – even car-park trees in the case of A. cordata, or for awkward damp places. This is unfortunate, because some alders are truly beautiful in shape and foliage features, and many have attractive catkins in early spring. For flowering effect A. maximowiczii, especially the provenance from Ullung-do, South Korea, is outstanding, with fat green catkins in late winter, but it is curiously scarce and seldom seen. Alnus sieboldiana and A. cordata are also very showy in spring catkin. Most alders are pioneer species, germinating on open, often disturbed ground and growing rapidly until out-competed by other species that establish in their shade. In cultivation they require a similarly open site, and are particularly useful for stabilising reclaimed land. Although most will do best in moist soil they do not necessarily need

Plate 110. One of the most attractive alders, Alnus pendula has arching stems bearing strongly veined leaves. Image T. Kirkham.

Figure 14 (opposite). Alnus fauriei: habit with male catkins and seed cones (A). A. pendula: habit with mature and immature seed cones (B); immature seed cone (C); mature seed cone (D).

136

Alnus

New Trees

ALNUS

Mill.

Key characters for Alnus subgenera Alnus and Alnobetula, from information supplied by K. Ashburner

Subgenus Alnus Alders – mostly trees (e.g. A. glutinosa)

Subgenus Alnobetula Green Alders – mostly shrubs (e.g. A. viridis)

Bud scales two, but absent in the A. japonica group

Bud scales numerous, spirally arranged Leaves usually narrow, pointed, with deeply

Leaves usually large, rounded Pistillate flowers exposed in winter, scales open in spring

impressed lateral veins Pistillate flowers emerge in spring Fruits light, adapted for wind-dispersal,

Fruits often dense, adapted for flotation,

with wide, thin wings

with thick corky wings, but sometimes

Cone scales thinner

thin (A. rubra, A. lanata and possibly A. ferdinandi-coburgii)

Wood remains white on exposure

Cone scales thickly woody Wood turns bright brown on exposure

to be planted in marshy conditions and many will be happy in drier sites, although their growth rate may be slower. The recently introduced species described here are in general still rather scarce in cultivation and represented only in specialist collections. In the United Kingdom there are three National Plant Collections of Alnus – in Jersey (Jersey Association of Men of the Trees: not visited), at Blagdon, Northumberland (Lord Ridley), and at Stone Lane Gardens, Devon (Kenneth Ashburner). In addition there are good collections of Alnus at the Hillier Gardens, Howick, Kew and Ness. Most arboreta in Europe and North America have a moderate representation of the genus, but with few of the more recent introductions. Alnus jorullensis from Mexico was described by Clarke (1988) but with a rather negative report on its hardiness. More recent plantings seem to be more successful, and in these warmer times it should be tried more widely. Seed, sown on the surface and kept moist, provides the best means of propagating alders, but hybridisation can be a problem in collections. It is important to transplant seedlings with care so as not to disturb their roots, and to use a well-aerated, nonsterile or inoculated compost to ensure nodulation (H. McAllister, pers. comm. 2007). Alnus seedlings are somewhat prone to damping off (K. Ashburner, pers. comm. 2007), so appropriate precautions should be taken. Early summer cuttings rooted under mist are perhaps the best option for propagating selected clones or rare individuals (Ashburner 1986).

Alnus acuminata Kunth

(Subgen. Alnus)

Alnus acuminata subsp. acuminata

Andean Alder, Aliso

Tree to 25 m, to 1 m dbh; often multistemmed, rarely shrubby or prostrate. Branchlets dull or lustrous, somewhat glaucous, sparsely pubescent and with small yellowish brown glands. Buds resinous. Leaves deciduous, 3.5–9.5(–19) × (2–)3.5–9(–11) cm, ovate to elliptic, upper surface glabrous, lower surface with limited pubescence, 10–16 lateral veins on each side of the midvein, margins slightly revolute and serrate or serrulate, apex long-acuminate to acute, obtuse or rounded; petiole glabrous or pubescent, 0.7–1.6 cm long. Staminate inflorescences catkin-like, 3.5–15 cm long; pistillate inflorescences in racemes of two to four, pedunculate, globose to oblong, 0.3–0.8 × 0.15–0.32 cm. Cones woody, 1.5–3 × 0.8–1.2 cm, bracts 0.3–0.5 cm wide. Furlow 1979a. Distribution ARGENTINA: northern provinces; BOLIVIA; COLOMBIA; ECUADOR; PERU; VENEZUELA. Habitat Stream banks and moist slopes between 1500 and 2800 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk (whole species).

Section II. Species Accounts

Alnus

137

A key to the subspecies is provided below, but the morphological distinctions between them are slight and only accessions of known geographical provenance can be identified with certainty. 1a. Leaves lanceolate to narrowly ovate, lower surface glabrous; Mexico (Durango to Oaxaca) ................................................................................. subsp. glabrata 1b. Leaves ovate to obovate, lower surface pubescent ........................................................................... 2 2a. Leaves finely serrate or serrulate; South America (Venezuela to Argentina) ............. subsp. acuminata 2b. Leaves doubly serrate; Central America (Mexico to Panama) ......................................... subsp. arguta

Alnus acuminata subsp. arguta (Schltdl.) Furlow This subspecies differs from subsp. acuminata in that its leaves are coarser and more deeply toothed. The leaves of the type subspecies are often serrate, while those of subsp. arguta are doubly serrated. Furlow 1979a. Distribution COSTA RICA; EL SALVADOR; GUATEMALA; MEXICO: Chiapas, Chihuahua, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sinaloa, Sonora, Veracruz; PANAMA. Habitat Stream banks and moist slopes between 1500 and 3700 m asl. USDA Hardiness Zone 9. Illustration NT137.

Alnus acuminata subsp. glabrata (Fernald) Furlow This subspecies overlaps with subsp. arguta, from which it can be distinguished by its entirely glabrous lower leaf surface and the lanceolate to narrowly ovate, acuminate leaves. However, hybridisation between the two subspecies does occur, creating intermediate progeny. Furlow 1979a. Distribution MEXICO: central Durango, Guanajuato, Guerrero, Hidalgo, México, north-central Oaxaca, Puebla, Tlaxcala. Habitat Stream banks and moist slopes between 1500 and 3000 m asl. USDA Hardiness Zone 9.

Taken as a whole, Alnus acuminata is rare in cultivation, but all three subspecies are represented in several British collections and members of the group are cultivated in the San Francisco Bay Area botanical gardens. Subsp. acuminata is perhaps the least commonly grown, reflecting its distribution away from the normal haunts of temperate dendrologists. At Stone Lane Gardens an 11 m specimen from the Tucuman area of northern Argentina is doing well, although it is probably a little too heavily shaded for optimal growth. It has a good straight trunk (11 cm dbh, TROBI), with dark brown bark. TROBI records other specimens at Bute Park in Cardiff, Glamorgan, and at Batsford Park, Gloucestershire. Adjacent to the tree at Stone Lane Farm is a specimen of what is probably subsp. glabrata from Mexico, again doing well, at 7 m, despite the shade. It is also cultivated at Tregrehan. Subsp. arguta is the most frequently grown of the three, probably mostly from Mexican plants although there is a specimen of Guatemalan origin at the University of California Botanical Garden at Berkeley. The tallest specimen recorded in Britain was 11 m at Borde Hill, West Sussex in 1962, but in recent years 9 m specimens have been measured at both Wakehurst Place and Westonbirt (TROBI). Despite its southern origins, A. acuminata seems to have retained many of the hardiness genes associated with more northerly alders, but a warm place would seem to be advisable, and there seems to be some variation between the taxa. At Blagdon, for example, subsp. glabrata has proved to be hardier than subsp. arguta (M. Ridley, collection notes). Its principal interest in horticulture is its biogeography, as the tree and its foliage are not particularly attractive, though the male catkins are showy.

Plate 111. The coarsely toothed leaves of the Central American Alnus acuminata subsp. arguta are distinctive. Image J.R.P. van Hoey Smith.

138

Alnus

New Trees

A. ×aschersoniana Callier K132 A. cordata (Loisel.) Loisel. B272, S70, K132

Alnus fauriei H. Lév. & Vaniot

A. cremastogyne Burkill B273, S71, K132 A. ×elliptica Req. B273, K133

(Subgen. Alnus)

Large shrub or rarely a small tree to 7 m, often decumbent. Branchlets glabrous, purplish brown or glaucous. Buds with two glabrous, ribbed scales. Leaves deciduous, 5–12 × 4–11 cm, obovate to cuneate, upper surface glabrous, bright yellow-green, glossy, lower surface pale green, with dense tufts of brown hair in axils of veins, six to seven lateral veins on each side of the midvein, margins doubly serrated, though serration small, apex rounded or emarginate; petiole glabrous, 0.5–1.5 cm long. Staminate inflorescences catkin-like, 6.5– 22 cm long; pistillate inflorescences in racemes of up to five, pedunculate, globose to oblong, 1.6–3 × 0.4– 0.6 cm. Cone woody, 2.5–4 × 0.6–0.8 cm, bracts 0.3 cm wide. Flowering May to June, fruiting September to October (Japan). Ohwi 1965. Distribution JAPAN: northern and central Honshu. Habitat On soils with permanent moisture, between 200 and 1000 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT134.

Alnus fauriei is one of several species described here that is usually a large shrub but is capable of achieving tree-stature. Its large, broad, strongly veined leaves are its principal feature. They may be distinctly emarginate, with a notch at the tip, as in specimens growing at Howick (collected by Motowo and Yoriko Kobayashi, from Ishikawa Prefecture, Honshu), or rounded, as in trees at Stone Lane Garden (from Bambejima, northern Honshu). The large pale green stipules are also conspicuous. It is not commonly grown but there are good specimens in several British arboreta, of which the tallest recorded was one of 6.8 m in the Hillier Gardens in 2003 (but now dead) (TROBI). It is probable that most will not exceed 5 m in height, but with their multistemmed habit they could be considerably wider than this. The male catkins are a pleasing pink and grey (M. Ridley, collection notes).

Alnus ferdinandi-coburgii C.K. Schneid.

(Subgen. Alnus)

Tree to 20 m. Bark smooth, dark grey. Branchlets densely pubescent and ferruginous. Buds with two glabrous scales. Leaves deciduous, 5–16 × 3–7 cm, ovate to elliptic or oblong, rarely lanceolate, both surfaces with yellow pubescence along the veins, 12–17 lateral veins on each side of the midvein, margins entire or with minute serrations, apex abruptly acute; petiole with dense yellow pubescence, 1–2 cm long. Staminate inflorescences catkin-like, 1.5–5.5 cm long; pistillate inflorescences solitary, pedunculate, globose to oblong, 1.5–3 × 1–1.5 cm. Cone woody, 1.5–1.8 × 0.8–1 cm, bracts 0.3–0.4 cm wide. Flowering May to July, fruiting August to September (China). Li & Skvortsov 1999. Distribution CHINA: Guizhou, southwest Sichuan, Yunnan. Habitat Near permanent water sources in montane forest, between 1500 and 3000 m asl. USDA Hardiness Zone 6, or possibly lower. Conservation status Not evaluated. Illustration Li & Skvortsov 1999.

This Chinese alder was discovered by Camillo Schneider on his expedition to Yunnan in 1914 with Heinrich Handel-Mazzetti, and was named by him in honour of Tsar Ferdinand I of Bulgaria (1861–1948, abdicated 1918), who was a keen botanist and gardener. A few years ago Matthew Ridley happened to find himself sitting next to Ferdinand’s grandson, Tsar Simeon II (ruled under a regency 1943–1946; elected Prime Minister of Bulgaria 2001–2005, as Simeon Saxe-Coburg-Gotha), and mentioned Ferdinand’s interest in plants. ‘Yes, he was a great botanist,’ was the reply. ‘He was always in the mountains in full dress uniform on an enormous white horse, with a sword in one hand and a trowel in the other!’ It is unclear when A. ferdinandi-coburgii was first introduced but it is now represented in several collections, and seems to be hardy throughout the British Isles. At Howick there are a number of specimens grown from a collection by Charles Howick (H 1660) at 2150 m in the Luoji Shan, Sichuan in 1992. The largest was about 10 m in 2005

Section II. Species Accounts

Alnus

and seemed healthy, with glossy leaves. Alnus ferdinandi-coburgii is a straight-growing tree, with ascending branches, potentially capable of becoming quite large. A. firma Siebold & Zucc. B274, S71, K133 A. firma var. hirtella (NOW A. firma Siebold & Zucc.) B274, K133 A. firma var. multinervis (NOW A. pendula Matsum., NT143) B274, K133 A. firma var. sieboldiana (NOW A. sieboldiana Matsum., NT144) B274

Alnus formosana (Burkill) Makino

(Subgen. Alnus)

Tree to 20 m. Bark dark grey to brown. Branchlets sparsely pubescent and purplish brown. Buds with two glabrous, ribbed scales. Leaves deciduous, 6–12 × 2–5 cm, elliptic to oblong, rarely ovate, upper surface almost glabrous, lower surface with dense pubescence in the axils of the lateral veins, six to seven lateral veins on each side of the midvein, margins with minute, irregular serrations, apex acute or acuminate; petiole with dense pubescence restricted to the furrow, 1.2–2.2 cm long. Staminate inflorescences catkinlike, 3–8 cm long; pistillate inflorescences solitary or in racemes of two to four, pedunculate, ellipsoid, 1–2.5 cm long. Cone woody, 1.1–1.8 × 0.8–1.2 cm, bracts 0.3–0.4 cm wide. Flowering January to March, fruiting July to September (Taiwan). Li & Skvortsov 1999. Distribution TAIWAN. Habitat Typically, forming pure stands by riverbanks, between 0 and 2900 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Taxonomic note This species appears to be more closely related to the eastern North American species A. maritima Nutt. and A. nitida Endl. than to other Asian alders (Chen & Li 2004), and it has indeed been known as A. maritima var. formosana!

Alnus formosana is not only a large handsome tree but apparently hardy throughout most of the British Isles: it should be planted more widely. There are some beautiful specimens at the Royal Botanic Garden Edinburgh, where a Treecreeper Certhia familiaris was enjoying the long straight bole of the largest (16 m, dbh 38 cm, planted 1926) while notes were being taken for this book; another tree there, of 15 m, has a much thicker, fluted bole (110 cm dbh, TROBI). The spreading branches create a pyramidal shape, and bear a dense canopy of narrow, long-pointed leaves; younger specimens resemble Prunus padus. Alnus formosana has been gathered on several occasions in the past few decades and is represented in many collections in the United Kingdom and elsewhere, including Quarryhill. A. fruticosa (NOW A. viridis subsp. fruticosa (Rupr.) Nyman) K133 A. glutinosa (L.) Gaertn. B274, S71, K133 A. glutinosa var. barbata (NOW A. glutinosa subsp. barbata (C.A. Mey.) Yalt.) B275, K133 A. glutinosa f. graeca Callier K133 A. glutinosa f. incisa (NOW A. glutinosa ‘Incisa’) B275 A. glutinosa f. lacera (Mela) Mela K133 A. glutinosa f. parvifolia (NOW A. glutinosa ‘Parvifolia’) K133 A. glutinosa f. pyramidalis (NOW A. glutinosa ‘Pyramidalis’) B276 A. glutinosa f. quercifolia (NOW A. glutinosa ‘Quercifolia’) B276

Alnus henryi C.K. Schneid.

(Subgen. Alnus)

Tree to 20 m (?). Branchlets yellowish green and sparsely pubescent. Leaves deciduous, 4–8 × 2.5–5 cm, ovate or elliptic, both surfaces glabrous or with minimal pubescence, seven to nine lateral veins on each side of the midvein, margins with minute serrations towards the apex, apex obtuse or acute; petiole with pubescence limited to the upper furrow, 1–1.6 cm long. Staminate inflorescences catkin-like, 3–8 cm long; pistillate inflorescences subsessile, 5–13 in a panicle, ellipsoid, 1.3–1.5 cm long. Cone woody, 1.2–1.5 × 0.6–0.8 cm, bracts 0.4 cm wide. Flowering in autumn (Taiwan). Li & Skvortsov

Plate 112. Alnus henryi is rare in cultivation, but has been established at Kew from ETOT 40, collected in Taiwan in 1992. Image T. Kirkham.

139

140

Alnus

New Trees

1999. Distribution TAIWAN. Habitat This is a pioneer species and can be found in a variety of habitats and elevations. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT139. Taxonomic note Alnus henryi is poorly known and may be conspecific with A. formosana. The only major difference between the two appears to be one of phenology: A. formosana flowers in spring while A. henryi flowers in autumn.

Neither Flora of China nor any other authority is able to provide a mature height for Alnus henryi, but it can be expected to achieve much the same stature as A. formosana. Seed was collected from 5 m trees at 200 m in Taichung Co. by Kirkham and Flanagan during their 1992 expedition to Taiwan (ETOT 40), and their field notes describe it as an abundant pioneer, and ‘a common and successful tree’ – but it would seem that it has a limited distribution on the island. They also note that it grows on ‘south-west facing slopes in full sun’, suggesting that a warm site is needed in cultivation. This collection established the species in cultivation, but it is rare. There are several trees at Wakehurst Place; the champion, however, is a 9 m (15 cm dbh) specimen at Sandling Park, Kent, described by Owen Johnson (2007) as a ‘tree of great grace’. A. hirsuta (Spach) Rupr. B276, S71, K134 A. hirsuta var. sibirica (NOW A. hirsuta (Spach) Rupr.) B277, S71, K134 A. incana (L.) Moench B277, S71, K134 A. incana f. angustissima Holmb. B277 A. incana var. hypochlora (NOW A. incana (L.) Moench subsp. incana) K135 A. incana f. microphylla Callier K136 A. incana f. orbicularis (NOW A. incana (L.) Moench subsp. incana) B278 A. incana f. parvifolia (NOW A. incana (L.) Moench subsp. incana) K136

Plate 113. Alnus inokumae grows fast and straight. This group, planted in 1986, is at Stone Lane Gardens, Devon. Image Stone Lane Gardens.

Alnus inokumae Murai & Kusaka

(Subgen. Alnus)

Syn. A. hirsuta f. inokumae (Murai & Kusaka) H. Ohba Tree 25–30 m, 0.5–0.7 m dbh. Bark smooth to scabrous, greyish brown. Branchlets slender, purplish brown, densely covered with appressed grey hairs. Buds stipitate, black, densely covered with grey hairs. Leaves deciduous, 2–5 × 3 cm (larger in cultivation), ovate to orbicular, upper surface dark green with hairs on the veins, lower surface pale with yellowish brown hairs on the nerves when young, eight to nine lateral veins on each side of the midvein, margins double-serrate, apex acute; petiole purplish black, ~2 cm long, densely covered with grey hairs. Staminate inflorescences solitary or in groups of two to four (to five), ~8 cm long. Pistillate inflorescences usually in groups of two to three (to five), more numerous than in A. hirsuta, pedunculate. Flowers inconspicuous. Cone woody, oblong to ovoid, 1–1.3 × 0.8 cm; bracts ~0.3 cm wide. Fruit a samara with membranous wings. Flowering from March, fruiting in autumn (Japan). Murai 1962. Distribution JAPAN: Hokkaido, northern Honshu; KOREA (?). Habitat Mesic habitats, not confined to riparian areas. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT140. Taxonomic note Alnus inokumae was recently reduced to a form of A. hirsuta by Ohba (2006), but Hugh McAllister (pers. comm. 2007) disagrees with this dramatic reduction in status, pointing out that it is ‘quite distinct in appearance from A. hirsuta mainly because of its smaller (2–5 cm long, vs. 4–9 cm long in A. hirsuta), glabrous leaves, and in being a taller growing tree with a thinner canopy. However, the best precise distinguishing characters appear to be that the tertiary veins are arched forwards, whereas the comparable veins in A. hirsuta are straight; and the more sharply triangular lobing of the leaves. Also, A. inokumae is diploid (2n = 28) whereas A. hirsuta is tetraploid (2n = 56).’ They are, however, clearly closely related, as can be seen from a comparison of the two taxa growing side by side at Stone Lane Gardens.

Putting aside discussions over the taxonomic status of Alnus inokumae, the trees themselves are notable for their extremely fast, straight growth, as demonstrated by specimens at Ness and at Stone

Section II. Species Accounts

Alnus

Lane Gardens. Several trees in a group at Stone Lane Gardens, planted in 1986, from Honshu, are very uniform in height and size, the largest being about 12 m tall (19 cm dbh) when observed in May 2007. These individuals had leaves that were not noticeably smaller than those of the adjacent A. hirsuta, but were a very attractive dark green, with irregular margins in their upper halves. This is an impressive species and could be planted widely wherever fast-growing screening trees are needed. A. japonica (Thunb.) Steud. B278, S71, K136 A. japonica var. koreana Callier K136 A. japonica var. minor Miq. K136

Alnus lanata Duthie ex Bean

A. jorullensis Kunth S72, K137 A. jorullensis subsp. lutea Furlow S72 A. ×koehnei Callier K137

(Subgen. Alnus)

Tree to 20 m. Bark smooth, yellowish grey. Branchlets greyish to purplish brown, lined, densely covered in yellowish brown tomentum when young. Buds stipitate, with two sparsely pubescent scales. Leaves deciduous, 5–14 × 3–8 cm, obovate to oblong, upper surface sparsely villous, lower surface densely covered with yellow-brown tomentum, becoming sparsely pubescent at maturity, 10–13 lateral veins on each side of the midvein, margins irregularly and minutely serrate, apex abruptly acute; petiole 1–2 cm long, densely tomentose when young. Pistillate inflorescences solitary, pedunculate, oblong, 1.5–4 × 0.8–2 cm. Cone woody, pendent, bracts 0.3–0.5 cm wide. Flowering May to July, fruiting August to September (China). Li & Skvortsov 1999. Distribution CHINA: western Sichuan (Kangding Xian, Luding Xian). Habitat Streamsides in montane forest, between 1600 and 2300 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Cross-references B273, K137.

Alnus lanata received a brief description from Bean (1976a), in which the hairy leaves and solitary cone were highlighted, but no indication was given of any cultural requirements. It remains a scarce tree, but it is grown in several important collections. Most specimens in the United Kingdom owe their origin to Matthew Ridley, whose tale of their introduction is worth repeating from his letter of May 2007. ‘I asked Professor Hong Tao [of the Chinese Academy of Forestry, Beijing] if he could get me seeds of Alnus lanata … He said it would be possible, but because there are so many bandits he would need a party of soldiers to protect him and the soldiers’ wages for the week would cost £10,000. I said “Thank you, no, I cannot manage that but never mind, it is nice to know it still exists.” Ten days later a large packet of seed arrived from him and he said “I did not need any soldiers, I have got the seed for you and the cost of the bus fare was £5.00”, so I sent him that.’ Trees from this collection, made at c. 2000 m at Luding, Sichuan in Yunnan in 1997, are flourishing at Blagdon, growing straight and very fast, but although fruiting has occurred the seeds seem to be infertile (M. Ridley, pers. comm. 2007). At Stone Lane Gardens, although the tallest has reached 8 m, several individuals were dead or dying when seen in May 2007, possibly due to unsatisfactory soil conditions or excessive shade (P. Bartlett, pers. comm. 2007). A specimen at Ness is only 3–4 m tall, but very tolerant of exposure. The foliage is distinctly woolly, especially on the underside.

Alnus mandshurica (Callier ex C.K. Schneid.) Hand.-Mazz.

(Subgen. Alnus)

Shrub or tree to 10 m. Bark smooth, dark grey. Branchlets grey-brown, glabrous. Buds sessile, with three to six scales. Leaves deciduous, 4–10 × 2.5–8 cm, elliptic to ovate or broadly so, upper surface glabrous, lower surface glabrous except for tufts of hairs in vein axils, 7–13 lateral veins on each side of the midvein, margins densely and finely serrate or biserrate, apex acute, base rounded; petiole 0.5–2 cm long, glabrous or sparsely pubescent. Pistillate inflorescences three to six per raceme, borne on pendulous peduncles, oblong to rounded,

141

142

Alnus

New Trees

1–2 cm long. Cone woody, bracts 0.3–0.4 cm wide. Flowering May to July, fruiting July to August (China). Li & Skvortsov 1999. Distribution CHINA: Heilongjiang, Jilin, Liaoning, Nei Mongol; NORTH KOREA; RUSSIAN FEDERATION: Manchuria. Habitat Streamsides in temperate forest, between 200 and 1900 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Li & Skvortsov 1999.

Alnus mandschurica is not common in cultivation, but with its northerly distribution would seem to have promise for areas with harsh continental climates. It is in cultivation in the United States, from an introduction as seed (CBS-088) collected at 800 m in Changbai Co. of Jilin Province by the North America–China Plant Exploration Consortium 1997 Jilin China Expedition. A group of specimens from this source, planted out in 2000, were faring with mixed fortunes at the Morton Arboretum when seen in June 2006: one was dead, one was struggling, and the third was a vigorous young plant of 1.8 m. This last had big ovate leaves, of a dull matt green, although they had a slightly ‘pewtered’ appearance, with very finely toothed margins. A. maritima (Marshall) Muhl. ex Nutt. B278, S72, K137

Alnus matsumurae Callier

(Subgen. Alnus)

Tree to 17 m, dbh 45 cm, or more. Branchlets reddish brown or purplish grey and glabrous, with numerous lenticels. Leaves deciduous, deeply veined, 5–9 × 4.5–7 cm, obovate, upper surface dull green and glabrous or sparsely pubescent, lower surface white with some hairs on the veins and tufts of hair in vein axils, seven to nine lateral veins on each side of the midvein, margins deeply serrate, apex strongly emarginate; petiole glabrous or with sparse pubescence, 1.5–3 cm long. Staminate inflorescences catkin-like, 4–8 cm long; pistillate inflorescences solitary or in racemes of two to five. Cone woody, 1.3–1.7 × 1–1.2 cm, bracts 0.3–0.4 cm wide. Flowering May to June, fruiting November (Japan). Ohwi 1965. Distribution JAPAN: central and northern Honshu. Habitat Montane forest. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT142. Cross-reference B277, K137.

Plate 114. The apical ‘notch’ in the leaves of Alnus matsumurae makes it easily recognisable. Image P. Williams.

Bean (1976a) gave Alnus matsumurae a very short description, but this beautiful tree deserves more comment. It forms a good straight trunk bearing horizontally spreading branches that hold a solid canopy of foliage. The strongly veined, broadly rounded leaves are distinct by being conspicuously emarginate, although they can be merely truncate. The 17 m tree at Kew noted by Bean has gone, but there is a similarly sized one (16 m, dbh 45 cm in 2001) at Alice Holt, Hampshire (TROBI). At Stone Lane Gardens there is an 8 m specimen, planted in 2001. Alnus matsumurae is not common but seems to grow well throughout the British Isles, and probably also in much harsher conditions, although it may not always make a good tree. A shrubby specimen seen at the Morton Arboretum was received as wild-collected seed in 1995 from Arboretum National des Barres, France. A. maximowiczii Callier ex C.K. Schneid. B279, K137

Alnus ×mayrii Callier

(Subgen. Alnus)

There are several naturally occurring hybrids in Alnus, many of which are unnamed and of uncertain origin. Alnus ×mayrii is allegedly the result of a cross between A. hirsuta Turcz. and A. japonica Siebold & Zucc. (Ohwi 1965), though it is not recognised in the World Checklist of Fagales (Govaerts & Frodin 1998). It resembles A. japonica (see Bean 1976a), but the leaves are broader (8–11 cm vs. 2–5 cm), and elliptic to oblong rather than lanceolate or narrowly ovate. The hybrid has dense, ferruginous pubescence on the branchlets, new shoots and lower leaf surfaces, as in A. hirsuta. Ohwi 1965. Distribution JAPAN: Hokkaido; KOREA. Habitat Marshy areas. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Cross-reference S71.

Section II. Species Accounts

Alnus

143

Plants bearing this name are found in several arboreta in our area, specimens for the current work having been observed at Quarryhill, Howick and Kew. There is considerable variation between them, some showing more or less the characteristics of one or other parent, while others are intermediate. Most collections seem to have been made from hybrid parents in the wild, making the cultivated offspring the F2 generation, in which such segregation is to be expected. At Quarryhill, trees grown from a collection in Hokkaido in 1987 (Warner & Howick 510), planted in 1991, were 12–15 m tall when seen in 2004, looking very much like most alders, but bearing conspicuous clusters of attractive large cones. At Howick trees from the same collection are much shorter but still doing well in a considerably cooler locality. Kew has two trees of separate South Korean origin, the older (now 9 m) from a 1968 accession received from the US Department of Agriculture, the other (8 m) from the Morris Arboretum in 1985, and showing strong characters from A. japonica. Although many specimens of A. ×mayrii are attractive trees they have no merits greater than those of either parent. A. nepalensis D. Don B279, K137 A. nitida (Spach) Endl. B280, S72, K137

Alnus pendula Matsum.

A. oblongifolia Torr. K137 A. orientalis Decne. B280, S72, K138

(Subgen. Alnobetula)

Syn. A. firma var. multinervis Regel Large shrub or tree, 3–8 m; multistemmed. Branchlets dark greyish brown, slender and pendulous, with short-lived silky hairs. Buds with two glabrous, membranous bracts. Leaves deciduous, 4.5–12 × 2.2–4.5 cm, narrowly ovate to broadly lanceolate, upper surface green and not glossy, lower surface pale green, appressed, silky hairs on the veins, 20–26 lateral veins on each side of the midvein, margins doubly serrated, apex longacuminate; petiole densely pubescent, 0.3–0.8 cm long. Staminate inflorescences catkin-like, 5–12 cm long; pistillate inflorescences in racemes of three to six, pedunculate, ellipsoid, 0.8–1.2 × 0.6–0.8 cm. Cone woody, 1.2–1.6 × 0.8–1.2 cm, bracts 0.3 cm wide. Flowering April to May, fruiting September to October (Japan). Ohwi 1965. Distribution JAPAN: Hokkaido, Honshu – very common in northern Honshu on waste ground and by roadsides (K. Ashburner, pers. comm. 2007); NORTH KOREA; SOUTH KOREA. Habitat Montane forest to 1500 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT134, NT135, NT143. Cross-references B274, K133 (both as A. firma var. multinervis).

This exceptionally attractive green alder is without question more a shrub than a tree, but it could probably be trained into a single-stemmed tree if required. The branches arise from the base and arch outwards, bearing pendulous shoots that carry the narrow, sharply pointed and strongly veined leaves; comparison with leaves of Carpinus is not inappropriate. The effect is extremely elegant, and this would be a beautiful plant for a lakeside. There is a good group at Stone Lane Gardens, and specimens from EHOK 54, gathered by Tony Kirkham, Giles Coode-Adams, Charles Howick and Bill McNamara on Hokkaido in 1997, are grown at Howick and Kew and in several private collections. The field notes of this expedition record a height of 2.5 m, with a spread of 4 m. Charles Howick (pers. comm. 2005) has found it hard to establish, and the tree seen at Howick was less than 1.5 m tall in 2005. In South Korea another group from Kew – the Kirkham, Flanagan and Boyce Expedition of 1989 – found it growing to 8 m tall at 60 m asl on Namhae Island, Kyongsangnam Province. Plants from this collection (KFBX 125) are in cultivation at Kew and at Sandling Park, Kent, where they had also reached 8 m by 2006 when measured by Owen Johnson for TROBI. A. ×pubescens (NOW A. ×hybrida Rehb.) B276, K138

A. ×purpusii Callier K138 A. rhombifolia Nutt. B281, K138

Plate 115. The male catkins of Alnus pendula. The catkins add greatly to the charms of most Alnus. Image Stone Lane Gardens.

144

Alnus

New Trees

A. rubra Bong. B281, S73, K138 A. rugosa (NOW A. incana subsp. rugosa (Du Roi) Clausen) B281, S73, K138 A. rugosa var. americana (NOW A. incana subsp. rugosa (Du Roi) Clausen) B282, K138

Alnus sieboldiana Matsum.

A. rugosa f. emersoniana (NOW A. incana subsp. rugosa (Du Roi) Clausen) K138 A. serrulata (Aiton) Willd. B282, S73, K138

(Subgen. Alnobetula)

Syn. A. firma var. sieboldiana (Matsum.) Winkler Large shrub or tree, to 12 m or more; multistemmed. Branchlets stout, glabrous, yellowish to greyish brown. Buds with two glabrous, membranous bracts. Leaves deciduous, 6–10 × 3–6 cm, ovate to deltoid, upper surface green, lower surface pale green with appressed pubescence on veins, 12–15 lateral veins on each side of the midvein, margins doubly serrated with mucronate teeth, apex acute to shortly acuminate; petiole glabrous, 1–1.5 cm long. Staminate inflorescences catkin-like, robust, 4.5–9 cm long; pistillate inflorescences solitary, pedunculate, ellipsoid, 2.4–2.8 × 0.6–0.8 cm. Cone woody, 2.5–3 × 1.5–2 cm, bracts 0.5–0.6 cm wide. Flowering March to June, fruiting September to October (Japan). Ohwi 1965. Distribution JAPAN: Honshu. Habitat Lowlands, foothills, especially coastal areas. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT26. Cross-reference B274 (as A. firma var. sieboldiana).

A unique feature of the plantings at Stone Lane Gardens is the way that several specimens from a single wild-origin collection are planted in a group together – a pattern that enables natural variation to be observed and maintained in a way that is only too rare. Among these groups is a planting of Alnus sieboldiana, grown from a collection made by Kenneth Ashburner at Katanuma Lake, near Sendai, Honshu in 1980, and now forming a wonderful grove of sinuous grey trunks. Although Ohwi (1965) allows the wild tree to reach only 3 m, these are 8–9 m in height, growing on multiple stems from the base that support spreading limbs and a rounded canopy. The leaves are large, lanceolate to ovate, with an acute tip and a very crisply toothed margin, and are a handsome feature in their own right. They are retained well into December (K. Ashburner, pers. comm. 2007). The male catkins are almost globular and are extremely showy in spring with yellow anthers, while the very large cones, changing from green to russet-brown and held upright on the twigs, are a further good point. At Howick, where there are three trees from a Motowo and Yoriko Kobayashi collection from Aichi Prefecture, Honshu, it has not been easy to get it established (C. Howick, pers. comm. 2005), but the survivors were about 5 m tall in 2005. A. ×silesiaca Fiek & Pax K138 A. sinuata (NOW A. viridis subsp. sinuata (Regel) Á. Löve & D. Löve) B282, S73, K139 A. ×spaethii Callier B278, S72, K139 A. ×spectabilis Callier K139 A. subcordata C.A. Mey. B282, S73, K139

Alnus trabeculosa Hand.-Mazz. Figure 15 (opposite). Alnus trabeculosa: habit with seed cones and immature catkins.

A. tenuifolia (NOW A. incana subsp. tenuifolia (Nutt.) Breitung) B283, S74, K139 A. tenuifolia var. occidentalis (NOW A. incana subsp. tenuifolia (Nutt.) Breitung) B283, K139 A. tenuifolia var. virescens (NOW A. incana subsp. tenuifolia (Nutt.) Breitung) K139

(Subgen. Alnus)

Tree to 10 m. Bark smooth, grey to grey-brown. Branchlets green in first season, becoming grey-brown with yellow pubescence. Buds with two glabrous, ribbed scales. Leaves deciduous, 6–16 × 2.5–7 cm, obovate to oblong, upper surface glabrous, lower surface glandular, glabrous, but for dense pubescence in the axils of

Section II. Species Accounts

Alnus

1 cm

145

146

Alnus

New Trees

the lateral veins, 6–13 lateral veins on each side of the midvein, margins with minute serrations, apex acute, acuminate or caudate; petiole largely glabrous, 0.5–3 cm long. Staminate inflorescences catkin-like, 3–4 cm long; pistillate inflorescences in racemes of two to four, pedunculate, oblong, 1–2.5 × 1–1.5 cm. Cone woody, 1.8–2 × 0.7–1 cm, bracts 0.5–0.7 cm wide. Flowering May to June, fruiting July to August (China). Li & Skvortsov 1999. Distribution CHINA: Anhui, Fujian, northern Guangdong, Guizhou, southern Henan, Hubei, eastern Hunan, Jiangsu, Jiangxi, Zhejiang; JAPAN: Honshu. Habitat Riverbanks in montane forest, between 200 and 1000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT145.

Alnus trabeculosa is rare in cultivation although widely distributed as a wild plant. There are scattered trees in collections across Europe: for example, there is one at the National Botanical Garden of Belgium, Meise, originating from the Hangzhou Botanical Garden, accessioned in 1991, and it also grows at the Botanischer Garten Berlin-Dahlem, and Freiburg-Günterstal Arboretum in Germany. In the United Kingdom it seems to be known only from an introduction in early 1997 of seeds given to Ray Townsend and Mark Bridger at the Forest Tree Breeding Centre at Juo Town in Ibaraki Prefecture, Honshu. Our illustration (Figure 15) was drawn from one of the resulting trees at Kew, now 1.6 m tall, though with a broken leader. At Howick it has also been slow, one specimen there being less than 2 m tall when seen in 2005. The leaves are an attractive mid-green, and when young the midrib and principal veins are red. A. viridis (Chaix) DC. B283, S74, K139 A. viridis var. pumila (NOW A. viridis subsp. fruticosa (Rupr.) Nyman) B283, K139 A. viridis subsp. suaveolens (Requien) P.W. Ball S74

TAXACEAE

AMENTOTAXUS

Figure 16 (opposite). Amentotaxus argotaenia: habit with female cones (A); habit with male strobili (B); detail of stem (C).

Pilg.

Amentotaxus comprises six species of small dioecious trees or shrubs that grow in damp forest understorey in southeastern Asia, often in ravines or along streams at altitudes of 300–1600 m. The branches are thin and spreading, producing opposite branchlets. The comparatively broad, leathery leaves are glossy dark green, and persist two or three years. They are opposite with a short petiole, usually linear-elliptic to linearlanceolate, margins slightly revolute and with a prominent midrib between two broad and conspicuous white or fulvous stomatal bands. Although decussate in arrangement they tend to align themselves to the light and thus often appear to be held in a single plane. Male strobili are borne in terminal clusters of one to five, held erect when young but becoming pendulous with age, 3–7 cm long with 8–10 microsporophylls; the catkin-like bodies give the genus its name, which translates literally as ‘catkin yew’. Ovules are borne on peduncles 1–1.5 cm long, subtended by 10–15 persistent scales. The ovoid or ellipsoid arillate fruits are reddish yellow, becoming purple, and are resinous. They ripen and fall after one year on the tree, but it is thought that the embryo takes longer to mature and germination occurs after at least one further year. Amentotaxus is probably most closely related to Torreya, but is the only member of the Taxaceae to have resin in its ducts or canals (Li 1952, Ferguson 1992, Cope 1998). Amentotaxus are attractive small trees, the silvery stomatal bands being their most appealing feature. They are all rather rare in the wild, threatened by habitat destruction, and very scarce in cultivation. Originating in dense understorey of subtropical

Section II. Species Accounts

1 cm

Amentotaxus

C

1 cm

A B

147

148

Amentotaxus

New Trees

forests, at only moderate altitudes, they will require specialist conditions of shade and high humidity but as much warmth as possible. Only in exceptional conditions should these rare trees be attempted outside in our area. In addition to A. argotaenia, described below, A. formosana H.L. Li (Critically Endangered) is in cultivation in both Europe and North America, but wisely maintained under glass: one plant from Edinburgh failed to survive outside at Tregrehan (see Plate 35, p. 21). Amentotaxus yunnanensis H.L. Li (Endangered in the wild) is also tenuously in cultivation under glass, having been recently collected by an expedition to Vietnam led by Rob Nicholson, Conservatory Manager at Smith College, Massachusetts, and successfully propagated from cuttings there (Smith College 2005a). Plate 116. The foliage and fruits of Amentoxus argotaenia are extremely decorative. The aril almost entirely covers the seed. Image R. Unwin.

Amentotaxus argotaenia (Hance) Pilg. Shrub or tree to 6(–10) m. Bark flaking, grey-brown, showing reddish orange below. Branches spreading. Branchlets subterete to quadrangular. Leaves thickly coriaceous, linear-lanceolate, 4–8 × 0.65–1.5 cm, usually straight but occasionally falcate towards tip, apex acute to obtuse, stomatal bands silvery white, 1.2–1.8 mm broad. Male strobili pendulous, in clusters of (one to) two to three (to five), 5–6.5 cm, shortly pedunculate. Fruits 2.5 × 1.5 cm, pendulous on peduncles to 2 cm, red when immature, becoming purple, the seed protruding slightly from the aril. Li 1952, Luu & Thomas 2004. Distribution CHINA: Fujian, Gansu, Guangdong, Guangxi, Guizhou, western Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Xizang, Zhejiang; VIETNAM. Habitat Wet rocky sites in forest. USDA Hardiness Zone 9–10. Conservation status Vulnerable. Illustration Luu & Thomas 2004; NT147, NT148. Cross-reference K50.

Amentotaxus argotaenia is present in collections throughout our area but is mainly grown under glass, as for example at Edinburgh. There is a very small plant from Sichuan outside at Kew, but it is not thriving. The species was introduced to North America in 1994 by Piroche Plants (2002–2005) but does not seem to have become established in gardens, in our area at least. It is probably better suited to conditions in the southeastern United States.

A. cathayensis (NOW A. argotaenia (Hance) Pilg., NT148) K50 A. formosana H.L. Li K50 A. yunnanensis H.L. Li K50

MYRTACEAE

AMOMYRTUS

(Burret) D. Legrand & Kausel

The two species of Amomyrtus are endemic to the wet temperate forests of southcentral Chile and bordering Argentina. They are aromatic trees or shrubs with smooth or scaly bark. The evergreen leaves are opposite, leathery, petiolate and typically lanceolate or ovate. The flowers are solitary or on short shoots with up to six flowers. They are hermaphrodite and 5-merous; bracteoles caducous; calyx lobes persistent; petals white; stamens whitish, 30–80. The fruit is a berry containing one to four hard seeds, each shaped like a flattened snail shell (Landrum & Salywon 2004).

Section II. Species Accounts

Amomyrtus

149

Amomyrtus luma (Molina) D. Legrand & Kausel was introduced from Chile in the 1920s by Harold Comber, and was described by Bean and Krüssmann (B765, K316), as Myrtus lechleriana, but remains comparatively little known despite its apparent hardiness and magnificence when in full flower (Gardner & Hechenleitner 2005). Amomyrtus meli, described below, also has great garden qualities.

Amomyrtus meli (Phil.) D. Legrand & Kausel

Luma Blanca, Meli

Tree to 20 m. Bark smooth, whitish, not strongly mottled. Branchlets smooth, greyish white or light reddish brown, obscurely pubescent to glabrous. Leaves evergreen, stiff, leathery and strongly aromatic, 2–5(–9) × 0.7–2.5(–3) cm, ovate, lanceolate or elliptic, upper surface dull or slightly lustrous, secondary veins indistinct, or approx. seven pairs faintly visible, margins entire, apex acute, often mucronate; petiole 0.2–0.4 cm long, yellowish brown. Flowers white; peduncles 0.4–2 cm long, glabrous or sparsely pubescent; calyx lobes triangular, ~0.1 cm long; petals subcircular, ~0.3–0.4 cm long; hypanthium conical, densely glandular; stamens ~40–80. Fruit black, subglobose, 1–1.5 cm diameter. Flowering October to December, fruiting January to May (Chile). Landrum & Salywon 2004. Distribution CHILE: Araucanía, Bío-Bío, Los Lagos. Habitat Wet temperate forest between 0 and 600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT149.

‘Smelly meli’, the name coined by Martin Gardner for this tree, is both a catchy sobriquet and a mnemonic, as the foliage has a very distinctive strong fragrance, reminiscent of old-fashioned fruitflavoured boiled sweets, that is certainly not unpleasant. The foliage looks like that of many myrtles, small and tidy in dark green when mature, but flushing dark red-bronze. The cream-coloured flowers likewise are unmistakeably those of any myrtle, and are borne profusely in late summer. In the wild it can form a tree up to 20 m tall, with a clean bole of shining pale bark (Gardner & Hechenleitner 2005), but in cultivation the largest plants are at present no more than erect shrubs of about 3 m tall. The only collection known was made on the joint Chilean–Edinburgh expedition (ICE 127) in 1996, from which plants are now well established in several Scottish and Irish gardens. Amomyrtus meli seems to thrive in mild, moist conditions but has not been widely tested. It has not been made available to commerce.

ARALIACEAE

ARALIA

L.

Angelica Trees, Aralias, Devil’s Walking Stick, Hercules’ Club Aralia currently has 69 species, and is distributed primarily in the northern hemisphere, though with extension into Malesia and New Guinea. There are also disjunct populations in Mexico, Central America, the Greater Antilles and interior South America (Frodin et al. 2003). Aralias are typically small trees or shrubs, though climbing and

Plate 117. Cultivated plants of Amomyrtus meli have a long way to go to reach the magnificent size of this wild tree in Chile. Image M. Gardner.

150

Aralia

Plate 118. Aralia echinocaulis has ferociously spiny stems when young. It was introduced to cultivation by the Glasnevin Central China Expedition in 2002 (GCCE 259). Image S. O’Brien.

New Trees

herbaceous species are known. The variety of morphological forms is reflected in the number of common names used for this genus. The stems are often stout and spiny (hence the vernacular names Devil’s Walking Stick, Hercules’ Club) or unarmed. The leaves are alternate and pinnate, with one to four orders of branching. Typically, the leaves have stipules and the rachis is articulated. The flowers are hermaphrodite, in terminal inflorescences. These can be paniculate, corymbose or umbellate, and are composed of multiple umbels, racemes or heads. Rarely, the inflorescences comprise solitary umbels only. The individual flowers are 5- to 8merous. The fruit is a globose berry (Wen 1993). Aralia is closely related to Panax L. (ginseng) and Sciadodendron Griseb., and DNA studies indicate that the boundaries between these genera may have to be altered (Wen 2001). As currently delimited, Aralia is a genus that morphs comfortably albeit unusually between herbs, shrubs and true trees. Most species are noted for their bold foliage, and the most familiar in gardens – A. elata – is particularly valued in its variegated clones. With the current fashion for big bold-foliaged plants Aralia has become very popular, and species of all growth forms find a valued niche in planting schemes where their stature is appreciated. The large compound inflorescence can also be spectacular, and is an often overlooked asset in members of this genus. The plants are not in general fussy about soils, but appreciate adequate moisture, and in the case of the larger-leaved species, shelter from wind is useful. Many species of Aralia in southeastern Asia are potentially tree-forming but may also be suckering multistemmed shrubs – a difficult group to categorise. They all have some degree of garden merit for their handsome foliage and large inflorescences, and it is probable that species will continue to be introduced. Among those in cultivation, A. bipinnata Blanco is potentially a tree to 7 m, its stems covered in stiff, conical prickles and bearing big bipinnate leaves with glabrous leaflets. It is found in dry places in Taiwan, where it has recently been collected (for example, B&SWJ 3137, RWJ 10060). Others include the widely distributed A. foliolosa Hance, up to 10 m tall with tripinnate leaves, and A. stipulata Franch., from Yunnan, also to 10 m but with bipinnate leaves. Aralia leschenaultii (DC.) J. Wen (syn. A. fragrans (D. Don) Jebb & J. Wen) has been grown for some time under the generic name Pentapanax but has not become widely known. It is a small tree, climber or epiphytic shrub, 5–15 m, with relatively small evergreen leaves. It has a wide distribution in wet forest conditions in southeastern Asia but has recently been introduced from Nepal (for example, HWJK 2385). A. chinensis L. B307, K162 A. chinensis var. dasyphylloides (NOW A. dasyphylloides (Hand.-Mazz.) J. Wen) K162 A. chinensis var. nuda (NOW A. elata (Miq.) Seem. var. elata) B307, K162

Aralia echinocaulis Hand.-Mazz. Shrub or small tree, 2–10 m, usually single-stemmed. Bark brownish; stem densely covered with sharp, needle-like spines, 0.5–2 cm long. Leaves bipinnate, 60–100 × 50–75 cm, stipulate; stipules lanceolate or linear, 1–2 cm long; petiole purplish, 30–45 cm long, usually unarmed; rachis purplish, unarmed, with pairs of accessory leaflets at each division; two to four pairs of pinnae, each with 5–11 leaflets; leaflets membranous to

Section II. Species Accounts

Aralia

papery, 6–14.5 × 3–8 cm, ovate to oblong, rarely lanceolate, upper surface dark green, shiny and glabrous, lower surface glabrous with easily erased white wax, 12–18 lateral veins per leaflet, margins serrate, apex acuminate. Inflorescences terminal, paniculate, 35–50 cm long, unarmed, purplish; primary branches 10 or more, each 10–20 cm long; umbels 1.5 cm diameter, with 12–20(–30) flowers. Flowers white or purplish white, fragrant. Fruit a reddish green to black berry, 0.3–0.5 cm diameter, with persistent radiating style arms. Flowering June to August, fruiting September to November (China). Wen 1991, Xiang & Lowry 2006. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang. Habitat Along roadsides or streams, in dense thickets or on rocky cliffs between 1000 and 2600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT150.

In its young stages at least, Aralia echinocaulis is a most striking plant, with huge bipinnate leaves and dense rich brown spines on its stem. Such young plants have been used to great effect by garden designer Jimi Blake at Hunting Brook Gardens, Co. Wicklow, among bold perennials and grasses. They were grown from seed collected under the number GCCE 259 by the 2002 Glasnevin Central China Expedition (in association with Wuhan Botanical Gardens and the Chinese Academy of Sciences), that traced some of Augustine Henry’s collecting areas in the Three Gorges area before they were irrevocably flooded by the new dam. As a wild tree growing in mountain thickets and secondary scrub in the Badong area of western Hubei, A. echinocaulis is a single-stemmed plant to 5 m (S. O’Brien, pers. comm. 2007), but in cultivation it has a slight tendency to sucker. As a result of the Glasnevin Central China Expedition it is represented in several Irish gardens, and seems to be hardy under normal winter conditions there. A. elata (Miq.) Seem. B306, K162 A. hispida Vent. K163

A. nudicaulis L. K163 A. spinosa L. B308, K163

ARAUCARIACEAE

ARAUCARIA

Juss.

Monkey-puzzles The genus Araucaria contains some of the most distinctive trees in existence, including the widely grown A. araucana, the Monkey-puzzle, and the Norfolk Island Pine A. heterophylla, whose whorled branches are so familiar a sight in tropical gardens. There are 19 species in the genus, with a scattered distribution in former Gondwanaland (although they occurred in Laurasia as well). Two are from South America, while the others are from a cluster of localities in Australasia centred on New Caledonia, where an astonishing 13 species occur as endemics or near endemics. All are substantial trees, with a stout, straight and usually unbranched main trunk bearing similarly stout, spreading branches, in whorls. The bark is resinous. In youth the branches occur from the base, but in maturity the lower branches usually senesce, leaving the tree with an often ragged-looking crown. The branches are clad along their length with stiff evergreen scale leaves, varying from small and needle-like to broad and rigid, usually sharp-tipped. Buds are indistinct among the foliage. The trees are usually dioecious, but hermaphrodites sometimes occur, and are self-fertile. Male strobili are solitary or

151

152

Araucaria

Plate 119. The massive growth of Araucaria bidwillii suggests a butch antiquity, appropriate in a genus that co-existed with the dinosaurs. Image A. Farjon.

New Trees

clustered, forming dense cylindrical ‘cones’ borne upright from the branches. Female cones are large and globose, formed of many scales which fall apart at maturity, persisting for two to three years on the tree. Each scale has one (usually winged) seed adherent to it (Dallimore et al. 1966, Krüssmann 1985b, Farjon 2001). The Monkey-puzzle Araucaria araucana – so beloved of the Victorians, and still commonly planted – is generally appreciated and reviled in about equal measure. It must be said that a solitary scrawny specimen in a suburban setting is not an inspiring sight, but a well-grown young one is a handsome object and with thoughtful modern planting around it, need not appear so out of place as it often does. It is the regular branching that makes the tropical and subtropical species of Araucaria so attractive when young, and gives the impetus to attempts to grow them in our area. In addition to the species described below, A. cunninghamii D. Don from Australia (Queensland) and New Guinea may be worth attempting in mild coastal gardens, having reached 18 m at Penjerrick, Cornwall in the much cooler past (1928 record, TROBI). Araucaria hunsteinii K. Schum. from New Guinea is in cultivation at Tregrehan, where a young tree is growing steadily. Although Krüssmann (1985b) describes several other tropical species, there is no evidence that these have ever been cultivated outdoors in our area, and they are omitted from our cross-references. Propagation is by seed.

Araucaria angustifolia (Bertol) Kuntze

Brazilian Monkey-puzzle

Tree to 35–40 m, 1.5 m dbh, with single straight trunk. Bark scaly, with horizontal striations. Branches in whorls of four to eight, dying from base as tree ages to leave a flat-topped crown of gaunt appearance. Leaves loosely imbricate, lanceolate, 2–6 × 0.5–0.8 cm, apex acute, leathery and stiff, dark green or glaucous, shorter and more spirally arranged on fertile shoots. Male strobili borne on short fertile shoots, forming dense erect cones to 8–20 × 1.3–2 cm. Female cones wider than long, narrowing from the centre towards the tip, 12 cm × 16 cm, each scale with stout recurved appendage. Seeds edible, cuneiform, 3 cm long, chestnutcoloured. Dallimore et al. 1966, Krüssmann 1985b, Silba 1986, Covas 1995. Distribution BRAZIL: southeast; ARGENTINA: northeast. Habitat Mixed forest between 500 and 2300 m asl on acidic, laterite soils with up to 1500 mm rain p/a. USDA Hardiness Zone 8–9. Conservation status Critically Endangered, due to logging. Illustration NT22. Cross-reference K51.

Araucaria angustifolia resembles a smaller-leaved, less tidy A. araucana when young and is obviously closely related to that species, with apparent intermediates occurring in parts of Chile (S. Hogan, pers. comm. 2007). Older reference works suggest that it is not hardy in the United Kingdom (Dallimore et al. 1966) but recent experience suggests that it is well worth trying – even in less favoured situations than Cornwall! It is true that the finest specimens known at present in the United Kingdom are just over that county’s boundary, at Casa di Sole in Devon, where there are three of 6, 7 and 8.7 m (in 2006), doing well though looking spindly (TROBI), but other good examples are known. Another 6 m specimen was growing vigorously until recently in Tony Titchen’s garden at Portishead, Somerset, before it was snapped off at the base by a falling tree, and there are vigorous young individuals both at Nymans, in East Sussex, and at Peasmarsh Place, West Sussex. The latter was 3.5 m in 2006, having been planted only in 2001. It was collected as seed in Brazil by Lord Devonport. Young trees have been seen in an ordinary garden centre in Gloucestershire, and it

Section II. Species Accounts

Araucaria

153

is available in specialist nurseries in Europe and North America. It would seem to be worth trying in the mild parts of maritime Europe and western North America. A. araucana (Molina) K. Koch B308, S86, K52 A. beccarii (NOW A. cunninghamii Aiton ex D. Don var. papuana Lauterb.) K52

Araucaria bidwillii Hook.

Bunya Pine

Tree to 50 m with straight unbranched trunk, to 1.3 m dbh. Bark hard and rough, dark brown to black, peeling in thin layers. Branches long and spreading when mature, forming a dome-shaped canopy with leaves at the tips; trees conical or pyramidal when young. Leaves dimorphic between erect and spreading shoots, and between juvenile and adult phases, though juvenile leaves are usually just smaller than their adult counterparts; on erect shoots the leaves are narrowly triangular to needle-like, on branches they are narrowly triangular with a broad base decurrent on the stem, 2.5–3 × 0.3–1 cm, glossy dark green above, paler below. Male strobili pendulous, sessile, cylindrical, 6–11 × 1–1.5 cm. Female cones massive, ovoid, 20–30 × 15–20 cm, scales winged with a long-acuminate apex. Seeds ovoid, 20–25 × 15–20 mm. Dallimore et al. 1966, Hill 1998. Distribution AUSTRALIA: Queensland. Habitat Montane rain forests on deep soils. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration NT152. Cross-reference K53.

The Bunya Pine is a magnificent tree in its native Queensland, and is grown quite widely in Australia and elsewhere for its ornamental value (Elliot & Jones 1982). Mature trees can be somewhat hazardous, on account of the risk of being hit by a falling cone. At present there seems to be little danger of this in our area, where it is on the very edge of its tolerance, even in the mildest locations. It has however reached 11 m (33 cm dbh) in the past at Glendurgan, Cornwall (TROBI record from 1965), and the current British and Irish champion is a 6 m specimen at Earlscliffe, Baily, Co. Dublin (TROBI). It is therefore worth attempting, in the mildest coastal areas of Europe and western North America, but great size and longevity are perhaps too much to hope for. A. cunninghamii Aiton ex D. Don K54

Araucaria heterophylla

Norfolk Island Pine

(Salisb.) Franco Syn. A. excelsa hort. non (Lamb.) R. Br. Tree to 50(–70) m with straight stem, to 3.5 m dbh. Bark grey-brown, peeling in small scales. Branches in widely spaced whorls, especially in young trees, ascending, often becoming ragged-looking with age when the attractive conical shape is lost. Leaves dimorphic; those on juvenile growth soft, needle-shaped, to 1.2 cm and spreading away from the stem, light to mid-green; mature leaves dark green, hard to the touch, narrow, densely placed and overlapping, 4–5 mm long and incurved at apex, but broader and imbricated on fertile shoots. Male strobili pendulous, clustered, 4 cm long. Female cones 10–12 × 7.5 cm, with triangular scales and long-pointed incurved tips. Seeds to 3 × 1.2 cm, winged. Dallimore et al. 1966, Silba 1986, Hill 1998. Distribution NORFOLK ISLAND. Habitat Lowland forest. USDA Hardiness Zone 9–10. Conservation status Vulnerable. Illustration NT153. Cross-reference K54.

The symmetry and shape of the Norfolk Island Pine as a young tree are extremely attractive, earning it a place in many tropical gardens, but as it matures it can look very raddled and in smaller gardens should be replaced regularly. Owen Johnson (2007) has commented that it is ‘so spectacular that gardeners are always going to try to grow it – though I know of no trees in central London, where it ought to thrive, and no old ones on the coasts of Cork

Plate 120. The regularity of its branching when young makes Araucaria heterophylla a popular plant in tropical gardens, though it often looks awful when old. It is only suitable for the mildest extremities of our area, such as here at the San Francisco Botanical Garden. Image J. Grimshaw.

154

Araucaria

New Trees

and Kerry, where it could have done.’ The largest recorded in the British Isles was a 25 m (74 cm dbh) specimen at Tresco Abbey, killed by frost in 1987. Replacements there are doing well (Johnson 2007), but on the mainland the story is less rosy with most trees, even in the classic coastal and Cornish sites, struggling along to only a few metres high. An interesting exception is a 2.5 m specimen doing well in a garden in Ipswich, Suffolk (Johnson 2007, reported by D. Sanford). As the species is sold in huge numbers in the juvenile phase as a houseplant it would not be surprising if there were other such individuals growing in sheltered urban localities. A. klinkii (NOW A. hunsteinii K. Schum.) K54

ERICACEAE

ARBUTUS

L.

Strawberry Trees, Madrones This is a genus of approximately 14 species of small to medium-sized trees or shrubs, often with a twisted trunk and a rounded but irregular crown. The bark is thin and red-brown, peeling in strips to reveal smooth yellow-green new bark; or dark brown, furrowed and fibrous, not peeling. The leaves are evergreen, simple, alternate, margins entire or toothed, leathery, with a well-developed petiole. The flowers are bisexual, in elongated panicles at the ends of branchlets, small, urn- or bell-shaped, white or pale pink, with a persistent five-lobed calyx, five fused petals, 10 stamens, anthers with two awns projecting from the back, gynoecium solitary with a single style. The fruit is berry-like, with a warty surface and a thin fleshy region surrounding a hard stone containing seeds (Elias 1980). Arbutus is a well-known genus in the more temperate parts of our area, with the European species A. unedo, A. andrachne and their hybrid A. ×andrachnoides having long been valued for their numerous merits. This European group has been joined in recent years by the outstanding hybrid ‘Marina’, released to the horticultural trade in 1984 by the Saratoga Horticultural Research Foundation. The origins of this hybrid are complicated, it apparently having been shipped (unrecognised) from Europe to San Francisco in 1917 as a landscaping tree for the Exposition that year. It was propagated by Charles Abrahams at his Western Nursery in the Marina district of San Francisco, and one of the resulting plants was grown at the Strybing Arboretum (now San Francisco Botanical Garden). A cutting from this came into the hands of the well-known plantsman Victor Reiter in 1933, and it was from this now large tree (15 m) that the introduced material was taken (Saratoga Horticutural Research Foundation 2003). ‘Marina’ is now considered to belong to A. ×reyorum Demoly, the hybrid between A. ×andrachnoides and A. canariensis. Arbutus ×thuretiana Demoly is A. canariensis × A. andrachne. ‘Marina’ has excellent reddish bark, broad leaves and large inflorescences of white and pink flowers, followed by red fruits. It is also lime tolerant, and could make a good, small street tree. If only one Arbutus were to be planted this should be it. A 5 m tree of A. canariensis grows at Lamorran, Cornwall (Johnson 2007), and young plants are in circulation elsewhere in England. It also grows in the San Francisco

Section II. Species Accounts

Arbutus

Botanical Garden and other Californian collections. It has large, rather soft shiny leaves with a glaucescent underside, where there are some hairs on the midrib (Krüssmann 1984, Hogan 2008). In western North America is the magnificent Madrone A. menziesii Pursh, with superb red bark and great presence. It is difficult to establish and also intolerant of lime. It is related to the two Mexican species described below. Recent collectors in Mexico have been puzzled by the diversity of Arbutus there, and it is possible that species other than A. arizonica and A. xalapensis will appear from their collections. Arbutus glandulosa Mart. & Gal. is especially common and is distinct from A. xalapensis in being glandularsetose in all parts, in flowering earlier and in having rough, flaking and persistent bark, unlike the red flaking bark of A. xalapensis; it is often the most abundant species in the mountain forests of western Mexico from Chihuahua southwards (McVaugh & Rosatti 1978). A shrubby species in this group, A. occidentalis McVaugh & Rosatti, is in cultivation in the western United States. Seeds germinate reasonably freely but seedlings transplant and establish rather poorly, especially in the case of the American species. It is generally suggested that seedlings should be planted out as young as possible. Successful micropropagation of A. xalapensis has been reported (Mackay 1996), but no mention was made of later establishment! It is curious that no discussion of the role of mycorrhizae in the growth of Arbutus is evident in the horticultural literature, as it would seem likely that, as with most Ericaceae, this is an important factor in the plant’s development. Planting sites should be sunny, well drained and of reasonable fertility. Summer irrigation is best avoided with the species from Mediterranean climates (Hogan 2008). The degree of tolerance to lime of the more southerly American species is not known. A. andrachne L. B311, K164

Arbutus arizonica (A. Gray) Sarg.

A. ×andrachnoides Link B311, K164

Arizona Madrone

Small to medium-sized tree, 6–15 m, dbh to 60 cm, with dense, compact crown. Bark pale grey, thick, furrowed and scaly, dark red and peeling on branches and twigs. Leaves lanceolate, 3.7–7.5 × 1.2–2.5 cm, apex obtuse to acute, margins entire or finely denticulate, coriaceous, pale green; petiole long. Inflorescence a loose panicle 5–8 cm long. Corolla urceolate, 6–8 mm, white to pink, ovary glabrous. Fruits rounded, 7–10 mm across, orange-red, ripening October or November. Flowering April to September (Mexico). Standley 1924, Powell 1998. Distribution MEXICO: Sonora, Chihuahua, Durango, Zacatecas; USA: southwestern Arizona, southeastern New Mexico. Habitat Dry gravelly terraces and mountain slopes between 1200 and 2400 m asl, oak and pine woodland. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hogan 2008. Cross-reference K164.

Arbutus arizonica is rare in cultivation, probably because of the difficulties associated with getting it established. It is thought to be hardy to at least –12 ºC, but high-altitude provenances should be sought, that may have greater frost tolerance (Hogan 2008). There are trees in the University of California Botanical Garden at Berkeley, grown from a collection made by Sean Hogan in Coquise Co., Arizona in 1991, but elsewhere any plants are still relatively small or hopeful seedlings. A. canariensis Lindl. K164 A. glandulosa M. Martens & Galeotti S87

A. menziesii Pursh B312, S87, K164 A. texana Buckley S87

155

Plate 121. Arbutus ‘Marina’ is a truly superb small evergreen tree. Image S. O’Brien.

156

Arbutus

New Trees

A. unedo L. B313, K164 A. unedo f. rubra (Aiton) Rehder B314

Arbutus xalapensis Kunth

Texas Madrone

Syn. A. texana Buckley Shrub or tree to 15 m. Bark thin, red-brown, peeling off in large papery sheets. Branches crooked, stout, spreading; new shoots hairy when young. Leaves alternate, oblong to ovate or oval, 3–10 × 4.5 cm, apex acute to obtuse, margins entire or serrate, coriaceous, usually tomentose below when young, glabrescent later. Inflorescence a panicle with tomentose branchlets. Corolla ovoid-urceolate, white, often pinktinged, 7 mm, calyx lobes broadly ovate or orbicular, obtuse, pinkish white, slow to fall, ovary pubescent. Fruit dark red, 8–10 mm across, edible. Flowering February to May (Mexico). Standley 1924, Powell 1998. Distribution GUATEMALA; HONDURAS; MEXICO: Chihuahua and Nuevo León to Veracruz, Oaxaca and Sinaloa; USA: southern New Mexico, western Texas. Habitat Wooded canyons and mountain slopes, between 1300 and 2100 m asl, oak forest/pine-oak forest; moister sites than A. arizonica (Martin et al. 1998). USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Hudson 2004, Sternberg 2004; NT33, NT156. Crossreference K164. Taxonomic note This is a very variable species, with numerous synonyms, including A. texana Buckley, sometimes A. xalapensis var. texana (Buckley) Gray. The name A. texana is maintained by McVaugh & Rosatti (1978), who note that a thorough revision of these important Mexican trees is required.

Plate 122. A scene wholly typical of the mountains of Mexico: Arbutus xalapensis growing with pines and oaks in Durango. Image N. Macer.

Even more than Arbutus arizonica, A. xalapensis is worthy of any attempt to get it established, as its bark is perhaps the most spectacular of all in the genus, and a highlight of its native habitats (Martin et al. 1998). The US champion is 9 m tall, 2.8 m dbh, with a 13 m crown-spread (Powell 1998). Again at Berkeley, there is a specimen of A. xalapensis from a collection made by D.E. Breedlove and D. Mahoney in Coahuila State in 1994, and there is another tree in the San Francisco Botanical Garden. A young plant at Tregrehan, grown from a 1994 collection by Maurice Foster in the Sierra Peña Nevada, Nuevo León, is fully established, flowering each year in early summer as well as having well-developed shaggy red bark. This is paler on the undersides of the branches.

ARIA

ROSACEAE

(Pers.) Host

See discussion with Sorbus (pp. 815–823).

BANKSIA Figure 17 (opposite). Banksia integrifolia subsp. monticola: (A) habit with inflorescence, flowers in bud; (B) inflorescence with open flowers; (C) spent inflorescence, dead flowers, immature follicles; (D) single leaf.

PROTEACEAE

L. f.

Banksias There are 76 species of Banksia and almost all of these are endemic to Australia, with over three-quarters occurring only in the southwestern corner of Western Australia. Banksias are trees or shrubs, some with prostrate and/or underground stems. The leaves are alternate or whorled and may be entire, dentate, serrate or with deep triangular

Section II. Species Accounts

Banksia

157

1 cm

A

1 cm

B

C

D

158

Banksia

New Trees

lobes. The inflorescences are erect or pendulous, cylindrical, ovoid or spherical and with a whorl of narrow, hairy, often caducous bracts around the base. The flowers are numerous and in pairs; the pairs are arranged in longitudinal rows along the length of the inflorescence. The flowers are 4-merous; the tepals are free or partially united, the stamens are adnate to the tepals and the style is wiry and elongated. Only a limited number of flowers per inflorescence will set seed. Those that do, develop into a woody follicle with one or two seeds, separated by a two-winged plate. The follicles remain attached to the tomentose inflorescence axis, and the whole structure is known as a ‘banksia cone’. In most Banksia species, fire stimulates the follicles to open, though in some the follicles open as soon as the seeds are mature. The seeds have a wedgeshaped papery wing (George 1999). The genus Banksia, with its extraordinary ‘cone’, is one of the most typically Australian plants: one imagines a kookaburra perched atop every bush. Long cosseted as greenhouse plants in the northern hemisphere, they are now emerging to be tested in the open air. Those described below are true trees, and particularly hardy. Others in cultivation in England (which effectively means Cornwall) at the present time are: B. canei J.H. Willis, B. ericifolia, B. grandis Willd., B. menziesii R. Br., B. praemorsa Andrews, B. robur Cav., B. serrata, B. speciosa and B. spinulosa, mostly rather shrubby in nature. Comments on these and their cultivation requirements in Cornwall are given by Moore (2004). Further species will be found in cultivation in California and other places with a Mediterranean climate. As with most members of the Proteaceae, Banksia has very specific requirements for successful cultivation. These are described in detail elsewhere (Elliot & Jones 1982, Moore 2004), but in summary, a free-draining, infertile acid soil (pH 3.5–6.5) in full sun is essential. A raised bed or the upper part of a bank from which frosty air drains off are indicated, especially where conditions are marginal. Lean soil will favour the production of hardened-off shoots that are better able to withstand winter than long growth produced by plants in richer conditions, but if protection is required then a wrapping of horticultural fleece will help, and a mulch of pine-needles or straw will insulate the surface roots. Most members of the Proteaceae have a mass of fine roots near the surface which efficiently catch any moisture and nutrients available in their generally spartan and arid natural habitats. The provision of extra nutrients should therefore be avoided, whether by the well-intended application of an organic mulch or as chemical fertiliser: high phosphate levels are particularly dangerous. Water need only be supplied if there is an extended drought period.

B. baueri R. Br. K188 B. baxteri R. Br. K188 B. coccinea R. Br. K188

Banksia integrifolia L. f.

B. collina R. Br. K188 B. ericifolia L. f. K188 B. goodii R. Br. K188

Coast Banksia, White Honeysuckle

Tree to 25 m. Bark rough and scaly. Branchlets pale brown and pubescent to almost glabrous. Leaves in whorls of three to five, narrowly obovate to elliptic, 4–20 × 1–2.6 cm, upper surface dull green and pubescent, lower surface white and woolly, margins entire, apex obtuse or emarginate; petiole 0.4–1 cm long. Inflorescences 5–12 cm long, subtended by tomentose bracts 0.2–1 cm long. Flowers pale yellow; tepals 2.2–2.5 cm long, pubescent outside; style 2.7–3.2 cm long, straight or curved; old flowers falling quickly to reveal the ‘cone’. Follicles up to 60, narrowly elliptic, 0.7–1.5 × 0.3–1 cm, smooth and tomentose; follicles

Section II. Species Accounts

Banksia

opening when mature, usually less than a year after flowering. Flowering January to July (Australia). George 1999. Distribution AUSTRALIA: from Proserpine, Queensland to Port Phillip Bay, Victoria. Habitat Coastal dunes and headland at sea-level to montane rain forest or cloud forest near the peaks of the Great Dividing Range. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Rosser 1993, George 1996. Cross-reference K188.

The Banksia integrifolia species complex has been examined a number of times by taxonomists (Thiele & Ladiges 1994, George 1999, Evans et al. 2002). As currently defined, it includes three subspecies. A key to these, modified from Thiele & Ladiges (1994) and George (1999), is presented below.

1a. Most adult leaves 17–26 mm wide .................................................................................................. 2 1b. Most adult leaves 10–18 mm wide; New South Wales (New England National Park to Mt. Wilson); montane forest over igneous rock .......................... subsp. monticola 2a. Most leaves 4–10 cm long, ± flat, dull green above; New South Wales, Queensland, Victoria; coastal or low elevations over sedimentary rock .............. subsp. integrifolia 2b. Most leaves 10–20 cm long, ± undulate, shining green above; Queensland (between Proserpine and Brisbane); coastal dunes or inland plains ........................ subsp. compar

Banksia integrifolia subsp. monticola

White Mountain Banksia

K.R. Thiele This subspecies differs from typical B. integrifolia in that the adult leaves are longer (10–13 cm long), more or less acute, and four to five times longer than wide. When the leaves are dried they have a dull bronze colour (pale greyish green in subsp. integrifolia). The follicles are less likely to open spontaneously in subsp. monticola. Thiele & Ladiges 1994, George 1999. Distribution AUSTRALIA: New South Wales, between New England National Park and Mt. Wilson in the Blue Mts. Habitat Montane forest over igneous rock. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration George 1996; NTviii, NT157.

Banksia integrifolia (s.l.) is said to be tolerant of frosts to –6 ºC (Moore 2004), although its subsp. monticola should be sought, as a high-altitude variant, for greatest levels of cold tolerance. Its stature is not affected by its habitat. Specimens at 1200–1400 m on the Dorrigo Plateau have been measured at 30 m tall with dbh of 119 cm, and elsewhere heights of up to 35 m have been recorded (Liber 2004). A collection (ETAZ 4) was made in 2000 by D. Hardman and A. Jackson from Barrington Tops, New South Wales. Specimens from this source are in cultivation at Wakehurst Place and Kew, and were distributed to other gardens in southern England. Some suffered frost damage in their early stages and are now growing as multistemmed shrubs; others that were undamaged are growing as single-stemmed specimens. Growth is rapid, most plants at Wakehurst Place averaging 3.5 m, and one exceptional specimen there is now 5 m tall, and has produced over 50 inflorescences since planting in 2002–2003 (D. Hardman, pers. comm. 2007). The plants at Kew are now 1.5–1.8 m, although some specimens in the open ground there are showing signs of chlorosis, with yellow leaves. The first inflorescences were produced outdoors in 2003 (Clennett 2004), and the plants are now flowering freely. The white underside to the leaves is striking, especially when they are ruffled by a breeze (D. Hardman, pers. comm. 2007). Specimens unidentified to subspecific level are grown elsewhere in the United Kingdom (and are commercially available), including an 8 m tree at Tresco Abbey, and one very slow-growing individual in Southend (Johnson 2007). Undifferentiated Banksia integrifolia is cultivated in Californian gardens, and subsp. monticola is offered

159

160

Banksia

New Trees

commercially there. According to Moore (2004), B. integrifolia is relatively tolerant of heavier soils, and tolerant of coastal exposure and drought when established. Subsp. compar (R. Br.) K.R. Thiele, from Queensland, is probably not very hardy in our area, but grows well in the Chelsea Physic Garden. B. marescens R. Br. K188

Banksia marginata Cav.

Silver Banksia

Shrub or tree 1–12 m, with or without a lignotuber, sometimes suckering. Bark smooth, grey, becoming scaly. Branchlets hirsute, tomentose. Leaves alternate, linear, oblong or narrowly cuneate, 1.5–6 × 0.3–1.3 cm, upper surface hirsute and tomentose, lower surface white tomentose, margins entire or occasionally serrate, slightly recurved to revolute, apex truncate or emarginate, rarely acute; petiole 0.2–0.5 cm long. Inflorescences 5–10 cm long, subtended by persistent, tomentose bracts ~1 cm long. Flowers pale yellow, often grey-tinged

Plate 123. Banksia marginata is one of the hardiest species in the genus, flowering well in mild British and Irish gardens. Image D. Luscombe.

in bud; tepals 1.6–2.4 cm long, pubescent outside; style 2–3.1 cm long, straight or curved downwards; old flowers persistent, sometimes falling. Follicles up to 150, narrowly elliptic, 0.7–1.7 × 0.2–0.4 cm, smooth, hirsute; follicles typically opening when mature, but some local variants require burning. Flowering February to May (Australia). George 1999. Distribution AUSTRALIA: New South Wales, South Australia, Tasmania, Victoria. Habitat Woodland, forest and shrubland; sometimes swamps, coastal dunes. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Rosser 1993, George 1996; NT160. Cross-reference K189. Taxonomic note Closely related to B. integrifolia, which has larger, whorled leaves and larger flowers.

Banksia marginata is considered to be among the hardiest of the genus, tolerating –10 ºC, as well as coastal conditions and dry soil when mature (Moore 2004). It has narrower leaves than B. integrifolia, but they are slightly glossier above. The inflorescence is also pale yellow, and produced in winter or early spring in the northern hemisphere. It is 9 m tall, 35 cm dbh, in the mild climate at Guincho in Ireland, and has reached significant size in the garden of Tim Pyner in Southend, Essex (Johnson 2007). Plants are also well established at Wakehurst Place, where they have flowered. This is certainly a species worth experimenting with away from the mildest places. B. media R. Br. K189 B. ornata F. Muell. K189 B. prionotes Lindl. K189 B. serrata L. f. K189 B. speciosa R. Br. K189 B. spinulosa Sm. K189

LAURACEAE

BEILSCHMIEDIA

Nees

The genus Beilschmiedia comprises about 250 species and occurs across the tropics with extensions south to central Chile and New Zealand. Beilschmiedia species are trees or shrubs with alternate, opposite or rarely clustered leaves. The leaves are entire, petiolate and pinninerved. Inflorescences are axillary and paniculate or racemose.

Section II. Species Accounts

Beilschmiedia

161

The flowers are small and rather inconspicuous; hermaphrodite and 3-merous with deciduous tepals. They have nine or six fertile stamens and a further whorl of short staminodes. The fruit is a drupe, attached to a woody pedicel (Rohwer 1993a, Nishida 1999, van der Werff 2003). This large genus of mostly tropical species is poorly known in cultivation. In addition to B. miersii, the Chilean B. berteroana (Gay) Kosterm. and the New Zealand B. tarairi (A. Cunn.) Kirk are cultivated at the University of California Botanical Garden at Berkeley, and B. erithrophloia Hayata from Taiwan and B. tawa Kirk from New Zealand are in the San Francisco Botanical Garden. The latter is certainly a candidate for mild areas. Beilschmiedia berteroana is now being offered in the European wholesale trade (Patagonia Plants 2006–2008). It is described by Gardner et al. (2006).

Beilschmiedia miersii (Gay) Kosterm.

Belloto del Norte

Tree to 25 m, 0.8 m dbh. Bark greyish, flaking in small pieces to reveal a reddish underlayer. Branchlets densely covered with erect curly or wavy hairs, though density decreasing with age. Leaf buds densely pubescent with erect curly hairs. Leaves evergreen, camphor-scented when crushed, opposite, (2.5–)5–12 × 1.5–6.5 cm, leathery, ovate, upper surface shiny, glabrous and pale green with a sunken midrib, lower surface glaucous and glabrous, (5–)7–8(–10) secondary veins on each side of the midrib, margins entire, apex obtuse to rounded; petiole 0.3–1 cm long, pubescent with erect curly or wavy hairs. Inflorescences axillary, densely pubescent with erect curly hairs, paniculate with few branches, 2–6(–9) cm long; 10–35 flowers per inflorescence. Flowers 3-merous and 0.25–0.3 cm long; tepals densely pubescent with curly hairs outside and long, straight hairs inside, stamens nine. Fruit an ellipsoid drupe, 4 × 2–3 cm, mottled yellow then brown. Flowering January to June and October to November, fruiting March to April (Chile). Rodríguez R. et al. 1983, Nishida 1999. Distribution CHILE: Cachapoal and Quillota Provinces. Habitat In open, humid forest or semi-arid vegetation between 120 and 1200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated (IUCN). Vulnerable (Gardner et al. 2006). The only protected population is in the La Campana National Park and these trees are currently threatened by introduced livestock, which eat the fruits and seedlings (Henríquez & Simonetti 2001). Illustration Rodríguez R. et al. 1983, Gardner et al. 2006; NT19, NT161.

Beilschmiedia miersii is a statuesque large tree, threatened in Chile by deforestation, habitat desiccation and grazing. The majority of surviving trees grow in ravine bottoms where there is plenty of moisture and these factors are least problematic. Seed has been collected on several occasions by botanists from Edinburgh, working in collaboration with their Chilean colleagues to develop conservation protocols and experiment with artificial propagation and replanting (Gardner et al. 2006). Some seedlings have been planted at Edinburgh and Logan, but at Edinburgh they are slow-growing, plants from the 1996 collection (ICE 7) being only 110 cm tall in 2005. At Tregrehan, however, it is doing well, the largest specimen (grown from Gardner & Knees 5698, collected in 1993) being now over 3 m, with a straight stem. At this stage the bark is still green. Abundant moisture is needed for success, and plants will die from extended periods of drought (M. Gardner, pers. comm. 2006).

Plate 124. The fruit and tiny flowers of Beilschmiedia miersii. Image M. Gardner.

162

Betula

New Trees

1 cm

Section II. Species Accounts

Betula

163

BETULACEAE

BETULA

L.

Birches One hundred and two species of Betula are recognised in the World Checklist of Fagales (Govaerts & Frodin 1998), distributed across the northern hemisphere. The number of species is, however, widely disputed: species delimitation is problematic and hybridisation is rampant. Birches are deciduous trees or shrubs, often multistemmed. They are primarily pioneer species, rapidly colonising disturbed areas, though as a consequence they are shade-intolerant and often short-lived. The bark is a major decorative feature and ranges in colour from dark brown to powdery white, with prominent, dark lenticels. It is often smooth and papery and may exfoliate in strips. For further description of birch bark, see Ashburner (1993). Branchlets are initially differentiated into long and short shoots; the long shoots are thin, flexible, often pendulous. Winter buds are sessile and acute with smooth, overlapping scales. Unlike Alnus species, most of which have two bud scales (though some have none), Betula have three to seven. The most typical leaves are usually those of the short shoots or the two at the base of long shoots which were pre-formed in the bud. Leaves on the long shoots can be variable in size and shape, especially towards the ends of the shoots, and are usually arranged in two ranks. They are ovate to elliptic or deltate, rather thin, with serrate or doubly serrate margins. The leaves are glabrous or pubescent and may have resin glands on the lower surface. Betula species are monoecious. The staminate inflorescences are catkin-like, terminal and solitary or in small groups. They form during the summer and are exposed in autumn and winter, finally expanding with the leaves in spring. The pistillate inflorescences are typically solitary and erect, catkin-like, and develop close to the staminate inflorescences. The individual flowers are tiny and subtended by a bract. The bracts are usually shed with the seeds (except in the group of species related to B. medwediewii and in B. globispica, B. delavayi and B. fargesii), rather than forming a woody cone (cf. Alnus). The fruit is a samara, usually with two lateral wings (absent in species related to B. schmidtii, B. delavayi and B. chinensis) (Rushforth 1975, Ashburner 1980, de Jong 1992a, Furlow 1997, Li & Skvortsov 1999). Guidance on the treatment of Betula for this account has been kindly provided by Hugh McAllister and Kenneth Ashburner. The current major reference to the genus is an IDS publication – Betula: Proceedings of the IDS Betula Symposium, 2–4 October 1992 (Hunt 1993a) – and this should be consulted by all with an interest in the genus. In preparation, however, is a monograph by Ashburner and McAllister that should become the standard work on birches. It will build on the work of Skvortsov (Skvortsov 2002), with whose generic classification the authors broadly agree – differing, however, in a few areas. Until this book is published a guide to names and their synonymy is provided by the World Checklist and Bibliography of Fagales (Govaerts & Frodin 1998), and this has been used in preparing the cross-references given below.

Figure 18 (opposite). Betula insignis: habit with immature catkins.

Plate 125. A group of Betula cordifolia at Stone Lane Gardens, Devon, showing the slightly reddish bark that helps differentiate it from its whitish-barked relative B. papyrifera. Image P. Williams.

164

Betula

Plate 126. Betula insignis is a notable addition to cultivated birches, generally performing well and capable of producing excellent autumn colours. This is one of the same trees as in Plate 129. Image J. Grimshaw.

New Trees

One area of difficulty lies with the birches of the former Soviet Union, where several named taxa are probably no more than local variants of species that are widespread and well known by other names. Among those found in collections are B. litwinowii Doluch., B. procurva Litv. and B. saposhnikovii Sukaczev, referred to B. pubescens by McAllister and Ashburner; also B. turkestanica Litv., which may be a form of B. raddeana (H. McAllister, pers. comm. 2007). A further development that can be foreshadowed here is the sinking into B. pendula of the B. platyphylla complex from eastern Asia. The close relationship between these taxa has long been recognised (see Bean 1976a), but the taxonomic position of the different members of the B. platyphylla complex has been the subject of much debate. They have been regarded as separate species (including B. japonica Siebold, B. mandshurica (Regel) Nakai and B. szechuanica (C.K. Schneid.) C.-A. Jansson) and, alternatively, as subspecies of B. platyphylla. In the other direction, Flora of China places them all in synonymy with B. platyphylla (Li & Skvortsov 1999). In their forthcoming monograph, McAllister and Ashburner treat the B. platyphylla complex as part of the variation within B. pendula, notwithstanding that its members do not have the familiar pendulous branches found in most European B. pendula, and most populations lack the typical double-toothing of the leaves. Birches, especially those with white bark, are one of the most popular groups of trees, valued for their elegance of habit, the colours of their bark and leaves, their usually rapid growth and comparatively small size. In consequence they are widely planted, both appropriately where a smaller tree is genuinely required, and inappropriately where a larger, more permanent tree would be more suitable. The word ‘smaller’ is used cautiously here, as although Betula species never achieve the solidity of, say, a Fagus or a Tilia, most of the species and cultivars recommended for ‘small gardens’ can become surprisingly tall and broad over time, and it is sad to see an elegant birch lopped about because it has exceeded its allotted space in a suburban plot. In such cases, and in many landscaping situations, it would be best to think of and treat Betula as the pioneer trees they are – rapidly growing but shortlived and dispensable. In much of eastern North America this approach is in fact imposed upon many birches by the Bronze Birch Borer Agrilus anxius, whose larvae feed on the phloem of the stem, just under the bark, girdling the tree and eventually killing it. Damage starts at the top of the tree and proceeds downwards. The insect has a wide range, mostly east of the Rocky Mountains, and here almost all white-barked, non-American birches will be affected. Despite this they remain very popular, and as they can become quite effective in the four or five years before the borer gets them, they are still planted in large numbers. For the North American dendrologist they perhaps offer a convenient way of growing self-limiting nurse trees around permanent plantings. A comprehensive discussion of borer resistance in familiar species and cultivars is given by Dirr (1998), and much information on this topic is available through the internet. Borers or no borers, the popularity of birches has led to the development of an ever-expanding range of selected clones of the more familiar species and hybrids between them, selected for bark or foliage characters. White stems remain the most popular (as in numerous selections of B. pendula and B. utilis var. jacquemontii), but there are also selections for those of us who prefer darker barks (for example, B. utilis ‘Wakehurst Place Chocolate’), or pinkish and buff tones (B. ‘Hergest’, B. utilis ‘Fascination’). Coloured foliage is an attractant for some, as seen in significant new

Section II. Species Accounts

Betula

introductions such as B. pendula ‘Golden Beauty’ (supposedly scorch-resistant), and several purple clones, including the glossy-leaved ‘Royal Frost’ (Dirr 1998, Dunn 2001, Hillier & Coombes 2002, van den Berk 2002). Although it seems disloyal to the ‘new’ species described below, it is undoubtedly such selections that will be most widely planted, and perhaps deservedly so. The apparently miraculously borerresistant birch ‘Whitespire Senior’, originating at the University of Wisconsin during the 1950s and long attributed to B. platyphylla (Dirr 1998), has now been found to be a native B. populifolia (Sternberg 2004), a species that is considered moderately resistant (Dirr 1998). It has been much propagated from seed, which explains variability in resistance among so-called Whitespire Birch. ‘Whitespire Senior’ is vegetatively propagated from the resistant parent and is a good choice for a white-stemmed birch in eastern North America. Birches are in general very tolerant of soil conditions, growing on most substrates where there is adequate moisture. In North America they can be afflicted by a range of pests and diseases (see Dirr 1998), but in Europe they seem to be mostly rather trouble-free. It is very important to remember that birches are extremely promiscuous, and arboretum-grown seed is likely to produce an assortment of mongrels. Some of these may be lovely trees but they probably should not be attributed to a species. Neither should it always be assumed that wild-origin seed represents a pure species, as there are extensive hybrid zones. Good clones of most species can be propagated by cuttings with surprising ease, or they can be grafted in the more traditional manner. Being so popular and easy both to grow and to collect seeds from, Betula has attracted a lot of attention from plant explorers in recent years, resulting not only in new species being introduced, but in re-introductions of some well-known taxa. Many of these have offered characters new to the extant horticultural population and are valuable additions. Shrubby species, such as B. apoiensis and B. calcicola (see pp. 168, 169), are not described here.

B. aetnensis Raf. S119 B. albosinensis Burkill B415, S111, K221 B. albosinensis var. septentrionalis (NOW B. utilis D. Don var. utilis) B415, K221 B. alleghaniensis Britton S111, K221

B. alleghaniensis var. fallax Fassel. K222 B. alleghaniensis var. macrolepis Fernald K222 B. alnoides Buch.-Ham. ex D. Don B422, K222 B. apoiensis Nakai S113

Betula ×aurata Borkh. Syn. B. ×hybrida Blom, B. ×obscura Kotula This taxon is the hybrid progeny of two European native birches, B. pendula Roth. and B. pubescens Ehrh. However, it often occurs in the absence of one or both parent species, a testament to the capacity for dispersal of birch seeds and pollen. Betula ×aurata is intermediate between the parent species in its morphology, but identifying the hybrid can be challenging. It can be sterile or fully fertile, and can therefore form hybrid swarms through backcrossing with the parent species – especially the tetraploid B. pubescens (the diploid B. pendula can often be identified as remaining ‘pure’ in hybrid swarms) – producing a confusing range of morphologies. Because of these difficulties with identification, the distribution of the hybrid is uncertain. Stace 1997. Distribution UNITED KINGDOM. Habitat Disturbed areas and secondary vegetation. USDA Hardiness Zone 3. Conservation status Not evaluated. Cross-reference K222.

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This hybrid is occasionally found in collections – as, for example, one old specimen at Edinburgh – and more frequently where the parents meet in the wild. It is generally of scientific interest only.

Betula bomiensis P.C. Li See discussion with Betula delavayi (p. 168). B. borealis Spach K222 B. borggreveana Zabel K223 B. ×caerulea Blanch. S111, K223 B. callosa Notoe K223 B. celtiberica Rothmaler & Vasconcellos S120

Betula chichibuensis Hara

Chichibu Birch

Tree to 4 m, perhaps occasionally more. Bark initially brown, flaky but later developing conspicuous raised horizontal lenticels as in B. chinensis. Branchlets densely pubescent when young, a few glands present. Leaves deciduous, 3–6 × 1.5–3.2 cm, papery, ovate to oblong, upper surface green and glabrous, lower surface with dense, white hairs on the veins, 14–18 lateral veins on each side of the midvein, margins with minute serrations, apex short-acuminate; petiole 0.4–0.7 cm long, covered in dense, white hairs. Monoecious; staminate inflorescences catkin-like, densely clustered towards the ends of twigs, to 4 cm long, creamy yellow in colour; pistillate inflorescences catkin-like, solitary, erect, short-pedunculate, cylindrical, initially red, 1.5–2.5 × 0.7–1 cm. Flowers inconspicuous; bracts pubescent, deeply three-lobed. Fruiting catkins erect, persistent over the winter. Fruit a tiny nutlet with a narrow rim. Flowering May to June (Japan). Ohwi 1965. Distribution JAPAN: Honshu. Habitat Restricted to Mt. Chichibu between 600 and 1000 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated (IUCN); but this is one of the rarest of birches, reduced to 21 trees in the wild (McAllister 1993). Illustration NT166.

Plate 127. The strongly veined leaves of Betula chichibuensis give this small tree a quiet charm. Image P. Banaszczak.

The chief claim to fame for Betula chichibuensis is its rarity in the wild, as it is otherwise no more than a rather shrubby small tree, with a dense spreading crown of soft-green leaves, but of little horticultural merit. Seed was received during the 1980s at Ness Botanic Gardens from Prof. Ohba of Tokyo University Botanic Garden. The resultant seedlings were propagated and sets of eight clones were distributed to other gardens by Hugh McAllister (McAllister 1993). The clones vary somewhat in habit, some being low and shrubby, others growing as small single-stemmed trees. None has been seen over 3 m in height, and they often do not present an image of robust health, although they do well at Ness and at Stone Lane Gardens. The growth is twiggy, but the leaves are deeply veined and strongly hairy, and are subtly attractive. B. chinensis Maxim. B416, S112, K223 B. coerulea-grandis (NOW B. ×caerulea Blanch.) B416, S112, K223 B. ×coerulea (NOW B. ×caerulea Blanch.) B417, S111, K223 B. concinna Gunnarsson K223

Section II. Species Accounts

Betula cordifolia Regel Syn. B. papyrifera var. cordifolia (Regel) Fernald Betula cordifolia is difficult to differentiate from the more familiar B. papyrifera, and is often treated as an ecological variant of it. However, B. cordifolia is diploid (2n = 28) while B. papyrifera is hexaploid (2n = 84), indicating that they do not normally interbreed, and behave genetically and ecologically as quite distinct species (H. McAllister, pers. comm. 2007). Despite this, they are visually extremely similar and it is easiest to describe B. cordifolia in terms of its differences from B. papyrifera. Betula cordifolia has pinkish or brownish white to russet or bronze bark, rather than chalk-white or (rarely) dark brown as in B. papyrifera. Leaves of B. cordifolia have a cordate base and 9–12 pairs of lateral veins, while those of B. papyrifera have a cuneate, rounded or truncate base and nine or fewer pairs of lateral veins. The most reliable distinguishing characteristic is that the central lobe of the fruiting catkin scale is parallel-sided in B. cordifolia but rhombic-diamond shaped in B. papyrifera. Brittain & Grant 1965, Furlow 1997. Distribution CANADA: New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Is., Quebec; ST. PIERRE & MIQUELON; USA: Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New York, North Carolina, Pennsylvania, Vermont, Virginia, West Virginia, Wisconsin. Habitat Open forest or moist rocky slopes between 800 and 2000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT163. Cross-references B426, S117, K229.

Not acknowledged as a distinct entity by American dendrological authors, Betula cordifolia is a cryptospecies, obscured by a more familiar relative. Its generally darker bark is clearly visible in the stands of trees of Canadian origin growing at Stone Lane Gardens, where the colour varies from light reddish cream to dark red-brown. It is slower-growing in cultivation than B. papyrifera, and its young seedlings are less densely hairy than those of that species (H. McAllister, pers. comm. 2007), but there is little else to distinguish the two. Given its more northerly distribution it is probably hardier and more tolerant of a short growing season. In addition to Kenneth Ashburner’s collections, growing well in Devon and at Ness Botanic Gardens and elsewhere, it has been introduced to the United Kingdom on several occasions: for example, by Tony Schilling from a collection made on Mount Washington, New Hampshire in 1979 (Schilling 2379), where it formed a tree 10 m tall. It is also cultivated at Edinburgh from a collection made by T.E. Clarke. B. coriacea Gunnarsson K223 B. corylifolia Regel & Maxim. B417, K223 B. costata Trautv. B418, K223

Betula cylindrostachya Lindl. ex Wall. Tree to 30 m. Bark brown or greyish black. Branchlets yellowish brown with dense, yellow pubescence. Leaves deciduous, 5–14 × 2–8 cm, ovate to elliptic, oblong or ovate-lanceolate, both surfaces densely pubescent when young, lower surface with multiple resin glands, tufts of hair in the vein axils, 13–14 lateral veins on each side of the midvein, margins with irregular double serrations, apex acuminate; petiole 0.8–1.5 cm long with dense yellow pubescence. Monoecious; staminate inflorescences catkin-like, solitary and to 14 cm long; pistillate inflorescences catkin-like, in pairs, pedunculate, long, narrow and cylindrical, 2.5–10 × 0.5–0.7 cm. Flowers inconspicuous; bracts pubescent to spongy at the base, three-lobed. Fruit a tiny, pubescent samara with membranous wings. Flowering April to June, fruiting July to August (China). Li & Skvortsov 1999. Distribution BHUTAN; CHINA: Sichuan, Xizang, Yunnan; INDIA: Assam; MYANMAR; NEPAL. Habitat Subtropical to warm-temperate broadleaved forest between 1400 and 2800 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Cross-references B422, K224. Taxonomic note The tetraploid B. cylindrostachya is a member of subgenus Acuminatae and closely related to the diploid B. alnoides and B. luminifera, with which it has been confused. It can be distinguished from B. alnoides by its spring rather than autumn–winter flowering period, its wider fruiting catkins and more cordate leaf bases. Some material in cultivation introduced as B. alnoides is probably B. cylindrostachya (Ashburner & McAllister, in prep.). Betula luminifera is morphologically very similar, but has (usually) solitary female catkins (groups of two to six catkins in the other two).

Betula

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New Trees

Betula cylindrostachya is rare in cultivation, perhaps because it comes from lower altitudes in a more southerly range and is less hardy than most birches. It is potentially a large tree but is tender when young, and particularly vulnerable as this group of birches (subgenus Acuminatae) lacks dormant buds to come to the rescue if new growth is damaged by frost. Despite this it does well in mild and coastal areas, with collections made in Bhutan (by Keith Rushforth) and northwestern India (by Kenneth Ashburner) thriving at Ness Botanic Gardens (Ashburner & McAllister, in prep.). At Tregrehan there are two trees originating from a collection by Peter Cox and Steve Hootman (CH 9042). These are growing fast and in 2007 were about 10 m tall, with attractive dark brown, shiny trunks, and long showy catkins in early spring (T. Hudson, pers. comm. 2007). B. davurica (NOW B. dahurica Pall.) B417, S112, K224

Betula delavayi Franch.

Plate 128. The erect female catkins of Betula delavayi, growing at Ness Botanic Gardens. Image P. Williams.

Shrub or tree to 8 m. Bark dark grey. Branchlets brown with dense, yellow pubescence. Leaves deciduous, 2–7 × 1–4 cm, ovate to elliptic or oblong, upper surface with dense, silky yellow pubescence when young, lower surface with sparse resin glands and white silky pubescence on the veins, (5–)9–15 lateral veins on each side of the midvein, margins with minute, double serrations, apex acuminate or rounded; petiole 0.5–1 cm long with sparse pubescence. Monoecious; staminate inflorescences catkin-like, solitary or in groups of two to four, 4–6 cm long; pistillate inflorescences catkin-like, solitary, pedunculate, oblong to cylindrical, 1–2.5 × 0.5–1 cm. Flowers inconspicuous; bracts pubescent, three-lobed. Fruiting catkins erect, persistent over winter. Fruit a tiny (to 3 mm), pubescent nutlet with a narrow rim. Flowering June, fruiting July to August (China). Hexaploid, 2n = 84. Skvortsov 1998, Li & Skvortsov 1999. Distribution CHINA. Frequent in the Lijiang area of northwest Yunnan but certainly also identified in southwest Sichuan and a few other neighbouring areas. Other areas quoted in the literature probably often refer to occurrence of B. bomiensis, and perhaps another enigmatic tree species with more numerous veins to its leaves, represented by B. delavayi var. polyneura L.C. Hu, B. jiulungensis L.C. Hu, and possibly also B. gynoterminalis Y.C. Hsu & C.J. Wang. This mysterious taxon is not in cultivation as far as is known (H. McAllister, pers. comm. 2007). Habitat Deciduous forest and thickets between 2400 and 4000 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated (IUCN), but possibly of limited distribution. Illustration Li & Skvortsov 1999; NT168. Cross-reference K224. Taxonomic note This group, including the taxa B. delavayi (small tree), B. bomiensis (smaller tree), B. calcicola (W.W. Sm.) P.C. Li and B. potaninii Batalin (shrubs) is very confused (H. McAllister, pers. comm. 2007), and we therefore discuss them together, here below. They are separable not only on visible morphological characters but also by their ploidy and geographical distribution. In Flora of China (Li & Skvortsov 1999), B. bomiensis is referred to as a synonym of B. delavayi var. microstachya. We give its description below (despite the alphabetic derangement caused), for ease of comparison.

Betula bomiensis P.C. Li Syn. B. delavayi var. microstachya P.C. Li Betula bomiensis has shorter, much more deeply ribbed leaves than either var. delavayi or var. polyneura L.C. Hu (1.5–2 cm, vs. 3–7 cm in B. delavayi ), with 5–15 lateral veins (10–15 in B. delavayi ), and smaller pistillate catkins (1 × 0.5 cm, vs. 1.5–2.5 × 0.7–1 cm). Tetraploid, 2n = 56. Li & Skvortsov 1999. Distribution CHINA: Gansu, western Hubei, Qinghai, western Sichuan, northeast Xizang. Habitat Woodland to dry scrub with Caragana, Rosa, Artemisia. USDA Hardiness Zone 7. Conservation status Not evaluated.

Betula delavayi appears to have been first introduced by Roy Lancaster (Lancaster 1736) from Yunnan in 1986, but it achieved a much wider distribution from Chris Brickell and Alan Leslie’s collection (no. 12260) made in the Gang Ho Ba in Yunnan in October 1987. Further introductions have since been made from Edinburgh- and Kew-based expeditions, and the species is now well established in cultivation in our area. The distinction between B. delavayi and B. bomiensis has not been well understood, and plants with the same collection number may be found in different

Section II. Species Accounts

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169

arboreta with either name. SICH 1063, made in 1992 at c. 3130 m in Muli County, is B. bomiensis. At Quarryhill (correctly labelled) it is a multistemmed tree, of about 3 m in 2004. Both species are frequently multistemmed and not very tall, with a slightly sombre appearance from their grey bark and dull grey-green leaves. Betula calcicola (W.W. Sm.) P.C. Li is indubitably a shrub, though often of erect habit (to 4 m in cultivation at Ness), occurring like B. delavayi only in the Lijiang area of Yunnan. It is a diploid, 2n = 28, as also is B. potaninii Batalin, a spreading shrub (to 4 m in cultivation at Ness) with up to 21 vein-pairs in its leaves, known for certain only from around Kangding, Sichuan. B. ×eastwoodiae Sarg. K224 B. ermanii Cham. B417, S112, K224 B. ermanii var. japonica (Shirai) Koidz. B418, K225 B. ermanii var. lanata Regel S112 B. ermanii var. subcordata (NOW B. ermanii Cham. var. ermanii) B418, K225 B. exilis Sukachev S116 B. ×fennica Doerfl. K225 B. forrestii Hand.-Mazz. B418, S112, K225 B. fruticosa Pall. K225 B. glandulifera (NOW B. pumila L.) B419, K225 B. glandulosa Michx. B419, S113, K225 B. globispica Shirai B419, K226 B. grossa Siebold & Zucc. B419, K226 B. hallii Howell S113, K226 B. ×hornei Butler K226 B. humilis Schrank B420, S113, K226

Betula insignis Franch. Syn. B. austrosinensis Chun ex P.C. Li Tree to 25 m. Bark greyish black, brown or greyish brown, rough and fissured, fragrant (oil of wintergreen) when rubbed. Branchlets brown, sometimes with dense yellow pubescence when young, or glabrescent, later glabrous, fragrant. Leaves deciduous, aromatic of wintergreen when crushed, (5–)8–13 × (2–)3–6 cm, elliptic or ovate to lanceolate, upper surface with sparse pubescence, lower surface with numerous resin glands, pubescence on the veins and tufts of hair in the vein axils, 12–15 lateral veins on each side of the midvein, margins with sharp double serrations, apex acuminate to caudate; petiole 0.8–2 cm long with a few longitudinal hairs. Monoecious; staminate inflorescences catkin-like, to 25 cm, pale green; pistillate inflorescences catkinlike, erect, short-pedunculate, oblong, 2.5–4 × 1.5– 2 cm. Flowers inconspicuous; bracts conspicuous, pubescent and three-lobed. Fruit a tiny samara with opaque membranous wings. Flowering May to June, fruiting July to August (China). Li & Skvortsov 1999, McAllister 2005b. Distribution CHINA: Guizhou, western Hubei, Sichuan. Habitat Broadleaved forests between 1400 and 3400 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Li & Skvortsov

Plate 129. The spring display of Betula insignis is provided by its exceptionally long male catkins – seen here on trees growing by the lake at Kew. Image T. Kirkham.

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1999, McAllister 2005b; NT41, NT162, NT164, NT169. Cross-references S113, K226. Taxonomic note Betula austrosinensis is maintained as a separate species by Flora of China, but other authorities include it in B. insignis (Govaerts & Frodin 1998, McAllister 2005b).

Despite having been collected by Wilson in 1900 (Sargent 1916), Betula insignis did not become established in Europe, and was assumed to be somewhat tender. In recent years however this has been demonstrated not to be the case, and the species is now frequent in collections throughout the United Kingdom, forming beautiful trees of 12 m or more (McAllister 2005b). The principal source was the 1985 Fanjin Shan Guizhou Expedition of Simmons, Fliegner and Russell, who collected it at 1200 m (as GUIZ 82). The seeds came from a fallen branch of an invisible tree, proclaimed to be an Alnus by the accompanying Chinese botanist Prof. Huang. It is not known if B. insignis is cultivated in America. Material from northern Vietnam is also grown under the name B. jinpingensis, but this name is a synonym of B. utilis (Li & Skvortsov 1999); the Vietnamese trees may represent a local variant of B. insignis (H. McAllister, pers. comm. 2007). As seen at Tregrehan, where specimens have reached 5 m, the bark is very dark brown, with an attractive pattern of paler lenticels in horizontal rows, and the leaves are also exceptionally dark green, flushing bronze in spring. Betula insignis is a very handsome tree, with curiously metallic-looking bark, and big leaves that can turn an excellent yellow and russet in autumn. The male catkins are particularly striking, being up to 25 cm long, but the big fruiting catkins are also conspicuous and decorative. Interestingly, it is said to grow best in heavy wet clay (McAllister 2005b), which makes it particularly useful. B. ×intermedia (NOW B. ×alpestris Fr.) B424, K226 B. jacquemontii (NOW B. utilis var. jacquemontii (Spach) H. Winkl.) B434, S123, K226 B. ×koehnei C.K. Schneid. B428, K226

Betula lenta L.

Round-leaf Birch

This species was described by Bean (B420, S114) and Krüssmann (K227).

Betula lenta f. uber (Ashe) McAllister & Ashburner Syn. B. uber (Ashe) Fernald Forma uber is a small slender tree to 10 m (20 m in f. lenta). The leaves are 2–5 × 2–4 cm, suborbicular to elliptic, with two to six lateral veins on each side of the midvein; the margins are irregularly serrate or dentate and the apex is rounded or obtuse. In comparison, the leaves of f. lenta are 5–10 × 3–6 cm, ovate to oblong, with 12–18 lateral veins on each side of the midvein; the margins have minute, sharp serrations and the apex is acuminate. Furlow 1997. Distribution USA: Virginia (Cressy Creek). Habitat Streambanks and floodplains in broadleaved forest, about 500 m asl. USDA Hardiness Zone 3. Conservation status As B. uber, Critically Endangered (but see below). This taxon was thought extinct until its rediscovery in 1974. The native population has been reduced from 41 to 11 mature trees, though 20 new subpopulations have been established in the vicinity. Illustration Sternberg 2004, McAllister & Ashburner 2004; NT171. Cross-reference S114 (as B. uber).

Although it was briefly described by Clarke (1988), we give here an expanded account of this intriguing and beautiful small tree. A thorough review of its status has been made by McAllister & Ashburner (2004) who convincingly demonstrate that, far from being a distinct species (Betula uber), it should be regarded as a genetic variant occurring occasionally in B. lenta. Among seedlings from wild-collected ‘B. uber’ seed, only one per cent replicated their parental characteristics; the rest were f. lenta

Section II. Species Accounts

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(McAllister & Ashburner 2004). As B. uber it was the first tree to be listed as a ‘US Federally Endangered Species’, meaning that it cannot be collected or sold without a permit. This has not greatly restricted its occurrence in collections: in America it is represented in many arboreta as part of the conservation effort. There is one particularly nice specimen at Starhill Forest Arboretum; two tall (c. 12 m) trees at the Morton Arboretum, however, are ageing and looking rather sparse. Its rarity has perhaps inhibited a more objective view of its true relationship with B. lenta, of which it can be said to be merely a form with small, rounded leaves (McAllister & Ashburner 2004). Its conservation status should be reviewed. Under any name, however, it is readily recognisable and is a tidy, compact tree with high horticultural merit – genuinely suitable for a small garden. The leaves turn the same bright yellow as B. lenta. There are good specimens in several collections in Europe, including 6 m trees at Thenford House and Herkenrode. B. litwinowii Doluhanov S120 B. luminifera H. Winkl. B421, K227 B. lutea (NOW B. alleghaniensis Britton) B422, S114 B. mandshurica (Regel) Nakai S114 B. mandshurica var. japonica (Miq.) Rehder S115 B. mandshurica var. kamtschatica (Regel) Rehder S115 B. maximowicziana Regel B422, S115 B. medwediewii Regel B423, S115, K227 B. megrelica (NOW B. medwediewii Regel) B423, S116 B. michauxii Spach S116, K227 B. microphylla Bunge K227 B. middendorffii (NOW B. divaricata Ledeb.) K228 B. minor (Tuerck.) Fernald K228 B. nana L. B424, S116, K228 B. neoalaskana Sarg. S116 B. nigra L. B424, K228 B. ×obscura (NOW B. ×aurata Borkh., NT165) B428, K228 B. occidentalis Hook. B425, S117, K228 B. occidentalis var. fecunda Fernald K229 B. occidentalis var. inopina (Jeps.) C.L. Hitchc. S117 B. ovalifolia Rupr. S113 B. papyrifera Marshall B425, S117, K229 B. papyrifera var. commutata (NOW B. papyrifera Marshall var. papyrifera) B426, S117, K229 B. papyrifera var. cordifolia (NOW B. cordifolia Regel, NT167) B426, S117, K229 B. papyrifera var. humilis (NOW B. neoalaskana Sarg.) B426, S118, K229 B. papyrifera var. kenaica (NOW B. kenaica W.H. Evans) B426, S118, K229 B. papyrifera var. subcordata (NOW B. papyrifera Marshall var. papyrifera) B426, S118, K229 B. pendula Roth B427, S118 B. pendula f. crispa (NOW B. pendula Roth var. pendula) B427, S118 B. pendula var. lapponica (NOW B. pendula Roth var. pendula) S119 B. pendula f. oycowiensis (NOW B. pendula var. oycowiensis (Besser) Dippel) B428 B. platyphylla Sukaczev B429, S120, K229

Plate 130. Betula lenta f. uber is capable of producing the superb yellow autumn coloration expected from the species, but has much smaller leaves. Image J.R.P. van Hoey Smith.

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New Trees

B. platyphylla var. japonica (NOW B. mandshurica (Regel) Nakai var. japonica (Miq.) Rehder) B429, K229 B. platyphylla var. rockii (NOW B. rockii (Rehder) C.-A. Jansson) K229 B. platyphylla var. szechuanica (NOW B. szechuanica (C.K. Schneid.) C.-A. Jansson) B429, K229 B. populifolia Marshall B429, K229 B. potaninii Batalin B430, K231 B. pubescens Ehrh. B430, S120, K231

B. pubescens subsp. carpatica (NOW B. pubescens var. glabrata Wahlenb.) B431 B. pubescens var. glabra Andrejeff K231 B. pubescens subsp. tortuosa (Ledeb.) Nyman S120 B. pumila L. B432, K231 B. ×purpusii C.K. Schneid. K231 B. raddeana Trautv. B432, K231 B. rockii (Rehder) C.-A. Jansson S122 B. ×sandbergii Britton K232 B. schmidtii Regel B432, S121, K232 B. szechuanica (C.K. Schneid.) C.-A. Jansson S121

Betula tianschanica Rupr. Tree to 12 m. Bark yellowish brown or pinkish white, flaking. Branchlets greyish brown or dark brown, densely pubescent and with a small number of resin glands. Leaves deciduous, 2–7 × 1–6 cm, ovate to rhombic, both surfaces with sparse pubescence and resin glands when young, four to seven lateral veins on each side of the midvein, margins with coarse double serrations, teeth mucronate, apex acute or acuminate; petiole glabrous, 0.5–0.7 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkinlike, pendulous or erect, pedunculate, oblong to cylindrical, 1–4 × 0.5–1 cm. Flowers inconspicuous; bracts pubescent, three-lobed. Fruit a tiny samara with membranous wings. Flowering June to July, fruiting July to August (China). Kuzeneva 1970, Li & Skvortsov 1999. Distribution CHINA: Xinjiang; KAZAKHSTAN; KYRGYZSTAN; TAJIKISTAN. Habitat Temperate deciduous forests, streambanks, shady valleys or rocky slopes, between 1300 and 2500 m asl. USDA Hardiness Zone 6. Conservation status Endangered, due to limited distribution and rapid decline. Illustration Li & Skvortsov 1999. Cross-reference S122.

Unlike several other taxa from the same region, this central Asian birch does seem to be distinct, although it rather resembles Betula pendula. It has been collected on several occasions (for example, by John Whitehead in 1979: Clarke 1988), but in general it does not seem to flourish in the United Kingdom (H. McAllister, pers. comm. 2007). It is grown at Wakehurst Place from seed collected by Christopher Grey-Wilson in the Tien Shan near Almaty, Kazakhstan in 1991. It grows there in small stands, the trees not getting taller than about 10 m, developing a good white trunk and turning clear yellow in autumn (C. Grey-Wilson, pers. comm. 2007). Unfortunately, although its name at least is frequently found in arboreta and catalogues across our area, it is impossible to say whether or not the trees in question are correctly identified, and any that are not from wild-origin seed should be regarded with suspicion. B. turkestanica Litv. B432, K232 B. uber (NOW B. lenta f. uber (Ashe) McAllister & Ashburner, NT170) S114

Betula ×utahensis Britton This taxon is a natural hybrid of B. occidentalis and B. papyrifera. Its morphology is intermediate between the parent taxa. The branchlets are greenish brown and very resinous, and the ovate leaves are glabrous with blunt serrations. The pistillate catkins are very thick and slightly pubescent. Britton 1904, Furlow 1997. Distribution CANADA: Alberta, British Columbia, Yukon Territory; USA: Utah. Habitat Montane streambanks and lakeshores. USDA Hardiness Zone 1–2. Conservation status Not evaluated.

Section II. Species Accounts

Betula

173

This is another variable hybrid with no advantages over its parents. It is grown in major collections, including a large specimen at Edinburgh and propagations from this at Wakehurst Place. It has also been introduced as seeds from Montana by Kenneth Ashburner, although the identity of these trees is somewhat in doubt, as in the wild they were very large, which seems improbable for a hybrid involving B. occidentalis (H. McAllister, pers. comm. 2007). Trees in cultivation at Stone Lane Gardens have striking black bark.

B. utilis D. Don B433, S122, K232 B. utilis var. jacquemontii (Spach) Winkler S123 B. utilis var. occidentalis Kitamura S123 B. utilis var. prattii Burkill B433, K232

B. verrucosa Ehrh. (NOW B. pendula Roth var. pendula) K232 B. verrucosa var. oycowiensis (NOW B. pendula var. oycowiensis (Besser) Dippel) K233

PHYLLANTHACEAE (formerly EUPHORBIACEAE)

BISCHOFIA

Blume

There are two species of Bischofia: the evergreen B. javanica Blume, ranging from India through China and Japan to Australia and Polynesia, and the deciduous B. polycarpa, which is endemic to China (Govaerts et al. 2000, Radcliffe-Smith 2001). Bischofia species are large, dioecious (rarely monoecious) trees with red or reddish latex. The leaves are alternate, long-petiolate and pinnate with three (to five) leaflets; the leaflets have crenate to serrate margins. Stipules are small and caducous. The inflorescences are axillary, solitary, paniculate or racemose. The flowers are very small; they have five sepals, no petals, and no central disc; the staminate flowers are short-pedicellate, with five stamens, attached to the sepals; the pistillate flowers are pedicellate, soon caducous. The fruit is a small, indehiscent drupe with a papery endocarp, containing three to six seeds (Radcliffe-Smith 2001, Chang et al. 2005). Bischofia javanica has been cultivated for about a century in southern Florida and has been widely planted as a street tree there, but has become invasive, and its cultivation is now not encouraged (Langeland & Craddock Burks 1998). No such problems are known for B. polycarpa, which remains a scarce collector’s item.

Bischofia polycarpa (H. Lév.) Airy Shaw Tree to 15 m, 0.5(–1) m dbh. Bark reddish brown, peeling longitudinally. Branchlets green with grey-white lenticels. Leaves deciduous, pinnate, terminal leaflet larger than lateral leaflets; leaflets three, papery, 5–9(–14) × 3–6(–9) cm, ovate to elliptic, margins serrate, apex acuminate to acute; petiole 9–13.5 cm long. Inflorescences axillary, pendulous racemes. Dioecious; staminate inflorescences 8–13 cm long;

Plate 131. A young plant of Bischofia polycarpa in a Pennsylvania garden, displaying its handsome red-veined leaves. Image A. Bunting.

174

Bischofia

New Trees

pistillate inflorescences 3–12 cm long. Flowers small, sepals membranous, spreading. Drupe globose, 0.5–0.7 cm diameter, reddish brown. Flowering April to May, fruiting October to November (China). Chang et al. 2005. Distribution CHINA: Anhui, Fujian, northern Guangdong, Guangxi, Guizhou, Hunan, Jiangsu, Jiangxi, Shaanxi, Yunnan, Zhejiang. Habitat Montane evergreen forest between 200 and 1000 m asl. Planted in a variety of habitats in China, including as a street tree. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT173.

Bischofia polycarpa, although available from a few American nurseries, is nonetheless very scarce in cultivation. The only large specimen traced is at the JC Raulston Arboretum, currently about 14 m tall with dbh 34 cm. At one time there were large trees at the US National Arboretum, but these died after ‘extremely cold winters’ (Camellia Forest Nursery 2007–2008). The JCRA tree was grown from seed received by J.C. Raulston from China in 1988, and was reported on by him in 1994 as having survived a temperature low of –17 ºC in the winter of 1993–1994 (Raulston 1994). It is currently rather crowded, in an obscure corner, but has a rounded, somewhat open crown, with a canopy of light green leaves. B. trifoliata Blume K235

MYRTACEAE

BLEPHAROCALYX

O. Berg

Syn. Heteromyrtus Blume, Temu O. Berg

Blepharocalyx is a genus of evergreen trees or shrubs found in South America and the Lesser Antilles, closely related to Pimenta Lindl. and resembling several other small myrtle-like trees. There are three species, but the only one known to be in cultivation is B. cruckshanksii. There are simple or branched hairs (whitish, yellowish or reddish brown) on several parts of the plant. The inflorescence is a dichasium with 3–15 flowers or a panicle with approximately 35 flowers. The flowers themselves are 4-merous; the calyx is lobed and either closed or open in the bud; if closed, it tears into four lobes at anthesis and falls; if open, it may fall cleanly at anthesis or remain until the fruit ripens; the petals are whitish; the stamens, approximately 80–160, are folded into the centre of the flower in bud. The fruit is a globose berry with 1–15 seeds (Landrum 1986).

Blepharocalyx cruckshanksii (Hook. & Arn.) Nied.

Temu

Shrub or tree to 20 m, 0.4 m dbh. Bark smooth, reddish brown. Branchlets often four-angled, glabrous or with sparse, whitish dichotomous hairs. Leaves evergreen, opposite, leathery and aromatic, 1.7–5.5(–8) × 0.8–3 cm, elliptic to oblong or oblanceolate, both surfaces largely glabrous, secondary veins indistinct or up to 10 on each side of the midrib, margins entire, apex obtuse or emarginate; petiole 0.2–0.5 cm long, somewhat pubescent. Inflorescence axillary, peduncle 1–4.5 cm long, densely pubescent or glabrous, bearing a dichasium with 3–15 flowers. Flowers hermaphrodite, white, aromatic; calyx open in bud, persisting until fruit maturity; petals membranous; stamens ~90–140. Fruit globose, 0.85–1 cm diameter, purple. Flowering December to February, fruiting March (Chile). Rodríguez R. et al. 1983, Landrum 1986. Distribution

Section II. Species Accounts

Blepharocalyx

175

ARGENTINA: Neuquén, Rio Negro; CHILE: Bío-Bío, Coquimbo, Araucanía, Los Lagos, Maule, O’Higgins, Santiago, Valparaíso. Habitat Humid forest at about 400 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk, though ongoing habitat destruction may threaten this species in the future. Illustration Rodríguez R. et al. 1983; NT175, NT524.

Blepharocalyx cruckshanksii – perhaps a slightly marginal species for inclusion in this book – starts life as a dense shrub and slowly makes a thicker trunk as it becomes larger and develops into a rounded low tree. A smooth reddish brown bark covers the trunk, or trunks, rather like the bark of its better-known relative Luma apiculata, to which it is comparable in hardiness (Gardner & Hechenleitner 2005). Like Luma, it smothers itself in a mass of creamy white flowers in summer. The leaves are dark green, turning red as they senesce. The first introduction of B. cruckshanksii was by Harold Comber in 1927, and it persists in cultivation from that time, but collections have also been made during more recent expeditions to Chile by teams from the Royal Botanic Garden Edinburgh (Gardner & Hechenleitner 2005). Progeny from these are now well established in the Scottish botanical gardens and elsewhere. A plant at Logan dating from 1973 (presumably a Comber derivative) is however only a broad shrub, 3–4 m tall. It is available commercially, and is certainly a choice plant where a small evergreen tree or large shrub is wanted in situations protected from cold winds. Also in circulation is the socalled cultivar ‘Heaven Scent’, but this is probably no more than a selling name for a plant indistinguishable from the norm (Gardner & Hechenleitner 2005).

AKANIACEAE (formerly BRETSCHNEIDERACEAE)

BRETSCHNEIDERA

Hemsl.

The genus Bretschneidera is monospecific, comprising only the species B. sinensis. Bretschneidera has been placed in its own family Bretschneideraceae, although DNA data suggest that an amalgamation with the Australian Akaniaceae (otherwise only Akania Hook. f.) would be appropriate (APG 2003).

Plate 132. Blepharocalyx cruckshanksii flowering prolifically at Logan, where it has grown for many years but is reluctant to form a tree. Image R. Unwin.

176

Bretschneidera

1 cm

New Trees

Section II. Species Accounts

Bretschneidera

Bretschneidera sinensis Hemsl. Tree to 20 m, 1 m dbh. Bark greyish brown. Leaves deciduous, alternate, imparipinnate, green above and glaucous-green below, 25–75 cm long; leaflets 7–15, elliptic to oblong, 6–26 × 3–9 cm, leathery or papery, margins entire, apex acute to acuminate; petiole distinct, 10–25 cm long, swollen at base; petiolules to 1 cm long; lateral veins in 8–15 pairs per leaflet. Inflorescences terminal, erect and racemose, 20–36 cm long. Flowers hermaphrodite, 3–5 cm diameter; calyx large and cupular, 3.2 cm diameter, with five shallow teeth; petals five, free, white to pink, darkening with age, with longitudinal pink or red streaks, 1.8–2 × 1–1.5 cm, upper petal larger, covering the deflexed stamens and style. Fruit a capsule, 3–5.5 × 2–3.5 cm, warty and ellipsoidal to globose. Seeds red, 1.5–2.5 × 1.2–1.8 cm. Flowering March to September, fruiting August to April (China). Lu & Boufford 2001. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; LAOS (?); MYANMAR (?); TAIWAN; THAILAND; VIETNAM. Habitat Forested areas between 300 and 1700 m asl. USDA Hardiness Zone 8–9. Conservation status Endangered. Illustration Lu & Boufford 2001, Ronse de Craene et al. 2002; NT176.

Despite being a very ornamental tree with a wide distribution, Bretschneidera seems to have been introduced to the West only in the early 1990s – by Piroche Plants, Pitt Meadows, British Columbia (motto: ‘We boldly grow what no one has grown before’), although there have been later introductions since. It remains exceedingly rare, with only a handful of specimens in cultivation. Perhaps the best are two in the David C. Lam Asian Garden at the University of British Columbia. When seen in 2004 the larger specimen was about 3 m tall, forming a single straight stem with a tuft of leaves (75 cm long) at the top, but apparently growing well and vigorously in the shade of the huge conifers that form the spectacular setting for this collection. These plants were obtained from Piroche in 1997. At the JC Raulston Arboretum in North Carolina, however, it acts more like a herbaceous perennial; having been cut down by hard frosts, the largest of several shoots was only 1.3 m tall when seen in June 2006, although growing vigorously. This specimen was received in 1993 from Piroche, and is planted in full sun. At Tregrehan it has grown extremely slowly – less than 30 cm in three years (T. Hudson, pers. comm. 2005). It has recently become available in the Dutch nursery trade (M. Zwaan, pers. comm. 2007). Interest in Bretschneidera derives from its extremely attractive flowers and handsome pinnate leaves. The flowers appear in early summer and are white with pink or reddish veins, looking in photographs like a narrow Aesculus inflorescence. It is curious that such a striking tree should have evaded the horticultural net for so long. In consequence of its extreme rarity in cultivation, little can be said about its requirements, but a Chinese Ministry of Culture website (China Culture 2003) gives some useful information about its ecological needs. According to the anonymous author of this report, it is a subtropical species, growing in fertile acidic soil, in conditions where it experiences frost but not excessive heat. It germinates in shade, and is a successional emergent, tolerating shade as a young plant and eventually ‘escaping’ to the canopy and beginning to flower. It is said to be deep-rooted and wind-resistant, giving a fine quality of attractive timber. All these characters suggest that it will perform best in the mildest, moister areas of our region: the trees in Vancouver would seem to be ideally sited. Peter Wharton (pers. comm. 2006) wrote: ‘The key to growing this species is siting it in undisturbed native forest soils with semi-shade, where the high forest canopy is naturally thinning or can be thinned. Copes well with root competition, as one would expect. Open sunny sites with man-made soils kill this plant very effectively!’ Wharton also reported that the Vancouver specimens are proving tolerant of long dry spells without rainfall or irrigation. Bretschneidera may remain a rare tree but is one that should be attempted where such conditions can be provided.

Figure 19 (opposite). Bretschneidera sinensis: flowering shoot.

177

178

Buddleja

New Trees

SCROPHULARIACEAE

(formerly BUDDLEJACEAE, LOGANIACEAE)

BUDDLEJA

L.

Syn. Nicodemia Ten.

There are about 100 species of Buddleja, which occur in tropical, subtropical and warm-temperate America, Asia, and eastern and southern Africa. Buddleja species are shrubs or rarely trees in which the young stems, leaves and inflorescences are usually covered in a dense white tomentum, composed of branching, stellate and/or glandular hairs. The bark is fibrous, furrowed, greyish brown to black. Branchlets are terete to four-angled when young. The leaves are evergreen or deciduous, decussate (rarely alternate), stipulate, petiolate to sessile, simple, serrate-dentate (rarely entire or lobed). Inflorescences are terminal or axillary; roughly a thyrse, with one to four orders of branching. The flowers are actinomorphic, usually fragrant, 4-merous, hermaphrodite or functionally dioecious; the calyx tomentose outside, tubular or campanulate; the corolla tubular to campanulate, white, yellow, orange, pink or purple with an orange throat; the stamens inserted. The fruit is a dehiscent (rarely indehiscent) capsule (section Buddleja) or berry (section Nicodemia); the seeds often have wings (Norman 2000). Buddleja was very nearly excluded from New Trees, as the vast majority of its members – in cultivation, at least – are indubitably shrubby, branching freely from the base. Although some, including the ever-popular though weedy B. davidii, can form a trunk with age, it would be stretching the definition to call them ‘trees’. As can be seen from the cross-references below, a number of well-known varieties of Buddleja davidii are not recognised by Flora of China (Li & Leeuwenberg 2008), but they continue to be useful in a horticultural context. B. albiflora Hemsl. B446, K241 B. alternifolia Maxim. B447, K241 B. asiatica Lour. B446, K241 B. auriculata Benth. B447, K242 B. candida Dunn K242 B. caryopteridifolia (NOW B. crispa Benth.) B448, K242 B. colvilei Hook. f. & Thomson B449, K242 Plate 133. The handsome inflorescences of Buddleja cordata. Image N. Macer.

Buddleja cordata Kunth Shrub or tree 1–20 m, 10–45 cm dbh. Branchlets four-angled, tomentose. Leaves evergreen, membranous, (4–)8–20(–27) × 3–8(–18) cm, lanceolate to ovate, upper surface largely glabrous, lower surface sparsely to densely tomentose, margins entire, serrate or serrulate, apex acuminate or acute; petiole 1–4 cm long; stipules foliose or reduced to a line along the petiole. Inflorescence paniculate, with two to four orders of branching, 6–30 × 10–20 cm, as long as or longer than average leaves. Flowers fragrant, in clusters of 5–10; calyx

Section II. Species Accounts

Buddleja

179

campanulate, tomentose outside; corolla yellow to orange, tubular to campanulate, tube 1.5–2.5 mm long. Capsule cylindrical, 0.3–0.5 cm long, glandular, dehiscent; seeds winged. Flowering throughout the year, but primarily July to January, fruiting October to February (Mexico). Norman 2000. Distribution GUATEMALA; MEXICO: Aguascalientes, Chiapas, Chihuahua, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sinaloa, Tamaulipas, Tlaxcala, Veracruz, Zacatecas. Habitat Occurs in a wide range of habitats, from disturbed areas through desert scrub to pineoak woodland and cloud forest; between 1000 and 3000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Norman 2000, Stuart 2006; NT178, NT179. Taxonomic note Buddleja cordata subsp. ovandensis (Lundell ex E.M. Norman) E.M. Norman (Mexico: Chiapas) has leaves that appear glabrous underneath; the inflorescence is about half the length of average leaves. Buddleja cordata subsp. tomentella (Standl.) E.M. Norman (Mexico: Coahuila, Nuevo León, San Luis Potosí, Tamaulipas, Zacatecas) is usually a shrub of 1–5 m with white, greenish white or cream flowers.

The balance of persuasion was eventually tipped in favour of the inclusion here of Buddleja by photographs and information supplied by Nick Macer that we were unable to ignore. These showed and told of specimens of B. cordata growing to 25 m with a large bole on the Nevado de Colima, Jalisco, at 2500 m. The decision was sealed by the information that the species has grown outside for 13 years in his own garden in Stroud, Gloucestershire, although it must be said that it has yet to develop any such trunk there. The orange flowers are individually small but are borne in large branched panicles that are quite showy above the dark green leaves. It has been introduced by many different collectors, though is seldom seen in gardens. There is a good specimen of subsp. tomentella in the Centennial Border at the Hillier Gardens, grown from Sir Harold Hillier’s collection (no. 832) made in 1983. Buddleja cordata is clearly a species to investigate further, and on current evidence, would seem to be hardy in average English Zone 8 conditions. B. crispa Benth. B450, S126, K242 B. davidii Franch. B450, S126, K242 B. davidii var. alba (NOW B. davidii Franch.) B451 B. davidii var. magnifica (NOW B. davidii Franch.) B451, K243 B. davidii var. nanhoensis (NOW B. davidii Franch.) B451, K243 B. davidii var. superba (NOW B. davidii Franch.) K243 B. davidii var. veitchiana (NOW B. davidii Franch.) B451, K243 B. davidii var. wilsonii (NOW B. davidii Franch.) B451, K243 B. fallowiana L.B. Balf. & W.W. Sm. B452, K243 B. fallowiana var. alba Sabourin B452 B. farreri (NOW B. crispa var. farreri (L.B. Balf. & W.W. Sm.) Hand.-Mazz.) B453, K244 B. forrestii Diels B454, S126, K244 B. globosa Hope B454, S127, K244 B. heliophila (NOW B. delavayi Gagnep.) B455, K245 B. ×hybrida Farquhar K245 B. ×intermedia (Carrière) Rehder B456, K245 B. japonica Hemsl. B455, K245 B. ×lewisiana Everett K245 B. lindleyana Fortune ex Lindl. B456, K245 B. lindleyana var. sinuatodentata (NOW B. lindleyana Fortune ex Lindl.) B456

Plate 134. The Buddleja that could not be ignored: Buddleja cordata in Jalisco, Mexico. Image N. Macer.

180

Buddleja

New Trees

B. macrostachya Benth. S126 B. madagascariensis Lam. B446, K245 B. nappii Lorenz S127 B. nivea Duthie B456, K245 B. nivea var. yunnanensis (Don) Rehder & E.H. Wilson K245 B. officinalis Maxim. B456, K245 B. pulchella N.E. Br. K247 B. pterocaulis (NOW B. forrestii Diels) B454, K245

B. salviifolia (L.) Lam. B457, K247 B. stenostachya (NOW B. nivea Duthie) B457, K247 B. sterniana (NOW B. crispa Benth.) B448, K247 B. tibetica (NOW B. crispa Benth.) B453, K247 B. ×weyeriana Weyer B458, S127, K247 B. ×whiteana R.J. Moore K247

MYRTACEAE

CALLISTEMON

R. Br.

Bottlebrushes

Plate 135. The scarlet ‘bottlebrushes’ of Callistemon viminalis are much-loved by birds. Image J. Grimshaw.

The 35 species of Callistemon are endemic to Australia; the genus is closely related to Melaleuca L. (Brown et al. 2001). They are spreading shrubs or small trees with stiff, evergreen foliage. The leaves are alternate, entire, sessile or shortly petiolate; immature growth is often pinkish red and usually covered in silky hairs. The flowers are sessile and amassed along the stem in several parallel rows, forming the ‘bottlebrush’; the stem continues to grow before or after flowering, producing a leafy shoot beyond the inflorescence. The flowers are hermaphrodite and 5-merous; the sepals circular, fused to the bell- or urn-shaped hypanthium; the petals circular, longer than the sepals, greenish yellow, white, pink or purple; the stamens numerous, conspicuous, much longer than the petals, free (not in bundles as in Melaleuca), white, cream, yellow, pink, mauve, red or purple. The fruit is a sessile, woody capsule that may persist on the plant for many years; fire may be the stimulus that causes the capsules to open (Elliot & Jones 1982, Mitchem 1993, Spencer & Lumley 2002). Callistemon is another genus to have benefited in recent years from both the warmer climate and the greater inclination of gardeners to experiment, as several species and cultivars are now frequently to be seen in both public and private gardens throughout the United Kingdom. Many of these are short shrubby taxa, and few have achieved great size as yet, but the caution with which Bean (1976a) tentatively discussed them would not need to be repeated in a modern reference. They add a great deal of interest to the summer garden and are a welcome addition to the normal horticultural landscape, not only for the British Isles but for anywhere in milder parts of western Europe and the American West Coast. Few, however, form trees in our area, and of taxa not described by Bean, only C. viminalis is of tree-stature in its wild habitats. A warm, dry situation will give Callistemon the best chance of success; they seem to tolerate at least moderately alkaline conditions, but neutral to slightly acidic soil is probably preferable. Seedlings are easy to raise in moist, humid conditions but the species are prone to hybridise, so selected clones should be propagated by semi-ripe cuttings in late summer.

Section II. Species Accounts

Callistemon

181

The related genus Melaleuca (honeymyrtles, paperbarks, tea trees), comprising about 250 species, is also receiving attention at present, with northern temperate gardeners investigating the horticultural potential of this diverse group. The majority of species are rather shrubby, but with their white, yellowish green, yellow, pink, purple or red flowers they are attractive and interesting plants to experiment with in warm, well-drained sites on acidic soil. That the experiment is fully in progress is demonstrated by the listing in the RHS Plant Finder 2007–2008 of 40 species available in British nurseries. Elliot and Jones (1993) state that in Australian conditions the following (mostly shrubby) species have survived temperatures of –7 ºC: M. decussata R.Br., M. gibbosa Labill., M. lanceolata Otto, M. squamea Labill., M. uncinata R.Br. C. brachyandrus Lindl. K257 C. citrinus (Curtis) Stapf B471, K257 C. coccineus F. Muell. K257 C. linearis (Sm.) Colvill ex Sweet B471, K257 C. pallidus (Bonpl.) DC. B472 C. phoeniceus Lindl. B473, K257 C. pinifolius (J.C. Wendl.) Sweet K257 C. rigidus R. Br. B471, K257 C. salignus (Sm.) Colvill ex Sweet B471, K257 C. salignus var. viridiflora (NOW C. viridiflorus (Sieber ex Sims) Sweet) K257 C. sieberi DC. B472, K257 C. speciosus (NOW C. glaucus (Bonpl.) Sweet) B473, K257 C. subulatus Cheel B471

Callistemon viminalis

Weeping Bottlebrush

(Sol. ex Gaertn.) G. Don ex Loud. Shrub or tree 1–12 m. Bark grey, deeply fissured. Branchlets pendulous. New growth covered in silky hairs. Leaves stiff, spreading or appressed, 2–6.5 × 0.5–1 cm, linear to lanceolate, dull, dark green, bearing numerous oil glands, margins entire, apex acute; leaves sessile or with a poorly differentiated petiole. Flower spikes 5–20 × 3–6 cm. Flowers bright red to pink, widely spaced; calyx and corolla pale green, rachis densely tomentose. Capsule cup-shaped, 0.4–0.5 cm diameter; seeds not retained after flowering. Flowering September to December (Australia). Elliot & Jones 1982, Mitchem 1993. Distribution AUSTRALIA: New South Wales, Queensland. Habitat Occurs along the banks of watercourses. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Mitchem 1993; NT180, NT181. Cross-reference K257.

Callistemon viminalis is one of the most beautiful of flowering trees, combining a graceful habit with an abundance of bright red bottlebrush inflorescences. Whether with sunbirds in Africa or hummingbirds in California, a flowering tree in warmer places is constantly abuzz with small, flower-feeding birds that greatly add to its charm. Unfortunately these do not occur in northern Europe, and C. viminalis is not particularly successful here either, despite being freely available in the nursery trade (including a number of selected cultivars). The only specimen recorded by TROBI is a 3 m individual at Sidmouth, Devon, but it is probable that it is

Plate 136. Callistemon viminalis is a familiar sight in tropical gardens (here in Goba, Ethiopia) but may become better known further north as global temperatures rise. Image J. Grimshaw.

182

Callistemon

New Trees

grown quite widely in private gardens in southern and western England. Summer heat would seem to be the most important factor in its success, enabling ripening of the new growth, as it does well in both the southeastern United States and in California, at least as far north as San Francisco. Callistemon viminalis is among the species predicted by the Royal Horticultural Society to be a success in years to come if the climate of the British Isles continues to warm, and it is listed among their ‘Opportunities for Gardeners’ selections (Royal Horticultural Society Learning 2008), alongside species such as Acacia dealbata and Melia azederach that are already showing their appreciation of our warmer summers. C. viridiflorus (Sieber ex Sims) Sweet B472

CUPRESSACEAE

CALLITRIS

Vent.

Cypress Pines

Plate 137. A fertile shoot of Callitris preissii, showing the cones and very fine shoots typical of Callitris. Image A. Farjon.

Figure 20 (opposite). Callitris endlicheri: habit with female cones (A); detail of male strobili (B).

Callitris is an important genus of coniferous trees or shrubs in Australia, where there are 17 species, with a further two endemic to New Caledonia. The first part of the name is derived from the Greek kallos, ‘beauty’, which is appropriate for the fine branchlets usually found in the genus (tris is of uncertain derivation, possibly corrupted from trichos, ‘hair’, or treis in allusion to the trimerous phyllotaxis). Although some species attain timber size, the majority are smaller, with erect or fastigiate to spreading branches. As usual in Cupressaceae, the leaves exhibit dimorphism – in the juvenile phase being needle-shaped and held in whorls of four, spreading away from the stem, then rapidly replaced by the much smaller adult leaves, which are decurrent on the stem for most of their length, showing only a small triangular free tip, and borne in alternating whorls of three. The male strobili are solitary, paired or clustered at the tips of short branches, and are formed of alternating trimerous whorls of scales. Each scale bears two to six microsporangia on its inner surface. The female cones are solitary or clustered, formed of two whorls of three fertile scales, each bearing one to eight ovules. The seeds are winged. In Australia Callitris is regarded as a horticulturally desirable genus, tolerant of harsh conditions and often growing rapidly. In the wild most occur in dry sites, and in gardens full sun and unimpeded drainage are essential; most species are said to be very tolerant of frosts (Elliot & Jones 1997). As yet, the genus may be little known in our area, but these qualities are apparent in the few specimens seen in research for the current work, which seem to be very adaptable to northern temperate conditions. Elliot and Jones (1997) offer one very valuable point of cultural advice, as applicable elsewhere as in Australia: Callitris are irresistible to rabbits! Several other species are described by Krüssmann (1985b), but are not known to be cultivated within our area. Callitris species are most easily propagated from seed. C. baileyi C.T. White K58 C. canescens (Parl.) S.T. Blake K58

C. columellaris F. Muell. K58 C. drummondii (Parl.) F. Muell. K58

Section II. Species Accounts

Callitris

183

1 cm

0.5 cm

A B

184

Callitris

New Trees

Callitris endlicheri (Parl.) F.M. Bailey

Black Cypress-pine

Tree 15–20 m, though usually under 10 m. Branches ascending at an angle of 45º, forming an open pyramidal or conical crown. Adult leaves 0.2–0.6 cm, dark green, prominently keeled. Male strobili above female cones, numerous, solitary or paired, 1.5–2.5 mm long with 8–14 microsporophylls. Female cones terminal on short thick fruiting branchlets, solitary though often loosely clustered on higher order branches, ovoid to globose when closed, 1.3–2 × 1–1.6 cm, maturing in one to one and a half years, then caducous, brown or purplish brown, weathering to grey; scales six, smooth to rugose. Seeds five to nine on each scale, ~0.8 cm diameter, dark brown, with two to three wings. Farjon 2005c. Distribution AUSTRALIA: New South Wales, Queensland, eastern Victoria. Habitat Open Eucalyptus woodland, disturbed scrub or grassland between 350 and 1100 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Farjon 2005c; NT183, NT184. Cross-reference K58.

A very attractive specimen of Callitris endlicheri, accessioned in 1992 and 3.5 m tall in 2006, grows at Logan, forming a column of drooping, slender grass-green shoots. It was bearing both female cones and withered male strobili when observed in 2006. At Kew a 1999 accession from Aljos Farjon’s collection FRJA 413, made at 780 m in New South Wales, was 2 m in 2005, and has also made a dainty tree. Its young growth is somewhat bronzed. Wild trees in this site were up to 7 m.

C. macleayana (F. Muell.) F. Muell. K58 C. monticola J. Garden K58 C. muelleri (Parl.) Benth. & Hook. f. ex F. Muell. K58 C. neocaledonica Dummer K58 Plate 138. Narrow columns of Callitris endlicheri on the Newnes Plateau, New South Wales. Seedlings from these trees are hardy at Kew. Image A. Farjon.

Callitris oblonga Rich.

Tasmanian Cypress-pine, Pigmy Cypress-pine

Shrub or small tree 5–8 m. Branches dense, erect, branchlets drooping at tips. Adult leaves to 4 mm, dark green to glaucous, prominently but not acutely keeled. Male strobili solitary, or two to five, to 2 mm. Female cones clustered, sessile or on short thick fruiting branchlets, rounded, 1–2.4 cm, longer than broad, persisting for several years; scales six, thick with short, thick apical point on dorsal surface. Seeds ~0.2 cm diameter, dark brown, with two to three wings. Elliot & Jones 1997, Hill 1998. Distribution AUSTRALIA: New South Wales, Tasmania. Habitat Sandy soil and low wet sites in the tablelands. USDA Hardiness Zone 8–9. Conservation status Vulnerable. Illustration Van Gelderen & van Hoey Smith 1996. Cross-reference K60. Taxonomic note Three subspecies have been named: subsp. oblonga from Tasmania, with female cones 1.8–2.4 × 1.4–2.2 cm; subsp. corangensis K.D. Hill, with female cones 1.4–1.8 × 1.0–1.5 cm, alternate scales half the length of intervening scales, very rare in New South Wales; and subsp. parva K.D. Hill, with female cones 1.2–1.5 × 1.0–1.4 cm, alternate scales two-thirds of the length of intervening scales, rare in New South Wales.

Apparently rare in cultivation, and not commercially available in our area at present, Callitris oblonga is a columnar conifer with stiffly ascending branches. The best individual observed for the current work is at Tregrehan, a rounded pillar of feathery foliage, standing 7 m tall next to a good C. rhomboidea – an attractive pair, dating from 1990. Several specimens at Logan, in a rather shaded situation, were grown from Johnstone 220, collected in 1992, and are now approximately 1.6 m tall. The species seems to have a toe-hold in American cultivation (PLANTS Database 2008). In Australia it is recommended for cooler climates, suggesting a potential useful adaptability in the northern hemisphere.

Section II. Species Accounts

Callitris preissii Miq.

Callitris

185

Rottnest Island Cypress-pine, Mallee Pine

Shrub or tree to 25 m, to 1 m dbh; typically multistemmed or branching low down. Branches spreading or ascending, long, forming a pyramidal or broadly domed crown. Adult leaves 0.1–0.5 cm, yellowish green or glaucous, dorsal surface convex. Male strobili above female cones, numerous, solitary or in groups of two to three, 0.3–0.5 cm long with 15–20 microsporophylls. Female cones terminal on very short thick fruiting branchlets, solitary or more often clustered, ovoid to globose when closed, 2–3 × 2.2–3.5 cm, maturing in one to one and a half years, persistent, brown or purplish brown to black, weathering to grey; scales six, smooth to coarsely rugose, often covered with large pimple-like structures. Seeds 9–12 on each scale, ~1 cm diameter, dark brown or reddish brown, with two (to three) wings. Farjon 2005c. Distribution AUSTRALIA: New South Wales, South Australia, Victoria, Western Australia. Habitat Coastal and inland sand dunes, sandy floodplains and hillsides between 2 and 670 m asl. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Farjon 2005c; NT182, NT185. Cross-reference K60.

There are two specimens of Callitris preissii at Kew. The larger, currently at 2.3 m, is from FAWA 438, collected by Aljos Farjon and A. Watt in Western Australia in 1997. The parent population included trees up to 12 m tall, dbh 30 cm, and was growing amongst farmland at an altitude of 120 m. The other individual at Kew (1.2 m) was collected by Aljos Farjon (FRJA 394) from a parent tree growing on sand dunes on the northern tip of Garden Island, Western Australia, also in 1997 – perhaps the most improbable provenance of any tree in this book. Both seem to be healthy, with bright green shoots, and both have coned. Johnson (2007) records a 2.2 m specimen at Thorn House, near Plymouth, Devon, so despite its lowland provenance it seems to have some degree of hardiness.

C. preissii subsp. murrayensis (NOW C. preissii Miq.) K60 C. preissii subsp. verrucosa (NOW C. verrucosa (A. Cunn. ex Endl.) F. Muell.) K60

Callitris rhomboidea R. Br. ex L.C. Rich.

Oyster Bay Cypress-pine, Port Jackson Cypress-pine

Tree to 15 m, 0.4 m dbh, neatly pyramidal in outline when young. Bark smooth. Branches spreading to erect or fastigiate, with elegant drooping fine branchlets. Adult leaves to 2.5 mm, bright green to glaucous, prominently but not acutely keeled. Male strobili solitary or in clusters, to 2 mm. Female cones clustered, rounded, 1.2–2 cm diameter, persistent on the tree for years; scales with a short broad dorsal protuberance below the apex. Seeds ~0.1 cm diameter, dark brown, with two to three wings. Dallimore et al. 1966, Elliot & Jones 1997, Hill 1998. Distribution AUSTRALIA: eastern New South Wales, Queensland, South Australia, Tasmania, Victoria. Habitat Rocky hills, sandplains and near the coast. USDA Hardiness Zone 8a. Conservation status Lower Risk. Illustration Van Gelderen & van Hoey Smith 1996; NT186. Cross-reference K60.

In the United Kingdom the tallest specimen of Callitris rhomboidea recorded was a tree of 14 m at Westlake in Devon, measured by Alan Mitchell in 1984 (Johnson 2003). It is not known if this tree still exists. The finest observed for the current work is at Tregrehan, matching the 7 m of the adjacent C. oblonga, and also forming a plumy

Plate 139. Callitris preissii typically forms a rounded crown, as here on Garden Island, Western Australia. Image A. Farjon.

186

Callitris

New Trees

pillar. A shaded 4 m specimen at Logan is leaning badly; although rather open in habit, it is continuing to produce healthy new growth. There is also a young tree (2 m) at Kew, again growing well. Callitris rhomboidea is available in the UK nursery trade. As a rapidly growing species tolerant of drought and neglect it is popular in Australian horticulture, and a selection from Mount Zero, Victoria with golden-yellow foliage has been named ‘Golden Zero’ (Elliot & Jones 1997, Hill 1998). The species deserves to be tried more widely where a warm sunny site can be provided. Plate 140. Callitris rhomboidea. The shape of the cones is important in distinguishing Callitris species. Image A. Farjon.

C. roei (Endl.) F. Muell. K60

C. sulcata (Parl.) Schltr. K60

CUPRESSACEAE

CALOCEDRUS

Kurz

Incense Cedars Calocedrus contains three species: C. decurrens on the Pacific coast of North America, and C. macrolepis and C. formosana, in China and Taiwan, respectively. The genus was formerly included in Libocedrus (as in Bean 1981a), together with Austrocedrus, Papuacedrus and Pilgerodendron. Calocedrus species are large evergreen trees with a broadly conical or columnar habit. In some parts of eastern Britain the habit of C. decurrens becomes tightly fastigiate with very short branches, though the reasons for this change are unknown. The bark is initially smooth, becoming scaly or breaking into longitudinal plates; colour varies from white to purplish grey. Major branches are spreading to ascendant. Branchlets are dorsiventrally flattened, and fan-shaped. The leaves are in pairs, scale-like, appressed, decussate, strongly dimorphic in shape and size; the lateral pair overlapping the facial pair. Male and female cones are produced on different branches on the same tree. The male strobili are oblong, with 12–16 decussate scales; the female cones erect or pendulous, yellowish to reddish brown, ellipsoidal, mature in the first year. The seed scales are thin, woody, with a small, spiny umbo, in (two to) three decussate pairs; the distal pair is connate and sterile, the median pair fertile, the proximal pair reduced or absent. Each scale bears one to two lenticular seeds, each with one short, rudimentary wing and one long, fully formed wing (Watson & Eckenwalder 1993, Li & Keng 1994c, Fu et al. 1999e). The Californian Calocedrus decurrens is a justly popular tree, with a delicious fragrance when the shoots are crushed. The famous group of columnar specimens at Westonbirt, familiar to dendrologists from their portrait on the jacket of ‘Bean, Volume Two’, have also been accorded the accolade of a plate in Thomas Pakenham’s Meetings with Remarkable Trees (Pakenham 1996). Perhaps in consequence of these images the species is often thought to be strictly columnar but this is not usually the case, and a much more relaxed outline is normal. This tree is usually found as a native in summer-dry situations, but the Asian species are found in moister forest. Planting sites should be chosen accordingly. C. decurrens (Torr.) Florin B566 (as Libocedrus decurrens), S130, K60

Section II. Species Accounts

Calocedrus formosana (Florin) Florin

Calocedrus

187

Taiwan Incense Cedar

Tree to 25 m, to 1.5 m dbh. Bark smooth, purplish to reddish brown, becoming fissured when older. Crown initially pyramidal, later broad and rounded. Branchlets numerous and drooping. Leaves obtuse, dark green on the outside, pale green inside, 1.5–2.5 mm long; the lateral pairs large, flattened, partially obscuring the facial pairs. Male strobili terminal, ovoid or oblong, 0.4–0.8 cm long, yellow. Seed cones solitary, oblong or ovoid, sometimes slightly curved, 1–1.5 × 0.4–0.6 cm, reddish brown, persistent after seed dispersal. Seed scales in two (rarely three) decussate pairs, valvate, only the middle scales fertile, distal scales much reduced in size, one to two seeds per scale. Seeds ovoid or ellipsoid, 0.5–0.6 cm; wings either long or short, 0.3–0.6 cm long. Li & Keng 1994c, Fu et al. 1999e, Farjon 2005c. Distribution TAIWAN. Habitat North- and eastfacing slopes between 300 and 1900 m asl. This species is found on well-drained soil with moderate levels of organic matter. USDA Hardiness Zone 8. Conservation status Endangered. Illustration Li & Keng 1994c, Fu et al. 1999e, Flanagan & Kirkham 2005; NT187, NT187, NT246. Cross-reference B567 (as Libocedrus formosana), S130, K61. Taxonomic note This species is recognised only as C. macrolepis var. formosana (Florin) Kudô in Flora of China (Fu et al. 1999e). It can be differentiated from C. macrolepis by examination of the cone-bearing branchlets: in C. formosana they are flattened, while in C. macrolepis they are terete or four-angled – but this distinction is often difficult to observe.

Several recent expeditions to Taiwan have collected this taxon, and in consequence it has been planted quite widely. In the wild it is a large, if not always shapely tree, but it has yet to achieve more than a few metres in cultivation. An interesting account of collecting its seed is given by Flanagan and Kirkham (2005). A tree at Kew from their collection (ETOT 10) made at 1560 m in Taichung County, Taiwan in 1995, is doing well and is approximately 3.5 m tall. It has branched at the base to form three main stems. The shoots are much more ‘open’ than those of the familiar Calocedrus decurrens, giving them a fern-like look that is rather elegant. The younger shoots are also somewhat bronzed, which further adds to their appeal. A 2.2 m plant observed at Heronswood in 2005, grown from a Dan Hinkley collection, was in a shadier site, and here the younger growth was bright green. The species has been commercially distributed by Heronswood Nursery. Although not fully tested, its comparatively low altitudinal range suggests that it will perform best in the milder parts of our area. C. macrolepis Kurz B567 (as Libocedrus macrolepis), S130, K61

Plate 141 (far left). The plant-hunting duo Mark Flanagan and Tony Kirkham are dwarfed by the trunk of Calocedrus formosana, on their expedition to Taiwan in 1992. Image T. Kirkham. Plate 142 (near left). Seedlings from the giant Taiwanese C. formosana, are making steady growth in cultivation (here ETOT 6, at Kew). Image T. Kirkham.

188

Camellia

New Trees

THEACEAE

CAMELLIA

L.

Camellias

Plate 143. The large flowers of Camellia crapnelliana are magnificent but sparsely produced. Image M. Foster.

The most recent treatment of Camellia (Ming & Bartholomew 2007), on which this account is based, estimates that there are about 120 species in the genus. This estimate is conservative; Chang & Bartholomew (1984) recognised 200 species. Camellias occur from Nepal east to Japan and south to Indochina; in addition, Camellia lanceolata (Blume) Seem. occurs in Indonesia and the Philippines. They are evergreen trees or shrubs, grown primarily for their large, hermaphrodite flowers. The leaves are leathery with serrate or rarely entire margins; they are usually petiolate though they can be sessile or amplexicaul. The flowers are axillary or subterminal, and solitary or in clusters of up to three. Flowers may be pedicellate with 2–10 distinct bracteoles and five (to six) distinct sepals (subgenus Thea), or subsessile with around 10 undifferentiated bracteoles/sepals (subgenus Camellia). The petals, 5–8(–12), are white, pink, red or yellow; the stamens numerous, in two to six whorls, the outer whorl fused to the petals. The fruit is a globose or subglobose capsule, which splits from the apex via three to five valves; central column present or absent (Sealy 1958, Chang & Bartholomew 1984, Ming & Bartholomew 2007).

Section II. Species Accounts

Camellia has an enthusiastic following, including the members of the International Camellia Society, and numerous well-illustrated reference works are available (Sealy 1958, Chang 1981, Chang & Bartholomew 1984, Trehane 1990, Ming 2000, Gao et al. 2005, Trehane 2007). The present account describes only recently introduced species whose natural habit is to form a tree of more than 5 m tall, and which are cultivated in our core area. The following ‘new’ shrubby species (normally below 5 m tall) are also in cultivation in our area: C. amplexifolia Merr. & Chun, C. fluviatilis Hand.-Mazz., C. fraterna Hance, C. grijsii Hance, C. transarisanensis Hayata, C. trichoclada (Rehder) S.S. Chien, C. wardii Kobuski and C. xylocarpa (Hu) Hung T. Chang. In addition, the following are known to be in cultivation in southern California, and could conceivably be found in collections in our area where climatic conditions permit: C. chrysanthoides Hung T. Chang, C. crassicolumna Hung T. Chang, C. euryoides Lindl., C. flavida Hung T. Chang, C. gaudichaudii (Gagnep.) Sealy, C. impressinervis Hung T. Chang & S. Ye Liang, C. indochinensis Merr., C. mairei Melch., C. petelotii (Merr.) Sealy, C. salicifolia Champ., C. semiserrata C.W. Chi and C. synaptica Sealy. One of the most exciting discoveries and introductions in recent years has been C. cucphuongensis Tran Ninh & J.-C. Rosmann, from lowland Vietnam. Although it is almost certainly not hardy in our area, its gorgeous golden flowers make this a highly desirable plant for the conservatory. In addition to the nominate species described below, many infraspecific taxa exist, for details of which see other references, especially Ming & Bartholomew (2007). All species mentioned or described here are illustrated in Collected Species of the Genus Camellia: An Illustrated Outline (Gao et al. 2005). The establishment of England’s first commercial tea plantation (albeit on a small scale) at Tregothnan, Cornwall from 1999 onwards is an indication of the currently increasingly warm climate, and of the willingness of good gardeners to experiment and take risks. Camellia sinensis was described by Bean (1976a) but he did not predict that it could come to be grown outside in the British Isles, and it may be that some of the species listed above may also become growable in our area. Another development leading to the more widespread cultivation of camellias has been the intensive work carried out in the United States, in search of ever-increasing hardiness in ‘standard’ camellias. The interest in this of the Parks family of Camellia Forest Nursery, Chapel Hill, North Carolina started when a devastating freeze down to –23 ºC in 1985 killed almost all of Clifford Parks’s large collection. The survivors, which included C. oleifera and a handful of C. japonica cultivars and other hybrids, have since been used to breed and select new hardy cultivars, some of which are now considered hardy to Zone 6b. Among these are the C. sasanqua × C. oleifera hybrid ‘Survivor’ which withstood the 1985 frost and is now cultivated in Ontario, and ‘Mason Farm’ of the same parentage. Dr William Ackermann of the US National Arboretum has also used this combination of parents to create a number of very cold-tolerant cultivars, including the bright pink ‘Winter’s Joy’ (Ackermann 2007). Most of these start flowering in autumn and continue through the winter. The same breeders have also worked with C. japonica survivors to develop selections hardy to Zone 6b at least, including the April Series from Camellia Forest Nursery (Ward 2004). Although often thought of as a ‘shrubby’ genus on account of their dense growth and (in northern Europe at least) often low stature, many species of Camellia are naturally single-stemmed trees capable of reaching impressive size. These include the familiar C. japonica and C. reticulata, from which so many of the well-known garden camellias have been derived. The species described below are as yet mostly unknown to all but

Camellia

189

190

Camellia

New Trees

a few Camellia enthusiasts, principally in the United States, and only a handful are currently available in Europe. Unfortunately none have been observed in the course of research for New Trees, so notes are derived entirely from secondary sources. In almost all cases a warm sheltered site will be necessary, with attention to the usual Camellia preferences for acidic soil and ample moisture. In cultivation, propagation will usually be by cuttings.

Camellia brevistyla (Hayata) Cohen-Stuart Syn. C. brevissima Hung T. Chang, C. obtusifolia Hung T. Chang, C. puniceiflora Hung T. Chang Shrub 1–3.5 m, rarely tree 5–8 m. Branchlets purplish brown, grey-pubescent. Leaves thin and leathery, 3–5.5 × 1.5–3 cm, elliptic to obovate or oblong, upper surface dark green with some hairs along the midrib, lower surface pale green and sparsely villous along the midrib, five to six secondary veins on each side of the midrib, though somewhat obscured, margins minutely serrate, apex blunt to rounded; petiole 0.3– 0.5 cm long, pubescent. Flowers axillary, solitary, 1.5–2.5(–3) cm diameter, subsessile. Bracteoles/sepals 7–8(–10), caducous, outside grey-pubescent; petals five to seven, white or pink, obovate, 1.5–2.5 cm long, apex deeply emarginate; stamens numerous, 0.5–1 cm long; ovary yellow-tomentose. Capsule brown, globose, 1.5–1.8 cm long, usually with a single seed. Flowering October to December, fruiting September to October of the following year (China). Ming & Bartholomew 2007. Distribution CHINA: southern Anhui, Fujian, northwest Guangdong, northeast Guangxi, Guizhou, southern Hubei, Hunan, Jiangxi, Zhejiang; TAIWAN. Habitat Forest thickets between 200 and 1100 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984.

The freely produced but small flowers of Camellia brevistyla are usually white (pink in var. rubida P.L. Chiu), and have the advantage of appearing in autumn, above neat, small leaves. The bark is an attractive orange colour (Camellia Forest Nursery 2007–2008). Camellia brevistyla is related to C. sasanqua, with which it will hybridise (Gao et al. 2005), and C. oleifera. In North Carolina it has proved hardy and easy to cultivate at Camellia Forest Nursery, and a plant has been growing steadily at the JC Raulston Arboretum since 2001.

Camellia caudata Wall. Syn. C. assimilis Champ., C. membranacea Hung T. Chang, C. parvilapidea Hung T. Chang, C. percuspidata Hung T. Chang, C. triantha Hung T. Chang Shrub or tree 2–8 m. Branchlets yellowish brown, glabrous to pubescent. Leaves thin and leathery, 7–12 × 2–4(–5) cm, elliptic to oblong, upper surface dark green and shiny with minute hairs along the midrib, lower surface pale green and sparsely pubescent, though densely villous along the midrib, 8–10 secondary veins on each side of the midrib, margins minutely serrate, apex caudate; petiole 0.3–0.7 cm long, pubescent. Flowers axillary, solitary or up to three in a cluster; pedicel 0.2–0.4 cm long. Bracteoles four to five, 0.1–0.2 cm long, outside pubescent; sepals five, leathery, outside pubescent; petals five to seven, white, obovate, outer two petals 0.8–1 cm long, inner petals 1.3–2 cm long, apex rounded; stamens numerous, 1–1.5 cm long; ovary densely white-tomentose. Capsule ellipsoid to globose, 1.5–2 cm long, usually with a single seed. Flowering October to January, fruiting September to October (China). Ming & Bartholomew 2007. Distribution CHINA: Fujian, Guangdong, Guangxi, Hainan, Hubei, Hunan, Xizang, southeast Yunnan; INDIA; MYANMAR; NEPAL; TAIWAN; VIETNAM. Habitat Broadleaved evergreen forest between (200–)400 and 1400(–2200) m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984.

Camellia caudata is a southern, low-altitude species and Gao et al. (2005) caution that for horticultural use it should be sought from its coldest provenances. Its interest lies in the long-tipped leaves, rather than the small white flowers. It is tenuously in cultivation in southern England and New Zealand.

Section II. Species Accounts

Camellia

191

Camellia chekiangoleosa Hu Syn. C. crassissima Hung T. Chang & Shi, C. liberistamina Hung T. Chang & J.S. Kiu, C. lucidissima Hung T. Chang Shrub or tree 3–8 m. Branchlets reddish brown, glabrous. Leaves thick, leathery, 7–13 × 3–6 cm, elliptic to oblong, upper surface shiny green, glabrous, lower surface pale green to yellowish green, glabrous, seven to eight secondary veins on each side of the midrib, margins minutely serrate, apex acute to acuminate; petiole 1–1.5 cm long, glabrous. Flowers subterminal or axillary, solitary or paired, 7–10 cm diameter, subsessile. Bracteoles/sepals 9–11, inner four to six bracteoles/sepals persistent in fruit, others caducous, outside grey-villous; petals six to eight, bright red, obovate, 4–6 cm long, apex emarginate; stamens numerous, 2.5– 3 cm long; ovary glabrous. Capsule globose, 4–7.5 cm diameter, splitting via three valves, each section holding three to eight seeds. Flowering November to December, fruiting October of following year (China). Ming & Bartholomew 2007. Distribution CHINA: eastern Anhui, northern Fujian, eastern Hunan, Jiangxi, Zhejiang. Habitat Forest between 500 and 1300 m asl. USDA Hardiness Zone 7b–8. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984; NT191.

With large, rich red flowers displaying a boss of yellow stamens, Camellia chekiangoleosa is a valuable newcomer to the garden flora – ‘a thoroughly desirable addition to a collection’ (Hudson 2004). It is related to C. japonica, but has larger flowers of a purer red, and hybrids between the two species are also reported to have good red colour (Gao et al. 2005). Unfortunately it remains rare in cultivation, although it is apparently quite hardy. In China it is grown for the edible oil extracted from its seeds. C. chrysantha (NOW C. petelotii (Merr.) Sealy var. petelotii) S132

Camellia costei H. Lév. Syn. C. dubia Sealy, C. subacutissima Hung T. Chang Shrub or tree 1.5–5(–8) m. Branchlets yellowish grey, shortly pubescent. Leaves papery or thin and leathery, 5–8 × 1.5–3.5 cm, elliptic to oblong, upper surface dark green with minute hairs, particularly along the midrib, lower surface pale green and strigose, six to eight secondary veins on each side of the midrib, margins minutely serrate, apex acuminate to caudate; petiole 0.2–0.5 cm long, pubescent. Flowers axillary, solitary; pedicel 0.2–0.5 cm long. Bracteoles four to five, 0.05–0.15 cm long, outside densely pubescent; calyx fivelobed, outside densely pubescent; petals five (to seven), white or pale purplish red in bud, obovate, 1–2.5 cm long, apex emarginate; stamens numerous, 1.2–1.8 cm long; ovary glabrous. Capsule subglobose, 1–1.5 cm diameter, green to purplish red, surmounted by the elongated style, usually with a single seed. Flowering February to March, fruiting September to October (China). Ming & Bartholomew 2007. Distribution CHINA: northern Guangxi, Guizhou, western Hubei, western Hunan, Sichuan, Yunnan. Habitat Forest between 400 and 1500(–2000) m asl. USDA Hardiness Zone 8 (?). Conservation status Not evaluated. Illustration Chang & Bartholomew 1984.

Although its slightly scented flowers are rather small, they are freely produced in early spring and make Camellia costei a worthy garden plant (Gao et al. 2005). The neat narrow foliage is also attractive, especially as the new growth is reddish on emergence (Camellia Forest Nursery 2007–2008). It is cultivated in southern California, where it seems to do well, and is offered by Camellia Forest Nursery, North Carolina.

Plate 144. The sumptuous red flowers of Camellia chekiangoleosa are as yet seldom seen in cultivation, but it seems to be quite hardy. Image JC Raulston Arboretum.

192

Camellia

New Trees

Camellia crapnelliana Tutch. Syn. C. multibracteata Hung T. Chang, C. octopetala Hu Shrub or tree 2–10 m. Branchlets green to bright reddish brown, glabrous. Leaves rigidly leathery, 7–19 × 3–6 cm, elliptic to oblong, upper surface dark green and glabrous, lower surface pale green with brown glandular spots, seven to nine secondary veins on each side of the midrib, margins obscurely toothed, apex cuspidate; petiole 0.6–1.2 cm long, glabrous. Flowers axillary or subterminal, solitary or paired, 4–10 cm diameter, subsessile. Bracteoles/sepals 7–13, persistent, 0.3–2 cm long, outside brown-tomentose; petals six to eight, white, obovate to oblong, 3.5–6.5 cm long, apex rounded to emarginate; stamens extremely numerous, 1.5–1.7 cm long; ovary densely tomentose. Capsule subglobose, 5–7(–12) cm diameter, greyish brown, splitting via three to five valves, each section holding three to five seeds. Flowering December to January, fruiting September to October (China). Ming & Bartholomew 2007. Distribution CHINA: Fujian, Guangdong, southern Guangxi, eastern Jiangxi, southern Zhejiang. Habitat Forest between 100 and 800 m asl. USDA Hardiness Zone 9–10. Conservation status Vulnerable, due to habitat loss/degradation and overharvesting. Illustration Chang & Bartholomew 1984; NT188, NT192.

Plate 145. The bark of Camellia crapnelliana is one of its horticultural merits: seen here in Guangxi, southern China. Image M. Foster.

The outstanding horticultural feature of Camellia crapnelliana is its striking cinnamoncoloured bark, which shows up well on the trunk and branches. The branches are held rather stiffly upwards to create a neatly shaped tree. The white flowers are large but sparsely produced, and when successfully pollinated produce ‘tennis-ball sized’ round fruits that are an interesting feature in their own right. It is well established though scarce in cultivation in Australasia and the warmer parts of the United States, and in Cornwall, where it needs a very sheltered position (Hudson 2004). C. cuspidata (Kochs) H.J. Veitch B479, S133, K264

Camellia drupifera Lour. Shrub or tree 2–8 m, 0.1–0.3 m dbh. Branchlets reddish brown, glabrous, or green and villous when young. Leaves leathery, 5–12 × 3–5 cm, elliptic, upper surface dark green and shiny, bristly along the midrib, lower surface pale green and glabrous, seven to nine secondary veins on each side of the midrib, margins minutely serrate, apex acute to acuminate; petiole 0.5–0.7 cm long, glabrous. Flowers axillary, solitary, fragrant, 6–7.5 cm diameter, subsessile. Bracteoles/sepals 10–12 or more, caducous, glabrous; petals five to eight, white, obovate, 3–6 cm long, apex emarginate; stamens numerous, 1.2–1.7 cm long; ovary densely tomentose. Capsule globose to ovoid, 4–7 cm diameter, woody, splitting via three to five valves, each section holding one to four seeds. Flowering December to January, fruiting October (China). Ming & Bartholomew 2007. Distribution CHINA: southwest Guangdong, southern Guangxi, Hainan; VIETNAM. Habitat Forest between 100 and 700 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Taxonomic note The identity of C. drupifera has been uncertain for some time. Chang & Bartholomew (1984) treated it as a synonym of C. oleifera C. Abel, despite the former being an older name and thus having priority. Flora of China (Ming & Bartholomew 2007) recognises C. drupifera and C. oleifera as distinct species, differentiated by the glabrous nature of the branchlets and bracteoles, and outsides of sepals, in C. drupifera (pubescent to tomentose in C. oleifera). Camellia drupifera is widely cultivated in southern China and Vietnam and this can lead to difficulties in interpreting both the wild distribution and the extent of naturally occurring morphological variation.

This taxon is represented in cultivation by plants identified as Camellia vietnamensis, and as such is a beautiful small tree with big white and yellow scented flowers, well displayed against the dark green foliage in late autumn and winter. It is resistant to

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most Camellia diseases, but unfortunately is not very hardy: Gao et al. (2005) have stated that it is susceptible to temperatures below –6 ºC, although its hybrids (with C. sasanqua, for example) are much hardier and retain the floral showiness. It is in cultivation in the United States and in Australasia.

Camellia edithae Hance Shrub or tree 2–7 m. Branchlets greyish brown, densely covered in yellowish indumentum. Leaves leathery, 6–12.5(–15.5) × 2.5–4.5 cm, ovate to lanceolate, upper surface dark green and shiny, with yellow indumentum along the midrib, lower surface pale green and villous, seven to nine secondary veins on each side of the midrib, margins minutely serrate, apex acuminate; petiole 0.2–0.5 cm long, villous; leaves sometimes amplexicaul. Flowers subterminal, solitary, 5–6 cm diameter, subsessile. Bracteoles/sepals 9–11, persistent, pubescent, outer bracteoles/sepals suborbicular, 0.4–0.6 cm long, inner bracteoles/sepals ovate, 1.5–2.5 cm long; petals five to six, red or pink, obovate, 2.5–4.5 cm long, apex emarginate; stamens numerous, 2.5–3 cm long; ovary densely tomentose. Capsule subglobose, 1.5–2 cm diameter, brown, holding three to six seeds. Flowering January to March, fruiting October (China). Ming & Bartholomew 2007. Distribution CHINA: Fujian, northeast Guangdong, southeast Jiangxi. Habitat Forest between 200 and 1000 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated.

Camellia edithae is on the small side for inclusion here, but is notable for its handsome large leaves, appearing less glossy than they are from the effect of their intricate pattern of veins. The stems are densely hairy while young, becoming dark brown with age. The flowers are of medium size, and red. In the wild they are single, but in cultivation two doubles are known: ‘Momudan’ is dark red and ‘Jiuqu’ a formal-shaped deep pink. The Chinese name for the species, Dongnan Shancha, appears to be used in the United States as a cultivar name for ‘Jiuqu’ (Gao et al. 2005). It is possible that these are the only clones in cultivation at present, but the single, fertile forms should be sought as they have considerable breeding potential. The species appears to be very hardy, surviving –18 ºC in North Carolina (Parks 2002). It is well established in North American collections, but has not been located in Europe.

Camellia forrestii (Diels) Cohen-Stuart Syn. C. truncata Hung T. Chang & C.X. Ye Shrub or tree 1–6(–8) m. Branchlets greyish brown, densely pubescent. Leaves leathery, 2–7 × 1–2.5 cm, elliptic to ovate or oblong, upper surface dark green and slightly hairy along the midrib, lower surface pale green and sparsely pubescent with dense indumentum along the midrib, secondary veins obscured, margins minutely serrate, apex broadly obtuse to bluntly acute or acuminate; petiole 0.2–0.4 cm long, densely pubescent. Flowers axillary, solitary or paired, 1.5–2.5 cm diameter; pedicel 0.2–0.45 cm long. Bracteoles three to four, persistent, 0.1–0.2 cm long, outside glabrous; calyx five-lobed, outside glabrous; petals five (to six), white, occasionally pink in bud, obovate, 0.6–1.5 cm long, apex rounded to retuse; stamens numerous, 0.9–1.2 cm long; ovary glabrous. Capsule ovoid, 1.2–1.5 cm diameter, leathery, usually with a single seed. Flowering November to May, fruiting September to October (China). Ming & Bartholomew 2007. Distribution CHINA: Yunnan; VIETNAM. Habitat Forests and thickets, between (1200–)1600 and 2900(–3200) m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984; NT193. Taxonomic note Three varieties of C. forrestii are differentiated primarily on the basis of small differences in the shape and size of the sepals.

Camellia forrestii has been in cultivation for many years but has not achieved wide recognition, perhaps because it is rather tender, apparently surviving temperatures only down to –7 ºC (Gao et al. 2005). In the wild it is said to be a magnificent species, flowering profusely. The flowers are white and rather small but are produced in large numbers on each shoot to give this fine effect. The cluster-flowering habit is transmitted to its hybrids (Gao et al. 2005). It is cultivated in the milder parts of our area.

Plate 146. Camellia forrestii, a rather tender species. Image P. Williams.

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C. fraterna Hance B480, S133

Camellia furfuracea (Merr.) Cohen-Stuart Syn. C. oblata Hung T. Chang, C. parafurfuracea Liang ex Hung T. Chang, C. polypetala Hung T. Chang, C. suaveolens C.X. Ye, X.J. Wang & X.G. Shi Shrub or tree 2–7 m. Branchlets stout, greyish yellow to greyish brown, glabrous. Leaves leathery, 8–15 × 3–5.5 cm, elliptic to oblong, upper surface dark green, shiny, glabrous, lower surface pale green with brown glandular dots, 10 or more secondary veins on each side of the midrib, margins minutely serrate, apex acuminate; petiole 0.6–1 cm long, glabrous. Flowers axillary or subterminal, solitary or paired, 2–3.5 cm diameter, subsessile. Bracteoles/sepals 9–10, leathery, 0.2–1 cm long, yellow-tomentose; petals 7–10, white, obovate, 1.5– 2 cm long, apex rounded; stamens numerous, ~1.5 cm long; ovary tomentose. Capsule globose to subglobose, 2–4 cm diameter, greyish, with rough, flaky surface, splitting via three valves, each section holding two to five seeds, central column persistent. Flowering November to December, fruiting September to October of following year (China). Ming & Bartholomew 2007. Distribution CHINA: Fujian, Guangdong, Guangxi, Hainan, southern Hunan, southern Jiangxi; LAOS; TAIWAN; VIETNAM. Habitat Forest between 100 and 1000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984.

Plate 147. Most cultivated material of Camellia granthamiana derives from a solitary specimen growing in Hong Kong’s New Territory. Image J. Trehane.

For the curious-minded, the specific epithet furfuracea is derived from the Latin term furfuraceus, defined by W.T. Stearn (1983) as ‘scurfy, covered with bran-like scales or powder’ – as perhaps a tongue after a heavy drinking session might be, but in this case referring to the texture of the fruits, whose brown skin is rough and flaky. As a tree Camellia furfuracea can achieve 10 m and has handsome large leaves, but its flowers are small and inconspicuous. It is in cultivation in the United States, but its hardiness has yet to be fully assessed (Camellia Forest Nursery 2007–2008). As it is a relatively southern species, provenances should be selected with care.

Camellia granthamiana Sealy Syn. C. albogigas Hu Shrub or tree 3–9 m. Branchlets grey, pubescent. Leaves leathery, 7–11.5 × 3–4.5 cm, elliptic to oblong or obovate, upper surface dark green, shiny and rugose, glabrous, lower surface pale green with brown glandular dots and some hairs along the midrib, six to eight secondary veins on each side of the midrib, margins minutely serrate, apex acuminate to caudate; petiole 0.5–1 cm long, pubescent. Flowers axillary or subterminal, solitary, 10–14 cm diameter, subsessile. Bracteoles/sepals 12–17, persistent, grey-tomentose, outer bracteoles/sepals 0.4–0.8 cm long, inner bracteoles/sepals 3.5–4 cm long; petals 8–10, white, broadly obovate, 4.5–7 cm long, apex emarginate; stamens numerous, 2.5–3 cm long; ovary densely white-tomentose. Capsule subglobose, ~6 cm diameter, subtended by five persistent sepals, splitting via five valves. Flowering December to January, fruiting August to September of the following year (China). Ming & Bartholomew 2007. Distribution CHINA: eastern Guangdong. Habitat Forest between 100 and 300 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984, Trehane 2007; NT194. Cross-reference S133.

Camellia granthamiana was famously known for many years as a solitary specimen found growing in Hong Kong’s New Territory in 1955, and it is probably from this one tree that most, if not all, cultivated material is derived, although it has since been located elsewhere on mainland China. In addition to its curiosity value, C. granthamiana is a beautiful tree, with many fine horticultural qualities including good foliage and magnificent ‘fried-egg’ flowers. Its downside is that it is not very hardy and requires greenhouse

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cultivation in all except the mildest parts of our area (Hudson 2004, Gao et al. 2005). It succeeds in Cornish gardens such as Tregrehan, and is cultivated in southern California (for example, at the Huntington Botanical Garden). C. hongkongensis Seem. B482, K265 C. japonica L. B480, S134, K265 C. japonica subsp. rusticana (NOW C. japonica var. rusticana (Honda) T.L. Ming) B482, K265

Camellia kissii Wall. Syn. C. lutescens Dyer Shrub or tree 1.5–5(–13) m. Branchlets greyish brown, densely grey-pubescent. Leaves thin and leathery or rigidly leathery, 5–7 × 1.5–3.5 cm, oblong to elliptic, upper surface dark green and hairy along the midrib, lower surface pale green, sparsely hairy or glabrous, six to eight secondary veins on each side of the midrib, margins minutely serrate, apex acute, acuminate or caudate; petiole 0.3–0.7 cm long, densely pubescent. Flowers axillary, solitary or paired, subsessile. Bracteoles/sepals seven to nine, caducous, slightly pubescent to glabrous outside; petals five to eight, white, obovate to ovate, 0.8–1.5 cm long, apex emarginate; stamens numerous, 0.6–1 cm long; ovary white-tomentose. Capsule subglobose to globose or pyriform, 1.4–2.5 cm diameter, composed of a single segment with a single seed. Flowering November to December, fruiting September to October of the following year (China). Ming & Bartholomew 2007. Distribution BHUTAN; CAMBODIA; CHINA: Guangdong, Guangxi, Hainan, Yunnan; INDIA: Assam, Manipur, Nagaland, Sikkim; LAOS; MYANMAR; NEPAL; THAILAND; VIETNAM. Habitat Forest thickets between 300 and 2000(–3100) m asl. USDA Hardiness Zone 8–9 (?). Conservation status Not evaluated. Illustration Chang & Bartholomew 1984, Trehane 2007; NT195. Cross-reference S136.

The oil expressed from the seed of Camellia kissii, traditionally known as an emollient, is now used in a broad range of skin- and haircare products, and the plant is widely cultivated for this purpose. It is however of relatively little horticultural merit, its most interesting feature being the greenish tint in the white or creamy flowers. This can be transmitted to its hybrids: for example, ‘Buttermint’, which derives from a cross with C. sasanqua (Gao et al. 2005). It is in cultivation in specialist collections in Europe and North America.

Camellia lutchuensis Ito Syn. C. transnokoensis Hayata Shrub or tree 2–3(–6) m. Branchlets greyish brown with spreading pubescence, which lasts up to three years. Leaves thin and leathery, 2.5–4.5 × 1–1.8 cm, oblong to elliptic, upper surface bright green and sparsely pubescent along the midrib, lower surface pale green and sparsely pubescent along the midrib, six to eight secondary veins on each side of the midrib, margins minutely serrate, apex bluntly acute to acuminate; petiole 0.1–0.3 cm long, pubescent. Flowers subterminal, solitary, fragrant; pedicel 0.1–0.25 cm long. Bracteoles four to eight, 0.05–0.2 cm long, glabrous; sepals five, ovate to lanceolate, glabrous; petals five to six, white, obovate, 1–1.5 cm long, apex emarginate; stamens numerous, (0.5–)1–1.2 cm long. Capsule subglobose, ~1 cm diameter, usually with a single seed. Flowering January to March, fruiting September to October (China). Ming & Bartholomew 2007. Distribution CHINA: southern Guangxi, Hong Kong; JAPAN: Ryukyu Is.; TAIWAN. Habitat Forests and thickets, between (< 100–)400 and 1300(–2400) m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Trehane 2007; NT195. Cross-reference S137.

Plate 148 (above, top). The flowers of Camellia kissii are small but freely produced during the winter months. Image J. Grimshaw. Plate 149 (above). The flowers of Camellia lutchuensis are fragrant; in consequence it is in demand as a parent for breeding hardier, fragrant camellias. Image J. Trehane.

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Camellia

New Trees

Taxonomic note Camellia lutchuensis var. minutiflora (Hung T. Chang) T.L. Ming has lanceolate leaves, and small flowers with four to five bracteoles and petals 0.6–0.8 cm long. Typical C. lutchuensis occurs in Japan and Taiwan, while var. minutiflora occurs in Guangxi and Hong Kong.

As traditionally understood, Camellia lutchuensis occurs in the Ryukyu Islands of Japan, and is a small tree producing masses of pure white, fragrant flowers (Gao et al. 2005). As such it is a very desirable breeding plant, because although it is itself rather tender and its flowers are small, their abundance and fragrance are passed to the next generation while the hardiness of the other parent (especially C. japonica) is also inherited by the offspring (Gao et al. 2005). The inclusion in C. lutchuensis of the Taiwanese C. transnokoensis Hayata, and the mainland Chinese C. minutiflora Hung T. Chang (as C. lutchuensis var. minutiflora (Hung T. Chang) T.L. Ming) blurs this picture, but all are beautiful shrubs or small trees for the garden. Trehane (2007) recognises them all as distinct species. They have red tips on the outer petals, and although quite small the flowers are very fragrant, making these appealing garden plants. Generally considered tender and suitable only for the mildest locations in the United Kingdom (Trehane Nursery 2007), C. transnokoensis is nevertheless proving reasonably hardy in Zone 7b conditions in North Carolina (Camellia Forest Nursery 2007–2008). All taxa have attractive elegant leaves and growth habits. C. maliflora Lindl. B482 C. oleifera Abel B483, S136, K265 C. pitardii Cohen-Stuart B484, S137

Camellia ptilophylla Hung T. Chang Syn. C. pubescens Hung T. Chang & C.X. Ye

Plate 150. Camellia yunnanensis (see opposite) flowers for a long period through the winter, making it useful for mild gardens. Image M. Foster.

Shrub or tree to 6 m. Branchlets greyish yellow, pubescent. Leaves leathery, (9–)12–21 × (3–)4–6 cm, oblong, upper surface dark green and glabrous, lower surface pale green and pubescent, particularly along the midrib, 8–10 secondary veins on each side of the midrib, margins minutely serrate, apex acuminate; petiole 0.8–1 cm long, densely pubescent. Flowers axillary or subterminal, solitary, 2.5–3 cm diameter; pedicel 0.5–0.7 cm long. Bracteoles three, caducous; sepals five to six, ovate to suborbicular, outer surfaces covered in silky hairs; petals five (to eight), white, broadly obovate, 1.5–1.8 cm long; stamens numerous, ~1 cm long; ovary densely yellowish grey-pubescent. Capsule globose or three-sided, 1.5–2 cm diameter, splitting via three valves, each segment with one to two seeds. Flowering December, fruiting September to October of the following year (China). Ming & Bartholomew 2007. Distribution CHINA: northern Guangdong, southern Hunan. Habitat Forests between 200 and 500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

Camellia ptilophylla is very closely allied to C. sinensis, differing principally in the dense pubescence on its young shoots. This gives rise to its local name ‘white hair tea’, and the new growth is used to prepare a high-quality tea (Gao et al. 2005). The flowers are white with a large mass of stamens in proportion to the petals, but are rather unexciting. Cultivation requirements would seem to be the same as for C. sinensis, which is given a hardiness rating of Zone 6b–7b by Camellia Forest Nursery. (This perhaps reflects the effect of hot summers in the southeastern United States, as such a rating seems extremely optimistic from the British viewpoint.)

C. reticulata Lindl. B483, S136, K265 C. rosaeflora Hook. B483, S136 C. saluenensis Stapf ex Bean B484, K266 C. sasanqua Thunb. B485, S137, K266

C. shensiensis (NOW C. grijsii Hance var. shensiensis (Hung T. Chang) T.L. Ming) S136 C. sinensis (L.) Kuntze B485, K266

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C. sinensis var. assamica (J.W. Mast.) Kitam. B486, K267 C. taliensis (W.W. Sm.) Melch. B486 C. tsaii Hu B486, K267 C. uraku Kitam. S137

Camellia ×vernalis (Makino) Makino Syn. C. ×hiemalis Nakai

Several Camellia species are known only from cultivation and do not have wild populations. These include C. maliflora, C. uraku and C. wabiske. The origins of these taxa are uncertain, but two additional cultivated species, often called C. vernalis and C. hiemalis, are probably best treated as more-or-less ancient hybrids, with C. japonica and C. sasanqua as parents. In addition, many of the cultivars of ‘true’ C. sasanqua may actually be products of C. sasanqua × C. japonica hybrids that backcrossed with the C. sasanqua parent (Parks et al. 1981). According to Chang & Bartholomew (1984), all hybrids with C. japonica and C. sasanqua as parents (including many C. sasanqua cultivars) should be united under the oldest applicable name, C. ×vernalis. Camellia ×vernalis differs from C. sasanqua in that it has glabrous branchlets and larger, shiny, glabrous leaves. As the specific epithet suggests, it flowers in spring, usually in March. Camellia sasanqua flowers from September to the beginning of January, with most flowers produced in November. Plants known as C. ×hiemalis are more reminiscent of C. japonica, but they have pink or white flowers with a pubescent ovary (Sealy 1958, Chang & Bartholomew 1984). Many very good garden plants belong to this group, and in milder areas will flower through the winter. C. wabiske (Makino) Kitam. S137 C. ×williamsii W.W. Sm. B487, S138, K267

Camellia yunnanensis (Pit. ex Diels) Cohen-Stuart Syn. C. acutiserrata Hung T. Chang, C. henryana Cohen-Stuart, C. scariosisepala Hung T. Chang Shrub or tree 1–5(–7.5) m. Branchlets pale brown to purplish brown, pubescent. Leaves thinly leathery, 4–6.5(–11.5) × 2–3.5(–4) cm, ovate to elliptic, upper surface dark green and hairy along the midrib, lower surface pale green and sparsely villous, five to nine secondary veins on each side of the midrib, margins minutely serrate, apex acute, acuminate or caudate; petiole 0.2–0.5 cm long, pubescent. Flowers axillary or subterminal, solitary, 3–5 cm diameter, subsessile. Bracteoles/sepals 9–11, persistent, greenish brown, largely glabrous; petals 7–12, white, broadly obovate to elliptic, 2–4(–5) cm long, apex rounded; stamens numerous, 1.5–2.5 cm long; ovary glabrous. Capsule subglobose to globose, purplish red to brown, 4–6 cm diameter, splitting via five valves, each segment with two to three seeds. Flowering November to March, fruiting August to October (China). Ming & Bartholomew 2007. Distribution CHINA: southwest Guizhou, southwest Sichuan, Yunnan. Habitat Forests between 1100 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Chang & Bartholomew 1984; NT196. Cross-reference K267.

Camellia yunnanensis is an interesting plant with much horticultural potential to explore – a ‘top class’ species according to Hudson (2004). Individuals produce their fine white flowers between autumn and spring and, if pollination is successful,

Plate 151. Camellia ×vernalis is a group of hybrids between C. sasanqua and C. japonica that have come to prominence recently, valued for their early flowering. This is ‘Dawn’. Image JC Raulston Arboretum.

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follow them with large pomegranate-like fruits hanging below the shoots. The foliage is relatively small and neat, giving the tree a dainty look. It is not common in our area but is cultivated in Cornwall and the Pacific Northwest, so should be considered moderately hardy.

CORNACEAE (formerly NYSSACEAE)

CAMPTOTHECA

Decne.

Happytrees There are two species of Camptotheca, and the genus is endemic to China. They are medium-sized deciduous trees with papery, oblong-ovate leaves. The inflorescences are terminal or axillary heads with three bracts. The flowers are 5-merous and pale green, with the stamens mounted on a disc. The fruits are dry, contain a single seed and are winged. They are clustered in globose heads and have a persistent, apical disc. Until recently, only a single species of Camptotheca (C. acuminata) was recognised. However, in 1997 a second species (C. lowreyana S.Y. Li) was described, having ovate-cordate leaves with six to eight pairs of lateral veins (Qin & Chamlong 2005). This is grown at research institutions in Texas, but is not known to be cultivated as an ornamental. A dwarf selection named ‘Katie’ is said to be more cold- and drought-tolerant (Stephen F. Austin State University 2001). Camptotheca lowreyana has become an important element in research efforts into the anti-cancer drugs derived from camptothecins, currently obtained principally from C. acuminata.

Camptotheca acuminata Decne.

Chinese Happytree, Cancer Tree

Tree to 20 m. Bark pale grey and deeply furrowed. Branchlets purplish, pubescent to glabrous. Leaves deciduous, 12–28 × 6–12 cm, oblong to elliptic or ovate, rarely orbicular, upper surface glabrous to slightly pubescent, lower surface largely glabrous, but with tufts of hair in the vein axils, (4–)8–11(–15) secondary veins on each side of the midvein, margins entire, apex acute; petiole 1.5–3 cm long, slightly pubescent. Inflorescences terminal and axillary, terminal heads hermaphrodite, lateral heads staminate only, 1.5–2 cm diameter, spherical and composed of two to nine flowers, with three triangular bracts. Flowers hermaphrodite or unisexual, corolla pale green, 5-merous and 0.2 cm long; conspicuous disc on the ovary. Fruit 2.5–3.5 × 0.5–0.7 cm, grey-brown and smooth, with thin wings; fruits fall from receptacle separately. Kubitzki 2004, Qin & Chamlong 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang. Habitat By streams and forest margins to 1000 m asl. Common in cultivation in China, particularly along roadsides. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Hudson 2004; NT199, NT200. Cross-reference K271.

Figure 21 (opposite). Camptotheca acuminata: inflorescence with some open flowers (A); habit with immature inflorescence (B); infructescence (C).

Of considerable interest for its anti-cancer properties, Camptotheca acuminata is also an attractive ornamental tree with much merit for the garden. A beautiful 15 m specimen in the Medicinal Garden at the US National Arboretum shows what it can do. This has four straight stems from the base, with silvery pale brown bark, bearing a canopy of short, horizontal branches and large glossy dark green leaves. The foliage emerges pink, and the fruit clusters are attractive in autumn (Hudson 2004), although its leaves turn only to a ‘sickly chartreuse green’ (R. Olsen, pers. comm.

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1 cm

1 cm

C

1 cm

A

B

200

Camptotheca

Plate 152. New growth of Camptotheca acuminata is strikingly coloured, but it needs a hot summer to ripen. Image N. Macer.

New Trees

2006). Assessments of a tree’s attractiveness are quite subjective: my (JMG) view of this tree, recorded above, as seen briefly in Washington DC, is at variance with that of the staff at the National Arboretum, where it is not a favourite species on account of its habit of dropping limbs and producing copious seedlings to be weeded out (R. Olsen, pers. comm. 2006). This slightly weedy tendency needs to be watched for. It seems that the first introduction of C. acuminata to western horticulture was made by A.N. Steward, of the College of Agriculture and Forestry, Nanjing University, Nanjing, China, who sent seed to the USDA Plant Introduction Station in Chico, California in 1934 (where it received the plant introduction number PI 13229). From here it was distributed to gardens in southern Californian and the southeastern states, and it has generally been regarded as a Zone 10 subtropical tree (R. Olsen, pers. comm. 2006). It is obviously tolerant of cooler conditions than that, but the hot humid summers of the East Coast are evidently to its liking. It is happy in southern Europe (there is a nice tree in the Botanical Garden (Orto Botanico), Padua, for example), but no successful specimens have been located in the United Kingdom or northern Europe. At Tregrehan it grew for several seasons in a warm but dry situation, but the annual shoots succumbed to winter weather and the plants eventually fizzled out without building up a larger stem that could perhaps have seen them through: a moister spot might have been a better choice (T. Hudson, pers. comm. 2006). According to Nick Macer (Pan Global Plants catalogue 2006), plants are tender when young but become hardier when mature.

BETULACEAE

CARPINUS

L.

Hornbeams, Musclewoods

Plate 153 (opposite). The long infructescences of Carpinus fangiana have resulted in it being called Monkeytail Hornbeam. It is one of the outstanding tree introductions of recent years. Image R. Hitchin.

Up to 41 species of Carpinus are recognised (Govaerts & Frodin 1998), though this may be an overestimate. Hornbeams are deciduous trees or shrubs with a mainly temperate northern hemisphere distribution. The bark is typically smooth or fissured with inconspicuous lenticels, often subtly ridged and furrowed. The trunk is often irregular and ‘lumpy’, the suggestion of bulging muscles under the bark skin giving rise to the American name ‘musclewood’. The trunk tends to fork low down to form a bushy tree with numerous major branches arising from near its base. The branches are often smooth and slightly grooved in the same muscular way as the trunk. Young shoots are frequently somewhat pendulous, but often straighten up in subsequent growth. Winter buds are ovoid and smooth, with multiple scales. The expanding leaves are initially plicate (folded), though they flatten somewhat later, and are arranged in two ranks. They are simple, petiolate and with either serrated or double-serrated margins. The leaves range from ovate to obovate, may be glabrous or tomentose and may be glandular. Carpinus is monoecious. The staminate inflorescences (catkins) are pendulous, solitary or in small racemes, and are formed the previous season, emerging with the leaves in spring. The pistillate inflorescences (also catkins) are solitary, more or less erect, and situated on short, lateral shoots (rarely terminal); unlike on the staminate catkins, the

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flowers and bracts are not congested. The bracts are rather large and foliose, and each subtends two flowers. The flowers are insignificant. The fruit is a nutlet with distinct, longitudinal ribs and no wings. However, in some species, the papery bracts partially enclose the seed, forming a wing-like structure (Furlow 1997, Li & Skvortsov 1999). A number of accounts have been published in the horticultural literature (Rushforth 1985, 1986b, Muir 1986, Wright 1986), together with a comprehensive key to the species (Rushforth 1987b). Commencing his survey of Carpinus, Keith Rushforth (1985) commented on its status as ‘a neglected genus’. This is still largely true today, perhaps because the plants’ beauties are subtle compared with the more obvious allure of more popular genera, but the connoisseur of elegance will find much to appreciate. With the exception of the familiar large C. betulus and its close relatives, most species are apparently small trees and suitable for planting as understorey specimens in open woodland, or as larger elements in a border of shrubs, but it may be that over time they too will become quite large. The basal branching means that they can become quite broad quite quickly, so that trees are often broader than they are tall. The lightly shaded space under such trees would be an ideal situation for cultivating summer-dormant bulbs. All Carpinus seem to be tolerant of a range of soil types, and are successful on calcareous and clay soils, but many recently introduced species seem to suffer badly from dry conditions, at least when young. Hardiness is not as well understood as it might be, and several species from apparently suitable provenances remain poorly represented in collections despite repeated introductions. Another danger comes from late frost damage to expanding shoots.

Plate 154. The simple elegance of many hornbeams is clearly visible in this view of Carpinus caroliniana subsp. virginiana. Image P. Banaszczak.

C. betulus L. B504, S143, K279 C. betulus var. angustifolia (Medwed.) Radde K279 C. betulus f. carpinizza (NOW C. betulus L.) B505 C. betulus var. carpinizza (NOW C. betulus L.) B505, K279 C. betulus f. quercifolia (NOW C. betulus ‘Quercifolia’) B506

Carpinus caroliniana Walter

American Hornbeam, Ironwood

This species was described by Bean (B506, S143) and Krüssmann (K279).

Carpinus caroliniana subsp. virginiana (Marshall) Furlow Subsp. virginiana has an ovate to elliptical leaf, 8–12 cm long, with a caudate or acuminate apex and brown glands on the lower surface. The secondary teeth on the margins are almost as long as the primary teeth. In contrast, the type has an oblong to ovate leaf, 3–8.5 cm long, with an acute or obtuse apex and no abaxial glands. The secondary teeth are small and blunt. Furlow 1997. Distribution CANADA: Ontario, Quebec; USA: from Maine and Michigan south to Georgia and west to eastern Oklahoma. Habitat In the understorey of deciduous forests in wet areas, between 0 and 300 m asl. USDA Hardiness Zone 3b. Conservation status Not evaluated. Illustration NT202. Taxonomic note The ranges of the two Northern American subspecies of C. caroliniana overlap, and hybrids with intermediate

Section II. Species Accounts

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features are common. The very similar species C. tropicalis (Donn. Sm.) Lundell occurs in tropical Central America and has been collected there (for example, by Allen Coombes in Veracruz, 1995), but is very tender.

American botanists seldom make a distinction between varieties of their native Carpinus caroliniana, which seems reasonable, but subsp. virginiana is the more northerly variant. It is an attractive multistemmed tree that forms a rounded, broad dome, with good yellow autumn colour rather earlier than C. betulus. There are identified specimens at Kew (6 m tall by 6 m wide since 1969) and the Arnold Arboretum, but in most collections the subspecies is not acknowledged.

Carpinus cordata Blume This species was described by Bean (B506) and Krüssmann (K280).

Carpinus cordata var. chinensis Franch. Var. chinensis differs from the type variety in that its branchlets, petioles and inflorescences are densely villous, rather than glabrous, and in this respect it resembles var. mollis (Rehder) W.C. Cheng ex Chun. It differs from the latter in that the veins on the lower leaf surface are sparsely pubescent rather than densely pubescent. Var. mollis is restricted to Gansu, Ningxia and Shaanxi, while the type variety is found in northeast China, Japan, Korea and eastern Russia. Li & Skvortsov 1999. Distribution CHINA: Anhui, southeast Gansu, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, southwest Shaanxi, Sichuan, Zhejiang. Habitat Montane forest between 700 and 2400 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Li & Skvortsov 1999; NT203. Cross-references B507, K280.

A brief note in Bean (1976a) suggests that Wilson introduced Carpinus cordata var. chinensis in 1901, but this introduction seems not to have become established. The plant’s reintroduction – so far successful – was achieved from the Kew-led 1999 expedition to Sichuan, under the numbers SICH 1775, 2023 and 2078. Later expeditions have also collected seed. The parent from which SICH 2078 was collected was a 9 m specimen growing at the edge of mixed secondary woodland in the Gwangwu Shan: the tree could become larger than this in good conditions. Seedlings from these collections have been distributed quite widely. The examples at Kew are still small but are attractive due to their large leaves with strong venation. At this age at least, dark brown dry leaves are retained on the twigs in winter. C. coreana (NOW C. turczaninowii var. coreana (Nakai) W. Lee, NT211) S145 C. eximia Nakai B507, K280 C. faginea Lindl. S143

Carpinus fangiana Hu

Monkeytail Hornbeam

Tree to 20 m. Bark dark grey to brown, smooth or rarely scaly. Branchlets purplish brown and glabrous. Leaves deciduous, 6–27 × 2.5–8 cm, ovate-lanceolate, upper surface glabrous, lower surface with minor pubescence on the veins and tufts of hair in the vein axils, 24–34 secondary veins on each side of the midvein, margins irregularly double-serrate, apex acuminate; petiole glabrous, 1.5 cm long. Monoecious; staminate inflorescences catkin-like and solitary, 5–12 cm long, bracts distinct, to 0.5 cm long; pistillate inflorescences catkin-like, solitary and pedunculate, oblong to cylindrical, to 45–50 × 3–4 cm, densely pubescent. Flowers inconspicuous; bracts densely imbricate, elliptic, papery, 1.8–2.5 × 1–1.2 cm, with five veins from base, margins serrated. Fruit a nutlet with longitudinal ribs. Flowering May to June, fruiting July to September (China). Rushforth 1986b, Li & Skvortsov 1999. Distribution CHINA: northern Guangxi, Guizhou, Sichuan, eastern Yunnan. Habitat Lower montane forest, in shady valleys between 900 and 2000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Li & Skvortsov 1999, Wharton et al. 2005; NT201. Cross-reference K280.

Plate 155. Carpinus cordata var. chinensis grown from SICH 2023 at Kew, showing the strongly veined leaves characteristic of many species in the genus. Image T. Kirkham.

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Carpinus fangiana is one of the most attractive of recently introduced trees and should be widely planted. It combines handsome ridged foliage (emerging purple-bronze) with large, pale, pendulous fruit clusters, and a tree in full fruit is a fine sight (Wharton et al. 2005). There is a beauty near the entrance to the David C. Lam Asian Garden in Vancouver; as with so many hornbeams grown in full sun, this one is at present broader than it is tall (approximately 6 m tall). It was grown (as were others in the same garden) from a Shanghai Botanic Garden collection (SBG 270) made in 1986 at 1100 m in northwestern Hunan, where the parents were growing in mixed forest in an open rocky area. Peter Wharton (pers. comm. 2006) noted that it enjoys a slightly higher pH as a result of mulching with mushroom compost containing lime. This provenance seems to have given rise to much more amenable plants than those from Sichuan introduced by the Sichuan Expedition of 1991 (SICH 842), from 10 m trees growing at 2130 m on the Erlang Shan. Just one of these survives at Kew, only 2.5 m tall and rather narrow in width in 2006, and showing signs of stress from the hot, dry summer conditions of that year. Accessions from the 1986 Shanghai Botanic Garden collection are equal front-runners for the title ‘first in British cultivation’ with plants from that of Mikinori Ogisu (Ogisu 91103), made at Leibo in southwestern Sichuan in the same year and credited by Hillier & Coombes (2002) as the first introduction to the United Kingdom. The finest specimen of this Ogisu collection is in Roy Lancaster’s garden; planted as a seedling in 1992, it is now 4.5 m tall there and fruiting, its long fruiting spikes resembling ‘pale green lemur tails’ (R. Lancaster, pers. comm. 2006). There is a still-small specimen (1.8 m) from the same collection at the Hillier Gardens, and it is also grown in several private gardens and available from UK nurseries. It is tempting to think of C. fangiana as a small tree, but Peter Wharton (pers. comm. 2006) reported seeing individuals in Sichuan of over 20 m, ‘with colossal girths’.

Carpinus fargesiana H. Winkl. Tree to 20 m. Bark grey. Branchlets dark brown to grey and pubescent. Leaves deciduous, 2.5–7.5 × 2–2.5 cm, shape extremely variable, ovate to oblong to lanceolate, upper surface glabrous (slightly villous when young), lower surface veins villous, tufts of hair present in the vein axils, 12–16 secondary veins on each side of the midvein, margins irregularly double-serrate, teeth mucronate, apex acute to acuminate; petiole somewhat villous, 0.6–1 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 4–7 × 2.5–3 cm, villous. Flowers inconspicuous; bracts imbricate, ovate, papery, 1.3–1.5 × 0.6–0.8 cm, with five veins, margins irregularly serrate or lobed. Fruit a nutlet with longitudinal ribs. Flowering May to June, fruiting July to September (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: southern Gansu, western Hebei, western Henan, southern Shaanxi, Sichuan. Habitat Lower montane forest, in shady valleys between 1000 and 2600 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Cross-reference K280.

Notes made (JMG) on this species at Howick in 2005 use the word ‘elegant’ twice, and the same epithet was applied, in 2006, in notes on the specimen at Kew. The individuals observed are in both cases young, the Howick plants (4 m tall in 2005) having been grown from Shanghai Botanic Garden seed (SBG 93/24), while the one at Kew (3 m in 2006) is from SICH 2058. This was collected in 1999 at 1745 m in the Gwangwu Shan, Sichuan, from trees surviving amidst a failed conifer plantation. Both specimens have a single main stem with spreading branches and weeping branchlets, bearing pointed mid-green leaves. The 10 m tree noted by Rushforth (1985) at Kew has disappeared. At Rogów Arboretum trees from Emei Shan are not fully hardy (P. Banaszczak, pers. comm. 2007).

Section II. Species Accounts

Carpinus henryana (H. Winkl.) H. Winkl. This species was described by Bean (B507, S145) and Krüssmann (K280).

Carpinus henryana var. simplicidentata (Hu) Rushforth Var. simplicidentata differs from var. henryana in that its leaves are basically ovate, 2–3.5 × 1–3 cm, with mucronate, serrate margins. The leaves of the type variety are basically lanceolate, 5–8 × 2–3 cm, with serrated margins. Rushforth 1985. Distribution CHINA: eastern Gansu, western Hubei, southern Shaanxi. Habitat Temperate forest between 800 and 2100 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Taxonomic note This variety is not maintained by Flora of China.

As seen at Kew and the JC Raulston Arboretum, this taxon makes a small, upright and apparently fast-growing tree (at the JC Raulston Arboretum, 5.5 m since 1998 when the tree was obtained from Heronswood Nursery; at Kew, 4.5 m since 1999). The leaves are small and neat, emerging bronzed, with a glossy band in the centre of each inter-veinal section caused by the presence of a strip of appressed hairs. This, together with the strong venation, gives the leaf a very attractive look. The tree at Kew was grown by Lord Howick from seed supplied in 1995 from Tianshui in Gansu by the Qingpu Paradise Horticultural Company (possibly a short-lived commercial enterprise of the Shanghai Botanic Garden); there are others from the same source at Howick. Carpinus henryana var. simplicidentata has been hardy at Rogów since 1997 (P. Banaszczak, pers. comm. 2007). C. japonica Blume B507, S144, K280

Carpinus kawakamii Hayata Tree to 9 m. Bark dark grey. Branchlets brown, glabrous or somewhat pubescent. Leaves deciduous, 4–5 × 1.8–2.5 cm, ovate to lanceolate, upper surface glabrous (slightly villous when young), lower surface veins villous, 10–15 secondary veins on each side of the midvein, margins double-serrate to single-serrate, apex caudate to acuminate; petiole somewhat pubescent, 0.8–1.5 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 4–6 × 2–2.5 cm, densely pubescent. Flowers inconspicuous; bracts imbricate, elliptic, papery, 1.8–2 × 0.5 cm, with five veins, margins coarsely dentate. Fruit a nutlet with six longitudinal ribs. Flowering May to June, fruiting July to August (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: Fujian; TAIWAN. Habitat Open areas with subtropical forest, between 500 and 2000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated.

Rushforth (1985) mentioned that young trees of this species were in cultivation at Kew and the Hillier Gardens, but these individuals have died and been replaced, in both collections, by much later introductions. The Kew specimens came as seed from the Taipei Botanic Garden and the Taiwan Forestry Research Institute in 1998, while those at Hillier were from ETE 156, gathered in 1993 (this is not represented in the Edinburgh collection). The plants at Kew have already reached 5 m, with multiple erect stems from shortly above the ground. The pointed leaves are held stiffly in an attractive herringbone pattern, and are mid-green with a slight gloss at maturity, flushing bronze; there is a strong resemblance to Tilia kiusiana. These trees were still in perfect green leaf in mid-December 2006. Tom Hudson (pers. comm. 2005) has found that there is considerable variation in the size of leaves in seedlings raised from seed from the Taiwan Forestry Research Institute. From the same source are derived several specimens at Quarryhill, received in 2002 as seed collected at 1860 m in Taichung County, Taiwan, and planted out in 2003–2004. These are already 2–4 m tall, again with a sharply upright habit and multiple stems, and orderly branching (H.

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Higson, pers. comm. 2006). Collections of this or a closely related taxon have been commercially distributed from Heronswood Nursery and Crûg Farm as Carpinus aff. kawakamii, from BSWJ 3404. C. laxiflora (Siebold & Zucc.) Blume B508, K280 C. laxiflora var. macrostachya (NOW C. viminea Wall. ex Lindl., NT212) B509, S144, K282

Carpinus londoniana H. Winkl. Tree to 13 m. Bark dark grey to white. Branchlets black-brown, densely pubescent and pendulous. Leaves deciduous, 6–12 × 1.7–5 cm, primarily lanceolate, upper surface glabrous, lower surface with tufts of hair in the axils of veins, 11–13 secondary veins on each side of the midvein, margins irregularly double-serrate with mucronate tips, apex caudate to acuminate; petiole densely pubescent, 0.4–0.7 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 0.8–1 cm long, glabrous. Flowers inconspicuous; bracts loosely imbricate, with three to five veins, three-lobed, 2.5–3 × 0.7–0.8 cm. Fruit a nutlet with yellow resin and longitudinal ribs. Flowering April to June, fruiting July to August (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: southern Anhui, Fujian, northern Guangdong, Guangxi, southeast Guizhou, Hunan, Jiangxi, south central Sichuan, southern Yunnan, Zhejiang; LAOS; MYANMAR: southeast; THAILAND: north; VIETNAM: north. Habitat Subtropical and montane forests between 300 and 1800 m asl. USDA Hardiness Zone 9(–10). Conservation status Not evaluated. Illustration Li & Skvortsov 1999, Hudson 2004.

Plate 156. The dainty leaves of Carpinus monbeigiana, growing at the Rogów Arboretum, Poland. Image P. Banaszczak.

This southern species is extremely rare in cultivation and no living specimens have been traced in the northern hemisphere, although it is established in New Zealand. Specimens planted at Wakehurst Place and at Tregrehan did not survive for long. It has been described as a very ornamental tree for a sheltered position, and praised for its attractive pink and red-tinted new growth (Hudson 2004). The Wakehurst plant was cut to the ground each winter, however, and was removed to make way for something more rewarding (Kew records).

Carpinus monbeigiana Hand.-Mazz. Tree to 16 m. Bark grey. Branchlets dark greyish brown, initially pubescent, though gradually becoming glabrous. Leaves deciduous, 5–10 × 2.5–4 cm, primarily lanceolate, rarely elliptic, upper surface villous along the midrib, lower surface with tufts of hair in the axils of veins and villous on the vein surface, 14–18 secondary veins on each side of the midvein, margins irregularly double-serrate with mucronate tips, apex acute, acuminate or caudate; petiole with dense yellow pubescence, to 1 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkinlike, pedunculate, 5–8 × 2–2.5 cm, with dense, yellow pubescence. Flowers inconspicuous; bracts imbricate, 1.6–2 × 0.6–0.8 cm, with five veins, margins dentate, surface covered in yellow pubescence. Fruit a nutlet with brown or orange resin glands and prominent, longitudinal ribs. Flowering May to June, fruiting July to August (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: Xizang, Yunnan. Habitat Subtropical forest, sometimes on limestone, between 1700 and 2800 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Li & Skvortsov 1999; NT206.

Carpinus monbeigiana was apparently first introduced by a Sichuan Expedition team (Fliegner, Howick, McNamara & Staniforth), under the number SICH 1208. This seed was gathered at c.2460 m in Zhaojue County, Sichuan in October 1992, from a 5 m tree growing amongst rich broadleaf forest on a north-facing slope. Resultant seedlings at Kew have made small, rounded bushy trees up to 6 m

Section II. Species Accounts

Carpinus

tall, with multiple upright stems. The shoot tips weep attractively. At Quarryhill, where plants from the same collection have been placed in a hot site, the largest is now approximately 9 m tall, by 5.5 m wide, with multiple strong upright leaders, furnished with foliage to the ground (H. Higson, pers. comm. 2006). In the wild it was noted to turn yellow, but the leaves on the Kew trees were falling when merely a faded green in October 2006. It looks suitable for use as a lawn specimen, but the largest tree at Kew has had very severe squirrel damage. It is not fully hardy at Rogów, where trees are grown from a collection made at Chang-Hua, Zhejiang Province in 1987 (P. Banaszczak, pers. comm. 2007). Carpinus monbeigiana has also been collected and distributed in North America by Steve Hootman (SEH 1208).

Carpinus omeiensis Hu & W.P. Fang

Mount Omei Hornbeam

Tree to 7 m. Bark grey. Branchlets light brown, initially villous, though gradually becoming glabrous. Leaves deciduous, 6–8 × 2.5–3.5 cm, elliptic, upper surface largely glabrous, lower surface villous, with tufts of hair in the axils of veins, 12–16 secondary veins on each side of the midvein, margins serrate, apex acuminate; petiole with pale yellow pubescence, 0.5–0.8 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 6–8 × 1.5–2 cm, densely villous. Flowers inconspicuous; bracts imbricate and ovate, 1.5 × 0.5 cm, with four to five veins, margins slightly dentate. Fruit a nutlet with dense pubescence and prominent, longitudinal ribs. Flowering May to June, fruiting July to August (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: Guizhou, Sichuan. Habitat Deciduous forest between 1000 and 1900 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated.

Carpinus omeiensis seems to be extremely rare in cultivation, the only plant seen in research for the current work being at the JC Raulston Arboretum. Here it has made a very attractive tree of 2 m since it was planted in 2001. The branches and twigs are spreading, not pendulous, and bear beautiful small leaves with deep veins and the central appressed pubescence that causes them to shine in strips between the veins. The main spring flush is purple, according to Dan Hinkley (Heronswood Nursery catalogue 2000), and in summer in North Carolina the new leaves are red, but then fade to mid-green. In 1985 Rushforth described his collection KR 280 from Emei Shan as a hardy and attractive tree, although he was not at that time sure of its identification. He now (pers. comm. 2006) believes it to be C. omeiensis, and reports that it is 3–4 m tall in his wood in north Devon. In this specimen the young leaves are a rich coppery red on their undersides, fading as they mature. C. orientalis Mill. B509, S144, K282

Carpinus polyneura Franch. Tree to 15 m. Bark grey. Branchlets purple with sparse, white pubescence or glabrous. Leaves deciduous, 4–8 × 1.5–2.5 cm, primarily lanceolate, upper surface with dense pubescence along the midrib, lower surface villous along the veins and with tufts of hair in the axils of the veins, 16–20 secondary veins on each side of the midvein, margins regularly double-serrate, apex acuminate to caudate; petiole sparsely pubescent or not, 0.5–1 cm long. Monoecious; staminate inflorescences catkin-like, solitary, 1 cm long; pistillate inflorescences catkin-like, pedunculate, 3–6 × 1–2 cm, sparsely pubescent. Flowers inconspicuous; bracts imbricate and ovate, 0.8–1.5 × 0.5 cm, with five veins, margins slightly dentate to entire. Fruit a nutlet with sparse pubescence and longitudinal ribs. Flowering May to June, fruiting July to September (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: Fujian, northern Guandong, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, northeast Sichuan, Zhejiang. Habitat Subtropical forest or scrub between 400 and 2300 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Li & Skvortsov 1999. Cross-reference K282. Taxonomic note Has formerly been confused with C. turczaninowii var. ovalifolia.

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1 cm

1 cm

Section II. Species Accounts

Carpinus polyneura is another exceptional tree new to cultivation, although it remains rare. As a young plant it is often characterised by its slender appearance and long pendulous shoots, that strongly resemble the improbable trees of ‘willow pattern’ chinaware, but are rather more elegant. These long shoots are made more attractive by the red new leaves at their tips, the long, pointed leaves being also strongly veined. There is a nice 4 m specimen at Herkenrode, from a commercial source. At Kew a plant grown from Shanghai Botanic Garden seed originating in Sichuan in 1992 is 3 m tall, but has a denser habit than most. Koen Camelbeke (pers. comm. 2006) notes that C. polyneura is susceptible to drought, and that the leaves are late to fall.

Carpinus pubescens Burkill Tree to 17 m. Bark grey-brown. Branchlets dark brown, villous or glabrous. Leaves deciduous, 5–10 × 2–3.5 cm, shape extremely variable, from oblong to elliptic, upper surface glabrous, lower surface villous along the veins and with tufts of hair in the axils of the veins, 12–14 secondary veins on each side of the midvein, margins double-serrate, teeth minute and regular, apex acuminate; petiole sparsely pubescent or not, 0.4–1.5 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 5–7 × 1–2.5 cm, sparsely villous or glabrous. Flowers inconspicuous; bracts imbricate and ovate, 1–2.5 cm long, with five veins, margins slightly dentate to entire. Fruit a nutlet with dense pubescence (rarely glabrous) and prominent, longitudinal ribs. Flowering May to June, fruiting July to September (China). Rushforth 1985, Li & Skvortsov 1999. Distribution CHINA: Guizhou, Shaanxi, southern Sichuan, eastern Yunnan; VIETNAM: north. Habitat Montane forest and scrub on limestone, between 450 and 2000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Li & Skvortsov 1999. Taxonomic note This variable species incorporates at least 14 species named by H.H. Hu, discounted by Flora of China (q.v. for list).

This widespread tree has been collected on numerous occasions in recent years, possibly the first introduction being from Roy Lancaster’s 1980 gathering (L 654) from c. 2000 m in the Western Hills near Kunming (Rushforth 1985, Lancaster 1989). A seedling from this collection reached 3 m in 10 years, but failed to re-establish after transplantation (R. Lancaster, pers. comm. 2006). Lancaster (1989) notes that the young growth is a good coppery red, and Hudson (2004) mentions that the mature tree has a pleasing weeping habit. Despite these attractions and apparently suitable provenances, however, C. pubescens is rare in collections, the only ones seen for this work being at Howick where the largest is about 3.5 m. These individuals, originating from Yunnan via James Russell, showed some signs of damage after the long winter of 2005–2006 (C. Howick, pers. comm. 2006).

Carpinus rankanensis Hayata Tree to 10 m. Bark dark grey. Branchlets brown and glabrous. Leaves deciduous, 8–10 × 3–4 cm, oblong to elliptic, upper surface glabrous, lower surface villous along the veins, 20–25 secondary veins on each side of the midvein, margins irregularly double-serrate, apex acuminate; petiole glabrous, 0.5–1 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, terminal, pedunculate, 10–12 cm long, sparsely pubescent. Flowers inconspicuous; bracts densely imbricate, ovate to oblong, 0.7 × 1.3 cm, with three veins, margins slightly serrated. Fruit a nutlet with faint longitudinal ribs. Flowering May to June, fruiting July to October (Taiwan). Rushforth 1986b, Li & Skvortsov 1999. Distribution TAIWAN. Habitat Mixed forest between 1000 and 2000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT39, NT208, NT210.

The earliest introduction of this attractive species was apparently that made by Kirkham and Flanagan from their expedition to Taiwan in 1992 (ETOT 122), from a ravine full of choice plants at 1900 m on Taipingshan. Trees from this source are growing at Kew and Wakehurst Place and in private collections. The Kew tree is 3.5–4 m tall and

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Figure 22 (opposite). Carpinus rankanensis: habit with seed ‘cones’ and detail of leaf underside.

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New Trees

approximately 2–3 m broad. The species was also gathered by the Edinburgh Taiwan Expedition in 1993 (ETE 131), and a plant of this origin is now 3 m tall and growing well at Inverleith. In late October 2006 both these specimens were reported to be in full green leaf, with no sign of change to autumn colour (R. Bayton, J. Latta, pers. comms.); when observed again in December the Kew specimen was only just turning yellow. The leaves of C. rankanensis are very strongly veined, giving a corrugated effect, and are tinged red when young. With its elongate infructescences it is well worth cultivating (Hudson 2004), but is perhaps not quite in the same rank as C. fangiana. The new shoots are flushed red at their tips. Plate 157. Carpinus rankanensis has done very well in cultivation at Kew, as pictured here, from seeds collected from the tree seen in Plate 53 (p. 39) (ETOT 122). Image T. Kirkham.

Carpinus ×schuschaensis H. Winkl. This tree is sometimes recognised as a distinct species, though it is probably a hybrid between C. betulus L. and C. orientalis Mill. (Govaerts & Frodin 1998). Tree to 15 m (?). Branchlets reddish brown and pubescent. Leaves deciduous, 5–7 cm, ovate, upper surface glabrous, lower surface pubescent, 10–14 secondary veins on each side of the midvein, margins irregularly double-serrate, apex acuminate; petiole pubescent, 0.6–1 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like. Flowers inconspicuous; bracts imbricate, triangular, 2–3 × 1–1.5 cm, margins double-serrate. Fruit a nutlet with longitudinal ribs. Flowering March to April, fruiting June to July (Iran). Bobrov 1970. Distribution AZERBAIJAN; IRAN. USDA Hardiness Zone 7. Conservation status Not evaluated.

The best-known specimens of this hybrid in cultivation are at the Sir Harold Hillier Gardens, two of which were grown from seed collected by Roy Lancaster and Ann Ala (Lancaster & Ala 5) in 1972, now fine vigorous trees of 9–10 m. The habit is described as ‘upright’ by Hillier & Coombes (2002). Carpinus ×schuschaensis is available in the nursery trade in continental Europe, the United Kingdom and the United States.

Carpinus shensiensis Hu Tree to 15 m. Bark dark grey. Branchlets purplish brown, pubescent when young. Leaves deciduous, 6–9 × 3–4.5 cm, oblong to obovate, upper surface glabrous, lower surface sparsely pubescent along veins and with tufts of hair in axils of veins, 14–16 secondary veins on each side of the midvein, margins double-serrate, teeth minute and irregular, apex acute or acuminate; petiole densely pubescent, 0.7–1.7 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 7–9 × 4–4.5 cm, densely pubescent, with a few long hairs. Flowers inconspicuous; bracts imbricate, ovate, 2.5–3 × 1–1.2 cm, with four to five reticulate veins, margins irregularly dentate. Fruit a nutlet with prominent, longitudinal ribs. Flowering May to June, fruiting July to August (China). Rushforth 1986b, Li & Skvortsov 1999. Distribution CHINA: southern Gansu, southern Shaanxi. Habitat Temperate, deciduous forest between 800 and 1000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Li & Skvortsov 1999.

Seed of Carpinus shensiensis was probably first introduced to the West by Roy Lancaster through his contacts with the Shanghai Botanic Garden, in 1982. This material was collected on the Qin Ling Shan in southern Shaanxi, and specimens from it are growing at Wakehurst Place and at the Hillier Gardens, where it is 6 m tall. Other introductions followed, and it is now available commercially from several sources in Europe. Numerous branches from low on the trunk give it a broad, rounded outline, at least when young. The narrow leaves flush red in spring and change to pinkish shades in autumn (Mallet Court Nursery catalogue 2006). C. tschonoskii Maxim. B509, S145, K282

Section II. Species Accounts

Carpinus

211

Carpinus turczaninowii Hance This species was described by Bean (B510, S145) and Krüssmann (K282).

Carpinus turczaninowii var. coreana (Nakai) W. Lee Syn. C. coreana Nakai Large shrub or small tree to 7 m, dbh 0.5 m; crown densely branched. Bark smooth, pale brown or grey; branches pendulous. Branchlets reddish brown and pubescent with scattered lenticels. Leaves deciduous, 2–5 × 1.5–4 cm, ovate to elliptic, glossy green, lower surface with pubescence on the veins, (7–)10–12 secondary veins on each side of the midvein, apex bluntly acute. Pistillate inflorescences catkin-like, solitary and pedunculate, oblong to cylindrical, 2–7 × 1–3 cm long, glabrous. Flowers inconspicuous; bracts densely imbricate, elliptic, papery, 1.2–1.6 cm long, with four to six veins from base, margins double-serrated. Fruit a nutlet with longitudinal ribs. Fruiting July (Korea). Nakai 1926, Rushforth 1985. Distribution NORTH KOREA; SOUTH KOREA. Habitat Woodland and scrub on slopes and steep rock faces, between 0 and 90 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT211.

Many specimens of Carpinus turczaninowii var. coreana (usually labelled C. coreana) are rather dumpy, low-mounding trees, much broader than wide: a garden designer could have fun using them to suggest a stand of mushrooms. A good example of this habit is to be seen on a tree of 2.3 m height but 4 m wide growing near the Waterlily House at Kew, from a Chollipo Arboretum collection originating on Taebangi Island, Korea, received in 1981. The oldest specimen at Kew dates from 1979; collected on Mount Jiri, Korea, by Kwanak Arboretum, this one is similarly shaped though slightly less tidy. At the Scott Arboretum there is a specimen of 2 m height but 6 m diameter. Such trees tend to have a short length of clear trunk and then a mass of heavy radiating branches. The first recorded introduction was made by Sir Harold Hillier and Carl Miller (M&H 35) in 1976, of which one specimen survives at the Hillier Gardens (A. Coombes, pers. comm. 2008). A totally different habit is seen in other specimens, and although these have many shared characteristics with the dumpier trees, including dainty, glossy leaves and foliose bracts, they have an altogether more upright posture and make the link with C. turczaninowii more apparent. A group of such trees at the Morris Arboretum is attractive, despite growing in compacted ground (A. Aiello, pers. comm. 2006), and these individuals are now 6 m tall with a somewhat pendulous shape. They turn a good yellow in autumn (A. Aiello, pers. comm. 2006). These trees were grown from a collection made by the American expedition to northwestern Korea in 1984 (NW KNW 340), on Taechong Island, where the parents were 5–7 m tall. A similar taller specimen at Kew is labelled C. coreana var. major, although no such epithet has been published. It was collected as seed by the Kirkham, Flanagan and Boyce Expedition to Korea (KFBX 123) in 1989, from parents 8 m tall growing at an altitude of 8 m asl on Namhae Island. This plant is currently 4 m tall by 5 m broad, but has an open centre (unlike the dense centres of the rounded form), and has been described by Tony Kirkham as ‘a scruffy, shrubby tree with an untidy habit’ (Flanagan & Kirkham 2005).

Plate 158. Carpinus turczaninowii var. coreana often forms a rather dumpy bush, as here at Kew. Image T. Kirkham.

212

Carpinus

New Trees

Carpinus turczaninowii var. ovalifolia H. Winkl. This variety is not listed by IPNI or by the World Checklist of Fagales (Govaerts & Frodin 1998). However, the name is used both by Bean (1976a: B510) and by Rushforth (1985) for a taxon from western China, and there is a tree at Kew thus labelled. Now rather gaunt, but with attractive grey bark, it was collected by Wilson (Wilson 4105) from the Min River valley, in 1910. Rushforth’s description of var. ovalifolia does not readily distinguish it from typical C. turczaninowii, nor from var. stipulata (H. Winkl.) H. Winkl. (= C. stipulata H. Winkl. in Flora of China), and the two varieties are probably best placed in synonymy.

Carpinus viminea Lindl. Syn. C. fargesii Franch., C. laxiflora var. macrostachya Oliv. Tree to 20 m. Bark dark grey. Branchlets brown and glabrous. Leaves deciduous, 6–11 × 3–5 cm, elliptic, oblong or lanceolate, upper surface glabrous, lower surface sparsely pubescent along the veins, sometimes with tufts of hair in the axils of the veins, 12–15 secondary veins on each side of the midvein, margins double-serrate, teeth mucronate or bristle-like, apex acute, acuminate or caudate; petiole sparsely pubescent or glabrous, 1–3 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, pedunculate, 5–15 × 2.5–3 cm, sparsely pubescent. Flowers inconspicuous; bracts imbricate, ovate to lanceolate, 1.5–3 cm long, with four veins, margins coarsely dentate. Fruit a nutlet with prominent, longitudinal ribs. Flowering April to June, fruiting July to September (China). Rushforth 1986b, Li & Skvortsov 1999. Distribution BANGLADESH; BHUTAN; CHINA: Anhui, Fujian, northern Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Xizang, Yunnan, Zhejiang; INDIA: Assam, Jammu & Kashmir, Sikkim; MYANMAR; NEPAL; NORTH KOREA; SOUTH KOREA; THAILAND; VIETNAM. Habitat Subtropical, broadleaved forest between 400 and 2000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Li & Skvortsov 1999; NT212, NT976. Taxonomic note Clarke (1988) suggested that the tree known to dendrologists as C. laxiflora var. macrostachya (see B509, S144, K282) should be included in C. viminea, and while describing C. viminea indicated that it was not in cultivation under this name. The inclusion of C. laxiflora var. macrostachya in the synonymy of C. viminea is now well accepted (for example, Govaerts & Frodin 1998, Li & Skvortsov 1999), but for clarification and to discuss new introductions a full description is given here.

Plate 159. Carpinus viminea fruiting in Roy Lancaster’s garden, Hampshire. Image R. Lancaster.

Carpinus viminea has a very wide range, but tends to be a species of lower altitudes, so provenances from high altitude in the northern part of its range should be sought. Most introductions have originated in China, including two specimens grown at Wakehurst Place since 1988, derived from Chinese botanical gardens seedlists. Another, from the 1986 Hangzhou Botanical Garden seed distribution, has done extremely well for Roy Lancaster in Hampshire, being now a shapely 6 m tree with a spreading crown of almost pendent shoots. Its foliage emerges bronze-purple or reddish in spring, and it has fruited every year since 2000 (R. Lancaster, pers. comm. 2006). There are several young specimens at Howick, collected in southern Hunan in 1996 (QPH 96/45). According to Charles Howick (pers. comm. 2005), these are probably at the limits of this species’ tolerance in the United Kingdom, and have been very slow-growing. When seen in June 2005 they formed low bushy plants and were just coming into leaf, with red tints on the new growth. Carpinus viminea has also recently been introduced from Nepal (HWJK 2413), where the parent tree was found at c. 1900 m in 2002: it was praised by Dan Hinkley for its coppery new growth and long fruits (Heronswood Nursery catalogue 2005). It would seem wise to give this, as also several other of the Asian hornbeams, a sheltered, warm site if they are to perform well.

Section II. Species Accounts

Carpodetus

213

ROUSSEACEAE (formerly CARPODETACEAE)

CARPODETUS

J.R. Forst. & G. Forst.

The two species of Carpodetus occur in New Zealand (C. serratus, described below) and in New Guinea and the Solomon Islands (C. arboreus Schltr.). They are small evergreen trees or shrubs with simple, alternate leaves. The leaves are serrated with glandular margins. The inflorescences are lax, terminal and axillary panicles. The flowers are hermaphrodite only or with hermaphrodite and female flowers on separate trees. The calyx is conical with (four to) five to six lobes; petals and stamens match the number of teeth. The fruit is a leathery, indehiscent berry with numerous small seeds (Allan 1961, van Royen 1983). The relationships of Carpodetus have long puzzled systematists. Modern DNA-based taxonomy places it in the small family Rousseaceae (Lundberg 2001, APG 2003), though previously it has at different times been included in the Escalloniaceae, the Grossulariaceae, the Saxifragaceae, and in its own family Carpodetaceae (together with the closely related genera Abrophyllum Hook. f. ex Benth. and Cuttsia F. Muell.).

Carpodetus serratus J.R. Forst. & G. Forst.

Marble Leaf, Putaputaweta

Shrub or tree to 10 m, dbh 0.3 m. Branchlets pubescent; in immature form, branchlets slender, interwoven and zigzag. Leaves evergreen; in immature form, leaves membranous, 1–3 × 1–2 cm, broad-ovate to broadelliptic to subcircular, margins irregularly lobed, petiole to 1 cm long, pubescent; in mature form, leaves thin and leathery, 4–6 × 2–3 cm, ovate to elliptic, yellow-mottled, four to six veins on each side of the midrib, margins finely serrate, apex acute to obtuse, petiole ~1 cm long. Inflorescences terminal and axillary; panicles to 5 cm long and wide. Flowers hermaphrodite or female (on separate plants), 0.5–0.6 cm diameter, 5–6-merous; calyx lobes ~0.1 cm long, triangular; petals white, ovate, 0.3–0.4 cm long. Fruit subglobose, 0.4–0.6 cm diameter, purplish black, with a distinct ring around the circumference. Flowering November to March, fruiting January to April (New Zealand). Allan 1961, Poole & Adams 1963, Salmon 1980. Distribution NEW ZEALAND: North Is., South Is., Stewart Is. Habitat Coastal to montane forests. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT213.

The Putaputaweta is notable for two features: its divaricating growth habit in juvenile specimens, and the extraordinary lizard-skin effect of its foliage coloration. The occurrence of divarication in the New Zealand woody flora is discussed elsewhere (see Elaeocarpus hookerianus, p. 319). In Carpodetus serratus it results in a dense bush of twiggy growth around the central stem, thickly covered in the small leaves. These are mottled in darker and lighter green, the darker coloration occurring around the veins and margins, leaving the central interveinal areas pale. The effect is rather reptilian, but also suggests a mineral deficiency, where none exists. This pattern persists in adult leaves, which are larger and have more pronounced marginal teeth, borne on more normal-looking branches. The abundant flowers, produced on mature trees, are white and give quite an attractive effect. Carpodetus serratus is well established in cultivation in the milder and maritime parts of our area. There is a good group at Logan, currently about 6 m tall, and similarly sized trees occur in Cornwall. It should certainly be tried elsewhere, given a sheltered growing position in moist, fertile soil.

Plate 160. The foliage of Carpodetus serratus always looks as if it has a nutrient deficiency, but this is its natural state. Image J. Grimshaw.

214

Carya

New Trees

CARYA

JUGLANDACEAE

Nutt.

Hickories, Pecans There are about 18 species of Carya, distributed in North America, Mexico and eastern Asia. Hickories are monoecious, deciduous trees or rarely shrubs. The bark is grey to brown and smooth with some fissures in young trees, becoming deeply furrowed or breaking into plates or strips in older trees. Bark is often of taxonomic significance in Carya – though usually absent from herbarium specimens. The terminal buds are naked or protected by valvate or imbricate scales. The leaves are imparipinnate with 3–17(–21) leaflets; the leaflet margins are serrate, the lower surfaces covered with glandular scales and non-glandular hairs. The inflorescences are terminal or axillary, on old or new growth; the staminate and pistillate flowers occur on separate spikes; the staminate spikes axillary, pendulous, in clusters of three at the base of new growth or rarely on old growth; the pistillate spikes terminal, erect, on new growth. The staminate flowers are subtended by a bract, with (usually) no sepals and no petals; stamens (2–)3–7(–10). The pistillate flowers are subtended by a bract that is fused to the ovary, with no sepals and no petals; stigmatic disk four-lobed. The fruiting spikes are erect; the fruit is a nut, enclosed in a dehiscent, four-valved husk; the nuts may be smooth or pitted (Elias 1972, Stone & Whittemore 1997, Lu et al. 1999). Carya is a genus under-represented in European and especially British collections, which at first sight seems odd considering the magnificence of hickory trees in the eastern United States (Flanagan 1987, Andrews 2007). Bean (1976a) blamed it on the difficulty of obtaining good specimens from nurseries, but the problem is at least as likely to be the comparatively cool summers experienced in maritime Europe. Like many other North American trees the hickories need a very hot, humid summer to flourish to their best potential. With the exception of C. tomentosa (in Cornwall), all the UK champion Carya trees are in southeastern England, where summer temperatures are greatest. Even if summer temperatures continue to rise, the difficulties and discouragements presented by transplantation make these poor ‘nurseryman’s’ trees, so they are only likely to be planted by those few enthusiasts prepared to grow their own trees from seed. This is equally true in North America, where not many replacement hickories are being planted, leading both Dirr (1998) and Sternberg (2004) to plead for more planting to be done. Bean’s recommendation to plant out as young as possible is very sound – preferably into a rich soil. It is curious that none of the Asian species seem to be in cultivation. Carya cathayensis Sarg. was grown at Kew in the 1980s (M. Flanagan, pers. comm. 2007) but has since been lost. The four Chinese species are all from low altitudes with southerly distributions. Of the Mexican taxa, C. ovata var. mexicana (Hemsl.) W.E. Manning and another unidentified species from Nuevo León are in cultivation at the University of California Botanical Garden in Berkeley. C. aquatica (F. Michx.) Nutt. B512, K283 C. ×brownii Sarg. K283 C. buckleyi (NOW C. texana Buckley) B513 C. buckleyi var. arkansana (NOW C. texana Buckley) B513

Section II. Species Accounts

Carya

215

C. carolinae-septentrionalis (NOW C. ovata (Mill.) K. Koch var. australis (Ashe) Little, NT215) S147 C. cathayensis Sarg. B515, K285 C. cordiformis (Wangenh.) K. Koch. B513, S146, K285 C. glabra (Mill.) Sweet B514, S147, K285 C. glabra var. megacarpa (Sarg.) Sarg. K285 C. illinoensis (Wangenh.) K. Koch B514, S147, K285 C. laciniosa (F. Michx.) G. Don B514, S147, K285 C. ×laneyi Sarg. B516, K285 C. ×lecontei Little K285 C. myristiciformis (F. Michx.) Nutt. B515, K285 C. ovalis (NOW C. glabra (Mill.) Sweet) B515, S147, K285

Carya ovata (Mill.) K. Koch

Shagbark Hickory, Shellbark Hickory

This species was described by Bean (B516, S147) and Krüssmann (K285), and was comprehensively reviewed by Andrews (2007).

Carya ovata var. australis (Ashe) Little

Carolina Hickory

Syn. C. carolinae-septentrionalis (Ashe) Engl. & Graebn. Var. australis has slender, glabrous branchlets that turn black when they fall. Terminal buds reddish brown to black and largely glabrous. Leaves 20–30 cm long; leaflets 4–19 × 1–6.5 cm. Staminate catkins to 6 cm long. Fruits 2.5–3 cm long and wide. In comparison, var. ovata has stout, hirsute branchlets that retain their colour when they fall. Terminal buds tan to dark brown and tomentose. Leaves 30–60 cm long; leaflets 6–26 × 3–14 cm. Staminate catkins to 13 cm long. Fruits 3.5–4 cm long and wide. Stone & Whittemore 1997, Schaarschmidt 2002. Distribution USA: Alabama, Georgia, Mississippi, North Carolina, South Carolina, Tennessee. Habitat Rocky hillsides, limestone outcrops and wet, low-lying areas between 200 and 1500 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated.

The Shagbark Hickory is one of the most magnificent of eastern American broadleaved trees, and the source of the famous hickory wood for handles and barbecues, as well as its nuts. The differences between its varieties are rather small and technical, and var. australis makes as good a tree as any other. It is occasionally found in American collections, including one very fine umbrageous specimen at the Morris Arboretum (labelled Carya carolinae-septentrionalis), planted by John Morris some time between 1887 and 1915. This tree is over 30 m in height, dbh 92 cm. A seedling from it is growing at Wakehurst Place. The bark swirls in longitudinal plates and fissures, and is in itself a complete justification for planting this species, never mind its other fine qualities such as turning gold in autumn. Carya ovata (s.l.) is one of the more satisfactory hickories in maritime Europe, and should be planted more.

Carya pallida (Ashe) Engl. & Graebn.

Sand Hickory

Tree to 29 m, to 1.2 m dbh. Bark dark grey, ridged, often deeply furrowed. Branchlets reddish brown, slender, glabrous or pubescent. Leaves deciduous, imparipinnate, 30–60 cm long; leaflets (five to) seven (to nine), ovate to obovate or elliptic, 2–15 × 1–6 cm, leathery, upper surface largely glabrous, lower surface silvery

Plate 161. Like most hickories, Carya pallida (see below) has bold handsome foliage. Image P. Banaszczak.

216

Carya

New Trees

tan, hirsute towards the base, often with stellate hairs and large scales, margins finely to coarsely serrate, apex acuminate; petiolules 0–0.1 cm long; rachis densely hirsute and scaly; petiole 3–10 cm long. Staminate spikes to 13 cm long, hirsute, scaly. Fruits tan to reddish brown, 3–4 × 2–3 cm, obovoid to globose, slightly compressed, splitting to the middle or base; nuts finely wrinkled. Stone & Whittemore 1997, Schaarschmidt 1999, 2002. Distribution USA: Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, North Carolina, South Carolina, Tennessee, Virginia. Habitat Dry woodland on well-drained sandy or rocky soils between 0 and 500 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT215. Cross-reference K287.

Despite its wide range through the eastern United States Carya pallida was recognised as distinct as late as 1896 and is afforded brief mention by Dirr (1998) and by Sternberg (2004), apparently only for the sake of completeness. This overlooked tree is seldom seen in collections in our area, whether in the United States or in Europe, but there is one at Wakehurst Place, grown from seed collected by Howick and Warner (WAHO 183) in Virginia in 1986, and it is also grown at Arboretum Bokrijk, Genk, Belgium (J. De Langhe, pers. comm. 2007). C. texana Buckley K287 C. tomentosa (Poir.) Nutt. B517, S148, K287

FAGACEAE

CASTANEA

Mill.

Chestnuts, Chinquapins

Plate 162. Castanea seguinii can become a substantial tree, but bears fruits from a young age. Image T. Kirkham.

There are eight species in the genus Castanea, found in North America, eastern Europe, central and eastern Asia. The Sweet Chestnut, C. sativa Mill., is naturalised in many parts of western Europe (Govaerts & Frodin 1998). Chestnuts are deciduous trees or shrubs with vertically furrowed bark. The terminal buds on branchlets are aborted; the axillary bud nearest the stem tip then develops and is enclosed in two outer scales. Chestnut stems can be identified in winter as their ‘terminal’ bud has an adjacent leaf scar. The leaves are spirally arranged, but twisted to appear as if in two ranks. They are thin and leathery, with unbranched secondary veins running in parallel; each vein terminates in a marginal tooth. Stipules are prominent in young growth, but soon fall. Castanea is monoecious; inflorescences may be staminate only or may bear both staminate and pistillate flowers (androgynous). The inflorescences are erect, catkin-like and often produced in profusion in the axils of the leaves on the edge of the canopy. The staminate flowers are small, cream and clustered in groups of one to three (to five). The pistillate flowers are borne on the lower part of androgynous catkins and are subtended by a symmetrical

Section II. Species Accounts

Castanea

cupule; the cupule is spiny and has two to four valves. The fruit is a nut and there are one to three in each cupule (Nixon 1997, Huang et al. 1999). The numerous qualities of Castanea sativa give this small genus a particular significance. On another point of interest, the ravages of chestnut blight in the American Chestnut C. dentata are an object lesson in the necessity for rigorous phytosanitary checks on newly imported plant material – and indeed led to the introduction of phytosanitary laws in the United States. Anagnostakis (1992, 2001) has documented that the disease was almost certainly imported into the United States on plants of the Japanese C. crenata, distributed through the horticultural trade. In the United States the Chinese C. mollissima is the usual substitute for the native species, and there is an active programme to breed resistant hybrids with a majority of C. dentata genes (Sternberg 2004). C. ×alabamensis (NOW C. ozarkensis Ashe) K291 C. alnifolia (NOW C. pumila (L.) Mill.) B528, K291 C. crenata Siebold & Zucc. B528, K291 C. dentata (Marshall) Borkh. B528, K291

Castanea seguinii Dode Syn. Castanea davidii Dode

C. henryi (Skan) Rehder & E.H. Wilson B529, S149, K291 C. mollissima Blume B529, S149, K291 C. ×neglecta Dode B530, K292 C. ozarkensis Ashe B530, K292 C. pumila (L.) Mill. B530, K292 C. sativa Mill. B531, S149, K292

Chinese Chinquapin, Chinese Dwarf Chestnut, Seguin’s Chestnut

Shrub or tree to 12 m. Leaves deciduous, 6–14 × 3–5(–7) cm, oblong or obovate to elliptic, upper surface glabrous, lower surface covered with yellowish brown scale-like glands and sparse hairs along the veins (when young), 10–15 secondary veins on each side of the midvein, margins coarsely serrate, apex long-acuminate; petiole 0.5–1.5 cm long; stipules lanceolate, 0.7–1.5 cm long, falling when in fruit. Staminate inflorescences catkin-like, 5–12 cm long. Pistillate flowers solitary or few per cupule; cupule 3–5 cm diameter, covered with spine-like bracts, 0.6–1 cm long. Nuts two to three, 1.5–2 cm diameter. Flowering May to July, fruiting September to November (China). Huang et al. 1999. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Yunnan, Zhejiang. Habitat Mixed mesophytic forest, thickets and orchards between 400 and 2000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Huang et al. 1999; NT216. Cross-references B530, K292.

Mentioned by Bean (1976a) as a relative of the American Castanea pumila (L.) Mill., C. seguinii has been cultivated at Kew since 1942, when a specimen was donated by Hillier & Sons. This specimen was 10.05 m in 1970 (Kew database), and is now 18.9 m tall (1.21 m dbh), with a spread of 18 m (T. Kirkham, pers. comm. 2007). It therefore slightly exceeds the recognised British champion at Borde Hill, West Sussex, 18 m tall from planting in 1930 (Johnson 2003). The comparatively small leaves give C. seguinii a neat appearance. They are arranged alternately on the shoots, diminishing in size upwards, giving a broad ‘herringbone’ appearance. This was particularly visible on a vigorous young plant seen at Thenford House in August 2006, when each axil had flowered in succession: the sequence of buds, inflorescences and developing fruits was beautifully regular in their increasing size. In cultivation this taxon will probably thrive best in the fertile, neutral to acidic loam favoured by most Castanea species. Given its southern Chinese origins it is probable that it enjoys a warm, wet summer in the wild, and in the United States it is said to

217

218

Castanea

New Trees

do best in the southeast (American Chestnut Cooperators Foundation 1997–2008). Castanea seguinii has been crossed with C. dentata and C. mollissima, and hybrid cultivars are grown in North America (Oikos Tree Crops 2007–2008).

FAGACEAE

CASTANOPSIS

(D. Don) Spach

Berangans, Indian Chestnuts

Plate 163. The prickly cupules of Castanopsis orthacantha are an effective deterrent against intruders – including seed-collectors. Image P. Wharton.

Plate 164. Castanopsis carlesii in Taiwan. Fruits of Castanopsis have similarities to those of both Quercus and Castanea. Image A. Coombes.

Castanopsis comprises 134 species in tropical and subtropical Asia and Malesia (Govaerts & Frodin 1998). They are evergreen trees with alternate, distichous (rarely spirally arranged) leaves. The terminal buds are ovate to ellipsoid with decussate scales. Stipules are extrapetiolar. Castanopsis is monoecious, and the inflorescences are usually unisexual; they are erect, spicate or paniculate. The staminate flowers are small and grouped in fascicles of three to seven (rarely solitary); the pistillate flowers are solitary or in clusters of three to five (to seven) per cupule. The cupule is solitary, radially or bilaterally symmetric, rarely indehiscent and partially or completely enclosing the fruit; it is covered in spiny or scaly bracts or tubercles. The fruit is a nut, one to three in each cupule; these typically mature after their second year (Huang et al. 1999). Bean (1976a) commented that the genus Castanopsis was hardly represented in British gardens – a statement that is still largely true for the whole of our area, as was further deplored by Peter Wharton (pers. comm. 2007). One clue to this scarcity may be found in a commment by Allen Coombes (pers. comm. 2007): ‘I actually hate collecting them because of the hours I have spent shredding my fingers trying to get the seeds out of spiny husks only to find they are mostly not ripe or already eaten by insects.’ With the exception of the Japanese species C. cuspidata and C. sieboldii, these broadleaved evergreens are essentially tropical or subtropical in origin; they can be thought of as tropical chestnuts, differing only slightly from Castanea (Mabberley 1997a), and the fruits are sometimes used as chestnut substitutes. They will need maximum shelter to succeed, preferably in a lime-free soil (Hillier & Coombes 2002), but when happy can grow extremely well and could become very large. A young plant of C. delavayi (described by Bean) at Tregrehan put on more than 8 m of growth in five years (T. Hudson, pers. comm. 2005); see also the account below of C. carlesii in Vancouver. In addition to the species described here, there are young plants of C. fargesii Franch. at Tregrehan, and C. platyacantha Rehder & E.H. Wilson was offered for sale by a UK nursery in 2006. Peter Wharton identified C. tibetana Hance as a particularly fine and probably hardy species that has not yet been introduced.

Castanopsis carlesii (Hemsl.) Hayata Tree to 20 m. Branchlets and inflorescences sparsely covered in ferruginous, waxy scale-like trichomes. Leaves leathery, 4–12 × 1–4.5 cm, lanceolate to ovate, upper surface glabrous, lower surface with layers of reddish or yellowish brown scale-like trichomes that turn silvery grey with age, 8–13 secondary veins on each side of the

Section II. Species Accounts

Castanopsis

219

midrib, margins entire or with a few shallow teeth, apex acute to narrowly caudate; petiole ~1 cm long, base somewhat swollen. Cupules subglobose to ovoid, 1–1.5 cm diameter, bracts tuberculate or spiny (when spiny, 0.1–0.2 cm long), outer surface covered in yellowish to reddish brown, felt-like pubescence and waxy trichomes. Nuts one per cupule, subglobose to broadly conical. Flowering March to June, fruiting September to November (China). Huang et al. 1999. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; TAIWAN. Habitat Mixed and broadleaved evergreen forest below 1700 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Huang et al. 1999; NT218.

In Taiwan Castanopsis carlesii is noted to be a large canopy tree in the broadleaved evergreen forest of the lower mountain slopes (Flanagan & Kirkham 2005), but it is too recent an introduction to be anything larger than a sapling in cultivation in the West. Its first recorded introduction seems to have been from a collection made by John L. Creech on a joint USDA–Longwood Gardens expedition to Taiwan in 1967 (Ani´sko 2006), but it is not known what became of this material. A straight young tree seen at the David C. Lam Asian Garden in 2004 was extremely elegant, suggesting Ficus benjamina L. in its neat leaves and pendulous shoot tips. The leaves are elongate and acuminate, flushed bronze when young, shiny mid-green with a ‘metallic’ sheen below when mature. In 2004 the tree in the Asian Garden was 3 m tall; in November 2006 Peter Wharton reported that it was still ‘growing like a train’ and had reached over 5 m. This specimen was received in 1998 from the Taiwanese Forestry Research Institute, as seed collected at 1985 m, at Herhuanchi. A young tree (planted in 2005) is growing at Kalmthout, Belgium (Jan De Langhe, pers. comm. 2007). C. chinensis (Spreng.) Hance K292 C. concolor (NOW C. orthacantha Franch., NT219) K293 C. cuspidata (Thunb.) Schottky B533, S150, K293 C. delavayi Franch. B534, K293

Castanopsis orthacantha Franch. Syn. C. concolor Rehder & E.H. Wilson Tree to 20 m. Branchlets glabrous. Leaves 7–14 × 2.5–5 cm, ovate, elliptic or lanceolate, leathery, largely glabrous, 9–13 secondary veins on each side of the midrib, margins entire or shallowly serrate, apex acute and bent; petiole ~1 cm long. Staminate inflorescences catkin-like. Pistillate inflorescences solitary with two to three flowers per cupule. Cupules subglobose, 3–3.5 cm diameter, covered in small brown waxy trichomes, splitting into four sections; bracts spine-like, ~0.7 cm long, united into four to six rings or bundles. Nuts one to three per cupule, 1–1.5 cm diameter. Flowering April to May, fruiting September to November of the following year (China). Huang et al. 1999. Distribution CHINA: western Guizhou, southwest Sichuan, Yunnan. Habitat Mixed evergreen and broadleaved forest between 1500 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Liao 1996a; NT218, NT219.

For decades the only recorded cultivated trees of this species were the two at Caerhays, Cornwall, grown from seed collected by George Forrest in Yunnan (F 26848 or F 24758, according to different authorities!). These were measured in 1984 by Alan Mitchell at 14 m (dbh 35 cm) and 15 m (dbh 30 cm), respectively (Johnson 2003), but only one pollarded specimen remains, standing at 5 m tall in 2006 (Johnson 2007). Recent collections have added to the cultivated gene pool, with one tree of KR 3874 planted in 2000 at Lamellen, Cornwall being 5 m tall in 2006 (Johnson 2007). A

Plate 165. A young tree of Castanopsis orthacantha in Guizhou. Image P. Wharton.

220

Castanopsis

New Trees

collection made by Peter Wharton (PW 82) at 1395 m in the Dashahe Cathaya Reserve in northern Guizhou in 1994 has resulted in very fine young trees at the David C. Lam Asian Garden in Vancouver, over 7 m tall and proving to be hardy and vigorous. These are quite likely to reach their potential 20 m (P. Wharton, pers. comm. 2007).

Castanopsis sclerophylla (Lindl. & Paxton) Schottky

Chinese Tanbark-oak

Syn. C. chinensis (Abel) Schottky, Lithocarpus chinensis (Abel) A. Camus Tree to 20 m. Branchlets reddish brown, somewhat angular. Leaves leathery, 7–15 × 2.5–5.5 cm, oblong or ovate to elliptic, upper surface silver-grey, lower surface velvety, with a silver bloom, 10–15 secondary veins on each side of the midrib, margins serrulate or entire, apex acuminate, cuspidate or caudate; petiole 1.5–2.5 cm long. Staminate inflorescences catkin-like, to 13 cm long and in upper leaf axils. Pistillate inflorescences solitary and to 15 cm long. Cupules globose, 1.2–1.5 cm diameter, yellowish brown and completely (or almost completely) surrounding the nut; bracts scale-like, three- or four-angled. Nuts one (to three) per cupule, 1–1.4 cm diameter. Flowering April to May, fruiting October to November (China). Huang et al. 1999. Distribution CHINA: Anhui, Fujian, Guangxi, northeast Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, eastern Sichuan, Zhejiang. Habitat Evergreen, broadleaved forest between 200 and 1000 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Huang et al. 1999; NT220.

Plate 166. Castanopsis sclerophylla has thick, leathery leaves. Image O. Johnson.

Castanopsis sclerophylla is probably better known under its synonyms, and in the United States has been distributed from botanic gardens and in the trade as Lithocarpus chinensis. It seems to have been introduced in the late nineteenth century by the USDA Plant Introduction facility, perhaps to its southern station located near Savannah, Georgia (now Coastal Gardens). There are old, mature trees in this area, which have attractive tan-white, flaky bark (T. Lasseigne, pers. comm. 2006). Northwards, in our area, it seems to be limited by winter temperatures below –14 ºC, and is unusual. The only one seen in the research for this book is at the JC Raulston Arboretum, received there in 1989 and now 7–8 m tall, although badly suppressed by heavy shade from above. Despite this it seems to grow vigorously, and the species is obviously capable of making a handsome evergreen tree. The leaves are glossy dark green above, pale with very fine hairs below giving a metallic look, and toothed only in the upper third. Young trees from seed collected in Wuyishan, Fujian in 2003 are flourishing in Vancouver, and took the –9 ºC and heavy snow of November 2006 in their stride (P. Wharton, pers. comm. 2007). There are young specimens in a few arboreta in Belgium (Kalmthout, Arboretum Waasland) and at Jardin botanique de la Roche Fauconnière, Cherbourg in France (Jan De Langhe, pers. comm. 2007). Although C. sclerophylla is offered at present by one UK nursery, as well as by several American nurseries and the international wholesale seed trade, no specimens have been seen in the British Isles – despite there being no apparent reason why it should not be cultivated here.

Castanopsis sieboldii (Makino) Hatus. Syn. C. cuspidata var. sieboldii (Makino) Nakai Tree to at least 22 m, forming a wide canopy. Branchlets glabrous. Leaves leathery, 5–10 × 2–3 cm, ovate, oblong or broadly lanceolate, upper surface glabrous and deep green, lower surface covered with greyish or reddish brown scales, 8–11 secondary veins on each side of the midrib, margins undulate to serrate, apex acute; petiole 0.5–2 cm long. Staminate inflorescences to 10 cm long, pubescent. Pistillate inflorescences stiff, spreading and to 8 cm long. Cupules subglobose, 0.8–1.5 cm diameter and almost completely

Section II. Species Accounts

Castanopsis

221

enclosing the nut; bracts scale-like, 0.3–0.5 cm, covered in soft grey pubescence. Nuts one per cupule, acute at apex, 1.5–1.8 cm long. Flowering March to April, fruiting October (Japan). Makino 1909, Walker 1976. Distribution JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; SOUTH KOREA. Habitat Evergreen, broadleaved forest, often dominated by C. sieboldii, between 200 and 2100 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT221. Taxonomic note This species is very closely related to C. cuspidata (also of Japan and Korea), and has been treated as a variety of it (C. cuspidata var. sieboldii (Makino) Nakai). However, C. sieboldii has a larger nut and a thicker leaf due to two layers of epidermis rather than one (Kobayashi et al. 1998, Yamada & Miyaura 2000). Castanopsis sieboldii occurs in the Nansei-shoto (Ryukyu) as var. lutchuensis (Koidz.) T. Yamaz. & Mashiba.

This taxon is widely if infrequently cultivated, usually under the name Castanopsis cuspidata var. sieboldii. It is not clear when it was first introduced, but several recent collections have been made, including one in 1987 by Warner and Howick (WH 888) and another in 1985 by a US National Arboretum expedition to Korea. The authors of the report on this latter expedition (Dudley & Yinger 1987) considered it to be a ‘potentially valuable evergreen landscape tree’, noting that it has metallic-coppery lower leaf surfaces – and that the majority of its acorns had been eaten by their collectors! A tree from this source is now 13 m tall at the David C. Lam Asian Garden, and has proved to be totally hardy. Unfortunately this was not known at the time of its planting and it was placed in shelter, which has resulted in it forming a drawnup specimen rather than the broad-crowned one it would have become had it been sited in the open (P. Wharton, pers. comm. 2007). Similarly, at Quarryhill, a tree from Warner & Howick’s 1987 collection (WH 888) on Oshima Island, Japan, planted in 1990 but somewhat crowded by other trees, is now 8 m on a single trunk, 10 cm dbh; the crown width is 4.5 m (H. Higson, pers. comm. 2006). At the Sir Harold Hillier Gardens there are another two specimens from WH 888 but these are growing very slowly (A. Coombes, pers. comm. 2007). The same collection is also represented at Howick. Coming from 15 m asl, material of this provenance may not be ideal for colder areas. When not too crowded, C. sieboldii can be expected to make a rounded, evergreen tree very similar to the comparatively familiar C. cuspidata. Several variegated clones have been selected in Japan (Hirose & Yokoi 1998), and at least one (the marginally variegated ‘Angyo Yellow’) is in cultivation in the United States.

Castanopsis wattii (King) A. Camus Tree to 15 m or more. Branchlets purplish brown, pubescent or glabrous. Leaves firm and papery, (7–)11–20 × 3–5 cm, ovate, lanceolate or narrowly oblong, 13–19 secondary veins on each side of the midrib, margins with two to five shallow teeth towards the apex, apex long-acuminate; petiole 0.8–1.5 cm long. Pistillate inflorescences to 20 cm long with three flowers per cupule. Cupules subglobose, 3 cm diameter and yellowish grey with small, reddish brown, waxy trichomes; bracts spine-like, 0.5–0.8 cm long, often connate into bundles. Nuts (one to) two to three per cupule, 2–2.5 × 1–1.5 cm, hairy. Flowering July to September, fruiting August to October of the following year (China). Huang et al. 1999. Distribution CHINA: southeast Xizang, western Yunnan; INDIA: Assam, Sikkim. Habitat Evergreen, broadleaved forest between 900 and 1700 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

Plate 167. Castanopsis sieboldii ‘Angyo Yellow’ is a handsome variegated cultivar of a useful evergreen tree. Image JC Raulston Arboretum.

222

Castanopsis

New Trees

Castanopsis wattii is known in cultivation only from a few seedlings grown from an Allen Coombes collection (Coombes 512) made in Yunnan between Manwan and Jing Dong, in evergreen woodland at 2040 m in 1998, from a tree about 15 m tall.

CASUARINACEAE

CASUARINA

L.

She-oaks, Horsetail Trees

Plate 168. Casuarina cunninghamiana is often planted as an ornamental or for timber production in the tropics (here at Goba, Ethiopia), but is showing surprising hardiness in southern Britain. Image J. Grimshaw.

Casuarina has 17 species, ranging from Myanmar through southeastern Asia to Australia and the Pacific islands. Their articulated stems are reminiscent of Equisetum L., resulting in the colloquial name ‘horsetail tree’. The name ‘she-oak’ refers to the supposed similarity of the wood to that of true oaks (Quercus), the wood of Casuarina being said however to be of inferior strength (Wilson & Johnson 1989). The morphology of Casuarina is very similar to that of Allocasuarina, but Casuarina ‘cones’ have bracteoles that extend well beyond the cone body and lack a dorsal protuberance. They have 5–20 teeth per whorl, and the samaras are grey or yellowish brown and dull. In addition, all Casuarina species are trees, and most are dioecious though a few are monoecious (Wilson & Johnson 1989, 1990, Xia et al. 1999). For further detail, see the description of Allocasuarina (p. 131). That it should seem feasible to attempt to grow Casuarina in our area is an indicator both of the warmer temperatures currently being experienced and also of the boldness of gardeners and dendrologists prepared to try to grow any species of tree that comes their way. While C. equisetifolia is a familiar tropical coastline species, Casuarina is by no means always littoral, and different species occupy a diversity of habitats ranging from riverside forest in damp alluvial soils to dry woodland on sand. Propagation is by seed, but cuttings are also an option. In all cases it is important to plant out the young trees as soon as possible to prevent root problems, and they will benefit from light feeding if planted in nutrient-poor soil (Elliot & Jones 1982). In addition to the two species described below, Johnson (2007) mentions that C. glauca Spreng. is grown in the grounds of Buckingham Palace, London. The other species he lists under Casuarina are referrable to Allocasuarina. The long-term persistence of any Casuarina in our area away from the San Francisco Bay Area, where several taxa are grown, may be open to question, but their rapid growth and curious appearance make them well worth the attempt if conditions seem reasonable.

Casuarina cunninghamiana Miq.

River Oak, River She-oak

Tree 15–35 m. Bark greyish brown, finely fissured and scaly. Branchlets drooping (vigorous specimens) or erect (meagre specimens), articles 0.4–0.9 cm long, usually glabrous; phyllichnia prominently angular, glabrous. Leaves tooth-like; teeth 8–10, erect on new shoots, 0.03–0.05 cm long, yellow at the base, usually withering in time. Monoecious; staminate inflorescences spicate, 0.4–4 cm long with 11–13 whorls per centimetre; pistillate

Section II. Species Accounts

Casuarina

inflorescences sparsely pubescent, 0.7–1.4 × 0.4–0.6 cm, bracteoles broadly acute. Flowers inconspicuous. Fruit a samara, 0.3–0.4 cm long. Wilson & Johnson 1989. Distribution AUSTRALIA: northeast Queensland to southeast New South Wales, including the Australian Capital Territory. Habitat Grows along permanent freshwater streams. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT222.

Owen Johnson (2007) reports on several trees of Casuarina cunninghamiana growing on the western fringes of Britain and Ireland, the largest of which is a 6 m (14 cm dbh) tree in Brynmill Park, Swansea, which has survived on the site of a demolished greenhouse – although said to be ‘of little ornament’. There are trees of 5 m at Trengwainton and Tregothnan in Cornwall, and it was ‘thriving’ when seen at Glasnevin in 2003 (Johnson 2007). In Florida it is regarded as a ‘Prohibited aquatic plant, Class 1’ (PLANTS Database 2008) for its rapidly self-sowing tendencies, but in its native Australia it is valued as an ornamental (Metro Trees 2007).

Casuarina equisetifolia L. Australian Pine, Coast She-oak, Horsetail Tree Large, erect tree to 35 m. Bark scaly, greyish brown to black. Branchlets lax and drooping, up to 30 cm long, articles 0.5–1.3 cm long, furrows densely pubescent; phyllichnia angular or rarely flat, glabrous. Leaves tooth-like; teeth (six to) seven to eight, erect or rarely spreading, 0.03–0.08 cm long. Monoecious; staminate inflorescences spicate, 0.7–4 cm long with 7–12 whorls per centimetre; pistillate inflorescences on lateral branchlets, 0.3–1.3 cm long; cone 1–2.4 × 0.9–1.3 cm, bracteoles acute. Flowers inconspicuous. Fruit a samara, 0.6–0.8 cm long and dull. Wilson & Johnson 1989. Distribution AUSTRALIA: northeast New South Wales, Queensland; FIJI; FRENCH POLYNESIA; INDIA; INDONESIA; MALAYSIA; MYANMAR; NEW CALEDONIA; PAPUA NEW GUINEA; PHILIPPINES; THAILAND; VANUATU; VIETNAM. Casuarina equisetifolia is widely introduced and has become an invasive species in many countries. Its natural range is uncertain. Habitat Sandy coasts near sea-level. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Wilmot-Dear 2000. Cross-reference K293.

Casuarina equisetifolia is one of the most widely distributed strand plants of the Indian and Pacific Oceans, and will be familiar to anyone who has travelled in those regions. Its dark green tresses are now being exposed to Cornish conditions, with some success, and a thriving plant has also been reported from Surrey (T. & M. Milton, pers. comm. 2007). C. nana Siebold K293 C. stricta Dryand. K293

CATHAYA

C. torulosa (NOW Allocasuarina torulosa (Ait.) L.A.S. Johnson) K293

PINACEAE

Chun & Kuang

The genus Cathaya is monospecific, comprising only the species C. argyrophylla.

Cathaya argyrophylla Chun & Kuang Syn. C. nanchuanensis Chun & Kuang Tree to 20 m, trunk columnar, 0.4–0.6 m dbh. Bark smooth, grey, becoming scaly, may break into large irregular plates on the lower bole. Crown irregular, pyramidal, rather open. Branchlets slender, yellowish, becoming grey, conspicuously grooved, with circular or angular leaf scars; shoots dimorphic as in Larix, though less well defined; young shoots slightly pubescent, later glabrous; vegetative buds not resinous. Leaves spirally arranged, leaf density increasing towards the stem apex, (1.8–)2.8–4.5(–5.5) × 0.25–0.3 cm, straight, petiolate, margins slightly recurved, apex obtuse. Male strobili lateral, pendent, near shoot apex, 3–6 cm long, yellow, surrounded by a whorl of light brown scales. Female cones lateral, at right angles to the shoot (neither erect nor pendent), short-

223

224

Cathaya

New Trees

Plate 169. Mature trees of Cathaya argyrophylla on their misty ridge in the Jin Fu Shan. Image T. Kirkham. pedunculate or nearly sessile, ovoid to oblong with an acute apex, 3–5 × 1.5–2.5 cm, greenish, turning orangebrown later. Seed scales 13–16, ovate to orbicular, 1.5–2.5 × 1–2 cm. Bract scales triangular, 0.5–0.8 cm long, with a conspicuous point, included. Seeds olive-green with pale green spots, obovoid, 0.5–0.6 × 0.3–0.4 cm; wings cuneate or obovate, 1–1.5 × 0.4–0.6 cm. Farjon 1990, Fu et al. 1999c. Distribution CHINA: northeast Guangxi, northern Guizhou, southern Hunan, southeast Sichuan. Habitat Evergreen, sclerophyllous forest or broadleaved, deciduous forest, between 1200 and 1800 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk (IUCN); but despite this assessment, Cathaya has limited fertility (12.2% of cones with no seeds) and survival rates (seed germination rate in field, 21%). In China it is considered to be one of the eight most endangered plant species there (Ge et al. 1998), and access to material of the tree is (supposedly) strictly controlled. Illustration Krüssmann 1985b, Farjon 1990, Fu et al. 1999c; NTx, NT224, NT425. Cross-reference K62. Taxonomic note Cathaya is probably closely related to Larix and Pseudotsuga. Like Larix, its shoots are dimorphic, though the cones are on the longer shoots rather than the short shoots. The cones are very similar to those of the Asian species of Pseudotsuga, though the bract scales are short and unlobed (Frankis 1988).

In an article posted on the Quarryhill website, Bill McNamara (2007a) tells a lively tale of being taken to see a stand of Cathaya argyrophylla in a remote area of Sichuan, and of the difficulties placed in his party’s way before they got there. On arrival they found that access to the outcrop on whose top the trees were growing had been rendered almost impossible by the erasure of irregularities that would permit anyone to climb the cliff. A makeshift ladder did the trick, and eventually it was possible to admire the trees. As this story suggests, Cathaya is officially regarded as an important Chinese endemic, and access to material is supposedly strictly controlled. Despite this, however, the species is now available in commerce both in the United Kingdom and in the United States, and the website of the Oregon State University Department of Horticulture (1999–2008) lists it as a landscape plant. In the United Kingdom seedlings have been distributed to a few reliable growers from the International Conifer Conservation Programme at Edinburgh, the first accessions there dating to 1998. All of these are still very small, and it is difficult to record much about such young plants. Larger plants are growing in the United States, however, and here the growth habit is more apparent. The long, flattened needles are a dull olive-green and grow rather densely on the shoots, giving something of a foxtail appearance. They show little sign of the silvery white undersurface that gives the tree its specific name. A good specimen of 1.8 m at Plant Delights Nursery, Raleigh, North Carolina was producing vigorous new growth when seen in June 2006, and seems to thrive in the southern heat and humidity.

Section II. Species Accounts

CEDRUS

Cedrus

225

PINACEAE

Trew

True Cedars Cedrus is a genus of four species found in three disjunct areas: the Atlas Mountains of North Africa; mountainous parts of the eastern Mediterranean, including Turkey, Lebanon and Cyprus; and the Hindu Kush, Karakoram and Himalayan mountain ranges. Cedars are generally large, evergreen trees with straight, columnar trunks (though often forked or multistemmed). The bark is thin, grey-brown, later darkening and cracking into small plates. Young plants are conical, with regular branching, although as they mature several first-order branches may become co-dominant with the main stem (especially in C. libani subsp. libani); in C. deodara, however, apical dominance is usually maintained, which may account for this reaching the tallest heights among the cedar species. The branchlets have marked dimorphism: leading shoots are long and slender, lateral shoots short and stunted (‘short shoots’); vegetative buds are not resinous or only slightly so. The leaves are needle-like, dark green or glaucous-blue, rigid, spirally arranged, slightly narrow at the base, the apex acute. The male strobili are erect, solitary, catkin-like, terminating short shoots, and thus subtended by a whorl of leaves. The female cones are erect, also positioned on short shoots, less abundant than the strobili, but both are usually located on the outer branches, around the crown; the cones mature in the second year (after 17–18 months), glaucous-green turning dull brown. The seed scales are broad, somewhat papery, subtended by insignificant bract scales, spirally arranged around the central rachis; at maturity the scales fall to leave the rachis. Seeds are borne two per scale, partially enclosed in a membranous cup, which extends to form a wing. There appear to be few morphological characters to separate the species of cedar, though habit characteristics are useful with cultivated material (Farjon 1990). C. atlantica (Endl.) Manetti ex Carrière B558, S153, K63 C. atlantica f. fastigiata (NOW C. atlantica ‘Fastigiata’) B559, S154 C. atlantica f. glauca (NOW C. atlantica Glauca Group) B559, S154 C. atlantica f. pendula (NOW C. atlantica ‘Pendula’) B559 C. brevifolia (Hook. f.) A. Henry K64 C. deodara (Roxb.) G. Don B559, S154, K64 C. deodara var. robusta (NOW C. deodara (Roxb.) G. Don) B560 C. deodara var. viridis (NOW C. deodara (Roxb.) G. Don) B560

Cedrus libani A. Rich.

Cedar of Lebanon

This species was described by Bean (B560, S155) and Krüssmann (K65), and Farjon (2001) recognised C. libani subsp. stenocoma.

Plate 170. The pollenbearing strobili of Cedrus libani subsp. stenocoma. The male cones of conifers are often ignored in favour of the attractions of the female cones. Image M. Gardner.

226

Cedrus

New Trees

C. libani f. argentea (NOW C. libani A. Rich.) B561 C. libani var. brevifolia (NOW C. brevifolia (Hook. f.) A. Henry) B561, S156 C. libani f. fusiformis (NOW C. libani A. Rich.) K65

Cedrus libani subsp. stenocoma (O. Schwarz) P.H. Davis Subsp. stenocoma has a more conical habit than the type subspecies, and its leaves are grey-green, rather than dark green-glaucous. The morphology of subsp. stenocoma is intermediate between that of C. libani and

Plate 171. The narrow shape of Cedrus libani subsp. stenocoma is particularly evident in the wild in southern Turkey, but is retained in cultivation. Image D. Luscombe.

C. atlantica, though these species can be difficult to separate. Coode & Cullen (1965) note that the habit of Turkish specimens of C. libani is different to that of plants in the rest of its range. Turkish trees are tall compared to typical specimens, that have a crown wider than it is tall. However, both subsp. stenocoma and the type subspecies occur in Turkey, and so this difference may be habitat-related. Coode & Cullen 1965, Farjon 1990. Distribution TURKEY: Cilician Taurus Mts. Habitat North-facing mountain slopes between 1300 and 3000 m asl, on well-drained calcareous soils. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT17, NT225, NT226. Cross-reference K66.

The story of the first introduction of Cedrus libani subsp. stenocoma is a classic tale of intelligent sourcing of material to fit a horticultural need. In the United States, nominate C. libani grows only as far north as Pennsylvania, and its presence was lacked in gardens further northeast. In 1902 C.S. Sargent commissioned the botanist Walter Siehe, who was resident in Turkey, to collect seed from the highest locations of the species in the Taurus Mountains. The resultant plants did indeed thrive when planted in the Arnold Arboretum, and elsewhere – and are still flourishing there today (Hay 1995). Instead of forming the familiar wide-branched shape expected of Cedars of Lebanon, trees of subsp. stenocoma have a narrow, almost conical shape, retained into maturity. This taxon has been somewhat ignored in the British literature, being noted, if mentioned at all, only for its greater hardiness (Rushforth 1987a). It is this extra hardiness, however, that makes subsp. stenocoma so valuable to American horticulture, thriving as it does through much of the Midwest where subsp. libani fails. Dirr (1998) notes that it has withstood –31 ºC; although needle-loss occurred, the trees regenerated. This suggests that it would also be useful in cold, northern parts of Europe.

CANNABACEAE (or ULMACEAE)

CELTIS

L.

Nettle Trees, Hackberries Celtis has between 60 and 100 species and is primarily tropical in distribution, with a limited number of subtropical and temperate species. Celtis species are unarmed, deciduous or evergreen trees. Stipules are present or absent. The leaves are alternate and petiolate, with entire or serrated margins. Each leaf has three veins originating at the base. The flowers are arranged in panicles, racemes or clustered cymes. In temperate areas they are produced in early spring before the leaves unfurl. They are

Section II. Species Accounts

Celtis

generally rather small and insignificant, and may be unisexual or hermaphrodite. Staminate flowers occur in the lower leaf axils of one-year-old branches or grow directly from the stem (cauliflorous). Female and hermaphrodite flowers occur together in the upper leaf axils. The corolla and calyx are not differentiated from each other. The fruit is a fleshy drupe with a bony endocarp (Fu et al. 2003). Celtis was traditionally placed in the Ulmaceae, but DNA-based studies suggested splitting the family in two. Ulmus and Zelkova remain in the Ulmaceae, while genera such as Celtis and Trema Lour. were transferred into the Celtidaceae. Further studies, however, revealed that both Cannabis L. and Humulus L. (Cannabaceae) formed part of the Celtidaceae and the two families were combined, with the oldest name (Cannabaceae) taking precedence (Sytsma et al. 2002). Celtis is at first sight an undistinguished genus with no outstanding features, and is seldom enthused over by authors, but its species can be extremely hardy and are often able to tolerate harsh or difficult conditions, including the salt-spray of urban roadsides (Sternberg 2004). A number of selections have been made from North American species for their merits as street trees or for autumn colour (Dirr 1998, Sternberg 2004). It seems probable that some of the more recently introduced Asian species will have similar qualities, but many Celtis enjoy a warm summer to ripen their wood properly (Wharton et al. 2005) and do not flourish in much of maritime western Europe. Although tolerant of poorer conditions, Celtis will perform best and make the finest trees in good soil conditions, having particular requirements for good drainage and an open site (Wharton et al. 2005). In North America native Celtis are prone to various pests and diseases, especially a nipple gall and a tendency to form witches’ brooms following mite damage and powdery mildew infection (Dirr 1998). It is not clear if the Asian species are afflicted in the same way. Propagation is normally by seed, although Bean (1976a) says that grafting onto stocks of C. occidentalis is possible. Birds greatly appreciate the fruits: I (JMG) have observed Venetian pigeons performing extraordinary acrobatics to feed on the fruits of C. australis. C. australis L. B567, S157, K306 C. biondii Pampan. B568, S157, K306 C. biondii var. cavalieriei C.K. Schneid. K306 C. bungeana Blume B568, K306

C. bungeana var. heterophylla C.K. Schneid. K306 C. caucasica Willd. B568, S158, K307 C. cerasifera C.K. Schneid. K307

Celtis choseniana Nakai Large shrub or tree to 25 m, dbh 40 cm; main trunk typically branching close to ground level, forming a wide, open crown. First-year branchlets slightly pubescent, green, with prominent lenticels; at maturity, bark smooth, reddish brown; nodes prominent. Stipules absent. Leaves deciduous, 4.5–12 × 3.5–7.5 cm, narrow or broadly ovate, papery, upper surface glabrous, lower surface with some pubescence restricted to the veins, two (to three) secondary veins on each side of the midvein, margins serrate for three-quarters to half of their length, apex caudate, young growth slightly pink; petiole furrowed, yellowish green, somewhat pubescent. Infructescences unbranched, 2–3 cm long. Fruit solitary, black, 1 cm. Lee 2002. Distribution

227

Plate 172. Celtis sinensis is capable of producing magnificent autumn colours (seen here at Kew, November 2007). Image J. Grimshaw.

228

Celtis

New Trees

NORTH KOREA; SOUTH KOREA. Habitat Wooded slopes on sandy loam soils; only recorded between 30 and 35 m asl, though probably occurs higher. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Taxonomic note This species is rather poorly known and may be conspecific with C. sinensis or C. edulis. Lee (2002) recognises C. choseniana as a Korean endemic.

Celtis choseniana is one member of the genus that has achieved a warm reception, being highly praised by Douglas Justice for the winter pattern of its ‘horizontally layered, fan-like branches’ with zigzag shoots (Wharton et al. 2005). The specimens he describes in Vancouver were grown from wild seed collected in 1984 from parents 12 m tall, and are now nice rounded trees, likely to attain the same height. On Ullungdo individuals have been found up to 25 m tall, and seed from these was collected by the Kirkham, Flanagan and Boyce Expedition to Korea (KFBX 170) in 1989 (Flanagan & Kirkham 2005). Unlike the Vancouver trees, a seedling from this collection has not performed well at Kew, being an unhappy-looking 4 m and suffering badly from insect predation in June 2006. Neither has it done particularly well at the Morton Arboretum where, although 6 m tall from a 1986 accession, it suffers from canker after pruning (K. Kim, pers. comm. 2006). The autumn colour has been described by Kunso Kim as an ‘unremarkable yellowish’, and by Justice as ‘poor’ (Wharton et al. 2005). C. douglasii Planch. K307

Celtis edulis Nakai Large shrub or small tree (ultimate dimensions unknown); main trunk typically branching close to ground level, forming a compact but open crown. First-year branchlets glabrous, bright green, with prominent lenticels; at maturity, bark smooth or slightly puckered and grey. Stipules absent. Leaves deciduous, 5–10 × 3–4.5 cm, ovate to elliptical, papery, upper surface glabrous, lower surface with some pubescence restricted to the veins, two (to three) secondary veins on each side of the midvein, margins serrate for three-quarters to two-thirds of their length, apex caudate and curved, young growth reddish yellow; petiole slightly furrowed or not, yellowish green and pubescent. Infructescences unbranched, to 1.5 cm long. Fruit solitary, globose, 1 cm long. Lee 2002. Distribution NORTH KOREA; SOUTH KOREA. Habitat Forests. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Taxonomic note This species is also poorly known and may be conspecific with C. choseniana, though Lee (2002) recognises it.

Celtis edulis seems to be poorly represented in cultivation in our area. At Kew, a seedling from the Beyer, Erskine and Cowley Expedition to Korea (BECX 275) in 1982 is a rather sparse small tree of 2.5 m. The collection was made at 816 m in Chungcheongnam-do Province, South Korea. Another small tree, at the JC Raulston Arboretum, received in 1996, is now 2.3 m and looking good, with grass-green leaves that are neatly toothed and have a distinctive elongated tip. C. glabrata Planch. B569, S158, K307

Celtis jessoensis Koidz. Tree to 25 m. Branchlets slightly pubescent, reddish to blackish brown; lenticels prominent. Stipules absent. Leaves deciduous, 6–10 × 3–5 cm, narrow or broadly ovate, papery, upper surface glabrous, lower surface glaucous or pale green, with some pubescence restricted to the veins, four to six secondary veins on each side of the midvein, margins serrate, though often entire near the petiole, apex acuminate; petiole furrowed, 0.2–0.7 cm long, somewhat pubescent. Flowers arranged in densely clustered cymes. Infructescences unbranched, to 2 cm. Fruit solitary, ellipsoidal to globose, 1.1–1.4 cm diameter, orange-yellow. Ohwi 1965. Distribution JAPAN: Hokkaido, Honshu, Kyushu, Shikoku; NORTH KOREA (?); SOUTH KOREA. Habitat Deciduous forest between 200 and 1100 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration NT229. Cross-reference K307.

Section II. Species Accounts

Celtis

229

Celtis jessoensis is grown in several collections but is not common, despite having been cultivated at the Arnold Arboretum since 1892 (Dirr 1998), and for a long time at the Arboretum National des Barres. Descendants of the originals at the Arnold Arboretum are c. 20 m tall, forming upright to spreading trees with good dark foliage and apparent freedom from pests. Although somewhat suspicious of the merits of Asian Celtis, Dirr accepts on the basis of observations of these specimens that C. jessoensis has ‘a genuine place in the landscape’ (Dirr 1998). This would seem to be borne out by a 6 m roadside specimen at Swarthmore, Pennsylvania, that is growing well though battered by factors incidental to its position, such as power-company pruning and reversing cars (A. Bunting, pers. comm. 2006). A specimen at the University of Utrecht Botanical Garden, grown from seed from Les Barres in 1963 (H. Persoon, pers. comm. 2006), was 8 m in 2005, forming a rounded tree from two stems. The foliage is a dull dark green, giving it a rather sombre appearance. There are several at Kew, grown from BECX 242, collected in 1982 in Gyeonggi-do Province, South Korea. The tallest of these is 4 m, branching from 60 cm.

Celtis julianae C.K. Schneid. Tree to 30 m, dbh 15 cm. Branchlets dark brown with dense yellowish brown pubescence; at maturity, bark grey. Stipules absent. Leaves deciduous, 6–13 × 3.5–8 cm, elliptical to ovate, leathery to papery, upper surface smooth, lower surface distinctive, with dense, golden pubescence (sometimes limited to the veins), four to six secondary veins on each side of the midvein, margins dentate to entire, apex acuminate; petiole furrowed, 0.7–1.5 cm long, covered in dense, golden pubescence. Flowers arranged in densely clustered cymes. Infructescences unbranched, coated in dense yellowish brown pubescence, 0.7–1.5 cm. Fruit solitary, ellipsoidal to globose, 1.1–1.4 cm diameter, purple, orange-yellow or brown. Flowering March to April, fruiting September to October (China). Fu et al. 2003. Distribution CHINA: southern Anhui, Fujian, northern Guangdong, Guizhou, southern and western Henan, western Hubei, northwest Hunan, Jiangxi, southern Shaanxi, northern Sichuan, Yunnan, Zhejiang. Habitat Forested slopes and valleys between 300 and 1300 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Fu et al. 2003. Cross-reference K307.

Although Celtis julianae is available commercially both in Europe and in North America, there are few large specimens in collections. The finest seen in research for this book is a 4 m individual planted in 2003 at the JC Raulston Arboretum, which has obviously grown very fast. The long, new shoots arch outwards and blow in the breeze, giving an elegant appearance to the tree. The foliage is noted for its attractive goldenbrown hairs, especially when young. Like many other Celtis it thrives best in areas with hot summers: it does well in New Zealand (T. Hudson, pers. comm. 2006). C. koraiensis Nakai B569, S159, K308 C. labilis (NOW C. tetrandra Roxb., NT231) B570, K308 C. laevigata Willd. B570, S159, K308 C. laevigata var. smallii (NOW C. laevigata Willd.) B570, K308 C. laevigata var. texana (Scheele) Sarg. K308 C. lindheimeri Engl. K308 C. occidentalis L. B570, K308 C. occidentalis var. canina (Raf.) Sarg. K308 C. occidentalis var. cordata (Pers.) Willd. B571, K308

Plate 173. Celtis jessoensis can be a useful, tolerant street tree. Image A. Bunting.

230

Celtis

New Trees

C. occidentalis var. pumila Mohl. K308 C. pumila (NOW C. tenuifolia Nutt., NT231) B571, S159 C. reticulata (NOW C. laevigata var. reticulata (Torr.) L. Benson) B571, S159, K308

Celtis sinensis Pers. Tree (rarely a shrub) to 20 m, dbh 40 cm. Branchlets brown with some brown pubescence or glabrous; at maturity, bark grey. Stipules lanceolate, pubescent, 0.3–0.5 cm long; withering early. Leaves deciduous, 3–10 × 3.5–6 cm, elliptical to ovate, papery, upper surface with inconspicuous pubescence when young, lower surface with pubescence limited to the veins or in tufts in the vein axils, three to four secondary veins on each side of the midvein, margins subentire to crenate, apex acute to acuminate; petiole furrowed, 0.3–1 cm long, with pubescence above. Flowers arranged in densely clustered cymes in leaf axils and at base of young stems. Infructescences unbranched, one (to three) per leaf axil; stout, pubescent, 0.4–1 cm long. Fruit globose, 0.5–0.8 cm diameter, green to red to black. Flowering March to April, fruiting September to October (China). Fu et al. 2003. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guizhou, Henan, Jiangsu, Jiangxi, northeast Shandong, Sichuan, Zhejiang; JAPAN: Honshu, Kyushu, Shikoku; NORTH KOREA (?); SOUTH KOREA; TAIWAN. Habitat Very common in a variety of habitats, from hills to lowlands and roadsides, between 100 and 1500 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Valder 1999, Fu et al. 2003, Wharton et al. 2005; NT227, NT230, NT231. Cross-reference K308. Taxonomic note Celtis sinensis var. japonica (Planch.) Nakai from Japan and possibly Korea is recognised by several authors (for example, Ohwi 1965), though there appear to be no significant differences from the type variety.

Plate 174. Celtis sinensis ‘Green Cascade’ at Plant Delights Nursery, North Carolina, showing off its striking outline. Planted in 1998, it achieved 1.8 m of growth each year when young: this species likes hot summers. Image T. Avent.

Celtis sinensis is a good example of a tree thriving where summers are hot and failing to perform well where they are cool. At Kew there is a specimen from BECX 255, collected in South Korea in 1982, that is now only 3 m tall (but some 5.5 m wide) – although TROBI records an 11 m tree at Kew grown from seed collected in 1976. In North America, however, it responds to the extra warmth and grows very quickly into a large and stately tree. There are magnificent specimens both at Quarryhill (from SOJA 428, collected in Honshu in 1989, planted in 1991) and at the JC Raulston Arboretum (provenance unrecorded). Even with infestations of tent caterpillars, the largest Quarryhill specimen was over 10 m tall, 39 cm dbh in 2004, and looked extremely happy. In the very different conditions of Raleigh it was equally high but with lesser girth, forming a wide, shade-creating canopy of very dark leaves. At the US National Arboretum, a tree of Japanese origin has also grown very fast but has a thinner canopy. Celtis sinensis has long been valued in Chinese horticulture for its shade-giving, but also for its longevity and tolerance of poor conditions (Valder 1999), and it can become a large and characterful tree. The ‘catch’ with this species is that it has become a seriously invasive pest in the damper parts of Australia; it is a declared ‘noxious weed’ in New South Wales, where it was introduced ‘about 50 years ago’ as an ornamental (Ensbey 2002). It is also selfsowing at Quarryhill, and should perhaps be monitored for potential invasiveness in the southern parts of the United States.

Section II. Species Accounts

Celtis

231

Celtis sinensis is often used as a bonsai subject, and there is a lovely weeping clone ‘Green Cascade’ which deserves wide planting. It was selected from a batch of seedlings grown from seed collected from a famous pendulous specimen at Suwa Jinja shrine in the village of Kamiyamaguchimura in the Nagano Prefecture, Japan, by Cliff Parks of the Camellia Forest Nursery in Chapel Hill, North Carolina in 1983 (Creech 2003). Unsupported, ‘Green Cascade’ will sprawl on the ground, but it can be trained on a pergola into a very appealing curtain.

Celtis tenuifolia Nutt.

Georgia Hackberry, Dwarf Hackberry

Syn. C. georgiana Small Shrub or small tree to 10 m, dbh 35 cm or more; trunk short, as branching occurs early. Bark pale grey-brown, often warted, sometimes forming heavy plates. Branchlets green to reddish brown and pubescent, later glabrous; at maturity, bark light grey with distinctive ridges. Stipules absent. Leaves deciduous, alternate, 2.5–7 × 1.5–4 cm, broad at the base, ovate to cordate, leathery or papery, upper surface dark green, glabrous and rough to the touch, lower surface pale green, with conspicuous pubescence, three to four (to five) secondary veins on each side of the midvein, margins entire or with a few large teeth on each side, apex acuminate; petiole slender, 0.6–1.1 cm long, pubescent. Flowers greenish yellow, solitary or in sparse clusters. Infructescences solitary, unbranched. Fruit 0.7–1 cm diameter, orange-red to reddish brown. Flowering April to May, fruiting September to October (USA). Elias 1980. Distribution CANADA: Ontario; USA: Alabama, Arkansas, northern Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, Ohio, eastern Oklahoma, southeastern Pennsylvania, South Carolina, Tennessee, eastern Texas, Virginia, West Virginia. Habitat Dry, rocky or gravel-rich soils in the foothills, particularly in the Piedmont, southeastern USA. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration Elias 1980. Cross-reference K308.

Celtis tenuifolia is highly regarded by Sternberg (2004), who considers it to be a characterful tree suitable for small gardens. As a native of rocky places it is slow-growing (9 m in 30 years at Starhill Forest Arboretum) and tolerant of adverse conditions. It colours a good yellow in autumn, and its silvery brown bark and intricate branching pattern make the winter silhouette attractive. Celtis tenuifolia has been grown at Kew since 1900 (this plant was obtained originally from the German nursery firm of Späth), and there is another old tree at Wakehurst Place. The Kew tree is 10–12 m tall, dbh 35 cm, with somewhat pendent branches from ascending main stems. In addition to the Starhill Forest tree, American collections often have good specimens, and where conditions are particularly favourable it need not be slow-growing. A 10 m tree at the JC Raulston Arboretum was planted in 1998 and looks set to be large and shady in maturity. It has grown well at Rogów Arboretum since 1961 (P. Banaszczak, pers. comm. 2007), and would seem to be an excellent tree for continental climates. C. tenuifolia var. georgiana (NOW C. tenuifolia Nutt., NT231) S159

Celtis tetrandra Roxb. Syn. C. labilis C.K. Schneid., C. trinervia Koord., C. yunnanensis C.K. Schneid. Tree to 30 m, dbh 1 m; branches rather pendulous. Bark light brown, mostly smooth but can be warted. Branchlets brown with a dense covering of yellowish brown pubescence, though often glabrous with age; at maturity, bark greyish white. Stipules lanceolate, to 0.7 cm long, caducous. Leaves deciduous or rarely evergreen, immature growth pinkish red, 5–13 × 2.5–5.5 cm, ovate-elliptical to oblanceolate, papery, upper surface glabrous, lower surface with inconspicuous yellow pubescence limited to the veins, later glabrous, three to four secondary veins on each side of the midvein, margins entire or serrate, apex acuminate to caudate; petiole with a broad furrow, 0.6–1.3 cm long, brown and glabrous or slightly pubescent. Flowers arranged in densely clustered cymes, or rarely in racemes of two to three. Infructescences unbranched or rarely

Plate 175. Celtis sinensis has been cultivated in the United States since the latenineteenth century, but has long been popular in its native countries as a shade tree and, contrastingly, for bonsai. This specimen is at the US National Arboretum. Image J. Grimshaw.

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Celtis

New Trees

1 cm

Figure 23 (above). Celtis tetrandra: habit with fruits and detail of leaf underside.

forked, one to three per leaf axil; slender, glabrous or pubescent, 0.8–1.5 cm long. Fruit 0.7–0.8 cm diameter, orange-yellow. Flowering March to April, fruiting September to October (China). Fu et al. 2003. Distribution BANGLADESH; BHUTAN; CHINA: western Guangxi, Hainan, Sichuan, southern Xizang, central, eastern and southern Yunnan; INDIA; INDONESIA: Java and the Lesser Sunda Is., Sumatra (?); MYANMAR; NEPAL; TAIWAN; THAILAND; VIETNAM. Habitat Mixed, mesophytic forest in valleys and on slopes, between 700 and 1500 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Lancaster 1989, Fu et al. 2003; NT232, NT233. Cross-reference B570 (as C. labilis).

Section II. Species Accounts

Celtis

233

During his trip to Yunnan in 1981 Roy Lancaster was greatly impressed by magnificent trees of Celtis yunnanensis growing in the grounds of the Great Flower Monastery in the Western Hills near Kunming. He commented that the species was then unknown in the West (Lancaster 1989), but that it was very distinct by virtue of its acuminate leaves. These are indeed a conspicuous feature on the few trees observed in research for the current work, and as they are also a glossy dark green with strongly impressed veins they are rather handsome. The taxon grown since 1908 at Kew from Wilson 444, and described by Bean (1976a) as C. labilis, has more recently been identified as C. tetrandra. A re-propagation from 1965 was 8 m tall in 2001 (TROBI). Although this species is established in North American collections it has yet to become widely distributed. At the Morton Arboretum one specimen has formed a rounded, low tree of about 7 m, producing heavy horizontal limbs from upright stems. It seemed to be in poor health when seen in 2006, with a sparse canopy of rather pale leaves. This specimen, and others in the same collection, were grown from seed received in 1927 from the Istituto dell’Orto Botanico della Università in Rome, distributed as C. trinervia (a name applied by three different authors). There is a vigorous young tree at the JC Raulston Arboretum (labelled C. yunnanensis), 5 m tall in June 2006, grown from seed collected in Black Dragon Park in Lijiang, Yunnan in 1999 by Todd Lasseigne. C. tournefortii Lam. B569, S158, K308

Celtis vandervoetiana C.K. Schneid. Tree (rarely a shrub) to 25 m, dbh 60 cm. Branchlets brown, glabrous, with distinctive lenticels; at maturity, bark greyish brown. Stipules absent. Leaves deciduous, 8–14 × 3.5–7.5 cm, elliptical to ovate or oblong, papery, upper surface glabrous, lower surface with pubescence limited to the axils of veins, (two to) three to four secondary veins on each side of the midvein, margins finely serrate, apex acuminate to caudate; petiole deeply furrowed, 0.9–1.5(–2) cm long, brown and glabrous. Flowers arranged in densely clustered cymes. Infructescences solitary, unbranched, stout, glabrous, 1.7–3.5 cm long. Fruit 0.9–1.5 cm, orange-yellow. Flowering April, fruiting September to October (China). Fu et al. 2003. Distribution CHINA: Fujian, northern and western Guangdong, Guangxi, Guizhou, Hubei, northwest Hunan, southern Jiangxi, Sichuan, eastern Yunnan, eastern Zhejiang. Habitat Forested valleys between 600 and 1400 m asl. Celtis vandervoetiana typically occurs as an understorey species in shady areas. USDA Hardiness Zone 6. Conservation status Not evaluated.

The only collection of Celtis vandervoetiana traced is that made by the Sino-American Expedition to China in 1981 (under the number SABE 1490), in the Shennongjia Forest District of Hubei, at 2000 m. In contrast to most Celtis, this species seems to require a shaded site, and the field notes record that it was growing in the bottom of a canyon, along the Yingyu River. There is certainly a marked difference between the two trees of C. vandervoetiana at Kew, one of which is growing in full sun and does not look happy, with yellowish leaves; the other, by contrast, is in a shadier site and is much better, with healthy green foliage. This latter specimen has made a very wide, low (3.5 m) tree, with several trunks bearing spreading branches, noted on a hot June day to create a good pool of shade. It is also cultivated at the Arnold Arboretum.

Plate 176. The acuminate, glossy leaves of Celtis tetrandra are a useful clue to its identity. This is a young tree at the JC Raulston Arboretum. Image J. Grimshaw.

234

Cephalotaxus

New Trees

CEPHALOTAXACEAE

CEPHALOTAXUS

Siebold & Zucc. ex Endl.

Plum Yews

Plate 177. The abundant fruits, which become red in maturity, and the strong white stomatal bands on the foliage, make Cephalotaxus sinensis rather attractive. Image P. Banaszczak.

The taxonomy of Cephalotaxus is challenging and lacks a modern revision, though Farjon (2001) recognises 11 species. The genus is native to eastern Asia, from Assam through China to Korea and Japan in the east and Vietnam, Thailand, Peninsular Malaysia and Taiwan in the south. The major difference between the plum yews and the true yews (Taxus, Taxaceae) lies in the female cones. In Cephalotaxus they are composed of multiple decussate bracts, each of which bears two ovules; typically, only one to two ovules develop per cone, and these are completely surrounded by a fleshy, drupe-like aril (the ‘plum’). In Taxus there is only one fertile bract with one ovule, and this is only partially covered by a cup-like aril. The staminate strobili of Taxus are solitary, while in Cephalotaxus they are grouped in a capitulum or head (the generic name translates as ‘head yew’). There has been considerable debate as to whether to recognise the Cephalotaxaceae as a separate family, though this is supported by DNA-based studies (Cheng et al. 2000, Wang et al. 2001). Plum yews are small, multistemmed (rarely single-stemmed), evergreen trees or shrubs. The bark is smooth and reddish brown, but later becomes fibrous or scaly. The crown is typically broad and rounded or flat-topped in European and North American gardens, though both C. fortunei and C. harringtonii can form small, open trees in warmer areas. The branches are opposite or in whorls. The apical buds are ovate and covered in persistent, imbricate scales. The needle-like leaves are arranged spirally on terminal branchlets and in two ranks on lateral branchlets. In most species, the branchlets are dorsiventrally flattened, with a prominent adaxial V-shaped channel between the two ranks of leaves. The leaves are dark green, linear-lanceolate and with two abaxial glaucous-green bands of stomata separated by a conspicuous midrib. Within each of the two bands, the stomata are arranged in several rows. Cephalotaxus species are usually dioecious, but can be (rarely) monoecious. The male strobili develop along the previous season’s growth and are clustered into capitula. The capitula are solitary, axillary and partially sessile or pedunculate; where present, the peduncle bears several scales or is naked. The female cones are borne in groups (rarely solitary) at the base of the previous year’s growth and mature in the second year. The cones are pendent, pedunculate and formed from several decussate bracts, each of which bears one to two erect ovules. Typically, only one ovule matures per cone, and the resulting seed has a thin, hard shell. The entire seed is enclosed in a fleshy aril, which changes from green to purplish red. The resulting structure resembles a drupe such as that of an olive. The seed (rarely two seeds develop) is ovoid to globose and wingless (Li & Keng 1994b, Tripp 1995, Fu et al. 1999a). The species

Section II. Species Accounts

Cephalotaxus

of Cephalotaxus are rather difficult to separate, and commonly cited characters such as bark colour, needle shape and length are all influenced by the age of the plant and the environment in which it grows; specimens without an accurate provenance may be unidentifiable (Tripp 1995). Michael Dirr’s pertinent comment (Dirr 1998), on trying to find a reliable way to distinguish the species – that ‘life is too short for such frustration’ – is very apt. The Japanese C. harringtonii and the Chinese C. fortunei represent the extremes of morphological variation in the genus. Cephalotaxus is a genus where it is quite fair to say that the more recently introduced or less familiar taxa have no apparent horticultural advantages over the familiar species C. fortunei and C. harringtonii and their selections. All seem to make the same sort of sprawly, somewhat ill-defined shrubby tree. Cephalotaxus appears to enjoy summer heat, and in the southeastern United States C. harringtonii is an important landscaping species, used as a substitute for Taxus, and numerous cultivars have been selected (Dirr 1998). All species seem fairly tolerant of soil types. As with Taxus, they would seem to be understorey plants when young, and there is no doubt that they look much happier when not exposed to sun. C. fortunei Hook. B573, S159, K66 C. fortunei var. alpina L. K68 C. fortunei var. concolor Franch. K68 C. griffithii Hook. K68 C. hainanensis H.L. Li K68

C. harringtonii (Knight ex J. Forbes) K. Koch B574, S160, K68 C. harringtonii var. drupacea (NOW C. harringtonii (Knight ex J. Forbes) K. Koch var. harringtonii) B574, K68

Cephalotaxus koreana Nakai

Korean Plum Yew

Syn. C. harringtonii var. koreana (Nakai) Rehder This species is extremely poorly known; there are few published descriptions of it, and no material exists in the Herbarium at Kew. When first describing it, Nakai (1930) said that in most aspects it was similar to the familiar C. harringtonii. However, C. koreana forms a shrub of 1–1.5(–4) m tall, with multiple caespitose stems produced directly from the rootstock (Nakai 1930). The leaves of C. koreana are blackish green and glossy, even in winter, and measure approximately 5 × 0.3 cm. Tripp 1995. Distribution JAPAN: Hokkaido, Honshu; NORTH KOREA; SOUTH KOREA. Habitat Low to middle elevations. USDA Hardiness Zone 5. Conservation status Not evaluated. Cross-reference K68.

Cephalotaxus koreana is rare in cultivation, but can be seen in a few major collections. One is at Wakehurst Place, where it was received in 1990 as a young plant grown from material gathered in Korea by James Russell at Chollo Namdo, Wando-gun, Wando Island. Russell’s field notes (as recorded in the Kew database) describe the parent as a small tree, c. 4 m tall, growing in coastal forest behind sand dunes. At the Geneva Botanical Garden it has made a small single-stemmed tree that fruits abundantly (illustrated at the Arboretum de Villardebelle website: www.pinetum.org).

Cephalotaxus mannii Hook. f.

Assam Plum Yew

Syn. C. harringtonii var. thailandensis Silba Tree to 20 m, 1.1 m dbh. Bark flaky, light reddish brown. Crown broad, rounded. Leafy branchlets elliptical in outline, 9–19(–24) × 4.5–8(–9.5) cm with leaves held at 45°–80° to axis. Vegetative buds persistent. Leaves with petiole absent or to 0.1 cm long; shiny olive-green or dark green, arranged in two loose ranks, 1.5–4 × 0.25–0.4 cm, linear and straight or slightly falcate, tapering towards apex, midrib prominent on both adaxial and abaxial surfaces, apex cuspidate to mucronate. Abaxial stomata in two white or bluish white bands, each 0.7–1.6 mm wide, separated by the midrib, 19–23(–26) lines of stomata in each band; leaves with prominent

235

236

Cephalotaxus

New Trees

margins, 0.1–0.3 mm wide. Male strobili in capitula of six to eight, each strobilus with 7–13 microsporophylls. Capitula in leaf axils along the entire length of the branchlets, globose and 4–4.5 mm diameter, pedunculate; peduncle 4–5 mm long, with at least 10 bracts. Cones produced in axils of terminal buds, solitary or in groups of two to three, peduncle 0.6–1 cm long; aril green when immature, turning red when ripe, 2.2–3 × 1.1–1.2 cm, mature in second year. Seeds obovoid to ellipsoid, often compressed laterally, 2.2–2.8 cm long, apex cuspidate or mucronate. Fu et al. 1999a. Distribution CHINA: Guangdong, Guangxi, southeast Xizang, Yunnan; INDIA: Assam (Khasi, Jaintia, Naga Hills); MYANMAR; THAILAND; VIETNAM. Habitat Mixed conifer-broadleaf forest, particularly in moist, shady ravines at about 1100 m asl. USDA Hardiness Zone 9 (?). Conservation status Vulnerable. Illustration Fu et al. 1999a, Luu & Thomas 2004. Cross-reference K68.

Cephalotaxus mannii is a species with potential rather than presence in horticulture. It comes from tropical forest in Indochina, at comparatively low altitude and in high rainfall conditions. Nevertheless it grows in northern Vietnam with trees such as Fokienia hodginsii, and there is a chance that collections from higher altitudes and latitudes may be successful in our area (Luu & Thomas 2004). Young trees are said to have a good shape and to be suitable for ornamental use in the species’ homeland, while larger specimens have interesting bark patterns (Luu & Thomas 2004). The only plant known to have been cultivated in our area was a seedling at Quarryhill, from Lam Dong, Vietnam, noted to be very small in 2004, but dead by 2006, having probably been planted in too exposed and hot a site (H. Higson, pers. comm. 2006).

Cephalotaxus sinensis (Rehder & E.H. Wilson) H.L. Li

Chinese Plum Yew

Syn C. harringtonii var. sinensis (Rehder & E.H. Wilson) Rehder Shrub or tree to 15 m, 1.2 m dbh. Bark reddish or greyish brown. Crown broad, open and rounded or spreading. Leafy branchlets yellowish brown though becoming reddish brown after several years, elliptical to oblong in outline, 5–12(–18) × 4–8(–10) cm with leaves held at 50°–85° to the axis, either perpendicular to or directed forward along the axis. Vegetative buds ovoid and acute, persistent. Leaves with petiole 0.1–2.5 cm long; shiny green, soft and leathery, arranged in two loose ranks, (1–)1.8–5(–7) × 0.2–0.4 cm, linear and straight or slightly falcate, tapering towards the apex, though only slightly, margins parallel, midrib prominent on both adaxial and abaxial surfaces, apex acute and mucronate or long and acuminate. Abaxial stomata in two white (rarely green) bands, each 0.8–1.2 mm wide and separated by the midrib, (12–)13–15(–18) lines of stomata in each band; leaves with prominent margins, 0.1–0.3 mm wide. Male strobili in capitula of six to seven, each strobilus with 4–11 microsporophylls. Capitula in leaf axils along the entire length of the branchlets, globose and 4–7 mm diameter, pedunculate; peduncle 3 mm long, naked or with a few apical bracts. Cones produced in axils of terminal buds, solitary or in groups of two to five (to eight), peduncle 0.3–0.8 cm long; aril green when immature, turning red or purple when ripe, 1.6–2.5 × 0.8–1.6 cm with six prominent, longitudinal ridges, mature in the second year. Seeds obovoid to ellipsoid, 1.8–2.5 × 0.9–1.2 cm, apex cuspidate or mucronate. Fu et al. 1999a. Distribution CHINA: from eastern China to Sichuan and Yunnan in the west and Henan in the north. Habitat Dense or open mixed woodland in valley bottoms, between 600 and 3200 m asl. Found in soils over a variety of bedrocks, from granite to limestone. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Fu et al. 1999a; NT234. Cross-references B574, K68.

Bean (1976a) gives a brief note on Cephalotaxus sinensis, indicating that it was first introduced by Robert Fortune (1812–1880), whose collectors muddled the seed with that of C. fortunei. Wilson noted that it was a common plant in Hubei and Sichuan, especially ‘in rough, steep, limestone regions’ (Sargent 1913). Despite these early introductions, however, it remains an obscure plant, probably often confused with other taxa in cultivation. There is an old specimen of C. sinensis from Wilson 267, collected in 1908, at Edinburgh, and a plant propagated from this is at Wakehurst Place. As with the more familiar C. harringtonii, with which it has been confused, it does well in the southern and eastern parts of the United States, and there are vigorous young specimens at the US National Arboretum (forming a small bushy tree of 2.5 m in 2006) and at the JC Raulston Arboretum. Dan Hinkley, writing in the 2005 Heronswood Nursery catalogue, considers it to be ‘eminently worth cultivating’, and says that it will form

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237

a round-topped small tree up to c. 5 m. It is not fully hardy at Rogów Arboretum, but the trees there fruit regularly (P. Banaszczak, pers. comm. 2007). C. sinensis f. globosa (Rehder & E.H. Wilson) H.L. Li K69

Cephalotaxus wilsoniana Hayata

Taiwan Plum Yew

The taxonomic status of C. wilsoniana is contentious; it has been linked with C. harringtonii (Fu et al. 1999a) and with C. fortunei (Rushforth 1987), and Li & Fu (1997) and Fu et al. (1999a) recognised it only as a variety of C. sinensis. Cephalotaxus wilsoniana has leaves that are somewhat falcate or twisted, taper from well below the apex, and are about 10 times as long as wide (5–10 times as long as wide in C. sinensis: Fu et al. 1999a). In contrast, leaves of C. sinensis are almost entirely parallelsided and taper only near the apex. The leaves of C. wilsoniana are arranged in two ranks, but are often oriented in different directions, with no clear V-shaped channel between the ranks. The Taiwan Plum Yew forms a small tree to 10 m, 0.4 m dbh. New shoots bright green, turning dark reddish green after three or four years. Li & Keng 1994b, Fu et al. 1999a. Distribution TAIWAN. Habitat Mixed or coniferous forests in valley bottoms, between 1400 and 2000 m asl. USDA Hardiness Zone 8. Conservation status Endangered. Illustration Li & Keng 1994b, Fu et al. 1999a; NT237. Cross-reference K69.

The most distinctive identification character for this plant is that it comes from Taiwan, which is not very helpful for plants of unknown provenance. There are specimens grown from the 1992 Kirkham and Flanagan collection ETOT 105 at Kew, Wakehurst Place and Howick, and it was also collected by the Edinburgh Expedition to Taiwan (ETE) at several sites in 1993. Quarryhill grows plants from a 2001 expedition. Kirkham and Flanagan’s official field notes record that it grows in mixed forest with Sorbus, Pinus and Quercus, on a slightly shaded slope. In the more lively account of their travels in book form (Flanagan & Kirkham 2005), they reveal that the seeds had to be extracted ‘somewhat gingerly’ from monkey droppings. The resulting ETOT 105 plants are growing slowly, being approximately 1 m tall after 14 years (the wild trees were 3 m, according to the field notes). They have dark mid-green leaves, in contrast with the yellowish, sun-stressed specimens at Quarryhill. Potted plants of both C. wilsoniana and C. sinensis were fruiting at Cistus Nursery in July 2004. The fruits of C. wilsoniana were approximately 18 × 7.5 mm, compared with 24 × 15 mm for C. sinensis, but this apparent size difference may not be consistent.

LEGUMINOSAE (CAESALPINIOIDEAE)

CERATONIA

L.

Carob Trees Ceratonia comprises two species: the common C. siliqua of the Mediterranean and Middle East, and the rare and poorly known C. oreothauma Hillc., G.P. Lewis & Verdc. of Somalia and Oman (Hillcoat et al. 1980). Carobs are evergreen trees or shrubs with dense, broad, rounded crowns. They are unarmed, and have minute, caducous stipules.

Plate 178. Originating as a seed extracted from monkey dropppings, this Cephalotaxus wilsoniana from ETOT 105 is growing well at Kew. Image T. Kirkham.

238

Ceratonia

New Trees

The leaves are pinnate with an even number of leaflets (paripinnate), usually two to five pairs; they are typically glossy, dark green and leathery. Ceratonia species may be dioecious, polygamous or both. The axillary inflorescences are short, catkin-like racemes bearing 30–50 flowers. The flowers are 5-merous with a deciduous calyx and no petals. The fruit is a pendent, indehiscent legume containing a sweet mucilaginous pulp and 5–15 seeds (Ball 1968, Allen & Allen 1981).

Ceratonia siliqua L.

Carob Tree, Locust Bean, Saint John’s Bread

Tree (rarely shrub) to 10 m; crown hemispherical, to 14 m wide. Bark initially smooth and grey, later rough and dark brown. Branchlets stout. Leaves evergreen, paripinnate (rarely bipinnate), dark glossy green above, dull grey-green below, 12–30 × 3–15 cm; leaflets 4–8(–12), petiolule under 0.5 cm long, oblong or obovate, 2–8 × 1–4.5 cm, leathery, margins entire, apex rounded or emarginate; petiole and rachis contiguous, 7–15 cm long, reddish, with longitudinal furrow along upper surface. Inflorescences can be entirely staminate, entirely pistillate, or all flowers may be hermaphrodite. In addition, some inflorescences are polygamous, with staminate, pistillate and hermaphrodite flowers together. Inflorescences cylindrical, rigid, 3.5–15 × 0.8–2.5 cm, bearing 20–60 flowers. Flowers densely packed, 5-merous, petals absent; staminate flowers reddish yellow, with unpleasant odour; pistillate flowers greenish, with no odour. Fruit an oblong legume, compressed, curved or straight, 10–30 × 1.5–3.5 cm, leathery, shiny dark brown. Flowering July to November, fruiting period variable (Cyprus). Meikle 1977. Distribution Wild origin obscure. Cultivated and ± naturalised in ALBANIA; ALGERIA; CYPRUS; EGYPT: Sinai; GREECE (incl. Crete); ISRAEL; ITALY (incl. Sardinia, Sicily); JORDAN; LEBANON; LIBYA; MALTA; MOROCCO; SPAIN (incl. Balearic Is.); SYRIA; TURKEY; YEMEN. Habitat Dry hillsides in garrigue, coastal and submaritime maquis and in transitional zone between Mediterranean scrub and Sahara; between 0 and 600 m asl. USDA Hardiness Zone 10. Conservation status Not evaluated. Illustration NT238. Cross-reference K309.

Plate 179. The Carob, Ceratonia siliqua, has interesting flowers that do not immediately suggest that it is a legume, but its big broad pods are unmistakeable. Image J.R.P. van Hoey Smith.

The gnarled trunks of the Carob are a common sight in the Mediterranean, where its fruits are put to a variety of uses, especially as animal fodder. The dark pods dangle seductively in front of seed collectors, with the result that its cultivation is frequently attempted in northern Europe. The results for the British Isles are summed up by Johnson (2007): ‘Never recorded to tree size here.’ It is cultivated in California, at least as far north as the Bay Area, but this is really a tree for Mediterranean climates, where its handsome foliage can provide useful shade.

CUNONIACEAE

CERATOPETALUM

Sm.

The eight species of Ceratopetalum are endemic to eastern Australia, with the exception of C. succirubrum C.T. White, which extends into New Guinea (Fortune-Hopkins & Hoogland 2002). Most are tall rain-forest trees, though C. gummiferum is a shrub or small tree of sclerophyllous forest, and is the only one likely to have any chance in our area. Ceratopetalum have opposite, decussate leaves with one or three (rarely two) leaflets, prominent venation and no domatia, and resinous, caducous stipules. The inflorescences are terminal or axillary, rather sparse and subtended by reduced

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239

leaves or bracts. The branching pattern is basically decussate, with corymbs or cymes terminating the ultimate branches. The flowers are hermaphrodite and the petals are incised or absent. The fruit is an indehiscent capsule with woody wings formed from the persistent calyx lobes (Hoogland 1960, Fortune-Hopkins & Hoogland 2002, Rozefelds & Barnes 2002).

Ceratopetalum gummiferum Sm.

New South Wales Christmas Bush

Shrub or tree to 12 m. Bark rough. Branchlets with two longitudinal ridges above the leaves; quadrangular in section when young, later terete. Leaves evergreen and decussate, shiny and leathery, trifoliolate, terminal leaflet symmetrical, ovate to elliptical, 3–10 × 0.7–3 cm, lateral leaflets slightly asymmetrical, 1.8–6 × 0.7–2.3 cm, upper surface with flat or slightly raised midrib, lower surface glabrous, veins prominent, margins serrate, apex acute; petiole 1.1–2.4 cm long; stipules foliose, ovate, 1–1.5 mm long, somewhat resinous. Inflorescence terminal or rarely axillary, two to three decussate lower branches, terminating in irregular cymes. Monoecious; flowers hermaphrodite, pedicellate and generally 5-merous; calyx lobes bright red, petals deeply incised, with three to five lobes, 0.2–0.3 cm long. Fruit a green capsule with persistent calyx lobes (wings) to 1.6 cm long; petals and stamen filaments persist in the fruit. Flowering September to December, fruiting December to February (Australia). Hoogland 1960, Rozefelds & Barnes 2002, Bradford et al. 2004. Distribution AUSTRALIA: New South Wales (northeastern coast). Habitat Sclerophyllous woodland and other open habitats. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT239.

As its common name suggests, this species is an important seasonal plant, popular in Australian gardens and as a cut flower for the display made by the expanded red calyces after the petals have fallen. In full flower the white effect of the inflorescences is pleasant enough but the later display is spectacular, the best coloration being seen in specimens in full sun. Various selections have been made, including plants with white calyces (inevitably called ‘White Christmas’), larger calyces (‘Wildfire’), more compact habit (‘Albery’s Dwarf’), and purple-flushed new growth (‘Magenta Star’), and a variegated clone, ‘Christmas Snow’. Ceratopetalum gummiferum can be grown either as a shrub, with vigorous regrowth after pruning, or as a small tree, and is said to be ‘not affected by frost’ in New South Wales (Elliot & Jones 1984). It is rare in our area. At Tregrehan it is growing slowly but steadily and has flowered, but seems unlikely to form a tree there (T. Hudson, pers. comm. 2006). It is grown in the San Francisco Bay Area. Propagation is by seed, but selections may be propagated by (slow-rooting) cuttings (Elliot & Jones 1984).

Plate 180. The bright red ‘flowers’ of Ceratopetalum gummiferum are actually the expanded calyx, which enlarges after the true petals, which are white, have fallen. Image J.R.P. van Hoey Smith.

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Cercis

New Trees

LEGUMINOSAE (CAESALPINIOIDEAE)

CERCIS

L.

Judas Trees, Redbuds

Plate 181. Part of the redbud collection developed by J.C. Raulston, showing Cercis glabra in the foreground. Image JC Raulston Arboretum.

Cercis is a small genus of 7–10 species distributed in temperate forests across the northern hemisphere in four disjunct regions: the eastern United States to northeast Mexico, western North America, the Mediterranean region east to central Asia, and eastern Asia (Davis et al. 2002). Cercis species are unarmed, deciduous trees or shrubs. The leaves are simple, entire and may be heart-shaped or kidney-shaped; there is a long, distinct petiole. Stipules are caducous and may be small and scale-like or membranous. All Cercis species are dioecious and the flowers are produced directly on the surface of mature stems (cauliflory), prior to leaf expansion. The flowers are 5-merous and arranged in fascicles or clustered racemes, and are typically pink. The floral structure is similar to that in many other legumes, with a small uppermost petal (‘standard’) enclosed by two lateral ‘wing’ petals, subtended by two ‘keel’ petals. The 10 stamens are free, but somewhat enclosed by the keel petals. The leguminous fruit is flat, linear and acute at both ends; the fruits persist on the tree for many months, often well into winter, and can be very attractive in their own right. They are dehiscent, though slowly, shedding their many seeds over a long period (Robertson 1976, Allen & Allen 1981). The Judas Tree, Cercis siliquastrum, has long been a popular small tree in the milder parts of Europe, and in the current period of warming temperatures is escaping from south-facing walls to more open sites in more northern areas. With the exception of the purple-leaved C. canadensis ‘Forest Pansy’, one of the most striking of foliage plants, the eastern Asian and North American species remain comparatively poorly known in northern Europe. The diversity of cultivars of C. canadensis in North America is remarkable and expanding, including many superior selections that should be sought out if planting this species (Dirr 1998, Roethling 2006). It is curious that the Western Redbud, C. occidentalis, has apparently not produced horticultural selections. Among the Asian species, C. chinensis has given rise in Auckland, New Zealand to the very striking cultivar ‘Avondale’, which has bright clear pink flowers borne in great abundance. This has been available for some time, but is currently (2007) being heavily promoted as small grafted specimens in garden centres across the United Kingdom, and is popular in the United States. The genus as a whole responds to summer heat, and all species should be given as warm and open a site as possible, although some (for example, C. canadensis, C. chinensis) can withstand very low winter temperatures if the wood is well ripened. Cercis are often short-lived – incurable canker and Verticillium wilt being important diseases – but as they grow rapidly, flower profusely and harmonise with most garden plants it is well worth giving them even a comparatively temporary space in the garden.

Section II. Species Accounts

Cercis

241

An important review of Cercis in cultivation was given by J.C. Raulston (Raulston 1986), after which, in the remaining decade of his life, he continued to build up a magnificent collection of species and cultivars at the arboretum that now bears his name, and contributed to another review of the taxa (Burns & Raulston 1994). Unfortunately a new building has since been placed in the area where the majority of the collection grew, but the arboretum still has a very wide and interesting assortment to study. The Asian taxa described here do require study, as they are a confusing group, and the fundamental similarities between all Cercis do not help. Neither are they well described in the literature or frequent in herbaria, although the recently available draft Flora of China account (Dezhao et al. 2008) should help clarify the situation. This and the admirable webpage on Cercis by Laurence J. Hatch (1998–2006) make it clear that the Chinese species fall into two groups: those with clusters of flowers, sometimes cauliflorous (C. chinensis, C. chingii), and those with racemose inflorescences (C. chuniana, C. glabra, C. racemosa). Cultivated plants of C. gigantea have clustered flowers, but this mysterious taxon is not treated in the draft Flora of China account. All material of Asian Cercis needs reconsideration in the light of this new account, as it is clear that there are many mislabelled plants in circulation. The notes below reflect observations made on material cultivated under these names. The American taxa are equally muddled, and a really thorough modern analysis of the variation between populations is required. As Cercis species will hybridise in cultivation, seedlings from horticultural sources should be regarded with particular suspicion.

Cercis canadensis L.

Eastern Redbud

This species was described by Bean (B579, S160) and Krüssmann (K312). The following key to the varieties is adapted from Hopkins (1942), but it should be noted here, additionally, that although the leaves of var. canadensis are usually rather acutely pointed, the leaves of the other two varieties may be rounded or have a blunt point; both such shapes may be found on the same shoot. The degree of pubescence on the shoot is also variable, and as the two taxa overlap in central Texas it is probable that there are intermediates there (L. Hatch, pers. comm. 2007). It is almost impossible to differentiate the varieties of C. canadensis when plants are flowering, as they are then without leaves. The morphology of varieties texensis and mexicana is somewhat intermediate between that of true C. canadensis and the Western Redbud C. occidentalis Torr. ex A. Gray (Isely 1975), which has very rounded leaves, and it is apparent that the variation in and taxonomy of southern and southwestern American redbuds is far from being clearly understood. Cercis occidentalis is sometimes included in C. canadensis var. texensis (see, for example, Biota of North America Program 1999–2008), or called C. orbiculata Greene (USDA/ARS, National Genetic Resources Program 2008), although this is a later name. There is also a dispute over the type specimen between Californian and Texan material (see Jepson Flora Project 2006), resolved differently by different factions. DNA evidence, however, suggests that C. occidentalis is rather distantly related to C. canadensis (Davis et al. 2002). Cercis occidentalis was described by Bean (B580) and Krüssmann (K312). In this account we discuss only the eastern populations.

Plate 182. This clone of Cercis canadensis var. mexicana has extremely handsome leaves, the undulate margin being a striking feature (seen here at the JC Raulston Arboretum, June 2006). Image J. Grimshaw.

242

Cercis

New Trees

1a. Mature leaves thin and flexible, dull green on both surfaces, generally cordate, with acute apex; Canada (Ontario), USA (eastern states as far west as Texas) .......... var. canadensis 1b. Mature leaves thick and leathery, rich, deep-green and variably glaucous on both surfaces, reniform-cordate, usually with obtuse or emarginate apex ............................................ 2 2a. Pedicels and immature branchlets glabrous; Mexico (?), USA (Oklahoma, Texas) ............. var. texensis 2b. Pedicels and immature branchlets densely tomentose; Mexico (northeast), USA (Texas) ............................................................................... var. mexicana

C. canadensis f. alba Rehder B580

Cercis canadensis var. mexicana (Rose) M. Hopkins The two southern varieties of C. canadensis are restricted to arid areas with calcareous soils, reflected in their morphology. They both have thick, leathery leaves, shiny and glaucous, which reduces evaporative water loss. The pedicels and stems of var. mexicana are covered in a dense woolly tomentum, while those of var. texensis are glabrous. Hopkins 1942. Distribution MEXICO: northeast (incl. Coahuila, Nuevo León, San Luis Potosí); USA: Texas (Trans-Pecos). Habitat Dry, rocky, calcareous hills. USDA Hardiness Zone 7b/8a. Conservation status Not evaluated. Illustration NT241.

A shrubby tree of about 3 m tall and 5 m wide seen at the JC Raulston Arboretum in 2006 was a good example of this taxon (and may be the clone named ‘Sanderson’: see Hatch 1998–2006). The uppersides of the leaves appeared slightly pewtered, caused by a light layer of glaucous wax overlying their glossy surface, and they had beautifully undulate margins. The dark crimson fruits were also attractive. The taxon as a whole seems to be infrequent in cultivation, but good leaf forms should be sought out.

Cercis canadensis var. texensis (S. Watson) M. Hopkins Syn. C. reniformis A. Gray Plate 183. Cercis canadensis var. texensis ‘Traveller’ in full flower. Its long, weeping branches later bear large leaves. Image JC Raulston Arboretum.

See above for distinguishing characters. Distribution MEXICO (?); USA: Oklahoma (Arbuckle Mts.), Texas (central and western). Habitat Dry calcareous outcrops and exposed escarpments. USDA Hardiness Zone 6b. Conservation status Not evaluated. Illustration NT242.

Although sometimes said to be more shrubby than truly arborescent, var. texensis can make a rounded small tree to 10 m (Dirr 1998). With its big glossy green leaves it is attractive through the growing season. Selected clones include ‘Oklahoma’ with rosy magenta flowers, which J.C. Raulston rated extremely highly, and ‘Texas White’ with ‘masses of pure white flowers – stunning in bloom’ (Raulston 1986). More recent is the pendulous ‘Traveller’, with large leaves that flush copper-red but turn green as they mature, and rose-pink flowers (Dirr 1998); a specimen in the JC Raulston Arboretum is making a nice dome. Both var. texensis and var. mexicana would appear to be good candidates for gardens of Mediterranean climate, as they are somewhat less hardy than C. canadensis from

Section II. Species Accounts

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243

the more northerly parts of its range. Var. canadensis itself varies in hardiness dependent on its provenance, and gardeners in truly cold places such as Minnesota should choose a tree of local origin (Raulston 1986, Dirr 1998). C. chinensis Bunge B580, K312

Cercis chingii W.Y. Chun Shrub or small tree, ultimate height and girth unrecorded. Based on observations on cultivated plants in the eastern United States, C. chingii has a sprawling habit, with lax stems and forming broad mounds, wider than tall (R. Olsen, pers. comm. 2007). Stems somewhat pendulous. Branchlets greyish, with sparse brown hairs when young. Leaves ovate-orbicular to reniform, 5–11 × 5–12 cm, slightly leathery, principal veins five, prominent below, sparsely hairy on veins and vein axils, base cordate or truncate, apex shortly pointed or rounded; petiole 1.5–3 cm, subtended by large persistent stipules. Flowers clustered on branches, pink, to 10 mm long and similar to those of other Cercis species. Fruit 7–8.5 × c. 1.3 cm, thickly leathery, often twisted, not winged, with a straight robust beak, 8 × 2 mm, often early-dehiscent. Flowering February to March, fruiting September to October (China). Dezhao et al. 2008. Distribution CHINA: Anhui, Guangdong, Zhejiang. Habitat Open forest, scrub. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT243. Taxonomic note Cercis chingii is clearly related to C. chinensis, which has thinner-textured leaves, and tardily dehiscent fruits with wings and small curved beaks (Dezhao et al. 2008).

Cercis chingii is grown in the Asian Valley at the US National Arboretum, where it has made small trees, and has been in cultivation at the JC Raulston Arboretum since first accessioned from Chinese seed in 1984 (Raulston 1986) – although the current specimen there is a replacement. It was highly thought of by J.C. Raulston, and images of it suggest that it is a species of considerable horticultural merit, being not only the earliest Cercis to flower but also highly floriferous. An unnamed white clone is known in the United States (T. Lasseigne, pers. comm. 2007). Cercis chingii can easily be recognised by its large persistent stipules.

Cercis chuniana Metcalf Syn. C. likiangensis Chun Tree 6–27 m, 15–20 cm dbh. Branchlets glabrous, purplish above and green below. Leaves ovate to rhomboidal, 7–10 × 4 cm, glabrous on both surfaces although with sparse hairs in the axils of the veins below, and both surfaces sometimes white-farinose, veins prominent, three to five major veins diverging at the base, veins on lower surface elevated and reticulate, base asymmetrical, apex acuminate; petiole short, about 1 cm long. Inflorescence an axillary raceme 3–5 cm, with few (2–10) flowers. Flowers pink; from inspection of images of the flowers, they appear to be similar to those of other Cercis species. Fruit a purplish legume, elongate, narrowly elliptic, straight and flat, 6–10 × 1.8 cm, thin and papery, and with a narrow wing on one side and a short sharp beak. Metcalf 1940, Dezhao et al. 2008. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hunan, Jiangxi. Habitat Unrecorded. USDA Hardiness Zone 7–8. Conservation status Not evaluated.

A specimen labelled Cercis chuniana was observed in the JC Raulston Arboretum in May 2006, but has since been determined by Laurence J. Hatch to be incorrectly named (L. Hatch, pers. comm. 2007) and has been removed. This plant did not have the characteristic non-cordiform leaves or glaucous to farinose undersides of C. chuniana. Any propagations from it should therefore be regarded with suspicion. Our own fingers were burned over a specimen at Kew received in 1995 from a mysterious ‘University of Raleigh’ (almost certainly from J.C. Raulston, of North Carolina State University in Raleigh). Flowering material from this tree was drawn by Hazel Wilks for this book, but re-examination of the plant in the light of more recently available sources demonstrates quite clearly that it is not this species. The true C. chuniana may not be in cultivation.

Plate 184. The Chinese Cercis chingii – the earliest redbud to flower – has high horticultural merit. Image JC Raulston Arboretum.

244

Cercis

New Trees

Cercis gigantea F.C. Cheng & Keng. f.

Plate 185. Cercis gigantea is an enigmatic taxon, but there is no doubt that its leaves are very impressive. Image R. Houtman.

Giant Redbud

This species is enigmatic. There is no record of the publication of the name in either the International Plant Names Index (www.ipni.org) or the International Legume Database & Information Service (www.ildis.org), and it is not described in the (currently draft) Flora of China treatment, and yet it appears in the catalogues of several nurseries and botanic gardens. Davis et al. (2002) included it in their study of the evolutionary relationships of Cercis and concluded that it is most closely related to C. chinensis (the DNA used in the study came from a tree in cultivation at the JC Raulston Arboretum at North Carolina State University). The limited information available via the internet suggests that C. gigantea is similar to C. chinensis but has much larger leaves and a more vigorous growth rate. Plants originating from seed collected as C. chinensis during the 1980 Sino-American Botanical Expedition (SABE 1010, from Shennongjia Forest, Duanjiangping, western Hubei) were later identified as C. gigantea by Dr Ted Dudley at the US National Arboretum (R. Olsen, pers. comm. 2007), supporting this supposition of similarity between the two taxa. An important source of seed of C. gigantea was a large (over 10 m) specimen formerly growing in the redbud collection at the JC Raulston Arboretum, removed in 2001 (probably the same tree as mentioned above). It had a single stem to about 1 m, then several ascending stems, and bore pale pink flowers very early in the season (T. Lasseigne, pers. comm. 2007). It was received as seed from the Shanghai Botanic Garden. Descendants include one accession (NA 65489) at the US National Arboretum (R. Olsen, V. Tyson, pers. comms. 2007), but there are probably many more.

Cercis glabra Pamp. Syn. C. yunnanensis Hu & Cheng Tree to 6–16 m, 30 cm dbh. Branchlets dark. Leaves thickly papery to almost leathery, somewhat circular or rounded to reniform, 5–12 × 4.5–11 cm, glabrous or with tufts of hairs in vein axils below, major veins usually seven, inconspicuous, minor veins on lower surface reticulate, cordate at base, apex acuminate; petiole glabrous, 2–4.5 cm long. Inflorescence a short axillary raceme, 5–10 mm, bearing 2–10 flowers (or more). Flowers pink, to 1.5 mm long, and similar to those of other Cercis species. Fruit 9–14 × 1.2–1.5 cm, sutures unequal, with broad wing to 2 mm, apex acuminate, seeds one to eight. Flowering March to April, fruiting September to November (China). Pampanini 1910, Raulston 1986, Dezhao et al. 2008. Distribution CHINA: Anhui, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Shaanxi, Sichuan, Yunnan, Zhejiang. Habitat Forests on slopes, between 600 and 1900 m asl. USDA Hardiness Zone 7–8 (?). Conservation status Not evaluated. Illustration NT240, NT245.

Once again, there is a big problem in reconciling cultivated material labelled C. glabra with the descriptions of the species as a wild tree. For example, a tree at the US National Arboretum labelled Cercis glabra (NA 69139), grown from material received from the Xian Botanical Garden in 1998, was noted in 2006 to be indistinguishable from an adjacent ‘C. gigantea’ (NA 65489). This was checked (in 2007) by Richard Olsen, and he too could find no points of difference, with the fruits in both being clustered and not racemose. The name appears in collection lists of other American arboreta, but plants need individual checking to confirm their identities.

Section II. Species Accounts

Cercis

245

The name C. yunnanensis is applied as a synonym in the Flora of China account (Dezhao et al. 2008) but this has rung some alarm bells in the United States, where plants labelled C. yunnanensis are frequently cultivated (Dirr 1998). These tend to be rather densely pubescent (the hairiest of all redbuds, according to Todd Lasseigne, pers. comm. 2007), while the Flora of China account suggests that the only hairs on C. glabra should be confined to tufts in the vein axils on the undersides of the leaves. C. griffithii Boiss. S161, K312 C. occidentalis Torr. ex A. Gray B580, K312 C. racemosa Oliv. B580, K312 C. reniformis (NOW C. canadensis var. texensis (S. Watson) M. Hopkins, NT242) K312 C. siliquastrum L. B581, S161, K312 C. siliquastrum f. alba (West.) Rehder B581

Plate 186. The deep pink flowers of Cercis glabra are produced extremely freely, even on young trees. Image JC Raulston Arboretum.

CUPRESSACEAE

CHAMAECYPARIS

Spach

False Cypresses, White Cedars Farjon (2001) recognised six species in the genus Chamaecyparis, though C. nootkatensis has since been transferred into Xanthocyparis (Farjon et al. 2002). Chamaecyparis species are found in North America and eastern Asia. They are generally very large evergreen trees or more rarely shrubs, with a pyramidal shape and spreading branches; the leader shoot is nodding. The bark is smooth, reddish brown, and peels off in strips or scales, although later longitudinal fissures may form. The branchlets are terete to rhombic in cross-section, dorsiventrally flattened, fan-shaped. The leaves are in pairs, scale-like, appressed, decussate, ovate to rhombic, acuminate or obtuse; the lateral leaves are boat-shaped, overlapping the facial leaves, though of similar size. The male strobili are ovoid to oblong, red or yellow, with two to three pairs of microsporophylls. The female cones are solitary, terminal, green or violet to brown, globular, and mature within a year. The seed scales, 8–12 per cone, are decussate, thick and woody, with a small, mucronate umbo. The seeds, borne (one to) two (to five) per scale, are lenticular, with two membranous wings, of equal size. Chamaecyparis and Cupressus are often confused with each other, and some authors advocate placing the former genus in synonymy with the latter. However, DNA evidence suggests that Chamaecyparis is a distinct genus closely related to Fokienia (Gadek et al. 2000, Little et al. 2004). The combination Chamaecyparis hodginsii (Dunn) Rushforth has recently been made (Rushforth 2007). Chamaecyparis are large, stately conifers with great presence in the landscape, but having a tendency to produce a protean array of mutations of form and foliage colour. Such ‘dwarf’ and ‘coloured’ conifers may be disparaged by horticultural snobs but they frequently have a very valuable place in the garden. It is interesting

246

Chamaecyparis

New Trees

1 cm

A 1 cm

B 1 cm

C

D

E

Section II. Species Accounts

Chamaecyparis

that the Nootka Cypress – now Xanthocyparis nootkatensis, but formerly placed in Chamaecyparis – does not show this tendency to abundant mutations. The most serious limitation to cultivating the genus is root rot caused by the fungus Phytophthora lateralis, which is affecting the natural population of C. lawsoniana in Oregon and northern California, and cultivated trees throughout western North America. The disease effectively kills the roots, leading to the death of the tree, and is transmitted via water- or soil-borne spores. Long-distance dispersal is assisted by human agency, and then it spreads rapidly downslope. Large areas of the natural distribution of C. lawsoniana are affected, and the fungus has all but eliminated this species from cultivation in western North America (USDA Forest Service 2008). Other species seem not to be affected by the disease, and it is as yet unknown in Europe.

Figure 24 (opposite). Chamaecyparis obtusa var. formosana: habit with female cones (A). Thuja koraiensis: underside of branchlet (B); detail of branchlet and female cone (C). Calocedrus formosana: detail of branchlet with female cones (D). Chamaecyparis obtusa var. formosana: detail of branchlet with female cones (E).

C. formosensis Matsum. B592, S162, K69 C. funebris (NOW Cupressus funebris Endl.) K69 C. henryae (NOW C. thyoides var. henryae (H.L. Li) Little) B601

247

C. lawsoniana (A. Murr.) Parl. B592, S162, K70 C. nootkatensis (NOW Xanthocyparis nootkatensis (D. Don) Farjon & Harder) B596, S166, K83

Chamaecyparis obtusa (Siebold & Zucc.) Endl.

Hinoki Cypress

This species was described by Bean (B596, S167) and Krüssmann (K84).

Chamaecyparis obtusa var. formosana (Hayata) Hayata Syn. C. taiwanensis Masam. & S. Suzuki Var. formosana has shorter lateral (1–2 mm vs. 3 mm) and facial (1–1.2 mm vs. 1–1.5 mm) leaves when compared with the type variety. The leaves are typically thin with a subacute apex, while in the type they are thick with an obtuse apex. The cones of var. formosana are typically smaller (7–9 mm diameter vs. 8–12 mm) and the scales have a small central depression. Li & Keng 1994c, Fu et al. 1999e, Farjon 2005b. Distribution TAIWAN: Chiayi, Hualien, Ilan, Taichung, Taipei. Habitat Mesic, broadleaved forest or mixed forests between 1300 and 2800 m asl. Var. formosana can form pure stands or mixes with C. formosensis Matsum. at lower elevations. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Li & Keng 1994c, Fu et al. 1999e; NT246, NT247. Cross-references B598, K85. Taxonomic note DNA-based studies of Chamaecyparis suggest that C. obtusa is more closely related to the American species (C. thyoides, C. lawsoniana) than to the other Asian species. They also confirm the placement of var. formosana within C. obtusa (Li et al. 2003, Wang et al. 2003). Chamaecyparis obtusa var. formosana can be distinguished from the other Taiwanese taxon, C. formosensis, by the shape of the cones (globose rather than oblong) and the number of seed scales (8–10 vs. 10–13).

Travellers to Taiwan have long marvelled at the huge size of the two Chamaecyparis species found in the ‘foggy forest’ on the mountains, C. formosensis at lower altitudes, replaced slightly higher up by C. obtusa var. formosana (Flanagan & Kirkham 2005). H.J. Elwes, who visited Taiwan in 1912, was probably the first Western dendrologist to see them in the wild. He noted that they could be easily distinguished by their foliage colour, greyish green in C. formosensis and brighter green in C. obtusa var. formosana, whose ‘shapely pyramids’ he admired (Elwes 1935). He counted 400 rings in a log of ‘three feet diameter’ and concluded that this is a slow-growing species, but this may be due to crowding in dense forests on mountain slopes.

Plate 187. Chamaecyparis obtusa var. formosana does well in the eastern United States, where it has been grown since the 1950s. This tree at the Scott Arboretum was planted in 1984. Image R. Maurer.

248

Chamaecyparis

New Trees

The first recorded introduction was in 1910, when seed was sent from Taiwan by Jinzô Matsumura to Henry Clinton-Baker at Bayfordbury, Hertfordshire, but only one seed germinated (Dallimore et al. 1966), and it is not clear whether this resulted in the species becoming established in cultivation. Bean (1976a) does not mention any specimens. In 1976, however, it was collected by C.N. Page, and trees from this source are established at Benmore and are currently 4–5 m tall (M. Gardner, pers. comm. 2006). Further expeditions to Taiwan by Edinburgh and Kew have resulted in several more collections being made. None have been particularly fast-growing, one specimen at Wakehurst Place grown from ETOT 115, collected by Kirkham and Flanagan in 1993, being 2.2 m in 2005. The fine, somewhat ferny sprays of foliage are attractive, and although supposedly a rich green (Rushforth 1987), can be bronzed when young. In Taiwan, it grows in rather benign cloud-forest conditions, with ample moisture and humidity and a comparatively mild temperature, so planting sites should be chosen accordingly. C. pisifera (Siebold & Zucc.) Endl. B599, S168, K88 C. thyoides (L.) Britton, Sterns & Poggenb. B600, S169, K92 C. thyoides var. henryae (H.L. Li) Little B601, K92

BIGNONIACEAE

×CHITALPA

T.S. Elias & W. Wisura

The progeny of artificial crosses between Chilopsis and Catalpa, plants of the nothogenus ×Chitalpa are large shrubs or small trees to 10 m, usually single-stemmed, and forming a broad, dense crown. The leaves are deciduous, 10–17 × 2–4.5 cm, alternate or rarely opposite or ternate, the upper surface dull green, the lower lighter green and pilose, the margins entire, the apex attenuate; the petiole is distinct, 1–2.5 cm long. The inflorescences are terminal, erect and racemose or paniculate, with 15–40 flowers. The flowers are hermaphrodite, zygomorphic, the corolla tubular with five lobes, to 2.5 cm long, white to pink; the corolla lobes are frilled, the two upper lobes unmarked, the two lateral lobes and one lower lobe with interconnected purple lines entering the corolla. Fruit is not produced, due to hybrid sterility. In the United States the flowers appear from May to September (Elias & Wisura 1991, Barnes 2000). Until very recently all clones of ×Chitalpa were known as the hybrid ×Chitalpa tashkentensis T.S. Elias & W. Wisura, which was described as the product of a cross between Catalpa bignonioides Walter and Chilopsis linearis Sweet, first produced by Nikolai Rusanov at the Uzbek Academy of Sciences Botanical Garden in Tashkent, Uzbekistan in 1964, and reaching the United States in 1977 (Elias & Wisura 1991, Barnes 2000). Recently published research (Li et al. 2006) has revealed, however, that Chilopsis was the female parent and Catalpa the male – and, more problematically, that the two original clones named have different Catalpa fathers, rendering a single nothospecific epithet inaccurate. Catalpa ×galleana (C. ovata × C. speciosa) was responsible for ‘Pink Dawn’, while Catalpa speciosa fathered ‘Morning Cloud’. Richard Olsen has confirmed (pers. comm. 2007) that the type specimen is ‘Pink

Section II. Species Accounts

×Chitalpa

Dawn’, which should now be known as ×Chitalpa tashkentensis ‘Pink Dawn’ (Chilopsis linearis × Catalpa ×galleana). To avoid excessive proliferation of nothospecific epithets it is recommended that no new hybrid name is published for ‘Morning Cloud’, as it is likely to be joined by numerous other hybrids with diverse Catalpa parentages. The results of crosses between Chilopsis and Catalpa have become widely cultivated for their attractive flowers – and perhaps for their novelty value. The Desert Willow Chilopsis linearis is typically a plant of the (normally) dry river courses of the southwestern United States, where it produces long whippy growths of narrow leaves and terminal inflorescences. It is adapted to hot conditions with low rainfall, although the riverbeds and washes where it is most frequently found may hold some moisture through the year. It is not hardy enough to be growable in most of our area. Crossing it with catalpas from the southeastern United States, adapted to hot humid areas with summer rainfall, was a bold move, but the resulting seedlings have proved their worth in a range of conditions, so long as the summer is warm and preferably hot – to encourage flowering on the new growth and also to enable the wood to ripen. If this does not occur some dieback will result, and in Zone 6 conditions plants will be killed to the base; they are hardy from Zone 7 upwards. Growth can be very rapid in good conditions. In the eastern United States it is prone to powdery mildew and leaf spots and is not recommended there for areas of high humidity (Dirr 1998, Olsen et al. 2006). In Europe it is probably ideal for Mediterranean areas, or western France, but in the United Kingdom it is not very impressive, seldom achieving more than a few spindly metres with a thin tuft of growth on top. Of the two original clones named, ‘Pink Dawn’ is smaller and has light pink flowers while ‘Morning Cloud’ is larger and more vigorous, with a slightly pendulous habit and pale pink or white flowers (Elias & Wisura 1991), with prominent purple striations in the corolla. ‘Minsum’, sold under the name Summer Bells , is a more recent introduction and has slightly richer flower colour. In favourable conditions the hybrid flowers profusely and over a long season. As Dirr (1998) says, it does not ‘measure up to the better deciduous shrubs’ – but Richard Olsen is conducting a breeding programme at the US National Arboretum, in the hope of changing this.

ANACARDIACEAE

CHOEROSPONDIAS

B.L. Burtt & A.W. Hill

Choerospondias is monospecific, comprising only C. axillaris. A second species, C. auriculata D. Chandra, was described from India (Chandra 1978), but this was later proven to be a case of mistaken identity: the type was actually a fragmentary specimen of Ailanthus altissima (Mill.) Swingle (Simaroubaceae) (Mitra & Murthy 1996).

249

Plate 188. ‘Pink Dawn’ has been recognised as the type of the remarkable bigeneric hybrid ×Chitalpa tashkentensis. Image K. Camelbeke.

250

Choerospondias

New Trees

A

1 cm

B

Section II. Species Accounts

Choerospondias

Choerospondias axillaris (Roxb.) B.L. Burtt & A.W. Hill

Hog Plum, Lapsi

Fast-growing tree to 20 m, trunk buttressed, to 0.4 m dbh. Bark greyish brown, exuding a sticky, colourless resin and developing longitudinal splits that peel to reveal a pink inner layer. Sap turns black when exposed to the air. Crown broad and irregular. Leaves deciduous, alternate, fasciculate at the ends of branches, imparipinnate, 30–40 cm long, 4–15 pairs of leaflets; leaflets opposite, 4–12.5 × 2–6 cm, elliptical, upper surface green, lower surface glaucous and yellowish, leaves turning red before falling, margins entire or with some distal undulations and/or notches, apex long and tapering; petiole 0.5–0.8 cm long, somewhat swollen at node; leaf rachis grooved. Flowers yellowish or red, 0.3–0.5 cm diameter, in terminal or axillary panicles (male) or racemes (female); most plants dioecious, though occasional bisexual flowers occur. Fruit a drupe, 1.5 × 2.5 cm diameter, ovoid or globose, red, flesh edible though acidic. Seed with five distinct apical pores. Flowering April to June, fruiting July to September (Vietnam). Kostermans 1991, Hoang et al. 2004. Distribution CHINA: Guangdong (incl. Hainan), Guangxi, Guizhou, Hong Kong, Hubei, Sichuan, Yunnan; INDIA: Assam, Sikkim; JAPAN: Kyushu; LAOS; NEPAL; THAILAND; VIETNAM. Habitat Choerospondias is typically a coloniser of disturbed habitats below 600 m asl, though it reaches 1000 m asl in Sikkim. It prefers deep, wet clay or sandy clay soils. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Kostermans 1991, Hudson 2004; NT250. Taxonomic note The Japanese populations have been distinguished as C. axillaris var. japonica (Ohwi) Ohwi.

Although a commonly occurring tree over much of subtropical Asia, Choerospondias axillaris has slipped below the horticultural radar: no references to it will be found in the standard gardening encyclopaedias, and even the internet is silent on its possibilities in horticulture. There are a handful of individuals in cultivation. At Tregrehan it was grown, as Tom Hudson says, ‘as a flier’ (pers. comm. 2005), from seed from the Shanghai Botanic Garden in 1995. So far the ‘flier’ has worked. When seen in 2005 the largest of these trees was 8 m tall and growing vigorously, with new shoots of over 1 m, the stems of which are red. The handsome pinnate leaves are flushed red on emergence, becoming mid-green. The only problem noted so far is that the wood is brittle in strong wind (Hudson 2004). It has not yet flowered. A much older specimen (accessioned 1983) grows against a wall at Glasnevin, but its position adjacent to a roadway has meant that it has been heavily pruned and it is only 2.5 m tall. The fruits of C. axillaris, rich in vitamin C, are greatly valued in Nepal, where it is known as Lapsi and is considered to be an important crop plant (Pieber et al. 2002).

LAURACEAE

CINNAMOMUM

Schaeff.

Cinnamon Trees, Camphor Trees According to Rohwer (1993a), Cinnamomum comprises 350 species, most of which occur in tropical and subtropical Asia, Australia and the Pacific; this total also includes approximately 60 species from Central and South America, however, that were formerly included in Phoebe. Cinnamomum species are evergreen trees or shrubs and are often aromatic. The leaves are alternate or opposite and trinerved or triplinerved (rarely pinninerved). The inflorescences are axillary or terminal, paniculate, composed of cymes with one to three hermaphrodite (rarely polygamous) flowers. The flowers are yellow or white, rather small and campanulate. They are 3-merous with equal tepals;

251

Figure 25 (opposite). Choerospondias axillaris: habit with inflorescences (A); fruit (B).

252

Cinnamomum

Plate 189. Cinnamomum parthenoxylon, making a dense, upright tree in North Carolina. Image T. Avent.

New Trees

there are nine fertile stamens (rarely six) in three whorls and the innermost whorl is glandular; three staminodes are usually present. The fruit is fleshy and is subtended by a small or well-developed cupule (Rohwer 1993a, Liao 1996b, Li et al. 2005). Cinnamomum is one of the vast and difficult genera of the Lauraceae, a family bedevilled by indistinctness of both genera and species. Cinnamomum is however of particular importance and interest as the source of aromatic products: cinnamon comes from Cinnamomum verum J. Presl, originally native to Sri Lanka and southern India; C. camphora, when distilled, gives the aromatic camphor oil; and several other species yield useful products of lesser importance (Mabberley 1997a). Cinnamomum camphora is probably the best-known species in cultivation in our area, and where conditions are suitable it is capable of making an extremely beautiful tree, as in the famous avenue at Kirstenbosch in Cape Town, for example, or more generally in California. In cooler climates, as in maritime Europe, it is less successful, probably requiring more summer heat than it receives, but if cut back by frost it usually resprouts vigorously (Hogan 2008, Johnson 2007). As such it is worthy of wider planting and experimentation, especially with warming summers. It is probable that several other species will become available for testing in our area. The central Chinese species C. jensenianum Hand.Mazz. is established at Woodlanders Nursery in South Carolina, for example, and available commercially from there (Woodlanders 2007–2008), and C. tamala (Buch.-Ham.) T. Nees & C.H. Eberm. from the eastern Himalaya and western China is cultivated in the Temperate House at Kew and should be tried outside. The beauty of Cinnamomum lies in their elegant foliage and the shape of the trees, as the flowers are small and do not provide a ‘show’ – though they can be pleasantly fragrant. All Lauraceae prefer an acidic soil with ample moisture in summer, and in the case of Cinnamomum at least, high temperatures will give the best results, although trees should not be placed in full sun where scorching is a possibility. Frost-hardiness is surprising in the species described, but will be assisted by full ripening of the new growth. All Cinnamomum are able to resprout from basal wood if the top is harmed, and will soon recover from frost damage. C. camphora (L.) T. Nees & C.H. Eberm. B614, S172, K327

Cinnamomum glanduliferum (Wall.) Meissn. Tree 5–15(–20) m, 0.3 m dbh. Bark greyish brown with deep, longitudinal fissures, revealing reddish brown inner bark; camphor-scented. Branchlets robust, angular, greenish brown. Leaves evergreen, alternate, 6–15 × 4–6.5 cm, shape extremely variable, elliptic to ovate or lanceolate, leathery, upper surface glossy dark green and glabrous, lower surface glaucous, usually glabrous, four to five pairs of lateral veins, vein axils conspicuously puckered, margins entire, apex acute to short-acuminate; petiole 1.5–3.5 cm long, robust, glabrous. Inflorescence axillary, paniculate, 4–10 cm long. Flowers small, to 0.3 cm long, yellowish; perianth six-lobed, hairy inside; stamens nine, staminodes three. Drupe globose, to 1 cm diameter, black; cupule about 1 cm long, red. Flowering March to May, fruiting July to September (China). Li et al. 2005. Distribution CHINA: Guizhou, Sichuan, Xizang, Yunnan; INDIA; MALAYSIA; MYANMAR; NEPAL; THAILAND. Habitat Broadleaved evergreen forest between 1500 and 2500(–3000) m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Cross-references B614, S172, K327.

Section II. Species Accounts

Cinnamomum

253

Cinnamomum glanduliferum received minimal treatment by Bean (1976a) and Clarke (1988), but seems to have been in cultivation in southwestern England for some time. The specimen at Trewidden, Cornwall noted by Bean achieved 10 m, while the current British champion is 9 m at Ventnor Botanic Garden, Isle of Wight (Johnson 2007). The origins of these trees are unknown. It is also cultivated in California, but trees on the Stanford University campus have apparently been damaged by frost (Trees of Stanford 2008). Johnson (2007) considers it to be ‘a better prospect’ in the United Kingdom than C. camphora, but it does not appear to be as hardy as C. japonicum or C. parthenoxylon.

Cinnamomum japonicum Siebold Syn. C. chekiangense Nakai, C. insularimontanum Hayata, C. pedunculatum Nees, C. tenuifolium J. Sugimoto Tree to 15 m, 0.35 m dbh. Branchlets slender and red or reddish brown, glabrous and fragrant. Leaves evergreen, subopposite to alternate, 7–10 × 3–3.5 cm, oblong to ovate or lanceolate, leathery, upper surface dark green and glabrous, lower surface greyish green, opaque and glabrous, triplinerved with lateral nerves arising 1–1.5 cm above the base, margins entire, apex acute to acuminate; petiole robust, 0.8–2 cm long, reddish brown and glabrous. Inflorescence axillary and paniculate, shorter than the leaves, 3–4.5(–10) cm long, branching to bear cymes. Flowers three to five per cyme, 4.5 mm long. Drupe black, ellipsoid, 0.7 × 0.5 cm; cupule shallowly cup-shaped, margins entire or dentate. Flowering April to May, fruiting July to September (China). Ohwi 1965, Li et al. 2005. Distribution CHINA: Anhui, Fujian, Jiangsu, Jiangxi, Zhejiang; JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; NORTH KOREA; SOUTH KOREA; TAIWAN. Habitat Evergreen broadleaved forest at low elevation (between 300 and 1000 m asl), often near the coast. USDA Hardiness Zone 7–8. Conservation status Lower Risk; but Cinnamomum japonicum occurs in isolated populations, often on coastal islands, and is susceptible to habitat degradation and loss. Illustration NT253, NT255. Cross-reference K328.

Cinnamomum japonicum is well established in cultivation in North America but poorly known in western Europe, although there seems to be no reason why it should not thrive here, in milder areas. Two principal sources of introduction have led to the existence in cultivation of two stocks of material, under the names C. chekiangense and C. japonicum, but any differences probably represent natural variation within the one broadly circumscribed species, the introductions having come from widely separated areas. The stock known as C. chekiangense (frequently misspelled as chekiangensis) in North America was first introduced to the United States by Cliff Parks in the 1980s and has proved to be remarkably hardy, frequently surviving temperatures of –18 ºC, although with some damage to stems during a prolonged period of –22 ºC at Camellia Forest Nursery, North Carolina in the 1980s (Hogan 2008), and stocks known as C. japonicum seem to be equally tolerant. The principal source for the plants labelled C. japonicum in North America seems to have been an importation from Nanjing Botanic Garden made by Piroche Plants in the 1990s. Under either name this is an exceptionally beautiful tree with great elegance. While young it forms a narrow column, but with age it extends horizontally spreading branches with drooping shoots. The leaves are also pendulous, and equally beautiful, their long outline enhanced by the three veins. On emergence they are pink or reddish, but mature to a slightly glossy dark green with a dull grey-glaucous reverse. The bark

Plate 190. The elegant, three-veined leaves of Cinnamomum japonicum (here in the form known as C. chekiangense) – a superb hardy evergreen. Image T. Avent.

254

Cinnamomum

New Trees

remains green for several years. It is probably best grown in light or dappled shade, with plenty of moisture during the growing season. In such conditions it thrives in the Pacific Northwest at least as far north as Vancouver, while in the east it is hardy in North Carolina and should be tried in sheltered sites further north.

Cinnamomum micranthum (Hayata) Hayata Tree 14–20(–30) m, 0.25–0.65 m dbh. Bark rigid, blackish brown or reddish brown with irregular, longitudinal fissures. Branchlets pale brown with convex lenticels, glabrous. Leaves evergreen, alternate, though inserted on the upper side of the branchlet, 7.5–9.5(–10) × 4–5(–6) cm, oblong to ovate or elliptic, papery or leathery, upper surface glossy yellowish green and glabrous, lower surface yellowish brown and glabrous, pinninerved with four to five pairs of lateral veins, margins cartilaginous and involute, apex short-acuminate; petiole 2–3 cm long, pale brown and glabrous. Inflorescence terminal or axillary, paniculate, 3–5 cm long, branching near the base. Flowers 2.5 mm long, white or purple-red and scented. Drupe ellipsoid and 1.5–2.2 × 1.5–2 cm, greenish; cupule urn-shaped, margins entire or undulate. Flowering July to August, fruiting October (China). Liao 1996b, Li et al. 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Jiangxi; TAIWAN; VIETNAM. Habitat Lowland rain forest in valleys, on mountain slopes and along rivers and roadsides between 300 and 650 m asl (up to 1800 m asl in Taiwan). Cinnamomum micranthum almost always co-occurs with C. parthenoxylon. USDA Hardiness Zone 9–10. Conservation status Lower Risk, though susceptible to habitat degradation and loss.

Cinnamomum micranthum is still very rare in cultivation, but is commercially available in the United Kingdom. No large specimens have yet been recorded and it is not known how hardy the species will prove to be, but its large glossy leaves that flush pinkish orange make it well worth experimenting with.

Cinnamomum parthenoxylon (Jack) Meisn. Syn. C. porrectum (Roxb.) Kosterm. Tree to 20 m, 0.4 m dbh. Bark dark greenish brown to yellow-grey with deep longitudinal fissures; peeling in thin strips. Branchlets angular, greyish green and glabrous. Leaves evergreen, alternate, 6–12 × 3–6 cm, leaves on fertile branches smaller, elliptic to ovate, leathery, upper surface dark green and glabrous, lower surface glaucous-green and glabrous, pinninerved with four to five pairs of lateral veins, margins entire, apex acute to acuminate; petiole 1.5–3 cm long, glabrous. Inflorescence axillary to subterminal, paniculate, 4.5–8 cm long. Flowers four to seven per cyme, 3 mm long, greenish yellow. Drupe black and globose, 0.6–0.8 cm diameter; cupule red and turbinate. Flowering March to May, fruiting April to October (China). Li et al. 2005. Distribution CAMBODIA; CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Sichuan, Yunnan; INDIA; INDONESIA; LAOS; MALAYSIA; PAKISTAN; PHILIPPINES; THAILAND; VIETNAM. Habitat Evergreen broadleaved forest below 1500 m asl. USDA Hardiness Zone 7. Conservation status Data Deficient. Cinnamomum parthenoxylon is still relatively common on a global scale, but in Vietnam it is critically endangered due to excessive exploitation of its roots for its volatile oils and camphor (IUCN 2007–2008). Illustration NT252.

Cinnamomum parthenoxylon has the unlikely distinction of being the only species in New Trees to have been found in a general internet search to be offered on eBay (as C. porrectum seeds, May 2007). As a selling point the vendor was claiming it to be the hardiest Cinnamomum, suitable for Zone 7a conditions. That it is reasonably hardy is supported by observations at Camellia Forest Nursery (Zone 7b), where it has not suffered any damage at –8 ºC (Camellia Forest Nursery 2007–2008). Seed is also offered by several major companies specialising in tree seed, but this has yet to turn into abundant plants, it would seem, as the species remains rare in cultivation. Figure 26 (opposite). Cinnamomum japonicum: habit (A); inflorescence (B); single flower (C); infructescence (D).

Cinnamomum wilsonii Gamble Tree to 25 m, 0.3 m dbh. Branchlets dark brown or purplish brown. Leaves evergreen, opposite or alternate, 8.5–18 × 3.2–3.5 cm, ovate to oblong, leathery, upper surface dark green and glabrous, lower surface greyish green, opaque and with white, silky hairs when young, soon glabrous, triplinerved with lateral nerves arising

Section II. Species Accounts

Cinnamomum

0.25 cm

C

1 cm

B

D 1 cm

1 cm

A

255

256

Cinnamomum

New Trees

0.05–0.15 cm above the base; there may also be an additional 3–10 lateral veins; margins cartilaginous and involute, apex acuminate; petiole 1–1.5 cm long and glabrous. Inflorescence axillary and paniculate, branching to bear cymes or racemes. Flowers two to five per cyme, 6.5 mm long, white. Drupe black-brown and ellipsoid, 1–1.5 × 0.5–0.8 cm; cupule inconspicuous, margins shallowly lobed or entire. Flowering April to May, fruiting September (China). Li et al. 2005. Distribution CHINA: Guangdong, Guangxi, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan. Habitat Forest on mountain slopes, in valleys or along rivers between 800 and 2400 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated.

The only specimen of Cinnamomum wilsonii traced in our area is at the JC Raulston Arboretum, planted in 2000. This is a beautiful young tree, measured at 5.2 m in November 2006 (JC Raulston Arboretum database), having apparently put on a metre of growth since being observed for New Trees in May 2006, when it was approximately 4 m tall. Such rapid growth rates are typical of Cinnamomum when they are well suited. It is clearly flourishing in North Carolina, growing up straight and shapely – not quite as elegant as C. japonicum would be at the same size, but highly attractive, with reflective olive- to mid-green leaves that have a glaucous underside. Cinnamomum wilsonii would seem to be well worth trying wherever C. japonicum thrives. C. zeylanicum Blume K328

RUTACEAE

CITRUS

L.

Citrus, Lemons, Limes, Oranges As with many plant genera of economic significance, the taxonomy of Citrus is complex; hybridisation is common and hybrid lines are perpetuated by apomixis. Swingle (1944) recognised 12 species with edible fruit and six species without, but the number of species with edible fruit may be as few as four (Mabberley 1997b). To further complicate the issue, DNA studies suggest that the related genera Microcitrus Swingle, Poncirus Raf. and Fortunella Swingle should be merged with Citrus (Freitas da Araújo et al. 2003). Citrus species are evergreen trees or shrubs, often with spiny branches. The leaves are alternate, fragrant, and usually have a winged petiole. The flowers occur in axillary clusters and are usually white and sweetly scented. They have a cup- or urn-shaped calyx with three to five segments; four to eight thick, imbricate petals; and 20–60 stamens with their filaments variously fused towards the base. The fruit is a hesperidium – a type of berry with a rough, leathery skin in which the flesh is divided into segments, and each segment is filled with juice-containing vesicles (Chang & Hartley 1993). One of the most remarkable sights observed during the preparation of New Trees was a Grapefruit tree growing outdoors in a sheltered corner of the Chelsea Physic Garden, London, laden with ripe fruit at the end of January 2008 (see Plate 20, p. 8). This remarkable specimen, grown from a pip in 1948, stood outside in a pot in a nearby garden from the 1950s until 1990, when it was donated to the Physic Garden. Basking in the London heat island (see Mayor of London 2006), it is currently exceptional but is perhaps a precursor (and warning) of things to come. Marmalade is produced from the fruits (Chelsea Physic Garden database; D. Frodin, pers. comm.

Section II. Species Accounts

Citrus

257

2008). Several other Citrus taxa usually considered too tender for outdoor cultivation, including cultivars of C. ×limon, are maintained in pots but kept outside year-round in this remarkable garden. These examples aside, the vast majority of Citrus are trees only for Mediterranean climates or the cool greenhouse; the two species described below, however, seem to have genuine hardiness and are worth trying, especially in areas with high summer temperatures to enable the wood to ripen. The shelter of a warm wall is to be recommended, so long as the soil is not too dry in summer. In areas where summer irrigation is practised, Sean Hogan recommends withholding water in late summer to encourage the wood to harden up (Cistus Nursery 2007–2008). Temperate gardeners can also try Meyer’s Lemon, C. ×limon ‘Meyer’, in very sheltered sites, while Cistus Nursery considers Citrus ‘Eustis’ and C. limettioides Tanaka to be hardy to –7 ºC. Just outside our area, Woodlanders Nursery in Aiken, South Carolina is pushing the boundaries of Citrus cultivation by offering a number of other cultivars. Many are hybrids with Citrus (Poncirus) trifoliata, in the group widely known as ‘citranges’, but a number of taxa are involved in the parentages. The nomenclature of cultivated Citrus is a muddle, to say the least, and names should perhaps always be accepted at face value only. There is something very pleasing in the idea of growing one’s own citrus outdoors, and it could be attempted more often in the milder parts of our area: C. trifoliata is all very well, but it makes truly horrible marmalade. All Citrus should be grown in fertile acidic soils with pH 5–6 and abundant available iron, but excessive organic material should be avoided. Patent fertilisers for Citrus are available and are used for C. tachibana at Quarryhill (W. McNamara, pers. comm. 2004).

C. ×aurantiifolia (Christm.) Swingle K335 C. ×aurantium L. (NOW includes Sour Orange Group, Sweet Orange Group, Grapefruit Group) K335

Citrus cavaleriei H. Lév.

Ichang Lemon

Syn. C. ichangensis Swingle Shrub or tree to 5 m. Branchlets conspicuously angled, with numerous straight spines, 1–2(–3) cm long. Leaves evergreen, leathery, 8–11.5 × 1.8–3 cm (lamina), ovate to elliptic, secondary veins indistinct, margins entire to crenate, apex acuminate and often emarginate; petiole winged and foliose, often wider than the lamina, 3.5–6 × 2–3 cm, obovate to spathulate. Flower solitary and axillary, 2.5–3 cm diameter, white, 5-merous, prominently glandular. Pedicel 0.4–0.6 cm long, calyx thick and fleshy, petals 1.2–1.8 cm long, stamens 20. Fruit subglobose, resembling a large, squat lemon, 8–11 × 7–10 cm, skin rough, segments 8–11. Swingle 1913. Distribution CHINA: Guizhou, Hubei, Sichuan; INDIA: Assam (Khasi Hills). Habitat Between 500 and 3000 m asl. USDA Hardiness Zone (7b–)8–9. Conservation status Not evaluated. Illustration Swingle 1913; NT258. Cross-reference K335. Taxonomic note Recent research has shown C. cavaleriei to be the prior name for this species, thus displacing the familiar name C. ichangensis (Zhang & Mabberley 2008).

Citrus cavaleriei has perhaps the longest track-record in cultivation of any hardy Citrus, having been grown (as C. ichangensis) at the Hillier Gardens for over 30 years (Hillier & Coombes 2002) – now as a newer specimen replacing the famous old tree, which

Plate 191. Citrus tachibana – the wild form of the cultivated C. reticulata – is one of the hardiest Citrus and should be tried more widely. Image J. Grimshaw.

258

Citrus

Plate 192. The wings of the petiole of Citrus cavaleriei are often almost as large as, or larger than, the true lamina. Image J. Grimshaw.

New Trees

died for no obvious reason (A. Coombes, pers. comm. 2006). Despite this long history in cultivation, however, it remains seldom seen, and is not currently offered by British nurseries. It is available from a handful of nurseries in the western United States, and seems to flourish both in temperate parts of the West Coast and in the southern states. A 2 m plant (planted out in 2000) observed at the JC Raulston Arboretum in 2006 looked extremely healthy and vigorous, making a solid bush of dark green, although there were no signs of flowers or fruits. A conspicuous feature is the very large wing on each side of the petiole, which may be expanded to be larger than the true leaf. An important factor in the hardiness of this species is the ripening of its wood, which is helped by hot summers. When ripening is successful it can survive temperatures below –18 ºC, but around –10 ºC may be about its limit in areas with cooler summers (Hogan 2008). Citrus cavaleriei has long been cultivated in China, especially as a stock for more edible cultivars. Frank Meyer may have been the first to introduce it to the West, collecting material in Hubei in 1917 (Valder 1999), although the name C. ichangensis was given to material collected by E.H. Wilson in western China between 1903 and 1907, from both cultivated and apparently wild plants (Swingle 1913). The fruit is considered to be more or less inedible, with little juice, though it can be used as a lemon substitute for lemonade; the Chinese value it most for perfuming rooms (Valder 1999). The floral fragrance lives up to expectations for orange-blossom (Hogan 2008). C. japonica Thunberg (WAS Fortunella hindsii, F. japonica, F. margarita K82) C. limetta Risso K335 C. ×limon (L.) Osbeck K335 C. maxima (Burm.) Merr. K335 C. medica L. K335 C. paradisi (NOW C. ×aurantium L. Grapefruit Group) K335 C. reticulata Blanco K335 C. sinensis (NOW C. ×aurantium L. Sour Orange Group) K336

Citrus tachibana (Makino) Yu. Tanaka

Tachibana

Shrub or tree 3–10(–12) m. Branchlets conspicuously angled, with numerous straight thorns, 2–2.5 cm long. Leaves evergreen, chartaceous, 4–8 × 2–4.5 cm (lamina), lanceolate to oblong, secondary veins inconspicuous, margins entire to crenate, apex acuminate and often emarginate; petiole 0.5–1 cm long, narrowly winged. Flower white, 1.2–1.4 cm diameter, 5-merous, axillary, solitary or in clusters of two to three. Pedicel 0.4–0.5 cm long, calyx cup-shaped, petals 1–1.2 cm long, stamens ~20. Fruit yellow, globose, 3.5 × 2–2.5 cm, segments six to eight. Flowering June (Japan). Chang & Hartley 1993, Ohba 1999, Zhang & Mabberley 2008. Distribution JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; NORTH KOREA; SOUTH KOREA; TAIWAN. Habitat Evergreen woodland. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT257. Taxonomic note Citrus tachibana probably represents the wild ancestor of C. reticulata (the cultivated Mandarin or Tangerine, widely grown in the warm parts of the world, including the Mediterranean basin) (D. Mabberley, pers. comm. 2007).

Citrus tachibana has yet to make its mark in horticulture, but is potentially a very exciting addition to our gardens, being the hardiest version of the Mandarin (though sadly without its culinary qualities). The only specimens seen in research for the current work are at Quarryhill, where they have made densely clad bushy trees of 3 m,

Section II. Species Accounts

Citrus

259

covered in orange fruits when observed in July 2004. These plants were grown from SOJA 362, collected in 1989 in Yakushima, Japan. The parents were found in dense, subtropical evergreen woodland, making substantial trees reaching 10–12 m (W. McNamara, pers comm. 2004). The Quarryhill plants seem to be perfectly happy in northern California conditions, and the website of Trade Winds Fruit (2007–2008) credits the species with hardiness to ‘the low 20s [ºF]’, perhaps –6 ºC. Flowers are borne in winter, with fruit ripening some 18 months later. The fruits are of the Mandarin type, somewhat flattened, with soft, easily peeled skin. The flesh is bitter and somewhat dry and stringy, but tolerable: in the wild it is eaten by monkeys (SOJA 362, collection notes). C. trifoliata L. (WAS Poncirus trifoliata B292, K424) C. wilsonii (NOW C. ×junos Siebold ex Tanaka) K336

CLETHRACEAE

CLETHRA

L.

Clethra comprises 64 species of evergreen or deciduous trees or shrubs, found in a disjunct distribution very similar to that of Persea, with one centre of diversity in eastern and southeastern Asia (Japan to New Guinea), another in southeastern North America, Central America and eastern South America, and one species on Madeira. The plant is generally hairy, the hairs varying in type from simple to stellate or fascicled. The leaves are usually entire or dentate, the toothing being most pronounced in juvenile plants; the secondary veins are decurrent on the midrib. The inflorescence is terminal, usually a solitary simple raceme, but sometimes with racemes being produced from the upper leaf axils on the shoot to give a more compound inflorescence, whose arrangement is an important specific character. Also necessary for identification are the bracts, which usually fall quickly, and the proportions of the pedicels. The flower is usually white (occasionally cream or yellowish) and fragrant (occasionally unscented). The calyx is five-lobed, the lobes becoming lignified in fruit. The corolla is also five-lobed, the petals usually being free but sometimes united at the base or for up to one-third of their length, obovate to spathulate and either entire or variously toothed or fringed, sometimes with a ciliate margin at their apex. The stamens are placed in two whorls, and the style has three lobes leading to a tricarpellate ovary. The fruit is a hairy subglobular or slightly three-sided capsule (Sleumer 1967). Clethra is a useful genus for the garden where ericaceous plants predominate as it enjoys the same conditions – a high canopy, acidic soil – as many rhododendrons, but has the advantage of flowering later in summer. The most familiar species, C. alnifolia

Plate 193. The exceptional Clethra pringlei ‘White Water’ in the wild in Tamaulipas, Mexico, with its particularly long inflorescences. Image C. Schoenfeld.

260

Clethra

New Trees

from eastern North America, is justifiably popular, and there has been a flurry of cultivar selections in recent years (see Dirr 1998). Others are less well known, but the bark of some species can be extremely attractive. C. acuminata Michx. B668, K355 C. alnifolia L. B669, K355 C. arborea Aiton B669, K355 C. barbinervis Siebold & Zucc. B670, K355 C. delavayi Franch. B670, K355 C. fargesii Franch. B671, K356 C. monostachya (NOW C. delavayi Franch.) B671, K356

Clethra poilanei Gagnep. ex Dop Tree 6–9 m. Branchlets reddish-hairy at tips. Leaves obovate to obovate-elliptic, 9–11 × 4–5 cm, dark green, chartaceous, base cuneate, not uneven, apex shortly acute-acuminate, hairy on the veins; petiole 1.5–2 cm, tomentose. Inflorescence formed of several fascicled racemes to 40 cm, densely tomentose on rachis and pedicels; bracts c. 3 mm, caducous; pedicels thick, 2–3 mm; calyx lobes oblong-ovate, 2.5 mm, densely stellate-pubescent; petals obovate, 3 × 3 mm, glabrous, white and scented. Capsule subglobose, 2.5 mm across. Sleumer 1967. Distribution LAOS; VIETNAM. Habitat Not recorded; presumably upland forest. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

Clethra poilanei is in cultivation in southwestern England, but remains very rare. At Tregrehan it is doing very well, although it has yet to flower, forming straight stems with pale bark and showing promise of becoming a true tree. The hairy foliage flushes pinkish red and is attractive both at this stage and in maturity, when it retains a dull red tinge on the undersides; the petioles are also red.

Clethra pringlei Watson Shrub or tree, 5–15 m, to 45 cm dbh. Branches spreading. Branchlets ascending, reddish-hairy at tips. Leaves elliptic-oblong to oblanceolate, 4–8 × 2–4 cm, dark green, thinly coriaceous, base cuneate, unequal, apex shortly attenuate or subacuminate, upper surface loosely stellate-pubescent when young, then glabrescent, lower surface densely hairy; petiole 0.4–0.6 cm. Inflorescence formed of several racemes 10–15(–25) cm, the central raceme sometimes branched, densely brown-pubescent on rachis; bracts 2–3 mm, quickly caducous; pedicels slender, 5–7 mm at flowering, elongating slightly later; calyx lobes ovate-acuminate, 2.5 mm; petals obovate-spathulate, to 3.5 × 2.5 mm, fimbriate and ciliate at apex, surfaces glabrous, white and scented of cinnamon. Capsule flattened, three-lobed, 3.5 mm across. Sleumer 1967. Distribution MEXICO: Tamaulipas, San Luis Potosí, Nuevo León, Hidalgo. Habitat Wooded slopes on calcareous hills. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Ward 2004; NT259.

Clethra pringlei is well established in cultivation, in the nursery trade at least, in the United States and in Europe, although no mature specimens have been observed in the research for this book. It is highly valued in southeastern North America – for its long racemes of white flowers with a strong cinnamon scent, but also for its foliage, bronze when young, a solid dark green later (Hudson 2004). Its hardiness is not entirely clear but it can certainly withstand some frost. Dirr (1998) reports that it was killed back at about –15 ºC in Georgia. A warm site, even in full sun, will help ripen the new shoots. Yucca Do Nursery, Texas offers a named clone, ‘White Water’, with particularly long (25 cm), pendulous inflorescences, selected at 1400 m in Tamaulipas in an area where many reasonably hardy plants grow (Ward 2004). C. tomentosa Lam. B672, K356

Section II. Species Accounts

Cornus

261

CORNACEAE

CORNUS

L.

Syn. Afrocrania (Harms) Hutch., Chamaepericlymenum Hill, Dendrobenthamia Hutch., Swida Opiz, Yinquania Z.Y. Zhu, etc.

Dogwoods, Cornels Cornus has been the subject of considerable scrutiny by taxonomists attempting to subdivide the genus. Several segregate genera have been proposed (Dendrobenthamia, Swida, etc.), though often these do not reflect groupings identified by DNA and other evidence (Murrell 1993, Xiang et al. 1996, Fan & Xiang 2001). This account follows Eyde (1987) and Flora of China (Xiang & Boufford 2005) in recognising Cornus in a broad sense, with 50–60 species in the temperate northern hemisphere, but also one to two species in South America and one in Africa. Specific recognition can also be difficult, and several taxa are much confused in horticulture. Notwithstanding this taxonomic uncertainty, there are four easily distinguished groups within Cornus: the cornelian cherries (for example, C. mas), the dwarf cornels (for example, C. canadensis), the large-bract dogwoods (for example, C. florida) and the bractless dogwoods (for example, C. sanguinea) (Eyde 1987). They can be shrubs, trees or rhizomatous ‘herbs’ (actually miniature shrubs), with deciduous (rarely evergreen) leaves. The rough bark of the tree-forming species does not compare with the colourful bark of C. alba or C. sericea. The stems are typically pubescent, with distinctive T-shaped trichomes. Winter buds are terminal or axillary, covered or exposed. The leaves are opposite (alternate in C. alternifolia and C. controversa), simple, elliptic to ovate and glabrous or densely pubescent: details of hair types and abundance are important for identification. Flowering may occur before or after spring leaf expan-

Plate 194. A new look at an old friend. Some of the recent reintroductions of Cornus capitata are producing magnificent, broad inflorescences, and proving hardier than previously thought. This is Ogisu 93333, at the Hillier Gardens in 2007. Image A. Coombes.

262

Cornus

New Trees

1 cm

1 cm

Section II. Species Accounts

sion, and most species are monoecious (dioecy is restricted to the African C. volkensii Harms.). Inflorescences are terminal (axillary in C. chinensis) and may be surrounded by petal-like bracts. The flowers are arranged in dense heads or open panicles, umbels, etc. They are hermaphrodite (rarely unisexual), 4-merous and with inconspicuous, valvate petals. The fruit is a fleshy, pedunculate drupe and may be black, blue, white or red. One or two seeds are enclosed within the hard endocarp, which in the cornelian cherries is riddled with cavities (Kubitzki 2004, Cappiello & Shadow 2005, Xiang & Boufford 2005). In the Asian large-bract dogwoods of subgenus Syncarpea (for example, C. kousa), all the fruits in the inflorescence fuse (syncarpy) to form a compound fruit, containing multiple stones. This may be an adaptation to seed dispersal by monkeys (Eyde 1985). Allen Coombes (pers. comm. 2007) reports of the fruits of C. hongkongensis: ‘These are eaten in China (as I suppose all the others are as well). We saw them for sale in Hunan in 2004, tied in bunches with raffia. Our driver would quickly devour fruits of all the flowering dogwoods we collected!’ When not required as a snack, these fruits are very ornamental in the garden. The dogwoods are an extremely popular group of small trees and shrubs, whether grown for their stems, foliage or floral display, and have been the subject of a recent horticultural monograph (Cappiello & Shadow 2005) that describes – though not always in sufficient detail – the vast number of horticultural selections currently available. The majority of these are ‘flowering dogwoods’ with conspicuous bracts around the flower clusters, and most are cultivars of C. florida or C. kousa. The hybrid between C. florida and C. kousa (sometimes known as C. ×rutgersiensis or C. ×rutgersensis, though neither form has been validly published) combines the characters of these two superb species in different proportions; most importantly, however, the hybrid plants are also largely resistant to the anthracnose disease caused by Discula destructiva now so prevalent on C. florida in the eastern United States. The Stellar Series, raised by Dr Elwin Orton of Rutgers University, New Jersey, is the principal group of these hybrids, and several excellent clones have been selected and promoted under strict patenting procedures. These include ‘Rutcan’ (sold as Constellation), with masses of white ‘flowers’, and ‘Rutgan’ (Stellar Pink), with pink. Dr Orton has also crossed C. kousa and C. nuttallii, and backcrossed their progeny: ‘KN30-8’ (Venus) is a spectacularly large-flowered clone that has recently been released to commerce (Eberts 2007). A number of selections have been made in C. nuttallii, but this species’ main contribution has been as a parent of some exceptional hybrids with C. florida, that perform better in maritime Europe than either of the parents. These include ‘Eddie’s White Wonder’ with very large inflorescences (usually highly praised on both sides of the Atlantic, and given the Award of Garden Merit by the Royal Horticultural Society, though somewhat damned by Dirr (1998) for lack of hardiness in East Coast conditions), and the beautiful ‘Ormonde’, raised at Kew – both discussed by Clarke (1988). A further group of hybrids involving C. kousa and C. capitata first originated in the garden of Norman Hadden of Porlock, Devon in the 1950s (Clarke 1988, Andrews 1990), of which both ‘Norman Hadden’ and ‘Porlock’ are of exceptional merit and well deserve their Awards of Garden Merit. The evergreen species described below add persistent leaves to many of the qualities of their deciduous relatives, but as yet comparatively few selections of these have

Cornus

263

Plate 195. Fruits of Cornus hongkongensis for sale as a snack in the Mangshan, Hunan (reported to be rather too sour for Western tastes). Image A. Coombes.

Figure 27 (opposite). Cornus hongkongensis subsp. melanotricha: flowering branch, with detail of hairs in the vein axils of the lower leaf surface (see p. 268).

264

Cornus

New Trees

been made. The group is horribly muddled in cultivation and taxa may appear under any of several nomenclatural permutations. It is hoped that the present account will help to straighten this out, but close attention must be paid to details of the leaves to achieve an identification. A rich soil and warm conditions are preferred by most Cornus, and the evergreen species in particular will benefit from shelter from cold winter winds. C. alba L. B696, S183, K366 C. alternifolia L. f. B697, K367 C. amomum Mill. B698, K367 C. ×arnoldiana Rehder B709, K367 C. asperifolia var. drummondii (NOW C. drummondii C.A. Mey.) B698 C. australis (NOW C. sanguinea subsp. australis (C.A. Mey.) Jáv.) B699, S183, K367

Cornus capitata Wall.

C. australis var. koenigii (NOW C. sanguinea subsp. australis (C.A. Mey.) Jáv.) K367 C. baileyi (NOW C. sericea L. subsp. sericea) B699, K367 C. bretschneideri L. Henry K368 C. ×californica (NOW C. sericea L. subsp. sericea) B708 C. canadensis L. K368

Himalayan Evergreen Dogwood, Bentham’s Cornel

Syn. C. capitata subsp. emeiensis (W.P. Fang & Y.T. Hsieh) Q.Y. Xiang, C. capitata subsp. brevipedunculata (W.P Fang & Y.T. Hsieh) Q.Y. Xiang Shrub or tree to 20 m. Bark brown or greyish black. Branchlets grey-green, pubescent. Leaf buds exposed; floral buds exposed, subtended by four small, green bracts. Leaves evergreen, 5–12 × 2–4 cm, papery or leathery, elliptic to lanceolate, both surfaces grey-green, upper surface glabrous, lower surface densely pubescent with thick, white, appressed trichomes, three to four secondary veins on each side of the midvein, margins entire, apex acuminate to caudate; petiole 0.5–1 cm long, initially with white trichomes, later glabrous. Inflorescence terminal, globose cymes, to 1.2 cm diameter, composed of 50–100 flowers; floral bracts creamy yellow to whitish, sometimes with pink tinges, obovate (rarely orbicular), 3.5–6.2 × 1.5–5 cm. Flowers hermaphrodite, rather inconspicuous, with oblong petals to 0.4 cm long. Fruits syncarpous, resultant berry 1.5–2.5 cm diameter, flattened-globose, held on short, stout peduncle, purple-red at maturity, densely covered in white trichomes and with multiple stones. Flowering May to July, fruiting September to November (China). Gardener 1979, Xiang & Boufford 2005. Distribution BHUTAN; CHINA: Guizhou, Sichuan, Xizang, Yunnan; INDIA; MYANMAR; NEPAL. Habitat Deep shade in evergreen or mixed forest between 1000 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT261. Cross-references B699, K368.

Cornus capitata was described by Bean (1976a), but in recent years there has been an influx of material ascribed to it – although on investigation much of this turns out to belong to other species (see C. elliptica, C. hongkongensis, below). Cornus capitata in its usual form with semi-evergreen foliage has been introduced repeatedly since 1825 and has traditionally been regarded as being too tender for cultivation outdoors in any but the mildest areas of coastal Europe (Bean 1976a). In recent years however it seems that material has been collected from colder provenances, and this, together with the assistance provided by the present warmer climate, has led to it being grown quite widely in the British Isles. Only plants with a track-record of hardiness should be propagated from. Hogan (2008) suggests that a clone called ‘Yoko’ is particularly hardy, but recommends ‘Mountain Moon’ as an especially fine cultivar, with ‘flowers’ 13–15 cm across, introduced in 1992 from Bhutan by Piroche Plants. Another good introduction is Ogisu 93333, from Leibo, Sichuan, with inflorescences up to 10 cm across, borne on thick peduncles to 8 cm long (A. Coombes, pers. comm. 2007).

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The key character used by Flora of China (Xiang & Boufford 2005) to differentiate C. capitata and the related C. elliptica from the C. hongkongensis complex, the other evergreen members of Cornus subgenus Syncarpea in the Sinohimalaya, is the presence in C. capitata and C. elliptica of persistent short, grey or white hairs on the undersides of their leaves. These give the leaf both a pallid colour and a rough feel when rubbed with a finger. In C. hongkongensis the leaf underside is a dull green but not greyish, and is either glabrous or has deciduous hairs or tufts of hairs in the vein axils, depending on the subspecies in question, but the leaf undersides always feel smooth to the touch. This very simple test has important consequences for the identification of many cultivated dogwoods (see C. hongkongensis, below).

Cornus chinensis Wangerin Syn. C. chinensis f. jinyangensis (W.K. Hu) W.K. Hu Tree to 10 m, 60 cm dbh; single-stemmed. Bark dark brown. Branchlets dark brown. Leaf buds terminal or axillary, conical; floral buds lateral and in pairs, covered in yellowish brown trichomes. Leaves deciduous, 6–11(–30) × 2.8–5.5 cm, elliptic to lanceolate, upper surface glabrous and with deeply impressed veins, lower surface with dense greyish white trichomes, clusters of long, grey trichomes in vein axils, five to six secondary veins on each side of the midvein, margins entire, apex acuminate to caudate; petiole 1.2–2.5 cm long. Inflorescence umbellate and lateral, produced before the leaves, 2–3 cm diameter with 25–50 flowers; floral bracts papery or leathery, inconspicuous, pubescent, 0.6–0.7 cm long. Flowers hermaphrodite, rather inconspicuous, with lanceolate petals to 0.4 cm long. Fruit a black drupe, 0.6–1 × 0.4 cm; stones ribbed. Flowering March to April, fruiting September (China). Weaver 1976, Gardener 1979, Xiang et al. 2003, Cappiello & Shadow 2005, Xiang & Boufford 2005. Distribution CHINA: Gansu, Guangdong, Guizhou, Henan, Hubei, Shaanxi, Sichuan, Xizang, Yunnan, Zhejiang; MYANMAR (?). Habitat Dense forest, forest margins and slopes between 700 and 3500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT15, NT265. Cross-references B706, K368.

The seismic circumstances of the first collection of seed of this species, in Assam in 1950, were vividly recounted by Frank Kingdon-Ward (Kingdon-Ward 1960), but the derivative seedlings (KW 19300) did not prove generally hardy, though they were successful under glass (Bean 1976a) and in very mild situations, such as at Ventnor Botanic Garden on the Isle of Wight. In consequence, Cornus chinensis did not become firmly established in cultivation until much more recently, following its collection by several expeditions to Sichuan. These included SICH expeditions in 1988 and 1992 (SICH 307 and SICH 1222, respectively), the species being found, in both cases, in rich forests of broadleaved trees at between 2400 and 2500 m asl. Trees from these collections are growing well at Kew and have reached 5 m in height. There are several individuals from SICH 307 at Quarryhill and these too are flourishing (H. Higson, pers. comm. 2007), as also are specimens in Vancouver, the largest of which is a fine 7 m, ‘suggesting a Cornelian Cherry [C. mas] on steroids’ (P. Wharton, pers. comm. 2007). In the United States C. chinensis has been distributed from Heronswood Nursery, from a collection made in Sichuan by Dan Hinkley (DJHC 819) in 1996, and it has also

Plate 196. Cornus chinensis is a superb flowering tree for early spring. Chinese provenances are much hardier than Kingdon-Ward’s 1950 introduction from northern India. This specimen was at Baoxing, western Sichuan, in April 1990. Image M. Ogisu.

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been offered by Forestfarm Nursery, Oregon (without information on provenance). Cornus chinensis is a spectacular foliage plant, with ribbed, long-acuminate leaves that emerge with a pinkish tinge (Heronswood Nursery catalogue 2000) and colour to yellow with a pinkish tinge in autumn (D. Hinkley, pers. comm. 2007), and showy clusters of yellow flowers in early spring. The tenderness of the famously large-leaved Assamese stock has long been regretted by gardeners, so the apparently much greater hardiness of recent introductions is very welcome, even though the leaves are smaller. Dan Hinkley (pers. comm. 2007) even goes so far as to say that he considers it as hardy as C. mas. C. controversa Hemsl. B700, K368 C. coreana Wang K369 C. drummondii C.A. Mey. B698, K369

Cornus elliptica (Pojark.) Q.Y. Xiang & Boufford

Chinese Evergreen Dogwood

Syn. C. angustata (Chun) T.R. Dudley, C. capitata subsp. angustata (Chun) Q.Y. Xiang, C. capitata var. mollis Rehder, C. kousa subsp. angustata Chun

Plate 197. The bracts of Cornus elliptica change from pale green to white as the inflorescence matures. Visible here on a plant at Arboretum Wespelaar are the pale hairs on the underside of the leaf that are important for identification in this group. Image P. de Spoelberch.

Shrub or tree to 12 m. Bark grey or greyish brown. Branchlets grey-green with white trichomes. Leaf buds with triangular-lanceolate scales, subtending floral buds; floral buds exposed and subtended by four small, green bracts. Leaves evergreen, 7–9(–12) × 2–4 cm, leathery, shape variable, from oblong to elliptic to lanceolate, both surfaces grey-green and densely pubescent with white, appressed trichomes, sometimes tufts of soft trichomes in lower vein axils, three to four secondary veins on each side of the midvein, margins entire and somewhat revolute, apex acuminate to caudate; petiole 0.5–1.2 cm long, covered with white trichomes. Inflorescence terminal, globose cymes, 0.8–1.2 cm diameter, composed of 55–80(–95) flowers; floral bracts yellowish green, turning white, ovate to obovate, 2.5–5 × 0.9–2.2 cm. Flowers hermaphrodite, rather inconspicuous, with ovate petals to 0.3 cm long. Fruits syncarpous, resultant berry 1.5–2.5 cm diameter, globose, held on slender peduncle, red at maturity, densely covered in white trichomes and with multiple stones. Flowering June to July, fruiting October to November (China). Gardener 1979, Xiang & Boufford 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan. Habitat Forested slopes and streamsides between 300 and 2200 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT266. Taxonomic note See Cornus capitata for further comparisons and comment.

The sample list of synonyms given above (for complete synonymy, see Flora of China) demonstrates that Cornus elliptica has had a chequered taxonomic past, revolving principally around various combinations of the epithet angustata. Its status as a distinct species has only recently been confirmed. DNA evidence suggests that it is not as closely related to typical C. capitata as previously thought, and it is recognised as a separate species in Flora of China (Xiang & Boufford 2005). Morphologically the two can be distinguished by the shorter, thicker peduncles in C. capitata, with flattened globose infructescences, and the longer, more slender peduncles in C. elliptica, which has globose infructescences. This is the situation in typical specimens, but intermediates do occur (Xiang & Boufford 2005). In its typical form C. elliptica is quite distinct, having more abundant white hairs on the undersides of its leaves than C. capitata, which make them feel rougher. The upper leaf surfaces are also a glossier green than in C. capitata, in which they are a dullish grey-green. At the US National Arboretum in June 2006 some

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larger specimens (5–6 m) were flowering; as reported by others (for example, Hogan 2008), the ‘flowers’ are rather small, though on some trees they can be abundant. The lime-green of the unexpanded bracts is delightful – but it is as an appealing evergreen with benefits that this species is most likely to be cultivated. Hogan notes that it is considerably hardier than C. capitata, tolerating –12 ºC with minimal damage. In his experience it requires ample moisture and dappled shade to thrive. It does particularly well in such conditions in the Gully at RHS Rosemoor, Devon (C. Bailes, pers. comm. 2007). The first recorded collection was made by Dr Ted Dudley on the 1980 SinoAmerican Botanical Expedition (when it became known as Cornus angustata), and from this it came to be established in the United States, although later introductions have supplemented the population. It has been grown at the Hillier Gardens since the 1970s, however, when material of unknown antecedents was received from ‘a garden in Ireland’, as C. capitata × C. florida (A. Coombes, pers. comm. 2007). Selections have been made for good evergreen qualities, including ‘First Choice’ from the JC Raulston Arboretum, while ‘Elsbry’ (Empress of China) was chosen by John Elsley for its abundant blooms (Lasseigne 2001, Cappiello & Shadow 2005).

Cornus florida L.

Eastern Flowering Dogwood

This species was described by Bean (B701, S183) and Krüssmann (K369). The huge array of its cultivars is covered by Cappiello & Shadow (2005). C. florida f. rubra (NOW C. florida Rubra Group) B701, S184, K369

Cornus florida subsp. urbiniana (Rose) Rickett Syn. Cornus florida var. pringlei auctt. The Mexican subspecies of C. florida is semi-evergreen and has fewer flowers in the inflorescence. The floral bracts are acute and often adhere at the apices, forming a cage-like structure. There are typically only one to three comparatively large fruits in each cluster. In comparison, subsp. florida is deciduous and has free, rounded floral bracts with an apical notch. There are up to 20 flowers per inflorescence and up to 10 fruits per cluster. Rickett 1945, Sosa 1978, Dudley & Santamour 1992. Distribution MEXICO: Nuevo León, Veracruz. Habitat Montane forest between 1725 and 1950 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Ward 2004; NT267.

The clasping bract tips in this taxon give it a unique appearance while in flower, and certainly add a different effect to a collection of flowering dogwoods. Larger trees such as those in the US National Arboretum, now 6.5 m tall and 5 m wide, after planting in 1992 (United States National Arboretum 2007), can be covered in flowers and make a spectacular show. It is now widely cultivated in the United States, succeeding wherever normal C. florida is happy. Jacobson (1996) reported an 18.6 m tree in Seattle, 37 years old. In Europe it is still scarce but there is a 4 m tree at Tregrehan that is growing well. Cornus florida subsp. urbiniana was first introduced by F.G. Meyer in 1948, with fresh blood coming from reintroductions in the early 1990s by the Yucca Do Nursery team of Carl Schoenfeld and John Fairey, who have done so much to promote Mexican plants in horticulture. They have made two selections,

Plate 198. The bracts of the Mexican Cornus florida subsp. urbiniana usually remain clasped at the tips. Image R. Hitchin.

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whose names honour the tree’s discoverer, Cyrus Pringle: the striking ‘Pringle’s White’ and the faintly pink-flushed ‘Pringle’s Blush’. The illegitimate name var. pringlei still crops up in the literature (Cappiello & Shadow 2005) and in nursery lists. The foliage of these trees persists longer than in other C. florida taxa, but is not evergreen. In full growth it is an attractive deep-green, with a slight sheen.

C. glabrata Benth. B702, K370 C. hemsleyi C.K. Schneid. & Wangerin B702, K370 C. hessei (NOW C. alba ‘Hessei’) B702, K370

Cornus hongkongensis Hemsl.

Hong Kong Dogwood

Shrub or tree to 25 m. Bark smooth, grey or blackish brown. Branchlets green or purplish green with white or brown trichomes, rarely glabrous. Leaf buds with triangularlanceolate scales, subtending floral buds; floral buds exposed and subtended by four small, green bracts. Leaves evergreen, 6.2–16 × 2.5–7.5 cm, leathery, shape variable, from oblong to elliptic, upper surface green, lower surface pale green and/or powdery, glabrous or with white or brown trichomes when young, sometimes tufts of trichomes in vein axils, three to four (to five) secondary veins on each side of the midvein, margins entire and slightly revolute, apex acuminate to caudate; petiole 0.8–1.2 cm long, covered in brown trichomes or glabrous. Inflorescence terminal, capitate cymes, 0.7–2 cm diameter, composed of 40–70 flowers; floral bracts yellowish or white, elliptic, ovate or orbicular, 1.6–4 × 1.3–2 cm. Flowers hermaphrodite, rather inconspicuous, with petals to 0.4 cm long. Fruits syncarpous, resultant berry globose, 1.5–2.5 cm diameter, red or yellowish red at maturity, sparsely covered in white trichomes and with multiple stones. Flowering April to June, fruiting October to December (China). Gardener 1979, 1980, Walden & Hu 1987, Xiang & Boufford 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; LAOS; VIETNAM. Habitat Broadleaved evergreen forest between 600 and 1800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT262, NT263, NT268.

Six subspecies are recognised within this variable taxon, differing in details of pubescence and distribution. It is not entirely clear whether many of these are in cultivation, but Flora of China has a useful key, an adapted version of which is provided below. Plate 199. A dazzling display on Cornus hongkongensis in the wild. It appreciates a hot summer with plenty of moisture. Image M. Ogisu

1a. Leaf blade obovate, 8.5–16 × 3.8–7.5 cm, thick and leathery; inflorescences (excluding bracts) 1.5–2 cm diameter; bracts broadly obovate or orbicular, 4–5 × 3–4.2 cm; China (western Guizhou, southern Sichuan, northeastern Yunnan), northern Vietnam ....................... subsp. gigantea (Hand.-Mazz.) Q.Y. Xiang 1b. Leaf blade ovate to narrowly elliptic, 5.5–10(–13.5) × 2.7–5.8(–6.3) cm; inflorescences (excluding bracts) 0.7–1.3 cm diameter; bracts smaller and variously shaped .......................................................... 2 2a. Outer surface of petals glabrous or nearly so; style glabrous; China (southwestern Guangxi, southern Yunnan), northern Vietnam ........................................................... subsp. tonkinensis (W.P. Fang) Q.Y. Xiang 2b. Outer surface of petals and style pubescent ..................................................................................... 3

Section II. Species Accounts

3a. Lateral leaf veins inconspicuous; China (Fujian, Jiangxi, Zhejiang) ...................... subsp. elegans (W.P. Fang & Y.T. Hsieh) Q.Y. Xiang 3b. Lateral leaf veins conspicuous ......................................................................................................... 4 4a. Abaxial leaf surface and veins covered with dense reddish brown pubescence; China (Guangdong, Guangxi, Guizhou, Hunan, Jiangxi) ................................... subsp. ferruginea (Y.C. Wu) Q.Y. Xiang 4b. Abaxial leaf surface sparsely covered with brown and/or white pubescence; veins nearly glabrous ..................................................................................... 5 5a. Leaves somewhat leathery, tufts of trichomes present in axils of veins on abaxial surface, though surface itself glabrous or with some brown trichomes; China (Guizhou, Hunan, Sichuan, Yunnan) ..................... subsp. melanotricha (Pojark.) Q.Y. Xiang 5b. Leaves leathery or very leathery, with no tufts of trichomes in abaxial vein axils; abaxial surface sparsely pubescent with white and brown trichomes when young; mature leaves may be glabrous, but with conspicuous scars replacing hairs; China (Guangdong, Guangxi, Guizhou, Hunan), Laos, Vietnam ........ subsp. hongkongensis

Plants labelled Cornus hongkongensis are found occasionally in botanical gardens and other collections throughout our area, but few have been identified to subspecific level. In the United Kingdom subsp. melanotricha has been confirmed in cultivation, with trees from a collection by Mikinori Ogisu (Ogisu 94322) made in Sichuan in 1994 growing both at Kew and at the Sir Harold Hillier Gardens. The specimen from which our line drawing was made (Figure 27, p. 262) is a thriving small tree of about 3 m tall at the Hillier Gardens, from which stems were collected in sweltering heat in July 2006, conditions more enjoyed by the plant than by the author. This specimen also appears to fit best within the concept of subsp. melanotricha, recognised by the small tufts of hairs in the vein axils on the otherwise almost totally glabrous leaf undersides. It was obtained by Roy Lancaster from the Shanghai Botanic Garden in 1987, as C. kousa var. angustata – demonstrating the confusion over the identities of this group. A very attractive feature is the bronzy young foliage (A. Coombes, pers. comm. 2007). Recent collections from northern Vietnam are now available from Crûg Farm nursery in the United Kingdom: HWJ 1033 is identified only as C. hongkongensis, and HWJ 1022 as aff. tonkinensis. Confirmation will be required as these plants come into flower, as both subsp. gigantea and subsp. tonkinensis are recorded from this area. Hot summers seem to benefit the Hillier tree, which was flowering prolifically when observed in 2006, although it has yet to set fruit (A. Coombes, pers. comm. 2007). (In 2007 it flowered even more prolifically, with larger bracts, due to the abundant moisture that year.) Hogan (2008) also suggests that C. hongkongensis will be particularly useful in hot climates. The ‘flowers’ are not large by comparison with other species, but they look well over the dark evergreen foliage and the species is much more than just a botanical curiosity, deserving cultivation in suitable sites. The name Cornus capitata subsp. emeiensis (W.P. Fang & Y.T. Hsieh) Q.Y. Xiang, derived from Emei Shan, is not recognised by Flora of China, but in horticulture emeiensis appears in a diversity of orthographic variants (for example, omeiense) and taxonomic combinations in connection with a number of evergreen dogwoods – particularly in North America but increasingly in Europe as well. In North America, ‘C. omeiense’ became known through the release in 1990 by Piroche Plants of a seed-raised batch of plants named ‘Summer Passion’. It is important to note that these were not a uniform

Cornus

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cultivar (although still sold as such by Piroche) and that there is considerable variation between so-named specimens (Hogan 2008). The situation is further confused in that there is a suggestion that these are intermediates between C. capitata and C. elliptica (Wharton et al. 2005). However, these plants tend to have characteristics that identify them with C. hongkongensis rather than C. capitata or C. elliptica, notably the glossy upper surfaces of the leaves and the more or less glabrous, smooth-feeling lower leaf surfaces. Without examining material from a wide range of trees it is impossible to assert that all trees in cultivation as C. emeiensis or ‘Summer Passion’ are indeed C. hongkongensis, and if so, identify the subspecies to which they belong: readers should investigate for themselves. Whatever the true affinities of these trees in cultivation, however, they are usually very attractive, with dark glossy leaves that flush red, and abundant flowers. They seem to be hardy in much of southern England, western North America and the milder areas of the East Coast. One small specimen was seen flowering prolifically at the JC Raulston Arboretum in May 2006.

C. koenigii (NOW C. sanguinea subsp. australis (C.A. Mey.) Jáv.) S183 C. kousa F. Buerger ex Hance B703, S184, K370 C. kousa var. chinensis (NOW C. kousa subsp. chinensis (Osborn) Q.Y. Xiang) B704, K370 C. kousa × C. capitata S184 C. macrophylla Wall. B704, S185, K370 C. mas L. B705, K370 C. mas f. nana (NOW C. mas ‘Nana’) B705 C. mas f. sphaerocarpa Cretz. K370 C. monbeigii (NOW C. schindleri Wangerin subsp. schindleri, NT270) B706 C. nuttallii Audubon ex Torr. & A. Gray B706, S185, K371

C. obliqua (NOW C. amomum subsp. obliqua (Raf.) J.S. Wilson) B698, K371 C. oblonga Wall. B707, K371 C. occidentalis (NOW C. sericea subsp. occidentalis (Torr. & A. Gray) Fosberg) B708 C. officinalis Siebold & Zucc. B705, K371 C. paucinervis (NOW C. quinquenervis Franch.) B708, K371 C. poliophylla (NOW C. schindleri subsp. poliophylla (C.K. Schneid. & Wangerin) Q.Y. Xiang) S185 C. pumila (NOW C. alba L.) K371 C. racemosa Lam. B709, K372 C. rugosa Lam. B709, K372 C. sanguinea L. B710, K372 C. sanguinea f. viridissima (Dieck) Schelle B710

Cornus schindleri Wangerin Syn. C. monbeigii Hemsl., C. poliophylla C.K. Schneid. & Wangerin Shrub or tree to 10 m. Bark brown. Branchlets four-angled, densely covered with grey or brown hairs, rarely glabrous; older branches reddish or purplish brown, glabrous with white lenticels. Leaf buds exposed, covered with brown pubescence; floral buds pubescent. Leaves deciduous, 4–15 × 2.5–6.5 cm, papery, elliptic to ovate, upper surface dark green with sparse trichomes, lower surface pale green or greyish green, brown-white curling trichomes on veins or on the entire leaf surface, six to eight (to nine) secondary veins on each side of the midvein, margins entire or crenulate, apex acuminate; petiole 1–3 cm long, covered in dense brown pubescence. Inflorescence terminal, corymbose cymes, 5–10 cm diameter, densely coated in yellow, brown or rarely, red curly trichomes, composed of numerous flowers; floral bracts minute and caducous. Flowers hermaphrodite, white, with petals to 0.4 cm long. Fruit a reddish or purplish black drupe, 0.4–0.6 cm diam-

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eter; stones eight-ribbed. Flowering May to July, fruiting August to October (China). Gardener 1979, Xiang & Boufford 2005. Distribution CHINA: Guizhou, southern and western Sichuan, southeastern Xizang, northern Yunnan. Habitat Forest and thickets on hillsides and in valleys, between 1100 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Cross-references B706 (as C. monbeigii), S185 (as C. poliophylla; now C. schindleri subsp. poliophylla (C.K. Schneid. & Wangerin) Q.Y. Xiang).

Under the name Cornus monbeigii, Bean (1976a) described this plant as ‘a shrub of no particular merit’. It had been introduced by George Forrest in 1917, obviously to no great acclaim. The only recent introductions of C. schindleri are several made by expeditions to Sichuan in the early 1990s (SICH 598 in 1991, SICH 693 in 1992), material from which was distributed to several gardens in the United Kingdom and the United States. It is potentially a small tree, similar to the somewhat more familiar C. walteri, with spreading branches bearing pendulous leaves and upward-facing inflorescences of small white flowers – probably of greater botanical interest than horticultural merit. In England it is not very satisfactory. Plants at the Sir Harold Hillier Gardens are regularly cut to the ground by frost and sprout from the base (A. Coombes, pers. comm. 2008), and two surviving specimens at Kew are shrubby. Possibly it needs a hot summer to ripen the wood, as the SICH material has done well both at Quarryhill and at the David C. Lam Asian Garden in Vancouver, forming healthy small trees that flower in early summer (H. Higson, P. Wharton, pers. comms. 2007). C. sericea L. (WAS C. stolonifera B710, S186, K372) C. sessilis Torr. ex E. Durand B710, K372 C. ×slavinii Rehder B709, K372 C. stolonifera (NOW C. sericea L. subsp. sericea) B710, S186, K372 C. stolonifera var. coloradense (NOW C. sericea L. subsp. sericea) K372 C. stolonifera var. nitida (NOW C. sericea L. subsp. sericea) K372 C. stricta (NOW C. foemina Mill.) B709, K372 C. suecica L. K372 C. walteri Wangerin B711, K372

Cornus wilsoniana Wangerin Syn. C. fordii Hemsley Tree 5–10(–40) m. Bark grey or greenish grey, splitting and flaking into rectangular plates. Branchlets four-angled, pubescent with appressed grey hairs; older branches brown, glabrous with narrow lenticels. Leaves deciduous, 6–12 × 2–5.5 cm, papery, elliptic to ovate-elliptic, upper surface grey-green, lower surface densely covered by appressed white hairs, feeling scabrid, three to four (to five) secondary veins on each side of the midvein, margins slightly revolute, apex shortly acuminate to acuminate; petiole 0.8–2 cm long, not hairy. Inflorescence a terminal, paniculate to corymbose cyme, 6–10 cm diameter, with short white trichomes, composed of numerous flowers. Flowers hermaphrodite, white, with petals to 0.5 cm long. Fruit a purplish black drupe, 0.6–0.7 cm diameter, very rich in oil; stones with inconspicuous ribs. Flowering May, fruiting September to November (China). Xiang & Boufford 2005. Distribution CHINA: Fujian, Gansu, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Zhejiang. Habitat Forest, between 100 and 1100 m asl. USDA Hardiness Zone 7 (?). Conservation status Not evaluated. Illustration NT271.

Herbarium material of Cornus wilsoniana was first gathered by Augustine Henry, with the type collection being made by Ernest Wilson in 1901. It is not known when it was first introduced, but it is now to be found in collections across North America and Europe, and is commercially available on both sides of the Atlantic and in Australia, although it is not commonly grown anywhere. A tree planted in 1988 at the Hillier

Plate 200. Cornus wilsoniana has remarkable mottled bark, but is scarcely known in Western horticulture. With Liu Gang in Hunan, 1993. Image K. Gillanders.

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Gardens was 5.5 m when measured in 2004. The white undersides to the leaves give it a certain distinction, and the Forestfarm Nursery catalogue (2007) claims that it has red twigs, but its real merit lies in the beautifully mottled bark that develops as the trunk thickens. It has been suggested for use as a street tree, and its oily fruits and heavy hard timber are valued products (Xiang & Boufford 2005).

BETULACEAE

CORYLUS

L.

Hazels The 17 species of Corylus occur in the temperate northern hemisphere (Govaerts & Frodin 1998). Hazels are deciduous trees or shrubs with thin, grey bark, with no prominent lenticels, breaking into vertical strips and scales with age. The branchlets are often two-ranked; winter buds are ovoid, with several smooth scales. The leaves are alternate, petiolate and typically have double-serrate margins. Corylus is monoecious. The male inflorescences (catkins) are pendulous and are produced in small racemes on short lateral shoots. They are formed the previous season and exposed in winter; anthesis occurs before the leaves emerge in spring. The female inflorescences are much reduced and are composed of a small cluster of flowers, each within a bract, with only the style protruding from the bud. The involucral bracts are campanulate or tubular with lobed apices and are sometimes spiny; they expand to accommodate the mature fruit. The fruit is a subglobose or ovoid nut (Furlow 1997, Li & Skvortsov 1999). The hazels are justifiably popular trees or large shrubs, appreciated both for their form and for their catkins in spring, with the hope also (where squirrels are not too abundant) of fruit in autumn. Corylus colurna has become an important street tree, valued for its neat shape and tolerance of urban conditions. It has been hybridised recently with one of the purple-leaved hazels (probably C. maxima ‘Purpurea’) to give progeny with intermediate characters. Of these, ‘Te Terra Red’ is probably the best, with the potential to form a striking purple-leaved tree of C. colurna shape. Another interesting horticultural development is a hybrid between a purple cultivar and the Corkscrew Hazel (C. avellana ‘Contorta’), resulting in ‘Red Majestic’, with both red leaves and twisted stems – sure to become popular with those who like curiosities. All hazels are tolerant of most soil types and are extremely hardy. Softwood cuttings can be attempted, but the success rate is not very good (Dirr 1998); layering is also an option, but most selected clones are grafted on C. avellana or C. maxima. Seed should be used where possible, but there is the risk of hybridisation.

C. americana Walter B722, K377 C. avellana L. B723, K377 C. californica (NOW C. cornuta subsp. californica (A. DC.) A.E. Murray) K371 C. chinensis Franch. B724, K377 C. colurna L. B724, S189, K377

Section II. Species Accounts

Corylus

273

B

A

1 cm

C

C. ×colurnoides C.K. Schneid. S189, K378 C. cornuta Marshall B725, K378 C. cornuta var. californica (NOW C. cornuta subsp. californica (A. DC.) A.E. Murray) B725

Figure 28 (above). Corylus fargesii: habit with fruits (A); catkins (B); fruit cluster (C).

274

Corylus

New Trees

Corylus fargesii (Franch.) C.K. Schneid. Tree to 25 m. Bark yellowish brown, fissured. Branchlets slender and greyish brown, pubescent. Leaves deciduous, 6–9 × 3–5 cm, oblong to ovate or lanceolate, both surfaces sparsely pubescent, particularly along the veins, eight to ten secondary veins on each side of the midrib, margins coarsely and irregularly doubleserrate, apex acuminate; petiole 1–1.5 cm long, densely pubescent. Staminate catkins in clusters of two to eight, 2–6 cm long; pistillate flowers in clusters of two to four, bracts tubular, 2–5 cm long, apex lobed, densely covered in yellow tomentum. Nut 1–1.5 cm diameter, with greyish white pubescence on the apex. Flowering May to July, fruiting July to August (China). Li & Skvortsov 1999. Distribution CHINA: southern Gansu, Guizhou, Henan, Hubei, Jiangxi, southern Ningxia, Shaanxi, northeast Sichuan. Habitat Forest in mountain valleys between 800 and 3000 m asl. USDA Hardiness Zone 5 (or possibly lower). Conservation

Plate 201. The peeling bark of Corylus fargesii gives it great potential for use as a tree for the winter garden. This specimen is growing at the Morris Arboretum. Image A. Aiello.

status Not evaluated. Illustration NT273, NT274.

Corylus fargesii is well established in several American arboreta from material collected by the NACPEC 1996 Shaanxi & Gansu Province China Expedition at Dang Chuan Forest Station in Gansu. Trees from this are doing particularly well at the Morris Arboretum, where they have reached 8 m after 10 years, growing on single stems. They have excellent bark patterning, exfoliating to reveal patches of copper and russet, and for this alone are most ornamental, rivalling ‘the most attractive birches’ (Aiello 2006). There are also good specimens at the US National Arboretum and at Morton Arboretum, so it seems to be able to cope with high summer temperatures and humidity as well as cold winters. Further seed was collected in 2005 by another NACPEC expedition (Aiello 2006), and research is ongoing to discover a reliable technique for vegetative propagation, to enable this desirable tree to be distributed more widely (Aiello 2006). It is now in cultivation in Europe (R. Lancaster, pers. comm. 2007), though its route of introduction is unknown. C. ferox Wall. S189, K378 C. heterophylla Fisch. ex Trautv. B726, K378 C. heterophylla var. sutchensis Franch. K378 C. heterophylla var. yunnanensis (NOW C. yunnanensis (Franch.) A. Camus) K378 C. jacquemontii Decne. B725, S189, K378 C. maxima Mill. B726, K378 C. sieboldiana Blume B727, K378 C. sieboldiana var. mandshurica (Maxim.) C.K. Schneid. B726, K378 C. tibetica (NOW C. ferox Wall. var. tibetica (Batalin) Franch.) B727, K378 C. ×vilmorinii Rehder S189, K378

Section II. Species Accounts

Corymbia

275

MYRTACEAE

CORYMBIA

K.D. Hill & L.A.S. Johnson

Bloodwoods, Ghost Gums, Spotted Gums Corymbia comprises about 115 species, all but five of which are endemic to Australia, occurring in all states except Tasmania. The genus was split from Eucalyptus relatively recently (Hill & Johnson 1995); while not all eucalypt enthusiasts accept this subdivision of the genus (and further splits have been proposed), the prevailing opinion seems to be to recognise three genera: Angophora, Corymbia and Eucalyptus. Corymbia species are trees (rarely mallees) with persistent or shedding bark. The leaves are typically dimorphic: juvenile leaves are opposite, adult leaves alternate with closely spaced lateral veins and oil glands. Inflorescences are terminal or lateral, often extensively branched, and composed of numerous seven-flowered (rarely three-flowered) umbellasters. The flowers are hermaphrodite, 4- or 5-merous, and have a cup-shaped hypanthium; the sepals are fused into a calyptra; the petals are free, but fused to the calyptra, or fused together forming an inner calyptra. The fruit is a woody capsule with valves included (Hill 2002c). There is no single character that distinguishes Corymbia from Eucalyptus; in Corymbia the bark splits in small polygonal scales, and the inflorescences are compound and terminal, comprising regular umbellasters, which are conspicuous on the outside of the crown. As a largely tropical genus Corymbia is little known in temperate gardens. The Red-flowering Gum C. ficifolia is commonly grown in the milder parts of the temperate world, and is a favourite in the San Francisco Bay Area, but it cannot tolerate frost. Allen Coombes (pers. comm. 2008) was informed by Sir Harold Hillier that it was once planted along the seafront in Bournemouth, Dorset, but that the trees died in the winter of 1947. There is a 9 m specimen at Tresco Abbey in the Isles of Scilly (Johnson 2007), and bold planters in the mildest extremities of our area may care to try it. The related genus Angophora is apparently not in temperate cultivation. Tom Hudson (pers. comm. 2006) has tried and lost A. hispida (Sm.) Blaxell at Tregrehan.

Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson

Lemon-scented Gum

Tree 25–40(–50) m, forming a lignotuber. Bark smooth throughout, white to pink or coppery, often powdery, shedding in thin, curling flakes. Juvenile leaves petiolate, 14–21 × 4.5–8 cm, ovate to lanceolate and green. Adult leaves glossy green, usually lemon-scented, (7–)10–23 × 0.6–2.8(–3.5) cm, narrowly lanceolate to falcate, margins entire, apex acuminate; petiole flattened, 1.3–2 cm long. Inflorescences axillary, compound; umbellasters with three flowers. Flower buds obovoid to pyriform; hypanthium 0.5–0.7 cm wide; stamens white. Capsule urceolate to barrel-shaped, 0.8–1.5 × 0.7–1.2 cm; valves three, enclosed. Hill & Johnson 1995, Hill 2002c. Distribution AUSTRALIA: New South Wales, Queensland. Habitat Open woodland on shallow sand (over sandstone). USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT275. Taxonomic note Some authorities separate C. citriodora subsp. variegata (F. Muell.) A.R. Bean & M.W. McDonald, which does not have a lemon scent.

The inclusion of this species in New Trees is marginal as it is very tender, but it is easily raised from seed, and with its strong lemon scent is a popular foliage plant.

Plate 202. The Lemonscented Gum Corymbia citriodora has attractive flowers as well as aromatic leaves. Image R. Barbour.

276

Corymbia

New Trees

In consequence it is likely to be tried out of doors, and although it will probably be promptly killed by frost, a succession of mild winters may enable it to reach a larger and perhaps slightly hardier size. That this is possible is demonstrated by a tree of about 9 m (19 cm dbh) growing at Logan, which seemed when observed in 2006 to be vigorous, with a straight principal trunk, although the canopy was rather sparse and still composed of the broader juvenile leaves. C. ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson (WAS Eucalyptus ficifolia K49)

CORYNOCARPACEAE

CORYNOCARPUS

J.R. Forst. & G. Forst.

There are five species of Corynocarpus, occurring in New Guinea, New Caledonia, Australia and New Zealand. The genus has been assigned to many different families, though the consensus now is to place it in its own family Corynocarpaceae, in the order Cucurbitales (Philipson 1987, Wagstaff & Dawson 2000, APG 2003). They are evergreen trees or shrubs with simple, leathery leaves, C. laevigatus being the only candidate for cultivation in temperate latitudes. The leaves are alternate or rarely in whorls, and glabrous, rarely spiny. The inflorescences are rather thick, stiff panicles in a terminal position. The flowers are regular, hermaphrodite and 5-merous. The petals and sepals are free, but imbricate, and there are five staminodes as well as five stamens. The fruit is a drupe and the seeds have no endosperm (Allan 1961, Guymer 1984). Plate 203. Corynocarpus laevigatus ‘Aureus’ is a striking variegated clone of an excellent evergreen tree that also produces heavy crops of orange fruits. Image J.R.P. van Hoey Smith.

Corynocarpus laevigatus J.R. Forst. & G. Forst.

Karaka

Tree to 15 m, dbh 0.6 m; branches stout. Leaves evergreen, simple, thick, leathery, 10–15 × 5–7 cm, elliptic to oblong, upper surface dark green and glossy, lower surface pale green and glabrous, six to eight secondary veins on each side of the midvein, margins entire, recurved, apex obtuse to acute; petiole stout, 0.5–1.5 cm long. Inflorescence thick, rigid, to 20 cm long. Monoecious; flowers hermaphrodite, greenish yellow, 0.4– 0.5 cm across. Drupe orange, ellipsoidal to ovoid, 2.5–4 cm long; produced in abundance, creating an unpleasant odour when rotting. Flowering September to December, fruiting February to April (New Zealand). Allan 1961, Andrews 1986. Distribution NEW ZEALAND: North Is. (common), South Is. (rare), Kermadec Is., Chatham Is. Habitat Coastal and lowland forest. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Andrews 1986; NT276. Cross-reference K379.

A fine broadleaved evergreen tree in New Zealand, Corynocarpus laevigatus has been established in California for some time and is now being cultivated in Cornwall. Here it thrives only in the westernmost gardens near Penzance; at Tregrehan it survives but is not ‘comfy’ (T. Hudson, pers. comm. 2006). In addition to its broad glossy leaves (handsomely variegated in several cultivars) it bears heavy crops of orange fruits, that are quite ornamental while on the tree, but stink as they rot after falling. These fruits were formerly extremely valuable to the Maori, who ate the flesh raw, and carefully processed the poisonous seeds to remove toxins before cooking and eating them as a staple (Metcalf 2000, Salmon 1996). It should be grown in a very sheltered site, with moist fertile soil.

Section II. Species Accounts

Craibiodendron

ERICACEAE

CRAIBIODENDRON

W.W. Sm.

Craibiodendron is a small genus of five evergreen trees or shrubs from China and other parts of southeastern Asia from India to Vietnam. The leaves are alternate on glabrous shoots, and are simple with an entire margin, dark green and leathery in texture when mature, although they can be reddish when young, when there may be a few glandular hairs on both sides. The inflorescences overwinter in buds formed in the axils of the upper nodes of the previous year’s growth, developing into panicle- or raceme-like cymes, often two per node, their branches bearing scattered glandular hairs. The flowers are pendulous, usually 5-merous and usually fragrant, developing in the axil of a bract or terminal on the inflorescence branch, the pedicels usually glandular-hairy, with two bracteoles, elongating as the flower and fruit develop. The calyx has five imbricate lobes that persist in the fruit: these are pubescent with a margin of unicellular hairs. The somewhat fleshy corolla is urceolate to cylindrical or campanulate, with five short or long lobes, cream or white to red or grey-purple, externally glabrous to densely hairy, but hairless inside; there are usually ten stamens in two whorls, the swollen and curved filaments being inserted at the base of the corolla and bearing ovoid anthers. The glabrous or densely hairy ovary is superior, with five locules, and has a straight style that is slightly exserted from the corolla. The capsules are held erect and are more or less round in shape, robust and thick-walled. The stigma is truncate, obscurely five-lobed. The seeds are large and brown, with a conspicuous wing on one side. Craibiodendron is most closely related to Lyonia, and has a certain resemblance to Pieris. It should be cultivated in conditions suitable for such woody ericaceous plants, with an acidic soil that does not dry out too much, and preferably some high overhead shelter. The only species known to be in cultivation is C. yunnanense; the other species occur further south and may not be hardy. The generic name commemorates William G. Craib (1882–1933), a botanist at Kew.

Craibiodendron yunnanense W.W. Sm. Shrub or tree to 11 m. Bark grey and longitudinally furrowed. Branchlets glabrous to sparsely pubescent. Leaves elliptic or oblong to obovate or ovate, 4.3–15.5 × 1.5–3.8 cm, base cuneate, apex long-acuminate but with blunt tip, margin flat, sometimes revolute near base, black punctate-glandular below, midvein glabrous to sparsely pubescent in its lower half, secondary veins prominent; petiole 2–13 mm. Inflorescence a panicle-like cyme, 4.5–20 cm, the secondary branches bearing two to six (to eight) flowers and glabrous to sparsely pubescent. Pedicels robust, 1–6 mm, sparsely pubescent. Flowers numerous; calyx lobes broadly ovate-triangular, pointed, to 1.5 × 2.2 mm, glabrous externally; corolla urceolate to cylindrical, 4–6 × 1.5–4 mm, lobes very short, cream to red or grey-purple, externally glabrous except for papillae towards the base; filaments to 4 mm, anther to 1 mm; ovary and style glabrous. Capsules subglobose to ovoid, 6–11 × 7–13 mm; seeds 4–7 mm. Flowering (May to) June to August (to October) (China). Judd 1986, Fang & Stevens 2005. Distribution CHINA: Xizang, Yunnan; MYANMAR. Habitat Thickets and open rocky areas in temperate to warm-temperate forests, and at the edges of coniferous forests between 1200 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Judd 1986, Lancaster 1989; NT278. Cross-reference S194.

Considering the general interest in ericaceous plants it is somewhat surprising that Craibiodendron is not better known. It is arguably at its best as it flushes bright coppery red in spring, like Pieris, but the glossy green leaves are also attractive, even if

277

278

Craibiodendron

New Trees

B

0.5 cm

C D

A 1 cm

0.5 cm

Section II. Species Accounts

Craibiodendron

the flowers are perhaps less so (Lancaster 1989). Roy Lancaster gathered seed on the Da Shao, Yunnan in 1981, and in the same year it was collected by the Sino-British Cangshan Expedition, by a team from the Royal Botanic Garden Edinburgh (SBEC 117, 1147). Material from this latter expedition is cultivated under glass in Edinburgh and outside at Logan, as well as at Tregrehan. Here it is developing a single stem, about 5 m tall in 2008, and is reported to be ‘relatively hardy’ (Hudson 2004). A number of introductions have been attempted at the David C. Lam Asian Garden in Vancouver, but the only one to meet with success (so far) has been from Keith Rushforth’s gathering KR 7523 at 2400 m on the Lancang Daxue Shan, Yunnan. Although this specimen is still young it has so far survived a hot, droughty summer and heavy snow with temperatures down to –9 ºC (P. Wharton, pers. comm. 2006). The species has been offered commercially in the Pacific Northwest.

Figure 29 (opposite). Craibiodendron yunnanense: habit with flowers (A); detail of a flower (B); capsule viewed from above (C), viewed from the side (D).

ROSACEAE

CRATAEGUS

L.

Hawthorns There are about 140 species of hawthorn (Phipps et al. 2003), though Flora of China suggests that there are over 1000 (Gu et al. 2003). This huge disparity in the number of species included reflects the rather poor state of knowledge regarding the taxonomy of Crataegus. However, this ‘wild’ genus is gradually being tamed: a number of significant regional taxonomic accounts have been published (Phipps 1988, Christensen 1992, Phipps 1997, Gu et al. 2003), as has a guide to the cultivated species (Phipps et al. 2003), and a taxonomic revision of the entire genus is currently being prepared by the hawthorn expert Prof. J.B. Phipps. The genus is found throughout temperate Eurasia and North America, with some species penetrating deep into Mexico. Hawthorns are shrubs or small trees with deciduous or rarely semi-evergreen leaves. The thorns are 1.5–9 cm long and may comprise sharp-tipped shoots with indefinite growth, simple shoots with definite growth or branched thorns, usually on the trunk; unbranched thorns are straight to recurved, fine to stout and reddish brown to black at maturity. The leaves are alternate and petiolate; they may be lobed with entire, crenate or serrate margins, or unlobed with serrate or crenate margins. Stipules are deciduous or persistent, entire to serrate. The inflorescences are terminal panicles or corymbs, though rarely umbellate or with solitary flowers. The flowers are hermaphrodite and 5-merous with a bowl-shaped hypanthium, persistent (rarely deciduous) sepals, white (rarely pink or red-tinged) petals and numerous stamens with white, yellow, pink or purple anthers. The fruit is a red, yellow, orange, purple or black pome; the flesh may be dry and mealy or succulent and juicy. There are one to five seeds in each fruit, each enclosed in its own endocarp (Phipps 1988, Christensen 1992, Phipps 1997, Gu et al. 2003). One approaches the thicket of Crataegus with some trepidation. It is an important but usually overlooked genus, containing some excellent garden plants, though many others are very uninteresting. At the time of writing the spectacle of C. monogyna

279

280

Crataegus

Plate 204. The large edible fruits of Crataegus mexicana are popular in Mexico. This soft orange is their usual colour. Image A. Coombes.

New Trees

flowering in the English countryside in late spring serves to remind us what the genus can do. Their fruits are also often an important horticultural feature, and taxa such as C. ×lavallei should not be overlooked for their winter effect. Crataegus remain, however, a minority interest, with few arboreta containing a wide range, and even fewer specimens to be found in private gardens. Their thorns often make them an uncomfortable presence in the garden, and their status, intermediate between shrubs and trees, can make them difficult to place. Many species seem to start life as a tangled shrub and only slowly develop a main trunk and tree form, although they may have started flowering and fruiting at an early age. Making the selection for inclusion in this book was not easy, as there are many synonyms to unravel, and we are grateful for the guidance provided by Prof. Phipps, principal author of the recent Hawthorns and Medlars (2003) and many scientific papers on the genus. He has pointed out (pers. comm. 2006) that the names applied to many taxa in botanical gardens are ‘wildly erroneous’ and in general thoroughly unreliable (not that this applies only to Crataegus!). Most of the species described below are rather rare in collections and even rarer in commerce, but among them are some very desirable plants worthy of much wider cultivation. One important clarification on a point of horticultural taxonomy is that many fine cultivars such as ‘Paul’s Scarlet’ and ‘Rubra Plena’ are examples of the hybrid between C. laevigata and C. monogyna, C. ×media Bechst. (Phipps et al. 2003), rather than clones of C. laevigata as is usually stated (Bean 1976a, Krüssmann 1984, Dirr 1998, Hillier & Coombes 2002). This hybrid, usually with single white flowers, occurs frequently where its parents overlap in their wild ranges, and is intermediate in its characteristics. In general, good garden soil is suitable for almost all hawthorns, and all tolerate lime. The majority of species are extremely hardy, but those from southern areas are less so and will require sheltered places in most parts of our area. Propagation is usually by seed, though hybridisation can be a significant problem, or by grafting onto stocks of a common species. Cuttings are difficult to root (Phipps et al. 2003). A number of pests and diseases affect hawthorns, especially in North America. Of these, the most serious are several rusts caused by Gymnosporangium fungi, that affect rosaceous plants but have an alternate host on Juniperus virginiana (for example, Gymnosporangium globosum, Cedar-hawthorn Rust), and cause severe disfigurement to the tree (Phipps et al. 2003, Chatfield et al. 1996). An annual spray with a systemic fungicide can help. Attacks by tent caterpillars can be dealt with by insecticides or by removing them manually from smaller specimens (Phipps et al. 2003). C. altaica (NOW C. wattiana Hemsl. & Lace) B789, K394

Section II. Species Accounts

Crataegus ambigua Meyer ex Becker

Crataegus

281

Russian Hawthorn

Shrub or tree to 12 m. Branchlets glabrous; thorns stout, to 1.4 cm long. Buds 0.1–0.5 cm long. Leaves deciduous, leathery, 2.3–5.7 × 2.9–5.4 cm, roughly triangular, upper surface dark or bright green and glabrous to villous, lower surface greyish green and villous along the veins and in the vein axils, two to four secondary veins on each side of the midrib, margin with two to four lobes on each side of the midrib, lobe margins dentate particularly towards the apex, apex acute to rounded; petiole 0.6–3.5 cm long; stipules 0.4–1.8 cm long, entire or serrate. Inflorescence corymbose, rather lax, 4–5 cm long with 12–20 flowers. Flowers white; hypanthium glabrous, 0.2–0.4 cm long, sepals triangular and persistent, petals 0.5–0.7 cm long, stamens 18–20 with purple anthers. Fruit 0.8–1.4 × 0.7–1.3 cm, dark red or blackish purple with persistent reflexed sepals at the crown, flesh yellowish, seeds one to two (to three). Flowering May to June, fruiting July to October (wild plants). Christensen 1992. Distribution ARMENIA; IRAN; RUSSIAN FEDERATION; TURKEY; UKRAINE: Crimea. Habitat Woodland on rocky slopes, riversides, in gullies and on steppe, often over calcareous rock; between 0 and 2700 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Christensen 1992.

Crataegus ambigua is widely recommended by horticultural websites in North America as a useful landscaping plant, with numerous good qualities, but curiously it is omitted by Phipps et al. (2003). Its environmental tolerances are its chief asset – not only being extremely hardy, but also tolerating drought conditions and difficult sites (for example, where the soil is compacted) (Sedbrook 2007). As a tree it is rather similar in appearance to C. monogyna, with somewhat contorted limbs, but it has attractive yellowish bark that exfoliates, contributing to its winter interest. The abundantly produced fruits are dark purplish red. It is said to be resistant to Gymnosporangium juniperi-virginianae, Cedar-apple Rust. It is rare in European collections, but there is a shrubby 4 m specimen at Kew, received from Ashkhabad Botanical Garden in 1936, and a 7 m tree was measured at the Hillier Gardens in 2003 (Sir Harold Hillier Gardens database).

C. apiifolia (NOW C. marshallii Eggl., NT284) B764 C. aprica Beadle B764, K394 C. arkansana (NOW C. mollis (Torr. & A. Gray) Scheele) B775 C. arnoldiana (NOW C. submollis Sarg.) B775, K395 C. azarolus L. B765, K395 C. azarolus var. sinaica (NOW C. ×sinaica Boiss.) B765, K395

Crataegus baroussana Eggl. Small, erect tree to 7 m. Thorns straight and stout, 2–2.5 cm long. Leaves deciduous, 3–5 cm long, roughly rhombic, upper surface somewhat pubescent, lower surface initially glabrous, later scabrous, four to six secondary veins on each side of the midrib, margin with few shallow lobes near the apex, sharply serrate with teeth to 0.2 cm, apex acute; petiole ~1 cm long; stipules deciduous. Inflorescence corymbose or paniculate with 5–10 flowers. Flowers white, 1.5 cm diameter; hypanthium glabrous, sepals narrowly triangular with glandular margins, petals circular, stamens 10 with pink anthers. Fruit ~1.2 cm long, spherical, red with conspicuous reflexed sepals at the crown, seeds three to five. Flowering April (Mexico). Phipps 1997. Distribution MEXICO: Coahuila, Nuevo León. Habitat Oak-pine forest and meadows. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Phipps 1997; NT281, NT282.

Crataegus baroussana is barely known in cultivation, although its relatively large flowers and big fruits suggest that it has considerable garden merit. There are two trees of it at Kew, grown from Keith Rushforth’s 1985 collection KR 534 made at 2650 m in Canyon de Jame, Coahuila, Mexico, and Rushforth also maintains material in his private collection. This is probably var. jamensis J.B. Phipps, endemic to the

Plate 205. A subtle medley of autumnal colours on Crataegus baroussana growing at Kew. Image J. Grimshaw.

282

Crataegus

New Trees

1 cm

Figure 30 (above). Crataegus baroussana: habit with flowers (A); fruits (B).

Jame Canyon, which can be distinguished from var. baroussana by its more leathery leaves, unlobed or barely lobed, with teeth to 0.1 cm long. The fruits are somewhat longer (1.5–1.7 cm) than in the typical variety. The Kew specimens are now 1.5–2 m tall, forming rounded bushes.

Section II. Species Accounts

Crataegus

283

C. berberifolia (NOW C. engelmannii Sarg. (?)) B769 C. brachyacantha Sarg. & Engelm. B765, K395 C. calpodendron (Ehrh.) Medwed. K395 C. canbyi (NOW C. crus-galli L.) B769 C. chlorosarca Maxim. B766, K395 C. chrysocarpa Ashe B766, K395 C. chrysocarpa var. phoenicea Palmer B766, K395

Crataegus chungtienensis W.W. Sm. Shrub or small tree, 6–9 m, dbh ~0.2 m. Branchlets greyish brown, glabrous, lenticels sparse; unarmed. Buds purplish brown. Leaves deciduous, 4–7 × 3.5–5 cm long, broadly ovate, upper surface glabrous, lower surface pubescent, particularly along the veins, margin with two to three (to four) lobes on each side of the midrib, lobe margins sharply double-serrate, apex obtuse; petiole 1–1.2(–3) cm long; stipules ~0.8 cm long, ovatelanceolate, membranous, margins serrate. Inflorescence corymbose, 3–4 cm diameter with many flowers; pedicels 0.4–0.6 cm long, glabrous. Flowers white; hypanthium campanulate, sepals triangular-ovate, petals obovate, ~0.6 cm long, stamens 20. Fruit red, ~0.6 cm diameter, ellipsoid, crowned by reflexed sepals, seeds one to three. Flowering May, fruiting September (China). Gu et al. 2003. Distribution CHINA: northwest Yunnan (Zhongdian). Habitat Mixed forest along watercourses, between 2500 and 3500 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT283.

Crataegus chungtienensis has been in cultivation for a long time, probably having been introduced by Forrest. It is common in the Zhongdian area, to which Forrest travelled on several occasions, and is an attractive small shrubby tree there, producing abundant large haws that are collected and eaten by local people (C. Brickell, C. Grey-Wilson, pers. comms. 2007). In cultivation a number of larger, older trees have been recorded in the past, including specimens of over 9 m at both Birr Castle, Co. Offaly, and Nymans, West Sussex (TROBI), measured by Alan Mitchell in the 1980s. It is not known whether any of these old trees survive, but at Edinburgh a 4 m specimen dates to the 1930s, from a collection made by T.T. Yu (13588) in northwestern Yunnan. It has also been collected on several occasions by more recent expeditions to Yunnan, notably the Cangshan, Lijiang and Dali Expedition (CLD) and the Alpine Garden Society Expedition to China (ACE), in 1991 and 1994, respectively. Material distributed from these sources has enabled it to become quite widely grown. In addition to its ornamental flowers and fruits, its glossy chestnut-brown twigs, red-brown thorns and large shiny buds are attractive in winter. A specimen at Hergest Croft from ACE 1624 was 4 m tall in 2006. C. coccinioides Ashe B767, K395 C. collina Chapm. K395 C. columbiana (NOW C. chrysocarpa Ashe) S194 C. crus-gallii L. B768, S194, K395 C. crus-gallii var. arbutifolia Bean B768 C. crus-gallii var. capillata Sarg. B768 C. crus-gallii var. linearis DC. B769 C. crus-gallii var. pyracanthifolia Aiton B768 C. crus-gallii var. salicifolia Aiton B769 C. cuneata Siebold & Zucc. B769, K395 C. dahurica Koehne ex C.K. Schneid. B785, K396 C. dilatata (NOW C. coccinioides Ashe) B767

Plate 206. Crataegus chungtienensis both flowers and fruits well. It is common in Yunnan, where this image was taken. Image S. O’Brien.

284

Crataegus

New Trees

C. ×dippeliana Lange B769, K396 C. douglasii Lindl. B770, S194, K396 C. dsungarica Zabel ex Lange B770, K396 C. dunbarii Sarg. B767 C. dubrobrivensis (NOW C. coccinioides Ashe (?)) B771, K396 C. ellwangeriana Sarg. B781, K396 C. flabellata (Spach) K. Koch B771, K396 C. flava Aiton B772, K396 C. fontanesiana (NOW C. calpodendron (Ehrh.) Medik.) B769, K396

C. ×grignonensis Mouill. B774, K397 C. heldreichii Boiss. B774, K397 C. henryi (NOW C. scabrifolia (Franch.) Rehder) B772 C. heterophylla Flügge B772, K397 C. ×hiemalis Lange B781 C. holmesiana Ashe B781, K397 C. holmesiana var. villipes Ashe B781 C. intricata Lange B773, K397 C. intricata var. straminea Palmer B773 C. jackii Sarg. B767, K397 C. jonesiae Sarg. B767, K397

Crataegus jozana C.K. Schneid. Small tree to about 8 m, dbh ~0.2 m. Branchlets stout, dark purplish brown and tomentose-pubescent; thorns straight, 0.7–1.5 cm long. Buds 0.6–0.9 cm long, bud scales shiny, chestnut-coloured. Leaves deciduous, 6–12 × 3.5–10 cm, roughly ovate-elliptical, upper surface pubescent, lower surface tomentose, four to nine secondary veins on each side of the midrib, margin with four to seven (to nine) triangular lobes on each side of the midrib, lobe margins serrate, apex acute; petiole 1.3–5.5 cm long, pubescent; stipules conspicuous, 1.7–2.3 cm long, ovate to lanceolate with serrate margins. Inflorescence corymbose, tomentose, ~6 cm diameter with numerous flowers. Flowers white, ~1.5 cm diameter; sepals white-tomentose, triangular and slightly glandular, petals circular, stamens 20 with pale pink anthers. Fruit ~1 cm diameter, globose, black with conspicuous reflexed sepals at the crown, seeds five. Flowering June, fruiting October (Japan). Miyabe & Kudo 1986. Distribution JAPAN: Hokkaido; RUSSIAN FEDERATION: Sakhalin. Habitat Deciduous, broadleaved forest, between 0 and 300 m asl. USDA Hardiness Zone 3–4. Conservation status Not evaluated. Illustration Miyabe & Kudo 1986. Taxonomic note Crataegus jozana is closely related to C. chlorosarca but differs in being glabrous (Phipps et al. 2003).

Crataegus jozana is scarce in cultivation outside Japan, but grows in a handful of collections ranging from the Dominion Arboretum, Ottawa, Canada, to the Royal Botanic Garden Edinburgh and Rogów Arboretum in Poland, giving the impression that it must be very hardy. Unfortunately no specimens have been observed for the current work but it can be expected to have similar qualities to C. chlorosarca, and with its large leaves and black fruit, could be rather attractive. C. laciniata (NOW C. orientalis M. Bieb.) B773 C. laevigata (Poir.) DC. S194, K398 C. laevigata subsp. palmstruchii (Lindm.) Franco K398 C. ×lavallei Hérincq ex Lav. B774, S195, K398 C. macracantha (NOW C. succulenta Schrad. ex Link) B774 C. macrosperma var. acutiloba (Sarg.) Eggl. B771

Crataegus marshallii Eggl.

Parsley Haw

Syn. C. apiifolia (Marsh.) Michx. Shrub or small tree to 10 m, dbh ~0.2 m. Bark exfoliating and becoming smooth. Branchlets greyish brown, pubescent; thorns slender, straight or slightly recurved, (1–)2–3(–5) cm long. Leaves deciduous, 1.5–3 cm long, ovate to deltoid in outline, both surfaces densely pubescent when young, pubescence gradually eroding to remain on the veins only at maturity, two to eight secondary veins on each side of the midrib, margin with (two to) three to four (to five) deep or shallow lobes on each side of the midrib, lobe margins serrate, apex

Section II. Species Accounts

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285

acute; petiole 1–2 cm long, pubescent; stipules deciduous. Inflorescence pubescent, corymbose with three to eight flowers. Flowers white (rarely pink), 1.2–1.7 cm diameter; hypanthium largely glabrous, sepals narrowly triangular and glandular-serrate, petals elliptic, 0.6–0.8 cm long, stamens 20 with red anthers. Fruit 0.4–0.6 cm long, ellipsoid to spherical, glossy red (rarely dull orange), seeds one to two (to three). Flowering March to April (USA). Phipps 1998. Distribution USA: Alabama, Arkansas, Florida, Georgia, southern Illinois, Louisiana, Mississippi, southern Missouri, North Carolina, southeast Oklahoma, South Carolina, Tennessee, Texas, Virginia. Habitat Open, wooded areas with wet or well-drained soils, including forest clearings, woodland edges and fence lines. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Phipps 1998, Phipps et al. 2003; NT285.

The Parsley Haw is so-named on account of its small, deeply lobed leaves, perhaps the most ornamental foliage of any American Crataegus (Sternberg 2004) – though it should not be used as a garnish. The small flowers have red anthers and are succeeded by petite shining scarlet fruits, adding to the dainty appearance of the tree (Phipps et al. 2003, Sternberg 2004). In addition it has attractively exfoliating bark, peeling in shades of yellow, grey and brown. Phipps et al. (2003) describe it as a superior ornamental and a four-season tree, suggesting that it should be more widely cultivated. In its native habitat it can grow in wet places, an adaptation that should give it some horticultural flexibility, but it should be sought from the more northern parts of its distribution. Crataegus marshallii is popular with native plant enthusiasts in the southern United States, but is rare elsewhere. C. maximowiczii C.K. Schneid. B785, K398 C. ×media Bechst. K399

Crataegus mexicana Moc. & Sessé

Tejocote

Syn. C. pubescens f. stipulacea hort., C. pubescens var. stipulacea (Loudon) Stapf, C. stipulacea Loudon, C. stipulosa (HBK) Steudel Tree to 7 m. Branchlets robust; thorns straight and stout, 3.5–5 cm long. Leaves deciduous, leathery, 3.5–7.5 cm long, lanceolate to elliptic to narrowly obovate, upper surface somewhat pubescent, lower surface tomentose, particularly on the veins, six to eight secondary veins on each side of the midrib, margin unlobed, finely to coarsely serrate, apex acute; petiole 0.1–0.6 cm long; stipules deciduous. Inflorescence corymbose to almost umbellate, with 3–12 flowers; pedicels pubescent. Flowers white (rarely pinkish), 1.5–2 cm diameter; hypanthium bristly, sepals triangular and tomentose with entire-serrate margins, petals circular, stamens 20 with pink, purple or reddish anthers. Fruit (1.2–)1.5–2.5 cm diameter, spherical to turbinate, yellow to golden or copper-orange, sepals persisting at the crown, seeds four to five. Flowering February to March (to April) (Mexico). Phipps 1997. Distribution GUATEMALA; MEXICO: Guanajuato, Hidalgo, Jalisco, México, Michoacán, Oaxaca, Puebla, Querétaro, San Luis Potosí, Veracruz. Cultivated in Costa Rica. Habitat Extremely varied. Often cultivated for its edible fruit. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Phipps 1997; NTxvi, NT280, NT286. Cross-references B786 (as C. stipulacea), K401 (as C. pubescens f. stipulacea).

Crataegus mexicana, known as Tejocote in Mexico, is an important fruit-bearing plant, producing masses of large yellowish fruits that can be eaten from the hand or as a jelly, and may remain on the tree into winter, unless removed by either humans or birds (Hogan 2008). Some clones have been selected locally for the quality of their fruit. The fine visual effect of the fruit of this species has been inherited by its offspring C. ×lavallei, although in this hybrid – with male parent probably C. calpodendron (Phipps et al. 2003) – the haws are orange-red. Crataegus mexicana is unfortunately less hardy

Plate 207. As well as bearing the classic ‘mayflowers’, Crataegus marshallii has finely divided leaves. It is native to the southeastern United States. Image JC Raulston Arboretum.

286

Crataegus

Plate 208. Crataegus mexicana has been in cultivation for many years under the name C. pubescens var. stipulacea, the label attached to this tree at Kew. It is apparently hardy, and bears heavy crops of big yellow haws. Image J. Grimshaw.

New Trees

and is seldom found in European arboreta, although it is possible that some individuals are present under the name C. stipulacea Loudon (see Bean: B786). Plants under this latter name have been considered to be hardy where C. mexicana is not (Phipps et al. 2003), but there seem to be no significant differences, and all are now treated as C. mexicana. There are at present some young trees of wild-origin C. mexicana in cultivation in southern England, most notably at the Sir Harold Hillier Gardens, where there are several derived from collections made by Allen Coombes, the tallest of which has reached 3.9 m (2007); others are growing at Thenford House and at Kew. It is more successful in western North America – including one particularly fine tree at Berkeley – but although tolerant of dry summer conditions it does better with extra irrigation (Hogan 2008). It is generally more or less evergreen, with broad, shiny dark green leaves that may take on purplish tints in winter. Defoliation may occur if temperatures drop below –8 ºC, but it will tolerate temperatures to at least –18 ºC (Hogan 2008). In areas with cooler summers than California or Mexico it is probable that good ripening is needed for full hardiness to be achieved, and a warm sunny site should be selected. Its fruiting effect in the winter should not be overlooked.

Crataegus meyeri Pojark. Syn. C. persica Pojark., C. taurica Pojark., C. ucrainica Pojark. Shrub or tree to 5 m. Branchlets villous; thorns stout, to ~2 cm long. Buds 0.1–0.4 cm long. Leaves deciduous, 1.8–5 × 1.6–5.2 cm long, more or less rhomboid, upper surface dark green and villous, lower surface greyish green and villous, four to six secondary veins on each side of the midrib, margin with one to four lobes on each side of the midrib, lobe margins entire to irregularly serrate, apex acute to obtuse; petiole 0.2–2.1 cm long; stipules 0.4–2 cm long, entire to serrate. Inflorescence corymbose, 3–5 cm long with 9–20 flowers; pedicels villous. Flowers white; hypanthium villous, sepals triangular with entire or serrate (with one to two teeth) margins, petals 0.4–0.8 cm long, stamens 18–20 with purple anthers. Fruit 0.7–1.2(–2) cm long, subglobose to cylindrical, red and villous, crowned by reflexed sepals, seeds (one to) two (to three). Flowering May to June, fruiting June to October (wild plants). Christensen 1992. Distribution ARMENIA; AZERBAIJAN; GEORGIA; IRAN; IRAQ; TURKEY; UKRAINE. Habitat Thickets, woodlands. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Christensen 1992; NTxvi. Taxonomic note An extremely variable species, as evidenced by the number of regional synonyms.

Crataegus meyeri is closely related to C. monogyna but usually has two seeds per fruit. It is another collector’s item, not available in commerce, and with only a few specimens held by botanical gardens. In the United Kingdom there are trees at Kew and at the Hillier Gardens grown from seed collected in 1990 by the Flanagan and Pitman Expedition to Turkey (TURX 104) in the Amanus Mountains of Hatay Province, at about 1200 m. There it grew as a small tree up to 6 m tall, in more open sites within mixed deciduous woodland, and was described in the collectors’ field notes as a shapely, large-fruited species. At the Hillier Gardens it is now 3 m tall (2007). An older tree at Kew, grown from material supplied by the Botanical Garden of the Armenian Academy of Science in 1968, is now 5 m tall, with a dense, umbrella-shaped

Section II. Species Accounts

Crataegus

287

canopy. In North America it is maintained in the Woody Landscape Plants Germplasm Repository of the US National Arboretum, from material collected in Ukraine in 1999 by Widrlechner, Schutzki, Yukhnovsky and Sviatetsky (WSYUS 24), but it is not known to be cultivated elsewhere.

C. mollis (Torr. & A. Gray) Scheele B775, K399 C. monogyna Jacq. B776, S195, K399 C. monogyna subsp. azarella (Griseb.) Franco K399 C. monogyna subsp. brevispina (G. Kunze) Franco K399 C. monogyna f. laciniata (Loud.) Dippel B777 C. monogyna subsp. nordica Franco K399 C. monogyna f. pendula (NOW C. monogyna ‘Pendula’) B777 C. monogyna f. stricta (NOW C. monogyna ‘Stricta’) B777 C. ×mordenensis Boom B780, K399 C. nigra Waldst. & Kit. ex Willd. B778, K400 C. nitida (NOW C. viridis L.) B788, K400 C. oliveriana (NOW C. pentagyna Waldst. & Kit. ex Willd. subsp. pentagyna) B778 C. orientalis Pall. B773, K400 C. orentalis var. sanguinea (Schrad) Loudon K400 C. ovalifolia (Hornem.) DC. B784 C. oxyacantha (NOW C. laevigata (Poir.) DC.) B779, S194 C. oxyacantha f. aurea (NOW C. ×media Bechst.) B779 C. oxyacantha f. rosea (NOW C. ×media Bechst.) B780 C. pedicellata (NOW C. coccinea L.) B780, K400 C. pentagyna Waldst. & Kit. ex Willd. B781, K400 C. persistens Sarg. B769, K400 C. phaenopyrum (L. f.) Medik. B782, K400 C. pinnatifida Bunge B782, K400 C. pinnatifida var. major N.E. Br. B782, K401 C. pinnatifida var. psilosa C.K. Schneid. B783 C. pruinosa (Wendl.) K. Koch B783, K401 C. ×prunifolia (NOW C. ×persimilis Sarg.) B784, S195, K401

Crataegus pseudoheterophylla Pojark. Shrub or tree to 3 m. Branchlets glabrous or sparsely villous; thorns stout, to ~1.4 cm long. Buds 0.1–0.3 cm long. Leaves deciduous, 1.7–5.4 × 1.5–5.2 cm long, deltoid to rhomboid, upper surface dark green and villous along the veins, lower surface pale greyish green and villous in the vein axils, four to six secondary veins on each side of the midrib, margin with one to three lobes on each side of the midrib, lobe margins entire to irregularly serrate, apex acute to obtuse; petiole 0.6–3.6 cm long; stipules 0.4–2.1 cm long, serrate. Inflorescence corymbose, 2–4 cm long with 4–14 flowers; pedicels glabrous to villous. Flowers white; hypanthium glabrous, sepals triangular with entire margins (rarely with one to two teeth), petals 0.4–0.6 cm long, stamens 16–20 with purple anthers. Fruit 0.7–1.1 cm long, subglobose to ellipsoid, red, crowned by reflexed sepals, seeds one (to two). Flowering April to June, fruiting May to October (wild plants). Christensen 1992. Distribution AFGHANISTAN; ARMENIA; AZERBAIJAN; CHINA: Xizang; GEORGIA; INDIA: Kashmir; IRAN; KAZAKHSTAN; KYRGYZSTAN; PAKISTAN (?); RUSSIAN FEDERATION: Caucasus; TAJIKISTAN; TURKEY; TURKMENISTAN; UZBEKISTAN. Habitat Scrub, rocky mountain slopes and gorges, along rivers and on field margins, between 300 and 2700 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Christensen

Plate 209. Multiple stems of Crataegus pseudoheterophylla FLSX 497 at Kew. Image J. Grimshaw.

288

Crataegus

New Trees

1992; NTxvi, NT287. Taxonomic note Three subspecies are recognised in C. pseudoheterophylla. Subsp. turkestanica (Pojark.) K.I. Chr. has villous pubescence on the pedicels, hypanthium, fruits, and occasionally on the branchlets. It ranges from Iran through central Asia to Tibet. Subsp. turcomanica (Pojark.) K.I. Chr. is largely glabrous and the leaves on flowering shoots are rounded or narrowly cuneate at the base. It occurs only in Turkmenistan, but is in cultivation at the Morton Arboretum. Subsp. pseudoheterophylla has villous pubescence on the fruits, hypanthium and upper parts of the pedicel; the leaves on flowering shoots are cuneate at the base. It occurs in Asian Turkey, Iran and the Caucasus.

Also related to Crataegus monogyna, C. pseudoheterophylla is another hawthorn from wide tracts of Eurasia that has only a tentative presence in cultivation. At Kew there are trees derived from collections made in the Zagros Mountains of Iran in 1977 (FLSX 497), now 3 m with densely tangled growth, and Bolu Province, Turkey in 1990 (TURX 111), currently 2.5 m tall. Material from the latter source is also cultivated at the Hillier Gardens, where it was 1.7 m tall in 2007. A tree (of horticultural origin) seen at the Morton Arboretum in 2006 was 5 m tall, forming a low, rounded, bushy specimen with rather sparse fruit, that certainly had no advantage over C. monogyna. Crataegus pseudoheterophylla is currently offered commercially in the United Kingdom.

C. pubescens f. stipulacea (NOW C. mexicana, NT285) K401 C. punctata Jacq. B784, K401 C. punctata f. aurea (Aiton) Rehder B785 C. saligna Greene B765, K401 C. sanguinea Pall. B785, K401 C. schraderiana (NOW C. orientalis M. Bieb. subsp. orientalis) B774 C. songarica K. Koch B771 C. sorbifolia Lge. K401 C. spathulata Michx. B786, K401 C. splendens Lodd. B784 C. stipulacea (NOW C. mexicana, NT285) B786 C. submollis Sarg. B776, K401

Plate 210. Pink fruits of Cryptocarya alba. Image K. Gillanders.

C. succulenta Schrad. ex Link B786, K401 C. succulenta var. macracantha (NOW C. succulenta Schrad. ex Link) B774, K401 C. tanacetifolia (Poir.) Pers. B787, K401 C. tomentosa (NOW C. uniflora Muench.) B787 C. triflora Chapm. K401 C. uniflora Muench. B788, K402 C. ×vailiae Britton B788 C. viridis L. B788, K402 C. wattiana Hemsl. & Lace B789, K402 C. wilsonii Sarg. B789, K402

LAURACEAE

CRYPTOCARYA

R. Br.

Cryptocarya comprises about 350 species occurring primarily in South America, Malesia and Australia, though with a small number in eastern and southern Africa and Madagascar. In addition, the Madagascan genus Ravensara Sonn. (approximately 30 species) should be merged with it. Cryptocarya species are evergreen trees or shrubs. The leaves are alternate or rarely almost opposite and pinninerved or triplinerved. Inflorescences are axillary, subterminal and paniculate. The flowers are small and

Section II. Species Accounts

Cryptocarya

289

rather inconspicuous, hermaphrodite and 3-merous. The tepals are deciduous or persist as minute fragments, and there are nine fertile stamens with a further whorl of short staminodes. The fruit is a globose or ellipsoid drupe, completely enclosed in a hard or fleshy receptacle (Rohwer 1993a). The genus is not well known in cultivation and receives no mention in many standard works (for example, Huxley et al. 1992), but a few native species are occasionally grown in Australia (Ellison 1999). In addition to C. alba, described below, the only other species known to be cultivated in our area is the Chilean C. rubra (Molina) Skeels, of which there is a fine, broad-canopied specimen on a lawn in the San Francisco Botanical Garden.

Cryptocarya alba (Molina) Looser

Peumo

Tree to 15 m, 1 m dbh. Branchlets pale brown, glabrous; often with a hint of waxy bloom. Leaves evergreen, opposite or almost so, 1–5(–8) × 1.5–4.5 cm, leathery and fragrant, ovate-elliptical or oblong, upper surface glabrous and dark green, lower surface glabrous, glaucous and with conspicuous, raised tertiary veins, five to eight secondary veins on each side of the midrib, margins entire and often slightly wavy, apex obtuse; petiole 0.3–0.5 cm long, smooth, glabrous. Inflorescences axillary, racemose, 2–6 cm long. Flowers yellowish green, 0.3–0.4 cm long; tepals fleshy, slightly pubescent, united at the base to form a short tube. Fruit a pinkish red waxy drupe, ovate with a thin skin, 1.5– 1.8 × 0.7–1 cm. Flowering August to December, fruiting January to April (Chile). Rodríguez R. et al. 1983. Distribution CHILE: from Limarí to Cautín Province. Habitat Sclerophyllous forest to 1500 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT288, NT289.

In its wild habitat Cryptocarya alba grows with a number of other evergreen trees in sclerophyllous forest, and like many of them, now has a toe-hold in cultivation. Material has been maintained under glass at Edinburgh of a collection made in the 1920s by Harold Comber, but more recent collections by Edinburgh expeditions to Chile have enabled plants to be grown outside. The only ones seen in the research for New Trees are growing at Tregrehan, from the Araucaria Expedition of 1998 (MAWAX 82), and these remain small, slow-growing specimens so far. Mature trees have a heavy canopy of rather dull dark green leaves (although they flush red), amongst which the small greenish flowers are inconspicuous. The pinkish fruits are rather more obvious (Chilebosque 1999–2008b). It is also grown at the University of California Botanical Garden at Berkeley. It would seem that a warm, sheltered site is required for successful cultivation in our area.

Plate 211. The shade produced by this Cryptocarya alba in Santiago, Chile is evidently appreciated. Image J.R.P. van Hoey Smith.

290

Cupressus

New Trees

CUPRESSACEAE

CUPRESSUS

L.

True Cypresses

Plate 212. Bark of Cupressus sargentii. Image R. Hitchin.

Taxonomic treatments of Cupressus vary widely in the number of species they recognise: Silba (1981a, 1983, 1998) included 25 species while Farjon (2001, 2005c) recognised only 16. DNA-based studies suggest that further realignment of the species may be necessary (Bartel et al. 2003, Little et al. 2004), although this is strongly refuted by others (Farjon 2007a). Cupressus species usually occur in small, disjunct populations, and are distributed in the Mediterranean Basin and North Africa, southwestern North America and from the Himalaya to western China. True cypresses are evergreen trees or large shrubs with somewhat pendulous, terete or quadrangular branchlets. The branchlets are typically decussate, though in C. macnabiana they are flattened and comb-like. As in many Cupressaceae, there are two leaf forms: the juvenile leaves are needle-like and the mature leaves are scale-like. Adult leaves are decussate, appressed to divergent and with an abaxial resin gland in some species; the lateral and facial pairs are largely similar. The male strobili are terminal and solitary on short, lateral branchlets, with 6–16 decussate microsporophylls. The female cones are terminal, solitary, roughly globose, valvate, and mature in one or two years; the cones are dehiscent or shed their seeds after being burnt. The seed scales are arranged in three to six basally fused, decussate pairs; they are peltate, thick and woody with a mucronate apex; the umbo is small and spiny. There are 5–20 seeds per scale and they are lenticular with two narrow wings. Relationships within the Cupressaceae have been debated long and hard for many years, and the discussion continues at full force today. An enduring dilemma has been whether Cupressus should be combined with Chamaecyparis, but there are ample morphological and genetic differences to support their distinction (Wolf & Wagener 1948, Rushforth 1987a, Watson & Eckenwalder 1993, Silba 1998, Fu et al. 1999e). More recently, phylogenetic studies using DNA and morphological data suggest that Cupressus is more closely related to Juniperus and Xanthocyparis than to Chamaecyparis (Gadek et al. 2000, Little et al. 2004). Some researchers (Little et al. 2004, Xiang & Li 2005) suggest that Cupressus is not monophyletic, and propose various options for recognising this, including combining into one genus all members of Cupressus, Juniperus and Xanthocyparis, or retaining Juniperus and splitting Old and New World Cupressus into two genera. Little (2006) proceeded to establish a segregate genus for the New World cypresses, including the two species of Xanthocyparis (X. nootkatensis and X. vietnamensis), unfortunately using the disputed name Callitropsis (see the account of Xanthocyparis for a full exegesis), and making new combinations in Callitropsis for all the species involved. The name Xanthocyparis has now, however, been conserved against

Section II. Species Accounts

Cupressus

291

1 cm

B

1 cm

A

Callitropsis (Brummitt 2007), making use of the latter name illegitimate. If segregation of the New World cypresses is to be accepted, it will therefore have to be under the genus Xanthocyparis (in which no combinations have as yet been published). Farjon (2007a) rejects such an approach, claiming that the genetic differentiation found by

Figure 31 (above). Cupressus dupreziana var. dupreziana: habit (A); seed cone (B).

292

Cupressus

New Trees

Little et al. (2004) is insignificant, and that no justification for splitting the genus can be found in anatomical and morphological characters – a view that is followed here. It should also be noted that the option of including the two Xanthocyparis in Cupressus is favoured by some (Rushforth 2007), but that, as yet, a grand lumping together of Cupressus, Juniperus and Xanthocyparis has not been seriously proposed. Gardeners are faced by the presence in horticulture of several poorly defined species, and a plethora of names, over which botanists continue to wrangle. Most are from the mountains of the Sinohimalaya and their extensions into southeastern Asia, often with very narrow ranges and sometimes with natural distributions obscured by transplantations into cultivation. The apparently geographically and morphologically distinct Cupressus austrotibetica is a case in point (see below). Whether as the narrow columns of the Italian Cypress Cupressus sempervirens, or the craggy wide-stretched limbs of C. macrocarpa on the cliffs of California or coastal Europe, Cupressus has a notable part in the landscape of the more temperate parts of our region, especially where Mediterranean or near-Mediterranean climatic conditions prevail. The genus seems not to be highly regarded in the eastern United States, and neither Dirr (1998) nor Sternberg (2004) give it much space, though it is clear that some species will perform well in parts of the southeastern United States despite the high summer temperatures and humidity. Most cypresses seem to grow satisfactorily in any well-drained soil, including shallow chalk (Hillier & Coombes 2002), although they should be given a site in full sun. Many are very well adapted to dry conditions, but the distribution of British and Irish champions suggests that they do better in damper conditions (Johnson 2003). Cypress canker (Seiridium spp.) can be a problem, affecting the cambium layer and effectively cutting off the circulation to shoots beyond the point of infection, causing dieback. It seems to be most prevalent on Cupressus sempervirens in Europe, and C. macrocarpa and its derivative ×Cuprocyparis leylandii elsewhere, but it can affect other species in the genus and the wider Cupressaceae (Barnard & Leahy 2004). Smaller specimens can be treated by fungicide but treatment of larger specimens is difficult. Plate 213. A small group of Cupressus dupreziana var. atlantica at Kew, showing their stiffly columnar habit when young. Image J. Grimshaw.

C. abramsiana (NOW C. goveniana var. abramsiana (C.B. Wolf) Little, NT298) B803, S201, K103

Cupressus arizonica Greene Five varieties of Cupressus arizonica are recognised by Farjon (2001, 2005c), though prior to the revision by Little (1966) they were all regarded as separate species. The morphological characters that separate the varieties (bark colour and texture, leaf resin glands and leaf colour, cone serotiny) intergrade and may be the result of ecological factors. For these reasons, Watson & Eckenwalder (1993) employ a conservative taxonomic concept, recognising no varieties. Cupressus arizonica (including vars. arizonica, glabra and stephensonii) was described by Bean (B799, S199) and Krüss-

Section II. Species Accounts

mann (K103). Although the species is a commonly grown garden plant, a key to the currently accepted varieties is provided below, adapted from Little (1966). All seem to be hardy and easy to grow wherever C. arizonica can be cultivated.

1a. Bark of mature trees grey or dark brown, rough and furrowed ......................................................... 2 1b. Bark of mature trees reddish brown, smooth, peeling in thin, curling plates .................................... 4 2a. Cone scales open at maturity; Mexico (Baja California Norte) (see K105) ......................................... var. montana (Wiggins) Little 2b. Cones serotinous ........................................................................................................................... 3 3a. Leaf resin glands conspicuous and active; USA (California: Piute Mts.) (see K105) .......................................... var. nevadensis (Abrams) Little 3b. Leaf resin glands absent or inactive, rarely active; Mexico (Chihuahua, Coahuila, Durango, Tamaulipas, Zacatecas) (see B799, K103) .................................. var. arizonica 4a. Leaf resin glands inactive or slightly active; seeds usually over 5 mm long, not glaucous; Mexico (Baja California Norte), USA (California: Cuyamaca Mts.) (see B800, K105) ................... var. stephensonii (C.B. Wolf) Little 4b. Leaf resin glands very active, resulting in white flecks of resin on the foliage; seeds usually 4–5 mm long, glaucous; USA (Arizona: Coconino, Gila, Maricopa, Yavapai Counties) (see B799, S199, K103) ..... var. glabra (Sudw.) Little

Cupressus austrotibetica Silba A number of new species of Cupressus have been described in the various publications by John Silba (for example, Silba 1981a, 1983, 1998). While these species have not received wide recognition within the taxonomic community (see, for example, Farjon 2005c), seed has been distributed under some Silba names, including C. austrotibetica and C. tonkinensis. Some of the resultant plants do appear distinctive, causing confusion as to their identity, particularly in the absence of a horticultural authority on the subject. It must be pointed out that the seeds distributed by Silba (and his confederates in source countries) cannot be conclusively linked to particular Silba names; they may only be linked by a common source locality. Cultivated plants bearing these names should therefore be regarded with great suspicion. A recent molecular study suggests that there is considerable variation in eastern Asian Cupressus, variation that is not encompassed fully by modern taxonomic treatments (Rushforth et al. 2003). Both C. austrotibetica and C. tonkinensis (together with four other Silba names) are considered by Farjon (2005c) to be synonymous with C. torulosa var. torulosa. Cupressus austrotibetica was collected near Pome in southern Tibet, and has very fine, spreading foliage with irregularly disposed (not flattened) branchlets, relatively small female cones, and seedlings with two cotyledons only (Silba 1994). Silba later reduced it to Cupressus duclouxiana Hickel subsp. austrotibetica (Silba) Silba. Cupressus tonkinensis hails from Lang Son Province, Vietnam, and has slender or thread-like (not flattened) branchlets with bluntly acute to obtuse leaves, and ovoid to subglobose female cones with small umbos (Silba 1994). Silba later reduced it to Cupressus funebris Endl. subsp. tonkinensis (Silba) Silba. Keith Rushforth, however, regards both as good species with distinct morphologies and distributions (pers. comm. 2007).

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Cupressus bakeri Jeps.

Baker Cypress, Modoc Cypress, Siskiyou Cypress

Syn. C. bakeri subsp. matthewsii C.B. Wolf Tree to 30 m, trunk slender, to 0.6(–1) m dbh. Bark smooth and reddish brown, later grey with multiple layers to a thickness of 2 cm; plates curling upwards at the edges. Crown narrow and conical, sparse. Branchlets decussate or alternate, slender; branches that persist beyond the first year shed their leaves by expansion of the bark, which pushes the leaves off. Juvenile leaves needle-like; mature leaves scale-like, glaucous-green, decussate, appressed, densely crowded; the lateral and facial pairs are similar, 2(–10) × 1–4 mm, apex abruptly constricted; leaf resin gland abaxial, conspicuous and active, pit-like. Male strobili solitary and terminal, borne on short, lateral branches, 2–3 × 2–2.5 mm, subglobose, with 6–10 peltate microsporophylls. Female cones axillary, usually solitary, globose, valvate and 1–2 cm long, initially green though silvery (not glaucous) at maturity. Seed scales in three to four decussate pairs, valvate, covered with resin blisters, 8–10 seeds per scale; umbo prominent, in distal scales to 4 mm long and erect, often eroding in time. Seeds medium brown or tan, thin and angular, not or slightly glaucous; seed wings absent. Watson & Eckenwalder 1993, Farjon 2005c. Distribution USA: northern California, southern Oregon. Habitat Mixed evergreen forest between

Plate 214. The cones of all Cupressus have relatively few scales, maturing over one or two years. This is Cupresssus bakeri, at Arboretum Trompenburg. Image J.R.P. van Hoey Smith.

1100 and 2000 m asl. Cupressus bakeri is largely confined to volcanic or serpentine soils. USDA Hardiness Zone 6. Conservation status Vulnerable. Illustration NT294. Cross-references B805, K105.

With its origin at comparatively northerly latitude and high altitude, Cupressus bakeri is considered to be the hardiest American cypress (Rushforth 1987a, van Gelderen & van Hoey Smith 1996), and in Poland it is viewed as being the hardiest of all Cupressus (P. Banaszczak, pers. comm. 2007). Two subspecific taxa were formerly recognised, but Farjon (2001, 2005c) considers that the Siskiyou population, described as subsp. matthewsii on the basis of small cone characters, does not warrant recognition. The name, however, remains frequent in literature and on arboretum labels. In the wild, trees in the Siskiyou population (‘subsp. matthewsii’) on serpentine rock grow much taller (to 30 m) than do those of the nominate ‘subsp. bakeri’ growing on lava flows in northern California. In cultivation, this almost certainly habitat-induced distinction seems irrelevant, with C. bakeri from both sources performing well. Several are in the 14–15 m range, both at the Sir Harold Hillier Gardens – including the recognised champion (Johnson 2003) – and at Kew. Young plants at Howick are also growing very well. Trees from a collection made in Shasta County, California in 1990 are now 5 m tall at Rogów Arboretum (P. Banaszczak, pers. comm. 2007). The most attractive feature of C. bakeri is its shiny reddish to dark brown bark, which peels off in large curled flakes. When young the tree forms a dense column of bluish sage-green shoots, but with age it opens out, developing spreading branches and a more open habit. C. bakeri subsp. matthewsii (NOW C. bakeri Jeps., NT294) B805, K105 C. cashmeriana Royle ex Carrière B800, S200, K105

Cupressus chengiana S.Y. Hu

Cheng Cypress, Min River Cypress, Sichuan Cypress

Syn. C. fallax Franco, C. chengiana var. kansouensis Silba, C. chengiana var. wenchuanhsiensis Silba

Tree to 30 m, 1 m dbh. Bark greyish to reddish brown, delicately fissured, peeling in strips. Crown compact, densely columnar. Branchlets decussate or alternate, stout, terete, slightly drooping. Juvenile leaves needle-like; mature leaves scale-like, dull green, decussate, appressed, densely crowded; the lateral and facial pairs similar, 0.1–0.2 cm long, acute; leaf resin gland abaxial and active, rather long; foliage scented when crushed. Male strobili solitary and terminal, borne on short, lateral branches, 0.2–0.4 cm long, subglobose, with 12–16 peltate microsporophylls. Female cones axillary, usually solitary, on short, lateral branchlets, globose to subglobose and valvate; cones reddish brown to brown, 1.2–2 cm diameter. Seed scales in four to seven decussate pairs with

Section II. Species Accounts

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several seeds per scale; umbo small but prominent. Seeds tan coloured, ovate to triangular, not glaucous; seed wing tiny, < 0.1 cm wide, thick, opaque (see Silba 1981b). Fu et al. 1999e, Farjon 2005c. Distribution CHINA: southern Gansu, northwest Sichuan. Habitat Mountain slopes and valleys between 800 and 2900 m asl. USDA Hardiness Zone 6. Conservation status Vulnerable. Illustration Fu et al. 1999e.

The earliest recorded introduction of Cupressus chengiana to western horticulture seems to have been that made by John Silba in 1981, from Kangting, Sichuan. A tree from this collection is growing at Wakehurst Place. Also at Wakehurst Place are trees derived from a collection made by Jill Cowley (CLDX 1031) near the Camellia Temple, Yulong Shan, Yunnan – outside the species’ natural range and probably planted as an ornamental near the temple (A. Farjon, comment in Kew database). It is difficult to get excited about C. chengiana, it being ‘yet another’ columnar cypress with stiffly ascending branches, although it does have brighter mid-green foliage than most Cupressus. In cultivation it seems to grow steadily in a range of conditions. At the JC Raulston Arboretum it has achieved 5 m since being planted in 1995 (as var. kansouensis), forming a broad column, although here it has now unfortunately met a pine branch and has had its top rubbed out. It is potentially a large tree.

Cupressus chengiana var. jiangensis (N. Zhao) Silba Var. jiangensis differs from the type variety in the shape of its cones (oblong-ovoid, vs. globose in var. chengiana) and in the number of seed scales (10–14, vs. 8–10). The leaves are bright green. Silba 1998, Fu et al. 1999e, Farjon 2005c. Distribution CHINA: northern Sichuan (Jiange Xian). Habitat Similar to that of var. chengiana, at about 800 m asl. USDA Hardiness Zone 6. Illustration NT295. Conservation status Critically Endangered.

Despite its rarity this variant is quite widely grown. Kew distributed seedlings from Silba’s 1990 collection from the type tree to several gardens in southern England, and there have been later collections by Wang and others. The Kew database assessment is that it is tender, and plants there are maintained in the Temperate House. The rather low (840 m) collection site in the Jiange Xian suggests that this precaution may be wise, although trees from the same area are doing well at Howick, being 3 m tall and fruiting. There is a leaning specimen at the JC Raulston Arboretum, planted in 1998, which has produced vertical shoots from along the stem, but is clearly thriving despite its poor shape.

Cupressus corneyana

Plate 215. Cupressus chengiana var. jiangensis is regarded as Critically Endangered in its limited range but is well established in cultivation, where its fine shoots make it horticulturally attractive. Image R. Unwin.

See discussion under Cupressus himalaica (p. 299). C. duclouxiana Hickel B801, S200, K105

Cupressus dupreziana A. Camus Cupressus dupreziana var. dupreziana

Sahara Cypress

Tree to 20 m, 3(–4) m dbh. Bark greyish or reddish brown, with deep longitudinal fissures. The crown of mature, wild specimens is often contorted and mutilated by wind and sand storms, and grazing animals; in cultivation, young specimens are somewhat conical or bushy, and develop a broad, rounded crown. Branchlets typically decussate, though initially flattened on one plane. Juvenile leaves needle-like, with extremely active leaf resin

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glands; mature leaves scale-like, dull green or slightly glaucous, decussate, appressed, densely crowded; the lateral and facial pairs are similar, 0.1–0.15 cm long, apex acute; leaf resin glands abaxial, elongated and somewhat inconspicuous, except on very old leaves. Male strobili solitary and terminal, borne on short, lateral branches, yellow, 0.6 × 0.3 cm, subglobose, with 12 peltate microsporophylls. Female cones axillary, usually solitary, ovoid to oblong, valvate, 1.8–2.4 × 1.6–2 cm, dull grey or reddish brown. Seed scales in five to six (to nine) decussate pairs, valvate and rather thin; umbo rounded. Seeds reddish brown, spherical and flattened, 0.4–0.5 × 0.5–0.6 cm; seed wings thin and to 0.2 cm wide. Seedlings retain juvenile leaves for several years. Farjon 2005c. Distribution ALGERIA: Tamrit Plateau of the Tassili N’Ajjer massif. Habitat Wadis in the central

Plate 216. Botanical big game: Cupressus dupreziana var. dupreziana is restricted to the Tamrit Plateau of the Tassili N’Ajjer, Algeria – a relict of wetter times in the Sahara and now Critically Endangered. A trophy sighting in this magnificent setting, reached only by the intrepid. Image L. Jennings.

Sahara, between 1000 and 1800 m asl. Temperatures can range between –7 ºC and 30 ºC, and precipitation is minimal, though highly variable (mean annual precipitation 18 mm). USDA Hardiness Zone 7. Conservation status Critically Endangered. This taxon is entirely restricted to the Tamrit Plateau, where only 153 living specimens remain. Successful reproduction and seedling establishment is rare (only three known seedlings), and the plants are threatened by overgrazing and overexploitation for firewood (Stewart 1970). In the past the climate of the Sahara was much wetter, as evidenced by the few remaining populations of Nile Crocodiles, which still exist in some areas. Cupressus dupreziana var. dupreziana, like the crocodiles, is probably a relict of that period. Illustration NT291, NT296. Cross-references S203 (as C. sempervirens var. dupreziana), K105.

Coming from one of the least accessible parts of the world (physically and politically), and one of the harshest climates, it is not surprising that the Sahara Cypress is rather scarce in the world’s arboreta. On the other hand, there is a considerable challenge factor in going to Tassili N’Ajjer to find it, and this has obviously proved tempting on several occasions, resulting in striking photographs of picturesque gnarled trees growing in a barren rockscape. Once the challenge of collection has been met, the species seems to present no particular difficulty in cultivation. There is a group of trees at Kew, all ultimately derived as cuttings from a collection made in about 1970 by Mrs Pawluk. They are dull green in colour, and all narrowly columnar with very tightly packed shoots. In the British Isles the tallest specimen (11.8 m) is at the Hillier Gardens, where there is also another of 8 m (TROBI). The species has clear landscape potential for difficult dry places, having a strong resemblance (and close relationship) to Cupressus sempervirens, from which both subspecies of C. dupreziana can be distinguished by the presence of resin secreted by active glands on their leaves (Rushforth 1987a). Staff at the Botanic Garden of Smith College, Massachusetts, where C. dupreziana is grown under glass, from collections made in the Tassili mountains in 1985, have studied the propagation of the species from cuttings. Rooting is best when cuttings are treated with a 24-hour soak in low concentrations of indolebutyric acid, and placed under intermittent mist at 15–25 ºC, with bottom heat (Smith College 2005b).

Cupressus dupreziana var. atlantica (Gaussen) Silba

Atlas Cypress

Syn. C. atlantica Gaussen, C. sempervirens L. var. atlantica (Gaussen) Silba The crown of var. atlantica is typically rather narrow and conical, unlike the broad crown of the type variety, though environmental factors may be important. The cones have only four pairs of seed scales and the seed wings are narrow. Farjon 2005c. Distribution MOROCCO: southern Atlas Mts. over an area of 200 km2, in

Section II. Species Accounts

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297

particular the Oued N’fiss valley. Habitat Dry woodland on steep scree slopes between 1100 and 2000 m asl. The climate is essentially Mediterranean with 350–700 mm annual precipitation and a temperature range of –15 ºC to 30 ºC. USDA Hardiness Zone 7. Conservation status Endangered. Cross-reference S203 (as C. sempervirens var. atlantica).

Although from a slightly more convenient area than the Sahara Cypress, the Atlas Cypress is also rare in cultivation. Recent collections have, however, been made by expeditions from the Royal Botanic Garden Edinburgh. At Kew there is a very narrow specimen of about 10 m dating from 1980, when it was received from Edinburgh, from an original collection by Milde Arboretum of Bergen, Norway. C. forbesii (NOW C. guadelupensis S. Watson var. forbesii (Jeps.) Little) B801, K105 C. funebris Endl. B802, S201; K69 (as Chamaecyparis funebris)

Cupressus gigantea W.C. Cheng & L.K. Fu

Tsangpo Cypress

Tree to 45 m, 3(–6) m dbh. Bark greyish or purplish brown, with slight longitudinal fissures. Crown narrow, conical to columnar. Branchlets typically decussate, densely arranged. Juvenile leaves needle-like; mature leaves scale-like, glaucous, abaxial surface ridged or grooved, decussate, appressed, densely crowded; the lateral and facial pairs are similar, 0.1–0.2 cm long, apex obtuse or acute, but expanded; leaf resin glands abaxial, partially active, rounded. Male strobili solitary and terminal, borne on short, lateral branches. Female cones axillary, usually solitary, globose to oblong, valvate, 1.5–2 × 1.3–1.6 cm, shiny dark brown. Seed scales in six decussate pairs, valvate; umbo large and prominent. Seeds shiny chestnut-brown, slightly warty, oblong; seed wings thin and to 0.1 cm wide. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: southern Xizang, Tsangpo River valley. Habitat River valleys and plateaus between 3000 and 3400 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Fu et al. 1999e; NT297. Taxonomic note Cupressus gigantea is closely related to C. torulosa. It differs from that species in that its ultimate branchlets are thicker (1.5–2 mm vs. 1–1.4 mm) and not pendulous and the leaves are glaucous (Fu et al. 1999e).

This potentially huge cypress is endemic to the Tsangpo valley in southeastern Tibet, where it is a conspicuous tree, with young plants lining the riverbank in places after a mass germination along a high-water line (see photograph in Kingdon-Ward & Cox 2001). Curiously, Kingdon-Ward makes no mention of it, leaving its introduction to Ludlow, Sherriff and Elliot (LUSE 13345) in 1947. Trees from this collection are widely dispersed, and much propagated-from: as an example of the value of careful recordkeeping and the importance of maintaining the collection number with each generation of vegetatively propagated individuals,

Plate 217. Venerable trees of Cupressus gigantea in Linzhi, southern Tibet. Image J. Smith.

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there is a specimen at Quarryhill propagated from a tree at Berkeley that was itself a cutting from the original LUSE 13345 tree at Washington Park Arboretum. The resulting Quarryhill tree is now a good size, c. 8 m in 2004. Two originals at Kew are shapely straight columns of 10 and 15 m, showing no sign of broadening out. These trees are a greyish sage-green, but Keith Rushforth’s collection KR 5787 from 1997 has given rise to much more glaucous individuals, at least as seen at Quarryhill. Further collections have been made by Rushforth and others, and plants derived from KR 3353 (from 1995) are available from UK nurseries. Cupressus gigantea is clearly a reliable, hardy tree and is well worth planting where a very stately columnar cypress is desired.

C. glabra (NOW C. arizonica var. glabra (Sudw.) Little) B799, S199

Cupressus goveniana Gordon

Gowen Cypress, Mendocino Cypress

Syn. C. goveniana var. pigmaea Lemmon

This species was described by Bean (B802, S201) and Krüssmann (K106).

Cupressus goveniana var. abramsiana Plate 218. In maturity Cupressus goveniana var. abramsiana forms a handsome specimen with widespreading limbs, as here at the University of California Botanical Garden, Berkeley. Image J. Grimshaw.

Santa Cruz Cypress

(C.B. Wolf) Little Var. abramsiana has larger seed cones than the type variety (2–3 cm diameter, vs. 1.2–1.8 cm), and the seeds are slightly glaucous (vs. dark brown or black). Watson & Eckenwalder 1993, Farjon 2005c. Distribution USA: California (Santa Cruz Mts.). Habitat Mixed pine-oak forest on white sands at about 530 m asl. USDA Hardiness Zone 7. Conservation status Endangered. Illustration NT298. Cross-references B803, S201, K103.

This taxon is reduced to some 5200 trees in the Santa Cruz Mountains, where although the direct threat posed by housing development is staved off somewhat by protection for the trees, a more insidious threat to regeneration is caused by the alteration to fire regimes imposed by building. Without fires to open the cones, and freshly exposed soil in which seeds can germinate, regeneration will be minimal (Center for Plant Conservation 2007–2008). The Santa Cruz Cypress is scarce in cultivation but there are some notable specimens. The UK champion (25.8 m in 2000) is at the Sir Harold Hillier Gardens, grown from seed received in 1950 (Bean 1976a, Clarke 1988), and there is a magnificent individual of 20 m or more in the University of California Botanical Garden at Berkeley, with widely spreading limbs, from a 1975 collection. Even in less balmy climates it is fast-growing: at Howick, specimens from W&H 362 and W&H 364, collected in 1986, are up to 12 m tall and are at risk of blowing over, having grown too well (C. Howick, pers. comm. 2005). These are densely columnar specimens, but vary slightly in their ‘tidiness’.

C. goveniana var. pigmaea (NOW C. goveniana Gordon var. goveniana) B802, S201, K106 C. guadelupensis S. Watson K107

Section II. Species Accounts

Cupressus himalaica Silba

Cupressus

299

Bhutan Cypress

Syn. C. cashmeriana auctt. non Royle ex Carrière, C. corneyana auctt. non Knight & Perry ex Carrière Tree 40–60(–80) m, 2 m dbh. Bark brown, with shallow vertical fissures. Crown conical to columnar, with variably pendulous branchlets. Branchlets variably drooping, dark green; foliage in partially flattened sprays with facial and lateral leaves distinct. Juvenile leaves needle-like, 3–7 mm, in opposite pairs or whorls of three or four; mature leaves dark green, 1–3 × 1–2 mm, acute, on strong whip shoots, subacicular, with decurrent bases up to 8–10 mm long; leaf resin gland sunken, 1 mm long, forming a conspicuous longitudinal groove on facial leaves, present but less obvious on lateral leaves. Male strobili cylindrical, 4–8 × 1.5 mm, shedding pollen in autumn. Female cones produced singly or in clusters of up to 10 or more, dark green to brown, maturing dark blackish brown about 24 months after pollination, variably opening at maturity or remaining closed for a year or more, ovoid-globose, 1–2.2 × 1–1.8 cm, with 8–12 scales in opposite decussate pairs. Seed scales five- to six-sided, up to 1 cm wide, smooth, drying to become coarsely wrinkled after opening; umbo 1 mm long, 2–3 mm broad, dark green to brown. Seeds red-brown, 3–4 mm long, with two narrow ineffective seed wings on sides; 5–20 seeds per cone scale. Long 1980, Rushforth 1987a (as C. corneyana); Miehe & Miehe 1998. Distribution BHUTAN: Pho Chu valley, Punakha Tsang Chu valley. Habitat Mountain slopes on limestone between 2300 and 3000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated under this name (IUCN), but probably vulnerable in the wild, as for C. cashmeriana (IUCN 2007–2008). Illustration Rushforth 1987a (as C. corneyana), Farjon 1994; NT299.

The taxon described here is a distinctive, large tree with variably pendulous shoots that has suffered under a weight of muddled nomenclature. It was recognised as distinct by Long (1980), who recorded it as a wild species in Bhutan, but also as a cultivated plant there and elsewhere in the eastern Himalaya, applying the name C. corneyana Knight & Perry ex Carrière (as did Rushforth 1987a). Cupressus corneyana was originally published by Carrière in 1855, validating the Chelsea nurserymen Knight and Perry’s epithet, but this name is of uncertain application as the description is vague and there is no type specimen (Clarke 1988: S203; Farjon 1994). Knight and Perry did not know where the original material had come from but assumed northern China or Japan; in a splendid leap of imagination, they named it after a merchant in China who occasionally sent them seed, one Mr Corney (Elwes & Henry 1910). Cupressus corneyana Gordon, published in 1862, probably represents C. torulosa (Farjon 1994). Bean (1976a: B808) and Krüssmann (1985b: K111) attribute the name to a cultivar of C. torulosa (Bean as var. corneyana, Krüssmann as ‘Corneyana’), with pendulous branches and irregularly arranged shoots. Silba (1983), however, believed that older cultivated material labelled C. corneyana represents the Mexican C. lusitanica. The name should be abandoned, but persists in gardens and in the literature in reference to eastern Himalayan weeping cypresses, as well as in the miscellany mentioned above. According to Farjon (2001, 2005c) the eastern Himalayan weeping cypresses, now widely cultivated in both Europe and North America, should be recognised as forming part of the variation of Cupressus cashmeriana Royle ex Carrière. Although this species was covered by Bean (1976a), his description is of the longfamiliar selection with beautiful, long-weeping glaucous shoots often referred to as the Kashmir Cypress. The eastern Himalayan plants, which are cultivated under a number of often rather randomly applied names, seem quite different to this well-known but tender plant (although C. himalaica var. darjeelingensis Silba

Plate 219. Cupressus himalaica growing in Bhutan, where it is often planted near buildings. Image K. Rushforth/FLPA.

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Cupressus

New Trees

appears to refer to it). There are clear similarities with C. cashmeriana, but in view of morphological differences – principally the dark green, often less pendulous foliage, conspicuously glandular facial leaves (glands inconspicuous in C. cashmeriana) and smaller cones (1–2.2 × 1–1.8 cm, vs. 1–3 × 1–2.5 cm in C. cashmeriana) – and its clearly circumscribed natural distribution (the Kashmir Cypress is of unknown wild origin), we cautiously recognise the Bhutan Cypress as a distinct entity, under Silba’s name C. himalaica. In the wild it seems to be restricted to the limestone areas of the Pho Chu valley, around Norbding, and in the Punakha Tsang Chu valley (Long 1980, Miehe & Miehe 1998; K. Rushforth, pers. comm. 2008). Silba has also described another taxon, C. assamica Silba, with similar characters but from the West Kameng district of Arunachal Pradesh, India; this has flatter sprays and also occurs naturally on limestone on the northern slopes of Mount Piri (K. Rushforth, pers. comm. 2008). Rushforth (1987a) notes that mature trees of the Bhutan Cypress can reach 40 m, 2 m dbh, but trees up to 80 m – and possibly even taller – have been reported (Farjon 2005c), and must be a fine sight. The first verified introduction to Britain of Bhutanese material was Grierson & Long 234, from trees planted at the Dukye Dzong monastery northwest of Paro, in 1975 (Long 1980; illustrated in Rushforth 1987a); consequently only young plants a few metres tall are currently known in cultivation. Trees from Grierson & Long 234 have foliage which is only slightly pendulous. There is a particularly attractive specimen, worthy of propagation, at Quarryhill, under the name C. himalaica. Grown from a Bruce Bartholomew collection (BB 113) made in Bhutan, it was planted out in 1992 and by 2004 was about 7 m tall, with a very elegant weeping habit. Its growth has been steady rather than spectacular, as it is on a rather poor dry bank, but another specimen at Quarryhill, obtained from Heronswood Nursery as C. torulosa ‘Cashmeriana’ (now re-labelled C. himalaica var. darjeelingensis), had grown 3–4 m by 2004, since planting in 2001. The taxon is evidently tolerant of a wide range of conditions, as demonstrated by a beautifully columnar 7 m specimen in the JC Raulston Arboretum, planted in 1996 (labelled C. darjeelingensis). As C. corneyana, shapely young trees have been seen growing well at Glenwhan Garden in Dumfries & Galloway, at Bedgebury Pinetum in Kent, and at Exeter University and RHS Rosemoor in Devon. Seed distributed by John Silba as C. assamica in the 1980s was collected from street trees growing in the town of Bomdila near Assam, Arunachal Pradesh, which included introduced Mexican taxa. The resultant seedlings represent a hybrid swarm and should be discarded (K. Rushforth, pers. comm. 2008), and any tree so labelled should be viewed with great suspicion. As a wild plant C. assamica is restricted to limestone slopes in northern Arunachal Pradesh (see above). Very young seedlings from this area are now in cultivation (K. Rushforth, pers. comm. 2008), but will require further study as they mature.

C. lusitanica Mill. B803, S201, K107 C. lusitanica var. benthamii (NOW C. lusitanica Mill. var. lusitanica) B804, S201, K107 C. macnabiana A. Murray bis B804, S202, K108 C. macrocarpa Hartw. ex Gordon B805, S202, K108 C. macrocarpa f. fastigiata (NOW C. macrocarpa Hartw. ex Gordon) B806

Section II. Species Accounts

Cupressus sargentii Jeps.

Cupressus

301

Sargent Cypress

Tree to 25 m, though often a shrub of < 10 m, trunk straight and to 1 m dbh. Bark grey-brown to black, fibrous and splitting longitudinally, to 3 cm thick. Crown columnar and rather open, though in typical windswept habitat the crown becomes broader than tall. Branchlets rather inflexible, ultimate segments decussate. Juvenile leaves needle-like; mature leaves scale-like, dull green (though not glaucous), decussate, appressed, densely crowded; the lateral and facial pairs are similar, 1–2(–10) × 1(–4) mm, acute; leaf resin gland abaxial, inconspicuous, forming a shallow pit, usually inactive. Male strobili solitary and terminal, borne profusely on short, lateral branches, 0.3–0.4 × 0.2 cm, cylindrical to four-sided, with 10–12 peltate microsporophylls. Female cones axillary, usually solitary, on short, lateral branchlets, globose and valvate; initially 0.3–0.4 cm long and green, later turning glossy brown; in the second year becoming dull greyish brown with scattered resin blisters, 1.5–3 cm long. Seed scales in three to five decussate pairs, valvate, approximately 12 seeds per scale; umbo inconspicuous or to 0.4 cm long and prominent. Seeds dark brown, angular or flattened, glaucous; seed wings absent. Watson & Eckenwalder 1993, Farjon 2005c. Distribution USA: California (Coast Ranges). Habitat Chaparral, foothill woodlands and lower montane forest on serpentine soil, between 200 and 1100 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration NT290, NT301. Cross-reference K110.

In California this species tends to form a large, rounded tree when mature, sometimes assuming a more compact bushy shape in exposed sites, although it starts with a columnar shape. The foliage is a dusty-looking greyish green, and the whole tree can be coloured yellowish by the abundance of male strobili in spring (Peattie 1991). It is common over a wide area of western California. It is seldom seen in cultivation, although there are good specimens at Kew (13 m in 2001, TROBI) and Wakehurst Place (12 m in 2005), and some smaller specimens elsewhere. Where they overlap in northern California, Cupressus sargentii occasionally hybridises with C. macnabiana, to form the only known naturally occurring hybrid between species of Cupressus. Given the often disjunct geographical ranges of the Cupressus species, this scarcity of natural hybrids is perhaps not surprising (Little 2004). In cultivation, hybrids have been produced by crossing C. macrocarpa Hartw. ex Gordon with both C. sempervirens L. and C. lusitanica Mill. The as-yet unnamed Californian hybrid is most easily identified by its partially formed leaf resin glands; also, the arrangement of the ultimate branch segments and the width of the female cones are both intermediate between the parent species. The F1 hybrids appear to be fertile and backcross with the parent species; some hybrids therefore look rather more similar to one parent species (for some character traits), instead of being intermediate (Little 2004). There is a specimen of this hybrid at Kew.

C. sempervirens L. B806, S202, K110 C. sempervirens var. atlantica (NOW C. dupreziana var. atlantica (Gaussen) Silba, NT295) S203 C. sempervirens var. dupreziana (NOW C. dupreziana A. Camus var. dupreziana, NT295) S203 C. sempervirens var. horizontalis (NOW C. sempervirens L.) B806, K110 C. stephensonii (NOW C. arizonica var. stephensonii (C.B. Wolf) Little, NT292) B800 C. torulosa D. Don B807, S203, K110 C. torulosa var. corneyana (NOW C. corneyana (Knight & Perry) Carrière (?)) B808, S203

Plate 220. Cupressus sargentii in California. The American cypresses are considered by some to belong in a separate genus. Image R. Hitchin.

302

×Cuprocyparis

New Trees

CUPRESSACEAE

×CUPROCYPARIS

Farjon

Syn. ×Cupressocyparis Dallimore & A.B. Jackson

Hybrid Cypresses Xanthocyparis (Chamaecyparis) nootkatensis is one of the parents of three intergeneric hybrids – including the notorious Leyland Cypress, ×Cuprocyparis leylandii – that arose inadvertently in cultivation when X. nootkatensis was planted in close proximity to a number of Cupressus species. These first generation (F1) hybrids combine the hardiness and vigour of X. nootkatensis with the site-tolerance and fast growth rate of the various Cupressus species (hybrid vigour) (Rushforth 1987a). The current debate over the taxonomy of Cupressus and Xanthocyparis, reviewed more fully in their generic accounts (see pp. 290, 901), has implications for the nomenclature of these hybrids. Names for hybrid genera (nothogenera) must be formed from the first part or all of the name of one of the parent genera and the last part or all of the name of the other. When Chamaecyparis nootkatensis was transferred into Xanthocyparis a new nothogeneric name was required to replace the familiar ×Cupressocyparis. With this in mind, Farjon et al. (2002) published the name ×Cuprocyparis, which differs as little as possible from its predecessor, thus causing minimal disruption to the horticultural (and legal!) systems using it regularly. This consideration was important in the decision to conserve Xanthocyparis over Callitropsis, as a hybrid combination involving the latter name would be quite unfamiliar (Brummitt 2007). However, if the view taken by Little (2006), that all American Cupressaceae form a monophyletic group, becomes widely accepted, the nothogeneric names would no longer be needed. All these trees are tolerant of a wide range of growing conditions and will put on rapid growth, but are susceptible to the diseases that attack Cupressaceae, especially cypress canker (see p. 292). Plate 221. ×Cuprocyparis notabilis is a fast-growing hybrid cypress. Image P. Williams.

×C. leylandii (A.B. Jacks. & Dallim.) Farjon (WAS ×Cupressocyparis leylandii B797, S197, K101)

×Cuprocyparis notabilis

Alice Holt Cypress, Noble Cypress

(A.F. Mitchell) Farjon (Cupressus arizonica var. glabra × Xanthocyparis nootkatensis) Syn. ×Cupressocyparis notabilis A.F. Mitchell Tree to 20 m or more. Bark reddish brown to purple, scaly or flaky with patches of several different colours adjacent to each other. Crown conical, broader and more open than in ×C. leylandii. Major branches ascend-

Section II. Species Accounts

×Cuprocyparis

ing. Foliage branches flattened, pendulous, yellowish green with brown tinge, later becoming violet. Leaves blue-green with slight greyish bloom, decussate, imbricate, apex acute. Male strobili terminal, solitary, ovoid, yellowish. Seed cones globose, 12–18 mm diameter, cone blue-green with whitish bloom, ripening to dark brown, persistent after seed dispersal. Seed scales in two to four decussate pairs, valvate. Farjon 2005c. Distribution Only in cultivation. USDA Hardiness Zone 6 (?). Illustration NT302. Cross-references S198, K101.

The hybrid tree ×Cuprocyparis notabilis resulted from a chance cross in the 1950s between Cupressus arizonica var. glabra and Xanthocyparis nootkatensis at Leighton Hall, Powys, where its older half-sibling ×Cuprocyparis leylandii had appeared previously. Fortunately it is less common than this latter, as it also forms a tall shaggy column with pendulous shoots. A redeeming feature is the attractive mottled bark inherited from its mother. There are specimens of 15 m and over in several UK arboreta, the champion recognised by TROBI being a specimen at Westonbirt of 22 m in 2001. Another very fine tree at Wakehurst Place that has not been measured recently must, however, be almost as tall as this.

×Cuprocyparis ovensii (A.F. Mitchell) Farjon

Ovens’ Cypress

(Cupressus lusitanica × Xanthocyparis nootkatensis) Syn. ×Cupressocyparis ovensii A.F. Mitchell Tree to 15 m or more. Crown similar to that of X. nootkatensis. Foliage branches flattened, green-brown, later becoming suffused with red or purple coloration. Leaves strong blue-green, decussate, free and spreading towards the apices, apex acute; leaves releasing a sweet, lemon fragrance when crushed; stomata in prominent white lines on the abaxial surface. Seed cones globose, 10 mm diameter, cone green with heavy deposits of whitish bloom, ripening to violet, persistent after seed dispersal. Seed scales in two to three decussate pairs, valvate; umbo prominent, 3 mm long. Farjon 2005c. Distribution Only in cultivation. USDA Hardiness Zone 6–7 (?). Cross-references S199, K103.

This hybrid was raised by Mr Howard Ovens at Tan-y-Cae, Dyfed in the 1950s, and was named by Alan Mitchell in 1961. It is now widely cultivated throughout the temperate world, sometimes as a quick-growing shelter-belt tree, but it is not a particularly desirable arboretum specimen. It has the familiar shaggy ×Cuprocyparis appearance, with slightly finer foliage branches than the others, but equally capable of rapid growth. There are several notable specimens in the United Kingdom, the champion being one at Westonbirt measured at 17 m for TROBI in 2002 by Owen Johnson. A tree planted at the JC Raulston Arboretum in 1997 was 6 m in 2004 (JC Raulston Arboretum database), and Dirr (1998) reports that in trials in Georgia it was the fastest-growing ×Cuprocyparis, averaging almost a metre a year for six years.

LEGUMINOSAE ( PAPILIONOIDEAE)

DALBERGIA

L. f.

Dalbergia comprises about 250 species, mainly in tropical South and Central America, Africa and Madagascar, and southern Asia (Klitgaard & Laven 2005). They are unarmed trees, shrubs and lianas, many of which are prized for their decorative and often fragrant wood (including rosewood). The leaves are alternate and imparipinnate; with

303

304

Dalbergia

New Trees

stipules that are often small and caducous. The inflorescence is a terminal or axillary panicle; the bracts and bracteoles are usually small and caducous. The flowers are small and numerous; the calyx campanulate, five-toothed, the lower teeth larger than the upper teeth; the corolla white, pale green or rarely purple, the standard petal ovate, oblong or circular, the wing petals oblong and the keel petals obtuse, united above; the 9 or 10 stamens have their filaments fused, forming a single bundle or two bundles. The fruit is a flattened, indehiscent lomentum with one to many seeds (Chen & Nielsen 2006). Dalbergia is almost unknown in temperate cultivation, with only D. hupeana sneaking in for inclusion here, but in the tropics several of its members are well known as important timber trees, and many homes will be able to show a piece of furniture or a trinket made of Dalbergia wood – various ‘rosewoods’ and African blackwood being examples (Mabberley 1997a).

Dalbergia hupeana Hance

Plate 222. The pinnate leaves of Dalbergia hupeana do not emerge until June. Image A. Bunting.

Tree 10–20 m. Bark very shaggy, dull grey. Branchlets pale green, glabrous. Leaves imparipinnate; leaflets 7–11, elliptic to oblong, 3.5–6 × 2.5–4 cm, sub-leathery, upper surface shiny, margins entire, apex obtuse or slightly emarginate. Panicles terminal, sometimes also in the upper leaf axils, 15–20 × 10–20 cm; sparsely covered with rusty pubescence. Flowers white or pale purple; calyx campanulate, 0.2–0.3 cm long; standard petal circular, emarginate, wing petals obovate and half-moon shaped, keel petals auriculate; stamens 10, in two bundles of five. Lomentum oblong to broadly ligulate, 4–7 × 1.3–1.5 cm, thinly leathery, containing one to two (to three) seeds; seeds kidney-shaped. Flowering May to July, fruiting September to October (China). Chen & Nielsen 2006. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan (?), Hubei, Hunan, Jiangsu, Jiangxi, Shandong, Shanxi (?), Sichuan, Yunnan, Zhejiang; LAOS; VIETNAM. Habitat Forested areas on mountain slopes, in ravines and along streams, between 800 and 1400 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Prain 1904; NT304.

Dalbergia hupeana is extremely rare in cultivation, apparently being grown only in a handful of arboreta in the eastern United States. At the JC Raulston Arboretum it was received as seed in 1988 from the Shanghai Botanic Garden and has grown extremely well, forming a tree of about 12 m when seen in May 2006. Even at this season it had not started to develop any sign of buds, and indeed looked completely dead, but it is known for being exceptionally late to leaf out – the last tree in the collection to do so (T. Alderton, pers. comm. 2007). At the US National Arboretum it is grown from a collection made in the Wudang Shan, Hubei, by K. Conrad and P. Meyer in 1994 (WD 106), who recorded in their field notes that the parent tree was growing on a cut-over dry hillside with several other potentially large trees including Castanea mollissima, Maackia chinensis and Quercus species. It is also in cultivation at the Morris Arboretum from the same collection, but although it is growing steadily there (about 4 m tall in 2007) it is ‘not at all ornamental’ (A. Aiello, pers. comm. 2007). It would seem that D. hupeana has not been tried outside this relatively small area of the eastern United States, and that it is not commercially available. In consequence it is difficult to draw conclusions about its requirements in cultivation, but it seems to appreciate the hot humid summers and tolerate the winters of this area.

Section II. Species Accounts

Daphniphyllum

305

DAPHNIPHYLLACEAE

DAPHNIPHYLLUM

Blume

Daphniphyllum is the only genus in the Daphniphyllaceae and comprises 29 species in temperate and tropical southeast Asia (Govaerts 2002c). They are evergreen, dioecious trees or shrubs. The leaves are simple, alternate, fasciculate, whorled or rarely opposite; stipules are absent. The lamina is membranous to leathery, green or yellowish green, sometimes shiny above and often glaucous and papillate below; the margins are typically entire and revolute. Inflorescences are axillary or rarely subterminal, racemose, with one to several whorls of bracts at the base; the bracts may be larger than the flowers. The tiny flowers are unisexual; calyx absent or, when present, three- to six-lobed; corolla absent; the stamens, 5–14, are subsessile or have long filaments. The fruit is an obovoid to globose drupe with smooth, rugose or tuberculate skin; the styles are typically persistent (Huang 1997). The taxonomy and classification of Daphniphyllum is best (or most politely) described as a terrible mess, epithets having seemingly been combined almost at random by different ‘authorities’. Here we follow the Kew World Checklist (Govaerts 2002c) and the currently available draft version of the account of Daphniphyllum for Flora of China (Min & Kubitzki 2008), which miraculously seem to agree on some, though not all, names. The biggest problem is that the flowers, usually an important taxonomic character, are minuscule (in most cases less than 2 mm long), while the vegetative characters are all rather similar, but vary with population, habitat and situation – making them extremely uncooperative as subjects for study in the herbarium. The best known Daphniphyllum in horticulture is D. macropodum, a superlative hardy evergreen widely grown for its clusters of handsome leaves borne on red petioles. This name is upheld by the Kew World Checklist and Flora of China, but the RHS Plant Finder 2007–2008 prefers to call it D. himalaense (a misspelling of the correct himalayense) var. macropodum. All three sources agree, however, that the small Japanese form known as D. humile is merely a variant of D. macropodum. It may be distinct enough to warrant varietal status as D. macropodum var. humile (B. Wynn-Jones, pers. comm. 2007), but in horticulture such plants are probably more usefully known as the Humile Group. With such a handsome plant as the generic cover model, it is not surprising that plant hunters have begun turning their attention to other species of Daphniphyllum. The result has been numerous recent collections, especially by Bleddyn and Sue Wynn-Jones of Crûg Farm Plants in Gwynedd. The difficulties of identification have inevitably led to several of these being distributed without a confirmed name, so it is particularly important that collectors’ numbers are retained with every specimen. Recent collections have been made in northern Vietnam under the names D. chartaceum K. Rosenthal and D. longiracemosum K. Rosenthal (P. Wharton, pers. comm. 2007), but both these names are treated by Govaerts (2002c) as synonyms of D. himalayense subsp. himalayense. The name D. chartaceum is attached to material in cultivation in the United Kingdom distributed by Spinners Nursery that has a distinctly pendulous lamina (hanging almost at a right angle from the petiole), and a very green appearance to the whole plant. These individuals also have lilac flowers, in a dense panicle

Plate 223. Daphniphyllum teysmanii. Daphniphyllum is greatly appreciated for the beauty of its foliage, often contrasting red petioles with a dragon-green lamina, as here. Image J. Blake.

306

Daphniphyllum

New Trees

(B. Wynn-Jones, pers. comm. 2007). Still unidentified is Daphniphyllum BSWJ 4058 from Lantau Island, Hong Kong. This has been sold as D. glaucescens, but differs from the material collected in Taiwan under that name and now referred to D. pentandrum. It needs a particularly warm site, but has handsome glaucous leaves and fruits (B. Wynn-Jones, pers. comm. 2007). Daphniphyllum straddles the borderline between shrubs and trees, and new introductions could go either way depending on how they perform under different horticultural circumstances. A sheltered position in sun to semi-shade seems to suit them best, with moist fertile soil. Moisture is particularly important in the growing season (Hogan 2008). D. himalayense (Benth.) Müll. Arg S212 D. humile (NOW D. macropodum Miq. var. humile (Maxim. ex Franch. & Sav.) K. Rosenthal OR Humile Group) B23, K422 D. macropodum Miq. B23, S212, K422

Daphniphyllum pentandrum Hayata Syn. D. oldhamii (Hemsl.) K. Rosenthal, D. glaucescens Blume var. oldhamii Hemsl., D. glaucescens auct. non Blume, D. kengii Hurus. (and others not used in horticulture) Shrub or tree 4–10 m. Branchlets slender, brown. Leaves fasciculate, 9–14 × 2.5–4 cm, lanceolate, oblongor obovate-lanceolate to oblong, firmly papery, upper surface glossy green, lower surface glaucous and minutely papillose, lateral veins 8–15 pairs, slender, prominent on both surfaces, reticulate veins prominent above, margins revolute, apex acute to acuminate or shortly caudate, base cuneate or obtuse; petiole green or reddish, 2–3.5 cm long, slender. Female inflorescence 4–6 cm long, male inflorescence 2–4 cm, both with slender pedicels bearing minuscule flowers. Drupes dark brown with abundant glaucous wax, ellipsoid to obovate-globose, 0.8 × 0.6 cm, skin slightly tuberculate. Flowering March to May, fruiting August to November (China). Min & Kubitzki 2008. Distribution CHINA: Fujian, Guangdong, Hubei, Hunan, Jiangxi, Taiwan, Zhejiang; KOREA; JAPAN. Habitat Forests, between 100 and 1400 m asl. USDA Hardiness Zone (7b–)8. Conservation status Not evaluated. Taxonomic note Authorities differ about the name of this plant. The Kew Checklist uses D. pentandrum Hayata (1911) as the oldest specific name, but Flora of China uses D. oldhamii (not applied at specific level until 1919). As it is clear that both authorities refer to the same taxon, the prior name must be applied. The name D. glaucescens Blume should be restricted to a species found in Malaysia and Indonesia.

The wide range of this species is reflected in the variation seen in both the wild populations and cultivated specimens. In particular there is considerable variation in glaucescence. In the best forms the lower leaf surfaces are brightly white, while the new shoots flush a rich coppery red, making a very striking effect as the old and new leaves are seen together. The fruits are also very glaucous and can be freely produced, forming an important part of the display. The plants will vary somewhat in habit, but generally make a broad, somewhat shrubby tree, often as wide as it is tall. There are several very good specimens in the David C. Lam Asian Garden in Vancouver, the oldest dating to 1980. When seen in 2004 this was about 7 m tall, forming a bushy, rounded tree with two principal stems, although where branches sag to the ground they send up further vertical shoots. In dense forest it could clearly be drawn up into a single-stemmed tall tree, potentially becoming an emergent over 30 m tall (Wharton et al. 2005), but in more open situations the shrubby habit may predominate. The Vancouver specimen is not particularly glaucous, but its leaves, carried on pinkish red petioles, are bold and handsome. Also growing well at Vancouver are specimens from ETOT 0134 (Flanagan & Kirkham 2005), ‘making huge shrubs trying to be trees 5–6 m high, with highly variable new growth color from bronze-red,

Section II. Species Accounts

Daphniphyllum

307

mahogany-red to reddish orange, all with a varnish sheen’ (P. Wharton, pers. comm. 2007). All happily survived the –9 ºC and heavy wet snow experienced in early November 2006. How hardy material from different provenances will be remains to be tested in a range of conditions. Material is also available in commerce under the name D. kengii (for example, BSWJ 6872, BSWJ 7119), collected at lower altitudes in northern Taiwan from plants with a dwarfer, shrubbier habit than D. pentandrum, achieving only 2 m in height (Crûg Farm Plants 2007–2008). This has a rather different appearance, but may fit here as a local variant. It is also rather more tender, only just surviving –11 ºC at Crûg Farm (B. Wynn-Jones, pers. comm. 2007).

Daphniphyllum teysmannii Zoll. ex Teijsm. & Binn. Tree to 15 m, dbh 0.7 m. Bark smooth, yellowish to greyish brown. Leaves alternate, often concentrated on new growth, 6–15 cm long, narrowly oblong to elliptic or oblanceolate, leathery, upper surface lustrous, deep green, lower surface glaucous, 7–15 inconspicuous secondary veins on each side of midrib, margins entire, weakly revolute, apex acute to acuminate; petiole usually reddish, (2–)4–5 cm long; stipules linear, caducous. Male inflorescences racemose, 3–4 cm long with 10–15 flowers. Female inflorescences racemose, 2–6 cm long. Male flowers, calyx four-lobed (rarely three- or five-lobed); corolla absent; stamens 4–10. Female flowers, sepals three to five, persistent; corolla absent; styles three to four with recurved stigma. Drupes black, ellipsoid, 0.8–1.4 cm long. Flowering May to June (Japan). Noshiro 1999. Distribution JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; SOUTH KOREA. Habitat Coastal slopes. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT305, NT307. Taxonomic note The original spelling of the specific epithet is teysmannii, but it is often misspelt teijsmannii, following the Dutch convention. It commemorates the Dutch botanist Johannes Teijsmann (1809–1882) who also has a genus of palms named after him, Johannesteijsmannia.

Daphniphyllum teysmannii comes from southern Japan and some Korean islands (but not Ullung-do, according to Bleddyn Wynn-Jones: pers. comm. 2007), where it often grows in exposed coastal situations as a shrub or small tree. As an adaptation to this harsher environment it has short, thick leaves, which senesce to a rich red and can remain on the tree for some time in this state (Crûg Farm Plants 2007–2008). Red coloration is found in the stems and petioles, while the active leaves are bronze-green. It is tolerant of dry conditions, though it will remain rather short, and of salt spray – with the result that it is often planted on the verges of Japanese motorways (B. WynnJones, pers. comm. 2007). An early collection was made on Sohuksan Island, off the coast of South Korea, in September 1985, by a US National Arboretum expedition (KE 3550, NA 56544). Here the trees were up to 10 m tall, growing among boulders, and resisting frequent typhoons (P. Wharton, pers. comm. 2007). No material from this expedition has been traced in our research, but it is said to be hardy in Zone 7 winter temperatures (Hogan 2008). A plant from a 1997 collection on Shikoku is growing slowly in a rather dry place at Crûg Farm, but appears quite hardy there (B. WynnJones, pers. comm. 2007).

Plate 224. A variegated specimen of Daphniphyllum teysmannii, used to great effect at Heronswood. Variegated seedlings occur occasionally in Daphniphyllum, and are highly soughtafter. Image Phytophoto.

308

Diospyros

New Trees

EBENACEAE

DIOSPYROS

L.

Ebonies, Persimmons

Plate 225. Diospyros cathayensis forms bushy trees, well clad in glossy evergreen leaves. Image T. Kirkham.

There are estimated to be about 475 species of Diospyros, most of them found in the Old World tropics, with a few in temperate areas. They are trees or shrubs, usually evergreen, although some temperate species are deciduous. The bark is often dark and deeply ridged. The shoots lack a terminal bud but the twigs sometimes terminate as a spine. The leaves are usually alternate, but may be opposite, and are simple and entire, held on a petiole. They are frequently somewhat foetid. In deciduous species they often turn a good yellow in autumn. The inflorescences are axillary, composed of one or a few flowers, borne at the base of the new shoots. The flowers are usually dioecious, and usually unisexual (but monoecious species or bisexual flowers are known), with three to five (to seven) calyx lobes fused at the base and a tubular corolla with three to five (to seven) lobes. In male flowers the stamens are usually in two whorls, two to four times more numerous than the corolla lobes. The female flowers are often solitary, with a whorl of staminodes inside the corolla tube, and a bifid stigma. The fruit is a fleshy or drier, leathery-textured berry, usually with the enlarged calyx persisting. The seeds are often flattened. The genus Diospyros is an important source of fine timbers, including the original ebony (from the Sri Lankan Diospyros ebenum Koenig), and the tropical species can be impressively large trees. In the temperate zone the most familiar species are D. kaki the (Japanese) Persimmon or Sharon Fruit, D. lotus the Date Plum, and D. virginiana the (American) Persimmon, all with edible fruits. At the symposium dedicated to his memory held in Oxford in 1996, the story was told of how the late Frank White, the authority on African Diospyros, asked at a stall in the Oxford market for some persimmons, but was firmly told, ‘Them’s Sharon Fruit’ – an indication of the success of the Israeli fruit-marketing machine in promoting this unappealing name. Whether known as Sharon Fruit, Kaki or Persimmon, the fruits of D. kaki are a beautiful sight in the Mediterranean, hanging from the leafless trees in autumn and into winter like Christmas baubles – reason enough for its cultivation to be practised more frequently further north. Numerous cultivars of it and of D. virginiana, whose fruit is similarly persistent (Sternberg 2004), have been selected for their culinary qualities.

Section II. Species Accounts

A mysterious taxon widespread in cultivation is Diospyros wilsonii hort. This is grown in the Mediterranean (for example, at La Mortola, Italy, and at the Real Jardín Botánico in Madrid), and is praised for its delicious fruit (Zappa 2008). There is a tree against the nursery wall at Glasnevin, and it is growing well at the JC Raulston Arboretum, making a neat straight-trunked specimen with good dark leaves, 4 m tall when seen in 2006, from seed obtained from Jim Waddick in 1990. The taxon is not, however, mentioned by Flora of China or by Sargent (1916) in Plantae Wilsonianae, and its identity remains unclear, although it may be related to D. lotus. The name D. duclouxii Dode is also of somewhat uncertain application, but probably also refers to D. lotus. There are both male and female trees of D. duclouxii at the Hillier Gardens, reaching 8–10 m in 2007, looking very handsome with big glossy green leaves, and flowering well in June of that year. In addition to the Asian species described here, several other Diospyros could possibly be worthy of attention in temperate horticulture. The South African D. austroafricana De Winter may be either a shrub or a small tree to 10 m, with densely hairy leaves and red berries (Coates Palgrave 1990). In the garden of Peter and Susan Grimshaw in Maidenhead, Berkshire a specimen originating from a Denver Botanic Garden collection in Eastern Cape Province has been fully hardy since 1997, although growing exceedingly slowly – now being a magnificent 60 cm tall. This is probably a high-altitude form of subsp. microphylla (Burch.) F. White. Diospyros austroafricana is available commercially in the United Kingdom and is grown in Californian gardens. The San Francisco Bay Area botanical gardens have several species of Diospyros not described here, as well as D. austroafricana. Others are D. lycioides Desf. and D. whyteana (Hiern) F. White from southern Africa, D. morrisiana Hance from Hong Kong, D. oldhamii Maxim. from Taiwan, and D. palmeri Eastw. from Mexico. Diospyros texana Scheele, a small multistemmed deciduous tree with white bark, is sometimes cultivated in the southeastern United States. Jan De Langhe (pers. comm. 2007) reports that he has seen a young specimen of Diospyros xiangguiensis S. Lee at Arboretum Hof ter Saksen Beveren, Belgium, and it seems probable that other Asian species will be hardy and worth trying. There is clearly much potential for exploration of this genus in temperate gardens. All species of Diospyros appreciate hot summers, and a site in full sun should be found for them.

D. armata Hemsl. B55, K439

Diospyros cathayensis Steward Tree to 10 m, dbh 0.8 m. Branchlets brown, minutely pubescent, usually tipped with slender spines. Leaves mostly evergreen, 4–9(–11) × 1.5–3.6 cm, elliptic, upper surface glossy dark green, lower surface pale green with hairs on veins, apex acute to obtuse, lateral veins 10–12 per side, reticulate veins prominent; petiole 0.2–0.4 cm. Male flowers in axillary cymes, densely pubescent in all parts; pedicel 0.6–1.1 cm; calyx with four deep triangular lobes to 0.3 cm long; corolla pale yellow, urceolate with four short reflexed lobes, 0.5–0.7 cm long; stamens 16. Female flowers solitary; calyx lobes four, ovate, c.1 cm, puberulous, becoming glabrous and expanding to 1–2.5 cm in fruit; corolla white, tube c. 0.5 cm, lobes four; staminodes six; ovary villose. Fruit a yellow to orange rounded berry, to 3 cm diameter, with persistent enlarged calyx at base. Seeds four or more, to 1.5 cm. Flowering April to May, fruiting August to October (China). Li et al. 1996. Distribution CHINA: southern Anhui, Fujian, Guangxi, Guizhou, western Hubei, Hunan, central and eastern Sichuan, northeastern Yunnan. Habitat Forests in ravines, between 600 and 1500 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Li et al. 1996; NT308.

Diospyros

309

Plate 226. The mysterious Diospyros wilsonii is probably a form of D. lotus. This specimen is at the JC Raulston Arboretum, but it is grown on both sides of the Atlantic, and forms a good tree even in cooler climates. Image B. Ward.

310

Diospyros

New Trees

Diospyros cathayensis is a rare tree in our area, with specimens located only at the Sir Harold Hillier Gardens and the JC Raulston Arboretum. It has been in the Hillier collection since 1984, growing slowly, to about 2 m in 2007, but does not look happy. In North Carolina it is faster-growing, an accession from 1996 being 4 m when seen in 2006. This is a rather bushy tree, but has a central main stem that should form a respectable trunk in due course. The ascending branches covered in glossy dark green foliage are attractive, and when in fruit the orange globes are extremely ornamental. Diospyros cathayensis evidently has a lot of potential as an ornamental, winter-fruiting evergreen for the warmer parts of our area.

Diospyros japonica Siebold & Zucc. Syn. D. glaucifolia F.P. Metcalf Tree to 17 m, dbh 0.5 m. Branchlets dark brown to blackish brown, glabrous. Leaves deciduous, 7.5–17.5 × 3.5–7.5 cm, ovate to broadly elliptic to lanceolate, upper surface dark green, glabrous or with appressed hairs, lower surface glaucous, apex acuminate, lateral veins seven to eight per side, reticulate veins not prominent; petiole 1.2–2.5 cm. Male flowers in axillary cymes; pedicel 0.1 cm; calyx four-lobed; corolla pale yellow, urceolate with four lobes; stamens 16. Female flowers solitary, or two to three in cluster; calyx four-lobed, sparsely pubescent, expanding to 1.6 cm diameter in fruit; corolla yellowish, urceolate, c.0.7 cm, with four lobes. Fruit a glaucous yellow-orange to red rounded berry, 1.5–2(–3) cm diameter, with persistent enlarged calyx appressed to it at base. Seeds to 1.2 cm. Flowering April to July, fruiting September to November (China). Ohwi 1965, Li et al. 1996. Distribution CHINA: Anhui, Fujian, northwestern Guangdong, northeastern Guangxi, northwestern Guizhou, southwestern Hunan, Jiangxi, Sichuan, Yunnan (?), Zhejiang; JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; TAIWAN (?). Habitat Mixed forests on slopes or in ravines, between 600 and 1300 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Li et al. 1996.

Diospyros japonica is another scarce tree, perhaps more frequently known in cultivation as D. glaucifolia, a name that referred to Chinese forms. Some of these are valued in China for their tasty fruits (Li et al. 1996), and it might be advantageous to make collections of this species from the selected fruits on market stalls rather than at random. It has been cultivated at Kew (as D. glaucifolia), although a 6 m specimen measured by Owen Johnson in 2001 seems to be no more; in 2006, however, Johnson recorded a 6 m tree at the Ventnor Botanical Garden, Isle of Wight (TROBI). At the Hillier Gardens there are two specimens, both about 2 m tall in 2007. They have big, bold leaves of a good glossy green, glaucous below, and the tree would be worth growing for its foliage qualities alone. It has not been traced in collections in North America, but young seedlings have been distributed from the JC Raulston Arboretum (2002 plant distribution), with a note that they show good yellow autumn colour and are not subject to the leaf-spot disease that affects D. virginiana. D. kaki Thunb. B55, S217, K439 D. kaki var. silvestris Makino K439 D. lotus L. B56, S217, K439 D. morrisoniana Hance K439

Diospyros oleifera Cheng Tree to 14 m. Bark dark grey or greyish brown, flaking in large plates to reveal white underlayer. Branchlets sparsely villose to glabrescent. Leaves deciduous, 6.5–17 × 3.5–10 cm, oblong to oblong-lanceolate, occasionally obovate, both surfaces densely greyish yellow-pubescent, apex shortly acuminate, lateral veins five to seven per side; petiole 0.6–1.0 cm. Male flowers in axillary cymes of three to five, calyx densely pubescent, with four lobes; corolla c. 0.8 cm, four-lobed with ciliate lobe tips. Female flowers solitary; calyx lobes four;

Section II. Species Accounts

Diospyros

311

corolla c.1.5 cm, lobes four, pubescent; staminodes 12–14; ovary villose. Fruit a yellow ovoid or rounded berry, to 4.5–7 × 5(–8) cm, pubescent, with persistent enlarged calyx at base. Flowering April to May, fruiting August to October (China). Li et al. 1996. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Hunan, Jiangxi, Zhejiang. Habitat Forests; altitude unrecorded. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Li et al. 1996.

Like several other Asian Diospyros, D. oleifera is a source of persimmon oil, expressed from unripe fruit and used for waterproofing purposes (Li et al. 1996). In this case, however, the ripe fruit does not seem to be edible. It is very rare in cultivation, although it has been commercially available in the past. Tom Hudson (pers. comm. 2007) acquired a tree from Mallet Court Nursery in 1992 but this has only slowly built up growth, probably as a consequence of the wood failing to ripen without sufficient warmth. It is now about 2 m tall. An older tree at the Hillier Gardens was a multistemmed bush of about 3 m in 2007. The large leaves are softly hairy.

Diospyros rhombifolia Hemsl.

Princess Persimmon

Shrub or tree to 8 m. Branchlets pubescent, usually tipped with slender spines and often with shorter, stouter lateral spines. Leaves deciduous, 4–8.5 × 1.8–3.8 cm, rhomboid-obovate, upper surface dark green with yellowish brown hairs on veins, lower surface pale green with scattered appressed hairs, apex acute to acuminate, margin ciliate, lateral veins five to seven per side, reticulate veins prominent; petiole 0.2–0.4 cm. Male flowers in axillary cymes; pedicel c. 0.7 cm; calyx four-lobed; corolla urceolate with four lobes, 0.4 cm; stamens 16. Female flowers solitary; pedicel c.1.8 cm; calyx lobes four, lanceolate, deeply divided, c.1 cm, expanding to 1.6–2 cm in fruit; corolla urceolate with four villous ridges; ovary densely villose. Fruit an orange rounded or elongated berry, to 2 cm diameter, glabrous and glossy. Seeds two to four, c.1 cm. Flowering April to May, fruiting September to October (China). Li et al. 1996. Distribution CHINA: Anhui, Fujian, Jiangsu, Jiangxi, Zhejiang. Habitat Forests on slopes and by streams, between 300 and 800 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Li et al. 1996; NT311.

Diospyros rhombifolia is the most widely cultivated of the Diospyros species described here, with several noted in European collections by Jan De Langhe (pers. comm. 2007), including specimens at Arboretum Het Leen, Eeklo, Belgium and at Jardin botanique de la Roche Fauconnière, Cherbourg, France. In North America it is commercially available, and is used as a bonsai subject on account of its small leaves and bright orange fruits. It appears to have acquired there the vernacular name Princess Persimmon, while Diamond Leaf Persimmon is used by Piroche Plants, British Columbia, who claim to have introduced it in 1994. It seems to be usually more shrubby than tree-like, but can probably be pruned into a single-stemmed specimen such that its pale bark can be best appreciated (Piroche Plants 2002–2005).

D. sinensis Hemsl. K439 D. virginiana L. B56, S217, K439 D. virginiana var. platycarpa Sarg. K439 D. virginiana var. pubescens (Pursh) Rehder K439

Plate 227. A young specimen of Diospyros rhombifolia at the JC Raulston Arboretum. Image B. Ward.

312

Dipentodon

New Trees

DIPENTODONTACEAE

DIPENTODON

Dunn

Dipentodontaceae is a monospecific family erected by Merrill (1941) to contain only the species Dipentodon sinicus from southern China, northern Myanmar and northeastern India. Its taxonomic position remains uncertain and the family has been placed in Huerteales by the Angiosperm Phylogeny Group, alongside Tapisciaceae and the orphan genus Perrottetia, which lacks a family placement (Stevens 2001–2008).

Dipentodon sinicus Dunn Figure 32 (opposite). Dipentodon sinicus: habit with infructescences (A); inflorescence (B); unopened capsule (C); remains of capsule after dehiscence (D).

Plate 228. Dipentodon sinicus is botanically unique, the only member of the family Dipentodontaceae, and is also rare in gardens. Image M. Ogisu.

Tree to 10 m. Bark pale, warty and with large corky lenticels. Leaves lanceolate to broadly ovate-oblong, 7–15(–20) × 2–9 cm, glossy green above, more or less glabrous except for a few hairs on the veins below, apex acuminate, margins finely dentate, lateral veins looping just inside the margin (camptodromous); petiole 0.7–1 cm, subtended by two caducous stipules 1 cm long. Inflorescence an axillary umbellate cyme to 2.5 cm diameter, subtended by 5–12 caducous bracts 4–5 × 1.5–3 mm, forming an involucre when inflorescence is young, but falling before the flowers open; flowers numerous, up to 100 or more, white, with 10 (–14) perianth segments of c.1 mm long in two whorls borne on a cup-shaped disc, stamens inserted on the disc opposite the outer whorl of perianth segments, exceeding the segments in length; style 2–3 mm, ovary pubescent. Fruit a strangely shaped capsule curving from the thin proximal end to a swollen distal portion, splitting along three sutures to reveal the seed, illustrated here for the first time by Hazel Wilks (Figure 32). Flowering May to September, fruiting August to October (China). Dunn 1911, Merrill 1941, Jinshuang & Bartholomew 2007. Distribution CHINA: Guizhou, Guangxi, southeastern Xixang, Yunnan; INDIA; MYANMAR. Habitat Montane broadleaved evergreen forests, especially in open places by rivers or trails, between 900 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Merrill 1941; NT312, NT313.

Dipentodon sinicus was first found by Augustine Henry near Mengtze, Yunnan in 1898, and was immediately recognised as something curious. The name is derived from the odd floral morphology in which the calyx lobes and petals are identical and inserted, as if in one whorl, looking like a 10-lobed perianth (hence dipentodon, meaning ‘twice-five teeth’). It has a wide distribution and is not uncommon in western China and Myanmar, so its scarcity in cultivation is strange. It is grown at the San Francisco Botanical Garden, and was collected in 1997 by the Gaoligongshan Expedition of the Royal Botanic Garden Edinburgh (GSE 97), but the only specimen seen in research for the current work is at Tregrehan. This is a slender tree of about 5 m, with spreading branches and glossy dark green leaves that turn crimson in autumn (T. Hudson, pers. comm. 2005). The inflorescences are borne all along the shoots, attractively held above the foliage, and the fruits remain in the same position. Material is so limited that it is difficult to make any comments on the requirements of this species in cultivation, but it should be tried in a warm and possibly moist situation.

Section II. Species Accounts

Dipentodon

313

A

C 1 cm

1 cm

1 cm

D

B

314

Drimys

New Trees

WINTERACEAE

DRIMYS

J.R. Forst. & G. Forst.

For many years, the genus Drimys was thought to include species in both the Old and the New Worlds. The decision to place the Old World taxa into a separate genus Tasmannia (as championed by Smith 1969) was controversial, and opposed by some authors (Vink 1970, 1993). However, modern DNA-based techniques have shown that Drimys and Tasmannia together do not form a monophyletic group (Doust & Drinnan 2004), and are therefore best considered as separate genera. Drimys (s.s.) thus comprises four species: D. granadensis, ranging from Mexico to northwest South America; D. brasiliensis Miers in southeast Brazil and on Mount Roraima; D. confertifolia Phil. on the Juan Fernandez Islands; and D. winteri in Chile and Argentina. They are trees or shrubs, with evergreen leaves that are alternate, often irregularly crowded at or near the stem apex, leathery, and fragrant when crushed, with distinctive stomata on the lower surface. Inflorescences are axillary or terminal, umbellate or single-flowered. The flowers are hermaphrodite, pedicellate, with bracts that are early caducous; two (to three) sepals, papery to membranous, fused together to form a calyptra; 4–17(–25) petals, white, their size, shape and number varying considerably across the range; and 15–50(–65) stamens. The fruit is a slightly falcate berry, which may be dark purple or reddish black. In the reduced genus Drimys, only D. winteri is well known in cultivation. This has proven its horticultural worth over the past two centuries, since its introduction in 1827, as both a foliage and a flowering plant. Its variation is discussed at length by Bean (1981a) and Hogan (2008).

Drimys granadensis L. f. Shrub or tree to 13 m. Branchlets pale grey or brown, glaucous when young. Leaves thick and leathery, 5–16 × 1–5.5 cm, elliptic to oblong, upper surface olive-green to brown when dried, lower surface pale or glaucous, 8–19 secondary veins on each side of the midrib, margins entire and revolute, apex obtuse; petiole flattened or channelled, often winged, 0.4–2.5 cm long. Inflorescences terminal or axillary, umbellate, clustered or single-flowered; peduncle 0.7–9 cm long, slightly flattened. Flowers one to six (to eight) per inflorescence, pedicels 0.5–9 cm long; sepals papery or membranous, opaque, 0.4–1.2 cm long; petals 8–17(–25), membranous, oblong to elliptic, yellow-glandular, 0.5–2.5 cm long; stamens 25–50(–65). Berry dark purple or reddish black. Smith 1943. Distribution COLOMBIA; COSTA RICA; GUATEMALA; MEXICO: Guerrero, Veracruz; NICARAGUA; PANAMA; PERU; VENEZUELA. Habitat Temperate forest at high altitudes. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT315. Taxonomic note Smith (1943) recognised five varieties of D. granadensis: var. granadensis from Colombia, including the type of the species (Hieron rather unaccountably called this nominate variant var. grandiflora); var. uniflora (Turcz.) A.C. Sm. from Venezuela; var. mexicana (DC.) A.C. Sm. ranging from Mexico to Costa Rica; var. chiriquiensis A.C. Sm. from Panama; and var. peruviana A.C. Sm. from Peru. The Mexican variety, which has also been brought into cultivation, is only slightly different from typical D. granadensis (more slender habit, leaves thinner in texture, petals more numerous and slightly smaller).

Taken in a broad sense, Drimys granadensis is a tropical plant, with some populations extending into cooler areas. It would therefore seem to be at the limit of its tolerance in the mildest parts of our area, and this is reflected in its rarity in collections. It is in cultivation and commercially available in the United Kingdom, principally from a gathering made near Xalapa by James Russell, but does not seem to feature in any

Section II. Species Accounts

Drimys

315

of the major collections except Tregrehan, where it is making a rather untidy shrubby plant (T. Hudson, pers. comm. 2007). Specimens originating from a 1982 gathering by B. Anderson in Costa Rica – and therefore probably var. mexicana – are growing at the University of California Botanical Garden at Berkeley, and this and another unspecified variant are in cultivation at the San Francisco Botanical Garden, but the species does not seem to be commercially available in the United States. More recently, a 2004 introduction by Bleddyn and Sue Wynn-Jones (BSWJ 10777) from 3300 m in the paramo of La Caleva, south of Bogotá, Colombia has been offered under the name var. grandiflora Hieron, a synonym of var. granadensis. The interest in this tree derives from its handsome leaves, which are brightly white-glaucous below, and the clusters of large, pure white flowers. It should be given a warm, sheltered but not shady site, preferably in rich moist soil. D. lanceolata (NOW Tasmannia lanceolata (Poir.) A.C. Sm.) B68, K446 D. winteri J.R. Forst. & G. Forst. B69, S219, K446 D. winteri var. andina Reiche B71, K446 D. winteri var. chilensis (DC.) A. Gray B70, K446 D. winteri var. latifolia (NOW D. winteri var. chilensis (DC.) A. Gray) K446

Plate 229. Drimys granadensis at Tregrehan, April 2008. It seems to be a close relative of the familiar D. winteri. Image J. Grimshaw.

ELAEOCARPACEAE

ELAEOCARPUS

L.

Elaeocarpus comprises around 360 species of trees (rarely shrubs), found primarily in the Old World tropics. They are evergreen or semi-evergreen, with alternate or spirally arranged leaves and caducous stipules. The leaves are simple and may have a swelling at the apex of the petiole, which could indicate a reduction from trifoliolate to unifoliolate leaves. The margins are toothed or entire and the veins are prominent. Leaves typically turn bright red before falling. Inflorescences are racemose and either axillary or borne directly on the branch surfaces (ramiflorous). The flowers are hermaphrodite and 4- or 5-merous; the petals are often divided into linear lobes and the stamens are numerous. The fruit is a blue or black drupe containing a hard, deeply sculptured endocarp (Harden 2000b, Tang & Chamlong 2005). Elaeocarpus is large and diverse, containing some interesting trees for temperate gardens, with attractive foliage and outstanding fruits, but as a principally tropical genus the selection is limited. Its tropical background also suggests that any species tried outside in our area should be given a warm sheltered site. In addition to those described below, the Chinese E. glabripetalus Merr. has been in cultivation at Tregrehan since 1999 (grown from Qingpu 9712), but the specimens there have been

316

Elaeocarpus

New Trees

badly damaged by deer, and although growing back they were only about 1 m tall in 2007 (T. Hudson, pers. comm. 2007). The same garden also has young plants of E. lacunosus Wall. ex Kurz, grown from Keith Rushforth’s 1999 collection on Fan Si Pan, Vietnam (KR 1976), where it formed trees of 15–20 m. Fertile moist soil, acid to neutral in pH, will give the best results (Huxley et al. 1992). Propagation is usually from seed, but germination may be very slow and erratic, requiring a long soak in water to overcome germination inhibitors (Ellison 1999), or even physical violence to crack the drupe (Forest Farmers Association 2000). Semi-ripe cuttings (Huxley et al. 1992) would seem to offer an easier option. Plate 230. Vigorous new growth on a young plant of Elaeocarpus sylvestris – potentially the hardiest of the genus. Image S. O’Brien.

Elaeocarpus angustifolius Blume Syn. E. grandis F. Muell.

Silver Quandong, Blue Fig, Blue Marbletree

Tree to 40 m, with thin buttresses spreading to 6 m across. Branchlets slender and pubescent when young. Leaf buds not or rarely resinous. Leaves evergreen to deciduous; often, all the leaves on a single branch turn red, then fall at once. Leaves simple, scattered or grouped at stem apices, 8–19 × 1–4 cm, thin and papery when dry, elliptic to oblong with base narrowing into petiole, both surfaces glabrous or with some fine hairs, major veins prominent beneath, 6–14 secondary veins on each side of the midvein, margins finely serrulate, apex acute; petiole 0.5–2 cm long, slightly winged, pubescent. Inflorescences axillary, ramiflorous; racemes 6–10 cm long, bearing 12–26 flowers. Flowers hermaphrodite, 5-merous, to 1.5 cm long; petals divided into numerous segments. Fruit a globose, bright blue or purplish drupe, 1.5–2 cm diameter; endocarp sculptured, containing two to five seeds. Flowering March to May, fruiting all year round (Australia). Coode 1984, Harden 2000b. Distribution AUSTRALIA: New South Wales, Northern Territory, Queensland; INDIA; INDONESIA: Western New Guinea; NEW CALEDONIA; PAPUA NEW GUINEA; PHILIPPINES; SOLOMON ISLANDS; VANUATU. This species has been introduced to Malaysia, Sri Lanka and Hawaii. Habitat Riverine and periodically inundated forest between 0 and 80 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated.

Elaeocarpus angustifolius is largely a tree of tropical rain forests, but some southern Australian accessions are being cultivated in temperate areas, often under the synonym E. grandis. It is popular as a garden tree in Australia, where it is valued for its evergreen foliage, turning scarlet as it senesces, and abundant marble-sized blue fruits. It is in cultivation at the San Francisco Botanical Garden, but mature specimens have not been located elsewhere in our area. At Cistus Nursery seedlings are being tested for hardiness and evaluated for leaf-colour qualities (S. Hogan, pers. comm. 2007). E. cyaneus Sims K22

Elaeocarpus decipiens Hemsl.

Japanese Blueberry Tree

Tree to 15 m. Branchlets blackish brown, slightly pubescent to glabrous. Leaf buds covered in silky hairs. Leaves evergreen, simple, 7–13.5 × 2–4 cm, leathery or thick and papery, oblanceolate, glabrous, upper surface with conspicuous veinlets, lower surface with conspicuous major veins, seven to nine secondary veins on each side of the midvein, glands in the axils of the lateral veins present (var. changii ) or absent (var. decipiens), margins minutely serrate, apex acuminate; petiole 1–2 cm long, leaf base forming a narrow wing. Inflorescences in axils of fallen leaves; racemes 5–10 cm long, bearing 8–30 flowers. Flowers white and fragrant, hermaphrodite, 5-merous and to 0.6 cm long; upper half of petals incised, stamens up to 32. Fruit a black ellipsoid drupe, 2–3.5 × 1.5–2 cm; endocarp sculptured, containing one seed. Flowering June to July, fruiting November to January (China). Tang & Chamlong 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Yunnan, Zhejiang; JAPAN; TAIWAN; VIETNAM. Habitat Evergreen forest between 400 and 2400 m asl. USDA Hardiness Zone (7–)8. Conservation status Not evaluated. Illustration NT318.

Section II. Species Accounts

Elaeocarpus

Elaeocarpus decipiens is probably the most commonly cultivated species of this genus, relatively frequently grown in the warmer parts of the United States for its dense covering of glossy, evergreen leaves, flushing bronze in spring and senescing to a bright red. It can make a large, broad-crowned tree, but can also be pruned to form hedges or other clipped features. The fragrant flowers are white, borne on long racemes, and suggest a Pieris in flower. The blue-black berries that follow them are ornamental but not spectacular. Unlike other species languishing in the realm of enthusiasts, E. decipiens has been introduced to the mainstream horticultural trade by Monrovia, both as a normal-sized clone sold in its Shogun Series (evergreen Japanese trees), and as a more compact cultivar, ‘MonProud’, marketed as Little Emperor, said to achieve no more than 5 m in maturity (Monrovia 2004–2008). It has also been introduced by Piroche Plants. It will perform best when planted in a sheltered sunny site, in fertile and reasonably moist soil. When established in a suitable site it is tolerant of temperatures of –10 ºC without harm, and in still conditions it can tolerate even harder frosts, but it is susceptible to damage in strong freezing wind (Hogan 2008). Late frosts can cause damage to new shoots, and it is said to be intolerant of alkaline soils (Arnold 2005).

Elaeocarpus dentatus (J.R. Forst. & G. Forst.) Vahl

Hinau

Canopy tree to 35 m, dbh 1 m. Bark grey. Branchlets with short, soft hairs when young, later glabrous. Leaf buds resinous or not. Leaves evergreen, grouped towards the stem apices, simple, 6–13 × 1.5–3 cm, oblong to lanceolate, upper surface glabrous, lower surface covered with fine hairs, major veins conspicuous, though minor veins also conspicuous on the lower surface, six to nine secondary veins on each side of the midvein, often with deep pockets (domatia) in their axils, margins serrate, often emarginate, apex acute or obtuse; petiole 1–2.3 cm long, swollen at one or both ends, pubescent when young. Inflorescences crowded among the leaves or in the axils of fallen leaves; racemes 2–7 cm long, pubescent, bearing up to 12 flowers. Flowers hermaphrodite, 5-merous and to 1 cm long; petals divided into three lobes, stamens ~20. Fruit a drupe, globose-ellipsoid, 1.1–1.6 × 0.8–1 cm, yellow-grey or dark blue to purplish; endocarp sculptured. Flowering October to February, fruiting December to May (New Zealand). Allan 1961, Coode 1984. Distribution NEW ZEALAND: North and South Is. Habitat Lowland forest between 0 and 900 m asl. USDA Hardiness Zone 8b–9. Conservation status Not evaluated. Cross-reference K22.

Elaeocarpus dentatus is a large forest tree, growing with Nothofagus in New Zealand. Like E. hookerianus (see below), it starts life with distinctive juvenile growth, with long narrow leaves on thin twigs, developing a trunk for several metres before switching to its adult growth-form. A specimen at Tregrehan is currently in the transitional state after about 10 years of growth. It is little known in cultivation in our area, although it is grown in a few collections, but is appreciated in its native country for its dark green leathery leaves with pale undersides. The flowers, on short racemes, are white and fragrant, and are followed by coloured fruits. It is slow-growing, and only mature trees produce flowers. It should be planted in fertile, well-drained but moist soil, in a sheltered warm site (Metcalf 2000). Hogan (2008) assesses it as being rather tender, reporting leaf damage at –7 ºC and plants cut to the ground at –10 ºC.

Elaeocarpus ellipticus (Thunb.) Makino The true identity and distribution of this taxon is mysterious. In Japan and Korea it is regarded as a variety of E. sylvestris (Ohwi 1965, Lee 2002), but it may be synonymous with E. decipiens. The name does not appear to have been validly published in Elaeocarpus, and is based on that of Prunus elliptica Thunb. Plants seen under this name at Cistus Nursery in 2004 had narrowly lanceolate leaves, unlike the obovate-lanceolate leaves of E. decipiens nearby; Hogan (2008) thinks it is the larger plant of the two.

317

318

Elaeocarpus

A

New Trees

B

C

1 cm

D

Section II. Species Accounts

Elaeocarpus hookerianus Raoul

Elaeocarpus

319

Pokaka, Mahimahi

Canopy tree to 12 m; immature plants have divaricate branching. Branchlets slender, striate, initially pubescent. Leaf buds slightly resinous. Leaves evergreen, scattered or grouped towards stem apices, simple, (3–)4–8 × 1–2 cm, obovate, elliptic or oblong, glabrous, venation slightly or strongly prominent on the upper surface, less prominent below, five to nine secondary veins on each side of the midvein, margins crenate to serrate, apex acute or obtuse; petiole 0.5–1.5 cm long, slender, not swollen at either end; foliage of juvenile plants and suckers extremely variable in shape and size. Inflorescences crowded among the leaves or in the axils of fallen leaves, sometimes ramiflorous; racemes 2–4 cm long, bearing (2–)5–12 flowers. Flowers hermaphrodite, 5-merous, to 0.5 cm long; petals split into five to six tapering sections, stamens ~15. Fruit an ellipsoid drupe, 1.1–1.4 × 0.6–0.7 cm; endocarp ridged. Flowering October to January, fruiting November to March (New Zealand). Allan 1961, Coode 1984. Distribution NEW ZEALAND: North and South Is. Habitat Lowland to montane forest. USDA Hardiness Zone 8b–9. Conservation status Not evaluated. Illustration NT318.

The New Zealand flora contains a number of woody species, in several families, in which the young plant has a very curious growth-form, of intertwining or divaricate wiry branchlets, and small hard leaves. Once plants have reached a height of 2–4 m this branching type disappears, and through a series of transitional stages robust branches bearing large broad leaves develop and the individual becomes a normallooking tree. This syndrome is regarded, by some authorities at least (for example, Atkinson & Greenwood 1989), as an evolutionary strategy to minimise damage by the large, flightless moas that were formerly the largest terrestrial vertebrates and principal browsers in New Zealand. Above their reach the trees could safely develop broader, more succulent foliage, just as Ilex aquifolium produces spineless foliage above browse-height in Europe. A less exciting view is that the juvenile pattern of growth enables more efficient light-capture (Day & Gould 1997, Day 1998), although this seems counter-intuitive. Elaeocarpus hookerianus is perhaps the most notable of these moa-avoiders, turning from a tangled mass of wiry twigs and small leaves into a tall tree with a dense canopy of broad evergreen leaves. It is valued for both stages in New Zealand, but is very poorly known in the northern hemisphere. It is grown at Tregrehan by New Zealander Tom Hudson, and is doing well there since planting in 1992, forming a straight trunk, with whorls of juvenile growth now giving way to adult foliage at 2–2.5 m height. It may be fractionally hardier than E. dentatus, but not by much, so it too requires a warm sheltered site.

Elaeocarpus japonicus Siebold & Zucc. Tree to 25 m. Branchlets robust, glabrous or minutely pubescent. Leaf buds covered with silky hairs. Leaves evergreen, simple, 6–11(–17) × 3–6 cm, papery or leathery, ovate, elliptic, or lanceolate, both surfaces covered with silky grey hairs, lower surface with prominent veins and black glandular spots, six to eight secondary veins on each side of the midvein, margins sparsely dentate, apex acute or acuminate; petiole 3–6 cm long, initially pubescent, later glabrous. Inflorescences axillary; racemes 3–6 cm long, bearing 5–12 flowers. Flowers polygamous, 5- or 6-merous and to 0.5 cm long; petals pubescent, entire or incised, stamens 15. Fruit a shiny ellipsoid drupe, 1–1.3 × 0.8 cm; endocarp containing a single seed. Flowering April to May, fruiting May to July (China). Tang & Chamlong 2005. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; JAPAN; TAIWAN; VIETNAM. Habitat Evergreen forest between 400 and 2800 m asl. USDA Hardiness Zone 8b–9. Conservation status Not evaluated.

Research in Taiwan has demonstrated that maximum germination of Elaeocarpus japonicus seed (still only approx. 40 per cent) occurs after a minimum stratification period of four months at 4 ºC (Yang et al. 2001); similar conditions are probably valid for other temperate species of Elaeocarpus. It also suggests that it is subject to low temperatures in the wild, despite its southerly origins, and should therefore be

Figure 33 (opposite). Elaeocarpus hookerianus: dentate juvenile leaves (A); adult foliage with fruit (B); divaricate juvenile growth habit (C). E. decipiens: flowering shoot (D).

320

Elaeocarpus

New Trees

amenable to cultivation in a warm, sheltered site. It is not known to be in cultivation in Europe, but it is established in North America (for example, at the San Francisco Botanical Garden). At Cistus Nursery it has achieved 2.5 m in three years; while it has so far withstood –6 ºC there, lower temperatures will defoliate it (S. Hogan, pers. comm. 2007). It would be useful to seek out material from its coldest provenances, as its glossy, long-tipped leaves flush bronze-red, making this a very attractive evergreen tree, that could be planted more widely if hardier stocks were available.

Elaeocarpus reticulatus Sm.

Ash Quandong, Blueberry Ash, Fairy Petticoats

Shrub or tree to 15 m. Branchlets slender, somewhat pubescent, distinctive semicircular leaf scars present and these may have a raised central boss (the remains of fallen inflorescences). Leaf buds resinous. Leaves evergreen, scattered through the crown, simple, (3.5–)5–10(–12) × 1–3(–5) cm, elliptic to oblong or obovate, leathery and glabrous, primary and secondary venation prominent on both surfaces, 6–10 secondary veins on each side of the midvein, margins sharply serrated and with black or brown hair-points, apex acute; petiole (0.2–)0.3–1.8 cm long, straight and slender, slightly swollen at the base. Inflorescences either amongst or below the leaves; racemes 1.5–7 cm long, bearing 5–10 flowers. Flowers pink or white and fragrant, hermaphrodite, 5-merous and to 0.8 cm long; petals split into three irregular lobes that are subsequently split into three or four tapering sections, stamens 15–25. Fruit a globose or ellipsoid drupe, 0.7–1 × 0.5–0.9 cm, blue-grey; endocarp sculptured. Flowering November to December, fruiting January to May (Australia). Coode 1984. Distribution AUSTRALIA: New South Wales, Queensland, Tasmania (King Is.), Victoria. Habitat Open eucalypt forest, temperate rain forest and riverine forest between 0 and 850 m asl. USDA Hardiness Zone 8b–9a. Conservation status Not evaluated. Illustration NT320.

Potentially a respectable tree, Elaeocarpus reticulatus is more likely to be shrubby in marginal areas, as it is in Cornwall (Hudson 2004). In Australia it is a popular garden tree and widely planted (Australian National Botanic Gardens 2003a), valued for its masses of white flowers (pink in selected clones). These have the form of a dainty, fringed bell, and give it its alternative English name of Fairy Petticoats. The abundant blue fruits that follow can remain on the tree for up to six months (Ellison 1999), and are a fine feature in themselves. The narrow, mid-green leaves flush pinkish and senesce red. It is cultivated in the southern United States, but has been damaged at –6 ºC at Cistus Nursery, where a pink-flowered clone is grown. Sean Hogan (pers. comm. 2007) regards it as a good container plant, as flowering and fruiting seem to be stimulated by the confinement.

Plate 231. The dainty, fringed flowers of Elaeocarpus reticulatus have earned it the name Fairy Petticoats. This is a selected pink clone: usually the flowers are white. The bluish berries are an added attraction. Image K. Gillanders.

Section II. Species Accounts

Elaeocarpus

Elaeocarpus sylvestris (Lour.) Poir. Tree to 15 m. Branchlets slender, sparsely pubescent. Leaf buds covered in ferruginous hairs. Leaves evergreen, simple, glossy mid-green, 4–12 × 2–7 cm, papery, obovate or oblanceolate, both surfaces glabrous, four to five secondary veins on each side of the midvein, veins particularly prominent on the lower surface, margins crenate, apex obtuse or acuminate; petiole 1–1.5 cm long, sparsely pubescent when young, later glabrous. Inflorescences either amongst or below the leaves; racemes 4–6 cm long, bearing 8–18 flowers. Flowers hermaphrodite, 5-merous and to 0.5 cm long; petals divided in upper half into 10–12 segments, stamens 15. Fruit an ellipsoid drupe, 1–1.2 × 0.7 cm; endocarp thin and bony with three sutures. Flowering April to May, fruiting May to August (China). Tang & Chamlong 2005. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; VIETNAM. Habitat Evergreen forests between 300 and 2000 m asl. USDA Hardiness Zone 8b. Conservation status Not evaluated. Illustration NT316. Taxonomic note This species is very closely related to E. decipiens.

Elaeocarpus sylvestris is potentially the hardiest species of the genus, and comparatively well known in cultivation. It is commercially available in both Europe and North America. The limits of its hardiness are not fully established: the catalogue of Firma C. Esveld in Boskoop, the Netherlands says that it is not winter-hardy there, but it is grown throughout the maritime Pacific Northwest (withstanding –12 to –14 ºC in Vancouver: Hogan 2008), North Carolina and the British Isles. A specimen seen at Glasnevin in 2006, accessioned in 2000, was 1.8 m tall and apparently doing very well. The species has neat, narrow leaves of shiny bright green. The flower racemes are comparatively short, and the initially white flowers turn creamy yellow as they fade.

JUGLANDACEAE

ENGELHARDTIA

Lesch. ex Blume

There are thought to be about seven species of Engelhardtia, distributed in southern and southeastern Asia, but the genus is rather poorly understood, due to inadequate herbarium collections, and this number may change with further investigation. They are evergreen, semi-evergreen or deciduous trees. The terminal buds are oblong and naked. The leaves are paripinnate or rarely imparipinnate with 2–14 leaflets; the leaflet margins entire or serrate. Engelhardtia species are monoecious, rarely dioecious; the inflorescences are terminal or axillary, on old or new growth; the staminate and pistillate flowers held on separate spikes or combined in panicles; the staminate spikes pendulous, solitary or clustered; the pistillate spikes erect or recurved. The staminate flowers are subtended by a three-lobed bract, with one to four sepals (rarely none), no petals, and 3–15 stamens. The pistillate flowers, subtended by an enlarged threelobed bract, have four sepals, fused to the ovary, and no petals. The fruiting spikes are pendulous; the fruit is a three-winged nutlet (Lu et al. 1999). Engelhardtia is a genus almost entirely unknown to Western gardeners, and probably is indeed only for ‘the speculative plant addict’ (Hudson 2004). In their native habitats they are large trees, and some may have medicinal properties (Mabberley 1997a). According to Tom Hudson (pers. comm. 2006), E. spicata Blume is spectacular when seen in full flower in Yunnan, but this species is apparently not in cultivation.

321

322

Engelhardtia

New Trees

Engelhardtia roxburghiana Roxb. Syn. E. chrysolepis Hance, E. fenzelii Merr., E. formosana Hayata Tree to 30 m. Leaves evergreen or semi-evergreen, paripinnate, 1–25 cm long; leaflets 2–10, elliptic to lanceolate, 4.5–14 × 1.5–5 cm, leathery, glabrous, but with yellow scales on the undersides, margins entire, apex acuminate; petiolule 0.2–1.5 cm long; rachis glabrous; petiole 1–8 cm long, glabrous. Monoecious; inflorescences terminal on current growth; staminate flowers short-stalked, stamens (10–)12, enclosed in four-hooded floral parts; pistillate flowers stalked, styles absent, stigma four-lobed. Nutlets globose, 0.3–0.5 cm long, glabrous; middle wing 1.5–5 cm long, lateral wings 0.7–2.7 cm long. Flowering February to August, fruiting January to December (China). Lu et al. 1999. Distribution BANGLADESH; CAMBODIA; CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; INDONESIA; LAOS; MYANMAR; TAIWAN; THAILAND; VIETNAM. Habitat Mixed evergreen or broadleaved forest on loam or sandy soils between 200 and 1500 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Lu et al. 1999; NT322.

Plate 232. Engelhardtia roxburghiana at Tregrehan: a species for the ‘speculative plant addict’ (with a very mild garden). Image J. Grimshaw.

This species is included here on the strength of two young plants growing at Tregrehan, one from China in 2002 (as E. fenzelii), and one from Taiwan in 2004 (as E. roxburghiana). They are proving to be very slow-growing and late to flush into new growth, although the new leaves are an attractive bronze colour. When mature the leaves are dark green, with a very leathery texture. Both specimens seem to have become established, having come through the 2005–2006 winter successfully; the older plant is now 120 cm tall (T. Hudson, pers. comm. 2006). The distribution of the species in the lower-altitude forests of southeastern Asia does not, however, bode well for long-term success in our area, and if further material becomes available a very warm site is recommended.

ROSACEAE

ERIOBOTRYA

Lindl.

Loquats There are about 30 species of Eriobotrya, occurring only in the tropical and subtropical regions of eastern Asia. They are evergreen trees or shrubs with simple, stipulate leaves. The leaf margins are serrate or entire, with strong veins either reaching the margin or looped just within it; petiole usually present. Inflorescences are terminal panicles with numerous white (rarely yellow) flowers. The flowers are 5-merous, with emarginate petals and 20 stamens. The fruit is a yellow, red, orange or black pome with a persistent calyx and one to three large seeds (Robertson et al. 1991, Gu et al. 2003). The Loquat, Eriobotrya japonica (Thunb.) Lindl., is the best-known member of the genus, and although Bean (1981a) stated that it is ‘not hardy enough to have ever become widely cultivated’, and that it could only be grown against a warm wall at Kew, this handsome tree is now frequently seen in English gardens. Perhaps both global warming and the importation of fruits from Mediterranean holidays are implicated.

Section II. Species Accounts

Eriobotrya

323

In addition to the taxa discussed below, Eriobotrya cavaleriei (H. Lév.) Rehder is cultivated by Tony Avent at Plant Delights Nursery, Raleigh, North Carolina. His 2.5 m tree has typically leathery leaves, flushing bronze, and was grown from Shanghai Botanic Garden seed in 2003. It has tolerated –12 ºC without damage (T. Avent, pers. comm. 2006). A tree of E. elliptica Lindl. has been growing in the Temperate House at Kew for decades, derived from a collection made by Tony Schilling in Nepal in 1966. Although it originated at only c. 2500 m asl south of Kathmandu and has generally been considered to be tender (Zappi & Cooke 2001), in the current climate it would be interesting to try this species outdoors.

Eriobotrya deflexa (Hemsl.) Nakai Tree 5–12 m, dbh ≥ 40 cm. Branchlets stout and greyish brown, densely tomentose when young. Leaves clustered at branch apices, leathery, (9–)10–19 × (1.5–)3–7 cm, oblong to lanceolate or obovate, initially tomentose on both surfaces, upper surface lustrous, midrib prominent, 10–12 secondary veins on each side of the midrib, margins irregularly crenate and revolute, apex caudate to acuminate; petiole 2–4 cm long, glabrous; stipules caducous. Panicles 6–8 cm diameter, densely tomentose. Flowers 1.5–1.8 cm diameter; hypanthium cup-shaped, brown-tomentose; sepals acute to obtuse, brown-tomentose below, slightly shorter than hypanthium; petals white, orbicular to obovate; stamens 20. Fruit yellowish red, subglobose, 1.2–2 cm diameter with reflexed sepals. Flowering May to June, fruiting June to August (China). Gu et al. 2003. Distribution CHINA: Guangdong, Hainan; TAIWAN; VIETNAM. Habitat Broadleaved forest on slopes and in valleys, between 1000 and 2100 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Gu et al. 2003; NT323. Cross-reference K43 (as E. deflexicalyx).

In the warmer parts of the United States Eriobotrya deflexa is widely used as an evergreen landscaping tree, valued for its handsome leathery foliage that flushes a warm red-bronze, and its abundant panicles of white flowers. The plant is often pruned to form a single stem with a dense rounded crown. It is, however, regarded as being short-lived, with a susceptibility to fireblight (Gilman & Watson 1993a). In our area it is quite widely grown and readily available commercially, but its tolerances are not yet clear. According to Sean Hogan (pers. comm. 2006) it is marginal in Portland, but does better along the Oregon coast. At Tregrehan it is making a good specimen, and it is also grown at Glasnevin, against a warm wall. It is certainly a tree to try in warm sheltered situations. A selected clone named ‘Bronze Improved’ is sold on the strength of enhanced coloration in the spring flush. There is also an interesting series of bigeneric hybrids between E. deflexa and Rhaphiolepis indica, which have recently been named ×Rhaphiobotrya A.J. Coombes (Coombes & Robertson 2008). These tend to be rather shrubby but are potentially small trees, with very attractive leaves. The best known is ‘Coppertone’, selected as a chance seedling by Ernest Bordier of Bordier’s Nursery, Irvine, California in about 1993, but there are others, including ‘Majestic Beauty’ (often listed as a Rhaphiolepis). Both of these have good coppercoloured young leaves and abundant flowers of white or pale pink. ‘Coppertone’ is widely grown in the warmer areas of the United States and is hardier than E. deflexa in Portland (S. Hogan, pers. comm. 2006). Dirr (1998) indicates that ‘Majestic Beauty’ is killed at about –20 ºC. E. japonica (Thunb.) Lindl. B113, K44

Plate 233. Eriobotrya deflexa is a popular street tree in California, with red new growth appearing throughout the growing season. Image N. Macer.

324

Eucalyptus

New Trees

MYRTACEAE

EUCALYPTUS

L’Hér.

Eucalypts, Gum Trees, Ironbarks, Mallees, Peppermints, Sallees, Stringybarks Eucalyptus includes over 900 species and is largely endemic to Australia, though 16 species occur naturally in New Guinea, Indonesia and the Philippines (Hill 2002b). It is perhaps the most significant tree genus in Australia, occurring in almost every habitat type. Eucalypts are also widely grown outside Australia, to stabilise soil and as a source of timber, firewood, pulpwood and essential oils. Their use in such plantations is controversial but some of the supposedly deleterious effects have been exaggerated, and they seldom regenerate naturally (although where they do they can be invasive weeds). No genus of this size and importance is without taxonomic controversy, and in Eucalyptus the opposing taxonomic viewpoints are vigorously defended. The account of Eucalyptus in Flora of Australia (Chippendale 1988) recognises two genera: Angophora and Eucalyptus. However, a phylogenetic study (Johnson & Briggs 1984) led Johnson to propose that Eucalyptus should be split into 10 or 11 segregate genera. This proposal proved controversial (see ‘Letters to the Editor’ in the Australian Systematic Botany Society Newsletter, nos. 38/39) and was never implemented, though Hill & Johnson (1995) did later split the bloodwoods, spotted gums and ghost gums into a separate genus Corymbia K.D. Hill & L.A.S. Johnson (see p. 275). The recognition of three eucalypt genera in Australia (Angophora, Corymbia and Eucalyptus) is broadly in agreement with recent phylogenetic studies and has been accepted by most authors

Plate 234. A grove of Eucalyptus mannifera at Michelago, New South Wales – a scene evocative of the Australian landscape, and redolent of eucalyptus oil. Image R. Farrow.

Section II. Species Accounts

(for example, Ladiges & Udovicic 2000, Hill 2002a, 2002b, 2002c), though Brooker (2000) disputes this and recognises only Eucalyptus. The descriptions below are based on the Eucalyptus account in Flora of Australia (Chippendale 1988). Since 1988, however, numerous new species have been described, and taxonomic study of Eucalyptus has been intensive (see, for example, Johnson & Hill 1990a, 1990b, Hill & Johnson 1991a, 1991b, 1992, 1994, 1995, 1998, Johnson & Hill 1999, Hill & Johnson 2000, Hill et al. 2001). A comprehensive review of 894 Australian Eucalyptus species – EUCLID (third edition, usually known as EUCLID3) – was published in October 2006 by the Centre for Plant Biodiversity Research, Australian National Herbarium, Canberra, as a DVD. It is a guide to identification and a source of information, and should be used by anyone with a deep interest in this fascinating genus. Eucalyptus species are trees or large shrubs, or form dwarf shrubs with woody tubers producing numerous coppice shoots (mallees). They are often fast-growing (some of the hardy species are by far the fastest trees in temperate climates), and one species, the Australian Mountain Ash (E. regnans), is the tallest hardwood tree in the world. Eucalypt bark is extremely variable and often diagnostic. It may be persistent (the so-called rough barks) or partly or wholly deciduous (smooth barks). The leaves are evergreen and often have numerous oil glands. They are typically dimorphic: the shape and size of adult and juvenile leaves are different, and juvenile leaves are strictly opposite while adult leaves often appear alternate. Some species, however, retain juvenile-type leaves throughout their lives. Inflorescences are solitary and axillary or rarely clustered in terminal or axillary structures; they are composed of umbellasters with 1–30 flowers. The individual flowers are hermaphrodite (rarely male only) and have a cup-shaped hypanthium containing numerous stamens and a nectar-producing disc. The stamens are curled tightly inwards in bud and are released at anthesis, when the cap-like calyptra is shed. Eucalyptus flowers may have a single calyptra (formed from the fused calyx and corolla) or an inner (corolla) and an outer (calyx) calyptra, and these leave distinct scars when they are shed. After pollination the stamens are shed, leaving a scar (staminal ring), and the hypanthium becomes a woody capsule. Within the capsule the ovary breaks down via a number of valves, and is enclosed within the capsule (included) or may protrude from the top (exserted). The wingless seeds drop out of the capsules, though some species require that the capsules are burnt to enable seed release (Kelly et al. 1983, Chippendale 1988, Hill 2002b). Identification of Eucalyptus is not easy and requires both practice and the presence of fertile material. Knowledge of the provenance is often useful, as similar species often occupy different localities or ecological niches. There are numerous guides to Eucalyptus as wild trees in Australia and these should be consulted. The multi-volume works of Kelly et al. (1983) and Brooker & Kleinig (1999–2002) are very useful, but EUCLID3 is now the dominant source of information. There are also some excellent websites. In consequence of this abundance of information and its associated illustration by drawings or photographs, we have not indicated other sources of illustrations in our usual way. Eucalyptus is a genus that arouses strong emotions. Its members evoke the sundrenched Australian landscape, more perfectly perhaps than any other combination of tree and location, and they carry the redolence of the outback with them – even if many hardy species come from rain-soaked parts of Tasmania! They can be productive timber and firewood trees, yet are reviled by environmentalists for the damage that

Eucalyptus

325

Plate 235 (above, top). The buds of all Eucalyptus are covered by a cap-like calyptra (the reddish part in this E. gregsoniana), which surmounts the hypanthium (the lower green part) on which the reproductive parts are inserted. The calyptra is shed as the flowers open. Image A. Coombes. Plate 236 (above, centre). Eucalyptus flowers have no petals, the showy part consisting rather of a mass of stamens surrounding a nectariferous disc and the stigmata. This is E. lacrimans. Image R. Farrow. Plate 237 (above). Although slightly variable, the number and arrangement of valves of the fruit capsule are important characters for identification of eucalypts. In Eucalyptus kybeanensis, four included valves are typical. Image R. Unwin.

326

Eucalyptus

Figure 34 (opposite). Eucalyptus chapmaniana: habit with flowers (A); detail of flower with calyptra (B); capsules (C); juvenile foliage (D).

Plate 238. In favourable conditions Eucalyptus nitens can rocket upwards to form a tree of great beauty, as here at Ness Botanic Gardens. Image P. Williams.

New Trees

plantations of them can sometimes cause to water catchments and native vegetation. In horticulture they are often regarded with suspicion as being ‘not suitable for the English landscape’ (frequently by those who will happily plant a Sequoiadendron to punctuate the sky for the next millennium), or avoided ‘because they are not hardy’. To exclude Eucalyptus from a collection on any of these grounds is not sensible. Many of these species are among the most beautiful of trees, with grace and poise, and the shimmering of their foliage in a breeze is always a pleasure. Their bark, too, often rivals or exceeds anything offered by the birches or Pinus bungeana. All in all, they offer a great deal in the way of interest and beauty, and have the advantages of being often fast-growing and sometimes short-lived – useful if a quick but temporary screen is needed. The first horticultural consideration in Eucalyptus is hardiness. It is a recurrent theme in the dendrological literature, and enthusiasts are constantly scouring Australia for the coldest or highest provenances of each species. The importance of selecting seed from such locations cannot be overemphasised, as it can make a significant difference to the winter temperatures a tree can withstand, and where their survival in cultivation is marginal this is very important. In the past this effect was not so widely appreciated as it is now, and seed collections were often made at the first point of contact with a species – usually therefore at the lower end of its altitudinal range (a problem by no means confined to Eucalyptus). Fortunately seed collectors now frequently offer seed from stated provenances, enabling an informed choice to be made. This account of the genus describes 54 species currently established in cultivation, adding to the 17 described in full by Bean (1981a), and mention is made of several more that have been attempted but are not yet established in our area. This increase can be attributed to two factors. First, the quest for the hardiest provenances has enabled several species to become established where previous introductions had failed, and secondly, the steadily rising temperatures being experienced worldwide have given just sufficient leeway and encouragement for devotees to experiment ever more widely. It remains the case, however, that most Eucalyptus cannot be grown outside in most of the area covered by New Trees, and many of the species described below are distinctly marginal denizens here. It is probable that a severe winter would wipe out most of them. Gum trees have always been regarded as potentially ephemeral in northern Europe, and the words of H.J. Elwes from a century ago are relevant today: ‘[They] are so easy to raise from seed, that the certainty of their death after a few years will not deter gardeners from planting them’ (Elwes & Henry 1912). The point is that in ‘a few years’ most Eucalyptus will make a substantial tree of great beauty. Its loss would be regretted, but not nearly so much as if, like an oak, it had taken decades to reach that stature. The growth rate of some species, even in apparently less than ideal situations, can be staggering. The 16 m achieved in four years by E. nitens in Oxfordshire – by no means the warmest area of southern England – is

Section II. Species Accounts

Eucalyptus

327

A

1 cm

B

C

1 cm

1 cm

1 cm

D

328

Eucalyptus

New Trees

just an extreme demonstration of this. Growth rates slow as the tree branches and rounds out, but can still be rapid even then. There is good reason to believe that many species increase in hardiness as they mature, the younger plants being more vulnerable to frost by virtue of their lesser bulk, so a few mild winters before anything testing is a bonus. It is difficult to specify precise temperatures at which any given species will succumb because there are so many variables, including the effects of the previous summer and autumn, the wetness or dryness of the ground, and the duration of the frost. In the following species accounts, all-too-frequent mention has to be made of a devastating frost in November 2005 that wiped out a large number of Eucalyptus trees at Lullingstone Castle in Kent, home of Tom Hart Dyke, who had personally collected many as seed from the best possible provenances. Several factors were causative in this devastation. The site is a frost pocket on rather damp ground, and neither of these are ideal conditions for growing eucalypts – but the real damage was caused because up until the frost (20 November) the autumn had been mild and moist, and many plants, including the Eucalyptus, were still growing vigorously. There had been no prior hardening off with a gradual decline in temperatures, so the trees were unprepared for a first frost of –9 ºC, that many might have withstood if it had come after a suitable hardening period. On the other hand, John Purse (pers. comm. 2007) reports that many of his trees, of the same species, growing in an exposed site in north Kent, were unaffected by the same frost. He suggests that this is because in such a site they grow more slowly and more hardily (although the temperatures in the Lullingstone frost pocket were lower). His view is that very mild, apparently favourable sites can actually be less suitable for Eucalyptus than slightly harsher ones. Dry cold winds in a dry spring can kill eucalypts very effectively as well, and there is a good case to be made for wrapping young eucalypts in their first winter, or providing a shelter of horticultural fleece to moderate the wind. Even if the top growth of a Eucalyptus is cut by frost there is a strong chance that it will resprout from the roots and form an often attractive shrubby plant. From the resurgent shoots one can then be selected as a replacement main stem. Almost entirely excluded from northern gardens are those species with large red, pink or yellow flowers, which are simply insufficiently hardy to survive even light frosts. This explains why there is such an interest in finding a eucalypt with ‘coloured’ flowers hardy enough to grow outside in the north temperate region. With two exceptions the flowers of all those described below, or covered by Bean (1981a), are white or lightly cream-coloured. A few red-flowered gums can be cultivated in western North America as far north as the San Francisco Bay Area, and indeed Eucalyptus sideroxylon is used as a street tree in that city, along with the spectacular Corymbia ficifolia. Eucalyptus are in general very easy to raise from seed. This should always be sourced from specific provenances in Australia, or from proven trees in the northern hemisphere. Some seed merchants offer seed from orchards in South Island, New Zealand, and such sources may also be useful in the quest for hardiness. It should be noted that Eucalyptus are quite promiscuous, and even wild-origin seed may throw hybrid surprises. Seed should be surface-sown in gentle warmth in late winter or early spring. Some species require stratification, full details of which will be found in the book Eucalyptus Seed (Boland et al. 1980). Transplant the seedlings at the earliest opportunity and keep them growing vigorously, with regular repotting as necessary, at all times ensuring that the roots do not spiral the pot. From an early sowing young plants can be set out in their final sites in early summer, when no more than 30–45 cm

Section II. Species Accounts

tall. They should then grow away rapidly and produce good root systems to assure stability. Another option is to sow a little later and grow the plants to overwinter in a pot in a frame or polytunnel, to be planted out promptly in spring. The importance of keeping the roots active and unspiralled in the pot cannot be overemphasised, if good establishment and long-term stability are required. The system adopted by Cistus Nursery (and others in the United States) of growing Eucalyptus seedlings in batches, offering them to customers while still very young, and destroying them if they remain unsold after six weeks or two months in two-litre pots is greatly to be commended, and is an example that should be followed. This is a far cry from the usual pot-bound victims seen throughout the UK nursery trade – caveat emptor – although some specialist suppliers do promote the desirability of planting young plants. Some, it should also be noted, believe that planting at a larger size has advantages that can outweigh the problems caused by confined roots (G. Cooper, pers. comm. 2007). Modern potting concepts (see pp. 30–31) may be particularly advantageous for eucalypts. The ideal Eucalyptus planting site in our area would be in full sun, in good soil with perfect drainage, on a slope where cold air can flow off, and protected from cold winds from the east and north. In western locations some shelter from strong westerly winds is also advantageous. Some species are tolerant of moister soil, and a few will accept light shade, but these are exceptions. Most prefer acidic to neutral soil, but some tolerate higher alkalinity. In the British Isles the best specimens are almost all in southern or western locations, although the ameliorated climate of the west coast of Scotland and around the Irish coast makes it possible to grow many species into fine specimens at surprisingly northerly latitudes. The fine collection at Logan Botanical Garden on the Mull of Galloway is an outstanding testament to this, and the beautiful groves of Eucalyptus at Mount Usher in Co. Wicklow and the magnificent trees at the John F. Kennedy Arboretum, Co. Wexford, and many other locations along the eastern side of Ireland, are not very much further south. There are good collections at Kew and the RHS Garden at Wisley. The World Garden and grounds at Lullingstone Castle have an interesting range of survivors, and there are other collections in private hands in southern England, including a National Plant Collection owned by Mr & Mrs D.J. Smith at Wickham, Hampshire. One problem in maintaining collections of Eucalyptus, that became apparent while examining specimens in arboreta in the research for New Trees, is that the regularly sloughed bark makes it exceptionally difficult to attach a label to the trunk in the usual way. A regularly updated plan is particularly important for this genus. Most of continental Europe and North America within our area is off-limits to Eucalyptus, being too cold in winter for them to succeed. That said, the fascinating accounts of survival in Cincinnati from Frank Callia, passed on by Sean Hogan, suggest that more experimentation may yield surprising results. Hogan (2008) considers that

Eucalyptus

329

Plate 239. A massive Eucalyptus bridgesiana at Michelago, New South Wales. Many eucalypts can reach very large sizes. For stability it is important that their roots do not become spiralled in pots when young, and early planting is strongly recommended. Image R. Farrow.

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Eucalyptus

Plate 240. Eucalyptus neglecta has been found to be the most tolerant – not only of cold temperatures but also of the summer heat and humidity of the East Coast of the United States. This one is growing at Castle Howard, North Yorkshire. Image T. Kirkham.

New Trees

about 30 species are hardy in Zone 8 conditions in the United States. Eucalyptus are hardly grown in northern continental Europe, but most of the species described here would probably survive well in coastal France and northern Spain. In North America the hot humidity of the East Coast summer is not appreciated by most gum trees, even were they to survive the winters. A few are more tolerant, however, and some (unspecified) species are said to grow on the coast as far north as Delaware (L. Eirhart, pers. comm. 2007). Tony Avent conducted trials of Eucalyptus in North Carolina in the late 1980s and early 1990s (pers. comm. 2007), ‘before global warming’, and found that the hardiest tested was E. neglecta, which survived –18 ºC without any loss of the trunk. The other two species to survive this milestone temperature (0 ºF), but with at least 50 per cent trunk loss, were E. nova-anglica and E. parviflora. On the West Coast, as will be apparent from the accounts that follow, many species will survive and flourish along the Pacific Northwest seaboard and in milder areas inland, as far north as British Columbia. Good collections and plantings may be seen in the Portland area, at the Washington Park Arboretum and in Vancouver. The further south one goes in California the more eucalypts will be found, and the Bay Area botanical gardens have a very fine range of species (although in the interests of discussing true hardiness, specimens growing in California have not been cited here). These accounts of the species in cultivation were prepared with very considerable input from the ‘Gum Group’, a panel of Eucalyptus enthusiasts (Graham Blunt, Geoff Cooper, Tom Hart Dyke, Sean Hogan, Terry & Maria Milton, Steve Verge), who are duly most sincerely and gratefully acknowledged. General views expressed at the Eucalyptus Workshop held at Colesbourne, Gloucestershire in January 2007 are referenced ‘Gum Group 2007’; attributable individual comments are recorded in the usual way. Flowering and fruiting times are not given, as these vary widely between hemispheres and latitudes. The following species of Eucalyptus are known to be, or to have recently been, in cultivation but have been excluded from this account – principally because they are insufficiently hardy to form a tree in our area, or are too little known: E. approximans Maiden subsp. approximans and E. approximans subsp. codonocarpa (Blakely & McKie) L.A.S. Johnson & Blaxell (short mallees to 6 m with smooth bark, not established in our area: the 12 m trees with flaky bark at Logan labelled subsp. codonocarpa are incorrectly identified); E. badjensis Beuzev. & M.B. Welch (potentially very fast-growing, but not hardy in southern England); E. barberi L.A.S. Johnson & Blaxell; E. blaxlandii Maiden & Cambage; E. cosmophylla F. Muell. (regarded as very tender by the Gum Group (2007), who report trees killed at –2 ºC, but there is a suppressed (5 m) specimen from 1995 at Logan, and it grows on Tresco: TROBI); E. deanei Maiden; E. fasciculosa F. Muell. (small seedlings are grown by Gum Group members, not tested); E. formanii C.A. Gardner; E. goniocalyx Miq.; E. kitsoniana Maiden; E. leucoxylon F. Muell. subsp. leucoxylon, E. leucoxylon subsp. pruinosa (F. Muell. ex Miq.) Boland; E. ligustrina DC.; E. nitida Hook. f. (hardy but straggly, resembling E. coccifera); E. olsenii L.A.S. Johnson & Blaxell; E. paliformis L.A.S. Johnson & Blaxell; E. stricta Sieber ex Spreng.; E. sturgissiana L.A.S. Johnson & Blaxell; E. willisii Ladiges, Humphries & Brooker; E. yarraensis Maiden & Cambage; and E. youmanii Blakely &

Section II. Species Accounts

Eucalyptus

McKie. Enthusiasts are constantly experimenting with this genus, and given its rapid growth rates an ‘unknown’ species may suddenly feature as a substantial tree, so the total diversity in temperate gardens is always increasing.

Eucalyptus acaciiformis H. Deane & Maiden

Wattle-leaved Peppermint

Tree to 20 m. Bark greyish brown, rough, fibrous throughout. Branchlets green. Juvenile leaves alternate, petiolate, elliptic, greyish green. Adult leaves green, 5–10 × 1–1.5 cm, lanceolate, lateral veins just visible, margins entire, apex acuminate; petiole slightly flattened, 0.6–1.8 cm long. Inflorescences axillary and solitary; umbellasters with seven flowers. Flower buds ovoid to obovoid to fusiform; hypanthium hemispherical, 0.2–0.3 cm wide; stamens white or cream. Capsule hemispherical, 0.4–0.5 cm diameter; valves three to four, level or slightly exserted. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales (Northern Tablelands). Habitat Mixed woodland on slopes and ridges. USDA Hardiness Zone 8. Conservation status Not evaluated.

Eucalyptus acaciiformis is considered to be a good feature tree by the Gum Group (2007), forming a nicely shaped specimen with an open crown. The leaves are small, and could cause confusion with E. nicholii, but are darker green and shorter in the adult phase. The young growth flushes red-bronze and the twigs are red when young. It seems to be hardy in southern England, and in Oregon some provenances have withstood –6 ºC without damage, although trees from another provenance were damaged at –3 to –4 ºC (S. Hogan, pers. comm. 2007). Growth is rapid, with 8 m being achieved in five years in Surrey (M. & T. Milton, pers. comm. 2007), and 5.5 m in three years in Oregon (S. Hogan, pers. comm. 2007). E. aggregata H. Deane & Maiden B134, S230

Eucalyptus albida Maiden & Blakely

White-leaved Mallee

Mallee to 3 m. Bark white or greyish brown, often powdery, smooth throughout. Juvenile leaves white, waxy, sessile and amplexicaul, decussate, orbicular to cordate; the change from juvenile to adult foliage is abrupt. Adult leaves glossy, dark green, 4–7 × 0.5–1.5 cm, narrowly lanceolate, lateral veins obscure, margins entire, apex acute; petiole terete, 0.7–1.7 cm long. Inflorescences axillary and solitary; umbellasters with seven or nine flowers. Flower buds fusiform; hypanthium hemispherical or obconical, 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical or obconical, 0.4–0.8 cm diameter; valves three (to four), ± level. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: Western Australia (Tammin to Ravensthorpe). Habitat Heaths on white sand. USDA Hardiness Zone 9(–10). Conservation status Not evaluated.

As a juvenile plant Eucalyptus albida is perhaps the most silvery of all the eucalypts, well deserving its specific epithet. The leaves are very densely placed on the twigs, resulting in a remarkable silvery white bush, which can be maintained by coppicing. It also makes a good container plant. In adulthood the leaves are longer and glossy dark green. Never a large tree, E. albida is probably best regarded in our area as a striking ornamental foliage shrub, although adult specimens are known outside in the United Kingdom. It is very sensitive to excess moisture, and extremely sharp drainage is recommended. A sheltered site is also desirable, as the new growth is prone to damage from both wind and frost (Gum Group 2007).

Eucalyptus amygdalina Labill.

Black Peppermint

Syn. E. salicifolia Cav. Tree 15–30(–40) m tall, dbh 1 m. Bark grey to greyish brown and finely fibrous on trunk and larger branches; salmon-pink, white or grey on smaller branches and branchlets. Leaves have a strong peppermint odour. Juvenile leaves sessile, 2.8–5.5 × 0.2–1.1 cm, lanceolate and green to subglaucous. Adult

331

332

Eucalyptus

New Trees

leaves thin and dull green, 7–12 × 0.5–1.3 cm, lanceolate to linear and falcate, lateral veins indistinct, margins entire, apex acuminate or hooked; petiole flattened, 0.7–1 cm long. Inflorescences axillary and solitary; umbellasters with 11–15 flowers (rarely more). Flower buds green to yellow, smooth or slightly warty; hypanthium 0.2–0.3 cm wide; stamens white. Capsule hemispherical to cup-shaped, 0.5–0.7 cm diameter; valves three to four, flush with capsule mouth or protruding slightly. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Tasmania (central and northeast). Habitat Open sclerophyllous forest on hills and mountain slopes, between 0 and 750 m asl. USDA Hardiness Zone (8–)9–10. Conservation status Not evaluated. Cross-reference K48. Taxonomic note Closely related to E. pulchella Desf. (see p. 351), but that species has smooth bark.

This lowland Tasmanian species with narrow leaves has a marginal presence in our area, and is on the verge of hardiness in southern England. Tom Hart Dyke collected it from five provenances in 2002 and had trees doing very well at Lullingstone Castle, having reached 10 m, until the November frosts of 2005 killed them outright. Johnson (2007) has recorded a 13 m tree at Ventnor Botanical Garden on the Isle of Wight; another specimen was 13 m tall (32 cm dbh) in 2008, at the Sir Harold Hillier Gardens. There is a grove of 40 m trees at Glenealy, Co. Dublin, planted in 1935 (J. Purse, pers. comm. 2007).

Eucalyptus archeri Maiden & Blakely

Alpine Cider Gum

Small tree or mallee 3–10 m. Bark white, grey or greyish green and smooth throughout; occasionally with black horizontal scars. Branchlets reddish yellow. Juvenile leaves sessile, 1.3–3.9 × 0.9–3.2 cm, circular to cordate and greyish green. Adult leaves thick and greyish green, 5–8 × 1–2 cm, lanceolate, lateral veins indistinct, margins entire, apex acuminate; petiole terete and 1–1.5 cm long. Inflorescences axillary and solitary; umbellasters with three flowers. Flower buds green to yellow, smooth and obovoid; hypanthium 0.4–0.5 cm wide; stamens white. Capsule hemispherical to bell-shaped, slightly wrinkled, 0.6–0.8 cm diameter; valves three to four, flush or protruding slightly. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Tasmania (Central Plateau). Habitat Occurs on shallow soils between rock outcrops on plateaus and mountain peaks to 1400 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT333. Taxonomic note Very similar to E. gunnii, but with a more straggly habit and slightly wrinkled fruits.

The boundaries between Eucalyptus archeri and E. gunnii are somewhat indistinct, but in its typical form E. archeri is morphologically, ecologically and horticulturally separable. It can be recognised by its all-green appearance, with no hint of glaucescence. All-green stands occur in the highest parts of its range, but glaucescence appears increasingly with lower altitude, and it becomes difficult to separate from E. gunnii. Whether this is due to introgressive hybridisation, or E. archeri is merely a high-altitude variant of E. gunnii, has not yet been resolved (Gum Group 2007). The alpine habitat of typical E. archeri is rather nutrient-deficient and prone to waterlogging, resulting in small, mallee-like trees. Even in cultivation it is not a rapid grower, and thereby also differs from E. gunnii. At Lullingstone Castle seedlings from Tom Hart Dyke’s 2002 collection have achieved only 5.5 m at the time of writing, and others from the same collection are similarly slow at Kew (4 m in 2005), although already flowering. These trees are, however, quite distinct from E. gunnii, their green foliage borne on stiffly ascending yellowish twigs. Despite its alpine origins E. archeri is not as reliably hardy as E. gunnii, and in Oregon it has been killed at –8 ºC (S. Hogan, pers. comm. 2007). Once established it seems better able to resist cold, and TROBI records numerous significant specimens between Devon and Edinburgh, the tallest in the British Isles being an individual of 23 m in 2005, at Plas Newydd, Anglesey. Figure 35 (opposite). Eucalyptus archeri: habit with flowers (A), fruits (B); detail of capsule mouth (C).

E. bicostata (NOW E. globulus subsp. bicostata (Maiden, Blakely & Simmonds) J.B. Kirkp., NT341) B132, S229

Section II. Species Accounts

Eucalyptus

333

1 cm

A

B C

1 cm

334

Eucalyptus

New Trees

Eucalyptus blakelyi Maiden

Blakely’s Red Gum

Tree to 25 m. Bark white or grey with pink, yellow or greyish blue patches; smooth throughout. Branchlets greenish red. Juvenile leaves sessile, ovate to round and greyish green. Adult leaves thick or thin, bright green, grey-green or glaucous, 9–16 × 1–2 cm, lanceolate, lateral veins prominent, margins entire, apex acute, base tapering towards the petiole; petiole terete, 1.5–2.2 cm long. Inflorescences axillary and solitary; umbellasters with 7–11 flowers. Flower buds conical and glaucous; hypanthium 0.3–0.5 cm wide; stamens white or cream. Capsule globose or hemispherical, 0.4–0.8 cm diameter; valves three to four, exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (widespread in the east except on the coast), Queensland (southeast), Victoria (northeast). Habitat Woodland and open forest. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT334.

Plate 241. Fine trees of Eucalyptus blakelyi at Huntly, Australian Capital Territory – but the chances of successful regeneration are slim! Image R. Farrow.

Eucalyptus blakelyi was marginal on our list of species to be considered here, but has been included with a full account on the strength of news from John Purse (pers. comm. 2007) that in his north Kent location he has young trees planted in 2004 that have survived –7 ºC and flowered in 2007. These plants are derived from seed collected at the species’ highest-altitude sites. Giving a contrary view, Sean Hogan reports (pers. comm. 2007) that it has been killed at –3 ºC on the Oregon coast. It is worth growing, even for a short time, for its attractive and unusual juvenile foliage.

Eucalyptus bridgesiana F. Muell. ex R.T. Baker

Apple Box

Tree to 40 m. Bark grey to greyish brown, fibrous and flaky with white patches throughout. Branchlets green. Juvenile leaves opposite to subopposite, glaucous, orbicular to broadly obovate, crenulate, amplexicaul. Adult leaves alternate, dark green, 12–20 × 1.5–2.5 cm, lanceolate, lateral veins distinct, margins entire, apex acute to acuminate, falcate; petiole flattened or terete, 1.5–3 cm long. Inflorescences axillary and solitary; umbellasters with seven flowers. Flower buds ovoid, often apiculate; hypanthium hemispherical, 0.3–0.5 cm wide; stamens white or cream. Capsule hemispherical, 0.4–0.7 cm diameter; valves three to four, exserted. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales (Tablelands), Queensland (Stanthorpe), Victoria. Habitat Grassy woodland on drier sites. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT329.

Eucalyptus bridgesiana is a vigorous species and reasonably hardy; where happy it can make a very large tree indeed. The largest specimen recorded in the British Isles – one of a group of three at Mount Usher, Co. Wicklow – was 39.5 m tall, 130 cm dbh in 2000 (TROBI). The species has attractive white bark, and the upright new shoots flush pink before the leaves assume their usual light greenish blue as they mature, although there is some variation in foliage colour. It flowers prolifically in autumn, making it a very useful source of nectar for bees and other insects. It seems to be hardy to about –12 ºC, but will resprout as a coppice from lower temperatures that kill the top.

Eucalyptus brookeriana A.M. Gray Tree 10–40 m, dbh 1 m. Bark rough, grey and fibrous on the lower trunk; smooth and olive-green, orange-red or cream above. Branchlets greenish yellow or orange. Juvenile leaves sessile, ovate or round with crenulated margins, bright green. Adult leaves shiny green, 6.5–14 × 1.5–3 cm, ovate to lanceolate, lateral veins indistinct,

Section II. Species Accounts

Eucalyptus

335

margins crenulate and undulate, apex acute; petiole terete, 1–3 cm long. Inflorescences axillary and solitary; umbellasters usually with seven flowers, sometimes more. Flower buds spindle-shaped to obovoid; hypanthium 0.3–0.5 cm wide; stamens white or cream. Capsule conical to hemispherical, 0.5–0.7 cm diameter; valves three to four, exserted or level. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Tasmania (incl. King Is.), Victoria (Otway Ranges). Habitat Tall, open forest (rarely rain forest) on slopes and ridges or near watercourses, between 50 and 650 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated.

Eucalyptus brookeriana has not been extensively tested in our area, but it is a species for which Tom Hart Dyke has ‘huge hopes’, his trees having survived the infamous November 2005 frosts, albeit with the loss of their crowns. They had reached 6–7 m in less than three years. A 14 m tree was recorded at Glencormac, Co. Wicklow in 1991 (TROBI), and there are two trees that are probably of this species on the campus of Exeter University, Devon, that had reached 17 m and 18 m tall by 2004 (TROBI). Two even better specimens grow at the Sir Harold Hillier Gardens. Planted in 1987, these were 21.8 m (40 cm dbh) and 19.3 m (45 cm dbh) in 2008, when measured by H. Brown. Even if damaged, E. brookeriana will coppice readily from a lignotuber, when the crenulated, circular green juvenile leaves will reappear. As a green-leaved species it offers a useful contrast to the more familiar glaucous gums.

Eucalyptus camaldulensis Dehnh.

River Red Gum

Tree to 30(–45) m. Bark white, grey, brown or red, smooth throughout. Branchlets green. Juvenile leaves green, greyish green or blue-green, ovate to broadly lanceolate. Adult leaves green to greyish green, 8–30 × 0.7–2 cm, lanceolate, lateral veins obscure, margins entire, apex acuminate; petiole channelled or terete, 1.2–1.5 cm long. Inflorescences axillary and solitary; umbellasters with 7–11 flowers. Flower buds globularbeaked to conical; hypanthium hemispherical, 0.3–0.6 cm wide; stamens cream. Capsule hemispherical or ovoid, 0.5–0.8 cm diameter; valves three to five, exserted. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: Australian Capital Territory, New South Wales, Northern Territory, Queensland, South Australia, Victoria, Western Australia. Habitat Riverbanks and floodplains, preferring deep moist subsoils with clay content. USDA Hardiness Zone (9–)10. Conservation status Not evaluated. Illustration NT335. Taxonomic note Eucalyptus camaldulensis is an extremely widespread species in mainland Australia, and varies considerably across its range. Three infraspecific entities are recognised: subsp. camaldulensis, with greyish white bark, rough at the trunk base, and strongly beaked capsules (temperate Queensland to Victoria); var. obtusa Blakely, with reddish brown bark, smooth to the trunk base, and obtuse or rounded capsules (tropical and subtropical Australia); and subsp. simulata Brooker & Kleinig, with greyish white bark, smooth to the trunk base, and horn-shaped capsules (northeastern Queensland).

The River Red Gum is probably the Eucalyptus most widely planted for commercial forestry worldwide (Mabberley 1997a), and although often useful in supplying a range of timber products, it is also capable of causing environmental degradation. The handful of specimens in our area are unlikely to cause problems, however, as it is only marginally hardy. In Kent, young plants suffer frost damage when young but live through it, and eventually reach a size where they can tolerate average winter conditions – though inevitably as a multistemmed plant (Gum Group 2007). In milder conditions it will have a better chance of forming a single-stemmed tree. Whether it is worth the trouble to grow this iconic gum for such results is a point for discussion. The specific epithet refers to a monastery at Camaldoli near Naples in Italy: these trees were extensively planted in Italy during

Plate 242. A sight familiar in South Africa: in a baked landscape, dusty-looking Eucalyptus camaldulensis are often the only trees around. Image S. Andrews.

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New Trees

the nineteenth century to assist in draining malarious marshlands. As a riparian species it is capable of surviving flooding for short periods, and also has a considerable thirst for water (hence the environmental problems associated with plantations of it). Despite this, however, it is also able to withstand dry conditions.

Eucalyptus camphora R.T. Baker

Broad-leaved Sallee, Mountain Swamp Gum

Tree to 22 m. Bark grey or greyish brown to almost black and smooth throughout. Branchlets reddish orange or yellow. Juvenile leaves sessile, ovate, emarginate, green. Adult leaves shiny green, 6–13 × 3.8–5 cm, ovate to broadly lanceolate, lateral veins distinct, margins entire, apex rounded or sometimes emarginate; petiole terete, 2.5–4 cm long. Inflorescences axillary and solitary; umbellasters with seven flowers. Flower buds spindleshaped; hypanthium 0.3–0.5 cm wide; stamens white or cream. Capsule conical or cup-shaped, 0.4–0.6 cm diameter; valves three to four, level or slightly exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales, Queensland, Victoria. Habitat Montane forest, particularly in marshland. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT336. Cross-references B135, S230.

A key to the three subspecies of Eucalyptus camphora, modified from Johnson & Hill (1990b), is provided below.

1a. Petioles > 2 cm long ........................................................................................................................ 2 1b. Petioles < 2 cm long; Australia (New South Wales: Central Tablelands) .................... subsp. camphora

Plate 243. The juvenile leaves of Eucalyptus camphora are conspicuously notched (emarginate) at their apex. Image R. Farrow.

2a. Largest adult leaves < 2.5 cm wide; Australia (northeastern New South Wales: Northern Tablelands; southeastern Queensland: Racecourse Creek) ...................................... subsp. relicta L.A.S. Johnson & K.D. Hill 2b. Largest adult leaves > 2.5 cm wide; Australia (southeastern New South Wales, northeastern Victoria) .................... subsp. humeana L.A.S. Johnson & K.D. Hill

Eucalyptus camphora could be seen as a high-altitude form of E. ovata, which is less hardy. Both grow in wet ground in their native habitat. Eucalyptus camphora will also tolerate boggy and even flooded conditions in cultivation in southern England, and does not rock in the ground. It is, however, somewhat less hardy when grown in wet conditions than on drier sites (which it also tolerates well). Bean (1981a) recorded that it had been ‘recently introduced’ by R.C. Barnard, and predicted that it should be very hardy. This seems to be the case, although provenance is, as always, important. Trees from the population near Wee Jasper, New South Wales are particularly tough, and have withstood –16.5 ºC in Oregon and resprouted from much lower temperatures in Cincinnati (S. Hogan, pers. comm. 2007). Eucalyptus camphora is an attractive species, with rounded lime-green leaves when young, often with a slight sinus that gives them a camel’s-foot appearance. Adult leaves are more elongated, and a rich dark green (although material from higher altitudes will often show some glaucescence). The leaves flush reddish, and also turn a good red as they die. It is a rapid grower, some plants in Oxfordshire being almost 9 m after only six years (G. Cooper, pers. comm. 2007), and others in Oregon reaching 13 m in 10 years (S. Hogan, pers. comm. 2007). Despite all these promising signs, however, no older trees are known in the British Isles at present, the current TROBI-recognised champion being 9 m in 2004 at Fox Rosehill Garden, Cornwall. Larger specimens (up to 18 m in Devon) have been recorded in the past.

Section II. Species Accounts

Eucalyptus chapmaniana Cameron

Eucalyptus

337

Bogong Gum

Tree to 30 m. Bark greyish brown, fibrous and longitudinally fissured below; smooth and greyish white above. Branchlets yellowish orange. Juvenile leaves sessile, circular and glaucous. Adult leaves dull greyish green, 18–30 × 2.5–4 cm, lanceolate or falcate, lateral veins distinct, margins entire, apex acute; petiole terete, 1.8–3.5 cm long. Inflorescences axillary and solitary; umbellasters with three flowers. Flower buds spindle- or club-shaped; hypanthium 0.3–0.5 cm wide; stamens white or cream. Capsule ovoid and glaucous, 0.8–1 cm diameter; valves three to four, exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales, Victoria. Habitat Wet sclerophyllous forest with poor soils. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT327, NT337.

Eucalyptus chapmaniana is rare in cultivation, which is curious, especially since a specimen at Kew is one of the finest eucalypts there (14 m tall, 41 cm dbh in 2001, TROBI), and there is another at Wakehurst Place of 19 m, though this has two, thinner trunks. Both these trees were grown from seed collected in Victoria by Ken Hill in 1988 and are survivors of groups of three, the others having been killed as young plants in the winter of 1990 –1991 (Kew records). The Kew specimen has made a broad, rounded crown of spreading branches and pendulous twigs, the dull dark green leaves giving it a rather sombre appearance.

Eucalyptus cinerea Benth.

Argyle Apple, Silver Dollar Gum

Tree to 16 m. Bark reddish brown, rough and fibrous below; smooth and reddish brown or grey above. Branchlets brown. Juvenile leaves sessile or with a short petiole, circular to cordate and glaucous; juvenile and intermediate leaves often persist on adult trees. Adult leaves thick and glaucous, 7.5–11.5 × 1.5–2.5 cm, broadly lanceolate, lateral veins indistinct, margins entire, apex acuminate; petiole flattened and 0.5–1.1 cm long. Inflorescences axillary and solitary; umbellasters with three flowers. Flower buds spindle-shaped and glaucous; hypanthium 0.4–0.5 cm wide; stamens white or cream. Capsule conical or cylindrical, 0.5–0.9 cm diameter; valves three to five, slightly exserted. Chippendale 1988. Distribution AUSTRALIA: Australian Capital Territory, New South Wales, Victoria. Habitat Grows in wet areas with clay soils in sclerophyllous woodland. USDA Hardiness Zone 7. Conservation status Not evaluated.

Eucalyptus cinerea is one of the most distinctive of the hardy gums, having a fibrous reddish bark that looks well with the silvery leaves. When adult these are elongate, but they are particularly striking in the juvenile phase when they are rounded and very ‘white’, and held in opposite pairs close to the stem. Branchlets at this stage are an important article in the cut foliage market, to be used as ‘filler’ in flower arrangements, and coppiced plantations of E. cinerea are grown for this purpose in southern Europe. It is reliably hardy in southern England, at least in well-drained sites (less so in damp conditions). Some damage can be expected if temperatures drop below –10 ºC, but hardier provenances can tolerate a few degrees colder before dieback becomes serious (Hogan 2008). There are specimens throughout the British Isles, the champion being 18 m tall (32 cm dbh) at Marwood Hill, Devon in 2006 (TROBI). It is vigorous, but not excessively fast by Eucalyptus standards. A tree at Lamberhurst Vineyard, Kent achieved 10 m in six years; in Oregon it is slightly faster, and 8 m in five years has been observed (S. Hogan, pers. comm. 2007). It may also be coppiced on a regular basis to provide fast-growing juvenile shoots as a garden feature.

E. coccifera Hook. f. B128, S228, K48

E. cordata Labill. B129, S228, K48

Plate 244. Eucalyptus chapmaniana is curiously rare in cultivation. This specimen is at Kew (K. Hill 1413), where it is outstanding in the Eucalyptus collection. Image J. Grimshaw.

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Eucalyptus crenulata Blakely & Beuzev.

Buxton Gum, Silver Gum

Tree to 16 m. Bark rough, compact and grey on the lower trunk; smooth and grey to greyish brown above. Branchlets white or coppery red. Juvenile leaves sessile, ovate to cordate, crenulate and glaucous; rather similar to adult leaves. Adult leaves opposite and glaucous, 3.5–6.5 × 3–5.5 cm, broadly ovate, lateral veins distinct, margins crenulate, apex apiculate; petiole absent or terete and to 0.6 cm long. Inflorescences axillary and solitary; umbellasters with 7–11 flowers. Flower buds ovoid, beaked and glaucous; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule cylindrical, 0.4–0.6 cm diameter and initially glaucous; valves three to four, included. Chippendale 1988. Distribution AUSTRALIA: Victoria (valley of the Acheron River). Habitat Forms pure stands, in swampy areas along watercourses. USDA Hardiness Zone 8–9. Conservation status Not evaluated (IUCN), but regarded as endangered in Australia as it occurs in only two small natural populations (Dept. of Environment, Water, Heritage & Arts 2008).

Although rare in the wild, Eucalyptus crenulata is well established in horticulture, and seed from cultivated trees is freely available. As a mature tree it is apt to be short and somewhat crooked, but forms a nice rounded crown of silvery foliage. Leaf shape and posture change little between the juvenile and adult phases, leaves in both cases being held in stiff opposite pairs, but juvenile foliage is slightly more glaucous. The flowers, which can appear as early as the third year from seed, are individually small, held on short pedicels in the leaf axils, but are so numerous that they make a showy display along the length of the shoots. In cultivation E. crenulata is quite fast-growing, achieving 10 m or so in five years both in Oxfordshire and in Oregon (G. Cooper, S. Hogan, pers. comms. 2007). It is also considered to be among the hardiest species of Eucalyptus (Gum Group 2007), usually tolerating –12 ºC before being damaged; in the event that the main stem is killed, however, it does also coppice well. It has not been widely planted, but is grown in several specialist collections in the Pacific Northwest as well as in the British Isles.

Eucalyptus cypellocarpa L.A.S. Johnson

Mountain Grey Gum

Tree to 65 m. Bark yellowish white or grey, largely smooth, though may be rough on trunk and main branches. Branchlets green. Juvenile leaves opposite, shiny green, broadly lanceolate to ovate, sessile. Adult leaves alternate, green, 11–20 × 1–2.5 cm, lanceolate, lateral veins distinct, margins entire, apex acuminate, falcate; petiole slightly flattened, 1.5–2.5 cm long. Inflorescences axillary and solitary; umbellasters with seven flowers. Flower buds ovoid, angular; hypanthium cylindrical, ribbed, 0.4–0.5 cm wide; stamens white or cream. Capsule cylindrical to ovoid, 0.6–0.9 cm diameter; valves three, level or included. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales, Victoria. Habitat Wet forest on deep, fertile soils. USDA Hardiness Zone (9–)10. Conservation status Not evaluated.

The Gum Group (2007) consider this handsome blue gum to be well worth trying, but have found it to be very tender in its early stages. Once it has got going it may increase in hardiness, as a specimen in the John F. Kennedy Arboretum, Co. Wexford was 22 m tall (64 cm dbh) in 2000 (Johnson 2007). E. dalrympleana Maiden B130, S228, K48 E. debeuzevillei (NOW E. pauciflora subsp. debeuzevillei (Maiden) L.A.S. Johnson & Blaxell, NT354) S230

Eucalyptus delegatensis R.T. Baker

Alpine Ash

This species was described by Bean (B131) and Krüssmann (K48).

Eucalyptus delegatensis subsp. tasmaniensis Boland Subsp. tasmaniensis differs from typical E. delegatensis in that the seedlings have warty stems with conspicuous oil glands, and circular leaves with a prominent drip-tip; adult leaves 5–17 × 1.1–3.6 cm. Typical E. delegat-

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ensis seedlings, by contrast, have smooth stems and broadly lanceolate leaves; adult leaves 9–22 × 1.3–4 cm. Chippendale 1988. Distribution AUSTRALIA: Tasmania (incl. Maria Is.). Habitat Subalpine areas. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT339.

This is one of the most attractive of hardy gums, both in the wild and as young plants in cultivation (earning the comment ‘stunning!’ in notes made at Kew in 2005). The appeal comes from its very white stems, which are covered in a thick layer of wax. Coppicing would no doubt maintain this effect on new shoots; older trees develop a redwood-like fibrous bark that peels in long strips to reveal whitish or greyish blue patches below. There is a young tree at Kew (about 4 m tall in 2005), grown from Tom Hart Dyke’s collection (THD 96) made at 1193 m on the Stacks Bluff Trail in Tasmania in 2002. Other specimens from the same collection are growing at Wakehurst Place, where there are also trees that originate from the Ben Lomond area of Tasmania (ETAZ 74, collected in 2000 by D. Hardman and A. Jackson). Although this is generally considered to be a reasonably hardy plant, at Lullingstone Castle all specimens were killed in November 2005. Where circumstances are more fortunate and it gets away it can grow rapidly and well, and has achieved some 18 m in Oxfordshire, sheltered by other trees (S. Verge, pers. comm. 2007). In Oregon 14 m trees were undamaged by frosts of –8 ºC for several consecutive nights in 2001 (S. Hogan, pers. comm. 2007). It is not tolerant of chalky soils (Gum Group 2007).

Eucalyptus elliptica (Blakely & McKie) L.A.S. Johnson & K.D. Hill

Bendemeer White Gum, Brittle Gum

Syn. E. mannifera subsp. elliptica (Blakely & McKie) L.A.S. Johnson Tree to 20 m. Bark white, grey or yellow, powdery, smooth throughout. Branchlets green. Juvenile leaves opposite, glaucous, orbicular, ovate or broadly lanceolate, sessile. Adult leaves alternate, dull green, 15–25 × 1.5–3 cm, lanceolate, lateral veins distinct, margins entire, apex acute, falcate or not; petiole flattened or channelled, 1–3.6 cm long. Inflorescences axillary and solitary; umbellasters with seven flowers. Flower buds ovoid; hypanthium hemispherical to subglobose, 0.3–0.5 cm wide; stamens white or cream. Capsule ovoid, 0.5–0.8 cm diameter; valves three to four, exserted. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales, Queensland. Habitat Wet forest on deep, fertile soils. USDA Hardiness Zone 8. Conservation status Not evaluated. Taxonomic note See E. mannifera.

As might be expected given its close relationship with the variable Eucalyptus mannifera, E. elliptica is similarly variable, in appearance and also in its horticultural success. The best forms are both very hardy and very bluish or silvery: one such form is grown at Cistus Nursery in Oregon, from seeds collected at 860 m near Uralla in New South Wales at a site where –15 ºC has been recorded. These plants have achieved 5 m in three and a half years, but also in Oregon there are trees of about 30 years old that are now 15 m tall (S. Hogan, pers. comm. 2007), so it would not seem to maintain an explosive growth rate for long. It has not been extensively tried in the United Kingdom but the view of the Gum Group (2007) is that it is not a fussy species and is of reasonable hardiness, although the highest provenances should be sought. A 7 m tree at Cookscroft, Earnley, West Sussex in 1997 is the tallest recorded by TROBI, and a similarly sized specimen grows in Geoff Cooper’s wood near Witney, Oxfordshire, on rather damp clay soil. The species is prone to wind rock there (G. Cooper, pers.

Plate 245. When young at least, the trunk and branches of Eucalyptus delegatensis subsp. tasmaniensis are strikingly white. This is THD 96, at Kew. Image T. Kirkham.

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comm. 2007), but has not suffered frost damage. The bark can be among the whitest of all gums, and the whole tree has a slightly pendulous appearance caused by the large and rather heavy leaves.

Eucalyptus fastigata H. Deane & Maiden

Brown Barrel

Tree to 20–45(–60) m, dbh 1–2 m. Bark reddish or greyish brown, rough and furrowed on the trunk and larger branches; peeling off in long strips further up to reveal a smooth, white surface. Branchlets deep red or maroon. Juvenile leaves sessile, green and glossy with raised oil glands. Adult leaves thick, glossy green, 8–15 × 1.5–2.7 cm, lanceolate to ovate or falcate, lateral veins distinct, margins entire, apex acute or acuminate; petiole flattened or channelled, 1–1.5 cm long. Inflorescences axillary, usually paired; umbellasters with 11–15 flowers. Flower buds club-shaped and beaked; hypanthium 0.3 cm wide; stamens white or cream. Capsule conical to pear-shaped, 0.4–0.7 cm diameter; valves three, flush or exserted. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: New South Wales (Tablelands), Victoria (northeast). Habitat Open sclerophyllous forest in cold, wet valleys and on slopes, between 300 and 1400 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT340. Taxonomic note Differs from the closely related E. regnans in having rough bark on the larger branches.

Eucalyptus fastigata is rare in cultivation, but where it has been attempted in western parts of the United Kingdom it seems to be perfectly happy. The champion is at Marwood Hill, Devon and was 20 m tall (56 cm dbh) in 2006 (TROBI), and there is a group of three straight trees at Logan that were about 14 m tall (greatest dbh 35 cm) when seen in 2006. Plate 246. Reddish brown fibrous bark on the lower part of the trunk of Eucalyptus fastigata (this specimen is at Logan). Higher up, it peels to reveal a sleek, shining surface. Image R. Unwin.

E. ficifolia (NOW Corymbia ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson) K49

Eucalyptus fraxinoides H. Deane & Maiden

White Mountain Ash

Tree to 40 m, 1 m dbh. Bark greyish black and fibrous on the lower trunk; smooth, white, grey or yellow above, often with white ‘scribbles’ (insect tracks). Branchlets red. Juvenile leaves sessile, ovate to lanceolate, light grey or blue-green. Adult leaves thick and glossy green, 8–16 × 1–2 cm, lanceolate and/or falcate, lateral veins indistinct, margins entire, apex acuminate or hooked; petiole flattened or channelled, 1–1.5 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers. Flower buds ovoid or club-shaped; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule cylindrical, globose or urn-shaped, 0.6–1.1 cm diameter; valves four to five, included. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: New South Wales (Tablelands), Victoria (Howe Range). Habitat Sclerophyllous forest on cool, moist mountain slopes or peaks, between 150 and 1000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated.

In the view of the Gum Group (2007), Eucalyptus fraxinoides is one of the most beautiful of eucalypts, to the extent that the epithet ‘gorgeous’ was employed to describe it. Its beauty lies in part in the shape of the tree, which is conical around a straight trunk when young; also in its green and white peeling bark, and the red new growth that forms a haze around the tree when in active growth and illuminated by the sun shining through it. To counteract all this, it is not very hardy, especially as a young plant, and for success in our area needs good drainage in a sheltered site. It is also very intolerant of lime, and soon shows symptoms of chlorosis. There are a few specimens in the United Kingdom, however, and rapid growth rates have been recorded (11–12 m since planting in 2002 in Oxfordshire, for example), although others have found it rather slow-growing. On the positive side, trees coppiced down – either deliberately or by frost – produce a mass of the fabulous red young foliage.

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E. glaucescens Maiden & Blakely B133, S229

Eucalyptus globulus Labill.

Blue Gum

This species was described by Bean (B131, S228) and Krüssmann (K49). A key to the subspecies is provided below (adapted from Chippendale 1988). 1a. Umbellasters one-flowered ........................................................................................ subsp. globulus 1b. Umbellasters three- or seven-flowered ............................................................................................ 2 2a. Umbellasters seven-flowered .................................................... subsp. maidenii (F. Muell.) J.B. Kirkp. 2b. Umbellasters three-flowered ............................................................................................................ 3 3a. Flower buds and fruits pedicellate .................. subsp. pseudoglobulus (Naudin ex Maiden) J.B. Kirkp. 3b. Flower buds and fruits sessile ............................................ subsp. bicostata (Maiden et al.) J.B. Kirkp.

Eucalyptus globulus subsp. bicostata (Maiden, Blakely & Simmonds) J.B. Kirkp.

Eurabbie, Southern Blue Gum

This subspecies differs from typical E. globulus in that the umbellasters are three-flowered. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales (Tablelands, Western Slopes), South Australia (Mt. Bryan), Tasmania (West Sister Is. only), Victoria. Habitat Wet forest on fertile soils in sheltered areas away from the coast. USDA Hardiness Zone 9. Conservation status Not evaluated. Cross-references B132, S229 (as E. bicostata).

A brief description of ‘Eucalyptus bicostata’ was given by Bean (1981a), who mentioned a specimen of 13 m at Mount Usher in 1966. Since then, however, that record has been far superseded, the largest measured for TROBI being 28 m (64 cm dbh) at Fota Arboretum, Co. Cork in 2002, and another young tree of 17 m having been noted at Sheffield Park, West Sussex in 2003 (Johnson 2007). Looking very similar to the relatively familiar Blue Gum subsp. globulus, subsp. bicostata is probably a little hardier though slightly slower growing. Despite this, vigorous young plants were killed at Lullingstone in the November 2005 frosts. The tree has huge, beautifully glaucous leaves when young and is extremely attractive, with a particularly good fragrance. E. gomphocephala A. Cunn. ex DC. K49

Eucalyptus gregsoniana L.A.S. Johnson & Blaxell

Mallee Snow Gum

Syn. E. pauciflora var. nana Blakely Mallee to 5 m. Bark smooth and white or pale grey throughout; shedding as long ribbons. Branchlets greenish yellow to red. Juvenile leaves lanceolate and blue-green. Adult leaves thick and glossy, greyish green, 7–11 × 1.5–2.5 cm, lanceolate and/or falcate, lateral veins distinct, margins entire, apex acuminate; petiole thick, flattened or channelled, 0.8–1.2 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers. Flower buds club-shaped; hypanthium 0.4 cm wide; stamens white or cream. Capsule pear-shaped or conical, 0.6–0.8 cm diameter; valves three, included. Chippendale 1988. Distribution AUSTRALIA: New South Wales (southeast). Habitat Heathland vegetation on mountain peaks and tablelands. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT325, NT341.

Eucalyptus gregsoniana is well established in cultivation and freely available in commerce. Although a smallish mallee in the wild it can become much larger in cultivation, where the lignotuber is also produced. At Logan there are trees from 1989 that are now 8–9 m tall, and others from 1990–1991 that are 6–7 m. They tend to branch

Plate 247. Three included valves: characteristic of the capsules of Eucalyptus gregsoniana. Image R. Unwin.

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New Trees

low down forming large heavy limbs, clad in attractive pale grey bark that peels in irregular patches. In older, unshed areas the bark is reddish brown. Young stems are yellowish to orange-red and bear falcate leaves of typical eucalyptus grey-green when mature, although they flush red. Flowering starts when the tree is quite young, and can be very prolific. Eucalyptus gregsoniana can be regarded as a substitute E. pauciflora for small gardens, where its pale bark and abundant flowering will make it an attractive feature. It is slightly less hardy than E. pauciflora, but for most purposes in the United Kingdom (at least) it can be regarded as hardy at the present time; it also has the advantage of tolerating some lime in the soil (Gum Group 2007).

Eucalyptus gunnii Hook. f.

Cider Gum

This species was described by Bean (B132) and Krüssmann (K49).

Eucalyptus gunnii subsp. divaricata (McAulay & Brett) B.M. Potts Syn. E. divaricata McAulay & Brett

Miena Cider Gum

This taxon is intermediate between E. archeri and typical E. gunnii and can be distinguished in several ways. The adult leaves are slightly smaller and broader (4–8 × 1.5–3 cm) than those of E. archeri (5–8 × 1–2 cm) and typical E. gunnii (5–8 × 1.2–3 cm), and the heavy waxy covering on the branchlets, flower buds and capsules is more extensive. Specimens of subsp. divaricata are more likely to retain juvenile foliage and develop a woody tuber. Oil glands are not visible on the juvenile leaves. Potts et al. 2001. Distribution AUSTRALIA: Tasmania (Central Plateau). Habitat Frost hollows with poorly drained soils in open woodland. USDA Hardiness Zone 7. Conservation status Not evaluated (IUCN), though restricted to an area of 40 km2 in central Tasmania, and considered in Australia to be endangered (Dept. of Environment, Water, Heritage & Arts 2008).

Plate 248. Branching against the sky, Eucalyptus kybeanensis at Logan shows off its attractive mottled bark and its more or less upright leaves. Image R. Unwin.

The distinctions to be made between members of the Eucalyptus gunnii complex are perhaps tenuous at times, and the view of the Gum Group (2007) is that subsp. divaricata fits within the normal range of variation of E. gunnii (although the bark can be whiter and the leaves slightly more glaucous). In the quest for hardiness, however, it is useful to be able to recognise particular populations under different names. The origin of subsp. divaricata in frost pockets on the Central Plateau of Tasmania, where temperatures can fall to –22 ºC, gives it special interest in this respect, and it is ranked by the enthusiasts as equal first for hardiness in the genus alongside E. pauciflora subsp. debeuzevillei and subsp. niphophila. Eucalyptus gunnii subsp. divaricata is freely available in commerce and has been widely planted, but some (if not many) of these trees are merely glaucous forms of subsp. gunnii (J. Purse, pers. comm. 2007). Numerous good specimens have been recorded across the British Isles by TROBI, the largest 18 m tall, 31 cm dbh, at Batsford Park, Gloucestershire in 2003 (Johnson 2003). E. johnstonii Maiden B133, S229, K49

Eucalyptus kybeanensis

Kybean Mallee Ash

Maiden & Cambage Mallee to 6 m; rarely, tree to 18 m. Bark smooth, white, grey or greyish green throughout; shedding in ribbons. Branchlets yellowish brown. Juvenile leaves lanceolate, shiny green. Adult leaves thick, green, 5–9 × 0.6–1.3 cm, lanceolate and/or falcate, lateral veins indistinct, margins entire, apex acute or hooked; petiole thick, flattened or channelled, 0.3–0.5 cm long. Inflorescences solitary and axillary; umbellasters with 3–11

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flowers. Flower buds club-shaped or turbinate; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical or conical, 0.5–0.8 cm diameter; valves (three to) four to five, included. Chippendale 1988. Distribution AUSTRALIA: New South Wales (southeast), Victoria (northeast). Habitat Exposed, high-altitude mountains, plateaus. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT325, NT342. Taxonomic note Closely related to E. approximans (see p. 330), but with sessile buds and fruits, and hardier.

Eucalyptus kybeanensis is a distinctive smaller species, with a relatively slow growth rate, and is thus more appropriate for most gardens than many of the larger, fastergrowing species. Its principal distinction is conferred by the leaves, which are held stiffly horizontal or upright, contrasting with the pendulous-leaved species. It also has attractive silvery grey bark, peeling in large patches to reveal yellowish newer bark beneath. Flowering can be very abundant. In cultivation in the United Kingdom, however, it has had mixed success. There are some good specimens, the tallest recorded being one planted at the Hillier Gardens in 1986 which had reached 17 m by 2004 (TROBI), and there are leaning trees of about 12 m at Logan; but the Gum Group (2007) consider it to be a tree for sheltered situations in milder areas. It is very sensitive to lime in the soil.

Eucalyptus lacrimans L.A.S. Johnson & K.D. Hill

Weeping Snow Gum

Tree to 15 m. Bark smooth, powdery, white or grey throughout; shedding in short ribbons. Branchlets purplish grey. Juvenile leaves broad-lanceolate to ovate, 15 × 7 cm. Adult leaves thick and glossy green or greyish green, 7–15 × 0.7–2 cm, lanceolate to ovate, falcate, lateral veins distinct, margins entire, apex acuminate or apiculate; petiole 0.7–16 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers (or more). Flower buds club-shaped and glaucous; stamens white or cream. Capsule globose, hemispherical or conical, 0.5–0.9 cm diameter; valves three to four, included. Hill & Johnson 1991a. Distribution AUSTRALIA: New South Wales (Adaminaby-Kiandra district). Habitat Small, open copses on broad, flat, treeless grassy plains. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT325, NT343.

The Weeping Snow Gum was once assumed to be a pendulous form of Eucalyptus pauciflora subsp. niphophila, but its separate identity is now accepted. Like the Snow Gum it is regarded as being very hardy, and it comes from a cold upland area where drainage is often poor and the soil waterlogged. Opinions on its attractions vary, some finding its sparse weeping habit attractive, while others consider it gawky. It tends to grow fast and upright when young, developing pendulous branches with age, but these can often give it a one-sided look, and it can also suffer from wind rock. On the other hand, this skinny effect can be quite useful where an open light tree is wanted. Ample space should be given to allow it to develop its shape fully, and perhaps an early coppicing would encourage the development of a fuller and more stable tree. The best forms have good glaucous leaves with white bark. There are a few larger examples in the United Kingdom, but it is significant that Owen Johnson’s notes on his 2006 measurements for TROBI of two specimens at Marwood Hill record that the champion (12 m) is a ‘poor thin tree still’, and another of 6 m is ‘straggly’.

Eucalyptus laophila L.A.S. Johnson & Blaxell Mallee to 6 m. Bark smooth and grey, greyish brown or copper throughout; shedding in ribbons. Juvenile leaves sessile, narrowly lanceolate to linear and glossy green. Adult leaves thick and glossy green, 7–13 × 1–2 cm, linear or narrowly lanceolate, falcate, lateral veins indistinct, margins entire, apex acuminate or acute; petiole 0.3–1 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers (or more). Flower buds

Plate 249. The Nungar Plain, where these scraggylooking Eucalyptus lacrimans are growing, is a highaltitude frost pocket in the Kosciuszko area of New South Wales. In cultivation these trees are very hardy, but the blasted-heath look remains. Image R. Farrow.

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club- or pear-shaped; stamens white or cream. Capsule globose or urn-shaped, 0.8–1 cm diameter; valves four, included. Hill & Johnson 1991a. Distribution AUSTRALIA: New South Wales (Mt. Coricudgy district, Central Tablelands). Habitat Mallee shrub on shallow, sandy soils. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Johnson & Hill 1990b. Taxonomic note Considered by the EUCLID database (Brooker et al. 2002) to be synonymous with E. apiculata R.T. Baker & H.G. Sm., but distinguished by the bluish sheen and larger size of the adult leaves, and the larger fruits.

Eucalyptus laophila is a very rare species in cultivation, the only specimens located in the research for this book being at Logan where there are two small trees grown from a 1991 accession (Hind 5897). Their bark exfoliates in curling twists to leave smooth ‘skin’ below. The twiggy crowns bear narrow, willow-like leaves, and when seen in August 2006 they were heavily budded. The large fruits persist for several years. This is an interesting and attractive species that should be attempted more frequently. E. lehmannii (Schauer) Benth. K49

Eucalyptus leucoxylon F. Muell.

Yellow Gum

Only three of the six subspecies of Eucalyptus leucoxylon appear to be in cultivation in the temperate northern hemisphere. The key below, modified from those of Rule (1991, 1998), includes all recognised subspecies. A seventh subspecies was recently elevated to specific status as E. petiolaris (Boland) K. Rule (Rule 1992).

Eucalyptus leucoxylon subsp. leucoxylon Tree 10–30 m. Bark rough to 2 m, smooth above, grey or reddish brown or yellow. Juvenile leaves sessile, broadly lanceolate to ovate, dull green. Adult leaves dull green to blue-green, 9–13 × 1.3–2.5 cm, narrowly lanceolate, not falcate, lateral veins just visible, margins entire, apex acute; petiole flattened or channelled, 1–2 cm long. Inflorescences solitary, axillary; umbellasters with three flowers. Flower buds ovoid or fusiform; hypanthium 0.5–0.7 cm wide; stamens white, cream, pink or red. Capsule ovoid to subglobose, 0.7–1.4 × 0.8–1.3 cm; valves slightly inserted. Chippendale 1988. Distribution AUSTRALIA: South Australia (Fleurieu Peninsula, Kangaroo Is.). Habitat Open forest. USDA Hardiness Zone 9. Conservation status Not evaluated.

Subsp. leucoxylon is very rare in cultivation in our area. It was attempted at Logan in the 1990s but has not survived there (Royal Botanic Garden Edinburgh 2007–2008).

1a. Wax present on any of the following structures: juvenile leaves, branchlets, flower buds, fruits ............................................................................. 2 1b. Wax absent from all structures ......................................................................................................... 3 2a. Floral pedicels 15–27 mm long; flowers cream-white; Australia (Victoria: Bellarine Peninsula) ................................................... subsp. bellarinensis Rule 2b. Floral pedicels 3–8 mm long; flowers cream-white; Australia (southeastern South Australia, western Victoria) ................ subsp. pruinosa (Miq.) Boland 3a. Juvenile leaves often connate; flowers cream-white; Australia (Victoria: Brisbane Ranges) .............................................................. subsp. connata Rule 3b. Juvenile leaves never connate .......................................................................................................... 4 4a. Floral pedicels 3–7 mm long; flowers pink-red; dried membrane covering capsule mouth present; Australia (southeastern South Australia, western Victoria) ........................... subsp. stephaniae Rule 4b. Floral pedicels 8–30 mm long; dried membrane absent ................................................................... 5

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5a. Adult leaves > 2.5 cm wide; flowers cream-white to pink or red; fruits 12–16 × 10–15 mm; Australia (extreme southeastern South Australia) ............................................... subsp. megalocarpa Boland 5b. Adult leaves < 2.5 cm wide; flowers cream-white to pink; fruits 9–13 × 7–10 mm; Australia (South Australia: Fleurieu Peninsula, Kangaroo Is.) ........................................................................ subsp. leucoxylon

Eucalyptus leucoxylon subsp. megalocarpa Boland As the name suggests, this subspecies has larger fruits than subsp. leucoxylon, but also larger leaves (see key above). Chippendale 1988. Distribution AUSTRALIA: South Australia (extreme southeast). Habitat Calcareous soils. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT345.

As the only red-flowered Eucalyptus to show any hardiness in northern Europe, E. leucoxylon subsp. megalocarpa (sometimes found in horticultural literature as E. leucoxylon ‘Rosea’) excites considerable interest. There are a handful of small trees in southern England, the most notable being the 4 m specimen in the Chelsea Physic Garden, London, which flowers prolifically. At Lamberhurst in Kent, Graham Blunt has a small plant of 160 cm that flowers well in a sheltered site. There is an 8 m specimen at Tresco Abbey (TROBI), but the largest trees in the mainland United Kingdom are at Logan, where there are three rather unhappy specimens of about 6 m. If sufficiently mild and sheltered conditions cannot be provided to cultivate this taxon outdoors, it can be grown in a large container and given minimal frost-protection under cover in winter. Seedlings will flower when 1 m high, so its value as a flowering container plant is potentially considerable. The bark is reddish, peeling to reveal a paler underlayer, and the green leaves are narrow and somewhat contorted.

Eucalyptus leucoxylon subsp. pruinosa (Miq.) Boland This subspecies is notable for the waxy deposits that may occur on the juvenile leaves, branchlets, flower buds and fruits. Chippendale 1988. Distribution AUSTRALIA: South Australia (southeast), Victoria (central and west). Habitat Woodland with clay or sandy soils. USDA Hardiness Zone (9–)10. Conservation status Not evaluated.

This taxon is in cultivation but is even less hardy than subsp. megalocarpa, having been very seriously damaged by –5 ºC in Cornwall (J. Purse, pers. comm. 2007). E. linearis (NOW E. pulchella Desf.) B128, S228, K50

Eucalyptus macarthurii H. Deane & Maiden

Camden Woollybutt

Tree to 40 m, 1.2 m dbh. Bark rough, fibrous and greyish brown on lower trunk and major branches; smooth and grey above, peeling in ribbons that often accumulate in the crown. Branchlets red. Juvenile leaves sessile, lanceolate to ovate or rounded, dull green. Adult leaves thick and dull green, 8.5–19 × 0.8–1.6 cm, narrowly lanceolate, often falcate, lateral veins indistinct, margins entire, apex acuminate; petiole slightly flattened, 0.8–1.2 cm long. Inflorescences solitary, axillary; umbellasters with seven flowers (or more). Flower buds ovoid or spindle-shaped; hypanthium 0.2–0.3 cm wide; stamens white or cream. Capsule hemispherical, conical

Plate 250. Northern gardeners are frustrated by the fact that only one or two pink- or red-flowered eucalypts show any signs of hardiness. Eucalyptus leucoxylon subsp. megalocarpa is perhaps the hardiest, flourishing and flowering in warm sites in southern England, and blooming prolifically when still young. This one, however, was photographed in Australia. Image J.R.P. van Hoey Smith.

346

Eucalyptus

New Trees

or bell-shaped, 0.3–0.6 cm diameter; valves three to four, slightly exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (Central Tablelands). Habitat Open forest near watercourses between 500 and 1200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT346.

The Camden Woollybutt gets its extraordinary English name from the shaggy bark at the base of its trunk, and the town of Camden. It was in this area that the Macarthur family established the first Merino sheep flock in Australia, and the specific epithet commemorates the botanically interested Sir William Macarthur (Kelly et al. 1983). Eucalyptus macarthurii is one of the most magnificent of the gums that are genuinely hardy in most of the British Isles, although the finest specimens are in the usual gardens of the coastal fringe. The largest recorded was measured at 25 m (53 cm dbh) at the John F. Kennedy Arboretum, Co. Wexford, in 2000 (TROBI). At Logan a tree planted in 1989 was about 20 m tall (56 cm dbh) in 2006 (TROBI) and is a beautiful rounded specimen with spreading branches, well clad in narrow green leaves and abundant bright white flowers when observed for New Trees, also in 2006. The branches can develop from quite low down to result in a broad, heavy-set tree with a dense crown, rather unlike the more familiar upright, airy eucalypts. Young trees were undamaged at Lullingstone in the frosts of November 2005, and it is usually very well rooted into the ground so not prone to wind rock. One fault is that its top can blow out (Gum Group 2007), and it is (in Australia) prone to dieback and branch rot, and is thus recommended there more for use in open spaces than as a street tree (Kelly et al. 1983). Plate 251. Eucalyptus macarthurii, seen here flowering freely at Logan in 2006, is very hardy, and makes a broad, rounded tree of great presence. Image J. Grimshaw.

Eucalyptus macrorhyncha F. Muell. ex Benth.

Red Stringybark

Tree to 35 m. Bark persistent, dark brown and fibrous. Branchlets yellowish green. Juvenile leaves alternate, ovate and green. Adult leaves green, 9–18 × 1.2–2.7 cm, lanceolate, lateral veins distinct or not, margins entire, apex hooked; petiole flattened or channelled, 1–1.7 cm long. Inflorescences solitary and axillary; umbellasters with 3–11 flowers. Flower buds spindle-shaped; hypanthium 0.4–0.5 cm wide; stamens white or cream. Capsule globular, 0.7–1.4 cm diameter; valves three to four, slightly exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), South Australia (southeast), Victoria. Habitat Open forest near watercourses. USDA Hardiness Zone 9–10. Conservation status Not evaluated.

Eucalyptus macrorhyncha subsp. macrorhyncha has been attempted by members of the Gum Group, but has not proved satisfactory in southern England. It will survive and form a coppiced plant, but the judgement of the Group in 2007 is that it is ‘not worth the effort’.

Eucalyptus macrorhyncha subsp. cannonii

Cannon’s Stringybark

(R.T. Baker) L.A.S. Johnson & Blaxell Subsp. cannonii differs from subsp. macrorhyncha in that the umbellasters bear three to seven flowers (subsp. macrorhyncha has 7–11 flowers). Chippendale 1988. Distribution AUSTRALIA: New South Wales (Capertee Valley). Habitat Dry, sclerophyllous forest on rocky ridges or slopes. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

Cannon’s Stringybark seems to be a little hardier than the nominate subspecies, having grown at Logan since 1990. There it has made a good tree of 10 m, with three main trunks, supporting a rounded crown of greyish leaves that flush bronze and turn red as

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they senesce. The bark is indeed its most interesting feature, being soft, fibrous and reddish brown, rather like that of a Sequoia, peeling in longitudinal strips and fibres.

Eucalyptus mannifera Mudie

Mottled Gum, Brittle Gum

Tree to 25 m. Bark white, cream or grey, sometimes with red patches, smooth and powdery throughout. Branchlets greenish brown. Juvenile leaves alternate and petiolate, glaucous or not. Adult leaves dull blue- or greyish green, 6–25 × 0.8–3 cm, lanceolate, lateral veins indistinct, margins entire, apex acuminate; petiole terete or channelled, 0.6–2.7 cm long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds ovoid or rarely club-shaped; hypanthium 0.2–0.4 cm wide; stamens white or cream. Capsule hemispherical, ovoid or subglobular, 0.4–0.7 cm diameter; valves three, slightly exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), Queensland (extreme southeast), Victoria (east). Habitat Open forest on hills and tablelands. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT324, NT347.

Chippendale (1988) recognised five subspecies of Eucalyptus mannifera, but Johnson & Hill (1990b) elevated two, subsp. elliptica and subsp. praecox, to full species status. A key to the remaining subspecies (modified from Chippendale 1988) is provided below.

1a. Adult leaves < 2 cm wide ........................................................................... 2 1b. Adult leaves ≥ 2 cm wide; Australia (southeastern New South Wales, eastern Victoria) .......... subsp. mannifera 2a. Juvenile leaves glaucous; hypanthium hemispherical; Australia (southeastern New South Wales, eastern Victoria) ..................... subsp. maculosa (R.T. Baker) L.A.S. Johnson 2b. Juvenile leaves pale green; hypanthium conical; Australia (eastern New South Wales: Blue Mts.) .......................................... subsp. gullickii (R.T. Baker & H.G. Sm.) L.A.S. Johnson

The various currently recognised subspecies of E. mannifera are not well known in cultivation, although E. elliptica (see p. 339) is sometimes grown as E. mannifera subsp. elliptica. At Tresco in 2006 there was a 9 m specimen of subsp. gullickii recorded for TROBI, but this is the only example of the species to find its way into the register. At Logan there is a group of subsp. mannifera grown from Hind 5472, accessioned in 1989, that are approximately 12 m tall at the time of writing, the largest having a dbh of 25 cm. These have smooth, reddish brown bark which is unusual for this species, in which the bark is normally rather a striking white, or white with reddish patches. More horticultural exploration of Eucalyptus mannifera as a whole is needed, and the Gum Group has little experience of it. It should be noted, however, that in Australia it is notorious for shedding branches – hence the name Brittle Gum (Australian National Botanic Gardens 2003b).

Eucalyptus melliodora A. Cunn. ex Schauer

Yellow Box

Tree to 30 m. Bark grey, yellow or reddish brown, fibrous and/or flaky on the lower trunk and larger branches; smooth and yellowish white above. Branchlets reddish brown or orange. Juvenile leaves alternate, petiolate, ovate or elliptic, greyish green. Adult leaves green or greyish green, 6.5–14 × 0.8–1.8 cm, lanceolate, falcate, lateral veins distinct, margins entire, apex acuminate or acute; petiole terete or slightly flattened, 1–1.5 cm

Plate 252. There is no getting away from the fact that eucalypts can be extremely messy trees. Eucalyptus mannifera, here growing in Canberra, has a repution for shedding branches as well as bark. Image R. Farrow.

348

Eucalyptus

New Trees

long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds spindle- or clubshaped; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical, ovoid or subglobular, 0.4–0.7 cm diameter; valves five, flush or included. Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), Queensland (southeast), Victoria. Habitat Variable; low hills and dry areas, flats near watercourses and open forest. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT348.

There are conflicting reports on the hardiness of Eucalyptus melliodora. Ian Barclay, from near Olympia, Washington in the United States, regards it as tender, and finds that his plants are cut to the ground each winter (Hardy Eucalyptus Page 2004). In contrast, Tom Hart Dyke’s trees at Lullingstone Castle were only ‘cut in half’ by the November 2005 frosts and have regrown rapidly since (pers. comm. 2007), and John Purse’s trees in north Kent were not affected and seem to be reasonably hardy, though slow-growing (J. Purse, pers. comm. 2007). It needs maximum light and does not tolerate shade. In the San Francisco Bay Area it is commonly used as a street tree, and Sean Hogan (pers. comm. 2007) reports that it suffered only minor damage in a –10 ºC frost at Berkeley. In Australia this is the most important species of eucalypt for honey production, and it is noted for its very fragrant flowers. As an ornamental its principal feature is its patchwork bark in different colours, which sometimes peels and falls in circular rings. Plate 253. Eucalyptus melliodora is the most important source of nectar for eucalyptus honey in Australia. This is a superb tree at Burra, South Australia. Image R. Farrow.

Eucalyptus mitchelliana Cambage

Mount Buffalo Sallee, Weeping Sallee

Tree to 15 m. Bark smooth, greyish white, greyish brown or green. Branchlets yellow-orange. Juvenile leaves alternate, petiolate, lanceolate, dark green. Adult leaves moderately thick, 7.5–13 × 0.7–1.3 cm, lanceolate to narrowly lanceolate, lateral veins indistinct, margins entire, apex acuminate or acute; petiole terete, 1–1.5 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers. Flower buds spindle-shaped; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule subglobular, 0.5–0.7 cm diameter; valves flush or included. Chippendale 1988. Distribution AUSTRALIA: Victoria (Mt. Buffalo Plateau). Habitat Among granite outcrops in open eucalypt forest. USDA Hardiness Zone 8. Conservation status Not evaluated (IUCN), though with an extremely limited range, much of which was burnt in 2003 (J.Purse, pers. comm. 2007).

Eucalyptus mitchelliana is an attractive tree, very highly regarded by the Gum Group (2007) for its beauty and hardiness. Temperatures down to –13 ºC have been measured on Mount Buffalo, and this is reflected in the record of the species in cultivation. Young trees at Lullingstone Castle were unaffected by the frost in 2005, and there are mature and often large trees in collections throughout the British Isles, including a specimen at Benmore that was 17.5 m tall in 1995, and the British and Irish champion of 28 m (51 cm dbh) in 2000 at the John F. Kennedy Arboretum, Co. Wexford (TROBI). It is relatively fast-growing when young, achieving 4 m in three years at Lullingstone, and has a pleasing weeping habit, with orange-yellow twigs bearing narrow, pendulous leaves that flush dark red.

Eucalyptus moorei Maiden & Cambage Mallee to 8 m, more rarely a tree to 10 m. Bark smooth and greyish white, shedding in ribbons. Branchlets purplish red. Juvenile leaves opposite to alternate, sessile to petiolate, lanceolate. Adult leaves thick and dull greyish green, 4–7 × 0.5–1.7 cm, lanceolate to narrowly lanceolate, lateral veins indistinct, margins entire, apex acuminate or acute; petiole terete or flattened, 0.2–0.5 cm long. Inflorescences solitary and axillary; umbellasters with (7–)11–15 flowers. Flower buds spindle-shaped; hypanthium 0.1–0.3 cm wide; stamens

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white or cream. Capsule subglobular, 0.3–0.4 cm diameter; valves three, included. Chippendale 1988. Distribution AUSTRALIA: New South Wales (Gibraltar Range, Blue Mts., Southern Tablelands). Habitat Heathland with sandy soils. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT349. Taxonomic note The closely related E. latiuscula (Blakely) L.A.S. Johnson & K.D. Hill has ovate juvenile leaves and umbellasters that are sessile (or almost so). It forms a stouter plant with fewer stems (Johnson & Hill 1990b).

Eucalyptus moorei comes from comparatively high altitudes, giving a promise of cold tolerance that is not completely fulfilled in cultivation. Seedlings show great variation in their hardiness, and even the best cannot be relied upon for long-term survival. Once established in a favourable site, however, it can develop into a good tree. A plantation made in the 1950s by the US Forestry Service in Oregon now has trees up to 10 m (S. Hogan, pers. comm. 2007), and there is a forked tree of about 10 m at Logan (from Hind 6043, accessioned 1991). This has attractive pinkish grey bark, peeling and flaking in shaggy strips from the older parts. The crown is dense, composed of graceful narrow leaves. A slightly mysterious ‘var. nana’ is in cultivation and available from seed companies. This seems to be a particularly short-growing variant, with some merit as a shrub for smaller gardens. A specimen seen at Mount Usher had attractive reddish brown stems.

Eucalyptus morrisbyi Brett

Morrisby’s Gum

Tree to 15 m. Bark pale brown, grey, white or pink and smooth throughout; rough, scaly bark can develop at the base of old trees. Branchlets pinkish red. Juvenile leaves opposite, sessile, roughly circular, glaucous and with crenulate margins. Adult leaves thin and greyish green to glaucous, 5–10 × 1.2–2.3 cm, lanceolate, lateral veins indistinct, margins entire to undulate, apex acuminate; petiole terete, 1.2–2 cm long. Inflorescences solitary and axillary; umbellasters with three flowers. Flower buds turbinate and glaucous; hypanthium 0.4–0.7 cm wide; stamens white or cream. Capsule cylindrical and glaucous, 0.5–0.6 cm diameter; valves four to five, included. Chippendale 1988. Distribution AUSTRALIA: Tasmania (southeast). Habitat Dry, sclerophyllous forest on sandy soils, usually by the sea. USDA Hardiness Zone 9. Conservation status Endangered. Only four stands survive and these are threatened by habitat destruction and degradation.

Eucalyptus morrisbyi is closely related to E. gunnii and shares much of its hardiness, despite its origin close to the coast. It has a certain advantage over E. gunnii in looks, having better, smoother and paler bark, and more glaucous foliage borne on pink branches, the combination making it rather beautiful and well worth planting. Young trees at Lullingstone were unaffected by the 2005 November frosts, and elsewhere it has done very well. It is not common in cultivation but there is an 8 m specimen at Mount Usher, rather suppressed by having been planted below other big eucalypts.

Eucalyptus neglecta Maiden

Omeo Gum

Tree or mallee to 6 m. Bark persistent, grey, rough and fibrous on the lower trunk; smooth and green or greyish green above. Branchlets yellowish green. Juvenile leaves opposite, sessile, elliptic to roughly circular, greyish green and glaucous along the midribs. Adult leaves thick or thin and green, 7.5–15 × 2.5–3.8 cm, lanceolate, lateral veins indistinct, margins entire, apex acute, obtuse or rounded; petiole flattened, 1.2–2 cm long. Inflorescences solitary and axillary; umbellasters with 7–15 flowers. Flower buds ovoid or subglobular; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical, 0.4–0.5 cm diameter; valves three to four, flush or just exserted. Chippendale 1988. Distribution AUSTRALIA: Victoria (southeast). Habitat Along watercourses in high-altitude forest. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT330, NT350.

Plate 254. The green leaves of Eucalyptus moorei make an effective mass of foliage. It pays to site the daintier eucalypts where the wind shimmering through their leaves can be viewed and enjoyed. Image R. Unwin.

350

New Trees

Eucalyptus

1 cm

1 cm

Section II. Species Accounts

Eucalyptus

The Omeo Gum is a popular species and deservedly so, having spectacular large leaves on a small tree or large shrub that make it ideal for use as a screening plant. It is tolerant of some shade, and of both cold and humid heat, making it one of the few eucalypts suitable for the southeastern United States. In North Carolina, Tony Avent (pers. comm. 2007) has found it hardy to –18 ºC with only tip damage. As usual, circumstances can make a difference to survival: a plant grown by Frank Callia in Cincinnati is reported to have survived –27 ºC with minimal damage, only to freeze to the ground at –22 ºC another year (Hardy Eucalyptus Page 2004). It also seems to respond well to heat. The foliage has a habit of remaining juvenile for some time, even on apparently mature, flowering trees, and as it flushes reddish under the glaucous wax it is extremely attractive. Not the least of its charms, for those who like an aromatic garden, is its intense scent – a sort of ‘essence of eucalyptus’. As a mallee E. neglecta cannot be expected to achieve great height, and most specimens form a wide multi-trunked bush, but it achieved 13 m (18 cm dbh) between 1986 and 2008 at the Sir Harold Hillier Gardens, and 10 m in ten years at Plant Delights Nursery, North Carolina (T. Avent, pers. comm. 2008). Although fast-growing in warm climates it is much slower where cool: a bushy tree at Logan planted in 1966 is currently only 4–5 m tall. It can tolerate periodically damp ground (G. Cooper, pers. comm. 2007).

Eucalyptus nicholii Maiden & Blakely

Nichol’s Willow-leaved Peppermint

Tree to 18 m. Bark persistent, rough and fibrous, yellowish or greyish brown to grey throughout. Branchlets yellowish red. Juvenile leaves alternate, shortly petiolate, linear and greyish green. Adult leaves thin and dull greyish green to blue-green, 7.5–14 × 1–2.5 cm, narrowly lanceolate to lanceolate, lateral veins indistinct, margins entire, apex acuminate; petiole terete, 0.7–1.2 cm long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds ovoid or spindle-shaped; hypanthium 0.2 cm wide; stamens white or cream. Capsule hemispherical to conical, 0.3–0.4 cm diameter; valves three, exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (New England Tableland). Habitat Well-drained slopes and ridges with poor soils. USDA Hardiness Zone 9. Conservation status Not evaluated. Cross-reference K48.

Eucalyptus nicholii is a very ornamental tree with fine willowy growth and narrow leaves, growing rapidly for the first few years, but then slowing down. The orange-red bark and dark red young stems contrast well with the glaucous leaves. When crushed the leaves have a strong peppermint scent. Unfortunately trees grown from the normal seed sources are not particularly hardy, being killed at –8 or –9 ºC, and not resprouting, although hardiness does improve with maturity. From colder provenances they are much tougher – trees from 1200 m in the Central Tablelands of New South Wales, for example, surviving –11 to –14 ºC in the United States, though making a shorter and somewhat crooked tree (S. Hogan, pers. comm. 2007). It is very wind-resistant, and is a good choice for exposed sites (Hogan 2008). Its rather marginal hardiness has not stopped it being planted widely in the United Kingdom, as indeed it deserves to be, and many notable specimens in the southern counties are listed by TROBI, the tallest being one of 15 m on Battleston Hill at Wisley in 2000. A rather similar species, E. pulchella Desf. (White Peppermint) from Tasmania, also has narrow leaves on a weeping tree, but the foliage is so dense that the tree is not ‘see-through’. It is said to be even more beautiful than E. nicholii, but usually to be less hardy (Gum Group 2007). However it has survived three winters at Lullingstone Castle, achieving 5 m in that time, so it is clearly a species to investigate. E. niphophila (NOW E. pauciflora subsp. niphophila (Maiden & Blakely) L.A.S. Johnson & Blaxell) B136, S230, K50

351

Figure 36 (opposite). Eucalyptus neglecta: habit with flower buds and details of capsules.

352

Eucalyptus

New Trees

Eucalyptus nitens (H. Deane & Maiden) Maiden

Shining Gum

Tree to 70 m (occasionally 90 m). Bark generally smooth, shiny and yellowish white or grey throughout; may become dark, rough and flaky at the base of the trunk. Branchlets pinkish red. Juvenile leaves opposite, sessile, broadly lanceolate to ovate and glaucous. Adult leaves thick and glossy green, 13–24 × 1.5–2.5 cm, narrowly lanceolate to lanceolate, lateral veins distinct, margins entire, apex acuminate; petiole terete or channelled, 1.5–2.2 cm long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds ovoid or cylindrical; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule cylindrical to ovoid, often ribbed, 0.4–0.6 cm diameter; valves three to four, flush or slightly exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales, Victoria. Habitat Open forest (incl. pure stands) on slopes and mountain tops. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT326, NT352.

Plate 255. Beautiful patchwork bark on columnar trunks: Eucalyptus nitens at Ness Botanic Gardens. Image P. Williams.

Eucalyptus gunnii is often considered to be the fastest-growing tree in the British Isles but it is slow when compared to the growth rate achievable by E. nitens. In Oxfordshire Steve Verge (pers. comm. 2007) planted trees at 45 cm in April 2002. These put on 1.5 m of growth in the first year, 3 m in the second and 5 m in the third, and by 2006 were 16 m tall, forming magnificent straight trunks. Such a growth rate is not exceptional and there are fine tall trees throughout the British Isles, many having made big thick trunks as befits an important timber species. An exceptional grove is to be found in the Brentry area of the Hillier Gardens, where six specimens planted in 1986 are all over 20 m tall, with three over 30 m. The largest of these was measured by H. Brown in 2006 at 33.8 m tall with a dbh of 73 cm (Sir Harold Hillier Gardens database). This is not a tree for small gardens! Once established and maturing it is not damaged by frost in British conditions, but young plants are a little more tender. They will coppice up to the age of about four years, when the tree will begin to flower, but not thereafter. Good shining bark is visible from an early age and together with the good glaucous leaves makes this a very handsome tree. The only drawback is that it can shed branches.

Eucalyptus nova-anglica H. Deane & Maiden

New England Peppermint

Tree to 25 m. Bark rough, fibrous and grey or blackish on the trunk and larger branches; smooth and grey or pale brown above. Branchlets red. Juvenile leaves opposite, sessile, roughly circular to cordate and glaucous. Adult leaves thick, dull or semi-glossy green, 7.5–15 × 0.7–1 cm, narrowly lanceolate to lanceolate, lateral veins distinct, margins entire, apex acuminate; petiole terete, 1.5–2.5 cm long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds ovoid; hypanthium 0.4 cm wide; stamens white or cream. Capsule hemispherical to conical, sometimes glaucous, 0.4–0.5 cm diameter; valves three to four, exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (northeast), Queensland (extreme southeast). Habitat Poorly drained areas on slopes and in valleys, often with heavy soils. USDA Hardiness Zone 8. Conservation status Not evaluated.

Eucalyptus nova-anglica is regarded as being remarkably cold-tolerant considering its comparatively northern origin, and is said to be hardy to about –12 ºC (Hardy

Section II. Species Accounts

Eucalyptus

Eucalyptus Page 2004). It will resprout very vigorously if coppiced by frost (or other means). It was not damaged by the frost at Lullingstone in 2005. Growth is vigorous, trees achieving 6 m in three years in England and 10 m in four years in Oregon (Gum Group 2007). The rounded juvenile foliage is attractive and ‘fairly’ blue, changing to a duller green in the lanceolate adult phase. The only large specimen noted in the United Kingdom is at Marwood Hill, Devon, where in 2006 it was 27 m tall (21 cm dbh) (TROBI). This would seem to be a species with which to experiment more widely.

Eucalyptus obliqua L’Hér.

Messmate, Messmate Stringybark

Tree to 45–90 m, 1.2 m dbh. Bark grey to reddish brown, fibrous and furrowed throughout; shedding in ribbons. Branchlets red to maroon. Juvenile leaves ovate, short-acuminate and shiny. Adult leaves thick, dark glossy green, 10–15 × 1.5–3.3 cm, broadly lanceolate, falcate, lateral veins indistinct, margins entire, apex acute or obtuse; petiole channelled, 0.7–1.7 cm long. Inflorescences solitary and axillary; umbellasters with 11 flowers or more. Flower buds club-shaped; hypanthium 0.2–0.3 cm wide; stamens white or cream. Capsule ovoid, subglobular or barrel-shaped, 0.5–0.9 cm diameter; valves three to four, flush or included. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), Queensland (extreme southeast), South Australia (southeast), Tasmania, Victoria. Habitat Tall, open forest on hills and mountains between 0 and 1200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Cross-reference K48.

Eucalyptus obliqua is one of the largest gums, and while not one of the hardiest, is capable of becoming a big tree quite quickly in maritime Europe. In Oxfordshire young trees have grown 10–12 m since 2002 (S. Verge, pers. comm. 2007), and there are several specimens of over 20 m in Devon gardens, the tallest recorded being two of 23 m at Thorn House, Wembury in 2004 (TROBI). The new growth is spectacular, flushing red before turning green, and when mature the prolifically shedding soft bark has a sort of scruffy charm. It is not, however, totally undemanding in its requirements. It is rather tender when young, and the Gum Group (2007) recommend wrapping it in its first winter. Once established it can tolerate temperatures down as low as –10 ºC. It is also very calcifuge and flourishes best at pH 4–6, preferably where moisture is abundant year-round as it is intolerant of drought conditions.

Eucalyptus oreades R.T. Baker

Blue Mountains Ash

Tree to 30–40 m, 1.8 m dbh. Bark grey and fibrous at the base of the trunk; smooth and white, grey or yellow above, shedding in long ribbons. Branchlets red. Juvenile leaves ovate, dull greyish green. Adult leaves thick, shiny green, 11–17 × 1.5–2.3 cm, lanceolate, falcate, lateral veins indistinct, margins entire, apex acute or acuminate; petiole flattened, 1.5–2.2 cm long. Inflorescences solitary and axillary; umbellasters with seven flowers. Flower buds club-shaped and slightly curved; hypanthium 0.4–0.5 cm wide; stamens white or cream. Capsule pear-shaped or hemispherical or subglobular, 0.6–1 cm diameter; valves four to five, flush or included. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: New South Wales (Gibraltar Range, Blue Mts., Port Macquarie), Queensland (McPherson Range). Habitat Open forest on cliff tops and rock outcrops, between 750 and 1150 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated.

The Blue Mountains Ash is poorly known in cultivation, the only significant specimen seen in research for this book being at Logan, where it is a thin tree about 7 m tall from a 1990 accession of seed collected in New South Wales by P.D. Hind (no. 5860). Its most conspicuous feature is its flaking bark, peeling to reveal greyish-greenish white patches that are quite attractive. When attempted at Lullingstone Castle it has been chlorotic (T. Hart Dyke, pers. comm. 2007). It would seem to be worth seeking out seed from the coldest provenances and experimenting further with this species. E. ovata Labill. B134, S229, K50 E. parvifolia (NOW E. parvula L.A.S. Johnson & K.D. Hill) B135, S230, K50

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Eucalyptus pauciflora Sieber ex Spreng.

Cabbage Gum, Snow Gum, White Sallee

This species was described by Bean (B135) and Krüssmann (K50), and a key to the subspecies, based on that of Rule (1994), is provided below. 1a. Wax present on any of the following structures: juvenile leaves, branchlets, flower buds, fruits ............................................................................. 2 1b. Wax absent from all structures; Australia (Victoria: Baw Baw Plateau, Mt. Useful) ............................................ subsp. acerina Rule 2a. Flower buds pedicellate .................................................................................................................. 3 2b. Flower buds sessile; Australia (Victoria: Victorian Alps) ........................................ subsp. hedraia Rule 3a. Flower buds not angular .................................................................................................................. 4 3b. Flower buds angular; Australia (Australian Capital Territory; New South Wales: Jounama Peaks; Victoria) ......................................... subsp. debeuzevillei (Maiden) L.A.S. Johnson & Blaxell 4a. Longest adult leaves < 12 cm long, crowded on branchlets ............................................................. 5 4b. Longest adult leaves 12–22 cm long, sparse; Australia (New South Wales, Queensland, Tasmania, Victoria) ............................ subsp. pauciflora 5a. Adult leaves narrow-lanceolate to lanceolate-ovate, < 2 cm wide; Australia (Victoria: Mt. William Range) ...................................................... subsp. parvifructa Rule 5b. Adult leaves broad-lanceolate, ovate or elliptical, > 2 cm wide; Australia (New South Wales, Victoria) ............................ subsp. niphophila (Maiden & Blakely) L.A.S. Johnson & Blaxell

Eucalyptus pauciflora subsp. debeuzevillei

Jounama Snow Gum

(Maiden) L.A.S. Johnson & Blaxell Syn. E. debeuzevillei Maiden Subsp. debeuzevillei forms a multistemmed shrub or tree to 9 m tall (rarely 18 m). It differs from subsp. niphophila in that its juvenile and adult leaves are lanceolate rather than ovate. It differs from subsp. pauciflora in that the flower buds are glaucous. Chippendale 1988. Distribution AUSTRALIA: Australian Capital Territory (Brindabella Range), New South Wales (Jounama Peaks), Victoria (Falls Creek). Habitat Grassy subalpine woodland on steep slopes, plateaus and ridges. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT355.

The Snow Gums are not only about the hardiest of eucalypts but fortunately also among the most attractive for horticulture, their pale bark being the most outstanding feature. Of all of them, subsp. debeuzevillei is accounted as being probably the hardiest – by the Gum Group (2007) at least – with trees having been known to survive –25 ºC in Germany (G. Cooper, pers. comm. 2007), and very limited damage seen at the longterm trial plantations by the Forestry Commission at Thetford, Norfolk (Evans 1986). It should be noted, however, that this taxon has a relatively wide distribution, and not all provenances will give reliably hardy plants. In Oregon, material from some provenances has been killed at –7 ºC, but the population growing near the summit of Mount Ginini in the Australian Capital Territory has been known to experience –16 to –23 ºC in the wild, and trees from this source have resprouted from –30 ºC in Cincinnati (S. Hogan, pers. comm. 2007). It is from locations such as this that seed should be

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Plate 256. Eucalyptus pauciflora subsp. debeuzevillei forms treeline woodland on Mount Ginini, Australian Capital Territory. This subspecies is generally accounted the hardiest of all gum trees. Image R. Farrow.

sought. Seed is freely available in commerce and subsp. debeuzevillei is now seen in garden centres throughout the United Kingdom, usually as a gangly pot-bound young tree with a conspicuous label; it is also offered by many North American nurseries. Although not necessarily a large tree in the wild, it can achieve respectable sizes in cultivation. Several 16 m specimens are recorded throughout England by TROBI, including trees at Wisley and Marwood Hill, and there is one of 13–14 m at Logan. It will thrive best where there is excellent drainage. The botanical differences between subsp. debeuzevillei and the better-known subsp. niphophila are relatively slight and of minimal horticultural importance. The bark is almost equally good in subsp. debeuzevillei, forming striking patterns, and the young growths can be very white-waxy. A form from Mount Buffalo, Victoria has more rounded foliage than normal, and orange new growth (Gum Group 2007). E. perriniana F. Muell. ex Rodway B133, S229

Eucalyptus praecox Maiden

Brittle Gum

Syn. E. mannifera subsp. praecox (Maiden) L.A.S. Johnson Tree to 15 m. Bark smooth, white or grey and powdery throughout; shedding in short ribbons or large plates. Branchlets reddish green. Juvenile leaves alternate and petiolate, glaucous. Adult leaves thin, dull green or greyish green, 8–14 × 1–2 cm, lanceolate, falcate, lateral veins indistinct, margins entire, apex acute; petiole 1–1.5 cm long. Inflorescences solitary and axillary; umbellasters with 7–11 flowers. Flower buds ovoid and glaucous; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule globose or ovoid, 0.5–0.6 cm diameter; valves three to four, exserted. Chippendale 1988. Distribution AUSTRALIA: New South Wales (Central Tablelands). Habitat Dry, sclerophyllous woodland on shallow, sandy soils. USDA Hardiness Zone 9. Conservation status Not evaluated. Taxonomic note EUCLID3 (2006) treats this as E. mannifera subsp. praecox.

The Gum Group (2007) considers Eucalyptus praecox to be ‘interesting and decorative’ but not very hardy (less so than its relative E. elliptica) – a view that seems to be borne out by the absence of any large specimens in cultivation in our area. Young trees of 3–4 m in southern England are the largest known to members of the Group. Young trees at Lullingstone were killed by the November frost in 2005. The attractiveness of E. praecox emanates both from its good bark characters and its foliage, which

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can vary considerably in colour from dull green to rather bluish when mature, but emerges red. This is a species that deserves further experimentation and selection of the best hardy forms. E. pulverulenta Sims B130, S228

Eucalyptus radiata Sieber ex DC.

Narrow-leaved Peppermint

Tree to 10–30 m, 1 m dbh. Bark grey to greyish brown and shortly fibrous throughout. Branchlets orange-red. Juvenile leaves lanceolate and dull green. Adult leaves thin, green, 7–15 × 0.7–1.5 cm, lanceolate to linear, falcate or not, lateral veins distinct, margins entire, apex acute or acuminate; petiole terete, 0.5–1.5 cm long. Inflorescences solitary and axillary; umbellasters with 7–23 flowers. Flower buds club-shaped, green; hypanthium 0.2–0.3 cm wide; stamens yellow or cream. Capsule hemispherical or subglobular, 0.4– 0.7 cm diameter; valves three to four, flush or included. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Australian Capital Territory, New South Wales (southeast), Victoria (south central). Habitat Tall, open forest, between 50 and 1200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT356. Taxonomic note Eucalyptus radiata subsp. sejuncta L.A.S. Johnson & K.D. Hill occurs only in northeastern New South Wales and has broadly lanceolate leaves. Two species recently separated from E. radiata are E. robertsonii Blakely and E. croajingolensis L.A.S. Johnson & K.D. Hill. The former has linear to narrowly lanceolate adult and juvenile leaves and glaucous flower buds, while the latter has broad-lanceolate, dull blue adult and juvenile leaves and glaucous flower buds (Hill & Johnson 1991a).

Plate 257. Dense masses of flowers wreathe the shoots of Eucalyptus radiata. Image R. Farrow.

Eucalyptus radiata is chiefly valued by the Gum Group (2007) as a stool for the herbaceous border, resprouting vigorously when coppiced, when it produces densely clad, somewhat weeping shoots. At Cistus Nursery this character was discovered when their specimen was run over by the truck exchanging their portable toilets (S. Hogan, pers. comm. 2007). If not coppiced (by whatever agency) it can make a fast-growing tree of some stature, a specimen of 16 m being recorded from Cotehele, Cornwall in 2006 (TROBI). It is not, however, very hardy, with bark being split at only –6 ºC, and is intolerant of any prolonged subzero temperatures. At Lullingstone Castle in 2005 both E. radiata and the related E. robertsonii were dead even before the infamous mid-November frosts (T. Hart Dyke, pers. comm. 2007).

Eucalyptus regnans F. Muell.

Australian Mountain Ash, Swamp Gum

Tree to 55–75(–100) m (specimens taller still have been recorded); 2.5 m dbh. Bark rough and fibrous on the lower trunk; smooth and white or greyish green above, shedding in long ribbons. Branchlets greenish red. Juvenile leaves alternate, petiolate, and ovate to broadly lanceolate. Adult leaves green, 9–14 × 1.6–2.7 cm, lanceolate to broadly lanceolate, falcate, lateral veins distinct, margins entire, apex acuminate; petiole channelled, 1.2–2.2 cm long. Inflorescences axillary and paired; umbellasters with 9–15 flowers. Flower buds club-shaped; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule conical or pear-shaped, 0.4–0.7 cm diameter; valves three, flush or partially excluded. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Tasmania (Huon and Derwent River valleys), Victoria (southeast). Habitat Tall, open forest, between 150 and 1100 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT357.

Once upon a time, but long ago, specimens of Eucalyptus regnans were the world’s tallest trees, including well-attested individuals over 130 m and claims of some trees over 150 m (Mabberley 1997a). Unfortunately most of these giants were destroyed

Section II. Species Accounts

Eucalyptus

as settlers cleared forest for farmland, and destruction by logging continues apace, but some giant trees still survive, including specimens of over 90 m in both Victoria and Tasmania. The current champion is 99 m in Tasmania (Tallest Trees 2006). For comparison, the champion Sequoia sempervirens, the Hyperion tree, discovered in 2006 in Redwood National Park, California is 115 m tall (Wikipedia 2008c). The adventurous and/or megalomaniac in our area may thus enjoy the chance to grow E. regnans that the current mild climate affords. So far even the impressive 39 m tree at Mount Stewart, Co. Down, recorded in 1991 by Alan Mitchell (TROBI), has been somewhat short of the mark (that specimen has now gone) – but it is clear that in favourable conditions in the wetter, milder parts of the British Isles it can become a very good tree indeed. A fine specimen of Victorian origin at Logan, planted in 1990, was 15–20 m tall (dbh 34 cm) when observed in 2006, and growing vigorously. Eucalyptus regnans is considered by the Gum Group (2007) to be slower than E. nitens for the first 20 years, but thereafter to grow faster. In Oxfordshire it has grown to 12 m in four years, whereas E. nitens has achieved 16 m in the same time (S. Verge, pers. comm. 2007). It has survived there undamaged at the minimum recorded temperature (–7 ºC) during this period, and is certainly hardier than E. globulus in central England (Gum Group 2007). Provenance is important for hardiness, however, and seedlings from parents of unselected origin growing in California have not been successful in Oregon (S. Hogan, pers. comm. 2007).

Eucalyptus remota Blakely

Kangaroo Island Mallee Ash

Mallee to 4 m. Bark fibrous close to the base; smooth and white or grey above. Branchlets yellowish red. Juvenile leaves ovate to lanceolate and greyish green. Adult leaves thick and dark green, 7.5–15 × 1.9–3.2 cm, lanceolate, lateral veins distinct, margins entire, apex acuminate; petiole channelled, 1.4–1.7 cm long. Inflorescences simple and axillary; umbellasters with 9–20 flowers. Flower buds club-shaped; hypanthium 0.3–0.5 cm wide; stamens white or cream. Capsule hemispherical (rarely subglobular), 0.5–0.8 cm diameter; valves three to five, almost flush. Chippendale 1988. Distribution AUSTRALIA: South Australia (Kangaroo Is.). Habitat Mallee scrub. USDA Hardiness Zone 8. Conservation status Not evaluated.

Eucalyptus remota is rather rare in cultivation, the only specimen traced being one at Logan planted in 1995. In 2006 this was only 5 m tall and leaning, having probably been suppressed by its neighbours, but the crown was healthy and thick – suggesting that in another situation it would be more successful. A notable feature was that the tree had a distinctly reddish appearance, derived from the coloration of the stems, petioles, leaf margins and dying leaves, as well as the ruddy bark. It would certainly seem to deserve wider trial, although its coastal origin does not portend great hardiness.

Eucalyptus risdonii Hook. f.

Risdon Peppermint

Shrub, mallee or tree to 8 m. Bark white, grey or yellowish, sometimes with greyish pink patches, smooth throughout. Branchlets glaucous, with characteristic scars encircling them. Juvenile leaves sessile, glaucous, initially free and elliptical, later connate and ovate. Adult leaves not often seen; green to glaucous, 6.5–10 × 1.5–2 cm, lanceolate, lateral veins indistinct, margins entire, apex acuminate; petiole terete, 0.6–1.5 cm long. Inflorescences axillary and solitary; umbellasters with 7–15 flowers. Flower buds club-shaped, glaucous;

357

Plate 258. Specimens of Eucalyptus regnans were once the tallest trees in the world. These are in Tasmania – where the species remains the target of loggers, who replant its sites with other species instead of permitting natural regeneration. Image J.R.P. van Hoey Smith.

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hypanthium conical to pyriform, 0.2–0.3 cm wide; stamens white. Capsule hemispherical to subglobose, glaucous, 0.7–0.9 cm diameter; valves (three to) four, level or included. Brooker & Kleinig 1983, Chippendale 1988. Distribution AUSTRALIA: Tasmania (between Risdon and Cambridge). Habitat Grows in (almost) pure stands in open shrubland. USDA Hardiness Zone 9–10. Conservation status Not evaluated.

The Gum Group (2007) consider Eucalyptus risdonii to be one of the most beautiful trees of the genus, but bemoan its tenderness – although this can vary. In the United Kingdom it will occasionally survive for a few years, the current champion being a poor 6 m individual at Marwood Hill (measured by Owen Johnson in 2006 for TROBI), but it is more useful as a potted specimen. In mild climates, such as along the southern Oregon coast (an anomalous Zone 10), it will form a good tree (S. Hogan, pers. comm. 2007).

Eucalyptus rodwayi R.T. Baker & H.T. Sm.

Swamp Peppermint

Tree to 25 m. Bark compact, grey, rough and fibrous or with white, flaky patches on the trunk and larger branches; smooth and white above. Branchlets red. Juvenile leaves sessile or petiolate, lanceolate. Adult leaves thick and glossy green, 5–12 × 1–1.5 cm, lanceolate, falcate, lateral veins indistinct, margins entire, apex acute or obtuse; petiole terete, 0.7–1.4 cm long. Inflorescences simple and axillary; umbellasters with 7–11 flowers. Flower buds ovoid or spindle-shaped; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical or conical, 0.3–0.4 cm diameter; valves three to four, flush or partially exserted. Chippendale 1988. Distribution AUSTRALIA: Tasmania (central and east). Habitat Swampy valleys. USDA Hardiness Zone 8. Conservation status Not evaluated. Taxonomic note Very similar to E. aggregata, but with more flowers in the umbellasters. Some seed sources in the United Kingdom consistently supply E. aggregata seed instead of true E. rodwayi (Gum Group 2007).

Eucalyptus rodwayi is regarded as being very hardy and tolerant of a range of conditions that can be challenging for eucalypts, including calcareous soil. It is capable both of withstanding drought and of growing in wet ground, and can form a good potted specimen. Part of this adaptability may be due to its having strong lateral roots rather than a tap root, and it is said to be able to tolerate root disturbance (Gum Group 2007). It will develop into a substantial tree, its canopy formed by short, stiffly held and rather thick leaves. Young plants have survived well at Lullingstone Castle, and there are good big trees throughout the British Isles, including notable specimens at Kew and at Westonbirt. It does particularly well in Ireland, where there are good trees of over 20 m at the John F. Kennedy Arboretum, and the current champion is 24 m (59 cm dbh), at Mount Usher (TROI/TROBI).

Eucalyptus rubida H. Deane & Maiden

Candlebark

Tree 30–40 m, 1 m dbh. Bark smooth, white, red or reddish brown throughout; wild specimens often have horizontal insect scars. Branchlets greenish yellow to red. Juvenile leaves sessile, opposite, circular or elliptical and glaucous. Adult leaves thick and dull greyish green or glaucous, 9–15 × 0.8–1.5 cm, lanceolate to narrowly lanceolate, falcate, lateral veins distinct, margins entire, apex acute; petiole terete, 1.3–2.5 cm long. Inflorescences simple and axillary; umbellasters with three to seven flowers. Flower buds ovoid and often glaucous; hypanthium 0.4–0.5 cm wide; stamens white or cream. Capsule hemispherical to subglobular, 0.5–0.7 cm diameter; valves three to four, exserted. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), South Australia (Mt. Lofty Range), Tasmania (eastern plateau), Victoria (east). Habitat Woodland and open forest with shallow soils on plateaus, tablelands and hills, between 75 and 1400 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT359. Taxonomic note Similar to E. dalrympleana, but with glaucous juvenile leaves and white, red or reddish brown bark.

In cultivation distinctions have not been made between the four subspecies of Eucalyptus rubida, but as these seem to be useful and perhaps a pointer to different provenances, a key is provided below (modified from that of Hill & Johnson 1991a).

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359

1a. Umbellasters three-flowered ............................................................................................................ 2 1b. Umbellasters seven-flowered; Australia (New South Wales, Victoria) ..................... subsp. septemflora L.A.S. Johnson & K.D. Hill 2a. Trunk smooth to base; juvenile leaves circular ................................................................................. 3 2b. Trunk with short, black stocking at base; juvenile leaves elliptical; Australia (New South Wales: Northern Tablelands) .............. subsp. barbigerorum L.A.S. Johnson & K.D. Hill 3a. Coppice shoots terete; juvenile leaves mostly < 4 cm wide; Australia (South Australia, Tasmania) ........................................................................ subsp. rubida 3b. Coppice shoots quadrangular; juvenile leaves mostly > 5 cm wide; Australia (New South Wales: Mt. Canobolas) ......... subsp. canobolensis L.A.S. Johnson & K.D. Hill

The variability seen in Eucalyptus rubida should probably be more carefully investigated in horticulture; what is not in doubt, however, is that it can be an extremely beautiful tree. The rounded juvenile foliage is often an excellent blue colour, but may also show red tints as it flushes. In mature specimens the often multicoloured smooth bark is an important feature. When happy it can grow fast, young trees in Portland, Oregon achieving 10 m in five years (S. Hogan, pers. comm. 2007). It is reasonably hardy – there are mature specimens at the Celyn Vale Eucalyptus Nurseries near Corwen, Clwyd – but the largest recorded in the British Isles, at Castlewellan, Co. Down, was 25 m (58 cm dbh) in 2000 (TROI).

Eucalyptus saligna Sm.

Sydney Blue Gum

Tree to 55 m, 1.2–1.5 m dbh. Bark white or blue-grey, smooth, but rough, greyish brown and flaky at the base and up the trunk to 4 m. Branchlets green. Juvenile leaves ovate to broad-lanceolate, glossy green, petiolate. Adult leaves glossy dark green, 9–25 × 2–3 cm, broad-lanceolate, lateral veins obscure, margins entire, apex falcate; petiole flattened or channelled, 1.5–2.5 cm long. Inflorescences axillary and solitary; umbellasters with 7–11 flowers. Flower buds fusiform or ovoid; hypanthium hemispherical, cylindrical or campanulate, 0.3–0.4 cm wide; stamens white or cream. Capsule cylindrical, campanulate or subpyriform, 0.4–0.7 cm diameter; valves three to four, exserted. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales, Queensland. Habitat Wet forest, often on slopes; primarily coastal. USDA Hardiness Zone (9–)10. Conservation status Not evaluated.

The Sydney Blue Gum offers only a slight chance of success in most of our area, being reliably killed by frost at around –5 ºC, so that it is suitable only for the very mildest locations. It does, however, grow very fast, putting on 10–12 m in four years in Oregon (S. Hogan, pers. comm. 2007), and while doing so is attractive, the new growth appearing red before turning a good glaucous blue. As the name suggests, Eucalyptus saligna has a distinctly willow-like appearance when young, but mature specimens are beautifully straight, and important for timber.

Plate 259. Eucalyptus rubida is a shapely hardy species, with good bark and foliage characters. This is subsp. rubida, at Burra, South Australia. Image R. Farrow.

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Eucalyptus sideroxylon A. Cunn. ex Woolls

Mugga, Red Ironbark

Syn. E. sideroxylon var. rosea Rehder Tree to 35 m. Bark reddish brown to black, hard, deeply furrowed throughout, or smooth and white on upper branches. Branchlets green. Juvenile leaves alternate, green or greyish green, linear to lanceolate or ovate, petiolate. Adult leaves alternate, green, greyish green or blue-green, 7–14 × 1.2–1.8 cm, lanceolate, lateral veins indistinct, margins entire, apex acuminate or uncinate; petiole terete, 1–2 cm long. Inflorescences axillary and solitary; umbellasters with three or seven flowers. Flower buds ovoid, beaked; hypanthium ovoid to hemispherical; stamens white, cream, yellow, pink or red. Capsule globose or hemispherical or ovoid, 0.5–0.9 cm diameter; valves five to six, included. Chippendale 1988, Hill 2004. Distribution AUSTRALIA: New South Wales, Queensland, Victoria. Habitat Sclerophyllous woodland on poor soils. USDA Hardiness Zone 10. Conservation status Not evaluated. Illustration NT360. Taxonomic note In subsp. sideroxylon the umbellasters are seven-flowered, while in subsp. tricarpa L.A.S. Johnson they are three-flowered.

Plate 260. Eucalyptus sideroxylon is not really hardy in our area, but rising temperatures may make it more widely growable. Not all have such good red flowers. Image J.R.P. van Hoey Smith.

Figure 37 (opposite). Eucalyptus stellulata: habit with fruits and flower buds, with detail of capsules.

Eucalyptus sideroxylon is another species that is only marginally hardy in our area, but is a popular street and landscaping tree in Australia and southern California, valued for its upright growth, reddish bark and handsome appearance. The flowers are normally white but can be yellow, pink or red, and it is this variation that makes it interesting to enthusiasts seeking the elusive hardy red-flowered gum tree. Alas, it is not quite hardy enough, with potted plants grown under the protection of a polytunnel in Kent suffering slight damage in winter (G. Blunt, pers. comm. 2007). For John Purse (pers comm. 2007), specimens from high-altitude provenance are surviving in north Kent, though growing very slowly, and subsp. tricarpa flowered for him in Cornwall, in 2007. If tried outdoors this tree should be afforded a very favourable site, and in coastal or inner-city locations it may prove satisfactory. E. sieberiana (NOW E. sieberi L.A.S. Johnson) K50 E. simmondsii (NOW E. nitida Hook. f.) B129, S228, K50

Eucalyptus stellulata Sieber ex DC. Plate 261. Eucalyptus stellulata forms a broad, multistemmed tree. The red new twigs show beautifully in autumn sunlight – here at Kew in November 2007. Image J. Grimshaw.

Black Sallee

Tree to 15(–20) m, or more. Bark smooth throughout or shortly fibrous below, dark grey, greyish black or olivegreen. Branchlets yellowish red. Juvenile leaves sessile and opposite, though becoming petiolate, circular to ovate and green. Adult leaves thick and glossy green, 5–9 × 1.3–2.3 cm, elliptic to broadly lanceolate, lateral veins distinct, margins entire, apex acute or obtuse; petiole terete or flattened, 0.4–0.9 cm long. Inflorescences simple and axillary; umbellasters with 7–23 flowers. Flower buds spindle-shaped; hypanthium 0.2–0.3 cm wide; stamens white or cream. Capsule globular, 0.5–0.7 cm diameter; valves three, included. Chippendale 1988. Distribution AUSTRALIA: New South Wales (east), Victoria (east). Habitat Open woodland on flat areas between mountains and tablelands. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT360, NT361. Taxonomic note Similar to E. mitchelliana and E. moorei, but with broader leaves.

Eucalyptus stellulata has much to recommend it for temperate gardens. Not least among its favourable attributes is its cold tolerance, which is not far short of that of the hardier E. pauciflora taxa, but E. stellulata will grow in damper sites than those will tolerate (though any moisture in the soil should not be stagnant). It will tolerate seasonally boggy conditions in the United Kingdom (G. Cooper, pers. comm. 2007). As always, planting young will maximise stability, especially in slightly soft ground. The mature tree tends to be short and slightly crooked, often with a somewhat pendulous and twisted look. It is not fast-growing, one specimen at Kew planted in 1972 having reached about 15 m at the time of writing. This tree is wider than it is tall, with heavy

Section II. Species Accounts

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1 cm

1 cm

361

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New Trees

branching from near the base, and has the dense canopy of dull green leaves associated with the species. Its most beautiful character, however, is its bark, which is basically dull dark grey but flakes in large rounded plates to leave greenish patches that give it a lovely swirly cetacean effect. There are good large specimens throughout the British Isles, the champion being one of 21 m (52 cm dbh) at Knoll Gardens, Dorset in 2006 (TROBI). As a young specimen in pots it is particularly susceptible to attack by Vine Weevil larvae (Otiorhynchus sulcatus) (T. & M. Milton, pers. comm. 2007).

Eucalyptus subcrenulata Maiden & Blakely Tasmanian Alpine Yellow Gum Tree to 18 m. Bark smooth throughout, grey to white or yellowish green. Branchlets yellowish green. Juvenile leaves green, sessile or short-petiolate, opposite, elliptic to ovate (rarely orbicular), margins crenulate. Adult leaves alternate, shiny green, 5–10 × 1.5–2.5 cm, lanceolate, lateral veins indistinct, margins subcrenulate, apex acuminate; petiole terete, 1.5–2.5 cm long. Inflorescences axillary and solitary; umbellasters with three flowers. Flower buds ovoid, slightly wrinkled, 0.3–0.4 cm long; hypanthium campanulate, 0.4–0.5 cm wide; stamens white. Capsule hemispherical to campanulate, sometimes two-ribbed, 0.5–0.8 cm diameter; valves three to four, flush or exserted. Chippendale 1988. Distribution AUSTRALIA: Tasmania (between Lake Fenton and Lake Dobson). Habitat Occurs at altitudes above 800 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT362.

Plate 262. The beauty of the small flowers of Eucalyptus subcrenulata is revealed by this close-up image, which also shows the unusual dark green leaves. Image R. Unwin.

Eucalyptus subcrenulata brings a welcome change of foliage colour, having leaves that are a glossy dark green instead of the usual greyish colour expected in the genus. It also has excellent bark, reddish when the tree is young but becoming smooth silvery grey and cream, flaking to reveal patches of yellow-orange or green. It forms an upright, columnar specimen, growing quite rapidly, and in Oregon has achieved 8 m in three and a half years (S. Hogan, pers. comm. 2007). The white flowers, appearing in late summer, contrast well with the dark foliage. Its origin in damp conditions in Tasmania brings many advantages, particularly its wide-spreading and very stable root system, and its adaptability to garden conditions. It is hardy to about –12 ºC but below that will suffer dieback of the trunk, although sprouting from the lignotuber has occurred after temperatures that dipped below –20 ºC (Hogan 2008). There are several fine specimens in the Hillier Gardens, of which the largest (planted in 1981) was 21.4 m (35 cm dbh) in 2008.

Eucalyptus tenuiramis Miq.

Silver Peppermint

Tree 8–25 m, 1 m dbh. Bark whitish grey to yellow, smooth throughout. Branchlets pinkish red to white. Juvenile leaves ovate to almost circular, connate and glaucous. Adult leaves thin and greyish green or glaucous, 5.5–13 × 0.9–2.5 cm, elliptic to broadly lanceolate, lateral veins indistinct, margins entire, apex acuminate or hooked; petiole terete or angular, 0.7–1.2 cm long. Inflorescences simple and axillary; umbellasters with 11–15 flowers. Flower buds club-shaped and glaucous; hypanthium 0.3–0.4 cm wide; stamens white or cream. Capsule hemispherical to conical, glaucous, 0.6–1.1 cm diameter; valves four, flush. Boland et al. 1984, Chippendale 1988. Distribution AUSTRALIA: Tasmania (eastern and southern mainland, Flinders Is.). Habitat A component of open forest or forming pure stands on hills and in lowlands, between 0 and 450 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated.

The weeping habit gives young trees of Eucalyptus tenuiramis a very elegant appearance, especially when the sun catches their pendulous tresses of silver leaves. As they mature, however, they straighten up and the leaves darken, so that an older specimen is not particularly exciting. The species is not very hardy – all of Tom Hart Dyke’s young trees were killed in November 2005 (pers. comm. 2007) – but once established it

Section II. Species Accounts

Eucalyptus

363

seems to gain some hardiness. The largest specimen in the United Kingdom is at Kew. Grown from seed collected by Ken Hill in Tasmania in 1988, this has two straight trunks from the base, and was measured at 13 m in 2001 (TROBI). E. urnigera Hook. f. B137, S231, K50

Eucalyptus viminalis Labill.

E. vernicosa Hook. f. K50

Manna Gum, Ribbon Gum, White Gum

This species was described by Bean (B138) and Krüssmann (K50).

Eucalyptus viminalis subsp. cygnetensis Boomsma

Rough-barked Manna Gum

Subsp. cygnetensis differs from typical E. viminalis in that the bark on the trunk and larger branches is rough (vs. smooth in subsp. viminalis) and the umbellasters have seven flowers (vs. three flowers). Chippendale 1988. Distribution AUSTRALIA: South Australia (Eyre Peninsula, Kangaroo Is., extreme southeast), Victoria (Grampians). Habitat Open forest and woodland in flat or gently undulating country. USDA Hardiness Zone 9. Conservation status Not evaluated.

The nominate subsp. viminalis is rather tender, but can form immense trees in favoured parts of our area: Johnson (2007) records up to 43.5 m at Mount Usher! There is no real reason to suppose that subsp. cygnetensis will be very much hardier, but it has been attempted on several occasions in recent years. It has died at Logan and at Lullingstone Castle (T. Hart Dyke, pers. comm. 2007). It is, however, very fast-growing (to 180 cm in the first year), so in very mild localities it has a sporting chance of forming a good specimen quickly and thus being better able to withstand frosts.

CUNONIACEAE

EUCRYPHIA

Cav.

There are seven species of Eucryphia, three in mainland Australia, two in Tasmania and two in Chile (Forster & Hyland 1996). They form columnar trees or shrubs with glabrous or pubescent branchlets and sticky, resinous terminal buds. The leaves are evergreen (rarely deciduous in cultivation), opposite and simple or pinnate. Stipules are always present, though they are caducous. The flowers are produced singly or, less often, in small clusters. They are hermaphrodite and 4-merous, with an open bowl of white petals. The calyx lobes are imbricate and united at their apices; they detach at floral maturity by abscising at the base, forming a four-lobed calyptra. The fruit is a woody capsule with distinctive persistent styles (Bausch 1938, Dress 1956, Wright 1983, Harden 2000a). Eucryphia are justifiably popular in milder areas for their evergreen foliage and white flowers: the larger species are among the most attractive of evergreen trees hardy in our area. Most are fully described in standard works, but two were discovered relatively recently in Queensland. Eucryphia wilkiei was first found in 1970, and has been introduced to the nursery trade (see description below), but the 1994 discovery, E. jinksii P.I. Forst., is not known to be in cultivation, except in Australian botanical gardens. It is a tree to 25 m, with white, fragrant flowers 5 cm across.

Plate 263. More experimentation is needed to assess the hardiness of Eucryphia wilkiei, which comes from Queensland. Image K. Gillanders.

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Eucryphia

New Trees

E. cordifolia Cav. B140, S232, K52 E. glutinosa (Poepp. & Endl.) Baill. B140, K52 E. ×hillieri Ivens B142, S232, K52

Eucryphia milliganii Hook. f.

E. ×hybrida Bausch K53 E. ×intermedia Bausch B141, K53 E. lucida (Labill.) Baill. B142, S232, K53 E. lucida × E. cordifolia B143

Dwarf Leatherwood

Shrub or tree to 14 m, rather densely branched and with a columnar habit. Bark smooth and blackish brown. Branchlets light brown, terete to ridged, glabrous to pubescent and resinous. Leaves evergreen and leathery, opposite and crowded, simple, 0.4–1.4 × 0.2–0.6 cm, elliptic to oblong, upper surface dark green and glossy, lower surface glaucous and glabrous, venation conspicuous on both surfaces, five to seven secondary veins on each side of the midvein, margins entire, apex strongly emarginate; petiole to 0.2 cm long, glabrous; stipules ovate, blackish brown, to 0.1 cm long. Monoecious; flowers hermaphrodite, pedicellate, solitary and axillary, subtended by brown bracts; petals white, to 0.8 cm long. Fruit a dark brown woody or leathery capsule to 1 cm long, with four to five valves; each valve holding one to two winged seeds. Flowering January to May, fruiting March to July (Australia). Bausch 1938. Distribution AUSTRALIA: northern Tasmania. Habitat To 1050 m asl in alpine areas. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT364. Cross-references B142, K53. Taxonomic note The two Tasmanian species of Eucryphia, E. milliganii and E. lucida (Labill.) Baill., are closely related and readily form hybrids (Eucryphia ×hybrida) in the wild (Bausch 1938). Both may be found in horticulture. Some authors consider E. milliganii to be merely a stunted, alpine form of E. lucida, though this is disputed (Bausch 1938, Dress 1956).

Plate 264. The daintiness of Eucryphia milliganii is deceptive, as it can form a substantial but neat columnar tree. Image P. Baxter.

Eucryphia milliganii was introduced by Harold Comber in 1929 but received only an undeservedly short note from Bean (1981a). It is a most attractive small tree, forming a column of dense small dark leaves sprinkled over with the pure white flowers, perhaps more resembling a myrtle than other eucryphias. There is an exceptionally fine example at Logan House (adjacent to Logan Botanical Garden), approximately 9 m tall in 2006 (dbh 32 cm), and covered in flowers when seen in late July. TROBI records a scattering of good specimens along the western fringes of the British Isles, but it also grows well away from the mildest areas (for example, at the Hillier Gardens). A cool site with abundant moisture and soil that is more or less lime-free seem to be important. Its frost tolerance is not known, but –10 ºC is suggested as a limit for the closely related E. lucida (Hogan 2008). It seems to be rare in Europe, and also in the United States although it is in cultivation in the western states, where it should do well in milder coastal areas.

Eucryphia milliganii subsp. pubescens R.W. Barnes, G.J. Jordan, R.S. Hill & C.J. McCoull This subspecies differs from typical E. milliganii in having ovate leaves with a pubescent underside, a dense fringe of trichomes on the leaf margins, and white or pink flowers. Barnes et al. 2000. Distribution AUSTRALIA: southern Tasmania. Habitat As for typical E. milliganii. USDA Hardiness Zone 8. Conservation status Not evaluated.

The broader leaves with their hairy undersides make this taxon easily distinguishable from subsp. milliganii. It is represented in cultivation by the clone ‘Pink Whisper’, discovered by Alan Gray and Ken Gillanders in Tasmania in 1976, which has pale pink flowers (Coombes 2007). This clone has also been attributed to E. ×hybrida (Seaforde Gardens 2007). Cuttings of ‘Pink Whisper’ were brought home from Australia by Sir Harold Hillier in 1977,

Section II. Species Accounts

Eucryphia

but it remains rare. There is a 4 m specimen at the Hillier Gardens, and it is commercially available in the United Kingdom. E. moorei F. Muell. B143, S232, K53

E. ×nymansensis Bausch B143, S232, K53

Eucryphia wilkiei B. Hyland Shrub or small tree 3–4 m; densely branched with a rounded crown. Branchlets villous, never resinous. Leaves evergreen and leathery, opposite, simple or compound with two to three (to five) leaflets; leaflets 2–4.5 × 0.3–1.2 cm, elliptic-oblong to lanceolate-oblong, upper surface dark green and glossy, lower surface glaucous, 12–20 secondary veins on each side of the midvein, margins entire, apex acute; petiole 0.3–0.5 cm long, villous; stipules lanceolate, 0.4–0.6 cm long, caducous. Flowers solitary, axillary, pedunculate; peduncle densely tomentose, four to five brown bracts subtending each flower, bracts covered in silky hairs; sepals four, lanceolate, decussate, outer two densely tomentose, inner two covered with silky hairs; petals four, white, 1.2–1.5 cm long and wide; stamens numerous (~150). Capsule somewhat woody, ~1 × 0.7–0.8 cm with seven to nine valves; capsule hairy on the outside. Forster & Hyland 1997. Distribution AUSTRALIA: northeastern Queensland (Mt. Bartle Frere). Habitat Vine thickets among large granite boulders, between 1200 and 1400 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated (IUCN), but in Australia this species is considered vulnerable due to its extremely limited distribution (Dept. of Environment, Water, Heritage & Arts 2008). Illustration Forster & Hyland 1997; NT363.

The discovery of Eucryphia wilkiei (and later E. jinksii ) in Queensland extended the range of the genus into subtropical areas. This is not a good indication for hardiness, but as E. wilkiei is in cultivation both in Australasia and the United Kingdom it has been included here. It was found in 1970 growing at the summit of Mount Bartle Frere in Queensland, at an altitude of 1200–1400 m – high enough to give a hope of hardiness. A few specimens have been attempted in our area, and there is one report of it surviving a mild winter (Seaforde Gardens 2007), but its long-term prospects have yet to be assessed. It flowers at a very young age, and resembles E. moorei (Seaforde Gardens 2007).

HAMAMELIDACEAE

EXBUCKLANDIA

R.W. Brown

Exbucklandia comprises four species of evergreen trees in southeast Asia. The branchlets are stout, with distinct nodes, and bear alternate leaves subtended by conspicuous stipules which leave a large scar on falling. The leaves are simple or palmately three- to five-lobed on young growth, thickly leathery, with palmate venation and an entire margin. The flowers are borne in small (7- to 16-flowered) pedunculate capitate or racemose inflorescences in the leaf axils, and are either hermaphrodite or only female, with or without small white linear petals; in hermaphrodite flowers there are numerous stamens bearing two-locular anthers, but female flowers are composed only of the gynoecium with three styles. The infructescence is rounded, with several loculicidal capsules, each locule bearing five to seven seeds of which only the lower one to two are fertile and bear a narrow wing. The curious name results from the original name Bucklandia having been invalidly published by Robert Brown. William Buckland (1784–1856) was both Dean of

365

366

Exbucklandia

New Trees

1 cm

A

1 cm

1 cm

B

C

D

Section II. Species Accounts

Exbucklandia

367

Westminster and Professor of Mineralogy at Oxford; the change to Exbucklandia, by the American botanist Roland W. Brown (Veldkamp 1998, Zhang 1999), seems entirely appropriate for the notoriously eccentric Buckland. (His son Frank was even worse.) Only one species, E. populnea, is established in cultivation, although seed of E. tonkinensis (Lecomte) H.T. Chang has been collected recently in Vietnam (D. Hinkley, pers. comm. 2006).

Exbucklandia populnea (R. Br. ex W. Griffith) R.W. Brown

Malayan Aspen

Syn. Bucklandia populnea R. Br. ex W. Griffith, Symingtonia populnea (R. Br. ex W. Griffith) Steenis Tree 16–20(–30) m. Branchlets pubescent, green when young. Stipules large and conspicuous, especially on vigorous new shoots, 2–3 × 1–2 cm, elliptic to obovate. Leaves alternate, 10–17 × 9–13 cm, broadly ovate, sometimes weakly three-lobed, apex acuminate, base broadly cuneate, margins entire, slightly glossy dark green, tomentose when young, more or less glabrous when mature; petiole 3–6 cm, longer on young shoots. Inflorescences capitate on short peduncles or occasionally racemose, two to five in leaf axils, each with 8–13 flowers. Flowers hermaphrodite or female. Hermaphrodite flowers have no sepals but five linear petals, 2–3 mm long, and 10–15 stamens, 5 mm long: these form an inflorescence looking like a mass of stamens, although styles are also present. Female flowers have no sepals and no petals, so are composed only of three yellow-brown styles and gynoecia surrounded by a ring of lobules. Capsules ellipsoid, 7–9 × 5–6 mm, smooth, dehiscing above middle. Seeds narrowly winged. Flowering May to July, fruiting August to October (China). Kaul & Kapil 1974, Zhang et al. 2003b. Distribution BHUTAN; CHINA: Guangxi, Guizhou, Xizang, Yunnan; INDIA; INDONESIA; MALAYSIA; MYANMAR; NEPAL; SIKKIM; THAILAND; VIETNAM. Habitat Slopes in evergreen forests, c.1200(–2500) m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated (IUCN). The white, soft but durable timber is used in India, and the tree is also planted for afforestation in Sumatra. Illustration NT366, NT367.

Described as ‘a large poplar on steroids’ when mature (Hudson 2004), Exbucklandia populnea is a most distinctive and interesting tree, although in cultivation no specimens have yet reached the stature of even a small poplar. The first introductions to the West, by George Forrest, did not become established (Hudson 2004), the current stock having been introduced in more recent years. An early collection is represented by a specimen at the University of California Botanical Garden at Berkeley, derived from a gathering by B. Bartholomew in Bhutan in 1974. This is approximately 7.5 m tall with a spread of 4.5 m (Hogan 2008). Since then the species has achieved a reasonable distribution in milder gardens in the United States, where it is commercially available – although in the absence of fresh seed it is very difficult to propagate, as cuttings are extremely slow to root (Hogan 2008). The largest seen in research for the current work is a specimen of 5 m planted against the gable end of Tony Avent’s house at Plant Delights Nursery, Raleigh, North Carolina, now reaching above the roof line. This was grown from seed obtained from the Kunming Botanical Garden in 1996 and was planted out in 1999, since when it has withstood –10 ºC with only leaf-tip damage (T. Avent, pers. comm. 2006). Clearly thriving in the North Carolina heat, it seems also to do quite well in sheltered sites such as the woodland garden at Heronswood Nursery. Heronswood has sold Dan Hinkley’s collection (DJHC 549) from 1600 m in Yunnan in 1996. In Europe E. populnea is very rare, but it is growing – very fast – at Tregrehan, reaching 3 m in three years after accession. It clearly enjoys a mild, moist situation.

Plate 265. Exbucklandia populnea growing vigorously against the wall of Tony Avent’s house, North Carolina. Image T. Avent.

Figure 38 (opposite). Exbucklandia populnea: habit with open fruit capsules (A); three-lobed leaf (B); bract with immature inflorescences (C); inflorescence (D).

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Exbucklandia

New Trees

The attractive leaves are dark green (bronzed when young or after a cold spell), and are said to tremble on the tree like those of an aspen in a light breeze, but it is the large leathery stipules pointing straight up that give the shoot its distinctive appearance. The growth pattern is curious as the terminal bud is suppressed and new growth continues from below the apex of the previous shoot, giving the stem a somewhat zigzag look.

FAGACEAE

FAGUS

L.

Beeches

Plate 266. Chocolatebrown autumnal leaves of Fagus japonica var. multinervis, growing at Arboretum Wespelaar. Image P. de Spoelberch.

Ten species of Fagus are found across the northern hemisphere (Govaerts & Frodin 1998). Beeches are deciduous trees with smooth bark and acute, elongated winter buds. The leaves are alternate, distichous and plicate in bud; the lamina is thin and the lateral veins are parallel, terminating with an acute or obscure marginal tooth. Stipules are prominent in young growth, but soon fall. Fagus is monoecious and the inflorescences are unisexual. Staminate inflorescences are produced in axils at the base of branchlets; they are capitate and contain numerous insignificant flowers. Pistillate inflorescences are short, stiff and axillary and bear two flowers. These are subtended by a single cupule, three- or four-valved; the cupule is dehiscent, with short, stout spines. The fruit is a nut and there are two per cupule; they are distinctly three-angled and may have a small wing (Nixon 1997, Huang et al. 1999). There are few trees more noble than the European Beech F. sylvatica: it is no wonder that Elwes & Henry (1906 ) began their epic work with its account, and that this ran to 28 pages of text. Excellent new cultivars continue to be selected, adding to the many already known, and often incorporating several forms of variation in one tree. ‘Black Swan’, for example, is a beautiful darkleaved weeping clone. Other beeches are also handsome and useful trees, but seldom have all the same qualities. In the hot and humid parts of East Coast North America, from about Washington DC southwards, F. sylvatica fails to thrive and is better replaced by the suckering native F. grandifolia, or perhaps by some of the Asian species. F. crenata Blume B174, S237, K68 F. engleriana Seem. ex Diels B174, S237, K69

Section II. Species Accounts

Fagus grandifolia Ehrh.

Fagus

American Beech

This species was described by Bean (B175, S237) and Krüssmann (K69). F. grandifolia var. caroliniana (NOW F. grandifolia Ehrh. subsp. grandifolia) B175, K69

Fagus grandifolia subsp. mexicana

Mexican Beech, Haya

(Martínez) E. Murray Tree to 35 m, 1.1 m dbh. Bark grey with white spots. Buds shiny brown and to 0.9 cm long with overlapping scales. Leaves leathery, 5–8 × 3–5 cm, elliptic, margins crenate to dentate, apex acuminate; petiole 0.6 cm long. Nuts two, 1.2–1.3 cm long. The Mexican Beech has smaller leaves and smaller nuts than the American subspecies (in subsp. grandifolia, leaves 6–12 × 2.5–7.5 cm, nuts 1.5–2 cm long). Flowering March to April, fruiting July to August (Mexico). Little 1965, López Mata & Cházaro Basáñez 1995. Distribution MEXICO: from southern Tamaulipas to Hidalgo and Puebla. Habitat High-altitude cloud forest. USDA Hardiness Zone 7b–8. Conservation status Not evaluated (IUCN), but the Mexican Beech is restricted to 10 populations (of 2–35 hectares) in the Sierra Madre Occidental (Williams-Linera et al. 2003). Studies of these trees have shown surprising levels of genetic variation when compared with American subsp. grandifolia (Rowden et al. 2004), and a higher conservation status may be warranted.

The Mexican Beech or Haya is one of the ‘temperate’ trees forming the forests of the Sierra Madre Occidental, that make this area so interesting to the botanist and plant explorer. It is, however, extremely rare there and has been the subject of much research. Neither is it common in cultivation, but there are some specimens scattered through collections in our area. In 1995 Raulston, Fairey and Schonfeld reported it as new to cultivation and showing good tolerance to heat stress, although with the potential problem of frost damage to the early-emerging shoots (Raulston et al. 1995). This prediction seems to have been confirmed with the passage of time, since the Mexican Beech seems no longer to be cultivated in eastern North America. There is, however, a specimen at Berkeley, from a Fairey collection in Tamaulipas in 1991, suggesting that the mild Bay Area climate is more favourable. On the other hand, there is a slender tree of 4.5 m in Arboretum Trompenburg, donated by J.C. Raulston in 1994, that is doing well and has proved hardy to date (G. Fortgens, pers. comm. 2005). F. grandifolia f. pubescens (NOW F. grandifolia Ehrh. subsp. grandifolia) B175, K69

Fagus japonica Maxim.

Japanese Blue Beech

This species was described by Bean (B175, S238) and Krüssmann (K69).

Fagus japonica var. multinervis (Nakai) Y.N. Lee ex Govaerts & Frodin Tree to 30 m, 0.7 m dbh. Branchlets glabrous, reddish grey. Leaves 9–17 × 5–10.5 cm, ovate, both surfaces with some hairs, glabrous at maturity, six to eight lateral veins on each side of midvein, margins undulate, apex obtuse; petiole 0.7–1 cm long; stipules silky, deciduous. The only useful character distinguishing var. multinervis from typical F. japonica is its distribution. Nakai 1918. Distribution SOUTH KOREA: Ullung-do. Habitat Mountain forests. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT368.

This Ullung-do endemic is rare in cultivation, perhaps because of its typical beech habit of fruiting abundantly in mast years and hardly at all in others – a frustrating trait for the seed collector, as described by Tony Kirkham in his account of his quest for the tree (Flanagan & Kirkham 2005). The seedlings collected on that occasion did not survive, perhaps because they lacked their normal mycorrhizal connections (T. Kirkham, pers. comm. 2007). The only specimen seen for New Trees was at the Scott

369

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New Trees

1 cm

A

Section II. Species Accounts

Fagus

371

Arboretum, where there is a young plant donated by the US National Arboretum. This was 4 m tall in May 2006, with wide-spreading branches, and its dark green leaves were very noticeably different from those of more familiar beeches. It is also in cultivation at the Morris Arboretum. F. longipetiolata Seem. B176, S238, K69 F. lucida Rehder & E.H. Wilson B176, K69 F. ×moesiaca (NOW F. ×taurica Popl.) B184, K69

F. orientalis Lipsky B176, S238, K69 F. sylvatica L. B177, S238, K69 F. ×taurica Popl. B177

MORACEAE

FICUS

L.

Figs Ficus is a large pantropical genus of approximately 750 species, including around 500 species in Asia and Australia, around 150 in tropical America, and around 100 in Africa and Madagascar. Ficus species are trees, shrubs, climbers, stranglers or woody epiphytes, all having a milky sap. The leaves are alternate (rarely opposite or whorled), simple or lobed, with entire or dentate margins, and pinnate or subpalmate venation. Stipules are lateral to amplexicaul, free or fused together, often forming a caducous sheath around the terminal bud. The inflorescence in Ficus is a unique structure known as a syconium – a hollow structure containing minute flowers. Syconia are ovoid, globose or pyriform, and are produced in leaf axils or directly from the stem (cauliflory). After fertilisation they swell and turn into figs. Pollination is by female fig wasps (family Agaonidae). These enter the syconium via a small hole at its apex (the ostiole) and lay eggs in the ovaries of some female flowers, which then host the wasp larvae. Fig flowers are unisexual and the female flowers have two forms: short female flowers (gall flowers) are parasitised by fig wasps, but in long female flowers (seed flowers) the ovary cannot be reached by the wasps and in consequence these flowers set seed. Syconia may be hermaphrodite (with all three flower types) or functionally unisexual (male and gall flowers only, or seed flowers only). For example, the edible Common Fig F. carica produces unisexual syconia: those with male and gall flowers give rise to a fruit that is dry, pithy and inedible (caprifigs); those with seed flowers produce the edible fig (Rohwer 1993b). Ficus is arguably one of the most important genera of trees in the world, at least in terms of its essential role in tropical forest ecosystems, where a tree in fruit will be a raucous centre of attention for birds and primates – though most are inedible to man. Generally receiving no attention at all (and showing it) are the numerous species used as houseplants and in interior landscaping. Among these long-suffering taxa are F. benjamina L. and F. elastica Roxb. ex Hornem., both of which metamorphose into trees of great beauty when grown in gardens in suitable conditions in the tropics, or even on the Mediterranean coast. From here it is only a short distance for evergreen figs to knock at the door of our area, especially in our currently warming climate.

Figure 39 (opposite). Ficus johannis subsp. afghanistanica: habit with immature fruits.

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Ficus

New Trees

There are some signs that this is already happening. Sean Hogan in Oregon is trying F. roxburghii Wall. outdoors (pers. comm. 2007), and F. auriculata Lour. has been tried outside, unsuccessfully, at the JC Raulston Arboretum. These are the vanguard, with others to come. It is clear that evergreen figs have generally been written off as garden prospects, but with such a huge diversity to investigate, an open mind and good provenances may yield some extraordinary surprises. At present, however, deciduous figs offer more certainty of success. In the Middle East and across central Asia there is a great diversity of forms and allies of F. carica and F. johannis to investigate, and Yucca Do Nursery of Hempstead, Texas (admittedly outside our area) has recently introduced F. lacor Buch.-Ham., a deciduous species from northern China that is claimed to be hardy from Zones 8b to 10 (Yucca Do 2008). This has lanceolate leaves that flush red, borne on wide-spreading branches, and is clearly a species that should be tried. F. benjamina L. K75 F. carica L. B190, K75

F. elastica Roxb. ex Hornem. K75

Ficus johannis Boiss. Ficus johannis is principally represented in cultivation by subsp. afghanistanica (see below). Subsp. johannis, which seems to be a smaller, shrubbier plant, is grown outside the Temperate House at Kew (labelled with the synonym F. geraniifolia Miq.), as bushes pruned down to the level of the pediment. It was introduced by Christopher Grey-Wilson in 1966, from the southern Zagros mountains of Iran. Plate 267. The finely dissected foliage of Ficus johannis subsp. afghanistanica ‘Silver Lyre’, selected at Cistus Nursery, makes it a very desirable plant. Image Phytophoto.

Ficus johannis subsp. afghanistanica (Warb.) Browicz

Afghan Fig

Syn. F. afghanica (Popov) Drobow, F. carica L. var. afghanica Popov Shrub or tree to 10 m or more (in cultivation this species probably grows much larger than published accounts describing wild plants suggest). Branchlets pubescent to subglabrous. Leaves deciduous, 7–9(–13) cm long, somewhat heart-shaped, three- to five-lobed, reminiscent of a maple leaf, upper surface rough, lower surface with some pubescence, margins distinctly dentate, apex obtuse; petiole to 5 cm long, pubescent or glabrous. Figs edible, 2–3(–3.5) cm long, pyriform; peduncle ~2 cm long. Browicz 1982. Distribution AFGHANISTAN; IRAN; TAJIKISTAN; TURKMENISTAN. Habitat Wooded slopes on sandy loam soils; only recorded from 30–35 m asl, though probably occurs higher. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT370, NT372. Taxonomic note Ficus johannis subsp. johannis has smaller leaves and fruits (leaves 1–3(–6) cm long, fruits 1–1.5(–2) cm long). Subsp. afghanistanica may be a cultivated form, but F. johannis, F. carica and F. palmata Forssk. are a confusing group, with several intermediate forms; F. johannis subsp. afghanistanica hybridises with F. carica subsp. carica in the north of its range (Browicz 1982).

Ficus johannis subsp. afghanistanica has entered cultivation by a number of routes. In the United States, rather unconventionally, it arrived at Yucca Do Nursery, Texas as a mysterious packet of seeds from a customer who had obtained them from northern Iran (Yucca Do 2003). From this source, and others in the United States, it has been distributed quite widely, and is proving to be a very satisfactory garden tree. Several selections have been made by Cistus Nursery, Oregon, including ‘Silver Lyre’ which has particularly good foliage. The beauty of this species lies in its elegantly dissected leaves; they would not be suitable for use as a

Section II. Species Accounts

Ficus

373

discreet cover for nudity in an emergency, their laciness suggesting something far more seductive. It is certainly a species to look out for and obtain in its best forms, for cultivation in a hot sunny site. In good conditions it has the potential to make a fine tree, rather resembling a big F. carica. F. lyrata Warb. K75 F. macrophylla Desf. ex Pers. K75 F. microcarpa L. f. K76 F. pumila L. B190, K76

F. religiosa L. K76 F. rubiginosa Desf. K76 F. sycamorus L. K76

OLEACEAE

FRAXINUS

L.

Ashes There are 40–50 species of Fraxinus, distributed primarily in the temperate and subtropical northern hemisphere (Wallander & Albert 2000). They are typically deciduous trees, though evergreen and shrubby species occur. The branches and branchlets are covered with lenticels. The leaves are imparipinnate and opposite or rarely whorled; the petioles and petiolules are swollen at the base. Inflorescences are terminal or axillary on current growth, or in a lateral position on branches produced the previous year. They are paniculate and composed of numerous, small flowers. Fraxinus species are typically dioecious, but may be monoecious or polygamous. The calyx is four-lobed or absent; the corolla is white or yellowish and is four-lobed or has four free petals, or is absent; there are only two stamens. Unusually in the Oleaceae, the fruit is a samara with a single, elongated wing, known in English as a ‘key’ (Chang et al. 1996). A monograph of Fraxinus is currently being prepared by Eva Wallander of Gothenburg University in Sweden and this is expected to propose major changes in the taxonomy of the genus, including a significant reduction of the number of species recognised. Some of these are presaged in Wallander & Albert (2000), and the crossreferences given in the accounts that follow reflect this taxonomy. In some cases, however, a name has not, at the time of writing, been included in the published work of Wallander and her co-workers, and its position or synonymy cannot be stated. Such names are marked here with an asterisk (*); it is probable that in the monograph most will be treated as synonyms. Fraxinus is an important genus of large handsome trees, but seems to generate very little enthusiasm among dendrologists, at least in Europe. Whether this is because of

Plate 268. Fraxinus chinensis has a huge distribution and varies accordingly, making recognition of variants rather pointless. Image J.R.P. van Hoey Smith.

Since the completion of this account, Wallander’s new phylogeny of Fraxinus (2008), based on DNA analysis and morphology, has reduced the number of recognised species to 43.

374

Fraxinus

New Trees

A

B

1 cm

Section II. Species Accounts

Fraxinus

375

the free-seeding, almost weedy nature of the European Ash F. excelsior and hence its frequency in the landscape, or some other reason, is not clear. The lack of interest is evident in the paucity of new cultivars of F. excelsior: even the important street tree cultivars ‘Atlas’ and ‘Westhof’s Glorie’ were selected as long ago as the 1940s (Krüssmann 1985a). This compares to the plethora of selections made recently in American ashes, particularly F. americana and F. pennsylvanica, valued for their solid presence in the landscape and often fine autumnal colour. Most such selections are male trees and thus do not produce a large crop of seed and seedlings to deal with. Dirr (1998) lists and describes a wide range of such clones, but also mentions a number of pests and diseases that can be a problem, even within the trees’ native range. In addition to these problems, American Fraxinus are facing a new threat from an introduced insect, the Emerald Ash Borer Agrilus planipennis from Asia, first discovered in Michigan in 2002. Since that time it has killed over 20 million ash trees in Michigan, Ohio and Indiana, and has also been found in Ontario. Quarantines on moving ash wood and plants are in place in these states, in an effort to contain the pest, and the problem has received widespread publicity in the United States. A very comprehensive website (www.emeraldashborer.info) is available for those seeking further information. Several recent collections have been made of Fraxinus sikkimensis (Lingelsh.) Hand.Mazz., a taxon recognised by Flora of China but not by Wallander & Albert (2000), who include it in F. paxiana (see Bean and Krüssmann: B223, K92). According to the key in Flora of China (Chang et al. 1996), the differences between these two taxa are at best slight, based on variations in leaf hairiness and shape of the leaf rachis, with some separation of distributions. Trees labelled F. sikkimensis seen in research for the current work are attractive, with large leaves that are russet-hairy below. Examples include a specimen of 8 m in 2004 at Quarryhill, grown from SICH 116, and a slightly shorter one from KGB 0659 in the David C. Lam Asian Garden in Vancouver. It is said to have good bronzy red autumn colour in China (W. McNamara, pers. comm. 2004), and to have the showiest inflorescences of the entire genus (Wharton et al. 2005). Most species of ash were introduced many years ago, but the majority have now become rather scarce in cultivation. The various Mexican species are the exception, as most have not yet been introduced. If parallels with other genera are useful, these could represent an interesting new pool of diversity. Fraxinus species are in general tolerant of growing conditions throughout our area, but the American species thrive best in areas with hot summers. The genus seems to be tolerant of most soil types, but appreciates good living. Propagation is by seed (and for once hybridisation does not seem to be a recorded problem) or by grafting onto stocks of species from the same section of the genus.

F. americana L. B209, K85 F. americana var. juglandifolia (NOW F. americana L.) K85 F. americana var. microcarpa (NOW F. americana L.) B210 F. angustifolia Vahl B210, K85 F. angustifolia var. australis (Gay) Schneid. K85 * ( * see p. 373, above ) F. angustifolia var. lentiscifolia Henry B210 *

F. anomala Torr. B211, K86 F. anomala var. lowellii (NOW F. anomala Torr.) K86 F. berlandieriana DC. B225, K86 F. biltmoreana (NOW F. americana L.) B211, K86 F. bungeana DC. B212, K86 F. caroliniana Mill. B212, K86

Figure 40 (opposite). Fraxinus lanuginosa: habit (A); infructescence (B).

376

Fraxinus

New Trees

Fraxinus chinensis Roxb. Syn. F. japonica Blume ex K. Koch, F. rhynchophylla Hance, F. sargentiana Lingelsh. Tree 3–20 m. Branchlets glabrous to tomentose; buds covered with brown tomentum or glandular hairs. Leaves deciduous, imparipinnate, 12–35 cm long; leaflets three to seven (to nine), ovate to lanceolate or elliptic, 4–16 × 2–7 cm, papery, glabrous or with small hairs, 5–10 secondary veins on each side of the midrib, margins regularly serrate or entire in the lower half, apex acute to long-acuminate or caudate; petiolule 0.2–1.5 cm long; petioles 3–9 cm long; rachis initially pubescent, densely tomentose or glabrous at point of leaflet attachment. Dioecious; inflorescences paniculate, terminal or axillary on current growth, 5–10 cm long. Flowers opening in spring as leaves unfurl; staminate flowers congested, calyx cup-shaped, corolla absent; pistillate flowers lax, calyx tubular, corolla absent. Fruit a spathulate samara, 2.5–4 × 0.3–1.5 cm. Flowering April to May, fruiting July to October (China). Chang et al. 1996. Distribution CHINA; JAPAN; NORTH KOREA; RUSSIAN FEDERATION; SOUTH KOREA; VIETNAM. Habitat Montane woodland and roadsides between 800 and 2300 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Chang et al. 1996; NT373. Cross-references B213, K86. Taxonomic note Flora of China recognises subsp. chinensis and subsp. rhynchophylla (Hance) E. Murray, which differ primarily in the shape and size of the terminal leaflet (Chang et al. 1996), but their ranges overlap across wide areas of their vast distributions and they are (wisely) combined by Wallander & Albert (2000).

Bean (1981a) reported that Fraxinus chinensis (i.e. subsp. chinensis) was not in cultivation at the time of his writing, but that subsp. rhynchophylla had been introduced to the Arnold Arboretum in 1881. A few older trees in cultivation are assigned to subsp. rhynchophylla – among them the British champion at Stanmer Park, East Sussex, planted in 1964 and recorded as being 16 m (33 cm dbh) in 2002 (TROBI), as well as mature trees in the Arnold and Morton Arboreta and probably elsewhere in the United States. In recent years F. chinensis (s.l.) has been collected quite frequently (by NACPEC and SICH, for example, and other expeditions and travellers in all parts of China), and in consequence young trees are quite common in arboreta across our area. This makes it possible to observe the wide range of variation in leaflet size and shape found in wild populations of F. chinensis, faithfully reproduced in even small groups of trees in Western arboreta, however labelled. It seems to be a good hardy tree and the foliage is handsome, especially in some individuals with particularly large leaves. One leaf measured at Edinburgh, from a young tree labelled subsp. rhynchophylla, from Jilin, was 49 cm long, with a terminal leaflet 21 × 11 cm. The Royal Botanic Garden Edinburgh also grows a tree labelled var. acuminata Lingelsh. (another name now sunk into the undivided species), collected by George Forrest (F 21355), in which the leaflets are narrower than most. This specimen is now 15 m tall (50 cm dbh) and has good grey bark. The crown is rounded, and although somewhat sparse, reminds us that this species is capable of becoming quite a large tree. F. chinensis var. acuminata (NOW F. chinensis Roxb.) B214, K86 F. chinensis var. rhynchophylla (NOW F. chinensis Roxb.) B213

Fraxinus cuspidata Torr.

Flowering Ash, Fragrant Ash

Syn. F. macropetala Eastw. Shrub or small tree to 6(–12) m, 0.2–0.3 m dbh. Branchlets slender and glabrous; buds dark reddish brown. Leaves deciduous, imparipinnate, 18 cm long; leaflets three to nine, ovate to oblanceolate or lanceolate, 3.5–7 cm long, thin and shiny, margins entire to coarsely toothed, apex long-acuminate to cuspidate. Inflorescences paniculate, terminal or axillary on current growth, 7.5–10 cm long. Flowers opening in spring as leaves unfurl; flowers conspicuous; white and fragrant with large petals. Fruit a samara, oblong-obovate to lanceolate. Flowering May to June (USA). Kearney & Peebles 1951, Correll & Johnston 1970. Distribution MEXICO: north; USA: northern Arizona to western Texas. Habitat Steep rocky slopes, ledges and cliffs,

Section II. Species Accounts

Fraxinus

377

often in shaded areas, between 1200 and 2300 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Cross-references B214, K86. Taxonomic note Rehder (1917) recognised var. macropetala (Eastw.) Rehder, which typically has fewer, broader leaflets and only occurs in northern Arizona (incl. Grand Canyon National Park).

Bean (1981a) wrote that Fraxinus cuspidata was perhaps not in cultivation in the British Isles. It is now, but only in a very tenuous way, being absent from all the principal arboreta: TROBI records one specimen of 3 m growing at Peasmarsh Place, East Sussex, derived from a Keith Rushforth collection in Mexico. It has previously reached flowering size at the Hillier Gardens, but no trees survive there now (A. Coombes, pers. comm. 2008). In continental Europe Jan De Langhe has recorded it at the botanical garden in Wageningen in the Netherlands, at Arboretum de Chèvreloup Rocquencourt, France, and at the Botanischer Garten Berlin-Dahlem, Germany – but these are the only records traced, so it would seem to be rather rare throughout Europe. It is cultivated in the United States, but not frequently, and is not represented in any of our principal reference collections there. These omissions would seem to be unfortunate, as F. cuspidata is a tidy small tree with neat foliage and prolific white flowers in early summer, and is also drought-resistant and heat-tolerant – therefore potentially of great value as a water-wise landscaping tree. F. dipetala Hook. & Arn. B214, K86 F. dippeliana Lingelsh. B212 * F. elonza Dippel B214 * F. excelsior L. B215, K88 F. excelsior f. angustifolia hort. B215, K88 F. excelsior f. diversifolia (NOW F. excelsior L. Diversifolia Group) B216, K88 F. floribunda Wall. B218, K89 F. greggii A. Gray K91 F. griffithii C.B. Clarke B218, K91 F. holotricha Koehne B219, K91 * F. hookeri Wenz. K91 *

Fraxinus lanuginosa Koidz. Tree 5–15 m, with wide-spreading branches. Branchlets greyish brown and glabrous below, though usually pubescent above; buds smooth or hairy. Leaves deciduous, imparipinnate, 9–20 cm long; leaflets five to seven, ovate to oblong, 3–10 × 1.5–5 cm, pubescent, five to eight secondary veins on each side of the midrib, margins regularly serrate, apex acute to attenuate; leaflets almost sessile or with petiolules 0.5–2 cm long (apical leaflet); petiole 2–8 cm long, pubescent. Polygamous; inflorescences paniculate, terminal or axillary on current growth, 5–10 cm long. Flowers opening in spring as leaves unfurl; staminate flowers congested, calyx absent, corolla with four small white petals; hermaphrodite flowers lax, calyx small and irregularly dentate, corolla as in staminate flowers. Fruit an oblanceolate samara, 1.8–2.5 × 0.3–0.5 cm. Flowering May to June (Japan). Ohwi 1965. Distribution JAPAN: Hokkaido, Honshu, Kuril Is., Kyushu, Shikoku. Habitat Deciduous forest between 700 and 1800 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT374, NT377. Cross-references B227, K91. Taxonomic note Typical F. lanuginosa is restricted to central and northern Honshu. Var. serrata (Nakai) Hara, which can be distinguished by the glabrous or sparsely hairy buds and glabrous branchlets, is more widespread.

Several recent expeditions have introduced Fraxinus lanuginosa, mainly from collections made in Hokkaido (for example, W&H 483 in 1989, EHOK 112 in 1997). The

Plate 269. Fraxinus lanuginosa. The parent tree of EHOK 112 in Hokkaido, photographed in 1997, in pleasantly subtle autumn colours. Image T. Kirkham.

378

Fraxinus

New Trees

plants show considerable variation in pubescence characters, and distinctions between varieties that rely on these features should be viewed with caution. The young shoots can be either almost glabrous, or densely pubescent as in one specimen at Edinburgh from W&H 483, on which the hairs are retained for several years, giving the 8 m tree a very distinctive look. On other trees the (less hairy) shoots, young leaves and fruits are tinged purple. The mature leaves are usually a pale mid-green but when heatstressed, as at Quarryhill, they become purplish, and the field notes for EHOK 112 indicate that the autumn colour can also be purple, when the straw-coloured bunches of keys form a pleasing contrast. It can be a big tree – 15 m tall with a branch-spread of 12 m in the case of the parent of the EHOK 112 collection – but young trees seem to be quite slow-growing, at least in some locations.

F. latifolia Benth. B220, K91 F. longicuspis Siebold & Zucc. B225, K91 F. mandschurica Rupr. B220, K91 F. mariesii (NOW F. sieboldiana Blume) B221 F. nigra Marshall B221, K91 F. numidica Dippel K92 * F. obliqua Tausch B222, K92 * F. ornus L. B222, K92 F. ornus var. juglandifolia (NOW F. ornus L.) K92 F. ornus var. rotundifolia (NOW F. ornus L.) B223, K92 F. oxycarpa (NOW F. angustifolia subsp. oxycarpa (M. Bieb. ex Willd.) Franco & Rocha Afonso) B210 F. pallisiae (NOW F. angustifolia subsp. oxycarpa (M. Bieb. ex Willd.) Franco & Rocha Afonso) B219 F. parvifolia (NOW F. angustifolia Vahl) B227 F. paxiana Lingelsh. B223, K92 F. paxiana var. sikkimensis (NOW F. paxiana Lingelsh.) B224 F. pennsylvanica Marshall B224, K92 F. pennsylvanica var. subintegerrima (NOW F. pennsylvanica Marshall) B224 F. platypoda Oliver B225, K92 F. potamophila (NOW F. angustifolia subsp. syriaca (Boiss.) Yalt.) K82

F. pubinervis (NOW F. longicuspis Siebold & Zucc.) B225 F. quadrangulata Michx. B226, K93 F. raibocarpa Regel K93 F. retusa (NOW F. floribunda Wall.) K93 F. retusa var. henryana (NOW F. floribunda Wall.) K93 F. rhynchophylla (NOW F. chinensis Roxb.) K93 F. rotundifolia (NOW F. angustifolia Vahl) B226, K93 F. sieboldiana Blume B227, K93 F. sogdiana (NOW F. angustifolia subsp. syriaca (Boiss.) Yalt.) B228 F. spaethiana Lingelsh. B228, K93 F. syriaca (NOW F. angustifolia subsp. syriaca (Boiss.) Yalt.) B229, K94 F. texensis (A. Gray) Sarg. B229, K94 F. tomentosa (NOW F. profunda (Bush) Bush) B230 F. uhdei (Wenz.) Lingelsh. K94 F. velutina Torr. B231, K94 F. velutina var. toumeyi (Britt.) Rehd. B231 F. xanthoxyloides (G. Don) DC. B231, K94 F. xanthoxyloides var. dimorpha (NOW F. xanthoxyloides (G. Don) DC.) B232, K94 F. xanthoxyloides var. dumosa (NOW F. xanthoxyloides (G. Don) DC.) B232, K94

Section II. Species Accounts

Glochidion

379

PHYLLANTHACEAE (formerly EUPHORBIACEAE)

GLOCHIDION

J.R. Forst. & G. Forst.

Glochidion is a genus of over 300 species in Asia, Australia and the Pacific (Govaerts et al. 2000). It is closely related to (and perhaps should be merged with) the large genus Phyllanthus (Samuel et al. 2005), and the Madagascan species of Glochidion have been transferred into that genus (Hoffmann & McPherson 2003). Euphorbiaceae has itself been split into several smaller families based on DNA evidence (APG 2003). Glochidion species are monoecious or dioecious evergreen (rarely deciduous) trees and shrubs. The leaves are alternate, simple and arranged in two ranks. Stipules are thick, persistent and scale-like. Inflorescences are axillary fascicles. The flowers are pedicellate and have no petals. The fruit is a dehiscent capsule with three or more lobes divided by prominent grooves. The seeds bear a fleshy (often colourful) sarcotesta (Radcliffe-Smith 2001, Chang et al. 2005). Some species are pollinated by moths of the genus Epicephalus (Gracilariidae), which also lay their eggs in the style, allowing their caterpillars to consume some of the tree’s seed. Of the Glochidion species tested, each appears to have its own exclusive pollinator, and reproduction of either the tree or the moth is impossible in the absence of its partner (Kawakita et al. 2004). Glochidion is almost unknown in temperate horticulture, yet as seen in North Carolina, G. triandrum at least is well worth growing. The shrubby G. wilsonii Hutchinson is in cultivation in the United States: at the Morris Arboretum it is marginally hardy and suffers winter dieback (A. Aiello, pers. comm. 2006).

Glochidion puberum (L.) Hutch.

Abacus Plant

Syn. G. fortunei Hance Shrub or tree to 10 m; usually multistemmed. Bark brown with closely spaced longitudinal furrows. Branchlets greyish brown, densely pubescent. Leaves deciduous, simple, 3–8 × 1–2.5(–3) cm, papery or leathery, oblong to obovate, rarely lanceolate, upper surface greyish green and glabrous, lower surface green, densely pubescent and with raised veins, four to nine secondary veins on each side of the midvein, margins entire, apex obtuse, acute or rounded; petiole 0.1–0.4 cm long, covered in ferruginous pubescence; stipules triangular, about 0.1 cm long. Inflorescences are axillary fascicles bearing 2–5(–10) monoecious, greenish yellow flowers. Fruit a rounded capsule, yellowish green to red, densely pubescent, 0.8–1.5 cm diameter. Seeds red to orange. Flowering April to August, fruiting July to November (China). Fearn & Urbatsch 2001, Chang et al. 2005. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hong Kong, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, Xizang, Yunnan, Zhejiang; TAIWAN. Naturalised in Alabama and Florida, USA. Habitat A variety of habitats including montane slopes, forest marginal scrub and streambanks between 300 and 2200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT380. Cross-reference K116.

Krüssmann (1985a) notes tersely that Glochidion puberum is ‘only for the collector’, and the genus has otherwise been resolutely ignored by the horticultural literature. Krüssmann also says that it is cultivated at Arboretum National des Barres. It was probably first introduced by Wilson (Sargent 1916) but in recent years has been grown from Shanghai Botanic Garden seed, and plants from this source are established at

Plate 270. The sideshoots of Glochidion triandrum look like pinnate leaves, but the axillary flowers give the game away. Seen here in early June at the JC Raulston Arboretum. Image J. Grimshaw.

380

Glochidion

New Trees

1 cm

C

1 cm

B

1 cm

A

Section II. Species Accounts

Glochidion

Tregrehan. In most temperate gardens it will probably grow as a shrub. It has some value for its ‘pinnate leaves’, that are in reality the shoots, and the reddish fruits along the branches. A large shrubby specimen (7 × 7 m) labelled G. puberum has grown at the Hillier Gardens for many years, but its identity is in doubt as it has glabrous leaf undersides (A. Coombes, pers. comm. 2008).

Glochidion triandrum (Blanco) C.B. Rob. Shrub or tree to ≥ 10 m. Bark light brown, peeling in narrow longitudinal strips. Branchlets angular and with dense ferruginous pubescence. Leaves deciduous, simple, 4–13 × 2–4.5 cm, papery or membranous, oblongelliptic or lanceolate, upper surface green and glabrous, lower surface glaucous with dense white pubescence, five to seven secondary veins on each side of the midvein, margins entire, apex acute, acuminate or obtuse; petiole 0.2–0.4 cm long, sparsely pubescent; stipules ovate-triangular, 0.15 cm long, fulvous-pubescent. Inflorescences axillary fascicles bearing five to six monoecious flowers. Fruit a rounded capsule, sparsely pubescent, 0.4 × 0.5–1 cm, reddish. Seeds reddish brown. Flowering March to July, fruiting July to December (China). Chang et al. 2005. Distribution CAMBODIA; CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Sichuan, Yunnan; INDIA: Sikkim; JAPAN; NEPAL; PHILIPPINES; TAIWAN; THAILAND. Habitat Montane forest and riverine scrub between 500 and 2600 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT379.

In suitable conditions Glochidion triandrum is a potentially handsome tree, and it deserves to be more widely grown. The only specimens seen in the research for the present work are both at the JC Raulston Arboretum: 10 m and 7 m tall, respectively, and multistemmed, forming a spreading canopy from upright trunks. The species has a strong tendency to sucker from the roots, especially when young, and planting as a lawn specimen may be advisable, so that unwanted suckers can be mown off. The flowering shoots, bearing leaves as well as flowers, are apparently annual, dying back each year but persisting on the branches to give them a rather spiky appearance. The annual crop of such shoots conceals this spikiness during summer at least, with new growth flushing reddish before turning green. The leaves are held pointing more or less upwards and the clusters of flowers between the leaves are surprisingly conspicuous, opening in succession along the shoot. The reddish tint on the new growth persists well into early summer and is an appealing feature of the tree, but it does not colour in autumn (T. Lasseigne, pers. comm. 2007). In the absence of other observations it is difficult to make recommendations for cultivation, but this is probably a tree that appreciates hot summers. The two specimens in Raleigh are very fast-growing, having been planted only in 1997.

PROTEACEAE

GREVILLEA

R. Br. ex Knight

Grevilleas, Silky Oaks, Spiderflowers Makinson (2000) recognises 362 species of Grevillea and the vast majority of these are endemic to Australia (only seven species occur outside Australia, in New Guinea, New Caledonia and Sulawesi). They are usually erect or prostrate shrubs, but there are a few trees. The leaves are extremely variable; they may be entire, toothed or with up to three orders of division, and can be sessile or petiolate; leaf venation is pinnate

381

Figure 41 (opposite). Glochidion puberum: habit with flowers (A); habit with fruits (B); fruit opening (C).

382

Grevillea

New Trees

or parallel. The inflorescences also are very variable in form. Common forms include ‘toothbrush’ (with flowers arranged along one side of the axis), ‘spider’ (the flowers in a rounded head, with the individual styles emerging from the centre like legs), and ‘brush’ (a conspicuous cylindrical raceme). The flowers are usually in pairs with a common bract. The flowers are 4-merous (rarely 3-merous); the tepals separate after anthesis to release the style; they may be glabrous or pubescent; the anthers are sessile and the style is extended. The fruit is a follicle or achene with one to two seeds, with or without wings (Makinson 2000). Grevillea is one of the most important horticultural genera in Australia, with a great diversity of plant forms and shapes and colours of inflorescence. In addition to the species and their selections, an ever-expanding range of hybrids is available. Many Grevillea are being tested in the north temperate area and proving to be not only hardy but also extremely attractive. A very comprehensive account is provided by Elliot & Jones (1990), including detailed cultivation recommendations for all species. G. acanthifolia A. Cunn. B295, K118 G. alpina Lindl. B296, K118 G. glabrata (NOW G. manglesii (Graham) McGill. subsp. manglesii) K118 G. ornithopoda (NOW G. manglesii subsp. ornithopoda (Meisn.) McGill.) K118

Grevillea robusta A. Cunn. ex R. Br.

Silky Oak

Vigorous, long-lived tree 15–40 m. Bark greyish brown and fissured. Branchlets angular and rusty-tomentose. Leaves fern-like, 10–34 × 9–15 cm, bipinnate or tripinnate, with 11–24(–31) primary lobes, lobes entire or divided, ultimate lobes 0.5–5 × 0.2–1 cm, upper surface glabrous or with sparse silky hairs, lower surface silky to tomentose, margins recurved; petiole 1.5–7 cm long. Inflorescences erect, terminal and simple or with up to four branches, each spike 12–16 cm long with many flowers. Flowers golden-yellow to orange outside, inside with red dots; tepals 0.6–0.7 cm long; style yellow-orange, 2–3 cm long. Fruit a follicle, laterally compressed, 1.2–1.6 × 1 cm. Flowering September to November (Australia). McGillivray 1993, Olde & Marriott 1995, Makinson 2000. Distribution AUSTRALIA: northeastern New South Wales, southwestern Queensland. Habitat Three distinct habitats: gallery rain forest and forest margins with Castanospermum australe A. Cunn. & C. Fraser ex Hook.; riverine evergreen forest with Casuarina cunninghamiana; and Araucaria cunninghamii forest on steep slopes and hills. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT382. Cross-reference K118.

Plate 271. Grevillea robusta is often cultivated in the tropics and subtropics (here in Arusha, Tanzania) as a rapidly growing shelter and timber tree. Finely dissected leaves and abundant flowers give it considerable horticultural merit, but it is not very hardy. Image J. Grimshaw.

This fine tree is by far the most commonly cultivated Grevillea, being grown in plantations and as a street or shade tree throughout the tropics and subtropics, and giving serviceable timber. It is also very much the biggest member of the genus, and one of only a handful to form straight-trunked trees. When in flower it is a wonderful sight. In our area it is at the edge of its tolerance, but is not a hopeless case. There is a 12 m tree in Brynmill Park, Swansea which has survived the removal of its originally protective greenhouse, and trees up to 9 m have been recorded in Devon (Johnson 2007, TROBI). Other specimens may be accidental survivors of bedding schemes in which young plants were used as centre-pieces, as in the case of two growing outside Rotherhithe Police Station. Although showing signs of frost damage, the larger of these two trees was 8.5 m in 2005 (TROBI). It is worth a try in maritime situations in our

Section II. Species Accounts

Grevillea

383

area, where it should be given a site in full sun in moist soil. It becomes hardier with age, so young plants (grown from seed) should be protected for their first few winters, but adult trees can survive temperatures down to –7 ºC (Moore 2004). G. rosmarinifolia A. Cunn. B296, S257, K118 G. ×semperflorens F.E. Briggs ex Mulligan K118

G. sulphurea (NOW G. juniperina R. Br. subsp. sulphurea (A. Cunn.) Makinson) B297, S257, K118 G. thelemanniana Hügel ex Endl. K118

ROSACEAE

HAGENIA

J.F. Gmel.

The genus Hagenia is monospecific, comprising only the species H. abyssinica.

Hagenia abyssinica (Bruce) J.F. Gmel.

African Redwood, Kosso

Tree to 18 m, ≥ 1 m dbh. Crown rounded to umbrella-shaped. Bark reddish brown to brown, ridged, flaky. Branches massive, wide-spreading. Branchlets densely covered with golden hairs, leaf scars prominent. Leaves imparipinnate, to 40 cm long with five to seven (to eight) pairs of major leaflets, alternating with one (to three) very small, subcircular leaflets; rachis covered with soft, drooping hairs; major leaflets narrowly oblong, 12–15 × 3.5–5.5 cm, upper surface largely glabrous, viscid, lower surface covered in silky hairs, margins finely dentate, apex acuminate; petiole to 15 cm long, with hairs as on rachis; stipules (3–)6–9 cm long, membranous, reddish to brown, almost entirely fused to the petiole. Inflorescences paniculate, terminal, drooping, to 60 cm long with numerous flowers; male and female flowers typically on separate plants. Male flowers white to orange, ~0.8 cm diameter; female (and hermaphrodite) flowers red, viscid, to 1.5 cm diameter; epicalyx present, sepals (four to) five, petals (four to) five, stamens up to 20. Fruit an achene, enclosed within the calyx tube. Graham 1960, Mendes 1978. Distribution BURUNDI; DEM. REP. CONGO; ETHIOPIA; KENYA; MALAWI; RWANDA; SUDAN; TANZANIA; UGANDA; ZAMBIA. Habitat Montane rain forest, deciduous woodland and evergreen bushland between 1950 and 3000 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Graham 1960; NT383.

Hagenia abyssinica is one of the iconic trees of the Afromontane forests of East Africa, always looming somewhere in the misty background of any documentary on Mountain Gorillas. With its massive trunk and wide-spreading limbs, big pinnate leaves and pendulous reddish inflorescences, it is immediately recognisable. In its native forests it requires an open site for germination and establishment, often regenerating

Plate 272. Hagenia abyssinica is a characteristic tree of the upper levels of East African montane forests, in this case on Mount Kenya. Image J. Grimshaw.

384

Hagenia

New Trees

following a disturbance event such as a landslide or fire, and is only found in the cooler, misty upper parts of the forest (Grimshaw 1996). Here the nocturnal temperatures drop to close to freezing point most nights of the year, but at ground level a frost would be exceptional. Establishment outside the forest is rare and such seedlings are regularly frozen and damaged. As a consequence H. abyssinica, while a highly desirable tree, is unlikely to become frequent in our area, where few regions are cool enough and yet sufficiently frost-free for it to be successful. Woodland gardens with a high canopy in the Celtic extremities of western Europe would be ideal, and it is grown in just such conditions at Tregrehan, where a young plant is doing well and is now 1.5 m tall after two seasons in the ground (T. Hudson, pers. comm. 2007). Another area where it should flourish is the California coastal mist belt, centred on San Francisco, but there is no evidence of its being cultivated there. It is, however, grown in New Zealand (T. Hudson, pers. comm. 2007). In areas where it grows wild local populations value it for its medicinal properties – a ‘popular and highly effective anthelmintic’, according to the Flora of Tropical East Africa (Graham 1960).

STYRACACEAE

HALESIA

J. Ellis ex L.

Silverbells

Plate 273. The abundant flowers of Halesia macgregorii are produced in spring before the leaves appear, and are thus displayed to full effect, as here in the JC Raulston Arboretum. Image JC Raulston Arboretum.

Halesia, as currently defined, contains three species, two in North America and one in China. They are deciduous trees or shrubs with winter buds enclosed in scales. The leaves are alternate with serrate margins; stipules are absent. The white flowers occur in axillary fascicles or short racemes on one-year-old branchlets. Flowering occurs before the leaves emerge; pedicels are slender and jointed. The flowers are hermaphrodite, 4-merous, with a tubular calyx, four-ribbed and opening into four teeth, a campanulate corolla, four- to five-lobed, and 8–16 stamens, in one series. The fruit is a dry, indehiscent drupe with two to four wings and a short beak (Hwang & Grimes 1996). The taxonomic position of the Chinese H. macgregorii is not entirely satisfactory, as it has been shown to be more closely related to the Asian genus Rehderodendron than to the American Halesia (Fritsch et al. 2001), but at present it has not been assigned to any other genus. In the field it is easily mistaken for a Rehderodendron (T. Hudson, pers. comm. 2007). The American silverbells, especially forms of H. carolina, are justifiably popular garden trees, valued for their masses of pure white pendent flowers in early summer. Unfortunately their names are becoming very confused as different points of taxonomic view are presented. A recent revision of the genus at the California Academy of Sciences, San Francisco has concluded that there are only two species in North America, H. carolina and H. diptera, the name H. carolina being applied to a single variable taxon that subsumes H. tetraptera, H. monticola and H. parviflora, and the various combinations under which these epithets have appeared (Fritsch & Lucas 2000). This position will be that used in the forthcoming Flora of North America account of the genus (P. Fritsch, pers. comm. 2007), and is adopted in our cross-referencing. Earlier work by Reveal and Seldin (1976) also recognises two species, but admits that there

Section II. Species Accounts

Halesia

385

is a case for recognising four. In this scenario all taxa are maintained as separate species or varieties, the name H. carolina being restricted to the small-flowered southern variants also known as H. parviflora. This viewpoint has been embraced by American horticulturists, and was given wide publicity in an article by Rick Darke (2006), but has not been adopted in Europe. Peter Fritsch (pers. comm. 2007) recommends the use of cultivar group names to denote horticulturally recognisable entities within the H. carolina complex (for example, H. carolina Monticola Group). It seems certain that the nomenclature of these trees in horticulture will be muddled for years to come. The American Halesia require moist, fertile acidic soil and flourish best in areas with hot summers, and there seems to be no evidence that H. macgregorii requires anything different. H. carolina L. B305, S258, K121 H. carolina f. dialypetala (NOW H. carolina ‘Dialypetala’) B306, K122 H. carolina var. mollis (NOW H. carolina Mollis Group) B305, K122 H. diptera Ellis B306, K122 H. diptera var. magniflora (NOW H. diptera Magniflora Group) B307, K122

Halesia macgregorii Chun Tree to 24 m, 0.45 m dbh. Branchlets purplish brown. Leaves 5–13 × 3–4.5 cm, elliptic to ovate-elliptic, upper surface glabrous, lower surface pubescent when young, later almost glabrous, 10–24 secondary veins on each side of midrib, margins serrate, apex curved, acuminate; petiole 5–10 cm long. Flowers pendulous, ~1.5 cm long; pedicel 0.5–0.8 cm long, slender. Calyx ~3 mm long, corolla tube 1–1.5 cm long, four-lobed, ciliate, stamens eight, four long, four short. Drupe yellowish or brownish red, ellipsoid to ovate, 2.5–4 × 2–3 cm. Flowering March to April, fruiting July to October (China). Hwang & Grimes 1996. Distribution CHINA: northwest Fukien, northern Guangdong, northern Guangxi, southern Guizhou, southwest Hunan, southern Jiangxi, Zhejiang. Habitat Damp, shaded areas on forested slopes or at forest edges, between 700 and 1200 m asl. USDA Hardiness Zone 8–9. Conservation status Vulnerable, due to habitat loss and degradation. Illustration Hwang & Grimes 1996; NT384, NT385.

Darke (2006) states that Halesia macgregorii is ‘virtually unknown in Western gardens’. It is more apt to say that it is little known, but becoming more widely grown, especially in North America. It seems principally to have been introduced as seed from Shanghai Botanic Garden. At the David C. Lam Asian Garden one seed germinated from a batch from the Shanghai distribution in 1997, collected at 400 m on Hengshan mountain, Hunan. This plant and two clonal descendants are now doing very well in Vancouver, standing at 5 m in 2007, with no damage from the difficult winter of 2006–2007 (minimum –9 ºC in November, with heavy snow, which slipped off the fully leafed trees without causing damage). The leaves are attractive, with pink petioles and strongly pleated laminas. The first flowers (in 2003) were yellow-green, but in subsequent seasons they have been creamy white. Peter Wharton, to whom we are indebted for this information, commented (pers. comm. 2007) that it is a graceful, elegant tree, with poise, but that its flowers are not equal to those of either Rehderodendron or the American halesias. Halesia macgregorii is also cultivated successfully in North Carolina (T. Lasseigne, pers. comm.

Plate 274. Halesia macgregorii is more closely related to Rehderodendron than to the American Halesia species, but at present it has no other name to use. Image JC Raulston Arboretum.

386

Halesia

New Trees

2007). In Europe it remains rare. The only plant seen in the research for New Trees is at Tregrehan. This is a vigorous young specimen, 2 m tall in 2007, whose new shoots are a dull purple-red; it has not yet flowered. It was obtained from Mike Hudson, of Gwavas Station, Hawkes Bay, New Zealand, in whose garden it has outstanding autumn colour (T. Hudson, pers. comm. 2007). In Vancouver it tolerates full sun so long as moisture is available in the soil (P. Wharton, pers. comm. 2007). H. monticola (NOW H. carolina Monticola Group) B307, K122 H. monticola var. vestita (NOW H. carolina Vestita Group) B308, K122

STILBACEAE (formerly SCROPHULARIACEAE)

HALLERIA

Plate 275. The vermilion flowers of Halleria lucida can be borne directly from the trunk or branches. Plants are sometimes shrubby, but on the slopes of Table Mountain it forms trees. Image G. Duncan.

L.

Halleria comprises four species, two in tropical and southern Africa and two in Madagascar. They are small trees or shrubs with quadrangular or winged stems. The leaves are opposite, petiolate, ovate or elliptic and dentate to almost entire. The flowers are produced in axillary clusters, with a three- to five-lobed cup-shaped calyx, a campanulate corolla, four- to five-lobed, red to orange, tube elongated, curved or straight, and four stamens. The fruit is a fleshy berry; the seeds narrowly winged (Philcox 1990, Fischer 2004).

Halleria lucida L.

African Honeysuckle, Tree Fuchsia

Straggly shrub 2–3 m tall or small tree to 12 m. Bark pale grey, longitudinally fissured, rather rough. Branchlets subquadrangular. Leaves thinly leathery, 4.5–10 × 2–6.2 cm, broadly ovate, glabrous, but with minute glands below, margins serrate, apex caudate to acuminate; petiole 0.4–1.2 cm long. Inflorescences usually on old wood, often partially concealed by the leaves; pedicels 1–1.4 cm long. Flowers hermaphrodite, 2.5–4 cm long, brick-red to orange-yellow; calyx three- to five-lobed, corolla unequally four- to five-lobed, tube curved, widening to 0.6–1 cm diameter, stamens four, attached to the corolla tube. Berry ovoid to subglobose, 1.2–1.8 cm long, blackish purple, often crowned by a long, thread-like, persistent style. Flowering May to December, fruiting August onwards (South Africa). Coates Palgrave 1990, Philcox 1990. Distribution ANGOLA; BOTSWANA; ETHIOPIA; KENYA; LESOTHO; MALAWI; MOZAMBIQUE; SAUDI ARABIA; SOUTH AFRICA; SWAZILAND; TANZANIA; YEMEN; ZAMBIA; ZIMBABWE. Habitat Extremely varied, including coastal scrub, karoo scrub, evergreen forest, forest margins and rocky slopes. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Coates Palgrave 1990; NT386.

In some places, such as the slopes of Table Mountain above the Kirstenbosch National Botanical Garden, Cape Town, Halleria lucida forms a true tree, with multiple straight trunks supporting the canopy, but elsewhere (perhaps without the protection from fire afforded by localities such as this) it is apt to be a much smaller shrub. Its interest lies in the abundant tubular red flowers, which are an important food source for sunbirds; its attractiveness to birds in general is one recommendation for its cultivation in southern

Section II. Species Accounts

Halleria

387

African gardens (Coates Palgrave 1990). It has been cultivated in the San Francisco area since at least 1970, when it was added to the collection at Berkeley, and should be well suited to that climate. The best specimen known in western Europe is an old, semi-collapsed tree at Tresco (6 m tall, 40 cm diameter at 60 cm) (Johnson 2007). It is also grown in mainland Cornwall, but the Tregrehan specimen remains shrubby. A warm sunny site with good drainage is required. It can be propagated by seed or from cuttings rooted in high humidity in late summer (Huxley et al. 1992).

PODOCARPACEAE

HALOCARPUS

C.J. Quinn

The three species of Halocarpus are endemic to New Zealand. All were formerly placed in Dacrydium but are not closely related to members of that genus as currently defined (Quinn 1982). They are dioecious trees or shrubs with an abrupt demarcation between juvenile and adult leaf forms. Juvenile leaves are flat and linear; adult leaves small but broad, imbricate, appressed and scale-like. Male strobili are solitary, sessile, terminal; female cones solitary, sessile, terminal, with several elongated, foliose scales, of which one to five are fertile, terminating in a central, sterile appendage. Each fertile scale bears a single, inverted ovule, completely enclosed at maturity in the epimatium, which changes colour from green to dark brown or black. A white, fleshy, aril-like collar surrounds the base of the mature cone (Quinn 1982) – the ‘halo’ from which the generic name is derived. Two species of Halocarpus are described here, but both are extremely rare in cultivation. A third species, the shrubby H. bidwillii, has been cultivated for some time (see Bean and Krüssmann: B3, K111; in both cases as Dacrydium bidwillii Hook. f. ex Kirk), but remains scarce. All are best propagated from seed, though cuttings are also possible. A mild, moist situation would be most suitable.

Halocarpus biformis (Hook.) Quinn Syn. Dacrydium biforme (Hooker) Pilger Small tree to 10 m, 60 cm dbh. Bark silver-grey, peeling in small flakes, exposing a reddish brown inner layer. Branches stout, spreading, to make a rounded crown; in exposed sites it forms a compact shrub; branchlets 3–4 mm diameter, quadrangular. Juvenile leaves spreading, linear, 1–2 × 0.15–0.3 cm, narrowed into a short, twisted petiole, midvein usually distinct. Mature leaves scale-like, densely imbricate, appressed to the stem, 2 mm long, blunt, very thick with translucent margins, prominently keeled. Male strobili solitary, c. 4 mm long, at the tips of branchlets. Female cones solitary or paired. Seeds 2–3 mm with orange aril, produced rather irregularly. Allan 1961, Salmon 1996. Distribution NEW ZEALAND: North Is., South Is., Stewart Is. Habitat Forests and scrub above the treeline, between 0 and 1400 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Van Gelderen & van Hoey Smith 1996; NT387, NT445.

Halocarpus biformis is well named, as the transition from juvenile to adult growth can be very abrupt on a single shoot (see Figure 50, p. 445) – although tufts of juvenile growth can appear even on an otherwise fully mature specimen. In the wild it forms

Plate 276. Halocarpus biformis is very slowgrowing and can form a small tree or, as here in New Zealand, a low-domed bush. Image D. Luscombe.

388

Halocarpus

New Trees

a compact small tree, with very dense wood, but in cultivation in the northern hemisphere it is as yet only a small shrub. Jan De Langhe has recorded it at Jardin botanique de la Roche Fauconnière, Cherbourg, France, and at Trengwainton in Cornwall (J. De Langhe, pers. comm. 2007), but the only living specimen seen in the research for the current work grows at Tregrehan: a 1996 accession, 80 cm tall in 2005. The new growth on juvenile shoots is bright green.

Halocarpus kirkii (F. Muell. ex Parl.) Quinn

Monoao

Syn. Dacrydium kirkii F. Muell. ex Parl. Tree to 25 m, 1 m dbh. Bark greyish brown, flaking in rounded plates. Branches spreading to erect; branchlets pendulous. Juvenile leaves 1.5–4 × 0.1–0.3 cm, linear, usually acute, held at right angles to the shoot, soft in texture, persisting until the tree is at least 10 m tall and then co-occurring with adult leaves for some time. Adult leaves 0.2–0.3 cm, scale-like, obtuse, hard in texture, margins hyaline. Male strobili solitary, terminal, sessile, to 1 cm long. Female strobili in terminal clusters of three to five. Seeds 3–8 mm long, with an orange aril. Allan 1961, Salmon 1996. Distribution NEW ZEALAND: Great Barrier Is., northern part of North Is. Habitat Lowland forest to 700 m, usually with Agathis australis. USDA Hardiness Zone 9–10. Conservation status Vulnerable. Illustration Van Gelderen & van Hoey Smith 1996; NT388.

Plate 277. When young, Halocarpus kirkii has long, narrow leaves and resembles a normal ‘conifer’, but once trees reach c.10 m they become small and scaly. In cultivation, however, this is likely to take many years. Image J. Grimshaw.

In the wild Halocarpus kirkii is a fine but little-known tree, apparently rather scarce throughout its natural range (Gymnosperm Database 2007a). Other than in New Zealand, its situation in horticulture is rather similar. The only specimen traced in cultivation in the northern hemisphere is at Tregrehan, where in 2005 it had achieved 1.5 m after 10 years, being particularly slow-growing when young (T. Hudson, pers. comm. 2005). It has a pleasant soft appearance (and feel), from the bright grass-green juvenile leaves. The species should be tried in sheltered, moist sites in warm gardens.

MONIMIACEAE

HEDYCARYA

J.R. Forst. & G. Forst.

Hedycarya comprises about 12 species, most of which are endemic to New Caledonia. Hedycarya arborea, however, is endemic to New Zealand, and there is one species in Australia (H. angustifolia A. Cunn.) and one on the Pacific Islands of Fiji, Samoa and Vanuatu (H. dorstenioides A. Gray). Of these, only H. arborea is cultivated in our area. Hedycarya species are dioecious trees or shrubs with opposite or subopposite, entire or dentate leaves. Inflorescences are paniculate and include one to many flowers; they may be solitary or clustered, axillary or terminal, and can be produced on the major branches (ramiflory) or the main stem (cauliflory). The flowers are rather small, with a cup-shaped receptacle and insignificant tepals; staminate flowers have approximately 15 stamens inserted into a glabrous receptacle; the receptacle of pistillate flowers is pubescent inside and contains 5–60 carpels. Each ripe carpel is drupe-like, and they may be entirely free or may fuse together to form a compound fruit (Jérémie 1978).

Section II. Species Accounts

Hedycarya

389

1 cm

A

C

Hedycarya arborea J.R. Forst. & G. Forst.

B 1 cm

Pigeonwood, Poraikaiwihiri

Shrub or small tree to 12 m, multistemmed. Branchlets pubescent or almost glabrous. Leaves evergreen, opposite or subopposite, leathery and aromatic, (5–)8–11.5 × (2–)3–5.5 cm, elliptic, both surfaces pubescent, particularly when young, midrib prominent below, six to eight secondary veins on each side of the midrib, margins dentate with 6–11 teeth, apex apiculate; petiole 0.8–1.2 cm long and pubescent. Inflorescences axillary, paniculate, 3–4 cm long and with 3–20 flowers. Staminate flowers ~0.7 cm diameter with 15–20 stamens; pistillate flowers ~0.4 cm diameter with 10–20 carpels. Ripe carpels solitary and drupe-like, bright orange-red. Flowering October, fruiting April (New Zealand). Jérémie 1978. Distribution NEW ZEALAND: North Is., South Is. as far south as the Banks Peninsula. Habitat Lowland and montane forest. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Jérémie 1978; NT389.

Forming a stocky small or medium-sized tree, Hedycarya arborea is known as Pigeonwood on account of its fruits, that attract large numbers of pigeons when ripe. The birds gorge on the orange fruits, becoming rather drowsy in the process (Salmon

Figure 42 (above). Hedycarya arborea: habit with flowers (A); fruit cluster (B); single fruit (C).

390

Hedycarya

New Trees

1996). It is considered useful in New Zealand horticulture for its dense canopy of glossy dark green leaves, amongst which the pale green flowers are rather inconspicuous. The new shoots are bright fresh green, but rather frost-sensitive, so the tree should be sited in a sheltered position where spring frosts are rare. Rich deep soil is recommended (Metcalf 2000). A specimen has been growing steadily at Tregrehan since 1994 and now flowers, and it is also in cultivation at the San Francisco Botanical Garden.

STYRACACEAE

HUODENDRON

Rehder

There are four species of Huodendron, occurring in China, Myanmar, Thailand and Vietnam. They are evergreen trees or shrubs with naked buds. The leaves are alternate with entire or serrate margins; stipules are absent. Inflorescences are terminal or axillary, paniculate or subcorymbose. The flowers are small, hermaphrodite and 5-merous, with a tubular calyx, free petals, reflexed after anthesis, and 8–10 stamens, exserted. The fruit is an ovoid capsule, partially surrounded by the calyx, dehiscing via two valves; the seeds do not have wings (Hwang & Grimes 1996). The genus Huodendron is completely new to cultivation and gardeners are still very much at the stage of assessing it: it will probably be several more years before it is possible to say anything definitive about its potential and tolerances. As typical representatives of Styracaceae, however, its species can be expected to enjoy warm summers, preferably in fertile, moisture-retaining acidic soil.

Huodendron biaristatum (W.W. Sm.) Rehder Shrub or tree, usually to 12 m but can reach 20 m or more, 0.25 m dbh. Branchlets tomentose or glabrous. Leaves 5–17 × 2.5–6 cm, elliptic to lanceolate or oblong, upper surface glabrous or with some grey hairs on the midrib, lower surface glabrous except for tufts of hair in the vein axils, 4–9(–11) secondary veins on each side of the midrib, veins impressed above, margins remotely serrate, apex acute, obtuse or acuminate; petiole 0.5–1.5 cm long. Inflorescences terminal or axillary, subcorymbose, 3–10 cm long, grey-tomentose; pedicels ~1 cm long. Flowers yellowish; calyx pubescent, petals narrowly oblong, 0.6–0.9 cm long, stamens 8–10. Capsule ovoid, ~0.5 cm long, densely tomentose. Flowering April to May, fruiting June to October (China). Hwang & Grimes 1996. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Yunnan; MYANMAR; THAILAND; VIETNAM. Habitat Between 200 and 600 m asl. USDA Hardiness Zone 9 (?). Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT390.

Plate 278. In addition to the charms of its foliage and flowers Huodendron biaristatum has attractively peeling bark, which becomes more conspicuous with age. Image J. Grimshaw.

Huodendron biaristatum holds considerable promise of being an attractive flowering tree for the garden, having dense clusters of white flowers, even on relatively young plants. A flowering tree in the wild is a spectacular sight (T. Hudson, pers. comm. 2005), so it is to be hoped that it will be hardy enough for wider planting. The most obvious features of the flowers are the long-exserted stamens, as the petals recurve and are quite inconspicuous (R. Lancaster, pers. comm. 2007). The leaves are lanceolate, with long drip-tips, and are a glossy dark green – there is a distinct resemblance to Ficus benjamina! They flush pink in

Section II. Species Accounts

Huodendron

391

spring (Hudson 2004), and another attractive feature is the rich red-brown bark. Precise dates of introduction are not known for certain, but seed has been offered by the Shanghai Botanic Garden. A tree that has been growing at Tregrehan since 1999 was 3 m tall when seen in 2005 and has been flowering for several years, getting better and better with age (T. Hudson, pers. comm. 2007). It has a wide range in southeastern Asia, but at rather low altitudes, so a particularly warm sheltered site is indicated. When mature it can be a rather large tree: Tom Hudson (pers. comm. 2005) has seen it over 20 m tall in northern Vietnam.

Huodendron tibeticum (J. Anthony) Rehder Shrub or tree, 6–25 m, 0.25 m dbh. Branchlets dark brown. Leaves papery, 6–11 × 2.5–4 cm, lanceolate to elliptic, largely glabrous, five to nine secondary veins on each side of the midrib, margins entire or slightly serrate, apex acuminate to acute; petiole 0.5–1 cm long. Inflorescences terminal, subcorymbose, 4–8 cm long with 8–12 flowers; pedicels 0.3–0.5 cm long. Calyx tubular, petals linear-oblong, 0.6–0.7 cm long. Capsule ovoid, ~0.3 cm long. Flowering March to May, fruiting August to September (China). Hwang & Grimes 1996. Distribution CHINA: northeastern Guangxi, Guizhou, western Hunan, southeastern Xizang, Yunnan; VIETNAM. Habitat Dense forest between 1000 and 3000 m asl. USDA Hardiness Zone 9 (?). Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT391.

Huodendron tibeticum is established and growing well at Tregrehan, forming dense bushes clad in glossy dark green leaves. It is commercially available in the United Kingdom and is being planted by enthusiasts anxious to obtain the latest novelty, but young plants are not always easy to establish. It may be worth growing them on to achieve a larger size before planting them out. In terms of the distribution of the different species in the genus, as recorded in Flora of China, this should be the hardiest.

PITTOSPORACEAE

HYMENOSPORUM

F. Muell.

Hymenosporum is monospecific, comprising only the species H. flavum. It is wideranging through Australia, Indonesia and Papua New Guinea, and correspondingly variable in form – from a large tree in rain forest to smaller trees or shrubs in the more temperate parts of its range (Elliot & Jones 1990). Provenance selection is likely to be important if this beautiful tree is to become known to a wider circle of gardeners in our area. Selections from the highest altitudes in the Blue Mountains, New South Wales should be sought.

Hymenosporum flavum (Hook.) F. Muell.

Australian Native Frangipani, Sweetshade

Shrub or tree 4–20 m, with a narrow, almost columnar crown. Bark smooth and greyish brown. Branchlets initially pubescent. Leaves evergreen, alternate, often clustered at the tips of branches, 6–15 × 2–6 cm, lanceolate, upper surface dark green and glossy, lower surface pale green and pubescent when young, five

Plate 279. Huodendron tibeticum at Tregrehan, showing its glossy evergreen leaves. Image J. Grimshaw.

392

Hymenosporum

New Trees

1 cm

A B

Section II. Species Accounts

Hymenosporum

to seven primary veins on each side of the midrib, margins entire, apex acute; petiole 1–1.5 cm long, merging into the lamina. Inflorescences terminal, umbellate and about 20 cm diameter. Flowers hermaphrodite, strongly fragrant, 4 × 3 cm; calyx five-lobed, eventually disintegrating; corolla composed of a long tube that flares out abruptly into five distinct club-shaped petals, initially pale cream, maturing to yellowish orange or

393

Figure 43 (opposite). Hymenosporum flavum: habit with flowers (A); open capsules after seed release (B).

even red. Fruit a brown pear-shaped capsule, ~3 cm long, which splits in two, releasing numerous winged seeds. Flowering September to January, fruiting October to June (Australia). Elliot & Jones 1990. Distribution AUSTRALIA: along the coast southwards from the Cape York Peninsula, Queensland to the Blue Mountains of New South Wales; INDONESIA: Western New Guinea; PAPUA NEW GUINEA. Habitat Rain forest and tall, open forest. USDA Hardiness Zone 9a. Conservation status Not evaluated. Illustration NT392, NT393. Cross-reference K160.

Hymenosporum flavum is a characteristic tree of gardens in southern California, where I (JMG) first saw it at the Los Angeles County Arboretum in 1986 and was captivated by the beauty of the yellow and cream flowers and their lovely rich scent. In southern California and Australia it is popular as a garden and street tree, but further north it does less well. It is cultivated in the San Francisco Bay Area; beyond there, however, it is only happy in mild places along the Oregon coast (S. Hogan, pers. comm. 2007). At Tregrehan it is not successful outside without protection (T. Hudson, pers. comm. 2006), but it does well on Tresco (Johnson 2007). When happy Hymenosporum is fast-growing, preferring good soil with adequate moisture, but can be weedy with selfsown seedlings – and messy, as the sticky fruits attach themselves to feet and carpets (D. Gimbel, pers. comm. 2007). Mature trees can tolerate some frost, but young plants are sensitive and can be severely damaged (Elliot & Jones 1990).

ILEX

AQUIFOLIACEAE

L.

Syn. Nemopanthus Raf.

Hollies Ilex is the only genus in the Aquifoliaceae and has well over 400 species, though Galle (1997) considered that there may be as many as 800. In addition, the monospecific mountain holly genus Nemopanthus has recently been placed in synonymy with Ilex (Powell et al. 2000). The hollies have an almost worldwide distribution in temperate, tropical and subtropical climatic zones, and are particularly diverse in eastern and southeastern Asia and South America. The genus is best known for its evergreens but there are about 30 deciduous species. In growth form they range from small, creeping shrubs to large trees; there are also several epiphytic species and a few climbers (for example, I. clemensiae Heine, I. scandens Cuatrec.). Hollies are generally slow-growing. Their branches are covered in lenticels, which are highly conspicuous in the deciduous species. The leaves are extremely variable in shape and size, and by no means always spiny. The leaves are alternate (rarely opposite) and typically thick and leathery, though they may also be thin and papery, and the veins may be prominent or obscure. Most hollies have serrate, crenulate or entire leaf margins, and marginal spines – as found in I. aquifolium – are actually rather rare; the degree of armature on the leaves can change with age, and even in I. aquifolium the mature leaves are sometimes entire. Stipules are present in most species, though they are often very small (< 1 mm). Ilex is

Plate 280. Hymenosporum flavum can smother itself in fragrant yellow flowers. A wonderful tree for the mildest parts of our area. Image J.R.P. van Hoey Smith.

394

Ilex

Plate 281. Ilex bioritsensis has neat, evergreen leaves and produces a festive abundance of berries. GUIZ 85 at Kew, November 2007. Image J. Grimshaw.

New Trees

dioecious, with unisexual flowers on separate plants. The flowers can be either solitary or in groups (cymes) and the cymes can in turn be either solitary or fasciculate. Solitary inflorescences are produced by species that flower on new growth, fasciculate inflorescences by species that flower on stems from previous seasons. Holly inflorescences are often inconspicuous, and the pistillate inflorescences usually have fewer flowers than those of staminate plants. The flowers are typically white, cream, pale yellow or greenish, though pink, red and brown flowers occur. They range in size from 0.3–0.4 to 1–1.3 cm diameter and may be fragrant. The fruit is fleshy with a thin, papery skin and multiple seeds. Most species have red fruits, though white, yellow and orange forms occur in some species; black fruits are particularly common in the South American species. The fruits are produced on pedicels that vary in length between 0.2 and 4.5 cm. The ‘seeds’ are actually pyrenes, with a woody, bony or leathery endocarp enclosing the true seed (Hu 1949a, 1949b, 1950, Galle 1997). Valued for both its presence in the landscape and its decorative fruits, Ilex is an important genus of trees and shrubs, and is one of those for which there is a specialist society. The Holly Society of America, founded in 1947 and based in the United States, promotes interest in all members of the genus and produces the useful Holly Society Journal, published twice a year. It is the International Cultivar Registration Authority for Ilex and accredits good holly collections as Holly Arboreta and Experimental Test Centres for the education of the public in the use of holly. Most horticultural attention is rightly paid to the abundant selections of the popular species and hybrids. These are described in great detail in Fred C. Galle’s Hollies, The Genus Ilex (1997), which should be consulted for information on the vast array of cultivars available. More recently, Hollies for Gardeners by Chris Bailes (2006) has been published, providing a useful adjunct to Galle. Galle’s invaluable book also describes a very large number of wild species of Ilex, most of which are not in cultivation. A surprising number of them are tropical or subtropical in origin and therefore unlikely ever to be useful subjects in our area, but there are also many horticulturally unknown ones from China and elsewhere in temperate eastern Asia to provide a challenge to collectors. One tropical species that could occasionally appear in temperate gardens as a pot plant is I. paraguariensis A. St. Hil., from Paraguay, Argentina and Brazil. In South America it is used to make a popular stimulating ‘tea’, mate (the plant being known there as Yerba Mate), and it is sometimes cultivated as a curiosity. Mate is an acquired taste, especially for palates accustomed to infusions of Camellia sinensis. It is likely that many other hollies are being tested in cultivation. For example, the following are currently being grown under glass at Arboretum Bokrijk, Genk, Belgium, and some might well be hardy in milder parts of maritime Europe: I. canariensis Poir., I. formosana Maxim., I. lonicerifolia Hayata, I. maximowicziana Loes. (J. Van Meulder, pers. comm. 2007). Many gardens and arboreta have fine collections of hollies, often dominated by

Section II. Species Accounts

Ilex

the popular species and cultivars, but usually containing a fair representation of the ‘others’. In Europe the largest collection is at Arboretum Bokrijk, with over 600 taxa, including several of those described here. In France a large collection forms the Conservatoire National d’Ilex, at Arboretum des Près de Coulands, Orléans. In the United Kingdom the long-established collection at Kew is comprehensive, and there is a National Plant Collection of Ilex at RHS Rosemoor, Devon. The Valley Gardens at Windsor Great Park also hold a major collection of Ilex. In the United States Ilex is well represented in many arboreta, including the important and developing collection at the Washington Park Arboretum; also the US National Arboretum, the Morris Arboretum, the Bernheim Arboretum and Research Forest, Kentucky, and the Polly Hill Arboretum, Martha’s Vineyard, Massachusetts. In general hollies are quite tolerant of soil type, although they thrive best where they do not become too dry in summer. The species described below are of varying degrees of hardiness, and planting sites should be chosen accordingly. Propagation is by cuttings or seed, but germination can be erratic and hybridisation is frequent. The dioecious nature of hollies requires that both sexes are present for viable seed to be set, but the pollinator can be another related species. This is unimportant if all that is required is a decent crop of berries, but for conservation purposes, especially of the rarer species, it is vital that groups of mixed male and female clones are maintained, to avoid the problem of having a cultivated population of plants of only one sex. I. ×altaclerensis (hort. ex Loudon) Dallim. B429, S284, K171 I. ambigua (Michx.) Torr. K172 I. amelanchier M.A. Curtis B442, K172 I. aquifolium L. B432, S285, K172 I. aquifolium f. bacciflava (West.) Rehder B434, K173 I. aquifolium var. balearica (Desf.) Loes. B435, S285

I. aquifolium var. chinensis Loes. B435, S285 I. aquifolium f. heterophylla (NOW I. aquifolium L. Heterophylla Group) K174 I. aquifolium f. pendula (NOW I. aquifolium L. ‘Pendula’) B437 I. ×aquipernyi Gable ex Whittem K176 I. ×attenuata Ashe K178 I. ×beanii Rehder B443, K178

Ilex bioritsensis Hayata Syn. I. pernyi Franch. var. veitchii Bean Large shrub or small tree 1.5–10 m; crown densely branched. Branchlets glabrous or slightly pubescent, greyish brown and without lenticels. Leaves evergreen, retained for up to four years, 2.5–6 × 1.5–3.5 cm, ovate to oblong, thick and leathery, upper surface glossy, lower surface opaque and glaucous, four to six secondary veins on each side of the midrib, margins sinuate with three to four spines on each side, apex acuminate; petiole pubescent, 0.3 cm long. Inflorescences axillary, fasciculate. Flowers creamy white to white, 2–4-merous and 0.3–0.4 cm diameter; staminate flowers with partially fused petals, stamens longer than the petals; pistillate flowers with free petals and short staminodes. Fruit fleshy, ellipsoid to spherical, red and 0.7–1 cm diameter, with one to two (to four) pyrenes. Flowering April to May, fruiting July to October (China). Hu 1949b, Lu 1993a, Galle 1997, Chen et al. 2006. Distribution CHINA: Guizhou, southwestern Hebei, southwestern Hubei, Hunan, Sichuan, Yunnan; MYANMAR; TAIWAN. Habitat Evergreen broadleaved forest between 900 and 4000 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Phillips & Rix 1989, Lu 1993a, Andrews 1997, Galle 1997; NT394. Cross-references B451 (as I. pernyi var. veitchii), K178. Taxonomic note Ilex bioritsensis is sometimes cultivated under the name I. ficoidea Hemsl., especially in the United States. True I. ficoidea is not known to be in cultivation.

Ilex bioritsensis has been in cultivation since it was introduced by E.H. Wilson from his early expedition for the Veitch nurseries (Wilson 803 ex Hort. Veitch). It was then

395

396

Ilex

New Trees

known as I. pernyi var. veitchii, under which name references will be found in older literature. There is indeed a strong similarity between I. bioritsensis and I. pernyi, but the latter is a much stiffer-looking plant with stronger marginal spines on its leaves, and has four pyrenes (rather than two as in I. bioritsensis). Ilex bioritsensis is an attractive holly, sometimes shrubby but capable of forming a single-trunked tree with a tidy shape when young, though somewhat loose and straggly when older. There is a specimen at Wakehurst Place, of about 4 m when seen in June 2005, grown from SICH 1192, collected by the Fliegner, Howick, McNamara & Staniforth team in October 1992 at c. 2460 m in Zhaojue Co., Sichuan. Here it grew as a 2 m shrub, in an open situation on a steep north-facing slope amongst an interesting assortment of broadleaved woody plants. SICH 1144 was gathered by the same expedition from an 8 m tree growing at 2770 m in Muli Co. In 1985 it was collected by the Simmons, Fliegner & Russell expedition to Guizhou (GUIZ 85). There are numerous plants from these collections at Kew. At Wakehurst Place there is also an older plant, of unknown planting date, derived from the early introductions, which was 11 m in 2005 and producing many suckers from the base (TROBI). The species is widely cultivated in western Europe and there is a particularly large, broad-canopied specimen at Arboretum Bokrijk, Genk, Belgium. This has three trunks, the largest of which is 50 cm dbh, although the tree itself is only 7 m tall (J. Van Meulder, pers. comm. 2007). In North America it has proven to be hardy and heat-tolerant, being successful on the West Coast and in the eastern and southeastern parts of the United States, and is considered to be a resilient species for any conditions so long as the soil is well drained (Wharton et al. 2005).

Ilex buergeri Miq. Plate 282. The absence of spines on its leaves had dire consequences for this specimen of Ilex buergeri at the Washington Park Arboretum … Image S. Andrews.

Shrub or tree 7–15 m, c. 0.3 m dbh; crown densely branched. Branchlets pubescent with smooth, greyish bark. Leaves evergreen, pink when young, 4–8 × 1.5–3 cm, ovate to oblong, thin and leathery, upper surface lustrous dark green with a prominent midrib, lower surface dull, five to seven secondary veins on each side of the midrib, margins irregularly serrate, apex obtuse; petiole slender, pubescent, 0.4–1.2 cm long. Inflorescences axillary, fasciculate. Flowers yellowish green, fragrant, 4-merous and 0.6 cm diameter; staminate flowers with stamens longer than the petals. Fruit fleshy, globose, red and 0.5–0.6 cm diameter, with four pyrenes. Flowering April to June, fruiting October to November (China). Ohwi 1965, Galle 1997, Chen et al. 2006. Distribution CHINA: southern Anhui, Fujian, Guangdong, Guangxi, Hubei, Hunan, Jiangxi, Zhejiang; JAPAN: Honshu, Kyushu, Shikoku. Habitat Evergreen broadleaved forests between 100 and 700 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Hayashi et al. 1985, Andrews 1997; NT396.

Ilex buergeri var. buergeri is rare in cultivation, possibly due to being deemed tender in our area, while I. buergeri var. rolfei (Elmer) Loes. of the Philippines is certainly not hardy and probably not in cultivation. Var. buergeri is available commercially in the southeastern United States and is found in a few arboreta and private gardens south of Washington DC, including the JC Raulston Arboretum, where a tree planted in 2001 had reached 2.5 m in 2004 (JC Raulston Arboretum database). Susyn Andrews (pers. comm. 2007) reports having seen a densely foliaged 6 m specimen in the garden of B.M. Bauers at Mann’s Harbour, North Carolina in 1994, from seed distributed by the US National

Section II. Species Accounts

Ilex

Arboretum. It seems to be scarce in the western states, but there was a male clone at the Washington Park Arboretum, growing there from 1964 when it was obtained from the Morris Arboretum (Omar 1994). Randall Hitchin (pers. comm. 2007) has supplied more details: ‘We had four plants of Ilex buergeri, from a single, clonal (male) accession. These appear to have been hardy and grew well, albeit slowly. At ~40 years of age, they were somewhere around 8–12 ' high [2.4–3.6 m] – more of a large shrub. I suspect that they might be stronger growers with more summer heat and rainfall. Sadly, we no longer have them as they were cut to the ground by homeless persons to make a brush shelter and the re-propagated plants did not establish.’ Now we know why hollies evolved spines … I. canariensis Poir. K178 I. cassine L. B437, K178 I. centrochinensis S.Y. Hu S285, K178 I. chinensis Sims K178 I. ciliospinosa Loes. B438, K178 I. colchica Poyark. S285 I. corallina Franch. B438, S286, K178 I. cornuta Lindl. & Paxton B439, K178 I. cornuta var. fortunei (Lindl.) Hu B439 I. crenata Thunb. ex Murray B440, S286, K178

I. crenata f. latifolia (Goldring) Rehder B440, K179 I. crenata f. longifolia (Goldring) Rehder B440, K179 I. crenata var. paludosa (Nakai) Hara B440, K179 I. cyrtura Merr. B441, S286 I. decidua Walter B442, K179 I. dipyrena Wall. B442, S286, K179 I. fargesii Franch. K179

Ilex forrestii Comber Shrub or small tree to 7 m. Branchlets pubescent and slightly wrinkled with small, sparse lenticels. Leaves evergreen, (5–)7–9(–11) × (1.5–)2–3(–4) cm, oblong to elliptical-lanceolate, thin and leathery, upper surface somewhat pubescent, lower surface glabrous, midribs impressed, seven to nine secondary veins on each side of the midrib, margins entire in the lower half of the leaf, crenulate to serrate in the upper half, apex acuminate; petiole 0.5–1.2 cm long. Inflorescences fasciculate, axillary and somewhat pubescent. Flowers yellowish green, (4–)5-merous, 0.3–0.4 cm diameter. Fruit fleshy, globose, red and 0.3–0.5 cm diameter, with five to seven pyrenes. Flowering June to July, fruiting September to November (China). Galle 1997, Chen et al. 2006. Distribution CHINA: western Sichuan, Xizang, Yunnan; endemic to the parallel valleys of the Mekong, Salween and Yangtze Rivers. Habitat Evergreen and deciduous broadleaved forest between 1800 and 2900(–3500) m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Chen & Feng 1999. Cross-reference B439. Taxonomic note Specimens with glabrous branches have been distinguished as var. glabra S.Y. Hu.

Ilex forrestii has been in cultivation since its introduction by George Forrest but has remained scarce, with no large specimens recorded. It is possible that trees derived from this source may be found in British or Irish gardens. More recently, it has been collected in Yunnan by the Gaoligong Shan Expedition of 1996, under the number GSE 96. Young plants from this collection are growing at Edinburgh. They have elegant narrow leaves with a long ‘drip-tip’. In the early 1970s holly seedlings were distributed from the Morris Arboretum as I. forrestii but these have since been confirmed as examples of I. ×attenuata (I. opaca × I. cassine). Among them is a tree with red fruits at the Washington Park Arboretum, described as I. forrestii by Omar (1994) but identified as I. ×attenuata by Susyn Andrews (pers. comm. 2007). Another, at Longwood Gardens, Pennsylvania, has yellow fruits. When this too was found to be the hybrid, records at the Morris Arboretum were checked and it was found that the seed had indeed been collected from I. ×attenuata

397

398

Ilex

New Trees

‘Fosteri’: a typist’s error had transmogrified it to I. forrestii. This yellow-berried clone is now called I. ×attenuata ‘Longwood Gold’ (Longwood Gardens 2008). The identity of any tree in the United States labelled I. forrestii should be checked. I. franchetiana (NOW I. fargesii Franch. subsp. fargesii) B447, S287, K179 I. geniculata Maxim. B444, K179 I. georgei Comber B451, K179 I. glabra (L.) A. Gray B444, K179

Ilex hayatana Loes. Tree to 12 m. Bark pale greyish black. Branchlets slen-

Plate 283. Ilex hayatana ETOT 131, fruiting heavily on Chilanshan, Taiwan in 1992. Its descendants have not thrived in cultivation. Image T. Kirkham.

der, pubescent and with conspicuous lenticels. Leaves evergreen, 2–5 × 1–2 cm, ovate to elliptical, thin and leathery, upper surface somewhat scabrous, though hairs mostly restricted to the midrib, lower surface also somewhat scabrous and with an elevated midrib, four to five secondary veins on each side of the midrib, margins entire, apex acuminate; petiole 0.2–0.7 cm long. Inflorescences fasciculate, axillary, each axis with a single flower. Flowers 4-merous. Fruit fleshy, globose, red and 0.5–0.7 cm diameter, with four pyrenes. Flowering in summer, fruiting in autumn until February of the following year (Taiwan). Lu 1993a, Galle 1997, Chen et al. 2006. Distribution JAPAN: Ryukyu Is.; TAIWAN: north and central provinces only. Habitat Medium-altitude montane forest between 2300 and 3000 m asl (Taiwan). USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Walker 1976, Lu 1993a; NT398. Taxonomic note There has been some confusion as to the identity and distribution of I. hayatana Loes. The species was originally described from Taiwanese specimens, but Ohwi (1965) and Ohba & Akiyama (1999) recognised I. hayatana auct. non Loes. as a synonym of I. goshiensis Hayata. The latter occurs not only in Taiwan and the Ryukyu Islands, but also on Honshu, Kyushu and Shikoku, and possibly in China (Hainan). According to Hu (1953), I. hayatana differs from I. goshiensis in that the leaves are narrower with acuminate or caudate (not obtuse) apices. The inflorescences are fasciculate with single-flowered branches, while those of I. goshiensis are fasciculate with three- to seven-flowered branches.

The only collection of Ilex hayatana ever made seems to be ETOT 131, gathered by Tony Kirkham and Mark Flanagan on Chilanshan, Taiwan in 1992. Here it grew at about 1900 m in rich forest of mixed conifers and broadleaves; in the field notes it is recorded as forming a tree of up to 18 m with a narrow spread of only 4 m, but in the published account of the expedition it is described as a 4 m shrub, with abundant but unexciting fruits (Flanagan & Kirkham 2005). A seedling from this collection is growing at Kew, and in 2007 it was a lanky, gappy shrub, 1.8 m tall by 2.3 m wide, with a few fruits among the yellowing foliage (S. Andrews, pers. comm. 2007). It has neat ovate leaves with a broadly acuminate apex.

Ilex hookeri King Shrub or tree to c. 18 m. Branchlets chestnut-coloured, turning yellowish brown to grey; lenticels absent. Leaves evergreen, 6.4–14.3 × 2–3.6 cm, lanceolate to elliptical, thick and leathery, upper surface glabrous, midrib depressed, lower surface glabrous and with a prominent midrib, 7–10 secondary veins on each side of the midrib, margins finely serrate, apex acute or acuminate; petiole 1–2.3 cm long, glabrous. Inflorescences axillary, fasciculate. Flowers reddish pink, 4-merous, 0.4 cm diameter. Fruit fleshy, globose, red and 0.4–0.6 cm diameter, with four pyrenes. Flowering May to June, fruiting October (China). Andrews 1991, Galle 1997, Chen et al. 2006. Distribution BHUTAN; CHINA: Xizang (Chumbi Valley), northwestern Yunnan; INDIA: Sikkim; MYANMAR; NEPAL. Habitat Margins of both broadleaved and coniferous forests between 2100 and 3300 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Andrews 1991, 1997. Cross-reference B447.

Section II. Species Accounts

Ilex

399

Bean’s brief mention of Ilex hookeri (1981a) noted that it was rare in cultivation, and the situation does not seem to have changed much since that observation. The only current record of the species in TROBI is of an 8 m individual in the Ventnor Botanical Garden on the Isle of Wight, and it would seem to be distinctly tender. There is, however, a tree at Wakehurst Place, collected by Tony Schilling in mixed temperate forest on the Yallung Ridge, Nepal in 1981 (SCHL 2537). This was 2.1 m tall in 1996 (Kew database), but has since lost its main stem and is now producing shoots from its base up to 2 m tall (S. Andrews, pers. comm. 2007). Plants previously grown by Hillier Nurseries in the United Kingdom have turned out to be I. dipyrena or I. kingiana. All three species have very spiny juvenile foliage and they are easily confused. I. integra Thunb. ex Murray B445, K180 I. integra var. leucoclada Maxim. B445 I. intricata Hook. f. B445, S287, K180 I. kingiana Cockerell B446, S287, K180 I. ×koehneana Loes. B447, K180 I. laevigata (Pursh) A. Gray B446, K180 I. laevigata f. henryi Robins. B446 I. latifolia Thunb. ex Murray B446, K180

Ilex limii C.J. Tseng Tree to 10 m. Branchlets purplish black, glabrous, lenticels inconspicuous. Leaves evergreen, 7–13 × 3–4 cm, oblong or oblong-elliptic, leathery, glabrous, 10–14 secondary veins on each side of the midrib, veins slightly raised on both surfaces, margins entire, recurved, apex acuminate; petiole glabrous, 1–1.3 cm long. Flower details unrecorded. Infructescence cymose, solitary and axillary; fruiting peduncles 0.5–0.7 cm long, densely pubescent. Fruit one to three per infructescence, ellipsoidal, 0.5–0.7 cm diameter, with five pyrenes. Fruiting August to November (China). Chen et al. 2006. Distribution CHINA: Fujian, Guangdong, Jiangxi, Zhejiang. Habitat Evergreen broadleaved or pine forest between 500 and 1200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT399.

The only specimen of Ilex limii traced in cultivation is at Ness. Growing healthily, it was over 2 m tall when seen in 2006, and has large, rather pale green leaves. It was received as seed from Shanghai Botanic Garden in 1985, under the name I. elmerrilliana S.Y. Hu; its first flowering and fruiting in 1996, however, led to its eventual identification as I. limii. It seems quite hardy in the windy conditions of Ness, where it has now grown outside for many years, and should clearly be attempted elsewhere. I. longipes Chapm. ex Trel. K180 I. macrocarpa Oliver B447, S287, K180 I. macropoda Miq. K180

Ilex mitis (L.) Radlk.

I. melanotricha (NOW I. fargesii Franch. subsp. melanotricha (Merr.) S. Andrews) B447, K180

African Holly, Cape Holly

Shrub or tree to 40 m, dbh 0.3–1 m, rarely to 5.5 m. Branchlets slightly pubescent; mature bark smooth, grey or pinkish red. Leaves evergreen, 2.5–14 × 1.3–4.6(–5.3) cm, shape extremely variable, though basically elliptic, thin and leathery, upper surface glabrous, dark green, midrib depressed, lower surface glabrous, pale green, seven to nine secondary veins on each side of the midrib, margins entire or with spiny teeth near apex, apex

Plate 284. The specimen of Ilex limii at Ness Botanic Gardens is the only one known in cultivation. Such rarities should be priorities for propagation and distribution. Image P. Williams.

400

Ilex

New Trees

acute, apiculate or rounded; petiole 0.5–1 cm long, glabrous. Inflorescences axillary, fasciculate or rarely solitary, each axis with one to four (to five) flowers (female) or one to six (to seven) flowers (male). Flowers white, fragrant, 4–6(–8)-merous. Fruit fleshy, ripening from greenish pink to scarlet, globose, 0.4–0.7 cm diameter, with four to six (to eight) pyrenes. Flowering September to February, fruiting December to June (South Africa). Verdcourt 1968, Andrews 1990, Galle 1997. Distribution ANGOLA; CAMEROON; EQUATORIAL GUINEA: Bioco; ERITREA; ETHIOPIA; KENYA; MADAGASCAR; MALAWI; MOZAMBIQUE; NIGERIA; SIERRA LEONE; SOUTH AFRICA; SUDAN; TANZANIA; UGANDA; ZAMBIA; ZIMBABWE. Habitat Upland rain forest, dry evergreen forest and secondary scrub, typically near streams or rivers. Altitude ranges from between 7 and 600 m asl (at the coast), to between 900 and 3150 m asl (inland). USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Verdcourt 1968; NT400. Taxonomic note Ilex mitis exhibits considerable morphological variation across its wide range. Numerous segregate species, subspecies and varieties have been described and these are best referred back to I. mitis.

Plate 285. Found in montane forest throughout Africa, Ilex mitis can form a large tree, as here on Kilimanjaro, covered in lichens. Image J. Grimshaw.

Like Juniperus procera, Ilex mitis is both the largest species of its genus and the only member of it which occurs in sub-Saharan Africa. It grows there in cool Afromontane forest, and can achieve spectacular dimensions and make a fine tree. In the Kilimanjaro forest it is most frequent at about 2500 m and is conspicuous by its pale grey bark. It is an important constituent of the forests of South Africa, and can be easily observed on the slopes of Table Mountain. A number of medicinal properties are attributed to it in southern Africa, one of the more noteworthy practices being the Zulu custom of bathing influenza-sufferers in a lather made of the leaves rubbed in water (Coates Palgrave 1990). Its origins in essentially frost-free conditions have not encouraged many to grow it, although optimistic travellers have occasionally brought home seed from the Cape, as Sir Harold Hillier did in 1973 (A. Coombes, pers. comm. 2008). There are a couple of notable exceptions. Susyn Andrews has a 2.5 m specimen in her garden at Kew, originally a potted plant moved indoors for the winter, but now too large for this and thus left outside in its pot – with no damage so far after several years. This specimen is a male, and flowers each year. Another is in the former African Garden of David and Colleen Fenwick in Plymouth, Devon, grown originally at K. Sahin Zaden B.V. in the Netherlands, from South African seed, and passed by me (JMG) to the Fenwicks. Although pruned to keep it within bounds in this small garden it has made an attractive specimen, with a conspicuous pale stem and a neat crown of dark green leaves. A young tree at Arboretum Bokrijk has survived two mild winters and is growing fast, but has yet to be properly tested (J. Van Meulder, pers. comm. 2007). On this evidence it would seem that I. mitis is worth attempting in the milder parts of the United Kingdom and western Europe, and it would certainly be successful in coastal California. I. montana Torr. & A. Gray B448, K181 I. mutchagara Makino B441

I. myrtifolia Walter B438, K181

Ilex nothofagifolia Kingdon-Ward Syn. I. intricata Hook. f. var. oblata W.E. Evans Small tree 3–5(–9) m; some young specimens may be epiphytic in the wild. Branchlets glabrous, with longitudinal rows of conspicuous, corky warts; in some specimens, the branches are flattened horizontally, as in Cotoneaster horizontalis Decne. Leaves evergreen, 0.5–1.7 × 0.5–1.2 cm, broadly elliptic, thin and leathery, upper

Section II. Species Accounts

Ilex

401

1 mm

C

1 cm

D

1 cm

A

B 1 cm

surface glossy with a sunken midrib, lower surface somewhat glaucous with pubescence, particularly on veins, two to three secondary veins on each side of the midrib, margins serrate, with four to seven teeth on each side, apex obtuse to cuspidate; petiole slender, 0.4–0.5 cm long. Inflorescences axillary, fasciculate. Flowers white, 4merous, inconspicuous. Fruit fleshy, red, globose and depressed, 0.3–0.4 cm, with four pyrenes. Flowering May to August, fruiting October to November (China). Galle 1997, Chen et al. 2006. Distribution CHINA: southeastern Xizang, northwestern Yunnan; INDIA: Assam; MYANMAR; VIETNAM (Fan Si Pan). Habitat Temperate cloud forest between 2300 and 3000 m asl. Ilex nothofagifolia grows in dense shade and is often covered in mosses and lichens. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Li et al. 2001; NT401. Cross-reference B445. Taxonomic note The epithet ‘nothofagifolia’ refers to the close similarity of the leaves to those of Nothofagus. The name was originally published as ‘nothofagacifolia’, but was later corrected.

Ilex nothofagifolia has been introduced several times in the past century, first and perhaps unsuccessfully by Kingdon-Ward, but more recently by Peter Cox and Peter Hutchison (Cox & Hutchison 424), from their expedition to northeastern India in 1965. Plants from this collection grow well in the Cox family garden at Baravalla, Argyll on the west coast of Scotland, in comparatively mild conditions. Another specimen from the same collection has done very well in Vancouver since 1989 and has shown no sign of winter damage there, being now a bushy 4 m tall. This example has vigorous vertical stems as well as the spreading branches associated with the species, and looks set to become a nice tree, its dainty appearance a useful foil to heavy-leaved rhododendrons (P. Wharton, pers. comm. 2007). Other than this, however, I. notho-

Figure 44 (above). Ilex nothofagifolia: habit (A); corky growths on stem (B); male flower (C); fruits (D).

402

Ilex

New Trees

fagifolia is scarcely known in North America. Kenneth Cox (pers. comm. 2007), who has also collected the species, in Arunachal Pradesh, reports that only the female trees have the distinctive horizontal branching while the males are less regular, but Susyn Andrews (pers. comm. 2007) has observed male plants with regular branching in cultivation. The specimen from which our illustration (Figure 44) was made is a potted plant growing at Westonbirt and derives from a collection made by Maurice Foster in Yunnan in 1994 (Foster 94116A). Potted plants at Westonbirt have, however, been badly damaged or killed by frost (S. Andrews, pers. comm. 2007). Susyn Andrews believes that it likes mild, very wet conditions to thrive, citing a successful specimen long grown at Inverewe on the west coast of northern Scotland. It is rare in European collections, probably because, as at Arboretum Bokrijk, it does not survive harsh winters. With its diminutive, tightly placed leaves and flattened shoots, it is a very distinctive plant. I. opaca Aiton B448, K181 I. opaca f. xanthocarpa Rehder B448, K181 I. paraguariensis St. Hil. K181 I. pedunculosa Miq. B449, K181 I. pedunculosa var. continentalis (Loes.) Bean K181 I. perado Aiton B449, S287, K181 I. perado var. azorica (NOW I. perado subsp. azorica (Loes.) Tutin) B449, S287, K181

Ilex purpurea Hassk.

I. perado subsp. iberica (Loes.) S. Andrews S288 I. perado var. platyphylla (NOW I. perado subsp. platyphylla (Webb & Berth.) Tutin) B449, S287, K181 I. pernyi Franch. B450, K181 I. pernyi var. manipurensis Loes. B451, K181 I. pernyi var. veitchii (NOW I. bioritsensis Hayata, NT395) B451

Chinese Holly, Kashi Holly

Syn. I. oldhamii Miq. Large tree to 15 m. Bark smooth, pale grey. Branchlets glabrous, smooth and dark grey. Leaves evergreen, 5–11 × 2–4 cm, elliptic, lanceolate or oval, thin and leathery, upper surface glabrous, lower surface glabrous or somewhat scabrous, five to seven secondary veins on each side of the midrib, margins crenate or rarely serrate, apex acuminate; petiole 0.8–1 cm long. Inflorescences solitary, axillary cymes with 7–15 flowers. Flowers purple, pink or red, 4–5-merous and 0.5 cm diameter. Fruit fleshy, shiny red, ellipsoidal and 1–1.2 × 0.6–0.8 cm, with four to five pyrenes; prominent, persistent stigma on fruits. Flowering April to July, fruiting July to December (China). Galle 1997. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Yunnan, Zhejiang; JAPAN: Honshu, Kyushu, Shikoku; TAIWAN; VIETNAM (?). Habitat Evergreen broadleaved forests between 0 and 2000 m asl. USDA Hardiness Zone 8b. Conservation status Not evaluated. Illustration Hayashi et al. 1985, Galle 1997; NT403. Cross-reference K178 (as I. chinensis). Taxonomic note Ilex purpurea has been cultivated for many years as I. chinensis, but I. chinensis Sims is a mysterious taxon with white flowers and pubescent stems, illustrated in Curtis’s Botanical Magazine in 1819, of which no herbarium specimen can be traced (S. Andrews, pers. comm. 2007). Chinese botanists, and the Flora of China account, however, insist that I. chinensis Sims is the correct name for this species, and place I. purpurea in synonymy.

The date 1810 is claimed for the introduction of Ilex purpurea (Hu 1949a, Krüssmann 1985a, Galle 1997), but in view of the confusion with the mysterious I. chinensis this date should be regarded with suspicion. It seems most likely that it was introduced from Japan (where it is probably not native) in the mid-nineteenth century, and it has undoubtedly been reintroduced on numerous occasions since. In China the fruiting shoots are an important household decoration at Chinese New Year, their glossy

Section II. Species Accounts

green leaves and abundant scarlet berries providing the same cheering winter colour as do Western hollies at Christmas. As a horticultural subject, I. purpurea is a very attractive tree, forming a dense canopy above a pale trunk; its purplish flowers are a curiosity in the normally white-flowered genus. The young growth is said to be bright pink (Hillier & Coombes 2002). It is widely and increasingly cultivated in the southeastern United States, where it can reach at least 15 m, and clearly enjoys the summer heat and humidity there. It has been assumed to be somewhat tender, but as usual, provenance matters, and some stocks are hardier than others. Of numerous accessions at Arboretum Bokrijk, those from China are the hardiest and some are 3–4 m tall (J. Van Meulder, pers. comm. 2007). A male clone has been grown at the Washington Park Arboretum for about 60 years and makes a beautiful evergreen tree there (Zone 8) (R. Hitchin, pers. comm. 2007). Hogan (2008) reports that a clone from the US National Arboretum is fully hardy in Zone 7 conditions, but in general it will do best where temperatures do not fall much below –10 ºC. In the United Kingdom it is slowgrowing and is defoliated by hard winters (Hillier & Coombes 2002) but there are several good male specimens at the Hillier Gardens, the largest of which was 10.5 m tall in 2007, with two main stems. It has evidently appreciated the recent warm summers and mild winters, having grown from 7.8 m in 2001. I. rotunda Thunb. ex Murray B451, K182 I. rotunda var. microcarpa (Paxt.) S.Y. Hu B451

Ilex rubra S. Watson Small tree 4–10 m. Branchlets slightly pubescent. Leaves evergreen, thickly leathery, (2.5–)4.3–6(–7) × 1.6–3 cm, ovate to elliptic, upper surface glossy dark green, glabrous or minutely pubescent along the midrib, lower surface minutely pubescent, 6–10 secondary veins on each side of the midrib, margins somewhat thickened and revolute, entire to serrate, rarely spinose, apex acute to acuminate; petiole thickened, puberulent, 0.3–0.7 cm. Inflorescences axillary, solitary. Flowers solitary or clustered, 4-merous. Fruit dark red, shiny and globose to subglobose, large for the genus, 0.7–0.9 cm diameter, with four pyrenes. Loesener 1901, Edwin 1964, Galle 1997. Distribution MEXICO: Chihuahua, Nuevo León, Sinaloa, Tamaulipas. Habitat Coniferous forests, c.1000 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated.

This small holly is still rare in cultivation but it is represented in both North American and European gardens, and with its large fruits deserves to be more widely grown. It seems to have been first introduced by Yucca Do Nursery, Hempstead, Texas, in the early 1990s, from collections made in the San Carlos mountains, Tamaulipas. Material from this source is growing at the University of California Botanical Garden at Berkeley. The few examples known in the United Kingdom seem also to be derived from Yucca Do, including a dense 1.8 m shrub at Westonbirt (S. Andrews, pers. comm. 2007). A plant at Tregrehan is now 3 m tall and flourishing after a slow start (T. Hudson, pers. comm. 2007). It does well at Arboretum Trompenburg, where a specimen obtained from J.C. Raulston in 1994 is now 2 m tall (J. Van Meulder, pers. comm. 2007).

Ilex

403

Plate 286. The pinkish to purplish flowers of Ilex purpurea are unusual in this mostly white-flowered genus. Image R. Lancaster.

404

Ilex

New Trees

I. rugosa Fr. Schmidt B452, S288, K182 I. serrata Thunb. ex Murray B452, K182

I. serrata f. leucocarpa Beissn. B452 I. serrata f. xanthocarpa (Rehder) Rehder B452

Ilex shennongjiaensis T.R. Dudley & S.C. Sun Small tree to 10 m, 0.25 m dbh. Branchlets reddish brown, glossy. Leaves evergreen, thickly leathery, 2.5–4(–5) × (1–)1.5–2.5(–3) cm, elliptic-ovate, upper surface glossy dark green, glabrous, lower surface dull yellowish green, six to seven secondary veins on each side of the midrib, though obscure, margins minutely serrate or crenate, apex acute, minutely mucronate; petiole pubescent, 0.25–0.4 cm long, deeply grooved. Inflorescences axillary, solitary. Flower details unrecorded. Fruit globose to subglobose, dark cherry-red, glossy, 0.8–1.2 cm diameter, with four to five pyrenes. Fruiting August to September (China). Bartholomew et al. 1983, Dudley 1983, Chen et al. 2006. Distribution CHINA: western Hubei (Shennongjia forest). Habitat Forests between 1800 and 2100 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Dudley 1983; NT404.

Plate 287. The appearance of fruits on Ilex shennongjiaensis at the US National Arboretum was a surprise, as the plants had been thought to be male! Image R. Olsen.

Ilex shennongjiaensis was discovered and introduced to cultivation by the SinoAmerican Botanical Expedition to Western Hubei in 1980, and all plants in horticulture are apparently derived from this introduction, under the expedition number SABE 1554. The species was included in the seminal analysis by Michael Dosmann and Peter del Tredici (2003) of the success of a seed-collecting expedition (see also p. 23). Dosmann and del Tredici found that I. shennongjiaensis, though new to both science and horticulture and thus of considerable interest, was represented in only two botanical institutions – and in both cases only by male plants. For a tree whose chief interest lies in its fruits this is not an ideal situation, and not exactly good for the gene pool either! Material has been distributed by one of these institutions, the US National Arboretum, and it is to be assumed that all cultivated specimens of I. shennongjiaensis are male (and WLTM …). In 2007, however, Richard Olsen of the US National Arboretum reported that the three growing there had produced a sparing crop of fruit. Occasional perfect flowers have been reported in hollies (Galle 1997), so this may be the explanation here too. All three are about 2 m tall, of pyramidal shape, but not densely leafy (R. Olsen, pers. comm. 2007). Material of the USNA accession NA 49246 C proved to be ‘very hardy’ at Heronswood, and good tolerance of colder conditions has been predicted (Heronswood Nursery catalogue 1999). This clone was sold for several years by Heronswood Nursery and is probably the one most widely represented in cultivation. For example, it is grown at Arboretum Trompenburg where, like most specimens now beginning to appear in collections, it is still a small plant. Until the elusive female is introduced, these bachelors are destined to remain neat small trees with dark green foliage, but female trees would bear normal red berries. I. sikkimensis Kurz S287

Ilex spinigera (Loes.) Loes.

Persian Holly, Iranian Holly

Syn. I. aquifolium L. var. caspia Loes. f. spinigera Loes., I. hyrcana Pojark.

Figure 45 (opposite). Ilex spinigera: habit with fruits.

Shrub or small tree to ≥ 6 m. Densely branched; branchlets, buds and young leaves densely pubescent. Leaves evergreen, 3–4.5 × 1.6–2.5 cm, elliptic-ovate, undulate, upper surface glossy dark green, glabrous or with pubescence on the veins and margins, lower surface pubescent, somewhat punctate and with prominent vein ridges, three to six secondary veins on each side of the midrib, margins revolute, with two to four sharp spines on each side, apex reflexed and acuminate; petiole pubescent, 0.2–0.3 cm long and deeply grooved. Inflorescences fasciculate, axillary, each axis with a single flower (female) or three to four flowers (male). Flowers yellowish green, 4-merous, 0.8–1(–1.5) cm diameter. Fruit fleshy, red and globose-ellipsoid, 0.6–1 × 0.8–1 cm, with four pyrenes. Dudley 1981, Galle 1997. Distribution AZERBAIJAN: southeast; IRAN: northwest (Caspian Sea coast). Habitat Relict forests at about 600 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Galle 1997; NT405. Cross-reference S285.

Section II. Species Accounts

Ilex

1 cm

405

406

Ilex

New Trees

Ilex spinigera may have been introduced to Europe some time prior to 1903, when it was illustrated in a publication by Camillo Schneider (Dudley 1980, 1981), but if so there is no evidence that this material persisted in cultivation. Its first modern introduction was from an extraordinarily productive two-day foray into the Elburz mountains and Caspian forest of Iran by Roy Lancaster and Ann Ala, in December 1972, that led to several of the species described in this work becoming established in cultivation. A faulty gearbox gave the opportunity for a quick trip into the snow-clad Camarlou forest and, in Roy Lancaster’s words, ‘the forester struck a heap of snow with his axe, the resulting vibrations shaking free the branches of an unusual holly – Ilex spinigera’ (Lancaster 1974). Fruits borne by this individual became A&L 18 and the source of many of the plants currently in cultivation. Among these is the female growing in the Valley Gardens of Windsor Great Park, from which the material illustrated here (Figure 45) was collected. This is now a bushy tree, about 3 m tall with a spread of 6 m; such bushiness seems to be a feature of the species. The biggest individual recorded by TROBI was at Caerhays Castle, 4 m tall when measured by Owen Johnson in 2006. In addition to the Ala & Lancaster stock, trees are in cultivation from other gatherings. For example, there are a male (3 m tall in 2007) and a female (2.2 m) specimen at the Hillier Gardens derived from seed from Gilan, Iran, sent by the Iranian Botanical Garden of Tehran University in 1989; and Clarke (1988) mentions a collection made by Fliegner and Simmons in 1977 (although no material of this can now be traced). The species is grown in several European collections. At Arboretum Bokrijk all specimens planted in the open have died, but a survivor in the shelter of the woodland garden is currently 4 m tall (J. Van Meulder, pers. comm. 2007). It reached the United States in 1975, when seeds of wild origin were received at the US National Arboretum (Dudley 1981), but it has remained rare in that country, although commercially available there (as it is in Europe). Dudley (1980) tabulated the points of difference between I. spinigera and the related I. colchica and I. aquifolium. I. sugerokii Maxim. B454, K182 I. verticillata (L.) A. Gray B452, S288, K182 I. verticillata var. fastigiata (Bickn.) Fernald B453 I. verticillata var. padifolia (Willd.) Torr. & Gr. B453, K182

I. verticillata var. tenuifolia (Torr.) S. Watson B453, K182 I. vomitoria Aiton B453, K182 I. yunnanensis Franch. B454, K182 I. yunnanensis f. gentilis Loes. B454, K182

ILLICIACEAE

ILLICIUM

L.

Anise Trees Illicium is a genus of 40–50 species of evergreen shrubs or trees, found principally in southeast Asia from eastern India to northern Sumatra and extending northwards to Japan. A smaller number occur in the southeastern United States and adjacent Caribbean islands. Illicium species are almost all glabrous throughout the plant, but a few

Section II. Species Accounts

may have occasional hairs on new shoots. The buds are enclosed in conspicuous but caducous bud scales. The leaves are usually alternate but may be clustered or in false whorls at the ends of branchlets, usually dark green, paler below; the petioles with a channel on the upper surface; the lamina entire, chartaceous to coriaceous, decurrent on the petiole, the venation pinnate. The flowers are solitary, though sometimes appearing as if in small clusters, and are usually borne in leaf axils towards the shoot tips; they are hermaphrodite, and hypogynous; with numerous perianth segments (7–33), usually in several whorls, glandular, increasing in size inwards, the outermost usually small (but inner segments can also be smaller), either membranous or fleshy; 4–50 stamens, in one to several whorls, anthers bearing four sporangia; carpels (usually 7–15) free, in a single whorl, often closely pressed together, erect or spreading, with a flattened ovary attenuate into the short style, the stigmatic surface on the underside of the stigma. The fruit is a follicetum composed of a single whorl of spreading follicles, that dehisce ventrally. The seeds are ellipsoid or obovate, straw-coloured or brown. Familiar to cooks in the shape of the spice star anise (the fruit of Illicium verum), the genus Illicium takes its name from the Latin for ‘allurement’, a reference to the enticing aromas that emanate from all parts of the plant. Not only their aroma renders them alluring to the gardener; they are good-looking evergreens capable of making handsome small trees (although shrubby when young or in cool areas), bearing attractive flowers. It is worth noting, however, that they are usually poisonous in all parts, and experiments in anise substitutes should not be attempted. The monographer of Illicium, A.C. Smith (1947), had to record that the genus is ‘extraordinarily complex and taxonomically difficult’. He observed of I. floridanum: ‘it is a rare satisfaction to find a species of Illicium upon the identity of which all authors agree.’ Smith accepted 42 species, but the Flora of China treatment recognises several more. A few species are reasonably well known in temperate gardens, mostly those from more northerly areas, including the Japanese I. anisatum, the Chinese I. henryi, and I. floridanum from the southeastern United States. A number of selections of I. anisatum and I. floridanum are grown in the United States and are occasionally offered in Europe, and these have more recently been joined in cultivation by several other species from North America and Asia. Material of Mexican origin is commonly grown in North America under the name I. mexicanum A.C. Smith. This is treated as synonymous with I. floridanum by M.A. Vincent in Flora of North America (1997), as there are many overlapping characters between the two, although a study cited by Dirr (1998) suggested that there were chemical differences. In general, the appearance and tolerances of I. mexicanum are much the same as for I. floridanum. A clone selected by J.C. Raulston, ‘Aztec Fire’, has large, showy, dark red flowers and is widely recommended as a good garden plant for the southeastern United States. A seedling from a cross between I. mexicanum and I. floridanum ‘Album’ has been named ‘Woodland Ruby’ by Woodlanders Nursery, Aiken, South Carolina, and has large pink flowers. Although many Asian species have a southerly distribution, it is conceivable that others of them will be introduced and prove to be as hardy (or otherwise!) as the ones already established in cultivation.

Illicium

407

Plate 288. Illicium lanceolatum. Illicium flowers are made up of several whorls of perianth segments, surrounding the anthers and array of follicles at their centre. Image J. Grimshaw.

Plate 289. Illicium lanceolatum at the US National Arboretum. An increasing number of Illicium species are being cultivated, valued as much for their evergreen foliage as for their flowers. Image R. Olsen.

408

Illicium

New Trees

All require hot summers to flourish and will do best where this warmth is coupled with high humidity, but when the wood is fully ripened they are capable of withstanding quite low temperatures. They are typically understorey plants, at least when young, but in cooler areas they should be planted in sun or very light shade. A moist acidic soil is most suitable. The strong odour of their foliage is repellent to deer. I. anisatum L. B454, K183 I. floridanum Ellis B455, K183

I. henryi Diels B455, K183

Illicium lanceolatum A.C. Smith Shrub or tree, 3–10 m. Bark pale grey to greyish brown. Branchlets slender. Leaves alternate, or more densely placed at branchlet ends, leathery, 5–15 × 1.5–4.5 cm, lanceolate, oblanceolate or obovate-elliptic, base narrowly cuneate, apex caudate to acuminate; midrib slightly prominent below, slightly impressed above, reticulate veins inconspicuous; petiole 0.7–1.5 cm, slender. Flowers axillary or subterminal, solitary or in fascicles of two or three, borne on peduncles 1.5–5 cm; perianth segments 10–15, fleshy, red to dark red, the largest 8–13 × 6–8 mm; stamens 6–11; follicles 10–14, 2.8–3.9 mm long at flowering. Fruiting peduncle to 6(–8) cm; follicetum 3.4–4 cm diameter; follicles 14–21 × 5–9 × 3–5 mm, apex with a recurved 3–7 mm hooked beak. Flowering April to June, fruiting August to October (China). Yuhu et al. 2008. Distribution CHINA: Anhui, Fujian, Guizhou, Hubei, Hunan, southern Jiangsu, Jiangxi, Zhejiang. Habitat Mixed forests, thickets, between 300 and 1500 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration NT407, NT407.

Illicium lanceolatum is commercially available in the United States, but is apparently still quite scarce. It seems to have considerable garden potential as an attractive flowering shrub or small tree, but has not been fully tested yet. Plants at the JC Raulston Arboretum have been growing steadily since 1997, the largest 1.8 m in 2005 (JC Raulston Arboretum database). In the United Kingdom one that has been growing at Spinners, Hampshire for several years is now flowering (A. Coombes, pers. comm. 2008).

Illicium majus Hook. f. & Thomson Plate 290. The native Illicium parviflorum is appreciated in the southeastern United States for its dense masses of evergreen foliage. This is the yellow-leaved ‘Florida Sunshine’. Image T. Avent.

Tree to 20 m tall. Branchlets brownish or purplish when young, lenticellate; grey when older. Leaves in false whorls, sub-leathery, 5–15 × 1.5–4.5 cm, oblong-lanceolate to oblanceolate, base cuneate, apex acuminate; midrib prominent below, slightly impressed above, six to nine secondary veins on each side of the midrib; petiole 1–2.5 cm. Flowers axillary or subterminal, solitary or in fascicles of two to four, borne on peduncles 1.8–4.5(–6) cm; perianth segments 15–21, white or pink, the outermost pellucid-glandular, the inner ones fleshy, the largest 8–15 × 4–9 mm; stamens 12–21; follicles (9–)11–14, 4–5.5 mm long at flowering. Follicetum 4–4.5 cm diameter; follicles 12–25 × 5–15 × 3–5 mm, apex abruptly narrowed and elongated into a 3–7 mm beak. Flowering April to June, fruiting July to October (China). Yuhu et al. 2008. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hunan, Yunnan; MYANMAR; VIETNAM. Habitat Mixed forests, thickets, rocky slopes, along riverbanks. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

At present Illicium majus is scarcely known in cultivation, but it is strongly recommended by Tom Hudson (pers. comm. 2007; Hudson 2004) for its showy pale flowers in spring. It has been grown at Tregrehan (and in other Cornish gardens) for several years, from seed originally collected in China by the New Zealander Garry Clapperton (GWC 0224). It has reached 2 m tall at Tregrehan and is growing well.

Illicium parviflorum Michx. ex Vent.

Swamp Star-anise, Yellow Anise

Shrubby tree to 6 m; sometimes suckering and usually forming a wide, rounded crown. Leaves alternate, but clustered at shoot tips, dull green to olive-green, 5–13(–21) × 2–4(–6) cm, elliptic to obovate-elliptic, base acute, apex obtuse or rounded; petiole 0.8–1.6 cm. Flowers axillary at shoot tips, pendulous below the leaves, small, 0.8–1.2 cm diameter, solitary or sometimes two together, borne on peduncles 0.7–2.4 cm; perianth

Section II. Species Accounts

Illicium

409

segments 11–16, yellow-green; stamens six to seven; follicles 10–13. Follicetum 2–3.5 cm diameter. Flowering late spring (Florida). Elias 1980, Vincent 1997. Distribution USA: Florida, Georgia. Habitat Moist woods, swamps, between 0 and 70 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated, but with a limited range and specialised habitat. Illustration Elias 1980; NT408.

Illicium parviflorum is praised by Michael Dirr (1998) as the ‘most rugged landscape performer’ of all Illicium species, and is recommended by him as a solid foliage plant for gardens in the southeastern United States; the flowers are insignificant. Its performance in cooler, less humid areas is more uncertain, but it is clearly worth trying in a warm, moist situation. Dirr has introduced ‘Forest Green’, which has a more rounded, darker green leaf than normal. It seems to be very tolerant of exposure to full sunlight (Lasseigne 2001).

Illicium simonsii Maxim. Syn. I. yunnanense Franch. ex Finet & Gagnep. Tree 9–15 m. Branchlets brownish green, slightly ridged, grey when older. Leaves subopposite or alternate, sometimes in fascicles of three to five, leathery, 5–10 × 1.5–3.5 cm, lanceolate to elliptic, base attenuate to cuneate and decurrent along petiole, apex acute to short-acuminate; midrib impressed above, narrowly furrowed to petiole; secondary veins usually inconspicuous; petiole 0.7–2 cm, narrowly winged, adaxially furrowed. Flowers axillary at shoot tips, borne on peduncles to 0.8 cm; perianth segments 18–23(–26), thinly papery, yellow to cream, white or occasionally pink, becoming narrower towards centre; stamens 16–28; follicles 8–13, 3–4.5 mm long at flowering. Fruiting peduncle 0.5–1.6 cm; follicetum 4 cm diameter; follicles 11–20 × 6–9 × 2–4 mm, apex with a narrow 3–7 mm beak. Flowering most of the year but principally February to May, fruiting June to October (China). Yuhu et al. 2008. Distribution CHINA: western Guizhou, southwestern Sichuan, Yunnan; INDIA: northeast; MYANMAR: north. Habitat Thickets, forests, open fields, ravines, along rivers, wet places, between 1700 and 3200(–4000) m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Hudson 2004, Ward 2004; NT409.

Illicium simonsii is a notable new introduction that seems to have wide tolerances coupled with great beauty. One of the earliest collections was made by Bill McNamara and Charles Howick (H&M 1400), from Bai Baiding in Sichuan in 1990; from this it has become well established at Quarryhill, where there are several good specimens now approaching 4 m in height, and elsewhere. There have been other introductions as well (for example, SICH 1479, BWJ 8024) and it is now rather widely cultivated and freely available commercially, but the origins of different stocks are rather blurred. Its attractions are manifold. Its habit is a neat narrow cone or pyramid, with a tapering tip, at least in full sun (in shade it is rounder), with dark green foliage that has a bluish sheen to it, and its masses of cream to yellow flowers, produced mainly in spring, release a strong fragrance. It is hardy to –11 ºC (Hogan 2008) but perhaps not much below that. It should certainly be attempted in any suitable garden. Flora of China treats I. yunnanense as a synonym of I. simonsii, which is clearly a variable species with a wide range. Plants bearing the two names grow side by side at Tregrehan and differ in a number of characters. According to Tom Hudson (pers. comm. 2007), that known as I. yunnanense is the better. It has a long flowering season and a very strong fragrance, and the new growth is red; it probably deserves a cultivar name. It is important to note that Flora of China records that all parts of I. simonsii are very poisonous.

Plate 291. Illicium simonsii. H&M 1400 at Quarryhill – an outstanding recent introduction. Image B. Ward.

410

Illicium

New Trees

Illicium verum Hook. f.

Star Anise

Tree 10–15 m. Bark dark grey. Branchlets congested. Leaves irregularly alternate, more densely placed at branchlet ends, thickly leathery, densely pellucid-punctate with oily glands, 5–15 × 2–5 cm, obovate-elliptic, oblanceolate or elliptic, base attenuate to cuneate, apex cuspidate to short-acuminate; midrib prominent below, slightly impressed above; petiole 0.8–2 cm, narrowly winged. Flowers solitary, axillary at shoot tips, borne on peduncles to 4 cm; perianth segments 7–12, thinly papery, inconspicuously pellucid-punctate, pink to dark red, the largest 0.9–1.2 × 0.8–1.2 cm; stamens 11–20; follicles 7–9(–11), 2.5–4.5 mm long at flowering. Fruiting peduncle 2–5.6 cm; follicetum 3.5–4 cm diameter; follicles 14–20 × 7–12 × 3–6 mm, apex obtuse to obtusely beaked. Flowering March to May and August to October, fruiting September to October and March to April (China). Yuhu et al. 2008. Distribution CHINA: considered native in southern and western Guangxi, but widely cultivated in China and elsewhere in southeast Asia. Habitat Forests, between 200 and 1600 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated.

The southern origins of Illicium verum would seem to suggest that it had no hope of growing outside in our area, but a 2 m tree at Tregrehan demonstrates otherwise. This does have a sheltered spot in a sheltered garden, but has not been damaged by frost since planting in 2003. The cultivated trees from which the seed was obtained were 15–20 m tall. If attempted, I. verum should be given a very warm site.

SALICACEAE (formerly FLACOURTIACEAE)

ITOA Plate 292. The huge leaves of Itoa orientalis at Earlscliffe, Dublin. The species needs to be tested away from mild coastal gardens. Image S. O’Brien.

Hemsl.

Itoa comprises two species, one in southern China and Indochina (I. orientalis), which is in cultivation, and another in eastern Indonesia (I. stapfii (Koord.) Sleumer). The two species are very similar, and if it were not for their divergent distributions they might easily be lumped together. They are evergreen trees with large, simple, spirally arranged leaves; the leaves have a sturdy petiole, crenate margins and no stipules. Both species are dioecious, the staminate flowers held in erect, terminal panicles, the pistillate flowers solitary and axillary. The flowers have a leathery, valvate calyx, with three (to four) lobes, and no petals; the staminate flowers have numerous stamens, the anthers minute. The fruit is a large, egg-shaped capsule, which eventually divides (partially) into (five to) six to eight segments, releasing numerous winged seeds (Sleumer 1954).

Itoa orientalis Hemsl. Tree to 13 m, 0.15 m dbh. Branchlets initially covered with yellowish hairs, later glabrous and lenticellate. Leaves evergreen, 9–42 (or longer) × 5–18 cm, elliptic to obovate or broad-lanceolate, upper surface largely glabrous, lower surface with stiff hairs, particularly on the veins, 10–26 secondary veins on each side of the midrib, margins almost entire to regularly crenate or serrate, apex acute or emarginate; petiole 1.5–6 cm long, pubescent. Staminate inflorescences paniculate, ~5 cm long with ~12 flowers, axes pubescent; staminate flowers ribbed and densely tomentose in bud. Pistillate flowers small, solitary. Capsule pale yellow, ovoid, tomentose, 8–9 × 4–6 cm with a six- to eight-lobed stigma at the tip; fruiting peduncle robust. Seed small, with wing to 2 cm. Flowering May to June, fruiting September to October (China). Yang & Zmarzty 2007. Distribution CHINA: Guizhou, Sichuan, Yunnan; LAOS; VIETNAM. Habitat Between 600 and 1300 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Hudson 2004; NT410.

Section II. Species Accounts

Itoa

A big plant of Itoa orientalis is one of many surprises at Tregrehan, where its huge leaves obscure the wall against which it is grown. This specimen is now 8 m tall after 10 years, but also very broad, with wide-spreading branches from the pale-barked trunk that span 3–4 m. The leaves are up to 40 cm long, with a 9 cm petiole, and are a lustrous dark green with conspicuous veins. In high winds they are vulnerable and the tree can be defoliated, as it is by hard frost, but in shelter it remains evergreen (T. Hudson, pers. comm. 2005). The flowers are insignificant, but are followed by a large, beaked fruit that is quite ornamental. There are other specimens in Cornwall and in Ireland (Wickham 2001, Johnson 2007), and it is grown in New Zealand, but no record of it in cultivation in North America has been traced. A sheltered site with rich moist soil is indicated.

JUGLANDACEAE

JUGLANS

L.

Walnuts About 20 species of Juglans are distributed throughout temperate Eurasia and temperate and tropical America from Canada to Argentina and the Caribbean islands. Amongst them, 10 species are tropical or subtropical (although these usually grow at higher altitudes). Walnuts are usually large deciduous trees, with a thick trunk and wide-spreading limbs. New shoots are thick and bear pinnate leaves that leave a distinctive leaf scar on falling. The shoots and leaves are strongly aromatic, especially when young, and with practice this aroma can be helpful in identification. The flowers are unisexual, borne on separate racemes on the same tree, but in most cases crosspollination is required. Male inflorescences arise from buds on the previous year’s growth, and are long, slender catkin-like racemes composed of many flowers, each subtended by a single entire bract and with three to six sepals and 6–40 stamens. Female inflorescences are terminal on new shoots, and are erect spikes with fewer flowers; the flowers have four sepals, adnate to the ovary but free at the tips, and two styles, stout, with fimbriate stigmatic surfaces. The fruiting spike is erect or pendulous, bearing small clusters of fruits, each being a hard-shelled nut surrounded by a dehiscent or indehiscent husk. The walnuts are familiar and popular trees in horticulture, but only a handful of species – Juglans regia, J. nigra and possibly J. mandschurica (s.l.) – and their cultivars are encountered frequently. The horticultural diversity of the temperate taxa has been described in an article in the IDS Yearbook 2003 (Grimshaw 2004), which should be consulted for information concerning species and their cultivars not described here, and the very numerous hybrids in this promiscuous genus. The frequency of hybrids makes identification of cultivated Juglans difficult. One hybrid not mentioned in the Yearbook 2003 is that between J. nigra and J. ailantifolia, known by the unpublished name ‘J. ×segreziensis’ from its origin at the Arboretum de Segrez, Saint-Sulpice-deFavières, France (Picard 2004). The 10 tropical or subtropical species from Central and South America related to J. nigra remain a temptation to the temperate dendrologist. In the wonderful climate of

411

412

Juglans

Plate 293. Juglans major, in autumn colour at Kew, November 2007. A close relative of the familiar J. nigra, J. major is a smaller tree from more arid areas. Image J. Grimshaw.

New Trees

the University of California Botanical Garden at Berkeley, J. guatemalensis Manning is well established from a collection made by D. Wilamowski in Guatemala in 1992, producing big hairy leaves. An unidentified species also growing at Berkeley was collected in 1997 by Carl Schoenfeld and John Fairey from Nuevo León and may be J. mollis Engelm., which grows in the fog belt of the mountains of eastern Mexico at altitudes of at least 2200 m (Manning 1957). This may be the most hopeful of these species for wider cultivation in our area. As part of his extensive National Plant Collection of Juglans at Upton Wold, Gloucestershire, Ian Bond grows J. boliviana Dode (Bolivia), J. neotropica Diels (Colombia, Ecuador, Peru) (see Plate 15, p. 5) and J. olanchana Standl. & L.O. Williams (Guatemala, Honduras, Mexico, Nicaragua), as potted conservatory specimens, but has not tried any outdoors. Spring frosts are the biggest threat to the successful growth of Juglans species, and plants should be sited to minimise the risk of such damage. A number of fungal and bacterial diseases can be a problem – especially in commercial situations in North America (Grimshaw 2004) – but the most alarming is Butternut canker (Sirococcus clavigignenti-juglandacearum), which is killing trees of J. cinerea across its distribution; no regeneration occurs, and the species’ range is diminishing (Whittemore & Stone 1997). Butternut canker has been equated with chestnut blight and Dutch elm disease as a scourge of the North American forest (Schlarbaum et al. 1999); fortunately, it does not seem to affect other species significantly. Propagation is by seed (with the caveat that hybrids can be expected from arboretum-grown nuts) or by grafting onto a stock of a related species. Plants should not be confined to pots for longer than is strictly necessary, to avoid contortion of the long, robust tap roots. Juglans are greedy feeders and appreciate rich, moist ground. They thrive best in areas with long hot summers, provided there is sufficient moisture. J. ailantifolia Carr. B472, S289, K191 J. ailantifolia var. cordiformis (Maxim.) Rehder B472, K191 J. californica S. Wats. B473, K191 J. cathayensis (NOW J. mandschurica Maxim.) B473, S289, K191

J. cinerea L. B474, S289, K193 J. hindsii (Jeps.) R.E. Smith B473, K193 J. ×intermedia Carr. B474, S290, K193 J. ×intermedia var. pyriformis (NOW J. ×intermedia ‘Pyriformis’) K193 J. ×intermedia var. vilmoreana (NOW J. ×intermedia ‘Vilmoreana’) K193

Juglans major (Torr.) Heller

Arizona Walnut

Syn. J. elaeopyren Dode, J. microcarpa var. major (Torr.) L.D. Benson Tree 10–18 m, 1.3 m dbh. Bark smooth, thin and light grey when young, becoming dark grey to brownish black, thick and deeply ridged, with irregular scales developing on the ridges. Branches stout and spreading, forming an open, rounded crown; they may become pendulous with age. Branchlets slender, with rufous hairs when young, becoming reddish brown and smooth with small lenticels, and silvery brown later; leaf

Section II. Species Accounts

Juglans

413

scars large, triangular with rounded corners, suggesting a shark’s tooth in outline, and conspicuously pale. Leaves 22–32 cm long including petiole, with 9–15(–19) shortly stalked leaflets 4.5–10 × 1.5–4 cm, ovate to lanceolate, usually curved, long-acuminate at apex, tapering to rounded or unequal at base, margins coarsely toothed, yellowish green in colour, paler beneath, pubescent above when young but becoming smooth with scattered solitary hairs below, the rachis remaining pubescent with white hairs (var. major). Male catkins yellowish, slender, 12–20 cm long, each flower with 30–40 stamens; female flowers one to four. Fruits solitary or sometimes two, 2.5–3.5 cm diameter, globose to almost ovoid, with a small sharp point at apex, husk fibrous, densely hairy. Nuts globose, flattened at base, 2.5–4 cm diameter, dark brown to black, with deep, broad grooves in the thick shell; kernel large and sweet. Manning 1957, Elias 1980, Whittemore & Stone 1997. Distribution MEXICO: Chihuahua, Durango, Sonora, Sinaloa; USA: Arizona, New Mexico. Habitat Streamsides and floodplains, between 700 and 2300 m asl. The town of Nogales in Arizona is said to be named for the stands of this walnut tree that once grew there (Elias 1980). USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Elias 1980; NT412. Cross-references B475 (as J. microcarpa var. major), K193. Taxonomic note Juglans major is the name accepted by Manning (1957) and the authors of Flora of North America; European authors (Wijnands 1989) have adopted J. elaeopyren, but J. major has priority.

It is not clear when true Juglans major was introduced to Europe, as this short to medium-sized tree has been much confused, in gardens and by botanists, with the related J. microcarpa. The two species are genetically quite distinct (Stanford et al. 2000), with disjunct distributions, but they will hybridise. They can be distinguished by the following key characters. Leaflets 9–15(–19), usually (1.5–)2–3.5 cm wide when mature; stamens 30–40; fruits 2.5–3.5 cm diameter ................................................................................................ J. major Leaflets (15–)17–23, usually 1.5(–1.7) cm wide or less; stamens 20–30; fruits not more than 2 cm diameter ........................................................................... J. microcarpa

Juglans major is considered to be less hardy than the daintier, more attractive J. microcarpa, and in cultivation should probably be given a warm sheltered site, but it seems to be happy in much of England, where there is a scattering of good specimens from Yorkshire southwards (TROBI). The tallest, at 18 m, but with a dbh of only 25 cm (in 2004) is at Thorp Perrow Arboretum, Yorkshire. A stouter specimen at Cambridge Botanic Garden was measured at 17.5 m tall (69 cm dbh) in 2002; this was planted in 1923. At Kew a tree planted in 1982 had reached 5.5 m by 2004 and appears to be growing strongly, without evidence that it has suffered any frost damage. J. mandschurica Maxim. B475 J. microcarpa Berl. B475, S290 J. microcarpa var. major (NOW J. major (Torr.) Heller, NT412) B475 J. nigra L. B476, S290, K193

Juglans sigillata Dode

J. ×notha Rehder K193 J. ×quadrangulata (Carr.) Rehder K193 J. regia L. B476, S290, K194 J. regia subsp. fallax (Dode) Popov K194

Iron Walnut

Tree to 25 m. Leaves deciduous, imparipinnate, 15–50 cm long; leaflets 9 or 11(–15), ovate- or ellipticlanceolate, 6–18 × 3–8 cm, glabrescent, margins entire or obscurely serrulate, apex acuminate; lateral petiolules very short, terminal petiolule 2–3 cm long; rachis glabrescent; petiole 7–12.5 cm long, glabrescent. Male spikes 13.5–18 cm long; flowers with 24–27 stamens. Fruiting spikes with one to three fruits; fruits glabrescent, 3.4–6 × 3–5 cm, globose to subglobose, irregularly dehiscent; nuts valvate, valve forming a prominent, circumferential ridge, surface otherwise irregularly pitted; the shell forms deep ridges inside, which penetrate the seed. Flowering March to April, fruiting September (China). Lu et al. 1999. Distribution

Figure 46. Juglans sigillata: nuts in various perspectives, one shown in transverse section (two-thirds life-size).

414

Juglans

New Trees

BHUTAN; CHINA: Guizhou, Sichuan, southeast Xizang, Yunnan; INDIA: Sikkim. Habitat Forests in valleys and on mountain slopes between 1300 and 3300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT38, NT413. Taxonomic note Juglans sigillata is closely related to the Walnut, J. regia L., but can be distinguished by the number of leaflets (9–15, vs. 5–9 in J. regia) and by the shell of the nut (extremely hard and covered with numerous deep pits, while in J. regia the shell is wrinkled, not pitted).

In the course of researching Juglans it came to light that J. sigillata, a Chinese species, had apparently never been introduced to Europe or North America, although it was said to be in cultivation in New Zealand. It seemed odd that a Juglans species cultivated for its nuts should never have been collected, so I (JMG) asked my friend Michiel Zwaan of the seed company K. Sahin Zaden B.V. to look out for it when travelling on business in Yunnan. He was unable to locate it in person, but asked the China National Tree Seed Corporation if they could help. The result was that 5 kg of nuts arrived on my doorstep in December 2005. As shown in the illustration (Figure 46), they varied considerably in size and degree of pitting, but their extremely hard shells warranted the Chinese name Iron Walnut. The nuts were distributed to dendrologists throughout the United Kingdom and Europe and good germination resulted, so this species should appear in many arboreta in the near future. The seedlings have grown very fast (over a metre in height by July 2007 in one cultivated by Susan Grimshaw in Maidenhead, Berkshire); they have narrower, more acute leaflets than J. regia, but the relationship is clear. Juglans sigillata should make a tree very similar to J. regia and require the same conditions. The species was also collected in the wild in the autumn of 2005 by Keith Rushforth and Koen Camelbeke, and it has been growing at Hackfalls in New Zealand for some years (A. Coombes, pers. comm. 2004). J. ×sinensis (DC.) Dode K194 J. stenocarpa (NOW J. mandschurica Maxim.) B478, K194

CUPRESSACEAE

JUNIPERUS

L.

Syn. Arceuthos Antoine & Kotschy, Sabina Mill.

Junipers Most genera in the Cupressaceae have narrow distributions and a limited number of species; indeed 18 of the 30 genera are monospecific. In this respect Juniperus is somewhat aberrant, in that it is extremely widespread with many species. The 53 species of juniper (Farjon 2001, 2005c) comprise just under 40 per cent of all the species in the family, and are found across Eurasia and North America, with J. procera extending into southern Africa. The Common Juniper (J. communis L.) is the most widespread of all conifer species. Two further unusual attributes of junipers are the high prevalence of dioecy (monoecy is the norm in the family) and the fleshy cones, which attract animal seed-dispersers. Though commonly referred to as a berry, technically a juniper cone is known as a galbulus. Junipers are evergreen and range in habit from prostrate

Section II. Species Accounts

shrubs to large trees of 30 m or more. The branchlets are terete, four- to six-angled and variously orientated, though typically not flattened. As in many Cupressaceae, there are two leaf forms: juvenile leaves are needle-like, non-decurrent and arranged in whorls of three; adult leaves are scale-like, decurrent, appressed to divergent, and with an abaxial resin gland visible in some species. Mature leaves are decussate or alternate in whorls of three forming six ranks; the lateral and facial pairs largely similar. The male strobili are terminal and solitary on short, lateral branchlets, with three to seven pairs or trios of microsporophylls. The female cones are terminal, solitary, globose to ovoid and mature in one or two years. The seed scales are peltate or valvate, fused together and fleshy or fibrous, or (rarely) woody; they are arranged in one to five pairs or trios, each bearing one to three seeds; the cone is usually berry-like and may be sweet, bitter or resinous; the umbo is small or absent (Farjon 1992, Watson & Eckenwalder 1993, Fu et al. 1999e). The seeds are hard and wingless; parasitic insect larvae can cause the development of cones with bare seeds protruding (gymnocarpy). Juniperus has traditionally been divided into two large sections: in section Juniperus all leaves are of juvenile form (scale-like leaves being found only on the cone peduncle), while in section Sabina juvenile leaves are restricted to seedlings and the lowermost branches; mature leaves are scale-like, decurrent, decussate or rarely whorled (Farjon 1992). These leaf characters are somewhat plastic, and mutants with unusual leaf morphologies are not uncommon, both in cultivation and in nature. Several members of section Sabina have only a single seed in the cone (monoseed), and in this respect they resemble Microbiota Kom. (Rushforth 1987a). Phylogenetic studies using DNA and morphological data suggest that Juniperus is most closely related to Cupressus and Xanthocyparis (Gadek et al. 2000, Little et al. 2004) (see p. 290), though these studies included only a few representatives of this large genus. As with many other genera of Cupressaceae, the name ‘cedar’ is applied to several species of juniper. The principal reference works for the genus are Robert P. Adams’ Junipers of the World: The Genus Juniperus (2004) and Aljos Farjon’s A Monograph of Cupressaceae and Sciadopitys (2005c), both of which contain detailed descriptions and numerous illustrations of almost every species. These should be consulted for further botanical details. Very comprehensive illustration of many species and a huge range of cultivars is to be found in D.M. van Gelderen and J.R.P. van Hoey Smith’s Conifers: The Illustrated Encyclopaedia (1996). Many also feature in Richard L. Bitner’s recent Conifers for Gardens (2007). Illustrations appearing in these works are not mentioned in the species accounts that follow. Juniperus is an extremely important genus of conifers, but has an image problem in consequence of the plethora of dwarfish cultivars, in various colours and shapes, used only too frequently in boring ‘landscaping’. As so often the fault lies not really in the plants, but in a lack of imagination on the part of planters or designers. To compound the problem, many of these cultivars are susceptible to fungal diseases which can cause them to die off in large patches, necessitating their removal. In consequence it seems that junipers are seldom treated with great respect – which is a shame since many, both species and cultivars, have really valuable garden qualities when well sited.

Juniperus

415

Plate 294. Not all junipers are shrubs for amenity plantings: Juniperus procera in the Cherangani Hills, Kenya. Image J. Grimshaw.

416

Juniperus

New Trees

1 cm

Section II. Species Accounts

Juniperus

417

One particularly attractive species, given a short description by Bean (B487), is J. formosana. This has been cultivated for a long time. Dallimore & Jackson (1966) suggest that it may even have been introduced by Fortune in 1844, and it was probably also collected by Wilson (Sargent 1916). A few old trees exist – for example, at Bedgebury, where the oldest specimen was planted in 1935. In 2007 this was 6 m tall, with three trunks, the largest of which has a dbh of 15 cm (D. Luscombe, pers. comm. 2007). Juniperus formosana has been reintroduced in recent years, from both mainland China (for example, SICH 616) and Taiwan (ETOT 89), and is now much more frequent in arboreta than before. As a young tree it makes a beautiful column of pendulous light green foliage, given a special ‘edge’ by the broad white stomatal bands on both leaf surfaces. It seems to be widely tolerant, good specimens having been seen at the JC Raulston Arboretum, Quarryhill and Kew. One species that could certainly be attempted more frequently, especially in sunny, drier gardens, is J. deppeana Steud., the Alligator Juniper, so-named for its beautiful bark, but although popular in North America this is very seldom seen in Europe. It can have excellent blue foliage, and is the most glaucous of all Juniperus species. A superior clone, ‘McFetters’, from Arizona, has done well at the JC Raulston Arboretum (Dirr 1998) and is obviously worth seeking out. It is curious that with the exception of J. scopulorum the western American junipers have received little horticultural attention. Among these is J. osteosperma (Torr.) Little, a familiar, common species of the Great Basin and Colorado Plateau, which would surely make a useful water-wise plant for gardens in the southwestern United States and in the drier parts of Europe. Both of these species can be very slow-growing when young, especially in arid conditions (Nold 2008). From central Asia (Xinjiang, China), usually forming a spreading shrub but occasionally a small tree, is J. pseudosabina Fisch. & C.A. Mey. This has rather glaucous foliage and is considered by Daniel Luscombe of the National Pinetum, Bedgebury, Kent, to be an unusually attractive species (pers. comm. 2008) and well worth growing. The species described below are mostly collectors’ items, but several have unexpected distributions in the wild that give them an added interest. It would seem that (as can often be the case with tropical members of usually temperate genera) the genes for hardiness have not altogether been lost. Planting sites should however be chosen with regard to origins! Propagation of Juniperus is by seed, or by cuttings, but these can result in poor root systems that lead to wind rock, especially of columnar forms (Dirr 1998). Several major pests and diseases afflict the genus, especially fungal diseases caused by Phomopsis, Phytophthora and Kabatina which result in dieback of the shoots and often lead to the death of the plant. Bagworm caterpillar infestations are a problem in North America (Huxley et al. 1992, Dirr 1998). There are many others! Planting in a lean, dry, sunny site may help reduce the risk. J. ashei J. Buchholz K126

Juniperus bermudiana L.

J. barbadensis L. K126

Bermuda Juniper

Tree to 15(–23) m, trunk slender. Bark greyish brown, thin and flaky, peeling in long, narrow strips. Crown narrow and conical initially, later broad and rounded, often broader than tall. Branchlets decussate to alternate. Juvenile leaves whitish above and bright green below; mature leaves dark green, slightly appressed, 0.1–0.2 × 0.1–0.2 mm, apex acute to obtuse. Dioecious. Male strobili 0.4–0.8 cm long, subglobose to cylindrical,

Figure 47 (opposite). Juniperus bermudiana: habit with female cones or ‘berries’.

418

Juniperus

New Trees

microsporophylls 10–12. Female cones fleshy, usually solitary, subglobose to reniform, 0.4–0.5 × 0.6–0.8 cm, dark blue with greyish bloom. Seeds one to two (to three) per cone. Britton 1918, Adams 1995. Distribution BERMUDA. Habitat Once the dominant tree species on Bermuda, forming pure forests on hillsides and on the margins of marshes. Extent now much reduced. USDA Hardiness Zone 9. Conservation status Critically Endangered. Juniperus bermudiana has suffered a rapid collapse in its population due to the introduction, in the 1940s, of two non-native species of scale insects. Perhaps only one per cent of the original population still survives, and this has had severe repercussions for the island’s economy. Not only was juniper the only significant timber species, but the aesthetic appeal of an island that relies on tourism has been reduced. A number of non-native trees have been introduced to conceal the dying juniper forests, but these could potentially impact upon juniper regeneration in the future (Challinor & Wingate 1971). Illustration NT416. Cross-reference K126. Taxonomic note Juniperus bermudiana is most closely related to J. virginiana of eastern North America.

Juniperus bermudiana attracts attention principally for its occurrence on Bermuda, where it was once an important source of ship-building timber. Bermuda has a mild, frost-free climate, but J. bermudiana is successfully grown at several locations in our area – mostly in very favourable sites at the western extremities of Europe and in San Francisco, but this may be because of an expectation of tenderness, rather than an actuality. The tallest specimen known in cultivation is a tree at Fota, Co. Cork, measured at 19.5 m tall and with a dbh of 45 cm in 2000 (TROBI). There are short trees at Tregrehan and Kew, all planted in sheltered sites, but also two at the Hillier Gardens where temperatures are not particularly mild. Planted in 1995, these were 1.8 m and 2.2 m tall in 2006. The specimen illustrated (Figure 47) was taken from a scraggy old tree lurking behind the Tropical Nursery at Kew which is the source of foliage each year for the wreath of tropical flowers laid at the Cenotaph in Whitehall on Remembrance Sunday by the British Foreign and Commonwealth Secretary, on behalf of Britain’s Overseas Territories, of which Bermuda is one. This tree, and one at Tregrehan, have a mixture of adult and juveniles leaves, the juvenile phase being brighter green than the dark green of the mature shoots. J. brevifolia (Seub.) Antoine K126 J. californica Carrière K126

Juniperus cedrus Webb & Berthel.

Canary Islands Juniper

Shrub or tree to 30 m, 0.5–1.2 m dbh. Bark orange-brown, peeling in long, narrow strips. Crown narrow and conical initially, later somewhat columnar and open, though wild specimens are often contorted. Leaves of a juvenile form, 0.8–1.2 × 0.1–0.15 cm, white-striped above, green below, apex acute to obtuse. Dioecious. Male strobili 0.4–0.7 cm long, subglobose to cylindrical, microsporophylls eight. Female cones fleshy, usually solitary, subglobose to globose, 0.9–1.2 × 0.4–0.7 cm, mature after 18 months, dark blue with greyish bloom, reddish yellow at maturity. Seeds three, coalesced into a single dispersal unit. Press 1994, Farjon 2005c. Distribution PORTUGAL: Madeira; SPAIN: Canary Is. (La Palma, Tenerife). Habitat Laurisilva forest and other high-altitude areas up to 2300 m asl. USDA Hardiness Zone 9. Conservation status Endangered. Juniperus cedrus has declined because of overgrazing and timber exploitation. Mature trees have become restricted to inaccessible cliffs. Illustration NT419. Cross-references B489, S294, K132. Taxonomic note Juniperus cedrus is closely related to J. oxycedrus L. in the Mediterranean and J. brevifolia (Seub.) Antoine in the Azores.

The occurrence of Juniperus cedrus in the mild climates of the Canary Islands and Madeira seems to have discouraged its planting elsewhere – ‘presumably because no one expected it to be hardy here’ suggests Chris Page (2004), writing about the absence of old specimens in Cornish gardens. Page notes the currently successful cultivation of young trees of J. cedrus in four gardens in that county, and TROBI records its presence in other very mild locations. The current champion appears to be a specimen of 10.5 m (24 cm dbh) at Mount Usher, measured in 2000 for TROI. There was formerly

Section II. Species Accounts

Juniperus

419

a double-trunked tree of 7 m (both trunks 38 cm dbh) at Highdown, Goring, West Sussex, but this has not been recorded again since it was measured by Alan Mitchell in 1983. In the wild it can form a fine tree with pendulous side branches. It grows successfully at Bedgebury, where three young specimens were planted in 1996 as part of the Conifer Conservation Programme. These derive from seed collected in 1992 by a team from the Royal Botanic Garden Edinburgh (A. Ensoll, F. Nelson, A. Wright 1) at 1000 m on Madeira. The tallest was a multistemmed 4.5 m in 2007; a smaller individual is now fruiting (D. Luscombe, pers. comm. 2007). J. centrasiatica (NOW J. pseudosabina Fisch. & C.A. Mey.) K126 J. chinensis L. B479, S291, K126 J. chinensis var. hondoensis Satake K131 J. chinensis var. jackii Rehder K132 J. chinensis var. sargentii A. Henry B481 J. communis L. B482, S292, K130 J. communis subsp. depressa (NOW J. communis var. depressa Pursh) B482, K131 J. communis subsp. hemisphaerica (NOW J. communis L. var. communis) B483, K131 J. communis subsp. nana (NOW J. communis var. saxatilis Pall.) B483, K133 J. communis f. oblonga (NOW J. communis var. saxatilis Pall.) K133 J. communis f. suecica (NOW J. communis L. var. communis) B484 J. conferta (NOW J. rigida subsp. conferta (Parl.) Kitam.) B484, K135

Juniperus foetidissima Willd.

J. convallium Rehder & E.H. Wilson K135 J. davurica (NOW J. sabina var. davurica (Pall.) Farjon) B481, S292, K135 J. deppeana Steud. K135 J. deppeana var. pachyphlaea (Torr.) Martínez B485, S292 J. distans (NOW J. tibetica Kom., NT423) K136 J. drupacea Labill. B485, S292, K136 J. durangensis Martínez K136 J. excelsa M.-Bieb. B486, S293, K136 J. flaccida Schltdl. B486, S293, K136 J. flaccida var. poblana Martínez K137

Stinking Juniper

Shrub or tree (rarely prostrate) to 15(–20) m, 1 m dbh. Bark initially smooth with papery flakes; later grey, fibrous, peeling in long strips. Crown pyramidal, becoming broad and irregular with age; shrub or prostrate habit develops at high altitude. Branchlets in dense, irregular sprays. Juvenile leaves 0.5–0.8 × 0.1–0.2 cm, keeled; mature leaves shiny green or yellowish green, appressed, 0.2–0.5 cm long, apex acute; foliage has a somewhat unpleasant smell when crushed. Dioecious. Male strobili yellow or yellowish brown, 0.2–0.35 cm long, globose to ovoid, microsporophylls 8–12. Female cones globose, 0.5–1.3 cm diameter, dark blue or black, pruinose; becoming somewhat resinous and woody. Seeds one to two (to three) per cone, coalesced into a single dispersal unit, 0.5–0.7 cm diameter. Farjon 2005c. Distribution ALBANIA; ARMENIA; AZERBAIJAN; CYPRUS;

Plate 295. Juniperus cedrus on the Canadas del Teide, Tenerife, Canary Isles. Image A. Farjon.

420

Juniperus

New Trees

GREECE; LEBANON; MACEDONIA; TURKEY; UKRAINE: Crimea. Habitat Dry, rocky slopes with shallow soils, between 0 and 2000 m asl. Annual precipitation between 400 and 1000 mm. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Farjon 1992; NT420. Cross-references B486, K137.

In the wild, despite its often rather arid habitat, Juniperus foetidissima can become immense and very ancient. Trees are known in Turkey with measurements of up to 42 m tall, dbh 200 cm, and one of 27 m has been recorded with a dbh of 462 cm (Gymnosperm Database 2007b). In cultivation, however, there appear to be very few trees, which is curious – especially with provenances so close to western Europe as the Balkans. At the Hillier Gardens a slow-growing specimen planted before 1976 has now reached 5.5 m (7 cm dbh), but this is the only one traced.

Plate 296. Juniperus foetidissima can form a huge tree in Turkey, but it is surprisingly rare in cultivation. Image J.R.P. van Hoey Smith.

J. foetidissima var. pindicola (NOW J. foetidissima Willd.) K137 J. formosana Hayata B487, S293, K137 J. glaucescens (NOW J. komarovii Florin, NT420) K137

Juniperus komarovii Florin

J. horizontalis Moench B487, S293, K137 J. ×kanitzii (NOW J. sabina L. var. sabina) K139 J. kansuensis (NOW J. squamata Buch.-Ham. ex D. Don) K139

Komarov Juniper

Syn. J. glaucescens Florin Tree (or shrub) to 20 m. Bark grey or greyish brown, fibrous, peeling in long strips. Crown broad and ovoid; a shrub habit can develop at high altitudes. Branchlets loosely arranged, straight or slightly curved, terete to four-angled. Juvenile leaves needle-like, basally decurrent; mature leaves greyish green, decussate or rarely in whorls of three, appressed, 0.15–0.6 cm long, apex acute, slightly incurved; leaf resin glands prominent, abaxial, near the leaf base. Monoecious. Male strobili 0.2–0.3 cm long, globose to ovoid, microsporophylls 10. Female cones globose, 0.8–1.2 cm diameter, purplish black, slightly glaucous. Seeds one per cone. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: northern Sichuan. Habitat High-altitude forest between 3000 and 4000 m asl. USDA Hardiness Zone 5. Conservation status Lower Risk. Cross-reference K139.

Juniperus komarovii is extremely rare in cultivation, specimens having been traced only at Quarryhill and Howick. In both cases the plants were grown from SICH 716, collected in 1991 at 3360 m near the Liuba river, Sichuan. When seen in 2004 one tree at Quarryhill was 3–4 m tall, forming a multistemmed column with erect branches and spreading to drooping branchlets, but this has since died of Armillaria (H. Higson, pers. comm. 2007). The foliage is a dull sage-green, and as the old foliage is retained and visible the tree has a distinctly dusty look to it. Older trees develop spreading limbs. According to Bill McNamara (pers. comm. 2004), cuttings are difficult to root. J. macropoda (NOW J. excelsa subsp. polycarpos (K. Koch) Takht.) K140 J. ×media (NOW J. ×pfitzeriana (Späth) Schmidt) K140 J. mekongensis (NOW J. convallium Rehder & E.H. Wilson) K141 J. monosperma (Engelm.) Sarg. S293, K141 J. monosperma var. gracilis (NOW J. angosturana R.P. Adams) K142 J. morrisonicola (NOW J. squamata Buch.-Ham. ex D. Don) B496, K142

J. occidentalis Hook. B488, K142 J. osteosperma (Torr.) Little K142 J. oxycedrus L. B488, S294, K142 J. oxycedrus var. brachyphylla (NOW J. oxycedrus L. subsp. oxycedrus) K142 J. oxycedrus subsp. macrocarpa (Sibth. & Sm.) Neilr. B489, K142 J. phoenicea L. B490, K142 J. phoenicea var. turbinata (NOW J. phoenicea subsp. turbinata (Guss.) Nyman) B490, K142 J. pinchotii Sudw. K142

Section II. Species Accounts

Juniperus pingii W.C. Cheng ex Ferré

Juniperus

Ping Juniper

Shrub or tree to 30 m. Bark greyish brown and fissured, peeling in long strips. Habit variable, from a narrow, conical tree to a dwarf, prostrate shrub. Branchlets pendulous, prominently six-angled. Leaves of a juvenile form, yellowish green, glaucous, concave, 0.3–0.5(–0.7) × 0.1–0.15 cm, keeled, upper surface with inconspicuous white stripes, apex acuminate. Monoecious. Male strobili 0.3–0.4 cm long, ovoid or globose, microsporophylls six to nine. Female cones subglobose to ovoid, 0.7–0.9 cm diameter, lustrous black. Seeds one per cone. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: western Sichuan, northwest Yunnan. Habitat Montane forests between 2600 and 3800 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk.

Juniperus pingii is apparently closely related to J. squamata, and there has been some confusion amongst cultivated plants in the past, but J. pingii can be distinguished by its leaves, which have a keel on the underside and lack longitudinal grooves (Fu et al. 1999e). The species is well established in cultivation and is available commercially, although often in the form of selected cultivars. The typical horticultural form is a multistemmed shrub, at least when the plant is young, with ascending branches clad in light green leaves. It is not clear when or by whom this was introduced.

Juniperus pingii var. wilsonii (Rehder) Silba Syn. J. pingii var. carinata Y.F. Yu & L.K. Fu Var. wilsonii has stout branchlets and typically forms a shrub or small tree to 2 m. The branchlets may be sixangled (var. carinata) or not. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: Gansu, Hubei, Qinghai, Shaanxi, Sichuan, Xizang, Yunnan. Habitat Thickets on mountain slopes between 2600 and 4900 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk. Cross-reference K149 (as J. squamata ‘Loderi’).

This dwarf, alpine shrub has been in cultivation since it was found by E.H. Wilson (as J. squamata var. wilsonii Rehder) in 1909, and several selections were named early in the twentieth century. Among these was ‘Loderi’, a particularly dwarf clone with somewhat columnar habit (Krüssmann 1985b), which is probably the most frequent representative of var. wilsonii. Wild material has been collected by SICH expeditions in several years (SICH 138 in 1988, SICH 549 in 1991, SICH 2320 in 1993), all from low bushes growing at high altitudes. J. potaninii (NOW J. tibetica Kom., NT423) K142

Juniperus procera Hochst. ex Endl.

African Pencil Cedar, East African Juniper

Tree to 40 m, single-stemmed (rarely multistemmed), to at least 2.29 m dbh. Bark initially purplish, smooth with papery flakes, later brown or grey-brown with deep, longitudinal furrows, peeling in long strips. Crown pyramidal initially, becoming broad, domed or flat-topped, irregular and open with age. Branchlets in flattened sprays or with an irregular arrangement. Juvenile leaves in whorls of three or almost decussate, 0.8–1 × 0.1 cm; mature leaves light green or yellowish green, basally appressed, c. 0.1(–0.6) cm long; leaf resin glands conspicuous and active. Dioecious. Male strobili borne on short, lateral branches, green to orangebrown, 0.3–0.5 cm long, globose to ovoid, microsporophylls 10–12. Female cones solitary, ovoid, 0.3–0.7 cm diameter, colour variable (bluish or brownish or purplish black). Seeds (one to) two to three (to four) per cone. Farjon 1992, 2005c. Distribution CONGO (DEM. REP.); DJIBOUTI; ETHIOPIA; KENYA; MALAWI; SAUDI ARABIA; SOMALIA; SUDAN; TANZANIA; UGANDA; YEMEN; ZIMBABWE. The only species of Juniperus occurring south of the Equator. Habitat Primarily a species of African mountains between 1050 and 3600 m asl, though also occurs in upland savannas and on the Red Sea coast. Tolerates a wide range of rainfall regimes, from 1000–1200 mm (annual precipitation) in East Africa to as little as 400 mm. USDA Hardiness Zone 9. Conservation status Lower Risk. Several local populations of J. procera are endangered; the Zimbabwe population (Inyanga Mt.) has been reduced to just one individual (Coates Palgrave 1990). Illustration Farjon 1992; NT29, NT415, NT422. Cross-reference K143.

Juniperus procera is a characteristic Afromontane forest tree, but is dependent upon open ground to germinate and establish. Its presence is therefore a witness to past

421

422

Juniperus

New Trees

environmental events, and a single massive specimen growing amongst dense ‘virgin’ broadleaved Afromontane forest gave me (JMG) the clue to understanding the importance of fire and climatic change in affecting the composition of the forest in my study area on the northern slope of Kilimanjaro (Grimshaw 1996, 1998). This individual had a dbh of 229 cm and stood at least 30 m tall: a truly magnificent tree that was probably at least 300 years old. Juniperus procera is a species for which I have a great deal of affection, and I have enjoyed seeing it across parts of its range, from Ethiopia southwards to that solitary tree in Zimbabwe, clinging to its cliff some 1500 km south of all its relatives. It has therefore been pleasant also to see it thriving in cultivation. At Tregrehan a tree passed on from Kew is about 3 m tall and looking very well. When seen in 2005 this was just developing adult foliage, after about ten years. It has never shown any signs of frost damage (T. Hudson, pers. comm. 2005). TROBI has recorded several specimens in the past, the largest of which, at Fota, Co. Cork, was 14 m tall in 1987 but has since been broken off. Its girth is impressive, however, at 105 cm dbh. Although it may never achieve East African proportions, in the current climate J. procera is certainly worth attempting in the milder parts of our area. Plate 297. The tree of Juniperus procera, in broadleaved forest on Kilimanjaro, that gave the clue to a thesis (shown here with field assistants Lembris Kephas Mollel and Mtapa Abdallah). Image J. Grimshaw.

J. procumbens (Siebold ex Endl.) Miq. B490, K143 J. przewalskii Kom. K143 J. pseudosabina Fisch. & C.A. Mey. B498, K143 J. ramulosa (NOW J. convallium Rehder & E.H. Wilson) K144 J. recurva Buch.-Ham. ex D. Don B490, S294, K144 J. recurva var. coxii (A.B. Jacks.) Melville B491, K144 J. rigida Siebold & Zucc. B492, S294, K144

J. rigida subsp. nipponica (NOW J. communis var. nipponica (Maxim.) E.H. Wilson) B492, K144 J. sabina L. B493, S294, K144 J. sabina var. tamariscifolia (NOW J. sabina L. var. sabina) B494, S294 J. saltuaria Rehder & E.H. Wilson B494, K146 J. sargentii (NOW J. chinensis var. sargentii A. Henry) K146 J. scopulorum Sarg. B495, S294, K146

Section II. Species Accounts

Juniperus

Juniperus semiglobosa Regel

Russian Juniper

Tree (rarely a shrub) to 20 m, single-stemmed (rarely multistemmed), to 2 m dbh. Bark initially reddish brown, smooth with papery flakes, later reddish to greyish brown with longitudinal furrows, peeling in long strips. Crown open or dense, usually broadly pyramidal. Branchlets compact, often pendulous with an irregular arrangement. Juvenile leaves 0.8–1 × 0.1 cm; mature leaves glossy green (with a very thick cuticle), decussate or in whorls of three, appressed, 0.1–0.2(–0.9) cm long, apex acute; leaf resin glands large, conspicuous and active. Dioecious. Male strobili green to yellow, 0.3–0.5 cm long, microsporophylls 8–10. Female cones subglobose to triangular, rarely globose, 0.2–0.3 cm diameter, light brown to bluish black, pruinose, soft and fleshy, but becoming rather hard with age. Seeds (one to) two to three (to four) per cone, though usually two. Fu et al. 1999e, Farjon 2005c. Distribution AFGHANISTAN; CHINA: western Xizang; INDIA: Himachal Pradesh, Jammu & Kashmir; KAZAKHSTAN; KYRGYZSTAN; PAKISTAN; TAJIKISTAN; UZBEKISTAN. Habitat High, semi-arid valleys in the central Asian mountain ranges, between 1600 and 4300 m asl. Juniperus semiglobosa is tolerant of heat and drought, but also of extremely low temperatures, frost and snow. USDA Hardiness Zone 4. Conservation status Lower Risk. Illustration Farjon 1992. Cross-reference K147.

Juniperus semiglobosa has a wide range in the arid heart of Asia and can form either a tree or a shrub, depending on local conditions. It is extremely hardy and droughtresistant, often surviving in the wild on snowmelt water (Farjon 1992). It is in cultivation, but very rare. The only specimen traced is a young plant at Kew received as a seedling from Saint Petersburg Botanical Garden in 1997, but a cultivated specimen is illustrated by van Gelderen & van Hoey Smith (1996). The species epithet apparently refers to the rather flattened shape of the fruits. J. seravshanica (NOW J. excelsa subsp. polycarpos (K. Koch) Takht.) K147 J. silicicola (NOW J. virginiana var. silicicola (Small) E. Murray, NT424) K147 J. squamata Buch.-Ham. ex D. Don B495, S295, K148 J. squamata var. fargesii (NOW J. squamata Buch.-Ham. ex D. Don) B495, K148

J. squamata f. wilsonii (NOW J. pingii W.C. Cheng ex Ferré var. wilsonii (Rehder) Silba, NT421) B496 J. taxifolia Hook. & Arn. K149 J. taxifolia var. luchuenensis (NOW J. taxifolia Hook. & Arn.) K150 J. thurifera L. B496, S295, K150 J. thurifera var. gallica (NOW J. thurifera L.) K150

Juniperus tibetica Kom.

Tibetan Juniper

Syn. J. distans Florin, J. potaninii Kom., J. zaidamensis Kom. Tree (rarely a shrub) to 30 m, single-stemmed (rarely multistemmed). Bark pale brown, peeling in long, papery sheets. Crown dense and ovoid. Branchlets straight, terete or four-angled, densely or loosely arranged. Juvenile leaves 0.4–0.8 cm long, bright green with two glaucous stripes on the inner face; mature leaves dark green, decussate or (rarely) in whorls of three, appressed, 0.1–0.3 cm long, apex obtuse; leaf resin glands conspicuous. Monoecious (rarely dioecious). Male strobili 0.3–0.4 cm long, microsporophylls six to eight. Female cones ovoid to subglobose, 0.9–1.6 × 0.7–1.3 cm, colour variable (reddish or greyish brown to black). Seeds one per cone. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: Gansu, Qinghai, Sichuan, Xizang. Habitat Forested mountain slopes and valleys between 2700 and 4800 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration NT1. Cross-reference K150.

As with many of the junipers found in Tibet and neighbouring countries, the branches of Juniperus tibetica are used for incense in Buddhist rituals, as well as for normal firewood and building purposes, and their continued gathering for all uses has led some to express concern for the survival of the species (Adams 2004). Where moisture is adequate, it can become a large tree in the wild, and it has the distinction of forming the highest treeline in the northern hemisphere, at 4900 m in southern Tibet

423

424

Juniperus

New Trees

(Miehe et al. 2001). It has been collected by at least two expeditions recently: first in Sichuan by the 1994 Alpine Garden Society Expedition to China (ACE 1816), from which source plants are growing at Edinburgh and probably elsewhere; and then by the 2003 Sichuan Expedition of Kirkham, Flanagan, Jamieson and Clements (SICH 2329), at 3040 m in Ruoergai Co., Sichuan. Young plants from this latter trip are still in the nursery at Kew. There are older specimens growing in the Hillier Gardens, the tallest of which (planted 1982) had reached 6.9 m in 2007. J. turkestanica (NOW J. pseudosabina Fisch. & C.A. Mey.) K153

Juniperus virginiana L.

Pencil Cedar, Eastern Red Cedar

This species was described by Bean (B497, S295) and Krüssmann (K150).

Juniperus virginiana var. silicicola (Small) E. Murray Var. silicicola has slender, rather pendulous branchlets and small seed cones when compared with the type variety (3–4 mm, vs. 4–7 mm in var. virginiana). The crown is flat-topped rather than narrow and erect. Distinguishing the varieties is challenging, particularly as the morphological characters intergrade in some locations. Watson & Eckenwalder 1993, Farjon 2005c. Distribution USA: Georgia, Florida, North Carolina, South Carolina. Habitat Coastal sand dunes and sandy riverbanks near sea-level. USDA Hardiness Zone 7–8. Conservation status Lower Risk. Illustration NT424.

Juniperus virginiana var. silicicola is best distinguished from var. virginiana by its sand-dune habitat, and for most horticultural purposes appears to have no real distinction from the type, save that it is less hardy. Its advantage may come as a tree for coastal planting. It is found in arboreta quite frequently, and some selections have been made, including the dark green, columnar ‘Brodie’ (Dirr 1998). Plate 298. Juniperus virginiana var. silicicola grows on sand dunes on the coast of the southeastern United States. Image D. Luscombe.

J. wallichiana (NOW J. indica Bertol.) B498, S295, K152 J. zaidamensis (NOW J. tibetica Kom., NT423) K153

PINACEAE

KETELEERIA Figure 48 (opposite). Chinese conifers. Cathaya argyrophylla: detail of stem (A); habit with seed cone (B). Keteleeria evelyniana: seed cone (C); habit with male strobili (D); detail of stem (E).

Carrière

Keteleeria was revised by Farjon (1989), and in the process the number of species was reduced drastically, from fourteen to three. The genus occurs primarily in China and Taiwan, though there are outlying populations in northern Laos and southern Vietnam. Keteleeria species are medium-sized, evergreen trees with straight trunks. The bark is rather thin, though in older trees it thickens and can develop scales and longitudinal fissures. Branching is irregular, and the primary branches are rigid and

Section II. Species Accounts

Keteleeria

425

A 1 cm

1 cm

C

B 1 cm

1 cm

E D

426

Keteleeria

Plate 299. The endangered Keteleeria davidiana var. formosana demonstrates the long erect cones that are characteristic of the genus. ETOT 108, in Taiwan, 1992. Image T. Kirkham.

New Trees

spreading. Forms with pendulous branches are known, though these may be a result of coppicing. Immature branchlets may be pubescent or glabrous, and are yellowish to reddish brown. The buds are covered in persistent, non-resinous, triangular bud scales. The needle-like leaves exhibit a weak dimorphism, whereby the juvenile leaves are broad, lanceolate and thin, while mature leaves are narrow, linear and thick. Juvenile leaves are found on young plants and on secondary branches of more mature plants; juvenile characters may also occur in coppiced specimens. This variation in leaf morphology within species may partly account for previously inflated numbers of species. The leaves are spirally arranged and resemble those of Abies: the leaf bases are twisted, the leaves are arranged roughly in two ranks and the stomata are arranged in two rows separated by the midrib. Male strobili are not pendulous, and form umbellate clusters at terminal or lateral buds. There are between five and ten strobili in each cluster. The cones are erect and restricted to the upper part of the crown. They have a long, leafy peduncle, and mature in one year. The cone scales are spirally arranged around a central rachis, and remain attached to the rachis at maturity. However, after a few years, the cone rachis breaks up and scales and rachis are shed from the tree; the seeds are not released until the cone breaks up, except during windy weather. The bract scales are half the length of the cone scales, and may be included or partially exserted. There are two seeds on each scale, and these are partially enclosed in a membranous cup, which extends to form a persistent wing. The seeds are rather large. When identifying Keteleeria species, the shape of the cone scales is particularly important (Farjon 1989, 1990). Keteleeria has never been a very satisfactory genus in maritime Europe, apparently requiring hot summers and an absence of late spring frosts to do well: Mediterranean Europe, Texas, California and Australia seem to offer the best climates for the genus. Trees should be planted in well-drained to dry sites. In the United Kingdom only K. davidiana has formed a respectable tree, and then only in a limited number of gardens. The current champion, at Wakehurst Place, was planted in 1918 but is only 11 m tall (Johnson 2003).The first species to be introduced – K. fortunei, from eastern China – is particularly unsatisfactory and is now extremely rare in cultivation. New introductions from different provenances should perhaps be sought. K. chienpeii (NOW K. davidiana (Bertrand) Beissn. var. davidiana) K154 K. cyclolepis (NOW K. fortunei (A. Murray) Carrière) K154

Keteleeria davidiana (Bertrand) Beissn. This species was described by Bean (B507, S298) and Krüssmann (K154).

Keteleeria davidiana var. formosana (Hayata) Hayata This variety differs from the type in that the shoots are glabrous, the leaf scars protrude noticeably from the branchlets, and the leaf apex is acute or obtuse, rather than truncate or emarginate. The cones are shorter, the bract scales are spathulate and contracted above the midpoint, and the seed is narrower than in the type. Hayata 1914, Farjon 1989, Fu et al. 1999c. Distribution TAIWAN. Habitat Mixed mesophytic forest between 300

Section II. Species Accounts

Keteleeria

and 900 m asl. In northern Taiwan, var. formosana occurs in small groups or as isolated individuals on steep ridge crests. It survives coppicing. USDA Hardiness Zone 9. Conservation status Endangered. Illustration Li & Keng 1994a, Fu et al. 1999c, Flanagan & Kirkham 2005; NT426. Cross-reference K154.

Keteleeria davidiana var. formosana is in cultivation from seed collected in 1992 by Kirkham & Flanagan (ETOT 108) at Pinlin in Taiwan. This area, at 680 m, with about 200 trees growing on sticky reddish loam, is one of only two localities for this endangered endemic taxon. Seedlings from ETOT 108 were distributed relatively widely to arboreta in the United Kingdom and Ireland, but it has failed to establish outside at Kew, and survives there only in the Temperate House. K. esquirolii (NOW K. davidiana (Bertrand) Beissn. var. davidiana) K154

Keteleeria evelyniana Mast. Tree to 40 m, trunk straight and occasionally forked, 1–1.5 m dbh. Bark grey-brown, thick with corky flakes, becoming darker and scaly in older trees. Crown broad and conical, somewhat irregular. Branchlets slender, yellowish or reddish brown, becoming grey-brown with age, conspicuously grooved, leaf scars circular; young shoots pinkish green; vegetative buds not resinous. Leaves glaucous or dark green above, greenish white below, (2–)3–6.5(–8) × 0.2–0.4 cm, apex mucronate or obtuse. Male strobili lateral or terminal, pedunculate, 1–1.5 cm long, yellow with brown perular scales. Cones solitary, erect, peduncles 2–6 cm long; cone cylindrical, (4–)9–20(–25) × (3–)4–6.5(–9) cm, apex obtuse, cone green or purple, ripening to pale brown. Seed scales striated on upper surface, subcordate to oblong, 3–4 × 2.5–3 cm. Bract scales ligulate to spathulate, 1–1.5 cm long, partially exserted. Seeds dull brown, wings 2–3 × 1.2–1.5 cm. Farjon 1989, 1990, Fu et al. 1999c. Distribution CHINA: Guangxi, Sichuan, Yunnan; LAOS; VIETNAM. Habitat Mountainous areas in tropical environments, between 700 and 2000(–2700) m asl. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Lancaster 1989, Farjon 1990, Fu et al. 1999c; NT425. Cross-reference K155.

Keteleeria evelyniana is a conspicuous tree in the Western Hills of Yunnan, and in consequence has been collected on several occasions since Roy Lancaster’s visits in the early 1980s, recorded with gusto in Travels in China (1989). Young specimens are widespread in the United States, thriving in Texas and California at least, although acting as a ‘herbaceous perennial’ for Tony Avent (pers. comm. 2006) in North Carolina. One seen at Quarryhill in 2004 was a shapely 2.5 m, reached since planting in 2000, although this has since succumbed to Armillaria, as had others earlier from the same batch (W. McNamara, pers. comms. 2004, 2007). It was also doing well in the San Francisco Botanical Garden in 2004. In the United Kingdom results are mixed. There is a good 2 m specimen of Yunnanese origin at Tregrehan, apparently growing well since accession in 1996, but a tree at Wakehurst Place (from Rushforth 371) is still only 2.5 m since 1981 and looks very unhappy, with yellowish foliage and no leader. K. fortunei (A. Murray) Carrière B507, K155 K. roulletii (NOW K. evelyniana Mast., NT427) K155

PROTEACEAE

KNIGHTIA

R. Br.

Knightia comprises three species: one in New Zealand, which is cultivated, and two in New Caledonia. They are trees or shrubs with alternate, petiolate leaves, which are entire or dentate, simple or (rarely) forked. The inflorescences are in small, terminal or axillary groups. The flowers are numerous and in pairs; the floral bracts small or large,

427

428

Knightia

New Trees

membranous or brightly coloured, usually caducous. The flowers are 4-merous; the perianth is cylindrical and the tepals curl spirally; the stamens have short filaments; the style is extended. The fruit is a woody follicle with two valves, and the seeds are winged at the apex (Allan 1961, Virot 1968).

Knightia excelsa R. Br.

New Zealand Honeysuckle, Rewarewa

Tree to 30 m, 1 m dbh; often unbranched up to 15 m. Bark greyish green and finely textured. Branchlets angled, covered in ferruginous tomentum. Juvenile leaves ±30 cm long, linear to lanceolate with serrated margins, rarely forked. Adult leaves very thick and rigid, narrow oblong to obovate, rarely forked, 10–15(–20) × 2.5–4 cm, upper surface glossy green with a reddish midrib, lower surface covered with pale tomentum, secondary veins indistinct, margins coarsely serrated, apex acute; petiole stout, c.1 cm long. Inflorescences stout and racemose, ± 10 cm long. Flowers reddish brown with an unpleasant odour; perianth splitting longitudinally, tepals coiled around the base of the flower; style to 3 cm long. Follicles 3–4 cm long, valvate and tomentose, tapering towards a persistent style; seeds winged. Flowering October to December, fruiting October to December the following year (New Zealand). Allan 1961, Salmon 1980. Distribution NEW ZEALAND: North Is. (widespread), South Is. (Marlborough Sounds). Habitat Lowland or montane forest between 0 and 850 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT428.

Plate 300. The spire-like shape of Knightia excelsa gives it a distinctive outline in its native New Zealand. Image J.R.P. van Hoey Smith.

Knightia excelsa is one of the most distinctive New Zealand trees, with a decidedly fastigiate or at least upright habit, and thus has a conspicuous outline in native vegetation. This shape, coupled with its glossy dark leaves, makes it welcome as a specimen tree in New Zealand gardens (Metcalf 2000). The clusters of dull red flowers are attractive (though foetid), but rather invisible when high among the foliage. The long, narrow, rather hard leaves are also attractive and make it well worth growing even where flowers or great stature cannot be expected. In New Zealand it is considered hardy over much of the country, but late summer shoots may get frosted occasionally. Well-drained, but moist, acid soil in sun or shade is suggested (Metcalf 2000, Moore 2004). It is currently being tried quite widely, and seems to flourish on the west coast of Ireland, where specimens over 5 m are known, and it is also growing at Inverewe in northwest Scotland (Anderson 2002). In Cornwall it survives and grows quite well, but is considered frost tolerant to only –5 °C (Moore 2004), while in Essex it is cut to the ground each winter (Johnson 2007).

SAPINDACEAE

KOELREUTERIA

Laxm.

Golden-rain Trees, Pride of India Trees Koelreuteria comprises three species: K. paniculata and K. bipinnata from China, and K. elegans from Taiwan and Fiji. They are single- or multistemmed trees with thick, sometimes fissured bark and prominent lenticels on the branchlets and petioles. The leaves are deciduous, alternate and imparipinnate; the leaflets elliptic to ovate, entire,

Section II. Species Accounts

serrate or crenate, glabrous to sparsely pubescent; the median leaflets are usually the largest. Inflorescences are terminal, paniculate and pyramidal. The flowers are unisexual or hermaphrodite; they have five calyx lobes, three long and two short, often glandular, four to five (to six) petals, strongly reflexed, yellow, turning orange-red, and eight (to nine) stamens with hairy filaments. The fruit is an inflated capsule with papery wing-like valves (Meyer 1976). Koelreuteria paniculata is justly popular for its handsome pinnate leaves, broad inflorescences of yellow flowers, and inflated fruits. A number of recent selections have been named, with attributes ranging from later flowering (‘September’) to pinkflushed capsules (for example, ‘Rose Lantern’) and pink-flushed shoots (‘Coral Sun’). These are probably worth seeking out for planting instead of unnamed seedlings. In addition there is the older ‘Fastigiata’ which is perfect for small gardens, though it prefers summers warmer than those of the United Kingdom. Koelreuteria paniculata has no particular foibles for cultivation and it may be assumed that, where the climate is appropriate, the other species will be equally tolerant of soil conditions. They should all be planted in full sun.

Koelreuteria bipinnata Franch. Syn. K. integrifoliola Merr. Tree to 20 m, 0.6 m dbh. Bark brown, splitting into small square plates. Branchlets glabrous or slightly pubescent; lenticels circular, prominent and corky. Leaves bipinnate, 27–30 cm long; leaflets alternate to opposite, (3–)8–10(–12) on each major division, narrowly ovate to elliptic, 7.8–14 × 2–5 cm, upper surface dull dark green with short hairs on the midrib, lower surface with longer tufts of hair and some glandular trichomes, margins entire to uniformly serrate, apex acute to short-acuminate; leaflets sessile or with petiolules to 0.3 cm long; rachis with line of hairs on upper surface or glabrous. Inflorescences 35–70 × 20–40 cm, densely pubescent; pedicels 0.2–0.3 cm long. Flowers: calyx lobes ovate to deltoid, glandular, petals four, 0.5–1 cm long, stamens exserted. Capsules ellipsoidal, 3.7–6.6 × 3–5 cm, rose-purple when young, brown at maturity. Flowering July to September, fruiting August to October (China). Meyer 1976. Distribution CHINA: Anhui, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Sichuan, Yunnan, Zhejiang. Widely cultivated both in China and elsewhere. Habitat Open fields, hillside forests, thickets and similar, between 250 and 2600 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Meyer 1976; NT429. Cross-references B509, K199.

Koelreuteria bipinnata was introduced to the United States by Francesco Franceschi of Santa Barbara, California in 1911, and this material became established in cultivation, whereas that sent by Delavay from

Koelreuteria

429

Plate 301. The inflated fruits of Koelreuteria bipinnata are its prime glory, although the masses of yellow flowers in early summer are also striking. Image T. Kirkham.

430

Koelreuteria

New Trees

Yunnan to France in 1887 did not. It was offered by Simon-Louis Frères in 1908, which resulted in a tree at Birr Castle and another at La Mortola, according to Meyer (1976). The species is now thoroughly established in American horticulture, and offers a useful variation on the Koelreuteria theme. Its particular value comes from its flowering in September, when there are few flowering trees and when, as Dirr (1998) says, it ‘shines like a yellow star’. The flowers are followed by inflated pink capsules that continue the display as the foliage turns its autumnal yellow. It can become quite a large tree, with heavy branches that have the potential to create an open canopy: Dirr (1998) recommends careful formative pruning. The tallest specimen seen in the research for New Trees was one planted in 1979 at the US National Arboretum, 15–16 m tall, and very elegant and shapely. It is accounted fully hardy on the East Coast, at least as far north as Philadelphia (Meyer 1976) and possibly further. Bean (1981a) says that the species is not hardy in London or Paris, but the passage of time suggests that it would now be worth planting K. bipinnata at least as far north as southern England. There is a 7 m tree at Kew, and other respectable specimens elsewhere from Cambridge to Bristol (Johnson 2007).

Koelreuteria elegans (Seem.) A.C. Sm. This species has a very unusual distribution: subsp. elegans occurs in Fiji in the southern hemisphere, while subsp. formosana occurs in Taiwan in the northern hemisphere. Their morphology, however, is extremely similar. Owing to its tropical origins, subsp. elegans is unsuitable for outdoor cultivation in temperate areas.

Koelreuteria elegans subsp. formosana (Hayata) F.G. Meyer

Flamegold

Syn. K. henryi Dummer Tree 7–25 m, 0.5–2 m dbh. Bark rough, furrowed, ±corky, peeling off in square plates. Leaves bipinnate, though the terminal leaflet may be missing, 25–60 ×15–44 cm; leaflets 8–17 on each major division, lanceolate to narrowly ovate or elliptic, 5.5–9.2(–10.2) × 1.3–3(–4.2) cm, glabrous or with scattered hairs on the veins, tufts of hair in vein axils below, margins coarsely serrate, apex long-acuminate to caudate; petiolules 0.4–0.5(–1) cm; rachis glabrous or with short hairs. Inflorescences 30–50 × 20–25 cm, densely pubescent, glandular. Flowers sweetly fragrant; petals acute, four to five, 0.6–0.7 cm long. Capsules ellipsoidal, 3.4–5(–6) × 3–4.6 cm, deep rose-purple when young, brown at maturity. Flowering September to October, fruiting November (Taiwan). Meyer 1976. Distribution TAIWAN. Habitat Forest edges. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Meyer 1976. Cross-reference S299. Taxonomic note Subsp. elegans has entire or sparsely serrate leaflets, petiolules 0.1–0.3 cm long, and slightly larger, obtuse or rounded petals.

Koelreuteria elegans subsp. formosana was introduced to the United States from Taiwan in 1915 by David Fairchild’s Office of Foreign Plant Introduction. It has proved to be extremely successful in the southern states, especially Florida, and in southern California, where its rounded crown, evergreen leaves, spectacular orange-yellow flowers and inflated pink fruits make it a popular street and specimen tree (Gilman & Watson 1993c). Unfortunately its reproductive prowess has led to it becoming invasive in parts of Florida, Hawaii and Australia. In our area, where it is on the edge of its tolerance, this is not likely to be a problem. It requires a very warm summer to perform well, and is unlikely to succeed in most of northern Europe. A recent introduction by Bleddyn and Sue Wynn-Jones of seed given to them by the Institute of Taiwan Endemic Species in 1999 (BSWJ 7038) has been distributed from Crûg Farm, Gwynedd. The only survivors traced are a couple of specimens struggling along at

Section II. Species Accounts

Koelreuteria

431

Tregrehan, where they die back each winter and have not got above a metre in height (T. Hudson, pers. comm. 2007). K. paniculata Laxm. B508, S299, K200 K. paniculata var. apiculata (NOW K. paniculata Laxm.) B508, K200

LYTHRACEAE

LAGERSTROEMIA

L.

Crape-myrtles Lagerstroemia includes about 55 species in Australia and eastern Asia as far north as Japan (Qing et al. 2007). They are evergreen or deciduous trees or shrubs with showy flowers and attractive bark. The branchlets are terete or four-angled, rarely with small wings. The leaves are alternate, opposite or in between. The flowers are solitary or in terminal and axillary paniculate cymes; they are hermaphrodite and 6-merous, though 5-merous and 7-merous flowers are common. The calyx is campanulate or funnelshaped with 6–12(–14) veins or ribs; it opens out into narrow or broadly triangular sepals. An additional whorl of sepal-like bracts (epicalyx) may subtend the calyx. The petals are free and alternate with the sepals; they are rounded or oblong with a long, narrow stalk (claw or limb) that inserts into the calyx. The petals are folded in the bud and appear wrinkled when the flower opens; they may be pink, purple or white. The stamens are usually dimorphic, with six solitary stamens with thick filaments and large anthers, surrounding a cluster of 12 to 100 or more stamens with thin filaments and small anthers. The fruit is a hard, dry capsule that splits along three to six longitudinal valves to release numerous one-winged seeds (Furtado & Srisuko 1969, Qing et al. 2007). The long-cultivated Lagerstroemia indica, the Crape-myrtle, is a classic example of the effect of the differences between the climates of the eastern United States and northern Europe. Even in the warmest sites in southern England it makes a bush that flowers only after the most favourable summers, and is for the most part a waste of space as a garden plant. Where conditions are particularly favourable, as at Killerton in Devon, it can make a trunk and thus display its lovely cream and pinkish red bark. In much of the southern United States, however, and in the Mediterranean,

Plate 302. The old trees of Lagerstroemia fauriei at the JC Raulston Arboretum, from the first introduction of the species by John Creech, are now magnificent, multistemmed specimens. This is the original ‘Townhouse’ tree, now widely propagated. Image P. Gentille/B. Ward.

432

Lagerstroemia

New Trees

it is among the most magnificent of all small flowering trees, and justly popular. A vast array of cultivars has been selected, some being hybrids with L. fauriei, with characters in combinations of improved flower colours, autumn leaf colouring, bark effects and mildew resistance. Many were created through the work of Dr Donald Egolf and others at the US National Arboretum over several decades (Dirr 1998). The development of the Crape-myrtle is a most important contribution to horticulture, and has made it an exceptionally valuable small tree for gardens in areas with hot summers. Dirr (1998) gives a summary list of L. indica clones and hybrids, and nursery catalogues and websites will provide others. In addition to the true landscape clones there are numerous seed-raised selections of L. indica in varying degrees of dwarfness, grown as pot or bedding plants for their abundant, rapidly produced flower heads. These have their place, perhaps, but are not a substitute for selected, tree-forming clones. In addition to the species described below, Lagerstroemia speciosa (L.) Pers. is in cultivation in the warmest areas of the United States. It is a large tropical tree with fine inflorescences of purplish or white flowers, with individual flowers 8 cm across, but is not hardy in our area (Dirr 1998). All Lagerstroemia will perform best in hot, sunny conditions: it is important to realise that their failure to perform in maritime Europe is not because they are frost tender – they can tolerate temperatures down to at least –20 °C before becoming herbaceous (Dirr 1998) – but is due to the lack of summer heat to encourage vigorous growth and harden the wood. Even in favoured localities it is important to complete pruning by early August to enable new growth to ripen before winter (Dirr 1998). Propagation is by seed or from soft or semi-woody cuttings taken in early summer.

Lagerstroemia fauriei Koehne Shrub or tree to 20 m, often multistemmed. Bark peeling in strips and plates, shades of reddish brown and whitish. Branchlets somewhat terete, reddish or yellowish brown, glabrous. Leaves deciduous, 8–10 × 2.3–5 cm, oblong to ovate, leathery, both surfaces largely glabrous, but for occasional tuft of hair in vein axils below, 8–13 secondary veins on each side of midrib, apex obtuse; petiole 0.8–1 cm long. Panicles 5–10 cm long, slightly narrower than long, densely flowered, glabrous. Flowers 6-merous; calyx tube cup-shaped with 12 nerves; petals small, white; stamens 30–36, bright yellow. Ohwi 1965. Distribution JAPAN: Kyushu, Yakushima. Habitat Riparian, warm temperate forests. USDA Hardiness Zone (6–)7. Conservation status Not evaluated (though rare on Yakushima). Illustration NT431, NT432. Taxonomic note This species is closely related to L. subcostata and might be better represented as a subspecies.

Plate 303. The bark of Lagerstroemia fauriei is exceptional in its beautiful mottling. Image JC Raulston Arboretum.

As seen at the JC Raulston Arboretum, which has become the locus classicus for the species, Lagerstroemia fauriei is one of the most desirable of recent tree introductions. Here there are large trees, with multiple stems that show off their prime feature, the glorious mottled red and white peeling bark – among the finest of all patterned barks. The trunks rise straight up to a broad system of wide-spreading branches, supporting a dense canopy of leaves: individuals are often wider than they are tall. This is a beautiful medium-sized shade tree, and is suitable for street planting as well as in gardens (Gilman & Watson 1993b). The foliage is an unexceptional mid-green, turning yellow before falling. The flowers are white, and while much smaller and less showy than those of L. indica, a tree in full bloom in early summer is still an attractive sight. Lagerstroemia fauriei was introduced to cultivation in 1957, having been collected as seed on Yakushima by John L. Creech, and then cultivated at the US National Arboretum (Dirr 1998, Ani´sko 2006). The JCRA trees are from this introduction, dis-

Section II. Species Accounts

Lagerstroemia

433

tributed to the North Carolina State University. Two clones have been named from here: ‘Townhouse’ (from its position in the ‘townhouse’ demonstration garden), with dark reddish bark of exceptional quality (Raulston 1993, Dirr 1998), and ‘Fantasy’, which has lighter-coloured bark. They deserve wide planting, especially as the species is considerably hardier than L. indica, flourishing on the East Coast at least as far north as the Philadelphia area (a 14-year-old ‘Townhouse’ at the Scott Arboretum has reached 6 m), and worth trying as far north as Boston (A. Bunting, pers. comm. 2006). It appears to be tolerant of most soil types and is very drought-resistant, as well as being immune to most pests and diseases (Gilman & Watson 1993b). The hardiness and resistance to powdery mildew of L. fauriei have been passed in varying degrees to its offspring with L. indica, including ‘Muskogee’ (lavender-pink), ‘Natchez’ (white), ‘Tuscarora’ (deep coral) and numerous others. In many cases these also have excellent bark. L. indica L. B515, K203

Lagerstroemia limii Merr. Syn. L. chekiangensis W.C. Cheng Shrub or tree to 7 m or more, multistemmed. Bark brown, peeling slightly to reveal redder bark below. Branchlets terete with dense grey or yellowish brown pubescence. Leaves deciduous, opposite to subopposite, 6–9 × 2.5–4 cm, oblong to elliptic, thin and leathery, upper surface green and sparsely pubescent, lower surface densely pubescent along the midrib and veins, 9–17 secondary veins on each side of the midrib, apex acute or acuminate; petiole 0.2–0.5 cm long and pubescent. Panicles terminal, pyramidal, 8–18 cm long, open and densely pubescent. Flowers (5–)6-merous; calyx tube cup-shaped, 0.5–0.8 cm long with 12–14 deep ribs and covered in yellowish brown pubescence or nearly glabrous; epicalyx segments conspicuous and half as long as the sepals; petals reddish pink, 0.9–1.2 cm; stamens ~35, dimorphic. Capsule elliptic to oblong, 0.8–1.2 × 0.5–0.8 cm with four to six valves. Flowering May to June, fruiting July to August (China). Furtado & Srisuko 1969, Qing et al. 2007. Distribution CHINA: Fujian, Hubei, Zhejiang. Habitat Mixed forests at low altitudes. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Furtado & Srisuko 1969; NT433. Taxonomic note Lagerstroemia chekiangensis is only a more vigorous and hairy form of L. limii (Furtado & Srisuko 1969).

Lagerstroemia limii is in some ways a poor relation of L. fauriei and L. indica – having neither bark nor outstanding floral features to commend it – but if they did not exist it would be thought pleasant enough. It is often rather more shrubby than tree-like, although there is a 5 m specimen at the JC Raulston Arboretum that is on a single stem. The leaves are large, bluish green, and the flowers lavender-purple. In its favour, it is hardier than L. indica, and the purple coloration is useful in breeding: the US National Arboretum has recently released a series of cultivars with intensely coloured flowers that are three-way hybrids involving L. fauriei, L. indica and L. limii. Among these are ‘Arapaho’ (with deep red flowers) and ‘Cheyenne’ (neon red). The species is occasionally encountered in botanical collections in the United States as either L. limii or L. chekiangensis, and under the latter name is becoming better known in Europe. In Bute Park, Cardiff it has made a 3 m bush (Johnson 2007). L. speciosa (L.) Pers. K203

Plate 304. Lagerstroemia limii is important as a parent in breeding, contributing hardiness and flower colour. Image R. Olsen.

434

Larix

New Trees

1 cm

C

D

1 cm

A

1 cm

B

1 cm

G

H

E 1 cm

F

Section II. Species Accounts

Lagerstroemia

435

Lagerstroemia subcostata Koehne Shrub or tree to 14 m, multistemmed. Bark grey, peeling to reveal reddish patches. Branchlets grey, glabrous or pubescent; four longitudinal striations may be visible when young. Leaves deciduous, opposite or subopposite, 2–9(–11) × 1–5 cm, shape variable, oblong, ovate, elliptic or lanceolate, papery, upper surface glabrous, lower surface glabrous or minutely pubescent, 3–10 secondary veins on each side of the midrib, apex acuminate; petiole 0.2–0.4 cm long and largely glabrous. Panicles terminal or axillary, pyramidal, 7–16(–30) cm long, densely flowered, sometimes with greyish brown pubescence. Flowers 6-merous; calyx tube cup-shaped, 0.2 cm long with (10–)12(–14) darkened veins or obscure ribs, pubescent or glabrous; epicalyx absent; petals white, pink or purple, 0.7–1 cm long (incl. stalk); stamens 15–30, dimorphic. Capsule globose to oblong, 0.6–11 × 0.4–0.6 cm with four to six valves. Flowering June to August, fruiting July to October (China). Ohwi 1965, Furtado & Srisuko 1969, Qing et al. 2007. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Hubei, Hunan, Jiangsu, Jiangxi, Qinghai, Sichuan, Zhejiang; JAPAN; PHILIPPINES; TAIWAN. Habitat Forest edges, streamsides, at low altitudes. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Furtado & Srisuko 1969.

Along with Lagerstroemia limii, L. subcostata also is overshadowed by its relatives, but Dirr’s (1998) comment that he finds ‘minimal redeeming qualities’ in these ‘other’ species is perhaps a little harsh. The bark of L. subcostata is smooth and superficially grey or white but it can flake off to reveal reddish patches. As with L. fauriei the plant is usually multistemmed, with stiffly upright trunks bearing a very wide canopy. The flowers are small, white with a pink tinge, and do not make much show. There is a fine specimen at the US National Arboretum, with a very white trunk; this was grown from an offering in the Index Seminum of the Botanical Garden of Osaka City University, Japan, in 1961 (R. Olsen, pers. comm. 2007). At Quarryhill, grown from seed collected in Japan in 1989 (SOJA 353), L. subcostata has made trees up to 8 m tall. It is in cultivation elsewhere in the United States from other collections, possibly including those made by John L. Creech in Taiwan in 1967 (Ani´sko 2006).

PINACEAE

LARIX

Mill.

Larches Larix is a genus of 10–15 species, dependent on taxonomic viewpoint, distributed across the northern hemisphere. Some authors recognise local varieties as full species, and the situation is further complicated by extensive hybrid zones where species meet. Three species (L. gmelinii, L. laricina and L. sibirica) are widespread in the boreal forests of Eurasia and North America, while the others are restricted to montane or subalpine vegetation at high elevations. Larches are tall trees with straight, columnar (rarely forked) trunks. Together with the Golden Larch (Pseudolarix amabilis (J. Nelson) Rehder), they are the only deciduous members of the Pinaceae. The bark is smooth but soon becomes thick, scaly and fissured. The wood is rich in resins, and the crown can be conical, broad or irregular. Primary branches are produced in regular whorls, though internodal branching is common. There is marked shoot dimorphism, with regularly spaced short shoots on the long shoots. Short shoots develop by a build-up of rosettes of densely packed perular scales and bases of the annual whorls of needles. Immature branchlets may be pubescent or glabrous, and change in colour as they

Figure 49 (opposite). Larix sibirica: habit with seed cones (A); habit after leaf fall (B); leaf lower surface (C), upper surface (D). L. potaninii: habit with seed cones (E); gall cone (F); leaf lower surface (G), upper surface (H).

436

Larix

Plate 305. Larix himalaica, seen here in the wild, has proved to be difficult to grow in British gardens. Image K. Rushforth/FLPA.

New Trees

mature. The apical buds are small and continue the growth of the long shoots, while the axillary buds develop into short shoots. In some larch species the shoots occasionally continue to grow through the cones (proliferation), though these shoots do not survive beyond the maturation of the cone. The needle-like leaves are restricted to the short shoots and first-year long shoots; older branches have no leaves. The leaves on short shoots are often shorter and narrower than those on long shoots. They are arranged spirally, and are attached to short pulvini. The stomata are arranged in two rows on the lower leaf surface, separated by a keel, and are often also present on the upper surface of the leaf (amphistomatic). The male strobili are small, solitary and borne at the apex of short shoots, after which the shoot dies. Female cones also form on short shoots, and can occur in all parts of the crown. They develop from the apex of short shoots and are usually erect (occasionally spreading or pendulous). The cones mature in four to seven months from pollination, and are usually persistent, falling only with shed branches. The seed scales are spirally arranged, concave to convex, pedicellate, and open at maturity to release the seeds. Immature cones may be red, purple or green, becoming pale to dark brown at maturity. The bract scales are variable and can be long and exserted or short and included. There are two seeds on each scale; they are partially enclosed in a membranous cup, which extends to form a persistent wing. Recent genetic research has shown that the former classification of Larix into two sections based on bract scale length and leaf morphology (Farjon 1990) is an artificial split, with the major divergence in fact falling between Eurasian and American species (Gernandt & Liston 1999). There is a secondary division within the Eurasian species, between the short- and long-bracted species (Gros-Louis et al. 2005). Michael Frankis has summarised this work into the following classification.

LARIX

Mill.

A guide to the infrageneric classification of Larix

Section Larix (Eurasia)

Series Larix (short bract scales) L. decidua, L. gmelinii, L. kaempferi, L. principis-rupprechtii, L. sibirica Series Griffithianae Sukacz. (long bract scales) L. griffithii, L. himalaica, L. kongboensis, L. mastersiana, L. potaninii, L. speciosa

Section Grandibractea A.E. Murray (North America)

Series Lyallianae Sukacz. L. laricina, L. lyallii, L. occidentalis

Larches readily form hybrids, both in the wild and in cultivation, and there are few barriers to hybridisation, though intersectional crosses have very low seed yields (Dallimore et al. 1966). One hybrid, L. ×marschlinsii (L. kaempferi × L. decidua, better known under its older synonym L. ×eurolepis), is very widely cultivated.

Section II. Species Accounts

Larix

The larches have long been a group of great interest to foresters, and most species have been introduced and tested for commercial purposes. Few have proved to be useful away from cold climates, however, as their origins in high places or cold regions make them susceptible to spring frosts and various fungal and insect problems in gentler conditions (Dallimore et al. 1966). Although shapely when young they are apt to be gaunt and somewhat gawky with age, and, if successful, potentially very large trees, so they are not well suited to smaller gardens. They are redeemed, however, by the beauty of their foliage, fresh green in spring and glorious yellow in autumn, and for this they are an essential component of a large landscape or parkland planting where a small group can be positioned together. Although tolerant of a wide range of soil types, they do best on a well-drained slope. Many species and their infraspecific taxa have been very well covered by Bean (1981a) and Krüssmann (1985b). Synonymy in the genus is extensive and ‘new’ names are likely to be encountered occasionally. A reference to Farjon’s World Checklist and Bibliography of Conifers (2001) is invaluable for attributing these to recognised species, but it should not be forgotten that such names may refer to local populations with useful (or otherwise) horticultural qualities, and that opinions on the taxonomic status of these plants differ. Identification often requires mature cones, and may sometimes depend on reasonably accurate knowledge of a specimen’s provenance. A taxon that collectors should look out for is Larix speciosa W.C. Cheng & L.K. Fu, from far western Yunnan and northeastern Myanmar (syn. L. griffithii var. speciosa (W.C. Cheng & L.K. Fu) Farjon – although it is most closely related to L. potaninii var. australis). This is the world’s southernmost larch, occurring south to about 25° 50’ N. It was collected on several occasions by George Forrest under the name L. griffithii (Mill 1999); no specimens are currently known to have survived but it could conceivably be found in arboreta mislabelled as L. griffithii or L. potaninii. We are grateful to Michael Frankis and Keith Rushforth for their help with this account. There is a reasonable representation of larches in many arboreta. The Coram Experimental Forest near Hungry Horse, Montana holds the International Larix Arboretum. This was established in 1992 to enable direct comparisons to be made between the different species, and a representative collection has been planted (USDA Forest Service 2003). So far, however, no comparative data seem to have been published. L. ×czekanowskii Szafer K158 L. decidua Mill. B519, S300, K158 L. decidua f. adenocarpa (NOW L. decidua Mill. var. decidua) K159 L. decidua f. pendula (NOW L. decidua Mill. var. decidua) B520 L. decidua var. polonica (Racib. ex Wóycicki) Ostenf. & Syrach B520, S300, K159 L. ×eurokurilensis Rohm & Dimpflmeier K160 L. ×eurolepis (NOW L. ×marschlinsii Coaz) B520, S300, K160 L. gmelinii (Rupr.) Kuzen. B521, S301, K160

L. gmelinii var. japonica (Maxim. ex Regel) Pilg. B521, S301, K160 L. gmelinii var. olgensis (A. Henry) Ostenf. & Syrach B522, K160 L. gmelinii var. principis-rupprechtii (NOW L. principis-rupprechtii Mayr) B522, S301, K160 L. gmelinii var. prostrata (NOW L. gmelinii (Rupr.) Kuzen. var. gmelinii) K161 L. griffithiana (NOW L. griffithii Hook. f.) S301, K161 L. griffithii Hook. f. B522, S301

437

438

Larix

New Trees

Larix himalaica W.C. Cheng & L.K. Fu

Langtang Larch

(Sect. Larix, Ser. Griffithianae) Syn. L. potaninii var. himalaica (W.C. Cheng & L.K. Fu) Farjon & Silba Tree to 40 m, 0.8 m dbh. Bark smooth, becoming fissured in older trees. Branchlets slender, pendulous, yellowish or reddish brown, becoming grey with age, glabrous, grooved; short shoots cylindrical, 0.2–0.5 cm diameter; vegetative buds resinous. Leaves bright green, turning yellow in autumn, 1–2.5 × 0.1 cm, narrow to linear, keeled on lower surface and at the base on the upper surface; 20–40 leaves per short shoot. Female cones on short peduncles, ovoid-cylindrical, sometimes slightly curved, 2–6.5 × 2.8–3.2 cm, light green with yellow-orange bracts, turning light yellow-grey with darker bracts when mature. Seed scales 30–40, suborbicular to oblong-orbicular, 1.2–1.5 × 0.9–1.3 cm. Bract scales lanceolate-oblong, 1.4–1.7 cm long, apex obtuse, exserted and straight, not or only slightly longer than the seed scales. Seeds light brown, ovoid-cuneate, wings yellowish brown, obovate, 0.6–0.8 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: south-central Xizang; NEPAL: Bagmati Zone. Habitat High mountains between 3000 and 3500 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Farjon 1990, Fu et al. 1999c; NT436. Cross-reference S302. Taxonomic note Larix himalaica is sometimes treated as a distinct species (Farjon 1990, Fu et al. 1999c) and sometimes as a variety of L. potaninii (Mill 1999, Farjon 2001). There are, however, sufficient grounds for it to be treated as a separate species. It is disjunct from populations of L. potaninii by over 1,000 km, with the range of L. griffithii sandwiched between them. Its placement as a variety of L. potaninii relies heavily on its straight vs. reflexed bract scales (a character which in the Sino-Himalayan larches appears to be correlated with monsoon intensity, with straight bracts in drier areas and reflexed bracts in areas of high rainfall), while neglecting other characters and comparisons (notably the shorter bracts and the pale yellow-brown shoots and mature cones of L. himalaica, unlike the longer bracts and red-brown shoots and dark purple-brown cones of both L. griffithii and L. potaninii) (M. Frankis, pers. comm. 2008).

Larix himalaica was collected several times during the period when Nepal was a regular destination for plant hunters in the 1970s and early 1980s. One gathering was made by Adam Stainton in the Langtang Valley in 1971 (Clarke 1988), and there were coning trees from this source at Wakehurst Place, up to 2 m tall in the mid-1980s, although these died prior to 1993 (Kew database); another was made by Ron McBeath in 1990 (McBeath 2240). The Langtang is the locus classicus for the species but it is also found in the valleys on the northern side of Mount Everest. A 2001 collection by the Edinburgh Nepal Expedition (ENEP 425) has resulted in a good number of seedlings that were planted out in the Scottish botanical gardens in 2007 (M. Gardner, pers. comm. 2008). Keith Rushforth (pers. comm. 2007) has tried it on several occasions but has not been able to get seedlings through the first year. L. kaempferi (Lamb.) Carrière B523, S301, K161

Larix kongboensis R.R. Mill

(Sect. Larix, Ser. Griffithianae)

Kongbo Larch

Tree 15–35 m, 0.6 m dbh. Bark smooth, brown, quickly becoming fissured; in older trees, scaly. Crown conical when young, columnar in old trees. Branchlets slender, glabrous, shiny light reddish brown, becoming grey in the grooves in the second year and subsequently all over; lightly covered with whitish resin in the first winter, the linear ridges on the first-year shoots ending in the very short free and largely appressed pulvinus; short shoots cylindrical, broader than long, 0.2–0.45 × 0.45–0.6 cm; vegetative buds resinous, rounded conical, 0.3–0.4 cm. Leaves bright green, turning yellow in autumn, 0.9–2.2 × 0.06–0.11 cm, linear-oblong, straight or slightly falcate, only keeled adaxially and at the base abaxially, apex obtuse; c. 30–50 leaves per short shoot. Male strobili broadly conical, shortly pedunculate, 0.6–0.8 × 0.55–0.65 cm long, reddish. Female cones on 1–1.3 cm peduncles, oblong-ellipsoid, 3–5 × 2.2–2.5 cm, purple-brown to grey-brown; seed scales c. 60–75, broadly obovate-reniform, 0.8–1 × 1 cm, minutely white-hairy on the broadly rounded, entire or shallowly retuse apices; bracts exserted, c.1.8 cm, reflexed to strongly reflexed, lanceolate, dark purple-brown, 0.5 cm broad where they emerge, gradually tapering, then abruptly into a 0.15–0.4 cm cusp; seed 0.3 × 0.2 cm, with wing 0.6–0.7 × 3 mm. Mill 1999. Distribution CHINA: southeast Xizang. Habitat Mountain slopes between 3200 and 3500 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT439. Taxonomic note This species was described in 1999 but was placed by Farjon (2001) in synonymy with

Section II. Species Accounts

Larix

439

L. griffithii, though it differs in several important features, notably its smaller cones (3–5 cm, vs. 5–8(–11) cm) and other reproductive parts. Larix kongboensis has glabrous, darker-coloured shiny shoots (vs. yellowish brown and matt in L. griffithii), flecked with resin on vigorous shoots; it has resinous buds (vs. non-resinous), short shoots that are wider than they are long, and shorter, narrower leaves (0.9–2.2 cm × 0.6–1.1 mm, vs. 2.5–5.5 cm × 1.0–1.8 mm). It differs from L. himalaica in its reflexed bracts (vs. nearly straight), which are 8 mm longer than the seed scales (vs. only slightly exserted), in its smaller seed scales (8–10 mm, vs. 12–15 mm) and narrower cones (2.2–2.5 cm, vs. 2.8–3.2 cm), and in its reddish brown (vs. yellow or yellow-brown) shoots.

As well as being distinct in terms of morphological characters, as outlined above, Larix kongboensis occurs on the drier northern side of the Himalaya, occupying the valleys draining northwards into Tibet, whereas L. griffithii is from the much wetter southern slopes in eastern Nepal, Sikkim, Bhutan and Arunachal Pradesh. According to Keith Rushforth (pers. comm. 2007) it was first collected by Frank Kingdon-Ward in 1924, and then by Frank Ludlow and George Sherriff in the 1930s, but was misidentified as L. griffithii or L. mastersiana. If it was introduced by these earlier collectors there is no record of surviving plants. Gatherings were made by Keith Rushforth in 1995 from the Doshong La (KR 3431) and from Pasum Tso (KR 3795), and it is now found in a number of collections in the United Kingdom, where it is doing well. At Tregrehan it has made a tree 4 m in height with a dbh of 10 cm, and is coning freely (K. Rushforth, pers. comm. 2008). L. laricina (Du Roi) K. Koch B524, S302, K162 L. laricina var. lutea (NOW L. laricina (Du Roi) K. Koch) K162 L. laricina var. parvistrobus (NOW L. laricina (Du Roi) K. Koch) K162 L. lyallii Parl. B525, K162

Larix mastersiana Rehder & E.H. Wilson

Masters Larch

(Sect. Larix, Ser. Griffithianae) Tree to 25 m, 0.8 m dbh. Bark smooth, yellowish brown, quickly becoming fissured; in older trees, the bark disintegrates into grey plates. Crown broad and domed, though often conical in dense stands. Branchlets slender, pendulous, yellowish or reddish brown, becoming grey with age, glabrous, grooved; short shoots cylindrical, 0.3–1.5 cm long; vegetative buds resinous. Leaves bright green, turning yellow in autumn, (1.2–)2–3(–3.5) × 0.1 cm, narrow to linear, keeled on both surfaces, apex obtuse to acute; 20–40 leaves per short shoot. Male strobili pedunculate, erect or pendent, 1–1.5 cm long, yellow with reddish brown perular scales. Female cones on short peduncles, ovoid-cylindrical, sometimes slightly curved, 2.5–4.5 × 1.5–2.5 cm, light green with yellow-orange bracts, turning light brown with darker bracts when mature. Seed scales 30–40, obcordate to orbicular, 0.6–1 × 0.7–1.2 cm. Bract scales lanceolate, apex triangular, 2–2.3 cm long, exserted and reflexed. Seeds light brown, ovoid-cuneate, wings yellowish brown, obovate, 0.6–0.8 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: western Sichuan. Habitat High mountains between 2000 and 3500 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Farjon 1990, Fu et al. 1999c. Cross-reference K163.

Larix mastersiana was discovered by Ernest Wilson in 1908, but his collections apparently did not result in any successful trees. It is now in cultivation, but extremely rare. Somewhat surprisingly, several flourishing specimens were seen at Quarryhill in 2004,

Plate 306. Larix kongboensis has a limited distribution in southeastern Tibet. The long-exserted bract scales are one of its distinguishing characters. Image J. Grimshaw.

440

Larix

New Trees

but by 2007 only two had survived the ravages of Armillaria. These were from material collected in 1989 at 3000 m in Sichuan by Dr Yin Kaipu (Yin 92.2). Although planted out only in 2000 they were approximately 6 m tall seven years later, producing very long extension growth each year. Three specimens at Kew from the same collection have died. The species seems to be in limited cultivation elsewhere in the United States, and a number of examples were planted in 1993 at the International Larix Arboretum (Mill 1999), but unfortunately no follow-up has been available on these. L. occidentalis Nutt. B524, S302, K163 L. ×pendula (NOW L. laricina (Du Roi) K. Koch) B525, S302, K163

Larix potaninii Batalin

Potanin Larch, Chinese Larch

(Sect. Larix, Ser. Griffithianae) Tree to 15–30 m (rarely 50 m), 0.3–1(–1.5) m dbh, trunk sometimes forked. Bark smooth, reddish brown, quickly flaking, becoming rough and scaly, with grey plates and dark brown fissures. Crown broadly conical or domed to irregular, and (in cultivation) often gaunt and sparse. Branchlets slender to stout, variably pendulous, deep reddish brown, becoming grey, glabrous, grooved; short shoots 0.3–0.5 cm long; vegetative buds resinous. Leaves bright green to glaucous green, turning yellow in autumn, 1.2–3.5 × 0.1 cm, keeled on lower surfaces, apex obtuse to acute; 20–40 leaves per short shoot. Male strobili 1 cm long, yellow. Female cones on short peduncles, cylindrical-elliptical, 3–8(–9) × 1.5–3(–4) cm, violet with purple bracts, turning dark brown with purplish black bracts when mature. Seed scales 35–140, suborbicular, 0.9–2 × 0.9–1.6 cm. Bract scales ligulatelanceolate, apex acute, 1.2–2.5 × 0.4–0.5 cm, exserted 6–9 mm beyond scale apex, midrib paler than bract; brittle and commonly broken or lost on old cones. Seeds light brown, ovoid-triangular, wings purplish brown, ovate-oblong, 0.6–0.8 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Gansu, Sichuan, Xizang, Yunnan. Habitat High mountains between 2350 and 4300 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Farjon 1990; NT434. Cross-references B527, S302, K163.

Several varieties of Larix potaninii have been described; three are recognised here, and a key is provided below. 1a. Branchlets deep reddish brown ....................................................................................................... 2 1b. Cones small (2.5–5 × 1.5–2.5 cm); branchlets yellow-brown, grey-brown or yellow-orange; north-central China (south Shaanxi) ............................................. var. chinensis 2a. Cones large (5–9 × 2.5–4 cm); seed scales 50–140; south China (southwest Sichuan, northwest Yunnan) ................................................... var. australis 2b. Cones small (3–5(–5.5) × 1.5–2.5(–3) cm); seed scales 35–65; China (south Gansu, west Sichuan, east Xizang) ........................................................ var. potaninii

Larix potaninii var. chinensis (Beissn.) L.K. Fu & Nan Li Var. chinensis has greyish or brownish yellow branchlets and seed scales that are strigose below. Fu & Li 1997, Fu et al. 1999c. Distribution CHINA: south Shaanxi (north of var. potaninii). Habitat As for the type variety. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Fu et al. 1999c.

Larix potaninii var. australis A. Henry ex Hand.-Mazz. Syn. L. potaninii var. macrocarpa Y.W. Law This variety has reddish brown branchlets, and larger cones than either of the other varieties (5–9 × 2.5–4 cm), and the seed scales are more numerous (50–140). Farjon 1990, Fu et al. 1999c. Distribution CHINA: southwest Sichuan, northwest Yunnan (south of var. potaninii). Habitat As for the type variety. USDA Hardiness Zone (7–)8. Conservation status Not evaluated. Illustration Farjon 1990. Taxonomic note Larix potaninii

Section II. Species Accounts

Larix

441

var. australis has priority over the perhaps better-known var. macrocarpa (Mill 1999). Farjon (2001) treats var. australis as a synonym of the type variety, but this is not in accord with the original description of var. australis, which cites 7 cm cones.

Larix potaninii (s.l.) is reasonably frequently found in cultivation, as it comes from areas of western China that are regularly visited by seed collectors, and it was introduced by both Wilson and Forrest. Some of the early introductions reached heights of 16–20 m in southern England (TROBI) but most now seem to have died out. It has been collected on numerous recent expeditions and there are young trees in many arboreta. The varieties seem somewhat tenuous in differentiation on foliage characters but are distinct in cone morphology and have distinct distributions. Apart from the type variety, only var. australis is cultivated; many (if not most) older specimens of L. potaninii in Britain have large cones (up to 9 cm long, 4 cm broad and with up to 140 scales), placing them firmly in this variety, perhaps deriving from the several collections made by Forrest close to its type locality in Yunnan (Mill 1999). There have been more recent collections, however, now forming young trees. Specimens seen at Howick were collected on the Cangshan, Lijiang and Dali Expedition of 1991 (CLD 123) and were 2 m tall in 2005. It has also been collected by the Alpine Garden Society Expedition to China in 1994 (ACE 1425) and the Sichuan Expedition of 1992 (SICH 1068). Charles Howick (pers. comm 2005) has observed that mature trees in the wild are not distinguishable in vegetative characters from var. potaninii. L. russica (NOW L. sibirica Ledeb., NT441) K163

Larix sibirica Ledeb.

(Sect. Larix, Ser. Larix)

Siberian Larch

Syn. L. russica (Endl.) Sabine ex Trautv., L. sukaczewii Dylis Tree to 40 m, 1–1.5 m dbh. Bark light orange-brown or grey, becoming light greybrown, rough and scaly. Crown broadly conical and irregular. Branchlets slender, flexible, dull red-brown to grey, glabrous, grooved; short shoots 0.4–1 cm long; vegetative buds not resinous. Leaves light green, turning yellow in autumn, (2–)2.5– 4(–5) × 0.05–0.1 cm, soft and flexible, faint keel on lower surfaces, apex obtuse to acute; 20–40 leaves per short shoot. Male strobili 0.5–1 × 0.5–0.6 cm, pale yellow. Female cones on thick, curved peduncles, ovoid-subglobose, (2.5–)3–4.5(–5.5) × (1.8–)2.5–3.5(–4) cm, red or rose-green, turning light red-brown when mature. Seed scales 25–40, suborbicular to ovate, 1.2–2 × 1.2–1.8 cm. Bract scales ligulate-linear, included; in immature cones, the bract scales are distinctively reddish brown with a central green stripe. Seeds light brown, ovoid-cuneate, wings reddish brown or orange-brown, oblique-ovate, 0.8–1.6 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Xinjiang, Xizang; MONGOLIA; RUSSIAN FEDERATION: Altai, Irkutsk, Krasnoyarsk, Tuva, West Siberia. Habitat One of the characteristic tree species of the taiga, from close to sea-level, it also occurs in the Altai mountains up to 2400 m asl. USDA Hardiness Zone 2. Conservation status Lower Risk. Illustration Farjon 1990; NT434, NT441. Cross-references B520; K163 (as L. russica). Taxonomic note Trees from the west of the range (west of the Ob-Irtysh drainage) are sometimes distinguished as L. sukaczewii Dylis or L. sibirica var. sukaczewii (Dylis) Gorchakovsky & Shiyatov. This differs in having broader cones with broad, incurved scales; it is not generally considered sufficiently distinct for specific recognition (Farjon 1990), though does show genetic differentiation (Farjon 1990), and recognition as a variety appears justified. Larix sibirica forms a hybrid zone with L. gmelinii in the east of its range, the hybrid being named L. ×czekanowskii Szafer.

The cultivation of Larix sibirica in the British Isles has been attempted many times, from as early as 1806 according to Elwes & Henry (1907), but the comment of those authors, ‘It appears to have no value in this country’, sums up the situation well.

Plate 307. Regenerating Larix sibirica in the Aktru valley of the Siberian Altai. Image J. Grimshaw.

442

Larix

New Trees

Nonetheless, it is still being planted (sometimes as var. sukaczewii), and occasional lingering specimens may be found. An individual at Kew, obtained from Göteborg Botanic Garden in 1969, is a case in point, being a small misshapen tree with very long branches but no leader. Occasionally one will do reasonably well, as for example the British and Irish champion at Birr Castle, Co. Offaly, measured at 16.5 m (32 cm dbh) by Aubrey Fennell in 2004 (TROBI). As with some of the northern species of Abies and other genera, mild winters cause the trees to shoot too early, with consequent frost damage and general debilitation. Outside the British Isles, it is a different story. It grows with better success in Scandinavian and eastern European collections, although even at Rogów (where there are 54 specimens) it is ‘rather weak and not as strong and healthy as L. decidua’ (P. Banasczak, pers. comm. 2007). There is a good example of var. sukaczewii, about 18–20 m tall, at Hørsholm in Denmark, and this variety has also proved the best tree for forestry planting in Iceland and southwest Greenland (Ødum 2003), showing better growth and greater resistance to larch canker Lachnellula willkommii than trees of central Siberian origins (Blöndal & Snorrason 1995). Many, if not most plants in European cultivation are likely to refer to this taxon. As is perhaps to be expected, young trees at the University of Minneapolis Landscape Arboretum are thriving in the extreme continental climate of Minnesota. When seen in 2006 these were clad in vigorous new growth, with the dense plumy foliage on the long shoots being particularly attractive. The taller specimens were at least 10 m in height, and the largest in the group had a dbh of 24 cm. More surprising was to find a large, mature tree, at least 15 m tall, looking very well at the Arnold Arboretum and bearing a note on the label saying ‘H.J. Elwes 1900’. This would suggest that it was grown from seed Elwes collected himself on his journey to the Siberian Altai in 1897; in The Trees of Great Britain and Ireland (Vol. II, 1907), however, he says that his own experiments at Colesbourne were made with seed sent to him from the Altai in 1902. These saplings were not successful even in ‘a very cold and exposed situation’ – of which there seem to be many at Colesbourne, though evidently not sufficiently so for this species. Elwes (1935) bemoaned the excessive felling in the Altai, but a hundred years later there were still fine large trees of L. sibirica to admire there (JMG, pers. obs. 1997).

ATHEROSPERMATACEAE

LAURELIA

Juss.

The genus Laurelia comprises two species: L. novae-zelandiae in New Zealand and L. sempervirens (Ruiz & Pav.) Tul. in southern Chile and Argentina. A third species, also in southern South America, and formerly known as Laurelia serrata, is now recognised under the monotypic genus Laureliopsis Schodde, and further reorganisation may occur, as DNA evidence suggests that Laurelia is not monophyletic (Renner 1999). Laurelia species are trees with simple hairs on their branchlets and inflorescences. They are dioecious or have unisexual and hermaphrodite flowers on the same plant. The flowers have a cup-shaped floral tube (hypanthium), into which the stamens are inserted; pollen is released from the anthers by way of two apical valves; pistillate flowers have numerous staminodes. The fruits are small nutlets or achenes and are

Section II. Species Accounts

Laurelia

443

covered in silky hairs. They are produced within the hypanthium, which becomes woody and warty (Philipson 1993). The Chilean Laurelia sempervirens (syn. L. serrata Bert.) and Laureliopsis philippiana (Looser) Schodde (syn. Laurelia serrata Phil.) are reasonably well known in cultivation, although still uncommon and mostly confined to warmer and maritime gardens in the British Isles. All prefer a warm, moist site sheltered from cold wind.

Laurelia novae-zelandiae A. Cunn.

Pukatea

Large tree to 30 m, 1.6 m dbh; trunk with large, radiating buttresses. Branchlets foursided, pubescent. Leaves evergreen, opposite, leathery, aromatic, 4–7.5 × 1.5–4 cm, oblong, glossy and glabrous, six to eight secondary veins on each side of the midrib, margins with shallow, rounded serrations, apex obtuse; petiole 0.4–0.6 cm long. Inflorescences axillary, racemose, 4–8 cm long, dioecious or with some hermaphrodite flowers; flowers rather small, 0.3–0.5 cm diameter. Fruit a small achene with silky hairs to 3 cm long; 6–12 achenes are produced in a four-valved, vase-shaped hypanthium. Flowering October to November, fruiting March (New Zealand). Cockayne & Phillips Turner 1958, Poole & Adams 1963. Distribution NEW ZEALAND: North Is., South Is. (as far south as Marlborough and Nelson). Habitat Lowland swamp forest (~200 m asl) or somewhat drier areas. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT443. Cross-reference K205.

Laurelia novae-zelandiae is potentially a large canopy tree, forming buttresses at the base of the trunk, but is slow-growing and unlikely to achieve its full size in gardens, even in New Zealand. It has attractive glossy green leaves (glossier than the South American species), held in opposite pairs on the twigs and forming a dense mass of greenery that makes it a good specimen plant. The pale greenish flowers are small and insignificant (Metcalf 2000). It is being grown in Cornwall, and a young plant was flourishing at Tregrehan until it was stolen (T. Hudson, pers. comm. 2006). It will grow best in deep fertile moist soil, doing particularly well in waterside plantings. It can be grown from seed or cuttings (Metcalf 2000). L. sempervirens (Ruiz & Pav.) Tul. B528, S302, K205 L. serrata sensu Phil. non Bert. (NOW Laureliopsis philippiana (Looser) Schodde) B528, S302, K205

MYRTACEAE

LEGRANDIA

Kausel

Legrandia is monospecific, comprising only the species L. concinna.

Legrandia concinna (Phil.) Kausel

Luma del Norte

Small tree to ~8 m. Branchlets four-angled, reddish brown, moderately pubescent, becoming grey and rough with age. Leaves evergreen, somewhat leathery, fragrant, 2–5.5 × 0.8–3 cm, elliptic to ovate or obovate, glabrous or sparsely pubescent along the midrib and margins, often with cavities in vein axils of lower surface, five to eight secondary veins on each side of midrib, margins entire, apex obtuse to rounded; petiole 0.1–0.3 cm long,

Plate 308. New growth on a small plant of Laurelia novae-zelandiae at Tregrehan. Image J. Grimshaw.

444

Legrandia

New Trees

shallowly channelled. Flowers 4-merous, solitary, axillary, subtended by leafy bracteoles, 0.7–0.9 cm long; peduncles 1–3.5 cm long, glabrous or sparsely pubescent; calyx lobes triangular or semicircular, 0.3–0.4 cm long; petals subcircular to obovate, 0.7–1 cm long; hypanthium conical to campanulate, densely pubescent; stamens ~200–400, 0.7–1.2 cm long. Fruit yellowish, subglobose, 1.5–2.5 cm long, containing a single seed (rarely, two to five seeds). Landrum 1986. Distribution CHILE: Bío-Bío, Maule. Habitat Wet temperate forest in the Andes. USDA Hardiness Zone 8. Conservation status Not evaluated (IUCN). Critically endangered (Gardner et al. 2006). Illustration Landrum 1986, Gardner & Hechenleitner 2005, Gardner et al. 2006; NT444.

Plate 309. The endangered Legrandia concinna has great potential as an ornamental garden plant, with good flowers and foliage. Image P. Hechenleitner V.

Legrandia is an extremely attractive myrtle from the temperate forests of central Chile, where it is confined to less than a total of 75 ha in five known subpopulations (Gardner et al. 2006). Here it grows with a number of other evergreens described in this book – Aextoxicon, Cryptocarya, Persea lingue and Quillaja – which together with better-known Nothofagus and Luma species make up a fascinating ecosystem. As with all of these, Legrandia should be given a sheltered warm site in rich moist soil, if and when it becomes available to horticulture. At present it is known in cultivation only in the gardens of the Royal Botanic Garden Edinburgh, grown from a collection made by Bernardo Escobar in Región VII in 1999. At Inverleith it is planted against a glasshouse wall and has grown steadily, now being about 2 m tall. When mature it has beautifully exfoliating bark, reminiscent of the familiar Luma apiculata (DC.) Burret, on trunks that carry the tree to 8 m. The leaves are comparatively large and broad, extremely glossy dark green when mature but emerging ‘deep plum-red … which rivals the young growth of any Photinia’ (Gardner & Hechenleitner 2005). The foliage alone makes it worth growing, but it is also capable of smothering itself in abundant large white myrtle flowers. These are followed by as fine a show of big red fruits. With all these qualities it is evidently a highly desirable species, and Martin Gardner (pers. comm. 2005) believes that it would be a good commercial plant – with due regard to the Convention on Biological Diversity and agreements with the Chilean authorities for benefit sharing. It can be propagated from seed or by cuttings (Gardner et al. 2006).

PODOCARPACEAE

LEPIDOTHAMNUS

Phil.

Lepidothamnus comprises one species in sub-Antarctic Chile (L. fonkii) and two in New Zealand (L. intermedius, L. laxifolius). They are dioecious or monoecious trees, shrubs or creepers. The juvenile leaves are narrow, linear and spreading, and give way gradually to the adult leaves, which are subulate to scale-like, decurrent, appressed and

Section II. Species Accounts

Lepidothamnus

445

1 cm

B

A

C

strongly keeled. The male strobili are solitary, sessile, terminal or axillary. The female cones are solitary, terminal, with three to five scales, of which only one or two are fertile. Each fertile scale bears a single, upright ovule, which at maturity is enclosed in a membranous epimatium to one-quarter of its length; the whole structure often subtended by a pink or red fleshy receptacle (Quinn 1982). Only L. laxifolius is at all well known in cultivation, and then only to specialists or collectors of curiosities: it is said to be the smallest conifer in the world. All seem to require cool, wet places in acidic soil to thrive. Propagation is by seed or cuttings.

Figure 50 (above). Lepidothamnus intermedius: juvenile habit (A); adult habit with female cones (B). Halocarpus biformis: branchlet exhibiting both juvenile and adult foliage (C).

446

Lepidothamnus

New Trees

L. fonkii Phil. (WAS Dacrydium fonkii S208, K113)

Lepidothamnus intermedius (Kirk) Quinn

Yellow Silver Pine

Syn. Dacrydium intermedium Kirk Tree to 15 m, 30–60 cm dbh. Bark brownish grey, peeling in small flakes, reddish brown underneath. Branches spreading. Juvenile leaves spreading, 9–15 mm, narrowly linear-subulate, acute, recurved. Intermediate leaves shorter, wider, transitioning into mature leaves. Mature leaves scale-like, densely imbricate, appressed to the stem in apparently four rows, 1.5–3 mm long, rhomboid, blunt, very thick, keeled. Dioecious. Male strobili solitary but abundant, 5–6 × 2 mm, at the tips of branchlets. Ovules solitary, terminal on branchlet tips. Seeds 3–5 mm, black, with short red aril. Allan 1961, Salmon 1996, Metcalf 2000. Distribution NEW ZEALAND: North Is., South Is., Stewart Is. Habitat Lowland, montane and subalpine forest, in wet or very wet conditions, 0–900 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Allan 1961, Salmon 1996, Metcalf 2000; NT445. Cross-reference K114 (as Dacrydium intermedium).

Lepidothamnus intermedius is extremely rare in cultivation, with only one specimen having been traced in our research, growing at Tregrehan. This was planted in 1995 and is now 3 m tall, forming a narrow column (T. Hudson, pers. comm. 2007). It is one of the obscure gymnosperms that Tom Hudson calls ‘New Zealand swamp lurkers’, best suited to mild areas with very high rainfall. It is unlikely to make a significant tree in our area. L. laxifolius (Hook. f.) Quinn (WAS Dacrydium laxifolium S208, K114)

LEGUMINOSAE (MIMOSOIDEAE)

LEUCAENA

Benth.

Twenty-two species of Leucaena are recognised, all occurring in the New World, from Texas south to Peru. Among these, L. leucocephala is an important fodder crop, and has become a widespread weed in tropical areas around the world; it is also the only member of the genus to be cultivated in temperate gardens. Leucaena species are evergreen, unarmed trees or shrubs that branch at ground level or form a short bole of 3–5 m. Young stems are terete or, rarely, angled and the bark is greyish brown with rusty fissures. Stipules are ovate, subulate or long and pointed, and have small, asymmetrical basal wings; they are persistent or deciduous. The leaves are bipinnate and paripinnate and the rachis has a single-stalked (rarely double) nectary; nectaries are also present at the base of the terminal (and some subterminal) pairs of pinnae. The pinnae occur as two to many pairs, with few to numerous pinnules; the pinnules are opposite, sessile or short-petiolate, oblong to elliptic and with acute or rounded apices; venation is obscure. The inflorescences are capitate and in axillary fascicles of one to many; the peduncle has a whorl of fused bracts. The flowers are mainly hermaphrodite, though a few staminate flowers may occur at the base of the inflorescence; they are 5-merous and subtended by persistent, peltate bracts; the sepals

Section II. Species Accounts

Leucaena

447

and petals are rather insignificant, but the stamens are prominent, white or cream (rarely yellow or red); one distinctive feature of Leucaena is the anthers, which are hairy. The fruit is a pendent, dehiscent legume with a small apical beak (Allen & Allen 1981, Hughes 1998).

Leucaena leucocephala (Lam.) de Wit

Horse Tamarind, Lead Tree, Leucaena, White Popinac

Syn. L. glauca (L.) Benth. Shrub or tree to 20 m, 50 cm dbh; habit extremely variable, though the crown is typically narrow and open. Bark rough, dark greyish brown with rust-coloured longitudinal fissures. Branchlets smooth and greyish brown, terete and covered in white hairs or glabrous. Leaves bipinnate, green though lower surface paler, (10–)12–25 × (5–)7–15 cm; pinnae (four to) six to eight (to nine) pairs, pinnae rachis with one to two (to three) nectaries; pinnules 13–21 pairs, linear to oblong or elliptic, 0.9–1.6(–2.1) × 0.2–0.4 cm, sessile and asymmetrical, apex acute to acuminate, margin ciliate; petiole 1.3–3.4 cm long, green or yellowish green and with a single nectary; rachis (5–)7–15.5 cm long with one to two (to four) small, concave nectaries, apex extending beyond terminal pinnae as a mucro 0.2–0.5 cm long; stipules ovate or lanceolate, 0.3–0.4 cm long with a pair of asymmetrical wings, persistent though shrinking. Inflorescences capitate, 1.2–2.1 cm diameter, bearing 100–180 flowers; these in fascicles of two to six in the axils of new shoots only; peduncle 1.5–2 cm long with a whorl of dentate bracts near the apex. Flowers densely-packed, 5-merous, sepals and petals pale green, rather insignificant; stamens with white filaments. Legumes (3–)5–20 per capitulum; pendulous, linear-oblong, compressed, 11–19 × 1.5–2.1 cm, papery and dehiscent. Hughes 1998. Distribution The exact range of L. leucocephala is difficult to determine because of human activity, though it is probably native to Mexico and Central America. Habitat As a pantropical weed, it tolerates a range of conditions, but is particularly often found in open (often coastal or riverine) habitats, semi-natural, disturbed, degraded habitats and urban sites. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT447. Taxonomic note Three subspecies of L. leucocephala are recognised by Hughes (1998). Subsp. leucocephala (‘Common’ or ‘Hawaiian’ type) was transported to the Philippines by the Spanish before 1815 and is now pantropical. It is more often shrubby than tree-like. Subsp. glabrata (Rose) Zárate (‘Giant’ or ‘Salvador’ type) is typically arborescent and was widely introduced across the tropics in the 1970s and 1980s (Hughes 2005). Subsp. ixtahuacana C.E. Hughes is not known outside its native range (Hughes 1998).

Leucaena leucocephala is an extremely important tree in the semi-arid tropics and subtropics, where its vigorous growth even in difficult circumstances makes it a valuable source of a range of forage products and firewood (Mabberley 1997a). Its ubiquity in these areas and its temptingly obvious pods make it an easy target for casual collectors on holiday, and it is probable that its cultivation is often attempted – indeed, Susyn Andrews (pers. comm. 2008) reports that it is quite frequently submitted to the Enquiry Unit at Kew for identification. It could therefore be included here as a speculative species. In the Hoyt Arboretum, however, it is well established, a group of trees there being now about 4.5 m tall – limited somewhat in development by the dry summers of Portland (S. Hogan, pers. comm. 2007). Provenance does matter, as other stocks have frozen back to the ground at Cistus Nursery, on low-lying Sauvie Island. Summer warmth to ripen the wood and a winter that is not too severe are probably essential requirements for its success. As a tree seen in the tropics it is apt to be rather gaunt, but the slightly pewtered bipinnate leaves and white flower pompoms are not unattractive. As with most legumes, the seeds should be soaked in very hot water before sowing.

Plate 310. Leucaena leucocephala is a very important agroforestry tree in the tropics, but its often gaunt appearance and heavy bunches of legumes do tend to suggest a moulting camel. Image J. Grimshaw.

448

Libocedrus

New Trees

CUPRESSACEAE

LIBOCEDRUS

Endl.

Libocedrus in its current delimitation includes only five species: three in New Caledonia and two in New Zealand (Farjon 2001). Libocedrus species are small to large evergreen trees or shrubs with a conical habit. The bark is thin and fibrous, and sheds in long strips. The branchlets are dorsiventrally flattened, distichous and fan-shaped. The juvenile leaves are long and spreading. The mature leaves are in pairs, scale-like, appressed and decussate; they are acute and somewhat dimorphic. Male and female strobili are solitary and terminal, and produced on different branches on the same tree. The male strobili are oblong, with 6–12 decussate sporophylls. The female cones are ovoid and erect, valvate, woody and mature in the first year. The seed scales are arranged in two basally fused, decussate pairs, though only the inner pair is fertile; the seed scales have a triangular, spiny umbo. There are one or two lenticular seeds per fertile scale, and each seed develops a short, rudimentary wing and a long, fully formed wing. The species from New Caledonia are unlikely to be hardy in temperate areas, but the two from New Zealand (L. bidwillii and L. plumosa (D. Don) Sarg.) are both in cultivation in Europe (Allan 1961, Dallimore et al. 1966, Salmon 1980). L. austrocaledonica Brongn. & Griseb. K164 Plate 311. In New Zealand Libocedrus bidwillii can form a substantial tree, but in cultivation it seems to be relatively short-lived. Image J.R.P. van Hoey Smith.

Libocedrus bidwillii Hook. f.

Mountain Cedar, Pahautea

Tree to 21 m, trunk long and straight, to 1 m dbh. Bark thin, fibrous, reminiscent of parchment, peeling in long strips. Crown initially fastigiate, later pyramidical or conical. Juvenile foliage branchlets slightly flattened, fern-like; mature branchlets entirely distichous. Juvenile leaves dimorphic, with laterals to 0.3 cm long and facials to 0.1 cm long; mature leaves triangular, decussate, appressed, densely crowded, 0.2 cm long and only slightly dimorphic, the lateral pairs slightly longer than the facial pairs. Male strobili 0.6–1.1 cm long, with 10–12 microsporophylls; several adjacent shoots bearing solitary strobili, giving the appearance of a cluster. Female cones ovoid, 0.7–0.8 cm long, greenish black, turning pale brown. Seed scales in two decussate pairs, valvate, only inner scales fertile, one seed per scale; umbo to 0.5 cm long, foliose. Seeds lenticular, wings two, uneven, 0.1–0.2 cm long and 0.7–0.8 cm long, golden brown. Allan 1961, Farjon 2005b. Distribution NEW ZEALAND: North Is., South Is. Habitat Montane, subalpine and lowland forests between 250 and 1850 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Salmon 1996; NT448. Cross-references B567, K164. Taxonomic note Libocedrus plumosa is the other New Zealand native species, and can be distinguished from L. bidwillii by its larger cones (1.5 cm long or more) and strongly dimorphic lateral and facial leaves.

Libocedrus bidwillii was briefly discussed by Bean (1981a) but it is now slightly more frequently grown, and certainly deserving of more attention as a very handsome tree. A 3 m specimen seen at Logan is a dense column of dark green foliage, on neatly branched shoots, perhaps a little less sculpted than L. plumosa growing nearby, but doing well even if rather shaded. This specimen is derived from a collection made by C.N. Page (no. 106643) in South Island, New Zealand in 1976. It is grown in a scattering of gardens

Section II. Species Accounts

Libocedrus

449

in the south and west of the British Isles, but could be tried more widely since it is at least as hardy as L. plumosa (more so, according to Dallimore et al. 1966). The tallest individual recorded in the British Isles was 9 m (13 cm dbh) at Blackmoor, Bordon, Hampshire, but a more substantial specimen at Headfort, Co. Meath was 8.5 m with a diameter of 34 cm at 1 m when measured by Alan Mitchell in 1980 (TROBI). Johnson (2007) regards it as a short-lived species in the British Isles. It should be given a sheltered warm place in fertile, preferably acidic, moist soil. L. chevalieri J. Buchholz K166 L. chilensis (NOW Austrocedrus chilensis (D. Don) Pic. Serm. & Bizzarri) B565, S97 L. decurrens (NOW Calocedrus decurrens (Torr.) Florin) B566, S130; K60 (as C. decurrens) L. formosana (NOW Calocedrus formosana (Florin) Florin) B567, S130; K61 (as C. formosana)

L. macrolepis (NOW Calocedrus macrolepis Kurz) B567, S130; K61 (as C. macrolepis) L. plumosa (D. Don) Sarg. B567, S306, K166 L. uvifera (NOW Pilgerodendron uviferum (D. Don) Florin, K206) B568, S306 L. yateensis Guillaumin K166

LAURACEAE

LINDERA

Thunb.

Spicebushes There are approximately 100 species of Lindera, most of which occur in Asia, though there is one in Australia and three in North America. They are evergreen or deciduous trees or shrubs. The leaves are aromatic, alternate or opposite, and may be triplinerved or pinninerved. Lindera species are largely dioecious, though a few hermaphrodite flowers may occur. The inflorescences are composed of solitary or clustered umbels, each containing 3–15 flowers; these may be arranged in a dense raceme, on a short shoot or sessile; in deciduous species they are produced before or as the leaves emerge. Two pairs of semi-persistent, decussate bracts subtend each cluster. The flowers are 3-merous or irregular with up to six equal tepals (or none), which often fall during anthesis; staminate flowers have 9–15 fertile stamens and the innermost whorl is glandular, staminodes absent; pistillate flowers have a variable number of staminodes. The fruit is a one-seeded drupe, which may have a small cupule, or sit freely on a thickened pedicel (Rohwer 1993a, Liao 1996b). Lindera is probably not monophyletic (Li & Christophel 2000) and is badly in need of taxonomic revision. As of 2008 it has not been tackled for Flora of China. Members of the genus Lindera have been in cultivation for a long time but its full diversity, and its horticultural merit, are only now beginning to be more widely appreciated. This is perhaps particularly true in the United States, where hotter summers seem to provide conditions more to the liking of these species than in (at least) maritime Europe. This may be exemplified by contrasting two references to the East

Plate 312. The flowers of Lindera erythrocarpa are produced after the foliage expands, making them much less conspicuous than in the precocious-flowering species. Image P. de Spoelberch.

450

Lindera

New Trees

A B

Section II. Species Accounts

Coast native L. benzoin. Bean (1981a) describes it as ‘a neat bush of no particular merit or distinction’, but Dirr (1998) enthuses ‘Good shrub … in full sun it makes a splendid plant in flower and fall color; a harbinger of spring’. The Asian species are poorly covered in the horticultural literature and we have bent our rules slightly to include some species that are shrubby rather than tree-forming, to enable us to provide more useful coverage of the genus. Since most species are dioecious it is important to plant several clones together to obtain the fruit, which adds a further charm to the autumnal plants. There are not many big collections of Lindera. That at the JC Raulston Arboretum is perhaps the most comprehensive in our area, and there is also a good selection at Arboretum Wespelaar and Herkenrode. Most arboreta contain a few, but seldom more than that. A number of other species are represented in cultivation by individuals in a handful of collections. Among these are L. neesiana Kurz, noted as a shrub at the US National Arboretum, and L. rubronervia Gamble, of which there are several specimens forming shrubs about 4 m tall in the Sir Harold Hillier Gardens. The oldest of these has been there for at least 30 years, but the species is assessed as tender by Hillier & Coombes (2002). Its glossy leaves (glaucous below) colour well in autumn. All Lindera seem to flourish best in warm or even hot conditions with ample moisture during the growing season. An acidic soil is required; chlorosis soon becomes apparent in alkaline soil, though this can be reversed with the usual application of sequestered iron (S. Hogan, pers. comm. 2007). Light high shade or full sun (if there is sufficient moisture) will give the best results, especially for autumn colour. Propagation is by seed, which requires a cold stratification (Wharton et al. 2005) or from cuttings rooted with warmth and high humidity.

Lindera aggregata (Sims) Kosterm. Syn. L. strychnifolia Villar Shrub or tree to 5 m. Branchlets blue-green with dense golden silky hairs. Leaves evergreen, alternate, 3.5–7 × 2–4 cm, ovate or elliptic, leathery, immature leaves densely covered in golden silky hairs, mature leaves upper surface lustrous green and glabrous, lower surface glaucous with soft brown hairs, triplinerved, margins entire, apex caudate to acuminate; petiole 0.6–1 cm long and pubescent. Inflorescence clusters axillary, with 6–13 flowers and one bract, densely covered with tomentum. Flowers yellowish green, tepals six with soft, white hair outside and glabrous inside; staminate flowers with nine fertile stamens; pistillate flowers with nine staminodes and a capitate stigma. Fruit ellipsoidal, reddish brown to black, 0.8–1 × 0.4–0.7 cm. Flowering October to April, fruiting November to December (Taiwan). Liao 1988, 1996b. Distribution CHINA: Anhui, Fujian, Guangdong, Hubei, Hunan, Jiangsu, Jiangxi, Zhejiang; JAPAN (naturalised); PHILIPPINES; TAIWAN; VIETNAM. Habitat Forest, between 200 and 1000 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Liao 1996b; NT452.

Lindera aggregata is a small evergreen tree whose foliage is its principal feature. The aspen-like leaves are glossy green above and glaucous below, covered with golden silky hairs when young. To get full benefit of their beauty the plant should be placed

Lindera

451

Figure 51 (opposite). Lindera praetermissa: habit with leaves (A); with flowers (B).

Plate 313. The autumn colours of Lindera glauca are considered by some to be among the best of all. This is the form known as L. salicifolia in gardens, seen here at the Scott Arboretum. Image R. Maurer.

452

Lindera

New Trees

where it receives sun for at least part of the day – preferably in the evening, so that light can be reflected off the undersides of the leaves; training it up into a low standard also helps reveal the beauty of the leaf undersides. The fragrant flowers are pleasing as well, particularly in male plants (S. Hogan, pers. comm. 2007). They are held in clusters about 1 cm across, and on female plants are succeeded by attractive black fruit. The species is rare in cultivation, but it is offered commercially in the western United States; some plants were observed at Cistus Nursery in 2004. Plate 314. Neat glossy leaves with glaucous undersides make Lindera aggregata a useful evergreen. Image R. Olsen.

L. benzoin (L.) Blume B577, K223 L. cercidifolia (NOW L. praetermissa A.J.C. Grierson & D.C. Long) B579, S308 (as L. praetermissa), K223

Lindera chienii Cheng Shrub or tree to 5 m. Branchlets reddish or grey and villous, quickly glabrous. Leaves deciduous, alternate, 6–11 × 2–5.5 cm, oblanceolate or obovate, membranous, both surfaces glabrous or with tufts of hair in the vein axils, pinninerved with seven to nine conspicuous veins on each side of the midrib, margins entire or ciliate, apex acuminate to acute; petiole 0.2–0.5 cm long and villous. Umbels solitary, axillary, with 6–12 flowers and subtended by four bracts. Flowers greenish yellow with a six-lobed villous perianth tube. Fruit subglobose, scarlet and ~1 cm diameter. Flowering April to May or earlier, fruiting September to August (China). Cheng 1934. Distribution CHINA. Habitat Forest. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Cheng 1934.

Forming a small, shrubby tree, Lindera chienii is most valued for its heavy production of yellow flowers in early spring; Dirr (1998) records a January flowering period in Atlanta, Georgia, while the JC Raulston Arboretum website illustrates the plant flowering in February. Individually the flowers are small, but they are numerous in each umbel. In autumn the leaves turn a good yellow before falling. It is quite widely grown in the United States but is less frequent in Europe, though there are several specimens at Arboretum Wespelaar and Herkenrode (where it has survived –13 °C), and a few in English collections.

Lindera communis Hemsl. Tree to 10 m, 0.3 m dbh. Branchlets reddish or blackish brown with dense golden or black pubescence. Leaves deciduous, alternate, 5–10 × 2–3.5 cm, oblong to oblanceolate, thick, papery, upper surface greenish brown and glabrous, lower surface with yellowish brown tomentum, four to six lateral veins on each side of the midrib, margins entire, apex caudate to acuminate; petiole 0.5–0.6 cm long, pubescent below. Inflorescence clusters axillary, with five to six flowers and four bracts. Flowers yellowish green, tepals six, slightly pubescent outside; staminate flowers with nine fertile stamens; pistillate flowers smaller, with nine staminodes. Fruit ellipsoidal to globose, deep red, 0.8 × 0.5 cm. Flowering April, fruiting October to November (Taiwan). Liao 1996b. Distribution CHINA: Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Shaanxi, Sichuan, Yunnan, Zhejiang; INDIA: Assam; JAPAN: Ryukyu Is.; MYANMAR; TAIWAN; VIETNAM. Habitat Broadleaved forest to elevations of 2300 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated.

Lindera communis is commercially available in both North America and the United Kingdom, but the only provenanced stock traced in our research is that derived

Section II. Species Accounts

Lindera

453

from Dan Hinkley’s collection (DJHC 030) made near Kunming, Yunnan in 1996. It is currently sold as vegetatively propagated plants from a specimen that has grown at Heronswood since then, tolerating –8 °C without damage (Heronswood Nursery catalogue 2005). Sean Hogan (pers. comm. 2007) reports that this species does well in the shelter of central Portland, but less well out of town at Cistus Nursery on Sauvie Island, where it has been cut to the ground by frost. The flowers are greenish yellow and are followed by red fruit.

Lindera erythrocarpa Makino Tree to 12 m, 0.25 m dbh. Branchlets yellowish brown and pubescent, though later glabrous with sparse lenticels. Leaves deciduous, alternate, 4–17 × 1.5–3.5 cm, oblong to oblanceolate, papery, upper surface green and glabrous, lower surface glaucous and glabrous or with some silky hairs, purple-ferruginous when dry, four to eight lateral veins on each side of the midrib, margins entire, apex acute to obtuse; petiole 0.5–1.4 cm long, glabrous. Inflorescences produced with first leaves; clusters axillary, with 10–15 flowers and four caducous bracts. Flowers small, yellowish green, tepals six, slightly pubescent on both surfaces; staminate flowers with nine fertile stamens; pistillate flowers with nine staminodes. Fruit globose and shiny scarlet, pulp oily and fragrant, 0.7–0.8 cm diameter. Flowering May, fruiting October (Taiwan). Liao 1988, 1996b. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Sichuan, Zhejiang; JAPAN: Honshu, Kyushu, Shikoku; NORTH KOREA; SOUTH KOREA; TAIWAN. Habitat Broadleaved forest to elevations of 2300 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT449, NT453. Cross-reference S307.

Lindera erythrocarpa is one of the highlights of the genus, capable of forming a true, single-stemmed tree that blazes with bright yellow foliage in autumn. The abundant, clear yellow flowers appear in spring and are followed by heavy crops of red fruits that can be quite ornamental in their own right. It can form a more shrubby specimen (Dirr 1998), but at the Scott Arboretum there is a group of three trees some 10 m tall with clean single trunks up to 15 cm dbh. It is also grown as a single-stemmed tree at Arboretum Wespelaar. It is in relatively widespread cultivation in Europe and North America, and is freely available commercially. The species has been introduced on numerous occasions, Chollipo Arboretum having been a source of material from Korea since at least 1981 (Kew records). Material from Japan is also cultivated (for example, WAHO 841, collected by Warner & Howick in Honshu in 1987), but no collections from China have been traced.

Lindera floribunda (C.K. Allen) H.P. Tsui Tree to 15 m. Branchlets dark brown with golden pubescence. Leaves deciduous, alternate, 5–7 × 2.5–3 cm, ovate, upper surface green and glabrous, lower surface glaucous with sparse golden hairs and a dense fringe along the veins and midrib, triplinerved, margins entire, apex caudate; petiole 0.5–0.7 cm long and pubescent. Inflorescences axillary umbels with two to five flowers. Flower and fruit characters not recorded. Allen 1941. Distribution CHINA: Gansu, Guangdong, Guizhou, Hubei, Hunan, Shaanxi, Sichuan. Habitat Forest. USDA Hardiness Zone 9. Conservation status Not evaluated.

Lindera floribunda is very poorly known, both to botany and to horticulture, but would seem to be worth the attention of gardeners. A specimen seen at Quarryhill in 2004 (grown from WD 137, collected in Hubei in 1994) was 1.8 m tall and still in a rather shrubby state. The foliage is attractive, with a combination of glaucous underside and golden hairs, at least when young. The three principal veins are paler than the leaf

Plate 315. Seen here in the wild in South Korea, Lindera erythrocarpa produces masses of red fruits, as its name suggests. Image T. Kirkham.

454

Lindera

New Trees

surface and thus rather conspicuous. The promise of abundant flowers offered by its specific name has yet to be tested. Another specimen from the same collection is growing at the US National Arboretum.

Lindera glauca Blume Shrub or small tree to 5 m, usually multistemmed. Branchlets pale green-brown, glabrous. Leaves deciduous, alternate, 3–6.5 × 2–4 cm, oblong to elliptic or ovate, immature leaves with a dense covering of silky hairs, mature leaves upper surface green and glabrous, lower surface with some greenish white hairs, midrib elevated below, five to seven lateral veins on each side of the midrib, margins entire, undulate, apex acute; petiole 0.2–0.4 cm long, pubescent; dead, dry leaves do not fall until the spring. Inflorescence clusters axillary, with 5–10 flowers. Flowers pale yellowish green, tepals six; staminate flowers with nine fertile stamens; pistillate flowers with nine staminodes. Fruit globose, black, 0.6–0.7 cm diameter. Flowering March to April, fruiting October (Taiwan). Ohwi 1965, Liao 1996b. Distribution CHINA: Anhui, Fujian, Gansu, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Zhejiang; JAPAN: Honshu, Kyushu, Shikoku; TAIWAN. Habitat Mixed deciduous forest. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT451, NT454, NT454. Cross-reference K223. Taxonomic note Both L. angustifolia Cheng and L. salicifolia (Nakai) C.M. Pak (an invalidly published name, according to IPNI) are clearly very close to, if not conspecific with this species, and here we treat them as variants of it. Lee (2002) has already made the combination L. glauca var. salicifolia (Nakai) T. Lee, although again the validity of this publication is not certain. These taxa differ only in insignificant details, and overall they fall within the range of variation of L. glauca.

Plate 316 (above top). Lindera glauca bears abundant clusters of bright yellow flowers early in spring. Image P. de Spoelberch. Plate 317 (above). Glossy black fruits, conspicuous among the faded but persistent leaves of Lindera glauca (L. salicifolia). Image R. Maurer.

A full botanical assessment in the context of the whole genus is required to settle the question of the relationships of the three taxa covered here (Lindera angustifolia, L. glauca, L. salicifolia), but horticulturally they have very similar merits and effects. These are great, and the plant should be grown under any name. It is fair to say that these are not really trees, but large multistemmed shrubs; with firm pruning or dense low competitors a single stem might be achievable, but it is not the natural state. The foliage in summer is unremarkable, pale mid-green above and rather dully glaucous below, but in autumn it turns to magnificent shades of pumpkin-orange and red – Andrew Bunting of the Scott Arboretum regards it as ‘the best fall color of any tree or shrub’ (pers. comm. 2006) – before fading to tan, and then persisting on the plants through the winter. This is itself a valuable feature of the species, much admired by those who value winter effects – and not only visual ones. Dan Hinkley (Heronswood Nursery catalogue 1999) writes of enjoying the ‘clatter’ of the dry leaves as they rustle in the wind. The fruits are black and (at least in stocks labelled L. salicifolia) freely produced. This taxon is monoecious, or at least its representatives in cultivation are, and single clones can therefore be relied upon to fruit (A. Aiello, pers. comm. 2006). All these taxa are widely grown in North America and seem to perform well throughout the United States. In Chicago Botanical Garden ‘L. salicifolia’ is perfectly hardy, though it does not flower freely (B. Tankersley, pers. comm. 2007). They all seem to make multistemmed shrubs up to about 5 m tall (8 m has been recorded for ‘L. angustifolia’: Cheng, in P’ei 1933). They are much rarer in Europe, only a scattering of specimens having been traced, in Belgian collections (J. De Langhe, pers. comm. 2007), together with a few in England. This is clearly an overlooked species here.

Section II. Species Accounts

L. heterophylla Meissn. S308 L. megaphylla Hemsl. B578, S307, K223

Lindera

455

L. obtusiloba Blume B578, S308, K224 L. praecox (Siebold & Zucc.) Blume B579, S308, K224

Lindera praetermissa A.J.C. Grierson & D.C. Long Shrub or small tree to 12 m. Branchlets dark or reddish brown with silky hairs. Leaves deciduous, alternate, 6–11 × 5–9 cm, ovate to elliptic or orbicular, immature leaves with a dense covering of golden silky hairs, mature leaves upper surface green and glabrous, lower surface with golden silky hairs fringing the veins, triplinerved, margins entire, apex obtuse to acute; petiole 1.5–3.5 cm long. Inflorescences subsessile and axillary, produced just below the newly expanding leaves, umbels usually clustered with 4–14 flowers, pedicels with long, dense golden hairs. Flowers pale yellow and fragrant, opening as the leaves unfold. Fruit ellipsoid, to 0.8 × 0.6 cm. Flowering in spring, fruiting in August (China). Grierson & Long 1978, Long 1984. Distribution CHINA: Xizang, Yunnan; INDIA: Assam; MYANMAR. Habitat Forest. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT450. Cross-reference S308. Bean (B579) and Krüssmann (K223) describe the confused taxon L. cercidifolia.

A brief description and historical note on this taxon was given by Clarke (1988), discussing its long-term confusion with Lindera obtusiloba and the name L. cercidifolia, as well as with L. heterophylla, and its original introduction by George Forrest (probably as F 29087). Bean (1981a) described it as L. cercidifolia, noting its RHS Award of Merit in 1952 for its flowers, and recording that a tree at Exbury was 8 m tall in 1964. These endorsements have not, however, made it a widely grown plant: on the contrary, it seems to be extremely rare and in urgent need of propagation. The only recent record traced is of an 8 m tree at Westonbirt, measured in 2002 (TROBI). This is a multistemmed specimen with a spread of about 3 m, flowering profusely in late March on naked twigs (H. Angus, pers. comm. 2007). Lindera praetermissa may still be grown elsewhere as well, under one of its pseudonyms.

Lindera pulcherrima (Nees) Benth. ex Hook. f. Shrub or small tree to 5 m. Branchlets dark brown with short, stiff golden hairs. Leaves evergreen, alternate, 6–12 × 2.5–6 cm, elliptic to lanceolate, immature leaves covered in dense, silvery hairs, mature leaves upper surface green, glabrous, lower surface glaucous with some white silky hairs, triplinerved, margins entire, apex caudate or long-acuminate; petiole 0.8–1.2 cm long. Inflorescences subsessile, axillary, produced just below the newly expanding leaves, umbels clustered with 2–20 flowers or solitary, pedicels with short white-golden hairs. Flowers with deciduous perianth. Fruit ellipsoid, 1 × 0.7 cm. Flowering April to June (Bhutan). Long 1984. Distribution BHUTAN; INDIA: Sikkim; NEPAL. Habitat Evergreen forest, between 2000 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT455. Cross-reference S308.

Lindera pulcherrima subsp. pulcherrima was introduced to Wakehurst Place as a single seedling by Tony Schilling (Schilling 2617) from the Dorandi valley of the Gurkha Himal in central Nepal, in 1983. Schilling (pers. comm. 2005) notes that the parent trees were large evergreens, growing as understorey in evergreen oak forest. As a young plant it was mentioned by Clarke (1988) as having survived the 1986 winter, and it is still growing at Wakehurst Place, having reached 3 m by 2007, as an erect rounded, bushy tree with several stems. The leaves are a glossy mid-green with a pale underside. No flowers have yet been observed (D. Hardman, pers. comm. 2007). Lindera pulcherrima is a typical warm temperate forest plant, with long drip-tips on its conspicuously three-veined leaves (Hudson 2004), but could certainly be attempted in the milder, moister parts of our area. Seed of subsp. thomsonii (C.K. Allen) D.G. Long was collected in Sichuan in 1995 by the Fliegner, Howick, Erskine and McNamara expedition (SICH 1602), but failed

Plate 318. This plant of Lindera pulcherrima was collected as a seedling in Nepal (Schilling 2617) in 1983, and has grown steadily at Wakehurst Place ever since. Image D. Hardman.

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Lindera

New Trees

to germinate at Kew and Quarryhill. The two subspecies differ principally in their leaves, which are 6–8 cm long in subsp. thomsonii, with a narrow, caudate apex 1.5–2.5 cm long; subsp. pulcherrima has leaves 8–12 cm long, of which the apex is 0.8–1.5 cm long (Long 1984).

Lindera reflexa Hemsl. Shrub or small tree to 4 m. Branchlets pale yellowish brown or purple and glabrous. Leaves deciduous, alternate, 3–14 × 2–7 cm, ovate to obovate, papery, upper surface dark green and glabrous, lower surface pale green with small hairs along the veins and midrib, five to seven lateral veins on each side of the midrib, margins entire, apex acuminate; petiole 0.5–1.5 cm long and glabrous. Inflorescences subsessile and axillary, produced just below the newly expanding leaves, umbels clustered with up to 10 flowers, pedicels with short grey hairs. Fruit bright red. Flowering February to April, fruiting July to October (China). Forbes & Hemsley 1891. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Yunnan, Zhejiang. Habitat Mixed forest between 200 and 1500 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated.

Lindera reflexa seems to be principally a small or medium-sized shrub, with several green-barked stems from the base. It has comparatively large, almost magnolia-like leaves that are slightly aromatic. The early flowers are followed by red fruits. Once again it is not common in cultivation, with only a scattered presence in collections in the eastern United States. A specimen at the JC Raulston Arboretum, received there in 2001, was 1.8 m tall in 2006 but showed no signs of flowering or fruiting when observed in May. In Europe it is represented in some Belgian collections (J. De Langhe, pers. comm. 2007), but although it is available from several nurseries in the United Kingdom no plants have been seen here.

Lindera sericea Blume Shrub or small tree to 4 m. Branchlets initially yellowish green with silky hairs, becoming reddish brown or black and glabrous. Leaves deciduous, alternate, 6–20 × 3–7 cm, narrowly obovate, both surfaces with short, persistent hairs, 6–12 lateral veins on each side of the midrib, margins entire, apex acuminate to acute; petiole 0.5–1.5 cm long. Inflorescences subsessile and axillary, produced just below the newly expanding leaves, umbels with four to seven flowers, solitary or clustered, pedicels with short golden hairs. Fruit globose, black, 0.7 cm diameter. Ohwi 1965, Liao 1988. Distribution JAPAN: Honshu, Kyushu, Shikoku; NORTH KOREA; SOUTH KOREA. Habitat Moist slopes between 300 and 1200 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Cross-references S309, K224. Taxonomic note Lindera sericea var. glabrata Blume also occurs in Japan (Honshu, Kyushu, Shikoku), and has smaller, thinner leaves than the type variety, without short hairs on the leaf surfaces. There are, however, scattered long hairs on the lower surface (Ohwi 1965).

Clarke (1988) mentions that J.G. Veitch introduced Lindera sericea to Western gardens but that it was frost-sensitive at Kew. It has been collected again from Japan in recent years: there is material from SOJA 155, gathered on Shikoku in 1989, growing at Quarryhill, and the Wynn-Joneses made collections from Kyushu in 2005 (BSWJ 11123, 11141) (Crûg Farm Plants 2007–2008). The rather southerly distribution of this shrubby species, together with its track record of tenderness and general absence from cultivation, do suggest that this is not a particularly hardy plant. It is worth attempting in warm gardens, however, for its dark stems and bright yellow autumn foliage.

L. triloba Blume K224 L. umbellata Thunb. S309 L. umbellata var. lancea Momijama S309, K224 L. umbellata var. membranacea (Maxim.) Momijama S309

Section II. Species Accounts

Liquidambar

457

ALTINGIACEAE

LIQUIDAMBAR

L.

Sweet Gums Liquidambar comprises four species with a disjunct distribution, in North America (L. styraciflua L.) and eastern and southwestern Asia (L. acalycina, L. formosana and L. orientalis). Sweet gums are medium to large deciduous trees with a conical or spreading crown. The bark is thick and the branches often have distinctive corky wings. The leaves are palmate with three lobes (Chinese species) or five (to seven) lobes (American species and L. orientalis), and can produce a spectacular display of autumn colour. They are alternate and have serrated margins. Stipules are typically present and may be partially fused to the petiole; they are deciduous and leave a distinctive scar. Liquidambar is monoecious, with unisexual flowers on separate inflorescences. The individual flowers are rather inconspicuous, as petals and sepals are absent. The male inflorescence is a spike or a globose head, and several are gathered together in a raceme. Each inflorescence is subtended by a pubescent, foliose bract. The male flowers have multiple stamens, which conceal the individual flowers. Female inflorescences are globose, pedunculate and subtended by a bract. The female flowers have a curved or hooked style, but are otherwise inconspicuous. The fruit is a woody capsule with two valves and is surrounded by scales formed from persistent staminodes. The style is persistent and conspicuous in the fruit. Seeds are produced in abundance, though many are sterile. They have a membranous wing (Zhang et al. 2003b). Liquidambar is often considered a member of the Hamamelidaceae, as in the Flora of China treatment (Zhang et al. 2003b). Within that family it was placed in subfamily Altingioideae, together with Altingia Noronha and Semiliquidambar H.T. Chang. The recognition of the Altingiaceae as a separate family was suggested as early as 1828, and its independent status has since been confirmed by DNA-based studies (APG 2003). Within the Altingiaceae, generic delimitation is problematic. Liquidambar and Altingia are easily separated, but species with intermediate morphology were placed in the genus Semiliquidambar. The work of Shi et al. (2001), however, using DNA data, has shown that none of the three genera can be maintained in their present formats, and suggests that all species should be merged into Liquidambar. The horticultural merits and requirements of the genus Liquidambar have recently been reviewed comprehensively by Eric Hsu and Susyn Andrews (2005). Dirr (1998) provides further information on the cultivars and cultural requirements of L. styraciflua, which is by far the most important species with its superb autumn colour and range of cultivars, even if its prickly fruit clusters are not always welcome to the tidy-minded. Although it is still sometimes seen thus-labelled, the Mexican and Central American taxon L. macrophylla Oerst. is now regarded as synonymous with L. styraciflua, forming a disjunct population in the Central American mountains south to Nicaragua, like many such principally North American species. In cultivation it leafs out earlier and retains its leaves longer, and is slightly less hardy than trees from more northerly provenances (Hsu & Andrews 2005). From a strictly botanical viewpoint, the Chinese L. formosana var. monticola Rehder & E.H. Wilson should be regarded as indistinguishable from and synonymous with L. formosana (originally described from

Plate 319. The new foliage of Liquidambar acalycina, produced throughout the summer, is flushed red. This is SABE 1950 at Kew. Image T. Kirkham.

458

Liquidambar

New Trees

Taiwan), as their characters overlap. To distinguish the two provenances and indicate (for garden use) the possibly greater hardiness of the mainland material, these trees should be labelled L. formosana Monticola Group (Hsu & Andrews 2005). In general Liquidambar species appreciate a hot summer, ample soil moisture and fertility, and preferably acidic or neutral conditions.

Liquidambar acalycina H.T. Chang Tree to 25 m. Bark smooth or corky and blackish brown; branchlets glabrous and with numerous lenticels. Crown broadly conical to rounded. Leaves deciduous, 8–13 × 8–15 cm, alternate, three-lobed, central lobe broadly ovate and lateral lobes triangular, venation prominent, margins serrate, apex delicate and elongated, somewhat caudate; in young leaves, both surfaces may be glabrous or pubescent; petiole 4–8 cm long; stipules brown, tomentose and 0.3–1 cm long; buds with glossy scales. Monoecious. Male inflorescences globose, 2–2.5 cm wide, several arranged in a raceme, peduncle 2–3 cm long. Female inflorescences globose, solitary, with 15–26 flowers, peduncle 3–6 cm long. Female flowers with styles 0.5–0.7 cm long, brown and pubescent. Fruit a woody capsule, persistent style recurved. Flowering March to June, fruiting July to September (China). Zhang et al. 2003b. Distribution CHINA: Anhui, Guangdong, Guangxi, Guizhou, Hubei, Jiangsu, Jiangxi, Sichuan. Habitat Montane evergreen forests between 600 and 1000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Zhang et al. 2003b; NTiv, NT457, NT459.

Liquidambar acalycina is perhaps one of the most important recent tree introductions, growing well across much of our region and generally making a handsome young tree. Its most distinctive and attractive character is the bronze or red flush to the new growth, which continues as the shoots develop throughout the summer. The intensity of this coloration varies between individuals and some are brighter red than the majority; younger plants may also show a more intense flush than older specimens, in which the foliage becomes much smaller than on vigorous young individuals. A particularly red one has been named ‘Burgundy Flush’ (Hsu & Andrews 2005). The species was first introduced to cultivation by the Sino-American Botanical Expedition of 1980, which collected seed in the ‘Metasequoia region’ of western Hubei (under the number SABE 1950). In this area it grows with other fine broadleaved trees in poorly drained soil subject to flooding (Bartholomew et al. 1983). Material from this collection was widely distributed and many arboreta can show trees grown from it. At the US National Arboretum there is a fine, double-trunked tree, of about 12 m in 2006 (trunks 20 and 17 cm dbh), and a tree of similar height but greater girth (32 cm dbh in 2006) at the Morris Arboretum is the finest example of the species seen during research for this book. A conspicuous example in Europe is the elegant specimen growing near the Orangery at Kew, now approaching 10 m, but there are many more in gardens and arboreta that are also doing well. It would seem to be a better grower, in English gardens at least, than L. styraciflua, but although the leaves are late to fall it does not colour well in autumn here. In Vancouver, however, it is said to develop superb orange and deep purple tints before the leaves fall in December (Wharton et al. 2005). The claim by Piroche Plants (2002–2005) that they were responsible for its introduction in 1995 is clearly wrong, but they have certainly been responsible for importing material from China regularly since that time (S. Hogan, pers. comm. 2007). Hsu & Andrews (2005) record an introduction to the United Kingdom in 1996 of seed from the Shanghai Botanic Garden, and it may be that this has been the source for other importations. It is now impossible to trace the origin of the mass of plants available in the nursery trade.

Section II. Species Accounts

Liquidambar

459

1 cm

L. formosana Hance B581, S310, K225 L. orientalis Mill. B582, S310, K226 L. styraciflua L. B583, S310, K226

Figure 52 (above). Liquidambar acalycina: habit with immature fruits.

FAGACEAE

LITHOCARPUS

Blume

Syn. Pasania (Miq.) Oerst., Limlia Masam. & Tomiya

Stone Oaks Three hundred and twenty-five species of Lithocarpus are recognised by Govaerts & Frodin (1998). Most occur in Asia and Malesia, with L. densiflorus (Hook. & Arn.) Rehder growing in California and Oregon. The stone oaks are evergreen trees (rarely shrubs) with terminal winter buds and extrapetiolar stipules. The leaves are spirally arranged, leathery and entire or with a toothed or serrate margin. Their secondary veins are unbranched and run in parallel, extending to the margins. Lithocarpus is

460

Lithocarpus

New Trees

monoecious and the inflorescences may be staminate, pistillate or androgynous. They are erect, simple or branched and produced in leaf axils at the base of branchlets; alternatively, they form paniculate clusters on subterminal shoots. The staminate flowers are small and in clusters of three to five (to seven); the pistillate flowers solitary or in clusters of (two to) three (to five), though usually only one or two develop fully. Cupules are clustered on the rachis, but many abort; they are corky, woody or crustaceous, and partially or completely enclose the single nut that forms the fruit (Nixon 1997, Huang et al. 1999). Lithocarpus is a comparatively unfamiliar genus, but through its close relationship to Quercus, it is receiving increased attention from oak enthusiasts, and others who value handsome evergreen trees. Lithocarpus densiflorus, from California and Oregon, is an overlooked treasure, hardy throughout the British Isles, where the largest is in Edinburgh (12 m in 2004: TROBI). Its var. echinoides (R. Br. ter.) Abrams is a shortgrowing form from serpentine habitats, with particularly handsome bluish foliage and new growth covered in golden hairs, while f. attenuato-dentatus (J.M. Tucker) Sundahl & D.O. Hall is noted for both its long marginal teeth and white indumentum (Hogan 2008). Lithocarpus edulis from Japan has been cultivated since 1842, but remains seldom seen. A number of species were introduced from China by the early-twentieth century plant hunters and a few older specimens persist in the great Cornish gardens, especially at Caerhays and occasionally elsewhere (Johnson 2007). Several of these, including L. cleistocarpus, L. henryi and L. pachyphyllus, have been described by Bean (1981a). Also mentioned by Johnson (2007) is L. glaber (Thunb. ex Murray) Nakai, which has reached 9.5 m in southern England in the past – although Allen Coombes (pers. comm. 2007) believes that these trees may have been L. edulis. Lithocarpus glaber is now represented in British horticulture only by young seedlings, from a recent introduction by Allen Coombes. A tree labelled L. glaber in the JC Raulston Arboretum is approximately 8 m tall (JC Raulston Arboretum database). In addition to the species described below, a series of contemporary introductions have resulted in the following being represented in cultivation by young plants, mostly in private gardens in the United Kingdom, although there are some in North America: L. brevicaudatus (Skan) Hayata, L. konishii (Hayata) Hayata, L. lepidocarpus (Hayata) Hayata, L. paniculatus Hand.-Mazz. (at Arboretum Waasland, Belgium), L. polystachyus (Wall. ex A. DC.) Rehder (at Firma C. Esveld, Boskoop, in the Netherlands), L. truncatus (King ex Hook. f.) Rehder and L. xylocarpus (Kurz) Markgr. (pers. comms. C. Battle, A. Coombes, J. De Langhe, T. Lasseigne, P. Wharton 2007). Material received at the Hillier Gardens, and possibly elsewhere, as L. confinis C.C. Huang ex Y.C. Hsu & H.W. Jen and L. harlandii (Hance ex Walp.) Rehder has turned out to be of L. dealbatus and L. henryi, respectively (A. Coombes, pers. comm. 2007). Neither L. confinis nor L. harlandii is known to be in cultivation. As with many genera there are also a number of unidentified introductions in arboreta, under collectors’ numbers, flowering and fruiting of which are awaited before identification will become possible. Among these is stock labelled ‘L. pathsapsis’ – a name that does not feature in botanical references. Allen Coombes (pers. comm. 2008) suggests that L. pachylepis A. Camus may be the root for this mutation. The climate of Vancouver seems ideally suited to the successful growth of Lithocarpus from warm temperate areas, and several species are doing extremely well in the David C. Lam Asian Garden. Peter Wharton (pers. comm. 2007) attributed the success of L. variolosus there (despite the root competition it has to endure from the magnifi-

Section II. Species Accounts

cent mature native conifers in the garden, and consequent droughty summer conditions) to its dense, white, ramifying mycorrhizae system, exemplifying the desirability of encouraging such an association. The evidence suggests that some Lithocarpus species are capable of doing well in many of the milder parts of our area, but that others may have a more marginal existence here, growing in only the most favoured locations. All seem to appreciate mild and moist conditions, and like to be as warm as possible in the summer, but not scorched in full sun. A site with a high canopy is advisable, at least when the trees are young. Although some occur on limestone in the wild, in cultivation calcareous soils are probably best avoided. Propagation is most reliable from fresh seed. Cuttings are in general not very successful, but do work occasionally (Hogan 2008), and presumably grafting would be an option if a suitable stock was available. L. cleistocarpus (Seem.) Rehder & E.H. Wilson B587, S311, K227

Lithocarpus corneus (Lour.) Rehder Tree to 15 m dbh. Branchlets pale grey, silvery or tawny brown, glabrous or pubescent, sparsely lenticellate. Leaves congested at branch apices; papery to leathery, (5–)10–15 × 2–4.5 cm, lanceolate to obovate or elliptic, upper surface glabrous, lower surface glabrous or pubescent, with minute scale-like glands, 9–26 secondary veins on each side of the midrib, margins dentate to entire, undulate, apex acuminate to acute; petiole 0.5–4.5 cm long. Monoecious. Male inflorescences often with female flowers at the base. Female inflorescences < 10 cm long. Cupules in clusters of three or rarely solitary; cupule cup-shaped to subglobose, 2.2–4.5 × 2.5–5.5 cm, covered with triangular to rhomboid, imbricate bracts, more or less united into concentric rings. Nut subglobose to turbinate, apex rounded, flat or concave. Flowering almost all year, mainly May to July, fruit maturing on one-year-old branchlets (China). Huang et al. 1999. Distribution CHINA: southern Fujian, Guangdong, Guangxi, southern Guizhou, Hainan, southern Hunan, Yunnan; TAIWAN; VIETNAM. Habitat Broadleaved, evergreen forest below 1000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Huang et al. 1999. Taxonomic note Six varieties of L. corneus are recognised, distinguished by minor differences in leaf shape, pubescence, etc.

The confusion over the identity of trees in the United States grown for decades as L. corneus is described in the account for L. uvariifolius, to which species they should be referred. True L. corneus is currently in cultivation, but in the form of seedlings from a collection made by Allen Coombes in Taiwan in 2003.

Lithocarpus dealbatus (Hook. f. & Thomson ex Miq.) Rehder Tree to 20 m. Bud scales, branchlets, petioles, inflorescence rachises and cupule scales all covered in short, tawny hairs. Leaves papery or leathery, 7–14 × 2–5 cm, ovate to elliptic or lanceolate, upper surface green, glabrous, lower surface same colour as above or greyish and with waxy scales, (8–)10–13 secondary veins on each side of the midrib, tertiary veins conspicuous on lower surface, margins entire or with a few apical notches, apex long-acuminate to acute; petiole 1–2 cm long. Monoecious. Staminate inflorescences to 15 cm long, clustered at branch apices. Pistillate inflorescences to 20 cm long. Rarely androgynous. Cupules

Lithocarpus

461

Plate 320. Lithocarpus kawakamii TH 001 at Tregrehan. The potential of Lithocarpus is being explored as the merits of these fine evergreen trees are becoming more widely appreciated. Image J. Grimshaw.

462

Lithocarpus

New Trees

in clusters of three (to five); cupule 0.8–1.4 cm diameter, covered with triangular, imbricate bracts; enclosing half of the nut. Nut globose with a depressed apex. Flowering August to October, fruiting August to October of the following year (China). Huang et al. 1999. Distribution BHUTAN; CHINA: Guizhou, southwest Sichuan, southeast Xizang, Yunnan; INDIA: northeast; LAOS; MYANMAR; THAILAND; VIETNAM. Habitat Mixed mesophytic forest with Pinus yunnanensis and other Fagaceae, between 1000 and 3100 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Huang et al. 1999; NT462, NT464. Taxonomic note Lithocarpus dealbatus subsp. leucostachyus (A. Camus) A. Camus is now treated as a synonym of L. variolosus (Huang et al. 1999).

Plate 321. Lithocarpus dealbatus. A male inflorescence produced by a young specimen (Rippin 203) at the Hillier Gardens, September 2007. Image J. Grimshaw.

The principal source for Lithocarpus dealbatus in cultivation seems to be Charles Howick & Bill McNamara’s collections in Sichuan in 1990. At Quarryhill there is a tree from H&M 1376, standing 2.5 m tall in 2004. It seems not to appreciate the Californian heat and high light intensity, producing much smaller, paler leaves than its parents in the wild (W. McNamara, pers. comm. 2004), but it has flowered and fruited nonetheless. It did not do well in Vancouver as it kept growing through the autumn, and new growth was invariably damaged (P. Wharton, pers. comm. 2007). In southern England, however, it is proving to be a success in cultivation and it looks as if it will be a valuable new addition to the garden landscape. At the Hillier Gardens a vigorous young tree from H&M 1483, planted in 1995, was 4 m tall and developing inflorescences when seen in October 2006; the preceding hot summer seemed to have stimulated several species there to flower, albeit very late in the year. By April 2008 it was 5.2 m (6 cm dbh) (A. Coombes, pers. comm. 2008). Flowering can be precocious, however, as a tree grown from a collection made by John Rippin in Yunnan in 1999 (as L. confinis) also first flowered there in (September) 2006, when it was less than 2 m tall. The specimens at Kew are again from H&M 1483, collected at the upper limit of the species’ existence at 3080 m on Mount Luoji, where it grows over limestone. The pendulous dark green leaves with paler undersides are attractive. L. densiflorus (Hook. & Arn.) Rehder B587, S312, K227 L. densiflorus var. echinoides (R. Br.) Abrams B587 L. densiflorus var. montanus (NOW L. densiflorus (Hook. & Arn.) var. densiflorus) K227 L. edulis (Makino) Nakai B588, K227 L. glaber (Thunb.) Nakai B588, K228

Lithocarpus hancei (Benth.) Rehder Tree to 15 m. Branchlets grey to pale brown, somewhat waxy. Leaves thin and papery to rigid and leathery, 5–10 × 2.5–5 cm, shape extremely variable, ovate to elliptic to lanceolate, both surfaces glabrous, concolorous, upper surfaces occasionally farinose, 6–13 secondary veins on each side of the midrib, margins entire, apex variable; petiole 0.5–4 cm long. Monoecious. Male inflorescences paniculate, to 10 cm long, often with female flowers towards base. Female inflorescences congested with two to many rachillae. Cupules shallowly bowl-shaped, 0.3–0.7 × 1–2 cm diameter, covered with triangular, imbricate bracts in ± concentric rings. Nut depressed globose or conical with a rounded apex. Flowering July to August, fruiting August to November of following year (China). Huang et al. 1999. Distribution CHINA: Fujian, Guangdong, Guizhou, Hainan, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; TAIWAN. Habitat Occurs in a variety of habitats across its range, though usually below 2600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Huang et al. 1999; NT463. Taxonomic note The wide range of this species has led to a number of variants being given specific names, but these have all been reduced to synonymy (Govaerts & Frodin 1998).

Section II. Species Accounts

Lithocarpus

463

Lithocarpus hancei is very rare in cultivation, but is represented by both old and young specimens. There are two plants at the David C. Lam Asian Garden, 2 m high in 2007 and growing vigorously. These came from wild collections made by the Taiwanese Research Institute in 1998, and were planted out in the garden in 2002. Peter Wharton (pers. comm. 2007) described the species in glowing terms: ‘The young shoots and unfurling leaves are suffused a brilliant lipstick red in early May, contrasting wonderfully well with their dark green, tapered leaves. A magnificent plant – imagine a mature tree, joining other Lithocarpus and Castanopsis painting whole hillsides orange, yellow, cream, purple and red as the monsoon descends on these rich broadleaved evergreen forests of southeastern China and Taiwan.’ Owen Johnson (2007) has recently identified trees of L. hancei at Caerhays, Cornwall, up to 9 m tall (28 cm dbh), and there are young seedlings in some British collections. L. henryi (Seem.) Rehder & E.H. Wilson B588, S312, K228

Lithocarpus kawakamii (Hayata) Hayata Tree to 15 m, 0.7 m dbh. Branchlets greyish and densely covered in lenticels. Leaves papery or thin and leathery, 12–25 × 5–7.2 cm, oblong to obovate, upper surface glabrous, lower surface with rusty scales or tomentum along the midrib, 12–25 secondary veins on each side of the midrib, tertiary veins conspicuous on lower leaf surface, margins with a few apical teeth or entire, apex acute to acuminate; petiole 2–5 cm long. Monoecious. Staminate inflorescences paniculate, to 20 cm long. Pistillate inflorescences with cupules in clusters of three; cupule plate-shaped, 0.7–1 cm diameter, covered with triangular or rhomboid, imbricate bracts; enclosing one-fifth to one-quarter of the nut. Nut globose and with a depressed apex or conical, 1.6–2.2 cm long. Flowering May to August, fruiting August to November of the following year (Taiwan). Huang et al. 1999. Distribution TAIWAN. Habitat Evergreen broadleaved forest between 700 and 2900 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT461.

Lithocarpus kawakamii is sparsely represented in cultivation, but appears to be a vigorous grower. At Tregrehan there are a few trees derived from Tom Hudson’s first numbered collection, TH 001, made at Hsitou on the slopes of Alishan in 1989, and planted out in 1992. They have done very well, being 5 m tall when seen in 2005, forming shapely rounded trees covered in large dull dark green leaves that are paler beneath. The most vigorous individual there is growing in a particularly damp site. The species is also grown at the David C. Lam Asian Garden in Vancouver, where it is represented by a solitary survivor of a collection by the Taiwanese Research Institute’s Botanical Garden, made at Yakou, Taiwan at 2355 m, in 2000. This individual was unfortunately gnawed by voles soon after planting in 2002, but has now recovered and is making good growth (P. Wharton, pers. comm. 2007). L. pachyphyllus (Kurz) Rehder B589, S312, K228

Lithocarpus uvariifolius (Hance) Rehder Tree 10–15 m. Branches with large, prominent bud scars; branchlets densely covered with ferruginous tomentum. Leaves leathery or thickly papery, 9–22 × 5–10 cm, ovate to obovate or elliptic, upper surface glabrous, lower surface pubescent, concolorous, 25–35 secondary veins on each side of the midrib, margins entire, though becoming dentate towards the apex, apex rounded, obtuse, acute or shortly caudate; petiole 1–3.5 cm long, densely tomentose. Monoecious. Male inflorescences spicate, solitary in leaf axils, or clustered at branchlet apices; rachis densely tomentose. Female flowers solitary or in groups of three, borne at the base of the male inflorescences. Cupule cup-shaped to subglobose, 2–3.5 × 3.5–5 cm, densely covered with prominent bracts and scurfy indumentum; enclosing over half of the nut. Nut subglobose, pubescent, apex rounded, flat or rarely concave. Flowering May to July, fruiting October to December of the following

Plate 322. The new growth of Lithocarpus hancei emerges in shades of bronze and red. Image P. Wharton.

464

Lithocarpus

New Trees

1 cm

C

1 cm

A

1 cm

D

B

Section II. Species Accounts

year (China). Huang et al. 1999. Distribution CHINA: southwest Fujian, north and northeast Guangdong, Guangxi. Habitat Broadleaved evergreen forest, or in association with Castanopsis / Quercus subgenus Cyclobalanopsis or Pinus massoniana; between 200 and 800 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Huang et al. 1999. Taxonomic note There has been some confusion between this species and the much more widespread L. corneus. According to Flora of China (Huang et al. 1999), the leaves of L. corneus are glabrous below, or have sparse hairs on the midvein and the axils of the lateral veins; the leaf margins are typically dentate; the petiole glabrous. Lithocarpus uvariifolius leaves are pubescent below; the margins are largely entire, with some teeth towards the apex; and the petiole is tomentose.

Lithocarpus

465

Figure 53 (opposite). Lithocarpus variolosus: habit with female inflorescences (A), with male inflorescences (B); detail of stem with lenticels (C). L. dealbatus: infructescence (D).

Lithocarpus uvariifolius has been in cultivation in the United States for many years, masquerading under the name L. corneus. David Fairchild recorded finding large, edible acorns of what he called Quercus cornea for sale in a market in Hong Kong in 1900 and sending these to the Plant Introduction Station (now the University of Georgia Bamboo Farm and Coastal Gardens), Savannah, Georgia (Fairchild 1941). There is still a specimen labelled Lithocarpus corneus there, but this may derive from an introduction from Hong Kong by F.A. McClure, in 1926. Several plants in this collection were identified as L. uvariifolius by Allen Coombes during a visit in 2000, and later confirmed as such by Prof. Zhekun Zhou of Kunming (Coombes 2001). Todd Lasseigne (pers. comm. 2006) reported that they were rather shrubby specimens, and believed that they had been damaged by periodic hard freezes (down to around –12 °C), that prevented them from attaining tree size. On the eastern side of the Atlantic, L. uvariifolius has also been in cultivation for a long time, as evidenced by an old stump with regenerating shoots 3 m tall at Caerhays Castle, recorded by Owen Johnson in 2006 (Johnson 2007). Formerly labelled L. garrettianus, its identity was confirmed by Allen Coombes (pers. comm. 2008). Young seedlings are also currently in cultivation in the United Kingdom (C. Battle, pers. comm. 2007).

Lithocarpus variolosus (Franch.) Chun Tree to 20 m. Branchlets blackish and covered in greyish brown lenticels. Leaves thick and papery or leathery, 6–15(–24) × 3–5(–7) cm, ovate to elliptic or lanceolate, upper surface glabrous, lower surface glaucous and with thick, waxy, scale-like trichomes, 6–10 secondary veins on each side of the midrib, tertiary veins inconspicuous on lower leaf surface, margins entire, apex acuminate and falcate; petiole 1(–1.5) cm long. Monoecious. Staminate inflorescences paniculate or solitary, 5–7 cm long. Pistillate inflorescences terminal clusters, 3–6(–10) cm long. Cupule 0.6–1.8 cm diameter, covered with reddish or greyish brown, triangular bracts; enclosing between half and most of the nut. Nut globose and with a depressed apex, 1–2 cm long. Flowering May to July, fruiting July to September of the following year (China). Huang et al. 1999. Distribution CHINA: southwest Sichuan, northwest Yunnan; VIETNAM. Habitat Mixed mesophytic forest, in association with Abies and Picea; between 2500 and 3000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Wharton et al. 2005; NT464, NT465.

Among all the recently introduced Lithocarpus, L. variolosus probably offers most promise of horticultural success, apparently tolerating a wide range of conditions and, when happy, growing very fast. The first and principal introduction was another made by the Howick and McNamara team on their Sichuan expedition in 1991. They collected the species twice, under numbers H&M 1404 and H&M 1482, the latter from trees growing with L. dealbatus at the treeline on Mount Luoji (see p. 462). At Quarryhill specimens from H&M 1404 planted in the open on a hot hillside have not really flourished, forming somewhat shrubby, multistemmed low trees, of about 3 m in 2004. A different picture can be seen in the mild, moist climate of Vancouver, however, where specimens from the same gatherings are forming elegant trees of great beauty and showing promise for a magnificent maturity (Wharton et al. 2005, Hogan

Plate 323. The dark evergreen foliage of all the stone oaks makes them very useful in mixed plantings. This is Lithocarpus variolosus H&M 1482, photographed at Kew. Image J. Grimshaw.

466

Lithocarpus

New Trees

2008). When observed in 2004 they were approximately 8 m tall, and by 2007 some had reached over 10 m (P. Wharton, pers. comm. 2007). Interestingly, Peter Wharton observed that the progeny from the two collections have different characteristics in cultivation: H&M 1482 is producing ‘huskier’ trees with broad leaves, while seedlings from H&M 1404 are also vigorous but have narrower leaves, that partially twist to display their pale undersides. The branches are held horizontally from the single, silvery-barked trunk, with the foliage hanging vertically from the twigs. The leaves flush out a bronzed brown, turning to shiny dark green above and rather shiny pale green below, giving a charming shimmery effect in a breeze. As with many species in the genus, L. variolosus flowers and fruits young, freely producing knobbly clusters of its acorns if a group is grown together. It is also doing well in England, with good trees at Kew and the Hillier Gardens. It is easily propagated from cuttings (Hogan 2008), so it should become more readily available over time.

ANACARDIACEAE

LITHRAEA

Plate 324. A plant that needs a safety warning: the sap of Lithraea caustica is indeed caustic, and specimens must be handled with great care. Image M. Gardner.

(Miers) Hook. & Arn.

The three (or four) species of Lithraea are restricted to South America, and only the Chilean endemic L. caustica is of interest to temperate gardeners. Lithraea species are small, evergreen trees or shrubs. As in many Anacardiaceae, contact with plants can cause dermatitis because of their poisonous sap; the lesions caused by L. caustica are particularly painful and persistent. The leaves are simple and ovate or imparipinnate, and have a winged petiole and rachis. Lithraea is dioecious, though occasional bisexual flowers occur in the inflorescences. These are paniculate and lateral, typically clustered near the shoot apex. The individual flowers are yellow and 5-merous. The fruit is a drupe with white flesh (Rodríguez R. et al. 1983, de Dios Muñoz 2000).

Lithraea caustica (Molina) Hook. & Arn.

Litre

Shub or tree to 6 m, trunk contorted, to 0.5 m dbh. Bark green to tan, becoming dark greyish brown with age, forming heavy plates and furrows. Crown rounded; trunk branching just above the base; branches slender, erect and densely clothed with leaves. Branchlets dark red. Leaves evergreen, 1.6–5.6 × 1.8–3.3 cm, simple, coriaceous, alternate, petiole 0.3 cm long, margins entire and undulating, veins prominent and greenish white; leaf shape variable, generally oval to ovate with a rounded, acuminate or emarginate apex; upper surface green, glabrous, lower surface ferruginous, pilose or glabrous. Dioecious. Inflorescences paniculate, in the axils of upper leaves, rachis pubescent, 2–6 cm long. Flowers yellowish green, with short peduncles, unisexual. Fruit a drupe, 0.5–0.8 cm diameter, yellowish white and shiny. Flowering September to December, fruiting February to March (Chile). Rodríguez R. et al. 1983. Distribution CHILE: from Coquimbo Province to Malleco Province, particularly in the Coastal Range and the lower foothills of the Andes. Habitat Dry matorral in open areas or in the transitional forests of the coast. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT466, NT515.

Lithraea caustica has been cultivated at Berkeley since 1983, and at Logan since 1990, when it was grown from seed collected in

Section II. Species Accounts

Lithraea

Chile by Martin Gardner and Sabina Knees (G&K 4380). A seedling from this collection, donated by Martin Gardner, grows in Neil Murray’s garden in Dublin, but remains a shrub (S. Andrews, pers. comm. 2008). It is otherwise more or less unknown in horticulture. It forms a bushy small tree, with small, hard-textured, dark green leaves, well adapted to its arid habitat. The small axillary clusters of yellowish cream flowers are followed by yellowish berries. A Health and Safety risk assessment would undoubtedly condemn this tree as being too dangerous for gardens, on account of its toxic sap, so perhaps its rarity in cultivation is for once a good thing.

LAURACEAE

LITSEA

Lam.

Syn. Adenodaphne S. Moore

The genus Litsea may contain anywhere between 200 and 400 species. It is probably not monophyletic (Li & Christophel 2000), and is badly in need of taxonomic revision. As currently defined, most species occur in Asia, Australia and the Pacific, though about five occur in Central and North America. Litsea species are evergreen or deciduous trees or shrubs. The leaves are alternate or opposite and pinninerved (rarely triplinerved). They are dioecious; the inflorescences axillary, composed of solitary or clustered umbels, each containing 1–15 small, but distinctive flowers, surrounded by a whorl of persistent, decussate bracts. The flowers are 3-merous or irregular with up to nine deciduous tepals (or none). Staminate flowers have (5–)9(–20) fertile stamens, some of which are glandular; staminodes usually absent. Pistillate flowers have a variable number of staminodes. The fruit has a cupule formed from the receptacle (Rohwer 1993a, Li et al. 2005). As with most genera in the Lauraceae, Litsea is in a mess, and identifications are not easy. The three species described below seem to be well defined, but many are not, and it is probable that there are others in cultivation that have yet to be identified. Tom Hudson has sent an apposite quote from A Field Guide to the Forest Trees of Northern Thailand (Gardener et al. 2000): ‘Lauraceae is one of the most difficult families to identify – it is often impossible to be sure of the species even with a microscope.’ Generic delimitations are also frequently difficult to define. In his survey of tender woody plants growing in the British Isles Johnson (2007) mentions unconfirmed records of tree-sized individuals of L. aciculata Blume and ‘L. zeylanica’ (four different authors have described plants under this name, according to IPNI). More species are cultivated in the San Francisco Bay Area, including the Mexican L. neesiana (Schauer) Hemsl. and L. parvifolia Mez at the University of California Botanical Garden at Berkeley, and in the San Francisco Botanical Garden there are specimens of L. javanica Blume from Indonesia, and L. calicaris (A. Cunn.) Benth. & Hook. f. ex Kirk, the Maneao, from North Island, New Zealand (where it grows as an evergreen tree to 15 m). The shrubby L. aestivalis (L.) Fernald (Pondspice), a rare native of the eastern United States from Louisiana to Maryland, is in cultivation on both sides of the Atlantic. It produces yellow flowers in early spring before the leaves expand. As interesting plants with attractive aromatic foliage Litsea are well worth cultivating

467

468

Litsea

New Trees

in a warm, sheltered site, preferably with moist, fertile acidic soil. Propagation is by seed or cuttings rooted in warmth and high humidity The genus Neolitsea is very close to Litsea, but plants are distinguished by having four rather than six perianth lobes. Neolitsea sericea (Blume) Koidz. is well established in cultivation, and admired for its sensuous silky leaves. There are 45 species of Neolitsea in China, and others may be expected to appear in cultivation. Among them is N. aurata (Hayata) Koidz., a tree of up to 15 m, with variable silver or gold indumentum. Seedlings are in cultivation at Cistus Nursery, and their development is eagerly awaited.

Litsea cubeba (Lour.) Pers.

Mountain Pepper, May Chang

Shrub or small tree to 10 m. Branchlets glabrous or covered in silky hairs. Leaves deciduous, alternate, 4–11 × 1.1–2.4 cm, oblong or elliptic, upper surface glabrous, lower surface glaucous, glabrous or covered in silky hairs, 6–16 secondary veins on each side of midrib, margins entire, apex acuminate or acute; petiole 0.6–2 cm long, glabrous. Inflorescences produced before or with the leaves; umbels solitary or clustered with four to six flowers per umbel; flowers 0.8–1 cm diameter, yellowish brown, with six tepals. Staminate flowers with nine stamens. Fruit black, subglobose, ~0.5 cm diameter. Li et al. 2005. Distribution BRUNEI; CAMBODIA; CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Xizang, Yunnan, Zhejiang; INDONESIA; LAOS; MALAYSIA; MYANMAR; PHILIPPINES; SINGAPORE; TAIWAN; THAILAND; VIETNAM. Habitat Sparse forest, thickets and along streams, rivers and roads, between 500 and 3200 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Hudson 2004; NT468.

Plate 325. Litsea cubeba, flowering in early spring in the Lushan, Jiangxi. Image P. de Spoelberch.

Litsea cubeba is perhaps best known as the source of a widely used essential oil, revealed through an internet search to be much favoured by aromatherapists and herbalists for its apparently numerous and diverse applications and benefits, ranging from being ‘an effective tool in the fight against acne and excessive perspiration’ to insect repellent. To get the oil, however, one has to have a fruiting tree. Despite its southerly origins it seems to be rather surprisingly tolerant of conditions in the milder parts of our area, and could be tried more widely. Sean Hogan (pers. comm. 2007) finds that it is successful in much of the Pacific Northwest, so long as ample water is available in summer. In Cornwall it is reported to be a fast-growing tree (Hudson 2004), and specimens at Tregehan are now 6 m tall (T. Hudson, pers. comm. 2007). Its pale cream flowers appear in early spring before the leaves expand, and although small are ornamental at that season.

Litsea glaucescens Kunth

Mexican Bay-leaf

Shrub or small tree to 10 m, 0.5 m dbh. Branchlets dark brown, reddish brown or olive, glabrous or slightly pubescent. Leaves evergreen, alternate, fragrant, (4–)7–9(–12.5) × (1–)2–3(–4) cm, lanceolate or narrowly elliptic to ovate, leathery to membranous, glabrous, six to eight secondary veins on each side of the midrib, margins entire and slightly thickened, apex acute to acuminate, often with a mucro; petiole 0.4–2 cm long and glabrous or rarely slightly pubescent. Inflorescences axillary, umbels (with three to five flowers) solitary

Section II. Species Accounts

Litsea

469

or clustered with two pairs of decussate, deciduous bracts; staminate flowers to 0.3 cm long, yellowish and with six to eight tepals and 9 or 12 fertile stamens. Pistillate flowers to 0.2 cm long with six tepals and nine staminodes. Fruit a black, spherical berry, 0.8–1.2 cm diameter, sitting in a small disc-shaped cupule. Flowering February to May, fruiting August to September (Mexico). Allen 1945. Distribution COSTA RICA; EL SALVADOR; GUATEMALA; HONDURAS; MEXICO: all states except Coahuila, Durango, Nuevo León, Sonora; NICARAGUA. Habitat Montane and humid pine-oak forest between 800 and 2800 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT469.

Litsea glaucescens has a limited presence in cultivation in the western United States and would be worth trying in the mildest parts of western Europe. A 5 m tree seen in the San Francisco Botanical Garden had pendulous branches densely clad in glossy dark green leaves, and was bearing green unripe fruit when seen in July 2004. The leaves are lightly but pleasantly aromatic when crushed.

Litsea japonica (Thunb.) Juss. Shrub or tree to 12 m. Branchlets initially covered in dense yellowish red tomentum, later almost glabrous; branchlets covered with large leaf abscission scars giving a knobbly appearance. Leaves evergreen, alternate, 7–15(–25) × 2–8 cm, oblong to elliptic (rarely obovate), thick and leathery, upper surface shiny yellowish green and glabrous, lower surface pale green with tawny or ferruginous tomentum and prominent venation, 8–12 secondary veins on each side of the midrib, margins entire and recurved, apex obtuse; petiole 1.5–3.5 cm long and densely covered with brown tomentum. Inflorescences axillary, umbels solitary with tomentose bracts; flowers tomentose and ~1 cm diameter; staminate flowers with deciduous tepals and nine fertile stamens. Pistillate flowers with nine staminodes. Fruit purplish blue and ellipsoidal, 1.5–2 × 1.5 cm, sitting in a shallow disc-shaped cupule. Flowering August to October, fruiting February to May (Japan). Ohwi 1965, Walker 1976. Distribution JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; SOUTH KOREA. Habitat Montane and humid pine-oak forest between 800 and 2800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Walker 1976. Cross-reference K229.

Of the three species described here, Litsea japonica is probably the most widely cultivated, although it could certainly not be described as common. There are scattered records of it in cultivation in the United States, where Woodlanders Nursery in Aiken, South Carolina claim to have introduced it (Woodlanders 2007–2008). In Europe, as might be expected, it is found in a few Cornish gardens, including Tregrehan and Tresco Abbey on the Isles of Scilly, and in Ireland. At Glasnevin it is grown against a warm wall, and although the specimen seen in 2006 was only 1.4 m tall it seemed to be thriving, with a dominant main stem forming from a shrubby base. The foliage is held upright in a distinctive posture and the upper surface of the leaves is somewhat glaucous, giving a bluish lustre. The undersides are densely covered in red-brown tomentum, which extends to the margin so that the ‘fur lining’ is visible from above. The buds, still small in September, are also densely pubescent.

ROSACEAE

MADDENIA

Hook. f. & Thomson

Maddencherries Maddenia comprises about seven species of deciduous trees or shrubs, all of which are restricted to the Himalaya and China. The leaves are alternate, simple and with gland-tipped marginal teeth. Stipules are large and persistent. The inflorescences are racemose with numerous small flowers. The flowers have a bell-shaped hypanthium

Plate 326. The Mexican Litsea glaucescens is an elegant evergreen that is rare in cultivation. Here it is seen growing in the San Francisco Botanical Garden (formerly known as the Strybing Arboretum). Image J. Grimshaw.

470

Maddenia

New Trees

1 cm

1 cm

Section II. Species Accounts

Maddenia

and may be hermaphrodite or pistillate only. They have 10–12 perianth segments (the petals and sepals are largely identical), and 20–40 stamens in two whorls. The fruit is a drupe with thin flesh and one or two bony seeds (Gu et al. 2003). The omission of Maddenia hypoleuca from Bean (1981a) was a rare oversight, rectified by Clarke (1988). The criticism levelled at M. hypoleuca by Clarke, who said it is of ‘little garden value’, is even more applicable to M. wilsonii, as the former is redeemed at least somewhat by the bright white undersides of the leaves. Both, however, are tolerant hardy plants with a certain curiosity interest for their apparent lack of petals. M. hypoleuca Koehne S317, K265

Maddenia wilsonii Koehne Shrub or tree 3–5 m. Branchlets initially yellowish brown and densely tomentose; later purplish brown, glabrous and lustrous. Winter buds purple-brown, tomentose, scales 1.5 × 0.8 cm long. Leaves 3.5–12 × 1.8–6 cm, oblong to oblanceolate, upper surface greenish brown and largely glabrous, lower surface pale green to brown with dense yellowish brown or white pubescence, 15–20 secondary veins on each side of the midrib, margins irregularly serrate or double-serrate, apex acute; petiole 0.2–0.7 cm long, yellowish brown-villous; stipules lanceolate, membranous and sparsely pubescent. Racemes 3–4 cm long with oblong, submembranous bracts. Hermaphrodite flowers 0.2–0.4 cm diameter, perianth segments triangular-ovate, caducous, green (lacking the red tinge found in M. hypoleuca), stamens 30–40. Drupe black, ovoid, ~0.8 cm diameter. Flowering April to June, fruiting June (China). Gu et al. 2003. Distribution CHINA: southern Gansu, Guizhou, western Hubei, Shaanxi, Sichuan. Habitat Scrub and riverbanks between 1500 and 3600 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT470.

Maddenia wilsonii has largely slipped under the horticultural radar since it was introduced from western Hupei in 1908 by its eponymous discoverer (under the number Wilson 909), escaping even Krüssmann’s notice and attracting only a brief entry in the Hillier Manual (Hillier & Coombes 2002). During this time it has skulked in the collections of the Royal Botanic Garden Edinburgh, from which source all stock in cultivation seems ultimately to derive. At the Hillier Gardens it has formed a single-stemmed small tree of about 5 m. The deeply corrugated, long leaves are quite distinctive.

MAESACEAE (formerly MYRSINACEAE)

MAESA

Forssk.

Maesa comprises about 200 species, which occur in the Old World from Africa to Australia and the Pacific. They are shrubs or rarely small trees, with simple, usually punctate leaves with entire, serrate or dentate margins. They may be dioecious, or individual plants may bear a few flowers of the opposite gender or a few hermaphrodite flowers. Inflorescences are racemose or paniculate and bear multiple small bracts. The flowers are small, 5-merous and subtended by two bracteoles; the calyx is funnel-shaped and the corolla is white or yellow and bell-shaped. The fruit is a berry or a drupe (Chen & Pipoly 1996). In addition to Maesa montana, described below, M. japonica (Thunb.) Moritzi is commercially available in the United Kingdom and the United States. It is said to be a

Figure 54 (opposite). Maddenia wilsonii: fruiting stem, with detail of leaf venation.

471

472

Maesa

New Trees

1 cm

A

B

Section II. Species Accounts

Maesa

shrub or small tree, to 5 m (Huxley et al. 1992), and is sometimes grown under glass. Maesa hupehensis Rehder is in cultivation at Berkeley and perhaps elsewhere in the United States. Maesa argentea (Wall.) A. DC. is grown at the San Francisco Botanical Garden. All are rather shrubby.

473

Figure 55 (opposite). Maesa montana: habit with flowers (A); fruits (B).

Maesa montana A. DC. Syn. M. formosana Mez, M. henryi Hu, M. martinii H. Lév. Shrub or small tree 2–3(–10) m, multistemmed. Branchlets covered with soft white hairs, though later almost glabrous. Leaves evergreen, membranous, 7–14(–23) × 3–7(–9) cm, elliptic to oblong or lanceolate, covered with small bristly hairs or glabrous, 8–12 secondary veins on each side of the midrib, margins coarsely dentate or undulate, apex acute or acuminate; petiole 1–1.5 cm long with a deep channel. Inflorescences axillary, racemose or paniculate, 2–7(–10) cm long and hirsute; bracteoles tiny. Flowers very small, calyx lobed, corolla white and bell-shaped, lobed, stamens included. Fruit white, globose or ovoid and with orange spots. Flowering February to April, fruiting October to December (China). Chen & Pipoly 1996. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Sichuan, southeast Xizang, Yunnan; INDIA; MYANMAR; TAIWAN; THAILAND. Habitat Mixed forest between 400 and 2800 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Chen & Pipoly 1996, Hudson 2004; NT472.

A small and usually multistemmed tree in the wild, Maesa montana has a toe-hold in cultivation in the United Kingdom. It is offered by one nursery in Cornwall, and at Tregrehan there is a plant of Yunnanese origin. This has so far failed to make a trunk, and is growing as a rather undistinguished shrub, but it has quite bold, handsome leaves of glossy dark green, and the small white fruits are pretty. A sheltered site in fertile moist soil will probably give the best chance of success to those who wish to make the attempt to grow it.

MAGNOLIACEAE

MAGNOLIA

L.

Syn. Alcimandra Dandy, Aromadendron Blume, Dugandiodendron Lozano, Elmerrillia Dandy, Houpoëa N.H. Xia & C.Y. Wu, Kmeria Dandy, Manglietia Blume, Manglietiastrum Y.W. Law, Michelia L., Pachylarnax Dandy, Parakmeria Hu & W.C. Cheng, Paramanglietia Hu & W.C. Cheng, Paramichelia Hu, Talauma Juss., Tsoongiodendron Chun, Woonyoungia Y.W. Law, Yulania Spach

Magnolias Magnolias are evergreen or deciduous trees or shrubs with alternate, entire, pinninerved leaves. Stipules are present and initially enclose the terminal bud, later falling leaving a scar; they are often called ‘perules’ when covering an overwintering flower bud, and are often attractively hairy. Magnolia flowers are solitary, hermaphrodite or rarely unisexual; they are terminal on long shoots or on short axillary shoots (brachyblasts). The floral parts are arranged in turn along an elongated receptacle; the perianth is composed of six or more distinct petal-like tepals, and occasionally the outer three tepals may differ from the inner ones; stamens are numerous, spirally arranged

Plate 327. Some of the Asian evergreen magnolias challenge familiar species with the beauty of their foliage and flowers. This is Magnolia foveolata. Image R. Olsen.

474

Magnolia

Plate 328. The large, showy flowers of Magnolia make the genus extremely popular. Its numbers have been swelled by the addition of many species formerly placed in other genera. This is Magnolia maudiae (section Michelia), with female parts borne above the anthers on a stipe. Image Phytophoto.

New Trees

and flattened and the anther is poorly differentiated from the filament. The pistillate part of the flower (gynoecium) may be sessile or stipitate (with a stalk). Carpels are numerous (rarely solitary) and spirally arranged; they may be free (apocarpous) or fused (syncarpous). Fruiting carpels (follicles) are usually dehiscent, and each produces one or more large seeds. The carpels may be fleshy, and can fuse together to form a berry-like fruit (the term ‘fruit’ will be used here to refer to the aggregate of follicles, whether fused together or not). After dehiscence, the follicles often become woody and persist on the tree. The seeds each have a red or orange fleshy aril and are often pendulous, hanging out from the carpel on a slender thread (Chen & Nooteboom 1993). Magnolia in its traditional interpretation is well known to gardeners and collectors, and numerous species were described by Bean (1981a) and Krüssmann (1985a). In recent years, however, there have been major changes in the taxonomy of the Magnoliaceae, largely as the result of the publication of several phylogenetic studies (for example, Azuma et al. 1999, 2000a, Ueda et al. 2000, Azuma et al. 2001, Kim et al. 2001, Li & Conran 2003) demonstrating the close relationship of all groups within the subfamily Magnolioideae. This DNA-based work has been confirmed by recent critical interpretations of magnolioid morphology (Figlar 2006). The outcome of these changes is that the Magnoliaceae family now comprises only two genera, Liriodendron L. and Magnolia; all other genera (including Michelia and Manglietia, and the others indicated as generic synonyms above) have been subsumed into Magnolia to preserve monophyly (Chen & Nooteboom 1993, Figlar 2000, Nooteboom 2000, Figlar & Nooteboom 2004, Kumar 2006). An accessible exposition of the reasons for change has been given by Magnolia expert Richard B. (Dick) Figlar (Figlar 2006), who has also kindly advised us for this account. The crux of the matter is that to recognise separate genera (for example, Michelia, Manglietia), as some traditionalists would like to do, logically requires the dismemberment of Magnolia itself – an act that would serve neither phylogeny nor taxonomic stability. (Yulania ×soulangeana anyone?) In consequence, Magnolia now contains three subgenera (Magnolia, Yulania, Gynopodium), twelve sections and thirteen subsections, each clearly supported by both DNA and morphological characters. A complete summary of Magnolia classification is provided by Figlar (Figlar 2006). The new classification has been adopted by the Magnolia Society International, and 224 species of Magnolia are now recognised (Figlar 2005a). About four-fifths of these occur in eastern Asia, from the Himalaya east to Japan and south to New Guinea. The remaining fifth occur in eastern North America, Central America and northern and central South America. Many of the tropical species are not known in cultivation in our area. A summary of the infrageneric classification of Magnolia and the key characters defining each group, for the species covered in this book, is presented in the table opposite. The current adherence of Chinese botanists and the recently published Flora of China (Xia et al. 2008) to a fragmented view of Magnoliaceae means that two parallel taxonomies are in use, so the alternative names in Michelia, Manglietia, etc. are likely to persist in both literature and nurseries for many years to come. The lead given by the Magnolia Society in adopting the broad view of Magnolia is to be applauded and

Section II. Species Accounts

Magnolia

475

should be followed in horticulture. The online Kew World Checklist of Magnoliaceae and the IUCN Red List of Magnoliaceae (Cicuzza et al. 2007) both follow the unified Magnolia approach.

MAGNOLIA

L.

A guide to the infrageneric classification of Magnolia species covered in New Trees

Subgenus Magnolia

Section Magnolia (e.g. M. grandiflora, M. virginiana)

Leaf vernation conduplicate (folded in half)

Leaves evergreen, sub-evergreen or deciduous

Flowers terminal on long shoots Mid- to late-flowering season

Stipules adnate to the petiole base (or adnate to most of petiole, in M. virginiana)

Gynoecium sessile

Ovules two per carpel

Fruit ovoid-ellipsoid, with fused carpels until dehiscence

Section Manglietia (e.g. M. insignis) Leaves evergreen (not M. decidua!) Early-season leaves sometimes produced in a false whorl Ovules four or more per carpel Section Macrophylla (e.g. M. macrophylla) Leaves deciduous Leaf bases cordate to auriculate Tepals with purple spot at base of upper side

Subgenus Yulania Leaf vernation conduplicate Stipules adnate to base of petiole Flowers terminal and/or on brachyblasts Flowering precocious (before new leaves produced) Gynoecium sessile or stalked Fruit more or less cylindrical, carpels fused or not

Subgenus Gynopodium Leaf vernation open (not folded) Stipules free Plants entirely glabrous Gynoecium stalked (rarely sessile) Fruit more or less ovoid-ellipsoid, with fused carpels until dehiscence

Section Yulania (e.g. M. campbellii, M. denudata) Leaves deciduous Flowers terminal or occasionally on brachyblasts Carpels fused Ovules approx. two per carpel Section Michelia (e.g. M. figo, M. doltsopa) Leaves evergreen Flowers on brachyblasts Carpels not fused Ovules two to six per carpel Section Gynopodium (e.g. M. nitida) Gynoecium stalked Carpels split via the upper valve Ovules two (to four) per carpel Section Manglietiastrum (e.g. M. sinica) Gynoecium sessile Carpels split via the lower valve Ovules three to eight per carpel

For a complete summary see Figlar (2006).

Magnolia has long been one of the most universally popular genera of flowering trees in gardens around the world, contributing a major part of the spring floral display. Most of these early, precocious-blooming plants belong to section Yulania, a relatively small group of the genus overall, although under the influence of cultivation and the work of hybridisers the number of named taxa in the group is now vast and ever-

Plate 329. Magnolia laevifolia, fruiting heavily at Quarryhill. In section Michelia the carpels are separate rather than fused together – one of the points of distinction used to separate it from section Yulania. Image J. Grimshaw.

476

Magnolia

Plate 330. The flowers of Magnolia yuyuanensis are beautiful, but ephemeral. A member of section Manglietia, it is is very hardy and easily grown in a wide range of conditions. This tree is at the Hillier Gardens. Image J. Grimshaw.

Figure 56 (opposite). Magnolia laevifolia: flowering shoot and leaves.

New Trees

expanding. Breeding work is adding genes from other sections to this pool, but the pink and white flowers of section Yulania are the most familiar face of Magnolia (discussed and explored in a range of horticultural literature). Members of other sections of the ‘traditional’ genus Magnolia are generally much less familiar, with the exception of M. grandiflora (section Magnolia), unchallenged as the finest flowering evergreen tree for temperate gardens. Other summerflowering species have tended to be more plants for the enthusiast rather than the general gardener. Beyond the narrow circumscription of Magnolia the sections Michelia and Manglietia have been represented in cultivation by a few noble old trees in the mildest parts of Cornwall, and in pockets of the United States. The beauty of the old trees of M. doltsopa and M. floribunda at Caerhays Castle should have sparked a wider interest earlier, but it is only within the past 10–15 years that Asian evergreen magnolias have really come to the attention of horticulture (Wharton 2007, Figlar 2008, Robinson et al. 2008). The wave of excitement they have caused started in western North America, where introductions by Piroche Plants and others, and enthusiastic promotion by horticulturists such as Sean Hogan, have led to them becoming very much a part of the landscape in the Pacific Northwest. This interest has spread in recent years to Europe, and nurseries are now offering a wide range of these trees. Many are too new in cultivation to allow much to be said of their long-term performance in European conditions, but for warmer parts of maritime Europe, in a time of rising temperatures, they hold immense promise. Tom Hudson (2004) has summed up the position admirably: ‘Michelia are exceptionally ornamental plants in habit and flower, and many an unexciting old magnolia hybrid should be tidied up by an adventurous gardener, to make way for a Michelia.’ Hybridisation is in progress in Australasia and it is probable that a wave of new hybrid cultivars will appear before long (Robinson et al. 2008). Introductions from China and Vietnam continue apace and it is probable that many collections of new taxa, or of ‘familiar’ species from new provenances (such as dark red-flowered forms of Magnolia delavayi and M. insignis, already in cultivation), will be entering horticulture in the next few years. Identifications will often follow or need revision after trees have flowered. Magnolias of China (Liu et al. 2004) gives a very tempting view of the richness of the Magnoliaceae in China, and shows that although we have had a chance to grow many taxa, there is a huge diversity still to be explored in horticulture. For example, only four deciduous ‘traditional’ magnolias of section Yulania are described in the accounts that follow, but to judge from the illustrations in Magnolias of China there are several more taxa with considerable horticultural

Section II. Species Accounts

1 cm

Magnolia

477

478

Magnolia

Plate 331. A large number of magnolias are threatened or endangered in the wild, usually through habitat loss or felling for timber. Illustrating the problem, this Magnolia macrophylla var. dealbata (classed as Endangered by IUCN) in Mexico is surrounded by a maize field. Image N. Macer.

New Trees

potential awaiting introduction to Western gardens; very many evergreen species in other sections remain to be explored as well. With the exception of M. tamaulipana, the numerous species of Magnolia from Latin America are also almost unknown in cultivation, but a handful are being grown at Berkeley, including M. guatemalensis Donn. Sm., M. schiedeana Schltl., and M. sharpii V.V. Miranda. The critical state of many Magnolia populations, as a result of deforestation and habitat degradation, has been highlighted by the publication of The Red List of Magnoliaceae (Cicuzza et al. 2007). This provides the stark warning that 131 of the 245 members of Magnoliaceae – over half – are threatened with extinction in the wild, and that the ‘safety’ of the others should not be taken for granted. Ninety-four species have not been evaluated at all, including many from areas well known to be under severe pressure from habitat destruction and degradation. The revised conservation status of each species is given in the descriptions that follow. Conservation orchards of magnolias have been established in China, and it is hoped that these will provide a source of material for future reintroductions. Cicuzza et al. (2007) report that nursery-grown seedlings of M. sinica are already being planted in native forests to boost numbers of this critically endangered tree. However, seed from these sources should be treated with some caution, as hybridisation is facilitated by the close proximity of different species. Magnolias are in general relatively easy to raise from seed, with fresh seed giving the best results and fastest germination times (almost immediate for evergreen species sown from the newly dehisced fruit: Hogan 2008). Propagation by cuttings under conditions of high humidity and bottom heat, with a rooting hormone, is also usually not difficult, but is best achieved with vigorous non-flowering shoots. Material from older trees becomes less susceptible to the propagator’s skills. For michelias in particular, Sean Hogan recommends the use of shoots from the trunk or the base of the plant. Grafting onto a stock of a section Yulania magnolia works very well for members of section Manglietia, at least, and could perhaps be tried for other sections. Magnolias can take many years to flower from seed (vegetatively propagated plants are usually much quicker to flower), so the raiser must be patient. Many of the more recently introduced Asian evergreen species described here have yet to flower ‘in captivity’ and their blooming is eagerly awaited. In the meantime, however, they are often extremely handsome foliage plants. As always, the ecology of the species in the wild should be considered. Many species of evergreen Magnolia germinate and spend their juvenile period in the shade of the forest understorey, gradually growing in low light conditions until a gap opens and they can rise to become emergents or canopy trees flowering in the sunlight. Many are indeed huge timber trees, a world away from the dainty magnolias of suburbia. Young trees therefore require a sheltered position where they are not scorched by the hottest afternoon sun – although in northern gardens especially they need all the heat they can get if they are to grow and flower successfully. They also enjoy ample moisture during the growing season, and should not be allowed to become dry for more than a very short period. In most cases it would seem that the evergreens prefer a mildly acidic soil, but a few, such as M. laevifolia, seem to be happy in soil with a higher pH. More experimentation is needed to ascertain the lime tolerance of most of the species described here.

Section II. Species Accounts

Magnolia

Hogan (2008) repeatedly stresses the need for an adequate supply of nitrates and iron, and sometimes magnesium, for the successful growth of Asian evergreen magnolias. Without this they soon become yellowish and less vigorous – effects that are particularly significant in cooler climates where such warmth-loving plants can be slow to start growing in spring. In the accounts that follow, notes on flowering time in the botanical descriptions refer to trees in the wild; times may differ significantly in cultivation. For example, members of section Yulania often flower earlier in cultivation than in their native habitat. With such an enthusiastic following there are many great Magnolia collections around the world, and these and their growing conditions are detailed by Gardiner (2000). Fewer gardens have a good range of the Asian evergreens but there is a centre of diversity of these around Portland, Oregon, especially in the collection gathered by Sean Hogan of Cistus Nursery. Quarryhill Botanical Garden and the David C. Lam Asian Garden at the University of British Columbia’s Botanical Garden also have good and expanding collections in western North America. In the southeastern United States michelias are popular, thriving in high heat and humidity, and collections are being developed in several locations including the garden of the University of Florida, the North Florida Research and Education Center, Quincy, Florida, and the South Carolina Botanical Garden at Clemson, South Carolina – and in the same state there is Dick Figlar’s own collection at Magnolian Grove Arboretum, Pickens. In our area there are useful selections at the JC Raulston Arboretum and in other gardens in the North Carolina piedmont; also at the US National Arboretum and at the Norfolk Botanical Garden, Norfolk, Virginia. Further north, however, they are more or less unknown. The more recent advent of these trees in Europe means that while many are growing them and numerous species are available commercially, few gardens have collections with sizable trees. An exception is Tregrehan, where they flourish in the mild, moist conditions. Several further species are cultivated in American collections outside our area and are likely to be tried further north. They include the Endangered Chinese M. lacei (W.W. Sm.) Figlar and the Vulnerable M. odora (Chun) Figlar from southern China and northern Vietnam (both in section Michelia). The latter is also in cultivation in Europe, but its hardiness is as yet unknown. M. acuminata (L.) L. B643, S318, K268

Magnolia ×alba (DC.) Figlar & Noot.

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia ×alba DC. Tree to 30 m, 0.8 m dbh. Bark grey. Branchlets green with dense, appressed grey pubescence, though soon almost glabrous. Leaves evergreen, thin and leathery, 10–35 × 4–11 cm, elliptic to obovate, upper surface glabrous, lower surface with sparse pubescence, 6–12 secondary veins on each side of the midrib, margins entire, apex acuminate; petiole 1.5–5 cm long, pubescent or glabrous; stipules with similar pubescence as on branchlets. Flowers on axillary shoots; shoots pubescent and with two to three evenly distributed scars. Flowers numerous, white and scented; tepals 10–12, lanceolate, 3–5.5 × 0.3–0.5 cm; stamens yellowish brown; gynoecium stipitate with ~10 pubescent carpels. Fruits 10–13 cm long; most carpels abort, but those that ripen are red, 1.2–1.8 cm long, hairy and beaked. Flowering April to September, fruiting October to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution This hybrid does not occur in the wild, but is cultivated in the Chinese provinces of Fujian, Guangdong, Guangxi, Hainan and Yunnan, and throughout subtropical and tropical southeast Asia. USDA Hardiness Zone 9–10. Illustration Liu et al. 2004. Taxonomic note Magnolia ×alba is probably the result of a cross between M. champaca and M. montana (Blume) Figlar (Chen & Nooteboom 1993).

479

Plate 332. The endangered Magnolia lacei in cultivation in China. Just becoming known in the West, this has promise as a good-looking evergreen. Image R. Figlar.

480

Magnolia

New Trees Magnolia ×alba is prized above all else for its fragrance, and its flowers are widely used in Asia for ceremonial gifts and temple offerings as well as for household and personal decoration. Its popularity has travelled with Asian immigrants to the United States and it is now widely grown there, especially by Asian families in California (S. Hogan, pers. comm. 2007). It is, however, a large tropical tree and distinctly tender, not growing outside north of the San Francisco area (S. Hogan, pers. comm. 2007). In Europe it is only known as a glasshouse plant.

Magnolia amoena W.C. Cheng (Subgen. Yulania, Sect. Yulania)

Beautiful Magnolia, Tienmu Magnolia

Tree to 12 m. Bark grey or greyish white. Branchlets slender, glabrous and purplish brown. Leaves deciduous, thin and leathery, 10–15 × 3.5–5 cm, elliptic to obovate, upper surface glabrous, lower surface covered with curly hairs, plus long white hairs on the midrib and veins, 10–13 secondary veins on each side of the midrib, margins entire, apex acute to cuspidate; petiole 0.8–1.3 cm long and pubescent; stipules adnate to the petiole. Flowers terminal and produced before the leaves, pale pink with a darker centre, slightly scented and ~6 cm diameter; peduncle densely hairy. Tepals nine, spathulate or oblanceolate, 5–6.5 cm long; stamens purplish red; gynoecium sessile. Fruits 4–6 cm long and cylindrical, though some carpels may abort causing the fruit to be contorted; ripe carpels oblong, ~1 cm long, woody, tuberculate and dehiscing along a dorsal suture. Flowering April to May, fruiting September to October (China). Chen & Nooteboom 1993, Gardiner 2000, Liu et al. 2004. Distribution CHINA: Anhui, Jiangsu, Jiangxi, Zhejiang. Habitat Forests between 200 and 1000 m asl. USDA Hardiness Zone 5. Conservation status Vulnerable, due to habitat loss and the gathering of firewood and floral buds for medicine. Illustration Liu et al. 2004.

Magnolia amoena is a classic deciduous species, with abundant white and pink flowers appearing in early spring (usually late March in northern Europe). If they avoid frost these go on to produce long red sausage-shaped fruits and a tree may carry literally hundreds of these, presenting another attractive sight in autumn (J. Gallagher, pers. comm. 2007). It has been available as seed from the Shanghai Botanic and Hangzhou Botanical Gardens for many years, but the genetic purity of such material has been questioned (Spongberg 1998). Such seedlings are quite widely cultivated in Europe and North America. In 1994, however, scionwood was sent from Hangzhou Botanical Garden to Dr James Waddick of Kansas City, Missouri, and grafted specimens from this are now grown in North America. It seems to be correctly identified and it is assumed that the parent tree was of wild origin (C. Tubesing, pers. comm. to P. Wharton 2007). Magnolia amoena seems to do well wherever deciduous magnolias thrive. A tree at the Morris Arboretum planted in 1992 was 6 m tall when seen in 2006.

Magnolia aromatica (Dandy) V.S. Kumar

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia aromatica Dandy, Paramanglietia aromatica (Dandy) Hu & W.C. Cheng

Plate 333. Many Asian evergreen magnolias can be large timber trees when mature – an observation that should be borne in mind when planting them. Neither are they slowgrowing. This is Magnolia aromatica, flourishing in Kunming. Image R. Figlar.

Tree to 35 m, 1.5 m dbh. Bark smooth, grey. Branchlets pale green with short, appressed grey or brown hairs, or largely glabrous. Leaves evergreen, fragrant when crushed, thin and leathery, 17–22.5 × 6–9.4 cm, narrowly obovate, both surfaces glabrous with prominent reticulate venation, 9–16 secondary veins on each side of the midrib, margins entire, apex mucronate or acuminate; petiole 2.7–3.5 cm long, glabrous, narrowing towards base; stipules adnate to petiole, densely covered with long, yellowish hairs. Flowers terminal, white, fragrant; tepals 12, obovate, 6–8 × 2.5 cm; gynoecium sessile with 29–39 carpels. Fruits 8–8.5 cm long, subglobose to ovoid; ripe carpels red, shiny, later thick and woody, 1–2.5 cm long, dehiscing along both dorsal and ventral sutures. Flowering May to June, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangxi, Guizhou, southeast Yunnan; VIETNAM. Habitat Mixed forest on limestone hills between 1300 and 1900 m asl. USDA Hardiness Zone 9–10. Conservation status Endangered, due to habitat loss and firewood extraction. Illustration Chen & Nooteboom 1993, Liu et al. 2004; NT480.

Seed labelled Magnolia aromatica was sent to Cistus Nursery from the Kunming Botanical Institute during the 1990s and young plants have been distributed from

Section II. Species Accounts

Magnolia

481

the nursery under this name. Unfortunately it seems that some of these at least have not been the true species but possibly hybrids, or even another taxon altogether (S. Hogan, pers. comm. 2007). One such was planted in the David C. Lam Asian Garden in Vancouver and has done extremely well, reaching 5.5 m and tolerating frosts to –9 °C, but on flowering the hairs on the bud scales were found to be reddish instead of the expected white, and the tree has since been assigned to a taxon near M. conifera (Wharton 2007). Individuals from this source should therefore be observed carefully as they come into flower. There are specimens at Quarryhill forming sparse, upright young trees but these have not yet flowered. Their leaves are bronzed when young and are very aromatic when crushed, with a hint of mango. Authorities differ in the amount of pubescence M. aromatica should show: Liu et al. (2004) say that it should be glabrous except for white-hairy buds, but other authorities (Chen & Nooteboom 1993) allow it to have hairy twigs. The Quarryhill trees have fulvous pubescence on the twigs. It is therefore not clear whether true M. aromatica is in cultivation, and to ascertain this it will be necessary for more trees to flower. The true species is likely to be on the tender side as it has a southern distribution. M. ashei (NOW M. macrophylla var. ashei (Weath.) D.L. Johnson) B658, K267

Magnolia biondii Pamp. (Subgen. Yulania, Sect. Yulania) Tree to 12 m, 1 m dbh; single- or multistemmed. Bark smooth and pale grey. Branchlets slender, greyish green and glabrous. Leaves deciduous, papery, 10–22 × 3.5–11 cm, ovate to elliptic or rarely oblanceolate, upper surface dull green, lower surface pale green with long, colourless hairs along the midrib and veins, 10–15 secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 1–2 cm long; stipules adnate to the base of the petiole and densely covered with short white or yellowish hairs. Flowers terminal and produced before the leaves, white with a pinkish purple centre and fragrant; tepals 9(–12), the outer three linear and 0.8–1.1 cm long, the inner six spathulate and 4–5 × 1.3–2.5 cm; stamens purple; gynoecium sessile. Fruits 6–14.5 cm long, purplish red, cylindrical though some carpels may abort causing the fruit to be contorted; ripe carpels pale brown or black, globose, tuberculate and 0.9–1 cm long, dehiscing along the dorsal sutures. Flowering February to March, fruiting September (China). Chen & Nooteboom 1993, Gardiner 2000, Liu et al. 2004. Distribution CHINA: Gansu, Henan, Hubei, Shaanxi, Sichuan. Habitat Forest between 400 and 2000 m asl. USDA Hardiness Zone 5. Conservation status Data Deficient. Illustration Liu et al. 2004; NT481. Cross-references S327, K268.

The Chinese name for Magnolia biondii is Hope of Spring (Forestfarm Nursery catalogue 2007), which expresses a sentiment many feel as they see magnolia buds swelling. Unfortunately the flowers of M. biondii are rather small and are not produced by young trees, so there are those who feel that this species is of limited horticultural value (J. Gallagher, pers. comm. 2007). The opening flowers are said to be able to withstand light frosts, and although they are typically white with dark purplepink basal staining, can vary from cream to purple (Gardiner 2000). Wilson failed to

Plate 334. Magnolia biondii, a member of section Yulania, is terribly slow to bloom from seed, and the flowers are on the small side. Against that, however, they appear very early in the year, and many admire the beautifully hairy perules. Image K. Camelbeke.

482

Magnolia

New Trees

introduce it, so this honour goes to Prof. Y.C. Ting of Boston College, Massachusetts, who collected seed from Henan in 1977. This was distributed to the Arnold Arboretum and the Magnolia Society, with the result that the species rapidly became established in cultivation throughout the United States and beyond (Spongberg 1998). The first flowering occurred in 1986 in North Carolina; the Arnold Arboretum specimens took until 1991, however, and John Gallagher (pers. comm. 2007) has grown it for twelve years without a flower. Once flowering has started the trees may sometimes produce a second flush, to judge from the secondary buds seen on a 7 m specimen at the JC Raulston Arboretum in May 2006. The narrow leaves give the tree a light and graceful appearance in summer. Seed imported from Henan in 1996 and distributed though the Magnolia Society International seedlist (1996 #5) has proved to be a mixed batch, including hybrids with nine equal tepals, but some of the plants raised from this source do have the correct six large and three sepaloid tepals (P. de Spoelberch, pers. comm. 2007). At Arboretum Wespelaar and Herkenrode there are vigorous upright trees that flower in February or March; the small flowers are judged by Philippe de Spoelberch to be ‘of botanical interest only’, though their early appearance and fragrance are welcome.

M. ×brooklynensis Kalmb. S318, K268 M. campbellii Hook. f. & Thomson B644, S319, K268 M. campbellii var. alba Treseder B644, S319, K268 M. campbellii var. mollicomata (W.W. Sm.) Kingdon-Ward B644, S319, K268

Magnolia cathcartii (Hook. f. & Thomson) Noot. (Subgen. Yulania, Sect. Michelia) Syn. Alcimandra cathcartii (Hook. f. & Thomson) Dandy, Michelia cathcartii Hook. f. & Thomson Tree 25–50 m, 0.5 m dbh. Branchlets slender, dark brown, pilose; buds white-villous. Leaves evergreen, thin and leathery, 6.5–17 × 3–5.6 cm, ovate to elliptic (rarely obovate), upper surface glossy green, lower surface glabrous or villous along the midrib, 12–15 veins on each side of the midrib, margins entire, apex long-acuminate; petiole pubescent, 0.2–2 cm long, without stipule scars; stipules free, hairy. Flowers solitary, terminal, fragrant, tepals 9–11; outer three tepals oblong, 5.5–6 × 2 cm, pale green; inner tepals obovate to elliptic, white; stamens ~40, white to yellowish green; gynoecium stalked. Fruit clusters spicate, 3.5–4 cm long; ripe carpels 3–16, compressed globose, lenticellate. Flowering May, fruiting August to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Xizang, Yunnan; INDIA: Assam, Sikkim; MYANMAR; VIETNAM. Habitat Montane evergreen broadleaved forest between 1200 and 2800 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Liu et al. 2004.

Magnolia cathcartii is the only member of section Michelia subsection Maingola to be known in cultivation. Subsection Maingola differs from subsection Michelia (to which all other michelias mentioned here belong) in bearing flowers on long shoots, and only occasionally on brachyblasts, and in having anthers that dehisce towards the centre of the flower (introrse dehiscence) rather than at the edges (latrorse dehiscence). It has attractive creamy white flowers that are held at the end of the branchlets; the large size of the three outer tepals is distinctive. The species is as yet poorly known in our area, but is established in New Zealand. A recent collection was made in northern Vietnam by Dan Hinkley and Bleddyn and Sue Wynn-Jones (in 2003, under the number HWJ 874), from large trees growing at 2300 m on Fan Si Pan (Crûg Farm Plants 2007–2008).

Section II. Species Accounts

Magnolia

Magnolia cavaleriei (Finet & Gagnep.) Figlar

483

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia cavaleriei Finet & Gagnep. Tree to 20 m, 0.5 m dbh; multistemmed. Bark grey-white. Branchlets green becoming grey and densely covered with short or long, clear or brown hairs. Leaves evergreen, thin, leathery, (10–)12–20(–24) × 3.5–5.5(–7) cm, narrowly elliptic to obovate, upper surface dark green with scattered clear or brown hairs, lower surface pale green with short, clear or brown hairs except on the midrib, midrib conspicuous below, 11–15 secondary veins on each side of the midrib, margins entire, apex short-acuminate; petiole 1.5–3 cm long without stipule scars; stipules free from petiole and densely covered with short or long, clear or brown hairs. Flowers on axillary shoots 0.5–2.5 cm long, white, fragrant; tepals 9–12, outer three to four tepals obovate to elliptic and 4.5–7 × 2–2.5 cm, the inner tepals narrowly obovate to spathulate becoming gradually smaller; stamens yellowish grey; gynoecium stipitate with 6–14 carpels, hairy. Fruits 5–15 cm long, greenish brown and spicate; ripe carpels dark brown, ovoid to obovoid, smooth or lenticellate, 1–2.5 cm long and beaked; dehiscing along both dorsal and ventral sutures. Flowering March, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Sichuan, Yunnan. Habitat Forest between 800 and 1500 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Liu et al. 2004; NT483.

Magnolia cavaleriei is now established in cultivation in both North America and Europe, and has reached flowering size at around 4 m in Oregon (S. Hogan, pers. comm. 2007) and at the JC Raulston Arboretum; the majority of plants, however, are still very young, and it is difficult to comment on its tolerances. It is potentially a neat, small tree with dense foliage and abundant flowers, but the flowers open early, usually in February, and are apt to be damaged by frost (R. Figlar, pers. comm. 2007).

Magnolia champaca (L.) Baill. ex Pierre

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia champaca L. Tree to 40 m, 1 m dbh. Branchlets greyish brown with clear or pale yellow appressed or erect hairs. Leaves evergreen, thin and leathery, 8–23(–34) × 3.4–9(–12) cm, ovate to oblong or lanceolate, upper surface glabrous, lower surface pubescent, 11–22 secondary veins on each side of the midrib, margins entire, apex acute to long-acuminate; petiole 2–3.5 cm long and pubescent; stipules adnate to the petiole for over half of its length, densely pubescent. Flowers on axillary shoots, ivory to yellow or orange and very fragrant, subtended by three to four bracts, brachyblast slender, 0.7–1.2 cm long and tomentose; tepals 12–15(–21), the outer four to six tepals narrowly obovate or linear to spathulate and 2–4 × 0.7–0.9 cm, the inner tepals gradually smaller; stamens yellow-orange; gynoecium stipitate with ~30 carpels, tomentose. Fruits 2–15 cm long; ripe carpels ovoid to ellipsoid and densely lenticellate, 1–2 cm long and without a beak. Flowering May to July, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: southeast Xizang, southern and southwest Yunnan (cultivated in Guangdong, Hainan, Jiangxi); INDIA; MYANMAR; NEPAL; VIETNAM. Habitat Evergreen broadleaved forest between 650 and 1600 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Liu et al. 2004.

During the New Trees workshop in January 2007 Carol Gurney, then Chairman of the International Dendrology Society, produced from his pocket a small bottle he had obtained in Myanmar into which a number of flowers of Magnolia champaca had been packed, then preserved in liquid, which had taken on their orange colouring. With some difficulty the stopper was extracted and we had the pleasure of experiencing in the chilly Cotswolds something of the fabulous ‘tropical’ fragrance of this tree. Carol Gurney has been brave enough to plant a specimen outside in his Suffolk garden, although Tom Hudson has yet to risk it at Tregrehan (pers. comms. 2007). Like M. ×alba it is a big tropical tree and greatly valued in Asia, but its long-term success in our area would seem improbable except in the very mildest and most sheltered places: in western America, –2 °C is sufficient to damage the plants (Hogan 2008).

Plate 335. Magnolia cavaleriei photographed at Piroche Plants, British Columbia – a nursery that has been at the forefront of promoting Asian evergreen magnolias, especially in western North America. Image R. Figlar.

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Magnolia chapensis (Dandy) Sima

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia chapensis Dandy, Michelia tsoi Dandy Tree to 30 m, 1 m dbh. Bark smooth greyish brown. Branchlets dull brown and glabrous or with dense, short, brown hairs. Leaves evergreen, thin and leathery, somewhat puckered, 5.5–16 × 2.6–6.5 cm, obovate to oblong or occasionally elliptic, both surfaces glabrous, 9–12 secondary veins on each side of the midrib, margins entire, apex acuminate; petiole slender, 1.5–2.5 cm long, glabrous and without scars; stipules free from the petiole, glabrous or slightly pubescent outside. Flowers on axillary shoots, pale yellow and fragrant, brachyblast 0.3–1.1 cm long and slightly tomentose; tepals six, the outer three obovate to oblong, convex and 3–3.5 cm long, the inner tepals gradually smaller; stamens yellow-orange; gynoecium stipitate with 14 or more carpels, glabrous or slightly hairy. Fruits 3–10 cm long and cylindrical; ripe carpels ovoid to oblong, 0.6–1.5 cm long with a short beak and sparse, inconspicuous lenticels. Flowering March to April, fruiting August to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Yunnan; VIETNAM. Habitat Mixed evergreen and broadleaved forest between 500 and 1650 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Chen & Nooteboom 1993.

Magnolia chapensis seems to offer the prospect of being a good, fairly hardy tree, with vigorous specimens growing in several parts of the United States. At the JC Raulston Arboretum an individual planted in 2000 is now 5–6 m tall and doing well, although it has yet to flower. In Oregon fast-growing young trees of 4–5 m have produced a few flowers, but have yet to get into their floral stride. They form a good dark green canopy, and do not demand extra iron in the soil to retain this healthy look (S. Hogan, pers. comm. 2007). If the promise of these specimens is fulfilled this lovely tree, with its abundant creamy flowers, should be worthy of wide planting in suitable areas. M. compressa Maxim. (WAS Michelia compressa B737, K306)

Magnolia conifera (Dandy) V.S. Kumar

(Subgen. Magnolia, Sect. Manglietia)

Syn. Magnolia ovoidea (H.T. Chang & B.L. Chen) V.S. Kumar, Manglietia conifera Dandy, Manglietia glaucifolia Y.W. Law & Y.F. Wu, Manglietia ovoidea H.T. Chang & B.L. Chen Tree to 28 m, 0.5 m dbh. Branchlets black-brown with ferruginous pubescence and numerous annular stipule scars. Leaves evergreen, thin and leathery, 12.3–19.6 × 4.3–6.4 cm, elliptic to narrowly obovate, upper surface dark glossy green and glabrous, lower surface pale green to glaucous and glabrous, or with appressed brown hairs when young, 12–14(–17) secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 1–1.5 cm long and pubescent; stipules pubescent, adnate to the base of the petiole. Flowers terminal, peduncle curved outwards or pendulous; tepals 9–11, the outer three obovate and leathery, 3.5 × 2.4 cm and yellowish green or green, inner tepals spathulate and fleshy, 2.8 × 1.4 cm and yellowish with a hint of purple at the base; stamens pinkish red; gynoecium sessile with 20–28 carpels, glabrous. Fruits 3.2–5.4 cm long and globose to ovoid; carpels elliptic, 1.6–2.2 cm long, and dehiscing along the dorsal suture or both the dorsal and ventral sutures. Flowering May to June, fruiting September to October (China). Chen & Nooteboom 1993. Distribution CHINA: Yunnan; VIETNAM. Habitat Mixed evergreen forest between 500 and 1700 m asl. USDA Hardiness Zone 7b. Conservation status Magnolia ovoidea (H.T. Chang & B.L. Chen) V.S. Kumar (treated as a distinct species) is Critically Endangered (IUCN), fewer than 50 individuals surviving in the wild. Magnolia conifera and var. chingii have not been evaluated. Illustration Chen & Nooteboom 1993. Taxonomic note There has been much confusion over the identity of this species and the related Manglietia chingii Dandy. Kumar (2006) recognises the latter as Magnolia conifera var. chingii (Dandy) V.S. Kumar, with a more easterly distribution in Guangdong and Guangxi. This variety can be distinguished from typical M. conifera by its longer petiole (2–3 cm), longer stamens (1.5–2 cm vs. ~1 cm), and elliptic outer tepals. Dick Figlar (pers. comm. 2006) believes that most plants in cultivation under the name M. conifera are actually var. chingii.

The taxonomic deliberations discussed above are not helped by a general confusion in cultivated plants as to the identity of plants labelled either Magnolia/Manglietia conifera or chingii. Sean Hogan (pers. comm. 2007) has found that successive batches of seed sent from Nanjing Botanic Garden as Manglietia chingii have given rise to a

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‘congested’ form of Magnolia insignis, recognisable by its naked leaf buds at the tips of the shoots. On the other hand, seed distributed from the Kunming Botanical Institute as Manglietia ovoidea has been correct for the broader species Magnolia conifera, with long-petiolate, elongated leaves and pendulous flowers. This confusion does not help assessments of garden performance, but a plant sold as M. conifera has survived for three winters for Thomas Methuen-Campbell at Penrice Castle in South Wales, and M. conifera var. chingii is doing well for Mike Robinson in East Sussex (Robinson et al. 2008). In Oregon plants grown as Manglietia ovoidea have long narrow leaves that emerge ‘a pleasing shell-pink’ (Hogan 2008). The leaves of Magnolia conifera are thick and a shiny dark green, reminiscent of those of M. grandiflora, while the pendulous white flower with its deep red stamens suggests M. sieboldii (Figlar 2008). M. cordata (NOW M. acuminata var. subcordata (Spach) Dandy) B647, S320, K268

Magnolia cylindrica E.H. Wilson

(Subgen. Yulania, Sect. Yulania)

The description for this species given by Bean (B648) in fact relates to a clone cultivated by Hillier Nurseries, now believed to be a hybrid (possibly Magnolia cylindrica × M. denudata), and named ‘Pegasus’ (Hunt 1998). The true species has since been introduced and is described here. Tree to 10 m, 0.3 m dbh. Bark smooth, greyish white. Branchlets purplish brown, glabrous or with yellowish appressed hairs when young. Leaves deciduous, papery, 8–15 × 3–9 cm, elliptic to obovate, upper surface dark green, glabrous, lower surface pale green with fine colourless hairs, 8–11 secondary veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole 0.7–1 cm long with yellowish appressed hairs; stipules densely pubescent, adnate to petiole. Flowers terminal, produced before the leaves, fragrant, white to purplish pink. Tepals nine, the outer three subulate, 2–2.5 cm long, the inner ones broadly spathulate to obovate and 6.5–10 cm long; stamens purple; gynoecium sessile with green carpels. Fruits pendulous, 5–7.5 cm long, cylindrical, pinkish red; ripe carpels woody, tuberculate, the follicles dehiscent with the upper part falling away to reveal the bright red seeds suspended on the central axis – a unique trait in the genus. Flowering May to June (March to April in cultivation), fruiting August to September (China). Chen & Nooteboom 1993, Spongberg 1998, Gardiner 2000, Liu et al. 2004. Distribution CHINA: Anhui, Fujian, Jiangxi, Zhejiang. Habitat Montane forests between 300 and 1700 m asl. USDA Hardiness Zone 4–5. Conservation status Vulnerable, due to habitat loss, firewood extraction and the collection of floral buds for medicine. Illustration NT485, NT486. Taxonomic note True M. cylindrica has dimorphic tepals, the outer three sepaloid, the remainder petaloid; the supposed hybrids derived from the 1936 introduction to the United States from the Lu-Shan Arboretum and Botanical Garden (of which ‘Pegasus’ is one) have nine petaloid tepals and do not fruit (Hunt 1998, Spongberg 1998). Comparative illustrations are given in Magnolias and their Allies (Hunt 1998).

The dust seems to have settled on the controversy over the identity of Magnolia cylindrica, and the true species is well established in collections throughout North America and Europe. Introductions have principally been through the agency of the seed lists of Chinese botanical gardens, but collections have been made by other expeditions, including vegetative propagations from trees in the Hwangshan, Anhui, collected in 1988 by Peter Bristol, Lawrence Lee and Peter Wharton. The oldest trees in cultivation seem to be two growing in the David C. Lam Asian Garden in Vancouver, from seed collected in Zhejiang and distributed by the Shanghai Botanic Garden in 1980, and now standing 8–10 m tall. The finest tree known in Europe is in Roy Lancaster’s garden in Hampshire

Plate 336. The finest specimen of Magnolia cylindrica known in Europe, in Roy Lancaster’s garden in Hampshire – seen here flowering prolifically – was grown from seed distributed by the Shanghai Botanic Garden. Image R. Lancaster.

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and is of the same provenance, although sown in 1984; first flowering in 1990 (Lancaster 1998), it has grown well ever since, reaching 11 m (24 cm dbh) by December 2006 (R. Lancaster, pers. comm. 2006) and flowering and fruiting prolifically each year. This tree and one grown by John Gallagher that is of similar height have a straight stem with ascending branches. The flowers are smaller than those of ‘Pegasus’, and the latter remains a very desirable garden tree. ‘Good magnolia conditions’ will suit all forms of M. cylindrica; it is interesting, however, that the Anhui grafts mentioned above grow in ‘deep forest conditions’ in Vancouver, but flower well every year (P. Wharton, pers. comm. 2007). Material from these has been distributed commercially by Otto Eisenhut’s nursery in Ticino, Switzerland (Eisenhut 2008). Plate 337. The fruits of Magnolia cylindrica are typical of section Yulania, comprised of ‘fused’ carpels – often very decorative in their own right. Image R. Lancaster.

M. dawsoniana Rehder & E.H. Wilson B648, S320, K269

Magnolia decidua (Q.Y. Zheng) V.S. Kumar

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia decidua Q.Y. Zheng Tree to 15 m, 45 cm dbh. Bark greyish white. Branchlets purple-brown with round pale lenticels, glabrous. Leaves deciduous, mostly terminal on the shoots, thin and leathery, 14–20 × 3.5–7 cm, oblong-obovate to elliptic, dark green and glabrous above, pale below with white hairs when young, midrib conspicuous above, lateral veins inconspicuous, margins entire, apex obtuse or shortly acute, base cuneate; petiole slender, glabrous or sparsely hairy, with stipule scars one-quarter to half of the length of the petiole. Flowers terminal, yellowish white and fragrant; tepals 15(–16), very unequal, the outermost three c. 7 × 2 cm, becoming shorter and narrower, until the inner three are almost linear; stamens numerous, with very short filaments; gynoecium sessile, elongate-ovoid. Fruits 4.7–7 × 4–5.5 cm, subglobose to ovoid, rufous at maturity with pale round lenticels, dehiscent along both sutures. Flowering May, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Jiangxi. Habitat Broadleaved forest between 450 and 650 m asl. USDA Hardiness Zone 8. Conservation status Endangered, with fewer than 500 individuals in only one known location. Illustration Liu et al. 2004.

Recognised only in 1995 (Cicuzza et al. 2007), and endangered in the wild, Magnolia decidua is unique in the otherwise entirely evergreen section Manglietia for the character that gives it its name. Specimens in cultivation also drop their foliage, but the brown leaves sometimes hang on the twigs for a while. Magnolia decidua is very rare in cultivation as well as in the wild, the only known specimens all being derived from seed obtained from China by Philippe de Spoelberch in 1999 and distributed by him. It is established at Arboretum Wespelaar, growing well below pines, and has reached 3 m although has yet to flower (P. de Spoelberch, pers. comm. 2007). At the Magnolian Grove Arboretum, Pickens, South Carolina it originally grew vigorously, but after planting out the saplings did not prosper and gradually died out for reasons that are not clear (R. Figlar, pers. comm. 2008). M. delavayi Franch. B649, S321, K269 M. denudata Desr. B650, S321, K269 M. denudata var. purpurascens (NOW M. sprengeri Pamp.) B650, K269 M. doltsopa (Buch.-Ham. ex DC.) Figlar (WAS Michelia doltsopa B738, K307)

Magnolia duclouxii (Finet & Gagnep.) Hu

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia duclouxii Finet & Gagnep. Tree 6–8 m. Branchlets slender, glabrous. Leaves evergreen, thin and leathery, 8–16 × 2.5–4 cm, oblanceolate to obovate-elliptic, dark green and glabrous above, greyish green and glabrous or with sparse appressed brown hairs and longer pale ones at the margin and on midrib below, 9–11 secondary veins on each side of the midrib, apex acuminate, base cuneate; petiole 1–1.2 cm, slightly grooved above, stipular scar 2–3 mm long.

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Flowers terminal, pinkish, fragrant; tepals nine, concave, obovate to broadly obovate, 2.6–4.5 × 1.5–2.5 cm, outer three tepals the largest; stamens numerous; gynoecium sessile with 45–55 carpels, ferruginous-pubescent. Fruits reddish, 5–6 cm long, ovoid-ellipsoid. Flowering May to June, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: southeast Sichuan, northeast Yunnan; VIETNAM. Habitat Evergreen broadleaved forest between 700 and 1800(–2300) m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Liu et al. 2004.

Magnolia duclouxii seems to be a rather small, almost dainty tree, with small flowers and short narrow leaves. It is in cultivation in Europe, as young plants, some specimens at least originating as seed from Kunming Botanical Garden, although it is also commercially available. Mike Robinson (pers. comm. 2008) has two young unflowered trees, 2 and 3 m high, that have been hardy since planting in 2000 and 2003, respectively. They have an upright habit, and their glory so far has been the ‘superb shining maroon young growth’. A plant at Arboretum Wespelaar was eaten by deer (K. Camelbeke, pers. comm. 2007).

Magnolia ernestii Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia wilsonii Finet & Gagnep., Michelia sinensis Hemsl. & E.H. Wilson, Michelia szechuanica Dandy Tree to 20 m. Branchlets yellow or black-brown, glabrous or tomentose. Leaves evergreen, thin, leathery, 11.5–14(–18) × 4–6 cm, obovate to elliptic, upper surface dark green and glossy with pubescence particularly on the midrib, lower surface glaucous with dense, minute yellowish brown hairs, 8–13 secondary veins on each side of the midrib, margins entire, apex short-acuminate; petiole 1.2–1.5 cm long and pubescent; stipules adnate to base of petiole, densely pubescent. Flowers on axillary shoots, yellowish white, fragrant, brachyblast 0.7–1 cm long with three (to four) bracts; tepals 9–12, 4–5 × 1–2.5 cm, obovate to spathulate; stamens green to yellow; gynoecium stipitate with many brown- or silver-tomentose carpels. Fruits 13.5–15.5 cm long, cylindrical; ripe carpels subglobose, purplish brown, 1–2 cm long with a hooked beak and lenticels. Flowering March to May, fruiting August to September (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guizhou, Sichuan, Yunnan. Habitat Forests and temple gardens between 600 and 2000 m asl. USDA Hardiness Zone 7a. Conservation status Near Threatened, with ongoing losses due to habitat destruction. Illustration Liu et al. 2004; NT487. Taxonomic note The epithet ernestii was given to commemorate Ernest Wilson, whose Magnolia takes precedence over his Michelia when the genera are combined.

Piroche Plants of British Columbia offered Magnolia ernestii (as Michelia wilsonii) and several other species in 1993, in one of the earliest ‘modern’ introductions of Asian evergreen magnolias. This material was rapidly passed around among enthusiasts, and in 1995 Sean Hogan gave a plant to the University of British Columbia Botanical Garden. This is now an extraordinary 16 m tall, forming a handsome big evergreen. In a good (i.e. wet) season it grows at over 60 cm per year. The top of this specimen was broken by snow in November 2006, but it was unaffected by the –9 °C experienced at the same time. The only problem with having it as such a large tree is that the flowers are almost invisible up in the crown, but they are so fragrant that their scent perfumes the air around (Wharton 2007). In Portland Sean Hogan and the late Parker Sanderson have used it as a street tree with great success, complementing older plantings nearby of Magnolia virginiana (var. australis). It is doing well in the few gardens where it has been planted in the United Kingdom, including a tree at Tregrehan that had reached about 8 m in 2007 (T. Hudson, pers. comm. 2007), but like many michelias it does appreciate a warm summer to perform at its best. It typically defoliates at about –6 °C, with the lamina detaching from the petiole, although the tree itself will tolerate lower temperatures, surviving equably to –12 °C and sometimes less (Hogan 2008).

Plate 338. The flowers of Magnolia ernestii are not very large and often somewhat invisible in the canopy, but are very strongly scented and will perfume the air around. Image Phytophoto.

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Magnolia figo (Lour.) DC.

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia figo (Lour.) Spreng., Michelia amoena Q.F. Zheng & M.M. Lin

This species was described by Bean (B738), who called it a ‘cheerful evergreen’ and assessed it as hardy in the milder parts of the British Isles. Several varieties have since been recognised, however, and a key for these is presented below. Recent selections available in commerce include ‘Port Wine’, ‘Purple Queen’, and ‘Stubbs Purple’ with a strong purplish suffusion through the tepals. ‘Stubbs Purple’ is said to be hardier than most (Eisenhut 2008). It is not clear if these darker-flowered cultivars are referable to var. figo or var. crassipes. The taxonomy of the plant formerly known as Michelia skinneriana is dubious (see below) but it is horticulturally distinct, and the name Magnolia figo Skinneriana Group is provided here to recognise these differences. 1a. Shrub or tree to 5 m tall; leaves 7–13 × 2.5–4 cm with 6–9 pairs of lateral veins; brachyblast 0.3–0.4 cm long; flowers purple or reddish purple with thin tepals 1.8–2 cm long, gynoecium shorter than androecium; China (north Guangdong, northeast Guangxi) ........................................................... var. crassipes 1b. Shrub or tree to 15 m tall; leaves 2–12 × 1.5–4.5 cm with 7–13 pairs of lateral veins; brachyblast 0.4–2.7 cm long; flowers white or yellow with thick tepals 1.5–2.5 cm long, gynoecium longer than androecium ...................................... 2 2a. Branchlets dark grey to brown; leaves with 7–12 pairs of lateral veins; China (Anhui, Guangdong, Guangxi, Jiangxi, Zhejiang) .................................................... var. figo 2b. Branchlets tan to tawny; leaves with 10–13 pairs of lateral veins; China (Fujian, Guangdong, Guangxi, Hunan, Jiangxi, Zhejiang) ...................... Skinneriana Group

Plate 339. The flowers of Magnolia figo var. crassipes differ from those of var. figo not only in the richness of their colour, but in their survival for a couple of days – the type being notorious for the fugacity of its blooms. Image Phytophoto.

Magnolia figo var. crassipes (Y.W. Law) Figlar & Noot. Syn. Michelia crassipes Y.W. Law Var. crassipes appears to be reasonably distinct from typical Magnolia figo, as its flowers are a different colour (purple, vs. creamy white or yellow in var. figo) and it forms a small tree of 5 m or less. It also has a short, stout brachyblast and fewer lateral veins in the leaves. Figlar 2005b. Distribution CHINA: northern Guangdong, northeast Guangxi, southern Hunan. Habitat Forests between 300 and 700 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Liu et al. 2004; NT488.

In addition to the botanical distinctions noted above, var. crassipes has certain horticultural differences that make it more useful in the garden than var. figo. Most valuable of these is that its flowers last for two to three days, instead of one, and are a good dark red. The plant itself tends to be of denser habit and has thicker leaves.

Magnolia figo Skinneriana Group Syn. Michelia skinneriana Dunn See key above. Figlar 2005b. Distribution CHINA: Fujian, Guangdong, Guangxi, Hunan, Jiangxi, Zhejiang. Habitat Forests below 1200 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Liu et al. 2004.

In preparing this account it was found that the name skinneriana had not been validly transferred to Magnolia figo, and correspondence with Magnolia taxonomist Dick Figlar ensued (pers. comms. 2006, 2007). His advice is that the name should be placed in synonymy with M. figo var. figo, as proposed by Chen & Nooteboom

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(1993), but that it is worth maintaining the connection with the horticultural entity by referring to it as M. figo Skinneriana Group. Members of this group seem to be much more vigorous, tree-forming plants than the other somewhat shrubby varieties of M. figo, and will form a straight-growing main trunk. One in the Chinese Garden in central Portland is now approximately 8 m tall (S. Hogan, pers. comm. 2007). Its flowers are paler than the deep cream of var. figo and lack any reddish staining. Specimens are reported to have survived –20 °C without damage in the United States (Hogan 2008), and it is hardier than M. figo in southern England (M. Robinson, pers. comm. 2008).

Magnolia floribunda (Finet & Gagnep.) Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia floribunda Finet & Gagnep. Tree to 28 m, 1 m dbh. Bark smooth and grey. Branchlets slender and brown to purplish brown to purplish black; initially with greyish white or yellowish brown hairs, though quickly glabrous. Leaves evergreen, thin and leathery, 6–14.5(–17) × 1–4.5(–5) cm, narrowly elliptic to ovate or lanceolate, upper surface dark green and glossy with sparse, clear hairs particularly on the midrib, lower surface glaucous or not, with sparse, rather long, dark or clear hairs, 8–14 secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 0.9–2.5 cm long and pubescent; stipules adnate to the petiole and densely pubescent. Flowers on axillary shoots, white and fragrant, brachyblast 0.3–0.8 cm long with three (to four) bracts; tepals 12–15, spathulate to broadly obovate or oblanceolate, constricted at the base and 2.5–3.5 cm long; stamens yellow; gynoecium stipitate. Fruits 2.5–6 cm long and cylindrical or twisted; ripe carpels subglobose, brown and lenticellate, 0.7–2 cm long and beaked. Flowering February to June, fruiting July to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangxi, Guizhou, Hubei, Jiangxi, Sichuan, Yunnan; LAOS; MYANMAR; THAILAND; VIETNAM. Habitat Forests between 800 and 2700 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Liu et al. 2004; NT489.

Four large trees at Caerhays Castle, Cornwall have been identified as Magnolia floribunda by Owen Johnson, the largest being 20 m tall with a trunk diameter of 103 cm at 50 cm above the ground (TROBI). The others are 16 m tall or more, and all presumably date from an introduction before World War II. With this impressive record of survival and growth it would seem well worth trying it in suitable mild sites throughout maritime Europe and along the American West Coast, as well as in the milder parts of the southeastern United States. At Tregrehan plants of Vietnamese origin are building up steadily and getting better each year, having now reached about 4 m (T. Hudson, pers. comm. 2007), while in Oregon trees of 5–6 m are beginning to flower sparsely (S. Hogan, pers. comm. 2007). A collection made by Dan Hinkley (DJHC 548) in northwest Yunnan in 1996 is proving vigorous in Vancouver (Wharton 2007) and was not affected by –9 °C in November 2006, when its branches bowed but did not break under a deep load of wet snow (P. Wharton, pers. comm. 2007). The glaucous underside of the leaves in some forms is very attractive, while the silky new growth makes this a very tactile tree. Young specimens have an open, airy appearance and form a pyramidal shape, but become denser and more rounded with age (Hogan 2008).

Plate 340. Narrow tepals and the glaucous leaf undersides of some clones make Magnolia floribunda quite distinct among its relatives in section Michelia. Image Phytophoto.

Magnolia ×foggii Figlar

Magnolia ×foggii Figlar, Proc. Internat. Symp. Fam. Magnoliac. 1998: 21–22, 2000, nom. inval., no holotype cited (Art. 37.1). Holotypus: USA: North Carolina, Raleigh, North Carolina State University Arboretum (now JC Raulston Arboretum), Alice B. Russell 127, 5 April 1994 (NCSC).

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia ×foggii Savage, nom. nud. Tree to 20 m. Leaves thin and leathery, 10–18 × 4–6 cm, elliptic, upper surface glossy green and glabrous, lower surface pale green with sparse rufous pubescence. Flowers on axillary shoots, fragrant, white to cream or with pink edges, 10–13 cm diameter; stamens yellow. Figlar 2000. Distribution In cultivation only. USDA Hardiness Zone 7b. Illustration Liu et al. 2004; NT490.

This artificial hybrid is the result of a cross between Magnolia figo and M. doltsopa made in 1972 by John M. Fogg, a magnolia enthusiast and one-time Director of the Morris

Nomenclatural novelty Magnolia ×foggii Figlar nothosp. nov.

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Arboretum. It combines the good qualities of its parents to make erect, vigorous handsome shrubs up to 6 m tall (potentially taller) with dense dark foliage, widely used for landscaping purposes in the southern United States, and even recommended for hedging (Virtual Plant Tags 2008). A number of clones have been selected and named, of which probably the best known are ‘Allspice’, with large pure white flowers and very strong fragrance, and ‘Jack Fogg’, with medium to large flowers, the tepals white with a purple edge. A tree of ‘Jack Fogg’ planted by John Gallagher over 15 years ago in Dorset is 11–12 m tall, still growing well, and flowers abundantly each year. This individual has never been damaged by frost (J. Gallagher, pers. comm. 2007), and the cultivar is reported to suffer little damage even at –18 °C in the southeastern United States (Hogan 2008). Hardiness differs between clones, however, and ‘Picotee’ is less hardy than the two mentioned above (K. Hughes, pers. comm. 2008). As its name suggests, this latter clone also has white tepals edged with reddish purple. Plate 341. Magnolia ×foggii, offspring of crosses between two well-known species, is a precursor of many hybrid evergreen magnolias to come. This is ‘Allspice’ at Tregrehan. Image J. Grimshaw.

Magnolia fordiana (Oliv.) Hu

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia fordiana Oliv.

Magnolia fordiana var. fordiana Tree to 30 m, 1.5 m dbh. Bark smooth and greyish brown. Branchlets glabrous and yellowish brown. Leaves evergreen, thin and leathery, 8–16(–20) × 2.5–5.4(–7) cm, narrowly obovate to elliptic, both surfaces glabrous, or with minute hairs below, 8–12(–17) secondary veins on each side of the midrib, margins entire, apex caudate-acuminate; petiole 1.4–4.2 cm long; stipules covered with ferruginous hairs, adnate to the base of the petiole. Flowers terminal, pure white and fragrant; tepals nine, concave, obovate to elliptic, 5.5–7 × 2.5–4 cm, outer three tepals slightly larger, 6–7 × 3–4 cm; stamens pinkish red; gynoecium sessile with (12–)24–36 carpels, glabrous. Fruits pinkish purple, 2.5–6 cm long, ovoid; ripe carpels 1.3–1.7 cm long, and dehiscing along both the dorsal and ventral sutures. Flowering April to May, fruiting August to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hong Kong, Hunan, Jiangxi, Yunnan; VIETNAM. Habitat Subtropical evergreen broadleaved forest between 500 and 1300 m asl. USDA Hardiness Zone 6b–7a. Conservation status Not evaluated. Illustration Liu et al. 2004. Taxonomic note Three additional varieties exist within the M. fordiana complex: var. calcarea (X.H. Song) V.S. Kumar with glabrous branchlets and leaves, and narrowly elliptic carpels (Guizhou); var. forrestii (W.W. Sm. ex Dandy) V.S. Kumar with brown pubescence on the branchlets, stipules, leaf undersides and petioles, and larger leaves, 24.5 × 9.6 cm (Guangxi, Yunnan; Myanmar); and var. kwangtungensis (Merr.) V.S. Kumar with rufous indumentum, and smaller flowers with many more (44–49) carpels (Guangdong, Guangxi). See also Magnolia yuyuanensis.

Notes made on different coasts of the United States, two years apart, both compare Magnolia fordiana to a Ficus (of the F. elastica persuasion), on account of its glossy, broad, leathery leaves. The two trees observed were at Quarryhill (2.5 m in 2004) and the US National Arboretum (4 m in 2006) but both shared the same strictly upright stems and short spreading branches that give young trees a conical shape. Growth can be rapid, the Quarryhill tree putting on 75 cm in a year (W. McNamara, pers. comm. 2004), but specimens grown in Vancouver from a collection made by Peter Bristol, Lawrence Lee and Peter Wharton in 1988 in southern Anhui province have not performed very well, being apt to be chlorotic and of unattractive shape. Their branches are also prone to break under the weight of snow (Wharton 2007). Magnolia fordiana seems to be able to tolerate cold to about –6 °C (S. Hogan, pers. comm. 2007). It is

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Magnolia

491

still scarce in the United Kingdom but young plants are growing at Tregrehan. Dick Figlar (pers. comm. 2007) cautions that many plants in cultivation labelled M. fordiana are probably the very closely related M. yuyuanensis (see p. 504). M. fordiana var. forrestii (W.W. Sm. ex Dandy) V.S. Kumar (WAS Manglietia forrestii B719, K298)

Magnolia foveolata (Merr. ex Dandy) Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia foveolata Merr. ex Dandy Tree to 45 m, 0.9 m dbh. Bark pale or dark grey. Branchlets yellow or brown with short yellow or brown hairs; older branchlets purplish brown, lenticellate. Leaves evergreen, rigid and leathery, 9.5–26 × 4.5–12.5 cm, obovate to elliptic, upper surface dark green and glossy with brown or clear hairs particularly on the midrib, lower surface densely covered with russet brown hairs (occasionally silvery in var. cinerascens), 12–16 secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 1.5–3.5 cm long without scars; stipules free from the petiole, densely tomentose. Flowers on axillary shoots, pale yellow to white or greenish white, fragrant, brachyblast 1.3–2.5 cm long with three to four (to five) bracts; tepals 9–12, spathulate to broadly obovate, purple at base, 3–4.5 cm long; stamens yellow with purple filaments; gynoecium stipitate with many tomentose carpels. Fruits 5.5–14 cm long, cylindrical; ripe carpels subglobose or obovoid, black-brown, lenticellate, 0.8–2.2 cm long, beaked. Flowering March to April, fruiting September to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Yunnan, Zhejiang; VIETNAM. Habitat Evergreen broadleaved and mixed forests between 500 and 1800 m asl. USDA Hardiness Zone 7a. Conservation status Not evaluated. Illustration Liu et al. 2004; NT473, NT491. Taxonomic note Liu et al. (2004) recognise M. foveolata var. cinerascens Y.W. Law & Y.F. Wu, a minor variant with greyish white hairs on the branchlets, petioles and lower leaf surfaces. Young plants are in cultivation.

Magnolia foveolata was first introduced from Nanjing Botanic Garden by Piroche Plants in 1993 and is a beautiful and distinctive species with amazing russet appressed indumentum on all parts, that shimmers in the light. This, coupled with the breadth and rigidity of the leaves, confers considerable grandeur on the tree; Peter Wharton commented that when mature and flowering it will ‘give Magnolia grandiflora a run for its money’ (Wharton 2007). In the wild specimens can be huge, but cultivated individuals are all still small, and flowering has yet to occur in either Cornwall or western America (S. Hogan, T. Hudson, pers. comms. 2007). The flowers are large, with creamy white tepals, and have comparatively large reddish anthers and a prominently exserted gynoecium. It has proved completely hardy in Vancouver (Wharton 2007), with only minimal damage from snow in November 2006 and none from the cold. M. fraseri Walter B651, S321, K269

Magnolia fulva (H.T. Chang & B.L. Chen) Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia fulva H.T. Chang & B.L. Chen Tree to 16 m, 0.5 m dbh. Bark dark grey. Branchlets dull brown with long brown or rufous hairs. Leaves evergreen, leathery and somewhat rigid, (14–)18–24(–29) × 7–10(–12) cm, obovate to elliptic, upper surface dark green with scattered pubescence, lower surface glaucous with long brown or rufous hairs or glabrous, 12–14 secondary veins on each side of the midrib, margins slightly revolute, apex acute to short-acuminate; petiole 2.7–4 cm long and pubescent; stipules with long silky hairs outside, leathery and free from the petiole.

Plate 342. Magnolia foveolata – a clone selected by Akira Shibamichi for its particularly handsome foliage. There is much potential for elite cultivars among the mass of seedling evergreen magnolias now available. Image R. Figlar.

492

Magnolia

New Trees

Flowers large, on axillary shoots, fragrant, initially white, but turning pale yellow, brachyblast 2–2.2 cm long with two to three tomentose bracts; tepals 12–13, fleshy, obovate to elliptic and 4.4–5.3 cm long, the inner tepals slightly smaller than the outer three; stamens yellowish brown; gynoecium stipitate with ~152 pubescent carpels. Fruits spicate; ripe carpels ovoid, woody, 1–1.5 cm, short-beaked. Flowering April, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Yunnan. Habitat Forests on limestone between 1690 and 1950 m asl. USDA Hardiness Zone 9b. Conservation status Not evaluated. Illustration Chen & Nooteboom 1993.

Var. fulva is apparently rare in cultivation. A young plant at Quarryhill, grown from Yunnanese seed in 1999, seems to be this taxon, as a juvenile, but maturity will tell.

Magnolia fulva var. calcicola (C.Y. Wu ex Y.W. Law & Y.F. Wu) Sima & Yu Syn. Michelia calcicola C.Y. Wu ex Y.W. Law & Y.F. Wu Var. calcicola forms a small tree 3–8 m tall. The branchlets are covered in thick, yellow woolly tomentum and the leaves are 13–18 × 4.5–7 cm. Stipules are free from the petiole. The flowers are yellow with nine tepals and glabrous carpels, appearing in mid- to late spring. Liu et al. 2004. Distribution CHINA: Guangxi, Yunnan. Habitat Broadleaved forests between 590 and 1500 m asl. USDA Hardiness Zone 8b. Conservation status Not evaluated, but Magnolia ingrata (see Taxonomic note below) is considered Endangered. Illustration Liu et al. 2004. Taxonomic note This variety is treated as a distinct species by Liu et al. (2004), and as a synonym of the very poorly known Michelia ingrata B.L. Chen & S.C. Yang by Chen & Nooteboom (1993). The latter (now Magnolia ingrata (B.L. Chen & S.C. Yang) Figlar) is regarded as a full species by Liu et al. (2004) but Dick Figlar (pers. comm. 2007) advises us that it and M. fulva var. calcicola are probably synonymous.

This taxon, whatever its correct nomenclature, is an exciting plant that will need further observation to ascertain its garden merits, but on early acquaintance seems to promise something special. It combines rather glaucous leaves with golden indumentum and yellow flowers, which have been produced in its fifth year from seed. At first the growth is rather inelegant and sparse, but older specimens begin to thicken up (Hogan 2008). Although it has survived –7 °C in Portland as young plants, its ultimate hardiness is not known, but as it comes from further north than var. fulva it is likely to be somewhat more hardy (R. Figlar, pers. comm. 2007). Young plants are in cultivation at Tregrehan but have not yet been planted outside (T. Hudson, pers. comm. 2007). Some confusion has arisen over the erroneous use in Kunming Botanical Garden and in literature (for example, in Hunt 1998) of the name Michelia xanthantha for this plant. Dick Figlar writes (pers. comm 2007): ‘The true Magnolia xanthantha (C.Y. Wu ex Y.W. Law) Figlar has glabrous leaves and buds with yellowish flowers of only six tepals. This is different from the very hairy leaves, buds, and stems of M. fulva var. calcicola, which also has nine-tepalled flowers. Sima Yongkang has not been able to find a living plant of the M. xanthantha but he believes that it probably belongs with M. martinii whose description it closely resembles. Whatever it is, it is not in cultivation outside of China, and may not even be in cultivation there!’ M. globosa Hook. f. B652, S321, K269

M. grandiflora L. B652, S322, K270

Magnolia grandis (Hu & W.C. Cheng) V.S. Kumar

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia grandis Hu & W.C. Cheng Tree to 20 m, 0.35 m dbh. Branchlets glabrous, pale grey and waxy. Leaves evergreen, leathery, 20–35.5 × 10.5–13 cm, narrowly obovate, upper surface glossy green and glabrous, lower surface densely covered with white powdery dots, 17–26 secondary veins on each side of the midrib, margins entire, apex acuminate; petiole 2.6–4 cm long; stipules adnate to the base of the petiole. Flowers terminal, large, pale red and fragrant; tepals 12, outer three thin, obovate to oblong, 9–11 cm long, inner tepals fleshy, obovate to spathulate, 8–12 cm long and with dark red lines in the upper portions; stamens red; gynoecium sessile with 90–110 carpels. Fruits pinkish purple, 10–16 cm long, oblong to ovoid; ripe carpels 3–4 cm long with a sharp, slightly recurved beak,

Section II. Species Accounts

Magnolia

493

dehiscing along both the dorsal and ventral sutures. Flowering May to June, fruiting October to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: southwest Guangxi, southeast Yunnan. Habitat Evergreen broadleaved forest on limestone mountains between 800 and 1500 m asl. USDA Hardiness Zone 9. Conservation status Critically Endangered, due to habitat destruction. Illustration Chen & Nooteboom 1993, Liu et al. 2004.

Potentially a very grand plant indeed, Magnolia grandis is being assessed for its tolerances in western North America, with very limited material also being grown in Europe. The first introduction was made by Roger Warner in the mid-1980s, as seed obtained from a Chinese collector, and most if not all plants in cultivation derive from this source (K. Hughes, pers. comm. 2008). As always, the choice of site is extremely significant, shelter from both wind and sun, constant moisture and protection from frosts being important. Experiences in the Pacific Northwest suggest that it is able to tolerate short spells at about –8 or –9 °C, but –12 °C has killed young plants in Vancouver (Hogan 2008). When young and in a suitable site it can grow very rapidly indeed. One plant at Quarryhill accessioned in 1999 had achieved 6 m by 2004 (although sunburnt leaves, observed at this time, suggest that it is not in an ideal site), and Hogan (2008) records growth rates of up to 1.2 m per year at Camellia Mountain Botanical Garden in California. Both Sean Hogan and I (JMG), on first seeing the species, were struck by its similarity to a rubber plant Ficus elastica Roxb. ex Hornem., but unlike that ambivalent species (magnificent as a tree in appropriate climates, sad as a houseplant), the broad leaves of Magnolia grandis are complemented by the glaucous waxiness of the new shoots and the long pale red stipules peeling away as the leaves emerge. On first appearance, at least on the Quarryhill specimen observed, the leaves are bronzed, becoming dull mid-green with a slightly glaucous underside. The species is rare in Europe but there is a young tree of about 4 m at Tregrehan, again derived from Roger Warner’s introduction, imported to the United Kingdom in 1988 by Kevin Hughes (pers. comm. 2008). No tree has yet flowered in cultivation, but the large, deep pink flowers should be worth waiting for. M. ×highdownensis (NOW M. wilsonii (Finet & Gagnep.) Rehder) B665, K270 M. hypoleuca (NOW M. obovata Thunb.) B653, S324, K270 M. insignis Wall. (WAS Manglietia insignis B719, K298; incl. Manglietia hookeri Cubitt & W.W. Sm. B719, K298) M. kobus DC. B655, S324, K271 M. kobus var. borealis (NOW M. kobus DC.) B655, K271

Magnolia kwangtungensis Merr. (Subgen. Magnolia, Sect. Manglietia) Syn. Manglietia moto Dandy, Magnolia moto (Dandy) V.S. Kumar Tree to 20 m, 0.6 m dbh. Bark dark grey with prominent lenticels. Branchlets densely covered with long, curly, dark brown or rufous hairs. Leaves evergreen, leathery, 11–19 × 5–7 cm, obovate, upper surface glossy green and glabrous, lower surface pale green with scattered undulate or curly dark brown hairs, 9–19 secondary veins on each side of the midrib, margins entire, apex mucronate or acuminate; petiole 1.5–3.7 cm long and densely pubescent; stipules covered in dense, rusty tomentum, adnate to the petiole. Flowers terminal, creamy white and fragrant, peduncle curved outwards or pendulous; tepals nine, outer three leathery, oblong to ovate and 3.5–5.7 cm long, inner tepals fleshy, spathulate to obovate and 9–12 cm long; stamens red; gynoecium

Plate 343. Magnolia kwangtungensis has rounded, pendulous flowers carried on long pedicels covered in rufous hairs. Image R. Figlar.

494

Magnolia

New Trees

sessile with 48–71 carpels. Fruits 5–7 cm long, ovoid; ripe carpels tuberculate, with a short beak. Flowering May to June, fruiting August to September (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Fujian, Guangdong, Guangxi, Hunan, Yunnan. Habitat Mixed forest between 400 and 1200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Liu et al. 2004; NT493.

While less spectacular in leaf dimensions and pubescence than Magnolia megaphylla, its relative M. kwangtungensis seems to be a much more amenable garden tree, flowering freely from about 10 years of age and tolerating –18 °C or colder with impunity in the JC Raulston Arboretum (Hogan 2008), although accounted among the less hardy by Figlar (2008). It is also somewhat more tolerant of sun and dry spells, but a sheltered moist location should still be the aim. An introduction made by Cliff Parks of Chapel Hill, North Carolina as seed collected in Guangdong Province in 1992 seems to have been the first, and the source of much of the stock in American cultivation. A tree at Camellia Forest Nursery is now 10 m tall (Figlar 2008), and as noted above, there is another at the JC Raulston Arboretum. Planted in 1995, this was only 4 m tall in 2006 but is doing well, forming a straight tree with dense foliage. The rufous pubescence on the twigs and petioles is a conspicuous feature of M. kwangtungensis, but it is much sparser on the leaf undersides than in M. megaphylla. A tree at Quarryhill is also 4 m tall, from a 1999 accession, but its foliage is sun-scorched and it has been damaged by frosts. Once again, high heat and humidity seem to be necessary for good growth. In Dorset (not noted for either of these climatic effects) John Gallagher’s specimen has gained a grand 15 cm in five years (pers. comm. 2007), while Kevin Hughes’ plant in Hampshire was killed outright by –6 °C following the cool summer of 2007.

Magnolia laevifolia (Y.W. Law & Y.F. Wu) Noot.

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia yunnanensis Franch. ex Finet & Gagnep., Magnolia dianica Sima & Figlar Shrub or small tree to 12 m. Branchlets green or greyish brown to purple, covered in red, brown, black or grey, appressed or spreading hairs; the hairs can also be found on the buds, stipules, petioles, brachyblasts and carpels. Leaves evergreen, leathery or membranous, 2–10 × 1–4 cm, obovate to elliptic, upper surface bright green with brown pubescence, lower surface greenish with dense or sparse pubescence initially, seven to nine secondary veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole stout, 0.5–1 cm long and pubescent; stipules adnate along almost the whole length of the petiole, pubescent outside. Flowers on axillary shoots, yellowish or greenish white and heavily scented, brachyblast 0.4–1.4 cm long with three bracts; tepals 6–12(–17), the outer three or four obovate to elliptic, constricted at the base and 2.2–3.5 cm long, the inner tepals oblong to spathulate and 2–2.2 cm long; stamens golden yellow; gynoecium stipitate with ≤ 15 carpels. Fruits 1–4.5 cm long and spicate; ripe carpels subglobose, dull brown, 0.7–1.4 cm long with a long beak and lenticels. Flowering March to April, fruiting August to September (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guizhou, Sichuan, Yunnan. Habitat Montane forest and thickets between 1100 and 2300 m asl. USDA Hardiness Zone 7a. Conservation status Not evaluated. Illustration Liu et al. 2004; NT10, NT475, NT477, NT495. Taxonomic note The transfer of Michelia and other genera into Magnolia has led to various nomenclatural problems. Among these, Parakmeria yunnanensis became Magnolia yunnanensis first, leaving no room for Michelia yunnanensis to retain its specific epithet in the genus Magnolia. In consequence a new name was required and the epithet laevifolia – a synonym in Michelia for Michelia yunnanensis – was chosen by Figlar. Unfortunately the publication in Magnolia was originally deemed invalid; in consequence the name Magnolia dianica was coined and this has to some extent been adopted in the literature, but a closer look at the Botanical Code has since enabled the name laevifolia to be validated in Magnolia by Nooteboom, and this should now be used.

Magnolia laevifolia, still often known as Michelia yunnanensis or Magnolia dianica, is one of the very best of the michelias for widespread garden use, with plants thriving on both sides of North America and in maritime Europe, including in gardens in Belgium and the Netherlands: Koen Camelbeke (pers. comm. 2007) reports seeing it flowering spectacularly in the garden of Wim Rutten in Leende, the Netherlands. It seems to have

Section II. Species Accounts

Magnolia

reached gardens as Michelia yunnanensis in the 1980s, the first known introduction being as seed from Kunming Botanical Garden, received by Glyn Church in New Zealand in 1986 (Church 2002). Material imported from New Zealand in the mid1990s by Tom Hudson (pers. comm. 2008) was probably the first introduction to the United Kingdom. It is probable that it had been introduced earlier to the United States as M. crassipes, and seed lots from Kunming have also been received in North America (S. Hogan, pers. comm. 2008). There have been occasional wild collections as well, such as DJHC 27, from Aan Feng Yin, Yunnan in 1996. It is more often seen as a shrub than as a tree, forming a wide bush of dark green foliage often spangled with its white flowers emerging from russet buds as it repeat-flowers through the season. The blooms are extremely fragrant and the scent will waft around the garden. Fruit is usually set rather prolifically and can be quite attractive in its own right. Magnolia laevifolia is equally happy in full sun (including the hot hillsides of Quarryhill) or shade, and seems to be lime-tolerant, Kevin Hughes (pers. comm. 2007) reporting a plant growing well on chalky soil in southern England without chlorosis. A young plant growing on in a pot at Colesbourne and irrigated only with water from the limestone aquifer shows no sign of chlorosis after two years. It is variable in size and habit and some good selections are being made, including the broad-tepalled clone ‘Velvet and Cream’ from New Zealand. Forms with pink in the flower are also being developed there (T. Hudson, pers. comm. 2007). In Europe a clone has been illegitimately named ‘Summer Snowflake’ (this is a vernacular name for Leucojum aestivum and not available as a cultivar name), and in the United States Tony Avent of Plant Delights Nursery, North Carolina has named a particularly floriferous clone ‘Michelle’, for his wife. Remarkably, seedlings can flower in their second year (K. Hughes, pers. comm. 2008).

Magnolia lanuginosa (Wall.) Figlar & Noot.

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia lanuginosa Wall., Michelia velutina DC. Tree to 20 m, 0.9 m dbh. Bark dull brown. Branchlets brown or purplish black with short appressed or spreading undulate or curly hairs. Leaves evergreen, papery or thin and leathery, (6–)11–24(–30) × (2.5–)3.5–6.5(–8.5) cm, elliptic, upper surface dark green and glabrous or with scattered undulate hairs particularly on the midrib, lower surface pale green with a dense covering of long brown or clear hairs, almost velvety, 11–23(–28) secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 0.9–2.3 cm long and

495

Plate 344. Magnolia laevifolia was formerly known as Michelia yunnanensis – and, temporarily, as Magnolia dianica. Under any name it is a superb, floriferous addition to horticulture, and tolerant of a wide range of conditions. Image J. Grimshaw.

496

Magnolia

New Trees

densely pubescent; stipules with dense pubescence on the outside, adnate to the petiole. Flowers solitary, on axillary shoots, yellowish white and very fragrant, brachyblast 0.4–1.7 cm long with three pubescent bracts; tepals 10–12(–13), spathulate to elliptic and clawed at the base, 2.2–5.5 cm long; gynoecium stipitate with ~35 densely pubescent carpels. Fruits 3.5–13 cm long and oblong; ripe carpels ovoid to ellipsoid, dull brown and densely lenticellate, 0.7–2.5 cm long. Flowering May to June, fruiting August to September (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution BHUTAN; CHINA: southern Xizang, northwest Yunnan; NEPAL. Habitat Mixed forests between 1500 and 2300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Liu et al. 2004.

Magnolia lanuginosa is in cultivation in the western United States and in Cornwall but has yet to make much impact, principally because it is rather slow to flower, reaching about 6 m before it does so in Oregon (S. Hogan, pers. comm. 2007). It seems to be related to M. maudiae, but the creamy flowers appear later in spring. At Tregrehan it is growing well from a collection by Keith Rushforth made at 2400 m in Bhutan in the early 1990s (KR 1784). It is ‘reasonably hardy’ there but seems to be missing enough light to flower freely (Hudson 2004) – illustrating the difficulties in siting such trees, that need shelter but also good light. The densely pubescent long, pointed leaves are attractive. M. liliiflora Desr. B656, S326 (as M. quinquepeta), K271 M. ×loebneri Kache B657, S325, K272

Magnolia lotungensis Chun & C.H. Tsoong (Subgen. Gynopodium, Sect. Gynopodium) Syn. Parakmeria lotungensis (Chun & C.H. Tsoong) Y.W. Law

Plate 345. Some clones of Magnolia lotungensis have excellent red new growth and should be sought out. The leaves are always small and neat. Indeed, this should be considered principally as a foliage tree, the flowers, when (or if) produced, being small and inconspicuous. Image R. Figlar.

Tree to 30 m, 0.9 m dbh. Bark pale brown or grey. Branchlets dull greenish brown and glabrous with distinctive bamboo-like internodes. Leaves evergreen, leathery and glabrous, 6–11 × 2.5–3.5(–5) cm, elliptic, upper surface glossy dark green, lower surface green or brownish green, 9–13 secondary veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole 1.5–2 cm long; stipules free from the petiole. Flowers terminal and androdioecious; staminate flowers pale yellow with 9–12 tepals, tepals thin, obovate to oblong and 2.5–3.5 cm long, stamens 30–70 with purplish red filaments; hermaphrodite flowers similar, but smaller, stamens 10–35, also with purplish red filaments, gynoecium sessile with 10–20 (rarely fewer) green carpels. Fruits red, 3.5–4.5 cm long, oblong to ovoid; ripe carpels 1.8–2.2 cm long, turning brown with a short beak, dehiscing along the dorsal suture. Flowering April to May, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hainan, Hunan, Sichuan, Zhejiang. Habitat Broadleaved forest between 700 and 1700 m asl. USDA Hardiness Zone 6b–7a. Conservation status Endangered. Illustration Liu et al. 2004; NT496. Taxonomic note Based on their examination of herbarium specimens, Chen & Nooteboom (1993) treated Magnolia lotungensis as a variety of M. nitida W.W. Sm., but it has since been shown to be a hexaploid and genetically quite distinct from M. nitida (Chen et al. 2000); it also has purple-red coloured stamens, compared to white in M. nitida, and its flowers are androdioecious, rather than bisexual as in M. nitida. Recently Lin et al. (2006) have suggested that the very similar M. omeiensis (Hu & C.Y. Cheng) Dandy be merged with M. lotungensis, but this approach has not been adopted for the forthcoming revised edition of the World Checklist and Bibliography of Magnoliaceae (Govaerts & Figlar, in prep.) (R. Figlar, pers. comm. 2008).

This species is relatively widely grown, and is perhaps most to be valued for its stature, as a potentially tall but narrow evergreen tree, whose small glossy dark green leaves can flush bronze to purplish red. Certainly its flowers are disappointingly small, and likely to be more or less invisible among the foliage when the trees finally get round to producing them (no trees have yet been known to flower in cultivation: Figlar

Section II. Species Accounts

Magnolia

2008). It was introduced in 1993 by Piroche Plants, and has been planted widely in the United States and British Columbia. Seedlings are rather variable, and Sean Hogan (pers. comm. 2007) reports that several selections have been made for superior foliage qualities, including one with brilliantly red new growth, the colour persisting into summer, and another with a slightly bluish sheen to the leaves. Wharton (2007) also praises the red-flushing clones. It is almost impossible to root from cuttings but grafts very easily onto stocks of section Yulania, so it should be possible to increase stocks of desirable clones very rapidly (Figlar 2008). Young trees seen in 2006 at the JC Raulston Arboretum and at Plant Delights Nursery in North Carolina were thriving, forming good straight-stemmed trees that were well clad with glossy leaves. Fortunately this lovely tree seems to be remarkably hardy, and has shown no cold damage in either the Portland area (where trees are up to 8 m tall), or Vancouver (over 4 m tall) where temperatures of –9 °C were recorded in the winter of 2006–2007. It has been reported to withstand –18 °C without damage (Hogan 2008). Although it is commercially available in the United Kingdom, the only specimen here traced in our research is a young one of about 3 m, flourishing at Tregrehan.

Magnolia macclurei (Dandy) Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia macclurei Dandy Tree to 30 m, 1 m dbh. Bark smooth and grey-white. Branchlets yellowish or purplish brown with a dense covering of short brown, rufous or clear hairs. Leaves evergreen, leathery, 6.5–14 × 4–6.5 cm, elliptic to ovate, upper surface dark green with silky hairs, lower surface covered with rufous or yellowish hairs, 10–15 secondary veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole 2.5–4 cm long; stipules with a dense covering of short brown, rufous or clear hairs, free from the petiole. Flowers solitary or in groups of two to three, on axillary shoots, white and very fragrant, brachyblast 1–1.3 cm long with scars from three bracts; tepals 9–12, the outer three narrowly obovate to spathulate, 3.5–4.5 cm long, the inner tepals smaller than the outer ones; stamens purple; gynoecium stipitate with ~28 carpels. Fruits 3–7 cm long and cylindrical; ripe carpels ellipsoid or subglobose, dull brown and sometimes lenticellate, 1.5–2.3 cm long. Flowering March to April, fruiting September to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangdong, Guangxi, Hainan; VIETNAM. Habitat Evergreen broadleaved forests between 500 and 1000 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Liu et al. 2004. Taxonomic note Liu et al. (2004) and the Magnolia Society (Figlar 2005a) recognise M. macclurei var. sublanea Dandy, a minor variant with slightly larger flowers and densely tomentose branchlets, petioles, stipules and bracts. The species is closely related to M. mediocris (Dandy) Figlar and is included in it by some.

Magnolia macclurei is represented in cultivation only by small young plants, but it has flowered at a reasonable 2.5 m in Portland (S. Hogan, pers. comm. 2007). The flowers are a good white and possess an excellent fragrance. Figlar (2001) records how ‘when Floyd McClure discovered this species on a mountainside in Guangdong Province (near Canton or Guangzhou) in 1925, he remarked in his notebook, “The fragrance of the flowers is the most intoxicating I ever breathed.” ’ A photograph in Magnolias of China (Liu et al. 2004) shows a tree absolutely laden with blooms, which must be an incredible visual and olfactory experience. Whether it will ever perform well in our area remains to be seen. It comes from low, hot regions, and in the United States is most likely to succeed in Florida. It was introduced to the United Kingdom by Kevin Hughes, who through his nursery Kevin Hughes Plants, Heale Gardens, Wiltshire has been responsible for distributing several of the rarer evergreen magnolias, from material largely supplied by Cistus Nursery and other American sources. Plants from Cistus Nursery have shown damage at –3 °C, which does not bode well, and Kevin Hughes’ plants have been repeatedly defoliated at –4 °C, though they recover as the

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weather warms up. Perhaps demonstrating the benefit of a properly hot summer, at Magnolian Grove Arboretum, Pickens, South Carolina it has survived two consecutive winters with temperatures down to –11 °C (R. Figlar, pers. comm. 2007).

Magnolia macrophylla Michx.

Bigleaf Magnolia

(Subgen. Magnolia, Sect. Macrophylla)

Magnolia macrophylla var. macrophylla and var. ashei were described by Bean (B657) and Krüssmann (K267, K272).

Magnolia macrophylla var. dealbata (Zucc.) D.L. Johnson Syn. Magnolia dealbata Zucc. Var. dealbata differs from typical M. macrophylla in that the mature carpels are oblong rather than ovoid or globose. It differs from var. ashei in that its fruits are 8–15 cm long (vs. 4–5 cm) and have > 70 carpels (vs. < 50). In addition, the ranges of the three do not overlap. Tobe 1998. Distribution MEXICO: Hidalgo, Oaxaca, Veracruz. Habitat Cloud forest between 600 and 1600 m asl. USDA Hardiness Zone 9. Conservation status Endangered, due to habitat loss, wood extraction and poor reproductive success. Illustration NT478, NT498. Cross-reference S326. Taxonomic note The Magnolia Society recognises this taxon as a variety of M. macrophylla, together with var. ashei (Weath.) D.L. Johnson (Figlar 2005a). Tobe (1998) proposed recognising both at subspecies level (subsp. ashei (Weath.) Spongberg, subsp. dealbata (Zucc.) J.D. Tobe).

Plate 346. Magnolia macrophylla var. dealbata – demonstrating why its name is so appropriate. Image N. Macer.

The splendid big leaves and creamy flowers of typical Magnolia macrophylla are also found in its var. dealbata, which has the additional advantages of being easier to grow and quicker to come into flower than its more northerly counterpart. It has therefore been recommended for gardens – in Cornwall at least (Hudson 2004), although it seems probable that the same qualities will be demonstrated in other localities as well. The physical differences between the varieties are slight, however, and it is not always easy to distinguish them on morphological characters alone (N. Macer, pers. comm. 2007). The leaves of var. dealbata are slightly more succulent than those of var. macrophylla and are somewhat glaucous below; they also persist on the trees longer in the autumn, especially where the climate is mild (S. Hogan, pers. comm. 2007). A grove of trees approaching 10 m tall at Berkeley, from a collection made by G. Pattison in 1985, only lose their leaves in colder weather, and have survived a freeze of –10.5 °C there (S. Hogan, pers. comm. 2007). There are some fine trees in the United Kingdom as well, most notably the 13 m champion planted in 1980 at Chyverton, Cornwall, and a 7 m tree at Caerhays Castle (TROBI), but it does require a sheltered and relatively calm situation, as wind can severely damage the very large leaves. It is said, however, that the leaves of var. dealbata have stouter petioles and are more wind-resistant than those of var. macrophylla (M. Robinson, pers. comm. 2008). A 5.2 m (2008) plant at the Hillier Gardens was grown from seed collected by Harold Hillier in 1979. The older trees mentioned above must derive from this introduction or a gathering of six seeds by James Russell in 1983 (JR 413).

Magnolia martinii H. Lév.

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia martinii (H. Lév.) H. Lév. Tree to 20 m, 0.5 m dbh. Bark smooth and grey. Branchlets yellowish green or dark brown, glabrous or with a few hairs. Leaves evergreen, thin and leathery, 6.5–18 × 2–5.5 cm, elliptic to oblong or obovate, both surfaces

Section II. Species Accounts

Magnolia

glabrous, 7–17 secondary veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole 1.5–2 cm long; stipules with a dense covering of brown or grey hairs, free from the petiole. Flowers solitary, on axillary shoots, white to yellow and fragrant, brachyblast 0.7–1.5 cm long with three to six bracts; tepals six (to eight), the outer three broadly obovate to oblong or spathulate, 5–7 cm long, inner tepals 3–6 cm long, broadly elliptic to oblong; stamens yellow with purple filaments; gynoecium stipitate with many green carpels. Fruits 6.5–10 cm long and spicate; ripe carpels ellipsoid or subglobose, dull brown and lenticellate, 1–1.6 cm long, dehiscing along both dorsal and ventral sutures. Flowering February to March, fruiting August to September (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangdong, Guangxi, Guizhou, Henan, Hubei, Sichuan, Yunnan; VIETNAM. Habitat Forests between 1000 and 2000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Liu et al. 2004.

Magnolia martinii is another species with just a few young plants in cultivation and therefore brings with it the excitement of the unknown, but also a slight whiff of uncertainty. Tom Hudson (pers. comm. 2007) believes that the plants he grows are of botanic garden origin and therefore perhaps of dubious identity – an issue that can only be resolved when they bloom. The flowers should be pale yellow in colour, borne amongst neat, narrow leaves. For Sean Hogan in Oregon plants up to 3 m tall have yet to flower, but in north Devon John Marston has raised seedlings to 2 m in three years, with bud-set apparent for 2008 (Robinson et al. 2008). The first introduction to the United Kingdom was a plant given to Kevin Hughes in 1988 by Roger Warner: this is planted at Spinners Garden, near Lymington, Hampshire, where it is fully hardy, and has been the source of numerous vegetative progeny (K. Hughes, pers. comm. 2008). The species seems to be reasonably tough, with trees in Vancouver being undamaged by –9 °C in November 2006 and suffering only minor damage from heavy snow (P. Wharton, pers. comm. 2007).

Magnolia maudiae (Dunn) Figlar

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia maudiae Dunn, Michelia chingii W.C. Cheng

Magnolia maudiae var. maudiae Tree to 20 m, 0.6 m dbh. Bark pale grey or greyish brown. Branchlets green becoming grey, glabrous. Leaves evergreen, leathery, 9.5–17.5 × 3–7 cm, elliptic to obovate, both surfaces glabrous, 7–12 secondary veins on each side of the midrib, margins entire, apex abruptly short-acuminate; petiole 1–3 cm long; stipules glabrous and free from the petiole. Flowers solitary or rarely paired, on axillary shoots, white and fragrant, brachyblast 1–2.8 cm long with two to four bracts; tepals six to nine, the outer three broadly obovate and attenuate at the base, 5–8 cm long, inner tepals 4.5–5 cm long, broadly obovate to elliptic or spathulate; stamens with pale purple filaments; gynoecium stipitate with many carpels. Fruits 10–12(–14) cm long and spicate; ripe carpels obovoid to ovoid, dull brown and lenticellate, 1–2.5 cm long with a short beak. Flowering February to March, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hong Kong, Hunan, Jiangxi, Zhejiang. Habitat Evergreen broadleaved forests between 500 and 1500 m asl. USDA Hardiness Zone 8a. Conservation status Not evaluated. Illustration Liu et al. 2004; NT474, NT500.

If just one member of section Michelia had to be chosen for a garden it would be a hard decision, but Magnolia maudiae var. maudiae would surely be on the shortlist. It combines large white flowers with good foliage and a pleasing shape of tree, plus good tolerance of a wide range of cultural conditions. Its first introduction to cultivation was again by Piroche Plants, as seedlings from Nanjing, and the resultant plants are now widely grown across the United States wherever conditions are suitable (Hogan 2008). Within this initial gene pool there is ample scope for selections, although it seems that few have actually been named. Other collections have been made, such as Peter Wharton’s (PW 126) from Guangxi, plants from which have the advantage of flowering in April and May, rather than earlier in the year as is typical of the Piroche

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Plate 347. The sumptuous scented flowers of Magnolia maudiae place it in the forefront of flowering trees. It is triumphant as a street tree in Portland, Oregon. Image Phytophoto.

* Xia et al. (2008) treat this taxon as a variety of Magnolia cavaleriei.

† The earliest valid name has now been shown to be Magnolia dandyi Gagnep., which should be adopted (Xia et al. 2008).

New Trees

importations. They are thus less liable to be damaged in areas suffering from spring frost. Where the late winter and early spring are mild, however, M. maudiae’s display begins in February and continues into early summer, with even a few autumn blooms occurring after a good growing season. The scent released by the flowers is amazing, and a famous street planting by Hogan and Sanderson in Portland perfumes the air for a whole block around and was a city sensation when the trees first bloomed profusely in 1999 (Wharton 2007, Hogan 2008). Magnolia maudiae flowers at an early age, with every axil bearing buds that can expand to be (in some clones) as much as 15 cm across. The colour ranges from pure white to cream, and some have a pink flush (including the selection ‘Touch of Pink’). The species has proved itself hardy to –18 °C in British Columbia, and has not been affected by temperatures of –10 °C in Oregon or southern England, where enthusiasts have been growing it for several years. Following the cool summer of 2007, however, when its growth failed to ripen, a plant grown by Kevin Hughes (pers. comm. 2008) in Hampshire was severely defoliated when temperatures fell to only –6 °C in the following winter. There is no doubt that it is a greedy feeder, and susceptible to chlorosis if not supplied with sufficient nitrogen, iron and magnesium (Hogan 2008), especially in areas with cooler summers. It also requires a consistent moisture level in the soil.

Magnolia maudiae var. platypetala (Hand.-Mazz.) Sima Unlike typical M. maudiae, which is completely glabrous (except for some tiny rufous hairs visible with a hand lens at the apex of flower buds), var. platypetala has rufous silky hairs on the buds, immature branchlets and young leaves. The leaves are slightly larger (11–20 × 4–7 cm) and the flowers have broader tepals. Liu et al. 2004, Figlar 2005b. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hubei, Hunan. Habitat Forests between 1200 and 1500 m asl. USDA Hardiness Zone 7b. Conservation status Not evaluated. Illustration Liu et al. 2004. Taxonomic note This taxon probably ought to be recognised at the specific level, as M. platypetala, as it differs considerably from M. maudiae both in its hairiness and its later bud-break (R. Figlar, pers. comm. 2007). In the absence of a valid name in Magnolia or detailed study, however, we maintain the status quo here.* The Magnolia Society (Figlar 2005a) also recognise M. maudiae var. hunanensis (C.L. Peng & L.H. Yan) Sima.

Magnolia maudiae var. platypetala is a less amenable and attractive garden plant than var. maudiae, being less willing to establish and grow, and forming a sparser tree with smaller flowers, but the bronze indumentum gives it a distinct appearance. Hogan (2008) recommends a slightly shaded situation and the same abundant moisture as for var. maudiae, and notes that it is at least as hardy as the type, if not more so.

Magnolia megaphylla (Hu & W.C. Cheng) V.S. Kumar † (Subgen. Magnolia, Sect. Manglietia) Syn. Manglietia megaphylla Hu & W.C. Cheng Tree to 40 m, 1 m dbh. Branchlets stout and blackish brown, densely covered with long curly or undulate dark brown or rufous hairs. Leaves evergreen, often in clusters of four to five at branch tips, thin and leathery, 23–40 × 9.4–17 cm, obovate, upper surface dark green and glabrous, lower surface pale green with scattered dark brown curly or undulate hairs, 20–22 veins on each side of the midrib, margins entire, apex acute to short-acuminate; petiole 1.5–3.7 cm long and densely pubescent; stipules adnate to the base of the petiole and densely pubescent. Flowers large and terminal, pale green to white and fragrant; tepals 9–12, the outer three obovate to oblong, 4.5–5 × 2.5 cm, the inner tepals narrower; stamens purplish red; gynoecium sessile with 57–65 carpels. Fruits 6.5–11 cm long, purplish red and globose to ovoid or oblong; ripe carpels, 2.5–3 cm

Section II. Species Accounts

Magnolia

long with a sharp beak, dehiscing along both the dorsal and ventral sutures. Flowering April to June, fruiting September to October (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: Guangxi, Yunnan. Habitat Evergreen broadleaved forest between 800 and 1500 m asl. USDA Hardiness Zone 9. Conservation status Critically Endangered, due to habitat loss and firewood extraction. Illustration Chen & Nooteboom 1993, Liu et al. 2004.

The glory of Magnolia megaphylla surely lies in the sumptuous russet pubescence of its shoots and on the underside of its huge leaves, velvety to the touch. The leaves, being up to 45 cm long on vigorous young plants, are striking in themselves and flush bronze: perhaps with tongue slightly in cheek, Sean Hogan (2008) suggests using it as a herbaceous plant, for the vigorous new shoots and huge new leaves that a coppiced stump will produce. When not so treated it can form a dense-crowned tree, although conditions need to be perfect for this to occur. Despite their size the leaves are rather thin, and scorch very easily, as seen at Quarryhill where it is planted on an open hillside. Critical requirements seem to be high humidity and constant moisture, together with some shelter from both sun and wind, at least when young – all pointing to this being a plant accustomed to spending its juvenile years in forest understorey. Frost-sensitivity seems to depend on location, with summer heat being implicated in assisting winter-hardiness: a tree in the Atlanta Botanic Garden, Georgia was not damaged by –10 to –11 °C in 2003, but –12 °C has killed trees in both North Carolina and British Columbia (Hogan 2008). It should clearly not be risked in areas where it would normally experience anything more than light frost. No trees are known to have flowered in cultivation yet, but as the flowers are comparatively small and held high in the canopy of mature trees this is not a significant disadvantage. M. nitida W.W. Sm. B658, S326, K272 M. obovata Thunb. (WAS M. hypoleuca B653, K270) M. officinalis Rehder & E.H. Wilson B659, S326, K272 M. officinalis var. biloba Rehder & E.H. Wilson B659, K272

Magnolia opipara (H.T. Chang & B.L. Chen) Sima

(Subgen. Yulania, Sect. Michelia)

Syn. Michelia opipara H.T. Chang & B.L. Chen Tree to 16 m, 0.5 m dbh. Branchlets brown, glabrous or pubescent with greyish yellow lenticels. Leaves evergreen, thin and leathery, 20–27 × 7–11 cm, obovate, upper surface glossy green and glabrous or with greyish white pubescence, lower surface glaucous with greyish white pubescence, margins entire, apex acute; stipules adnate to the petiole. Flowers solitary, on axillary shoots, yellow-white and fragrant; tepals eight, the outer three obovate and ~3.8 cm long, inner tepals oblanceolate; gynoecium stipitate with many pilose carpels. Fruits 11–15 cm long and spicate; ripe carpels ovoid, lenticellate and with a short beak. Flowering April, fruiting September to October (China). Liu et al. 2004. Distribution CHINA: Yunnan. Habitat Evergreen broadleaved forests between 1600 and 1900 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note This species is treated as a synonym of M. doltsopa by Chen & Nooteboom (1993).

Magnolia opipara is still little known in cultivation, but is established in western North America. At Quarryhill a seedling planted in 2000 had achieved 6–7 m when observed in 2004, forming a narrow, upright young tree, although it has not yet flowered (H. Higson, pers. comm. 2008). Unlike many other evergreen magnolias at Quarryhill, it has not scorched in the intense sunlight and dry heat there. Two clones originating from Kunming Botanical Garden are grown by Sean Hogan, who appreciates them for their very glaucous, almost blue leaf undersides. After five years of growth they have achieved 4 m but have not yet flowered – but neither have they suffered any frost damage in that time (S. Hogan, pers. comm. 2007).

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M. ×proctoriana Rehder B662, K272 M. pyramidata (NOW M. fraseri var. pyramidata (Bartram) Pamp.) B660, K273 M. rostrata W.W. Sm. B660, S327, K273 M. salicifolia (Siebold & Zucc.) Maxim. B661, S327, K273 M. salicifolia var. concolor (NOW M. salicifolia (Siebold & Zucc.) Maxim.) B661, K273

M. sargentiana Rehder & E.H. Wilson B662, S328, K273 M. sargentiana var. robusta Rehder & E.H. Wilson B662, K273 M. sieboldii K. Koch B664, S328, K273 M. sinensis (NOW M. sieboldii subsp. sinensis (Rehder & E.H. Wilson) Spongberg) B664, S328, K273

Magnolia sinica (Y.W. Law) Noot. (Subgen. Gynopodium, Sect. Manglietiastrum) Syn. Manglietia sinica (Y.W. Law) B.L. Chen & Noot., Manglietiastrum sinicum Y.W. Law Tree to 40 m, 1.2 m dbh. Bark grey and longitudinally fissured. Branchlets dark green to brown and glabrous. Leaves evergreen, leathery, 15–26(–30) × 5–8(–9.5) cm, narrowly obovate, upper surface glossy green and glabrous, lower surface pale green and glabrous, 13–16 secondary veins on each side of the midrib, margins entire and slightly revolute, apex short-acuminate; petiole 1.5–2 cm long, glabrous and slightly thickened at the base; stipules free from the petiole. Flowers solitary and terminal, fragrant; tepals nine, outer three oblong to spathulate, deep red outside and reddish pink inside, inner tepals obovate to spathulate, white and smaller than outer tepals; stamens cream to red; gynoecium sessile with 13–16 carpels. Fruits 5–8.5 cm long, obovoid to ellipsoid and green to brown; ripe carpels thick and woody, lenticellate, oblong to elliptic and 2.5–4 cm long, opening along the ventral suture and splitting at the apex. Flowering late April, fruiting October to November (China). Chen & Nooteboom 1993, Liu et al. 2004. Distribution CHINA: southeast Yunnan. Habitat Evergreen broadleaved forest between 1300 and 1550 m asl. USDA Hardiness Zone 9–10. Conservation status Critically Endangered. Known from a single population, with fewer than 10 individuals, and threatened by habitat loss, wood extraction and poor regeneration. Illustration Liu et al. 2004.

Given the extreme rarity of Magnolia sinica in the wild, it is good to know that it is in cultivation in the western hemisphere. Seed was obtained from Xichou Co., Yunnan by the University of California Botanical Garden at Berkeley in 1995, and from this introduction plants have been distributed to other collections, as well as being grown at Berkeley. At Quarryhill, a specimen from this source had achieved 4 m by 2004. It looks like a fastigiate Cherry Laurel (Prunus laurocerasus) or perhaps a narrowleaved Magnolia grandiflora, with the difference that the new leaves flush a handsome bronzy red. The leaves of the Quarryhill individual were somewhat sunburnt on the southwestern side when observed, indicating that some shade would be advisable. Magnolia sinica has apparently not been tried outside beyond California, and until a sufficiency of stock has been built up from cuttings it would seem inadvisable to risk material of this species in experimental plantings.

M. ×soulangeana Soul.-Bod. B665, S329, K274 M. sprengeri Pamp. B668, S331, K275 M. sprengeri var. diva (NOW M. sprengeri Pamp. var. sprengeri) B668, K275

M. sprengeri var. elongata (Rehder & E.H. Wilson) Johnstone B668, K275 M. stellata (Siebold & Zucc.) Maxim. B669, S331, K275

Section II. Species Accounts

Magnolia tamaulipana A. Vázquez

Magnolia

503

(Subgen. Magnolia, Sect. Magnolia)

Tree 20–30 m, 0.4–0.5 m dbh. Bark rough and grey. Branchlets densely covered in pale yellow silky hairs. Leaves evergreen, (10–)12–20(–23) × (4.5–)5–9 cm, narrowly oblanceolate to elliptic, upper surface lustrous green and glabrous, lower surface pale green to glaucous and sparsely pubescent, ~10–15 secondary veins on each side of the midrib, margins entire, apex abruptly acute to acuminate; petiole 1–4.2 cm long, glabrous; stipules linear, 4.8–7 cm long, densely covered with dark brown or yellow silky hairs. Flowers terminal, creamy white, 12–15 cm diameter; peduncle densely greenish-hairy. Sepals three, oblong-obovate, concave, 6.5–9.6 × 3–4.5 cm, whitish green; petals six, obovate, 4.5–9 × 2–4.5 cm; stamens 140–145, pale yellowish green; gynoecium sessile with (38–)53–57(–73) carpels. Fruits 5–9 × 2.3–4.5 cm, roughly ovoid; ripe carpels to 2.7 cm long, dehiscing along a dorsal suture. Flowering May to July, fruiting September (Mexico). Vázquez-G. 1994. Distribution MEXICO: Nuevo Léon (?), Tamaulipas (Sierra de Guatemala). Habitat Deciduous cloud forest in deep canyons between 700 and 1900 m asl. USDA Hardiness Zone 7. Conservation status Endangered, due to habitat loss and the gathering of firewood and floral buds for medicine. Illustration Vázquez-G. 1994; NT503. Taxonomic note This species is the closest living relative of M. grandiflora, but differs from it in several technical ways, as well as looking quite different: it has fewer carpels (38–73 vs. 75–90) and stamens (140–145 vs. > 250) per flower, the outer petals are shorter (6.5–9.5 cm vs. 10.5–14.5 cm), and the lower surface of the leaf is covered in minute hairs, rather than the dense, reddish silky hairs so distinctive in M. grandiflora.

Magnolia tamaulipana is the only one of the numerous species of magnolia found in Mexico, Central and northern South America and the Caribbean to have been introduced to temperate horticulture. It has proved to be remarkably hardy, flourishing on the East Coast at least as far north as North Carolina, and on the West Coast as far north as Seattle. The earliest cultivated specimen known is in fact at the University of Washington Arboretum, from a collection made by F.G. Meyer and D.J. Rogers (Meyer & Rogers 2793) in 1948. The tree has flowered there since 1971, and is now nearly 9 m tall (Hogan 2008). It was originally labelled M. schiedeana Schlecht. – a related species with which M. tamaulipana has often been confused, but M. schiedeana is a smaller tree with glabrous branchlets, smaller flowers and fewer floral parts. In our area M. schiedeana is only in cultivation at Berkeley; Clarke (1988: S322) records that it was introduced to the United Kingdom by James Russell in 1984, but (as predicted) no plants from this introduction seem to have survived. Magnolia tamaulipana has been re-collected on several occasions since 1948, one trip by the Yucca Do Nursery team in the early 1990s yielding cuttings of an exciting narrow-growing form with purplebronze new leaves. This has been named ‘Bronze Sentinel’ and is proving an excellent garden plant of considerable hardiness, unaffected by frost to –18 °C, although it will be damaged by persistent lower temperatures. It seems to be a bit hardier than other clones, which can be damaged at –12 °C. This surprising tolerance to cold is explained by the fact that weather fronts carrying cold air from Canada can sometimes reach central Mexico, to the extent that many species there are well adapted to cold (Hogan 2008). The other side of the coin, however, is that M. tamaulipana does appreciate a hot summer to flourish. It is inevitable that comparisons with M. grandiflora will be drawn. Magnolia tamaulipana has the advantage of bronzed or coppery new leaves, but in most clones the growth is a bit gawky, not forming a

Plate 348. The Mexican Magnolia tamaulipana is the closest relative of M. grandiflora but lacks its substance and beauty. Image R. Figlar.

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solid mass of foliage. The flowers are large and sweetly scented, but narrower in outline than those of M. grandiflora, with the tepals being a dirtier white and pinkish brown on their exterior surfaces. If there were no comparison to be made the Mexican would be considered dashingly handsome, but in a straight contest the Southern Belle retains her crown. M. ×thompsoniana de Vos B670, S331, K275 M. tripetala (L.) L. B671, S332, K275 M. ×veitchii Bean B671, S332, K275 M. virginiana L. B672, S332, K276 M. virginiana var. australis (NOW M. virginiana L.) B672

Magnolia yunnanensis (Hu) Noot.

M. ×watsonii (NOW M. ×wieseneri Carr.) B673, S332, K276 M. wilsonii (Finet & Gagnep.) Rehder B674, K276

(Subgen. Gynopodium, Sect. Gynopodium)

Syn. Parakmeria yunnanensis Hu Tree to 40 m, 1 m dbh. Branchlets pale green and glabrous with distinctive bamboo-like internodes. Leaves evergreen, thin and leathery, 6.5–15 × 2–5 cm, ovate to oblong or elliptic, leaves glabrous on both surfaces, pinkish red when immature, 9–13 secondary veins on each side of the midrib, margins entire, apex shortacuminate; petiole 1.5–2.5 cm long; stipules free from the petiole. Flowers terminal and androdioecious; staminate flowers white with 9–12 tepals, outer three tepals thin, obovate and ~4 × ~2 cm, inner tepals fleshy and obovate to spathulate, stamens ~30 with red filaments; hermaphrodite flowers similar to staminate flowers, gynoecium sessile with 10–20 green carpels. Fruits reddish pink, ~6 cm long, ellipsoid to ovoid; ripe carpels rhomboid and united before maturity, dehiscing along the dorsal suture. Flowering April to May, fruiting September to October (China). Liu et al. 2004. Distribution CHINA: northern Guangxi, southeast Yunnan; VIETNAM. Habitat Evergreen broadleaved forest between 1200 and 1500 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Liu et al. 2004. Taxonomic note Chen & Nooteboom (1993) treat this species as a synonym of Magnolia nitida, but like M. lotungensis it is a distinct hexaploid (Chen et al. 2000) (see p. 496). See Magnolia laevifolia (p. 494) for commentary on specific name yunnanensis.

Enthusiasts such as Tom Hudson and Sean Hogan (pers. comms. 2007) are impressed by Magnolia yunnanensis, admiring it for its elegant narrow foliage and pinkish red new growth (‘bronzy orange to lipstick crimson’ according to Peter Wharton), as well as a more gracile habit than its relatives M. lotungensis and M. nitida, but with the potential for forming a big vigorous tree. It is growing well for both but has yet to flower at Tregrehan, where the largest trees are 4 m tall; in Oregon a tree of 5 m has so far produced one flower. It is also flourishing in Vancouver, and its prospects as a reasonably hardy tree for the milder parts of our area seem good (Wharton 2007), although it is probably less hardy than M. lotungensis, –12 °C being suggested as the minimum it will normally tolerate (Hogan 2008). An early introduction was made by Monrovia Nurseries but it has been collected on several other occasions since, by expeditions and private collectors.

Magnolia yuyuanensis (Y.W. Law) V.S. Kumar

(Subgen. Magnolia, Sect. Manglietia)

Syn. Manglietia yuyuanensis Y.W. Law Magnolia yuyuanensis was treated as synonymous with M. fordiana var. fordiana by Chen & Nooteboom (1993). However, Kumar (2006) resurrected the species, which can be distinguished from M. fordiana using several characters. The branchlets are yellowish brown (vs. reddish brown), the leaf apex is caudate to acuminate (vs. acute), the peduncle is 1.5–2 cm long (vs. 0.5–1 cm), and the outer tepals are greenish and 3.5–4 × 1.8–2 cm

Section II. Species Accounts

Magnolia

505

(vs. white, 6–7 × 3–4 cm). In addition, M. yuyuanensis is completely glabrous. Kumar 2006. Dick Figlar (pers. comm. 2006) suggests that M. yuyuanensis is more common in cultivation than M. fordiana, and probably more cold-hardy! Distribution CHINA: Anhui, Fujian, Guangdong, Hunan, Jiangxi, Zhejiang. Habitat Rich mesic slopes between 700 and 1200 m asl. This species has almost exactly the same distribution and altitudinal range as M. cylindrica. USDA Hardiness Zone (6–)7. Conservation status Not evaluated. Illustration Liu et al. 2004; NT476, NT505.

Magnolia yuyuanensis is established in cultivation and commerce throughout the temperate world, but specimens in collections remain rather scarce, and many are labelled M. fordiana. It has been grown at the Hillier Gardens since 1983, the tallest specimen there being 6.7 m in 2008 (A. Coombes, pers. comm. 2008). An unusually old tree donated by J.C. Raulston to the David C. Lam Asian Garden in Vancouver in 1989 is a fine shapely specimen, that now flowers abundantly. Although beautiful, with cream tepals and purple anthers, the flowers are something of a let-down, each lasting only 36 hours and having a disappointing fragrance, but they are produced over several weeks in high summer and do give a good visual display (Wharton 2007). This species performs very much better in Vancouver than the related M. fordiana. A young plant at the JC Raulston Arboretum has flowered at less than a metre high (S. Hogan, pers. comm. 2007), and a plant obtained from New Zealand is growing well at Tregrehan. A distinctive feature is the boat-shape of the leaves, with a pointed tip. As illustrated in Magnolias of China (Liu et al. 2004), the rounded, compact fruits have the appearance of enormous strawberries.

Magnolia zenii W.C. Cheng

(Subgen. Yulania, Sect. Yulania)

Tree to 11 m, 0.3 m dbh. Bark smooth and pale grey. Branchlets purplish brown and glabrous with sparse lenticels. Leaves deciduous, papery, 7–16 × 3–7 cm, obovate, upper surface dull green and glabrous, lower surface pale green with long curly hairs along the midrib and veins, 8–12 secondary veins on each side of the midrib, margins entire, apex short-acuminate; petiole 0.6–1.5 cm long and somewhat pubescent; stipules pubescent, adnate to the base of the petiole. Flowers terminal and produced before the leaves, pinkish to white with a darker centre and a dark pink streak on seven of the tepals, strongly scented; peduncle densely hairy. Tepals 9–12, spathulate, 7–8 × 3–4 cm, all equal in length; stamens purple; gynoecium sessile with numerous carpels. Fruits 5–7 cm long and cylindrical; ripe carpels pinkish red, subglobose and tuberculate. Flowering April to May (February to March in cultivation), fruiting August to September (China). Chen & Nooteboom 1993, Gardiner 2000, Liu et al. 2004. Distribution CHINA: Jiangsu. Habitat Forests between 250 and 300 m asl. USDA Hardiness Zone 5. Conservation status Critically Endangered, due to poor regeneration. Reduced to a single population (18 individuals only) on Mt. Baohua. Illustration Liu et al. 2004; NT506 (hybrid).

Magnolia zenii is a classic pink and white magnolia, on which opinions differ. Some say that it is not amongst the cream of the crop, having rather small flowers that are apt to be damaged by frost, while others view it as very attractive! It has been in cultivation in the United States since the Sino-American Botanical Expedition (SABE) of 1980, when a few seeds were donated to Stephen Spongberg (Arnold Arboretum) and Ted Dudley (US National Arboretum) by Prof. He of the Jiangsu Institute of Botany (Gardiner 2000). The Arnold Arboretum was the first to flower the tree, in 1988, since when it has been consistently the earliest Magnolia to flower there (Spongberg 1998). Vegetative propagations have been distributed from the Arnold Arboretum and a tree from this source, seen at the Morris Arboretum in 2006, had achieved 10 m since being planted in 1989, with a columnar shape from multiple erect stems. Such upright growth seems to be typical of the species, and a similar propagation from an Arnold

Plate 349. The rounded fruits of Magnolia yuyuanensis suggest a large berry-fruit. The boat-shaped leaves are characteristic. Image R. Figlar.

506

Magnolia

New Trees

1 cm

Figure 57 (above). Magnolia zenii hybrid: branchlet with fruit.

Arboretum specimen in Vancouver is now 16 m tall (P. Wharton, pers. comm. 2007). The flowers are among the earliest to appear (alongside M. biondii), and benefit from a long winter to prevent them opening too soon, when frost can damage them, especially in eastern North America (A. Aiello, pers. comm. 2006). This is also the case in Belgium (P. de Spoelberch, pers. comm. 2007). Peter Wharton (pers. comm. 2007), however, enthused over the effect in late winter of the very furry buds, covered as they are in long silky, silvery hairs, borne in large numbers on the trees. He also highlighted the intense fragrance of the flowers. Magnolia zenii hybridises freely with other members of section Yulania – the hybridity of the offspring often being revealed by the presence of an outer whorl of small sepaloid tepals – and any seed-propagated stock should be checked carefully. One such seedling from the Arnold Arboretum has been named ‘Pink Parchment’ by Michael Dirr: it is sometimes offered as a form of M. zenii, but is of hybrid origin.

Section II. Species Accounts

Mallotus

507

EUPHORBIACEAE

MALLOTUS

Lour.

There are about 140 species of Mallotus, ranging from tropical Africa through Asia to the Pacific (Govaerts et al. 2000). They are dioecious (rarely monoecious) trees, shrubs or rarely scramblers. The leaves are alternate or opposite, petiolate, sometimes peltate, simple or lobed, entire or with dentate margins; stipules usually small. The inflorescences are terminal, subterminal or axillary; unisexual, with one to many flowers in spicate, racemose, paniculate or thyrsiform arrangements, and with small bracts. The male flowers are pedicellate; the calyx valvate, in (two to) three to four (to five) parts; the corolla absent; stamens 20–200(–250), with free filaments. The female flowers are pedicellate; the calyx 3–5(–10)-lobed, the lobes imbricate or valvate, persistent or caducous; corolla absent; the ovary smooth to spiny. The fruit is globose or (two to) three (to four)-sided, with a smooth, spiny, scaly or tomentose coat, and dehiscent (Radcliffe-Smith 2001). Only two species of this widespread, largely tropical genus are cultivated outside in temperate areas, namely M. apelta (described below) and M. japonicus. The latter was described by Bean (1981a), who praised its foliage, although his commentary was rather brief. It is certainly worth trying both of these species in a warm, sunny site, for their handsome heart-shaped leaves, but even in climatically suitable locations they should probably be regarded as short-lived plants and it would be wise to renew them occasionally, from seed if possible, or semi-ripe cuttings.

Mallotus apelta (Lour.) Müll. Arg. Syn. M. castanopsis F.P. Metcalf, M. paxii Pamp., M. tenuifolius Pax Shrub or tree 2–10 m. Branchlets, petioles and inflorescences densely covered in yellowish, stellate tomentum and orange glands. Leaves deciduous, alternate, 6–16(–25) cm long and wide, upper surface glabrous or sparsely pubescent, lower surface covered with greyish white stellate tomentum and orange glands, six to seven lateral veins on each side of the midrib, margins sparsely serrate, apex acute or acuminate; petiole 5–15 cm long. Inflorescences terminal or lateral, spicate or paniculate, 15–30 cm long; bracts very small. Male flowers pedicellate; calyx four-lobed, densely yellow tomentose outside, glandular inside; corolla absent; stamens 50–75. Female flowers pedicellate or almost sessile; calyx three- to five-lobed, densely white tomentose and glandular; corolla absent; styles three to four, stigma feathery. Capsule subglobose, 0.5–1 cm long, densely covered in greyish white stellate hairs and soft yellowish spines. Flowering June to September, fruiting August to November (China). Qiu & Gilbert 2008. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Hainan, Henan, Hong Kong, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Yunnan, Zhejiang. Habitat Montane forest. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT507. Taxonomic note The horticultural literature often falls into the trap of writing the epithet apetala which, although true, is incorrect.

Mallotus apelta is very little known in cultivation, but is admired by those who do grow it for its umbrella-like outline and soft, velvety leaves that turn yellow or orange in autumn (Cistus Nursery 2007–2008). The flowers are insignificant. It is commercially available in the United States, and is found in some collections

Plate 350. The large leaves of Mallotus apelta are beautifully soft, and turn good colours in autumn. Image Phytophoto.

508

Mallotus

New Trees

there. At the JC Raulston Arboretum a specimen planted in 1996 had achieved 5.5 m by 2004 (JC Raulston Arboretum database), growing as a single-stemmed tree. At Tregrehan plants only lasted a couple of years before fading away, probably through failing to ripen their growth properly (T. Hudson, pers. comm. 2007). It appreciates ample moisture and heat in the growing season. M. japonicus (L. f.) Müll. Arg. B690, K283

ROSACEAE

MALUS

Mill.

Apples, Crabapples, Crabs

Plate 351. The prolific flowers of Malus rockii are followed by clusters of small red fruits. Image R. Unwin.

The taxonomy of Malus has traditionally been challenging. There are few morphological characters to distinguish the species, almost all of which readily form hybrids. Cultivars of the Domestic Apple have been widely planted around the world and have occasionally hybridised with wild species. Indeed, the nomenclature of the Domestic Apple has only recently been resolved (the correct name being Malus pumila Mill.: Mabberley et al. 2001). Several taxa of horticultural interest are unknown in the wild and may represent interspecific hybrids or the products of introgression or horticultural selection. Because of this ongoing uncertainty in Malus taxonomy, the number of species recognised fluctuates, but it ranges between 25 and 47 (Robinson et al. 2001). Apples are deciduous (rarely evergreen or semi-evergreen) trees or shrubs native to Asia, Europe and North America. They are usually unarmed and have simple, alternate, stipulate leaves. The leaf margins are serrate or lobed, and venation can be craspedodromous or camptodromous. Inflorescences are corymbose to racemose. The flowers are white or pink, 5-merous, with 15–50 stamens and a bowl-shaped hypanthium. The fruit is a green, yellow or red pome with mealy flesh and a tough core (Robertson et al. 1991, Fiala 1994, Gu et al. 2003). One of the most interesting horticobotanical stories to be elucidated in recent years is that of the Domestic Apple Malus pumila, traced to its origins in the wild ‘fruit forests’ of central Asia by Barrie Juniper and others, and the unravelling of a complex taxonomy to reveal the correct name to be applied to the plant (Mabberley et al. 2001). Perhaps the most remarkable discovery is that our culinary apples seem to be unhybridised and more or less accurately reflect the variation found in wild populations of M. pumila (Juniper & Mabberley 2006). Among variants that have not been selected for cultivation, unsurprisingly, are the occasional fiercely armed trees to be found in the same central Asian fruit forests

Section II. Species Accounts

(B. Juniper, pers. comm. 2007). Leaving aside its culinary values, the Domestic Apple is an excellent ornamental tree, producing reliable, beautiful blossom and good crops of attractive fruit, while in old age it can be picturesquely gnarled: it lacks, usually, only good autumn colour. Wild-origin material is often found in collections under the name M. sieversii (Ledeb.) M. Roem. The heavily red-pigmented apple known as M. niedwetzkyana is apparently a mutation occurring very infrequently in wild populations (B. Juniper, pers. comm. 2007). The taxa described below are an assortment of obvious hybrids, putative hybrids and apparently ‘good’ species, probably of most interest to the serious collector. They do not stand up to a comparison with the more recent hybrid crabapple cultivars, which are frequently outstanding for both floral and fruit effect. A handful of particularly good new cultivars are mentioned here, but for further information there are several useful monographs that could be consulted, including Fr John Fiala’s Flowering Crabapples (1994) – although this is now somewhat out of date with regard to newer cultivars. Dirr (1998) also discusses a wide range, with special reference to their disease tolerances. The International Ornamental Crabapple Society is the International Cultivar Registration Authority for crabapples; new cultivars are discussed in their journal Malus, and the Society promotes trial and evaluation collections, comparing cultivars under prevailing conditions at 24 sites across the United States. A good range of cultivars can also be seen in many public gardens elsewhere, including two National Plant Collections in the United Kingdom. Chris Sanders has kindly provided notes on the following recent cultivars, notable for having proved themselves as reliable garden trees and which should be among the first considered for a collection. The French-origin ‘Evereste’ has red buds opening to white flowers that produce heavy crops of distinctive, orange-red fruits, persisting until December. It makes a small round-headed tree with good disease resistance, and was released by the Institut National de la Recherche Agronomique (INRA) in about 1980. With the same floral coloration, and also from France, raised by Jean-Pierre Hennebelle in the early 1980s, is ‘Comtesse de Paris’ whose globular yellow fruits persist unscathed on the tree well into the new year and outdo any other yellow-fruited crabapple. Similarly coloured flowers again are a feature of the American cultivars ‘Adirondack’, bred by Don Egolf of the US National Arboretum and introduced in 1987, and ‘Snowcloud’, from Princeton Nursery, New Jersey in 1970. ‘Adirondack’ is compact and slow-growing but with an upright habit, and is a good choice for smaller spaces. Its fruits are bronze-red. ‘Snowcloud’ has abundant semi-double flowers and produces a relatively sparse crop of yellow fruits, but has a vigorous upright habit that makes it a very useful garden tree. It is said to be susceptible to scab in the United States, but this is not a problem in the United Kingdom. Bright pink flowers opening from even darker buds are among the attractive characters of ‘Indian Magic’, introduced by Simpson Nursery, Indiana in 1975. The fruits change from glossy red to golden-orange and persist well on the tree, which also produces good autumn colour. ‘Princeton Cardinal’ (introduced by Princeton Nursery in 1990) has the brightest red flowers of this assortment of suggestions, abundantly produced and opening early in the season, combined with glossy red disease-resistant foliage on this small but broadly vase-shaped cultivar. As extremely cold-hardy trees Malus cultivars are popular in North America, where they can withstand severe winters with impunity, but some are susceptible to a range of pests and diseases, and appropriate homework is wise before a choice is made.

Malus

509

510

Malus

New Trees

M. ×adstringens Zab. ex Rehder B696, K283 M. angustifolia (Aiton) Michx. B692, K284 M. ×astracanica Dum.-Cours. B696, K284 M. ×arnoldiana Sarg. B692, K284 M. ×atrosanguinea (Spath) C.K. Schneid. B700, K284 M. baccata (L.) Borkh. B693, S336, K284

Malus brevipes Rehder

M. baccata var. himalaica (NOW M. rockii Rehder, NT513) B693, K284 M. baccata var. jackii Rehder K284 M. baccata var. mandshurica (NOW M. mandshurica (Maxim.) Kom.) B694, K284 M. bracteata Rehder K284

Nippon Crabapple

This species is closely related to the well-known Japanese flowering crab Malus ×floribunda Siebold, and like it, is probably a hybrid. Malus brevipes differs from M. ×floribunda in that it has a shorter, denser and somewhat stiffer habit. The leaves are smaller with more closely serrate margins, and the flowers are smaller and somewhat paler. The fruits are bright red, subglobose, 1.5 cm diameter, slightly ribbed and borne in profusion on upright pedicels. Krüssmann 1985b, Fiala 1994. Distribution In cultivation only; unknown in the wild. USDA Hardiness Zone 4. Illustration NT510. Cross-reference K284.

Malus brevipes is widely grown and with its tidier habit is easier to place in smaller gardens than M. ×floribunda. It differs also in its pure white flowers opening from slightly pink-tinted buds, which are produced in great abundance. These are followed by persistent dark red fruits that are again ornamental, making it a very useful tree that should be even more widely planted than it is. It is freely available in commerce in the United Kingdom, both under its own name and under the selling name Malus Wedding Bouquet, recently applied by Frank P. Matthews Ltd., Worcestershire (N. Dunn, S. Priest, pers. comms. 2008). According to Krüssmann (1985b), it was introduced prior to 1883. M. coronaria (L.) Mill. B695, K285 M. coronaria var. dasicalyx (Rehder) Fernald B695, K285 M. coronaria var. elongata (Rehder) Rehder K285 Plate 352. The selling name Wedding Bouquet for this clone of Malus brevipes is very apt: it is a very floriferous crabapple. Image Frank P. Matthews, Trees for Life.

Malus ×dawsoniana Rehder

Dawson Crabapple

This species is a hybrid between the North American Malus fusca (Raf.) C.K. Schneid. and the introduced Domestic Apple. It forms an upright, densely twiggy tree with a rounded crown. Leaves 4–9 cm long, elliptic to oblong and unlobed; excellent autumn colour. Flowers white, 2.5–3.5 cm wide. Pome yellowish green to red, 4 × 2.5 cm, elliptic to oblong. Fiala 1994. Distribution USA: originally collected in Oregon. USDA Hardiness Zone 4. Illustration NT511. Cross-reference K285.

Despite praise for its autumnal colour (Fiala 1994) and its attractive elongated fruits Malus ×dawsoniana is not commonly grown, and is most likely to be found in specialist collections. There is an unhappy-looking specimen in the Hillier Gardens, measured at 6.4 m in 2004 (Sir Harold Hillier Gardens database), that would not encourage its wider cultivation. M. ×denboerii Krüssm. K285 M. domestica (NOW M. pumila Mill.) B695

M. ×eleyi (Bean) Hesse B696 M. florentina (Zuccagni) C.K. Schneid. B697, K285

Section II. Species Accounts

Malus

511

1 cm

M. ×floribunda Siebold ex Van Houtte B698, K285

M. formosana (NOW M. doumeri A. Chev.) K285

Figure 58 (above). Malus ×dawsoniana: habit with flowers and fruit.

512

Malus

New Trees

M. fusca (Raf.) C.K. Schneid. B699, K285 M. glabrata Rehder K286 M. glaucescens Rehder K286 M. ×gloriosa Lem. K286

Malus honanensis Rehder

M. halliana Koehne B699, K286 M. halliana var. spontanea (Makino) Koidz. B699, K286 M. ×hartwigii Koehne B700, K287 M. heterophylla Spach K287

Honan Crabapple

Shrub or tree 5–7 m. Branchlets slender, reddish brown, pubescent when young. Buds ovoid, reddish brown, scales with villous margins. Leaves deciduous, 4–7 × 3.5–6 cm, broadly ovate, somewhat pubescent on both surfaces, though hairs soon eroded on the upper surface, margins doubly serrate with three to six lobes, apex acute; petiole 1.5–2.5 cm long, pubescent; stipules caducous, ~0.6 cm long, pubescent. Corymb 4–6.5 cm diameter, somewhat umbel-like, with 5–10 flowers. Flowers ~1.5 cm diameter; hypanthium bellshaped, sparsely pubescent; sepals triangular-ovate, shorter than hypanthium; petals pinkish white, ovate, 0.7–0.8 cm long; stamens ~20. Styles three to four. Pome yellowish green with a red blush, subglobose, ~0.8 cm diameter with persistent sepals. Flowering May, fruiting August to September (China). Fiala 1994, Gu et al. 2003. Distribution CHINA: Gansu, Hebei, Henan, Hubei, Shaanxi, Shanxi. Habitat Thickets on slopes and in valleys, between 800 and 2600 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Cross-reference K287.

Malus honanensis is one of the low-growing, rather bushy small-fruited Chinese crabapples – somewhat resembling M. yunnanensis, to which it is related and from which it differs only in number of styles (five in M. yunnanensis) and in pubescence characters. In foliage and floral characters it resembles M. kansuensis, but has more strongly lobed leaves and a rounder fruit than that species (Gu et al. 2003). These small Chinese species are more pleasant than beautiful in flower, but may produce good autumn colours. Malus honanensis is in cultivation in specialist collections, and seed is available through the wholesale trade.

M. hupehensis (Pampan.) Rehder B700 M. hupehensis f. rosea Rehder B700, K287 M. ioensis (Wood) Britt. B701, K288 M. ioensis var. bushii Rehder K288 M. ioensis var. creniserrata Rehder K288

M. ioensis var. palmeri Rehder K288 M. ioensis var. spinosa Rehder K288 M. ioensis var. texana Rehder K288 M. kansuensis (Batal.) C.K. Schneid. B701, K288 M. kansuensis f. calva (NOW M. kansuensis var. calva (Rehder) T.C. Ku & Spongberg) B702, K288

Malus kirghisorum Al. Fed. & Fed.

Kirghiz Apple

Syn. M. sieversii (Ledeb.) M. Roem. var. kirghisorum (Al. Fed. & Fed.) Ponomar. Tree to 10 m; crown broad and umbrella-shaped. Branchlets long, thin and unarmed. Leaves deciduous, papery, 5–10 × 3–6 cm, broadly oblanceolate, upper surface glabrous, lower surface glabrous or slightly pubescent, margins denticulate, apex acute; petiole short, pubescent. Flowers 3–5 cm diameter, pale pink. Fruits extremely variable; yellowish, greenish or reddish, globose to cylindrical, 3–8 × 3–8 cm. Flowering April to May, fruiting August to September (Kazakhstan). Dzhangaliev et al. 2003. Distribution KAZAKHSTAN; KYRGYZSTAN. Habitat Forms pure apple forests or mixes with other small trees, primarily on north-facing slopes between 1200 and 1800 m asl. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration Juniper & Mabberley 2006; NT513. Taxonomic note The exact status of the Kirghiz Apple is debated. Fiala (1994) treated it as a crabapple cultivar (Malus ‘Kirghisorum’). Dzhangaliev et al. (2003) maintain it as a full species,

Section II. Species Accounts

Malus

513

while Juniper & Mabberley (2006) regard it as a distinct species occurring sympatrically with M. pumila in the Tian Shan, and intermediate between it and M. baccata in characters. Local botanists reported to Barrie Juniper that hybrids exist between M. kirghisorum, M. pumila and M. baccata, but he did not personally observe any (B. Juniper, pers. comm. 2007).

Malus kirghisorum is well established in cultivation throughout our area, flourishing in areas as widely disparate as Los Angeles and Warsaw, though principally in botanical rather than private gardens. Numerous accessions from the wild are maintained at the USDA Plant Genetic Resources Unit (part of the National Germplasm Repository) at Geneva, New York and in other research collections. The British champion is an 8.5 m specimen at the Hillier Gardens which bears a striking resemblance, it has to be said, to any old apple tree. It has a broad rounded crown on a short trunk. The flowers are pretty, but the crabs are its principal feature, colouring well in the autumn.

M. lancifolia Rehder B702, K288 M. ×magdeburgensis Hartw. K288 M. ×micromalus Makino B710, K288 M. ×moerlandsii Doorenbos K288 M. niedzwetzkyana (NOW M. pumila Mill.) B702, K289 M. orthocarpa Lav. B706 M. ×platycarpa Rehder K288 M. prattii (Hemsl.) C.K. Schneid. B703, K289 M. prunifolia (Willd.) Borkh. B704, K289 M. prunifolia var. rinki (NOW M. asiatica Nakai) B704, K289 M. pumila Mill. B704, K289 M. pumila var. paradisiaca Sch. K289 M. ×purpurea (Barbier) Rehder B705, K289 M. ×robusta (Carrière) Rehder B706, K289

Malus rockii Rehder Tree 8–10 m, branches somewhat pendulous. Branchlets dark brown, villous when young. Buds ovoid, reddish brown, scales with slightly pubescent margins. Leaves deciduous, 6–12 × 3.5–7 cm, elliptic to ovate, upper surface sparsely pubescent along the midrib, lower surface sparsely pubescent along the midrib and lateral veins, margins serrate, apex acuminate; petiole 2–4 cm long, villous; stipules caducous, 0.5–0.6 cm long, membranous. Corymb 4–6 cm diameter, somewhat umbel-like, with four to eight flowers. Flowers 2.5–3 cm diameter; hypanthium bell-shaped, densely villous; sepals triangular-lanceolate, slightly longer than hypanthium; petals white, obovate, 1.2–1.5 cm long; stamens 25, shorter than petals. Pome red, ovoid or subglobose, 1–1.5 cm diameter with caducous sepals. Flowering May to June, fruiting September (China). Gu et al. 2003. Distribution BHUTAN; CHINA: southwest Sichuan, southeast Xizang, northwest Yunnan. Habitat Mixed forest in valleys, between 2400 and 3800 m asl. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration Gu et al. 2003; NTxvi, NT508. Cross-references B693, K284 (both as M. baccata var. himalaica); K290. Taxonomic note Fiala (1994) considered this species to be a cultivar, Malus ‘Rockii’.

The taxonomy of the Malus section Malus series Baccatae, to which this and other relatives of M. baccata belong, is complicated by their being a mixture of cultivated and wild populations, with hybridisation probably in the equation as well. It is not even clear whether the Chinese M. rockii is conspecific with the Himalayan M. sikkimensis (Juniper & Mabberley 2006), although Flora of China treats them separately. Bean (1981a) discusses several collections under the name M. baccata var. himalaica

Plate 353. Unripe fruits on Malus kirghisorum look very sour, but mature to a good red colour and are merely tart: apple enthusiast Barrie Juniper uses them in his apple juice mixture. Image P. Williams.

514

Malus

New Trees

which seem to refer to this taxon. In recent times it has been collected quite frequently in Yunnan, and representative wild-origin material is being grown at Kew (M. Foster 93051) and Edinburgh (CLD 874). It forms a small tree producing the abundant flowers to be expected of a relative of M. baccata, and attractive fruit in autumn. M. sargentii (NOW M. toringo (Siebold) Siebold ex de Vriese) B706, K290 M. ×scheideckeri Zab. B707, K290 M. sieboldii (NOW M. toringo (Siebold) Siebold ex de Vriese) B708, K290 M. sieboldii var. arborescens (NOW M. toringo (Siebold) Siebold ex de Vriese) K290 M. sikkimensis (Wenzig) Koehne B708, S336, K290 M. ×soulardii (Bailey) Britt. B701, K290 M. spectabilis (Aiton) Borkh. B709, K290 M. ×sublobata Rehder B708, K291 M. sylvestris (L.) Mill. B710, K290

M. sylvestris var. domestica (NOW M. pumila Mill.) K290 M. toringo (Siebold) Siebold ex de Vriese (WAS M. sargentii B706, K290; OR M. sieboldii B708, K290) M. toringoides (Rehder) Hughes B710, S336, K291 M. transitoria (Batal.) C.K. Schneid. B711, K291 M. trilobata (Labill.) C.K. Schneid. B711, K291 M. tschonoskii (Maxim.) C.K. Schneid. B712, K291 M. yunnanensis (Franch.) C.K. Schneid. B712, K291 M. yunnanensis var. veitchii (Osborn) Rehder B713, K291 M. ×zumi (Matsum.) Rehder B713, K291

CELASTRACEAE

MAYTENUS

Molina

Maytens

Figure 59 (opposite). Maytenus magellanica: habit with fruits (A), with flowers (B); detail of capsule with a seed (C). Lithraea caustica: habit with flowers (D); fruit (E). Aextoxicon punctatum: habit with flowers (F); fruit (G).

Maytenus includes about 200 species in the tropical and warm temperate regions of the world, with greatest diversity in Central America. It is absent from Europe, with the exception of M. senegalensis (Lam.) Exell subsp. europaeus (Boiss.) Rivas Mart. in southern Spain. Maytenus species are robust shrubs or small trees with stems that may be pubescent or glabrous, spiny or unarmed. The leaves are evergreen, alternate, petiolate and entire; stipules are small and deciduous. They are monoecious or dioecious; inflorescences are axillary and cymose or, rarely, solitary. The flowers are usually hermaphrodite and 5-merous. The fruit is a two- or three-lobed capsule, which splits into sections (septicidal) at maturity, revealing the seeds. The seeds have a brightly coloured, fleshy aril in a basal position (Lourteig & O’Donell 1955, Long 1991). The genus is most familiar in cultivation through the elegance of M. boaria, whose hardiness and charms are becoming more widely appreciated. Maytenus disticha (Hook. f.) Urb., a low-growing Chilean shrub with small neat leaves, grows in the Scottish botanical gardens from collections by various expeditions, and is also in commerce in the United Kingdom. It is allied to M. chubutensis, as mentioned by Bean (1981a).

Section II. Species Accounts

Maytenus

515

1 cm 1 cm

B

A

C

0.5 cm

1 cm

D 1 cm

E 0.5 cm

F

0.5 cm

G

516

Maytenus

New Trees

M. boaria Molina B721, S337, K299 M. chubutensis (Speg.) Lourteig, O’Donell & Sleumer B722, K300

Maytenus magellanica Hook. f.

Maíten Negro

Shrub or small tree to 5 m, 0.3 m dbh; branches in whorls, may form a columnar shrub with both pendulous and erect branches. Branchlets grey-green to reddish brown, often clustered towards the ends of branches. Leaves evergreen, 1.4–8(–10) × 0.6–3.5(–4) cm, elliptic to lanceolate, rarely obovate, thick and leathery, upper surface dark green with a prominent midrib, lower surface yellowish or grey-green, midrib also prominent, three to four (to five) secondary veins on each side of the midrib, margins thick and recurved, serrate with 4–11 short teeth, apex acute or mucronate; petiole 0.2–0.8 cm long, grey-green to purple, often with three prominent ridges. Inflorescences composed of a single flower, or more commonly a cluster of two to six flowers; sessile or cymose. Dioecious. Flowers unisexual (rarely hermaphrodite), burgundy-coloured and fragrant, 5-merous (rarely 4-merous) and 0.3–0.4 cm diameter. Fruit a septicidal capsule, the shape varying with the number of seeds, though often bilobed and heart-shaped, 0.5–0.7 × 0.4–0.7 cm, pale peach colour; the capsule splitting in two across (not between) the lobes. Seeds one to two, dark reddish brown with a pale orange, basal aril. Flowering October to March, fruiting December to May (Argentina, Chile). Sands 1974, Rodríguez R. et al. 1983. Distribution ARGENTINA: from Neuquén Prov. to Tierra del Fuego Prov.; CHILE: from Concepción Prov. (Bío-Bío Region) to Tierra del Fuego Prov. (Magallanes Region). Habitat Coastal scrub to moist Nothofagus forest, between 0 and 1300 m asl or more. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT515. Cross-references B722, S337, K300.

Maytenus magellanica was apparently first introduced to cultivation by Collingwood Ingram, who collected seed from a street tree in Puerto Montt, Chile and grew it in his garden at Benenden Grange, Kent (Bean 1981a, Clarke 1988). It has since been reintroduced by expeditions to Chile from Edinburgh and has become more widely grown, offered now by nurseries in both Europe and North America. It can have either an erect or a weeping habit, but when pendulous lacks the elegance of M. boaria. It seems to be quite hardy in British conditions.

SABIACEAE

MELIOSMA

Blume

Meliosma comprises 20–25 species in southeast Asia and Central and South America. They are evergreen or occasionally deciduous trees or shrubs with simple or imparipinnate leaves. The branchlets have prominent leaf scars and numerous lenticels, and the buds are pubescent. The inflorescences are terminal (rarely axillary) panicles, with up to four orders of branching and lenticels on the branches. The flowers are very small, numerous, hermaphrodite and sessile or with a short pedicel. The fruit is a small, subglobose or pyriform drupe with a single stone (van Beusekom 1971). Meliosma is one of those genera that never appears outside specialist nurseries or collectors’ gardens, but its members are valued for their handsome foliage and panicles of scented white flowers. The generic name means ‘honey-scented’ – although in North America the extraordinary, ugly name ‘worm-head tree’ has been adopted or invented for the genus, apparently for the worm-like radicle of the germinating seed (Wharton et al. 2005). Several species were described by Bean (1981a) but most remain very rare in cultivation and many have not been re-collected in recent years. Older specimens,

Section II. Species Accounts

Meliosma

517

grown from collections by Wilson and others, should be considered as candidates for conservation propagation to ensure that they are not lost from cultivation. In general Meliosma species are tolerant of a wide range of conditions but they clearly do best in good fertile soil in warm gardens. Wharton et al. (2005) note that some species, especially M. pinnata (Roxb.) Walp. subsp. arnottiana (Walp.) Beusekom var. oldhamii (Maxim.) Beusekom (see Bean and Krüssmann: B727, S339, K302 – mostly under the mercifully shorter name M. oldhamii), are prone to damage from spring frosts through expanding their growth early in the season, and this may be a reason why M. simplicifolia subsp. pungens, described below, has generally been considered tender. M. beaniana (NOW M. alba (Schlect.) Walp.) B726, S338, K302 M. cuneifolia (NOW M. dilleniifolia subsp. cuneifolia (Franch.) Beusekom) B726, S338, K302 M. dilleniifolia (Wall. ex Wight & Arn.) Walp. S338, K302 M. dilleniifolia subsp. cuneifolia (Franch.) Beusekom S338 M. dilleniifolia subsp. flexuosa (Pamp.) Beusekom S339 M. dilleniifolia subsp. tenuis (Maxim.) Beusekom S339 M. flexuosa (NOW M. dilleniifolia subsp. flexuosa (Pamp.) Beusekom) K302 M. myriantha Siebold & Zucc. B727, S339, K302 M. oldhamii (NOW M. pinnata subsp. arnottiana (Walp.) Beusekom var. oldhamii (Maxim.) Beusekom) B727, S339, K302 M. parviflora Lecomte B727, K302 M. pendens (NOW M. dilleniifolia subsp. flexuosa (Pamp.) Beusekom) B728, S339 M. pinnata (Roxb.) Walp. S339

Meliosma simplicifolia (Roxb.) Walp. Shrub or tree to 20 m. Branchlets terete, glabrous to tomentose. Leaves evergreen, entire, 3–50 × 1–18 cm, elliptic or obovate to lanceolate, papery to leathery, upper surface dull or shiny, lower surface paler, glabrous to tomentose particularly below and on the midrib and veins, 7–25 secondary veins on each side of the midrib, margins entire to dentate (often with spiny teeth), apex acute to acuminate; petiole 0.5–6 cm long, glabrous to pubescent, clasping at base. Panicles terminal (very rarely axillary), pyramidal, erect, dense to lax, (4–)10–50(–60) cm long, branched to two to four orders, sparsely pubescent to densely tomentose; pedicels absent or very small (0.3 cm). Flowers white; sepals (four to) five, though the addition of similar bracts can raise the number to 11, ovate, glabrous to pubescent; outer petals glabrous, inner petals deeply bifid, glabrous or ciliate. Fruit globose or subglobose, 0.4–1 cm diameter, stone keeled. Meliosma simplicifolia is widely distributed, and flowering and fruiting times vary significantly. Van Beusekom 1971. Distribution BANGLADESH; CAMBODIA; CHINA; INDIA; INDONESIA; JAPAN; LAOS; MALAYSIA; MYANMAR; PHILIPPINES; SRI LANKA; TAIWAN; THAILAND; VIETNAM. Habitat Usually montane tropical or subtropical forest up to 3000 m asl, but also at sea-level. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT517.

Meliosma simplicifolia is divided into eight subspecies, but only subsp. pungens (Walp.) Beusekom and subsp. rigida (Siebold & Zucc.) Beusekom are in cultivation in temperate areas. A key to these is provided below (a key to all eight subspecies can be found in van Beusekom 1971).

Plate 354. New leaves of Meliosma simplicifolia subsp. rigida at Tregrehan in April. The strongly veined leaves flush bronze. Image J. Grimshaw.

518

Meliosma

New Trees

1a. Leaflets elliptic to oblong, rarely lanceolate, margins entire or with a few teeth at the apex, dense tufts of hair in the vein axils of the lower surface present; panicles (5–)10–55 cm long, with primary branches subtended by reduced leaves; sepals (8–)9–11(–13); India (southeast), Indonesia (Sumatra), Sri Lanka ............................ subsp. pungens 1b. Leaflets obovate-oblong or obovate-lanceolate, margins coarsely dentate, dense tufts of hair in the vein axils of the lower surface absent; panicles 10–30 cm long, primary branches only rarely subtended by reduced leaves; sepals (4–)5; China (Fujian, Guangdong, Guangxi, Guizhou, southwest Hubei, Hunan, Jiangxi, south Yunnan, Zhejiang), Japan (east Honshu, Kyushu, Ryukyu Is., Shikoku), Laos, Philippines (north Luzon), Taiwan, Vietnam ....................................................... subsp. rigida

Meliosma simplicifolia has a limited presence in horticulture. Subsp. pungens has evidently been in cultivation for many years, as the largest recorded specimen was 11 m tall (25 cm dbh) at Caerhays Castle, Cornwall when measured by Alan Mitchell in 1984 (TROBI). This has since disappeared, but another 8 m specimen and a younger individual were noted there by Owen Johnson in 2006, who also measured a 7 m tree at nearby Trewithen (TROBI). It has been commercially available in British nurseries within the past decade, and a few young specimens have been traced in research for the current work, including a planting in the grounds of Buckingham Palace (TROBI, Johnson 2007), and others in collectors’ gardens such as Tregrehan. It is rather shrubby, according to Hillier & Coombes (2002), and has long had a reputation for tenderness (Chittenden 1951) – perhaps explaining its exclusion from Bean (1981a). Also at Tregrehan is subsp. rigida, grown from seed supplied by the Qingpu Paradise Horticultural Company (no. 97167). When seen in 2005 this Tregrehan specimen was growing vigorously, forming a single straight stem with spreading branches, and by 2007 it had reached 5 m (T. Hudson, pers. comm. 2007). The big deciduous leaves develop from reddish brown buds and are flushed reddish before turning dark green above, paler below. This is clearly a taxon to watch for, and coming from more temperate latitudes it should be hardier than subsp. pungens. It is not easy to propagate, however (T. Hudson, pers. comm. 2007). M. tenuis (NOW M. dilleniifolia subsp. tenuis (Maxim.) Beusekom) B728, S339, K303 M. veitchiorum Hemsl. B729, S340, K303

STYRACACEAE

MELLIODENDRON

Hand.-Mazz.

Melliodendron is monospecific, comprising only the species M. xylocarpum.

Melliodendron xylocarpum Hand.-Mazz. Tree 6–20 m, 0.2 m dbh. Bark greyish brown, often peeling irregularly. Leaves papery, 9.5–21 × 3–8 cm, ovate to lanceolate or oblong, densely covered with stellate tomentum when young, largely glabrous at maturity, though some tomentum may remain on the veins, seven to nine secondary veins on each side of the midrib, margins serrate, apex short-acuminate to acute; petiole 0.3–1 cm long. Flowers solitary or in pairs, situated

Section II. Species Accounts

Melliodendron

519

B 1 cm

A

in the leaf axils of older shoots, opening when the leaves emerge; subsessile or with a pedicel to 1.5 cm long. Calyx ~0.3 cm long, tubular and four-lobed, corolla campanulate and five-lobed, divided almost to the base, lobes 2–3 cm long, stamens 10 in one whorl, much shorter than corolla. Capsule attached to a persistent calyx, woody and indehiscent, obovoid to pyriform, 2–7 cm long, 5- to 10-ribbed, densely tomentose. Flowering April to May, fruiting July to October (China). Hwang & Grimes 1996. Distribution CHINA: Fukien, northern Guangdong, northwest Guangxi, Guizhou, Hunan, Jiangxi, southern Sichuan, southeast Yunnan. Habitat Forest ravines between 600 and 1500 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT519, NT520.

It is difficult to pin down the date of introduction of Melliodendron xylocarpum to Western horticulture, but in scarcely more than a decade it has become quite widely planted and much talked about. It seems to have arrived through multiple channels of the nursery trade, and plants and seeds are available from Chinese nurseries. The earliest record found is for 1994, when it was introduced to North America by Piroche Plants, British Columbia. It reached Europe at about the same time, as a plant obtained

Figure 60 (above). Melliodendron xylocarpum: habit with flowers (A); single leaf (B).

520

Melliodendron

Plate 355. Melliodendron xylocarpum flourishes in the David C. Lam Asian Garden in Vancouver, where specimens were planted soon after its introduction by Piroche Plants in 1994. Image P. Wharton.

New Trees

from the Shanghai Botanic Garden by Ken Beckett was being propagated at Hillier Nurseries in 1996 (A. Coombes, pers. comm. 2007). Some early material in Dutch nurseries at least was in fact Pterostyrax corymbosus – an error that was revealed when the trees came into flower (G. Fortgens, pers. comm. 2007). Authentic material is now being propagated in Boskoop (M. Bulk, pers. comm. via G. Fortgens 2007). The trees at the David C. Lam Asian Garden in Vancouver are perhaps the best known examples of the species, and derive from the Piroche introduction. They have done well in this woodland garden, forming single-stemmed specimens with spreading branches, up to 6 m tall. The leaves are a slightly glossy bright mid-green, with a long drip-tip, and fall late in the autumn (Wharton et al. 2005). The flowers, which are borne by even quite young trees, are its principal feature, being remarkably large (6–7 cm across when fully open). There seems to be a spectrum of colours of flowers, ranging from pure white to uniformly clear pink (and possibly darker), including some specimens that open white from pink-tinged buds (P. Wharton, pers. comm. 2008). Melliodendron seems to grow well in warm, moist situations, and appreciates summer heat so long as there is adequate moisture and some light shade. It has a very southern and rather low-altitude distribution in China, which may explain why it was not introduced earlier, but despite this it seems to be winter-hardy, at least in Zone 8 temperatures and possibly into Zone 7b as well (it has survived without problem for four years in North Carolina: T. Avent, pers. comm. 2007). It flowers and leafs out in early spring and may therefore be at risk from spring frosts, so a site with some shelter – perhaps a high tree canopy – seems to be advisable. If its relatives Styrax and Halesia are taken as models, it will probably not enjoy a calcareous soil.

MYRTACEAE

METROSIDEROS

Banks ex Gaertn.

The approximately 50 species of Metrosideros are widespread in the Pacific, ranging from the Philippines to Hawaii and New Zealand; there is also a single species in South Africa (M. angustifolia Sm.). They are epiphytic or terrestrial trees, shrubs or climbers. The leaves are opposite, petiolate and leathery; usually pubescent when young. Inflorescences are axillary or terminal racemes or cymes, rarely single-flowered. The flowers are usually 5-merous, red, pink, yellow or white; the hypanthium tubular to cup-shaped, lobes imbricate, petals orbicular, stamens numerous. The fruit is a leathery or woody capsule, partially or fully enclosed in the hypanthium, dehiscing by way of three valves. The seeds are numerous, and sometimes winged (Dawson 1976). The boundaries of the genus are somewhat uncertain, and a number of segregate genera are recognised by some authors (for example, Carpolepis J.W. Dawson, Mearnsia Merr., Thaleropia Peter G. Wilson). Metrosideros skirmishes along the frontier of our area, seldom growing further than a short distance from the sea in the mildest areas. Among the species that have a toehold in temperate gardens M. umbellata, described below, is the hardiest and most likely to succeed, but others may become more widely grown if global temperatures continue to rise. Several are discussed by Owen Johnson in his report on Half-hardy

Section II. Species Accounts

Metrosideros

521

Trees in Britain and Ireland (2007), and the comments that follow are based largely on this. Metrosideros excelsa, the New Zealand Christmas Tree, is of particular importance. There is a group of big trees at Tresco Abbey on the Isles of Scilly, up to 20 m or more in height, with trunks fattened by layer upon layer of aerial roots to a maximum of 223 cm diameter at 80 cm above the ground; when flowering, ‘their huge crowns turn scarlet and are visible far out at sea’ (Johnson 2007). There are a few specimens on the mainlands of Britain (far western Cornwall) and Ireland (Cork) in exceptionally favoured places, but it has been killed by frost even in so sheltered a garden as Tregrehan. As Johnson says, it could be tried in the heat island of central London (although ample water would be necessary). Metrosideros kermadecensis Oliv. is similar but has rounder leaves. This too grows on Tresco, and there is a surprise record of a plant of its cultivar ‘Variegata’ at Chapel Knap Garden, Porlock, Somerset. In the same garden, M. robusta has been planted – and again this also grows well on Tresco. At Tregrehan, Tom Hudson has planted the climbing species M. carminea Oliv. and M. diffusa. Small flowering pot plants of ‘plain’ and variegated Metrosideros (either M. kermadecensis or M. excelsa) are often available in garden centres and could conceivably be planted out in gardens. The curious outlier in the Cape, M. angustifolia (L.) Sm., has grown in the University of California Botanical Garden in Berkeley since 1906, and has been outside at Cistus Nursery for four years (S. Hogan, pers. comm. 2007). There is a good selection of the New Zealand species and their cultivars in the San Francisco Botanical Garden, and they grow well on the Pacific coast, from Ventura Co., California northwards to mid-Oregon (S. Hogan, pers. comm. 2007). Success is most likely if the plants become established for several years before suffering any damaging frost. For most temperate gardeners, however, these will probably always be trees to go to visit. M. diffusa (G. Forst.) Sm. K306 M. excelsa Sol. ex Gaertn. K306 M. robusta A. Cunn. K306

Metrosideros umbellata Cav.

Southern Rata

Syn. M. lucida A. Rich. Tree to 15 m, 1 m dbh or more. In the wild, large trees produce adventitious roots which descend from the canopy to root into the ground. These roots can fuse with the main trunk, greatly increasing the girth of the adult tree. Bark papery. Branchlets glabrous. Leaves evergreen, leathery, (2.5–)3–5(–6) × (1–)1.5–2 cm, elliptic to lanceolate, initially covered in silky hairs, later glabrous, secondary veins indistinct, margins entire, apex acute to rounded; petiole ~0.5 cm long. Inflorescences extremely variable in structure; flowers may be solitary or paired, but are always axillary. Typically, the vegetative bud at the tip of a flowering stem aborts; some of the nodes below the aborted bud produce flowers (either singly or in pairs); peduncles to 10 cm long. Flowers hermaphrodite, scarlet; hypanthium cup-shaped, initially covered in silky hairs, later glabrous, petals suborbicular, stamens numerous, ~2 cm long. Capsule woody, urn-shaped, ~0.8 cm long, completely enclosed in the hypanthium. Flowering November to January (New Zealand). Wardle 1971. Distribution NEW ZEALAND: Auckland Is., North Is. (Great Barrier Is., Little Barrier Is., Coromandel Range, Mt. Te Aroha, Tararua Range), South Is. (predominantly north, west and southern coasts), Stewart Is. Habitat Intolerant of dense vegetation; generally found on poor soils or in harsh, exposed sites between 0 and 1100 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT521, NT522. Cross-reference K306.

Plate 356. Metrosideros umbellata is the hardiest of the genus, but still needs a very mild situation, as here at Inverewe, Ross-shire. Image S. Andrews.

522

Metrosideros

New Trees

Plate 357. The carpet of fallen leaves and stamens below the old specimen of Metrosideros umbellata at Logan. The beauty of trees can be revealed in unusual ways. Image J. Grimshaw.

Metrosideros umbellata could be planted with some expectation of success anywhere along the western coasts of Europe, but perhaps only within earshot of the sea. The finest specimen known in our area is at Ilnacullin (Garinish Island), off western Cork, currently 14 m tall, but there are others on the mainland of Ireland at Ballywalter Park and Mount Stewart, both in Co. Down (Johnson 2007). On mainland Britain the best known is at Logan, planted in 1959. This has grown slowly but steadily to form a wider than tall multistemmed specimen, approximately 6 m in height. When seen in July 2006 it was just finishing flowering but the ground below the tree was covered in a mass of fallen stamens and yellow leaves and gave an indication of how spectacular it must have been when in full flower. The leaves are a glossy, brownish dark green, with a reddish or purplish flush on their paler undersides. There are younger trees at Logan. An example of the tolerance of the species is a 2.8 m bushy individual growing slowly in Tim Pyner’s garden at Southend, Essex (Johnson 2007): this suggests that it could be tried in sheltered gardens all along the southern coast of England.

SCROPHULARIACEAE (formerly MYOPORACEAE)

MYOPORUM

Banks ex Sol. & G. Forst.

The 28 species of Myoporum occur mainly in Australia and New Guinea, but with representatives in Mauritius, eastern Asia, New Zealand and Hawaii. They are small trees or shrubs with entire, alternate, petiolate leaves which are usually lanceolate, acute and with dentate margins. Inflorescences are axillary, composed of numerous clustered cymes; peduncles reduced or absent. The flowers have a five-lobed campanulate calyx; the corolla, usually white, is also five-lobed, with petals equal in size or with two larger petals below; stamens four (to five). The fruit is an ovoid drupe of various colours, from white, pink and purple to black (Theisen & Fischer 2004). With the exception of M. laetum, the genus Myoporum is scarcely known in temperate horticulture but a number of other species are cultivated in warmer climates, and can be particularly useful in coastal and sandy areas. Their principal horticultural value lies in their thick-textured evergreen foliage, as the flowers are usually small and inconspicuous, but the fruits in various colours also add a later season of interest (Huxley et al. 1992).

Section II. Species Accounts

Myoporum

523

M. acuminatum R. Br. K313

Myoporum laetum G. Forst.

New Zealand Manatoka, Ngaio

Shrub or tree 6–10 m, 0.5 m dbh; attractive, rounded tree with short spreading branches. Bark greyish brown, rough and corky. Immature branchlets and leaves green-bronze, sticky. Leaves somewhat fleshy, lush, 4–10 × 1–4.5 cm, narrow to broadly elliptic or obovate, covered with large conspicuous translucent glands, margins entire to serrulate, apex acute, mucronate or short-acuminate; petiole 0–1 cm long. Inflorescences axillary cymes with two to six flowers, located in the upper leaf axils; peduncles to 0.6 cm long. Flowers hermaphrodite, 1–1.5 cm diameter; calyx five-lobed, lobes lanceolate to ovate, corolla five-lobed, campanulate, petals white with purple spots, stamens four, attached to the corolla tube. Drupe broad oblong to ovoid, 0.5–1 cm long, pale purple to black. Salmon 1980, Sykes 1987. Distribution NEW ZEALAND: North Is. (coastal areas), South Is. (south to Otago). Habitat Coastal regions down to the high-tide line. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT523. Cross-reference K313.

Myoporum laetum is essentially a coastal plant, both as a native in New Zealand and in cultivation. It can be seen in seaside plantings around the Mediterranean, and in California where it has become invasive (cal-IPC 2006–2009). In such situations it is usually grown as a municipally pruned shrub, but it is potentially an attractive small tree forming a rounded crown with spreading branches, often with a gnarled and windswept look. The rounded leaves are a slightly yellowish mid-green, with the dull white, five-lobed flowers peering out from between them. It is currently doing well in Cornwall – there is a 5 m tree at Pine Lodge (Johnson 2007), and others elsewhere – and it could be tried along western coasts among seaward shelterbelts. In New Zealand young plants are considered to be a bit tender but when older it tolerates quite severe frosts (Metcalf 2000). It will grow best in good soil, but also copes with drier sites. Propagation is from seed or by cuttings. M. serratum R. Br. K313

MYRTACEAE

MYRCEUGENIA

O. Berg

There are 39 species of Myrceugenia, mostly in South America, but with two on the Juan Fernández Islands. They are small trees or shrubs, typically with reddish brown, yellowish or whitish branched or simple hairs on the branchlets, leaves and flowers. The leaves are opposite, leathery or membranous and with a prominent midrib. The inflorescence is an axillary dichasium or a terminal or axillary raceme; or, less often, a single flower. Bracteoles subtend the flowers until fruit set. The flowers are 4-merous with a shallow hypanthium; the calyx is four-lobed or the lobes are fused together into a cap-like calyptra, which is shed when the flower opens; the petals are small and the stamens numerous (approximately 40–500). The fruit is a fleshy berry containing one to five seeds. It is yellow, orange red or dark purple (Landrum 1981, 1984).

Plate 358. Myoporum laetum is a very useful evergreen for coastal plantings. The small white flowers lurk among the foliage. Image S. Andrews.

524

Myrceugenia

New Trees

1 cm 1 cm

C

A

1 cm

B

Section II. Species Accounts

Myrceugenia

Myrceugenia is very poorly known in cultivation, but appears to offer considerable horticultural potential as a group of attractive and apparently reasonably hardy shrubs (Gardner & Hechenleitner 2005). They are immediately recognisable as myrtles, displaying the familiar glossy dark green leaves and masses of many-stamened white flowers, followed by an abundant crop of fruits in colours ranging from purple to yellow. New growth may be flushed red, as in M. ovata. A brief review of the genus was recently provided by Gardner & Hechenleitner (2005) but does not mention all the species currently cultivated in the United Kingdom. These include: M. chrysocarpa (O. Berg) Kausel; M. lanceolata (Juss. ex J. St.-Hil.) Kausel; M. leptospermoides (DC.) Kausel, considered to be the most attractive by Gardner & Hechenleitner (2005); M. ovata (Hook. & Arn.) O. Berg; M. ovata var. nannophylla (Burret) Landrum; M. pinifolia (Phil.) Kausel. Most are in the collections of the Royal Botanic Garden Edinburgh, derived from its numerous expeditions to Chile, and are not yet widely distributed. With the exception of M. planipes, Myrceugenia species are low-growing shrubs. Hardiness varies, but a sheltered site seems advisable.

Myrceugenia planipes (Hook. & Arn.) O. Berg

Plate 359. Myrceugenia chrysocarpa at Logan – one of several shrubby species of this genus of myrtles from Chile. Image R. Unwin.

Pitra

Small tree to 8 m, 0.3 m dbh. Bark smooth, greyish brown. Branchlets pale grey with dense or sparse pubescence; hairs usually white or yellowish, rarely reddish brown, dichotomous. Leaves evergreen, leathery, aromatic, 2.2–8 × 1–3 cm, elliptic, upper surface dull green and glabrous, lower surface yellowish green with moderate or sparse pubescence and a prominent midrib, secondary veins indistinct or up to 30 pairs visible, margins entire, apex acuminate; petiole 0.2–0.6 cm long, channelled. Flowers hermaphrodite, white, fragrant, 1–1.5 cm diameter; solitary or in groups of three (to four) in upper leaf axils, peduncles flattened, 0.7–3 cm long, with sparse or moderate pubescence. Bracteoles ovate to lanceolate, very small; calyx four-lobed, sparsely pubescent or glabrous; hypanthium densely pubescent; stamens 120–220. Fruit globose, purplish black, 0.8–1.5 cm diameter. Flowering December to February, fruiting March to May (Chile). Landrum 1981, Rodríguez R. et al. 1983. Distribution ARGENTINA; CHILE: Aisén, Arauco, Bío-Bío, Cantín, Chiloé, Concepción, Llanquihue, Malleco, Ñuble, Osorno, Valdivia Provinces. Habitat Montane forest and matorral. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT524.

Myrceugenia planipes was not discussed by Gardner & Hechenleitner (2005) but was first introduced by the Chile Darwin Initiative Expedition of 1995 (CDI 11). Further collections were made by Edinburgh teams in 1998 (UCEXC 437, Berberidopsis Expedition 16). From these it has become established at Inverleith and Logan, and has been ‘outhoused’ for safekeeping to appropriate gardens elsewhere. A specimen seen at Logan in 2006, grown from CDI 11, has formed a bushy small tree (2.2 m in 2006), with ascending branches arising from a single main stem. It looks remarkably like Myrtus communis and, out of flower, could not be said to appear very exciting.

ARALIACEAE

NEOPANAX

525

Allan

Neopanax was split from Pseudopanax by Allan (1961) and comprises five species in New Zealand and the Kermadec Islands (Frodin et al. 2003). The primary difference between the two genera lies in the ovary, which has two locules (Neopanax) or three to five locules (Pseudopanax). For the amateur botanist this character is difficult to assess, and a more useful guide is the style, which has two branches (Neopanax) or

Figure 61 (opposite). Chilean myrtles. Blepharocalyx cruckshanksii: habit with flowers (A); fruits (B). Myrceugenia planipes: habit with flowers (C).

526

Neopanax

New Trees

three to five branches (Pseudopanax) (Allan 1961). Neopanax species are small trees or shrubs with stipulate compound leaves. In some species the leaves have distinct adult and juvenile forms: juvenile leaves have 3–12 leaflets, but adult leaves typically have a single leaflet. Neopanax is monoecious or dioecious with flowers in simple or compound umbels. The individual flowers are 5-merous and rather insignificant. The fruit is dry and slightly compressed. The current popularity of exotic foliage plants, in the United Kingdom at least, has led to the development of great interest in woody evergreen members of the Araliaceae, amongst which are the genera Dendropanax, Eleutherococcus, Fatsia, Meryta, Metapanax, Neopanax, Pseudopanax, Schefflera and Tetrapanax, all of which produce attractive and sometimes magnificent foliage from shrubs or small trees. The inclusion of the word panax in a name should automatically excite interest; the shuffling of species between prefixes, however, has led to a proliferation of synonyms, and tracking these through the literature and catalogues requires a certain mental flexibility. Although some members of Neopanax are remarkably hardy, others are distinctly tender, and most need some shelter to preserve the large leaves from wind damage. Ample moisture, but with good drainage, is appreciated in the growing season. The genus is perhaps most familiar in the form of Neopanax arboreus (syn. Pseudopanax arboreus) – a handsome evergreen shrubby small tree, closely related to N. laetus (described below) but hardier, and grown for many years in mild gardens. Another species that may appear in gardens or catalogues is N. colensoi (Hook. f.) Allan, another New Zealand native but smaller in stature. Johnson (2007) records a specimen 2 m tall in Tim Pyner’s garden in Southend, Essex. Propagation is by sowing fresh seed or taking cuttings, which root readily. N. arboreus (L. f.) Allan K320

Neopanax laetus (Kirk) Allan Syn. Nothopanax laetus (Kirk) Cheeseman, Pseudopanax laetus (Kirk) Philipson Large shrub or small tree to over 5 m tall; the crown much branched and rounded. Leaves evergreen, very large, digitate, petiole purplish red and sheathing the stem, to 25 cm long; leaflets five to seven, 10–14 × 5–7 cm, narrow, ovate to oblong, green, though paler below, glossy, thick and leathery, margins coarsely dentate to serrate, midribs and lateral veins prominent, apex acuminate to acute; petiolules 0.8–2.2 cm long. Dioecious. Inflorescences terminal and compound, without a distinct primary axis, umbellate; primary branches 4–15, with 9–20 umbels; umbels with 13–36 flowers each. Flowers small, 0.3 cm wide in bud, brown. Fruit ribbed, 0.5 cm diameter, slightly compressed; two distinct apical stigmatic branches. Cheeseman 1923, Allan 1961. Distribution NEW ZEALAND: North Is. (Coromandel Peninsula to Taranaki). Habitat Lowland forest. USDA Hardiness Zone 9–10. Conservation status Not evaluated, but subject to browsing by introduced mammals. Illustration Phillips & Rix 1997; NT526. Cross-references B421 (as Pseudopanax laetus), K320.

Plate 360. A magnificent specimen of Neopanax laetus in the gardens of Dunloe Castle, Co. Kerry, encouraged by the mild climate. Image R. Lancaster.

Neopanax laetus is a truly magnificent shrubby tree, with huge glossy leaves. Unfortunately it is rather tender, with even catalogues suggesting that mature, established specimens can tolerate only –5 °C (for example, Trevena Cross Nurseries catalogue 2003). Despite this it is worth attempting, in appropriately mild, sheltered gardens – possibly having grown it under glass for some time before planting it out. The record in the British Isles is a 7.5 m specimen recorded at Castlewellan in Co. Down in 2004. Alternatively, it can be enjoyed as a very handsome pot or conservatory plant.

Section II. Species Accounts

Nestegis

527

OLEACEAE

NESTEGIS

Raf.

There are five species of Nestegis: four in New Zealand and one (N. sandwicensis (A. Gray) O. Deg., I. Deg. & L.A.S. Johnson) in Hawaii (Wallander & Albert 2000). They are evergreen trees and shrubs with leaves that are simple, opposite and entire. The leaves of juvenile plants are often of a different form to those of the adult. Inflorescences are axillary, decussate and racemose. The flowers are hermaphrodite or unisexual; the calyx small, four-lobed, cup-shaped; the corolla four-lobed or absent; stamens two to six. The fruit is a reddish drupe (Degener et al. 1958, Green 1963, 2004). With the exception of the few specimens mentioned below, Nestegis is almost entirely unknown in gardens of the northern hemisphere and their literature. In New Zealand, however, the endemic species are appreciated for their dense evergreen canopies and their coloured fruits, which are eaten by birds. In addition to N. cunninghamii and N. lanceolata covered here, there are young plants of the narrow-leaved N. montana (Hook. f.) L.A.S. Johnson at Tregrehan. It and N. apetala (Vahl) L.A.S. Johnson are cultivated in New Zealand, and like the others, could be tried in mild coastal gardens in our area.

Nestegis cunninghamii (Hook. f.) L.A.S. Johnson

Black Maire

Syn. Gymnelaea cunninghamii (Hook. f.) L.A.S. Johnson Tree to 20 m, 1.5 m dbh. Branchlets pubescent to glabrous. Leaves evergreen and leathery, (5.5–)7–12(–21) × 1.5–4.5 cm, narrowly lanceolate to elliptic or ovate, hairs present on immature shoots and inflorescences, secondary veins obscure, 8–10 on each side of the sunken midrib, margins entire and slightly thickened, apex acute or rarely obtuse; petiole 0.4–1.7 cm long and pubescent when young. Monoecious or dioecious.Inflorescences axillary and decussate, borne below the leaves, 1.5–4 cm long and bearing 9–19 flowers. Flowers rather insignificant, unisexual or rarely hermaphrodite; calyx campanulate with four irregular lobes; corolla absent; stamens two. Fruit a reddish drupe, 1–1.5 cm long. Flowering September, fruiting October to November, ripening the year after flowering (New Zealand). Green 1963, 1967, Salmon 1996. Distribution NEW ZEALAND: North Is. (widespread), South Is. (extreme north only). Habitat Lowland and montane forest. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT527. Cross-reference K219.

Although potentially making a large and beautiful forest tree, valued, additionally, for its very hard wood, Nestegis cunninghamii is slow-growing – a specimen in Christchurch Botanic Gardens having reached only 5 m after 25 years (Metcalf 2000). At Tregrehan it has achieved 2 m in 10 years and is doing well. The dark evergreen foliage is attractive, with opposite pairs of very narrow leaves. The flowers are inconspicuous but red fruits are produced in abundance, giving the tree a glow of colour (Salmon 1996). Deep rich, well-drained soil is preferred, with propagation by seed or from cuttings (Metcalf 2000).

Nestegis lanceolata (Hook. f.) L.A.S. Johnson

White Maire

Syn. Gymnelaea lanceolata (Hook. f.) L.A.S. Johnson Tree to 15 m, 1 m dbh. Branchlets slender, with pale bark. Leaves evergreen and leathery, (3.5–)5–9(–12) × (0.7–)1–2.5(–3.5) cm, lanceolate or narrowly lanceolate, glabrous, upper surface glossy, four to six (to seven)

Plate 361. The characteristic opposite leaves found in Oleaceae are clearly visible in Nestegis cunninghamii from New Zealand. Image J. Grimshaw.

528

Nestegis

New Trees

secondary veins on each side of the midrib, though inconspicuous, margins entire, apex acuminate to acute; petiole 0.4–1.1 cm long, slightly pubescent. Monoecious or dioecious. Racemes axillary or ramiflorous, decussate, one to three per axil, 1–3 cm long and bearing 5–10(–17) flowers. Flowers rather insignificant, unisexual or rarely hermaphrodite, pale greenish white; calyx campanulate with four irregular lobes; corolla absent; stamens two to four (to six). Drupe ellipsoid to oblong, 0.8–1.2 cm long, crimson, red or orange. Flowering November to January, fruiting December to February (New Zealand). Allan 1961, Green 1963, Salmon 1980. Distribution NEW ZEALAND: North Is. (widespread), South Is. (north only). Habitat Lowland and lower montane forest. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note This species is similar to N. cunninghamii, though slightly smaller, with narrower leaves and paler branchlets. A hybrid (N. cunninghamii × N. lanceolata) is relatively common in the wild.

A 4.5 m tree of unknown origin at Logan Botanic Garden is the only specimen of Nestegis lanceolata traced in our area in the research for New Trees. It seems to be doing well, making a neat, openly columnar shape, from the many stiffly ascending branches that arise from just above the base. The leaves are a dull dark green, with a paler midrib. The tree was in bud when observed in August 2006.

LAURACEAE

NOTHAPHOEBE

Plate 362. Nothaphoebe cavaleriei is a very distinguished evergreen tree, but sadly rare in cultivation. Image R. Lancaster.

Blume

Nothaphoebe is a genus of about 40 species, most of which occur in southeast Asia. They are small or large, evergreen trees or shrubs. The leaves are alternate and pinninerved. Inflorescences are terminal or axillary panicles. The flowers are hermaphrodite, 3-merous, with two whorls of tepals of different sizes (outer tepals smaller). They have nine fertile stamens in three whorls, with glands on the innermost whorl; a fourth whorl of small staminodes may also be present. The fruit is a drupe or single-seeded berry and is partially enclosed by, or sits on a scarcely thickened pedicel. Nothaphoebe is sometimes regarded as a synonym of Persea (Rohwer 1993a, Li et al. 2005). The genus is almost unknown in cultivation, but judging from the effect of N. cavaleriei, other species would be worth trying. A sheltered site with moist acidic soil would be most appropriate. Propagation is by seed or from cuttings, which root reasonably well, at least when the parent is young (T. Lasseigne, R. Olsen, pers. comms. 2007).

Nothaphoebe cavaleriei (H. Lév.) Yang Tree 3–7(–13) m or more. Bark reddish brown with longitudinal striations, forming small flakes at the base. Branches remaining green-barked. Branchlets glabrous, yellowish brown with dense oblong lenticels. Leaves evergreen, alternate, 10–18 × 2.5–5 cm, leathery, oblanceolate to obovate, upper surface dark green and glabrous, lower surface greenish white with tiny hairs (only visible under magnification) and a prominent elevated midrib, 8–12 secondary veins on each side of the midrib, margins entire, apex short-acuminate; petiole 1.5–2 cm long, glabrous. Inflorescence axillary, paniculate, lax, 9–16 cm long. Flowers yellow or yellowish white, about 0.3 cm long with a short, six-lobed perianth tube; outer three tepals half as long as the inner three, all tepals sparsely pubescent on the outside and densely villous inside; stamens nine, inner three with short-stalked reniform glands near the base. Fruit globose, 1.2–1.4 cm diameter with persistent tepals at the base. Flowering May to July, fruiting August to September (China). Li et al. 2005. Distribution CHINA: Guizhou, Sichuan, Yunnan. Habitat Montane forest margins between 500 and 1900 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NTxiii, NT528.

Section II. Species Accounts

Nothaphoebe

Nothaphoebe cavaleriei is one of the most beautiful of broadleaved evergreen trees, but sadly (and curiously) scarce in cultivation, although commercially available in the United States. A tree of 15 m with 22 cm dbh, forming a good conical shape, was one of the glories of Heronswood, and there is a fine tree in Aiken, South Carolina (T. Lasseigne, pers. comm. 2007). In the United Kingdom a striking specimen grows in Roy Lancaster’s garden, reaching 6 m since 1996 and described by him as ‘A most handsome evergreen … much admired by visitors’ (R. Lancaster, pers. comm. 2006). These three are all the same clone, propagated by cuttings from a tree raised from Index Seminum seed in the early 1990s in what was then the North Carolina State University Arboretum. Richard Olsen (pers. comm. 2007), an NCSU student at that time, recalls how excited J.C. Raulston was when it germinated and how keen he was to pass it around – hence the gifts to Dan Hinkley and Roy Lancaster – because he feared it would not grow in North Carolina. This pessimism was justified as the original plant was killed by its first winter outdoors (T. Lasseigne, pers. comm. 2007). The tree in Aiken, planted by Bob McCartney of Woodlanders Nursery, has reached about 6 m, but its top is frozen back at temperatures below –7 to –8 °C, suffering more damage than two species of Phoebe nearby (T. Lasseigne, pers. comm. 2007). The great beauty of this plant comes from its broad glossy dark green leaves, glaucous grey-white below, and conspicuously veined. They are pleasantly spicily scented when crushed.

NOTHOFAGACEAE (formerly FAGACEAE)

NOTHOFAGUS

Blume

False Beeches, Southern Beeches Nothofagus is restricted to the southern hemisphere. Its 34 species are found in southern South America, southeast Australia and Tasmania, New Zealand, New Caledonia and New Guinea (including New Britain) (Govaerts & Frodin 1998). The genus has been separated from Fagaceae into its own family Nothofagaceae, but both are included in the order Fagales, together with Betulaceae, Casuarinaceae, Juglandaceae, Myricaceae and Ticodendraceae (APG 2003). The southern beeches are deciduous or evergreen trees or shrubs. The leaves are distichous, though appear decussate in bud, and are often plicate prior to expansion. They are entire or toothed, thin or firm in texture and covered in resinous glands. The veins are usually conspicuous, and their number can be a significant taxonomic character. Stipules are often large and peltate and may be persistent or caducous. Nothofagus is monoecious and bears separate staminate and pistillate flowers. The staminate flowers are axillary, solitary or in groups of three, and sessile or with a short peduncle. The pistillate flowers are borne above the staminate flowers and are solitary or in groups of three (rarely seven); they are also axillary, and are subtended by a cupule with two to four valves. The cupule has foliose or glandular appendages. The fruit is a nut and there are three in each cupule; the central nut has two wings while the two lateral nuts have three wings (van Steenis 1953, Hewson 1989).

529

530

Nothofagus

New Trees

1 cm

B

1 cm

A

Section II. Species Accounts

A key to the species in cultivation in the British Isles is given by Clarke (1971), though this does not incorporate all the species described below, and Grant & Clement (2004) present a key to the deciduous species. There is also a website devoted to Nothofagus (in French) which is comprehensive, well illustrated and highly recommendable (Nothofagus 2007–2008). After Eucalyptus, Nothofagus is the most important southern hemisphere genus of trees for temperate gardens, with some species such as the robust Chilean N. obliqua quickly forming handsome trees in a range of different conditions. Many others, however, are less successful. As in Eucalyptus, there are many species that are not fully hardy in northern Europe and thrive only in the mildest parts. Some have very narrow ecological requirements, that can make them apparently almost ungrowable. The New Guinean and New Caledonian species, which make up the largest part of the genus, are almost entirely unknown in cultivation and are probably extremely tender. Of these, Nothofagus pullei Steenis has been attempted by Tom Hudson (pers. comm. 2007), but he reports that it is ‘very tender and dies if it is a cloudy day’. Good drainage, a mild but not too warm site, high humidity and shelter from strong winds all seem to be important factors for growing the less frequently seen species. All require acidic or neutral soil. These requirements do limit the area in which Nothofagus can be grown, and they are found only in gardens on the western fringes of Europe and North America; their relative frequency in British gardens is deceptive. There are good representatives in many British and Irish arboreta, and no less than three National Plant Collections of Nothofagus: at Wakehurst Place, Mount Usher and Crarae Garden, Argyll. To propagate endangered Chilean species, Gardner et al. (2006) recommend cuttings made from the tips of basal suckers and placed in a mist unit, with or without bottom heat. Soaking the seed for 24 hours in a 250 ppm solution of gibberellic acid enhances germination (Gardner et al. 2006). Seed from arboretum-grown specimens is quite likely to give hybrid offspring. This is exemplified by the recently described N. ×eugenanana K. Gillanders, the progeny of N. alessandrii and N. fusca, which arose at the Tasmanian Arboretum at Eugenana, Tasmania (Gillanders 2008). In recent years there has been an important change to the nomenclature of the well-known species called Raulí in Chile, which may bring some order to a state of confusion. Bean (1976b: B16) and Krüssmann (1985a: K327) both used the name N. procera (Poepp. & Endl.) Oerst., with N. nervosa (Phil.) Krasser as a synonym. Poeppig and Endlicher (1838) originally named two species, one from high-altitude areas (N. alpina), the other from lower altitudes (N. procera), but both of these are forms of Raulí. The name N. procera Poepp. & Endl. was illegitimate (it duplicates an earlier name) and was later changed to N. nervosa (Lennon et al. 1987). Van Steenis (1953) first suggested that N. alpina was a hybrid, and Lennon et al. (1987) identified the parents as N. nervosa and N. obliqua (Mirb.) Blume. However, after examination of type material, Grant & Clement (2004) have determined that the correct name for Raulí is Nothofagus alpina, with N. nervosa and N. procera as synonyms. Nothofagus alpina does form a hybrid with N. obliqua, and this has been named N. ×dodecaphleps (see below).

Nothofagus

531

Figure 62 (opposite). Nothofagus gunnii: habit with cupules (A); cupule with seeds (B).

Plate 363. Nothofagus alpina is now the accepted name for Raulí, a wellknown Chilean species, seen here with Volcan Llaima in the background. Image S. O’Brien.

532

Nothofagus

New Trees

Nothofagus alessandrii Espinosa

Ruil

Tree to 30 m, to 1 m dbh. Bark grey, breaking into irregular plates with age. Branchlets brown and tomentose. Leaves deciduous, somewhat leathery, 7–13 × 4–9 cm, ovate to cordate, rarely lanceolate, immature leaves with golden silky hairs along the veins and midrib on both surfaces and with a fringe of hairs around the margins, mature leaves largely glabrous, but for some golden hairs along the midrib, 11–13 secondary veins on each side of the midrib, margins dentate, with tiny spines terminating the secondary veins, apex acute to acuminate; petiole short, 0.6–1.1 cm long, softly hairy; stipules leathery, oblong to lanceolate and caducous. Leaves turn yellow in winter. Staminate flowers in groups of three (rarely four) and with short peduncles; stamens 10–20, 1–1.4 cm long. Pistillate flowers in groups of three to seven; cupule sessile, 1 cm long, pyramidal, four-valved and covered with woody scales. Nuts three to seven, winged. Flowering September, fruiting January to February (Chile). Rodríguez R. et al. 1983. Distribution CHILE: Maule Region, though previously widespread in central Chile. Habitat Known from only nine localities in the coastal mountains between 160 and 440 m asl. USDA Hardiness Zone 8. Conservation status Endangered, due to habitat loss for forestry and agriculture. Illustration Rodríguez R. et al. 1983. Cross-references B16, S347, K324.

The decline of Nothofagus alessandrii as a wild tree has been extremely rapid as its habitat has been lost to plantations of Pinus radiata and to agriculture, and the species now grows in highly fragmented patches over a total area of less than 3.5 km2 (Gardner et al. 2006). It is a fine large tree, with handsome, strongly veined leaves that colour to rich orange in autumn. It seems to be reasonably well established in cultivation, with good specimens in several British gardens. The best are a group of three trees ranging between 17 and 22 m tall at Plas Newydd, Anglesey, measured by Owen Johnson in 2005 (TROBI), but it is flourishing in Park Wood at Hergest Croft as well, and approaching 20 m there (L. Banks, pers. comm. 2007). It is also in cultivation in Australasia. N. antarctica (G. Forst.) Oerst. B8, S345, K324 N. antarctica var. bicrenata (NOW N. pumilio (Poepp. & Endl.) Krasser) B9 N. antarctica var. uliginosa (NOW N. antarctica (G. Forst.) Oerst.) B9, K325 N. ×apiculata (Colenso) Cockayne K325 N. betuloides (Mirb.) Oerst. B9, S345, K325 N. blairii (NOW N. ×apiculata nothovar. blairii (Kirk) Govaerts) K325 N. cliffortioides (NOW N. solanderi var. cliffortioides (Hook. f.) Poole) K325 N. cunninghamii (Hook.) Oerst. B10, S345, K326

Nothofagus ×dodecaphleps Mike L. Grant & E.J. Clement This taxon is a hybrid between N. alpina and N. obliqua. It has leaves with 10–14 pairs of secondary veins and an oblique or truncate base; the cupule scales are 1–4 mm long with sparse glands. In comparison, N. alpina has leaves with 12–18 pairs of secondary veins and a cuneate or truncate base, cupule scales 3–8 mm long with numerous glands; N. obliqua has leaves with 7–12 pairs of secondary veins and an oblique base; cupule scales 1–2 mm long with no glands. Grant & Clement 2004. Distribution CHILE: in any area where the ranges of the two parent species overlap. Also in cultivation. USDA Hardiness Zone 8. Cross-reference S346.

Nothofagus ×dodecaphleps is apparently rare in cultivation, but it could occur from arboretum- or even wild-collected seed and should be looked for in seedling batches. A recognised specimen has grown at Tregrehan since 1994 and is currently about 8 m tall (T. Hudson, pers. comm. 2007). N. dombeyi (Mirb.) Oerst. B10, S345, K326 N. fusca (Hook. f.) Oerst. B11, S345, K327 N. fusca var. colensoi (Hook. f.) Cheeseman K327 N. glauca (Phil.) Krasser B15, S347, K327

Section II. Species Accounts

Nothofagus gunnii (Hook. f.) Oerst.

Nothofagus

533

Tanglefoot

Shrub or tree to 3 m (rarely to 15 m); typically multistemmed. Branchlets short and yellow-pubescent. Leaves deciduous, somewhat leathery, distinctly folded, 1–2 × 0.9–1.7 cm, ovate to orbicular, upper surface with scattered golden hairs particularly along the midrib, lower surface with golden hairs restricted to the veins and midrib, four to six secondary veins on each side of the midrib, margins crenate, apex obtuse or emarginate; petiole 0–0.3 cm; stipules to 0.3 cm long, ± persistent. Leaves turn golden-yellow (rarely red or orange) before falling. Staminate flowers in groups of one to three and with recurved peduncles; stamens 6–12. Pistillate flowers in groups of three; cupule 0.8 cm long, four-valved and covered with recurved hook-like scales. Nuts three, winged. Flowering October to February, fruiting March to May (Australia). Van Steenis 1953, Hewson 1989. Distribution AUSTRALIA: Tasmania. Habitat Subalpine communities between 500 and 1300 m asl on the western and central plateau mountains. On exposed sites, makes a wiry, tangled shrub forming dense, impenetrable stands. USDA Hardiness Zone 8 (?). Conservation status Not evaluated. Illustration Hewson 1989; NT530, NT533. Cross-references B18, S348.

In the event, Nothofagus gunnii has probably been included here somewhat under false pretences. It is notoriously difficult to grow in cultivation, but when the list of species to include in New Trees was drawn up it was growing at Wakehurst Place. The propagation team there had succeeded in raising a single seedling from a collection made by David Hardman and Andy Jackson in Tasmania in 2000 (ETAZ 34). It had been planted out and had achieved a height of about 60 cm when someone dug or pulled it up, rather carelessly, damaging the roots and thus reducing even further its chances of survival. The thief clearly recognised its value and interest and is probably among those who will read this book – a keen dendrologist. The theft was widely reported in the British press but as usual no suspect was ever traced. No further specimens are known in British gardens. In its native Tasmania, where it is the only native deciduous tree (Malahide 1971), it has an ‘outstanding’ presence (Elliot & Jones 1997), producing stunning autumn colours from appealingly contorted trees. The same authors say, however, that it is difficult to ‘tame in cultivation’; they prescribe a cool, sheltered, moist but freely draining site, and note that although it experiences harsh conditions in the wild, it does not tolerate long periods of cold weather in Europe or North America. In Australian conditions it can apparently be grown in pots of acidic medium, and even used for bonsai (Elliot & Jones 1997). Experiments should be made with mycorrhizal inoculation of seedlings. Ken Gillanders (2008) reports that seed from cultivated N. gunnii in Tasmania can give hybrid offspring, but that the other parent(s) have yet to be identified.

Nothofagus ×leonii Espinosa

Huala

This taxon is a hybrid between N. obliqua and N. glauca. It has reddish brown inner bark and greyish red or dark brown outer bark (soft or hard). The branchlets have few or no short hairs and few or many long hairs, and the leaves are dark green and have a cuneate or rounded base. In comparison, N. obliqua has brown inner bark and hard, dark brown outer bark, branchlets largely glabrous, leaves dark green with a cuneate or rounded base; N. glauca has reddish inner bark and soft, greyish red outer bark, branchlets densely pubescent, leaves glaucous green with a cordate or truncate base. Donoso & Landrum 1979. Distribution CHILE: in any area where the ranges of the two parent species overlap. USDA Hardiness Zone 8. Illustration Rodríguez R. et al. 1983; NT16, NT534. Cross-references B16, S347, K327.

Plate 364. Nothofagus gunnii (foreground), in habitat in Tasmania. It has never been tamed in the northern hemisphere. Image P. Baxter.

534

Nothofagus

New Trees The success of Nothofagus ×leonii in Forestry Commission trials started in 1979 gained it a brief mention in Clarke (1988), but no expanded account of its horticultural merit has ever been published. As might be expected from its parentage it is a very handsome tree, and grows rapidly into a good specimen. The best in the United Kingdom is a magnificent tree in the Brentry area of the Sir Harold Hillier Gardens, received from the Forestry Commission in 1982, measured at 21.5 m (40 cm dbh) in 2006 (Sir Harold Hillier Gardens database), which has a columnar trunk supporting a dense canopy. A younger specimen grown from David Rae and Peter Baxter’s collection (no. 22) in Chile in 1996 is doing very well on an open hillside at Benmore. It is clear that this hybrid will flourish in most parts of the British Isles and by extension the coastal margins of Europe and the Pacific Northwest. Some variability can be expected, and it is possible that some trees in cultivation are second-generation seedlings from wild-origin primary hybrids, and therefore may show grandparental characteristics in different proportions. It is now most likely to occur from cultivated seed, as its parent N. alessandrii is endangered by habitat loss in the wild.

Plate 365. Nothofagus ×leonii (Rae & Baxter 22), flourishing at Benmore. The silvery sheen on the leaves is caused by the presence of many small glands. Image R. Unwin.

N. menziesii (Hook. f.) Oerst. B13, S346, K327

Nothofagus menziesii (Hook. f.) Oerst. × N. obliqua (Mirb.) Blume A semi-evergreen tree intermediate in characters between its parents. Bark cherry-like, purple-brown, with slender horizontal bands of pale lenticels, becoming grey and vertically fissured at the base. Young shoots slender, tomentose. Leaves thinly leathery, rhombic-ovate, to 2.5 × 1.3 cm (on vigorous shoots to 3 × 1.5 cm), glossy green and glabrous above, pale blue-green and glabrous beneath except for sparse hairs along the midrib, secondary veins four to six on each side of the midrib, sharply double-toothed or even shallowly lobed, base entire, broadly cuneate and sometimes slightly unequal; petiole tomentose, 3 mm. A. Coombes, pers. comm. 2007. Distribution Only in cultivation. USDA Hardiness Zone 8.

This unique hybrid between an evergreen species from New Zealand (N. menziesii) and a deciduous one from Chile (N. obliqua) arose in cultivation in the United Kingdom, the earliest record being from Weston Park on the Shropshire/Staffordshire border (Wigston 1979). It remains rare in cultivation, with only a few specimens recorded in the major British collections, but it is capable of achieving good stature quite rapidly; Owen Johnson has measured trees of 15 m at Kew (2001) and 16 m at Wakehurst Place (2005) (TROBI). At the Hillier Gardens two specimens were received from the Forestry Commission at Alice Holt in 1982 (without further information), of which the survivor had reached 12.5 m (38 cm dbh) in 2007 (A. Coombes, pers. comm. 2007). Allen Coombes, to whom we are indebted for the description of this tree, reported in early December 2007 that the tree was still in full leaf at that time, though a few leaves were turning yellow. He has not observed flowers or fruit. The fine, straight Kew specimen was half-bare in January 2008, and many of the remaining leaves were yellowish. The strongly double-toothed or weakly lobed margins give the leaf a very distinctive outline. N. moorei (F. Muell.) Krasser B13, S346, K327

Section II. Species Accounts

Nothofagus

Nothofagus nitida (Phil.) Krasser

535

Coigüe de Chiloé

Tree to 35 m, to 2 m dbh. Bark greyish, breaking into plates with age. Branchlets densely covered in short hairs. Leaves evergreen, leathery, 2–4 × 1.6–2.5 cm, ovate to lanceolate with an uneven base, upper surface glabrous, lower surface with distinct venation, four to six secondary veins on each side of the midrib, margins irregularly and minutely serrate, apex acute; petiole 0.2–0.7 cm long; stipules membranous and caducous. Staminate flowers in closely knit groups of three and with a short peduncle; stamens five to eight. Pistillate flowers in groups of three to five; cupule sessile, 0.2–0.4 cm long, four-valved and covered with softly hairy scales. Nuts three, winged. Flowering September to November, fruiting March to May (Chile). Rodríguez R. et al. 1983. Distribution ARGENTINA (?); CHILE: Aisén and Los Lagos Regions. Habitat Occurs in perhumid forest in the coastal mountain range and the Andes up to 1000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT535. Cross-references B11, S345, K327.

Nothofagus nitida is one of the most attractive species in the genus, with stiff, neatly toothed glossy leaves, held regularly on the shoots, that have the added merit of flushing red-bronze. When young it is particularly elegant, but it develops into a substantial tree that needs to be given adequate space. The largest recorded in the British Isles – a specimen at Royal Holloway College, Surrey – was measured at 18 m (48 cm dbh) by Owen Johnson in 2001 (TROBI). According to Clarke (1988), the species was not introduced until 1976 when the Forestry Commission added it to its trials. If the Royal Holloway College tree, and another of 16 m at Benmore in 1994 (TROBI), are from this introduction then it must be very fast-growing indeed. More recently, collections have been made by teams from Edinburgh, from which specimens are growing well in Scottish gardens, and there have been commercial importations also, but this is not a common tree and should certainly be planted more widely. N. obliqua (Mirb.) Oerst. B14, S346, K327 N. obliqua × N. procera (NOW N. ×dodecaphleps Mike L. Grant & E.J. Clement, NT532) S346 N. procera (NOW N. alpina (Poepp. & Endl.) Oerst.) B16, S347, K327 N. pumilio (Poepp. & Endl.) Krasser B18, S347, K327 N. solanderi (Hook. f.) Oerst. B19, S348, K327 N. solanderi var. cliffortioides (Hook. f.) Poole B19, S348 N. truncata (NOW N. fusca var. colensoi (Hook. f.) Cheeseman) B12

PINACEAE

NOTHOTSUGA

Hu ex C.N. Page

The monospecific genus Nothotsuga is closely related to Keteleeria and Pseudolarix, all three genera having terminally clustered male strobili and cones on long, leafy peduncles. In all three also, the seed scales are shed by disintegration of the rachis, rather than abscission of the individual scales as in Abies and Cedrus (Frankis 1988). Nothotsuga longibracteata was formerly classified as a species of Tsuga, and its vegetative morphology resembles that of Tsuga in many ways. It can be distinguished, however, by the presence of a long, leafy peduncle on the female cone, by its clustered male strobili, and by the exserted, spathulate bract scales of the cone (Page 1988).

Plate 366. Emerging bronze, the leaves of Nothofagus nitida remain glossy throughout their life and are a very neat shape. It is a vigorous large tree. Image M. Gardner.

536

Nothotsuga

New Trees

Nothotsuga longibracteata

Bristlecone Hemlock

(W.C. Cheng) Hu ex C.N. Page Syn. Tsuga longibracteata W.C. Cheng Tree to 30 m, though sometimes shrub-like, trunk often forked or multistemmed, 1–1.2 m dbh. Bark rough, scaly, greyish brown. Crown conical initially, with drooping leader, later dense and bushy with a flat top. Branchlets slender, firm, yellowish brown to brown, glabrous, with delicate grooves, branching somewhat dimorphic as in Cathaya, with small, lateral shoots developing on young branches. These do not extend significantly (0.5–1.5 cm long), and terminate with a tuft of leaves and a bud. Vegetative buds not resinous. Leaves dark, glossy green, spirally arranged and more or less pectinate, 1.1–2.4 × 0.1–0.25 cm, linear, petiolate, with a slightly twisted base, apex acute; stomata in two strips separated by the insignificant midrib. Male strobili clustered and pendent, terminal or subterminal on small, lateral shoots, pedunculate, 0.5–1 cm long, yellow-brown. Female cones erect, ovoid to oblong, apex obtusetruncate, (2–)2.5–5(–5.8) × 1.5–2.5(–3) cm, purplish or red, turning dark brown later, pedunculate (the peduncle is actually a leafy shoot); the cones remain attached to the tree for several years before disintegrating, or snapping off at the peduncle. Seed scales 20–30, suborbicular to peltate, 1–2.2 × 1.2–2.5 cm. Bract scales spathulate, 0.7–1.8 cm long, slightly exserted. Seeds brown, ovoid, wings reddish brown, ovate to oblong, 0.7–1.2 × 0.5–0.6 cm. Farjon 1990. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi. Habitat Low to medium elevation mountains, between 300 and 2300 m asl. USDA Hardiness Zone 7. Conservation status Endangered. Illustration Farjon 1990, Fu et al. 1999c; NT536, NT870.

Plate 367. The endangered Nothotsuga longibracteata is represented in cultivation only by young plants, grown on behalf of the International Conifer Conservation Programme. Image J. Grimshaw.

The endangered Nothotsuga longibracteata has been introduced to cultivation as part of the International Conifer Conservation Programme (ICCP) of the Royal Botanic Garden Edinburgh. Two collections of seed have been received for this project. The first was a gift in 1999, from the director of Shenzen Botanical Garden, of seed collected by the Garden’s staff on the Hunan side of the Nan Ling Mountains (P. Thomas, pers. comm. 2007), registered under the number TNL 11. A second introduction for the ICCP came from Nanjing Botanic Garden via the US National Germplasm Repository and Bedgebury. From these two sources a limited number of seedlings have germinated. Some are being maintained in the Edinburgh collection while others have been outhoused to gardens with different conditions, such as Bedgebury. The plants are all still very small and it is too early to make useful comments on their performance. Coming from low altitudes in southern provinces of China it is possible that it will require considerable summer heat to do well, in the same way as the related Keteleeria does.

CORNACEAE (formerly NYSSACEAE)

NYSSA

L.

Tupelos There are 11 species of Nyssa, four in North and Central America and seven in eastern and southeastern Asia (Andrews 2001). They exemplify the classical eastern Asia/North America biogeographical pattern (Wen & Stuessy 1993). Nyssa species are small to medium-sized, deciduous (or evergreen) trees and are often characteristic of wet and flooded forests. The bark is grey and deeply furrowed; emergent root arches may be formed when the tree grows in water. The leaves are simple, elliptic

Section II. Species Accounts

or ovate and alternate; they may be membranous or leathery, and produce a range of autumn colours. Typically, they are clustered at the branch tips. All Nyssa species are dioecious, with single flowers or inflorescences in an axillary position. Staminate flowers are produced in heads or racemes and are typically 5-merous. Pistillate flowers (rarely, bisexual flowers occur) are solitary or in heads of two to four; they are (4–)5merous with an urn-like tubular corolla. The fruit is an ovoid or elliptical drupe with a fleshy mesocarp and a woody endocarp. Fruits are red, purple or blue-black, and the endocarp has several conspicuous longitudinal ridges or papery wings (Andrews 2001, Qin & Chamlong 2007). The genus has been comprehensively reviewed from a horticultural viewpoint by Susyn Andrews (2001). The name Nyssa is always likely to conjure up the picture of a flaming specimen of N. sylvatica lighting up the autumn landscape. This is a classic garden tree, with numerous selected cultivars, though requiring moisture, acidic soil and warm summers to perform at its best. Its qualities give its relatives an interest that they might perhaps not otherwise excite, especially in cooler areas. Of the other members of the genus, N. sinensis seems to be the next best bet for our area, colouring brilliantly in autumn, but although it tolerates cooler climates somewhat better than N. sylvatica (C. Howick, reported in Andrews 2001) it only forms a good tree in warmer parts. Nyssa is a typical example of a genus from places with stickily hot summers with one member that tolerates less torrid climes, the rest, however, always pining for the heat. The danger of relying on USDA Hardiness Zones as a guide to ‘growability’ is also shown particularly clearly in this case. Even the southeastern N. ogeche can be rated in Zones 7–9 in terms of the winter temperatures it can tolerate – but without its full measure of summer heat it will fail to prosper. Propagation is by seed, which requires a cool stratification period (Dirr 1998). Cultivars of N. sylvatica can be grafted, but cuttings are generally not very successful. Seedlings should be planted out young, as they develop a tap root and resent disturbance (Dirr 1998, Hudson 2004). N. aquatica L. B22, K329

Nyssa leptophylla Fang & T.P. Chen Nyssa leptophylla was unknown to the authors of the Flora of China account (Qin & Chamlong 2007) except through the original description, so it is surprising to find trees under this name in cultivation, but from seed from the Qingpu Paradise Horticultural Co. Ltd., in Shanghai, Tom Hudson at Tregrehan has raised a number of seedlings (Qingpu 98149) that resemble N. sinensis and also colour well. It seems wise not to attempt an identification until these trees have flowered, however, when a choice can be made from among the seven species described in Flora of China.

Nyssa

537

Plate 368. Nyssa sylvatica var. ursina – distinguished by its small leaves. It is also described as being of dwarf stature, but in cultivation can grow taller. Image B. Ward.

538

Nyssa

New Trees

Nyssa ogeche Marshall

Ogeechee Lime, Ogeechee Tupelo

Small tree or large shrub 5–8(–28) m (US champion 1.5 m dbh, Apalichicola National Forest, Florida, whose base is said by Sternberg (2004) to resemble ‘a giant cottonmouth [snake] that has swallowed a family of beavers’); producing several main stems from a swollen base. Branchlets green. Leaves deciduous, green, turning orange, purple, red and yellow in autumn; 8–18 × 3–8 cm, widely lanceolate to ovate, upper surface glabrous, lower surface pubescent, margins entire, often recurved, apex rounded to acute; petiole 0.5–1.5 cm long. Male inflorescences racemose to spicate to capitate or umbellate; female inflorescences solitary, sessile, peduncle 0.5–2 cm long; flowers occasionally bear stamens. Drupes oblong, dull yellow to olive-brown to orange-red, 2–4 cm long. Burckhalter 1992, Andrews 2001. Distribution USA: northern Florida, southeast Georgia, South Carolina (Beaufort Co. only). Habitat Sandy-bottom swamps, bogs and along riverbanks. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Elias 1980. Cross-references B22, K329.

In considering the cultivation of Nyssa ogeche it is important to remember that it comes from the swampy coastline of the southeastern United States, where mean temperatures remain over 20 °C at all times from May through September, often rising very much higher (July mean temperature 27.8 °C) (National Climatic Data Center 2007), and humidity is correspondingly high. In the light of this it is not surprising that it has never become established in northern Europe, despite persistent attempts (see Bean 1976b, Andrews 2001) – with the exception of one specimen reported from L’Arboretum de Balaine, near Villeneuve-sur-Allier in central France (Andrews 2001). Even in the United States reports are mixed (Dirr 1998); where it grows in the southeast (not necessarily in swamp conditions) it is said to form low, rounded trees, covered in dark green glossy leaves that do not usually produce good autumn colours. The flowers, though insignificant, are an important food source for bees, and good honey is made from tupelo nectar (Dirr 1998). The flowers are followed by juicy, sour fruits that can be used in cookery, hence the vernacular name Ogeechee Lime. It will survive on the East Coast at least as far north as Pennsylvania (Andrews 2001). N. sinensis Oliv. B22, K329

Plate 369. Not found in the average car-park planting scheme: Nyssa sylvatica var. ursina at the JC Raulston Arboretum. Image B. Ward.

Nyssa sylvatica Marshall

Sour Gum, Tupelo

This species was described by Bean (B23, S348) and Krüssmann (K329). N. sylvatica var. biflora (Walter) Sarg. B23, K329

Nyssa sylvatica var. ursina (Small) J. Wen & Stuessy

Dwarf Tupelo

Syn. N. ursina Small Var. ursina differs from typical N. sylvatica in that in the wild it is a small tree or shrub to 3 m with a buttressed stem (var. sylvatica is a large tree to 30 m and the trunk is never buttressed). The leaves of var. ursina are 3–6 × 1–2 cm and the pistillate flowers are in pairs, or rarely one or three (leaves of var. sylvatica are 6–18 × 3–8 cm and the pistillate flowers are in groups of three to nine, or rarely paired in upland areas). Small 1927, Burckhalter 1992, Andrews 2001. Distribution USA: Florida, in the vicinity of the Apalachicola and Ochlokonee Rivers. Habitat Low, moist flatwoods or inundated swamps just above sea-level (var. sylvatica may occur in moist woodland but is more common in upland areas, and is generally intolerant of flooding). USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT537, NT538.

This diminutive segregate of the well-known and beautiful Nyssa sylvatica is probably no more than a collector’s curiosity. It is ignored by American authors (Dirr 1998, Sternberg 2004), and even Andrews in her comprehensive review (2001) could find no evidence of it in cultivation. The only specimen located in the research for New Trees is at the JC Raulston Arboretum, planted in 2002. As this individual is now about

Section II. Species Accounts

Nyssa

4 m tall it is perhaps not so dwarf after all, but it has an open growth habit and small leaves. It seems to cope well with the currently prevailing severe drought in North Carolina, despite being sited in a dry position (D. Werner, pers. comm. 2007).

OLEACEAE

OLEA

L.

Olives Green (2002) recognised 33 species of Olea in tropical and subtropical regions of the Old World. Olives are evergreen trees and shrubs, that may have peltate scales on young branchlets. The leaves are opposite, entire or serrated and leathery or papery. They may be glabrous or with peltate scales on both surfaces; venation is usually obscure. Inflorescences are terminal or axillary, racemose or paniculate. Olea species may have hermaphrodite flowers only or a mixture of staminate and hermaphrodite flowers. The calyx is small and tubular with four short lobes; the corolla is tubular with four lobes; stamens two or four. The fruit is a dark purple or black drupe, often with thick, oily flesh (Green 2002). The only member of the genus familiar to gardeners is O. europaea, and in this we have another striking example of how the horticultural climate has changed. Where Bean (1976b) wrote of the ‘few fruits’ on the old tree in the Chelsea Physic Garden as exceptional, O. europaea is now a commonly planted species across England, and fruits even in tiny back gardens. A commercial olive grove has been planted in Devon (press reports 2007), and with the Mediterranean becoming increasingly arid a northwards trend in the area of production is inevitable. The range of O. europaea in western America has also expanded greatly, and it is planted now as a commercial crop into northern Oregon. With the exception of O. yuennanensis, described below, the other species of Olea are unknown to temperate horticulture. There are thirteen species in China, but all these seem to occur at low altitudes in southerly areas and may be too tender for our area.

Olea europaea L.

European Olive

The European Olive (see Bean and Krüssmann: B25, K331) has long been known in cultivation, with a history that needs no elaboration here. The taxon that occurs most commonly is Olea europaea subsp. europaea, with var. europaea being the cultivated Domestic Olive, and var. sylvestris (Mill.) Lehr (formerly var. oleaster (Hoffm. & Link) DC.) the wild, Mediterranean Olive (K331). Numerous cultivars have been selected, whether for fruit or solely for their ornamental qualities, and these should be chosen in preference to the unspecified plants sold as tiny saplings with a bottle of olive oil strung round their necks, or as pillaged veterans of ancient groves. In total, six subspecies of O. europaea are recognised, of which subsp. cuspidata is described below. They are largely distinguished by leaf size and distribution. Subsp. cerasiformis G. Kunkel & Sunding of Madeira and subsp. guanchica P. Vargas et al. of the Canary Islands have linear to narrowly elliptic leaves, (3–)4–6(–8) ×

539

540

Olea

New Trees

(0.3–)0.4–0.6(–0.8) cm. Subsp. laperrinei (Batt. & Trab.) Cif. of the Sahara and subsp. maroccana (Greuter & Burdet) P. Vargas et al. of Morocco have narrowly elliptic leaves, (3–)4–5(–7) × (0.5–)0.6–1(–1.5) cm (Green 2002). These would probably all be worth trying in favourable sunny sites, if material were to become available.

Olea europaea subsp. cuspidata (Wall. ex G. Don) Cif. Syn. O. africana Mill., O. chrysophylla Lam., O. ferruginea Royle Subsp. cuspidata differs from subsp. europaea in that the fruits are smaller (0.5–1.2 cm long, vs. 1.0–3.5 cm in subsp. europaea), with a thin but oily flesh. Tree 5–10(–18) m. Leaves narrowly elliptic to elliptic, (3–)5–6(–9)

Plate 370. Olea europaea subsp. cuspidata, in the form often called O. africana, growing at Kirstenbosch National Botanical Garden, Cape Town. It is a very important food source for many birds. Image J. Grimshaw.

× (0.5–)1–1.5(–3) cm; lower surface covered with silvery to rusty red scales. Green 2002. Distribution AFGHANISTAN; ANGOLA; BOTSWANA; BURUNDI; CHINA: Sichuan, Yunnan; CONGO (Dem. Rep.); EGYPT; ERITREA; ETHIOPIA; INDIA: Kashmir, Uttar Pradesh; IRAN; KENYA; LESOTHO; MALAWI; MAURITIUS; MOZAMBIQUE; OMAN; PAKISTAN; RÉUNION; RWANDA; SAUDI ARABIA; SOMALIA; SOUTH AFRICA; SUDAN; SWAZILAND; TANZANIA; UGANDA; YEMEN; ZAMBIA; ZIMBABWE. Habitat Extremely variable, usually scrubby open areas, forest margins. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Coates Palgrave 1990; NT540.

With such a huge range it is not surprising that hardy provenances of Olea europaea subsp. cuspidata should occur, but most of those currently in cultivation are apparently of South African origin, usually grown as O. africana, the small-fruited African Olive. Apart from a tree dating to 1948 at Berkeley, none are particularly big. There is a pruneddown specimen outside the Curvilinear Range at Glasnevin (accessioned in 1996) that is apparently thriving, with healthy dark foliage. In Portishead, Somerset there is a 6 m individual in the former garden of Tony Titchen, grown from seed distributed from Kirstenbosch where it occurs as an indigenous Afromontane forest tree (T. Titchen, pers. comm. 2007; Johnson 2007). It closely resembles a normal olive except that the leaves are narrower and perhaps more silvery on the underside, and the fruits are very small. They are an important food source for many frugivorous birds. In eastern Africa, the African Olive is an important constituent of lower-altitude dry Afromontane forest, often growing with Juniperus procera. On the northern slopes of Kilimanjaro in Tanzania it forms large tracts of monodominant forest following mass regeneration from seed after a fire, and can become a large tree (Grimshaw 1998). Its hard wood is unfortunately excellent for both construction and fuel, with the consequence that it is becoming much reduced in its African range. Collections from elsewhere in the subspecies’ wide

Section II. Species Accounts

Olea

distribution would be interesting. Material in cultivation in North America under the name O. ferruginea is presumably of Asian origin. Stock of two different clones grown by Sean Hogan (pers. comm. 2008) originated from the olive collection of the University of California, Davis. O. europaea var. oleaster (NOW O. europaea L. subsp. europaea var. sylvestris (Mill.) Lehr) K331 O. europaea var. sativa (NOW O. europaea L. subsp. europaea var. europaea) K331

Olea yuennanensis Hand.-Mazz. Shrub or tree 1–12 m. Branchlets with some fine hairs. Leaves evergreen and leathery, (3–)5–7(–10) × 1.2– 4.5 cm, elliptic to oblanceolate, glabrous, secondary veins sunken or obscure, six on each side of the midrib, margins entire or with sharp teeth 0.5–1 mm long, apex acute or rarely obtuse; petiole 0.3–0.7 cm long with fine hairs. Inflorescences axillary and paniculate, flowers in groups 2–4 cm long, glabrous or with sparse hairs. Flowers staminate or hermaphrodite; calyx with four triangular lobes, ciliate; corolla white or creamy yellow, tube 0.1–0.3 cm long. Drupe black and slightly fleshy, 0.7–1 cm long. Flowering February to November fruiting May to December (China). Green 2002. Distribution CHINA: Sichuan, Yunnan. Habitat Forests or thickets. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note Olea yuennanensis was placed in synonymy with O. tsoongii (Merr.) P.S. Green by Green (1995), and this treatment was followed by Flora of China (Chang et al. 1996). However, O. yuennanensis was later reinstated by Green (2002). Olea tsoongii differs from O. yuennanensis in that the branchlets and petioles are glabrous and the inflorescences are 7–18 cm long (Green 2002). The incorrect spelling yunnanensis is a more or less inevitable trap.

Olea yuennanensis is still little known, but promises to be a useful broadleaved evergreen, with much wider leaves than expected in olives. Dan Hinkley (pers. comm. 2008) has seen it growing at low altitudes in dry areas along the Salween River in Yunnan, but in cultivation at least it is not a xerophyte and likes reliable summer moisture (Hogan 2008). Light shade from the hottest sun and shelter from very cold winds are also appreciated. It does seem to prefer a hot summer, however, and was not a success at Heronswood, where summers are too cool, and winter damage occurred at about –10 °C. Despite this it was offered for a few years (for example, Heronswood Nursery catalogues 1999–2001). The original plant may possibly have come from J.C. Raulston (D. Hinkley, pers. comm. 2008); no further information on its introduction has been traced. It is established in the southeastern and western United States, and the Cistus Nursery catalogue even suggests that it is a useful hedging plant.

OLEACEAE

OSMANTHUS

Lour.

There are about 30 species of Osmanthus, mostly occurring in subtropical eastern Asia, though one or two species are found in North America (Wallander & Albert 2000). They are evergreen shrubs or small trees with simple, opposite leaves. The leaves are glabrous, entire, serrated or spiny and often covered with glands. Inflorescences are terminal or axillary panicles or fascicled cymes. The flowers are hermaphrodite, though usually becoming unisexual, and the plants are subsequently dioecious or

541

542

Osmanthus

New Trees

1 cm

1 cm

C A

Figure 63 (above). Osmanthus fragrans: habit (A); inflorescence (B); fruits (C).

0.5 cm

B

androdioecious. The calyx is four-lobed and campanulate; the corolla is four-lobed, white or yellow and campanulate or tubular; the lobes are imbricate, obtuse and often reflexed; stamens two (to four). The fruit is a drupe with a hard or bony endocarp (Green 1958, Grohmann 1974, Chang et al. 1996). The genus Osmanthus is most familiar in the form of several bushy evergreen shrubs or small trees that bear fragrant white flowers, sometimes in great profusion (for

Section II. Species Accounts

Osmanthus

543

example, O. delavayi), or add foliage interest to the garden (for example, O. heterophyllus). Despite their being usually treated as shrubs it seems that many species are in fact capable of becoming broad-crowned small trees – although this may require warmer conditions than experienced in northern European gardens. Several species described in Flora of China have not yet been introduced to cultivation and could be looked for by collectors. Osmanthus are easily propagated by cuttings rooted in warmth in summer, or by seed, although this is not often produced in cultivation. O. americanus (L.) Knobl. K336 O. armatus Diels B55, K337 O. ×burkwoodii (Burkwood & Skipw.) P.S. Green K56

Osmanthus fragrans Lour.

O. decorus (Boiss. & Balansa) Kasapligil B56 O. delavayi Franch. B56, K337 O. ×fortunei Carrière B58, K337

Fragrant Olive

Syn. O. aurantiacus (Makino) Nakai Shrub or small tree 2–12(–18) m. Branchlets brown and glabrous. Leaves evergreen and leathery, 7–14.5 × 2.6–4.5 cm, elliptic to almost lanceolate, glabrous, secondary veins 6–8(–10), margins entire or serrate in the upper half, apex acuminate; petiole 0.8–1.2 cm long. Inflorescences cymose, in axillary fascicles. Flowers white, yellow or orange, fragrant, pedicel 0.4–1 cm long; calyx 0.1 cm diameter; corolla tubular, divided almost to the base, 0.3–0.4 cm diameter. Fruit ellipsoid and purplish black, 1–1.5 cm diameter. Flowering September to October, fruiting March (China). Green 1958, Chang et al. 1996. Distribution BANGLADESH; BHUTAN; CAMBODIA; CHINA; INDIA: Himalaya from Kashmir to Sikkim and Assam; JAPAN; MYANMAR; NEPAL; PAKISTAN; TAIWAN; THAILAND. Osmanthus fragrans is widely cultivated and its natural distribution is uncertain. Habitat Lowland evergreen forest. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Chang et al. 1996; NT2, NT542, NT543. Cross-references B58, K337. Taxonomic note Osmanthus fragrans has long been cultivated in eastern Asia (Green 1958). Considerable variation in morphology, particularly flower colour, has been noted in cultivated material, and numerous subspecies and forms have been described. However, these taxa warrant recognition only as cultivars (Chang et al. 1996).

In his brief note on it Bean (1976b) said that Osmanthus fragrans is too tender for outdoor cultivation in the British Isles. It is probably still true to say that it is too tender for general cultivation here, but given a warm site it is not a hopeless case, and is worth the attempt on account of its superb fragrance which ‘once encountered, is never forgotten: it is full of tropical overtones, especially on a warm evening’ (Hudson 2004). Dirr (1998) proclaims ‘not to try the plant is to cheat one’s garden’, giving it a Hardiness Zone rating of 7–10. It is clear, however, that it does need summer heat to thrive, and winters that are not too cold. This combination of requirements means that it will tend to be more shrubby than tree-forming in most of our area, but in suitable conditions it can form a sizeable tree. In most of northern Europe this is unlikely, although Owen Johnson measured a specimen of 6 m at Tregothnan, Cornwall in 2006 (TROBI). The flowers, which may be white to orange in different cultivars, are visually rather insignificant. They are principally produced in autumn, but may appear through the winter and into spring. Even when they are not present the large glossy evergreen leaves are handsome. Numerous cultivars have been selected in Asia (Green 1958), and some are available in our area. Dirr (1998) lists several and recommends the clone known as var. semperflorens for its hardiness and more or less continual flowering; ‘Fudingzhu’ has similar qualities. The name f. aurantiacus (Mak.) P.S. Green appears to be attached in cultivation to a single clone with pale orange flowers, but presumably embraces all yellow- and orange-flowered forms.

Plate 371. The flowers of Osmanthus fragrans may be white through yellow to orange. Visually rather insignificant, they have superb fragrance. Image JC Raulston Arboretum.

544

Osmanthus

New Trees

O. heterophyllus (G. Don) P.S. Green B58, K337 O. serrulatus Rehder B60, K337

O. suavis King ex C.B. Clarke B60, K337 O. yunnanensis (Franch.) P.S. Green B61, K337

HAMAMELIDACEAE

PARROTIA .

C.A. Mey.

Ironwoods Parrotia is a genus of two species of deciduous trees or large shrubs: the familiar P. persica, originating from the Caspian forest of Iran and Azerbaijan, and the recently recognised P. subaequalis from China. The trunk is usually short and thick, producing thick, spreading to erect branches that form a twiggy crown; the branchlets pubescent when young. The alternate leaves are simple with dentate margins, the veins terminating in marginal teeth (craspedodromous venation), with stellate pubescence on both sides of the lamina, at least when young; the petioles are short; stipules caducous. The inflorescence is a terminal or axillary capitate spike with three to seven flowers surrounded by brown bracts. The flowers are either male or hermaphrodite, composed of 7–10 spirally arranged, irregularly sized sepals and the reproductive parts inserted onto a shallow floral cup or receptacle; there are no petals. The stamens, 5–15, have conspicuous anthers; the ovary is semi-inferior, with long styles. The fruit is a sessile, woody nut-like capsule with one seed in each locule, densely stellate-pubescent outside (Zhang et al. 2003b, Andrews 2008). Parrotia persica is a justifiably popular garden tree, valued for its late winter flowers and its excellent autumn colours. Although the flowers have no petals the large anthers, which open from dark brown to pinkish red, contrive to make a pleasing show while the tree is in bloom. The usual form seen in cultivation is rather low, broad-spreading and shrub-like in shape, probably because the species has been propagated largely from individuals of this nature; trees raised from wild-collected seed give a much more upright and better-shaped plant, and are to be preferred wherever possible. Seed-raised trees also vary in their autumnal coloration, and good clones could be selected and named from those in cultivation. It is generally thought to prefer acidic soils, but is tolerant of alkaline conditions if the soil is reasonably deep and moist. P. persica (DC.) C.A. Mey. B91, S352, K353

Parrotia subaequalis (H.T. Chang) R.M. Hao & H.T. Wei Syn. Hamamelis subaequalis Hung T. Chang, Shaniodendron subaequale (Hung T. Chang) M.B. Deng, H.T. Wei & X.Q. Wang Small tree, 10–12 m, apparently resembling P. persica in many features. Leaves obovate, narrowly ovate or elliptic, 4–6.5 × 2–4.5 cm, with four to five pairs of veins on each side of the midrib, dark green above with stellate hairs on the veins, densely stellate-pubescent below, apex acute, base rounded to truncate or subcordate, margin with irregular blunt teeth, often with a purple edge; petiole 5–7 mm; stipules lanceolate. Inflorescence a terminal capitate spike with one to two male flowers at the base and four to five hermaphrodite flowers above, all surrounded by brown bracts, borne on a peduncle to 1 cm; floral cup indistinct, sepals

Section II. Species Accounts

Parrotia

545

c. 3 mm; stamens 5–10, with filaments 15–20 mm, anthers 4–4.5 mm; styles c. 2 mm. Capsule rounded, 8–9 mm diameter, with persistent styles and slightly enlarged floral cup. Seeds 6–7 mm, sharply pointed at each end, shiny brown. Flowering March to April, fruiting September to October (China). Chang 1960, Li et al. 1997, Zhang et al. 2003b, Andrews 2008. Distribution CHINA: Anhui (Jinzhai Xian, Jixi Xian, Shucheng Xian), southern Jiangsu (Yixing Xian), northern Zhejiang (Anji Xian). Habitat Montane forests, 600–700 m asl. USDA Hardiness Zone (5–)6–7. Conservation status Not evaluated (IUCN). Critically endangered, according to Flora of China. Illustration Andrews 2008, Li & Del Tredici 2008; NT545.

The recognition of this species as a Parrotia took some time, with it passing through Hamamelis and Shaniodendron before its close similarity to P. persica was acknowledged. It is difficult to point out features by which the two species can be reliably separated, as P. subaequalis is so far represented in cultivation only by a small population of young plants, of limited clonal diversity, that have yet to flower, and it seems to be poorly known even to Chinese botanists. It is too soon to state anything about its ultimate size or cultivation requirements, although P. persica is probably a good guide; the Chinese species’ hardiness limits have not yet been widely tested. What can be said with certainty is that it has the potential to produce spectacular autumn colours of scarlet, crimson and burgundy, as even very young plants colour magnificently. In the wild trees have been noted to have attractively exfoliating bark, generating a patchwork of green, beige and black (Li & Del Tredici 2008). In the same article, these authors have also provided a very interesting account of P. subaequalis in cultivation in China – where they have even seen it being used as penjing (bonsai)! The introduction of another species of Parrotia to Western gardens is an exciting event and it seems that credit must be given to the Belgian nurseryman Antoine Bultinck-Meuleman of pépinière De Ceder, Evergem. In 1998 a group of French horticulturists on a tour (Ginkgo 98) visited the Nanjing Botanic Garden and were shown a plant of P. subaequalis. Despite their entreaties they were not given any propagating material at that time, but in February 2000 four young plants were received by Bultinck-Meuleman, whose requests had been more determined and persuasive than those of the others (Colin 2000). Most specimens in cultivation in Europe are derived from this stock, which has now been propagated extensively and can be found in many major collections, including individuals up to 2 m tall at Ghent University Botanical Garden, Belgium (planted 2001) and at Hergest Croft (planted 2003) (Andrews 2008). The species roots readily from summer cuttings treated with rooting hormone and placed under mist in a heated propagation unit (Li & Del Tredici 2008). Mikinori Ogisu introduced it to Japan in 1998, and he reports (pers. comm. via R. Lancaster 2008) that a specimen planted near Osaka in that year has reached 5 m. Ogisu has distributed material from Jiangsu in both England (Andrews 2008) and the United States (D. Hinkley, R. Lancaster, pers. comms. 2008). The first plants in the United Kingdom were distributed by Ogisu in 2001, and one of these specimens is now well established and growing vigorously in Roy Lancaster’s garden, where it had reached 2 m by August 2008 (R. Lancaster, pers. comm. 2008); it has also been propagated (Andrews 2008). A plant from the same importation was passed to the National Arboretum, Westonbirt but failed to become established, and a third was donated to HRH The Prince of Wales. Another introduction from China has resulted in specimens

Plate 372. Parrotia subaequalis is an exciting new introduction, showing great promise as a hardy tree with superb autumn colour. Image R. Lancaster.

546

Parrotia

New Trees

at the Arnold Arboretum that had reached 1.5 m by 2008 (P. Del Tredici, pers. comm. 2008), having survived two winters outdoors; although not fully assessed, it seems that the species will be hardy in the Boston area (M. Dosmann, pers. comm. 2008).

PAULOWNIACEAE (formerly SCROPHULARIACEAE)

PAULOWNIA

Siebold & Zucc.

Foxglove Trees There are seven species of Paulownia, all occurring in China and Taiwan, though P. fortunei extends into Laos and Vietnam. They are deciduous trees (evergreen in tropical regions) with smooth bark on the trunk and conspicuous lenticels on the immature stems. The leaves are opposite (rarely in whorls of three) and entire or with three to five shallow lobes; when coppiced or growing vigorously, Paulownia species produce extremely large leaves. The thyrsoid inflorescences are large and numerous; they may be pyramidal or cylindrical and contain (one to) three to five (to eight) flowers. The flowers are purple or white; the calyx is campanulate and tomentose; the corolla campanulate or tubular with five lobes and a slightly curved and constricted base; there are four stamens. The fruit is a woody capsule with two to four valves, containing numerous seeds with membranous wings (Hong et al. 1998). Paulownia species are widely cultivated in China, and assessing their natural distributions is difficult. A key to the genus is provided by Hong et al. (1998). Despite the beauty and popularity of Paulownia tomentosa, other members of the genus are seldom seen, though most have been in cultivation for many years. Paulownia tomentosa is an aggressive weed species in some parts of the United States, and in areas where its weediness is a problem any other Paulownia species should be planted only after due care and consideration. The other side of the coin is that Paulownia are very fast-growing trees, producing timber that is highly valued in the Far East. While environmentalists wring their hands over its invasiveness, others actively promote its culture as a plantation tree! It is also used in reclamation of degraded land – after strip-mining, for example. Dirr (1998) wisely points out that it is a short-lived pioneer that will be out-competed by later successional species. The species principally used as a plantation tree in warm areas is P. elongata, on account of its particularly rapid growth (World Paulownia Europe 2007–2008). As a whole the genus appreciates hot summers and good living in terms of soil and moisture conditions. Propagation is by seed or from root cuttings – both playing a part in the weediness problem.

Paulownia catalpifolia T. Gong ex D.Y. Hong

Princess Tree

Large tree with a broad crown. Leaves deciduous, twice as long as wide, narrowly ovate to cordate, upper surface glabrous, lower surface with dense stellate tomentum, margins entire to undulate, apex acuminate. Inflorescences pyramidal or narrowly conical, usually less than 35 cm long. Flowers hermaphrodite; calyx campanulate, less than 2 cm wide and largely glabrous; corolla pale purple with dark purple spots inside, tubular, 7–8 × 3.5 cm at its widest point. Capsule ellipsoid, covered with stellate tomentum, 4.5–5.5 cm

Section II. Species Accounts

Paulownia

547

long. Flowering from April, fruiting July to August (China). Hong et al. 1998. Distribution CHINA: Hebei, Henan, Shandong, Shanxi. Habitat Low elevations. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Hong et al. 1998. Taxonomic note A putative hybrid between P. catalpifolia and P. tomentosa has been described as P. ×henanensis C.Y. Zhang & Y.H. Zhao (Hong et al. 1998).

Paulownia catalpifolia is still little known in horticulture, although it is a recommended species for plantations in cooler areas (World Paulownia Europe 2007–2008) and is freely available in commerce. It has rather pale flowers but they are generously produced, in areas with hot summers. P. coreana Uyeki S354 P. elongata S.Y. Hu K360 P. fargesii Franch. S353, K360 P. fortunei (Seem.) Hemsl. B100, K361 P. glabrata (NOW P. tomentosa var. tsinlingensis (Y.Y. Pai) T. Gong) K361

P. kawakamii T. Itô S353, K361 P. lilacina (NOW P. tomentosa (Thunb.) Steud.) B101

Paulownia ×taiwaniana T.W. Hu & H.J. Chang Large tree with a broad crown. Leaves deciduous, ovate to cordate, upper surface glabrous, lower surface densely hairy or tomentose, margins entire to undulate, apex acute. Inflorescences broadly conical, to 80 cm long. Flowers hermaphrodite; calyx deeply lobed, largely glabrous; corolla purple-white with two conspicuous longitudinal folds, tubular to campanulate, 5–7.5 cm long. Capsule ellipsoid, initially covered with stellate tomentum, ~4 cm long. Flowering March to April, fruiting July to August (China). Hong et al. 1998. Distribution CHINA: Fujian, Guangdong, Hunan, Zhejiang; TAIWAN. Habitat Secondary forest below 1200 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Hong et al. 1998; NT547. Taxonomic note Paulownia ×taiwaniana is intermediate between P. kawakamii and P. fortunei, and is a hybrid between these two species (Hong et al. 1998).

Although of hybrid origin Paulownia ×taiwaniana is apparently widely cultivated in Taiwan and elsewhere in the tropics and subtropics, and is grown from seed to give recognisably similar seedlings. It is noted for its large, richly coloured flowers that are heavily spotted with purple in the throat. In our area it seems to be rather scarce, but it has been grown at Kew since 1979 when seeds were received from the Taipei Botanic Garden and Taiwan Forestry Research Institute. This accession is now represented by two trees that have developed from root suckers, each over 10 m tall (though one is much younger than the other). Flowering up to now has been very sparse and insignificant, but both were bearing abundant buds in January 2008, which expanded into a good display of flowers in May. Paulownia ×taiwaniana has also been introduced as seed from a wild tree growing at Taroko in eastern Taiwan, by Bleddyn and Sue Wynn-Jones (BSWJ 7134), which formed a broad-crowned specimen of 17 m, with leaves up to 28 cm long (Crûg Farm Plants 2007–2008). In trials in China it was found to be one of the less hardy members of the genus, and like its parent P. kawakamii, cannot tolerate temperatures much below –10 °C without significant damage (staff of the Chinese Academy of Forestry 1986). In growing on seedlings of BSWJ 7134 Bleddyn WynnJones (pers. comm. 2007) has found that they need heat in summer to enable them to form a woody stem; without it they tend to die back to a lower bud. P. tomentosa (Thunb.) Steud. B102, S354, K362

Plate 373. Leaves of Paulownia ×taiwaniana catching the sunlight at Kew. All members of the genus are handsome foliage plants. Image J. Grimshaw.

548

Pennantia

New Trees

A

B

1 cm

C 1 cm

1 cm

Section II. Species Accounts

Pennantia

ICACINACEAE

PENNANTIA

J.R. Forst. & G. Forst.

Pennantia is a small genus of shrubs or trees found in Australia, Norfolk Island and New Zealand. The leaves are alternate, entire or toothed, with hair tufts in the axils of the veins on the lower surface. The flowers are borne on articulate pedicels in terminal panicles, and may be either hermaphrodite or unisexual; with a calyx that is rudimentary or small and shallowly five-lobed; five petals, white, glabrous; five stamens; filaments filiform. The ovary has one locule containing one ovule, the style short or obsolete, the stigma three-lobed. The fruit is a single-seeded small drupe, the seed hard and three-sided. The genus is named for Thomas Pennant (1726–1798), the British zoologist and antiquary. Often called ‘the rarest tree in the world’, P. baylisiana (W.R.B. Oliv.) G.T.S. Baylis is known in the wild only as a single female specimen on the Three Kings Islands, New Zealand. With broad glossy leaves it is a handsome ornamental, and as such is cultivated in New Zealand. In the United Kingdom it is available from County Park Nursery, Essex, but their assessment is that it will only tolerate a degree or two of frost (County Park Nursery 2008).

Pennantia corymbosa J.R. Forst. & G. Forst.

Kaikomako

Tree to 10 m, but shrubby when young with intertwining divaricate flexible branches. Trunk slender, bark grey. Branchlets pubescent. Juvenile leaves widely spaced and alternate, or fascicled, 0.7–1.5 × 5–10 mm, more or less obovate, base cuneate, somewhat lobed or toothed towards apex; petioles short, slender, pubescent. Adult leaves opposite to alternate or whorled, oblong to obovate-oblong, (2–)5–10 × 1–4 cm, coriaceous, margins sinuate or irregularly coarsely crenate-dentate or lobed or occasionally entire; petioles to 1 cm, slender. Inflorescence a terminal panicle, 4–8 cm long, with pubescent branches. Flowers small, unisexual, fragrant; petals five, white; male flowers with filaments exceeding petals, anthers large, female flowers with filaments shorter than the petals, and anthers smaller; ovary oblong, stigma three-lobed. Fruit 8–9 mm, black. Flowering in summer, fruiting in autumn (New Zealand). Allan 1961, Salmon 1996. Distribution NEW ZEALAND: North Is., South Is. (from 35 °S). Habitat Woodland and thickets. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Salmon 1996; NT548.

Pennantia corymbosa is greatly appreciated in New Zealand as an ornamental native plant, and is recommended for many landscaping situations. When mature it has attractive white flowers followed by black fruits, but it is in the juvenile stage that it is perhaps most interesting. As with several New Zealand trees and shrubs it has a very strange divaricate branching pattern when young. (The ‘wirenetting bush’ Corokia cotoneaster Raoul is the most familiar example of this in horticulture; Elaeocarpus hookerianus and Carpodetus serratus are others described in this book.) The pattern is retained until the tree is 2.5–3 m tall, when it turns into a ‘normal’ broadleaved, round-crowned tree, which is fertile. One theory is that this is a way of optimising light capture (Day 1998), but others would suggest that it was a response to moa-browsing (see the account for Elaeocarpus hookerianus above, p. 319). Outside New Zealand P. corymbosa is very rare, although it is commercially available in the United Kingdom. It is grown at Logan Botanic Garden as a 1990 accession from Howick & Darby 1168, collected on South Island, and has reached 1.5 m there, ‘doing well enough’ (B. Unwin, pers. comm. 2006). At Tregrehan a 2002 accession has so far reached 1.5 m also, suggesting a preference for somewhat warmer conditions.

Figure 64 (opposite). Pennantia corymbosa: mature habit with inflorescences (A); fruits (B); immature habit (C).

549

550

Persea

New Trees

LAURACEAE

PERSEA

Mill.

Avocados, Bays

Plate 374. Persea thunbergii is a fine, tolerant evergreen tree, with red new growth. Image J. Grimshaw.

Persea is a genus of 200–240 species of small to large evergreen trees, found mostly in eastern Asia and Central and South America, with a few species in eastern North America and one on eastern Atlantic islands (Macaronesia). They are usually singlestemmed, with a rather smooth, pale brown bark; younger stems and branches often remain green and smooth for many years, eventually becoming corky. Leaves are alternate, borne at the tips of the branches, simple in shape with entire margins, and are usually rather firm in texture; in many species the young leaves flush bronze, brown or red. The inflorescence consists of several subterminal, axillary panicles, the individual flowers small and inconspicuous, borne on short pedicels that may become fleshy and enlarged in fruit. The flowers are bisexual, with six perianth segments in two whorls arising from a short tube, the perianth segments persisting and sometimes enlarging, but not becoming appressed to the fruit; stamens six to nine, in two to three whorls; stigma and ovary solitary. The fruit is a berry, usually small and black, sometimes much larger, green or purplish. Generic limits within the Lauraceae are often difficult to define, but there seems to be wide acceptance now of Kostermans’ (1974) inclusion in Persea of Asian species formerly placed in the genus Machilus – species with reflexed persistent perianths at fruiting (in Persea s.s. the perianth segments are either deciduous or persist in appressed or patent positions when in fruit) – although the name Machilus is still regularly found in horticultural literature. Specific delimitation seems to be somewhat easier, with the species described here all being recognisably distinct. Persea is famous for the large fruits of the Avocado P. americana but most species have rather small fruits that are adapted for dispersal by birds, and the familiar avocados – dispersed principally by primates but much loved also by carnivores (Jaguars in the Americas, Leopards in Africa) – are in fact unusual in the genus. The Lauraceae contribute to horticulture some of the finest of broadleaved evergreens, and Persea is firmly established in the pantheon of the very elite, with bold glossy green foliage often preceded by a striking spring flush of red, brown or glaucous leaves. In general its members are much less well known than they ought to be, especially in Europe – perhaps because they do enjoy a hot summer, but maybe also because they seem too improbably exotic to be thought worthy of a trial. The longterm success of the Chinese P. ichangensis in southern England indicates that this is not necessarily true. The yellowish inflorescences of Persea, while composed of

Section II. Species Accounts

Persea

551

the usual small lauraceous flowers, are comparatively conspicuous and may form an attractive feature as growth starts in spring; they can also be pleasingly fragrant. The hardier species should be planted in a warm site, preferably with some shelter from cold winds and late frost, especially when young. An acid to neutral soil seems to be most suitable, and ample moisture during the summer is an important requirement. Avocados are susceptible to Phytophthora root rots, especially P. cinnamomi, and these may also cause trouble in the temperate species. Propagation is by seed or by grafting onto suitable rootstocks; cuttings are most successful when taken in late summer and rooted with heat and mist (Hogan 2008).

Persea americana Mill.

Avocado

Tree to 40 m. Branchlets thick, pubescent or glabrous, frequently with groups of bract scars at the base of each season’s growth; terminal buds pubescent. Leaves evergreen to semi-deciduous, spaced along the branches or gathered towards the apex, papery, sometimes aniseed-scented, (6–)10–18(–30) × (2.5–)5–12 cm, extremely variable in shape, though usually elliptic, upper surface glabrous, lower surface green to glaucous, glabrous or variously pubescent, 6–8(–10) secondary veins on each side of the midrib, margins entire, apex rounded, obtuse or acute, rarely acuminate; petiole 1–5 cm long, pubescent or glabrous. Inflorescences axillary, or at the base of new branches, (3.5–)5–11 cm long, glabrous or pubescent, pedicels 0.4–0.8 cm long. Flowers ~0.5 cm long, yellowish, inconspicuous; tepals six, elliptic, 0.3–0.6 cm long, densely pubescent; fertile stamens six, filaments pubescent, staminodes three or more, glandular. Fruit a pyriform or globose berry with rough green or purple skin and oily flesh, 5–15 cm long, depending on the cultivar. Flowering January to March, fruiting April to June (Mexico). Van der Werff & Lorea 1997. Distribution The Avocado originates in Mexico or Central America, but is now grown in tropical climates around the world. Habitat Extremely variable. In Querétaro, Mexico it grows primarily in montane, mesophytic forest between 850 and 1700 m asl. However, the seed germinates easily; consequently, it is common in disturbed habitats. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Van der Werff & Lorea 1997; NT551. Cross-reference K370.

Persea americana, the Avocado, is the best-known species in the genus, cultivated throughout warm temperate and tropical areas for its large, nutritious fruit, consumed by itself or as a component in salads. The ease with which its seeds germinate (whether or not supported by crossed toothpicks over a glass of water) makes it a popular novelty subject, and the resultant seedlings are sometimes planted in temperate gardens – usually to be killed promptly by frost. Indeed, its inclusion in this book might seem dubious, but for the fact that there are several trees growing and fruiting happily in central London. A more striking example of the effects of microclimate could hardly be sought: Johnson (2007) mentions trees in Chelsea (6 m) and Stepney (4.5 m), while Martin Gibbons of the Palm Centre, Richmond (pers. comm. 2006) has drawn our attention to another in Ladbroke Grove. This one was about 5 m tall and rather broad at the base, fully clad in healthy dark green foliage and bearing many unripe fruits when observed by Martin Gibbons in July 2006. These specimens are, of course, exceptions, but they demonstrate the point that plants may well be ‘worth a try’ and that with care, and/or luck, boundaries may successfully be pushed when planting marginal species. Hogan (2008) comments that similar individuals can be found in western American cities ‘between freezes’, but that the species is more generally successful on the southern Oregon coast, specially around the mild enclave of Brookings. Similarly, there are substantial trees in Cornwall and on the Scilly Isles. For those of us who do not garden in such benevolent areas, however, the climate will

Plate 375. An Avocado, Persea americana, laden with fruits in Ladbroke Grove, London. Nurtured at present by the London heat island, it may be a precursor of things to come as the climate warms. Image M. Joseph.

552

Persea

New Trees

have to change dramatically before we can safely plant P. americana (for which any persistent frost is a danger). A useful summary of Avocado culture under commercial conditions is given by Huxley et al. (1992).

Persea borbonia (L.) Spreng.

Redbay

Tree to 20 m, but usually shorter and sometimes shrubby. Trunk to 1 m dbh, often leaning. Bark 1.2–2 cm thick, reddish brown, irregularly furrowed with shallow interlacing fissures and flattened ridges. Branches held more or less upright, green when young. Leaves 5–20 × 2–8 cm, lanceolate or ± ovate, broadest in the middle, base cuneate, apex acute, bright shiny green on upper surface, lower surface white-waxy, with very short appressed hairs (appearing hairless); winter buds covered with dense, reddish hairs. Inflorescence formed of a number of few-flowered, subterminal axillary cymes, with peduncles that are usually shorter than the adjacent petiole; flowers 3–3.5 mm long, yellowish green, appearing in spring. Fruits 10–12 mm, subglobose, blue-black with a white waxy bloom, maturing in autumn. Kopp 1966, Elias 1980. Distribution MEXICO; USA: Gulf and Atlantic Coastal Plain, Virginia south to Florida and Texas. Habitat Mixed forest on sandy to rich moist soils at low altitudes, especially near water. USDA Hardiness Zone 7. Conservation status Not evaluated (IUCN). Endangered in Maryland (USDA PLANTS Database 2008). Illustration NT552. Cross-reference K370.

Plate 376. The small blackish fruits of Persea borbonia persist well into the winter, as here at the North Carolina Botanical Garden, January 1999. Image J. Grimshaw.

Redbay takes its name from the reddish bark and the aromatic leaves that can be used in cooking. Its cylindrical shape with a dense crown of bright green leaves makes it a pleasant addition to the garden, but it is likely to thrive best in warm, humid locations. For this reason it is an admirable vigorous evergreen for the southeastern United States. It also does well on the West Coast, however, and a young tree at Heronswood Nursery in coastal Washington was growing vigorously when seen in 2004, when it was about 7 m tall. It is rare in Europe, and the only specimen seen in research for the current work, a 3 m tree against a wall at Glasnevin, looked rather chlorotic, although evidently growing steadily. The blue-black fruits are striking, and persist into the winter. Hogan (2008) mentions its variety pubescens (Pursh) Little, which is somewhat hairier than normal, and particularly commends a clone from Coahuila, Mexico for its silvery appressed hairs.

Persea bracteata (Lecomte) Kosterm. Syn. Machilus bracteata Lecomte Shrub or tree to 12 m or more, forming a rounded canopy. Branchlets yellowish green, somewhat flattened, ridged, with pointed terminal buds enclosed in two sericeous scales. Leaves 7–10(–21) × 2.5–4.5 cm, lanceolate to narrowly obovate, apex shortly acuminate, coriaceous, glabrous, dark shiny green on upper surface, lower surface waxy and pale whitish green; petiole 1.3–2 cm, yellowish green. Inflorescence of axillary panicles 6–14 cm long, subtended by large bracts to 7 mm that fall as the inflorescence develops; flowers held in sub-umbels on panicle branches, 4–6 mm long, glabrous outside, hairy within, yellow or yellowish green, fragrant. Fruits in clusters, 7 mm, globose, green becoming purple-black. Flowering March, fruiting September (China). Lecomte 1913, Wharton et al. 2005. Distribution CHINA: Yunnan. Habitat Forest and forest edges, between 1370 and 2600 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Wharton et al. 2005.

In the Washington Park Arboretum there is a magnificent Persea tree forming a dense rounded canopy of elongated dark green leaves with glaucous undersides – a really fine plant that is rightly much admired by the horticultural community of the Pacific Northwest. It has been grown there since 1938 and was collected by Prof. T.T. Yu, probably in Yunnan in 1937, under the number Yu 7835. Until recently it had always been known as P. yunnanensis, but its true identity has been the subject of consider-

Section II. Species Accounts

Persea

able debate (R. Hitchin, pers. comm. 2004) and it has now been identified as P. bracteata (Wharton et al. 2005). This famous tree, currently about 12 m tall, fruits prolifically, and self-sown seedlings are frequent; its progeny are to be found in numerous West Coast gardens and collections, labelled P. yunnanensis. The foliage emerges erect, displaying the glaucous undersides like a cluster of ‘silver swords’ (Wharton et al. 2005), and Peter Wharton described it (in the same work, The Jade Garden) as ‘without doubt one of the most desirable evergreens for general cultivation’. Having withstood the Seattle climate for decades it can be considered hardy for the Pacific Northwest and western Europe. True Persea yunnanensis (Lecomte) Kosterm. has shorter, ovate to broadly lanceolate leaves: George Forrest found it at 2400 m in central northern Yunnan (G. Forrest 23536, June 1923), and it might also be worthy of the attention of contemporary collectors.

Persea breviflora (Benth.) Pax Syn. Alseodaphne breviflora Benth., Machilus breviflora (Benth.) Hemsl. Tree to 10 m. Branchlets slender, reddish brown to brown. Leaves evergreen, leathery, 3–9 × 1–2.5 cm, obovate to broadly lanceolate or elliptic, upper surface shiny and glabrous, lower surface glaucous and minutely pubescent, 8–10 inconspicuous secondary veins on each side of the midrib, margins entire, slightly revolute, apex acute to acuminate or cuspidate; petiole 0.4–0.8 cm long, glabrous. Inflorescences axillary, fascicled with one to three branches, ~2 cm long with four to eight flowers. Flowers campanulate, ~0.3 cm diameter; tepals six, greenish yellow. Berry globose, black, 0.8–1 cm diameter. Kostermans 1974. Distribution CHINA: Guangdong, Hong Kong. Habitat Forests. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

The only specimens of Persea breviflora in cultivation located in our research are at Tregrehan, where the larger (planted in 1998) is forming a respectable small tree, of 2.3 m in 2006 (Johnson 2007). It is growing vigorously, producing long new shoots with narrow leaves that flush bright red in spring. This material came from Hong Kong (TH 1087), and its hardiness cannot be judged until it has become more widely grown. P. duthiei (Hook. f.) Kosterm. S355 P. ichangensis (Rehder & E.H. Wilson) Kosterm. B122, S355; K264 (as Machilus ichangensis)

Persea indica (L.) Spreng.

Viñátigo, Canary Islands Mahogany

Tree to 20 m, but usually shorter and sometimes shrubby. Trunk usually straight. Bark silvery, dark grey when old, thick with deep furrows. Branches more or less ascending, green when young, new shoots pubescent. Leaves 15–18 × 3–4 cm, oblong-lanceolate to lanceolate, flushing bronze, bright shiny green on upper surface, lower surface dull, sparsely hairy above, silky-hairy below when immature, glabrous on both surfaces when mature, apex obtuse to acute, base cuneate; petiole 2–3 cm. Old leaves become orange-red before they fall, at any time of the year. Inflorescence formed of subterminal axillary cymes, with peduncles exceeding petiole in length; flowers 3.5–6 mm long, yellowish green, appearing in spring or early summer. Fruits 15–16 mm, ovoid to subglobose, subtended by persistent corolla lobes, green becoming blue-black, with distinct smell of avocado, maturing in late spring. Arboles Ornamentales 2007–2008. Distribution AZORES; CANARY ISLANDS; MADEIRA. Habitat Laurisilva cloud forest on mountain slopes between (300–)400–500 and 1000–1100 m asl, especially with Laurus azorica (Seub.) Franco and Ocotea foetens Benth. & Hook. f. USDA Hardiness Zone 9. Conservation status Lower Risk.

Persea indica is an important constituent of the native damp forests of the Macaronesian islands, especially with Laurus azorica and Ocotea foetens – an association that gives rise to the term ‘laurisilva’ for such forests. The fruits of these ‘laurels’ are the most important food for the several species of endemic pigeon (Columba spp.) on the islands. Laurisilva was once extensive but is now reduced to remnant populations

553

554

Persea

New Trees

A 1 cm

1 mm

D

B

C 1 cm

1 cm

Section II. Species Accounts

Persea

555

on steeper slopes, where the mist forms each day and creates a cool, humid atmosphere. Recommended for and apparently widely planted in Florida and southern California (Schuch et al. 1992), P. indica seems, however, to be little known in temperate cultivation, although it is commercially available in England. A plant at Kew is grown in the Evolution House, reflecting the primitive nature of the Lauraceae. A warm, humid situation seems to offer the best chance of succeeding with it in our area. P. japonica (Siebold & Zucc.) Kosterm. S355

Persea liebmannii Mez Syn. P. podadenia S.F. Blake Shrub or tree to 15 m. Branchlets usually angular with dense, appressed pubescence; terminal buds densely pubescent. Leaves somewhat sparse, evergreen, papery, (4.5–)8–25 × (1–)2.5–4.5(–8.5) cm, elliptic to lanceolate or obovate, upper surface glabrous, lower surface sparsely or densely covered in trichomes, (5–)7–10 secondary veins on each side of the midrib, margins entire, often thickened, apex obtuse or acute; petiole 1–2.5 cm long, pubescent. Inflorescences axillary, 4–7(–20) cm long, with dense, appressed pubescence, pedicels 0.15–0.25 cm long. Flowers campanulate, 0.35–0.5 cm long, yellowish green, inconspicuous; tepals six, unequal, outer tepals smaller than inner, densely pubescent; stamens very small. Fruit a globose berry, ~1 cm diameter. Flowering April to June, fruiting June to December (Mexico). Van der Werff & Lorea 1997. Distribution MEXICO: Chiapas, Chihuahua, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sonora, Tamaulipas, Veracruz. Habitat Montane mesophytic, tropical deciduous and humid pine-oak forest between 600 and 1800 m asl. USDA Hardiness Zone 7–8. Conservation status Vulnerable. Illustration Van der Werff & Lorea 1997. Taxonomic note Older taxonomic works (such as Kopp 1966) retain P. podadenia and P. liebmannii as separate species, distinguished by their leaves, which are larger in P. liebmannii (10–25 × 3–8.5 cm) than in P. podadenia (6–16 × 1.5–3.5 cm).

Under the name Persea podadenia this species has a limited presence in cultivation in the United States, apparently from material introduced by Yucca Do Nursery, Hempstead, Texas (Hogan 2008; Woodlanders 2007–2008). It grows particularly happily in the southeastern states but also does well on the West Coast (Hogan 2008), forming a pleasant, densely crowned small tree that is hardy to –12 to –14 °C. It is similar to P. borbonia but is hairier on the twigs and leaf undersides. The American species of Persea flush green in spring, rather than showing the brighter colours of their Asian relatives.

Persea lingue (Ruiz & Pav.) Nees

Lingue

Tree 15 to 30 m, columnar at least when young, rounder in outline when mature, with spreading branches. Bark and branches not seen or recorded. Leaves 6–11 × 3.5–7 cm, elliptic to obovate, base cuneate to rounded, apex acute to rounded, subcoriaceous, flushing bronze, bright shiny green on upper surface, lower surface dull, sparsely hairy above when young, becoming ± glabrous, hairy below when young, glaucescent later; petiole 1–1.5 cm. Inflorescence of subterminal axillary panicles; peduncles red-hairy, 2–4 cm, not exceeding subtending leaf; flowers 5–6 mm long, yellowish green, pubescent. Fruits in clusters, 14–17 mm, ovoid to subglobose, subtended by persistent corolla lobes, green becoming black. Kopp 1966. Distribution CHILE. Habitat Several forest types, often with Nothofagus, between 0 and at least 850 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration NT554.

Lingue, as it is known in Chile, is an important timber tree, growing with other highly prized species in the moist forests of western Chile. H.J. Elwes reported (field note on specimen s.n. at Kew, 1902) that the wood was used for carriages and furniture, while the bark was used for tanning. Persea lingue grows in several different forest types, with many of the other Chilean trees described in this book and other species familiar in cultivation. It would seem, therefore, that it should do well in our area, in warmer gardens at least. Confirming this, a fine tree has grown in the University of California

Figure 65 (opposite). Persea lingue: leaf (A). P. palustris: habit with fruits (B). P. thunbergii: habit with inflorescences, showing caducous bracts at base of inflorescence (C); and single flower (D).

556

Persea

New Trees

Botanical Garden at Berkeley for at least 50 years (S. Hogan, pers. comm. 2004), and propagations from this are being grown by Sean Hogan in Portland. Also, a collection made by Eric Hammond in 2000 (ECEH 00114) was formerly offered by Heronswood Nursery. The species has been introduced to the United Kingdom on several occasions, notably through collections made by Martin Gardner and Sabina Knees, but it has not become well established in British cultivation. It ought to flourish in suitable gardens on the west coast but seldom does, for reasons that are not clear. Martin Gardner (pers. comm. 2008) reports that the best specimen he has seen recently is a 5 m tree growing at Mount Stuart on the Isle of Bute, off the Scottish west coast, derived from seed collected by Lady Bute in the early 1990s. Another 5 m individual, grown from GK 4392, is outstanding in the Chilean borders at Nymans, West Sussex, and fruits regularly there (E. Ikin, pers. comm. 2008). Provenance is probably important, as the species occurs from sea-level to at least 850 m, and it requires very good drainage. Several collectors have noted that it flowers and fruits as an immature tree, and it is said to be poisonous to stock. Kopp (1966) states that Persea meyeriana Nees was in cultivation at Berkeley in the early-twentieth century. This is another Chilean species, close to P. lingue but differing from it in being more bristly-hairy and in having a farinose waxy deposit on the leaves; the peduncles are also slightly longer. It grows further north and at higher altitudes than P. lingue, and is a species that collectors should look for.

Plate 377. Persea palustris differs from P. borbonia in its hairy leaves and different habitat. This specimen at Kew, from W&H 181, has made a broad bushy plant. Image J. Grimshaw.

Persea palustris (Raf.) Sarg.

Swamp Bay

Tree to 15 m, but usually shorter and sometimes shrubby. Bark to 8 mm thick, grey, fissured. Branches held more or less upright, green when young. Leaves 6.5–18 × 1.5–5.5 cm, obovate to ovate or lanceolate, base cuneate, occasionally obtuse, margins entire, apex acute, upper surface shiny green and glabrescent, lower surface glaucous, with short erect red hairs; petiole 0.8–2.5 cm. Inflorescence formed of a number of fewflowered, subterminal axillary cymes, with peduncles 1–7.5 cm, usually longer than subtending petiole; flowers 4.5–5 mm long, yellowish green, appearing in spring or early summer. Fruits 7–8 mm, subglobose to ellipsoid, slightly apiculate, black, maturing in autumn. Kopp 1966, Elias 1980. Distribution BAHAMAS; USA: Gulf and Atlantic Coastal Plain, Maryland (endangered), Virginia south to Florida and Texas. Habitat Coastal, on thin sandy soil, often in wet situations. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT554, NT556.

Although closely related to Persea borbonia and sometimes included within it by some authorities, P. palustris is distinct in both its ecology and morphology. The chief morphological distinction from P. borbonia is the presence of visible hairs on the underside of the leaves, but its habitat preference for pine barrens as opposed to rich bottomlands is another good character. It is seldom seen in cultivation, even in the United States, but a plant at Kew from a Warner & Howick collection (WH 181) made in coastal North Carolina is growing well, forming a broad-based shrubby tree, with a weak central stem to about 5 m, that flowers each year. Persea humilis Nash (syn. P. borbonia var. humilis (Nash) Kopp) is clearly closely related to P. palustris. From scrubland in Florida, where it is a small shrubby tree, it differs from P. palustris in having smaller leaves that are densely covered with copper-coloured hairs below. Some forms are very attractive, but it is not known to be in cultivation outside Florida.

Section II. Species Accounts

Persea

557

Persea pedunculata (Bl.) Kosterm. Syn. Actinodaphne pedunculata (Bl.) Meisn., Machilus grijsii Hance, Persea grijsii (Hance) Kosterm., P. velutina (Champ. ex Benth.) Kosterm. Shrub or tree (2–)4–8 m. Young growth so densely covered in velvety, ferruginous tomentum, as to obscure surface details completely. Branchlets dark brown, tomentum gradually eroding over several years, leaf scars prominent. Leaves evergreen, leathery, 4.5–13(–17) × 2–5 cm, ovate to elliptic, occasionally obovate, upper surface matt and glabrous, lower surface densely to sparsely tomentose, 4–12 secondary veins on each side of the midrib, margins entire, apex acute to acuminate; petiole 0.5–2 cm long, tomentose. Inflorescences axillary to subterminal, fascicled with six to eight brightly red-coloured branches, 2.5–6 cm long with 3–12 flowers. Flowers campanulate, 0.6–1 cm diameter; tepals six, yellow, pubescent outside. Berry globose, black, 0.8–1 cm diameter. Flowering November to April, fruiting January to June (China). Kostermans 1974. Distribution CHINA: Fujian, Guangdong, Guangxi, Hong Kong. Habitat Moist evergreen forest. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT557. Taxonomic note This species is usually grown under the name Persea grijsii, though Kostermans (1974) placed it in synonymy with P. pedunculata.

In notes on the hundreds of trees observed (JMG) for this book, the only time the description ‘gorgeous!’ appears is on the sheet for Persea pedunculata, seen at the JC Raulston Arboretum in 2006 (labelled P. grijsii, as it is most likely to be in horticulture). This gorgeousness derives from the amazing beauty of the silky hairs covering the new growth, complemented by the bright orange-red of the inflorescence branches (even after the flowers had fallen). The tree itself is a multistemmed specimen up to about 2.5 m tall, grown from seed received from Hangzhou Botanical Garden in 1988–1989 (JC Raulston Arboretum records). Situated in the shelter of the Lath House it is not exposed to the fiercest of winter conditions, but is evidently able to withstand some frost. The species does not seem to be widely grown as yet, although it is in cultivation at Cistus Nursery, but it is certainly an important one to watch out for.

Persea thunbergii (Siebold & Zucc.) Kosterm.

Tabunoki (Japan)

Syn. Machilus thunbergii Siebold & Zucc. Tree 15 to 25 m, columnar at least when young, rounder in outline when mature, with spreading branches, canopy to 15 m across. Bark smooth, green on branches when young, becoming brown with age. Branches in whorls. Leaves 7.5–15 × 3–6 cm, obovate or oblanceolate to elliptic, margins entire, base cuneate, apex acute or acuminate, coriaceous, flushing red or bronze, bright shiny green on upper surface, lower surface dull, waxy and pale whitish green; petiole 2–2.5 cm. Inflorescence formed of terminal panicles emerging in spring from overwintering buds protected by russet-hairy scales, the scales very quickly caducous; peduncles glabrous, elongating with age, red or green; flowers 4–6 mm long, glabrous, yellowish green, fragrant. Fruits in clusters, 10–12 mm, subglobose, subtended by persistent corolla lobes, green becoming purple-black. Flowering in spring, fruits maturing in autumn. Ohwi 1965, Kostermans 1974. Distribution CHINA: coastal provinces from Zhejiang to Hainan; JAPAN: Honshu to Ryukyu Is.; SOUTH KOREA; TAIWAN. Habitat Moist evergreen forest, often with other Lauraceae and Fagaceae, between 0 and at least 730 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT550, NT554. Cross-reference S355.

A brief description of Persea thunbergii was given by Clarke (1988), in which he indicated that it was then in cultivation at Wakehurst Place. It has since become a much more widely grown tree, having entered mainstream American nursery production (often under the name Machilus), and is available also from a few European sources. It is a very attractive species, with the intense red flush of the new shoots giving way to the bright green of the mature leaves. Wild trees are recorded as reaching 25 m, and in the southeastern United States in particular there seems to be no reason why it should not achieve the same stature in cultivation. It seems to flourish in the heat and humidity of the South, where many fine specimens can be seen, but it also does well in the western states. A specimen seen at Quarryhill in 2004 was approximately

Plate 378. Russet hairs on glossy leaves make the breaking foliage of Persea pedunculata rather special, as here in the Lath House at the JC Raulston Arboretum. The persistent red pedicels are also visible. Image J. Grimshaw.

558

Persea

New Trees

8 m in height, forming a column of foliage to the ground. This was planted in 1990, as a seedling grown from a collection made in Honshu in 1987 by Roger Warner and Charles Howick (WH 885). It has suffered occasional frost damage and is also prone, in its exposed situation, to sunburn (W. McNamara, pers. comm. 2004). (This does not seem to be a problem in East Coast gardens.) No really good specimens have been traced in Europe but it does survive in southern England, though growing much more slowly than in the United States. In the Herefordshire garden of Veronica Cross a young plant is growing steadily on heavy clay-loam. In Korea it is notable as a coastal species – some specimens becoming very distorted in consequence of their position – so it may be suited to coastal gardens. The timber is valued, and one particularly intriguing use was noted on a specimen collected in Fujian by H.H. Chung, in 1924, who recorded that ‘wood shavings yield a mucilage much used by ladies to dress their hair’. Clarke (1988) noted that the very similar P. japonica was in cultivation at Wakehurst Place, but it seems to have been lost from there since then. It differs in having slightly longer, narrower leaves than P. thunbergii. It should be reintroduced.

MONIMIACEAE

PEUMUS

Molina

Peumus is monospecific, comprising only the species P. boldus.

Peumus boldus Molina Plate 379. Peumus boldus is the source of a widely used herbal remedy, boldo, drunk as an infusion. Image R. Unwin.

Boldo

Large shrub or tree to 20 m, 1 m dbh. Bark pale grey, rough and flaky when mature. Branchlets tomentose when young. Leaves evergreen, opposite, leathery, 2.5–5 × 2–2.5 cm, ovate to elliptic, upper surface dull green with a prominent midrib and a dense covering of glands, lower surface pale green with dense, stiff fascicled hairs, 6–10 secondary veins on each side of the midrib, margins entire and revolute, apex obtuse; petiole 0.3–0.5 cm long, tomentose. Inflorescences axillary or terminal, composed of 5–12 flowers in a lax raceme. Dioecious. Flowers yellowish white and rather small; staminate flowers with 10–12 tepals in two to three whorls, the outer tepals densely pubescent, the interior tepals petaloid, stamens numerous; pistillate flowers similar to the staminate flowers or slightly smaller, carpels two to seven, pubescent. Fruit a drupe 0.6–0.8 cm long; usually two to five carpels ripen within each flower, though rarely solitary fruits are produced. Flowering June to August, fruiting December to January (Chile). Rodríguez R. et al. 1983. Distribution CHILE: Limarí Province to Osorno Province. Habitat Humid forest, but also adapted to rather dry conditions, between 5 and 1000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT558. Cross-reference K371.

Peumus boldus is highly regarded as a medicinal plant, both in Chile and throughout the world. The tree is the source of numerous alkaloids claimed to have beneficial properties for liver, gastric and cardiovascular function, and an infusion of its leaves

Section II. Species Accounts

Peumus

is sometimes drunk as a digestive tea (Taylor 2005). To harvest leaves for extraction of medicinal products it is apparently grown in plantations in Italy, North Africa and Brazil (Taylor 2005), but it is not well known as a horticultural subject further north. Its medicinal properties are perhaps its chief recommendation as the plant is not particularly attractive in itself, forming a dense and rather dark mass of foliage, although the leaves flush a paler green. When crushed they are very strongly scented, with something like the familiar kick-in-the-nostrils effect from Umbellularia californica (Hook. & Arn.) Nutt. In northern Europe the most notable site for this species may be Logan Botanic Garden, where it is grown from several collections, the trees showing slight variation in leaf width. The largest has reached c. 5 m tall, from a collection made by D. Contreras in 1987. It is also grown in Cornwall, where there is a tree at Tregrehan, and in the western United States.

LAURACEAE

PHOEBE

Nees

Phoebe is a genus of evergreen trees or shrubs with about 100 species, restricted to Asia. The leaves are alternate and pinninerved. Inflorescences are axillary or subterminal panicles with hermaphrodite (rarely unisexual) flowers. The flowers are 3-merous with six equal (or almost equal) tepals. Typically there are nine fertile stamens and three staminodes, though rarely one additional whorl of staminodes is produced, replacing a whorl of stamens. The stamens of the third whorl are glandular and the innermost staminodes are conspicuous and sagittate. The base of the fruit is clasped by persistent, hardened tepals. The genus is badly in need of taxonomic revision (Rohwer 1993a, Liao 1996b). The family Lauraceae is abundant in the moister, warmer temperate forests of Asia, as well as in the true tropics, often occurring with a diversity of other broadleaved evergreens that may be quite difficult to disentangle without careful observation. Among the genera represented in these areas is Phoebe, whose species seem at first glance rather unexciting dull evergreens; a second glance only strengthens the impression (although some observers are more charitable). They certainly do not have the qualities of Nothaphoebe or Persea – perhaps simply because the leaves are less eye-catchingly glossy. Several species are now in cultivation, and it is probable that others will be collected in future. They should be given a warm, sheltered site, with ample moisture and fertile soil, and will do best planted under taller trees to imitate their understorey position in the wild.

Phoebe formosana (Hayata) Hayata Small tree; ultimate height and girth unknown. Stems green, becoming brown at the base, with prominent lenticels. Branchlets angular and covered with short greyish brown hairs. Leaves evergreen, alternate, 12–18 × 4–6 cm, broad-obovate to oblanceolate, thick and papery, upper surface green and glabrous, lower surface glaucous and pubescent, 10 secondary veins on each side of the midrib, margins entire and slightly revolute, apex acute; petiole ~1.3 cm long and pubescent. Inflorescence axillary and paniculate, 10–15 cm long and

559

560

Phoebe

New Trees

pubescent. Flowers ~0.3 cm long and inconspicuous, with six equal, villous tepals, nine fertile stamens and three staminodes. Fruit purplish black, ellipsoidal and ~1 cm long. Flowering May to June, fruiting December to March (Taiwan). Liao 1996b. Distribution CHINA: Anhui; TAIWAN. Habitat Evergreen broadleaved forest between 100 and 2000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Liao 1996b; NT560.

When seen at Heronswood in July 2004 Phoebe formosana had made a rather shrubby tree of 3.5 m, with multiple stems from the base: it was not particularly exciting, even for a Phoebe. The leaves were slightly yellowish green, with a light gloss, although they flush with a bronze tint. This specimen was flowering at the time but the flowers are tiny, green and scentless. It is not common in cultivation. Plate 380. The flowers of Lauraceae are typically small and green, as in Phoebe formosana, making identification within the family quite difficult. Image J. Grimshaw.

Phoebe forrestii W.W. Sm. Tree to 7 m. Branchlets initially covered in golden hairs, though quickly becoming glabrous. Leaves evergreen, alternate, 8–16 × 1.5–3.5 cm, lanceolate, leathery or papery, upper surface bright green and glabrous, lower surface grey-blue or yellow and glabrous, but with a fringe of golden hairs along the veins and midrib, 10–14 secondary veins on each side of the midrib, margins entire, apex acuminate. Inflorescence densely hairy, solitary and axillary. Flowers in groups of four to eight, blue-yellow, perianth slightly villous, nine fertile stamens and three staminodes. Fruit subglobose and 1.2 × 1 cm. Flowering May (China). Smith 1921. Distribution CHINA: Sichuan, Yunnan; INDIA: Sikkim. Habitat Moist forest. USDA Hardiness Zone 7–8. Conservation status Not evaluated.

Phoebe forrestii is growing at Quarryhill from a collection made by Charles Howick and Bill McNamara (H&M 1377) in Sichuan in 1990. These specimens have formed erect narrow trees with a straight main stem and ascending branches, the largest having reached 6.7 m tall and 3.7 m wide by early 2007. They are chlorotic through exposure to bright sunshine, and although apparently healthy, would probably benefit from higher rainfall and more shade (H. Higson, W. McNamara, pers. comms. 2004, 2007). The new shoots flush red-bronze, but when mature are a dull mid-green, slightly paler below. As with all Phoebe, the early summer flowers are insignificant.

Phoebe sheareri Gamble Tree to 15 m, to 0.45 m dbh. Branchlets initially covered with a dense tangle of yellow and grey hairs, completely obscuring the bark; mature branchlets dark brown and only minutely pubescent. Leaves evergreen, alternate, 6–26 × 2.5–10 cm, obovate to elliptic, upper surface glossy green and glabrous or with some hairs along the midrib, lower surface with small, sparse hairs and a fringe of hairs along the veins and midrib, 5–10 secondary veins on each side of the midrib, margins entire, apex acuminate; petiole 1.5–2.5 cm long with dense pubescence. Inflorescence axillary and paniculate, densely pubescent. Flowers four to eight per cluster. Fruit black and ellipsoidal with a prominent six-lobed cupule. Flowering May (China). Liao 1996b, Wharton et al. 2005. Distribution CHINA: Anhui; TAIWAN. Habitat Moist forest at low elevations. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Wharton et al. 2005. Cross-reference K394.

Of the species of Phoebe described here, P. sheareri is perhaps the most handsome, with large, drooping obovate to oblanceolate leaves, dull green above but with ferruginous pubescence on the lower surface. The group in the David C. Lam Asian Garden in Vancouver, grown from NA 60723 collected by Peter Wharton in Anhui in 1988, has been extensively described and praised (Wharton et al. 2005). The plants seem to be hardy there and are making straight trees of about 7 m with spreading branches, although they are naturally rather sparsely clad in leaves. They survived

Section II. Species Accounts

Phoebe

561

–10 °C unscathed in November 2006 (P. Wharton, pers. comm. 2006). A specimen at Tregrehan has reached 7–8 m since 1994. Phoebe chekiangensis P.T. Li, originally described by Shang (1974) (though later validated by P.T. Li), is very similar to P. sheareri but has revolute leaf margins, a glabrous style, and blue-black fruits with persistent tepals at the base (Shang 1974). It is a localised endemic in China, occurring only in Fujian, Jiangxi and Zhejiang provinces, and is vulnerable to overexploitation (for firewood) and habitat degradation and loss. It was received at the JC Raulston Arboretum from the Hangzhou Botanical Garden in 1989, but was introduced to commerce by Cliff Parks of Camellia Forest Nursery, North Carolina, with later offerings by other American nurseries. It is particularly highly regarded in the southeastern states, where it is making attractive small trees (T. Lasseigne, pers. comm. 2007). At Heronswood it survived unscathed for several winters.

OLEACEAE

PICCONIA

DC.

There are two species of Picconia, one in the Azores (P. azorica), the other in the Canary Islands and Madeira (P. excelsa). They are evergreen shrubs or small trees with simple, opposite, entire or rarely serrulate leaves. Inflorescences are axillary, decussate racemes with semi-persistent bracts enclosing the flowers. The flowers are hermaphrodite; the calyx small and four-lobed; the corolla also four-lobed, the lobes alternating from the calyx lobes; stamens two. The fruit is a drupe (Green 2004). Picconia excelsa grows well in coastal southern England and Ireland and is capable of forming large evergreen trees in mild conditions. Both species can be propagated from cuttings, or by seed if available.

Picconia azorica (Tutin) Knobl.

Pau-branco

Shrub or small tree to 8 m. Bark smooth, pale. Leaves evergreen, leathery, 3–6 × 1–2.5 cm, lanceolate to obovate, glabrous, secondary veins inconspicuous, margins entire, apex obtuse; petiole short. Inflorescences axillary. Flowers rather small, white. Drupe ovoid, dark blue to black, to 1.5 cm long. Tutin 1933, Schäfer 2002. Distribution PORTUGAL: Azores. Habitat Scattered in coastal forest, mainly composed of introduced species, between 0 and 750 m asl. USDA Hardiness Zone 8–9. Conservation status Endangered, due to ongoing habitat loss, wood extraction and the introduction of alien species. Illustration NT561.

Picconia azorica is even less well known than its Madeiran relative, and on its horticutural merits is unlikely ever to become a popular plant. The only specimens traced in cultivation in the current research grow in a secluded shrubbery near Jermyn’s House at the Sir Harold Hillier Gardens, forming rather untidy bushy plants about 3 m tall. They derive from a collection made in the Azores by E. Sjögren in 1994. They are densely clad with dark green leaves, and suggest a not very exciting Phillyrea. It probably requires mild coastal conditions to achieve full stature. P. excelsa (Aiton) DC. B176; K324 (as Notelaea excelsa (Aiton) Webb & Bert.)

Plate 381. Picconia azorica is a rare small tree, very poorly known in cultivation. This one is at the Hillier Gardens. Image J. Grimshaw.

562

Picea

New Trees

PINACEAE

PICEA

A. Dietr.

Spruces Picea is a genus of 34 species (Farjon 2001), distributed across the northern hemisphere. As in Abies, there are a few widespread species that dominate the boreal forests of Eurasia and North America, and a larger group of species with isolated, relict distributions in mountain ranges further south. Unlike Abies, Picea is absent from the Mediterranean basin, and is also missing from a large part of northeastern Siberia. Spruces are tall, evergreen trees (the tallest is P. sitchensis) with straight, columnar trunks, often yielding good timber. The bark ranges in colour from grey to orange-brown, and when young is generally flaky with papery scales, though in older trees it becomes dark, rough and scaly (no longitudinal fissures). The crown usually remains conical unless damaged. Primary branches are produced in regular whorls and spread horizontally, but the leader shoot is rigid and upright. Immature branchlets are typically soft and fresh green, contrasting with the darker mature foliage. Branchlets are generally ridged and grooved. The buds vary in shape and size and can be resinous or non-resinous. Often, the subterminal leaves curve over the buds, concealing them. The needle-like leaves are of radial or assurgent arrangement, and can be flattened or quadrangular in cross-section. Their apices are often very sharp to the touch. The leaves are attached to pulvini, which are continuations of the ridges on the branchlets; the pulvini remain on the stem after leaf abscission, though if leaves are removed from living shoots, they detach with them. When branches are removed, the leaves detach within a few weeks – a process familiar to those who use Norway Spruce (P. abies) as a Christmas tree. Species with flattened leaves have stomata on the lower (adaxial) surface only (epistomatic), while those with quadrangular leaves have stomata on all faces (amphistomatic). The male strobili are small, oblong and reddish in colour, though changing to yellow when mature. Both male and female strobili are produced from axillary buds, and are crowded towards the tips of the previous year’s shoots. The cones are pedunculate or sessile, developing at the tips of long shoots, and are initially erect, becoming pendulous at maturity. They are extremely numerous on branches across the crown, or only on upper branches, and mature in one year. Their colour changes from red, purple or green to light brown, and they usually fall after releasing the seeds. The cone scales are imbricate, spirally arranged around a central rachis, persistent, and open at maturity. The bract scales are rudimentary and included. There are two seeds on each cone scale, partially enclosed in a membranous cup, which extends to form a persistent triangular wing. The wing and membrane are easily detached from the mature seed (Farjon 1990). Spruces are readily distinguished from the other genera of the Pinaceae by the combination of leaves with pulvini, pendulous cones with persistent seed scales, and minute bract scales (Rushforth 1977). Hemlock (Tsuga) branchlets also bear pulvini, but their flat leaves and small cones are unlike those of Picea (Warren 1982). The recent discovery of clonal P. abies in Sweden whose oldest wood has been carbon-14 dated to 9550 years old rewrites the record books for the longevity of individual organisms (Umeaº University 2008).

Section II. Species Accounts

Picea

563

1 cm

1 cm

The taxonomy adopted in this account largely follows that of Farjon’s World Checklist and Bibliography of Conifers (2001), although we recognise Picea martinezii as distinct from P. chihuahuana, and adopt a different approach to the P. likiangensis complex. A number of variants of familiar species are described here, as these names are attached to trees in cultivation, and keys to the recognised taxa are provided. These taxa often vary from typical material only in minor morphological characters that may or may not be discernible in cultivated specimens, but in many cases the

Figure 66 (above). Picea martinezii: habit with seed cones (A); detail of stem with leaves (B).

564

Picea

Plate 382. The glaucous Picea chihuahuana is a fast-growing tree, very shapely when young, and apparently with wide climatic tolerances. This one was photographed in the Fichtner-Mainwaring Park, Medford, Oregon in 2004. Image J. Grimshaw.

New Trees

taxon also has a distinct geographical range, and for the purposes of conservation at least the varietal name should be maintained in all records. It is clear that a thorough modern revision of Picea is urgently needed. The genus is undoubtedly best known in the shape of Picea abies – a shape so familiar that it is almost representative of the word ‘conifer’. ‘All too familiar’, indeed, is a descriptor that might be applied to this species, ubiquitous as a forestry tree, too frequent in inappropriate garden situations, and the prickly, gawky centre-piece of many a Christmas living room. It does not encourage a closer acquaintance with its relatives. The genus as a whole, with the exception of the frequently planted P. breweriana and P. omorika, is currently rather out of fashion, and the rarer species are now seldom planted. It is clear from the TROBI records that many species of Picea are currently represented in British arboreta by fewer than a hundred specimens (Johnson 2003). Most of the taxa described below are even more scarce, and many are confined to specialist collections. This situation is unfortunate, as many spruces are very ornamental as young plants, in shape, colour and cones, although it is true that they tend to age badly. Few avoid a sparse maturity, and this is exacerbated in dry situations. All prefer a cool moist site and a good soil. Propagation is by seed whenever possible, as grafted specimens tend not to develop a good shape nor to do as well as seed-grown trees (though for some of the rare species such as P. farreri it may be the only option to maintain stock in cultivation). Hybridisation can occur in arboreta. Picea is reasonably well represented in arboreta throughout our area, but its general preference for cooler conditions imposes some limits. In the United Kingdom the Royal Botanic Gardens of Kew and Edinburgh both have excellent collections, distributed throughout their gardens. Pests and diseases are numerous, especially in commercial forestry situations, but in the horticultural context they seem to be of relatively little significance. Aphids (including adelgids) may be damaging, especially when trees are young, and in North America various insect larvae attack either foliage or wood. Spider mites can be a problem, especially on the compact or dwarf cultivars that are the most frequent manifestation of Picea in gardens. Frost can cause considerable damage to new shoots, and as usual it is the more northerly species that are affected most frequently, especially in areas with mild winters. P. abies (L.) H. Karst. B178, S362, K175 P. abies var. alpestris (NOW P. abies (L.) H. Karst. var. abies) B178, K177 P. abies f. acuminata (NOW P. abies var. acuminata (Beck.) Dallim. & A.B. Jacks.) K177 P. abies f. apiculata (Beck.) Krüssm. K177 P. abies var. carpathica (NOW P. abies var. acuminata (Beck.) Dallim. & A.B. Jacks.) K177 P. abies f. chlorocarpa (Purk.) T. Fries K177

P. abies f. columnaris (Jacques) Rehder B179 P. abies f. deflexa (Tyszkiewicz) Krüssm. K179 P. abies f. erythrocarpa (Purk.) Rehder K180 P. abies f. gigantea (Beissn.) Boom K180 P. abies f. glomerulans (Kihlm.) Krüssm. K180 P. abies f. hercynica (Beissn.) Krüssm. K181 P. abies f. monstrosa (Loudon) Rehder B181 P. abies f. nigra (Loudon) T. Fries K183

Section II. Species Accounts

Picea

P. abies f. palustris (Berg.) Krüssm. K184 P. abies f. pendula (Laws.) N. Sylven B180, S362 P. abies f. squarrosa (Jacobasch) den Oud. & Boom K187 P. abies f. strigosa (Christ.) Dallim. & A.B. Jacks. K187 P. abies f. triloba (Asch. & Grab.) den Oud. & Boom K190 P. abies f. viminalis (Alstr.) Lindman B180 P. abies f. virgata (Jacques) Rehder B180 P. alcoquiana (Veitch ex Lindl.) Carrière B182, K190 P. alcoquiana var. acicularis (Maxim. ex Beissn.) Fitschen B182, K190 P. alcoquiana var. reflexa (Shiras.) Fitschen B182, K190 P. asperata Mast. B181, S362, K190 P. asperata var. heterolepis (NOW P. asperata var. notabilis Rehder & E.H. Wilson) B181, K190 P. asperata var. notabilis Rehder & E.H. Wilson B181, K190 P. asperata var. ponderosa Rehder & E.H. Wilson B181, K190 P. asperata var. retroflexa (NOW P. retroflexa Mast., NT577) B181 P. aurantiaca Mast. K191 P. bicolor (NOW P. alcoquiana (Veitch ex Lindl.) Carrière var. alcoquiana) B182, S363, K190 P. bicolor var. acicularis (NOW P. alcoquiana var. acicularis (Maxim. ex Beissn.) Fitschen) B182, K190 P. brachytyla (Franch.) E. Pritz. B182, S363, K191 P. brachytyla var. complanata (Mast.) W.C. Cheng ex Rehder K191 P. brachytyla f. latisquamea (NOW P. brachytyla (Franch.) E. Pritz. var. brachytyla) B183 P. brachytyla f. rhombisquamea (NOW P. brachytyla var. rhombisquamea Stapf) B183, K191 P. ×brewentalis G. Horstm. K191 P. breweriana S. Watson B183, S363, K191

Picea chihuahuana Martínez

565

Plate 383. Picea chihuahuana has been confused with P. martinezii, but differs in its dense, radiating, glaucous leaves, and longer cones. See also Plate 389 (p. 575). Image J. Grimshaw.

Chihuahua Spruce

Tree to 45 m, 1–1.2 m dbh. Bark grey, smooth then scaly in young trees, becoming dark grey-brown and breaking into small, irregular plates in older trees. Crown pyramidal, becoming rather open and irregular in mature trees. Branchlets firm, pale yellow-brown to grey, glabrous, pulvini well developed; vegetative buds slightly resinous. Leaves dense, assurgent above, parted below, olive-green or glaucous blue-green, quadrangular in cross-section, 1.2–2.3(–2.8) × 0.1–0.18 cm, somewhat falcate, apex acuminate, sharp to the touch. Male

566

Picea

New Trees

strobili 1–1.5 cm long, yellow. Cones subterminal, solitary or in groups of two to four, sessile, cylindrical, (7–)10–12(–17) × 4–5 cm, bright green, shiny brown when mature, resinous. Seed scales opening wide at maturity, cuneate-flabellate, (1.8–)2–2.5 × 1.4–2.1 cm, margin entire, rounded. Seeds dark red-brown, ovoid to cuneate, 0.3–0.6 cm long, wings yellowish, ovate to oblong, 1–1.5 × 0.5–0.8 cm. Rushforth 1986, Patterson 1988, Farjon 1990. Distribution MEXICO: southwest Chihuahua, southern Durango, Nuevo León. Habitat North-facing mountain slopes between 2150 and 3200 m asl. USDA Hardiness Zone 6–7. Conservation status Endangered. This species occurs in a small number of widely distributed valley-bottom sites, with small population sizes (100–350 mature trees). Illustration Farjon 1990; NT564, NT565. Cross-references S363, K191. Taxonomic note Picea chihuahuana does not appear to be closely related to the other North American spruces (though see P. martinezii), but rather to Asian species such as P. smithiana and P. torano (Siebold ex K. Koch) Koehne (Rushforth 1986a).

Picea chihuahuana should rank as one of the most notable of recent tree introductions and promises to be a handsome and versatile species, tolerating both heat and cold. The finest specimen observed for New Trees grows in Fichtner-Mainwaring Park, Medford, Oregon and was about 7 m tall when seen in 2004, growing vigorously, with a perfect shape from its regular, densely clad branches. It was grown from seed collected in the early 1990s by Frank Callahan at about 2250 m, near Rio Otores, Chihuahua. The parent trees were over 30 m tall, with huge boles bearing very robust limbs (F. Callahan, pers. comm. 2004). In its exposed situation in Medford it gets full hot sun and no supplementary water but is gaining height at a rate of at least 75 cm per year, far exceeding the locally expected growth rate of the commonly planted P. pungens (F. Callahan, pers. comm. 2004). Close up, it is remarkable for its bristling, extremely sharp leaves that radiate around the noticeably thick branchlets; they have good glaucous colour, though are not as blue as the best P. pungens selections. Similar plants are found elsewhere in American collections, including a group of four flourishing trees of about 4.5 m (in 2006) seen at the Arnold Arboretum, that give a strong indication of how adaptable the species seems to be, tolerating temperatures ‘in the low tens °C below freezing’ (K. Rushforth, pers. comm. 2007). It is commercially available in the United States, and in New Zealand, but seems to be rather scarce in Europe, although J. Hjerting & S. Ødum 12 from Chihuahua in 1989 is established in the United Kingdom and Denmark. In several arboreta trees referable to P. martinezii are labelled P. chihuahuana (see the description of P. martinezii) but the true glaucous P. chihuahuana, with its stiffly radiating leaves, is rarer. The only specimen seen in the United Kingdom grows in Keith Rushforth’s wood in north Devon, where it seems to be thriving. This is certainly a species that should be grown more frequently.

Picea crassifolia Kom.

Qinghai Spruce

Tree to 25 m, 1–1.2 m dbh. Bark orange-brown, smooth then flaking in young trees, becoming red-brown, rough and scaly in older trees. Crown pyramidal or conical, becoming rather open in mature trees. Branchlets firm, pale orange-yellow to grey, glabrous or with limited pubescence, pulvini well developed; vegetative buds not or slightly resinous. Leaves glossy dark green, upper leaves crowded and directed forwards, lower leaves curved upwards, quadrangular in cross-section, (0.9–)1.2–2.2(–3.5) × 0.15–0.25(–0.3) cm, apex acute-obtuse. Male strobili 1–1.5 cm long, yellowish pink with orange-brown perular scales. Cones terminal, solitary, sessile, ovoid-oblong or cylindrical, (5–)7–11 × 2.5–3.5 cm, initially green to purplish red, later green with purple margins to seed scales. Seed scales obovate-flabellate, 1.5–2 × 1–1.7 cm, margin entire and incurved. Seeds brown, ovoid to oblong, 0.3–0.35 cm long, wings orange-brown, ovate to oblong, 1–1.3 × 0.4–0.5 cm. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Gansu, Nei Mongol, Ningxia, Qinghai. Habitat North-facing slopes of high mountain ranges between 1600 and 3800 m asl. USDA Hardiness Zone 5. Conservation status Lower Risk. Illustration Farjon 1990; NT567. Taxonomic note When grown in Western Europe, P. crassifolia develops longer, flatter leaves than those found in wild material. The species may represent an eastern form of P. schrenkiana (Farjon 1990).

Section II. Species Accounts

Picea

Picea crassifolia is rare in cultivation and omitted from most texts. This may be due to confusion with P. asperata, under which name seed of P. crassifolia collected by Joseph Rock was distributed (Rushforth 1987a). A fine tree at Kew, currently approximately 20 m tall and retaining a good shape, may be from this source. It appears to be growing vigorously still, and is a rich dark green in colour. New shoots were emerging when it was observed towards the end of May 2005 and this late emergence, coupled with its natural tolerance of dry conditions, suggest that it could be a very useful tree for milder, drier parts of our area. More recent plantings are to be found in the Scottish botanical gardens, including a group of trees from a 1980 accession from Qinghai doing well at Dawyck. These have formed broad-based plants, the largest of which was 2.5 m tall in 2006. Their foliage is grey-green.

Picea engelmannii Parry ex Engelm.

Engelmann’s Spruce

This species was described by Bean (B184, S364) and Krüssmann (K191). P. engelmannii f. glauca (NOW P. engelmannii Parry ex Engelm.) B184

Picea engelmannii subsp. mexicana (Martínez) P.A. Schmidt Syn. P. mexicana Martínez Subsp. mexicana differs from the type subspecies in that its bark is lighter grey, its leaves are narrower (0.1–0.12 cm wide, vs. 0.15–0.2 cm in the type) and the bract scales are slightly longer (0.4–0.6 cm long, vs. 0.3–0.5 cm). Rushforth 1986, Farjon 1990, Ledig et al. 2004. Distribution MEXICO: southern Chihuahua, Coahuila, Nuevo León; USA: Arizona (Chiricahua Mts.), New Mexico (?). Gymnosperm Database 2002. Habitat North-facing mountain slopes, between 3000 and 3400 m asl. USDA Hardiness Zone 7. Conservation status Endangered. In 1975, one population (La Carmen) was decimated by a fire caused by visiting daytrippers (Rushforth 1986a). The other populations are also small and vulnerable to chance events. Crossreferences S364, K196 (both as P. mexicana).

Rushforth (1987a) treats this taxon as P. mexicana Martínez, and Ledig et al. (2004) in their recent study also consider that it should be recognised as a full species, P. mexicana, though they acknowledge that it is most closely related to P. engelmannii. If political considerations are left aside, however, it seems sensible to continue to treat it as a form of the widespread P. engelmannii from north of the border and to regard it as a relict from a wider distribution, in the same way that so many other North American species have isolated pockets of occurrence in Mexico. Disjunct populations of P. engelmannii in Arizona and New Mexico are also sometimes attributed to this taxon (Farjon 1990, Taylor et al. 1994). It is rare both in the wild and in cultivation, but in southern England it seems to grow well. Two specimens at Wakehurst Place grown from Keith Rushforth’s widely distributed collection KR 526 from La Carmen, Coahuila have pendulous shoots and very glaucous leaves; the larger of the two was about 8 m tall in 2005. A 9 m specimen was measured for TROBI in 2006 by Owen Johnson at Sandling Park, Kent. Plants from J. Hjerting & S. Ødum 2 collected on Cerro Mohinora in Chihuahua are also in cultivation. Its hardiness and tolerances are not yet fully known but P. engelmannii subsp. engelmannii is renowned as an extremely hardy and adaptable tree (Sternberg 2004); the glaucous foliage of subsp. mexicana is a valuable addition to the species’ diversity in cultivation.

567

Plate 384. A broad-based tree of Picea crassifolia at Arboretum Wespelaar. The foliage may be either dark green or somewhat glaucous. Image P. de Spoelberch.

568

Picea

New Trees

Picea farreri C.N. Page & Rushforth

Farrer’s Spruce

Tree to 35 m, 0.6–0.7 m dbh. Bark orange-brown, becoming grey-brown, rough and scaly in older trees. Crown broadly conical, irregular and very open. Branchlets slender, drooping or pendulous, pale orangeyellow or olive-brown, sparsely pubescent to glabrous, pulvini poorly developed; vegetative buds slightly resinous. Leaves spreading forwards, green-glaucous, flat in cross-section, (1.5–)1.8–2.3(–2.5) × 0.1–0.11 cm, apex acute, slightly pungent. Male strobili 1.5–2.5 cm long, yellowish. Cones terminal, pedunculate, ovoidoblong or ellipsoidal-cylindrical, (4–)6–12(–14) × 2.5–4.5 cm, green or purplish green, later brown to reddish brown when mature, deciduous. Seed scales obovate-oblong, 1.2–2.2 × 0.8–1.5 cm, upper margin irregularly rounded and recurved. Seeds dark brown, ovoid to oblong, 0.4–0.25 cm long, wings shiny, orange-brown, ovate to oblong, 1.3–1.5 × 0.6 cm. Page & Rushforth 1980, Farjon 1990, Fu et al. 1999c. Distribution CHINA: western Yunnan (Salween Valley); MYANMAR: Fen-Shui-Ling Valley. Habitat Limestone mountains between 2400 and 2700 m asl. USDA Hardiness Zone 8. Conservation status Endangered. Illustration Farjon 1990; NT568. Cross-reference S364.

Plate 385. Named in honour of Reginald Farrer, who first found it in Upper Burma before his death there in 1920, Picea farreri derives great grace from its narrow pendulous shoots. Its survival in cultivation is a model for the action needed regarding many rare species. Image J. Grimshaw.

Picea farreri was recognised as a species only in 1980, but commemorates that eccentric plant collector and rock gardener Reginald Farrer, who died a lonely death in 1920 in its homeland of upper Burma. He had made his collection Farrer 1435 there in 1919, and from this grew the tree that formed part of the type specimen for P. farreri. This apparently unique specimen tree grew at Exbury, Hampshire where it was planted in 1921 (Clarke 1988). It had reached 18 m in height and 56 cm dbh, but was left exposed after being damaged in the Great Storm of 1987 and eventually died of drought in 1995 (TROBI). Fortunately, a good number of specimens were propagated from it by Hillier Nurseries in the 1960s (one of these trees is in the Cambridge University Botanic Garden), and later by Keith Rushforth, and were widely distributed to collections throughout the United Kingdom (K. Rushforth, pers. comm. 2007). These form the current stock in cultivation and stand as an excellent example of the sort of conservation action required to preserve rare species in cultivation. Seedlings from the Exbury tree are apparently pure-bred (K. Rushforth, pers. comm. 2007). Picea farreri is a potentially beautiful species, with long pendulous branchlets bearing silvery green needles, though not all the grafted trees have formed elegant specimens. The finest seen in the current research is at Thenford House, where it has made a good straight stem estimated at 10–12 m in 2006, bearing very long branches with healthy growth at their tips. Another good specimen is reported to be growing at Lukesland, Ivybridge, Devon (Henderson 2004), and there is an attractive tree at Tregrehan, of about 6 m in 2008. It seems to enjoy moist, fertile conditions; one on a rather exposed slope at Wakehurst Place is unshapely and not thriving (2.8 m in 2005).

P. gemmata (NOW P. retroflexa Mast.) K193 P. glauca (Moench) Voss B185, S364, K193 P. glauca var. albertiana (S. Br.) Sarg. B185, K193 P. glehnii (F. Schmidt) Mast. B186, S364, K193 P. hirtella (NOW P. likiangensis subsp. balfouriana (Rehder & E.H. Wilson) Rushforth, NT572; OR P. likiangensis var. hirtella (Rehder & E.H. Wilson) W.C. Cheng) K194 P. ×hurstii De Hurst K194

Section II. Species Accounts

Picea jezoensis (Siebold & Zucc.) Carrière

Picea

569

Yezo Spruce

Tree to 50 m, 1–1.5 m dbh. Bark brown, smooth, becoming blackish brown or purplish grey, rough, scaly in older trees. Crown broadly conical or pyramidal, open in older trees. Branchlets slender, firm or flexible, pale yellow to orange-yellow or yellowish brown, shiny, glabrous or slightly pubescent; vegetative buds not resinous. Leaves spreading forwards, shiny green, flat to triangular in cross-section, 1–2(–2.4) × 0.15–0.2 cm, apex acute or mucronate. Male strobili 1.5–2 cm long, yellowish. Cones terminal, often clustered, sessile, cylindrical, 4–7(–9) × 2–3.5 cm, green, becoming light yellow to reddish brown when mature. Seed scales obovate-oblong, thin and papery, 1–1.2 × 0.6–0.8 cm, upper margin undulate and denticulate. Seeds light brown, ovoid to cuneate, 0.3 × 0.2 cm, wings light orange-brown, ovate-oblong, 0.6–1 × 0.4–0.5 cm. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Jilin; JAPAN: Hokkaido, northern Honshu; NORTH KOREA; RUSSIAN FEDERATION: Kamchatka, Kuril Is., Sakhalin, coastal Siberia. Habitat Occurs on a variety of soils between 0 and 2700 m asl. USDA Hardiness Zone 4. Conservation status Lower Risk. Illustration Farjon 1990; NT569. Cross-references B186, K194. Taxonomic note The epithet jezoensis is derived from the former name for Hokkaido: Yezo or Jezo.

Three taxa have been distinguished in Picea jezoensis, differing perhaps as much in their geographical origins as in morphology. A key is provided below. 1a. Cones small (3–4 × 2–2.2 cm); seed scales almost rhombic, flat; China (Jilin), North Korea ............................................................... subsp. jezoensis var. komarovii 1b. Cones large (4–7(–9) × 2–3.5 cm); seed scales obovate-oblong, flat or incurved; Japan, Russian Federation .................................................................................. 2 2a. Branchlets dark reddish brown in second year; leaves broad (1.8–2.2 cm); cones dark reddish brown at maturity; Japan (central Honshu) .......................... subsp. hondoensis 2b. Branchlets orange-yellow or yellowish brown in second year; leaves narrow (1.5–2 cm); cones light yellowish or reddish brown at maturity; Japan (Hokkaido, north Honshu), Russian Federation (Kuril Is., Sakhalin, Siberia) .............................................................. subsp. jezoensis var. jezoensis

Picea jezoensis subsp. jezoensis var. jezoensis Bean (1976b) considered that the only material of Picea jezoensis in cultivation was attributable to subsp. hondoensis, from Honshu, rather than the nominate subsp. jezoensis from Hokkaido. Subsp. hondoensis remains the dominant presence in cultivation throughout our area, making fine trees in suitable gardens; it enjoys cool, moist conditions, but will grow steadily in less favourable conditions, such as in Finland (K. Rushforth, pers. comm. 2007). Subsp. jezoensis is still very rare, although it has been introduced on several occasions since 1861. A collection made by Frank N. Meyer (d. 1918) in Siberia has been maintained in North America, and is currently represented by a grafted tree of 11 m (32.5 cm dbh) at the Morton Arboretum, derived from an original tree in the Arnold Arboretum (K. Kim, pers. comm. 2007). In the United Kingdom only one larger tree has been recorded by TROBI, growing at Darnaway in Moray, measured by Alan Mitchell at 11 m tall in 1989. Otherwise it seems to be represented, in Britain at least, only by young specimens grown from recent expeditions to Japan and the Russian Far East. From Hokkaido there is EHOK 20, collected in October 1997 in the Uryu Experimental Forest near Horokanai. Here the parent trees grew to 8 m tall, with a spread of 6 m, amongst mixed forest on volcanic slopes. It was also collected by Warner and Howick (W&H 550) in Hokkaido in 1987. Not surprisingly, plants from this provenance have not flourished at Quarryhill, resenting the heat, and the solitary survivor there (1 m tall) is in a lingering, yellowish state and

Plate 386. Young plants of Picea jezoensis subsp. jezoensis ESUS 176 have been very slow at Kew. Frost damage to new shoots in spring is a serious problem for many high-latitude spruces. Image J. Grimshaw.

570

Picea

New Trees

has not put on new growth for some time (H. Higson, pers. comm. 2007). At Howick, however, several specimens from W&H 550 are healthy, though slow-growing (up to 2.5 m in 2007) – unlike a tree of subsp. hondoensis that has shot up to 10–12 m in the same time (C. Howick, pers. comm. 2007). From Sakhalin in 1994 there is ESUS 176, which is also attributable to subsp. jezoensis. At Kew the plants from this collection are still very small and they are apt to have their first flush of growth frozen in spring frosts, which is a pity, as the bright grass-green new shoots are attractive. They seem to be as difficult in cultivation as their compatriot Abies sachalinensis (see p. 58), with which the original Sakhalin trees were growing – a problem that might be termed ‘Siberian conifer syndrome’. P. jezoensis var. hondoensis (NOW P. jezoensis subsp. hondoensis (Mayr) P.A. Schmidt) B186, S365, K194

Picea jezoensis subsp. jezoensis var. komarovii (V.N. Vassil.) W.C. Cheng & L.K. Fu The cones of var. komarovii are smaller than those of the type (see key, above), and the seed scales are flat, but strongly erose-denticulate. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Jilin; NORTH KOREA. Habitat Montane and subalpine forest between 700 and 2000 m asl. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration Fu et al. 1999c.

This taxon was first introduced as seeds sent out by the Chinese Academy of Forestry in the early 1980s (K. Rushforth, pers. comm. 2007), but is represented in cultivation by only a few young plants. It was introduced to North America by the North America–China Plant Exploration Consortium (NACPEC) 1993 Heilongjiang China Expedition, under the number HLJ 098. The parent trees were growing in wet upland forest on Jian Shan Jiao, Heilongjiang Sheng Province. At the Morton Arboretum two examples are still only 60 cm tall. They are described as ‘squatty’ by Kunso Kim (pers. comm. 2007), who ascribes their poor performance to deficient soil conditions – but ‘Siberian conifer syndrome’ is also a probability. Specimens growing at Edinburgh and Dawyck are derived from seed received from Jilin, China in 1995. At Dawyck there are several individuals from this accession, all about 45 cm tall in 2006 and just beginning to form a leader.

Picea koraiensis Nakai

Korean Spruce

Tree to 30 m, 0.6–0.8 m dbh. Bark purplish brown, smooth then flaking in young trees, becoming dark grey-brown, rough, scaly and fissured in older trees. Crown conical or pyramidal. Branchlets slender, firm, pale yellowish brown or red-brown, turning grey-brown, glabrous or slightly pubescent, pulvini small; vegetative buds very resinous. Leaves spreading forwards, glaucous- or bluish green, rhombic in cross-section, 1.2–2.2(–2.5) × 0.15–0.18 cm, apex acute or obtuse. Male strobili 1.5–2.5 cm long, yellowish. Cones terminal, sessile, ovoid-oblong or cylindrical, (4–)5–8 × 2.5–4 cm, green or purplish initially, orange-brown or dull brown when mature. Seed scales obovate-oblong, 1.3–1.9 × 1.1–1.6 cm, upper margin entire, rounded or obtuse. Seeds dark brown, ovoid-conical, 0.3–0.4 × 0.2–2.5 cm, wings yellowish, transparent, ovate-oblong, 1.2–1.6 × 0.6–0.8 cm. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Heilongjiang, Jilin; NORTH KOREA; RUSSIAN FEDERATION: Primorye. Habitat Mountain slopes and along streams between 1000 and 1500 m asl. USDA Hardiness Zone 5. Conservation status Lower Risk. Illustration Farjon 1990, Fu et al. 1999c; NT571. Taxonomic note Two varieties of P. koraiensis are recognised – var. pungsanensis (Uyeki ex Nakai) Farjon, from North Korea, and var. nenjiangensis S.Q. Nie & X.Y. Yuan, from northeast China – neither of which are known to be in cultivation.

In the past there seems to have been some confusion between this species and the Japanese Picea koyamae, making it somewhat difficult to trace its early introductions,

Section II. Species Accounts

Picea

but it arrived at Arboretum Mustula, Finland in the 1920s or ’30s (K. Rushforth, pers. comm. 2007). It has been grown since 1940 at the Arnold Arboretum, where there are also specimens from accessions in succeeding decades. The Scottish gardens have several trees as well, dating to 1973 in the case of an individual at Benmore of unrecorded origin, with later accessions coming from official sources in North Korea or China (Jilin, Nei Mongol, Heilongjiang). When young it is an attractive tree, forming a neat conical shape with branches to the ground, but as plants age they become sparser at the base. The foliage varies from a dull midgreen to quite glaucous, but the spring flush is an attractive pale green. The female cones can be a nice dark purple when young. It seems to grow well in many places, but a tree at Kew, received as seed collected in Jilin by the Chinese Academy of Forestry in 1979, has so far reached only 3 m and is becoming sparse at the base, suggesting that it resents the warm dry conditions of west London. In contrast, a slightly younger specimen at Wakehurst Place was 8 m tall in 2005, and a 1986 accession at the Morris Arboretum was a healthy and vigorous 6 m in 2006. The species is currently available commercially in Europe and North America, including from Golden Bough Tree Farm, Ontario, Canada (a nursery specialising in plants for cold climates, that describes itself as ‘a research station disguised as a business’: Golden Bough Tree Farm 2009).

P. koyamae Shiras. B187, S365, K194

Picea likiangensis (Franch.) E. Pritz.

Likiang Spruce

This comparatively familiar species with beautiful young cones was described by Bean (B188, S365) and Krüssmann (K194) and reviewed by Hunt (Hunt 1983), but the taxonomy has since been revised and a number of new names and concepts are in circulation. The status quo is the position of the Flora of China account (Fu et al. 1999c) and Farjon’s World Checklist (2001), both of which accept five varieties within the species (vars. likiangensis, hirtella, linzhiensis, montigena, rubescens), plus the related Picea purpurea Mast. (see Bean and Krüssmann: B118, K195, in both cases as P. likiangensis var. purpurea (Mast.) Dallim. & A.B. Jacks.). In a recent paper, however, Rushforth (2008) has reviewed the P. likiangensis complex and makes some very convincing proposals for rationalising the names and concepts within it, based not only on morphological characters but on his own extensive knowledge of the distribution of the taxa in the Sino-Himalaya. In addition to P. likiangensis subsp. likiangensis and P. purpurea, Rushforth (2008) recognises P. linzhiensis as a full species, while the three other varieties are treated together as subsp. balfouriana. The two classifications differ principally in the interpretation of the status of the taxa involved; we follow Rushforth’s view here as it has advantages to the horticultural community in simplifying the nomenclature of this difficult group, but also clearly represents the desirable biological species concept so often overlooked in herbarium-based studies. A key to the taxa is presented below.

571

Plate 387. Picea koraiensis var. koraiensis, with new shoots just emerging. This young tree at Kew is aready getting rather sparse at the base and would probably prefer a moister climate. Image J. Grimshaw.

572

Picea

New Trees

1a. Branchlets with glandular hairs; leaves epistomatic or rarely with one to two incomplete lines of stomata along each abaxial surface; cones (5–)6–9(–12) cm long; Xizang ........................................................................... P. linzhiensis 1b. Branchlets pubescent; leaves amphistomatic or rarely with stomatal lines absent from abaxial surfaces ............................................................................................... 2 2a. Branchlets slender, sparsely pubescent; leaves bluish, with four lines of stomata; cones (7–)10–12(–15) cm long; southwest Sichuan, Yunnan (Lijiang range, and adjacent areas) .................... P. likiangensis subsp. likiangensis 2b. Branchlets slender or stout, densely pubescent; cones 2.5–9(–10) cm long ...................................... 3 3a. Branchlets stout; leaves bluish green, with two broad bands of stomata on adaxial side and two narrower bands on abaxial side; cones 4.5–9(–10) cm long; west Sichuan, etc. ..................... P. likiangensis subsp. balfouriana 3b. Branchlets slender; leaves with dark green shiny abaxial surface lacking or with one to two incomplete stomatal lines; cones 2.5–5.5 cm long; northern Sichuan to southern Gansu ....................................... P. purpurea

Picea likiangensis subsp. likiangensis Crown broad, often open. Young branchlets thinly pubescent and pale pinkish brown. Leaves glaucous blue-green or silvery blue, 0.15–0.2 cm, thick. Cones large, 7–15 × 4–5.5 cm, usually purplish brown at maturity but sometimes yellowish brown. Seed scales thin and flexible. Mitchell 1972, Farjon 1990, Fu et al. 1999c. Distribution CHINA: Sichuan (southwest), Yunnan (Lijiang range). Habitat Montane forest. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Farjon 1990, Fu et al. 1999c. Crossreferences B188, K195.

Plate 388. The dark red young female cones of Picea likiangensis subsp. balfouriana combine well with the glaucous foliage. When they mature after fertilisation they will become pendulous, as in all spruces. Image J. Grimshaw.

Picea likiangensis subsp. likiangensis is well established in cultivation, principally from early-twentieth century introductions, although more recent gatherings have been made. Literature references to unspecified ‘P. likiangensis’, and trees so labelled, are usually referable here. It is less hardy than subsp. balfouriana, however, and is unlikely to be found in areas with hard winters.

Picea likiangensis subsp. balfouriana (Rehder & E.H. Wilson) Rushforth Syn. P. montigena Mast. (?), P. balfouriana Rehder & E.H. Wilson, P. likiangensis var. rubescens Rehder & E.H. Wilson, P. likiangensis var. balfouriana (Rehder & E.H. Wilson) Hillier ex Slavin, P. likiangensis var. hirtella (Rehder & E.H. Wilson) W.C. Cheng, P. likiangensis var. montigena (Mast.) W.C. Cheng Crown narrow, moderately dense. Bark breaking into small, square flakes. Young branchlets densely pubescent and orange- or reddish brown. Leaves grey-green or bluish green, arrangement dense, appressed above the shoot, 0.15–0.2 cm, thick. Cones small (4.5–10 × 3–4 cm), usually purplish brown at maturity but sometimes yellowish brown. Seed scales thin and leathery. Farjon 1990, Fu et al. 1999c. Distribution CHINA: southern Qinghai, western Sichuan, eastern Xizang, northwestern-most Yunnan. Subsp. balfouriana overlaps slightly with subsp. likiangensis in northwestern Yunnan, replacing it at higher altitude. (Rushforth 4100, from 3660 m near Zhongdian, is subsp. balfouriana.) Habitat Subalpine forest between 2700 and 3700 m asl. USDA Hardiness Zone (5–)6. Conservation status The population from southwest Sichuan recognised as var. montigena in China (Fu et al. 1999c, Farjon 2001) is regarded as Endangered, and var. hirtella from southwest Sichuan and southeast Xizang is classed as Vulnerable, but subsp. balfouriana is otherwise Lower Risk. Illustration Farjon 1990, Fu et al. 1999c; NT572. Cross-references B188, K195. Taxonomic note Rushforth (2008) argues convincingly for the lumping into a single entity of the three

Section II. Species Accounts

currently recognised but somewhat indistinct varieties hirtella, montigena and rubescens (as applied by Fu et al. 1999c, Farjon 2001). The cone characters used to separate them are very weak. The rank at which the resulting taxon is treated is a matter of opinion, but has bearing on the name to be applied. At specific level P. montigena Mast. has priority, though there are doubts over the validity of this name as the type specimen may be of hybrid origin (Bean 1976b). As a subspecies the epithet is balfouriana (adopted by Rushforth 1999), while as a variety rubescens has priority.

In its traditional horticultural sense subsp. balfouriana is one of the better-known and more widely grown forms of Picea likiangensis, differing from subsp. likiangensis in several morphological features, including the more hairy shoots and smaller cones, but also the imbricate leaves that droop from the sides of the shoot (rather than pointing upwards and outwards as in subsp. likiangensis). It is also geographically and ecologically distinct (Rushforth 1999). It has persisted in cultivation since its introduction by Ernest Wilson, and it is possible that most trees in arboreta are derived from Wilson’s collections, although in Scandinavian arboreta there are several from Harry Smith introductions, and the two trees at the Hillier Gardens may derive from one of these (K. Rushforth, pers. comm. 2007). There are good trees at Dawyck, 18 and 21 m tall in 1997 (Johnson 2003), grown from Wilson 4080, and this collection number is also represented by a grafted tree of 6 m (since 1980) at Kew. The taxon has been reintroduced from more recent expeditions, including Roy Lancaster’s gathering from the Pa La River valley in western Sichuan in 1987 (Lancaster 908), and the Sichuan Expedition’s SICH 704 from 1991 (a tidy 4 m at Dawyck in 2006). Its horticultural value lies in the pleasing combination of glaucous foliage and red female cones in spring. Trees have been in cultivation under the name var. hirtella since its discovery by Ernest Wilson in 1908 in western Sichuan (Wilson 2082, 2084). A resultant tree grew at Glasnevin, and a grafted specimen presumed to be from this is at the Hillier Gardens (K. Rushforth, pers. comm. 2007). Specimens grown at Kew from SICH 1126, collected by the Fliegner, Howick, McNamara and Staniforth team at c. 2950 m above Muli, Sichuan in 1992, are attributed to this taxon and seem to fit here, with their (variably) pubescent shoots and rather glaucous leaves. They have made rather sparse-looking trees with a distinctly bluish appearance. SICH 645 from 1991 is also attributed to var. hirtella, which is supposed to differ in its yellow-brown cones with denticulate seed scales. The existence of ‘true’ var. montigena in cultivation has long been discussed, and most if not all specimens so-named represent P. asperata (Mitchell 1972, Bean 1976b, Rushforth 2008).

P. likiangensis var. purpurea (NOW P. purpurea Mast.) B188, S365, K195

Picea linzhiensis (W.C. Cheng & L.K. Fu) Rushforth Syn. P. likiangensis var. linzhiensis W.C. Cheng & L.K. Fu Tree to 50 m, but usually only 30–40 m, to 2 m dbh in old trees but usually 0.6 m. Bark silvery grey, with thin brownish fissures. Crown columnar. Branchlets light brown or slightly orange-brown in first year, becoming greyish in second to fourth years, with dark brown glandular hairs (0.2 mm) in first year, pulvini 1 mm, glandular-hairy; vegetative buds ovoid-conical, bluntly pointed to pointed, resinous at the base with thinly resinous or non-resinous chestnut-brown scales, to 0.9 cm, persistent at the base of the first-year shoot. Foliage spreading above at c. 30 ° to the shoot and at the sides of the shoot at 60–80 °, widely parted below, leaves < 2(–3) × 0.1–0.15 cm, longest in mid-portion of shoot, nearly parallel-sided, tapering gently to the tip, which is short-acuminate, bony, needle-sharp, of nearly 1 mm; stomata on the lower surface only (or very rarely, one or two incomplete rows above), in two greyish green bands of four to six rows, upper surface glossy green. Cones 5–12 cm, purplish, ripening to brown. Scales free but appressed at the tip during the growing

Picea

573

574

Picea

New Trees

season, thin, flexible, rounded or rhombic, erose. Seeds dark brown, 4 × 2.5 mm, wings pale brown, 5 × 4 mm. Rushforth 2008. Distribution CHINA: southeast Xizang. Habitat Subalpine forest between 3000 and 3800 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated.

According to Rushforth (2008), Picea linzhiensis is more or less confined to the drainage of the Yarlung Tsangpo in southeastern Tibet, where it forms forests. The glandularpubescence distinguishes it from other members of the group, and may derive from introgression with either P. spinulosa or P. farreri, which both show this feature. The glandular hairs, however, are found only on mature shoots, not in young plants. It is represented in cultivation by specimens grown from introductions by Keith Rushforth in 1995, 1997, 1999 and 2000: KR 3835 from Pasum Tso is at the Hillier Gardens and Thenford House; KR 3548 from the Doshong La is grown at Wisley, where it has made 4 m and is coning; KR 3622 is currently 2 m tall in Rushforth’s own collection in Devon. Other gardens have young plants of KR 3657a from the Nyima La, KR 5580 and 6288 from the Showa La, KR 6334 from above Bagu on the way to the Nambu La, and KR 6432 from the Nambu La to Pasum Tso (K. Rushforth, pers. comm. 2008).

Picea ×lutzii Little

Lutz’s Spruce, Roche Spruce

Tree to 21 m, 0.3–0.45 m dbh. This taxon is a natural hybrid between P. sitchensis and P. glauca (Moench) Voss, and its morphology is intermediate between these species. The leaves are slightly quadrangular, the cones are intermediate in size or small (as in P. glauca) and the seed scales are short (as in P. glauca), but thin, light brown and irregularly toothed (as in P. sitchensis). Viereck & Little 1972, Farjon 1990, Thieret 1993. Distribution CANADA: British Columbia; USA: Alaska (Kenai Peninsula). Habitat Areas of overlap between the parent taxa; between 0 and 1200 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Cross-reference K195.

Picea ×lutzii is probably little more than a collector’s curiosity, but is grown in a few British gardens, including at the Royal Botanic Garden Edinburgh and in the Forestry Commission’s research arboretum at Alice Holt, Hampshire, where a tree was 10 m tall in 2001 (TROBI). The largest recorded in the United Kingdom were specimens of 14 and 13.5 m measured by John White at Vivod Forest Garden, Denbighshire in 1988 (TROBI). This is one of a select group of trees that have been recommended for planting in the milder parts of southwestern Greenland, where other relatively successful trees are Larix sibirica, Picea abies, Picea glauca and Pinus sylvestris (Ødum 2003). In areas where the range of trees available is rather wider, it may be most welcome in gardens in its dwarf clone ‘Machala’ (formerly attributed to P. ×mariorika; see Krüssmann: K196), which forms a neat greyish mound of congested growth. P. mariana (Mill.) Britton, Sterns & Poggenb. B189, S366, K195 P. ×mariorika Boom K196

Picea martinezii T.F. Patt.

Nuevo León Spruce

Tree to 40 m. Bark grey, thin and scaly. Crown conical and irregular. Branchlets yellow, glabrous, pulvini small; vegetative buds not resinous. Leaves spreading forwards, dark green, glossy, flattened in cross-section, though – uniquely in Picea – they are flattened from side to side rather than dorsiventrally, (1.6–)2.3–2.7 × 0.1–0.2 cm, apex acute and sharp. Male strobili unrecorded. Cones terminal, oblong-cylindrical, 8.5–16 × (4–)5.5–6.2 cm, green initially, reddish brown when mature. Seed scales obovate, (1.9–)2.6–3.2 × (1.8–)2.1– 2.5 cm, denticulate, apex reflexed. Seeds brown, fusiform, 0.5–0.8 cm long, wings 1.6–2.3 cm long. Rushforth 1986a, Patterson 1988. Distribution MEXICO: southwest Nuevo León (El Butano, Cañada La Tinaja). Habitat Temperate montane forest between 2150 and 2200 m asl. This species is known from only two locations in

Section II. Species Accounts

Picea

575

Nuevo León, where it grows in deep pockets of soil trapped between limestone blocks with a constant water supply. USDA Hardiness Zone 7–8. Conservation status Critically Endangered. Illustration NT563, NT575. Taxonomic note Picea martinezii was first described by Patterson (1988), who noted several characters that could be used to distinguish it from P. chihuahuana, but Farjon (2001) placed it in synonymy with P. chihuahuana. An analysis of the morphology and biochemistry of the Mexican spruces suggests that P. martinezii is a distinct taxon (Taylor et al. 1994), and cultivated material does appear to differ markedly from that of P. chihuahuana. The main features distinguishing the two are: leaf colour (glossy green in P. martinezii vs. blue-green in P. chihuahuana), leaf length (usually 2.3–2.8 cm vs. 1.2–2.3 cm), cone size (8.5–16 × 5.5–6 cm vs. 7–12 × 4–5 cm), seed scale density (12–16 scales per 10 cm cone length vs. 25–30 scales per 10 cm) and seed scale size (2.6–3.2 × 2.1–2.5 cm vs.1.8–2.3 × 1.4–2 cm). Another observed difference is a distinction in the arrangement of the leaves; in P. chihuahuana they are held more or less perpendicular to the stems (patent) and thus bristle outwards, while in P. martinezii they can be somewhat appressed on the upper surface of the shoot but patent on the lower surface.

Despite its rarity in the wild Picea martinezii is well established, if scarce, in cultivation. It certainly deserves to be grown, as a particularly attractive spruce, but this rarity makes it essential that material is carefully conserved, with details of its provenance maintained. It is thriving at Kew (where it is labelled as P. chihuahuana), forming densely clad, vigorous young trees. A group of three grown from Priest 108, collected at Ejido do la Encantada, Zaragoza, Nuevo León in 1984, are particularly attractive; they were approximately 5 m tall when observed in 2005 but have since grown considerably, and produce a heavy crop of cones each year. A tree from a collection made by Keith Rushforth (KR 551A) at the same site in 1984 is also doing well at Kew. At Arboretum Wespelaar it is flourishing from a collection made by Rob Nicholson and team from the Arnold Arboretum in 1997 at El Butano, Nuevo León, and shows the same dark green leaves as the Kew trees – a character that immediately sets it apart from the glaucous P. chihuahuana, although the needles are equally sharp. A 2.5 m tree growing at the JC Raulston Arboretum originating from Yucca Do Nursery, Hempstead, Texas is thriving, forming a shapely, dense specimen that withstood the 2006–2007 drought well (M. Weathington, pers. comm. 2007).

Picea maximowiczii Regel ex Mast.

Japanese Bush Spruce

Tree to 25 m, 0.5–0.6 m dbh, often a low shrub. Bark bright orange-brown, smooth then flaking in young trees, becoming grey-brown, rough, scaly and fissured in older trees. Crown conical or columnar, dense. Branchlets slender, rigid, yellowish brown or orange-brown, glabrous or slightly pubescent, pulvini small, slightly darker than the shoot; vegetative buds not or slightly resinous. Leaves spreading forwards, dark, shiny green, rhombic in cross-section, (0.8–)1–1.3(–1.6) × 0.1–0.14 cm, apex acute and rather sharp. Male strobili 1–1.5 cm long, numerous, yellowish. Cones terminal, short-pedunculate, ovoid-oblong or cylindrical, (3.5–)4–6.5(–9) × 2.5–3.5 cm, green, light red-brown or dull brown when mature. Seed scales obovate-cuneate, 1.3–1.8 × 1–1.5 cm, often resinous, upper margins rounded, entire or erose. Seeds dark brown or grey-brown, ovoidoblong, 0.3–0.45 × 0.25–0.3 cm, wings yellowish brown or orange-brown, ovate-oblong, 0.8–1 × 0.4–0.5 cm. Farjon 1990. Distribution JAPAN: Honshu (Fuji-san and Yatsugadake Mts.). Habitat Mountain slopes between 1100 and 2000 m asl. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Farjon 1990; NT576. Cross-references B190, S366, K196.

Bean (1976b) gave a brief description of Picea maximowiczii followed by a discussion as to whether the true species was currently in cultivation in the United Kingdom. This is now confirmed, with TROBI having records of about 20 specimens, of which the tallest is at Westonbirt (24 m, 64 cm dbh in 2002, planted in 1935) (Johnson 2003). A few more recent introductions have been made, including a 6 m tree at Kew

Plate 389. The dark green, sparse, spreading leaves and short, broad cones of Picea martinezii (this is Priest 108, at Kew). It is probably not closely related to P. chihuahuana (see Plate 383, p. 565). Image J. Grimshaw.

576

Picea

New Trees

originating in Honshu, donated by Atushi Kuyama in 1981. It has an upright, somewhat columnar shape, and when observed in April 2005 the particularly attractive bright green spring flush contrasted well with the dark green mature leaves.

Picea maximowiczii var. senanensis Hayashi This variety has shorter leaves than the type (0.6–1.5 cm, vs. 1–1.3 cm in var. maximowiczii) and smaller cones (2.5–4.5 cm long, vs. 4–6.5 cm). The cones have smaller seed scales, which are slightly pointed, and smaller seeds (0.25–0.3 × 0.15–0.2 cm). Farjon 1990. Distribution JAPAN: Honshu (Fuji-san and Yatsugadake Mts.). Habitat As for the type variety. USDA Hardiness Zone 7. Conservation status Vulnerable. Illustration Farjon 1990.

Picea maximowiczii var. senanensis was introduced to the Royal Botanic Garden Edinburgh as seed from a collection made in Nagano Prefecture, Honshu in 1976. A tree from this source grows at Dawyck, and there are two at Wakehurst Place, although the curation notes for one of these record Aljos Farjon’s opinion that the leaves are too long to be of this variety.

Plate 390. A densely clad, columnar specimen of Picea maximowiczii at Kew, with bright green new growth. Image J. Grimshaw.

P. mexicana (NOW P. engelmannii subsp. mexicana (Martínez) P.A. Schmidt, NT567) S364, K196

Picea meyeri Rehder & E.H. Wilson

Meyer’s Spruce

Tree to 30 m, 0.6 m dbh. Bark brown-grey, smooth then flaking in young trees, becoming grey, rough and scaly with papery flakes in older trees. Crown conical or columnar when growing in dense forest. Branchlets slender or thick, firm, pale yellow to light brown, glabrous or pubescent, pulvini well developed, slightly darker than the shoot; vegetative buds resinous. Leaves spreading forwards, glaucous- or bluish green, transversely rhombic in cross-section, (0.8–)1.3–2.5(–3) × 0.2 cm, apex acute. Male strobili 2–2.5 cm long, reddish yellow. Cones terminal, short-pedunculate or sessile, oval-oblong to cylindrical, (6–)7–10(–12) × 2.5–3.5(–4) cm, purplish red initially, reddish brown to grey-brown when mature. Seed scales obovate, 1.5–2 × 1–1.6 cm, upper margins rounded, entire or sometimes denticulate. Seeds brown or blackish brown, ovoid-oblong, 0.3–0.4 × 0.15–0.25 cm, wings yellowish brown or reddish brown, obovate-oblong, 1–1.5 × 0.5–0.65 cm. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Hebei, Nei Mongol, Shaanxi, Shanxi. Habitat Montane or subalpine forests, often on north-facing slopes, between 1600 and 2700 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Farjon 1990; NT577. Cross-reference K196.

As part of the Picea asperata complex P. meyeri has been rather confused with other related species, in the wild and in cultivation, but is now more clearly understood. The type specimen was collected by Frank Meyer in Shanxi in 1908, and later collections were made by William Purdom and Joseph Hers (credited by Rushforth with its introduction to cultivation) (Sargent 1916, Rushforth 1987a). The Scottish botanical gardens have trees attributed to Wilson (no collection number given: Govier et al. 2001), but he did not collect the species. In consequence of these early introductions there are mature trees of P. meyeri in arboreta on both sides of the Atlantic, although they are scarce. The largest recorded by TROBI was 19.5 m at Glen Tanar House, Aberdeen when measured by Alan Mitchell in 1980. At Bedgebury the largest was 13 m (44 cm dbh) in 1999 (Johnson 2003). Younger trees are found scattered through our area and are often very attractive, forming broad-based conical trees densely clad in foliage. This varies somewhat, from strongly glaucous (especially in new shoots) to dull green, but most trees appear grey rather than glaucous once the new growth has matured. Specimens seen in the United Kingdom include a fine young tree at Dawyck grown from a seed lot from the Chinese Academy of Forestry received in 1987, standing 5 m tall in 2006, and another of 4.5 m at Thenford House. It also seems capable of toler-

Section II. Species Accounts

Picea

577

ating much hotter conditions, as demonstrated by a good 2.5 m specimen at the JC Raulston Arboretum, and it flourishes at the Hørsholm Arboretum in Denmark (Forest & Landscape 2007). New stock came into the United States in the form of material collected (without a number) by a Morton Arboretum expedition to Shanxi in 1990, whose team found it growing in upland forest with Larix, Populus and Betula species. A tree from this collection at the Morton Arboretum is healthy and vigorous, and was 1.8 m tall in 2007 (K. Kim, pers. comm. 2007). P. montana (NOW P. abies (L.) H. Karst. var. abies) K196 P. montigena (NOW P. likiangensis subsp. balfouriana (Rehder & E.H. Wilson) Rushforth, NT572; OR P. likiangensis var. montigena (Mast.) W.C. Cheng) B189, K196 P. morrisonicola Hayata B190, S366, K196 P. ×moseri Mast. K198 P. neoveitchii Mast. K198 P. ×notha Rehder K198 P. obovata Ledeb. B191, K198 P. obovata var. coerulea Tigerstedt K198 P. obovata var. fennica (NOW P. ×fennica (Regel) Kom.) B191, K198 P. omorika (Pancˇic´) Purk. B191, S366, K198 P. orientalis (L.) Peterm. B192, S366, K199 P. polita (NOW P. torano (Siebold ex K. Koch) Koehne) B193, S367, K199 P. pungens Engelm. B193, S367, K199 P. pungens f. argentea (NOW P. pungens Engelm.) B194 P. pungens f. glauca (NOW P. pungens Engelm.) B194, K200 P. pungsaniensis (NOW P. koraiensis var. pungsanensis (Uyeki ex Nakai) Farjon) K203 P. purpurea Mast. (WAS P. likiangensis var. purpurea B188, S365, K195)

Picea retroflexa Mast.

Tapao Shan Spruce

Syn. P. asperata Mast. var. retroflexa (Mast.) W.C. Cheng Tree to 45 m, 1–1.5 m dbh. Bark light brown, smooth then flaking in young trees, becoming grey-brown or grey, rough and scaly. Crown columnar or narrowly conical. Branchlets short, firm, thick, light brown or orange-brown, glabrous or with ferruginous pubescence, pulvini strongly developed; vegetative buds resinous. Leaves spreading radially, curved forwards, light green or glaucous-green, pungent, quadrangular or transversely rhombic in cross-section, (1–)1.2–1.8(–2.5) × (0.12–)0.15–0.2 cm, apex acute. Male strobili 2–3.5 cm long, reddish yellow. Cones terminal, sessile, oval-oblong or cylindrical to conical, 8–13 × 2.5–4 cm, purplish red when immature, purplish or reddish brown when mature, finally shiny brown. Seed scales obovate-oblong, convex, 1.5–2 × 1.2–1.5 cm, upper margins rounded or obtuse, slightly erose-denticulate, straight or slightly reflexed. Seeds dark brown or red-brown, ovoid-oblong, 0.3–0.4 cm long, wings pale brown or yellowish brown, obovate-oblong, 1–1.5 × 0.5–0.7 cm. Farjon 1990. Distribution CHINA: western Sichuan (north and west of Kangding). Habitat Subalpine forest on north-facing slopes between 3000 and 4000 m asl. USDA Hardiness Zone 6. Conservation status Vulnerable. Illustration Farjon 1990. Cross-references B181 (as P. asperata var. retroflexa), K203.

According to Bean (1976b), Picea retroflexa was introduced by Wilson (Wilson 4083), and it seems probable that most if not all of the specimens in cultivation today are

Plate 391. Picea meyeri. With cones like this, who needs Christmas decorations? Image J.R.P. van Hoey Smith.

578

Picea

New Trees

derived from this collection, as no recent gatherings have been traced. In the wild, according to Wilson (Sargent 1916), it makes large gaunt trees with rather glaucous foliage, but in cultivation the leaves tend to be green. It has a limited presence in the United Kingdom, the two largest specimens having been measured at 19 and 15 m in Windsor Great Park in 2000 (Johnson 2003). The Wilson collection is also grown in North America (for example, at the Morton Arboretum). Related to this species and the other members of the Picea asperata complex is P. aurantiaca Mast., discovered by Wilson in western Sichuan in 1903. This appears to have a narrow range southwest of Kangding (Rushforth 1987a), where it is considered to be endangered. According to Wilson (Sargent 1916), the mature trees are very narrow, with pale grey or whitish bark. The name relates to the orange coloration of the new shoots, which fade slowly to grey after several years. This interesting-sounding tree has a toe-hold in cultivation, with one mature specimen listed in the catalogue of the Arnold Arboretum (Anon. 2003). Material has been distributed from there to the Hørsholm Arboretum, Denmark, resulting in a small number of grafted specimens in Europe (K. Rushforth, pers. comm. 2007). The identity of other specimens in the P. asperata complex collected by Wilson should be investigated. P. robertii (NOW P. schrenkiana Fisch. & C.A. Mey. subsp. schrenkiana) K203

Picea schrenkiana Fisch. & C.A. Mey.

P. rubens Sarg. B195, S367, K203 P. ×saaghyi Gayer K203

Asian Spruce, Schrenk’s Spruce

This species was described by Bean (B196, S367) and Krüssmann (K204).

Picea schrenkiana subsp. tianschanica (Rupr.) Bykov

Plate 392. Picea schrenkiana subsp. tianschanica in the wild in Kyrgyzstan. There is nothing to beat the experience of seeing trees in their original habitats. Image A. Farjon.

Subsp. tianschanica differs from the type primarily in its shorter, thicker leaves, (1–)1.5–2(–2.5) × 0.14–0.2 cm vs. (1.5–)2–3(–3.5) × 0.1–0.15 cm in the type. (This character may be a climatic adaptation only.) Also, the cones are elliptical-oblong rather than cylindrical-oblong, and larger (10–20 cm long vs. 6–11 cm in the type). Farjon 1990. Distribution KYRGYZSTAN: mountains surrounding the Naryn River. Habitat Montane or subalpine forest on north-facing slopes between 1300 and 3000 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Farjon 1990, Fu et al. 1999c; NT578.

The isolation of the population of Picea schrenkiana subsp. tianschanica in an area of exceptional beauty gives it a certain interest, but it probably has no great horticultural value and seems unlikely to achieve a widespread presence in cultivation. In its broad sense P. schrenkiana is considered to be hardy but susceptible to spring frosts (Rushforth 1987a), although it can occasionally reach a respectable size. At Dawyck two plants of var. tianschanica are growing slowly, from a 1979 accession. The larger was about 2 m tall in 2006 and forming a good leader; the other was struggling to get going at 1.2 m. The foliage is green with slight glaucescence. P. sitchensis (Bong.) Carrière B196, S367, K204 P. smithiana (Wall.) Boiss. B197, S368, K204 P. spinulosa (Griff.) A. Henry B198, S368, K204 P. wilsonii Mast. B198, S368, K204

Section II. Species Accounts

Pinus

579

PINACEAE

PINUS

L.

Pines, Pinyons Pinus is the largest conifer genus, with 110 species accepted by Farjon (2005a), while Businský (2008) recognises 116 – and others would acknowledge more. It is almost entirely restricted to the northern hemisphere, crossing the equator only in Sumatra (P. merkusii). Unlike the other genera of the Pinaceae, in Pinus the greatest diversity of species is found in the United States and Mexico, rather than in China and Japan. As with many conifer genera there are a few taxa that are widespread (P. sylvestris has the widest distribution), while most have a restricted range. Pinus is economically the most significant genus of conifers, the primary products being timber, pulp, tar and turpentine. Several attempts have been made to divide it into a number of smaller genera (including Strobus Opiz, Caryopitys Small and Ducampopinus A. Chev.), but the segregate genera have not received broad recognition. The morphology of Pinus is complex, and a number of botanical terms are applied only to it and a few related genera. These terms are defined in the glossary at the end of this book and also illustrated in Figures 67 and 68 (see below, pp. 581, 601). The lengthy descriptions given for the pines covered in the pages that follow are an inevitable consequence of this complexity, and details are critical to the identification of species. The habit of pines is extremely variable, plants ranging from large, monopodial trees to small, multistemmed shrubs, although environmental factors account for some of this variation. For example, Pinus torreyana in its native habitat is only 5–10 m tall and forms a short, gnarled trunk. In cultivation, however, it can become a large tree with a straight trunk of 30 m or more. The largest pine is the stately P. lambertiana, which can grow up to 75 m tall with a stem diameter of almost 4 m. In very cold and dry climates the growth rate is extremely slow, allowing some trees to reach advanced ages. The bark of pines is frequently useful in identifying species. It can break into small or large plates, form deep, longitudinal fissures, or peel continuously creating a mosaic pattern. It may begin to break and

Plate 393. The slender, pendulous needles of Pinus bhutanica shimmer in sunlight at Tregrehan. Image J. Grimshaw.

580

Pinus

New Trees

1 cm

A

C

1 cm

D

F

E 1 cm

1 cm

G

J H B

Section II. Species Accounts

peel early in life, or may remain smooth for several years. In the lace-bark pines (P. bungeana, P. gerardiana and P. squamata) it resembles that of Platanus, as it peels off in segments revealing the lighter-coloured new bark below. Pines are evergreen and aromatic, and often have resin in the wood, bark, leaves and cones. The crown is initially conical with regular (pseudo-) whorls of branches and an erect leader, though some may also be multistemmed. At maturity several lower branches may be shed, forming a broad and open crown. There is strong shoot dimorphism, with branching shoots and reduced foliage (dwarf) shoots. The branching shoots are stout, and may be glaucous or pubescent. Branching shoots generally produce a single flush of growth each season, ending with a winter bud. The winter bud can be terminal or subterminal, and is composed of the shoot apex and new needle fascicles, covered by scale leaves; winter buds are prominent features of pines throughout the winter. In spring the winter bud elongates into a long rather bare-looking shoot on which the short foliage shoots are present as small growths; at this stage the new shoots are known as ‘candles’, and are held vertically. The new secondary leaves then emerge from the short shoots and the shoot assumes its normal position. The foliage shoots are very small and comprise a bundle (fascicle) of secondary leaves with a persistent or deciduous sheath at the base; in lay terms they are the familiar clusters of ‘pine needles’. These foliage shoots do have a minute bud, though this develops only rarely, most typically after browsing damage to the shoot distal to the fascicle. Fascicles persist for 2–12 years or more and develop in the axils of cataphylls (see below). The secondary leaves within a fascicle remain attached to each other, usually falling as a single unit (except in section Quinquefolius, where the leaves may fall individually). The developing fascicle is terete (except in P. krempfii, where it is flattened) and contains several leaves, ranging in number from two to eight (a single leaf in P. monophylla), and the arrangement of the leaves as they develop in the fascicle determines the transverse shape of the individual leaves. The number of leaves in a fascicle is an important character in pine identification, though it can be subject to environmental influences (Yeaton et al. 1983). The needles may be epistomatic or amphistomatic, with the stomata arranged in longitudinal grooves that run the whole length of the leaf. The margins are usually entire, but may be serrate. Primary leaves are produced on shoots on young plants less than a year old (up to five years or more in a few species) but these are later replaced by cataphylls, which are scale-like, non-photosynthetic leaves. Cataphylls can have stomata on the upper surface (epistomatic), and form an elevated pulvinus (decurrent or non-decurrent) at the base. They may be shed before the needles or persist long afterwards. The male strobili are oblong to cylindrical and are clustered at the basal end of new long shoots. The female strobili (cones) are subterminal, solitary or clustered, and pendulous. They are sessile or pedunculate, and mature in the second or third year. The cones may be persistent or shed early, and may be serotinous, opening only after a fire. The seed scales are imbricate, spirally arranged around a central rachis, persistent, thin or woody. The exposed apex of the scale in a mature, closed cone (the apophysis) bears the remnant portion of the exposed scale that developed in the first year (umbo); in species where maturity occurs in the third year (for example, P. pinea), the umbo shows a second concentric

Pinus

581

Figure 67 (opposite). Pinus brutia: habit with immature cone (A). P. strobiformis: seed cone (B). P. massoniana: winged seed (C). P. cembroides: seed (D); seed scale, upper surface (E), lower surface (F). P. maximartinezii: seed scale, side view (G). P. pseudostrobus var. apulcensis: seed scale, side view (H). P. armandii var. mastersiana: seed scale, side view (J).

Plate 394. New shoots in the ‘candle’ stage on Pinus durangensis. The fascicles of secondary leaves – the ‘needles’ – are just emerging. Image P. Williams.

582

Pinus

New Trees

PINUS

L.

A guide to the infrageneric classification of Pinus

Subgenus Pinus – Hard pines

Section Pinus (e.g. P. sylvestris)

Cone scales with a sealing band

Leaves in fascicles of two to three

Pulvini decurrent Leaves with two vascular bundles

Europe, Asia (two species in North America)

Fascicle sheath persistent (deciduous in P. leiophylla, P. lumholtzii) Seed wings articulate (rarely weakly adnate) Subgenus Strobus – Soft pines Cone scales without a sealing band Leaves with one vascular bundle

Section Trifolius (e.g. P. radiata) Leaves in fascicles of two to five (or more) North America, Central America Section Nelsonia (P. nelsonii only) Leaves in fascicles of three, partially united on ventral surfaces Fascicle sheath persistent Umbo dorsal, obscure Seeds large, wingless Northeast Mexico Section Parrya (e.g. P. edulis) Leaves in fascicles of one to five Fascicle sheath semi-deciduous, leaving a basal rosette (deciduous in P. pinceana) Umbo dorsal Pulvini variably decurrent or not Seed wings articulate North America

Plate 395. Pinus armandii var. mastersiana is classified in subgenus Strobus, section Quinquefolius, members of which are characterised by their fine leaves held in fascicles of five. Image R. Unwin.

Section Quinquefolius (e.g. P. wallichiana) Leaves in fascicles of five (of two in P. krempfii, of three in P. bungeana, P. gerardiana, of four to five in P. squamata) Fascicle sheath deciduous Umbo terminal (dorsal in the above four species) Pulvini not decurrent Seed wings strongly adnate (articulate in the above four species) Eurasia, North America

ring. The umbo is located in a dorsal or terminal position and may have a spine or prickle. In subgenus Pinus there is a narrow sealing band on the scale stem at the base of the apophysis, which when present is often conspicuous by its different colour and smoother surface compared to the rest of the scale stem. Bract scales are insignificant and included (longer and rarely slightly exserted in P. torreyana). There are two seeds on each scale, partially enclosed in a membranous cup, which extends to form a persistent triangular wing. The wing may be vestigial and ineffective, as is often the case in species where the seeds are distributed by birds (in Pinus by jays and nutcrackers, amongst others). Many pines show adaptations that allow them to survive and even benefit from fires: thick bark can protect the cambium from heat, and serotinous cones release their seeds only after being scorched (Agee 1998). In a few pines, such as P. palustris, shoot elongation in the seedling is delayed while the leaves and roots expand, resulting in

Section II. Species Accounts

seedlings that look like tufts of grass (the ‘grass stage’). This protects the seedling from rapid grass fires by sacrificing the highly flammable leaves, reducing the exposure of the rest of the plant to heat. After a few years the tree then grows rapidly, to escape as soon as possible from low-level fires. Several pine species can regenerate from epicormic shoots beneath the bark (Agee 1998). Sources that were important in the preparation of the following accounts include published works on the genus Pinus (Richardson 1998, Anon. 2002, Farjon 2005a), together with regional accounts of pines in Mexico and Central America (Perry 1991, Farjon et al. 1997, Farjon & Styles 1997), North America (Elias 1980, Thieret 1993, Preston & Braham 2002), Eurasia (Businský 1999), and China and Taiwan (Li & Keng 1994a, Fu et al. 1999c), and the website The Gymnosperm Database (www. conifers.org) produced by C.J. Earle. Most of these have good illustrations, but the monograph Pines by Aljos Farjon (2005a) can be singled out for the quality of its drawings of mature trees and details of their foliage and cones, as can papers by Businský (1999, 2003, 2004) for the remarkable detail of the drawings of cones and seeds. Roman Businský has recently (2008) reviewed all his studies of pines, and has produced keys to the entire genus – in Czech only at present, alas, but an English version is planned. Our accounts have also benefited greatly from generous input from Michael Frankis and Keith Rushforth. The classification of pines is difficult, but molecular studies are beginning to be applied to attempt its elucidation (Price et al. 1998, Gernandt et al. 2005, Syring et al. 2005, Syring et al. 2007). It is clear that the genus divides on genetic characters into two subgenera, subgenus Pinus (hard pines) and subgenus Strobus (soft pines), that are monophyletic and could validly be regarded as separate genera on genetic criteria, were it not for the evident unity of the genus as a whole. The subgenera can be further divided into sections, subsections and series, where things become more complicated and less well agreed upon, although in general the species form easily recognised groups. The studies cited above have resulted in several transfers between sections and subsections, most notably the lace-bark pines from section Parrya (to which they are closer in morphology) to section Quinquefolius (to which they are closer in genetics). At the specific level, some conifer specialists perceive similarities across a range of variation, while others detect differences. We tend here to follow Farjon’s (2001, 2005a) broad-brush approach, with some emendation in the light of the above molecular studies and more recent publications. There are few genera of which it can be said that there is a species for all conditions in any garden, but this is almost true for Pinus, the only situation they universally dislike being heavy shade (although most require good drainage). While there are smaller and even shrubby species, however, the majority of pines are large trees, suitable only for larger spaces. They have major importance in the landscape, contributing different shapes and shades of green, contrasting well with broadleaves and more columnar conifers alike. This was recognised by Victorian planters, in whose relict pineta many venerable pines survive – now in an often picturesque maturity or old age – but has since been overlooked. Unfortunately, today pines seem to be even more out of fashion than most conifers as horticultural subjects. The commoner species continue to be planted in landscaping projects, as windbreaks and for forestry purposes – the latter activity in particular tending to stigmatise all conifers through their association with

Pinus

583

Plate 396. The large cones of Pinus torreyana (subgenus Pinus, section Trifolius), with prominent umbos, in their second year. Young cones from the current season are visible behind them. Image J.R.P. van Hoey Smith.

584

Pinus

Plate 397. A vigorous young tree of Pinus pseudostrobus var. pseudostrobus at Kew. The long, pendulous needles make this a very beautiful pine, even when young. Image J. Grimshaw.

New Trees

‘alien’ gloomy plantations, at least in the United Kingdom. Furthermore, and unlike in Abies and Picea, young trees of Pinus are often not particularly attractive, their beauty developing only with maturity. As already mentioned, they are also potentially very large trees, for which few gardens would have sufficient space. Only in the form of ‘dwarf’ cultivars do they seem to retain popularity, as a quick glance at the RHS Plant Finder will reveal. Although the rarer species may not be regularly available they should be sought and their cultivation encouraged. Particularly good collections of pines can be found in the holdings of Kew, the Royal Botanic Garden Edinburgh (especially at Benmore), Bedgebury National Pinetum, and the Sir Harold Hillier Gardens, where there is a National Plant Collection of Pinus. A smaller National Plant Collection is held at Quinta Arboretum, Swettenham, Cheshire. It is more difficult to find good collections of pines in continental Europe, but useful starting points are Pinetum Anthoine, Jamioulx in Belgium, Arboretum Blijdenstein in the Netherlands, and Hørsholm Arboretum in Denmark. The University of California Botanical Garden at Berkeley and the Institute of Forest Genetics at Placerville, California have particularly interesting and diverse collections, but most arboreta have a good representation of the species that will grow in their conditions. Many of the species described here are from Mexico and further south in Central America, where the diversity of pines is at its highest. Some have long been known in cultivation, as botanical exploration in the nineteenth century was much further advanced in Mexico than it was in Asia, and collectors sent back seed to fuel the Victorian conifer craze. From these and later collections several species have been in cultivation continuously for over 150 years – but only in a very few gardens, usually around the maritime fringes of western Europe. Recent collections, however, have made some of these more familiar, and current climatic conditions enable the more tender species to be attempted more widely, often with success. Many species remain unintroduced, or have been unsuccessfully introduced, and await the attentions of collectors. A notable horticultural absentee is Pinus lumholtzii B.L. Rob. & Fernald, which has a wide distribution in western Mexico. Seed has been introduced on at least two occasions (K. Rushforth 594, Jalisco, November 1984; Hjerting & Ødum 269, Chihuahua, October 1989) but it has not become established; Keith Rushforth (pers. comm. 2007) grew one tree to 2 m before it succumbed to Armillaria. It is superficially similar to P. patula but has exceptionally long, vertically pendent needles (15–)20–30(–40) cm long or more. The weeping appearance they give the tree has led to its local name of pino triste, the ‘sad pine’. Other potentially reasonably hardy Mexican species that have yet to be introduced or are not as yet established in cultivation include P. praetermissa Styles & McVaugh, from western Mexico (Jalisco, Nayarit, Sinaloa, and possibly southern Zacatecas) at altitudes of 900–1900 m. This taxon is related to P. oocarpa, and to P. stylesii Frankis ex Businský, from northeastern Mexico. The application of the latter name in July 2008 enables the few young trees in cultivation to be labelled. It is related to P. strobiformis, with which it has been confused (Businský 2008). Species occurring further south into Central America become more marginal prospects in our area, although they are often attempted. One such is P. tecunumanii Eguiluz & J.P. Perry, which has

Section II. Species Accounts

a wide distribution in seasonally dry areas from southern Mexico south to Nicaragua. It has been collected throughout its range for extensive forestry trials in Australia, Africa and elsewhere with subtropical or tropical climates (Birks & Barnes 1995), but with the exception of a few trees at Berkeley, it seems not to have been tried as an ornamental tree; in foliage it is similar to its close relative P. patula. It has been attempted at Tregrehan but was killed by cold there (T. Hudson, pers. comm. 2007). Seed of P. maximinoi H.E. Moore was sent to the Royal Botanic Garden Edinburgh from Guatemala in 1993. Seedlings were distributed from there to warmer sites, but it was promptly killed by frost at Tregrehan. More recently, seed of the same species collected by the Dendrological Atlas Project in Guatemala (DAP 40501X) has been received and grown on at Bedgebury; a number of young plants are growing there and others have been distributed elsewhere, including to Wakehurst Place, but it is very unlikely to be hardy in our area. Several of the Asian pines are extremely rare in the wild, to the extent that urgent ex situ conservation action is required. Among such species is P. amamiana Koidz. (Yakushima White Pine) from southern Japan (Tanegashima, Yakushima), which does not appear to have been introduced to Europe or North America. It is very susceptible to pine wilt from the introduced Pinewood Nematode Bursaphelenchus xylophilus, which causes significant mortality (see below, p. 586), and it is now threatened in the wild (Grierson et al. 1980). The establishment of plantings in areas free of pine wilt could be important for the survival of the species. Pinus squamata X.-W. Li is noteworthy for being the rarest pine known, with only 20–30 specimens surviving, all young trees growing on a largely deforested ridge in northern Yunnan with scattered P. yunnanensis (Li 1992). Pinus squamata has not been introduced to cultivation but has the potential to be an absolutely outstanding specimen tree, with its smooth, nearly white bark, very similar to P. bungeana but produced on a tall, straight trunk with a narrow conical crown, and its fast growth rate, combined with very attractive drooping foliage. As a low-altitude tropical or subtropical species, P. kesiya Royle ex Gordon is of most interest to foresters establishing softwood plantations in tropical countries, although it has several faults that make it less than totally useful as a timber-producing species (Armitage & Burley 1984). Its range gives it a curiosity value among enthusiasts, and it has been collected on several occasions, but it is probably too tender for all but the mildest gardens, thriving best in a monsoon climate with 1500 mm of rain per year or more, where humidity does not drop below 70 per cent and where the mean annual temperature is 18–25 °C (Luu & Thomas 2004). Tom Hudson collected seed at 1800 m in Thailand, but the resultant plants were tender even in the favourable conditions of Tregrehan. Hudson reports, however, that it will tolerate some frost in those areas of New Zealand that have the benefit of hot summers. Similarly tempting but equally hopeless is P. merkusii Jungh. & de Vriese – notable not only as being the single species of pine to cross the equator (in Sumatra), but also as the Old World’s tallest pine, with heights of 70 m being recorded (de Laubenfels 1988). Many pines are perfectly hardy in terms of winter temperatures but require a hot growing season to perform well. Among these are several species from the Coastal Plain of the southeastern United States; some of the southern Chinese species probably also appreciate hot summers, although they grow better in northern Europe than the southeastern Americans. The pinyons (section Parrya), typically from the arid parts of Mexico and the southwestern United States, also thrive on heat and tolerate

Pinus

585

586

Pinus

Plate 398. A young Pinus maximartinezii at Tregrehan, showing both primary and secondary foliage. The pinyons of section Parrya often retain juvenile foliage for several years; they are probably best left in pots until the mature growth appears. Image J. Grimshaw.

New Trees

drought exceptionally well, and they are very successful in New Zealand (T. Hudson, pers. comm. 2007). Pines are best grown from seed, and it may be that the absence of many good garden-worthy pines from the nursery trade is due to their seed being unobtainable, nurserymen therefore having frequently to resort to grafting. As always, wild-origin seed is best, but many pines are promiscuous and hybrids can occur in the wild as well as in cultivation. Many have been recorded in horticulture, as either accidental or deliberate crosses. Seedlings should be planted out when young, in a bright, open site, and given plenty of space to mature without crowding. In the case of species expected to be marginally hardy it is probably worth waiting for the tree to achieve a reasonable size in a container before planting it out. Tom Hudson (pers. comm. 2007) recommends that species in the pinyon complex should not be planted out until they have developed their first mature foliage. Good drainage is also essential for the majority of species. Pines are subject to many pests and diseases, although these are most problematic in forestry situations, and horticultural specimens are less likely to be affected. Growers of pines in North America are likely to have more problems than those in Europe, but nowhere is immune, as evidenced by the recent outbreak of red band needle blight (caused by the fungus Dothistroma septosporum) in Pinus nigra subsp. laricio in the United Kingdom (Brown et al. 2003), that is likely to have a major impact on its productivity. One of the worst diseases is white pine blister rust, from Cronartium ribicola, an Asian pathogen that has become a significant problem in Europe and North America, seriously restricting the growth of P. strobus, P. monticola and P. lambertiana as forestry species, causing cankers that effectively ring-bark the stems. It has its secondary host in Ribes, and a complex life cycle links currant and pine. North American members of section Quinquefolius are susceptible and the disease is conceivably a problem in arboreta, but good nursery hygiene and low-density planting – and an absence of Ribes – will minimise the risk (Forest Pathology 2008); the European and Asian species are largely resistant, and a good degree of natural selection for resistance has now occurred in P. strobus in North America. The unfortunate P. strobus is also the primary food plant for the White Pine Weevil Pissodes strobi – a serious pest of Picea engelmannii and Picea sitchensis as well, further west in North America. Although primarily a problem in forestry situations, the weevil can cause damage to a wide range of pines and spruces in ornamental horticulture. Its larvae penetrate the leader and feed within it, causing it to die back and resulting in trees with forked or crooked stems. Management to reduce the population of adult weevils seems to be a useful way of minimising damage (Hamid et al. 1995). Pine wilt disease, caused by the Pinewood Nematode Bursaphelenchus xylophilus, is a minor affliction of the North American pines with which it has coevolved, but European and Asian pines have little resistance to it; species like Pinus sylvestris are not long-lived where it is prevalent, mainly in the southeastern United States. It was introduced accidentally to Japan (by 1905), where it is causing major mortality in P. thunbergii and other species, including the endangered P. amamiana,

Section II. Species Accounts

Pinus

and later (by 1982) to China; it has also been found recently in Portugal (Mota et al. 2004). Internet sources should be consulted for up-to-date information on this and other pests and diseases of Pinus. P. albicaulis Engelm. B210, S372, K209 P. aristata Engelm. B214, S373, K209

Pinus arizonica Engelm.

P. aristata var. longaeva (NOW P. longaeva D.K. Bailey, NT606) K209

(Subgen. Pinus, Sect. Trifolius)

Arizona Pine

Syn. P. ponderosa Douglas ex C. Lawson var. arizonica (Engelm.) Shaw Tree to 35 m, trunk straight and slender, 1–1.2 m dbh. Bark thin, scaly, breaking into a series of large plates; outer bark reddish brown initially, later grey, inner bark reddish brown. Crown open and pyramidal, rounded or flat-topped in mature trees, often above a long, clear bole. Branchlets glaucous or orange-brown; vegetative buds not resinous. Leaves in fascicles of three to five, persisting for three to five years, yellowish green to glaucous, rigid or slightly lax, triangular in cross-section, (8–)10–20(–25) × 0.1–0.2 cm. Fascicle sheaths 1.5–3 cm long, orange- to reddish brown, turning grey-black, persistent. Cataphylls reflexed, 1.5 × 0.3–0.4 cm, dark brown. Male strobili 1.5–2 × 0.5 cm, yellow to yellowish brown. Female cones subterminal; peduncles short, curved, but appearing sessile at maturity. Cones (4.5–)5–10(–14) × 3.5–6(–8) cm, ovoid-globose, asymmetrical, with sharp spines when immature; mature in about 18 months, yellow-brown. Scales 90–140, thick, rigid, rectangular; apophysis usually symmetrical, rhombic to pentagonal, yellowish or reddish brown; umbo dorsal, with a minute, deciduous prickle. Seeds light brown; wings greyish brown, 1.2–2 cm long. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Chihuahua, Coahuila, Durango, Nuevo León, Sinaloa, Sonora, northeast Zacatecas; USA: southeast Arizona, southwest New Mexico. Habitat In deep soils in valleys and on mesas between 1300 and 3000 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Farjon & Styles 1997; NT588.

The varieties of Pinus arizonica are distinguished primarily on the basis of a few quantitative leaf characters and these, together with their respective distributions, overlap significantly. The key below is adapted from Farjon & Styles (1997).

1a. Leaves long, thick (14–25 × 0.14–0.18 cm); stomata in 8–12 lines on the lower surface; Mexico (south Coahuila, Nuevo León, San Luis Potosí, Zacatecas) ............... var. stormiae 1b. Leaves short or variable, < 0.14(–0.16) cm thick; stomata in 3–7 lines on the lower surface ......................................................................................................................... 2 2a. Leaves short (5–12 cm long), in fascicles of (three to) four to five, though usually five; Mexico (Chihuahua, Durango) ............................................................................. var. cooperi 2b. Leaves variable (8–23 cm long), in fascicles of three to five, though usually three to four; Mexico (Chihuahua, Durango, Sinaloa, Sonora, Zacatecas), USA (southeast Arizona, southwest New Mexico) .................................................... var. arizonica

Pinus arizonica var. cooperi (C.E. Blanco) Farjon This variety has shorter leaves than var. arizonica and var. stormiae, (5–)6–10(–12) cm long, in fascicles of three to five, though five-needle fascicles are most common. Farjon & Styles 1997. Distribution MEXICO: Chihuahua, Durango. Habitat As for var. arizonica. Co-occurs with the type variety over part of its range. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Farjon & Styles 1997.

Pinus arizonica var. stormiae Martínez This variety has longer and thicker leaves than the other two (14–25 × 0.14–0.18 cm) and cones with thinner, flatter scales. There are 8–12 lines of stomata on the lower leaf surface. Farjon & Styles 1997. Distribution MEXICO: southern Coahuila, southern Nuevo León, San Luis Potosí, Zacatecas. Habitat Similar to that of the type variety, though often more arid and at lower altitudes. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Farjon & Styles 1997.

587

588

Pinus

Plate 399. The developing cones of Pinus arizonica var. arizonica are covered in resin – always something of a hazard for those who love these fascinating objects. Image J. Grimshaw.

New Trees

Pinus arizonica is closely related to P. ponderosa, but has a more graceful appearance due to its more slender growth and finer needles. No mature examples of var. arizonica were seen in the research for this book, but there is a handsome young specimen on the lawn near the Main Gate at Kew, forming a neatly conical tree of 8–9 m in 2007, with branches to the ground. This was grown from seed collected in the Sierra Madre Occidental in Chihuahua in 1993 by an expedition from the Royal Veterinary and Agricultural University, Hørsholm, Denmark. A plant from the same collection at Arboretum Wespelaar also made an elegant tree, of 6 m, but is unfortunately suffering from dieback at present, caused by the fungal pest Sphaeropsis sapinea (K. Camelbeke, pers. comm. 2007). With its dark green, upwardpointing needles densely covering the branches this is an attractive tree, at least when young (images seen on the internet suggest that it becomes much more open and gaunt with age). It is also grown at Wakehurst Place, from material collected in Chihuahua by Peter Catt, but is less common in cultivation than var. cooperi, at least in the United Kingdom (although none of the varieties are likely to be found outside specialist collections). Var. cooperi has been grown in Britain for some time longer, having been included in the 1962 introduction of several Mexican conifers to the Forestry Commission (Mitchell 1972). There are large individuals in a number of collections, including two trees at Westonbirt (15 m in 2002), and some good specimens at Bedgebury. Var. stormiae was introduced to cultivation by Michael Frankis on his 1991 visit to Nuevo León (under the numbers M.P. Frankis 143, 163), and trees from this source are growing at Benmore and elsewhere. The cones are quite different from those of var. arizonica, and the taxon may be better treated as a distinct species, as suggested though not validly published by Gaussen (1960); it is also distinct in its long, twisted glaucous grey-green leaves. It is curious that P. arizonica and its varieties have generally slipped by the attention of horticulturists in both Europe and North America, as they appear to be attractive and hardy pines.

Pinus armandii Franch.

Chinese White Pine, Armand’s Pine

(Subgen. Strobus, Sect. Quinquefolius)

This species was described by Bean (B210, S372) and Krüssmann (K210). A key to the varieties is provided below.

1a. Male strobili slender, cylindrical, drooping; apophyses reddish brown to brown, slightly recurved; Taiwan ...................................................................................... var. mastersiana 1b. Male strobili stout, ovoid-ellipsoid, erect; apophyses yellowish brown to yellow ............................. 2 2a. Leaves short (5–14 cm); cones medium-length (< 17 cm), scales with a recurved margin; China (Dabie Shan) ............................................................... var. dabeshanensis 2b. Leaves longer (10–20 cm); cones variable in length (7–25 cm), scales straight; China (west, south), Myanmar (?) ............................................................................... var. armandii

Section II. Species Accounts

Pinus

589

P. armandii var. amamiana (NOW P. amamiana Koidz.) K210

Pinus armandii var. dabeshanensis

Dabie Shan Pine

(W.C. Cheng & Y.W. Law) Silba Syn. P. dabeshanensis W.C. Cheng & Y.W. Law, P. fenzeliana var. dabeshanensis (W.C. Cheng & Y.W. Law) L.K. Fu & Nan Li This variety has shorter leaves than var. armandii (5–14 cm long, vs. 10–20 cm in the type) and slightly shorter cones (< 17 cm long, vs. 7–25 cm in the type), with the apophyses recurved as in var. mastersiana. Fu et al. 1999c. Distribution CHINA: Anhui (Jingzhai, Yuxei), Henan (Shangcheng), Hubei (Luotian, Yingshan). Habitat Grows on cliffs and between large rocks in the Dabie Shan, between 900 and 1400 m asl. USDA Hardiness Zone 8–9. Conservation status Vulnerable. Illustration Businský 1999, Fu et al. 1999c.

The Dabie Shan Pine has had a slightly chequered taxonomic history, often accepted as a local variant of the widespread Pinus armandii with shorter leaves and smaller cones, though treated by Flora of China as a variety of P. fenzeliana (Fu et al. 1999c) – an approach that is not without merit, as both share cones with reflexed scale tips. Businský (1999) retains it as a separate species, P. dabeshanensis. It is very rare in the wild, with only a few trees known (Businský 1999). It was introduced to cultivation from a collection made in Anhui in 1999 by Roman Businský, under his number 46140, but no survivors are now known (M. Gardner, pers. comm. 2007).

Pinus armandii var. mastersiana (Hayata) Hayata

Masters Pine

The male strobili of var. mastersiana are slender, cylindrical and drooping, while in the type variety they are stout, ovoid-ellipsoid and erect. The cone apophyses are reddish brown to brown, triangular and slightly recurved distally, while in var. armandii they are yellowish brown to yellow, rhombic, and recurved only at the umbo or not at all. Li & Keng 1994a, Fu et al. 1999c. Distribution TAIWAN. Habitat Mountainous regions between 2300 and 3000 m asl, with well-drained, acidic soils. USDA Hardiness Zone 7. Conservation status Endangered. Illustration Fu et al. 1999c; NT580, NT582, NT589. Cross-reference K210.

Pinus armandii var. mastersiana is the Taiwanese representative of its species, morphologically differing only slightly from the typical variety, into which it has sometimes been sunk by some dendrological authors (Dallimore et al. 1966, Bean 1976b). Its name commemorates the British botanist Maxwell T. Masters, now best known for his work on teratology, but in his time a recognised conifer expert. He died in 1907, shortly before Bunzô Hayata published the name. Due to its treatment in the past as a synonym it is not easy to pinpoint a date for its introduction, but it is inconceivable that it was not collected by early-twentieth century travellers in Taiwan: H.J. Elwes (1935) specifically mentioned seeing nutcrackers feeding on its seeds on his visit to Taiwan in 1912. The earliest tree identified as var. mastersiana traced in research for this book is an individual at Edinburgh, probably from C.N. Page 10106 (M. Frankis, pers. comm. 2007), accessioned in 1974. From the mid-1970s onwards, however, it has been regularly collected in Taiwan, by both Taiwanese collectors and westerners, although it remains relatively scarce, especially outside botanical gardens. In the 1970s it was gathered by Chris Page, from whose collections trees are growing at Benmore (C.N. Page 10058, 10109, 10316), and the variety is further represented in the Scottish botanical gardens (and others) by material deriving from the Edinburgh Taiwan Expedition of 1993 (ETE 39, 52, 62, 63, 65). The oldest trees at Kew and Wakehurst Place were grown from seed sent from the Taipei Botanic Garden and Taiwan Forestry Research Institute in 1979. At Kew one of these is currently about 12 m tall, forming a very attractive tree, although its wide-spreading branches

Plate 400. The stout cone with broad, overlapping scales of Pinus armandii var. mastersiana, here photographed in Taiwan in 1992. Image T. Kirkham.

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suggest that it should be given ample space in which to develop its full potential. Var. mastersiana seems to thrive throughout the British Isles, but in colder climates may be less successful. A tree of wild origin at the Morris Arboretum is not very happy, suffering from winter burn and looking ‘rather thin’ by spring (A. Aiello, pers. comm. 2007). This is the only survivor of a group grown from seed received in 1983 from the Taiwan Forestry Research Institute, suggesting that a more sheltered site is desirable if it is to be attempted in the Philadelphia area. With its long, slightly bluish needles and substantial cones, var. mastersiana is a very attractive pine, but for horticultural purposes it is not very different from var. armandii (although Keith Rushforth finds that it grows faster: pers. comm. 2007).

P. attenuata Lemmon B212, S372, K210 P. attenuata × P. radiata (NOW P. ×attenuradiata Stockw. & Righter) S372 P. ×attenuradiata Stockw. & Righter K210 P. ayacahuite Ehrenb. ex Schltdl. B212, S372, K210

P. ayacahuite var. brachyptera (NOW P. strobiformis Engelm., NT619) B213, S373, K210 P. ayacahuite var. veitchii (Roezl) Shaw B213, K210 P. balfouriana Balf. B213, S373, K210 P. banksiana Lamb. B214, S373, K210

Pinus bhutanica Grierson, D.G. Long & C.N. Page

Bhutan Pine

(Subgen. Strobus, Sect. Quinquefolius) Syn. P. wallichiana subsp. bhutanica (D.G. Long & C.N. Page) Businský, P. bhutanica var. ludlowii Silba Tree to 25 m. Crown moderately open. Branchlets slender, greyish green with conspicuous, whitish bloom and glandular pubescence; vegetative buds not or slightly resinous. Leaves in fascicles of five, persisting for two to three years, very slender, pendulous and curved, triangular in cross-section, 12–28 cm long, apex acute, upper surface vivid green, lower surface with conspicuous whitish bloom. Fascicle sheaths conspicuous, 1.8–2.3 cm long, bright golden-brown, deciduous. Cataphylls triangular, golden-brown, deciduous. Male strobili orange. Female cones solitary, peduncle 4.5–6 cm long, bracteate; cone 12–20 × 3–7 cm, elongatecylindrical, mature in about 18 months, reddish brown to green, greenish brown at maturity. Scales elongated, thinly woody; apophysis 1–1.5 × 1.5–2.5 cm, rhombic, tan-brown; umbo terminal, triangular. Seeds brown, 6–9 mm; wings 2–2.5 × 0.7–1 cm, persistent. Grierson et al. 1980, Farjon 2005a. Distribution BHUTAN; CHINA: southeast Xizang, Yunnan (Dulong Co.); INDIA: Arunachal Pradesh. Habitat Moist, mixed broadleaved forest between 1750 and 2400 m asl. Mixes with P. wallichiana A.B. Jacks. at one site, though generally prefers lower altitudes with higher monsoon rainfall. USDA Hardiness Zone 8. Conservation status Least Concern. Illustration Grierson et al. 1980; NT579. Cross-reference S382.

Pinus bhutanica is closely related to the more familiar ‘Blue Pine’ P. wallichiana, from which it differs primarily in aspects of its habit. Pinus bhutanica has an open crown with long, sinuous branches, and branching is infrequent. The first-year shoots are covered in a conspicuous, whitish bloom with glandular pubescence, and the pendulous leaves are 12–28 cm long with conspicuous sheaths. In contrast, the crown of P. wallichiana appears congested, with many small twigs, and, where the species overlap, much shorter leaves. The first-year shoots of P. wallichiana are greenish (rarely with weak bloom) and glabrous, while the leaves are spreading to slightly pendulous and 11–18 cm long (Grierson et al. 1980). Although it had been collected previously, including by Frank Kingdon-Ward on his 1924 Tsangpo Gorge expedi-

Section II. Species Accounts

Pinus

tion, P. bhutanica was first recognised in the 1970s following fieldwork in Bhutan by Andrew Grierson and David Long as part of the Flora of Bhutan project at the Royal Botanic Garden Edinburgh, and was first introduced by them in 1979 (Grierson & Long 1986). Further introductions from Bhutan have also been received at Edinburgh, and progeny from these are being cultivated in the Scottish gardens and other collections to which material has been distributed. These gatherings include Sinclair & Long 5693 in 1984, Clark & Sinclair 1660 in 1990, and M.T. Heasman 9391 in 1997. Sinclair & Long 5693 is growing well at Edinburgh, noted at about 8–9 m tall in 2006 (M. Frankis, pers. comm. 2007). In general, however, P. bhutanica has not flourished in Scotland, and has done much better in gardens in southern England and Ireland, suggesting that it prefers a warmer climate (M. Gardner, pers. comm. 2007). Good trees are to be found in several collections. A specimen at Abbotsbury Subtropical Gardens, Dorset (grown from Sinclair & Long 5693) was 11 m tall when measured for TROBI by Owen Johnson in 2006, and another from the same collection at Tregrehan has reached approximately the same height, growing extremely well and becoming a beautiful tree (T. Hudson, pers. comm. 2007). Martin Gardner (pers. comm. 2007) reports that it is also thriving in Cornwall, at Glendurgan and on the Trevince Estate, where trees are now approaching 14 m. It seems to flourish in slightly less benign areas as well, trees at Westonbirt currently standing 9 and 10 m tall. With its long drooping needles and large cones, and potentially more elegant open habit than P. wallichiana, P. bhutanica is a choice and desirable tree. The most beautiful forms are to be found in southeastern Tibet (K. Rushforth, pers. comm. 2007).

Pinus brutia Ten.

(Subgen. Pinus, Sect. Pinus)

Calabrian Pine, Turkish Pine

Tree to 35 m, trunk straight and slender. Bark thin, flaky, reddish orange, becoming reddish brown, fracturing into plates separated by longitudinal fissures. Crown open and rounded. Branchlets slender, greyish brown; vegetative buds not resinous. Leaves in fascicles of two, persisting for one and a half to two and a half years, bright green or yellowish green, slender, straight and rigid, semicircular in cross-section, 10–18 × < 0.1 cm, margins serrulate, apex acute; juvenile leaves glaucous, 1.5–4 cm long, and produced for up to four years; adult leaves first appearing about nine months to two years after germination. Fascicle sheaths 1–1.5 cm long, persistent. Cataphylls subulate, 0.1–0.2 cm long, light to dark brown. Male strobili 1.8 × 0.4 cm. Female cones subterminal, in whorls of three to four or rarely solitary, sessile or pedunculate; cones 5–11(–13) × 5–7 cm, mature in about 24 months, ovoid-conical, green, ripening orange-brown to red-brown in spring. Scales thick, rigid, woody; apophysis 1–1.5 × 1.5–2 cm, rhombic to pentagonal; umbo dorsal, flat or slightly raised. Seeds dark greyish brown; wings 1.5–2 × 1 cm, brown with yellowish streaks. Frankis 1993, 1999, Farjon 2005a. Distribution CYPRUS; GREECE: Crete and east Aegean islands; LEBANON; SYRIA; TURKEY. Pinus brutia is also present (though probably introduced) in Calabria – formerly Brutia – Province in southern Italy. Habitat Grows in a variety of habitats in the eastern Mediterranean, between 10 and 1500 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Farjon 2005a; NT580. Cross-references B215, S373, K210.

There is considerable confusion regarding the infraspecific taxa of Pinus brutia. For example, Yaltirik & Boydak (2000) described var. densifolia from southern Anatolia, which had a dense, compact, spherical crown, but this feature of the habit was probably the result of environmental conditions or fungal infection (see discussion in Frankis 1999). A key to the varieties recognised by Farjon (2001) is presented below. The cones of one form of P. brutia var. brutia, f. kruepericola Frankis, do not open widely on weathering, so trap the seeds. However, Krüper’s Nuthatch (Sitta krueperi) removes seeds from the cones and distributes them around the forest (Frankis 1992).

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1a. Leaves long (20–29 cm); Turkey (Mugla Province) .................................................... var. pendulifolia 1b. Leaves shorter (5–18 cm) ................................................................................................................. 2 2a. Cones small (5–8 cm long); apophyses depressed, whitish grey; Azerbaijan and Georgia (Choban-Dagh Range) .......................................................... var. eldarica 2b. Cones larger (6–11 cm long); apophyses slightly raised, greyish brown ........................................... 3 3a. Leaves < 15 cm long; umbos indented; Caucasus (Georgia, Russia), Crimea ................... var. pityusa 3b. Leaves 10–18 cm long; umbos flat; Eastern Mediterranean (Bulgaria, Cyprus, Greece, Lebanon, Syria, Turkey) ......................................................... var. brutia

Pinus brutia var. brutia The typical variety has been considered rare in cultivation and was given a rather sparse description by Bean (1976b). When mature it can be quite an attractive tree, with a broad, rounded crown and many persistent cones thickening the canopy.

Pinus brutia var. eldarica (Medw.) Silba

Eilar Pine, Afghan Pine, Quetta Pine

This variety has shorter, stouter leaves (8–13 cm long) and smaller cones (5–8 cm long) than the type. The cone apophyses are depressed and whitish grey, and the seeds are at the larger end of the size range for the species. Frankis 1993, Farjon 2005a. Distribution AZERBAIJAN; GEORGIA. Habitat Restricted to a 500 ha area of the Choban-Dagh Range. The climate is semi-arid and steppe-like (Frankis 1993). USDA Hardiness Zone 7. Conservation status Data Deficient. Illustration NT592.

Pinus brutia var. eldarica is rare both as a truly wild tree and in cultivation in Europe, where it is grown in only a few collections, but it is widely cultivated in the southwestern United States where it copes well with dry heat and poor soils (Jacobson 1996). As a native tree it is restricted to a small area of Azerbaijan and Georgia, but it is widely naturalised or semi-cultivated across central Asia (Iran, Afghanistan and

Plate 401. Pinus brutia var. eldarica is a rather undistinguished member of the genus, but the reddish underlayers of thickly ridged bark are striking. It should be planted where the evening sun can strike the trunk. Image J. Grimshaw.

Section II. Species Accounts

Pinus

Pakistan). It has been speculated that it was transported by traders on the Silk Route (Conkle et al. 1988). There are several trees at Kew, grown from seeds received in 1978 from the Forestry Department of Afghanistan, at a time when such peaceable activities as seed-collecting were still possible there. These specimens range between 10 and 12 m in height, and vary slightly in habit, but all have very thick, strongly ridged reddish bark that oozes copious resin. In general the branches are held rather stiffly upright, but one tree has a more rounded outline. The bark peels from the branches in reddish flakes, and this alone makes it a curiously attractive tree. The American stock is also of Afghan origin, collected from the Herat region in the 1960s and distributed by the US Department of Agriculture (Jacobson 1996). Trees sold by Monrovia Nursery under the trademarked selling name Christmas Blue are apparently seedlings from a more glaucous parent tree (Jacobson 1996).

Pinus brutia var. pendulifolia Frankis This variety has longer, pendulous leaves (20–29 cm long), the trees superficially resembling P. canariensis from a distance. Frankis 1993, Farjon 2005a. Distribution TURKEY: Mugla Province. Habitat Similar to the type variety, with which it co-occurs. USDA Hardiness Zone 8. Conservation status Not evaluated.

This variety is in cultivation in Turkey (M. Frankis, pers. comm. 2007), but no trees have been traced in our area since Keith Rushforth’s specimen was killed by Armillaria.

Pinus brutia var. pityusa (Steven) Silba Syn. P. brutia var. stankewiczii (Sukacz.) Frankis This variety has narrow leaves up to 15 cm long and indented umbos. Frankis 1993, Farjon 2005a. Distribution GEORGIA: Abkhazia; RUSSIAN FEDERATION: Krasnodar; UKRAINE: Crimea. Habitat Similar to that of the type variety. USDA Hardiness Zone 7. Conservation status Vulnerable. Cross-references B216, K231.

Var. pityusa has a limited presence in cultivation, with a few trees scattered through our area. Jacobson (1996) states that in the United States it is very inferior in performance compared to var. brutia and var. eldarica, and is seldom seen. In the United Kingdom the best example is probably one of several at the Sir Harold Hillier Gardens, measured at 8.1 m in 2008 (Sir Harold Hillier Gardens database). These were grown from seed collected in the former USSR for the French seed company Versepuy, received in 1985. Given the number of varieties of P. brutia, confirmation of identity probably requires reliable knowledge of provenance. Ukrainian material is sometimes distinguished as var. stankewiczii, on the basis of some electrophoretic characters (Conkle et al. 1988, Frankis 1993), but no specimens of Ukrainian origin are currently known to be in cultivation in our area (M. Frankis, pers. comm. 2007). P. bungeana Zucc. ex Endl. B216, S373, K212 P. canariensis C. Sm. B217, S374, K212

Pinus cembroides complex

P. caribaea Morelet K213 P. cembra L. B217, S374, K213

(Subgen. Strobus, Sect. Parrya)

The delimitation of the taxa allied to Pinus cembroides is disputed, some (Farjon & Styles 1997, Farjon 2001, 2005a) regarding them as variants of a wide-ranging, morphologically variable species, while others (Perry 1991, Malusa 1992, Price et al. 1998, Richardson 1998, Gernandt et al. 2003) prefer to view them as separate species. The latter approach seems to be that most favoured by fieldworkers in Mexico, and

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we have adopted it here, especially as the taxa also have horticultural distinctions. A key to the species considered by Farjon (2001) to be intraspecific is given below, adapted from Farjon & Styles (1997) with the assistance of Michael Frankis. Specific accounts follow the normal alphabetical order. In this wide sense, Pinus cembroides is one of the most important producers of pinyon (pine nuts) in Mexico (Rodriguez-Franco 2002), and it also has considerable potential in horticulture. In most forms it is usually a rather low, multistemmed broad bush, but can develop into a taller tree, usually with stiffly spreading branches. The literature is vague as to the precise identity of cultivated material in the United States, where P. cembroides (s.l.) is recommended for its tolerance of drought and alkaline soils (Gilman & Watson 1994a) and is occasionally used in landscapes (Dirr 1998), but all the taxa in this group could clearly be more widely planted, in the United States and in Europe.

1a. Leaves wholly or largely epistomatic, with lower surface dark green, upper stomata bands white .......................................................................................................... 2 1b. Leaves amphistomatic, light green on all surfaces ............................................................................ 3 2a. Leaves in fascicles of three (rarely four); cones under 4.5 cm long; Mexico (Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, northeast Sonora, west Tamaulipas, Zacatecas), USA (southeast Arizona, southwest New Mexico) ................................................................................................ P. johannis 2b. Leaves in fascicles of three to four (rarely two or five); cones over 4.5 cm long; Mexico (Puebla, Tlaxcala, west Veracruz) ......................................................... P. orizabensis 3a. Leaves usually long, (2.5–)4–7(–8) cm, < 1 mm wide, mainly straight; Mexico (Baja California Sur) ............................................................. P. cembroides subsp. lagunae 3b. Leaves usually short, (2–)3–5(–6.5) cm, (0.6–)0.7–1.2 mm wide, mainly curved; in fascicles of two to three; Mexico (Aguascalientes, Chihuahua, Coahuila, Durango, Guanajuato, Hidalgo, Jalisco, México, Nuevo León, Puebla, Querétaro, San Luis Potosí, Sonora, Tamaulipas, Tlaxcala, Veracruz, Zacatecas), USA (southwest Texas) ............... P. cembroides subsp. cembroides

Pinus cembroides Zucc.

Mexican Pinyon

Pinus cembroides subsp. cembroides Shrub or tree to 25 m, trunk straight or contorted, 0.2–1.2 m dbh. Bark thin, smooth, blackish grey to greyish brown; in older trees, becoming thick and irregularly fissured with orangish new bark at the centre of the fissures. Crown broad, rounded and open. Branchlets slightly glaucous or orange-brown, becoming grey; vegetative buds not or slightly resinous. Leaves in fascicles of two to three, persisting for three to four years, dull green to yellow-green, amphistomatic, curved or nearly straight, rigid or slightly lax, triangular or semicircular in cross-section, (2–)3–6(–8) × 0.06–0.12 cm, apex acute. Fascicle sheaths 0.4–0.6 cm long, pale brown, bracts forming a rosette at the base of the fascicle. Cataphylls subulate or triangular, 0.2–0.4 cm long, light brown. Male strobili small, 0.5 × 0.3 cm, pollinating in spring. Female cones subterminal, paired or in whorls of three, mature cones sessile or short-pedunculate. Cones (2–)3–4.5 × 3–6 cm, globose or ovoid, green, maturing yellowish buff to orange-red, maturing in about 18 months, often resinous. Scales 25–40, irregular in shape, spreading easily; apophysis raised, rhombic to pentagonal; umbo dorsal, 6–9 mm wide, raised, with a minute prickle. Fertile seeds greyish black, infertile seeds light brown; wings rudimentary, remaining attached to the seed scale. Perry 1991, Farjon & Styles 1997. Distribution MEXICO: Aguascalientes, Chihuahua, Coahuila, Durango, Guanajuato, Hidalgo, Jalisco, México, Nuevo León, Puebla, Querétaro, San

Section II. Species Accounts

Pinus

Luis Potosí, Sonora, Tamaulipas, Tlaxcala, Veracruz, Zacatecas; USA: southwest Texas. Habitat Transitional areas between desert plateaus and valleys, and mesic coniferous forest (800–2800 m asl). USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT580. Crossreferences B219, K213.

Trees of subsp. cembroides from several collections in Mexico (for example, J. Hjerting & S. Ødum 17 from Chihuahua in 1989, and a number of gatherings by M.F. Gardner and S.G. Knees in Hidalgo in 1993) are grown in the Scottish botanical gardens and are happy in well-drained sites there. At the Hillier Gardens a specimen from Gardner & Knees 5185 was 1.6 m tall in 2007, suggesting that it is slow-growing in cultivation. As a drought-tolerant tree it would seem to be well suited to the drier parts of England or southern Europe. A gold-leaved selection found by John Fairey has been named ‘Peña Nevada Gold’ and is in cultivation at the University of California Botanical Garden at Berkeley. Pinus cembroides subsp. lagunae (Rob.-Pass.) D.K. Bailey is endemic to Baja California Sur, where it is the only pine, and so cannot be confused with any other species in the wild. Its leaves are straight, rather long, (2.5–)4–7(–8) cm, less than 1 mm wide, with two intermittent lines of stomata on each face (Perry 1991, Farjon & Styles 1997). It is not known to be in cultivation. P. cembroides var. edulis (NOW P. edulis Engelm., NT599) B219, K214 P. cembroides var. monophylla (NOW P. monophylla Torr. & Frem.) B219, S374, K223 P. cembroides var. parryana (NOW P. quadrifolia Parl. ex Sudw., NT618) B219

Pinus chiapensis (Martínez) Andresen

Chiapas White Pine

(Subgen. Strobus, Sect. Quinquefolius) Syn. P. strobus L. var. chiapensis Martínez Tree to 40 m, trunk straight and erect, 1–1.5 m dbh. Bark thin, smooth, silvery grey at first, in older trees thick, rough, scaly, dark brown to grey, with long shallow vertical fissures. Crown initially conical, becoming open and irregular with long horizontal branches in mature trees. Branchlets slender, smooth, finely pubescent at first, becoming glabrous; vegetative buds reddish brown, resinous. Leaves in fascicles of five, in sparse tufts near the ends of ultimate branches, persisting for two to three years, straight or pendent, often slightly twisted, light green on the outer face, glaucous bluish white on the inner faces, triangular in cross-section, (5–)7–13 × 0.06–0.08(–0.1) cm, margins serrulate, apex acute. Fascicle sheaths 1–1.5 cm long, orange-brown, rapidly disintegrating. Cataphylls 0.4–0.5 cm long, brown. Male strobili yellow to orange-brown, ovoid-oblong to cylindrical, 0.5–0.8 cm long. Female cones subterminal and axillary, solitary or in pairs or in whorls of three; peduncles long and slender, 1.5–4.5 cm long, erect then pendulous, falling with the cone. Cones (6–)8–15(–25) × 2–3 cm closed, green to dark brown, mature in about 15–18 months; mature cones variable, mainly cylindrical, occasionally slightly curved. Scales 50–90, opening obliquely; scales thin, straight, fragile; apophysis usually rather resinous, mid-brown; umbo terminal, greyish brown, resinous. Seeds dark grey-brown, 0.7–0.9 × 0.4–0.5 cm; wings adnate, 2–3 × 0.6–0.9 cm, light brown with dark streaks. Andresen 1966, Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution GUATEMALA; MEXICO: Chiapas, Guerrero, Oaxaca, eastern Puebla, Tabasco, Veracruz. Habitat Subtropical or warm temperate montane forests between 500 and 2200 m asl. USDA Hardiness Zone 9–10. Conservation status Vulnerable. Illustration Farjon & Styles 1997. Cross-references B242, K238.

Pinus chiapensis was first described by Martínez (1940) as a variety of P. strobus, and is still regarded as such by some (Farjon 2001, 2005a). Although few morphological foliage characters distinguish P. chiapensis from P. strobus, it is very distinct genetically,

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sharing no alleles with P. strobus and forming a distinct clade of its own, sister to two clades of American and Asian species (Liston et al. 2003, Syring et al. 2007). A few vegetative characters help identification. In P. chiapensis, the serrations on the leaf margins are larger, and there are fewer per unit length than in P. strobus. The proximal cone scales of P. chiapensis are straight, as in P. peuce and most other Eurasian white pines, while in P. strobus and P. monticola they are recurved. Most white pines are attractive, and this Mexican species is quite as beautiful as any other. It has been collected in Veracruz (Gardner & Knees 5377, in 1993), from which source trees are established at Benmore and elsewhere, but it is not commonly grown. Despite its southerly and low-altitude distribution it seems to be hardy in Britain but its wider hardiness is unknown, and it is presumably subject to the same fungal and pest problems that plague P. strobus. It has been investigated for use as a tropical plantation species (Dvorak et al. 2000). P. chihuahuana (NOW P. leiophylla subsp. chihuahuana (Engelm.) A.E. Murray, NT606) K214 P. clausa (Chapm. ex Engelm.) Sarg. K214 P. contorta Douglas ex Loudon B220, S374, K215 P. contorta var. bolanderi (NOW P. contorta Douglas ex Loudon var. contorta) K215

Pinus culminicola Andresen & Beaman

P. contorta var. latifolia Engelm. B220, S374, K215 P. contorta var. murrayana (Balf.) Engelm. B220, K215 P. coulteri D. Don B221, S374, K215

Potosí Pinyon

(Subgen. Strobus, Sect. Parrya) Shrub or tree to 5 m, trunk short, leaning, often forked, 0.1–0.25 m dbh, the branches spreading from the base for 3–4 m. Bark thin, dark grey, scaly on the lower trunk. Crown dense and shrubby. Branchlets stout, rough; vegetative buds 1–2 cm, pale grey-brown, slightly resinous. Leaves in fascicles of five, persisting for three to four years, slightly curved, rigid, epistomatic, dark green on outer face, glaucous blue-white on inner face, triangular in cross-section, 3–5 × 0.09–0.13 cm, apex acute. Fascicle sheaths to 0.6–0.8 cm long, light grey-brown. Cataphylls 0.5–0.7 cm long, grey. Male strobili yellow, ovoid to subglobose, 0.5–0.8 cm long, pollinating in summer. Female cones subterminal, solitary or in whorls of two to three; peduncles short, nearly sessile, with semi-persistent cataphylls. Cones (2–)2.5–4.5 × 3–5.5 cm, dark green, maturing dark brown, mature in about 15 months; mature cones globose or subglobose with a flat base, forming an irregular rosette when fully open. Scales 45–60 (of which 10–20 fertile), opening widely, weakly attached to cone rachis; apophysis raised, light brown to dark to reddish brown, coarsely wrinkled; umbo dorsal, 4 mm wide, flat to slightly raised, dark brown to grey with a minute, deciduous prickle. Fertile seeds dark grey-brown (infertile seeds pale buff), 0.9–1.3 × 0.8–0.9 cm; wings vestigial, remaining attached to the seed scale. Perry 1991. Distribution MEXICO: eastern Coahuila, western Nuevo León. Habitat Isolated mountain summits between 3000 and 3710 m asl. USDA Hardiness Zone 7. Conservation status Endangered. Illustration Perry 1991. Cross-reference K215.

Closely resembling Pinus johannis in form but easily distinguished by its leaves in fives (in threes in P. johannis), P. culminicola is an endangered species, confined to a few mountain summits in northeastern Mexico, and only abundant on the highest, Cerro Potosí, where it forms nearly pure stands at the 3710 m summit. There have been several introductions to cultivation since its discovery in 1961, including a gathering by Harold Hillier in 1979 (Lancaster 2005). A few individuals from this collection persist in private gardens in Hampshire and have recently been propagated (R. Lancaster, pers. comm. 2008). Others are on the Rock Garden at Edinburgh (grown

Section II. Species Accounts

Pinus

597

from Frankis 156 collected in 1991, and Compton, D’Arcy & Rix 1280 in 1993, both collections originating in Nuevo León). The dark green and glaucous foliage makes this a particularly attractive shrub, ideal for rock gardens or low landscaping and suitable even for small gardens.

Pinus densata Mast.

(Subgen. Pinus, Sect. Pinus)

Gaoshan Pine

Syn. P. tabuliformis var. densata (Mast.) Rehder Tree to 30 m, trunk erect and slender, 1.3 m dbh. Bark scaly, reddish brown, becoming greyish brown in older trees and developing longitudinal fissures, forming thick, irregular plates. Crown conical then broadly ovoid. Branchlets stout, shiny, yellowish to reddish brown; vegetative buds slightly resinous. Leaves in fascicles of two (to three), persisting for three years, straight, slightly twisted, triangular in cross-section, 8–14 × 0.1–0.15 cm, margins serrulate, apex acute. Fascicle sheaths 0.5–1 cm long, persistent. Cataphylls 0.7 cm long, triangular, dark brown to black. Male strobili cylindrical, 1–1.8 × 0.3–0.45 cm, yellowish brown. Female cones subterminal, solitary or in pairs, pendulous, sessile or short-pedunculate. Cones 4–7 × 4–7 cm, shiny chocolate-brown, ovoid, mature in about 18 months. Scales irregular, spreading wide at maturity; apophysis prominent, rhombic, 0.4–0.7 cm thick; umbo dorsal, with a short, recurved prickle. Seeds light greyish brown; wings 1.5–2 cm long. Fu et al. 1999c, Farjon 2005a. Distribution CHINA: southern Qinghai, western Sichuan, eastern Xizang, northwest Yunnan. Habitat Forested mountain slopes between 2600 and 4200 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Fu et al. 1999c; NT597. Taxonomic note Some authors have speculated that P. densata is a stabilised natural hybrid, with P. tabuliformis and P. yunnanensis as parents (Wang & Szmidt 1990, Wang et al. 1990).

Pinus densata has been cultivated for many years, usually as P. tabuliformis var. densata, but has remained obscure. It was collected by Ernest Wilson on numerous occasions during his years in China (Sargent 1916) and it may have been from one of his gatherings that trees first became established in cultivation; certainly it was reported to be thriving in some British gardens at the Royal Horticultural Society’s Conifer Conference in 1931. Wilson described it as resembling P. sylvestris, with mature trees having ‘a rounded or flattened head and pale red bark’, and recorded that it was the common pine of western Sichuan; it is also common in northwestern Yunnan and southeastern Tibet. No doubt because of this frequency, it has been reintroduced regularly since plant collectors entered China again in 1980, and it is now grown quite commonly in botanic gardens throughout our area. Whether it deserves widespread cultivation is another matter as it is not one of the most beautiful of pines, with dull green needles and improbably small cones for a species with rather thick stems. It seems to grow reasonably fast when young, several plants at Kew from the 1993 SICH 732 collection being now in the range of 4.5–5.5 m tall, although at Howick the growth rate in plants from the same collection is slower. Trees produce cones at an early age, both in natural habitats and in cultivation. Pinus densata var. pygmaea J.R. Xue, from dry mountainsides in Sichuan and Yunnan, is much smaller than the type variety, forming a multistemmed shrub to 2 m tall. The leaves are shorter than in var. densata (7–13 cm long), as are the cones (4–5 cm long), which do not open at maturity. Var. pygmaea is not known to be in cultivation, but sounds interesting. P. densiflora Siebold & Zucc. B221, S375, K215

Plate 402. Pines achieve their greatest beauty in maturity and old age, when they can become very picturesque. This is Pinus densata in the wild. Image J. Smith.

598

Pinus

New Trees

Pinus devoniana Lindl.

(Subgen. Pinus, Sect. Trifolius)

Michoacán Pine

Syn. P. michoacana Martínez, P. wincesteriana Gordon Tree to 30 m, trunk erect, slender or massive, 0.8–1 m dbh. Bark thick, very rough, reddish brown to dark brown, breaking into numerous elongated plates, this process beginning in very young trees. Crown broad, open, pyramidal or domed. Branchlets very rough, thick, scaly; vegetative buds large, not resinous. Leaves in fascicles of five (rarely four or six), persisting for two to three years, bright, lustrous green, straight or flexible, drooping, triangular in cross-section, (17–)25–40(–45) × 0.1–0.16 cm, apex acute. Fascicle sheaths 3–4 cm long, orange-brown, turning dark brown or black, very resinous. Cataphylls large, 2–2.5 cm long, subulate, dark brown to black. Male strobili cylindrical, 2–4 cm long. Female cones subterminal, solitary, paired or in whorls of three to four, peduncles thick and persistent, a few cone scales remaining when the cone is shed. Cones 15–35 × 8–15 cm, initially erect, pinkish purple, mature in winter at about 20 months old; mature cones often curved. Scales 175–225, irregular in shape, spreading wide at maturity, thick, woody and rigid or slightly flexible; apophysis mostly raised, rhombic; umbo dorsal, flat or depressed, prickle deciduous. Seeds light brown with dark spots; wings 2.5–3.5 × 1–1.5 cm, light brown with darker stripes; most seedlings having a ‘grass stage’ of development. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution GUATEMALA; MEXICO: Aguascalientes, Chiapas, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, Querétaro, San Luis Potosí, Tlaxcala, Veracruz, Zacatecas. Habitat Constituent of open, pine-oak forest and mixed pine forest, between 700 and 3500 m asl. USDA Hardiness Zone 10. Conservation status Lower Risk. Illustration Fu et al. 1999c.

Despite its wide range, Pinus devoniana seems to be seldom collected by visitors to Mexico, and records of only two recent introductions have been traced. (It is available from several British nurseries, but the authenticity of such plants has not been confirmed.) In 1981 it was collected (as P. michoacana) by B. Bartholomew and D.E. Breedlove in Chiapas, from which gathering there is a tree at Berkeley. Seed from a cone collected by Alan Mitchell on the 1982 IDS tour of Mexico was grown by Michael Frankis, and the plants distributed to a few gardens in Cornwall, but no seedlings are known to have survived. Although sometimes recorded as P. devoniana (Govier 2001), a collection made by Keith Rushforth in 1987 in Nuevo León (KR 497) is now known to be P. montezumae (M. Frankis, pers. comm. 2007). An intriguing reference in the TROBI list suggests an earlier introduction, however, with a record of a 4 m specimen of ‘P. michoacana cornutata’ growing in a garden in Herefordshire in 1993. A relative of the slightly better-known P. montezumae, P. devoniana has a robust growth habit, with thick shoots bearing terminal clusters of exceptionally long, stiff, spreading needles, and forming a rounded crown when mature. It requires a mild location and may not be hardy enough for cultivation in western Europe. P. ×digenea (NOW P. ×rhaetica Brügger) K217 P. douglasiana Martínez (NOW P. gordoniana Hartweg) K217

Pinus durangensis Martínez

(Subgen. Pinus, Sect. Trifolius)

Durango Pine

Syn. P. martinezii E. Larsen Tree to 40 m, trunk erect, straight, 0.8–1 m dbh. Bark rough, scaly, reddish brown; in older trees, breaking into large, irregular plates separated by shallow, longitudinal fissures. Crown dense and globose, trunk clear of branches for half or three quarters of its height. Branchlets glaucous, orange- or dark reddish brown, rough; vegetative buds not resinous. Leaves in fascicles of (four to) five to six (to seven, or rarely eight), persisting for two to three years, yellowish green to glaucous, straight or slightly curved, triangular in cross-section, 14–24 × 0.07–0.1 cm, apex acute. Fascicle sheaths 2–3 cm long, orange-brown. Cataphylls large, 1.5 cm long, subulate then reflexed, dark brown. Male strobili cylindrical to ovoid. Female cones subterminal, solitary, paired or in whorls of three to four, peduncles stout, persistent. Cones 5–9(–11) × 4–6(–7) cm, purple or glaucous, mature in winter at about 20 months old; mature cones ovoid, slightly curved. Scales 90–120, spreading easily at maturity, thick, woody, broadly oblong; apophysis raised or flat, rhombic to pentagonal; umbo dorsal, raised, prickle deciduous or persistent. Seeds light brown to grey; wings effective, 1.4–2 × 0.6–0.9 cm, light greyish brown.

Section II. Species Accounts

Pinus

599

Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Chihuahua, Durango, Jalisco, Michoacán, Sonora, Zacatecas. Habitat Pine-oak forests between 1400 and 3000 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk. The stem of P. durangensis is tall and straight, making it a popular target for timber exploitation. Many of the pure stands have been decimated, though the tree is still relatively common in mixed forest. Illustration Farjon & Styles 1997; NT581, NT599. Cross-reference K217.

In his important book Conifers in the British Isles Alan Mitchell (1972) rather baldly recorded that Pinus durangensis and a few other species were introduced in 1962, but provided no further information. The source of this seed has been a question of interest to conifer enthusiasts ever since, and has now been traced for us in the Forestry Commission records by Richard Jinks (pers. comms. 2007, via D. Luscombe). It was sent to the Forestry Commission by the Mexican Instituto Nacional de Investigaciones Forestales, reciprocated by a gift of seed from the United Kingdom, and was principally used to raise trees for trialling in arboreta and Forestry Commission sites. A further small introduction from the same source was made in 1973 for Alan Mitchell. The P. durangensis seed was collected in 1961 in Chihuahua. There are good trees at Bedgebury, Westonbirt and Alice Holt, Hampshire. The largest is at Bedgebury and was 16 m tall (70 cm dbh) when measured by Owen Johnson in 2005 (TROBI). Another 16 m specimen but with a smaller girth (49 cm) was measured in 2001 at Bicton Park Botanical Gardens, Devon. Several other introductions have been made since 1973, and the species grows in collections scattered through the milder parts of our area. It appears to do well in the climate of southern England, growing steadily though perhaps not rapidly; a tree at Wakehurst Place received as a young plant in 1989, grown from a collection made in Chihuahua by Peter Catt, was apparently vigorous but only 5 m tall when seen in 2005. With its upright but relatively slender needles and reddish bark this is an attractive tree, that could be planted more widely in warmer areas. P. echinata Mill. B222, K217

Pinus edulis Engelm. (Subgen. Strobus, Sect. Parrya)

Colorado Pinyon, Rocky Mountain Pinyon

Syn. P. cembroides var. edulis (Engelm.) Voss This species was mentioned by Bean (1976b) under the name P. cembroides var. edulis (Engelm.) Voss. Its gross morphology is akin to that of P. cembroides, though the leaves are almost invariably in pairs, the seeds have thinner shells, the cones are on average slightly larger with fewer, larger, thicker scales, and the umbo is often depressed (rather than raised or flat). In some populations of P. edulis the immature plants are dioecious (male and female cones restricted to separate trees). Mature trees produce both male and female cones, though there are more empty seeds per cone than in the cones from immature, female plants (Floyd 1982). Thieret 1993, Farjon 2005a. Distribution USA: Arizona, Colorado, New Mexico, western Oklahoma, northwest Texas, Utah, southern Wyoming. Habitat Arid, rocky slopes and mesas between 825 and 2350 m asl. USDA Hardiness Zone 4. Conservation status Lower Risk. Illustration Farjon 2005a. Cross-references B219, K214.

Away from its native range and the arid southwestern United States more generally, Pinus edulis is rare in cultivation, and for an attractive tree with very tasty nuts and

Plate 403. Radiating needles form broad tufts on the branch tips of the Mexican Pinus durangensis. Image J.R.P. van Hoey Smith.

600

Pinus

New Trees

huge cultural significance to Native Americans, this is surprising. Like all the pinyon group it has great potential as a relatively compact, densely furnished shrubby tree for landscaping, particularly in arid places, and it is indeed used for this purpose in its native range and adjacent areas (Lanner 1981, Nold 2008). It is now commercially available in the United Kingdom, but older specimens are rare in Europe. One at Edinburgh dating from before 1969 is the most venerable traced, but it is a poor plant (M. Gardner, pers. comm. 2007). There are larger, happier trees at Kew and the Cambridge University Botanic Garden. It is also grown at Pinetum Anthoine, Jamioulx, Belgium, along with the dwarf selection ‘Juno’ from Kenwith Nursery in Devon. The related P. monophylla is another attractive, tolerant but horticulturally under-used dryland pine that deserves more attention (Nold 2008).

Pinus elliottii Engelm.

(Subgen. Pinus, Sect. Trifolius)

Slash Pine

Tree to 30 m, trunk straight or twisted, 0.5–1 m dbh. Bark rough, scaly, reddish brown; in older trees, reddish brown to grey, breaking into large, irregular plates, divided by deep fissures. Crown rounded or flat-topped, and open. Branchlets thick, rigid, orange-brown; vegetative buds large, not resinous. Leaves in fascicles of two to three, dark green, straight or slightly twisted, rigid, semicircular in cross-section, (15–)18–25(–30) × 0.15 cm, apex acute. Fascicle sheaths 0.8–1.5 cm long, reddish brown, persistent. Cataphylls small, subulate, brown. Male strobili purplish to reddish brown, ovoid-oblong, 3–5 × 0.5–0.8 cm. Female cones subterminal, in whorls of three to five or more; peduncles stout, 0.1–0.2 cm long, scaly, deciduous. Cones (5–)7–15(–18) × (4–)6–9 cm, initially erect, later spreading or recurved, pinkish or pale purple with green apophyses, mature in about 18 months; mature cones basically ovoid, though shape varies. Scales 120–180, readily parting at maturity, flat, woody, oblong; apophysis flattened or slightly raised, rhombic, yellowish to reddish brown; umbo dorsal, raised, with a curved, persistent prickle. Seeds black or grey with dark spots; wings effective, 1.5–3(–3.5) × 1 cm, light brown. Thieret 1993, Farjon 2005a. Distribution USA: Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina. Naturalised and weedy in South Africa, Zimbabwe. Habitat Restricted to lowlands on the Coastal Plain where it often favours sandy soils. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Farjon 2005a. Cross-reference K217. Taxonomic note Pinus ellliottii, P. echinata and P. taeda form complex swarms of introgressed hybrids in much of the southeastern United States, and genetic purity cannot be expected in cultivated plants (L. Hatch, pers. comm. 2008).

Pinus elliottii is an important timber tree in the Coastal Plain of the southeastern United States, and should probably be left there. Planted as a forestry species, it has become invasive in Africa, and it has no advantages as an ornamental tree, within or outside its native range (Gilman & Watson 1994b). As with so many plants from this area it can tolerate cool winters, warranting a Zone 8 categorisation, but requires its summer heat and humidity to flourish, and is not hardy in most of North America (Sternberg 2004). It is therefore not well suited to most parts of our area, and although collectors will want it for their arboreta, great success should not be expected. In illustration of this, the largest specimen recorded in the British Isles by TROBI was a dead tree measured at 10.5 m in 2002 at the Hillier Gardens, where the species is no longer grown. The south Florida population of Slash Pine is currently recognised as P. elliottii var. densa Little & K.W. Dorman, though it has occasionally been considered a distinct species. The major differences between the two are that seedlings of var. densa have a definite ‘grass stage’, while those of the type variety do not, and more of the leaf fascicles have two leaves, rather than three as in var. elliottii. The leaves and cones are slightly smaller than in the type, and it also has harder wood (Thieret 1993, Farjon 2005a). Not thought to be cultivated in our area, it is best known for its sought-after hard timber. It is slower growing than var. elliottii, and forms a round-crowned tree; Gilman & Watson (1994b) concede that it could make a ‘wonderful street tree’.

Section II. Species Accounts

Pinus

Pinus engelmannii Carrière

601

Apache Pine, Arizona Longleaf Pine

(Subgen. Pinus, Sect. Trifolius) Syn. P. engelmannii var. blancoi (Martínez) Martínez

Tree to 25 m, trunk erect, straight, 0.7–0.9 m dbh. Bark reddish brown; in older trees dark brown, breaking into long, irregular plates divided by wide, shallow fissures. Crown broad, open and rounded; trunk clear of branches for half to a quarter of its height. Branchlets stout, very rough; vegetative buds not resinous. Leaves in fascicles of (two to) three (to four, rarely five), persisting for two to three years, pale or yellowish green, straight or slightly curved, triangular in cross-section, (18–)20–35(–43) × 0.15–0.2 cm, apex acute. Fascicle sheaths 1.5–4 cm long, reddish brown, persistent. Cataphylls conspicuous, 1.5–2 cm long, recurved, dark brown or black. Male strobili cylindrical to ovoid-oblong. Female cones subterminal, single, paired or in whorls of three to five, peduncles stout and curved, initially persistent though eventually deciduous. Cones 8–15 × 6–10 cm, light brown and glaucous, mature in about 18–20 months; mature cones appear sessile, ovoid-oblong, curved,

A

1 cm

C

1 cm

B 1 cm

D

Figure 68. Pinus engelmannii: leaf fascicle (A); stem with male strobili (B); detail of stem, showing reflexed cataphylls and fascicle sheaths (C). P. maximinoi: winter bud (D).

602

Pinus

New Trees

usually resinous. Scales 100–140, parting to release seeds, thick, woody, oblong; apophysis variably raised, rhombic to pentagonal, yellowish brown to light brown; umbo dorsal, with a 0.3 cm long, persistent, curved spine. Seeds light brown to grey with dark spots; wings effective, 1.8–2.5 × 0.7–1 cm, translucent yellowish brown; seedlings have a ‘grass stage’ of development. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Chihuahua, Durango, Sinaloa, Sonora, Zacatecas; USA: southeast Arizona, extreme southwest New Mexico. Habitat Mountain slopes and plateaus between 1200 and 3000 m asl. USDA Hardiness Zone (7?–)8. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT601, NT602. Cross-reference K217.

Plate 404. Pinus engelmannii, with its stout limbs and branches tipped with tufts of stiff needles, always brings a suggestion of the Wild West, even to the Hillier Gardens where this tree grows. Image K. Camelbeke.

Pinus engelmannii is an interesting species, very well adapted to survive fires, much as P. palustris is, although the two occur in very different habitats; in appearance it is much more like P. ponderosa, though obviously differing in the long leaves. Pinus engelmannii has a ‘grass stage’ in its youth, and then thick, fire-resistant bark from an early age as it develops a more normal shape. The tree has a massive appearance at all stages, with thick stems and branches bearing impressive tufts of long leaves at their tip, making it well worth planting as a specimen tree. An individual at Kew of about 8 m, with slightly gaunt and twisted branches, that originated as seed collected in Durango in 1961 by David Hunt, looks as if it has been transplanted from a Wild West film set. The name Apache Pine also conjures up images of its habitat in the Mexico and US borderland mountains. It was among the pines introduced to the Forestry Commission in 1962 (Mitchell 1972), and from this and later introductions is well established in British and European gardens, apparently being quite hardy. The best specimen in the United Kingdom is at the Hillier Gardens, on the West Scree Lawn near Jermyn’s House, measured at 16 m (45 cm dbh) in 2006 and forming a fine trunk with a good crown, but this is much larger and older than any grown from the 1962 introduction, and must therefore predate it (M. Frankis, pers. comm. 2007). A selection is commercially available in the United Kingdom, under the presumably illegitimate name ‘Glauca’.

P. flexilis E. James B222, S375, K218 P. gerardiana Wall. ex D. Don B223, K218 P. glabra Walter K218 P. greggii Engelm. ex Parl. B235, K218 P. hakkodensis Makino B218, K218 P. halepensis Mill. B223, S375, K218

Pinus henryi Mast.

P. halepensis var. eldarica (NOW P. brutia var. eldarica (Medw.) Silba, NT592) K218 P. hartwegii Lindl. B228, S377, K218 P. heldreichii H. Christ B224, K219 P. heldreichii var. leucodermis (NOW P. heldreichii H. Christ) B224, S375

(Subgen. Pinus, Sect. Pinus)

Syn. P. tabuliformis var. henryi (Mast.) C.T. Kuan, P. tabuliformis subsp. henryi (Mast.) Businský This species is treated as a variety of P. tabuliformis in Flora of China (Fu et al. 1999c), and as a subspecies of it by Businský (1999); it is somewhat indistinct, though Farjon (2001, 2005a) maintains it as a full species. It differs from P. tabuliformis in its needles, which are never wider than 1 mm. Also, the cones are smaller

Section II. Species Accounts

Pinus

603

(2.5–5 cm long, usually as wide as long when open), with a reflexed peduncle (as in P. sylvestris), and the seed scales have apophyses that are only slightly swollen. Fu et al. 1999c, Farjon 2005a. Distribution CHINA: Hebei, Hubei, Hunan, Shaanxi, Sichuan. Habitat Mountains between 1100 and 2000 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration NT603.

Pinus henryi was introduced to cultivation in 1996 under the collection number QLG 112 by a NACPEC expedition composed of personnel from several American and Chinese botanical gardens. They found it on a hillside in the Hong Shan, Shaanxi, from which all other trees had been felled, but which had evidently been floristically very rich (collection notes from USDA Germplasm Resources Information Network: USDA /ARS, National Genetic Resources Program 2008). Young trees are now growing in American collections and are rather striking in appearance, the new shoots forming ‘foxtails’ of dense, bright green needles. Specimens observed in 2006 at the US National Arboretum and the Morris Arboretum (both participatory in the NACPEC expedition) were 2 and 1.8 m tall respectively, growing vigorously and producing new leaders up to 60 cm long. By late autumn 2007 the USNA specimen had reached 4 m and was coning (R. Olsen, pers. comm. 2007). In maturity trees can be expected to become flat-topped, with a single straight trunk and reddish bark. The species has apparently not yet been introduced to Europe. P. ×holfordiana A.B. Jacks. B225, S376, K219 P. ×hunnewellii Alb. G. Johnson K219

Pinus hwangshanensis W.Y. Hsia (Subgen. Pinus, Sect. Pinus)

Huangshan Pine, Chinese Hard Pine

Tree to 25 m, trunk straight and to 1 m dbh. Bark scaly, dark grey or purplish grey, developing longitudinal fissures. Crown conical initially, later flat-topped. Branchlets dark brown to chestnut brown, glabrous; vegetative buds slightly resinous. Leaves in fascicles of two, persisting for three to four years, dark green, slender, semicircular in cross-section, 5–12 × 0.08–0.1 cm, margins serrulate, apex acute. Fascicle sheaths 0.5–1 cm long, chestnut brown, persistent. Cataphylls 0.6–0.8 cm, pale brown, early deciduous. Male strobili reddish brown. Female cones subterminal, sessile or short-pedunculate. Cones 3.5–7 × 4–7 cm, yellowish brown, broad-ovoid, maturing in about 18 months, deciduous or persistent, often losing a few basal scales on falling. Scales spreading very wide at maturity, to 90 ° or even reflexed, 1.8–3 × 0.8–1.4 cm; apophysis rounded, swollen, yellowish brown; umbo dorsal, with a minute, persistent prickle. Seeds dark brown; wings effective, 1.2–1.8 × 0.4–0.6 cm. Li & Keng 1994a, Fu et al. 1999c, Businský 2003. Distribution CHINA: Anhui, Fujian, Henan, Hunan, Jiangxi, Zhejiang. Habitat In open areas and on sunny ridges in warm temperate and montane forests, between 600 and 3400 m asl. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration NT604. Cross-reference S375. Taxonomic note The taxonomy of P. hwangshanensis is complex. It was treated as a synonym of P. taiwanensis by Fu et al. (1999c), but in the same publication Mill considered that P. taiwanensis was endemic to Taiwan, while all material from the Chinese mainland was referable to P. hwangshanensis. Farjon (2001), however, recognised P. taiwanensis var. damingshanensis W.C. Cheng & L.K. Fu on the Chinese mainland. Li (1997) described P. hwangshanensis and P. taiwanensis as subspecies of the Japanese P. luchuensis, and it is clear that these three taxa form a close group. The most recent account of P. hwangshanensis (Businský 2003) recognises a new subspecies, subsp. transfluminea Businský, from the Dabie Shan Mountains (Anhui, Hubei, Henan), with longer needles (10–16 cm long) and cones (4–8 cm long). This subspecies forms hybrids with P. massoniana on the northwest face of the Miaodoiu Shan Massif.

In its youth Pinus hwangshanensis is a rather unattractive, coarse-needled plant, but in maturity it transforms into one of the most beautiful and picturesque of all pines, forming flat-topped trees with tiers of spreading branches that appear at their best among the rounded rocks of the Huangshan itself in Anhui, giving this World Heritage Site a particular charm (Gymnosperm Database 2006). Named only in 1936, P. hwangshanensis appears to have evaded the attentions of the initial wave of western

Plate 405. New growth of Pinus henryi is a surprisingly vivid green. This young tree at the Morris Arboretum is surrounded by stakes to prevent deer thrashing their antlers against it. Image J. Grimshaw.

604

Pinus

New Trees

plant hunters in China, and the details of its first introduction to cultivation are obscure. It was accessioned at the Arnold Arboretum in 1976, at Edinburgh and Wakehurst Place in 1979, and at Kew and the Hillier Gardens in 1980. All these trees were grown from seed supplied by the Chinese Academy of Forestry. It was commercially available in the United Kingdom by 1985, when Charles Howick obtained two specimens from Fyne Trees. The latter are doing well at Howick, both being about 10 m tall when seen in 2005, and the oldest Hillier tree was measured at 11 m in 2007, but as yet none of these show any sign of developing the beautiful flat branches. Grafted plants are still available in the British nursery trade, and it is reasonably well represented in collections in the United Kingdom and in continental Europe. A plant at the US National Arboretum is labelled P. taiwanensis but is from seed collected by Lawrence Lee in the Huang Shan in 1988 and is therefore attributable to P. hwangshanensis; when seen in 2006 this specimen was about 4 m tall and somewhat misshapen, but apparently thriving. P. insularis (NOW P. kesiya Royle ex Gordon var. kesiya) K220 P. jeffreyi Balf. B226, S376, K220 Plate 406. The magnificent rockscape of the Huangshan, Anhui, a World Heritage Site, is perfectly complemented by the layered branches of Pinus hwangshanensis. Image J. Tumilowicz.

Pinus johannis Rob.-Pass.

Border Pinyon, Dwarf Pinyon

(Subgen. Strobus, Sect. Parrya) Syn. P. discolor D.K. Bailey & Hawksw., P. cembroides var. bicolor Little Shrub or tree to 5–12 m, trunk short, leaning, often forked, 0.1–0.25 m dbh, though trunk form may reflect environmental factors. Bark thin, dark grey, scaly on the lower trunk. Crown dense and shrubby. Branchlets stout, rough; vegetative buds 1–2 cm, pale grey-brown, slightly resinous. Leaves in fascicles of three to four, persisting for three to four years, slightly curved, rigid, dark green on outer face, glaucous blue-white on inner faces, triangular in cross-section, 3–5 × 0.09–0.13 cm, apex acute. Fascicle sheaths to 0.6–0.8 cm long, light grey-brown. Cataphylls 0.5–0.7 cm long, grey. Male strobili yellow, ovoid to subglobose, 0.5–0.8 cm long, pollinating in summer. Female cones subterminal, solitary or in whorls of two to three; peduncles short, nearly sessile, with semi-persistent cataphylls. Cones (2–)2.5–4.5 × 3–5.5 cm, dark green, maturing dark brown, mature in about 15 months; mature cones globose or subglobose with a flat base, forming an irregular rosette when fully open. Scales 45–60 (of which 10–20 fertile), opening widely, weakly attached to cone rachis; apophysis raised, light brown to dark to reddish brown, coarsely wrinkled; umbo dorsal, 4 mm wide, flat to slightly raised, dark brown to grey with a minute, deciduous prickle. Fertile seeds dark grey-brown (infertile

Section II. Species Accounts

Pinus

seeds pale buff), 0.9–1.3 × 0.8–0.9 cm; wings vestigial, remaining attached to the seed scale. In some populations plants are subdioecious (male and female cones largely restricted to separate trees) (Floyd 1982). Perry 1991. Distribution MEXICO: Chihuahua, Coahuila, Durango, Nuevo León, north and west San Luis Potosí, northeast Sonora, western Tamaulipas, Zacatecas; USA: southeast Arizona, southwest New Mexico. Habitat Similar to P. cembroides, though more often on exposed, arid slopes and ridges. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Farjon & Styles 1997.

The status of Pinus johannis (syn. P. cembroides var. bicolor) is controversial – most workers recognising it as one or two full species (Perry 1991, Malusa 1992, Passini 1994, Price et al. 1998, Richardson 1998, Gernandt et al. 2003), while a few (Farjon & Styles 1997, Farjon 2005a) consider it to be only a variety of P. cembroides. This situation is exacerbated at times by difficulty in distinguishing between small herbarium specimens, of taxa that may be quite easily differentiated in the field. Some further distinctions exist between eastern and western populations of P. johannis, that have implications for horticulture. In the northeastern Mexican states of Coahuila, Nuevo León and Zacatecas, it forms only low shrubs (to 4–5 m tall), comprising P. johannis s.s. In southern Arizona and New Mexico, and in the northwestern Mexican states of Chihuahua, Durango and Sonora, however, are populations that form trees of 9–15 m, and these are treated separately by some authors, as P. discolor. In foliage and cone characters there is a great deal of overlap, and P. discolor has been placed in synonymy with P. johannis by Passini (1994). Neither P. discolor nor P. johannis is reported to hybridise with P. cembroides, with which both sometimes grow, intimately mixed (Gymnosperm Database 2007c). In foliage characters, ecology and genetics, P. johannis is more closely related to P. culminicola than to P. cembroides (Malusa 1992, Gernandt et al. 2003). Pinus johannis is in cultivation at Berkeley from seed collected in Zacatecas in 1981 by Frank Callahan, and c.1989 by L. Briones. With its low-growing, shrubby habit and attractive blue-green foliage it has great horticultural potential, especially for use in water-wise gardens. In the United Kingdom it is grown at Benmore, from collections made by Michael Frankis in Nuevo León in 1991 (M.P. Frankis 114, 179). Keith Rushforth (pers. comm. 2007) has raised Frankis 179 to 1.5 m, and there is a 1 m specimen at the Hillier Gardens, where there is also a 2.6 m plant from John Horsman dating to 1986 (2007 measurements, from Sir Harold Hillier Gardens database); otherwise, however, it is rare in cultivation. P. khasya (NOW P. kesiya Royle ex Gordon var. kesiya) K220 P. koraiensis Siebold & Zucc. B226, S376, K220 P. krempfii Lecomte K220 P. lambertiana Douglas B227, S376, K220 P. lawsonii Roezl. ex Gordon K221

Pinus leiophylla Schiede ex Schltdl. & Cham. (Subgen. Pinus, Sect. Trifolius)

Chihuahua Pine, Smooth-leaf Pine

Tree to 35 m, trunk erect, sometimes forked, 0.2–0.85 m dbh. Bark scaly, flaking, reddish to greyish brown; in older trees, very thick, rough, dark greyish brown, breaking into scaly plates divided by deep, longitudinal fissures. Crown open and rounded or flat-topped. Branchlets glaucous, reddish brown to grey, scaly; vegetative buds not or slightly resinous. Leaves in fascicles of (four to) five (to six) (four more often than six), persisting for two to three years, light yellow-green to glaucous, straight, triangular in cross-section, (6–)8–15(–17) × 0.05–0.09 cm, apex acute. Fascicle sheaths 1.2–2 cm long, deciduous, so that mature leaves appear to have no fascicle sheath – an important identification character. Cataphylls small, light orange-brown, Male strobili yellowish pink then light brown. Female cones subterminal, solitary or in whorls of two to five; peduncles

605

606

Pinus

New Trees

slender or stout, 1–2.5 cm long. Cones (4–)5–7(–8) × (3–)4–5.5 cm, pink to purplish green or purplish brown, mature in about 30–32 months; mature cones narrowly ovoid-conical, symmetrical. Scales 50–70, opening gradually; scales oblong; apophysis greyish brown, with a prominent band around the umbo; umbo dorsal, with a blunt prickle. Seeds dark greyish brown to black with black spots; seed wings effective, 1–1.8 × 0.4–0.8 cm, yellowish brown, translucent. The tree can produce adventitious shoots from stumps or the trunk, allowing it to survive fires or limited coppicing. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: western Chihuahua, Durango, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, northeast Sonora, Tlaxcala, Veracruz, Zacatecas. Habitat Montane pine and pine-oak forest between 1500 and 3300 m asl. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a. Cross-reference K221.

Pinus leiophylla subsp. chihuahuana (Engelm.) A.E. Murray Subsp. chihuahuana is of slightly smaller stature than subsp. leiophylla, usually reaching only 25 m, with slightly shorter, stouter leaves, (4–)5–8(–9) cm long, in fascicles of (two to) three (to four, or rarely five). Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: western Chihuahua, Durango, northern Jalisco, Nayarit, northeast Sonora, Zacatecas; USA: southeast Arizona, southwest New Mexico. Habitat Almost entirely sympatric with the type subspecies, though extending further north and not so far south, subsp. chihuahuana is adapted to somewhat colder climates, occurring in semi-arid areas at elevations of between 1500 and 2950 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Farjon & Styles 1997.

Pinus leiophylla is rare in cultivation, and even when it is grown, is usually not identified to subspecific level. An early introduction, Gardner & Knees 5318, collected in México state in 1992, must be subsp. leiophylla. Only one example of the species is recorded by TROBI, an 8 m tree at Quinta Arboretum, Cheshire, measured in 2004 by Owen Johnson, but there are trees at Bedgebury also. Recently planted seedlings at Tregrehan were killed in the winter of 1996, when the temperature there reached –6 °C, but this was ‘not a fair test’ (T. Hudson, pers. comm. 2007). In the United States, subsp. chihuahuana may be used in the southwest in plantings of native trees, but the species is seldom grown in collections in our area, although there are two trees at Berkeley, of Jalisco origin. It has bright green to yellow-green foliage, less sombre and heavy-set than most other western American pines, making a fine tree but without great beauty for horticultural purposes. In overall appearance it is surprisingly similar (particularly subsp. chihuahuana) to the distantly related Mediterranean P. halepensis (M. Frankis, pers. comm. 2007). P. leucodermis (NOW P. heldreichii H. Christ) K221

Pinus longaeva D.K. Bailey (Subgen. Strobus, Sect. Parrya)

Great Basin Pine, Intermountain Bristlecone Pine

Tree to 18 m, trunk erect, strongly tapered, 0.3–0.6 m dbh, though mature trees in their natural habitat have massive gnarled and largely dead trunks up to 3.5 m dbh, with only small living parts remaining. Bark scaly, grooved and yellow or russet. Crown open and irregular; cultivated specimens are relatively fast-growing with a conical crown. Branchlets reddish brown to grey, hairy; vegetative buds not resinous. Leaves in fascicles of five (rarely three or four), persisting for 10–30 years in habitat, fascicles held closely together, arranged on branches like a bottlebrush, shiny greyish or yellowish green, straight, triangular in cross-section, 2.5–3.5 × 0.05 cm (to 5 cm long in cultivation), with two external, longitudinal resin ducts, resin droplets absent, apex acute. Fascicle sheaths peeling backwards, then mostly deciduous but the basal scales persisting. Cataphylls to 0.8 cm long, reddish brown to dark brown. Male strobili orange-brown, ovoid, 1–1.2 cm. Female cones subterminal, solitary or in pairs, sessile or short-pedunculate, 6–12 cm long, purple to rusty reddish brown, taking about 16 months to mature; mature cones ovoid with reddish resin deposits. Scales 100–140, opening at maturity; scales thick, soft, reddish brown; apophysis raised, rhombic, reddish brown; umbo dorsal, with a short, slender prickle. Seeds 0.5 cm long; seed wings effective, 1 cm long. Bailey 1970, Thieret 1993, Farjon 2005a. Distribution USA: eastern California, southern Nevada, Utah. Habitat Dry, rocky ridges or

Section II. Species Accounts

Pinus

607

slopes between 1700 and 3400 m asl. Pinus longaeva is intolerant of shade. Harsh environmental conditions of its natural habitat cause it to grow very slowly, such that individuals of this species are among the oldest trees in the world, some aged up to 5000 years. USDA Hardiness Zone 4–5. Conservation status Vulnerable. Illustration Farjon 2005a; NT607. Cross-reference S373. Taxonomic note Pinus longaeva is one of the three ‘foxtail’ pines (together with P. aristata and P. balfouriana), and was described relatively recently after investigation of this group by Bailey (1970).

One of the great dendrological experiences is to make the journey up the White Mountains in the Inyo National Forest of eastern California to see Pinus longaeva in its natural habitat. Here, in the bright light of these rather barren mountains, are the scattered stands of trees that contain some of the oldest living organisms on Earth. Their gnarled trunks, often seeming more dead than alive, and polished by exposure, are a photographer’s dream. (In the search for images for this book there were more submissions for P. longaeva than for any other species except Wollemia nobilis.) In these high dry mountains the growth rate of P. longaeva is exceedingly slow, adding a few centimetres each year at most, but in cultivation it grows more rapidly. A tree dating from 1972 at Kew is now 3.5 m tall, but does not look very happy as it is somewhat shaded, and shade is also a problem with specimens growing at Edinburgh from Bailey’s collection in the early 1970s. Considerably better-looking is one on the Rock Garden at Edinburgh grown from Paterson & Clarke 123, collected in 1991, which has a much denser, more compact appearance, more characteristic of the species in the wild; even in this case, however, new growth was 10–12 cm in 2005. It is clear that maximum light is required for the species to prosper, and probably rather lean soil also, but it is well established in cultivation, and in favoured sites may go on to form a respectable tree. It has no white resin flecks in its foliage – a very conspicuous feature in its close relative P. aristata and a useful identification character. Its other close relative, P. balfouriana, has long been established in cultivation (see Bean and Krüssmann: B213, S373, K210). Most if not all of the specimens in the United Kingdom, including the two well-known individuals at Edinburgh, and a probably contemporary but slightly larger tree in Stocksfield, Northumberland (the largest in Britain, 17 m tall and 45 cm dbh in 2007: M. Frankis, pers. comm. 2007), are of the recently described subspecies P. balfouriana subsp. austrina R. Mastrog. & J. Mastrog., from the southern Sierra Nevada. This is distinguished by smaller cones with smaller, thicker scales, and (in very old trees) orange rather than dark grey bark. Typical P. balfouriana subsp. balfouriana, from the Klamath mountains, may not be in cultivation in Britain at present, other than as young plants (M. Frankis, pers. comm. 2007). P. luchuensis Mayr K222

Pinus massoniana Lamb.

P. lumholtzii B.L. Rob. & Fernald K222

Chinese Red Pine, Masson Pine

(Subgen. Pinus, Sect. Pinus) Syn. P. massoniana var. shaxianensis D.X. Zhou Tree to 30(–45) m, trunk straight or crooked, 1.5 m dbh. Bark scaly, flaking irregularly, greyish brown, developing large longitudinal fissures, occasionally with transverse fissures. Crown irregular, broad and domed. Branchlets slender, smooth, yellowish brown or glaucous; vegetative buds slightly resinous. Leaves in fascicles of two (to three), slender, pliant, slightly twisted, pale green, semicircular in cross-section, 12–20 × 0.05–0.1 cm, apex

Plate 407. The growth rate of Pinus longaeva in the White Mountains of California is incredibly slow but they achieve considerable stature, and some are among the world’s oldest living organisms. To be among them is a great experience. Image J. Grimshaw.

608

Pinus

New Trees

acute. Fascicle sheaths 2 cm long, persistent. Cataphylls to 0.5 cm long. Male strobili reddish yellow, ovoid. Female cones subterminal, with a short peduncle, to 0.4 cm long. Cones 4–7 × 2.5–4 cm, green to chestnut brown, ovoid to conical or cylindrical, mature in about 18 months, falling early when ripe. Scales flat, oblongobovoid or rhombic; apophysis flat or slightly swollen; umbo dorsal, slightly sunken, spiny (var. shaxianensis) or obtuse. Seeds blackish brown; wings 1.1–1.5 cm long. Fu et al. 1999c, Farjon 2005a. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, western Henan, Hubei, Hunan, southern Jiangsu, Jiangxi, southeast Shaanxi, Sichuan, eastern Yunnan, Zhejiang; TAIWAN. Widely planted in Vietnam. Habitat Grows in a great variety of habitats between 200 and 2000 m asl. Cannot tolerate shade, and forms pure stands or mixes with other light-demanding trees. An important forestry species in China. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Fu et al. 1999c, Farjon 2005a; NT580, NT608. Cross-reference K222. Taxonomic note Farjon (2001) also recognises P. massoniana var. hainanensis W.C. Cheng & L.K. Fu, which is endangered and restricted to the hills of Hainan Island; it is not recorded in cultivation.

Plate 408. Male strobili developing at the base of the new shoot in Pinus massoniana. Male cones are the nearest a pine gets to a floral display. Image P. de Spoelberch.

Despite its wide distribution, Pinus massoniana has received little attention from horticulture. This may be because, in Wilson’s words (Sargent 1916), ‘as ordinarily met with it is a tree of no great beauty’; Wilson went on to say, however, that in a perfect mature state it is very beautiful, with a reddish upper trunk and a flattened or rounded crown. Krüssmann (1985b) gives 1829 as the date of its first introduction, but it is mentioned only as a footnote in Elwes & Henry (1910). It seems probable that it was first successfully introduced by one of the early-twentieth century collectors in China – possibly Wilson, who gathered material of it on several occasions. A 14.5 m tree measured by Alan Mitchell at Nymans, West Sussex in 1957 (TROBI) was presumably from such a source. Several specimens of 10–13 m have been recorded in southeastern England over the years. The largest contemporary tree at Kew, however, is of hybrid origin, grown from seed sent from Les Barres in 1957 (M. Frankis, pers. comm. 2007). Young specimens from more recent gatherings are relatively frequent in British and western European arboreta. In North America it seems to be rare, but a vigorous young plant was noted at the San Francisco Botanical Garden in 2004.

Pinus maximartinezii Rzed.

Martínez’s Pinyon, Big-cone Pinyon

(Subgen. Strobus, Sect. Parrya) Tree to 16 m, trunk short, twisted, contorted, 0.4–0.5 m dbh. Bark thin, smooth; in older trees grey, breaking into square plates. Crown open, rounded. Branchlets slender, glaucous or greyish green to orange-brown, slowgrowing; vegetative buds resinous. Leaves in fascicles of five, though rarely three or four, persisting for five years, in dense tufts near the ends of the branches, glaucous or green, triangular in cross-section, 7–11(–13) × 0.05–0.07 cm, apex acute. Fascicle sheaths 0.7–0.8 cm long, light brown. Cataphylls to 0.5 cm long, early deciduous. Male strobili yellowish, ovoid-oblong, 0.8–1 cm long. Female cones lateral, solitary, sessile or short-pedunculate. Cones (15–)17–25(–27) × 10–15 cm, mature in 27–28 months, green until fully grown; mature cones ovoid-truncate; cone rachis to 5 cm long; green cones can reach weights of 1.5–2 kg. Scales 80–110, opening gradually, though often not sufficiently to release the seeds; scales very thick, woody, with two deep seed cavities on the upper surface; apophysis very prominent, 3.5–5 × 2–3.5 cm, rhombic to pyramidal, often resinous; umbo dorsal, grey, sometimes with a minute prickle. Seeds oblong to ovoid, 2–2.8 cm long; wings absent. Donahue & Lopez 1995, Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: southern Zacatecas (Sierra de Morone). Habitat Summit ridges and eastern slopes between 1800 and 2400 m asl. USDA Hardiness Zone 10. Conservation status Endangered. Pinus maximartinezii is one of the most threatened pine species, due to its restricted distribution and small population size. Mature trees are protected, as the seeds are a valuable commodity, but regeneration is limited because of seed collection and overgrazing of the seedlings (Donahue & Lopez 1995). Illustration Farjon & Styles 1997; NT580, NT586.

The big cones, and the extraordinarily large seeds that they contain, are the unique features of Pinus maximartinezii – a somewhat surprisingly small and slenderly

Section II. Species Accounts

Pinus

branched tree given the size of its fruits. The long, fine blue-green foliage is also attractive, and it is occasionally grown as an ornamental in Mexico (A. Coombes, pers. comm. 2007). Not surprisingly, it is often collected. Unfortunately it seems to be rather tender, the only long-established trees known in cultivation being those growing in the University of California Botanical Garden at Berkeley (one from a collection made by Frank Callahan in 1987, and another from Zacatecas, accessioned in 1989 without further details). By 1994 a tree from Nigel Muir had reached 2 m at the Hillier Gardens (TROBI) but this has not survived to the present day. Seed was collected by Michael Frankis in 1991 (Frankis 185), but a tree from this source survived for only three years after being planted out in 2000 at Tregrehan (T. Hudson, pers. comm. 2005). Neither has it survived at Arboretum Wespelaar, where Koen Camelbeke judges it to be not hardy (pers. comm. 2007). The seedlings of P. maximartinezii have up to 24 cotyledons, more than in any other plant, and as in its closest relative, P. pinceana, juvenile growth with solitary glaucous needles persists for several years (Gymnosperm Database 2007d). The related and equally rare P. rzedowskii Madrigal & M. Caball from Michoacán has not been tested in our region, but coming as it does from 2000–2400 m asl in a tropical area with a minimum temperature of –5 °C (Farjon & Styles 1997), it is likely to be even less hardy than P. maximartinezii. P. merkusii Jungh. & de Vriese K222 P. michoacana (NOW P. devoniana Lindl., NT598) K222 P. monophylla Torr. & Frém. B219, S374 (as P. cembroides var. monophylla); K223 P. montezumae Lamb. B227, S377, K223 P. montezumae var. hartwegii (NOW P. hartwegii Lindl.) K223

Pinus morrisonicola Hayata

P. montezumae var. lindleyi (NOW P. montezumae Lamb. var. montezumae) B228, K223 P. montezumae f. macrocarpa (NOW P. montezumae Lamb. var. montezumae) K223 P. montezumae var. rudis (NOW P. hartwegii Lindl.) K223 P. monticola Douglas ex D. Don B229, S377, K223

Taiwan White Pine

(Subgen. Strobus, Sect. Quinquefolius) Tree to 30 m, trunk straight or crooked, 1.2 m dbh. Bark smooth to scaly, greyish to blackish brown, developing irregular, shallow, longitudinal fissures. Crown initially conical, then irregular and open, often flat-topped. Branchlets smooth, yellowish then reddish brown or glaucous; vegetative buds pale brown, not resinous. Leaves in fascicles of five (or four), slightly twisted, blue-grey to glossy green, triangular in cross-section, 4–10 × < 0.1 cm, apex acute. Leaf fascicles form tufts at the ends of the elongated branches. Fascicle sheaths minute, orange-brown. Cataphylls to 0.4 cm long, early deciduous. Female cones in whorls of three to four, peduncle stout, 0.5–1 cm long. Cones 7–13 × 5.5–7.5 cm, resinous, ovoid to conical, mature in about 18 months, deciduous. Scales oblong-obovoid, thick and woody; apophysis shiny brown, slightly swollen; umbo terminal, dark brown to black. Seeds ellipsoid-ovoid, 0.8–1.3 × 0.4–0.7 cm; wings short, pale brown, 1.5–2 × 0.5–0.8 cm. Li & Keng 1994a, Fu et al. 1999c, Businský 2004, Farjon 2005a. Distribution TAIWAN. Habitat Occurs in mixed coniferous or broadleaved forests in the Tsun-Yang Shanmo Range, on slopes and ridges between 300 and 2000 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Li & Keng 1994a, Fu et al. 1999c, Farjon 2005a. Cross-reference K223. Taxonomic note Recent studies of the soft pines of Taiwan (Businský 2004) have revealed that there are two distinct species on the island, P. morrisonicola and P. uyematsui Hayata, with a hybrid P. ×hayatana Businský occurring where they meet, forming zones of introgression. Formerly regarded as a synonym of P. morrisonicola, P. uyematsui is similar in foliage but differs markedly in the slender cones, 8–18 cm long with thin scales, and smaller seeds, 0.6–0.8 × 0.3–0.45 cm, with a long slender wing 1.5–3 × 0.6–1 cm, quite unlike the short broad wing of P. morrisonicola. It occurs at

609

610

Pinus

New Trees

higher altitudes (2000–2400 m) than P. morrisonicola, at least in the southern part of Taiwan (Businský 2004). Pinus uyematsui is not known to be in cultivation, but it is conceivable that collections from higher altitudes, such as ETE 581, could be this or the hybrid (K. Rushforth, pers. comm. 2007).

Pinus morrisonicola is potentially a very attractive tree, related to P. armandii and the other soft-needled Asian pines. Its blue-green foliage is shorter and less pendulous than that of most members of this group, however, and also very narrow. Its first introduction was probably through a collection made by Chris Page in Taiwan in 1976 (C.N. Page 10057), material from which is still in cultivation as part of the Royal Botanic Garden Edinburgh’s outhousing scheme. Edinburgh has been responsible for several further introductions, particularly through their Edinburgh Expedition to Taiwan of 1993, when several gatherings were made (ETE 91, 94, 581). At Tregrehan trees from ETE 581 have grown steadily. Less fortunate is a tree at Kew, grown from ETOT 109 (collected in 1992), that has lost its leader and is growing (apparently happily) as a horizontal shoot. In view of the resurrection of P. uyematsui from synonymy, it would be wise to check the identity of all Taiwanese soft pines as their cones are produced. P. mugo Turra B229, S377, K225 P. mugo var. uncinata (NOW P. mugo subsp. uncinata (Ramond ex DC.) Domin OR P. uncinata Ramond ex DC.) S377

Pinus nelsonii Shaw

Plate 409. Pinus nelsonii has recently been placed in its own section of subgenus Strobus, Nelsonia. The unique cones are borne on a stout pedicel. This was one of the first cones to be produced in cultivation, on Frankis 183 at the Royal Botanic Garden Edinburgh, in 2006. Image M. Frankis.

P. muricata D. Don B231, S377, K226 P. ×murraybanksiana Righter & Stockw. K226

(Subgen. Strobus, Sect. Nelsonia)

Nelson’s Pinyon

Tree to 10 m, trunk short, often forked, 0.2–0.3 m dbh. Bark thin, smooth, greyish brown; in older trees fissured, thin, breaking into irregular plates divided by longitudinal and rarely horizontal fissures on lower trunk. Crown broad, dense, rounded. Branchlets long, stout, upcurved, grey; vegetative buds red-brown, inconspicuous, not resinous. Leaves in fascicles of three (to four) but remaining connate unless separated by force, so appearing single, persisting for two to three years, in sparse tufts near ends of branchlets, straight, rigid, bright green, triangular in cross-section, 4–8(–10) × 0.07–0.08 cm, apex acute, margins serrated. Fascicle sheaths to 0.9 cm long, persistent. Cataphylls 0.5–0.8 cm long, early deciduous. Male strobili ovoid-oblong, 0.7–0.9 × 0.3–0.35 cm. Female cones lateral, not on ultimate branches, solitary or rarely in pairs; peduncles stout, curved, 3–6 cm long, 6–9 mm thick (usually stouter than distal shoot), remaining on the branch after the cones fall. Cones 6–12 × 4.5–6 cm, green ripening red, mature in two years; mature cones cylindrical, sometimes irregular. Scales 60–100, opening partially, thick, softly woody but fragile at base; apophysis irregular, rugose red-brown; umbo dorsal, large but ill defined due to continuous growth, grey to reddish with short, stout, blunt spike. Seeds dark red-brown, 12–15 mm; wings vestigial, remaining attached to the cone scales. Perry 1991, Farjon 2005a. Distribution MEXICO: Nuevo León, San Luis Potosí, Tamaulipas. Habitat Slopes in arid and semi-arid mountains, between 1600 and 3200 m asl. USDA Hardiness Zone 9. Conservation status Vulnerable. Illustration Farjon & Styles 1997, Farjon 2005a; NT610. Cross-references B219, S374, K226.

Pinus nelsonii is a thoroughly weird pine, unique in numerous features. Although discovered in 1904, it may not have been introduced until recently, as the specimen at Kew referred to by Bean (1976b) was later recognised as P. orizabensis (see p. 612). The cones of P. nelsonii are the strangest in the genus, with the conelet, unlike in any other pine, not ceasing growth in the first winter; the umbo is therefore large and grades into the apophysis. The cone is also unusual in that the peduncle occasionally bears needle fascicles (M. Frankis, pers. comm. 2007), again not seen in any other pine. The needles are unique in remaining connate throughout their lifetime (‘zippered’ together by the marginal teeth) (Bailey & Hawksworth 1988). Pinus nelsonii forms a short, bushy tree, with a crown shaped similarly to that of young P. pinea. The needles are bright green, and young plants bear green (not glaucous) juvenile leaves for up to ten years.

Section II. Species Accounts

Pinus

611

It has proved to be the most distinct pine of all genetically, not closely related to any other, and now placed in its own section, Nelsonia (Businský 2008). In the wild it grows in arid situations, often with P. cembroides. Gatherings have been made by a few collectors, including Frankis 183 from Nuevo León in 1991, a tree from which in the Rock Garden at Edinburgh was about 2 m tall and coning in 2006 – probably the first cones of this species ever produced in the United Kingdom. It has also been collected by Carl Schoenfeld and John Fairey, from whose material a tree has grown at Berkeley since 1997. Wider cultivation should be attempted, though more for its interest as a botanical curiosity than for its decorative qualities. P. nigra J.F. Arnold B232, S378, K226 P. nigra var. caramanica (NOW P. nigra subsp. pallasiana (Lamb.) Holmboc) B233, S378 P. nigra var. cebennensis (NOW P. nigra subsp. salzmannii (Dunal) Franco) B233, S378 P. nigra subsp. dalmatica (NOW P. nigra J.F. Arnold subsp. nigra) K226 P. nigra f. hornotina (NOW P. nigra J.F. Arnold subsp. nigra) K226 P. nigra subsp. laricio (Poiret) Maire K227 P. nigra var. maritima (NOW P. nigra subsp. laricio (Poiret) Maire) B233, S378 P. nigra subsp. pallasiana (Lamb.) Holmboc K227 P. nigra var. pyramidata (NOW P. nigra subsp. pallasiana var. fastigiata Businský) K227 P. nigra subsp. salzmannii (Dunal) Franco K227 P. oaxacana (NOW P. pseudostrobus var. apulcensis (Lindl.) Shaw, NT616) K227 P. occidentalis Sw. ex Schltdl. K228

Pinus oocarpa Schiede ex Schltdl.

Egg-cone Pine

(Subgen. Pinus, Sect. Trifolius) Tree to 35 m, trunk erect, straight, 1–1.25 m dbh. Bark thin, scaly, reddish brown; in older trees dark greyish brown, thick, rough, scaly, breaking into small or large plates divided by shallow, longitudinal fissures. Crown open, rounded or irregular. Branchlets rough, scaly, reddish brown; vegetative buds not resinous. Leaves in fascicles of (three to) five, persisting for two to three years, straight, rigid or rarely lax, lustrous yellow-green, triangular in cross-section, (17–)20–25(–30) × 0.08–0.14 cm, apex acute. Fascicle sheaths to 2.5 cm long, reddish brown to black, persistent. Cataphylls 1–1.5 cm long, brown to greyish black. Male strobili pink or reddish then yellowish brown, oblong-cylindrical, 1.5–2 × 0.5–0.6 cm. Female cones subterminal, solitary or in whorls of two to four; peduncles stout, to 3.5 cm long, bracteate, remaining attached to the cone. Cones 3–8(–10) × 3–9(–12) cm, often wider than long, purple to light brown, mature in 12–18 months; mature cones ovoid to subglobose, semi-serotinous. Scales 70–130, opening gradually, thick, woody, oblong; apophysis almost flat or slightly raised, yellowish brown to light brown; umbo dorsal, obtuse or with a minute prickle. Seeds greyish black with black spots; wings effective, 0.8–1.8 × 0.4–0.8 cm, greyish brown. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution EL SALVADOR; GUATEMALA; HONDURAS; MEXICO: Chiapas, southwest Durango, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, northern Puebla, Sinaloa, Sonora, Tlaxcala, southern Veracruz, southern Zacatecas; NICARAGUA. Habitat Open woodland or forest, in pure stands or in mixed

Plate 410. Pinus oocarpa var. oocarpa VERA 84, at Kew, showing its rich reddish brown bark. Image J. Grimshaw.

612

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New Trees

pine or pine-oak forests. Pinus oocarpa can be found between 200 and 2700 m asl, though conditions are optimal between 1000 and 1500 m. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT611. Cross-reference K228.

Pinus oocarpa, whose name relates to its egg-shaped cones, is a handsome species that can form a broad, rounded crown, each branchlet bearing large terminal clusters of needles. It has a wide range in southern Mexico and into adjacent Central American countries, and collectors should attempt to select provenance with some care. Trees from the northwest of its range commonly have only three leaves per fascicle and smaller cones (not over 5.5 cm long), and are distinguished as P. oocarpa var. trifoliata Martínez (syn. P. luzmariae Pérez de la Rosa); coming from a colder and drier climate, they are likely to be hardier and better suited to our area than the type. A tree of var. oocarpa grown from VERA 84, collected at 2000 m in Veracruz by M. Sparrow and P. Brewster in 1993, is growing vigorously at Kew and was about 5 m tall in 2007, with striking reddish bark. By contrast, a seedling from 100 m in Guatemala, outhoused to Tregrehan by the Royal Botanic Garden Edinburgh, died of cold after only a year. The species has been grown at Berkeley since 1979. Nurseries in both England and the western United States have offered it in recent years.

Pinus orizabensis (D.K. Bailey) D.K. Bailey & Hawksw.

Orizaba Pinyon

(Subgen. Strobus, Sect. Parrya) Syn. P. cembroides subsp. orizabensis D.K. Bailey Shrub or tree to 8–12 m, trunk short, 0.5–0.6 m dbh. Bark thin, dark grey, with vertical scaly fissures on the lower trunk, the fissures orange-yellow. Crown dense and shrubby. Branchlets rough, pale greyish buff; vegetative buds 1–2 cm, pale grey-brown, slightly resinous. Leaves in fascicles of three (to four) (occasionally five, exceptionally two), persisting for three to four years, slightly curved, rigid, dark green on outer face with few stomata, glaucous blue-white stomatal bands on inner faces, triangular in cross-section, 4–6 × 0.07–0.11 cm, apex acute. Fascicle sheaths to 0.6–0.8 cm long, light grey-brown. Cataphylls 0.5–0.7 cm long, orange-brown. Female cones subterminal, solitary or in whorls of two to three; peduncles short, nearly sessile, with semipersistent cataphylls. Cones 4.5–7.5 × 5–7.5 cm, dark green, maturing dark brown, mature in about 16 months; mature cones globose or subglobose with a flat base, forming an irregular rosette when fully open. Scales 30–35(–50) (of which 10–20 fertile), opening widely, weakly attached to cone rachis; apophysis thin, slightly raised with a transverse ridge, light brown to dark to reddish brown, smooth; umbo dorsal, 4–6 mm wide, slightly raised, dark brown to grey with a minute, deciduous prickle. Fertile seeds dark golden-brown (infertile seeds pale buff), 1.4–1.8 × 0.8–0.9 cm; wings vestigial, remaining attached to the seed scale. Perry 1991, Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Puebla, Tlaxcala, western Veracruz (in the high basin to the west of the mountains of Pico de Orizaba and Cofre de Perote). Habitat This species occurs in an area of scattered volcanoes, between 2100 and 2800 m asl. It mixes with P. cembroides in some areas. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Farjon & Styles 1997.

This species is in some respects intermediate between Pinus cembroides and P. johannis. The leaves have stomata on both outer and inner faces as in P. cembroides, but with only a few on the outer face and densely on the inner faces, giving it the same bicoloured aspect as P. johannis. The cones and seeds, however, are larger than in either of these other two. It was named after detective work elucidated the identity of a tree growing at Kew that had been mislabelled P. nelsonii, by comparing it with herbarium material and wild trees in Orizaba, Mexico (Bailey 1983, Bailey & Hawksworth 1992), although its true relationship to other members of the P. cembroides complex is still debated (Gymnosperm Database 2007e). The Kew tree was received from H. Clinton Baker in 1910, and is rather attractive, with an appearance strongly suggestive of dry hillsides. It is currently a shapely 10 m tall, with a somewhat glaucous appearance from stiffly erect, bristly needles. Other than a few seedlings from it at Wakehurst Place and elsewhere, this specimen is the only one known in cultivation.

Section II. Species Accounts

Pinus palustris Mill.

(Subgen. Pinus, Sect. Trifolius)

Pinus

613

Longleaf Pine

Syn. P. australis F. Michx., P. longifolia Salisb. Tree to 45 m, to 1.2 m dbh. Bark reddish brown, breaking into large, irregular plates. Crown open with spreading, usually crooked branches. Branchlets stout, to 2 cm thick, reddish brown; winter buds 3–4.5 cm long, white, scales with hairy margins. Leaves in fascicles of three (very rarely two or five), persisting for two years, bright green, flexible, triangular in cross-section; the needles of P. palustris are among the longest in the genus, 20–45 × 0.15 cm. Fascicle sheaths 2–3 cm long, base persistent. Male strobili purplish red, 4–7(–8) cm long. Female cones solitary or paired, 20–25 cm long, mature in about 18 months, then quickly shedding seeds and falling. Scales reflexed to spreading; apophysis raised, keeled; umbo triangular with broad, recurved prickle. Seeds large, 0.9–1.2 cm long; wings effective, 3–4 cm long; seedlings have a prominent ‘grass stage’ of development. Thieret 1993, Farjon 2005a. Distribution USA: Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Virginia. Habitat The warm temperate and subtropical Coastal Plain is typical for this species, though it does reach the foothills of the Appalachian Mts.; between 0 and 700 m asl. USDA Hardiness Zone 7–8. Conservation status Vulnerable. Illustration Farjon 2005a; NT613. Cross-reference K228.

Like Pinus elliottii, P. palustris is an important timber species of the southeastern United States and, again like P. elliottii, is really only suited to those conditions of great heat and humidity in summer. Beyond its native range it is not very satisfactory, even in the United States; Sternberg (2004) reports that it survives at Starhill Forest, but only as a ‘struggling botanical curiosity’. It has been introduced to Europe repeatedly since 1727 (Krüssmann 1985b) but only a handful of trees have ever developed into a significant specimen, and then ‘usually as a long, scantily branched tree of no decorative value’ (Dallimore et al. 1966). The champion recorded in the British Isles is a specimen at Glencormac, Co. Wicklow, measured at 20 m (67 cm dbh) in 2000 (TROI), but the identity of this should be confirmed. Its inclusion here at all might be questioned, were it not that at the present time it is freely available in British nurseries, being sold as young plants of about 50–60 cm, still in the ‘grass stage’ of their development. They are indeed very attractive, and find a particular welcome in the gardens of those keen on interesting foliage and structural effects, but in our area their charm is unlikely to last long. Where the species is better suited, young trees beyond the grass stage are of exceptional beauty, with ‘bottlebrush’ branches of long, grass-green needles, and the potential to develop into noble timber trees if all goes well. This is the iconic species of the famous Pinehurst Golf Resort, North Carolina, the course having been carved through a forest of P. palustris in 1895 – a little sporting snippet kindly contributed by Larry Hatch (pers. comm. 2008). P. parviflora Siebold & Zucc. B234, S378, K229 P. patula Schiede ex Schltdl. & Cham. B235, S379, K229 P. peuce Griseb. B236, S379, K230

Pinus pinaster Aiton

(Subgen. Pinus, Sect. Pinus)

Maritime Pine

This species was described by Bean (B236, S379) and Krüssmann (K230), but is briefly discussed here to recognise new names and concepts within its variation. The intraspecific taxonomy of P. pinaster is complex and understudied. While subsp. renoui

Plate 411. The grass stage of Pinus palustris, photographed here at Tregrehan, is an adaptation to surviving fires, but it results in a remarkable specimen for the garden. Image J. Grimshaw.

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New Trees

is geographically isolated in North Africa, the distributions of subsp. escarena and subsp. pinaster overlap in the western Mediterranean. In part this is due to the use of these trees in land reclamation – the largest man-made forest in the world being the 900,000 ha Les Landes plantation, predominantly of P. pinaster, along the Atlantic coast of France. The morphological characters used to identify the subspecies are at best tenuous, and a fresh study is needed to make sense of these characters and the wealth of synonyms in use. 1a. Leaves 18–25 cm long; cones 14–22 cm long; western Mediterranean (southeast France, Italy, Malta, Spain) .................................................................... subsp. escarena 1b. Leaves 10–20 cm long; cones 9–18 cm long ................................................................................... 2 2a. Umbo prominent and pyramidical, with a spike; North Africa ...................................... subsp. renoui 2b. Umbo flat or slightly raised, without a spike; Atlantic coast of Europe (France, Portugal, Spain) ......................................................................................... subsp. pinaster

Pinus pinaster subsp. escarena (Risso) K. Richt. Syn. P. pinaster subsp. hamiltonii (Ten.) Villar, P. pinaster var. mesogeensis (Fieschi & Gaussen) Silba This subspecies has longer leaves than the type (18–25 cm long vs. 10–20 cm), and larger cones (14–22 cm long vs. 9–18 cm). Farjon 2005a. Distribution FRANCE: Corsica, Mediterranean coast; ITALY: mainland west coast, Sardinia, Sicily; MALTA; SPAIN: Balearic Is., Mediterranean coast. Habitat Low-lying coastal plains in sandy soils, between 0 and 400 m asl (to 900 m asl in Corsica). USDA Hardiness Zone 8. Conservation status Not evaluated.

Pinus pinaster subsp. renoui (Villar) Maire Syn. P. pinaster var. maghrebiana Villar Subsp. renoui has prominent, pyramidal umbos that are armed with a spike. The seed scales are acute and 1.25–2.4 cm long. Farjon 2005a. Distribution ALGERIA: coast by Tunisian border; MOROCCO: northern provinces (Aberdouz, Agoudim, Amassine, Anefgou); TUNISIA: coast by Algerian border. Habitat Atlas Mts., to 2000 m asl. USDA Hardiness Zone 8. Conservation status Endangered.

Pinus pinaster is a commonly grown tree in western Europe, and its value has been recognised in the form of an Award of Garden Merit by the Royal Horticultural Society. It is particularly successful on sandy soils, and develops from a gawky adolescence into a handsome older tree. It is probable that individuals in cultivation are principally subsp. pinaster, and equally probable that they are not distinguishable with any degree of certainty. If future collections are made in the wild, however, the locality and varietal attribution of the population(s) should be retained with the trees. It is less likely that subsp. renoui will be found in general cultivation, but there is a specimen at Benmore, accessioned in 1976 (from a collection made by Sendergaard in Morocco), and there are several trees at Kew of similar age.

Pinus pinceana Gordon

Pince’s Pinyon, Weeping Pinyon

(Subgen. Strobus, Sect. Parrya) Tree to 12 m, trunk short, contorted, often forked, 0.2–0.3 m dbh. Bark thin, smooth, greyish brown; in older trees smooth, thin, breaking into irregular plates divided by longitudinal and rarely horizontal fissures on lower trunk. Crown broad, open and irregular, with some young branches trailing along the ground. Branchlets long, slender, flexible, arching, drooping and ultimately pendulous, greyish brown to grey; vegetative

Section II. Species Accounts

Pinus

615

buds inconspicuous, not resinous. Leaves in fascicles of three (to four), persisting for two to three years, in sparse tufts near the ends of branchlets, straight and rigid on pendulous shoots, drooping on stronger shoots, greyish green, triangular in cross-section, 5–12(–14) × 0.08–0.12 cm, apex acute. Fascicle sheaths to 1 cm long, slowly deciduous. Cataphylls 0.3–0.4 cm long, early deciduous. Male strobili purplish or yellowish, ovoid-oblong, 0.8–1 × 0.4–0.5 cm. Female cones lateral, not on ultimate branches, solitary or rarely in pairs; peduncles brittle, slender, straight or curved. Cones 5–10 × 3.5–6(–7) cm, green, ripening yellow-brown to orange-brown, mature in about 18 months; mature cones ovoid-oblong or cylindrical, sometimes irregular. Scales 60–80, opening partially or fully, thick, softly woody; apophysis irregularly domed, lustrous yellow- to orange-brown, occasionally with concentric rings due to irregular rainfall; umbo dorsal, grey with a minute prickle. Seeds golden-brown (infertile seeds paler), 11–13 mm; wings vestigial, remaining attached to the cone scales. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Coahuila, Hidalgo, Querétaro, San Luis Potosí, northern Zacatecas. Habitat Slopes and ravines in arid and semi-arid mountains, between 1400 and 2300 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT615. Cross-reference K231.

Pinus pinceana is another attractive pine that has great horticultural prospects, but as yet is little known in gardens. It forms a short, bushy tree of the usual pinyon sort but with a distinctly weeping habit. The needles are an attractive bright green, though young plants bear glaucous juvenile leaves for several years. In the wild it grows in very arid situations, with a selection of strongly xerophytic plants including Ferocactus, Opuntia and Agave, suggesting that it is suitable for dry sites (Gymnosperm Database 2007f). Gatherings have been made by several collectors, including Frankis 100 from Coahuila in 1991, and Gardner & Knees 5126 from Hidalgo in 1993, trees from both of which have been outhoused from Edinburgh. A first attempt at Tregrehan failed, probably because the seedlings were planted too young, but older plants have become established and are now about a metre high (T. Hudson, pers. comm. 2007). P. pinea L. B237, S379, K231 P. pityusa (NOW P. brutia var. pityusa (Steven) Silba, NT593) B216, K231 P. ponderosa Douglas ex C. Lawson B238, S379, K231

Pinus pseudostrobus Lindl.

P. ponderosa var. arizonica (NOW P. arizonica Engelm. var. arizonica, NT587) K231 P. ponderosa var. scopulorum Engelm. B238, S380, K233 P. pringlei Shaw K233

Smooth-bark Mexican Pine

(Subgen. Pinus, Sect. Trifolius) Tree to 45 m, trunk erect, 0.2–0.45 m dbh. Bark smooth, reddish to greyish brown, in older trees thick, scaly, dark greyish brown, breaking into elongated plates divided by deep, longitudinal fissures. Crown dense, wide, rounded or domed. Branchlets glaucous, slender, smooth; vegetative buds not resinous. Leaves in fascicles of (four to) five (to six), persisting for two to three years, in lax, pendent tufts on upturned branches, light green to glaucous, straight, slender, triangular in cross-section, (18–)20–30(–35) × 0.08–0.13 cm, apex acute. Fascicle sheaths 1.5–3.5 cm long, lustrous reddish brown. Cataphylls 1–1.5 cm long, falling soon after fascicles. Male strobili purplish or pinkish yellow, ovoid-oblong to cylindrical, 2–3.5 × 0.5–0.7 cm. Female cones subterminal, solitary or rarely in whorls of three to four; peduncles stout, short, persisting with a few attached scales after dispersal. Cones 7–16 × 6–13 cm, purplish to pinkish brown, mature in winter at about 20 months old; mature cones ovoid-oblong, asymmetrical, often curved. Scales 140–190, opening to release the seeds, thick, woody, straight or slightly curved; apophysis nearly flat to prominently raised, brown; umbo dorsal, darker than apophysis, with or without a prickle. Seeds dark greyish brown; wings effective, 2–2.5 × 0.7–1 cm, yellowish brown, translucent. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution EL SALVADOR;

Plate 412. Pinus pinceana is typical of other pinyon pines in its low stature, but unusual in having somewhat pendulous shoots. Image S. Knees.

616

Pinus

New Trees

GUATEMALA; HONDURAS; MEXICO: Chiapas, Durango, eastern Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Oaxaca, Puebla, Sinaloa, Tlaxcala, Veracruz. Habitat Montane or high-montane forest between 850 and 3250 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT584, NT617. Cross-references B229, K233.

Pinus pseudostrobus var. apulcensis (Lindl.) Shaw Syn. P. apulcensis Lindl., P. oaxacana Mirov The apophyses of var. apulcensis are elongated and prominently raised, at least in the lower part of the cone. The umbo is elongated and at an angle to the transverse keel. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution EL SALVADOR; GUATEMALA; MEXICO: Chiapas, Guerrero, Hidalgo, México, Oaxaca, Puebla, Tlaxcala, Veracruz. Habitat Often sympatric with the type variety, though absent from the driest areas. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Farjon & Styles 1997; NT580.

Pinus pseudostrobus is one of the most attractive pines, with its long, glossy green needles hanging elegantly from the shoots; in the right light conditions they shimmer beautifully. It is not a ‘new’ tree at all, having been introduced in 1839 according to Mitchell (1972), who gave the statistics of several notable specimens, including one at Pencarrow, Cornwall, planted in 1849, that was 20 m tall (68 cm dbh) in 1956 (albeit by then in a moribund state). Other trees over 20 m have been recorded in southern England by TROBI, though it seems that none of such size now remain. There are, however, plenty of younger ones coming on to replace the older generation, and these are doing well in many gardens in southern and western England, including Kew, the Sir Harold Hillier Gardens and Tregrehan, each of which has fine trees. The current champion is probably the magnificent individual growing near the big Quercus rysophylla in the Brentry House area of the Hillier Gardens, received in 1987 and measured at 15.7 m (70 cm dbh) in 2007. Trees at Kew come from James Russell’s collections (nos. 419 and 429) in Veracruz in 1983, specimens from which are 10 m and 10–12 m tall (respectively). The branches of P. pseudostrobus spread widely and the tree forms a broad, rounded crown, in its vigorous youth at least; it needs plenty of space to do itself justice. Some specimens are identified as P. pseudostrobus var. apulcensis, or are grown under its synonym P. oaxacana. They seem to do as well as var. pseudostrobus, and are indistinguishable as sterile plants. A specimen labelled P. oaxacana is growing happily at Ness and was 7 m tall in 2006. It originates from a collection made in Puebla in 1995 by G. Pattison, P. Catt and M. Hickson (PCH MEX 366). Pinus pseudostrobus is rare in continental Europe and has only a limited presence in North America, in California, but could certainly be grown in western France and the western United States. An ideal provenance would be from higher altitudes in the more northerly part of its range, but this may be an unattainable counsel of perfection and it would be worth planting any material of P. pseudostrobus obtainable. Pinus estevezii (Martínez) J.P. Perry (syn. P. pseudostrobus var. estevezii Martínez), from northeastern Mexico (Coahuila, Nuevo León, Tamaulipas), is recognised by Perry (1991) but not by Farjon & Styles (1997). It is distinct from P. pseudostrobus in its stouter branches and low, broad crown, to 15–20 m tall, and grows at low altitudes (800–1800 m) in a much drier climate than P. pseudostrobus. The foliage is spreading and less pendulous, the leaves 20–30 × 0.1 cm. The cones are stout, 9–14 cm long, and the scales have a swollen apophysis, with a small but prominent umbo spine. Although seed of this taxon has been collected on occasions in the past it has failed to become established, and is currently represented in cultivation only by very young seedlings (K. Rushforth, pers. comm. 2008).

Section II. Species Accounts

Pinus

617

C B A 1 cm 1 cm

1 cm

P. pumila (Pall.) Regel B218, K233 P. pungens Lamb. B238, S380, K233

Figure 69 (above). Pinus pseudostrobus var. pseudostrobus: habit (A); leaf fascicle (B); seed cone (C).

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New Trees

Pinus quadrifolia Parl. ex Sudw.

(Subgen. Strobus, Sect. Parrya)

Parry Pinyon

Syn. P. juarezensis Lanner Shrub or tree to 15 m, trunk short, often leaning or forked, 0.3–0.5 m dbh. Bark thick, dark reddish grey, scaly on lower trunk. Crown open, regular in young trees, becoming irregular with age. Branchlets stout, rough; vegetative buds 0.6–1 cm, pale buff, not resinous. Leaves in fascicles of (three to) four to five, persisting for three to seven years, slightly curved, rigid, epistomatic, dark green on outer face, glaucous blue-white on inner faces, triangular in cross-section, 3–5 × 0.1–0.15 cm, apex acute. Fascicle sheaths to 0.5–0.8 cm long, light buff-brown. Cataphylls 0.5–0.7 cm long, grey. Male strobili yellow, ovoid to subglobose, 0.5–0.8 cm long. Female cones subterminal, solitary or in whorls of two to three; peduncles short, nearly sessile, with semi-persistent cataphylls. Cones 4–6 × 4.5–7 cm, dark green, maturing yellow-brown to red-brown, mature in about 18 months; mature cones ovoid-conical to subglobose with rounded base, forming an irregular rosette when fully open. Scales 30–50 (of which 6–12 fertile), opening widely, weakly attached to cone rachis; apophysis pyramidal, yellowbrown to red-brown, smooth or finely wrinkled; umbo dorsal, 6–8 mm wide, flat to slightly raised, dark brown to grey with minute, deciduous prickle. Fertile seeds dark yellow-brown (infertile seeds pale buff), 1.2–1.8 × 0.8–1.2 cm; wings vestigial, remaining attached to seed scale. Perry 1991. Distribution MEXICO: northern Baja California; USA: southern California. Habitat Mountain ranges between 900 and 2700 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Perry 1991. Cross-reference K234.

Pinus quadrifolia is related to P. monophylla (Malusa 1992, Gernandt et al. 2003) but also shows similarities to the P. johannis – P. culminicola group, with cones similar to the former and epistomatic foliage more like the latter. It hybridises extensively with P. monophylla in the wild; Lanner (1974) suggested that the type specimen of P. quadrifolia was one of these hybrids and described P. juarezensis to cover plants considered to be free of P. monophylla introgression, but this interpretation is rejected by Farjon & Styles (1997). There have been several introductions to cultivation. Harold Hillier received seed in the 1970s (K. Rushforth, pers. comm. 2007), which was probably the source of a specimen at the Hillier Gardens, and there is a young tree at Kew. The dark green and glaucous foliage makes it an attractive shrub or small tree, well suited to very dry conditions. P. radiata D. Don B239, S380, K234

Pinus remota (Little) D.K. Bailey & Hawksw.

Paper-shell Pinyon

(Subgen. Strobus, Sect. Parrya) Syn. P. catarinae Rob.-Pass. Shrub or tree to 11 m, trunk short, contorted, often forked, 0.15–0.4 m dbh. Bark thin, smooth, but soon flaking, grey; in older trees thick, rough, scaly, grey to black, breaking into thin, scaly plates with longitudinal fissures in lower trunk. Crown dense, shrubby. Branchlets slender, rough; vegetative buds inconspicuous, not resinous. Leaves in fascicles of two (to three), persisting for four to five years, curved to falcate, rigid, amphistomatic, yellowish green or slightly glaucous, semicircular in cross-section (triangular in three-leaved fascicles), (2–)3–4.5(–5.5) × 0.08–0.11 cm, apex acute. Fascicle sheaths to 0.5 cm long, light brown. Cataphylls 0.5 cm long, grey. Male strobili pink or purplish to yellow, ovoid to subglobose, 0.4–0.5 cm long. Female cones subterminal, solitary or rarely in pairs; peduncles slender, curved, 0.5–0.8 cm long, with semi-persistent cataphylls. Cones (2–)2.5–4 × 3–6 cm, purplish to yellowish brown, mature in about 18 months; mature cones globose or subglobose with flat base, forming an irregular rosette when fully open. Scales 25–35, opening partially, weakly attached to cone rachis; apophysis raised, glossy yellow-brown; umbo dorsal, very small, 3 mm wide, recessed, dark brown to grey with minute, deciduous prickle. Fertile seeds dark grey (infertile seeds yellowish brown), 1.2–1.6 × 0.8–1 cm; wings vestigial, remaining attached to seed scale. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Chihuahua, Coahuila, western Nuevo León; USA: Texas (Edwards Plateau, western Río Grande valley). Habitat Isolated canyons and rocky mountain slopes between (450–)1200 and 1850 m asl. USDA Hardiness Zone 7–8. Conservation status Lower Risk. Illustration Perry 1991.

Otherwise resembling many other pinyon pines, Pinus remota is noteworthy for its very thin seed coat, which makes extraction of the nuts rather convenient. One of its

Section II. Species Accounts

Pinus

apparently few introductions to cultivation was made by Keith Rushforth (KR 0539), who bought a handful of seeds otherwise destined for consumption from a market in Saltillo, Coahuila. A tree from this source has been growing at Tregrehan since 1994 and is now about 2.5 m tall, although Tom Hudson (pers. comm. 2007) notes that its short needles on stiff branches do not make it the most attractive of pines. It is also grown at Berkeley, from collections by Frank Callahan in Nuevo León in 1985 and 1986. Pinus remota is said to be the most drought- and heat-tolerant of all the pinyons, and it also accepts alkaline soils (Texas Native Trees 2008), making it particularly useful for arid alkaline sites in the southwestern United States or Mediterranean Europe. P. resinosa Aiton B240, S380, K234 P. ×rhaetica Brügger K234 P. rigida Mill. B240, S380, K234 P. roxburghii Sarg. B217, K236 P. rudis (NOW P. hartwegii Lindl.) B228

Pinus serotina Michx.

P. rzedowskii Madrigal & M. Caball. K236 P. sabiniana Douglas ex D. Don B241, S380, K236 P. ×schwerinii Fitschen B225, S376, K236

(Subgen. Pinus, Sect. Trifolius)

Pond Pine, Pocosin Pine

Syn. P. rigida subsp. serotina (Michx.) R.T. Clausen Pinus serotina is sometimes referred to as a variety or subspecies of P. rigida Mill., and their respective ranges overlap. The two species form a hybrid zone in the Delmarva Peninsula, although P. serotina also hybridises with P. taeda. In most respects the morphology of P. serotina is very similar to that of P. rigida but there are some differences, as described below, and they also have distinct habitat preferences. The leaves of P. serotina are slender and flexible, and 15–20 cm long, while those of P. rigida are (as the name suggests) rigid, and 7–14 cm long. The cones of P. serotina are almost spherical, 5–9 × 5–7 cm, yellow, serotinous, the umbo with a weak, early deciduous prickle, and they are mature in about 18 months; in P. rigida, by contrast, cones are ovoid-conical, 3–7(–9) × 3–4 cm, yellow-brown, opening at maturity, and the umbo is armed with a short, rigid prickle. Serotinous cones are characteristic of P. serotina, but in coastal New Jersey and Maryland cones of P. rigida are serotinous also. When not in cone, P. serotina is very similar to P. taeda, though the former has very resinous buds while the latter does not. Thieret 1993, Farjon 2005a. Distribution USA: Alabama, Delaware, Florida, Georgia, Maryland, New Jersey, North Carolina, South Carolina, Virginia. Habitat Low, wet flatlands and peat-rich or sandy swamps in the Coastal Plain, between 0 and 60 m asl. For comparison, P. rigida is a montane species, only reaching the coast in the north of its range (between 0 and 1500 m asl). Both species are adapted to fire, and young trees can regenerate after coppicing. USDA Hardiness Zone 7. Conservation status Lower Risk. Illustration Farjon 2005a. Cross-references B241, K236.

Bean (1976b) dismissed Pinus serotina as tender, but more accurately, it is one of the southeastern Coastal Plain species that really requires a hot summer to thrive. It will grow reasonably well in southern England, as demonstrated by several half-decent trees of 10 –15 m at Kew, and on the East Coast of the United States as far north as Philadelphia. Beyond its interest to collectors, however, it has no horticultural merit. P. sibirica Du Tour B218, K236 P. ×sondereggeri Chapm. K236

Pinus strobiformis Engelm.

P. stankewiczii (NOW P. brutia var. pityusa (Steven) Silba, NT593) K236

Southwestern White Pine

(Subgen. Strobus, Sect. Quinquefolius) Syn. P. ayacahuite var. brachyptera G.R. Shaw, P. ayacahuite var. novogaliciana Carvajal Tree to 30 m, trunk straight and erect, 0.8–1 m dbh. Bark thin, smooth, silvery grey; in older trees thick, rough, scaly, dark brown to grey, breaking into small, irregular plates. Crown initially conical or pyramidal, becoming rounded or irregular in mature trees. Branchlets reddish brown, smooth, glabrous; vegetative buds not or

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New Trees

slightly resinous. Leaves in fascicles of five, in dense tufts near the ends of ultimate branches, persisting for three to five years, straight or slightly curved, sometimes slightly twisted, dark green or glaucous, triangular in cross-section, (5–)7–11(–12) × 0.06–0.11 cm, margins serrulate, apex acute. Fascicle sheaths 2–2.5 cm long, orange-brown, rapidly disintegrating. Cataphylls 0.5–1 cm long, brown. Male strobili yellow to orange-brown, ovoid-oblong to cylindrical, 0.6–1 cm long. Female cones subterminal and axillary, solitary or rarely in pairs or in whorls of three to four; peduncles stout, 1.5–2.5 cm long, erect then pendulous, falling with the cone. Cones 12–30(–60) × 7–11 cm, greenish purple to light brown, mature in about 18 months; mature cones variable, mainly cylindrical, often slightly curved. Scales 70–120, opening obliquely; scales thick, woody; apophysis usually rather resinous, light yellowish brown; umbo terminal, greyish brown, resinous. Seeds reddish brown to brown, 1.2–1.8 × 0.8–1.1 cm; wings vestigial, forming a fringe around the seed. Thieret 1993, Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: Chihuahua, Coahuila, Durango, Jalisco, western Nuevo León, San Luis Potosí, Sinaloa, Sonora, Zacatecas; USA: Arizona, New Mexico, Texas (Trans-Pecos). Habitat Typically occurs on north-facing slopes and along mountain streams between 1900 and 3500 m asl. USDA Hardiness Zone 5. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a; NT580. Cross-references K237 (B213, S373, K210 as P. ayacahuite var. brachyptera).

Pinus strobiformis is little known in cultivation but in the wild forms a substantial tree, with a relatively narrow crown in its youth, although this becomes more rounded with age, with far-reaching branches. It is related to P. ayacahuite and resembles it in many characters, but its leaves are shorter and the average sizes of its handsome cones are smaller. The seeds of P. strobiformis are functionally wingless (Perry 1991). Northern populations (United States, northernmost Mexico) are intermediate between P. strobiformis as described by Engelmann, from southern Chihuahua, and P. flexilis, with smaller cones (12–22 cm) and needles with only a few apical serrations, and have been distinguished as P. flexilis var. reflexa Engelm. or P. reflexa (Engelm.) Engelm. (Farjon & Styles 1997, Farjon 2005a). These northern trees are commonly cultivated in the United States and seem to have a wide tolerance, growing even in the Chicago area (for example, at the Morton Arboretum). In Europe P. strobiformis is much less familiar, although there are a few dwarf cultivars in circulation, and ‘Vanderwolf’s Pyramid’ is widely available (usually sold as P. flexilis). TROBI records a few individuals scattered through the United Kingdom, the recognised champion being an 11 m specimen at the Manor, Walton-in-Gordano, Somerset, measured by Owen Johnson in 2006. Two trees of 11 m and 10.8 m grow in the Hillier Gardens, where they were received in 1985 as P. ayacahuite (Priest 107), and it is possible that other specimens from this collection exist elsewhere (A. Coombes, pers. comm. 2008). It is also present in some collections in continental Europe, but could be grown much more widely. It is, however, very susceptible to white pine blister rust; there has been extensive mortality in New Mexico recently, since the disease invaded the state in 1990 (Conklin 2004), and a mature specimen at Hørsholm Arboretum in Denmark also died of it in 1986 (M. Frankis, pers. comm. 2007). Pinus veitchii Roezl from central Mexico has traditionally been included in P. ayacahuite as a variety, P. ayacahuite var. veitchii (Roezl) Shaw (see Bean and Krüssmann: B213, K210) – though one recent author (Businský 2004) treats it as a distinct species. It is much closer to P. strobiformis, however, matching it in cone scale thickness and seed size, and differing from it only in seed wing length and minor detail of curvature of cone apophysis. With its slender, thin-scaled cones and small seeds, it differs markedly from P. ayacahuite.

P. strobus L. B241, S381, K237 P. strobus f. nana (NOW P. strobus L. var. strobus) B242

Section II. Species Accounts

Pinus sylvestris L.

(Subgen. Pinus, Sect. Pinus)

Pinus

621

Scots Pine

This very familiar but magnificent species was described by Bean (B243, S381) and Krüssmann (K238). A large number of intraspecific taxa have been recognised within it, largely due to its huge distribution – the widest in the genus. Most of these were placed in synonymy by Farjon (2001), who recognised only two varieties, var. hamata and var. mongolica. These are grown in some collections and botanical gardens, and a key and brief botanical notes are provided below. For practical horticultural purposes, however, they are insignificantly distinct from any other P. sylvestris, and no horticultural commentary is necessary.

1a. Leaves remain blue-green in winter; apophyses often profoundly hooked; Balkans, Crimea, Caucasus, Turkey .............................................................................. var. hamata 1b. Leaves fade dull green to yellowish green in winter; apophyses not or only slightly hooked ......................................................................................... 2 2a. Buds usually extremely resinous; eastern Siberia, Mongolia, northern China .............. var. mongolica 2b. Buds usually slightly resinous; Eurasia (from Spain and Scotland to Pacific coast of Siberia) .............. var. sylvestris

P. sylvestris f. anguina Schröd. K242 P. sylvestris f. annulata Casp. K242 P. sylvestris var. argentea (NOW P. sylvestris var. hamata Steven, NT621) B244, K242 P. sylvestris var. armena (NOW P. sylvestris var. hamata Steven, NT621) K242 P. sylvestris f. bonapartei Seitz K242 P. sylvestris f. divaricata Wahlenb. K242 P. sylvestris var. engadinensis (NOW P. ×rhaetica Brügger) B244, K242 P. sylvestris f. erythranthera (NOW P. sylvestris L. var. sylvestris) K242 P. sylvestris f. fastigiata (Carrière) Beissn. B244 P. sylvestris f. gibberosa Kihlm. K242 P. sylvestris var. haguenensis (NOW P. sylvestris L. var. sylvestris) B244

Pinus sylvestris var. hamata Steven The leaves of the type variety turn dull green or even yellowish green in winter, but those of var. hamata remain strong blue-green. The apophyses of var. hamata are often hooked, though this character shows much overlap with var. sylvestris. It also differs significantly in resin composition. Mirov 1967, Farjon 2005a. Distribution ALBANIA; ARMENIA; AZERBAIJAN; BULGARIA; GEORGIA; GREECE; RUSSIAN FEDERATION: Caucusus; SERBIA & MONTENEGRO; TURKEY; UKRAINE: Crimea. Habitat Between 500 and 2600 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Cross-reference K242.

P. sylvestris f. kakateimos Graebn. K244 P. sylvestris f. kienitzii (NOW P. sylvestris L. var. sylvestris) K244 P. sylvestris var. lapponica (NOW P. sylvestris L. var. sylvestris) K244

Plate 413. A young, vigorous Pinus sylvestris var. mongolica growing at Kew. This is the easternmost variant of the species. Image J. Grimshaw.

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P. sylvestris f. latifolia Gordon K244 P. sylvestris f. lubonii Staszk. K244 P. sylvestris f. macrocarpa (NOW P. sylvestris L. var. sylvestris) K244

Pinus sylvestris var. mongolica Litv. The foliage of var. mongolica is dull and grey-green, with a tendency to become yellowish in winter. The buds are usually very resinous (though in some specimens of var. mongolica the buds are less resinous, while in some specimens of var. sylvestris they are very resinous). Fu et al. 1999c, Farjon 2005a. Distribution CHINA: Nei Mongol (northern Hinggan range); MONGOLIA; RUSSIAN FEDERATION: eastern Siberia, around Lake Baikal. Habitat Dry slopes with sandy soils, between 300 and 2000 m asl. USDA Hardiness Zone 2. Conservation status Not evaluated. Illustration Fu et al. 1999c; NT621.

P. sylvestris var. nevadensis (NOW P. sylvestris L. var. sylvestris) K244 P. sylvestris f. parvifolia (NOW P. sylvestris L. var. sylvestris) K244 P. sylvestris var. rigensis (NOW P. sylvestris L. var. sylvestris) B245, K244 P. sylvestris var. scotica (NOW P. sylvestris L. var. sylvestris) B245, K244 P. sylvestris f. seitzii (NOW P. sylvestris L. var. sylvestris) K245 P. sylvestris f. spiralis Carrière K245 P. sylvestris f. tortuosa Don K245 P. sylvestris f. turfusa Woerl. K245

Pinus tabuliformis Carrière

(Subgen. Pinus, Sect. Pinus)

Chinese (Red) Pine

This species was described by Bean (B245, S381) and Krüssmann (K245). A key to the varieties, adapted from Fu et al. (1999c), is presented below. Pinus tabuliformis var. henryi is treated here as P. henryi (p. 603).

1a. Trunk monopodial at the base, then branching to form a fan-shaped crown; China (Hebei, Liaoning) .................................................................................... var. umbraculifera 1b. Trunk monopodial, crown conical then flat-topped ......................................................................... 2

Plate 414. Burgeoning male strobili and new shoots enliven the usually sombre appearance of Pinus tabuliformis var. mukdensis. It is well established at Kew, but probably of ‘botanical interest only’. Image J. Grimshaw.

2a. Bark dark grey; branchlets greyish yellow to greyish brown; China (Jilin, Liaoning), North Korea ........................................................................ var. mukdensis 2b. Bark pale grey, brown-grey or reddish grey; branchlets yellowish brown; China (Gansu, Hebei, Henan, south Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan) .................................................... var. tabuliformis

P. tabuliformis var. densata (NOW P. densata Mast., NT597) K245

Pinus tabuliformis var. mukdensis (Uyeki ex Nakai) Uyeki This variety has dark grey bark (pale grey, brown-grey or reddish grey in var. tabuliformis) and more widely splayed needles than in the type. The branchlets are initially greyish yellow and then turn greyish brown (in the type they are yellowish brown). Fu et al. 1999c. Distribution CHINA: Jilin, Liaoning; NORTH KOREA. Habitat Wooded hills and mountains. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT622.

Pinus tabuliformis var. mukdensis has been grown at Kew since 1979, when plants were donated by the Arboretum of the Chinese Academy of Forestry in Beijing. The trees have done well and have reached 10 m in height, producing abundant cones, but

Section II. Species Accounts

Pinus

though worthy specimens they are distinctly dull. Perhaps, as in var. tabuliformis, they will attain a picturesque old age. The taxon is also occasionally grown by specialist collectors, as at the Anthoine Pinetum in Belgium, but is rare. Wilson 8815, collected in Korea, also belongs to this variety, and specimens under this number are growing at several arboreta (M. Frankis, pers. comm. 2007). Unlike the other varieties with monopodial stems, P. tabuliformis var. umbraculifera T.N. Liou & Q.L. Wang branches early, forming a fan-shaped crown (Fu et al. 1999c). This character may be induced by environmental factors, or the taxon may derive from horticultural selections, in which case a cultivar group name might be more appropriate (M. Frankis, pers. comm. 2007). It is not known to be in cultivation, but is of potential interest in ornamental horticulture.

Pinus taeda L.

(Subgen. Pinus, Sect. Trifolius)

Loblolly Pine

Tree to 45 m, trunk straight, erect or slightly crooked, 0.5–1 m dbh. Bark thin, scaly, blackish; in mature trees reddish brown to grey, breaking into flat, rectangular plates separated by longitudinal fissures. Crown dense and compact, rounded. Branchlets glabrous, yellowish brown, slender to stout; vegetative buds not resinous. Leaves in fascicles of (two to) three (to four), persisting for three to four years, long, slender, stiff, sometimes slightly twisted, pale green, triangular in cross-section, 15–22 cm long, apex acute. Fascicle sheaths 2.5 cm long, persistent. Cataphylls brown, deciduous. Male strobili yellow, cylindrical, 1.5–3 cm long. Female cones subterminal, solitary, sessile or with a short peduncle; cone 5–12(–15) cm long, yellow-buff to greybuff, mature in about 18 months; mature cones ovoid-cylindrical, sometimes leaving basal scales attached to branchlets when falling. Scales 110–140; apophysis flattened or wrinkled; umbo dorsal, armed with a sharp, stout spine. Seeds dark brown with black dots; wings effective, 2–2.5 cm long. Thieret 1993, Farjon 2005a. Distribution USA: Alabama, Arkansas, Delaware, northern Florida, Georgia, Louisiana, Maryland, Mississippi, southern New Jersey, North Carolina, southeast Oklahoma, South Carolina, southern Tennessee, eastern Texas, Virginia. Pinus taeda is an aggressive coloniser of secondary habitat, and has escaped from plantations in many countries where it is planted for timber. Habitat Flatlands and rolling hills between 0 and 700 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Farjon 2005a; NT624. Cross-reference K245. Taxonomic note Pinus taeda forms a natural hybrid (P. ×sondereggeri) with P. palustris Mill. where their ranges overlap.

Of all the American East Coast pines, Pinus taeda has the widest range. It was introduced to England by Bishop Compton before 1713 and has been in continuous cultivation since then (Elwes & Henry 1910), so its omission by Bean (1976b) is rather curious. It grows reasonably well in southern England and forms an attractive rather bushy-looking canopy, but inadequate summer heat sometimes manifests itself in slow growth and crooked stems, and in the cones being small (under 8 cm) and not maturing properly. There are specimens in several collections, including trees of 15 m or more at Kew, Bicton, Wakehurst Place and Bedgebury. In continental Europe it is not frequently grown, although it has the potential to flourish in many areas. It does very well around Bordeaux, for example (Elwes & Henry 1910). In the eastern United States it is too conspicuous and frequent in the countryside to be particularly desirable as a garden specimen, although it is often planted by landscapers (Dirr 1998). It certainly thrives as far north as Philadelphia, where a 15-year-old specimen at the Scott Arboretum was 12 m tall in 2006. By far the most interesting and horticulturally useful versions of P. taeda are the dwarf trees growing principally at the JC Raulston Arboretum. ‘Dwarf’ is a misleading term in this case, as it suggests a low bushy plant. These, rather, are slow-growing short trees with dense rounded heads: ‘semi-dwarf’ might be a better designation for them. J.C. Raulston himself (1987) wrote up their history and attributes: ‘Among the

623

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New Trees

Plate 415. A group of specimens of Pinus taeda NCSU Dwarf Group – superb short-statured pines, with huge landscaping potential if only they could be propagated sufficiently easily. Image B. Ward.

finest plants in the NCSU Arboretum is a group of about forty-five 30 year-old [sic] dwarf loblolly pines which arose as seedlings from witches broom cones originally collected by university forestry researchers. The slow growing seedlings now vary in size from 8’ to 15’ in height [2.4–4.6 m] with beautiful dense rounded crowns. Few dwarf pine cultivars are well adapted to the heat of the south and these pines would be magnificent ornamentals if commercially produced. Unfortunately [they] must be produced by side-veneer grafting on seedling loblolly pine understock. Southern growers do not graft conifers, and the northern growers who do graft pines do not have easy access to either understock or stock plants to produce the plants, so they remain unavailable. Perhaps one of the most beautiful and useful potential landscape plants in existence for southern gardens …’ Several accounts of the origin of these exceptional pines have circulated, but the definitive version is provided in a master’s thesis by a North Carolina State University student, Gery Allan Glover (Glover 1987), summarised here by Bobby Ward (pers. comm. 2007): ‘The seed from which they were grown was collected from a witch’s broom in a single tree in Virginia in 1964, as part of a NCSU Tree Improvement Program directed by Dr. John Duffield (NCSU Forestry Department). The seeds were germinated by James Cunningham, as an undergraduate research project. Duffield was interested in producing dwarfing rootstocks for loblollies for possible candidate Christmas tree production. At the conclusion of the Duffield-Cunningham project (apparently only a year or so later), Duffield offered plants to Dr. Fred Cochran (NCSU Horticulture Department). Cochran took cuttings from two-year old individuals that exhibited the dwarf habit in 1966, which at the time were 12 to 14 inches tall, compared to normal trees from the same seed lot which were then 3 to 4 feet tall.’ It was the trees raised from these cuttings (the seedlings themselves were destroyed) that were planted on and around the current JC Raulston Arboretum site and elsewhere (Glover 1987), though some were subsequently transplanted from their original positions by J.C. Raulston. By 2007 they had reached heights of between 4.6 and 6 m and developed rounded crowns 4–4.6 m wide. There is slight variation in stature between the individuals. Clonal propagation is limited by the difficulty of grafting mature growth, but seed raised from these trees gives about 20 per cent dwarf seedlings, recognisable after 4–5 months of growth. A batch of such seedlings raised at the JC Raulston Arboretum in 2006 has been distributed to nurserymen and other

Section II. Species Accounts

Pinus

625

gardens. Cuttings from seedlings can be rooted, and juvenile material grafts more easily (D. Werner, pers. comm. 2007). It is to be hoped that this will lead to their more widespread distribution in the southeastern United States, as J.C. Raulston wished to see. Prior to this, the only commercial distribution of this unusual form was a limited release of grafted trees in 2004 by Yucca Do Nursery, Hempstead, Texas, under the name ‘J.C. Raulston’ – although these were not propagated from a single clone (T. Doremus, pers. comm. via B. Ward 2007). (This paragraph was compiled from information provided by T. Avent, L. Hatch (including his New Ornamentals Society website, on P. taeda: Hatch 2005), B. Ward and D. Werner.) The trees at the JC Raulston Arboretum have been known collectively as P. taeda ‘Nana’, but as this is a post-1959 name it is invalid under the Cultivated Plant Code. Since the trees form a population with shared characters they should be treated as a cultivar group. The name Pinus taeda NCSU Dwarf Group has been proposed for them by Larry Hatch (2005), via the website of the New Ornamentals Society, and is adopted here with the approval of Dr Dennis Werner, Director of the JC Raulston Arboretum. This name covers all the ‘dwarf’ trees at and around the JC Raulston Arboretum and their progeny. The plants distributed by Yucca Do as ‘J.C. Raulston’ should be regarded as part of the NCSU Dwarf Group. Other dwarf selections from witches’ brooms, however, such as ‘Little Albert’, distributed by Louisiana Nursery as grafted specimens, should not be considered part of the NCSU Dwarf Group.

Pinus taiwanensis Hayata

(Subgen. Pinus, Sect. Pinus)

Taiwan Black Pine

Tree to 35 m, trunk straight, erect, to 1 m dbh. Bark rough, greyish brown to dark grey, breaking into plates separated by deep, longitudinal fissures. Crown open, ovoid to rounded, branches starting low on the trunk. Branchlets greenish brown, slender; vegetative buds not or slightly resinous. Leaves in fascicles of two, rigid, very thin, sometimes slightly twisted, semicircular in cross-section, 4.5–17 × 0.06–0.1 cm, margins serrulate, apex acute. Fascicle sheaths 0.5–1.4 cm long, persistent. Cataphylls reddish brown, 0.5 cm long, deciduous. Male strobili reddish or yellowish brown, 1–2 × 0.3–0.4 cm. Female cones subterminal, 3–6 × 3–5 cm, light chocolate-brown, mature cones ovoid or ovoid-conical, mature in about 20 months, persistent. Scales 1.8 × 0.8–1 cm; apophysis flat, slightly wrinkled; umbo dorsal, sometimes with a deciduous prickle. Seeds ellipsoid to ovoid; wings 1–1.4 × 0.5–0.6 cm. Li & Keng 1994a, Fu et al. 1999c, Farjon 2005a. Distribution TAIWAN. Habitat Montane forests inland and on the coast, between 750 and 2800 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk. Illustration Farjon 2005a; NT625. Cross-references S375, K245.

According to Mitchell (1972), Pinus taiwanensis was introduced to the British Isles in about 1930 and maintained a slim presence in cultivation thereafter, particularly at Borde Hill, West Sussex, where several were planted. Several recent expeditions have brought it back from Taiwan, notably groups from Kew in 1992 (ETOT 29, 155) and Edinburgh in 1993 (ETE 15, 64, 192). From these and other collections it is well established in cultivation, and it is currently available commercially both in the United States and in the United Kingdom. It seems to grow well in the British Isles, though it can sometimes be rather spindly (Flanagan & Kirkham 2005). At Wakehurst Place a tree from ETOT 29 was 6 m tall in 2005, while at Howick an ETOT 155 sapling was 4 m tall. In the wild it grows in rich mixed forests, but the ETOT collection notes mention that in Nantou Co. at least, where both these gatherings were made, it grows in very freely draining sites with little humus in the soil.

Plate 416. A damp-looking shoot of Pinus taiwanensis var. taiwanensis, photographed in Taiwan in 1992. Trees from the collection ETOT 155 are now well established in British arboreta. Image T. Kirkham.

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Pinus

New Trees

Pinus luchuensis Mayr is the Japanese representative of a group of closely related taxa that includes P. hwangshanensis as well as P. taiwanensis. It comes from low altitudes in the Ryukyu Islands, including Okinawa, and is likely to be tender in most of our area; it is, however, in cultivation at Berkeley.

P. teocote Schiede ex Schltdl. & Cham. B246, K245 P. thunbergii Parl. B246, S382, K246

Pinus torreyana Parry ex Carrière (Subgen. Pinus, Sect. Trifolius)

Torrey Pine, Del Mar Pine, Soledad Pine

Tree to 10(–23) m, though reaching 33 m or more in cultivation, trunk gnarled and irregular, 1 m dbh. Bark

Plate 417. The surviving population of Pinus torreyana subsp. torreyana occupies a small area of cliff tops north of San Diego, California. Most of the population is protected in the Torrey Pines State Reserve. Here the trees are stunted by the harsh conditions, but in cultivation they can become huge. Image J. Grimshaw.

smooth, dull grey; in older trees thick, scaly, dark reddish brown, weathering to grey, breaking into small plates divided by longitudinal fissures. Crown usually sparse and open. Branchlets glaucous, light green, though turning purplish brown; vegetative buds resinous. Leaves in fascicles of (four to) five, fascicles massive, persisting for two to three (to four) years, in large, terminal tufts, yellowish green to blue-green and glaucous, triangular in cross-section, 18–30 × 0.19–0.25 cm, margins serrate, apex acute. Fascicle sheaths huge, to 5 cm long, though weathering to 1–2 cm long. Cataphylls brown, deciduous. Male strobili 3.5–6 cm long. Female cones subterminal, solitary; peduncles stout, 2–4 cm long. Cones 9–16 × 10–13.5 cm, purplish brown through green to reddish brown, taking two and a half years to mature; mature cones ovoid-conical, symmetrical. Scales thick, woody, oblong, opening to release the seeds; apophysis pyramidal; umbo dorsal, 0.4–0.6 cm long, yellowish brown, with a broad spine. Seeds the second largest to be found in all pine species (after P. maximartinezii), 1.7–2.4 × 0.9–1.2 cm, ovoid, flattened, light to dark brown; wings ineffective, short and thick, 0.7–1 cm long, dark brown to black. Thieret 1993, Farjon 2005a. Distribution USA: California (Pacific coast north of San Diego). The single population extends 6 km along the coast and 1.6 km inland, and is divided by the Soledad River. Habitat Coastal slopes and ravines between 30 and 125 m asl. USDA Hardiness Zone 9. Conservation status Vulnerable. Most of the mainland population of P. torreyana is protected within the Torrey Pines State Reserve (Haller 1986). Illustration Farjon 2005a; NT583, NT626. Cross-reference K246.

Pinus torreyana, like P. radiata and Cupressus macrocarpa on the Monterey Peninsula, is another Californian conifer marooned on a cliff top by changing climatic circumstances. Like theirs, too, is its transformation from very unprepossessing, stunted little trees in the wild to magnificent specimens in cultivation. As seen in the Torrey Pines State Reserve on the coast north of San Diego, it is gnarled and dusty-looking, an appropriate companion to the yuccas and other xerophytic plants with which it grows. Away from there it can become huge, potentially developing a thick trunk and heavy limbs that support a rounded canopy, as in the San Francisco Botanical Garden. The largest recorded tree was 45 m tall (1.5 m dbh) at New Plymouth, New Zealand in 1982, and there are specimens of over 30 m throughout western California (Jacobson 1996). In North America it is considered to be frost-sensitive, but Arthur Lee Jacobson (2006) has recorded a tree of 10 m in Seattle. Jacobson gives the credit of its introduction to Britain to William Lobb in 1860. The traditional view, expressed in the ‘old’ RHS Dictionary of Gardening (Chittenden 1951), was that it was ‘Too tender for general cultivation in the British Isles’,

Section II. Species Accounts

Pinus

but in the light of changing climate patterns this statement is perhaps less true today. The champion tree, standing 22 m tall (53 cm dbh) in 2000 (TROI), enjoys the comparatively benign conditions of Powerscourt, Co. Wicklow, but there is a tree at the Sir Harold Hillier Gardens, planted prior to 1976, that is catching up with it rapidly, having reached 21 m (38 cm dbh) by 2007 (Sir Harold Hillier Gardens database). This suggests that, under current climatic circumstances, it could be planted much more widely in southern England and along the French coast. Growing in only a couple of groves on Santa Rosa Island in Santa Barbara Co., California is the island isolate known as P. torreyana subsp. insularis J.R. Haller. This differs in small details from subsp. torreyana, principally in having a broader, denser crown with bluish green leaves, cones that are broader (> 13.5 cm) than long, and smaller, darker seeds (mean > 1.1 cm wide). The endangered status and apparent isolation of this taxon have afforded it more interest than it perhaps deserves, as there are minimal genetic differences between the two populations (Waters & Schaal 1991). C.J. Earle considers that it is best to regard it at the varietal rank, as var. insularis (J.R. Haller) Silba (Gymnosperm Database 2008). Accessions of known origin should be maintained as such, especially as the Santa Rosa population is tiny and highly endangered, but the majority of cultivated specimens of P. torreyana are of unknown origin.

P. uncinata Ramond ex DC. (OR P. mugo subsp. uncinata (Ramond ex DC.) Domin) B230, K246 P. uncinata var. rotundata (Link) Antoine (OR P. mugo subsp. rotundata (Link) Janch. & H. Neumayer) B230, K246 P. virginiana Mill. B247, S382, K246 P. wallichiana A.B. Jacks. B247, S382, K246

Pinus wangii Hu & Cheng

Guangdong White Pine

(Subgen. Strobus, Sect. Quinquefolius) Tree to 20 m (rarely 30 m), trunk straight or crooked, 1 m dbh. Bark smooth to scaly, greyish to blackish brown, developing irregular, shallow, longitudinal fissures. Crown initially conical, then irregular and open, often flat-topped. Branchlets smooth, yellowish then reddish brown, sometimes glaucous when young, glabrous or variably pubescent; vegetative buds pale brown, slightly resinous. Leaves in fascicles of five (rarely two to four), short and stout, curved and often twisted, epistomatic, with a glossy blue-green outer face and greenish white to vivid white inner faces, triangular in cross-section, 3–6 × 0.1–0.16 cm, apex acute. Fascicle sheaths orange-brown, soon deciduous. Cataphylls to 0.4 cm long, early deciduous. Female cones single or in whorls of two to five, peduncles slender to medium-stout, 0.5–2.5 cm long. Cones 4–10 × 3.5–6.5 cm, slightly resinous, ovoid-cylindrical, mature in about 18 months, deciduous or persistent for a few years. Scales oblong-obovoid, thinly woody; apophysis yellow-brown, smooth, not thickened; umbo terminal, small, dark brown to black. Seeds ellipsoid-ovoid, 0.8–1.3 × 0.4–0.7 cm; wings pale brown, 0.4–1.8 × 0.5–1.0 cm. Fu et al. 1999c, Businský 2004. Distribution CHINA: Guangdong, Guangxi, Guizhou, Hunan, Yunnan; VIETNAM: Cao Bang Province. Habitat Occurs in mixed coniferous or broadleaved forests, on slopes and ridges between 500 and 1900 m asl. USDA Hardiness Zone 9–10. Illustration Fu et al. 1999c, Businský 2004.

The relationships of the Asian soft pines have recently been deciphered by Businský (2004); earlier literature is often very confused about the Pinus wangii group. Two recently described taxa are related to P. wangii: P. eremitana Businský (Vietnam, endangered) and P. orthophylla Businský (Hainan Island) (Businský 2004). Neither of these is known to be in cultivation, and both are probably too tender to be successful in our area (M. Frankis, pers. comm. 2007).

627

628

Pinus

New Trees

Pinus wangii subsp. wangii The type subspecies has strongly pubescent shoots, and leaves with inconspicuous stomatal bands. Businský 2004. Distribution CHINA: southeastern Yunnan. Habitat Restricted to steep limestone crags, between 1500 and 1800 m asl, though formerly down to 500 m before local deforestation (Businský 2004). USDA Hardiness Zone 9. Conservation status Endangered.

Pinus wangii subsp. kwangtungensis (Chun ex Tsiang) Businský Syn. P. kwangtungensis Chun ex Tsiang This subspecies has glabrous to thinly pubescent shoots, and leaves with vivid white stomatal bands. Businský 2004. Distribution CHINA: northern Guangdong, northeastern Guangxi, southern Guizhou, southern Hunan. Habitat Occurs on acidic volcanic and metamorphic rocks and granite outcrops, between 700 and 1600 m asl, and is the most widespread and numerous taxon in the group, stretching 550 km from east to west (Businský 2004). USDA Hardiness Zone 9. Conservation status Vulnerable. Illustration NT628. Taxonomic note This taxon has been included in P. fenzeliana Hand.-Mazz. by Farjon (2001, 2005a), but that species has been demonstrated by Businský (2004) to belong in subsection Flexiles, where it is related to P. armandii, rather than in subsection Strobus, where P. wangii is allied to P. parviflora. Pinus fenzeliana, from Hainan, is not in cultivation and is unlikely to be hardy.

Pinus wangii subsp. varifolia (Nan Li & Y.C. Zhong) Businský Syn. P. wangii var. varifolia Nan Li & Y.C. Zhong

Plate 418. Pinus wangii subsp. kwangtungensis produces cones from a very early age, as on this young specimen at Kew. The diagnostic white stomatal bands are clearly visible. Image J. Grimshaw.

This subspecies has fascicles with three to five leaves (uniquely for a white pine, all others fairly consistently having five). Businský 2004. Distribution CHINA: southwestern Guangxi; VIETNAM: Cao Bang Province. Habitat Occurs in scattered ridge-top populations, between 500 and 1400 m asl, over a narrow band of limestone 140 km long (Businský 2004). USDA Hardiness Zone 9. Conservation status Not evaluated.

Pinus wangii is related to P. parviflora, differing in its longer cone peduncle, more slender cones and stouter leaves. Its blue-green foliage is shorter, stouter and less pendulous than that of other white pines. Its constituent taxa have been the subject of much debate, now resolved, it is to be hoped, by Roman Businský’s extensive field studies (Businský 2004). Taxonomic wrangles aside, there is no doubt that these are all very attractive trees, with fine foliage and handsome cones. The cones appear at a surprisingly young age, as demonstrated by a young tree 1.3 m tall at Kew, which bore a few cones in 2005 and many more in 2007. This individual (labelled P. fenzeliana) was grown from seed collected as P. kwangtungensis in the Heng Shan of Hunan and distributed by the Shanghai Botanic Garden in 1993, and is a very pretty little tree. Another specimen from this source grows at Howick. The earliest introduction, however, was of seed received from northern Guangdong by the Washington Park Arboretum in 1940, and three trees from this accession are still growing there, having reached 10–11 m tall. They first produced cones in 1962 (R. Hitchin, pers. comm. 2007). These have been the source of material distributed to other collections in North America and Europe (K. Rushforth, pers. comm. 2007). Pinus wangii subsp. wangii has been cultivated by Keith Rushforth since 2003, and has reached a metre in height. P. washoensis (NOW P. ponderosa Douglas ex C. Lawson var. ponderosa) K248

Pinus yunnanensis Franch.

(Subgen. Pinus, Sect. Pinus)

Yunnan Pine

Syn. P. yunnanensis var. tenuifolia W.C. Cheng & Y.W. Law Tree to 30 m, trunk straight, erect, stately, 1 m dbh. Bark scaly, greyish or reddish brown, breaking into plates separated by longitudinal fissures. Crown dense, forming a dome. Branchlets reddish brown, thick; vegetative buds not resinous. Leaves in fascicles of three or sometimes in pairs, not or slightly pendulous, grey-

Section II. Species Accounts

Pinus

629

ish green or bright green, triangular in cross-section, 10–30 × 0.12 cm, apex acute. Fascicle sheaths persistent. Cataphylls dark brown to black, gradually eroding. Male strobili yellowish to yellowish brown, ovoid, 1.5 × 0.5 cm. Female cones lateral, in whorls of two to five, with short, stout peduncles; cones 5–10 cm long, green then yellow-brown to chestnut-brown, mature cones ovoid-conical, mature in about 20 months, opening in the following summer. Scales 3 × 1.5 cm, oblong-ellipsoid, hard, stiff, woody; apophysis swollen, rounded; umbo dorsal, slightly sunken or slightly protruding, with a minute prickle. Seeds brown, 5–6 mm; wings 1.2–1.4 cm long. Fu et al. 1999c, Farjon 2005a. Distribution CHINA: eastern Guangxi, eastern Guizhou, southern Sichuan, Yunnan. Habitat Mountains, high plateaus, river valleys, between 400 and 3100 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Fu et al. 1999c, Farjon 2005a; NTix, NT629. Cross-references B246, S381, K248. Taxonomic note Var. tenuifolia from river valleys in Guangxi and Guizhou, placed in synonymy by Farjon (2001), has pendulous leaves less than 0.1 cm wide.

Although it was introduced by Wilson, Pinus yunnanensis did not achieve wide cultivation until recently and was given only cursory treatment by Bean (1976b). It may not be the most spectacular pine in the world, but its frequent reintroductions in recent years are grounds for it receiving a fuller treatment here. The three old trees of P. yunnanensis surviving at Kew are from Wilson’s collections in Sichuan in November 1908 (Wilson 1396, 1399), sent from the Arnold Arboretum (where no examples of this species are currently grown). They have made good, though relatively short trees of 15–17 m, with dense crowns containing many long-persistent cones. The bark is thick and dark, though the ridges are reddish. A grafted young tree from Wilson 1399 grows with them. As noted above, recent reintroductions have been numerous; the 2001 catalogue of the Royal Botanic Garden Edinburgh lists accessions from six different sources, from the Sino-British Cangshan Expedition, 1981 (SBEC 109, 1043) through to Jennifer Bute’s gathering (no. 16) in 1997. The species seems to do well in most parts of the British Isles, and is grown in a few collections in continental Europe. In North America it is found in West Coast arboreta and nurseries, but seems to be absent from collections further east.

RUTACEAE

PITAVIA

Molina

Pitavia is monospecific, comprising only the species P. punctata.

Pitavia punctata Molina

Canelillo, Pitao

Tree to 15 m, 0.5 m dbh. Bark grey, tuberculate. Branchlets greyish to glaucous, glabrous and with longitudinal stripes; foliage dense. Leaves evergreen, opposite or in whorls of three, leathery, aromatic, 1–3.5 × 1.4–4.2 cm, oblong to oblanceolate, glabrous, covered with glands, upper surface bright green, lower surface yellowish, six to nine secondary veins on each side of the midrib, margins serrate and undulate, apex obtuse or emarginate; petiole 0.3–0.6 cm long, glabrous. Inflorescences axillary, racemose, 3.5–7 cm long. Flowers hermaphrodite or unisexual by abortion, white, 4-merous; sepals triangular, concave; petals alternating with the sepals, oblong to ovate, 0.4–0.6 cm long; stamens eight, in two rows. Fruit a drupe, 1.8–2.5 cm diameter, yellowish green with red spots. Flowering September to November, fruiting April (Chile). Rodríguez R. et al. 1983. Distribution CHILE: Bío-Bío, Maule. Habitat Humid forest, often near water; associated with Peumus

Plate 419. A young Pinus yunnanensis on the Great Black Mountain, Yunnan, with long shaggy needles. These become shorter as the tree ages. Image S. O’Brien.

630

Pitavia

New Trees

boldus, Lithraea caustica, Cryptocarya alba and Myrceugenia planipes. USDA Hardiness Zone 8. Conservation status Endangered (IUCN), due to habitat loss and degradation, and wood extraction. Critically endangered (Gardner et al. 2006). Illustration Rodríguez R. et al. 1983, Gardner et al. 2006; NT630.

Plate 420. Pitavia punctata is endangered in the wild, but is apparently hardy in the British Isles. Its pretty flowers would make it a welcome addition to horticulture. Image P. Hechenleitner V.

This central-Chilean endemic has a rather narrow niche in the wild, favouring damp sites at rather low altitudes, and has been subjected to forest clearance, fires and collection of wood for fuel, resulting in its current critical conservation status. Fortunately it is easy to grow, from freshly collected seed and from cuttings, and damaged trees are also often able to regenerate from suckers (Gardner et al. 2006), so with active conservation management its decline may be halted. Pitavia punctata is an attractive evergreen tree, with neat small leaves that flush a bright green and become a duller darker shade as they mature. The small white flowers are produced in early summer, and are succeeded by yellowish green fruits. It was first introduced to the Royal Botanic Garden Edinburgh in 1996, under the collection numbers ICE 658 and 659, and specimens from each of these are growing outdoors there. That from ICE 658, situated near the Glasshouses, was a flourishing bushy tree of 4 m when seen in June 2005, and was just finishing flowering at that time. No other established specimens have been located in the research for this book, but the species is currently being offered (2007) by the Dutch company Patagonia Plants BV. A mild moist site would seem to be appropriate.

PITTOSPORACEAE

PITTOSPORUM

Banks ex Sol.

Pittosporums Pittosporum includes about 150 species, restricted to the tropics and subtropics of the Old World. They are slender trees or shrubs with evergreen leaves. The leaves are alternate, though may appear opposite or whorled; they are leathery or membranous, entire and petiolate. Pittosporum flowers may be hermaphrodite or unisexual; the inflorescences are terminal or axillary, paniculate, corymbose or umbellate, or rarely the flowers are solitary. The individual flowers are 5-merous; sepals free, but rather small; petals free or partially connate. The fruit is a woody or leathery dehiscent capsule with two to five valves. The seeds are brightly coloured and immersed in sticky resin (Cooper 1956, Allan 1961, Cayzer et al. 2000, Zhang et al. 2003c). Pittosporum is a popular genus in areas with mild winters (Zone 8 and above), P. tenuifolium and P. tobira being particularly important for their excellent foliage qualities, and the latter for its fragrant flowers as well. For some of us brought up to believe that P. tobira, in particular, is tender in most of the British Isles (see, for example, Bean 1976b), it still comes as a pleasant surprise to see it thriving in many unlikely garden sites in central and eastern England – another indicator of how the gardening climate has changed in recent years. For others its appeal may be less: Dirr (1998) employs the word ‘overused’ twice in his account of the species and its cultivars. Despite such examples of wider growability, however, members of this largely tropical or subtropical

Section II. Species Accounts

genus are most likely to thrive in the mildest parts of our area. Pittosporum is one of those genera where the distinction between tree and shrub is difficult to make, even in the wild, the growth-form often varying with habitat and conditions. For example, in Africa P. viridiflorum can be a large shrub, or a single-stemmed tree, 20–30 m tall (Coates Palgrave 1990, Beentje 1994). In horticulture, species growing in marginal conditions are more likely to be shrubby than otherwise. Bean (1976b) reviewed 17 species – a somewhat surprisingly large range – but the number of taxa available to gardeners has greatly increased since then. The RHS Plant Finder 2007–2008 listed 21 species, often with several cultivars, available from British nurseries, and a number of other species are cultivated in the British Isles and elsewhere but are not commercially available. Those not mentioned by Bean and not described here include P. anomalum Laing & Gourlay (New Zealand; divaricate shrub), P. heterophyllum Franch. (China; shrub, with linear leaves and strongly scented yellow flowers: see Hogan 2008), P. illicioides Makino (China, Japan; large-leaved shrub: see Hogan 2008), P. lineare Laing & Gourlay (New Zealand; divaricate shrub), P. michiei Allan (New Zealand; shrub), P. obcordatum Raoul (New Zealand; small tree, with divaricating branches and tiny leaves), P. omeiense H.T. Chang & S.Z. Yan (China; low shrub, with long narrow leaves) (but note that some in cultivation under this name may be P. crispulum Gagnep.), P. pimeleoides A. Cunn. ex Putt. (New Zealand; shrub), P. rhombifolium Hook. (Australia; rainforest tree to 25 m, with abundant white flowers and orange fruits, grown on Tresco: see Johnson 2007), P. truncatum E. Pritz ex Diels (China; shrub, with small stiff leaves: see Wharton et al. 2005) and P. viridiflorum Sims (montane Africa; medium-sized tree, well established in California). A further assortment is cultivated in western North America – giving an indication of the range of species currently available in horticulture – including P. erioloma C. Moore & F. Muell. (Lord Howe Island, Australia; shrub or small tree to 8 m, with small leaves), P. kirkii Hook. f. ex J. Kirk (New Zealand; shrub, with elongate leaves), P. napaulense (DC.) Rehder & E.H. Wilson (Sino-Himalaya, from Pakistan to Yunnan; shrub or tree, medicinal, with large leathery leaves: see Hogan 2008), P. parvilimbum H.T. Chang & S.Z. Yan (China; shrub or small tree, with small leaves, white flowers, bluish fruits) and P. subulisepalum Hu & F.T. Wang (China; shrub, with medium-sized leaves). Many are of interest to gardeners not only for their evergreen foliage but also for their good scented flowers, especially the Asian species with white or yellow flowers. The Australasian species tend to have dark red, pinkish or dark yellow flowers. The majority of the Asian and Australian species like warm to hot conditions, whereas the hardier New Zealand species prefer cooler summers. They should not be allowed to become too dry in summer, but poor drainage should also be avoided. Most Pittosporum root easily from cuttings, either from semi-ripe growth in summer with mist and bottom heat, or from mature wood in autumn or winter, rooted in a cold frame; a few, however, including the beautiful P. dallii, are difficult (Huxley et al. 1992, Hogan 2008). Seed is another option, with the New Zealand species often requiring a cool stratification (Hogan 2008). Several members of the genus have become weedy in various parts of the world – notably P. undulatum, in Australia and elsewhere.

Pittosporum

631

Plate 421. Pittosporum daphniphylloides var. daphniphylloides. The handsome leaves are enhanced by the dense inflorescences of scented flowers. Image N. Macer.

632

Pittosporum

New Trees

P. adaphniphylloides (NOW P. daphniphylloides var. adaphniphylloides (Hu & F.T. Wang) W.T. Wang, NT633) B253

P. anomalum Laing & Gourlay K410 P. bicolor Hook. f. B253, K410

Pittosporum brevicalyx (Oliv.) Gagnep. Shrub or tree to 10 m, possibly more. Branchlets glabrous, or pubescent when young. Leaves evergreen (biennial), clustered at the tips of branches, 5–12 × 2–5 cm, thinly leathery, obovate-lanceolate, sometimes broader, upper surface glossy dark green, lower surface pubescent below when young, later more or less glabrous, 9–11 primary veins on each side of the midrib, margins entire, flat, apex acuminate; petiole 1–1.5 cm or more. Inflorescences in groups of three to five, in leaf axils at branchlet apices; corymbose, 3–4 cm long, finely hairy. Flowers hermaphrodite; sepals 2–2.5 mm, finely hairy; petals free, yellow, 0.6–0.8 cm long. Capsule subglobose, compressed, 0.7–0.8 cm diameter, dehiscing by two valves. Seeds 7–10. Flowering March to May, fruiting July to November (China). Zhang et al. 2003c. Distribution CHINA: Guangdong, Guangxi, Guizhou, western Hubei, Hunan, Jiangxi, Sichuan, southeastern Xizang, Yunnan. Habitat Forests and forest edges on limestone, or thickets in ravines and on slopes and cliffs, between 600 and 3500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Zhang et al. 2003c; NT632.

Plate 422. The flowers of Pittosporum brevicalyx ‘Golden Temple’ are strongly perfumed. A popular evergreen in the western United States. Image Phytophoto.

Pittosporum brevicalyx was introduced to western horticulture by the 1980 SABE team, from seed collected near the Golden Temple outside Kunming, Yunnan by Stephen A. Spongberg (SAS 26B). One of the resulting seedlings was successfully established at the Saratoga Horticultural Research Foundation, San Martin, California, and has been the source for most stock in cultivation (at least in North America), under the cultivar name ‘Golden Temple’. The original plant is now approximately 10 m tall (W. McNamara, pers. comm. 2004). This clone has become very well established in western American gardens and is valued for its dense evergreen foliage and masses of very fragrant yellow flowers (Wharton et al. 2005). It is also relatively drought-tolerant, in the experience of Bill McNamara (pers. comm. 2004) at Quarryhill at least. It sets copious seed and perhaps should be monitored for weediness. P. buchananii Hook. f. B254 P. colensoi Hook. f. B254, K410 P. cornifolium A. Cunn. B254 P. crassifolium Banks & Sol. ex A. Cunn. B255, S383, K410 P. dallii Cheeseman B255, K410

Pittosporum daphniphylloides Hayata Shrub or small tree 2–5(–8) m. Branchlets stout and glabrous, becoming reddish brown with age. Leaves evergreen (biennial), clustered at the tips of branches, 10–20 × 4–8 cm, leathery, oblong or elliptic, upper surface dark green and glossy, lower surface pale green and glabrous, 9–12 primary veins on each side of the midrib, margins entire, apex acute or acuminate; petiole 1.5–3 cm long. Inflorescences in groups of three to seven,

Section II. Species Accounts

Pittosporum

in leaf axils at branchlet apices; corymbose, 4–6 cm long, pubescent. Flowers hermaphrodite or unisexual; sepals free or connate at the base, margins ciliate; petals free, yellow, narrowly oblong and 0.6–0.8 cm long. Capsule globose and slightly compressed, 0.6–1 cm diameter, dehiscing by two valves. Seeds 10–23, red, though black when dry. Flowering March to June, fruiting June to December (China). Zhang et al. 2003c. Distribution CHINA: northern Guizhou, southwest Hubei, northwest Hunan, Sichuan; TAIWAN. Habitat Forest or thickets in ravines and on slopes and cliffs, between 500 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Zhang et al. 2003c; NT631. Cross-references B253 (as P. adaphniphylloides), K410. Taxonomic note Pittosporum daphniphylloides occurs as two varieties: var. daphniphylloides (leaf blade thin, seeds 10–15) in Taiwan, and var. adaphniphylloides (Hu & F.T. Wang) W.T. Wang (leaf blade thick, seeds 17–23) in China (Zhang et al. 2003c).

As Pittosporum adaphniphylloides this species was described by Bean (1976b), and plants so named are still to be found in cultivation. Pittosporum daphniphylloides var. adaphniphylloides, as it is now understood, is the mainland Chinese representative of the species, the nominate var. daphniphylloides coming from Taiwan. This has been collected on several occasions in recent years, perhaps first by the 1993 Edinburgh Taiwan Expedition (ETE 275), from which there are plants in the Scottish botanic gardens. Later collections include RWJ 9913 and BSWJ 6789, gathered by the WynnJoneses in northern Taiwan and offered by them through Crûg Farm Plants, Gwynedd. The species has handsome large leaves, and produces rounded panicles of abundant though individually small yellow flowers. When happy it can grow very rapidly, by as much as a metre a year (S. Hogan, pers. comm. 2008); this is most likely to be in areas with warm summers, so long as ample moisture is available.

P. divaricatum Cockayne B256, K412 P. eugenioides A. Cunn. B256, K412

Pittosporum huttonianum Kirk

P. glabratum Lindl. B257, K412 P. heterophyllum Franch. K412

Hutton’s Kohuhu

Shrub or tree to 10 m. Branchlets dark brown and covered with white tomentum (like cobwebs) when young. Leaves evergreen, clustered at the tips of branches, 4–12 × 2–5 cm, somewhat leathery, elliptic to oblong or obovate, glabrous or with white tomentum when young, ~12 primary veins on each side of the midrib, margins entire, flat or revolute, apex acute or obtuse; petiole 0.5–1.5 cm long with white, appressed tomentum when young. Flowers solitary or in terminal or axillary inflorescences; inflorescences with two to five flowers, often white-tomentose. Flowers hermaphrodite or unisexual; sepals with white tomentum outside, glabrous within; petals free, dark red to magenta, oblanceolate to linear and 1.2–1.8 cm long. Capsule subglobose to obovoid, covered in white tomentum when young, 1.2–2 cm diameter, dehiscing by (two to) three valves. Seeds 18–23, reddish black. Flowering October to November, fruiting March to May (New Zealand). Cooper 1956, Allan 1961. Distribution NEW ZEALAND: Coromandel Peninsula, Great Barrier Is., North Is. Habitat Forest edges and regenerating forest, between 0 and 700 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Cross-reference K410.

Pittosporum huttonianum is rare in our area but widely cultivated in New Zealand, where it is regarded as an attractive small tree. With quite large evergreen leaves and dull red flowers capable of withstanding strong winds, it is useful for shelter plantings (Auckland Botanic Gardens 2001). The flowers are strongly fragrant, the scent suggesting that of a Dianthus (S. Hogan, pers. comm. 2008). It grows fast into a tall, narrow specimen, achieving 4 m in three years in Oregon (S. Hogan, pers. comm. 2008). It has grown at Logan since 1983.

P. patulum Hook. f. B257, K412

633

634

Pittosporum

New Trees

Pittosporum phillyreoides DC.

Willow Pittosporum

Small tree to 10 m, with pendulous branches. Branchlets covered with dense indumentum, composed of grey T-shaped hairs. Leaves evergreen, alternate, 3.6–4 × 1.5–1.7 cm, elliptic, upper surface glabrous, lower surface covered with silver tomentum, primary veins indistinct, margins entire, apex rounded to mucronate; petiole to 0.6 cm long. Flowers solitary or in pairs, axillary or terminal. Flowers unisexual; sepals tiny, triangular, margins ciliate; petals free or partially fused, yellow, 0.6–0.8 cm long, margins slightly ciliate. Capsule elliptic, orange-brown, ~1.3 cm long, dehiscing by two to three valves. Seeds one to three, reddish brown. Flowering October to September, fruiting December to June (Australia). Cayzer et al. 2000. Distribution AUSTRALIA: Western Australia (from the Dampier Archipelago south to Kalbarri). Habitat Coastal limestone plateaus. USDA Hardiness Zone 10. Conservation status Not evaluated. Illustration Cayzer et al. 2000. Cross-reference K412. Taxonomic note Pittosporum phillyreoides is often mistaken for the more widespread P. angustifolium Lodd., which occurs across mainland Australia. However, P. angustifolium has linear to narrowly elliptic, falcate leaves that are glabrous, while those of P. phillyreoides are elliptic or wider, not falcate, and have dense indumentum on the lower surface (Cayzer et al. 2000).

The strongly pendulous branches give Pittosporum phillyreoides a very distinct appearance that makes it a useful component of landscapes where it will grow – mostly outside our area! It is frequently cultivated in southern California, and in its native Australia, being more tolerant of heat and drought than other pittosporums, even when planted in full sun (Canopy 2006), and is a useful street tree on account of its stature and shape. Sean Hogan (pers. comm. 2008) believes that a hot summer may be requisite for successful growth. It is also not very frost-tolerant so is suited only for the mildest parts of our area, and even in California is not grown much further north than the San Francisco Bay Area. It should, however, be tried in the London heat island. The small yellow flowers are strongly fragrant. P. ralphii Kirk. K412 P. revolutum Dryand. ex W.T. Aiton B258, K412 P. rigidum Hook. f. B258 P. tenuifolium Gaertn. B259, S383, K412

P. tobira (Thunb.) W.T. Aiton B260, K413 P. turneri Petrie K413 P. undulatum Vent. B260, K413 P. viridiflorum Sims K413

PLATANACEAE (or PROTEACEAE) Plate 423. Curiously, Platanus rzedowskii is not known to be in cultivation. Image A. Coombes.

PLATANUS

L.

Plane Trees, Sycamores Platanus comprises seven species, most of which occur in North and Central America, though P. orientalis is native to the eastern Mediterranean region, while P. kerrii Gagnep. is restricted to Vietnam and Laos. Platanus species are large, deciduous trees (P. kerrii evergreen) with distinctive, mottled bark. Branchlets are usually covered with branched or stellate tomentum and have swollen nodes; terminal buds are absent. The leaves are sweet-smelling; adult leaves are typically large, alternate and palmate with three to five (to seven) lobes and palmate venation; juvenile leaves (and adult leaves of P. kerrii) are typically unlobed, but serrated with pinnate venation. The petiole has an enlarged base that partially or completely surrounds the axillary bud. The stipules are typically large and foliose with parallel veins; they encircle the stem and may be lobed

Section II. Species Accounts

or serrated. Flowering occurs in spring; the inflorescences are unisexual and terminal (axillary in P. kerrii) and are composed of one to many spherical heads arranged in a raceme or spike. Each head comprises numerous, rather inconspicuous flowers; staminate heads break up after flowering, but the pistillate heads have a hard, central receptacle. The fruit is a small, hairy achene that detaches from the receptacle. A key to the species is provided by Nixon & Poole (2003). A number of DNA-based studies have indicated that the Platanaceae and Proteaceae are very closely related, and together with the Nelumbonaceae (sacred lotus), form the order Proteales (APG 2003, Feng et al. 2005). The APG II classification goes on to suggest that the Platanaceae could be merged with the Proteaceae (APG 2003). However, this suggestion has yet to find favour in the wider botanical community. The importance and interest of the small genus Platanus can be judged by the space afforded it by Bean (1976b), and in particular his account of the London Plane, which extends over six pages – considerably more than the comments on Quercus robur! The controversy over the correct scientific name for the London Plane continues, but the balance currently seems to be tipped in favour of P. ×hispanica Mill. ex Münchh. (see Orchard & Lepschi 2007). This name embraces both F1 hybrids between P. orientalis and P. occidentalis and their descendants in later generations. Some of these are significant clones in their own right and deserve the recognition of a cultivar name. The planes of Greater London have been studied by I.M. Chengappa, whose website (www.aranya.co.uk/planes) is a fascinating source of information about these trees, including several distinct but unacknowledged cultivars. With the exception of P. orientalis, members of this genus are of limited significance in horticulture and are only likely to be found in specialist collections. The interesting Indo-Chinese P. kerrii and the Mexican P. gentryi Nixon & J.M. Poole and P. rzedowskii Nixon & J.M. Poole are not known in cultivation. The consistent failure of P. occidentalis in British gardens is attributed to the effects of the anthracnose disease caused by Apiognomonia veneta on young plants already weakened by spring frosts and missing the summer heat of their native eastern North America. It has to be said, unfortunately, that the recent Mexican introductions described below are likely to suffer in a similar way, in areas where P. occidentalis does not thrive. Propagation of planes is by seed, cuttings or grafting.

P. ×acerifolia (NOW P. ×hispanica Mill. ex Münchh.) B265, S384, K415 P. ×acerifolia var. hispanica (NOW P. ×hispanica Mill. ex Münchh.) B268 P. ×acerifolia var. minor Ten. B268 P. ×hispanica Mill. ex Münchh. B269 (as P. ×acerifolia: B265, S384, K415) P. ×hybrida (NOW P. ×hispanica Mill. ex Münchh.) B270

Platanus

635

Plate 424. Platanus mexicana is a drought- and heat-tolerant species. Image M. Rodriguez-Coombes.

636

Platanus

New Trees

A

B

1 cm

Section II. Species Accounts

Platanus mexicana Moric.

Platanus

637

Mexican Plane, Mexican Sycamore

Syn. P. lindeniana M. Martens & Galeotti Tree to 35 m. Bark exfoliating, white and mottled. Branchlets brown or reddish brown with white or yellow tomentum. Leaves deciduous, thick and leathery, (3–)8–20(–25) × 10–20(–30) cm, broadly ovate in outline with three (to five) deltoid to triangular lobes, upper surface greyish green with sparse tomentum, soon glabrous, lower surface densely covered with interlocking white, grey or yellow tomentum, veins palmate and extending to the margins, margins entire or with triangular teeth, apex acuminate, sometimes glandular; petiole tomentose to glabrous, 3–9 cm long; stipules foliose and sharply pointed. Monoecious. Staminate inflorescences with two to four almost sessile heads; pistillate inflorescences lax, racemose or spicate, 10–26 cm long with (three to) five to seven globose heads; heads 1.4–3 cm diameter, brown. Achenes 0.5–0.7 cm long, yellowish brown. Nixon & Poole 2003. Distribution GUATEMALA; MEXICO: Chiapas, Hidalgo, Oaxaca, Puebla, Veracruz. Habitat Along streams in tropical forest, between 150 and 1850 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT635, NT636. Taxonomic note Platanus mexicana var. interior Nixon & J.M. Poole occurs in the Mexican states of Guanajuato, Querétaro and San Luis Potosí. It differs from typical P. mexicana in that the mature leaves have only a sparse covering of tomentum on the lower surface and there are only two to three heads in each pistillate inflorescence (Nixon & Poole 2003). The tree referred to as P. mexicana in many older works (including Standley 1922) is a separate species that has since been named P. rzedowskii Nixon & J.M. Poole. It occurs in the Mexican states of Nuevo León, San Luis Potosí and Tamaulipas, and differs from P. mexicana in that the leaves are usually five-lobed, and both the staminate and pistillate inflorescences are composed of a single globose head (Nixon & Poole 2003). It is not known to be in cultivation.

Platanus mexicana is now well established in American commercial and amenity horticulture, being particularly valued for its tolerance of hot dry conditions in the arid southern parts of the United States, used – as is traditional for planes – as a street tree. It forms a large tree with striking pale exfoliating bark, while the leaves are attractively bicoloured, showing their white-hairy undersides in a breeze, in just the same way as Tilia tomentosa ‘Petiolaris’. ‘Alamo’ is a trademarked name for a largeleaved clone said to be resistant to anthracnose, powdery mildew and other fungal diseases (Orange County Nursery 2005), but it is not clear if this is a selling name or a cultivar epithet; if the latter it is illegitimate, as Alamo is the Spanish vernacular name for Platanus species (L. Hatch, pers. comm. 2008). Although most frequently cultivated outside our area, P. mexicana will grow further north, as demonstrated by a beautiful and vigorous tree at the JC Raulston Arboretum (labelled P. lindeniana). Planted at 25 cm in 1999, it is currently approximately 10 m tall, and another specimen (since removed) achieved 6 m in four years (M. Weathington, pers. comm. 2008). There are also large specimens in Virginia (R. Olsen, M. Weathington, pers. comms. 2008). It does not seem to be frequently grown in the Pacific Northwest, however. Platanus mexicana has not so far proved very successful in the United Kingdom, the only specimen reported by Johnson (2007) being a tree at the Sir Harold Hillier Gardens grown from Frankis 134, collected in 1991, which reaches about 3 m annually before dying back in winter. Platanus racemosa var. wrightii (S. Watson) Benson (see Bean and Krüssmann: B277, K418), from Arizona, New Mexico, Chihuahua and Sonora, is another droughttolerant plane, widely planted in the southern and western United States but seldom seen further north. It has a darker trunk, especially at the base, and lacks the white indumentum of P. mexicana.

P. occidentalis L. B271, K416 P. occidentalis var. glabrata (Fernald) Sarg. B273, K416

P. orientalis L. B273, S385, K418 P. orientalis var. cretica Dode K418

Figure 70 (opposite). Platanus mexicana: habit with inflorescences (A); single leaf (B).

638

Platanus

New Trees

P. orientalis var. cuneata (Willd.) Loudon K418 P. orientalis f. digitata (NOW Platanus orientalis ‘Digitata’) K418

P. orientalis var. insularis A. DC. B275 P. racemosa Nutt. B277, K418 P. wrightii (NOW P. racemosa var. wrightii (S. Watson) Benson) B277, K418

PODOCARPACEAE

PODOCARPUS

Plate 425. Podocarpus henkelii may be the hardiest of the South African podocarps, and flourishes in the milder parts of our area. This specimen is at Kirstenbosch, Cape Town. Image J.R.P. van Hoey Smith.

L’Hér. ex Pers.

Podocarpus is the second largest genus of conifers after Pinus, with 107 species (Farjon 2001). Most are limited to the southern hemisphere: subgenus Podocarpus occurs in the temperate forests of New Zealand, Tasmania and Chile, extending into the tropical highlands of Africa, South America and New Caledonia; subgenus Foliolatus occurs primarily in the Asian-Pacific tropics. Podocarpus species are dioecious (rarely monoecious) evergreen trees or shrubs. The leaves are spirally arranged to subopposite, though they often appear crowded or two-ranked; there are minimal differences between adult and juvenile forms, though juvenile leaves tend to be larger and/or wider. The leaves are flattened, linear, lanceolate or oblong, with a distinct midrib. Male strobili are sessile or stalked, solitary or grouped, and produced in the axils of the upper leaves. Female cones are axillary (rarely terminal) and solitary; composed of a single fertile scale bearing one to two (to three) ovules, subtended by several sterile scales, which are usually fused together to form a receptacle. The receptacle becomes fleshy or leathery, and brightly coloured in some species, while in others it is obsolete; the epimatium completely encloses the seed, and may also become fleshy and brightly coloured (Hill 1998, Fu et al. 1999b). A taxonomic revision of this large genus has been produced (de Laubenfels 1985), but many of the species are poorly known. As generic concepts have developed, many species formerly in Podocarpus have been placed in distinct genera. Synonyms are given below where appropriate, but Farjon’s World Checklist and Bibliography of Conifers (2001) offers a more complete guide. A number of tropical species, including several in segregate genera, were described by Krüssmann (1985b), but have little if any chance of being hardy in our area. For horticultural purposes Podocarpus falls into two broad groups: low shrubs, mostly from Australasia; and true trees, from forest areas around the southern hemisphere. The shrubby species should not be ignored as they are often very useful and attractive ground-covering plants. In recent years, largely through the efforts of Graham Hutchins of County Park Nursery, Hornchurch, Essex,

Section II. Species Accounts

a considerable range of selections from P. lawrencei, P. nivalis and hybrids between them (and, to a lesser extent, from P. cunninghamii (syn. P. hallii) and P. acutifolius) have been released into the horticultural trade. Among these, ‘County Park Fire’ (P. lawrencei × P. nivalis) is widely available and offers a gamut of colours, from the yellow to salmon-pink of the new shoots to the purple-bronze of the foliage in winter (Hutchins 1996). Podocarpus is a familiar and important constituent of the cooler, moister forests of the southern hemisphere, and can form large and magnificent timber trees of considerable significance in the forest ecosystem. In particular the swollen receptacle of the ripe fruit, which is often red and becomes sweet-tasting, is an important food source for many birds, which later disperse the seeds. On Kilimanjaro the big ‘podos’ P. milanjianus growing in the upper levels of the Afromontane forest are much favoured by Red-fronted Parrots (Poicephalus gulielmi), Hartlaub’s Turaco (Tauraco hartlaubii) and Olive Pigeons (Columba arquatrix) (JMG, pers. obs.). All follow the sequence of tree species coming into fruit around the mountain, and will migrate to other forest areas in search of food. This goes a long way towards explaining the wide distribution of many Afromontane trees, including P. milanjianus – found on mountains apparently isolated by vast tracts of lowlands, but no obstacle to a fast-flying pigeon. In addition to the podocarps described below, hybrids between the frequently cultivated Chilean P. salignus and the New Zealand species P. totara and P. cunninghamii have occurred on several occasions where the parents are grown together in UK gardens (Allnutt et al. 1997). Podocarpus nubigenus Lindl. has been introduced to the Royal Botanic Garden Edinburgh on several occasions in recent decades as a result of collaboration with Chilean institutions. It is a potentially large, columnar tree up to 30 m tall and provides excellent timber, to the extent that it is a subject of conservation concern (Near Threatened, according to Gardner et al. 2006, although categorised by the IUCN as Lower Risk). Seedlings have been raised at Edinburgh using an embryo excision technique that has given greatly enhanced results (Brownless et al. 1997). Resulting plants are now in cultivation in the Scottish botanical gardens and the Bedgebury National Pinetum in Kent. They grow slowly when young, but those at Benmore are now up to 2 m tall and growing steadily, appreciating the wet conditions there and proving fully hardy (M. Gardner, pers. comm. 2008). The related Nageia Gaertn., of which N. nagi (Thunb.) Kuntze has long been cultivated under glass (see Bean and Krüssmann: B283, S387, K260), is a genus whose members might now be more successful outdoors in mild gardens. In addition to N. nagi, N. fleuryi (Hickel) de Laub. from southern China and Indochina, and the Taiwanese N. formosensis (Dümmer) C.N. Page are grown at the Royal Botanic Garden Edinburgh and elsewhere, and are candidates for planting outside in favoured sites (P. Thomas, pers. comm. 2007). Propagation of Podocarpus is by seed, which can be slow and erratic to germinate when sown in a normal way (P. Thomas, pers. comm. 2007), but embryo excision, though requiring considerable care, can give much better results (Brownless et al. 1997). Cuttings from firm young shoots are usually successful but may be slow to root. As young plants Podocarpus should not be exposed to hot bright sunshine, as most start life as understorey plants in the wild.

Podocarpus

639

Plate 426. Nageia fleuryi. Nageia differs most obviously from Podocarpus in its broad leaves. Global warming may in future permit N. fleuryi to be grown outdoors in our area, but at present material of this rare tree is cultivated under glass at the Royal Botanic Garden Edinburgh. Image R. Unwin.

640

Podocarpus

New Trees

Trees can be slow to establish, but respond well to the application of slow-release fertilisers. A moist acidic soil is generally preferred, but the alpine shrubs seem not to be fussy and tolerate both lime and drier conditions. P. acutifolius Kirk B286, S388, K250 P. affinis Seem. K250 P. alpinus (NOW P. lawrencei Hook. f.) B280, S386, K250 P. amarus (NOW Sundacarpus amarus (Blume) C.N. Page) K250 P. andinus (NOW Prumnopitys andina (Poepp. ex Endl.) de Laub.) B280, S386, K250 P. angustifolius Griseb. K251 P. annamiensis N.E. Gray K251 P. archboldii N.E. Gray K251 P. aristulatus Parl. K251 P. brassii Pilg. K251 P. brevifolius (Stapf) Foxw. K252 P. buchii (NOW P. aristulatus Parl.) K252 P. cardenasii (NOW P. glomeratus D. Don) K252 P. cinctus (NOW Dacrycarpus cinctus (Pilg.) de Laub.) K252 P. compactus (NOW Dacrycarpus compactus (Wasscher) de Laub.) K252

Podocarpus elatus R. Br. ex Endl.

P. comptonii (NOW Retrophyllum comptonii (J. Buchholz) C.N. Page) K252 P. coriaceus Rich. & A. Rich. K252 P. costalis C. Presl K252 P. cumingii (NOW Dacrycarpus cumingii (Parl.) de Laub.) K252 P. curvifolius (NOW P. parlatorei Pilg.) K252 P. dacrydioides (NOW Dacrycarpus dacrydioides (A. Rich.) de Laub.) B282, S386, K252 P. decipiens (NOW P. neriifolius D. Don) K252 P. decumbens N.E. Gray K254 P. deflexus Ridl. K254 P. dispermus C.T. White K254 P. distichus (NOW Prumnopitys ferruginoides (Compton) de Laub.) K254 P. drouynianus F. Muell. K254 P. ekmanii (NOW P. angustifolius Griseb.) K254

Illawarra Plum, Plum Pine

Tree 5–15(–30) m, 1(–2.5) m dbh. Trunk straight. Bark thin, greyish brown to dark brown, fibrous, often grooved. Branches spreading to ascending, branchlets ribbed. Leaves alternate or whorled, somewhat crowded at tips of branchlets, 6–18 × 0.5–1.6 cm, linear-lanceolate to oblong, acute or obtuse at apex, glossy dark green above, paler below, but flushing yellowish green. Male strobili 3–5 × 0.4–0.5 cm, sessile, usually four in an axillary cluster. Female strobili solitary, axillary on thick peduncles 3–10 mm long, the receptacle 15–25 mm long, fleshy, black or purple with a waxy bloom when mature, seed greenish, 14–22 × 12–15 mm. Elliot & Jones 1997, Hill 1998. Distribution AUSTRALIA: New South Wales, Northern Territory, Queensland. Habitat Coastal and subcoastal rain forests, often near water. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Hill 1998; NT641. Cross-reference K255.

In cultivation in Australia Podocarpus elatus requires well-drained acidic soil in a semi-shaded to sunny site (Elliot & Jones 1997). Elliot & Jones also note that the edible receptacles have an extremely high vitamin C content, although the flavour is rather resinous. The species is rare in cultivation outdoors in our area but a few trees have been located. A surprise is one individual at the University of Oxford’s Harcourt Arboretum, Nuneham Courtenay, Oxfordshire, of about 2.5 m in 2007. An ex-greenhouse specimen, it was planted out in 2005 and has experienced –9 ºC without significant damage (P. Newth, pers. comm. 2007). At Tregrehan it grows slowly but steadily, and has reached 1.5 m in about 10 years. There it gets browned by frost at approximately

Section II. Species Accounts

Podocarpus

641

–6 ºC (T. Hudson, pers. comm. 2007). Tom Hudson is also growing the Australian P. drouynianus and the New Guinean P. brassii outdoors, both of which are currently about 1 m tall. P. elongatus (Aiton) L’Hér. ex Pers. K255 P. ensiculus (NOW P. henkelii Stapf ex Dallim. & A.B. Jacks., NT641) K255 P. falcatus (NOW Afrocarpus falcatus (Thunb.) C.N. Page, NT121) K255 P. ferrugineus (NOW Prumnopitys ferruginea (G. Benn. ex D. Don) de Laub., NT655) B285, K255 P. ferruginoides (NOW Prumnopitys ferruginoides (Compton) de Laub.) K255 P. fleuryi (NOW Nageia fleuryi (Hickel) de Laub., NT639) K255 P. formosensis (NOW Nageia formosensis (Dummer) C.N. Page) K255 P. forrestii (NOW P. macrophyllus (Thunb.) Sweet var. macrophyllus, NT643) K255 P. gibbsiae N.E. Gray K256 P. glaucus Foxw. K256 P. glomeratus D. Don K256 P. gnidioides Carrière K256 P. gracilior (NOW Afrocarpus gracilior (Pilg.) C.N. Page) K256 P. guatemalensis Standl. K256 P. hallii (NOW P. cunninghamii Colenso) B286, S388, K256 P. harmsianus (NOW Prumnopitys harmsiana (Pilg.) de Laub.) K256

Podocarpus henkelii Stapf ex Dallim. & A.B. Jacks. Syn. P. ensiculus Melville

Henkel’s Yellowwood, Long-leaf Yellowwood

Tree to 20–30 m. Trunk straight, to 1 m dbh or more, becoming fluted and spirally twisted. Bark yellowish grey, brown or dark grey, becoming longitudinally fissured and peeling to reveal reddish brown underbark. Branches spreading or somewhat pendulous, densely covered in foliage. Leaves opposite or spirally arranged, pendulous, 9–17 × 0.65–1 cm, more or less linear and somewhat falcate, tapering to apex and base, shiny dark green. Male cones in clusters of one to five, erect, 3 × 0.4 cm, pink; female cones with smallish receptacle that remains bluish green. Seeds ovoid, 2.5 × 2 cm, green. Coates Palgrave 1990. Distribution MALAWI; SOUTH AFRICA: Eastern Cape, KwaZulu-Natal; TANZANIA. Habitat Moist montane forests and occasionally coastal forests. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Coates Palgrave 1990; NT638. Cross-reference K255 (as P. ensiculus), K256.

The long, pendulous and shiny leaves make Podocarpus henkelii an extremely attractive evergreen tree, a virtue recognised by its acceptance into mainstream horticulture in southern California and its native South Africa. It is established in cultivation in southwestern England, and is flourishing in a garden in northern Wales (Chamberlain 2008). Young trees are easily obtainable from British nurseries. At Tregrehan, Tom Hudson (pers. comm. 2005) has noted that it flushes later in the year than P. latifolius and is therefore more likely to avoid spring frosts. The new shoots of all Podocarpus are apt to be a lighter, brighter shade of green than the mature foliage, but in this species they may be tinged pink or red, and in one clone available in New Zealand new growth is lemon-yellow (Cedar Lodge Nursery 2002–2008).

Plate 427. Podocarpus elatus, with the characteristic fruits of Podocarpus clearly visible. The seed is held above the fleshy receptacle, which will ripen purplish or black. Image J.R.P. van Hoey Smith.

642

Podocarpus

New Trees

P. idenburgensis (NOW P. ledermannii Pilg.) K256 P. imbricatus (NOW Dacrycarpus imbricatus (Blume) de Laub. var. imbricatus) K256 P. imbricatus var. kinabaluensis (NOW Dacrycarpus kinabaluensis (Wasscher) de Laub.) K257

P. koordersii (NOW P. rumphii Blume) K257 P. ladei (NOW Prumnopitys ladei (F.M. Bailey) de Laub.) K257 P. lambertii Klotzsch K258

Podocarpus latifolius (Thunb.) R. Br. ex Mirb.

Real Yellowwood

Tree 20–30 m, occasionally shrubby in exposed sites. Trunk straight, to 3 m dbh, becoming fluted and twisted with age. Bark dark grey, smooth when young, becoming fissured and peeling with age. Branches spreading to ascending. Leaves nearly opposite or spiralled in tufts on the branchlets, erect, 4–6 × 0.6–0.8 cm, longer when young, broadly linear to narrowly elliptic, apex acute, glossy dark green above, paler and dull below, sometimes more glaucous; stomatal lines only on the underside. Male cones to 5 × 0.5 cm, pink. Female cones green, 1 cm long, developing into a purple-red receptacle 8–14 mm long and wide, and a rounded green to dark violet seed, c.1 cm diameter. Coates Palgrave 1990. Distribution SOUTH AFRICA: Eastern Cape north to Limpopo Province, Western Cape. Habitat Moist montane and coastal forests. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Coates Palgrave 1990; NT122, NT642. Cross-reference K258.

Plate 428. Podocarpus latifolius is an important constituent of South African forests, as here in the Drakensberg in the Royal Natal National Park. Image J. Grimshaw.

Podocarpus latifolius as currently defined is restricted to South Africa, where it has been an extremely important timber source and is now the national tree. It was formerly united with P. milanjianus from tropical Africa, and many references treat the two together. The South African tree is certainly very distinct from that seen in East Africa, with shorter, more erect leaves, and the separation seems warranted. Podocarpus latifolius lacks the elegance of P. henkelii and P. milanjianus, but is regarded as a valuable ornamental in South Africa and is probably tolerant of somewhat drier conditions than the others. Coates Palgrave (1990) notes that the fruiting tree covered in red receptacles is particularly attractive. Podocarpus latifolius is in cultivation in the United States, in the warmer parts at least; it appears to be infrequent even there, although it should be well suited to southern and coastal California. In the United Kingdom it is grown in Cornwall, but the online catalogue of Firma C. Esveld of the Netherlands can only recommend it for bonsai in Europe! At Tregrehan the new shoots are apt to be frosted in spring, but growth catches up later in the year (T. Hudson, pers. comm. 2005). The similar species P. elongatus (Aiton) L’Hér. ex Pers. (Breede River Yellowwood) from the Western Cape is cultivated in South Africa and could be tried elsewhere. The main difference is the presence in P. elongatus of stomatal lines on both leaf surfaces. An excellent glaucous clone of P. elongatus is grown at Kirstenbosch.

P. ledermannii Pilg. K258 P. leonii (NOW P. aristulatus Parl.) K258 P. longifoliolatus Pilg. K258 P. lucienii de Laub. K258

Section II. Species Accounts

Podocarpus macrophyllus (Thunb.) Sweet Podocarpus macrophyllus var. macrophyllus Syn. P. forrestii Craib & W.W. Sm. Tree to 20 m. Trunk to 0.6 m dbh, bark grey or grey-brown, flaking in small pieces. Branches spreading or ascending, densely spaced, branchlets glabrous to pubescent. Leaves sessile, spirally arranged, glossy dark green above, greyish or pale green below, 1.7–12 × 0.2–1 cm, linear-lanceolate, oblanceolate or oblonglanceolate, somewhat falcate, apex mucronate to acute or acuminate, base cuneate, midrib prominent on the upper surface, less so below. Male strobili axillary, borne on short peduncles in groups of three to five, erect, 3–5 cm long. Female strobili solitary in axils on short peduncles, receptacle red or red-purple when ripe, seed ellipsoid or ovoid, c.10 mm, green. Fu et al. 1999b. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; MYANMAR (?); TAIWAN (?); VIETNAM. Habitat Forests, thickets, between 0 and 1000 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Fu et al. 1999b. Cross-reference K258.

Podocarpus macrophyllus has long been known to Western horticulture in the form of var. maki from Japan and eastern China, and various selections from this (Bean 1976b, Krüssmann 1985b). The natural distribution of P. macrophyllus is obscured by its popularity in China as a garden or hedging tree, from which selections have also been made, and it is not entirely clear which populations can be regarded as native. Five varieties are recognised by Flora of China (Fu et al. 1999b): var. angustifolius, var. chingii (P. chingianus S.Y. Hu), var. macrophyllus, var. maki and var. piliramulus Z.X. Chen & Z.Q. Li. Farjon’s (2001) treatment of var. maki (Bean, Krüssmann: B282, S387, K258) as P. chinensis (Roxb.) Wall. var. chinensis is now conceded by him to be erroneous (Farjon 2007b). Of these five, two are not in cultivation: the columnar, broader-leaved var. chingii, and var. piliramulus with its darkly pubescent branchlets. The nominate var. macrophyllus seems to be poorly known in horticulture, but is apparently represented in British collections by material labelled P. forrestii Craib & W.W. Sm. This taxon was sunk into P. macrophyllus by de Laubenfels (1985) and the decision has been upheld by Farjon (2001). Flora of China treats them separately, on the basis that P. forrestii is shrubby and has male strobili in threes, unlike the treeforming P. macrophyllus which has male strobili in groups of three to five, but notes that P. forrestii may represent a juvenile form of P. macrophyllus. Podocarpus forrestii was named from material collected by George Forrest (F 4665) on ‘the eastern flank of the Tali range’ from a shrub of ‘2–5 feet’; no similar material has been seen since (P. Thomas, pers. comm. 2007). Seed labelled P. forrestii was introduced to the United Kingdom by the Chungtien, Lijiang & Dali Expedition of 1991 (under CLD 1565 and 1566B), and by the Alpine Garden Society Expedition to China, 1994 (under ACE 2543 A and B), all from the same group of cultivated trees up to 15 m tall growing in Dali, Yunnan (P. Thomas, pers. comm. 2007). Material from these collections is in cultivation under glass at the Royal Botanic Garden Edinburgh and in the open in Cornwall. Flora of China describes P. forrestii as a shrub of 3–5.5 m, with robust leafy branches. The leaves are shortly petiolate, elliptic to linear-elliptic, 2–9 × 0.6–1 cm, and matt (not glossy) green above. Reproductive parts are smaller than would be expected for P. macrophyllus. More study of wild and cultivated material is indicated. Krüssmann (1985b) notes that var. angustifolius is commonly planted in the United States. This has long narrow leaves, 5–12 × 0.3–0.6 cm, with acuminate or subacute apices, compared to the shorter, broader leaves (0.7–1 cm wide) of var. macrophyllus, and the shorter narrow leaves (1.7–7 × 0.5–0.7 cm) with mucronate, acute or obtuse apices of var. maki, but Farjon (2001) treats it as a synonym of var. macrophyllus.

Podocarpus

643

644

Podocarpus

New Trees

P. macrophyllus var. angustifolius Blume K258, NT643 P. macrophyllus var. chingii N.E. Gray K258 P. macrophyllus var. maki Siebold & Zucc. B282, S387, K258

P. macrophyllus var. nakaii (NOW P. nakaii Hayata) K258 P. madagascariensis Baker K258 P. magnifolius J. Buchholz & N.E. Gray K258 P. mannii (NOW Afrocarpus mannii (Hook. f.) C.N. Page) K260

Podocarpus matudae Lundell Syn. P. reichei J. Buchholz & N.E. Gray, P. matudae var. reichei (J. Buchholz & N.E. Gray) de Laub. & Silba Large tree to 20 m. Trunk straight, 0.6–1.5 m dbh, with greyish bark. Leaves coriaceous, dark green, 4–12(–16)

Plate 429. The Mexican Podocarpus matudae is showing great promise as a tree for mild gardens. The pendulous, fresh green leaves make it very elegant. Image J. Grimshaw.

× 1–1.5(–1.9) cm, lanceolate but sometimes falcate, apex acuminate, base shortly attenuate to short petiole, midrib prominent on upper surface near base, but not so towards apex, margins subrevolute. Male strobili sessile, axillary on the previous year’s growth, solitary or in pairs, 3–5 × 0.4 cm. Female strobili borne on peduncles 4–12 mm long, receptacle fleshy, red becoming brown, 4–12 mm, seed 8–15 × 12–13 mm. Lundell 1937, Buchholz & Gray 1948, Standley & Steyermark 1952. Distribution EL SALVADOR (?); GUATEMALA; MEXICO: Chiapas, Guerrero, Jalisco, Oaxaca, Puebla, San Luis Potosí, Tamaulipas, Veracruz. Habitat Mixed pine-hardwood-podocarpus forests on moist slopes, between (600–)1000 and 2600(–3500) m asl. USDA Hardiness Zone 8–9. Conservation status Near Threatened. Illustration NT14, NT644. Cross-reference K260. Taxonomic note Silba (1990) recognised three varieties of this species: var. matudae with short, broad, somewhat falcate leaves, from Chiapas and into El Salvador and Guatemala; var. reichei with longer leaves, from Puebla, Veracruz and Tamaulipas; and var. jaliscanus de Laub. & Silba, from Jalisco. These varieties are not recognised by Farjon (2001), however, or by other authorities (P. Thomas, pers. comm. 2007).

Plants are cultivated under the name Podocarpus reichei in California and Oregon, and young trees at Tregrehan are flourishing and really look as if they want to succeed, forming exceptionally attractive specimens in damp ground in the valley bottom, measuring up to 4 m tall in 2006 (Johnson 2007). These trees are now fruiting, despite having been planted within the past 10 years. They were grown from seed collected in Mexico and distributed by R. Nicholson, then of the New York Botanical Garden (T. Hudson, pers. comm. 2005). The hardiness of the species elsewhere is as yet untested but it deserves to be attempted in sheltered, moist locations. The long leaves give it a very elegant appearance.

P. milanjianus Rendle K260 P. minus (NOW Retrophyllum minus (Carrière) C.N. Page) K260 P. montanus (NOW Prumnopitys montana (Humb. & Bonpl. ex Willd.) de Laub.) K260 P. motleyi (NOW Nageia motleyi (Parl.) de Laub.) K260 P. nagi (NOW Nageia nagi (Thunb.) Kuntze) B283, S387, K260 P. nagi var. angustifolius Maxim. K260 P. nagi var. nankoensis (NOW Nageia formosensis (Dummer) C.N. Page) K260 P. nagi var. rotundifolius Maxim. K260 P. neriifolius D. Don K260 P. nivalis Hook. B283, K261 P. novae-caledoniae Vieill. K261

Section II. Species Accounts

P. nubigenus Lindl. B284, S387, K261 P. oleifolius D. Don K261 P. pallidus Gray K261 P. pendulifolius J. Buchholz & N.E. Gray K261 P. philippinensis (NOW P. rumphii Blume) K261 P. pilgeri Foxw. K261 P. pitteri (NOW P. salicifolius Klotzsch & H. Karst. ex Endl.) K261 P. polystachyus R. Br. ex Endl. K261 P. purdieanus Hook. K261 P. reichei (NOW P. matudae Lundell, NT644) K261 P. roraraimae Pilg. K262 P. rospigliosii (NOW Retrophyllum rospigliosii (Pilg.) C.N. Page) K262 P. rumphii Blume K263 P. salignus D. Don B284, S387, K263 P. salomoniensis Wasscher K263 P. sellowii Klotzsch K263 P. spicatus (NOW Prumnopitys taxifolia (Banks & Solander) de Laub.) K263 P. spinulosus (Sm.) R. Br. ex Mirb. K263 P. sprucei Parl. K263

Podocarpus

P. standleyi (NOW Prumnopitys standleyi (J. Buchholz & N.E. Gray) de Laub.) K263 P. steupii (NOW Dacrycarpus steupii (Wasscher) de Laub.) K263 P. steyermarkii J. Buchholz & N.E. Gray K263 P. sylvestris J. Buchholz K263 P. tepuiensis J. Buchholz & N.E. Gray K263 P. thevetiifolius (NOW P. polystachyus R. Br. ex Endl.) K263 P. totara G. Benn. ex D. Don B285, S387, K263 P. urbanii Pilg. K264 P. ustus (NOW Parasitaxus ustus (Vieill.) de Laub.) K264 P. utilior (NOW Prumnopitys harmsiana (Pilg.) de Laub.) K264 P. victorianus (NOW P. aristulatus Parl.) K264 P. vieillardii (NOW Dacrycarpus vieillardii (Parl.) de Laub.) K264 P. vitiensis (NOW Retrophyllum vitiense (Seem.) C.N. Page) K264 P. wallichianus (NOW Nageia wallichiana (C. Presl) Kuntze) K264

ROSACEAE

POLYLEPIS

Ruíz & Pav.

Fourteen species of Polylepis occur in the Andes (1800–5200 m asl), from Venezuela south to northern Chile and Argentina. They are deciduous or evergreen trees or shrubs with deep, many-layered red bark. The leaves are alternate and imparipinnate with one to nine pairs of leaflets. The leaflets have entire, revolute, crenate or serrate margins and are usually hairy below. Stipules are fused around the branchlets forming a sheath. The inflorescences are erect or pendent with 1–60 flowers. The flowers are hermaphrodite, 0.4–1 cm diameter with three to four sepals, no petals and 6–36 stamens. The fruit is an achene with spines, wings or other protuberances (Simpson 1979). This interesting genus, which deserves further horticultural investigation, has a similarity to the East African Hagenia but is perhaps most closely related to the herbaceous genus Acaena (Helfgott et al. 2000). Ecologically, Polylepis is of particular interest as it contains the world’s highest-altitude woody plants, woodlands of P. tarapacana Phil. growing at over 5000 m in Bolivia. Only P. australis is known to be

645

646

Polylepis

New Trees

established in cultivation, but P. pauta Hieron. from Ecuador and Peru has been offered commercially in the United Kingdom in recent years. The Chilean P. tomentella Wedd. is another high-altitude species worthy of attention (Gardner & Knees 2004). It too has superb exfoliating bark. The family Rosaceae contains several other woody genera with pinnate leaves, including Bencomia Webb & Berthel. and Dendriopoterium Svent., both from the Canary Islands, and allied to Sanguisorba L. (of which they have sometimes been considered to be woody members) (Helfgott et al. 2000). Of these, B. caudata Webb & Berthel. from Gran Canaria and Tenerife is cultivated at the Chelsea Physic Garden, London, forming a tall multistemmed shrub with attractive dark green pinnate leaves. Also in this remarkable garden is D. menendezii Svent., forming a bush with a dense canopy of beautiful glaucous leaves – a truly handsome plant that deserves cultivation wherever it is hardy. It was flowering well in January 2008, with panicles of small greenish flowers opening from pinkish buds.

Polylepis australis Bitter

Queñoa, Tabaquillo

Tree 1.5–10 m. Bark reddish brown, flaking and peeling in layers; branchlets also showing peeling bark. Leaves congested at branch apices, 2–7.2 × 1.8–5.3 cm, imparipinnate with (one to) two to three pairs of leaflets; rachis glandular with tufts of white trichomes at the point of leaflet attachment; leaflets broadly lanceolate to obovate, 1–4 × 0.3–1.5 cm, both surfaces glabrous or densely glandular, with a few scattered, twisted trichomes, margins crenate, apex obtuse; petiole long; stipules glabrous and/or glandular on the outer surface, with long white trichomes protruding from the inner surface. Inflorescences pendent, 1.8–7.3 cm long with 2–12 flowers and lanceolate floral bracts. Flowers hermaphrodite, 0.7–1 cm diameter, sepals three or four, stamens 8–16. Achene turbinate, with irregular and pronounced wings. Flowering June to July, October to April (Argentina). Simpson 1979. Distribution ARGENTINA: Catamarca, Córdoba, Jujuy, Salta, Tucumán. Habitat High-altitude forests in the Altiplano, between 1200 and 2900 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Simpson 1979, Krüssmann 1985a; NT646, NT647. Cross-reference K423.

Plate 430. The amazing bark of Polylepis australis is just one good feature of this attractive hardy tree. It develops from an early age but is best on larger trunks, as here at Logan Botanic Garden. Image J.Grimshaw.

Figure 71 (opposite). Polylepis australis: inflorescence (A); habit with inflorescences (B); single leaf (C); fruits (D).

Polylepis australis is an exceptional small tree, with extraordinary ‘millefeuille’, shiny reddish brown bark, peeling in thin sheets and adding to the layers already exfoliated. Where these layers have finally been shed the surface is beautifully smooth; it certainly ranks among the finest of all ornamental barks. The pinnate foliage is pleasant, and forms a rounded canopy over the usually multistemmed tree. The small greenish flowers are insignificant but abundantly produced. Native to the Argentinian Andes and forming high-altitude woodlands there, P. australis should not be considered to be a tender plant. Krüssmann (1985a) recorded that it was first introduced to the Copenhagen Botanic Garden in 1949, from seed collected at 2600 m in Tucumán, by J.P. Hjerting. A specimen planted outside in Copenhagen in 1962 was 3.1 m tall by 1975, forming a good bushy plant, that could be considered hardy in Danish conditions (Olsen 1976). It died in 1993 (J. Møller, pers. comm. 2008). The earliest accession date traced in the United Kingdom is 1972, for a plant at the Royal Botanic Garden Edinburgh, also grown from a collection made by J.P. Hjerting. This is very healthy, currently about 4 m tall with a dbh of 20 cm (M. Gardner, pers. comm. 2008). The biggest specimens in the United Kingdom are all on the west coast, however, including a very fine specimen at Logan (grown from S. Ødum 6766, collected in Provincia de Salta, Argentina and planted out in 1981), about 6 m tall with two major trunks of 30 cm and 24 cm dbh, and a similarly sized one at Calderstones Park, Merseyside (Johnson 2007). It is possible that it appreciates the higher rainfall of the west, as it is evidently not dependent on mild westerly conditions. There is a 4 m tree in Dundee University Botanical Garden, planted in 1980 (Johnson 2007), and a younger plant

Section II. Species Accounts

Polylepis

647

1 cm

A

1 cm

B

1 cm

1 cm

D

C

648

Polylepis

New Trees

is growing well (currently 2 m tall) in sticky clay at the Cotswold Garden Flowers nursery in the Vale of Evesham, Worcestershire. The Logan tree seeds freely, and seeds and seedlings are sold to visitors (B. Unwin, pers. comm. 2006). Seed is probably the easiest method of propagation, and young plants soon show flaky bark. Some variation is evident in cultivated material.

THEACEAE

POLYSPORA

Plate 431. A young tree of Polyspora hainanensis at Tregrehan, growing vigorously but so far without flowering. Image J. Grimshaw.

Sweet

Polyspora is a segregate genus resulting from the proposed division of the polyphyletic Gordonia (Prince & Parks 2001, Yang et al. 2004), Gordonia now being restricted to New World species, with the Asian species (approximately 40) transferred into Polyspora. These are evergreen trees or shrubs with leathery, pinnately veined leaves, which are often clustered at branchlet apices; the leaves are petiolate, entire or serrate. The flowers are hermaphrodite, axillary and solitary or in short racemes; with five sepals, caducous; five (to six) petals, slightly fused at the base; and numerous stamens, outer whorl filaments fused to the base of the petals. The fruit is an oblong to cylindrical woody capsule, that splits from the apex into five (rarely six to eight) sections, revealing a central column. The seeds are flat with an apical membranous wing (Ming & Bartholomew 2007). Polyspora is closely related to both Camellia and Pyrenaria, and the genera can be confused. For example, Camellia taliensis (see Bean: B486) is also known as Polyspora (Gordonia) yunnanensis Hu, and is cultivated in the United Kingdom under this name. The genera can be distinguished by examining the seeds, which are winged in Polyspora (and in Schima and Stewartia), but wingless in both Camellia and Pyrenaria. Polyspora will almost always be found as Gordonia in the relatively few gardens that have representatives. They are undoubtedly plants for the mildest extremities of our area, but do well in the valleys of Cornwall, where a high tree canopy, acidic soil and abundant moisture provide ideal conditions; if similar conditions can be provided elsewhere, however, they are certainly well worth attempting. Polyspora axillaris is fully established in cultivation but other species are not, including P. chrysandra, described by Bean (B294) and Krüssmann (K117). The genus has not attracted much attention from most collectors, but there is a range of species in southeastern Asia, all with attractive flowers and foliage. Gatherings of Polyspora have been made in China and northern Vietnam in recent years, but plants have yet to flower in cultivation so their identity remains uncertain. P. axillaris (Roxb. ex Ker Gawl.) Sweet (WAS Gordonia axillaris B293, K117) P. chrysandra (Cowan) Hu ex B.M. Bartholomew & T.L. Ming (WAS Gordonia chrysandra B294, K117)

Section II. Species Accounts

Polyspora

Polyspora hainanensis (Hung T. Chang) C.X. Ye ex B.M. Bartholomew & T.L. Ming Syn. Gordonia hainanensis Hung T. Chang Tree to 12 m. Branchlets slender and glabrous. Leaves leathery, 8–13 × 2–3 cm, narrowly oblong to oblanceolate, upper surface dark green, shiny and glabrous, lower surface pale green and glabrous, secondary veins obscure, margins undulate and serrate, apex bluntly acute; petiole 0.5–1 cm long, glabrous. Flowers axillary and solitary, ~4 cm diameter; pedicel ~0.5 cm long, pubescent. Bracteoles three, caducous, sepals five, orbicular to ovate, petals five, white, 2–2.5 cm long, stamens 8–10, ovary tomentose. Capsule oblong to cylindrical, 1.5–2.5 cm long, central column 1.5–1.8 cm long; seeds with wing to 1 cm long. Flowering November to December, fruiting October (China). Ming & Bartholomew 2007. Distribution CHINA: Hainan. Habitat Forests between 300 and 1500 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT648.

Polyspora hainanensis is a very rare plant in cultivation, specimens having been traced only at Tregrehan and at Eastwoodhill Arboretum in New Zealand. At Tregrehan a specimen derived from the stock grown in New Zealand is forming a vigorous bushy tree, densely furnished with glossy evergreen leaves, but has not yet flowered.

SALICACEAE

POPULUS

L.

Aspens, Cottonwoods, Poplars According to the most recent taxonomic study (Eckenwalder 1996), the genus Populus has 29 species, though Flora of China (Fang et al. 1999) suggests that there may be as many as 100. This discrepancy is in large part due to misidentification of hybrids as true species; hybridisation is rife in the poplars (as in Salix), and a vast number of selections have been made in the search for the ideal tree for forestry purposes. The DNA-based study of Hamzeh & Dayanandan (2004) even suggested that some wellknown species such as P. nigra are of hybrid origin. Poplars occur across temperate and subtropical Eurasia, North Africa and North America, with one species in tropical East Africa (P. ilicifolia (Engl.) Rouleau). They are fast-growing deciduous (or semi-evergreen) trees that sometimes produce prolific sucker shoots. Winter buds have several irregular scales; terminal buds are present. The bark is smooth or furrowed. The leaves are typically ovate to deltoid, though narrow-lanceolate (willow-like) leaves occur on P. angustifolia and may occur on immature growth in some species. Stipules are small and deciduous. Poplars are typically dioecious, though hermaphrodite flowers can occur (common in P. lasiocarpa). Inflorescences (catkins) are pendulous and are produced before the leaves emerge; inflorescence bracts are lobed or toothed, and caducous. The flowers have a cup-like floral disk, nectaries absent; staminate flowers have 5–60 stamens, the anthers dull red; pistillate flowers have a green stigma. The fruit is a capsule with two to four (to five) valves; seeds are few to numerous, each with a tuft of silky hair (Eckenwalder 1996, Fang et al. 1999). Several genera of trees have a specialist society devoted to them, but only Populus has a statutory body within the United Nations Food and Agriculture Organization – the International Poplar Commission – reflecting the immense value of poplars (and

649

650

Populus

New Trees

1 cm

A

C

1 cm

Figure 72 (above). Populus purdomii: habit with infructescence (A); detail of stem (B); detail of leaf veins (C).

B

1 cm

willows) to humans as producers of timber and biofuel, and in environmental enhancement. The International Poplar Commission maintains an extensive website with numerous links to further sources of information (International Poplar Commission 2009). Most interestingly, it promises (as of July 2008) a comprehensive new book, Poplars and Willows in the World, that will review all aspects of their biology and uses. It is planned that chapters will be available electronically online, as well as in

Section II. Species Accounts

Populus

a printed book. Although there had been suggestions that text would be completed by December 2006, at the time of writing no chapters have been posted.* It is not unknown, however, for book projects to run late. When the work does appear it will evidently be required reading for any with an interest in these two genera. Until then a useful reference to the diversity and origins of cultivated poplars is to be found in Jobling (1990). Many unfamiliar names appear in Flora of China (Fang et al. 1999) and it is conceivable that some of these will find their way into cultivation (although the species concept employed by Fang and his co-authors does not always equate with modern views in the West). It is a mark of the significance of Populus that P. trichocarpa was the first species of tree to have its full DNA sequence decoded (Tuskan et al. 2006), generating media interest worldwide. In horticulture, poplars are mostly trees for the grand landscape rather than for small sites, but when appropriately placed they have great presence and character, and their shimmering foliage can be a delight. The different shades of the emerging leaves and their often brilliant yellow autumn colour give them two very ornamental seasons each year. In consequence of their importance as forestry trees, innumerable, often hybrid, cultivars have been selected for various qualities, and these may be found in arboreta. Such clones are usually very difficult to identify, and this issue is not addressed here. Jacobson’s terse comment (1996), ‘Identification is difficult, experts disagree and confusion reigns’, sums up the position very well. Nomenclature also varies greatly – some authors, for example, using P. ×euramericana Guinier for the apparently more correct P. ×canadensis (P. deltoides × P. nigra). It is to be hoped that the situation will be clarified by Poplars and Willows in the World, but even with an authoritative text physical identification is always likely to be challenging. The problems caused, especially in plantation conditions, by bacterial canker in Europe (unknown in North America), canker from the Septoria fungus, and foliar fungal disease and insect damage, have driven much of the breeding and selection work in Populus, in the search for resistant cultivars. Propagation is usually by cuttings, as seed retains viability for a very short time. Most taxa propagate easily from winter hardwood cuttings but this does not work with some species (notoriously P. lasiocarpa). For these (and other Populus), summer cuttings rooted under mist are usually successful.

P. ×acuminata Rydb. B298, K427 P. adenopoda Maxim. B299, K427 P. alba L. B299, S389, K427 P. alba var. bachofenii (Wierzb. ex Rochel) Wesm. K427 P. ×andrewsii Sarg. K427 P. angulata (NOW P. deltoides Bartram ex Marshall subsp. deltoides) K427 P. angustifolia Torr. B301, K429 P. balsamifera L. B302, S389, K429 P. balsamifera var. michauxii (NOW P. balsamifera L. subsp. balsamifera) B302

P. balsamifera var. subcordata (NOW P. balsamifera L. subsp balsamifera) K429 P. balsamifera × P. trichocarpa B303, S389 P. ×berolinensis Dipp. B303, S389, K429 P. ×canadensis Moench B304, S390, K430 P. candicans (NOW P. balsamifera L. subsp. balsamifera, but usually applied to P. ×jackii Sarg.) B308, S391

651

* Two chapters were posted in December 2008, including Chapter 2, by D.I. Dickmann & J. Kuzovkina, ‘Poplars and Willows of the World, with Emphasis on Silviculturally Important Species’.

652

Populus

New Trees

P. ×canescens (Aiton) Sm. B308, S391, K431 P. cathayana Rehder B322, K431 P. ×charkowiensis (NOW P. ×canadensis Moench) K431

Populus ciliata Wall. ex Royle Tree 20–25 m. Bark grey and smooth when young, becoming brown and rougher later; crown large and spreading. Branchlets brown, tomentose to almost glabrous; buds large, up to 2.5 cm long, sticky. Leaves deciduous, 10–17 × 7–12 cm, ovate to cordate, upper surface dull green and glabrous, lower surface greyish green and pubescent along the veins, seven to nine secondary veins on each side of the midrib, margins glandular-serrate, densely ciliate, apex acute to acuminate; petiole 5–12 cm long, downy. Staminate catkins 6–10 cm long, rachis glabrous. Pistillate catkins to 15–30 cm long, rachis glabrous or pubescent. Capsule with four valves, ~1 cm long, glabrous or pubescent. Flowering April to May, fruiting June (China). Grierson & Long 1983, Fang et al. 1999. Distribution BHUTAN; CHINA: Xizang, Yunnan; INDIA; MYANMAR; NEPAL; PAKISTAN. Habitat Montane woodland, between 2200 and 3400 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Fang et al. 1999; NT652. Cross-reference S391. Taxonomic note Flora of China (Fang et al. 1999) recognises four varieties of P. ciliata; of these, only var. ciliata occurs outside China.

Plate 432. Smooth grey bark is a feature of younger specimens of Populus ciliata. This specimen at Benmore originated in Bhutan (Sinclair & Long 5699). Image R. Unwin.

Populus ciliata is a handsome large tree, notable for its attractive light grey bark when young, and large cordate leaves with pale undersides. It seems to have been introduced to the Forestry Commission’s Research Station at Alice Holt, Surrey in 1959 when material was sent from the Forest Research Institute in Dehradun, India. This accession is still cultivated among the very large reference collection of Populus grown as coppiced stools at Alice Holt (R. Jinks, pers. comm. 2008), but has also been distributed elsewhere, including to Kew. Several collections made in the wild have resulted in specimens becoming established in British arboreta: for example, Schilling 2684 from the Annapurna area, Nepal in 1983, and Sinclair & Long 5699 from the Thimpu area of Bhutan in 1984. In consequence it is represented in several collections, and it seems to thrive throughout the United Kingdom. The tallest individual recorded was 19 m (43 cm dbh) at Sandling Park, Kent (TROBI). This specimen, and another excellent tree of approximately 17 m (in 2008) at the Hillier Gardens, derive from stock imported by the Forestry Commission from the Valley of the Bee, Punjab, India (as P. ciliata clone 104) and passed on from Kew in 1984 (Kew records). In addition to being a good ornamental (though it needs to be given ample room in the arboretum), it is an important poplar for agroforestry, being used in many parts of the world for a variety of purposes, including erosion control (World Agroforestry Centre 2008). P. deltoides Bartram ex Marshall B310, S391, K431 P. deltoides var. missouriensis (NOW P. deltoides Bartram ex Marshall subsp. deltoides) B311 P. deltoides subsp. monilifera (Aiton) Eckenw. S391 P. deltoides subsp. wislizeni (S. Watson) Dorn S392 P. euphratica Oliv. K432 P. fremontii S. Watson B311, S392, K432 P. fremontii var. wislizeni (NOW P. deltoides Bartram ex Marshall subsp. wislizeni (S. Watson) Dorn) K432 P. ×generosa (NOW P. ×jackii Sarg.) B312, S392, K432

Section II. Species Accounts

Populus

653

Populus glauca Haines Syn. P. jacquemontiana Dode, P. wilsonii C.K. Schneid. Tree to 16 m. Bark grey. Branchlets brown or purplish brown, villous when young; buds softly hairy. Leaves deciduous, 18–25 × 15–20 cm, broadly ovate, purplish bronze when unfolding, upper surface blue-green, glabrous, lower surface glaucous green and pubescent along the veins, margins sharply serrulate, apex acute; petiole short, red and flattened, downy. Flowers typically hermaphrodite; catkin rachis densely pubescent, stamens 6–12. Fruiting catkin very long; capsule subglobose, pubescent and usually two-valved. Flowering April to June (China). Grierson & Long 1983, Fang et al. 1999, Schilling 1999. Distribution BHUTAN; CHINA: Sichuan, Xizang, Yunnan; INDIA: Sikkim; NEPAL. Habitat Mixed broadleaved forest, between 2500 and 3300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT653. Cross-reference S392. Taxonomic note Populus glauca is recognised as a full species by Grierson & Long (1983) and Fang et al. (1999), and also by Eckenwalder (1996), who includes P. wilsonii (described by Bean and Krüssmann: B327, K437) as a synonym. Kimura (1982) and Schilling (1999) treat it as a variety of P. jacquemontiana (often written incorrectly as ‘P. jacquemontii’).

Populus glauca has been enthusiastically described by Tony Schilling (1999), who claims its first introduction to British horticulture, with seedlings he collected from the Chepa Khola valley in the Gurkha Himal of Nepal (as Schilling 2620), in April 1983. These were the foundation of the stock most frequently seen in the United Kingdom, but it was also collected in eastern Nepal by the Kew-Edinburgh-Kanchenjunga Expedition (KEKE 1198) in 1989, and by Peter Cox in 1985. Credit for this poplar’s first introduction to cultivation goes, however, to Harry van de Laar, who brought a single seedling to the Netherlands from the Milka Danda ridge of eastern Nepal in 1973. This material has been commercially propagated by Dutch nurseries, and is probably the source of most specimens currently growing in continental Europe. It is not totally hardy there (Schilling 1999). The tree of Schilling 2620 at the Hillier Gardens, appropriately growing near the Gurkha memorial, is the British champion, measured for New Trees at 9.7 m (18 cm dbh) in 2008 by H. Brown. It is notorious for its late emergence – the first flush often not appearing until June or even early July – but the leaves are worth waiting for, as they start bronze-purple, becoming bluish green on their upper surfaces, and strongly glaucous below. The effect of the tree seen against more normal greens is very striking. Although it seems to be hardy in British conditions it is not very fast growing, and might do better in areas with warmer summers.

P. grandidentata Michx. B312, S392, K433 P. heterophylla L. B313, K433 P. hybrida (NOW P. ×canescens (Aiton) Sm.) B309 P. ×jackii Sarg. B302, K433 P. koreana Rehder K433 P. lasiocarpa Oliv. B314, S393, K433 P. laurifolia Ledeb. B315, S393, K433 P. laurifolia f. lindleyana (Carrière) Aschers. & Graebn. B316, K434 P. maximowiczii Henry B316, S393, K434

P. nigra L. B317, S393, K434 P. nigra var. betulifolia (NOW P. nigra subsp. betulifolia (Pursh) Wettst.) B318, K434 P. nigra var. pubescens Parl. B321 P. nigra var. thevestina (NOW P. nigra ‘Afghanica’) K474 P. nigra var. viadri (Rüdiger) Aschers. & Graebn. B321 P. ×petrowskiana R.I. Schröd. ex Regel K434 P. pruinosa Schrenk K435

Plate 433. The bluish-hued foliage of Populus glauca stands out among other trees, but does not emerge until June. This is the British champion, at the Hillier Gardens. Image J. Grimshaw.

654

Populus

New Trees

P. pseudograndidentata Dode (not a valid species: J. Smith, pers. comm. 2008) B313, K435

Populus purdomii Rehder Tree to 30 m. Bark greyish green to dark grey, furrowed, exfoliating when old. Branchlets yellowish brown or grey, glabrous; buds glabrous, sticky. Leaves deciduous, 7–14 × 4–9 cm (~25 × ~15 cm on suckers), long-ovate, upper surface bright green, glabrous, lower surface shiny green, glabrous, margins glandular-serrate or crenateserrate, ciliate, apex acuminate; petiole 2–5 cm long. Fruiting catkins 11(–13) cm long, glabrous. Capsule with three to four valves, ~0.7 cm long. Flowering April to May, fruiting May to June (China). Fang et al. 1999. Distribution CHINA: Gansu, Hebei, Henan, Hubei, Shaanxi, Sichuan. Habitat Mixed broadleaved forest, between 2500 and 3300 m asl. USDA Hardiness Zone 8 (?). Conservation status Not evaluated. Illustration Fang et al. 1999; NT650, NT654. Cross-reference K435. Taxonomic note Populus purdomii var. rockii (Rehder) C.F. Fang & H.L. Yang occurs only in southeast Gansu and has smooth bark that does not exfoliate. The veins on the underside of the leaf are pubescent. Populus purdomii is not recognised by Eckenwalder (1996).

Plate 434. Young growth on Populus purdomii can be flushed red. It is rare in cultivation. Image J. Smith.

Named after the overshadowed plant-hunter William Purdom (1880–1921), Populus purdomii is now, it seems, an extremely rare plant in cultivation, being maintained only in a few collections and with a very limited gene pool. At Alice Holt the stooled collection contains two accessions, one from Versailles via the French Poplar Commission in 1954, and the other from Kew in 1957 – although neither has been verified as P. purdomii (R. Jinks, pers. comm. 2008). The current tree at Kew represents the latter accession but was repropagated in 1990, from material returned from Alice Holt. This is a female clone and was just leafing out when seen in early May 2008, having avoided the mid-April frosts that had blackened the shoots of adjacent specimens of P. szechuanica; the 8 m tree observed was slim, with a straight trunk. The leaves are quite large, and can emerge with a brown tinge. P. ×rasumowskiana (Regel) Dipp. K435 P. ×rogalinensis Wróbl. K435 P. sargentii (NOW P. deltoides Bartram ex Marshall subsp. monilifera (Aiton) Eckenw.) B322, K435 P. sieboldii Miq. B299, K435 P. simonii Carrière B322, K435 P. suaveolens Fisch. B317, K436 P. szechuanica C.K. Schneid. B323, S394, K436 P. szechuanica var. tibetica C.K. Schneid. B323 P. ×tomentosa Carrière K436 P. tremula L. B324, K436 P. tremula var. davidiana (NOW P. davidiana Dode) B324, S394, K436 P. tremula var. villosa (Lang) Wesm. B324, K436 P. tremula × P. tremuloides B325

P. tremuloides Michx. B325, K436 P. tremuloides var. aurea (NOW P. tremuloides Michx.) K436 P. tremuloides var. vancouveriana (NOW P. tremuloides Michx.) B326, K436 P. trichocarpa (NOW P. balsamifera L. subsp. trichocarpa (Torr. & A. Gray ex Hook.) Brayshaw) B326, S394, K436 P. trichocarpa var. hastata (NOW P. balsamifera L. subsp. trichocarpa (Torr. & A. Gray ex Hook.) Brayshaw) K437 P. tristis Fisch. B327, K437 P. violascens Dode B323, K437 P. wilsonii (NOW P. glauca Haines, NT653) B327, K437 P. wislizeni (NOW P. deltoides Bartram ex Marshall subsp. wislizeni (S. Watson) Dorn) B312 P. ×woobstii (R.I. Schröd. ex Regel) Dode K437 P. yunnanensis Dode B328, S395, K437

Section II. Species Accounts

Prumnopitys

PODOCARPACEAE

PRUMNOPITYS

Phil.

Prumnopitys comprises nine species with a distribution in South and Central America (from Chile to Venezuela and Costa Rica), and the Pacific (northeast Australia, New Caledonia and New Zealand). They are densely branched, dioecious, evergreen trees or shrubs with an outward appearance not unlike that of Taxus. The leaves are small (< 2.5 cm long), linear, spirally arranged (though often appearing two-ranked), hypostomatic, and with a distinct midrib. Male strobili are solitary or grouped, on short, axillary shoots; female cones subterminal, solitary or grouped along a leafy or scaly shoot. The cone is reduced to a single fertile scale with a single ovule; the receptacle does not enlarge, and the fleshy epimatium completely encloses the seed (Hill 1998). The nomenclature of this genus is rather messy, most species having been formerly known as Podocarpus, often under different specific epithets, while the name Podocarpus spicatus has been used for both a New Zealand species, now considered to be Prumnopitys taxifolia, and the Chilean Prumnopitys andina (for which the combination Prumnopitys spicata (Poepp.) Molloy & Muñoz-Schick has also been published). The descriptions of Podocarpus spicatus in the standard literature refer to the New Zealand species Prumnopitys taxifolia, which remains a rare plant in our area, seen only in the mildest gardens (in Cornwall, for example, and in the Chelsea Physic Garden in London). The only Prumnopitys to have achieved relatively widespread cultivation is P. andina, which can form a substantial tree even away from mild maritime sites. P. andina (Poepp. ex Endl.) de Laub. (WAS Podocarpus andinus B280, S386, K250)

Prumnopitys ferruginea (G. Benn. ex D. Don) de Laub.

Miro

Syn. Podocarpus ferrugineus G. Benn. ex D. Don Tree to 25 m, 1.3 m dbh. Bark greyish brown, falling in thick flakes, leaving a distinct ‘hammer-mark’ pattern. Juvenile leaves to 3 cm long, narrow-linear; adult leaves sessile, 1.5–2.5 × 0.2–0.3 cm, falcate, midrib prominent, apex acute to subacute, margins recurved. Dioecious. Male cones solitary, axillary, sessile to subsessile, 0.5–1.5 cm long. Female cones solitary or rarely paired, to 2 cm long at maturity, on short branchlets to 1 cm long, the bases of which are densely covered with scales; seeds oblong to globose, covered by a fleshy, purple epimatium. Allan 1961. Distribution NEW ZEALAND: North Is., South Is., Stewart Is. Habitat Lowland forests. Seeds are distributed by the New Zealand Pigeon (Hemiphaga novaeseelandiae). USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration NT18, NT656. Cross-references B285, K255 (in both cases as Podocarpus ferrugineus). Taxonomic note The epithet ferruginea refers to the rusty colour of dried herbarium specimens.

Prumnopitys ferruginea is rare in cultivation, due to its lack of hardiness and its general unavailability. It is grown in the San Francisco Bay Area, and in the British Isles specimens are scattered along the western maritime fringes, the tallest being found in the John F. Kennedy Arboretum, Co. Wexford (up to 9.5 m, measured in 2003 by Aubrey Fennell, TROBI). Hillier & Coombes (2002) recorded that it was flourishing in a garden at Helens Bay, Co. Down, but no further news of this specimen has been traced

655

656

Prumnopitys

New Trees

1 cm

A B

Figure 73 (above). Prumnopitys ferruginea: branchlet with male strobili (A); branchlet with female cone (B).

(A. Coombes, pers. comm. 2008). Another example, 9 m tall, was recorded on Tresco in 1970, and there are old records of small trees in Sussex gardens (TROBI), but it is not known if these still exist. At Tregrehan a specimen planted in 1995 had achieved 2.5 m in 2005. As a young plant at least, its foliage bears a strong resemblance to a Yew (Taxus baccata), and this leaf shape is maintained into adulthood – unlike in P. taxifolia where the leaves change shape as the tree matures. In cultivation P. ferruginea shows no sign of developing into the large timber tree it can become in New Zealand.

P. ferruginoides (R.H. Compton) de Laub. (WAS Podocarpus ferruginoides K255) P. harmsiana (Pilg.) de Laub. (WAS Podocarpus harmsianus K256) P. ladei (F.M. Bailey) de Laub. (WAS Podocarpus ladei K257)

P. montana (Humb. & Bonpl. ex Willd.) de Laub. (WAS Podocarpus montanus K260) P. standleyi (J. Buchholz & N.E. Gray) de Laub. (WAS Podocarpus standleyi K263) P. taxifolia (Banks & Solander) de Laub. (WAS Podocarpus spicatus R. Br. (erroneously Podocarpus spicatus Mirb.) B285, K263)

Section II. Species Accounts

Prunus

657

ROSACEAE

PRUNUS

L.

Syn. Amygdalus L., Armeniaca Scop., Cerasus Mill., Laurocerasus Duham., Padus Mill., Persica Mill., Pygeum Gaertn.

Almonds, Apricots, Bird-cherries, Cherries, Gages, Peaches, Plums There are over 200 species of Prunus, most of which occur in the temperate northern hemisphere. While Prunus has in the past been divided into numerous segregate genera, DNA evidence suggests that the segregates are better recombined into a single genus (Bortiri et al. 2001), and that approach has been used here. Prunus species are shrubs or trees with deciduous or rarely evergreen leaves; they are usually unarmed, though thorns occur in some species (for example, P. spinosa, Blackthorn). The leaves are simple and alternate with entire, serrate or crenate margins; glands are usually present on the margins, or on the underside of the lamina, or as a pair on the petiole. Stipules are usually caducous. The inflorescence is basically a raceme and is usually unbranched; it may be reduced to a few-flowered umbel or to only a single flower (or pair of flowers). The flowers are hermaphrodite, 5-merous and either white or pink; the hypanthium is tubular or bowl-shaped and usually falls, with the sepals, before the fruit forms; the petals are inserted at the mouth of the hypanthium; stamens 10 to numerous. The fruit is a drupe with juicy or rather dry flesh and is indehiscent (dehiscent in the Almond P. dulcis). Each fruit contains a woody or bony stone (endocarp) with a smooth or rugged exterior; the stone is indehiscent or has two valves, and contains a single seed (the pit) (Mendes 1978, Elias 1980, Ohashi 1993a, Kalkman 2004). As so often is the case where a genus contains species that are edible and (or) ornamental, nomenclature within Prunus is as tangled as a Blackthorn hedge. Dismemberment of the genus at different times into segregates has contributed an excess of synonyms, and the ornamental cherries, especially in Japan, have added many more names to the register. Conveniently, however, there is a helpful website entitled ‘Sorting Prunus Names’ (University of Melbourne 1995–2020) and describing itself (accurately) as a ‘multilingual, multiscript plant name database’, that gives a synoptic account of Prunus nomenclature, enabling entities to be tracked down within the thicket of botanical names. Vernacular names are also provided, in appropriate scripts: for example, names are given in 25 languages for the edible Plum (P. domestica), including the Zulu umplaamuzi (try saying it). Cultivars are not covered, however, and there are many omissions (for example, P. himalaica, P. sogdiana, P. takesimensis: see accounts below).

Plate 435. Prunus takesimensis from Ullung-do (known as Takeshima during the Japanese occupation of Korea) is a pretty cherry with good edible fruits. Image J. De Langhe.

658

Prunus

Plate 436. Superb autumn colouring is characteristic of Prunus ‘Royal Burgundy’. Image Frank P. Matthews, Trees for Life.

New Trees

Prunus, in all its manifestations, is one of the most important genera of ornamental and culinary trees. Most fall outside the remit of this account, which as always focuses on wild species, but it is undoubtedly the Japanese flowering cherries (Sato-sakura) that are the most popular and conspicuous ornamental Prunus taxa in cultivation, and several books dealing with this group are available (for example, Ingram 1948, Kuitert 1999, in addition to works in Japanese). New cultivars continue to be introduced in all groups within the genus, but it is the flowering cherries that receive most attention. While working for Bridgemere Nurseries, Cheshire, Chris Sanders trialled an extensive array of new Japanese cherry cultivars raised in the 1960s by Masatoshi Asari, a schoolteacher from the town of Matsumae in Hokkaido, and has kindly provided notes on some of the most outstanding and distinctive. All Asari’s cultivar names were prefixed ‘Matsumae’ by the raiser, but recent Japanese accounts have omitted this in some cases (though not in all). Some have also been given selling names, which may vary in different countries. ‘Matsumae-beni-yutaka’ (syn. ‘Beni-yutaka’, introduced to the trade in 1961) is very early-flowering, with large semi-double pink flowers. It has an upright vase-shape when young but broadens with age, and is notable for its superb autumn colours. A little later in the season comes ‘Matsumae-usugasanesomei’ (1966), a hybrid of P. ×yedoensis and equally floriferous, with small to medium-sized clear pink flowers, that are usually single but may have a few extra petaloids. This will form a sparsely branched, round-headed, small tree. Of mid-season cultivars, ‘Matsumae-benigasa’ (syn. ‘Benigasa’, 1961) has large, fully double flowers, opening pale pink but fading to white, among bronze-green leaves on a broad, spreading tree. ‘Matsumae-fuki’ (sold in the United Kingdom as Chocolate Ice, 1961) is also mid-season but forms a more upright tree. It produces very large, more or less single flowers (up to 6.5 cm diameter) that open pale blush to almost white from pink buds. The young leaves are deep coppery bronze and appear with the flowers. ‘Matsumae-hanagasa’ (syn. ‘Hanagasa’, sold in the United Kingdom as Pink Parasol, 1963) has a spreading to pendulous habit and produces large, double, pale pink flowers with a conspicuous bunch of bright green, phylloid styles in the centre. The bronze young leaves emerge at the same time as the flowers. The same is true of the foliage of ‘Matsumae-shizuka’ (syn. ‘Shizuka’, sold in the United Kingdom as Fragrant Cloud, 1960), but this more upright tree has large, pure white flowers that are semi-double and strongly scented of vanilla. Mention should also be made of Prunus ‘Royal Burgundy’, propagated from a bud mutation found on a seedling of P. ‘Kanzan’ by Frank Parks of Speer & Sons Nursery, Woodburn, Oregon. This was introduced to the trade in the United States around 1990 and in the United Kingdom in 1999. The flowers are similar to those of ‘Kanzan’, but are a slightly darker magenta-pink and appear about a week later. The leaves are a striking dark reddish purple and the branches, stems and calyx are also reddish. In addition to cultivar names for flowering cherries not known by any other name, mostly derived from P. serrulata, there are a number of nothospecific names coined by Japanese botanists to cover hybrid groups within which cultivars have been selected. These names may appear in the literature or in catalogues. For

Section II. Species Accounts

Prunus

659

example, P. ×kanzakura Makino (the hybrid between P. cerasoides var. campanulata (Maxim.) Koidz. and P. jamasakura) includes several named cultivars, including ‘Kanzakura’, ‘Usu-kan-zakura’ and ‘Atami-zakura’ (Botanic Garden 2001–2008), which might appear in lists as stand-alone cultivars. Another such nothospecies, P. ×kobuku-zakura Ohwi (P. ×subhirtella × P. pseudocerasus), with small white, semi-double flowers, is in cultivation in the United Kingdom. The plethora of Prunus names means that it is always likely that new ‘species’ will appear in lists. A particularly interesting species, cultivated as an ornamental in California and South Africa, is P. africana (Hook. f.) Kalkman, a large evergreen tree from the montane forests of Africa and Madagascar. It has been used medicinally by many African peoples for various ailments, and apparently is also selected by elephants (JMG, pers. obs.), whose zoopharmacognosy often mirrors local human choices. The bark of P. africana yields the substance pygeum, used effectively in the treatment of prostate problems, including benign prostatic hypertrophy (cause of weak bladders in older men). In consequence it is in huge demand – trade in finished products was worth US$220 million per annum in the early 2000s – and the species is being overexploited in many parts of Africa (currently assessed as Vulnerable by the IUCN). Various attempts are being made to grow it as a commercial crop (see, for example, WWF 2003). Being a montane tree, P. africana has some cold tolerance, and would be worth attempting in milder gardens.

P. alabamensis (NOW P. serotina subsp. hirsuta (Elliott) McVaugh, NT665) K20 P. alleghaniensis Porter B350, K20 P. americana Marshall B351, K21 P. americana var. lanata (NOW P. lanata Mack. & Bush) B351 P. ×amygdalo-persica (NOW P. ×persicoides Dalla Torre & Sarnth.) B351, K21 P. angustifolia Marshall B352, K21 P. angustifolia var. watsonii (Sarg.) Bailey K21 P. apetala (Siebold & Zucc.) Franch. & Sav. B353, K21 P. apetala var. pilosa (Koidz.) E.H. Wilson K21 P. arabica (Oliv.) Meikle B353, K21 P. argentea (Lam.) Rehder B353, K21 P. armeniaca L. B354, K22 P. armeniaca var. ansu Maxim. B354, K22 P. ×arnoldiana Rehder B415, K22

P. avium (L.) L. B354, S396, K22 P. avium var. duracina (L.) Schübl. & Martens B356, K23 P. avium var. juliana (L.) Schübl. & Martens B356, K23 P. baldschuanica Regel K23 P. besseyi (NOW P. pumila subsp. besseyi (Bailey) Nizhnikev) B356, K23 P. bifrons Fritsch B377, K24 P. ×blireana André B361, S397, K24 P. bokhariensis Royle K24 P. brigantina Vill. B356, K24 P. bucharica (Korsh.) Fedtsch. K24 P. buergeriana Miq. K24 P. campanulata (NOW P. cerasoides var. campanulata (Maxim.) Koidz.) B357, K24 P. canescens Bois B358, K25 P. cantabrigiensis Stapf B359, S396 P. caroliniana (Mill.) Aiton B375, K25 P. cerasifera Ehrh. B360, S396, K25

Plate 437. The medicinal bark on this Prunus africana on Mount Kilimanjaro has been stripped by elephants, which have then rubbed against the trunk: new shoots are emerging from the base. Image J. Grimshaw.

660

Prunus

New Trees

P. cerasifera subsp. divaricata (Ledeb.) Bailey K25 P. cerasoides Buch.-Ham. ex D. Don B358, K26 P. cerasoides var. rubea Ingram K26 P. cerasus L. B362, K26 P. cerasus var. austera L. B362, K27 P. cerasus var. caproniana L. B362, K27 P. cerasus var. frutescens Neilr. B362, K27 P. cerasus var. marasca (Host) Viv. B362, K27 P. changyangensis (Ingram) Ingram K27 P. ×cistena (Hansen) Koehne B356, K27 P. cocomilia Ten. B363, K27 P. conadenia Koehne K27 P. concinna Koehne B364, K28 P. conradinae (NOW P. hirtipes Hemsl.) B364 P. consociiflora C.K. Schneid. B364, K28 P. cornuta (Wall. ex Royle) Steud. B365, K28 P. curdica Fenzl & Fritsch B410, K28 P. cuthbertii (NOW P. serotina subsp. hirsuta (Elliott) McVaugh, NT665) B365 P. cyclamina Koehne B367, K28 P. ×dasycarpa Ehrh. B366, K28 P. davidiana (NOW P. sibirica f. davidiana (Carrière) Kitag.) B366, K28 P. davidiana f. alba hort. B367 P. davidiana var. potaninii (Batal.) Rehder K28

P. davidiana f. rubra (Bean) Rehder B367 P. ×dawyckensis Sealy B367, K28 P. dielsiana C.K. Schneid. B367, K29 P. divaricata (NOW P. cerasifera subsp. divaricata (Ledeb.) C.K. Schneid.) B361 P. ×domestica L. B368, K29 P. ×domestica subsp. insititia (L.) C.K. Schneid. B368 P. ×domestica subsp. italica (Borkh.) Hegi B368 P. dulcis (Mill.) D.A. Webb B369, K29 P. dulcis var. amara (DC.) H.L. Moore B370, K30 P. dulcis var. fragilis (Borkh.) Focke K30 P. dulcis var. sativa (Ludwig) Koch K30 P. ×dunbarii Rehder K30 P. emarginata (Hook.) Eaton B371, K30 P. emarginata var. mollis (Hook.) Brew. & S. Watson K30 P. ×eminens Beck B372, K30 P. fasciculata (Torr.) Gray K30 P. fenzeliana Fritsch B370, K30 P. ×fontanesiana (Spach) C.K. Schneid. B371, K30 P. fruticosa Pall. B371, K30 P. ×gigantea (Spath) Koehne K30 P. glandulosa Thunb. B372, K30 P. ×gondouinii (Poiteau & Turpin) Rehder B363, K31 P. gracilis Engelm. & Gray K31 P. gravesii Small K31 P. grayana Maxim. B373, K31 P. gymnodonta Koehne K31 P. ×hillieri (NOW P. ‘Hillieri’ Hemsl.) K31

Prunus himalaica Kitam. Shrub or tree to 5 m (or more). Branchlets purplish, with dense reddish brown pubescence. Leaves deciduous, 6–8 × 4–5 cm, elliptic, upper surface bright green with minute hairs, lower surface pale green with dense brown hairs on the veins, 9–13 secondary veins on each side of the midrib, margin biserrate, apex caudate to acuminate, base rounded; petiole ~1 cm long, pubescent. Inflorescence umbellate with one to two flowers on pubescent pedicels 3.5–4.5 cm long. Flowers pale pink; hypanthium 1 cm long, glabrous, sepals ovate and glandular-serrate, 0.4 cm long, stamens ~45. Drupe a small cherry (details unrecorded). Kitamura 1954, Schilling 2007. Distribution NEPAL. Habitat Approx. 3900 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Schilling 2007; NT661. Cross-reference S398. Taxonomic note This species is evidently closely related to the Chinese P. serrula and the Himalayan P. rufa, but was distinguished

Section II. Species Accounts

Prunus

661

from the latter by Kitamura (1954) on the basis of having a biserrated leaf with a rounded base. Schilling (2007) notes that P. rufa is pubescent only along the midrib and veins and only while the leaf is young, unlike P. himalaica in which pubescence is more extensive, and persistent. Further collections are needed, however.

The introduction and subsequent horticultural history of Prunus himalaica has been recently recounted by Tony Schilling (2007). All trees in cultivation are descended from a single seedling collected in the Langtang Valley, Nepal in 1965, under the name Betula utilis and collection number Schilling 1138. The name was soon corrected, and the error is understandable, as the glory of P. himalaica is its dark brown, peeling bark with a distinct suggestion of the best forms of Betula utilis. It certainly rivals P. serrula for decorative effect, though it is a darker shade of brown, and like that species, should be planted in a conspicuous place where the smooth bark can be caressed. The flowers are small and the foliage unremarkable, but distinctly softly hairy, looking and feeling quite different to that of P. serrula. As it is easily propagated by cuttings (Schilling 2007) (and presumably by grafting) it has been gently spread around in British collections, and has recently been propagated for commercial release by Nick Dunn of Frank P. Matthews Ltd. The tallest specimen recorded, at 5.5 m, is at Castle Howard Arboretum, North Yorkshire; this seems to be about as big as it gets. It would be worth taking the trouble to train young trees into forming as long a single stem as possible, to maximise the effect of the bark.

P. hirtipes Hemsl. B364, K31 P. hortulana Bailey B373, K32 P. humilis Bunge B374, K32 P. ilicifolia (Hook. & Arn.) Walp. B374, K32 P. incana (Pall.) Batsch. B375, K32 P. incisa Thunb. B376, S397, K32 P. incisa var. kiukiensis (Koidz.) Ohwi S397 P. incisa var. serrata (Koidz.) E.H. Wilson B376 P. insititia (NOW P. ×domestica subsp. insititia (L.) C.K. Schneid.) K33 P. insititia var. italica (NOW P. ×domestica subsp. italica (Borkh.) Hegi) K33 P. insititia var. subsilvestris (NOW P. ×domestica subsp. insititia (L.) C.K. Schneid.) K33 P. insititia var. syriaca (NOW P. ×domestica subsp. syriaca (Borkh.) Janchen ex Mansfield) K33

P. involucrata (NOW P. pseudocerasus Lindl.) B360 P. jacquemontii Hook. f. B377, K33 P. jamasakura Siebold (WAS P. serrulata var. spontanea B398, K47) P. japonica Thunb. B373, K33 P. ×juddii E. Anderson B396, K34 P. kansuensis Rehder B377, K34 P. kurilensis (NOW P. nipponica var. kurilensis (Miyabe) E.H. Wilson) K34 P. kurilensis × P. sargentii K34 P. lanata (Sudw.) Mack. & Bush K35 P. lannesiana (Carrière) E.H. Wilson B409 P. latidentata Koehne B385 P. ×laucheana Bolle ex Lauche B388, K35 P. laurocerasus L. B378, S397, K35 P. litigiosa C.K. Schneid. B380, K38 P. lusitanica L. B380, K38

Plate 438. The bark of Prunus himalaica, introduced to the United Kingdom from Nepal by Tony Schilling in 1965, rivals its Chinese relative P. serrula for decorative effect. Image M. Flanagan.

662

Prunus

New Trees

P. lusitanica subsp. azorica (Mouillef.) Franco B381, K38 P. lyonii (Eastw.) Sarg. B374, K38 P. maackii Rupr. B381, K38 P. macradenia Koehne K38 P. mahaleb L. B382, K38 P. mahaleb f. xanthocarpa (Roem.) Rehder B382 P. mandshurica (NOW P. armeniaca var. mandshurica Maxim.) B408, K38 P. maritima Marshall B383, K38 P. maximowiczii Rupr. B383, K39 P. mexicana (NOW P. pensylvanica var. mollis (Hook.) B. Boivin) B351, K39 P. microcarpa C.A. Mey. B383, K39 P. microcarpa var. diffusa C.K. Schneid. K39 P. microcarpa var. pubescens (Bornm.) Meikle K39 P. mira Koehne B384, K39 P. mongolica Maxim. K39 P. monticola K. Koch K39 P. mugus Hand.-Mazz. B384, K40 P. mume (Siebold) Siebold & Zucc. B385, S397, K40 P. munsoniana W. Wight & Hedrick B374, K40 P. napaulensis (Ser.) Steud. B365 P. nigra Aiton B386, K40 P. ×nigrella Cumming K41 P. nipponica Matsum. B386, K41 P. nipponica var. kurilensis (Miyabe) E.H. Wilson B387 P. orthosepala Koehne B387, K41 P. padus L. B388, S397, K41 P. padus var. commutata Dipp. K41 P. padus var. pubescens Regel & Tiling K42 P. pedunculata (Pall.) Maxim. K42 P. pendula Maxim. (WAS P. ×subhirtella var. pendula OR P. ‘Pendula’ B412, K53) P. pensylvanica L. f. B389, K42 P. pensylvanica var. saximontana Rehder B389, K42 P. persica (L.) Batsch B390, K42

P. persica f. compressa (NOW P. persica var. compressa (Loudon) Bean) B390 P. persica var. nectarina (NOW P. simonii Carrière) B391 P. persica var. nucipersica C.K. Schneid. K43 P. persica var. platycarpa Bailey K43 P. petunnikowii (Litvin.) Rehder K43 P. pilosa (Turz.) Maxim. K43 P. pilosiuscula (NOW P. clarofolia C.K. Schneid.) B391, K43 P. pilosiuscula var. media Koehne K43 P. pilosiuscula var. subvestita (NOW P. clarofolia C.K. Schneid.) B391 P. pleiocerasus Koehne K44 P. polytricha Koehne B391 P. prostrata Labill. B391, K44 P. prostrata var. brachypetala (Boiss.) Ingram K44 P. prostrata var. concolor Boiss. K44 P. prostrata var. glabrifolia Moris K44 P. prostrata var. incana Litard. & Maire K44 P. pseudoarmeniaca Heldr. & Sart. K44 P. pseudocerasus Lindl. K44 P. pseudocerasus var. cantabrigiensis (NOW P. pseudocerasus ‘Cantabrigiensis’) K44 P. pumila L. B382, K44 P. pumila var. depressa (Pursh) Bean B392, K44 P. pumila var. susquehanae (Willd.) Jaeg. B392, K44 P. reverchonii Sarg. K44 P. rufa Hook. f. B393, K45 P. rufa f. trichantha (NOW P. trichantha Koehne) B393, S397 P. salicifolia (NOW P. serotina subsp. capuli (Cav.) McVaugh, NT663) B397, K45 P. salicina Lindl. B393, K45 P. sargentii Rehder B394, K45 P. ×schmittii Rehder B358, K45 P. scoparia (Spach) C.K. Schneid. B353, K46 P. sericea (Batal.) Koehne K46

Section II. Species Accounts

Prunus serotina Ehrh.

Prunus

663

American Black Cherry

This well-known and valuable species was described by Bean (B396) and Krüssmann (K46), but several local variants are now treated at subspecific level and may be found in some collections. A key to all the subspecies of Prunus serotina, modified from that of McVaugh (1951), is provided below. 1a. Branchlets and foliage entirely glabrous, leaves coarsely serrate, petiole long (~1.5 cm); USA (Texas: Edwards Plateau) (not traced in cultivation) .................. subsp. eximia 1b. Branchlets glabrous to hirsute, foliage rufous-pubescent below, leaves finely serrate, petiole short (< 1 cm) .................................................................................. 2 2a. Branchlets rufous-hirsute; leaves not or scarcely drooping, less than twice as long as wide, lower surface uniformly pubescent; USA (Alabama, Florida, Georgia) ........ subsp. hirsuta 2b. Branchlets glabrous or sparsely hirsute; leaves drooping, 2.5–3 times as long as wide, lower surface glabrous except for tufts of hair near base of midrib ................................. 3 3a. Branchlets glabrous; leaves narrowly lanceolate, usually 8–12 cm long and 2.5–3.5 times as long as wide, sometimes totally glabrous; racemes > 15 cm long; fruit to 2–2.5 cm diameter; USA (California), Mexico (southern), Central America, South America ................................................................................ subsp. capuli 3b. Branchlets glabrous or sparsely hirsute; leaves elliptic to ovate, usually 1.8–2.5 times as long as wide; racemes < 15 cm long; fruit to 0.6–1 cm diameter ....................... 4 4a. Xerophytic growth-form with small leaves, sparse branches; leaves 5–7(–9) cm long; racemes ~10 cm long; USA (Arizona, New Mexico, Texas), Mexico .......................... subsp. virens 4b. Mesophytic growth-form with large leaves, luxuriant growth; leaves 6–9(–15) cm long; racemes ~12 cm long; Canada, USA (eastern), high mountains of Mexico & Guatemala ............................................................................................. subsp. serotina

Prunus serotina subsp. capuli (Cav.) McVaugh

Capulín

Syn. P. salicifolia Kunth Large-fruited bird-cherry with long, willow-like leaves; inflorescences 15 cm long or more (with ~35 flowers). Specimens from South America are relatively uniform, but the morphology of those from Mexico and Central America can be variable, and hybridisation with other subspecies of P. serotina may be the cause. McVaugh 1951. Distribution BOLIVIA; COLOMBIA; ECUADOR; GUATEMALA; MEXICO: Guanajuato, Hidalgo, Jalisco, México, Michoacán, Querétaro; PERU; USA: California; VENEZUELA. Subsp. capuli is thought to have been indigenous to the highlands of southern Mexico and Guatemala, later introduced to South America and California. Habitat Woods, pastures, hedges, roadsides. Often found in disturbed areas. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Cross-references B397, K45 (in both cases as P. salicifolia).

Subsp. capuli is notable for the size of its fruits, up to 1.7 cm in diameter (Krüssmann 1986), which are produced on long pendulous racemes and look extremely tempting. They are indeed edible, and very highly prized by local people throughout its range in Central and South America: the Capulín’s native range has been blurred by its cultivation as a fruit tree (Office of International Affairs 1989). It seems to be rare in cultivation in our area – surprisingly, given that it is distinctly ornamental in fruit, and hardy in British and western European conditions. It is capable of achieving impressive stature: a specimen of 17 m (in 1981) formerly grew at Kew, but the current British champion, at Greenways, Devon, was measured at 20 m (85 cm dbh) by Owen Johnson in 2004 (TROBI). It is occasionally grown in continental Europe (Jan De Langhe, pers. comm. 2008), and is also in cultivation in California.

Plate 439. The racemes of plants in the Prunus serotina complex vary in length and in the number of flowers they bear. They are shortest in subsp. virens (seen here), from arid habitats. Image J. Grimshaw.

664

Prunus

New Trees

1 cm

1 cm

B A

Section II. Species Accounts

Prunus

665

Prunus serotina subsp. hirsuta (Elliott) McVaugh Syn. P. alabamensis Mohr, P. cuthbertii Small Subsp. hirsuta is readily distinguished from all other subspecies of P. serotina by the combination of stiffly spreading leaves and racemes, broad-obovate leaves, usually with uniform pubescence on the underside but sometimes hairy only on the midrib, and hirsute branchlets. McVaugh 1951. Distribution USA: Alabama, Florida, Georgia. Habitat Sandy soils, with Pinus palustris and Quercus marilandica. USDA Hardiness Zone 7. Conservation status Not evaluated. Cross-reference K20 (as P. alabamensis).

Prunus serotina subsp. hirsuta is probably better known as P. alabamensis, and this is the name under which it is usually found in collections. It is a vigorously growing tree and is capable of becoming quite large. The British champion is a specimen of 17.6 m (with two stems, of 31 cm and 34 cm dbh) at the Hillier Gardens, planted prior to 1977, and another individual in that collection, accessioned in 1983, was 10.5 m tall in 2004. At Kew a specimen received in 1965 is now 10 m tall by about the same wide. This was just beginning to turn yellow when seen in early November 2007 – rather later than most other trees in that exceptional autumn. P. serotina var. montana (Small) Britton K46 P. serotina f. phelloides Schwer. B397

Prunus serotina subsp. virens (Wooton & Standl.) McVaugh Syn. Padus virens Wooton & Standl. Subsp. virens is typical of arid regions and consequently has small leaves, 5–7(–9) cm long, and a rather sparse growth habit. McVaugh 1951. Distribution MEXICO: Chihuahua, Coahuila, Guanajuato, Jalisco, Nuevo León, San Luis Potosí, Sonora; USA: Arizona, New Mexico, Texas. Habitat Wooded valleys in arid and semi-arid mountains, above 1500 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT663. Cross-reference K56. Taxonomic note Typical subsp. virens is largely glabrous; specimens with thick rufous or grey pubescence on the branchlets and/or inflorescence axes are recognised as subsp. virens var. rufula (Wooton & Standl.) McVaugh.

Subsp. virens is the dryland representative of the Prunus serotina complex, and in most of our area is probably of interest only to collectors. In semi-arid regions of the southern and western United States it might be useful. A tree derived from a collection by Carl English in the Black Mountains of New Mexico has grown at Kew since 1970, reaching about 5 m, but is currently suffering greatly from dieback. The foliage and inflorescences are distinctly smaller than in other forms of P. serotina growing nearby. P. serrula Franch. B397, S398, K46 P. serrulata Lindl. B398, S398, K46 P. serrulata var. hupehensis Ingram K46 P. serrulata var. pubescens (NOW P. verecunda (Koidz.) Koehne) B399, S398, K47

Prunus sogdiana Vassilcz.

P. serrulata var. spontanea (NOW P. jamasakura Siebold) B398, K47 P. setulosa Batal. K50 P. sibirica L. B407, K50 P. ×sieboldii (Carrière) Wittm. B408 P. simonii Carrière B408, K50 P. ×skinneri Rehder K51

Alycha, Sogdijskaya Plum

Shrub or tree 2–8 m; generally not suckering. Bark dark grey to black. Branchlets green, then yellowish brown to reddish brown; spines present or absent. Leaves deciduous, (1.5–)4–5(–6) × (0.5–)2–4 cm, ovate to elliptic, upper surface dark green and glabrous, lower surface pale green with tufts of hair in the vein axils, margin serrate, apex acute to rounded; leaves turning lemon-yellow in autumn; petiole 0.4–1 cm long; stipules caducous. Flowers white, fragrant, 5-merous, 1.5–2.5 cm diameter, appearing before the leaves; hypanthium

Figure 74 (opposite). Prunus sogdiana: flowering stems (A); branchlet with leaves (B).

666

Prunus

New Trees

pinkish green, sepals reflexed, green with pink margins, petals almost circular, concave, 1.4–1.8 cm diameter, stamens ~20. Fruit a yellow, pink, red or blue plum, 1–1.5 cm diameter. Dzhangaliev et al. 2003. Distribution KAZAKHSTAN; KYRGYZSTAN; TAJIKISTAN; UZBEKISTAN (?). Habitat Forest and scrub in river valleys and mountain slopes, between 800 and 2200 m asl. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration NT664, NT666. Taxonomic note This little-known taxon may be synonymous with P. cerasifera Ehrh. subsp. divaricata (Ledeb.) C.K. Schneid.

Plate 440. Prunus sogdiana is a cherry-plum from Central Asia, attractive both in flower in spring, and in summer when it bears abundant sweet fruit. Figure 74 (p. 664) was drawn from material from this tree, growing at Evenley Wood, Northamptonshire. Image J. Whiteley.

Whatever its true nomenclatural position, Prunus sogdiana is essentially a central Asian member of the P. cerasifera alliance, and looks like it: in other words, it is a pretty, hardy little tree with abundant white blossom, followed by tasty plums. Its decorative qualities are highly praised by those who grow it. A multistemmed tree of 7.4 m in the Hillier Gardens, raised from seed sent by the Moscow Botanical Garden ‘about forty years ago’ (A. Coombes, pers. comm. 2008), seems to be the earliest recorded specimen in western cultivation. A recent batch of seedlings raised by Tim Whiteley at Evenley Wood, Northamptonshire have turned out to have fruits of different colours: the tree at Evenley Wood (illustrated here) has red fruits, while at Hergest Croft another two from the batch have purple or yellow fruits. These trees have currently reached c.1.8 m, from planting in 2004, first fruiting in 2007 at Hergest Croft, and are described by Lawrence Banks (pers. comm. 2008) as being ‘spectacular’ in flower in late March. P. speciosa (Koidz.) Ingram B409, S400, K51 P. spinosa L. B410, K51 P. spinosissima (Bunge) Franch. K51 P. spinulosa Siebold & Zucc. K51 P. ssiori F. Schmidt B411, K52 P. subcordata Benth. B411, K52 P. ×subhirtella Miq. B411, S400, K52

Prunus takesimensis Nakai

P. ×subhirtella var. ascendens (NOW P. pendula f. ascendens (Makino) Ohwi) B412, K52 P. ×subhirtella var. pendula (NOW P. pendula Maxim.) B412, K53 P. ×subhirtella × P. ×yedoensis K53 P. sweginzowii Koehne K53 P. szechuanica Batal. K53

Ullung-do Cherry, Takesimensis Cherry

Tree to 20 m, 0.4 m dbh. Branchlets green to greyish brown. Leaves deciduous, 15 × 9 cm, elliptic, upper surface bright green, lower surface pale green, margin serrate, apex acuminate; petiole ~3 cm long; stipules deciduous with marginal hairs. Inflorescence umbellate with two to five flowers on pedicels 1.5 cm long. Flowers white or pale pink, 2.6–3.2 cm diameter; hypanthium tubular, sepals lanceolate-acuminate, petals bifid. Drupe ~1 cm long, reddish purple. Nakai 1918, Chang et al. 2004. Distribution SOUTH KOREA: Ullung-do, Ullung-gun. Habitat Woodland. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT657.

Despite its relatively recent arrival in horticulture, this pretty cherry from Ullung-do has been honoured with mass plantings in the Tidal Basin area of Washington DC, taking its place in the annual display of flowering cherries there (and given the ‘English’ name of Takesimensis Cherry (!); Ullung-do Cherry would be more appropriate, we suggest). It was planted for its reputed ability to tolerate wet sites in the wild (National Parks Service 2007) – a physiological feature that has been confirmed by Jacobs & Johnson (1996), who found that of a number of different cherries, this was the most tolerant to flooding. It was introduced to the US National Arboretum through arrangements made by Roland Jefferson (of USNA) with Prof. Jae-wae Hang of the Department of Forestry

Section II. Species Accounts

Prunus

at Yeungnam University. With graduate students, Prof. Hang collected 27 accessions from trees across Ullung-do in 1986. In 1989, Skip March of the US National Arboretum made another collection, from Ullung-gun (R. Olsen, pers. comm. 2008). Seed has also been distributed by Chollipo Arboretum (to Arboretum Wespelaar, Belgium, for example, in 1995). Field notes from the 1989 collection (USNA accession 61613) were optimistic about its tolerances, including of wind, salt spray, and even concrete over its roots. A tree from this accession grows at Kew. Apart from the Washington trees and specimens in a few botanic gardens across our area, Prunus takesimensis seems to be largely unknown, and is apparently not in commerce, even in the United States. Richard Olsen (pers. comm. 2008) reports that its fruits are ‘sizeable and delicious’, and popular with staff at the US National Arboretum. P. tangutica (Batal.) Koehne B413, K53 P. tatsienensis Batal. K53 P. tenella (NOW P. nana (L.) Stokes) B414, K53 P. tenella var. campestris (Bess.) Rehder B414, K54 P. tenella var. georgica Desf. K54 P. tenella f. gessleriana (Kirchn.) Rehder B414 P. texana Dietr. K54 P. tomentosa Thunb. B414, K54 P. tomentosa var. endotricha Koehne K54 P. triloba Lindl. B415, K54 P. triloba f. simplex (Bunge) Rehder K55 P. umbellata Elliott K55 P. ursina Kotschy K55 P. ussuriensis Kovalev & Kostina K55 P. utahensis Koehne B356, K55 P. vaniotii (NOW P. obtusata Koehne) K55

P. vaniotii var. potaninii (Koehne) Rehder K55 P. vavilovii M. Pop. K55 P. verecunda (Koidz.) Koehne S398 P. virens (Wooton & Standl.) Shreve K56 P. virginiana L. B416, K56 P. virginiana var. demissa (Torr. & Gr.) Torr. B416, K56 P. virginiana f. leucocarpa (NOW P. virginiana var. leucocarpa S. Watson) B416 P. virginiana var. melanocarpa (NOW P. virginiana subsp. melanocarpa (A. Nelson) R.L. Taylor & McBride) B416, K56 P. wallichii Steud. K56 P. watsonii Sarg. B352 P. webbii (Spach) Vierh. B370, K56 P. wilsonii (C.K. Schneid.) Koehne K56 P. ×yedoensis Matsum. B416, S401, K57 P. zippeliana Miq. K58

ARALIACEAE

PSEUDOPANAX

K. Koch

Lancewoods Pseudopanax in its former sense included plants from New Zealand, Tasmania, New Caledonia and Chile, but with the transfer of some species to Neopanax, Polyscias Forster & Forster. f. and Raukaua Seem. it has been reduced to seven species, which are endemic to New Zealand and its adjacent islands (Frodin et al. 2003). The lancewoods are small to medium-sized trees or shrubs. The adult leaves are compound and palmate, though reduction in the number of leaflets occurs, and some species have

667

668

Pseudopanax

Plate 441. In maturity, Pseudopanax ferox loses its distinctive long, hardtoothed leaves and develops a most unferocious rounded crown of normal leaves, as seen in this specimen at Mount Usher, Co. Wicklow. Image N. Macer.

New Trees

one or three leaflets only. Heteroblasty, where different leaf-forms are produced in different age groups, is common in the genus (for example, P. crassifolius and P. ferox). The juvenile leaves are simple, linear, serrate and strongly reflexed. They encircle the trunk and are thought to have provided protection from herbivory by the now-extinct moas (Frodin et al. 2003). An array of intermediate leaf-forms can be found in wild specimens, and particularly on stump shoots and hybrids. Some species of Pseudopanax are grown almost entirely for their architectural juvenile leaves, but these are only produced for a limited period (10–20 years in P. crassifolius) before the development of adult leaves (Cave & Paddison 1999). Pseudopanax species are dioecious, with flowers in simple or compound umbels. The individual flowers are 5-merous and rather insignificant, and the fruit is fleshy (Allan 1961, Salmon 1996). With the increasing popularity of impressive foliage plants, coinciding with a warming climate, Pseudopanax has come to the fore, and juvenile plants of P. crassifolius and P. ferox are now frequently to be found in nurseries and garden centres, at least in Britain. Their principal attraction is the juvenile foliage, which provides a very dramatic shape in the garden. It is noticeable, though, that the numbers of individuals offered are not matched by numbers of plants to be seen in gardens, and one has to suspect a fairly high mortality rate. As with many slightly marginal plants it is probably worth keeping them in a pot until they have developed somewhat in size and solidity. A warm, sheltered but sunny site in a mild climate seems to be the ideal. They can be propagated from seed, which is probably the best method for the relatives of P. crassifolius, or from cuttings in the case of the multistemmed shrubby species. In addition to the two species described below, P. chathamicus Kirk, from the Chatham Islands and known in Maori as Hoho, is also offered commercially in the United Kingdom. It resembles P. crassifolius but the juvenile leaves are less strongly deflexed and more similar to those of the adult phase: a number of New Zealand plants have vicariants on the Chatham Islands in which protective adaptations, so common on the mainland, are moderated or absent – perhaps due to the absence of moas from these islands in the past (Atkinson & Greenwood 1989, Greenwood 1992). P. arboreus (NOW Neopanax arboreus (L. f.) Allan) B420 P. crassifolius (Sol. ex A. Cunn.) K. Koch B421, K58 P. davidii (NOW Metapanax davidii (Franch.) J. Wen & Frodin) B422 P. discolor (Kirk) Harms. K59

Pseudopanax ferox Kirk

Figure 75 (opposite). Pseudopanax ferox: adult habit with fruit (A); juvenile leaf (B); juvenile habit (C).

Toothed Lancewood

Shrub or small tree to over 5 m; trunk slender and developing a ‘braided’ pattern at maturity. Bark smooth and mottled grey, old leaf scars prominent. Leaves evergreen, heteroblastic; in unbranched juveniles, leaves to 50 cm long, narrow and linear, reflexed, green to purplish black though paler below, very thick and leathery, margins reminiscent of a chainsaw blade, with broad, rounded or serrate lobes, often crowded at the apex, midribs prominent, raised to 0.2 cm; in adults, leaves shorter, 5–15 × 1–2 cm, oblong to obovate, ascending, dark green though paler below, thick and leathery, margins serrate or entire, midribs prominent above, apex obtuse or mucronate; petiole stout, 1–2 cm long. Leaves of intermediate form common. Dioecious. Inflorescences terminal and compound, without a distinct primary axis, umbellate. Staminate inflorescence with 5–12 primary branches, 3–5 cm long, with flowers in racemes. Pistillate inflorescence with eight to nine primary

Section II. Species Accounts

Pseudopanax

669

1 cm

C 1 cm

A

1 cm

B

670

Pseudopanax

New Trees

branches, 1–3 cm long, with flowers in umbels of two to five. Flowers small, inconspicuous. Fruit ribbed, globose, with a disc-like apex, surmounted by five stigmatic branches, 0.9 cm diameter. Flowering and fruiting January to April (New Zealand). Allan 1961, Salmon 1996. Distribution NEW ZEALAND: North Is., South Is. Habitat Lowland forest and scrub, between 0 and 900 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration NT668, NT669. Cross-references B422, K59.

As a juvenile Pseudopanax ferox is an extreme foliage plant, with its marbled, narrow, hard, saw-blade leaves held at stiff angles from the stem, but like so many it loses the looks of its youth as it metamorphoses into the adult phase, when its rounded top on a straight stem can aptly be described as a blob on a pole. Although a single stem is the norm it can branch from its base when young, or it can sprout juvenile growth from the base of the adult trunk. It is a plant for lovers of curiosities, or admirers of structure: some will think it quite awful. As a juvenile it is well suited to town gardens, being narrow in outline, and will also benefit from the shelter and warmth of an urban situation. P. laetus (NOW Neopanax laetus (Kirk) Allan, NT526) B421

Pseudopanax lessonii (DC.) K. Koch

Houpara

Shrub or small tree to 6 m. Bark smooth and brown with prominent leaf scars. Leaves evergreen, digitate, clustered towards the ends of the branches; petiole stout, 5–15 cm long; leaflets three to five, 5–10 × 2–4 cm, obovate to cuneate, green, though paler below, thick and leathery, margins crenate to serrate, apex obtuse or acute; leaflets sessile or with a short petiolule (terminal leaflet). Juvenile leaves larger than those of the adult. Dioecious. Inflorescences terminal and compound, without a distinct primary axis, umbellate. Staminate inflorescence with four to eight primary branches, 4–5 cm long, with flowers in racemes. Pistillate inflorescence with six to eight primary branches, to 10 cm long, each with up to six umbels with three to five flowers. Flowers small, inconspicuous. Fruit ribbed, globose, with a disc-like apex, surmounted by five stigmatic branches, 0.5 × 0.7 cm. Flowering December to February (New Zealand). Allan 1961, Salmon 1996. Distribution NEW ZEALAND: North Is. (from Three Kings Is. to Poverty Bay). Habitat Coastal forest and scrub. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Ellison 1999. Cross-reference K59.

Pseudopanax lessonii is more likely to form a shrub than a tree, and will only be suitable for the mildest extremities of our area. In New Zealand it tolerates exposure and wind but not hard, prolonged frosts (Metcalf 2000). It can be used as a good tub or conservatory plant, however, and there are several cultivars with coloured foliage. Of these, ‘Gold Splash’ is an exceptionally fine variegated plant. ‘Nigra’ and ‘Purpureus’ are purple-pigmented clones, while ‘Black Ruby’ is particularly richly coloured. The boundaries of P. lessonii in horticulture are blurred by the existence of hybrids with other species, some of which are sometimes assigned to P. lessonii, or treated as unattributed cultivars. They are often very attractive shrubs for the milder garden, where temperatures seldom drop below –5 ºC. Among those with palmate leaves is Pseudopanax (Adiantifolius Group) ‘Cyril Watson’, with handsome glossy dark green, five-lobed leaves. More obviously intermediate between the palmate-leaved shrubs and the dimorphic trees with long juvenile leaves are a group of hybrids that include ‘Trident’ with narrowly three-pointed leaves, and ‘Sabre’ with lanceolate leaves. These appear to have arisen in New Zealand and to have been distributed from there by the horticultural trade. Also shrubby, occasionally forming a slow-growing small tree, with palmate leaves, is P. discolor. Its bronzed foliage is attractive but it is probably not very hardy (Huxley et al. 1992). A rich dark purple-leaved clone called ‘Rangatira’, probably a form of P. discolor, may appear in catalogues attributed to P. lessonii or as a floating cultivar.

Section II. Species Accounts

Pseudotsuga

671

PINACEAE

PSEUDOTSUGA

Carrière

Douglas-firs Pseudotsuga includes five to seven species, three in western North America and four in eastern Asia. The habit of Douglas-firs is rather variable, as P. menziesii is a massive tree with a columnar trunk, the tallest in the Pinaceae (up to 100 m), while the Asian species rarely reach half this height, with trunks usually dividing to form a broad crown. The Mexican P. lindleyana is probably the smallest in the genus, developing a slender conical crown, often only 25–30 m tall; the Californian P. macrocarpa is only slightly taller but is commonly much stouter. The bark is generally scaly and grey-brown, but later thickens, forming deep longitudinal cracks. Most species retain their lower branches into maturity, though abscission of lower branches is common in mature specimens of P. menziesii, which often have massive, clear boles. The branchlets are pubescent or glabrous, prominently grooved, and with raised, circular leaf scars. The buds are not resinous and are covered in red-brown, triangular scales. The needle-like leaves are dark green or glaucous-blue, rigid and spirally arranged. They form two untidy ranks, and are twisted at the base. They are grooved on the non-stomatal side, linear, with an acute or obtuse apex (American species) or emarginate apex (Asian species). Stomata are restricted to the lower surface, in two bands separated by the midrib. The male strobili are solitary, produced on branchlets in all parts of the crown, and buds are 1–2 cm long with distinctive red-brown perular scales, rather similar to those of Abies and Picea. The female cones are erect at pollination but become pendulous, and develop near the end of secondyear shoots, mainly in the upper crown but some also on low branches where exposed to good light. They mature in five to seven months, during which time they change from green or purple to brown. The cone scales are spirally arranged around a central rachis, and the cone falls whole after opening at maturity. The cone scales are broad, variously shaped, and pedicellate. They are persistent, and open to release the seeds. The bract scales are large, straight or reflexed, trilobate and exserted. There are two seeds on each cone scale, partially enclosed in a membranous cup, which extends to form a persistent wing (Farjon 1990). Pseudotsuga is long overdue a modern taxonomic review. In particular, many problems stem from the description by Flous (1934a, 1934b) of an excessively large number of ill-founded taxa throughout the American range of the genus, based on

Plate 442. Pseudotsuga sinensis var. wilsoniana, a Taiwanese endemic, requires warm conditions to grow well. Image T. Kirkham.

672

Pseudotsuga

New Trees

cone characters that proved poorly formulated and unreliable, and a subsequent highly conservative reaction against this interpretation by Little (1952), resulting in reduction to the generally familiar two species P. macrocarpa and P. menziesii – which reduction, however, overlooks apparently genuinely distinct taxa in Mexico. Within P. menziesii, only var. glauca (Beissn.) Franco (Blue or Rocky Mountains Douglas-fir) and the nominate var. menziesii (Green or Coast Douglas-fir) are currently accepted (Farjon 2001). Var. glauca shows very marked ecological differences from var. menziesii, which are matched by strong genetic differentiation (Li & Adams 1989), and it should probably be recognised at subspecific rank. Genetically it is subdivided into two (Li & Adams 1989) – a southern subgroup (subsp. glauca var. glauca) and a northern subgroup (subsp. glauca var. caesia) – and the divide is sharp, situated at about 44° N, running west-southwest along the Bighorn and Shoshone Rivers, across Yellowstone and along the Snake River. The mainland Asian taxa are nearly as complex and require further study. Flora of China (Fu et al. 1999c) recognises P. brevifolia, P. forrestii and P. sinensis (with the Taiwanese var. wilsoniana), principally distinguished by leaf length and seed scale characters, and this treatment is followed here. Pseudotsuga brevifolia W.C. Cheng & L.K. Fu (syn. P. sinensis var. brevifolia (W.C. Cheng & L.K. Fu) Farjon & Silba) is characterised by short, broad leaves (0.7–1.5 × 0.2–0.3 cm), the underside of which is flat, as in P. sinensis. It was introduced from northern Vietnam in 2003 and has so far proved hardy in western England, but is very slow-growing (K. Rushforth, pers. comm. 2008). It occurs in southwestern Guanxi and in Guizhou, but is more widespread across northeast Vietnam where it occurs on karst limestone ridges, with at least seven other conifer genera (Amentotaxus, Cephalotaxus, Nageia, Pinus, Podocarpus, Taxus, Tsuga, and possibly Calocedrus and Xanthocyparis); it may also occur in southeast Yunnan (K. Rushforth, pers. comm. 2008).

P. forrestii Craib B423 P. japonica (Shiras.) Beissn. B424, S401, K267

Pseudotsuga lindleyana (Roezl) Carrière

Mexican Douglas-fir

Syn. P. guinieri Flous, P. macrolepis Flous, P. menziesii var. oaxacana Debreczy & Rácz Tree to 25–30 m (rarely to 40 m), 0.4–0.8 m dbh (rarely to 1.25 m dbh). Bark shallowly fissured, greyish brown, becoming grey and rough in older trees. Crown slender, conical, usually fairly thin and sparsely foliaged. Branchlets slender, firm, grooved, grey-brown, quickly turning grey, glabrous, leaf scars raised, circular or angular; vegetative buds not or only slightly resinous. Leaves grey-green to mid-green, 1–2(–3) × 0.1–0.12 cm, forward-pointing to spreading, often somewhat curved, with two conspicuous greyish stomatal bands on the lower surface facing outward from the shoot, upper surface facing shoot mid-green without or with only a few stomata, apex acute. Male strobili 1.5–2 cm long, yellowish. Female cones pendent, ovoid to oblong, (2–)3–6(–7.5) × 2–2.5 cm, purple to red-purple with green or yellow-green bracts, maturing pale buff-brown; peduncle with a few leaves attached, 0.5–1.5 cm long. Seed scales obovate to slightly trilobed, 1.5–2 × 1.5–2.5 cm. Bract scales linear, apex tridentate, 2.5–3 cm long, exserted, straight to outcurved or reflexed, often twisted. Seeds brown, triangular-ovoid, 0.6–0.7 cm, wings narrow-oval, pale brown, 0.7–1 cm long. Debreczy & Rácz 1995; M. Frankis, pers. comm. 2008. Distribution MEXICO: Oaxaca (south locally to 16° 22' N), Sierra Madre Occidental, Sierra Madre Oriental, Sierra Madre del Sur (rarely). The northern boundary with P. menziesii, somewhere in northern Mexico, is not yet well determined. Habitat Mixed mesophytic forest at medium to high elevations, between 2300 and 3300 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Martínez 1953. Taxonomic note Pseudotsuga lindleyana was first described (as Tsuga lindleyana) in 1857 by Benedict Roezl, from trees found at Real del Monte near Pachuca, Hidalgo,

Section II. Species Accounts

Pseudotsuga

about 90 km north-northeast of Mexico City. It has widely been dismissed as part of P. menziesii subsp. glauca (see, for example, Farjon 2001). Preliminary genetic studies (Li & Adams 1989) have suggested, however, that it is very distinct, sister to the whole of P. menziesii. For this reason, and because of its easily distinguishable appearance both in the wild and in cultivation, it is treated as a distinct species here.

Pseudotsuga lindleyana was introduced to the United Kingdom in 1963 as seed collected at c. 2800 m near Tlaxco, Tlaxcala, as part of a seed exchange between the Mexican Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias and the UK Forestry Commission (Forestry Commission records; R. Jinks, pers. comms. via D. Luscombe 2007). The seed was received under the synonym P. macrolepis, and many of the resulting plants are still so-labelled. They are growing at several localities in southern England, the tallest, at Bicton Park, Devon, reaching 15 m in 2001 (Johnson 2003). The trees are not particularly decorative, having rather thin, sparse, drab green foliage (as do specimens in the wild). Their main value is in their exquisite cones, the bright yellow-green bracts setting off the purple scales very attractively; these are freely produced at eye level on young trees only 10–20 years old and 3–5 m tall. Another seed lot from the same exchange, in this case collected near Saltillo in northern Mexico, was distributed as P. flahaultii Flous (Forestry Commission records; R. Jinks, pers. comms. via D. Luscombe 2007); this is a synonym of P. menziesii subsp. glauca (Beissn.) Schwer. These trees, planted in the same arboreta, differ conspicuously from P. lindleyana in their denser foliage with somewhat longer, strongly glaucous blue-green leaves, as expected of P. menziesii subsp. glauca. The frequent inclusion of P. lindleyana in P. menziesii var. glauca is likely to mean that there are incorrectly identified specimens in arboreta, and material of known Mexican origin should be checked, but Frankis 149, from 3000 m asl on the moist east flank of Cerro Potosí in Nuevo León, matches P. lindleyana in its sparse foliage with short, dull green needles. P. macrocarpa (Vasey) Mayr B424, S402, K267 P. menziesii (Mirb.) Franco B424, S402, K267 P. menziesii f. brevibracteata (Antoine) Krüssm. K268 P. menziesii f. caesia (NOW P. menziesii subsp. glauca var. caesia (Schwer.) Franco) K268

Pseudotsuga sinensis Dode

P. menziesii var. caesia (NOW P. menziesii subsp. glauca var. caesia (Schwer.) Franco) B426 P. menziesii subsp. glauca (Beissn.) Schwer. B426, S402, K269 P. menziesii var. glauca (NOW P. menziesii subsp. glauca (Beissn.) Schwer.) B426, S402, K269

Chinese Douglas-fir

Tree to 50 m (usually much smaller), to 2 m dbh. Bark scaly, greyish brown, becoming grey and rough in older trees. Crown broad, domed or flat-topped. Branchlets slender, firm, grooved, reddish brown, quickly turning grey, minute pubescence in the grooves, later glabrous, leaf scars raised, circular or angular; vegetative buds not or only slightly resinous. Leaves dark green, (1.3–)2.5–4(–5) × (0.1–)0.15–0.2 cm, straight, apex emarginate or obtuse. Male strobili 1–1.5 cm long, yellowish. Female cones pendent, ovoid to oblong, (3.5–)4–6.5(–8) × (2.5–)3.5–5(–5.5) cm, purplish, turning purplish brown later; peduncle with a few leaves attached, 1–2.5 cm long. Seed scales orbicular to reniform, 2.5–3 × 3–3.5 cm. Bract scales ligulatelinear, apex trilobate, 3.5–4 cm long, exserted. Seeds light brown, cuneate-ovoid, wings cuneate to ovoid, 0.8–1.5 cm long. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Guizhou, Hubei, Hunan, Shaanxi, Sichuan, Yunnan; TAIWAN. Habitat Mixed mesophytic forest at low to medium elevations, between 600 and 3300 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable. Illustration Farjon 1990, Fu et al. 1999c. Cross-references B427, K271. Taxonomic note Within P. sinensis, Farjon (2001) recognises three

673

674

Pseudotsuga

New Trees

varieties: var. brevifolia, regarded by Fu et al. (1999c) as a distinct species (see above, p. 672); var. gaussenii (Flous) Silba, sunk into var. sinensis by Fu et al. (1999c) (and not known to be in cultivation, as var. gaussenii: K. Rushforth, pers. comm. 2007); and var. sinensis, into which he sinks P. forrestii and P. wilsoniana, as well as several other taxa. Pseudotsuga forrestii is, however, distinct from P. sinensis, separable by its longer leaves and different seed scale characters (Fu et al. 1999c). Keith Rushforth (pers. comm. 2008) also points out that in P. sinensis the leaf is flat on the underside, with acute angled margins, whereas in P. forrestii the margin is rounded so the underside of the leaf is not flat.

Pseudotsuga sinensis var. wilsoniana (Hayata) L.K. Fu & Nan Li Syn. P. wilsoniana Hayata Flora of China recognises var. wilsoniana on account of its occurrence in Taiwan, with the weak differentiation of its having greyish stomatal bands as opposed to the white ones of var. sinensis. It is restricted to the central mountains of Taiwan, and its geographical separation makes its retention at varietal level tenable. Fu et al. 1999c. Distribution TAIWAN. Habitat Mixed mesophytic forest, between 800 and 1500 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable. Illustration NT671, NT870. Cross-references B423, K271.

Seed of Pseudotsuga sinensis var. wilsoniana has been introduced from Taiwan by recent expeditions – for example, the Edinburgh Taiwan Expedition of 1993 (ETE 112, 149, 150, 157, 162, 177), from which young trees are growing in the Scottish botanical gardens and elsewhere, and collections by Kew (ETOT 7, 61). The ETOT field notes record that it grows amongst rich forest, but only where there is little organic material in the soil (even on bare rock faces). Martin Gardner (pers. comm. 2008) reports that it has been the least successful of the Taiwanese conifers introduced by Edinburgh, requiring warm temperate conditions to thrive. It has not done well in Scottish gardens, but specimens have been outhoused to arboreta in warmer situations such as Muncaster Castle, Cumbria and Foxhill Arboretum, Cheshire, and other locations in England, where some trees have currently reached about 3 m in height. In their early stages they are slow-growing and form broad bushy growth, from which a leader eventually emerges (M. Gardner, pers. comm. 2008). A tree from ETOT 61 seen at Kew in 2005 also lacked an obvious leader, and seemed unhappy there. The general experience with P. sinensis from mainland China is also that it requires a warm site, with ample moisture through the growing season, and is susceptible to spring frosts, particularly while young (Bean 1976b; K. Rushforth, pers. comm. 2008).

JUGLANDACEAE

PTEROCARYA

Kunth

Wingnuts Figure 76 (opposite). Pterocarya macroptera: stem with infructescence (A); single leaf (B); fruit of var. macroptera (C), var. insignis (D), var. delavayi (E).

Pterocarya is a genus of six species of deciduous medium-sized to large trees with single or multiple stems, sometimes suckering to form a thicket. The bark is furrowed. Young shoots are robust and vigorous, and often extend beyond the expanded leaves, taking on a distinctively ‘naked’ appearance, the bare shoot being terminated by a leaf bud (which will expand as the shoot continues to grow). The leaves are alternate, pinnate with up to 27 pinnae, and usually large; the leaflets elliptic to oblong, shortly

Section II. Species Accounts

Pterocarya

A

1 cm

B

1 cm

C

D

E

675

676

Pterocarya

Plate 443. The distinctive bare shoots of Pterocarya are terminated by a long bud. This is Pterocarya macroptera var. delavayi BRLL 12575 at Hergest Croft. Image J. Grimshaw.

New Trees

acuminate at the apex, with serrate margins, variably pubescent (pubescence most visible on young growth). The number of leaflets can vary quite markedly on leaves from the same tree, depending on the position and vigour of the shoot; they are largest on vigorously growing young trees. Separate male and female inflorescences are borne on the same tree, the male laterally on old wood, or at the base of new shoots, the female terminal on new shoots, developing as growth begins in spring. The pendulous fruiting spikes may be 50–60 cm long and bear numerous winged nutlets, 2–3 cm across, that are pale green when young, becoming brown later. Pterocarya is not easily confused with other genera, having a very distinctive appearance derived from its bold foliage and the elongating new shoots, while the long infructescences are a handsome feature of trees through the summer. Four species are well established in cultivation, P. fraxinifolia (from the Caucasus) and P. stenoptera (from China) being the most common. Their hybrid P. ×rehderiana is also frequently grown and forms an exceptionally magnificent tree (although prone to suckering). Pterocarya hupehensis (China) and P. rhoifolia (China, Japan) are less familiar, but are fully described by Bean (1976b) and Krüssmann (1986). The other species are P. macroptera, with three varieties, and P. tonkinensis, and these are described below. Cyclocarya paliurus (Batal.) Iljinsk. was formerly placed in Pterocarya, but differs in its round fruits and other characters. An exceptionally handsome P. stenoptera, with strongly toothed or pinnate leaflets, has been named ‘Fernleaf’. It originated as a chance seedling in a batch raised by Geoff Locke of Mount Pleasant Trees, Rockhampton, Gloucestershire in the early 1980s (G. Locke, pers. comm. 2008). The feathery, dark green leaves are unique and can be 50 cm long on vigorous long shoots, though on mature branches they are smaller. When stooled to the ground each year this makes a magnificent foliage plant for the border. All species grow best in fertile moist soil, but are susceptible to late frosts. Unripened young growth may also be damaged in winter. A warm, sheltered site is therefore recommended. Propagation is best from seed, but for selected clones vegetative methods are necessary. Firm softwood cuttings of some species can be rooted in early summer with the assistance of rooting hormone, but others (such as P. macroptera) will callus but not root under this regime (M. Fillan, pers. comm. 2008). Layering or hardwood cuttings in winter are further options. P. fraxinifolia (Lam.) Spach B431, S402, K61 P. fraxinifolia var. dumosa (Lavallée) C.K. Schneid. B432, K61 P. hupehensis Skan B432, K61

Pterocarya macroptera Batal. This is a widespread species in China, with three varieties (formerly recognised at specific rank but now treated as varieties by Flora of China: Lu et al. 1999). These occupy somewhat different natural distributions but their morphological distinctions are rather slight and they are not easy to recognise in cultivation, especially if sterile. The following key is adapted from the Flora of China account.

Section II. Species Accounts

Pterocarya

677

1a. Petiole 2–6 cm; rachis of infructescence glabrous; nutlets glabrous or nearly so .............. var. insignis 1b. Petiole 4–13 cm; rachis of infructescence pubescent; nutlets pubescent .......................................... 2 2a. Petiole 4–8 cm; nutlet wings elliptic-rhomboid, 2–3 × c. 2 cm .................................. var. macroptera 2b. Petiole 5–13 cm; nutlet wings orbicular-ovate to elliptic, 1–2.5 × 1–1.3 cm ................... var. delavayi

Pterocarya macroptera var. macroptera Tree to 15 m. Bark greyish brown, striated when young. Young shoots more or less glabrous, with long internodes, green with white lenticels, becoming brown later, terminal buds conspicuous, bright green. Leaves 23–30(–60) cm, dull mid-green, paler below, with narrow ridges at sides, pubescent; rachis pubescent; leaflets 7–17, lateral leaflets elliptic or elongate-elliptic, 9–21 × 3–6 cm, base oblique, cordate, apex acuminate, glabrous except for veins and whitish tufts of hairs in vein axils below; petiole 4–8 cm. Infructescence 45–70 cm, axis tomentose. Nutlets 7–9 mm, tomentose, wings elliptic-rhomboid, 2–3 × 2–2.5 cm. Lu et al. 1999. Distribution CHINA: southeast Gansu, southern Shaanxi, northeast Sichuan. Habitat Forested valleys and alongside streams, between 1600 and 3500 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT675, NT677.

Trees labelled Pterocarya macroptera are not infrequent in cultivation, but are often not attributed to variety. They form handsome, broad-crowned, single-stemmed trees that show no sign of suckering, and are well worth planting. Growth while young can be very vigorous, with shoots of 80 cm or more being produced in good years. Fertile material is required to distinguish accurately between var. macroptera and var. delavayi, and provenance is probably the most important character. A tree originating from Gansu was received at Kew as a seedling from the Chinese Academy of Forestry in 1979, and is almost certainly correctly identified as var. macroptera. Planted out in 1983, it was a shapely tree 8–9 m tall when seen in 2003; in July 2003 it was almost completely defoliated (probably the result of hot dry weather), but it recovered in subsequent seasons, and by 2008 was about 10 m tall. A moist situation is indicated.

Pterocarya macroptera var. delavayi (Franch.) W.E. Manning Syn. P. delavayi Franch., P. forrestii W.W. Sm. Tree to 15 m. Bark light grey-brown, with longitudinal striations. Terminal buds green, brownish in winter, to 10 cm. Leaves 20–52 cm, dark green, paler below, leaflets 7–21, elliptic or elliptic-ovate to elliptic-lanceolate, 7–21.5 × 3–6 cm, base oblique, slightly cordate to broadly cuneate, apex acute or acuminate, usually glabrous when mature except for hairs on the midrib below, axillary tufts sometimes present; petiole 5–13 cm with narrow ridges. Infructescence 50–60 cm, axis tomentose. Nutlets c. 8 mm, tomentose, wings orbicular-ovate to elliptic, 1–2.5 × 1–1.3 cm. Lu et al. 1999. Distribution CHINA: western Hubei, western Sichuan, Xizang, northwest Yunnan. Habitat Mountain forests, between 1900 and 3300 m asl, especially in gulleys. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Lu et al. 1999; NT675, NT676.

Var. delavayi is extremely variable, with the leaves especially varying in number, size and shape of the leaflets. It is well represented in herbaria by the collections of Forrest and Rock from Yunnan but remains scarce in cultivation, probably because it seems to be rather tender. A collection made by Brickell and Leslie (BRLL 12575), as P. forrestii, in a wooded valley on the Cangshan above Dali, Yunnan, was distributed

Plate 444. Pterocarya macroptera, here growing in the Royal Botanic Garden Edinburgh, seems not to produce suckers, forming a clean central stem. The varieties that make up the species are weakly distinguished. Image J. Grimshaw.

678

Pterocarya

New Trees

to various arboreta in the United Kingdom, but has died out in most. One specimen survives at Hergest Croft, and when young its new shoots were invariably killed by spring frosts, although they grew out vigorously later; in recent years however, with increasing size, it has escaped significant damage (L. Banks, pers. comm. 2006).

Pterocarya macroptera var. insignis (Rehder & E.H. Wilson) W.E. Manning Syn. P. insignis Rehder & E.H. Wilson Tree to 25 m, spreading to 16 m (SICH 1751), to 3 m dbh (W.P. Fang 2721, from Emei Shan). Bark grey, fissured. Terminal buds yellow-green. Leaves (20–)30–45 cm, mid-green, densely pubescent; leaflets (5–)7–13, ovate to elongate-elliptic, 14–29 × 4–6 cm, base oblique, rounded, apex acuminate, glabrous except for veins and axillary tufts below; petiole 2–6 cm. Infructescence to 70 cm, axis glabrous or nearly so. Nutlets c. 8 mm, glabrous, wings orbicular-ovate, 1.5(–2) × 2(–2.5) cm. Lu et al. 1999, Rix 2007. Distribution CHINA: western Hubei, Shaanxi, Sichuan, northwest Yunnan, Zhejiang. Habitat Mountain forests, between 1100 and 2700 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Lu et al. 1999, Rix 2007; NT675.

Pterocarya insignis, as it was then called, was first collected in 1908 by Wilson, from a single tree on the Wa-Shan, Sichuan, as W 3212 (Sargent 1917, Rix 2007), but no living older specimens have been traced. Several collections of var. insignis have been made more recently in Sichuan (for example, SICH 1751, 2156), and material from these is now well established in cultivation, at Kew and elsewhere (Rix 2007). From these trees it is clear that this taxon is quite variable, and the character of petiole length is seen to be somewhat unreliable. One specimen of SICH 1205 planted at Kew in 1995 (1995-636) has ‘authentic’ short petioles, but another (1995-2284) has petioles up to 14 cm long. Both are growing vigorously, but are prone to squirrel damage to the new shoots, and suffer from drought in dry summers. In 2008 they were up to 10 m tall and making very fine specimens, noticeably more robust and ‘solid’-looking than the nearby specimen of var. macroptera (mentioned above). They are now flowering, producing substantial infructescences: on the parent tree of SICH 1205, infructescences were recorded in the field notes to be a magnificent 70 cm long. P. paliurus (NOW Cyclocarya paliurus (Batal.) Iljinsk.) B432, S403, K61 P. ×rehderiana C.K. Schneid. B433, S403, K61 P. rhoifolia Siebold & Zucc. B433, S403, K61 P. stenoptera C. DC. B433, S403, K61

Pterocarya tonkinensis (Franch.) Dode Tree to 25–30 m. Bark whitish grey, becoming fissured. Leaves usually paripinnate, occasionally imparipinnate, to 18 cm or more; rachis without wings, sometimes ridged or grooved, pubescent or becoming glabrous; leaflets 6–24, sessile, 9–17 × 3–7 cm, ovate or elliptic-ovate, glabrous below except for hairs on midrib and larger veins, base oblique, rounded or broadly cuneate, apex acute to acuminate, margins sharply serrate; petiole 4.5–7 cm. Infructescence 13–30 cm. Nutlets rhomboid, 6–7 mm, glabrous, with linear wings 1–1.7 × 2–6 mm. Lu et al. 1999. Distribution CHINA: western Hubei, Shaanxi, Sichuan, Yunnan, Zhejiang. Habitat Riparian forest, between 200 and 1200 m asl (usually below 700 m in southern Yunnan). USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Lu et al. 1999; NT678.

Plate 445. Pterocarya tonkinensis flourishes in the JC Raulston Arboretum, producing abundant racemes of the characteristic winged seeds. Image J. Grimshaw.

Of all the Pterocarya species, P. tonkinensis is the least well known in cultivation, but it is grown in North America and New Zealand. No authentic specimens have been traced in the United Kingdom. A plant growing on the Chinese Hillside at Edinburgh, derived from the Kunming Botanical Institute, has the imparipinnate leaves and winged rachis of the closely related P. stenoptera, although the leaflets are smaller than normal in P. stenoptera. This may be one of the transitional forms mentioned by Flora of China (Lu et al. 1999). It is a large multistemmed shrub, 5–6 m high at present. At the JC

Section II. Species Accounts

Pterocarya

679

Raulston Arboretum, a seedling (also derived from Kunming) reached 10 m in nine years and formed a fine wide-spreading tree, from which seedlings have been widely distributed. The leaves turn a good clear yellow in some autumns. The southerly distribution of P. tonkinensis suggests that it is most likely to flourish in hot wet summer climates, that replicate the monsoon conditions of its habitat. It has been studied in the Xishuangbanna area of southern Yunnan by Apel (2001), who noted that its wood is soft and light and is not used for either timber or fuel – possibly boding well for its survival! The tree is used to make ritual fires by the Dai people of Xishuangbanna, and the leaves can be used to poison fish.

STYRACACEAE

PTEROSTYRAX

Siebold & Zucc.

Pterostyrax comprises four species in China, Japan and Myanmar. They are small to medium-sized, sometimes multistemmed trees, deciduous, with naked buds. The leaves are alternate, with serrate margins; stipules absent. Inflorescences are pendulous, the branches one-sided, with numerous flowers. The flowers are hermaphrodite and 5-merous; the calyx is campanulate, ribbed, the corolla divided almost to the base, pubescent, and there are ten stamens, five long and five short. The fruit is a dry ribbed or winged drupe with a persistent style, forming a beak, and each fruit has one to two fleshy seeds (Hwang & Grimes 1996). This small genus is most familiar in the form of Pterostyrax hispidus, the Epaulette-tree, which has been cultivated since 1875 (Bean 1976b). Most horticultural authorities say that this little tree comes from both China and Japan, but Hwang & Grimes (1996) do not acknowledge the presence of P. hispidus in China, confining it to Japan. Horticultural literature has generally assumed that Styrax and thus Pterostyrax are feminine names, but they are now treated as masculine (Nicolson & Steyskal 1976) – hence the change in the termination of the specific epithet from -a to -us. Another species, P. burmanicus W.W. Sm. & Farrer, has apparently never been introduced from Myanmar. All Pterostyrax will grow well in any good soil, including alkaline conditions, though not on shallow chalk soil (Hillier & Coombes 2002), and are very hardy. They do best in areas with long hot summers, but require ample moisture and light shade (P. Wharton, pers. comm. 2008). The flowers are pleasant, but often somewhat concealed by the foliage. Propagation is by seed, or by cuttings, which root easily in August (Dirr 1998).

Pterostyrax corymbosus Siebold & Zucc.

Little Epaulette-tree

Tree to 15 m, 0.45 m dbh. Bark brown, smooth with pale striations. Branchlets initially covered in stellate tomentum, soon almost glabrous. Leaves papery, 6–14 × 3.5–8 cm, elliptic to obovate, upper surface largely glabrous, lower surface densely covered with stellate tomentum, seven to nine secondary veins on each side of the midrib, margins minutely serrate to glandular-dentate, apex acute to acuminate; petiole 1–2 cm long.

Plate 446. Pterostyrax corymbosus is a success over most of our area, flowering freely in late spring, as here at Arboretum Wespelaar. Image P. de Spoelberch.

680

Pterostyrax

New Trees

Inflorescences paniculate, 3–8 cm long; pedicels 0.1–0.2 cm long. Flowers ~1 cm long; calyx ribbed, densely pubescent, corolla lobes oblong, ~1 cm long, stamens longer than corolla, filaments pubescent. Drupe obovoid, 1.2–2.2 cm long, five-winged, densely tomentose. Flowering March to April, fruiting May to September (China). Hwang & Grimes 1996. Distribution CHINA: northern Fujian, northern Guangdong, Hunan, Jiangsu, Jiangxi, northwest Zhejiang; JAPAN: western Honshu, Kyushu, Shikoku. Habitat Along forest streams, between 400 and 1600 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT679. Cross-references B436, S403, K64. Taxonomic note This species was described briefly by Bean (1976b), who noted that many specimens cultivated under this name are actually P. hispidus – the most significant difference being that the fruits of P. hispidus are five-ribbed, not five-winged, although the inflorescences of P. corymbosus are also usually shorter than the 10–22.5 cm expected in P. hispidus.

According to Jacobson (1996), Pterostyrax corymbosus was introduced to cultivation in 1850 and was commercially available in the United States by 1887; Clarke (1988) records that trees were received at the Washington Park Arboretum in 1957, so it is clear that plants under this name have been in (limited) circulation for quite a long time. It is always difficult to give accurate comments on a species when its identity in cultivation is known to be muddled. Trees labelled as P. corymbosus are grown successfully across our area, and many probably are correctly identified, but it would be useful if their identification could be confirmed. A further case of misidentification has led to this species being propagated in the Netherlands in place of Melliodendron xylocarpum (see p. 520). One such specimen planted at Arboretum Trompenburg in 1998 has done particularly well, and first flowered and fruited in 2002. When seen in 2005 it was 6–7 m tall and growing vigorously, forming a neat, attractive small tree, with pale green fruits dangling below the branches. Pterostyrax corymbosus is also a great success at Arboretum Wespelaar and Herkenrode (K. Camelbeke, pers. comm. 2007), and thrives at Kew, where several individuals are cultivated, grown from seed collected on Shikoku in 1999 (SOKU 28). The parent trees were found in dense shade in damp forest of the Odamiyama Gorge at 730 m (Townsend & Bridger field notes, Kew database). Dense shade would certainly not be advised in cultivation, where a position in full sun or under light high shade would be more appropriate, depending on the temperature expected in summer. It thrives in semi-shade between the tall conifers in the David C. Lam Asian Garden in Vancouver, however, forming

Plate 447. One needs to be able to get underneath Pterostyrax psilophyllus to appreciate its flowers properly. This tree was grown from SICH 2012 at Kew. Image T. Kirkham.

Section II. Species Accounts

a neat tree of up to 7 m, and flowering profusely (P. Wharton, pers. comm. 2008). As might be expected it flourishes on the East Coast of the United States, including one multistemmed tree of 12 m, seen in the US National Arboretum in 2006. The 1957 trees at Washington Park Arboretum are currently 10–13 m tall, and clearly flourish in the Seattle climate (but their identity has not been confirmed: R. Hitchin, pers. comm. 2008). A little further south, Sean Hogan (pers. comm. 2007) reports that it does well in the drier conditions of Portland, with the aid of small amounts of supplementary water. P. hispidus Siebold & Zucc. B435, S403, K64

Pterostyrax psilophyllus Diels ex Perkins Tree to 15 m or more, 0.45 m dbh. Branchlets stellate-tomentose. Leaves 5–15 × 5–9 cm, oblong to elliptic or obovate, upper surface largely glabrous, lower surface densely covered with grey stellate tomentum, 6–11 secondary veins on each side of the midrib, margins minutely to coarsely serrate, sometimes three-lobed, apex acute to acuminate; petiole 1–2 cm long, densely tomentose. Inflorescences paniculate, terminal or axillary, 10–15 cm long; pedicels ~0.2 cm long. Flowers 1.2–1.4 cm long; calyx ribbed, densely pubescent, corolla lobes oblong, filaments sparsely pubescent. Drupe subfusiform, ~2.5 cm long, (5- to) 10-ribbed, densely bristly. Flowering April to May, fruiting August to October (China). Hwang & Grimes 1996. Distribution CHINA: western Guangxi, Guizhou, southwest Hubei, eastern Sichuan, northeast Yunnan. Habitat Moist, shaded areas under forest, between 600 and 2500 m asl. USDA Hardiness Zone 5–6. Conservation status Vulnerable, due to habitat loss and degradation. Illustration Hwang & Grimes 1996; NT680. Cross-reference S403. Taxonomic note This species is often confused with the Japanese P. hispidus, but the hairs on the leaf veins of P. hispidus are primarily simple, not stellate (Hwang & Grimes 1996). It is probable that references to Chinese P. hispidus are to this species. A variant with three-lobed leaves from Guizhou was named P. leveillei Chun, but is no more than a local expression of P. psilophyllus (T. Hudson, P. Wharton, pers. comms. 2008).

Pterostyrax psilophyllus is the rarest of the three Pterostyrax in cultivation, but is grown in collections throughout our area and is commercially available in North America, where Jacobson (1996) records an introduction in 1983 and a release to the market by Piroche Plants in about 1993. Its inflorescences are intermediate in length between those of P. corymbosus and P. hispidus, and appear consistently earlier than those of the latter (Clarke 1988). A 6 m, single-stemmed specimen seen at the Morris Arboretum in late May 2006 had finished flowering, while a tree of P. hispidus nearby was in full flower. At Quarryhill, a tree grown from SICH 0845, planted in 1993, was 8 m tall in 2004. This had also formed a single stem, and had greyish brown bark. Another collection was made on the Sichuan Expedition of 1999, under the number SICH 2012, from trees reaching 15 m in regenerating broadleaved woodland, and a specimen from this material grows at Kew. The species has also been collected in Hubei (by the 1994 NACPEC expedition, for example, under 96750), giving rise to specimens in several American collections. The earliest introductions, as recorded by Clarke (1988), however, came by the more prosaic route of the Index Seminum of Beijing Botanical Garden, seed from this source being received at Kew in 1963. The specimen at Wakehurst Place mentioned by Clarke (1988) is still alive, and had reached 7 m when measured in 1996 (Kew database). At Westonbirt there is a tree of c.10 m, derived from Shanghai Botanic Garden seed (S. Andrews, pers. comm. 2008). In one of his last contributions to New Trees before his untimely death, Peter Wharton wrote from Vancouver (pers. comm. 2008): ‘We grow a number of collections of this species, notably two I made in 1994 in the Dashahe Cathaya Reserve, northern Guizhou under PW 6 and PW 59. In the wild this species has the capacity to become a large forest tree and is often a target for selective felling. Trees growing

Pterostyrax

681

682

Pterostyrax

New Trees

in the David C. Lam Asian Garden have been heavily damaged by voles gnawing at the lower trunks, severely reducing height growth. Two trees are now just over 4 m and appear to be growing away rapidly. We have also three trees derived from seed collected on Emei Shan by Shanghai Botanic Garden in 1992. These have proved to have immense vegetative vigour, growing to over 17 m, before being badly damaged by heavy snow in November 2006, when still in leaf. Although hardy here, Pterostyrax psilophyllus is weak-wooded, and the small terminal flowers are often hidden by heavy foliage.’

THEACEAE

PYRENARIA

Blume

Syn. Tutcheria Dunn Pyrenaria comprises about 30 species in eastern and southeastern Asia. They are evergreen trees or shrubs with alternate, spirally arranged leaves. The leaves are leathery or papery, petiolate and with serrate margins. The flowers are hermaphrodite, axillary and solitary or sometimes in clusters of two to three. They are subtended by two bracteoles, and have five to six unequal sepals, persistent or caducous, five to six petals (rarely 12), white or rarely pale yellow, slightly fused at the base, and numerous stamens, in three to six whorls. The fruit is either a capsule, which splits from the base into three to five (to six) segments, or a fleshy drupe; the seeds are wingless (Keng 1980, Stevens et al. 2004, Ming & Bartholomew 2007). In so far as it is known in horticulture (which is hardly at all), Pyrenaria is usually described under the synonym Tutcheria (Chittenden 1951, Huxley et al. 1992 – identical text!, Hudson 2004). It is very closely related to Camellia, differing in that the capsules of Camellia dehisce from the apex, whereas in Pyrenaria they dehisce from the base or not at all; also in that the seeds are somewhat rounded in Camellia, but longitudinally compresssed in Pyrenaria. They are handsome evergreens, with dense dark green foliage, but probably require mild moist conditions to thrive. Propagation and cultivation requirements are as for Camellia. In addition to P. spectabilis, described below, P. hirta (Hand.-Mazz.) H. Keng is being grown in a few Cornish gardens, but has yet to flower in cultivation (T. Hudson, pers. comm. 2005). It has lanceolate, glossy dark green leaves, and should produce its 4 cm-wide flowers in summer. Plate 448. The Belgian dendrologist Jan De Langhe maintains records on the trees he sees on his travels round Europe – a database he generously made freely available to us for our work on New Trees. He also documents the foliage, by the simple device of scanning a shoot, as here with Pyrenaria spectabilis from Ghent University Botanical Garden. Image J. De Langhe.

Pyrenaria spectabilis (Champ. ex Benth.) C.Y. Wu & S.X. Yang Syn. Camellia spectabilis Champ., Tutcheria spectabilis (Champ.) Dunn Tree 5–15 m. Branchlets yellowish brown to greyish brown, finely pubescent, though quickly glabrous. Leaves leathery, 16–18 × 4–7 cm, oblong, upper surface green to yellowish green, shiny and glabrous, lower surface pale green, sparsely pubescent, 12–16 secondary veins on each side of the midrib, margins serrate and undulate, apex acuminate; petiole 0.5–1 cm long. Flowers axillary or subterminal, solitary, 6–10 cm diameter; pedicel 0.2–0.6 cm long, pubescent. Bracteoles two, 1–1.5 cm long, yellow-pubescent outside; sepals 9–11, 2–3(–4) cm long, thick, yellow-pubescent outside; petals five to six, white, broadly obovate, 4–5 cm long; stamens numerous, ~1.5 cm long. Capsule woody, globose to subglobose, 4–8 cm diameter, densely yellow-tomentose. Flowering May to June, fruiting August to October (China). Ming & Bartholomew 2007. Distribution CHINA: southern Fujian, Guangdong, Guangxi; VIETNAM. Habitat Broadleaved, evergreen forest, between 300 and 1500 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT24, NT682.

Section II. Species Accounts

Pyrenaria

683

Pyrenaria spectabilis has been in cultivation for a long time, possibly from material collected in the vicinity of Hong Kong, but was treated as a tender glasshouse plant in the British Isles (Chittenden 1951), and seems to have ‘hung on’ in obscurity in a few collections. In Australia and New Zealand, however, it is more widely grown (T. Hudson, pers. comm. 2005), and seed from these countries has been the source of more recent accessions in the United Kingdom, where it is now commercially available. Small specimens growing in a sheltered site outside at the Ghent Botanical Garden in Belgium, accessioned in 2000, were grown from seed obtained by Damien Devos from the Kunming Botanical Garden (J. De Langhe, pers. comm. 2008). These suggest that it is worth attempting beyond the mild coastal extremities of Europe. Pyrenaria spectabilis is potentially a fine evergreen, with attractively pinkish red new shoots. Its big fried-egg flowers are produced in autumn, but plants will require a warm sheltered site for this to occur.

ROSACEAE

PYRUS

L.

Pears The genus Pyrus occurs naturally in Europe, North Africa and Asia, and includes 10–25 species (Lu et al. 2003, Kalkman 2004). Browicz (1993) lists 38 species in his conspectus of the genus but admits that this number may be inflated, as some apparently naturally occurring species may be of hybrid origin. Pears are deciduous (rarely semi-evergreen) trees or shrubs, which may have thorns. The leaves are simple or rarely lobed, with camptodromous venation and entire or serrated margins. Stipules are caducous. Inflorescences are corymbose to racemose, with few flowers. The flowers are white or rarely pink, and 5-merous, with 15–30 stamens and a cup-shaped hypanthium. The fruit is a pyriform (pear-shaped) or globose pome with brown to yellow skin, persistent to caducous sepals, and a membranous or cartilaginous core. The flesh is rich in stone cells (sclereids), giving it a gritty texture (Lu et al. 2003, Kalkman 2004). In the trio of ‘fruit trees’ that also contains Malus and Prunus, Pyrus is somewhat the poor relation in ornamental representatives, perhaps because they lack floral brilliance compared to the others. The pears have other charms, however, particularly in their autumn coloration, and they can make excellent long-lived landscape trees. Culinary pears aside, there are comparatively few selected cultivars. Most are American selections of P. calleryana, raised to replace the over-planted, brittle-wooded ‘Bradford’ – ‘one of the great widget trees of American commerce’ (Dirr 1998) (whatever that means). Of the numerous cultivars available in North America (see Jacobson 1996, Dirr 1998), though often not in Europe, the fastigiate ‘Chanticleer’ is generally considered to be the best; but again there is danger of this being planted too often.

Plate 449. Spectacular autumn coloration on Pyrus korshinskyi at Kew in November 2007. Pyrus leaves can colour magnificently, making up for their sometimes dowdy flowers. Image J. Grimshaw.

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New Trees

It is interesting to reflect that P. calleryana was first introduced by the US Department of Agriculture for investigation as a potential rootstock for cultivated pears. Pyrus are generally very hardy, and will grow in any good soil, the smaller species often tolerating rather dry sites. Fireblight can be a problem where this disease is prevalent, and the usual treatments apply. Propagation is by seed or grafting. The genus is usually well represented in arboreta, but particularly good collections may be found in the Morton Arboretum and at the Sir Harold Hillier Gardens. In the United States, the National Clonal Germplasm Repository at Corvallis, Oregon holds a magnificent collection of interesting edible (or potentially edible) plants, including many accessions of obscure Pyrus taxa – and as part of the US National Plant Germplasm System, has an admirable policy of freely distributing material on request. P. amygdaliformis Vill. B446, K73 P. amygdaliformis var. cuneifolia (Guss.) Bean B447, K73 P. amygdaliformis var. lobata (Decne.) Koehne B447, K73

P. amygdaliformis var. oblongifolia (Spach) Bean B447, K73 P. balansae Decne. K73 P. betulifolia Bunge B447, K73

Pyrus boissieriana Buhse Shrub or tree, 5–15 m. Branchlets spiny, initially brown-pubescent, later glabrous. Bud scales grey with ciliate margins. Leaves deciduous, 3–6 × 2.5–5 cm, circular to ovate, upper surface green and glabrous, lower surface pale green and somewhat woolly, margins serrulate, apex obtuse. Corymb with numerous flowers; pedicels ~3 cm long. Flowers white; sepals triangular-acuminate with glandular margins and ferruginous tomentum on the inner surface, petals ~0.8 cm wide. Pome reddish brown with white spots, globose to subpyriform, ~1.5 cm diameter with persistent sepals. Flowering April to May, fruiting autumn (Iran). Schönbeck-Temesy 1969. Distribution AZERBAIJAN; IRAN; TURKEY; TURKMENISTAN (?). Habitat Between 1000 and 2400 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Taxonomic note This species is sometimes treated as a synonym of P. communis.

Plate 450. Bark of the old specimen of Pyrus bretschneideri at Kew. Pyrus can make substantial, long-lived trees. Image J. Grimshaw.

Pyrus boissieriana could perhaps be perceived as being of botanical interest only, as part of the P. communis alliance (see below), but has been introduced from Iran on at least two occasions. Most notable is the specimen of about 12 m at the Hillier Gardens, grown from Ala & Lancaster 37, collected on that famous winter journey (Lancaster 1974). This is a beautiful sturdy tree, with wide-spreading branches bearing attractive smallish glossy leaves. The other known example in cultivation grows at Kew. Much smaller, measured at 5 m in 2001 (TROBI), it derives from a collection (FLSX 398) made by the Fliegner & Simmons Expedition to Iran in 1977, from c. 2400 m on the Kandaran Pass in the Elburz mountains. This attractive species deserves to be propagated and distributed more widely. P. bourgaeana Decne. K74

Pyrus bretschneideri Rehder

Ya Pear

Tree 5–15 m. Bark thick, dark, coarsely furrowed. Branchlets robust, initially densely pubescent, later glabrous and purplish brown. Buds dark purple, scales with ciliate margins. Leaves deciduous, 5–11× 3.5–6 cm, ovate to elliptic, both surfaces initially tomentose, soon almost glabrous, margins serrate (sometimes with tiny spines), apex acuminate or rarely acute; petiole 2.5–7 cm long, densely tomentose; stipules caducous, membranous, 1–1.5 cm long, linear to lanceolate. Racemes tomentose with 7–10 flowers; pedicels 1.5–3 cm long. Flowers white, 2–3.5 cm diameter; sepals triangular with glandular margins and brown tomentum on the inner surface, petals ovate, 1.2–1.4 cm long, stamens ~20. Pome yellow with fine spots, ovoid to subglobose, 2–2.5 cm diameter, sepals caducous. Flowering April, fruiting August to September (China). Lu et

Section II. Species Accounts

Pyrus

al. 2003. Distribution CHINA: Gansu, Hebei, Henan, Shaanxi, Shandong, Shanxi, Xinjiang. Habitat Slopes in dry, cold regions; between 100 and 2000 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT684. Cross-reference K74. Taxonomic note Jacobson (1996) considers P. bretschneideri to be a hybrid between P. pyrifolia and P. betulifolia.

Despite having been introduced to the United States in 1882, by Emil Bretschneider (Jacobson 1996), this remains a rare tree both there and elsewhere. Its merits are demonstrated by a big old specimen at Kew, measured at 17 m in 2001 (TROBI), which in autumn turns into a pillar of gold. This was received from Yashiroda in 1925, and although it has a slight lean to avoid a neighbour, is hale and hearty, with dense branching to the base. There are also two nice trees at the Hillier Gardens. The leaves, even when not in autumn plumage, are appealing, being aspen-like on long petioles, dark green but paler below. The yellow fruits are eaten in China, where there are selections with ‘excellent fruit’ (Lu et al. 2003). P. calleryana Decne. B448, S404, K74 P. ×canescens Spach B450, K74

Pyrus communis L.

Common Pear

This species was described by Bean (B448) and Krüssmann (K74). Identifying subspecies of the Common Pear is difficult. They are delimited partly by geography, so cultivated accessions with no collection data often cannot be named. In addition, the Domestic Pear (P. communis subsp. sativa (Lam. & DC.) Asch. & Gr.) occurs within the natural range of several other subspecies and forms hybrids with them. Pyrus cordata has also to be fitted into the equation, and it seems likely that some of the smaller-fruited taxa may be related to this. A key to the subspecies of Pyrus communis, modified from those of Browicz (1972) and Maire (1980), is given below. 1a. Branchlets unarmed; leaves large, to 7 × 5 cm; fruits large, > 5 cm long, solitary, with soft flesh; in cultivation in temperate areas around the world (the Domestic Pear) ....................................................................................... subsp. sativa 1b. Branchlets spiny; leaves small, to 3 × 3 cm; fruits small, up to 4 cm long, in groups of two to six, with hard flesh ........................................................................................ 2 2a. Distribution in Europe, western and central Asia ............................................................................. 3 2b. Distribution in North Africa ............................................................................................................. 4 3a. Leaves crenate-serrate or subentire, not ciliate; Europe ........................................... subsp. communis 3b. Leaves entire, ciliate; Greece (Thrace), Turkey (north and southwest Anatolia), Russian Federation (Caucasus), Ukraine (Crimea) ................................................ subsp. caucasica 4a. Leaves largely ovate-cordate; fruit subglobose to pyriform, 2–2.5 cm long, peduncle robust; seeds large, 0.8 × 0.7 cm ...................................................... subsp. mamorensis 4b. Leaves not cordate; fruit subglobose to obovate, 1–1.3 cm long, peduncle slender; seeds small, ~0.4 cm long .............................................................................. 5 5a. Leaves subcircular or largely ovate, apex short-acuminate; fruit subglobose, four to five locules ................................................................................................ subsp. longipes 5b. Leaves ovate-oblong or oblong, apex long-acuminate; fruit ± obovate, two to three (to four) locules ................................................................................ subsp. gharbiana

685

686

Pyrus

New Trees

Pyrus communis subsp. caucasica (Fed.) Browicz

Caucasian Pear

Subsp. caucasica is a tree to 25 m, with spiny branches and entire, ciliate leaves. The fruits are brown and globose-turbinate. Terpó & Franco 1968, Browicz 1972. Distribution GREECE: Thrace; RUSSIAN FEDERATION: Caucasus; TURKEY: northern and southwest Anatolia; UKRAINE: Crimea. Habitat Forests. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT686.

This is the easternmost version of Pyrus communis, and does not differ greatly from western European representatives except in its ciliate leaf margins. Like them it is a fine, densely clad, long-lived tree. It is not common in general cultivation but is grown by research institutions such as the National Clonal Germplasm Repository, Corvallis, Oregon, where there are numerous accessions of known wild origin (National Germplasm Repository 2008). There is a magnificent specimen of unknown origin at the Hillier Gardens, measured at 14.1 m (58 cm at 1 m) in 2008, with several principal vertical stems from a low trunk, forming a broad dark green crown. This was liberally furnished with bright green, very unripe pears when seen in June 2007. Mature trees are occasional in arboreta across our area, but young plants are also grown in some American collections: at the Morton Arboretum, for example, from seed obtained from the Midwest Plant Collecting Collaborative 2000 Republic of Georgia Contract Collection, gathered in the Imereti Region, Georgia. Like many other good plants from the Caucasus, it should be ideally suited to US Midwestern and continental European conditions. Plate 451. Young pears on the large specimen of Pyrus communis subsp. caucasica at the Hillier Gardens, in June 2007. This is a handsome tree with great horticultural potential, especially in cold areas. Image J. Grimshaw.

Pyrus communis subsp. gharbiana (Trabut) Maire Subsp. gharbiana has small, obovate fruits on slender pedicels, with two to three locules (rarely four). The flowering corymbs comprise 9–15 rather small flowers (~2.25 cm diameter). Maire 1980. Distribution MOROCCO: Atlas Mts. Habitat Calcareous mountains. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Maire 1980.

Subsp. gharbiana, which appears to be a small-fruited representative of the Pyrus communis alliance from North Africa, is included here mainly for completeness, as it seems to be principally grown by institutions with a particular interest in wild fruit genotypes. The only specimen located in the United Kingdom is at Kew, received in 1986 from the now-defunct Long Ashton Research Station. Several accessions of material of wild origin are maintained at the National Clonal Germplasm Repository, Corvallis (National Germplasm Repository 2008), and it may also be grown in specialist collections of fruit trees.

Pyrus communis subsp. longipes (Cosson & Durand) Maire

Algerian Pear

Syn. P. cossonii Rehder Subsp. longipes has subglobose fruits, slightly larger than in subsp. gharbiana, on slender pedicels, with four to five locules. Maire 1980. Distribution ALGERIA. Habitat Calcareous mountains. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Maire 1980. Cross-references B449, K75 (both as P. cossonii).

This taxon is relatively well known in cultivation as Pyrus cossonii, and occasionally as P. longipes. TROBI has recorded numerous specimens in gardens throughout the United Kingdom, the champion being a 20 m tree measured at Collingwood Grange, Benenden, Kent in 1995.

Section II. Species Accounts

Pyrus communis subsp. mamorensis

Pyrus

Mamor Mountain Pear

(Trabut) Maire Subsp. mamorensis has large, subglobose or pyriform fruits on robust pedicels, with two to four locules. Maire 1980. Distribution MOROCCO: Atlas Mts., Forest of Mamora. Habitat Cork Oak forest on the Moroccan western plain, but also in calcareous mountains. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Maire 1980; NTxvi.

The remarks made above for subsp. gharbiana apply equally to subsp. mamorensis, except that this is a large-fruited pear from further west, and the National Clonal Germplasm Repository holds 28 accessions, as against eight for subsp. gharbiana! P. cordata Desv. B449, K75 P. cossonii (NOW P. communis subsp. longipes (Cosson & Durand) Maire, NT686) B449, K75

P. dimorphophylla (NOW P. calleryana Decne.) B448

Pyrus elaeagnifolia Pall. Tree (rarely shrub) to 15 m, 0.5 m dbh. Branchlets robust, usually spiny, grey- or white-tomentose. Leaves deciduous, 3–8 × 1.5–4 cm, lanceolate to obovate, both surfaces covered with grey or white tomentum, margins entire, apex obtuse to acute; petiole 1–4 cm long; stipules caducous. Corymbs tomentose with 5–10 flowers; pedicels 1–2 cm long. Flowers white, ~3 cm diameter; hypanthium tomentose, sepals triangular, ~0.5 cm long, petals elliptical, ~1 cm long. Pomes single or in pairs, yellowish green, globose to pyriform, 2–3 cm diameter. Flowering April to May, fruiting autumn (Turkey). Terpó & Franco 1968, Schönbeck-Temesy 1969, Browicz 1972. Distribution ALBANIA; BULGARIA; GREECE; ROMANIA; TURKEY; UKRAINE: Crimea. Habitat Wooded hillsides. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NTxvi, NT6. Cross-reference K75. Taxonomic note The specific epithet is often, if not usually, misspelled as ‘elaeagrifolia’; it is strange, when the foliage so obviously resembles that of an Elaeagnus, that this mistake should have become so entrenched in the literature and on labels. Browicz (1972) recognises P. elaeagnifolia subsp. kotschyana (Boiss) Browicz (see Krüssmann: K75), with unarmed branchlets and white- (rather than grey-) tomentose leaves.

It is very curious that this beautiful tree was not given a full description by Bean (1976b), as it was introduced to horticulture in about 1800 and has been widely planted – and is hardy – throughout our area. Its grey- or white-hairy foliage on upright stems makes it useful in the landscape. It is a much neater tree than the ubiquitous Pyrus salicifolia ‘Pendula’ with its often uncoordinated sprawl of limbs. White Sails is a selling name attached to the thornless subsp. kotschyana (N. Dunn, pers. comm. 2008).

Pyrus fauriei C.K. Schneid.

Korean Pea Pear

Large shrub or small tree to 6 m. Immature branchlets unarmed, adult branchlets with thorns. Leaves deciduous, 2.5–5 cm long, elliptic to ovate, both surfaces glabrous, margins finely crenate, apex acuminate to caudate; petiole 0.9–1.8 cm long, pubescent. Flowering occurs when the tree is in leaf; corymbs with two to eight flowers on a densely tomentose peduncle; pedicels 1.6–2.7 cm long. Flowers white; sepals narrowly triangular, pubescent on the inside, petals four to six, often misshapen, stamens 20. Pome brownish with white dots, globose to obovoid, ~1.3 cm diameter with no stone cells. Zielinski 1965, Westwood 1968. Distribution NORTH KOREA; SOUTH KOREA. Habitat Unrecorded. USDA Hardiness Zone 4. Conservation status Not evaluated. Illustration NT688. Cross-reference K75. Taxonomic note This species is commonly confused with P. calleryana, but differs in a number of features. Pyrus calleryana forms a larger tree (to 12 m), which produces flowers before the leaves emerge. It has larger flower buds than P. fauriei, and more flowers per inflorescence cluster (10–13). Autumn leaf fall occurs from November to December (October to November in P. fauriei). In addition, when used as a rootstock for grafting, P. fauriei is found to be a dwarfing rootstock while P. calleryana is not (Zielinski 1965).

687

688

Pyrus

Plate 452. The vernacular name Korean Pea Pear fits Pyrus fauriei very well. Although diminutive, the massed fruits have much charm. Image J. Grimshaw.

New Trees

The difficult-to-quantify distinctions between Pyrus calleryana and P. fauriei have led to confusion in horticulture. Dirr (1998) notes that a vegetatively propagated clone of P. calleryana has been distributed in North America as P. fauriei, or ‘Fauriei’, and this will inevitably muddy the situation further. The two are clearly closely related, but true P. fauriei is a dumpy, shrub-like tree, forming a rounded mass at least as wide as it is tall. This is exemplified by a specimen at the Hillier Gardens, grown from KE 3681, collected in South Korea in 1985, and planted out in 1994, that is now 5 m tall but 8 m wide (A. Coombes, pers. comm. 2008). The species is not a great ornamental, but has abundant small fruits and attractive orange to red colours in autumn, and could be useful where a broad, bushy screen is required. It has been in cultivation since 1918, according to Krüssmann (1986). The earliest accession in the National Clonal Germplasm Repository dates to a wild collection made in Korea in 1939 (PI 132091), which was passed from the Arnold Arboretum via the Glenn Dale Research Station, Maryland to Corvallis, where it is currently but one of 35 accessions of the species (National Germplasm Repository 2008). Many of these are more recent wild collections. The cultivar ‘Westwood’, sold as Korean Sun, was selected by Mel Westwood of Oregon State University for its particularly good autumn colours. Released in about 1999, it has been widely planted, but as it is very susceptible to fireblight (at least along the East Coast) some major nurseries are no longer stocking it (L. Hatch, pers. comm. 2008). P. glabra (NOW P. syriaca subsp. glabra (Boiss.) Browicz) B450, S405 P. kawakamii Hayata K75

Pyrus korshinskyi Litv. Tree to 15 m. Branchlets unarmed or rarely spiny, grey-tomentose when young. Buds densely tomentose. Leaves deciduous, 4–11.5 × 1.5–4 cm, lanceolate, upper surface green and glabrous, lower surface glabrous or with pubescence on the veins, margins crenate to serrulate, apex long-acuminate; petiole 1.5–5 cm long; stipules caducous. Corymbs multiflowered; pedicels 2–4 cm long, tomentose. Flowers white, 2–2.5 cm diameter; sepals triangular-oblong, margins glandular, petals oblong to ovate. Pomes solitary or in pairs, yellowish green, subglobose to pyriform, 2.5–3 cm diameter. Schönbeck-Temesy 1969. Distribution AFGHANISTAN; KYRGYZSTAN; TAJIKISTAN; UZBEKISTAN. Habitat Mountains between 1000 and 2600 m asl. USDA Hardiness Zone 5. Conservation status Critically Endangered, due to its occurrence in tiny fragmented populations, with damage from overgrazing and overharvesting. Illustration NT683, NT689. Cross-reference K75.

Despite its apparent rarity in the wild, Pyrus korshinskyi is an important rootstock for domestic pears in the central Asian countries (the ’Stans) where it is said to be more drought-tolerant and have greater disease resistance than the other local contender, P. regelii (National Germplasm Repository 2008). Growers looking no further than this prosaic use, however, will be deprived of a truly superb autumn foliage plant. This is its chief ornamental value, although as with all these pears, the flowers and fruits are modestly charming. Outside the fruit-tree collections it is rare, and the only example observed for New Trees grows at Kew. A rounded, 6 m tall specimen with a roughbarked trunk, this was ablaze in scarlet foliage in early November 2007, rivalling any other tree in the garden. Amongst this brilliance the curiously warty pears were hardly visible. This individual was received from the Kórnik Arboretum, Poland, in 1949.

Section II. Species Accounts

Pyrus

689

1 cm

P. lindleyi Rehder K75 P. ×michauxii Bosc. ex Poir. B450, K76 P. nivalis Jacq. B450, K76

P. pashia Buch.-Ham. ex D. Don B451, K76 P. pashia var. kumaonia Stapf K76 P. persica Pers. B447, K76

Figure 77 (above). Pyrus korshinskyi: habit with fruits (A); habit with fruits, leaves removed (B).

690

Pyrus

New Trees

Pyrus phaeocarpa Rehder Tree 5–8 m. Branchlets purplish red and tomentose when young, purplish brown and glabrous when mature. Buds narrowly ovoid, scales tomentose at the margins. Leaves deciduous, 6–10 × 3.5–5 cm, elliptic to narrowly ovate, sparsely tomentose when young, soon glabrous, margins serrate, apex long-acuminate; petiole 2–6 cm long, sparsely pubescent; stipules linear-lanceolate, 0.1–0.2 cm long, caducous. Inflorescence an umbellate raceme with five to eight flowers; pedicels 2–2.5 cm long, largely glabrous. Flowers white, ~3 cm diameter; hypanthium bell-shaped and tomentose, sepals triangular-lanceolate, 0.2–0.3 cm long, petals ovate, 1–1.5 cm long, stamens 20. Pome brown with pale dots, globose or ovoid, 2–2.5 cm diameter. Flowering April, fruiting August to September (China). Lu et al. 2003. Distribution CHINA: Gansu, Hebei, Shaanxi, Shandong, Shanxi, Xinjiang. Habitat Mixed hillside forest of the Loess Plateau, between 100 and 1200 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NTxvi, NT690. Cross-reference K76.

Plate 453. The northwestern Chinese Pyrus phaeocarpa is unaccountably rare in arboreta, but its autumnal display should earn it a place. Image J. Grimshaw.

Pyrus phaeocarpa is another obscure pear with great potential as an ornamental autumn foliage tree – also burning brightly on that November 2007 visit to Kew. Its rather elongated glossy dark green leaves turn to shades of orange and orange-red, complementing the yellow ochre-coloured, semi-translucent fruits. The tree at Kew was received from the Long Ashton Research Station in 1986, and although 6 m tall it is much wider than high, suggesting that ample space is needed. Once again it has a very sparse presence in general European and American collections, and there are only two accessions at the National Clonal Germplasm Repository in Corvallis. The oldest of these (PI 46582) was received from South Korea in 1918, having been collected by F.C. Reimer in that year. He noted that it was used as a rootstock in the area around Seoul, as it is in China also (Lu et al. 2003). Pyrus phaeocarpa f. globosa Rehder, with more rounded fruit, is in cultivation (for example, at the Arnold Arboretum), but is not recognised by Flora of China.

P. pyraster (NOW P. communis L. subsp. communis) K77 P. pyrifolia (Burm. f.) Nakai B451, K77 P. pyrifolia var. culta (Makino) Nakai B452, K77 P. regelii Rehder B452, K77 P. salicifolia Pall. B453, K77 P. ×salviifolia DC. B451, K78 P. serrulata Rehder K78 P. syriaca Boiss. B449, K78 P. ussuriensis Maxim. B453, K78 P. ussuriensis var. hondoensis (Nakai & Kitachi) Rehder B454, K78 P. ussuriensis var. ovoidea (Rehder) Rehder B454, K78

Section II. Species Accounts

Quercus

691

FAGACEAE

QUERCUS

L.

Syn. Cyclobalanopsis Oerst.

Oaks The 400–450 species in the important genus Quercus are found across the northern hemisphere in North and Central America (south to Colombia), Europe (including Macaronesia) and Asia (south into Indonesia, extending into the southern hemisphere). The greatest species diversity is in the Sierra Madre Occidental of Mexico (see ValenciaA. 2004) and in eastern and southeastern Asia (Govaerts & Frodin 1998). New species continue to be named. Identification of oaks is complicated by variation and hybridity, and particular care must be taken with cultivated material, where the growth form may not be representative of the wild plant, and hybrids are particularly frequent. In addition, successful identification often depends upon the presence of acorns, requiring therefore both a reproductively mature tree and successful pollination. Most oaks are medium-sized to large trees, though shrubby or rhizomatous species occur, but appearance and stature is often strongly influenced by growing conditions. The bark is extremely variable, but is usually thick and somewhat rough when mature; Cork Oak (Quercus suber) is famous for its thick, corky bark, and the bark of many Mexican red oaks has a bloated appearance suggestive of pachydermatous hide, at least while young. Winter buds are covered in imbricate scales and may be spherical, ovoid, terete or angled. The leaves are spirally arranged and may be evergreen, sub-evergreen (sometimes termed ‘tardily deciduous’) or deciduous; it is not always easy to decide into which category species fall, and their behaviour in cultivation is not necessarily the same as in the wild. Leaves may be lobed or unlobed and with entire, dentate or serrate margins, sometimes with short bristles or awns at the tips of the lobes or teeth. These bristles are sometimes as spiny as those of some hollies (Ilex), but species with spiny leaves often produce non-spiny leaves higher up in the canopy, and some species have completely unarmed forms within natural populations. The size and shape of the leaves may vary greatly within species and individuals, and further variation is often introduced in the secondary growth flush frequently produced late in summer. In this the leaves may appear very different to those of the primary flush, often being smaller and less dissected, although sometimes the lobes are more distinct; they may also be tinted in shades of brown, bronze or red when young – an attractive feature that is usually less conspicuous in the first flush. The secondary veins are unbranched and run parallel to the margins, or branch early to form a network before reaching the margins. The presence and form of foliar hairs can be a helpful character for identification at the species level: they are usually visible with a 10× or 15× lens. Stipules are typically inconspicuous and caducous. The inflorescences are unisexual and are borne in the axils of leaves or bud scales. They are usually produced in spring, before or as the leaves emerge. As an identification character they are not

Plate 454. Male inflorescences of Quercus griffithii on a tree in Bhutan. Floral details are generally not important for identifying oaks. Image P. de Spoelberch.

692

Quercus

New Trees

QUERCUS

L.

A guide to the infrageneric classification of Quercus

Subgenus Cyclobalanopsis (e.g. Q. lamellosa, Q. gilva) Acorn cupule with concentric rings of scales Evergreen or sub-evergreen Asia Subgenus Quercus

Section Cerris (e.g. Q. cerris)

Acorn cupule with individual scales

Evergreen or deciduous

Evergreen or deciduous

Grey or yellow fascicled hairs on leaf undersides

Asia, Europe, North Africa, North America

Leaf margins entire, revolute or spiny Asia, Europe, North Africa Section Lobatae (red oaks) (e.g. Q. rubra) Deciduous (or evergreen) Leaves entire, serrate or lobed Bristles present on tips North America Section Protobalanus (e.g. Q. tomentella) Evergreen Leaves glaucous or waxy below Leaf margins entire or dentate North America Section Quercus (white oaks) (e.g. Q. alba) Deciduous (or evergreen) Leaves entire, serrate or lobed Bristles absent Asia, Europe, North America

Plate 455. Quercus georgiana is a member of section Lobatae – the red oaks – recognisable by the stiff bristles at the tips of the teeth on the leaf margin. Image P. de Spoelberch.

of great value, and are in most cases omitted from the accounts that follow, in favour of the fruiting characters. Staminate inflorescences are pendulous catkin-like spikes; they may be solitary or occur in clusters, and bear small, rather insignificant flowers. Pistillate inflorescences are generally short and stiff, with a terminal cupule and one to many lateral cupules. Not all the cupules develop to maturity. There is a single pistillate flower in each cupule, and the cupule (which does not have valves) may be sessile or pedunculate. There is great variation in cupule morphology; they may be cup-, bowl- or goblet-shaped and can cover most of the acorn or just the base; the scales may be adherent or reflexed, linear or conical, or reduced to tubercles. The fruit (acorn) is a nut. Acorns have a scar at the base where they were attached to the cupule and the remains of the style may persist at the acorn apex (stylopodium). Acorns mature either in the year of flowering (annual maturation) or the following year (biennial maturation) (Nixon 1997, Huang et al. 1999). Quercus is in need of taxonomic revision. Govaerts & Frodin (1998) recognised 531 species, but this is probably an overestimate (A. Coombes, pers. comm. 2008). Flora of China (Huang et al. 1999) and Flora of Taiwan (Liao 1996a), however, separate the genus Cyclobalanopsis, with about 150 species. Cyclobalanopsis can be distinguished from Quercus because the cupule scales of the former are fused into concen-

Section II. Species Accounts

Quercus

693

tric rings while those of the latter are free and spirally arranged (Huang et al. 1999). In the present treatment a broader definition of Quercus, encompassing Cyclobalanopsis, is applied. Within Quercus the subgeneric classification is controversial, and several systems have been proposed (see Govaerts & Frodin 1998). Although the details of these are not necessarily important to oak growers, a taxonomic distinction can also be a useful horticultural guide, and for this reason an indication of the infrageneric group to which a species belongs is given in the accounts that follow. A summary table is also provided (opposite). Of particular importance is the division of the majority of American oaks into two principal groups: the red oaks (section Lobatae) and the white oaks (section Quercus). Both are in subgenus Quercus. Red oaks have smooth or deeply furrowed bark at maturity, their leaves typically have bristles at the apex of the lobes or at the leaf apex (where unlobed), and the cupule scales are flattened and can be tuberculate (very seldom). In general, red oaks adapt well to cultivation in northern Europe, with its relatively cool summers. White oaks have scaly or papery bark at maturity, their leaves never have bristles on the lobes or at the apex, and the cupule scales are thickened and tuberculate. Many white oaks require a long, hot summer, and for this reason are less likely to flourish in northern Europe. In addition to a taxonomic revision being needed, great steps would be made in clarifying oak nomenclature if American authors would agree on standard common names for their native species. In our accounts, names as given in Flora of North America (Nixon 1997) have been used, but there are alternatives for most species. Within sections, Quercus species are promiscuous, and interspecific hybridisation occurs regularly both in the wild and in cultivation. Many nothospecies have been described and continue to be described. Listing all hybrids currently in cultivation is beyond the remit of this book, but some are described by Palmer (1948) and in numerous papers in the Journal of the International Oak Society (now International Oaks) and elsewhere. Acorns from arboreta are particularly unlikely to be true to name, and F1 hybrids should be expected. A complication is the collection and distribution of acorns from trees identified as hybrids in the wild, labelled with the nothospecific

Plate 456. Texas Live Oak Quercus fusiformis, here in Kerrville, Texas. The evergreen oaks of the American South are valued for their shade. Image E. Jablonski.

694

Quercus

New Trees

1 cm

1 cm

A

B

Section II. Species Accounts

name for the maternal parent: these are inevitably the F2 generation or backcrosses to either parent, so seedlings may exhibit any combination of characters from the original parents. Further confusion may arise if seed is gathered from known hybrids in collections, as these may well have been pollinated by yet another species, to create a triple hybrid. Among the plethora of seedlings an occasional exceptional tree will be worth selecting for propagation, but unless regular propagation and distribution are expected it is pointless to apply a cultivar name. Of great importance as the dominant trees in many landscapes, as a source of timber or forage, and supporting a huge diversity of wildlife, oaks have a special significance to many. In the arboretum their amazing variety makes them particularly popular, reflected in the dynamic International Oak Society and in the efforts of institutions and individuals across the world to introduce to cultivation as many species as possible. Some of the Mexican oaks are amongst the most remarkable and garden-worthy trees described in this book; indeed it is perhaps not too much to say that Quercus rysophylla is the outstanding single new introduction of the past 30 years. It is a measure of recent interest in Mexican and Central American species that in 1933 Sir Oscar Warburg and Edmund Warburg, in their review of oaks in cultivation in the British Isles (Warburg & Warburg 1933), listed only seven taxa, of which three were unidentified, and Bean (1976b) described only four; yet here we describe 29 species found principally in Mexico and Central America. Many of the oaks from colder parts of Mexico are deciduous in the wild, losing their leaves in winter or late winter, but these tend to be more evergreen in cultivation. Some areas of Mexico, especially the Sierra Madre Oriental, receive most of their rainfall in summer, with a long, dry season from autumn through to late spring. In consequence it would be a mistake to assume that Mexican oaks are necessarily drought-tolerant in cultivation: Shaun Haddock (pers. comm. 2006) has lost specimens and seen others severely damaged by the effects of summer drought in southwestern France. Conversely, moisture in summer can be fatal to some species of Quercus from areas of the western United States with a Mediterranean-type climate. The accounts that follow describe or discuss 95 species, on top of the 100 or so covered by Bean and Krüssmann (disentangling the synonymy makes for a certain vagueness), disregarding hybrids. In addition more than 40 other species are represented in cultivation principally by young plants (see below), bringing the total list of cultivated oaks to at least half the diversity of the genus – a remarkable number when it is considered that a large proportion of Quercus are tropical trees. Most collections also have an assortment of hybrids, of both wild and garden origin, raising the diversity total even higher. Many ‘Quercus sp.’ accessions go unidentified for years, or are annotated ‘aff.’ and remain so for some time before their identity is revealed. For example, at the Arboretum National des Barres there is an evergreen oak of subgenus Cyclobalanopsis, grown from acorns collected by Père Paul Farges – one of the great French missionary botanists – at Heoupin, near Chenkou in Sichuan, at an altitude of 1400 m, and received at Les Barres in March 1901 (Lamant 2004). Long considered to be Q. oxyodon, in 1998 it was identified by Zhekun Zhou as Q. liboensis Z.K. Zhou (Fourier 1999), under which name it has been propagated in recent years. With further study, however, it has become apparent that it is not Q. liboensis, which is close to Q. glauca and should have farinose leaf undersides. Rather, the French tree – now 10 m in height, dbh 23 cm, spread 10 m, and with waxy undersides to the leaves – seems

Quercus

Figure 78 (opposite). Quercus rysophylla: habit (A); acorn (B).

695

696

Quercus

New Trees

to be an annual fruiting relative of Q. multinervis (W.C. Cheng & T. Hong) Govaerts (A. Coombes, pers. comm. 2008). Plants are in cultivation as Q. liboensis, from a recent introduction, but their identity has not been confirmed. More successful has been the identification as Q. tungmaiensis Y.T. Chang (section Cerris?) of Keith Rushforth’s Tibetan collection KR 5765, growing as 2.5 m trees at Tregrehan and Chevithorne Barton, and showing distinctive lanceolate, strongly toothed leaves with impressed veins on the upper surface (Coombes & Zhou 2009). On the other hand, some species believed to have been in cultivation turn out to have been misidentified. For this reason, Q. rex Hemsl. has disappeared from the original list for New Trees (although its acorn is still illustrated below, p. 698). Some shrubby species of Quercus that are well established in cultivation, on either side of the Atlantic, are not described below because of shortage of space. These include the Critically Endangered Q. hinckleyi C.H. Mull., which forms a low mound in its semi-arid habitat in Presidio Co., Texas and northern Chihuahua, but can become taller in cultivation, and the short tree Q. john-tuckeri Nixon & C.H. Mull., from California. At the Hillier Gardens, shrubby Q. tinkhamii C.H. Mull. has made a small tree of 3.5 m (Coombes 371, San Luis Potosí, 1996), and the thicket-forming Q. microphylla Née is starting to spread by suckers (Coombes 409, Puebla, 1997). It is almost impossible to keep up with the flow of oaks into cultivation. As a demonstration of this, the following list is of additional species (disregarding variants and hybrids) not recorded by either Bean or Krüssmann, or covered elsewhere in New Trees, but currently grown by Michael Heathcoat Amory at Chevithorne Barton (as of October 2008). Deriving from numerous sources and collectors, many are still very young seedlings or are being maintained in pots or raised beds, and most are in other collections as well: Q. argyrotricha A. Camus, Q. berberidifolia Liebm., Q. cedrosensis C.H. Mull., Q. championii Benth., Q. cornelius-mulleri Nixon & K.P. Steele, Q. crispipilis Trel., Q. cubana A. Rich., Q. daimingshanensis (S.K. Lee) C.C. Huang, Q. depressa Bonpl., Q. greggii (A. DC.) Trel., Q. havardii Rydb., Q. hintoniorum Nixon & C.H. Mull., Q. hirtifolia M.L. Vázquez, S. Valencia & Nixon, Q. hondae Makino, Q. intricata Trel., Q. invaginata Trel., Q. jonesii Trel. (syn. Q. coccolobifolia Trel.), Q. laeta Liebm., Q. liebmannii Oerst. ex Trel., Q. miquihuanensis Nixon & C.H. Mull., Q. mohriana Buckley ex Rydb., Q. multinervis (W.C. Cheng & T. Hong) Govaerts, Q. pacifica Nixon & C.H. Mull., Q. peduncularis Née, Q. pentacycla Y.T. Chang, Q. potosina Trel., Q. pumila Walter, Q. pungens Liebm., Q. repanda Bonpl., Q. sapotifolia Liebm., Q. sessilifolia Blume, Q. vaseyana Buckley. At the Hillier Gardens are Q. delavayi Franch., grown from Coombes 481 (collected in Yunnan in 1998) and 1.5 m tall in 2008, and Q. sessilifolia Blume, from Costin & Lancaster 178A (gathered in Honshu in 1990 as Q. acuta) and now 5 m tall. A 3 m individual of Q. sessilifolia, derived from Hangzhou Botanic Garden, grows in the Jardin botanique de Nantes, France (F. Picard, pers. comm. via A. Coombes 2008). Thierry Lamant from Orléans, France has introduced Q. cupreata Trel. & C.H. Mull. and Q. tuberculata Liebm. to French gardens, from acorns collected in the Sierra Madre Oriental of Nuevo Léon in 2003, and believes that Q. cupreata will prove to be at least as hardy as Q. rysophylla (T. Lamant, pers. comm. 2008). In the United Kingdom there are outstanding National Plant Collections at the Sir Harold Hillier Gardens, Hampshire, developed, in particular, by Allen Coombes, and at Michael Heathcoat Amory’s home Chevithorne Barton, in central Devon. Despite Chevithorne Barton being a comparatively cool site at moderate elevation, many

Section II. Species Accounts

oaks seem to flourish here in fertile soil and rather high rainfall. A number of enthusiasts have good collections in France (see Lamant 2004), including Shaun Haddock at Arboretum de la Bergerette, Saint-Sardos, Dept. Tarn et Garonne. In Luxembourg there is a specialist collection at the LTA Arboretum (Lycée Technique Agricole), Ettelbruck, for which Eike Jablonski is responsible. Still in the Ardennes, but across the border in Germany, is another collection at Kruchten, a site similar to Ettelbruck in physical and climatic characteristics. Many interesting oaks are also grown at Arboretum Trompenburg in Rotterdam. Oaks are popular in the United States and most arboreta there have a good selection, Guy Sternberg’s collection at Starhill Forest Arboretum, Illinois being of particular note. Situated in an area with a severely continental climate, Starhill Forest is a useful comparator to those gardens with milder winters and cooler summers. In New Zealand there are many notable oaks at Eastwoodhill Arboretum and also at Hackfalls, where Bob and Lady Anne Berry have an outstanding collection, growing several species not mentioned here. Oaks receive prominent coverage in all dendrological works, but the only treatment of the whole genus is the massive Guide illustré des Chênes by Antoine le Hardÿ de Beaulieu and Thierry Lamant, published (in two volumes) in 2006 – sadly after the completion of most of the text of Quercus for New Trees. Profusely and finely illustrated, it is a major work of reference, and translations into other languages are eagerly awaited. It covers all the species described below, with illustrations, and as it is so comprehensive we do not reference these images individually in our accounts. Menitsky’s Oaks of Asia (2005), Miller & Lamb’s Oaks of North America (1985), and Diversidad del Género Quercus (Fagaceae) en México by Valencia-A. (2004) are all regionally important works. An invaluable source of nomenclatural information is the World Checklist and Bibliography of Fagales (Govaerts & Frodin 1998) and its counterpart online, available through the Kew World Checklist of Selected Plant Families website (2008). A further source of nomenclatural guidance is provided by the Oak Names Database (2007–2008), hosted by the International Oak Society, which is the International Cultivar Registration Authority for the genus Quercus. This database is particularly valuable for its coverage of hybrids and cultivars. In compiling our account we are greatly indebted to Allen Coombes of the Hillier Gardens for his enormous contribution of information over an extended period. In cultivation oaks are relatively tolerant of a range of growing conditions, and among the recently introduced taxa certain Mexican species are proving to be reliable in many locations. The distinction in climatic preference requirements between white and red oaks should be noted, and if a noble specimen is desired, northern European planters should probably avoid the American and Asian white oaks. Some oaks are intolerant of lime, and where this is known to be the case it is mentioned in the accounts that follow. Many of the recently introduced species have yet to be tested on calcareous soils, however, and their tolerance is unknown. Contrary to popular belief, many oaks grow extremely fast if happily situated, especially when young. Two or even three flushes of growth each year are possible, and can lead to rapid gains in stature. As the shoots are often coloured bronze or reddish, the new growth can be a very attractive feature in its own right.

Quercus

697

Plate 457. Quercus franchetii is relatively rare in cultivation but does well in a number of collections. The white-hairy leaf undersides make it a striking sight when wind ruffles the foliage. Image P. de Spoelberch.

698

Quercus

New Trees

B

D

E

C

G

H

F

A

1 cm

L K

J

M

N

P

Q

R

V

S

T

U

Section II. Species Accounts

They are best propagated from fresh acorns (of known wild origin whenever possible), sown individually in small pots or deep plug cells, where germination will often be prompt. Acorns should never be allowed to dry out before or after sowing, and care should be taken to prevent rodent predation. When growing vigorously young trees may be potted on into deep pots, but contortion of the taproot must be avoided. Planting should take place as early as possible, either direct from the pot or after a year or two of growth in nursery beds. In the absence of seed, rarities and selected clones can be propagated by grafting onto appropriate stocks, but cuttings are increasingly being used to obviate problems of incompatibility. This is a very exciting and rapidly developing field, with enormous potential benefits for horticulture. The recently published Red List of Oaks (Oldfield & Eastwood 2007) has highlighted conservation issues facing the genus: 78 species have been placed in IUCN Red List categories Critically Endangered to Near Threatened, while for a further 33 there are grounds for believing they may be threatened, though they are currently categorised as Data Deficient because of insufficient supporting information to confirm their status. Only 98 could be unequivocally assigned to the rank of Least Concern – the rest having not been evaluated at all. Oaks, officially categorised or not, are threatened globally by habitat destruction and land-use change, as well as overexploitation for timber and failure to regenerate, so it is probable that many of the species currently unevaluated are also under threat. As gardens contain about half the known diversity of the genus, they may be a valuable source of material for reintroductions in future. Oaks are famous for their hosting of a large number of other organisms, and when mature are of major importance in temperate forest ecology. While most of this biodiversity is innocuous to the host tree, there are some important pathogens that affect Quercus and can be devastating to both individuals and populations. Most alarming is the appearance of Phytophthora ramorum, the organism that causes the effect known as sudden oak death and has led to the deaths, particularly in Oregon and California, of large numbers of Quercus and Lithocarpus densiflorus, as well as other species. Symptoms are cankering of the stems, usually accompanied by a dark reddish or black trickling ooze, and the partial or total death of the canopy and eventually the tree. There is at present no known cure, and rigorous preventative measures are being put in place by national plant health authorities across North America and Europe. The water-borne pathogen also affects many other woody plants at sublethal levels, from which susceptible species can easily be infected. As these include popular ornamental shrubs such as Rhododendron and Viburnum, grown and sold in large numbers by nurseries, and frequently shipped long distances from their point of origin, this is a serious issue for horticulturists to address. It is of particular interest that the British Government’s fact sheet on P. ramorum (Defra 2006) states that all proven incidences in non-nursery specimens have been on plants in close proximity to rhododendrons. Governmental bodies and research institutions throughout our area publish regular updates on the state of research into sudden oak death, easily accessed by an internet search. Another serious fungal problem affecting oaks in eastern and central North America is oak wilt, caused by Ceratocystis fagacearum. Red oaks are particularly susceptible, and can be killed very quickly if infection takes place in early summer, while white oaks are somewhat more resistant and tend to die off branch by branch, over several years. Wounded trees are especially at risk of infection, and it is thought that the recent rapid spread of the disease is in part due to activities surrounding

Quercus

699

Figure 79 (opposite). Acorns of Quercus insignis (A); Q. spinosa (B); Q. schottkyana (C); Q. texana (D); Q. laurina (E); Q. mexicana (F); Q. laurifolia (G); Q. engelmannii (H); Q. rex (J), viewed also from above (K); Q. morii (L); Q. fusiformis (M); Q. conspersa (N); Q. candicans (P); Q. mongolica (Q); Q. rugosa (R); Q. grisea (S); Q. agrifolia var. oxyadenia (T); Q. castanea (U); and Q. brantii (V).

700

Quercus

New Trees

the construction of new homes in woodland, resulting in greater frequencies of wounded trees. Transmission is by nitulidid beetles carrying spores, or by tree-totree contact through interconnecting roots. This information is derived mostly from the USDA Forest Service website (US Forest Service 1999), but many other websites also carry information on this disease, and should be consulted for current advice. Major insect pests of oaks are also an increasing problem. In Europe the Oak Processionary Moth (Thaumetopoea processionea) is extending its range northwards, and larvae were found at Kew for the first time in 2006 – one of several breeding instances in the London area (T. Kirkham, pers. comm. 2006; Forest Research 2008b). The larvae are capable of causing massive defoliation of oak woodlands, and are also a human health hazard due to their hairs, that break off and float on the wind, and can give rise to severe irritation to skin and lungs. In ornamental trees the best cure is to catch the nests of caterpillars while they are still young and carefully cut them from the tree (T. Kirkham, pers. comm. 2007).

Quercus acerifolia (E.J. Palmer) Stoynoff & W.J. Hess

Maple-leaved Oak

(Subgen. Quercus, Sect. Lobatae) Syn. Q. shumardii Buckley var. acerifolia E.J. Palmer Shrub or tree to 15 m, 0.6 m dbh. Bark dark grey, rather smooth but with dark ridges on lower trunk. Crown rounded. Branchlets greyish or reddish brown and glabrous or sparsely pubescent. Leaves deciduous, 7–14 × (6–)10–15(–18) cm, oblate to broadly elliptic (in outline), upper surface glabrous, lower surface glabrous or with prominent tufts of hair in the vein axils, three to six secondary veins on each side of the midrib, raised on both surfaces, margins with five to seven (to nine) ovate to oblong lobes, the lobes typically expanding distally and terminating in bristles (11–48 per leaf), apex acute; petiole 2–4.5 cm long and glabrous. Cupule saucer- or cup-shaped, 1–2 × 0.4–0.7 cm, outer surface glabrous, inner surface pale reddish brown and glabrous or with a ring of pubescence around the scar; scales obtuse or acute, tightly appressed and with pale margins. Acorn ovoid to oblong, with one-quarter to one-third enclosed in the cupule, 1.5–2 cm long, pubescent or glabrous. Flowering spring, fruiting November (USA). Nixon 1997, Hess & Stoynoff 1998. Distribution USA: Arkansas (Magazine Mt., Porter Mt., Pryor Mt., Sugarloaf Mt.). Habitat Dry glades, slopes and ridge tops between 500 and 800 m asl. USDA Hardiness Zone 5. Conservation status Endangered, due to habitat loss and poor regeneration. Illustration NT700.

Plate 458. The beautiful specimen of Quercus acerifolia at the Morton Arboretum, growing there since 1950 – here showing off its autumn colour. Image P. de Spoelberch.

Closely related to Quercus shumardii, this species is little known in Europe but in the United States is regarded as being a useful medium-sized tree (Sternberg 2004), with good red autumn colour. The finest specimen in cultivation is generally accepted to be one at the Morton Arboretum, planted in 1950, which has formed a nicely rounded crown from heavy basal limbs. It is approximately 10 m tall, 39 cm dbh. A specimen at the Arnold Arboretum is of similar height but badly shaded (E. Hsu, pers. comm. 2006). Quercus acerifolia should thrive wherever other red oaks prosper. In the United Kingdom there are trees at the Sir Harold Hillier Gardens (planted in 1989), 5.1 m tall, 12 cm dbh in December 2006, and at Chevithorne Barton. The name is derived from the resemblance of the foliage, with its enlarged central pair of lobes and shortened apical portion, to the leaves of the Sugar Maple Acer saccharum.

Section II. Species Accounts

Quercus acherdophylla Trel.

Quercus

(Subgen. Quercus, Sect. Lobatae)

Tree to 15 m. Bark greenish grey and smooth when young. Branchlets stiff and slender, dull reddish brown with prominent white or brown lenticels. Leaves deciduous (to evergreen in cultivation), dark green, 6–7 × 2–3 cm, ovate, immature leaves with white and yellow stellate tomentum below; in the mature leaves the upper surface is glossy and glabrous but the lower surface retains some stellate tomentum, particularly along the midrib, 10–12 secondary veins on each side of the midrib, margins entire and slightly curled to undulate, lamina surface sometimes rather bullate, apex acute; petiole 0.2–0.4 cm long and largely glabrous. Infructescences 0.5 cm long with one to two cupules. Cupule saucer-shaped, to 1 cm diameter; scales brown, blunt and appressed. Acorn ovoid, with half of its length enclosed in the cupule, ~1.4 cm long. Flowering April (Mexico). Trelease 1924. Distribution MEXICO: Hidalgo, Puebla, Veracruz. Habitat Between 2400 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated.

One of the dark-leaved Mexican species, Quercus acherdophylla appears to have first been introduced by Michael Frankis in 1991 (under several MPF collection numbers: M. Frankis, pers. comm. 2006), with later collections by Allen Coombes in 1995 (no. 246) and L.R. Santamaria in 1996. Trees from these early introductions are growing well at the Hillier Gardens and at Chevithorne Barton, where the tallest is approximately 14 m (in 2008) and seems to be completely hardy. This is not a particularly attractive species, the sparsely clad long new shoots in late summer giving it an untidy look, and branches from the base can be heavy. Quercus acuta Thunb. B459, S405, K80

Quercus acutifolia Née

(Subgen. Quercus, Sect. Lobatae)

Tree to 35 m (generally smaller), 0.15–0.6(–1) m dbh. Bark grey, smooth when young. Branchlets with numerous yellow or pale brown lenticels. Leaves evergreen, dark green, 5–27 × 1.5–7 cm, lanceolate to ovate, immature leaves densely covered in stellate pubescence, strongly flushed red or bronze especially in the second flush; mature leaves glabrous above and with tufts of easily dislodged stellate hairs below, 10–12 secondary veins on each side of the midrib, margins with four to ten teeth on either side, apex obtuse or attenuate; petiole 0.8–2.5 cm long and brown. Infructescence 1 cm long with one to three cupules. Cupule shallow, 1.2–2 × 0.7–1 cm; scales dentate and interlocking, dark-edged and covered with silky hairs. Acorn ovoid, with one-third to half of its length enclosed in the cupule, ~1.5 cm long. Flowering January, fruiting November (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution MEXICO: Guerrero, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla. Habitat Transitional zone between montane and cloud forest, between 1000 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002.

Introduced by Allen Coombes (no. 293) from Puebla in 1995, and from later gatherings, this remains a rare tree, but it is established in some specialist collections. At Arboretum de la Bergerette a specimen from Coombes 412 is 6 m tall from planting in 1999, and has not been affected by cold or drought (S. Haddock, pers. comm. 2006). The finest specimen seen in the United Kingdom in the research for New Trees is at Chevithorne Barton, currently c. 7 m tall (2008) and growing well, and particularly attractive when seen in September as the second flush of growth was developing. The new leaves are red and hairy, soon losing the hairs and becoming bronze. In contrast, the older leaves are a rather dull dark green. A tree from Coombes 427 at Thenford House has developed a flat-topped, spreading habit.

Q. acutissima Carruth. B459, S405, K80 Q. acutissima subsp. chenii (NOW Q. chenii Nakai) B460 Q. afares Pomel B466, K80

701

702

Quercus

New Trees

A

1 cm

1 cm

B

Quercus affinis Scheidw. Figure 80 (above). Quercus affinis: habit (A); acorn (B).

(Subgen. Quercus, Sect. Lobatae)

Tree to 30 m. Bark smooth when young, cracking into fine fissures and plates below (not recorded from mature trees). Branchlets slender and reddish brown with small, pale lenticels; may be covered in flaky scales when very young. Leaves evergreen, dark green, 3.5–9 × 1.5–2 cm, oblong to lanceolate, shiny, upper surface glabrous, lower surface may have prominent tufts of tomentum in the vein axils, 10–12 secondary veins on each side of the midrib, margins sharply serrate, apex acute; petiole 0.5–1 cm long and glabrous. Infructescence < 1 cm long with one to two cupules. Cupule hemispheric, 1–1.4 × 0.6–0.8 cm; scales acute and appressed, brown and ciliate. Acorn subglobose, with one-third to half of its length enclosed in the cupule, 0.8–1 cm long, stylopodium small or absent. Fruiting in the second year (Mexico). Trelease 1924. Distribution MEXICO: Guanajuato, Hidalgo, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Tamaulipas, Veracruz. Habitat Pine-oak forest between 1200 and 2600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT12, NT702.

Section II. Species Accounts

Quercus

Quercus affinis is one of the Mexican evergreen oaks that have accepted British conditions with gusto, growing vigorously in all collections and sometimes fruiting freely, although frost damage can occur to unripened wood. In southwestern France it does well but can be killed by drought if grown in a dry site (S. Haddock, pers. comm. 2006). It was introduced by Jim Priest (no. 79) from a collection made at 2500 m in the Cerro Potosí, Nuevo León in 1984, and there have been later collections by others. The finest seen in the research for this book is at Kew, from VERA 88, forming a beautiful erect pillar of 12–13 m, which looks as if it will soon equal an adjacent rather columnar Q. ilex, and has a single straight trunk (21 cm dbh, November 2005). Another large specimen is at Chevithorne Barton, c.11 m in height (2008), forming an upright tree with large branches from the base. Late summer shoots are long and slender, sometimes but not always flushed red-bronze. On the Kew specimen mentioned above the summer shoots are up to 1.5 m long. In subsequent growth they broaden and become thickly clad in leaves, giving the tree a dense, almost sombre look. It should be given room to develop into the large tree it is.

Quercus agrifolia Née

(Subgen. Quercus, Sect. Lobatae)

Coast Live Oak

This species was described by Bean (B460, S406) and Krüssmann (K81).

Quercus agrifolia var. oxyadenia (Torr.) J.T. Howell This variety differs from typical Q. agrifolia in that persistent stellate pubescence forms a felt-like covering on the branchlets, petioles and lower leaf surfaces. Var. agrifolia is entirely glabrous. Howell 1931. Distribution MEXICO: Baja California; USA: southern California. Habitat High valleys and canyon floors at about 1400 m asl. USDA Hardiness Zone 8. Conservation status Least Concern. Illustration NT698. Taxonomic note Valencia-A. (2004) does not distinguish var. oxyadenia.

This taxon was introduced to the United Kingdom by Warner and Howick (WAHO 345) from a collection made in San Diego Co., California in 1986. At Kew a specimen from this gathering has made a fine tree of c.10 m, with numerous vertical branches, forming a dense canopy that extends to the ground. This was fruiting freely in November 2005.

Q. alba L. B460, S406, K81 Q. aliena Blume B461, S406, K81

Q. aliena var. acutiserrata Maxim. B461, K81 Q. alnifolia Poech B461, S406, K81

Quercus aquifolioides Rehder & E.H. Wilson

(Subgen. Quercus, Sect. Cerris)

Tree to 10 m (rarely 20 m). Branchlets pale greenish brown with stellate tomentum. Leaves evergreen, 2.5–7 × 1.5–3.5 cm, obovate to elliptic or orbicular, immature leaves densely covered in reddish brown glandular hairs; in mature leaves the upper surface is glabrous or with some pubescence along the midrib, the lower surface covered with slender reddish brown or dirty yellow hairs (both stellate and simple) or scale-like trichomes, six to eight secondary veins on each side of the midrib, margins slightly retuse, entire or with spiny teeth, apex obtuse; petiole 0.2–0.5 cm long or absent, tomentose. Infructescence 0.5–2.5(–4) cm long with one to four cupules. Cupule shallow, 5–6 × 0.9–1.2 cm, outside grey-pubescent, inside tomentose; scales ovate, elliptic or lanceolate, apices often free from cupule wall. Acorn ovoid, with only its base enclosed in the cupule, 1.2–2 cm long. Flowering May to June, fruiting September to October (China). Huang et al. 1999, Zhou & Coombes 2001. Distribution BHUTAN; CHINA: Guizhou, western Sichuan, Xizang, Yunnan; MYANMAR. Habitat From montane forest to subalpine scrub between 2000 and 4500 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Huang et al. 1999; NT705.

703

704

Quercus

New Trees

Quercus aquifolioides is one of twelve species of largely Chinese oaks in Quercus section Cerris. All of them are small to medium-sized evergreen trees or shrubs with thick, leathery leaves. The leaves are obovate, elliptic or orbicular and often revolute; they may be spinose or entire, with great variation within individual plants. The leaf underside is densely covered in grey or golden fascicled hairs, giving the group the name ‘golden oaks’ (Zhou & Coombes 2001). Golden oaks have been in cultivation in Europe since Q. semecarpifolia was introduced to Tregrehan in 1894 (Zhou & Coombes 2001), and most species appear to be hardy. In place of descriptions of all twelve of these rather similar species, a key is provided below and they are discussed, briefly, later within this account (pp. 704– 707). The key is that of Zhou & Coombes (2001), with only minor modifications. Flora of China (Huang et al. 1999) recognises just seven of these species, and the following list is a guide to their synonymy as attributed in that account: Quercus aquifolioides Rehder & E.H. Wilson Quercus guyavifolia H. Lév. Syn. Q. pannosa Hand.-Mazz. Quercus monimotricha (Hand.-Mazz.) Hand.-Mazz. Quercus rehderiana Hand.-Mazz. Quercus semecarpifolia Sm. Syn. Q. longispica (Hand.-Mazz.) A. Camus, Q. pseudosemecarpifolia A. Camus Quercus senescens Hand.-Mazz. Quercus spinosa David ex Franch. Syn. Q. gilliana Rehder & E.H. Wilson Plate 459. The ‘golden oaks’ take their name from the yellowish indumentum often found on their leaves. This is Quercus guyavifolia H&M 1471 at Quarryhill, collected in Sichuan in 1991. Image J. Grimshaw.

Golden oaks Key adapted from Zhou & Coombes (2001)

1a. Mature leaves with golden or grey hairs on the underside ............................................................... 2 1b. Mature leaves glabrous, or with a few hairs at the base of the midrib .............................................. 9 2a. Leaves with yellow hairs beneath .................................................................................................... 3 2b. Leaves with grey hairs beneath ........................................................................................................ 8 3a. Hairs densely covering the secondary veins; China (Sichuan, Yunnan) ............................. Q. pannosa 3b. Hairs not densely covering the secondary veins ............................................................................... 4 4a. Cupule with long, slender, linear or lanceolate scales, 0.4–0.5 cm long; China (Sichuan, Yunnan) .............................................................................................. Q. fimbriata

Figure 81 (opposite). Quercus aquifolioides: habit (A, B); leaves with varying degrees of spinescence, from the same tree (C); acorn (D).

4b. Cupule with short, lanceolate scales, < 0.4 cm long ........................................................................ 5 5a. Cupule hood-shaped, wall 0.2 cm thick; China (Sichuan, Yunnan) ............................... Q. guyavifolia 5b. Cupule not hood-shaped, wall 0.1 cm thick .................................................................................... 6

Section II. Species Accounts

Quercus

D

1 cm

1 cm

1 cm

A B

C

705

706

Quercus

New Trees

6a. Fruit spherical, 1.8–2.5 cm diameter, black when mature; Afghanistan, Bhutan, China (Xizang), India (Kumaun, Sikkim), Myanmar, Nepal, Pakistan ................... Q. semecarpifolia 6b. Fruit ovoid, < 1.5 cm diameter ........................................................................................................ 7 7a. Pistillate inflorescence 5–16 cm long; China (Sichuan, Yunnan) ..................................... Q. longispica 7b. Pistillate inflorescence ≤ 4 cm long; China (Guizhou, western Sichuan, Xizang, Yunnan), Myanmar ................................................................................................ Q. aquifolioides 8a. Small to medium-sized tree; leaves long-elliptic with dense hairs; China (Guizhou, Sichuan, Xizang, Yunnan) ............................................................... Q. senescens 8b. Shrub; leaves elliptic to obovate with scattered hairs; China (Sichuan, Yunnan), Myanmar ......................................................................Q. monimotricha 9a. Leaves 6–10 cm long, secondary veins not sunken ........................................................................ 10 9b. Leaves < 6 cm long, secondary veins sunken ................................................................................. 11 10a. Leaves with a few scattered hairs on underside; China (Sichuan, Xizang, Yunnan) ......................................................... Q. pseudosemecarpifolia 10b. Leaves largely glabrous on both sides; China (Guizhou, Sichuan, Xizang, Yunnan) .......................................................... Q. rehderiana 11a. Leaves with dense hairs at base of midrib (underside); China (Fujian, Gansu, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Xizang, Yunnan), Myanmar, Taiwan ............................................................. Q. spinosa 11b. Leaves without hairs at the base of the midrib; China (Gansu, Sichuan, Yunnan) .............. Q. gilliana

Plate 460. Quercus longispica, from western China, is distinguished by notably long female inflorescences. Image E. Jablonski.

Quercus semecarpifolia has been in cultivation for many years and is quite well known, with fine specimens at Arboretum Trompenburg, Tregrehan and Thenford House. Bean (1981a) records the introduction of Q. gilliana by Wilson, and provides a description, but it is not certain whether this species remains in cultivation. Quercus aquifolioides is in cultivation at Kew and Thenford House from a collection made at 3690 m on the Zheduo Shan, Sichuan (SICH 376), when it was noted to be a shrub amongst Rhododendron and Salix. At both these sites it is slowly growing into an upright young tree, of approximately 2 m in 2006. The indumentum on the underside of the leaves is a bright sulphur-yellow when young, darkening somewhat in older leaves. The Kew specimen has already flowered. Eike Jablonski (pers. comm. 2006) reports that at Göttingen Botanical Garden in central Germany a plant from 1996 has made a vigorously growing bush, 1.2 m tall by 1 m wide. Quercus longispica is well established at the Hillier Gardens from a 1981 collection made by Roy Lancaster (no. 960) as Q. semecarpifolia (see also Lancaster 1989). This 6.9 m specimen (January 2007) now fruits regularly and comes true from seed (A. Coombes, pers. comms. 2005, 2007). Again at the Hillier Gardens, 1999 collections made by John Rippin (no. 204) started to flower in 2005, when the plants were only 1.6–1.8 m tall (2.6 m in 2008). The leaves are dark green with a slight sheen above, densely golden-pubescent below, and quite variable between plants in the degree of toothing on the margins. Both the foliage and the distinctive long infructescence of Q. longispica are well illustrated by Zhou & Coombes (2001).

Section II. Species Accounts

Quercus

A vigorously growing plant of Q. pannosa at the Hillier Gardens, from a Tom Hudson collection, is a ferocious individual, with spiny dark green leaves and very dense yellow pubescence beneath; in 2008 it was 2 m tall. Specimens of Q. pseudosemecarpifolia (Coombes 479, Rippin 28) in the same arboretum have grown well, the tallest 3.1 m in 2008. As with other species in the group, trees show considerable variation in their degree of foliar spinescence, from very prickly (see Plate 37, p. 23) to almost smooth, but are distinctive for their glabrous, green undersides. Quercus pseudosemecarpifolia is growing vigorously at Ettelbruck and Kruchten, reaching 1.8 m by 2006 from a 1999 Jablonski collection from Yunnan (E. Jablonski, pers. comm. 2006). At Quarryhill there is a fine multistemmed tree of Q. guyavifolia grown from H&M 1471 (Plate 459, p. 704), at first misidentified as Q. monimotricha. This was 7–8 m tall when seen in 2004, forming a rounded dome of dark green foliage. The young foliage is covered by yellowish hairs with a hint of red, but the indumentum thins out to leave sparse white stellate hairs on the upper surface of the leaf, while below the hairs are yellowish fawn. On a plant seen at Chevithorne Barton the very bristly leaves are white below when young, becoming yellow with age – a factor that should be considered when using the above key. Young specimens of Q. guyavifolia are also cultivated at the Hillier Gardens, and at Ettelbruck plants have reached 1.6 m from acorns collected in Yunnan by Eike Jablonski in 1999. Quercus monimotricha is well established on the scree beds in front of Jermyn’s House at the Hillier Gardens, as low hedgehog-like shrubs grown from Lancaster 1667, collected in northwest Yunnan in 1986. This species is never arborescent, but with its grey indumentum on the lower surface of the leaves it is attractive for the rock garden. At Kruchten a seedling of Q. monimotricha from a Jablonski collection in Yunnan in 1999 flowered at two years old, and has continued to flower, though without setting acorns. Cuttings have been raised from it, however, with a 50 per cent success rate (E. Jablonski, pers. comm. 2006). Seedlings from a collection of Q. spinosa (Cao Ming 316) are now considered to be Q. dolicholepis (see p. 717) (A. Coombes, pers. comm. 2007), and Q. spinosa (acorn illustrated, p. 698) is not known to be in cultivation. Quercus fimbriata Y.C. Hsu & H. Wei Jen, known only from the type specimen, is considered to be a hybrid, with Q. dolicholepis and Q. aquifolioides as parents (Huang et al. 1999). Zhou (pers. comm. via A. Coombes 2006) has also recently found evidence of natural hybridisation within the group.

Quercus arizonica Sarg.

Arizona (White) Oak

(Subgen. Quercus, Sect. Quercus) Small to medium-sized tree 5–10(–18) m, 0.6–0.9 m dbh. Bark pale grey to white with deep fissures separating broad ridges. Crown irregular, with stout spreading branches. Branchlets yellowish with persistent tomentum. Leaves evergreen or sub-evergreen, (3–)4–8(–9) × 1.5–2.5 cm, elliptic or oblong to oblanceolate or obovate, thick and leathery, upper surface dark or blue-green with sparse stellate pubescence, lower surface dull green to glaucous with sparse curly branched hairs, 7–11 secondary veins on each side of the midrib, margins entire or with coarse teeth near the apex, revolute, apex acute to obtuse; petiole 0.3–1 cm long. Infructescence 1–1.5 cm long with one to two cupules. Cupule hemispheric or cup-shaped, 1–1.5 × 0.5–1 cm; scales cream to brown, ovate and strongly tuberculate, tomentose. Acorn ovoid or oblong, with half of its length enclosed in the cupule, 0.8–1.2 cm long, stylopodium umbilicate. Flowering June, fruiting September (USA). Nixon 1997. Distribution MEXICO: Chihuahua, Coahuila, Durango, Sonora; USA: Arizona, New Mexico, Texas.

707

Plate 461. A white oak from hot, dry conditions, as here in Texas, Quercus arizonica is unlikely to thrive in cultivation in northern Europe. Image E. Jablonski.

708

Quercus

New Trees

Habitat Oak and pine woodland and chaparral between 1300 and 3000 m asl. USDA Hardiness Zone 7. Conservation status Least Concern. Illustration Nixon 1997; NT707. Taxonomic note This species is closely related to Q. grisea and forms hybrids with it and other species (Melendrez 2000).

Quercus arizonica is an extremely rare tree in Europe, with only a few young plants in cultivation in the United Kingdom. Among these are a single small specimen in Michael Heathcoat Amory’s collection at Chevithorne Barton, originating in Pima Co., Arizona in 2001, and two youngsters at the Hillier Gardens, from Grant Co., New Mexico, also in 2001. Specimens from collections made by Eike Jablonski in the Gila National Forest, New Mexico are in cultivation at Ettelbruck. Melendrez (2000) notes that the leaves fall late, dependent on the severity of the climate, sometimes persisting until new leaves emerge. They are greyish but show good autumnal colour, turning burgundy-red. Q. arkansana Sarg. B462, S406, K81

Quercus aucheri Jaub. & Spach Plate 462. A tempting acorn on Quercus aucheri. The hard and spiny leaves are an adaptation to the dry conditions in its eastern Mediterranean habitat. Image E. Jablonski.

(Subgen. Quercus, Sect. Cerris)

Shrub or tree to 10 m. Branchlets somewhat pendulous, yellowish brown, densely stellate-tomentose. Leaves evergreen, leathery, 0.9–4 × 0.9–2.5 cm, broadly oblong to ovate, upper surface glabrous or with inconspicuous tomentum, lower surface grey-white with stellate tomentum, five to nine secondary veins on each side of the midrib, margins entire or serrate, apex rounded; serrate leaves occur on sterile long shoots, entire leaves on short shoots and older shoots; petiole absent or to 0.6 cm long. Cupule cup-shaped, sessile, to 2.5 cm diameter; scales ovate to lanceolate, appressed, pubescent. Acorn with one-third of its length enclosed in the cupule, apex flattened to acute; mature in second year. Browicz 1986, Hedge & Yaltirik 1994. Distribution GREECE: eastern Aegean islands; TURKEY: southwestern Anatolia. Habitat Maquis on limestone slopes, between 0 and 450 m asl. USDA Hardiness Zone 8. Conservation status Near Threatened. Illustration Browicz 1986; NT708. Cross-reference S407. Taxonomic note This species is closely related to Q. coccifera, which has largely glabrous leaves and a cupule 1–2 cm diameter.

Despite its origins in a botanically wellknown part of the world, Quercus aucheri has not received much attention from dendrologists, perhaps because of its similarity to the widespread Q. coccifera. Recent introductions are now established in cultivation, with small trees in major collections. At the Hillier Gardens it has proved to be slow-growing, saplings from a 1999 Turkish collection ranging in height from 30 to 100 cm in 2006 (Sir Harold Hillier Gardens database), although the tallest has now reached 1.7 m (A. Coombes, pers. comm. 2008). As a drought-adapted Mediterranean species, it should be planted in full sun in a warm site.

Q. ×audleyensis A. Henry K82

Section II. Species Accounts

Quercus austrina Small

Quercus

Bastard White Oak

(Subgen. Quercus, Sect. Quercus) Tree to 25 m. Branchlets dark brown or reddish brown with white, corky lenticels. Leaves deciduous, (4–)7–10(–20) × 3–5 cm, narrowly obovate or elliptic, immature leaves loosely covered in semi-erect stellate hairs; mature leaves largely glabrous, but some pubescence may remain on the lower surface near veins and midrib, four to six (to eight) secondary veins on each side of the midrib, margins irregularly and shallowly lobed, lobes rounded or obtuse, apex rounded; petiole 0.3–0.5 cm long. Infructescence 0.6– 0.8 cm long with one (to two) cupule(s). Cupule cup- or goblet-shaped, 1–1.3 × 0.9–1 cm; scales narrowly ovate, grey and loosely appressed. Acorn ovoid or elliptic, with one-third to half of its length enclosed in the cupule, ~1.7 cm long, stylopodium persistent. Flowering April, fruiting September to October (USA). Nixon 1997. Distribution USA: Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina. Habitat Wet forests and river bottoms between 0 and 200 m asl. USDA Hardiness Zone 5–6. Conservation status Least Concern. Illustration Nixon 1997. Cross-reference K82.

Quercus austrina is not well known in cultivation, either in its native United States or in Europe, and Michael Heathcoat Amory (pers. comm. 2006) describes it as ‘not very interesting’. In major collections it is represented as small plants (at Chevithorne Barton, Ettelbruck and Trompenburg, for example). As a white oak it is not likely to thrive in Europe, but Sternberg (2004) notes that it is much hardier in winter than its southern distribution would suggest. In his Starhill Forest Arboretum, with the hot summers it needs, young plants are currently just getting going and show no sign of winter dieback. Recent commercial offerings in the United Kingdom have been misidentified, being a form of Q. nigra (a red oak) (A. Coombes, pers. comm. 2006). Q. ×auzendi (NOW Q. ×auzendei Gren. & Godr.) B470

Quercus baloot Griff.

(Subgen. Quercus, Sect. Cerris)

Shrub or tree to 15 m, 1 m dbh. Bark dark grey and divided into rectangular plates. Branchlets greytomentose to brown and glabrous. Leaves evergreen, 2–4(–6) × 3–4.5(–8) cm, obovate or elliptic or rarely circular, leathery, upper surface greyish green, lower surface white or glaucous with stellate tomentum, six to seven (to eight) secondary veins on each side of the midrib, margins entire or with spiny teeth, revolute, apex acute to rounded; the leaves on one plant range from entire to having 1–14 holly-like spines; petiole 0.3–0.6 cm long with stellate pubescence. Infructescence 2–4.2 cm long with one cupule. Cupule cup-shaped with villous margins, 1.2–1.4 × 0.8–1 cm; scales elliptic to oblong and with appressed apices, lower scales tuberculate. Acorn elliptic, with half to three-quarters of its length enclosed in the cupule, 1.5–2.5 cm long, stylopodium prominent. Flowering April to May, fruiting September (Pakistan). Browicz & Menitsky 1971, Nasir 1976, Menitsky 2005. Distribution AFGHANISTAN; INDIA: Kashmir, Kumaun; PAKISTAN. Habitat Dry valleys of the Himalaya and Hindu Kush between 1800 and 3000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Menitsky 2005.

The origins of Quercus baloot might suggest that it was introduced by a nostalgic veteran of the Northwest Frontier many years ago, but it seems that most specimens in cultivation are derived from a gathering made by Shaun Haddock in the mountains of northwest Pakistan in 1995. Allen Coombes (pers. comm. 2005) recalls how Haddock, then an airline pilot, arrived at a meeting of oak enthusiasts with a bag of acorns of Q. baloot and distributed them around. In fact there were two gatherings represented in this distribution, made at c. 2100 m (Haddock 002) and 1200 m (Haddock 009), in the Swat valley (S. Haddock, pers. comm. 2006). (Enthusiasts of Edward Lear’s nonsense verse may be familiar with his poem The Akond of Swat; if not, it is to be recommended.) As a slow-growing species, adapted to drought, heat and extreme cold, vigour is not to be expected of Q. baloot, and it will remain a tree for patient enthusiasts.

709

710

Quercus

New Trees

A warm sunny site is indicated, but for Shaun Haddock in France it is slow even in such conditions. The specimen at the Hillier Gardens is the tallest seen for the present work, at 2.9 m (in 2008); at Chevithorne Barton it remains a small low bush. At Kruchten it has reached 1.8 m, with an open habit, and suffers only slight winter damage there (E. Jablonski, pers. comm. 2006). The only other introduction known is one made by the late Karl Fuchs in 1986. A specimen cultivated in his arboretum in the Odenwald of central Germany, which has not been damaged by the winters there, has very small, spiny leaves, resembling Q. coccifera (E. Jablonski, pers. comm. 2006). Typical Q. baloot is well equipped to repel browsing animals, as the leaf margin is undulate and both the up- and downpointing undulations have exceptionally sharp bristles. Haddock’s collections (supported by herbarium specimens) were from populations of spiny and non-spiny trees, but the seedlings from both populations gave spiny-leaved seedlings (A. Coombes, pers. comm. 2006). Only those from the wild spiny-leaved trees survived. Q. bambusifolia Hance K82 Q. baronii Skan B462, K82 Q. ×beadlei (NOW Q. ×saulii C.K. Schneid.) K82 Q. ×bebbiana C.K. Schneid. K82 Q. ×benderi Baen. K83 Q. bicolor Willd. B463, S406, K83

Quercus brantii Lindl.

Plate 463. Quercus brantii has a wide distribution in the Middle East. In cultivation it is slowgrowing. Image E. Jablonski.

Q. boissieri (NOW Q. infectoria subsp. veneris (A. Kern.) Meikle) B486 Q. brachyphylla (NOW Q. pubescens Willd. subsp. pubescens) B505

(Subgen. Quercus, Sect. Cerris)

Shrub or tree to 10 m, 0.8 m dbh. Bark greyish brown, rather smooth, becoming deeply furrowed and forming heavy ridges. Crown rounded. Branchlets covered in yellowish brown or grey tomentum. Leaves deciduous, 6–10(–15) × 3–7(–9) cm, ovate to oblong, upper surface dull green with sparse stellate hairs or glabrous, lower surface with dense pale yellowish grey stellate hairs, 6–16 secondary veins on each side of the midrib, margins regularly serrate with 8–14 teeth on each side of the midrib, apex acute; petiole 0.5–2 cm long. Infructescence to 15 cm long with one or two cupules. Cupule hemispheric, 3–4 × 2–3 cm, outside densely pubescent; lower scales rather short and blunt, apical scales with elongated apices that curl into and away from the acorn. Acorn elliptic, with one-third to half of its length enclosed in the cupule, to 1.8–5 cm long, stylopodium short. Fruiting August to October of the following year (Turkey). Browicz & Menitsky 1971, Hedge & Yaltirik 1994, Menitsky 2005. Distribution IRAN; IRAQ; SYRIA; TURKEY. Habitat Limestone slopes between 350 and 1700 m asl. Highly drought-tolerant. USDA Hardiness Zone 8. Conservation status Least Concern. Illustration Menitsky 2005; NT698, NT710. Cross-reference S412.

The nineteenth-century archaeologist Sir Austen Layard, who excavated the ruins of the ancient Assyrian city of Nineveh, sent acorns of Quercus brantii to the Horticultural Society of London in the 1840s, but trees from this introduction are long gone (Clarke 1988). It was reintroduced into the United Kingdom in 1977 by the Fliegner & Simmons Expedition to Iran (FLSX), but individuals have grown very differently. At Kew a specimen from FLSX 487, collected in the Zagros Mountains at 1500 m, has formed an erect small tree (c. 8 m) with ascending branches – although Allen Coombes has suggested (pers. comms. 2005, 2006) that this is an intermediate, as it resembles Q. libani, and the two species intergrade in the wild. There is a similar specimen at Chevithorne Barton. Another individual at Kew from FLSX 487 is a bushy, rather contorted tree, but it is growing upright, unlike two plants from

Section II. Species Accounts

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711

FLSX 458 at the Sir Harold Hillier Gardens which have both formed sprawling shrublike specimens, with sinuous stems along the ground. Neither form produces what could be described as an exciting plant. A 1987 introduction is grown at Arboretum Trompenburg. Young plants of Turkish origin are in cultivation at Ettelbruck, where they are growing very slowly (E. Jablonski, pers. comm. 2006), and there is now further Iranian material at the Hillier Gardens.

Q. ×brittonii W.T. Davis K83 Q. brutia (NOW Q. robur L. subsp. brutia (Ten.) O. Schwarz) B511, K104

Quercus buckleyi Nixon & Dorr

Buckley Oak, Texas Red Oak

(Subgen. Quercus, Sect. Lobatae) Syn. Q. texana Young Tree to 15 m. Branchlets grey, black or reddish brown, smooth or furrowed. Leaves deciduous, 5.5–10 × 5–11 cm, broadly elliptic to obovate or almost circular, glabrous, upper surface glossy green, lower surface coppery green, with tufts of hair in the vein axils, three to four secondary veins on each side of the midrib, margins with five to nine deeply divided lobes, lobes largely triangular, expanding and terminating in spiny bristles (12–35 in total), apex acute to acuminate; petiole 2–4.5 cm long, glabrous. Cupule cup- or goblet-shaped, 1–1.8 × 0.5–1.2 cm, outer surface glabrous, inner surface glabrous but for a few hairs on acorn scar; scales acute, occasionally tuberculate, apices appressed. Acorn broadly ovoid to ellipsoid, one-third to half of its length enclosed in the cupule, 1.2–1.9 cm long, stylopodium may be surrounded by several rings. Fruiting in the following year (USA). Nixon 1997. Distribution USA: Oklahoma, Texas. Habitat Limestone ridges and slopes and along small streams between 150 and 500 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997; NT711.

Quercus buckleyi is frequently confused with Q. texana Buckley and several other Texan red oaks. A key to the group in the wild state is therefore provided below.

1a. Leaves with petioles 0.5–2 cm long; lamina entire or with 3–5 pronounced lobes or 8–10 teeth or shallow lobes; within USA, restricted to Texas ................................................... 2 1b. Leaves with petioles 2–6 cm long; lamina with 5–11 pronounced oblong lobes; within USA, also occurring outside Texas .................................................................................... 3 2a. Tree to 13 m tall; leaves 4.5–14 × 2–12 cm, ovate to elliptic in outline, with 3–5 acute lobes and 9–20 bristles; cupule turbinate or deeply cup-shaped, covering one-third to half of acorn; USA (Texas: Davis, Glass and Chisos Mts.), Mexico (Coahuila) ............ Q. gravesii 2b. Tree to 8 m tall; leaves 4.5–9 × 1–2.5 cm, lanceolate to narrowly elliptic in outline, entire or with 8–10 teeth or shallow lobes, 1–9 bristles; cupule saucer-shaped, covering one-quarter to one-third of acorn; USA (Texas: Chisos Mts.) ..................... Q. graciliformis

Plate 464. Quercus buckleyi is noted for its excellent autumn colours – but in the wild these differ from population to population. It is not known whether this is a genetic or an environmental phenomenon. Image E. Jablonski.

712

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New Trees

3a. Tree to 15 m tall; leaf bud scales often distinctly ciliate; mature lamina glabrous below or with minute tufts of tomentum (often detectable only with magnification) in vein axils; USA (Oklahoma, Texas) .......................................................................... Q. buckleyi 3b. Tree 25–35 m tall; leaf bud scales usually entire; mature lamina with conspicuous tufts of tomentum (readily discernible to naked eye) in vein axils of lower surface ...................... 4 4a. Cupule with thin wall (< 1.5 mm thick), deeply goblet-shaped, covering one-third to half of acorn, inner surface pubescent; USA (Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Tennessee, Texas) ......................................................... Q. texana 4b. Cup with thick wall (> 1.5 mm thick), saucer- or cup-shaped, covering one-quarter to onethird of acorn, inner surface glabrous or with ring of hairs around scar; Canada (Ontario), USA (Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia) ................... Q. shumardii

Quercus buckleyi is a southern representative of the red oaks, allied to Q. shumardii, but slower growing and remaining a smaller tree, tolerant of drought and alkaline soils (Sternberg 2004). Melendrez (2000) has praised its autumnal colour, and noted the variation between deep to bright red and golden yellow in different localities in the wild. In summer the comparatively small leaves are a dull mid-green, with a red petiole. Quercus buckleyi would seem to be a useful red oak for warm, dry climates. It grows reasonably well in the United Kingdom, a specimen at the Hillier Gardens having reached over 10 m in height (date of planting unknown, but prior to 1976). A younger one (Sir Harold Hillier 563), accessioned as a seedling in 1986, is now c. 6 m tall. Eike Jablonski (pers. comm. 2006) collected Q. buckleyi, Q. gravesii and Q. shumardii on the same visit to New Mexico in 2000; all have done well at Ettelbruck and Kruchten, but Q. gravesii has the best autumn colour and Q. shumardii has grown fastest. Q. ×bushii Sarg. K83 Q. calliprinos (NOW Q. coccifera L.) B463, S406, K83 Q. canariensis Willd. B464, S407, K83

Quercus canbyi Trel.

(Subgen. Quercus, Sect. Lobatae)

Syn. Q. alamarensis C.H. Mull.

Canby Oak, Sierra Red Oak

Tree to 10 m, 0.7 m dbh, perhaps much larger in cultivation. Bark smooth when young, becoming furrowed and scaly at the base, forming square plates. Branchlets glabrous and glossy red or reddish grey with prominent lenticels. Leaves tardily deciduous, glossy dark green, 1.5–2.5 × 6–9 cm, narrowly lanceolate, often puckered, immature leaves may have minute flaky scales above and short hairs below; mature leaves glossy dark green or metallic and largely glabrous, but some pubescence may remain in the vein axils of the lower surface, six to eight poorly defined secondary veins on each side of the midrib, margins with deep or shallow lobes and 9–13 bristles, apex long-acuminate to caudate; petiole 1–2 cm long, yellowish and glabrous. Infructescence 0.5–3 cm long with one to four cupules. Cupule cup-shaped, 0.8–1 × 0.5 cm diameter; scales acute, silvery and appressed. Acorn elongated-ovoid, with one-third to half of its length enclosed in the cupule, covered in silky hairs, ~1.2 cm long, stylopodium persistent, elongated; maturing in the first year. Flowering March, fruiting August of the same year (Mexico). Trelease 1924. Distribution MEXICO: Nuevo León, Tamaulipas. Habitat Foothills of the Sierra Madre, between 650 and 2000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated.

Quercus canbyi is proving to be a vigorous, rapidly growing species wherever it has been cultivated. The first introduction to the United Kingdom appears to have been

Section II. Species Accounts

Quercus

713

from collections made by Sir Harold Hillier in Mexico in 1979. Trees from these accessions are now over 10 m in height at the Hillier Gardens, and may become much larger than recorded wild specimens. They are good-looking trees, well clad in dark leaves. Later collections are in cultivation and are also growing well. In the United States, Melendrez (2000) reports that Q. canbyi is an exceptionally rapid grower at Los Lunas, New Mexico (1500 m, Zone 6b), putting on 1.2–1.5 m of growth each year, with even the September flush hardening off before frosts in October. In these conditions it is semi-evergreen and has good maroon winter colour on long-persistent leaves. This is also the pattern at Kruchten, where the leaves fall in January, but here the upper third of the new shoots freezes off, to resprout the following May (E. Jablonski, pers. comm. 2006). It is said by Melendrez to grow well on alkaline limestone soil, and is happy at pH 7.0 at Kruchten, but Hillier & Coombes (2002) mark it as a calcifuge.

Quercus candicans Née

(Subgen. Quercus, Sect. Lobatae)

Tree to 30 m, 1 m dbh. Bark greenish grey, smooth and wrinkly when young, becoming scaly and fissured later. Branchlets dark reddish brown to grey and grooved, glabrous or with persistent, short stellate tomentum in the grooves. Leaves deciduous or sub-evergreen, 9–15(–26) × 4–8(–14) cm, obovate to elliptic, thin but rather hard, immature growth covered in yellow tomentum; in mature leaves, the upper surface shiny and glabrous or with some hairs along the midrib, lower surface with persistent buff tomentum and matted stellate hairs, but midrib and principal veins glabrous, 8–10(–14) secondary veins on each side of the midrib, margins minutely revolute, entire and undulate to coarsely dentate with 25 sharp bristles on each side of the midrib, apex acuminate or rarely rounded; petiole 1.5–4(–6) cm long, glabrous or tomentose. Infructescence 1.5–2 cm long with one to three cupules. Cupule hemispheric, 1.6–2 × 1–1.2 cm; scales ovate to lanceolate, closely appressed. Acorn ovoid, with about one-third of its length enclosed in the cupule, 1.5–1.8 cm long, stylopodium absent or very small. Flowering May, fruiting November (Mexico). Muller 1942, Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution GUATEMALA; MEXICO: Chihuahua, Chiapas, Distrito Federal, Durango, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, Sinaloa, Veracruz. Habitat Hill slopes, humid valleys and plains between 1200 and 2700 m asl. Common in cloud forest with Pinus and Abies. USDA Hardiness Zone (8–)9. Conservation status Least Concern. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002; NT698, NT713.

The big leaves of Quercus candicans, with their hairy white undersides, and curious pachydermatous bark, make this one of the most attractive of Mexican oaks. Fortunately, it also seems to be amenable to cultivation, enabling Michael Heathcoat Amory to record that it is ‘fast growing in Devon and seems hardy … no frost damage for five years’ (Chevithorne Barton Oak Collection notes). His largest specimen (from CDR 1109) has achieved 11 m in 15 years and is probably the UK champion. In all specimens seen in research for the present work the trunk has been straight and erect, and when young has wonderful greenish grey, hide-like bark. There is a particularly beautiful specimen in the San Francisco Botanical Garden, c.10 m tall in 2004. It is not clear when this species was first introduced to cultivation, but it has evidently been collected on several occasions.

Plate 465. Quercus candicans produces big, leathery leaves that are densely white-hairy beneath. There seems to be some variation in hardiness, perhaps related to provenance. Image P. de Spoelberch.

714

Quercus

New Trees

Quercus castanea Née

(Subgen. Quercus, Sect. Lobatae)

Tree to 20 m, 0.8 m dbh. Bark smooth above, cracking into thick plates at the base (not recorded from mature trees). Branchlets chestnut-colour and quickly glabrous, lenticels prominent. Leaves deciduous (semi-evergreen in cultivation), 2.5–15 × 1.3–5 cm, oblong, lanceolate or obovate, leathery and rigid, immature leaves with abundant yellow tomentum, short stellate pubescence and red glandular hairs; mature leaves largely glabrous above with a dense white stellate tomentum below, 7–12 secondary veins on each side of the midrib, margins flat or revolute, regularly dentate with five to nine sharp bristles on each side of the midrib or entire, the teeth being larger and more regularly spaced in late summer shoots, apex acute to rounded; petiole 0.3–1 cm long, yellow or brown, tomentose though quickly glabrous. Infructescence to 0.5 cm long with one to two (occasionally three) cupules. Cupule hemispheric, 1–1.4 × 0.5–1 cm; scales thin and grey. Acorn round to ovoid, with about half of its length enclosed in the cupule, 1.8–2.5 cm long, stylopodium small, sunken. Flowering June to July, fruiting August to December of the same year (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution EL SALVADOR; GUATEMALA; MEXICO: Chiapas, Colima, Distrito Federal, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, Sinaloa, San Luis Potosí, Sonora, Veracruz. Habitat Usually pine-oak forest on hill slopes, plateaus and valleys between 1450 and 3500 m asl. USDA Hardiness Zone (8–)9. Conservation status Least Concern. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002; NT698.

Represented in most oak collections, Quercus castanea has been gathered regularly. The tree at Kew is the finest seen for the present work; accessioned in 1982, it was c. 8 m tall in 2006, with a somewhat open top. This originated as a collection in the Sierra de Tecuan, Jalisco, made by a team from the George Landis Arboretum, Esperance, New York. Specimens elsewhere also suggest that Q. castanea is a comparatively slow-growing tree; at the Hillier Gardens a collection from Michoacán was less than 1 m in height after eight years. The foliage is attractive, being somewhat rugose or almost bullate and slightly reminiscent of Q. rysophylla, although the dense pale tomentum below prevents confusion with that species. Q. castaneifolia C.A. Mey. B465, S407, K84 Q. cerris L. B467, S407, K84 Q. cerris var. austriaca (NOW Q. cerris L.) K84 Q. cerris var. haliphloeos (NOW Q. cerris L.) K84

Quercus coccifera L.

Q. cerris var. pseudocerris (NOW Q. cerris L.) K85 Q. cerris subsp. tournefortii (NOW Q. cerris L.) K85 Q. chapmanii Sarg. K85 Q. chrysolepis Liebm. B468, K85

(Subgen. Quercus, Sect. Cerris)

Kermes Oak

This species was described by Bean (B469) and Krüssmann (K85).

Quercus coccifera subsp. rivas-martinezii J.H. Capelo & J.C. Costa Subsp. rivas-martinezii grows to 15 m, 0.6–0.7 m dbh. The distinguishing characters described by the original authors (Capelo & Costa 2001) appear to fall into the range exhibited by typical Q. coccifera (Christensen 1997). In subsp. rivas-martinezii the leaves are sub-entire or spinose-dentate, 1.9–3.4 × 0.9–1.25 cm, with 7–9(–11) pairs of secondary veins, while in typical Q. coccifera they are sub-entire or spinose-serrate, 1.1–5.2 × 0.7–2.9 cm, with 4–8 pairs of secondary veins. Christensen 1997, Capelo & Costa 2001. Distribution PORTUGAL: Serra da Arrábida, Serra de Grândola, Odemira. Quercus coccifera occurs around the Mediterranean basin, and subsp. rivas-martinezii is isolated on the Atlantic coast. This appears to be the only difference of note. Habitat Isolated limestone outcrops running parallel to the Atlantic coast. The vegetation is evergreen scrub dominated by oak and Viburnum tinus L. USDA Hardiness Zone 8. Conservation status Not evaluated.

At present this distinct Portuguese endemic is represented in collections only by young specimens that resemble the shrubby form typical of the Kermes Oak; it may

Section II. Species Accounts

Quercus

be some years before these attain tree-stature. New shoots in late summer are an attractive coppery red. It should be noted that Quercus coccifera can also attain treestature in other parts of its range.

Quercus cocciferoides Hand.-Mazz.

(Subgen. Quercus, Sect. Cerris)

Syn. Q. taliensis A. Camus Tree to 15 m, branching from the base. Branchlets tomentose. Leaves semi-evergreen, 3–8 × 1.5–3 cm, narrowly elliptic, ovate or somewhat lanceolate, papery, immature leaves pubescent, but mature leaves almost glabrous, six to eight secondary veins on each side of the midrib, margins serrate from middle to apex, apex acuminate; petiole 0.5–0.8 cm long, tomentose. Infructescence ~2.5 cm long with four to five cupules. Cupule cup- or kettle-shaped, 1–1.2 × 1–1.5 cm, with appressed hairs; scales triangular, not firmly attached to cupule wall. Acorn subglobose, with about three-quarters of its length enclosed in the cupule, 1–1.2 cm long, stylopodium persistent. Flowering April to June, fruiting September to November of the following year (China). Huang et al. 1999, Menitsky 2005. Distribution CHINA: Shaanxi, Sichuan, Yunnan. Habitat Mountain slopes and river valleys between 1000 and 2600 m asl. USDA Hardiness Zone (8–)9. Conservation status Not evaluated. Illustration Huang et al. 1999, Menitsky 2005.

The only specimens of Quercus cocciferoides known to be in cultivation are young plants at Wakehurst Place and the Hillier Gardens. Both of these were raised from Cao Ming 334, collected near Wuding, Yunnan in 1998. The Hillier plant was killed to the ground during the winter of 2005–2006, but resprouted in 2006.

Q. coccinea Münchh. B470, S408, K85 Q. congesta C. Presl B506, K85

Quercus conspersa Benth.

(Subgen. Quercus, Sect. Lobatae)

Syn. Q. candolleana Trel., Q. vexans Trel. Tree to 15 m, 0.5 m dbh. Branchlets reddish brown and glabrous, with numerous white lenticels. Leaves deciduous, (8–)11–17(–22) × (2–)3–6.5 cm, elliptic-ovate to lanceolate or oblanceolate, leathery, immature leaves reddish with simple and stellate tomentum, mature leaves glabrous, but with some glandular or stellate tomentum along the midrib at the base of the leaf, 7–10 conspicuous secondary veins on each side of the midrib, margins revolute and entire or with one to five teeth near the apex, apex acuminate or acute; petiole 0.8–1.5 cm long, reddish and pubescent. Infructescence 1.5–2 cm long with one cupule. Cupule hemispheric, 1.5–2.2 × 0.6–0.8 cm, margin curved inwards; scales obtuse, covered in white pubescence. Acorn ovoid, with about one-third of its length enclosed in the cupule, 1.2–2 cm long, stylopodium persistent. Fruiting December to February of the following year (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution MEXICO: Chiapas, Guerrero, Jalisco, México, Michoacán, Nuevo León, Oaxaca, Veracruz. Habitat Oak and pine forests between 400 and 2200 m asl. USDA Hardiness Zone 7–8. Conservation status Least Concern. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002; NT698.

The only specimens of Quercus conspersa observed for the present work are two trees of 6 and 7 m (2008) at Chevithorne Barton, which are growing well although with a rather sparse appearance. The leaves are dark green, and are noticeably more toothed in the upper part of the tree. The species is also cultivated by enthusiasts in France.

Q. crassifolia Bonpl. B471, S408, K85 Q. crassipes Bonpl. B471

Q. dalechampii Ten. B501, K85 Q. ×deamii Trel. K86

715

716

Quercus

New Trees

Quercus dentata Thunb.

(Subgen. Quercus, Sect. Quercus)

Daimio Oak

This species was described by Bean (B472, S408) and Krüssmann (K86).

Quercus dentata subsp. yunnanensis (Franch.) Menitsky Syn. Q. malacotricha A. Camus Subsp. yunnanensis was treated as a separate species (Q. yunnanensis Franch.) in Flora of China, though the authors admit that it only differs from typical Q. dentata in that its cupule scales are shorter (0.5–0.8 cm vs. 1 cm). Huang et al. 1999. Distribution CHINA: Guangdong, Guangxi, Guizhou, western Hubei, Sichuan, Yunnan. Habitat Broadleaved or mixed forest between 1000 and 2800 m asl. USDA Hardiness Zone 7–8. Conservation status Least Concern. Illustration Huang et al. 1999, Menitsky 2005; NT716. Taxonomic note Menitsky (2005) distinguishes subsp. yunnanensis on the basis that the leaves are smaller (10–18 cm long vs. up to 30 cm long in typical Q. dentata), with acute teeth (vs. rounded teeth) and 12–16 pairs of lateral veins (vs. 8–12 pairs). The cupule scales are said to be erect rather than recurved. Zhou Zhekun maintains Q. malacotricha as a distinct species (A. Coombes, pers. comm. 2006).

Young trees of Quercus dentata subsp. yunnanensis at the Hillier Gardens, grown as Q. malacotricha from collections made in Yunnan by John Rippin (nos. 169, 170), have large leaves with soft pubescence, rather unlike the coarser hairs of typical Q. dentata, although in other respects the two subspecies are similar. The tallest of the Hillier trees was about 1.8 m in 2005 and 3.1 m in 2008 – respectable growth from a 1999 collection planted in very acid ground in the Brentry area of the arboretum. This specimen had numerous marble galls in October 2005. Other trees are growing well throughout Germany from a Jablonski collection in Yunnan in 1999, although some died back in their second winter. They are not affected by chlorosis at pH 7 (E. Jablonski, pers. comm. 2007).

Plate 466. Quercus dentata subsp. yunnanensis (also in cultivation under the synonym Q. malacotricha) is likely to flourish best in areas with hot summers. Image E. Jablonski.

Q. dentata var. oxyloba (NOW Q. dentata subsp. yunnanensis (Franch.) Menitsky) K86

Quercus deserticola Trel.

(Subgen. Quercus, Sect. Quercus)

Shrub or small multistemmed tree, 2–8 m. Bark ridged. Branchlets yellowish green and densely tomentose; the tomentum stellate, turning black with time. Leaves deciduous or semi-evergreen, (2.5–)4–7.5(–8.5) × (1.3–) 2–3.5(–4.5) cm, oblong to elliptic or obovate, immature leaves reddish with short stellate tomentum; in mature leaves, upper surface with short stellate tomentum along the midrib and lateral veins, lower surface with dense stellate tomentum, six to nine secondary veins on each side of the midrib, margins revolute with two to five mucronate lobes or teeth on each side of the midrib, apex acute or obtuse, mucronate; petiole 0.2–0.6 cm long and pubescent. Infructescence 3 cm long with one to three cupules. Cupule hemispheric, 1.4–2 × 0.6–1 cm; scales obtuse and covered in white pubescence. Acorn ovoid, with about one-third of its length enclosed in the cupule, 1.1–1.9 cm long, stylopodium persistent. Flowering April, fruiting July to December (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution MEXICO: Distrito Federal, Guanajuato, Hidalgo, Jalisco, México, Michoacán, Oaxaca, Puebla, Querétaro, Sinaloa. Habitat Oak forests and dry woody scrub between 1600 and 2800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002.

The rather small, grey leaves of Quercus deserticola immediately suggest that this is a xerophytic plant from dry habitats, just as its name implies. The only one seen in cultivation in the research for New Trees is at Chevithorne Barton, now about 7 m

Section II. Species Accounts

Quercus

tall (2008), grown from a collection made by Allen Coombes at 2010 m in Hidalgo in 1995. It could be said to be struggling, but when seen in 2005 it had produced 80 cm of new growth that year; so perhaps it takes time to get going. The foliage is especially attractive when young, the dense tomentum overlying the bronze flush of the new leaves to give a very curious colour effect.

Quercus dolicholepis A. Camus

(Subgen. Quercus, Sect. Cerris)

Shrub or tree to 16 m, 0.6 m dbh. Crown compact, ovate in outline. Branchlets with yellowish grey stellate tomentum. Leaves evergreen, dark green, 2–8 × 1.5–4 cm, obovate to spathulate or elliptic, leathery, immature leaves pale green and covered in white hairs; in mature leaves, upper surface smooth, glossy and glabrous, lower surface pubescent or almost glabrous, seven to eight secondary veins on each side of the midrib, margins entire or apically serrate, apex obtuse to mucronate; petiole 0.4–0.5 cm long, yellowish brown-tomentose. Infructescence tomentose, ~1 cm long with one (to two) cupules. Cupule cup-shaped, ~1 × 2 cm, outside reddish brown; scales linear to lanceolate with a reflexed apex. Acorn ovoid to subglobose, with two-thirds to three-quarters of its length enclosed in the cupule, 1.2–1.7 cm long, stylopodium easily broken. Flowering March to May, fruiting October of the following year (China). Huang et al. 1999, Menitsky 2005. Distribution CHINA: Gansu, Guizhou, Henan, Hubei, Hunan, Shaanxi, Shanxi, Sichuan, Yunnan. Habitat Montane forest between 500 and 2800 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Huang et al. 1999, Menitsky 2005.

Quercus dolicholepis was apparently first introduced by the Fliegner, Howick, McNamara and Staniforth expedition to Sichuan in 1992, under the number SICH 982. The parent was noted to be 5 m in height, growing on a steep mountainside at c. 2510 m, with rhododendrons, pines and other shrubs. In cultivation it seems as if this height may be exceeded, as the specimen at Kew is now c. 4.5 m tall, forming a small, bushy tree. The stem forked close to the ground and the tree is built around multiple vertical stems in its centre, forming a dense and rather dull dark green mass. At the Hillier Gardens a young plant from Cao Ming 316, collected as Q. spinosa in Yunnan and distributed by the Kunming Botanical Garden, is now considered to be Q. dolicholepis. This too is growing well; although it lost its top in the 2005– 2006 winter, it was still 4 m tall in 2008. Another plant from the same collection is thriving at Chevithorne Barton, achieving the same height (A. Coombes, pers. comm. 2008). This is an attractive species, with conspicuous white hairs on the stems, and sparse creamish pubescence on the underside of the glossy leaves. Q. douglasii Hook. & Arn. B472, K86 Q. dumosa Nutt. S408 Q. durata Jeps. S408

Quercus durifolia Seemen ex Loes.

(Subgen. Quercus, Sect. Lobatae)

Tree to 9 m (or more), 0.6 m dbh. Bark dark grey, smooth when young, cracking up at base with age (not recorded from mature trees). Branchlets slender, ranging from grey-tomentose to glossy red and glabrous; grey-brown with white lenticels at maturity. Leaves deciduous (or semi-evergreen), 2.5–6.5 × 0.6–2.2 cm, lanceolate, immature leaves glossy green with stellate indumentum above, pale green with interlocking stellate indumentum below, mature leaves very glossy and almost glabrous above, but for short hairs on the midrib, lower surface grey to glaucous with short hairs, ~10 secondary veins on each side of the midrib, margins entire, undulate or with several small teeth, apex acute; petiole 0.5 cm long, pubescent. Infructescence with one to two cupules. Cupule hemispheric, 0.6–1 × 0.4 cm; scales blunt and appressed. Acorn ovoid, somewhat silky, with half of its length enclosed in the cupule, 1–1.2 cm long, stylopodium prominent. Fruiting September (Mexico). Trelease 1924. Distribution MEXICO: Chihuahua, Durango, Sinaloa, Sonora. Habitat Oak and pine-oak forest between 1700 and 2300 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated.

717

718

Quercus

New Trees

This is another oak that seems likely to reach greater heights in cultivation than it usually achieves in the wild. Two specimens seen in the United Kingdom, at the Hillier Gardens and Chevithorne Barton, are at about 8 m, after 24 and 14 years respectively, Curiously, both are leaning, and neither looks particularly attractive, with heavy masses of very dark foliage, although both are growing well. The Hampshire tree was grown from Sir Harold Hillier’s collection (no. 586) made in 1979, which was probably the first introduction of the species.

Quercus eduardii Trel.

(Subgen. Quercus, Sect. Lobatae)

Shrub or tree, 5–8 m. Bark black, rough, with square plates. Branchlets reddish brown with white or yellow stellate tomentum; later greyish brown with white lenticels. Leaves deciduous, 1.5–5.2 × 3–6 cm, oblong to elliptic, leathery and stiff, immature leaves dark glossy green above with minute stellate indumentum, pale green with dense stellate indumentum below, mature leaves glossy and almost glabrous above, lower surface with tufts of tomentum in the vein axils and sparse stellate tomentum, five to eight secondary veins on each side of the midrib, margins entire or with short teeth, bristles present on most leaves, apex acute; petiole 0.2–0.4 cm long, reddish and finely tomentose. Infructescence 0.2–0.8 cm long with two to three cupules. Cupule turbinate, 0.7–1 × 0.5 cm; scales rounded, pale brown and somewhat tomentose. Acorn ovoid, with half of its length enclosed in the cupule, 0.6–1.2 cm long, stylopodium prominent. Fruiting September (Mexico). Trelease 1924, Bacon & Spellenberg 1996. Distribution MEXICO: Aguascalientes, Chihuahua, Durango, Guanajuato, Hidalgo, Jalisco, Michoacán, Nayarit, Querétaro, San Luis Potosí, Tamaulipas, Veracruz, Zacatecas. Habitat Pine-oak forest between 1500 and 2650 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated.

Quercus eduardii is as yet represented in collections only by very young plants. At the Hillier Gardens there are two saplings from a 2001 gathering in Aguascalientes, Mexico which are surviving and growing surprisingly well, the larger 1.4 m tall in 2006, and 2.9 m in 2008 (A. Coombes, pers. comms. 2006, 2008). Q. ehrenbergii (NOW Q. ithaburensis subsp. macrolepis (Kotschy) Hedge & Yalt.) K86

Quercus ellipsoidalis E.J. Hill (Subgen. Quercus, Sect. Lobatae)

Northern Pin Oak, Jack Oak

Tree to 20 m, 1.5 m dbh. Bark thin, greyish brown, divided into thin plates by shallow fissures. Crown narrow, oblong, with many forked branches; stumps of dead branches often prominent at the base of the trunk. Branchlets dark reddish brown and glabrous. Leaves deciduous, 7–13 × 5–10 cm, elliptic to obovate, glabrous, though lower surface often has tufts of hair in the vein axils, three to four secondary veins on each side of the midrib, margins with five to seven deep lobes, lobes largely oblong, expanding distally and terminating in spiny bristles (15–55 in total), median lobes longer than other lobes, lobe sinuses over half the distance to the midrib, apex acute; petiole 2–5 cm long, glabrous. Cupule turbinate or deeply cup-shaped, 1–1.9 × 0.6–1.1 cm, outer surface reddish brown and slightly pubescent, inner surface light brown and glabrous; scales obtuse or acute, apices tightly appressed. Acorn broadly ovoid to ellipsoid, with one-third to half of its length enclosed in the cupule, 1–2 cm long, stylopodium may be surrounded by several faint rings. Flowering May, fruiting August of the following year (USA). Nixon 1997. Distribution CANADA: Ontario; USA: Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, Wisconsin. Habitat Limestone ridges and slopes, dry sandy sites and along small streams between 150 and 500 m asl. USDA Hardiness Zone 4. Conservation status Least Concern. Illustration Nixon 1997; NT9, NT719. Cross-references B499, S414, K86. Taxonomic note This species may be of hybrid origin (Jensen et al. 1984).

Briefly described by Bean (1976b), who mentions a moderately sized tree at the Royal Botanic Garden Edinburgh, Quercus ellipsoidalis is a species that has since become only slightly better known in Europe. It is apparently not greatly valued in North

Section II. Species Accounts

Quercus

America either (Sternberg 2004), although one tree collected by C.S. Sargent is still growing at the Arnold Arboretum and it is in most collections, including good specimens at the Morton Arboretum. The old Edinburgh tree still survives, and has been joined by two more recent plantings. One of these, accessioned in 1985 and now 8 m in height, has been badly damaged by Grey Squirrels and its trunk is covered in scars from their depredations. Specimens in southern England seem to have avoided this fate, and the largest ones observed for the present work, at the Hillier Gardens, are fine upright trees. One of these, sited near Brentry House, is apparently an unrecognised champion, measured in 2001 at 18.4 m (Sir Harold Hillier Gardens database) – the official champion being a tree at Borde Hill planted in 1935, 17 m in 1995 (Johnson 2003). When these trees are given plenty of space they have a tendency to develop wide-spreading branches to form a rounded crown. An individual at Kew, donated in 1974 by J.R.P. van Hoey Smith, is currently c.10 m tall and as much wide, with a dbh of 32 cm. This and another specimen at Kew coloured to a rich tan-brown in 2005 (a poor year for autumn colour in England), with the leaves hanging dry on the tree to great effect, but a brighter red can usually be expected; Sternberg (2004) notes the exceptional red autumnal colouring of this species, while Hillier & Coombes (2002) regard it as equal to the best forms of Q. coccinea. The cultivar ‘Hemelrijk’ has been propagated from a tree at the de Belder property noted for its reliable brilliant red colours in autumn, and the habit of retaining its tan leaves all winter. In spring the young leaves emerge pink, and then become an attractive deep green. ‘Hemelrijk’ was selected by Robert and Jelena de Belder in about 1980, and introduced to the nursery trade by M.M. Bömer, Zundert, the Netherlands (J. Bömer, pers. comm. 2006). Quercus ellipsoidalis is regarded as a calcifuge (Hillier & Coombes 2002), and at Kruchten succumbs to chlorosis at pH 6.8.

Quercus emoryi Torr.

(Subgen. Quercus, Sect. Lobatae)

Emory Oak

Tree, sometimes a shrub, to 15–20 m, occasionally to 30 m and 2 m dbh. Bark black or dark brown, smooth but warted when young, becoming broken into thick plates separated by deep fissures. Branches spreading, sometimes towards the ground, and forming a tall, domed crown. Branchlets pale reddish brown and pubescent. Leaves evergreen or sub-evergreen, 2.8–9.5 × 1.5–4.5 cm, ovate to oblong or obovate, hard and leathery, upper surface glabrous and glossy, lower surface covered in stellate tomentum, but this is easily rubbed off except for the tufts of tomentum on each side of the midrib at the base of the lamina, reticulate tertiary veins prominent, six to eight secondary veins on each side of the midrib, margins entire and cartilaginous or spinose with up to 13 bristles, apex acute to truncate; petiole 0.3–1 cm long, pubescent. Infructescence 0.6 cm long with one to two cupules. Cupule cup-shaped, 0.7–1.2 × 0.5–7.5 cm, both surfaces somewhat pubescent; scales blunt and appressed. Acorn ellipsoid to oblong, with one-quarter to half of its length enclosed in the cupule, 1–1.8 cm long, stylopodium prominent; ripening in the first year. Flowering April to May, fruiting July to September (USA). Standley 1922, Nixon 1997, Melendrez 2000. Distribution MEXICO: Chihuahua, Coahuila, Durango, Nuevo León, Sonora, Tamaulipas; USA: Arizona, New Mexico, Texas. Habitat Limestone ridges and slopes and along small streams between 150 and 2200 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997.

Quercus emoryi is slow-growing in the wild, where it often occurs on rocky ground with little or no topsoil, and is clearly tolerant of hot, dry conditions, as its grey, hollylike leaves suggest. In North America it has proved to be extremely hardy, remaining

719

Plate 467. The relative scarcity of Quercus ellipsoidalis in arboreta is surprising, as its autumn colour is brilliant – equal to that of most other red oaks. Image K. Camelbeke.

720

Quercus

New Trees

evergreen in Zone 6–7 conditions (Melendrez 2000). Although Melendrez suggests that it remains slow-growing in cultivation this is somewhat contradicted by young trees at the Hillier Gardens, collected as acorns in New Mexico in 1997 and now up to 3.5 m in height; also by specimens collected there by E. Jablonski in 2000, whose progeny are now 2.0 m at Ettelbruck and show no sign of winter damage (E. Jablonski, pers. comm. 2006). An older tree at the Hillier Gardens, grown in shade, has reached 7 m, but its planting date is not known. The acorns are sweet and are a valued food source for Native Americans, as well as being important to wildlife (Melendrez 2000).

Quercus engelmannii Greene

Engelmann Oak

(Subgen. Quercus, Sect. Quercus) Tree to 10 m. Bark thick and light grey-brown with broad ridges separated by narrow fissures. Branches thick, set at right angles to the trunk, forming a broad, irregular crown. Branchlets pale brown with sparse or dense stellate tomentum. Leaves sub-evergreen, (2–)3–6(–8) × (0.5–)1–2(–2.5) cm, oblong to elliptic, rarely lanceolate or ovate, grey or blue-green to glaucous, upper surface glabrous, lower surface with dense glandular tomentum that easily rubs off, though persistent at the base of the midrib, 7–8(–10) secondary veins on each side of the midrib, margins usually entire or with irregular teeth towards the apex, apex acute to rounded; petiole 0.2–0.6 cm long. Infructescence ~0.6 cm long with one to two cupules. Cupule cup-shaped, 1–1.5 × 0.8–1 cm; scales swollen and tuberculate near the base, grey and pubescent. Acorn ovoid to oblong, with one-third of its length enclosed in the cupule, 1.5–2.5 cm long, stylopodium short. Flowering April to May, fruiting September to November (USA). Nixon 1997. Distribution MEXICO: Baja California; USA: southern California (incl. Santa Catalina Is.). Habitat Oak woodland and the margins of chaparral between 50 and 1200 m asl. USDA Hardiness Zone (8–)9. Conservation status Vulnerable, due to habitat degradation and loss. Illustration Nixon 1997; NT698. Taxonomic note This species is closely related to Q. oblongifolia.

This characteristic oak of southern California is rare in cultivation. Young plants are struggling at both Arboretum de la Bergerette and Ettelbruck, losing their leaves and suffering some dieback each year (E. Jablonski, S. Haddock, pers. comms. 2006). The best specimen observed for the current work is one of some 4 m at Chevithorne Barton, apparently thriving. This is strange, considering its native habitat of the hot, dry hillsides south of Los Angeles, and its genealogy as a white oak. However, Nixon (2002) points out that Quercus engelmannii is a member of the subsection Glaucoideae, whose species are principally found in areas with summer rainfall. The main flush produces leaves that are typically rather rounded, without teeth, but in secondary flushes they are neatly toothed. Q. engleriana Seemen B473, S409, K86

Quercus sp. nov. aff. eugeniifolia

(Subgen. Quercus, Sect. Lobatae)

An evergreen oak with narrow leaves has been collected on several occasions from southern Mexico, and has been identified and distributed as Quercus eugeniifolia Liebm. This is a principally Central American species, recorded from Costa Rica, El Salvador, Guatemala and Panama, but was not listed in the preliminary checklist of oaks of Mexico (Valencia-A. 2004) and may not occur there. This placed in doubt the identity of young trees thus labelled in several collections, and for some time they have been suspected of representing a new species (A. Coombes, pers. comm. 2005). During October 2008 the indefatigable Allen Coombes collected this taxon in cloud forest in the mountains of Hidalgo, Mexico, and agrees with the view that it is indeed

Section II. Species Accounts

a new species – a description of which, by Susana Valencia-Avalos and Kevin Nixon, will appear in due course (A. Coombes, pers. comm. 2008). Specimens in European gardens and arboreta have originated from the Mexican mountains, where collectors have recorded the species at moderate altitude in cloud forest, supporting a garden of epiphytes (Sparrow & Brewster Expedition to Veracruz in 1993, VERA 34, field notes). Improbably, given their origins, the few young plants seen in the research for New Trees are thriving and indeed growing vigorously in several English gardens (see Plate 468). At both the Hillier Gardens and Arboretum de la Bergerette, trees grown from Coombes 219, collected in Veracruz in 1995, were 7.8 m tall by October 2008. At Chevithorne Barton, Michael Heathcoat Amory notes, this taxon grows vigorously; though his records give it as only ‘fairly hardy’, his specimen showed no damage after the winter of 2005–2006. Plants have not been affected by either frost or intense drought at La Bergerette, indicating considerable potential as a hardy tree (S. Haddock, pers. comm. 2006). It has reached 8 m there (2008), but in the drier climate has much smaller leaves than specimens growing in England (A. Coombes, pers. comm. 2008). The entire, dark green, leathery leaves of this new oak are a hint to its southern origins, resembling as they do the leaves of so many tropical trees. The new growth in late summer is a beautiful bright red, making this a very desirable species indeed. Careful siting is important, however, as the new growth may still be soft as winter sets in.

Q. ×exacta Trel. K87

Quercus fabri Hance

(Subgen. Quercus, Sect. Quercus)

Large shrub or tree to 20 m, 1 m dbh. Crown broad and spherical. Bark greyish or reddish brown. Branchlets with grey or greyish brown tomentum. Leaves deciduous, 7–15 × 3–8 cm, obovate to elliptic, both surfaces covered with yellowish grey stellate hairs, 8–12 secondary veins on each side of the midrib, margins undulate to serrate, apex obtuse to acuminate; petiole 0.3–0.5 cm and yellowish brown-pubescent. Infructescence 1–4 cm long with two to four cupules. Cupule cup-shaped, 0.4–0.8 × 0.8–1.1 cm; scales ovate to lanceolate, crowded. Acorn ovoid to ellipsoid, with one-third of its length enclosed in the cupule, 1.7–2.5 cm long, stylopodium persistent. Flowering April, fruiting October (China). Huang et al. 1999, Menitsky 2005. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, southern Shaanxi, Sichuan, Yunnan, Zhejiang. Habitat Mixed forest between 20 and 2000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Huang et al. 1999, Menitsky 2005; NT722. Cross-reference K87.

Although a native of mixed forest through much of southern China, Quercus fabri is scarce in cultivation in Europe, only a few young plants being found in the important oak collections. With its large leaves, the overall appearance of the species is similar to that of Q. mongolica subsp. crispula or Q. dentata. At present it is too early

Quercus

721

Plate 468. The oak formerly known as Quercus eugeniifolia, but now recognised as a new species. It comes from mist forest in southern Mexico but is surprisingly successful in Europe, as here at the Hillier Gardens. Image P. de Spoelberch.

722

Quercus

New Trees

to assess its potential in cultivation. In October 2005 a specimen at the Hillier Gardens (from Rippin 167, collected in Yunnan in 1999) had been badly insect-damaged and seemed to be struggling, though by 2008 it had reached 3.5 m. The species apparently fares better in continental Europe, young trees from Eike Jablonski’s 1999 collection from Yunnan thriving throughout Germany and up to 1.5 m tall in 2006 (E. Jablonski, pers. comm. 2006). There are larger specimens in the United States, one observed at Starhill Forest Arboretum being 7–8 m tall in 2006. The tree has nice glossy leaves that are paler below. Guy Sternberg (pers. comm. 2006) says that it has never shown signs of winter damage. Plate 469. Like many white oaks, Quercus fabri prefers a climate with reliably hot summers, but this specimen is growing well in Belgium. Image P. de Spoelberch.

Q. faginea Lam. B473, S409, K87 Q. falcata Michx. B474, S409, K87 Q. ×fernaldii Trel. K87

Quercus floribunda Lindl. ex A. Camus (Subgen. Quercus, Sect. Cerris)

Moru Oak

Syn. Q. dilatata Royle Tree to 30 m, 3 m dbh. Bark dark reddish brown or almost black, fissured into oblong scales. Branchlets dark brown or black with dense grey silky tomentum. Leaves sub-evergreen, 3–12 × 1.5–5.5 cm, ovate to elliptic or lanceolate, grey-green or glaucous, leathery and glabrous, 8–12 secondary veins on each side of the midrib, margins entire or with four to nine teeth, apex acute to obtuse; petiole 0.3–1 cm long and glabrous. Infructescence 1.5–3 cm long with two to three cupules. Cupule cup-shaped, 2–2.4 × 0.5–0.8 cm; scales appressed and pubescent. Acorn ovoid, with one-third to half of its length enclosed in the cupule, 2–2.5 cm long, stylopodium persistent. Flowering April to May, fruiting August to October of the following year (Pakistan). Nasir 1976, Menitsky 2005. Distribution AFGHANISTAN; INDIA; NEPAL; PAKISTAN. Habitat Himalayan oak forest between 1600 and 2900 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Menitsky 2005.

With the exception of one old tree at High Beeches, Sussex that may be of this species, Quercus floribunda is represented in the United Kingdom by young specimens, all grown from EPAK 172, collected in Pakistan in 1995 and quite widely distributed to British gardens from Kew (as Q. glauca): there are plants at the Hillier Gardens (4 m in August 2006, 5.3 m in October 2008) and at Wakehurst Place. At Shaun Haddock’s Arboretum de la Bergerette, where the hot summers and fertile soil result in generally ‘staggering growth’, Q. floribunda (from S. Haddock’s own collection) reached 4 m in nine years (Lamant 2004), and is now over 5 m tall (S. Haddock, pers. comm. 2006). Haddock’s collection was made in 1995 from Kalam in the Swat Valley, Northwest Frontier Province, Pakistan, at around 2100 m, where winter snows are deep; he also made subsequent gatherings at about 2200 m at Murree, northeast of Islamabad. In France at least, Q. floribunda seems to be a ‘good doer’ and drought-resistant (S. Haddock, pers. comm. 2006).

Section II. Species Accounts

Quercus

Q. frainetto Ten. B475, S409, K87

Quercus franchetii Skan

(Subgen. Quercus, Sect. Cerris)

Tree to 15 m. Bark dark grey. Branchlets densely covered with yellowish grey hairs. Leaves evergreen, 5–12 × 2.5–6 cm, obovate to elliptic, thin and leathery, immature leaves covered in yellowish grey glandular hairs; in mature leaves, upper surface glabrous while lower surface retains the hairs, 8–12 secondary veins on each side of the midrib, margins with gland-tipped serrations on the upper half, apex acuminate to obtuse; petiole 1–2 cm long and densely tomentose. Infructescence 1–2 cm long with five to six cupules. Cupule cup-shaped or discoid, 0.7–1.2 × 1–1.4 cm, outside grey-tomentose; scales triangular to tuberculate. Acorn subglobose, with half of its length enclosed in the cupule, 1.1–1.3 cm long, stylopodium persistent, to 0.3 cm long. Flowering February to March, fruiting September (China). Huang et al. 1999, Menitsky 2005. Distribution CHINA: Sichuan, Yunnan; THAILAND; VIETNAM. Habitat Mixed forest between 800 and 2600 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Huang et al. 1999, Menitsky 2005; NT697.

Quercus franchetii seems to be rare in cultivation, the largest seen for the present work being a specimen at Tregrehan. Grown from a young plant bought in 1990 from Susan Cooper, who received acorns from Kunming Botanical Garden, this is forming a nice, upright tree of about 6 m at present – rather unlike the somewhat shrubby specimens seen in the wild (T. Hudson, pers. comm. 2006). At Shaun Haddock’s Arboretum de la Bergerette it has achieved 6 m (2008) since being sown in 1998, from a collection made near Kunming by Zhou Zhekun, distributed through the International Oak Society seed exchange. The tree at La Bergerette is forming a spreading canopy, growing in a comparatively moist site (S. Haddock, pers. comm. 2006). A recently planted specimen at Starhill Forest Arboretum had densely pubescent new growth when seen in 2006, this new growth being a beautiful pink colour. The mature leaves retain long white hairs on their undersides.

Q. fruticosa (NOW Q. lusitanica Lam.) B475

Quercus fusiformis Small

(Subgen. Quercus, Sect. Quercus)

Texas Live Oak

Tree to 25 m, to 2.4 m dbh; can form shrubby rhizomatous copses by clonal reproduction (Sternberg 2004). In habit, resembles Q. virginiana. Branchlets pale grey with minute tomentum. Leaves sub-evergreen, (1–)3.5– 9(–15) × (1.5–)2–4(–8.5) cm, oblong-elliptic to lanceolate, thin and leathery, upper surface glossy dark green and largely glabrous or with sparse stellate hairs, lower surface white or glaucous with dense minute stellate hairs, 8–10 obscure secondary veins on each side of the midrib, margins flat or revolute, entire or with one to three mucronate teeth on each side, apex obtuse to acute; petiole 0.2–1.2 cm. Infructescence 0.3–3 cm long with one to three cupules. Cupule funnel-shaped or hemispheric, 0.6–1.5 × 0.8–1.5 cm, base constricted; scales basally thickened, acute to attenuate and slightly tomentose. Acorn subfusiform, with one-third of its length enclosed in the cupule, 2–3 cm long, stylopodium persistent. Flowering March to April, fruiting September to October (USA). Nixon 1997, Sternberg 2004. Distribution MEXICO: Coahuila, Nuevo León, Tamaulipas; USA: Oklahoma, Texas. Habitat Oak-juniper woodland, thorn scrub and grasslands between 0 and 1200 m asl. Often on limestone or calcareous soils. USDA Hardiness Zone (5~)6. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT693, NT698. Taxonomic note Quercus fusiformis is closely related to Q. virginiana and intergrades with it in parts of Texas.

Sternberg (2004) writes of this species with some enthusiasm as a potential substitute for Q. virginiana in places that are too cold or too alkaline for that coastal species to survive. At Sternberg’s own Starhill Forest Arboretum in Illinois (Zone 5) Q. fusiformis is proving surprisingly hardy, but is partially deciduous, and specimens are stunted. In Europe it seems to be represented only by young trees in the major collections. One at Thenford House is growing well, although still only 1.2 m tall.

723

724

Quercus

New Trees

Q. gambelii Nutt. B476, K87 Q. gambelii var. gunnisonii (NOW Q. gambelii Nutt.) B476

Quercus garryana Douglas ex Hook.

Oregon White Oak

(Subgen. Quercus, Sect. Quercus)

This species was described by Bean (B476) and Krüssmann (K87). A key to its varieties, modified from that of Nixon (1997), is presented below.

1a. Tree to 15 m, stem usually solitary; buds yellowish or cream, 0.6–1.2 cm long and densely pubescent; branchlets covered in spreading hairs; Canada (British Columbia), USA (California, Oregon, Washington) ........................... var. garryana 1b. Shrub or small tree to 5 m, multistemmed and spreading clonally; buds reddish brown, 0.2–0.5 cm long, sparsely pubescent; branchlets largely glabrous ....................... 2 2a. Leaf underside with sparse or dense stellate hairs with four to six rays; USA (California & Oregon: Siskiyou Mts.) ................................................................. var. fruticosa 2b. Leaf underside with sparse or dense stellate hairs with six to eight rays; USA (California: Sierra Nevada, Tehachapi Mts.; Oregon) ............................................ var. semota

Quercus garryana var. fruticosa (Engelm.) Govaerts Syn. Q. garryana var. breweri (Engelm.) Jepson Both var. fruticosa and var. semota occur at higher altitudes (1250–1900 m asl) than typical var. garryana (0–800 m asl). For this reason they tend to form small, multistemmed trees and shrubs, rather than larger trees. In var. fruticosa the stellate hairs on the leaf underside have four to six rays. Var. fruticosa (commonly known under the name var. breweri ) is endemic to the Siskiyou region on the California–Oregon border. Nixon 1997. Distribution USA: California, Oregon. Habitat Montane conifer forest and chaparral between 1400 and 1900 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997.

Quercus garryana var. semota Jeps. Var. semota occurs along the western slopes of the Sierra Nevada and the north slope of the Tehachapi Mts. The stellate hairs on the leaf underside have six to eight rays. Nixon 1997. Distribution USA: California, Oregon. Habitat Montane conifer forest and chaparral between 1250 and 1800 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997.

Both of these miniatures are in cultivation at the Sir Harold Hillier Gardens and have successfully retained their dwarf habit, var. fruticosa being 1.5 m after at least 30 years, and var. semota a flat-topped bush at 2.1 m after 25 years. They could be commended as small, characterful, gnarled-looking oaks for an ambitious rock garden.

Quercus geminata Small

(Subgen. Quercus, Sect. Quercus)

Sand Live Oak

Tree to 25 m, 1.5 m dbh; can form shrubby rhizomatous copses by clonal reproduction. Bark dark grey, deeply furrowed. Crown widely spreading. Branchlets yellowish to pale grey and quickly glabrous. Leaves sub-evergreen, (1–)3.5–6(–12) × (0.7–)1–3(–4.5) cm, narrowly lanceolate or elliptic, rarely orbicular, thin and leathery, upper surface glossy dark green and largely glabrous or with sparse stellate hairs, lower surface white or glaucous with dense minute fused-stellate hairs and scattered erect spreading hairs, 8–10(–12) deeply impressed secondary veins on each side of the midrib, margins strongly revolute and entire, apex acute (rarely obtuse); petiole 0.3–2 cm. Infructescence 1–10 cm long with one to three cupules. Cupule goblet-shaped or hemispheric, rarely saucer-shaped, 0.5–1.5 × 0.8–1.5 cm, base constricted; scales basally thickened, white or grey with reddish tips, acute to attenuate and slightly tomentose. Acorn ovoid, with one-third to half of its length enclosed in the cupule, 1.5–2 cm long, stylopodium persistent. Flowering

Section II. Species Accounts

Quercus

April to May, fruiting August to October (USA). Nixon 1997, Sternberg 2004. Distribution CUBA (?); USA: Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina. Habitat Open evergreen woodland and scrub on the deep sandy soils of the Coastal Plain between 0 and 200 m asl. USDA Hardiness Zone 7–8. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004. Taxonomic note Quercus geminata is closely related to Q. virginiana, and intergrades with it in North Carolina and in coastal Mississippi. Quercus cubana A. Rich., endemic to western Cuba, is believed to have originated as a hybrid swarm, with Q. geminata and Q. oleoides Schltdl. & Cham. as parents (Nixon 1997).

Its southern distribution and close relationship to Quercus virginiana suggest that Q. geminata is unlikely to perform very well in most of our area. In the wild it is found on sandy soils (Sternberg 2004). In Europe it is very rare. There is a 5.3 m specimen (2008) dating to 1997 at Arboretum de la Bergerette (S. Haddock, pers. comm. 2006), but the only one seen in England, in research for the present work, is a very young plant at Thenford House showing good growth for the season, with the shoot tip bronze. The species was cultivated at Arboretum Ettelbruck for a few years but plants were small, and died in the winter of 2005–2006 (E. Jablonski, pers. comm. 2006).

Quercus georgiana M.A. Curtis

Georgia Oak

(Subgen. Quercus, Sect. Lobatae) Tree to 15 m. Bark grey or pale brown and scaly. Branchlets deep reddish brown and glabrous. Leaves deciduous, glossy green, 4–13 × 2–9 cm, ovate to elliptic or obovate, largely glabrous, but with tufts of tomentum in the vein axils of the lower surface, five to seven secondary veins on each side of the midrib, margins with three to five (to seven) oblong to triangular lobes, terminating in spiny bristles (up to 10 in total), apex acute; petiole 0.6–2 cm long, glabrous or with a few hairs. Cupules one to two, sessile or with a peduncle to 0.5 cm; thin and saucer-shaped, 0.9–1.4 × 0.4–0.6 cm, both surfaces slightly pubescent or glabrous; scales acute and appressed. Acorn globose or ovoid, with one-third of its length enclosed in the cupule, 0.9–1.4 cm long, stylopodium prominent. Fruiting in the second year (USA). Nixon 1997. Distribution USA: Alabama, Georgia, South Carolina. Habitat Granitic outcrops and dry slopes between 50 and 500 m asl. USDA Hardiness Zone 5. Conservation status Endangered. Quercus georgiana has a limited range and is threatened by habitat loss. Illustration Nixon 1997, Sternberg 2004; NT692. Cross-reference K88.

Despite its very restricted natural habitat, Quercus georgiana is considered by Sternberg (2004) to be a useful as well as an attractive tree, with considerable hardiness. In particular he values it for its brilliant red autumn colour. In summer the leaves are a bright glossy green. In the wild it can form either a small single-stemmed tree or a suckering shrub, and both forms grow well in the Starhill Forest Arboretum, originating from different locations in Georgia. Dirr (1998) also recommends it strongly, and considers it suitable for use as a lawn tree. In northern Europe it seems less than totally satisfactory. At Arboretum Trompenburg it eventually made a small, round-topped tree, without a discernible leader, and there is a similar specimen at the Hillier Gardens. The champion tree in the United Kingdom is also at the Hillier Gardens – 11 m tall after about 30 years – but Allen Coombes is dubious as to the true identity of this individual (pers. comm. 2006). The species is intolerant of alkaline soil.

Quercus germana Schltdl. & Cham. (Subgen. Quercus, Sect. Quercus)

Avocado-leaf Oak, Mexican Royal Oak

Syn. Q. galeottii M. Martens & Galeotti Ultimate height and girth unknown. Branchlets pale grey-brown, slender and glabrous. Leaves deciduous, 9–13 × 3–5 cm, oblong to obovate or oblanceolate, largely glabrous and glaucous below, immature leaves bright pinkish purple, six to eight secondary veins on each side of the midrib, margins crenate to sinuate with 6–12 lobes in the upper third of the leaf, apex obtuse; petiole 0.2–0.5 cm long and glabrous. Infructescence 1–1.5 cm long with one cupule. Cupule hemispheric, 1.8–2.5 × 1.2 cm, outside rusty- or grey-tomentose; scales acute,

725

726

Quercus

New Trees

keeled and appressed. Acorn subglobose, rusty-tomentose, with three-quarters of its length enclosed in the cupule, 2 cm long, stylopodium prominent. Standley 1922, Trelease 1924. Distribution MEXICO: Hidalgo, Oaxaca, Puebla, San Luis Potosí, Tamaulipas, Veracruz. Habitat Montane cloud forest between 800 and 1800 m asl. USDA Hardiness Zone 8–9. Conservation status Vulnerable, due to habitat loss. Illustration NT726. Taxonomic note Trelease (1924) recognised specimens in Veracruz as var. lemmonii Trel., having longer petioles (1–2 cm) and ovate leaves of 12 × 6 cm. Valencia-A. (2004) does not recognise this variety.

Plate 470. Quercus germana is a Mexican white oak that needs hot summers to flourish, and can also be damaged by winter cold. This specimen is at the JC Raulston Arboretum, North Carolina. Image J. Grimshaw.

Threatened in the wild by habitat loss for coffee plantations, Quercus germana seems to be established in North American gardens, and is offered by both retail and wholesale nurseries. Its handsome large blue-green leaves flush bronze or reddish, and are densely pubescent in their early stages. Being a white oak, it will probably only thrive in areas with hot summers. At Yucca Do Nursery, Hempstead, Texas, for example, it has survived to –15 ºC (Yucca Do 2008), but in cooler situations it is less successful. Michael Heathcoat Amory notes that in Devon it is often cut back by frost; similarly, a specimen at Thenford House was cut to the ground in the 2005– 2006 winter. (Its response was a flush of shoots in a most amazing beetroot-red!) At the Hillier Gardens the species has consistently failed (A. Coombes, pers. comm. 2006). The only positive record of it in the United Kingdom comes from Tregrehan, where Tom Hudson (pers. comm. 2006) reports that it seems to have no hardiness problems. The tree at the JC Raulston Arboretum was 3.3 m tall, 12 cm dbh in 2006, but has lost its top, and the crown is rather bushy with some twig dieback. Q. gilliana Rehder & E.H. Wilson B476

Quercus gilva Blume

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis gilva (Blume) Oerst. Tree to 30 m. Bark dark grey and scaly. Branchlets (and immature growth) densely covered in pale orangebrown or tawny stellate tomentum; older branchlets spotted with pale lenticels. Leaves evergreen, 6–12 × 2–3.5 cm, narrowly oblanceolate to elliptic, lower surface covered with white or tawny stellate tomentum, secondary veins forming a prominent herring-bone pattern, 11–18 secondary veins on each side of the midrib, margins entire or finely serrated near the apex, apex acuminate; petiole 1–1.5 cm long and tawnytomentose. Infructescence orange-tomentose, 1 cm long, with two cupules. Cupule bowl-shaped, 0.6–0.8 × 1.1–1.5 cm, outside and inside pale greyish or reddish brown-pubescent; scales in six to seven rings. Acorn ellipsoid to globose, with one-quarter to half of its length enclosed in the cupule, 1.5–2 cm long, stylopodium prominent, tomentose. Flowering May, fruiting October (China). Muir 1996, Huang et al. 1999, Menitsky 2005. Distribution CHINA: Fujian, Guangdong, Guizhou, Hunan, Zhejiang; JAPAN; TAIWAN. Habitat Broadleaf evergreen forest between 300 and 1500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Huang et al. 1999, Menitsky 2005; NT727. Cross-reference K88.

Despite being widespread in well-botanised areas this species had not, it seems, been introduced to the United Kingdom prior to a collection made by McNamara and Maunder (MBMX 369) at the University of Kagoshima Field Centre in Kyushu, in 1996. Muir (1996) states that it has been in cultivation in southern Europe ‘for a long time’ and that it is established in Australasian collections, so its absence from British and, apparently, North American gardens is surprising. The specimen at Kew grown from MBMX 369 is now approximately 4 m in height, although somewhat sparsely branched. The foliage is attractive, with a contrast between the glossy dark green upper surface of the leaves and the light brown hairy undersides. Figure 82 (opposite). Quercus gilva: habit with male inflorescences (A); branchlet with acorns (B).

Q. glabrescens Benth. B477, S409 Q. glandulifera (NOW Q. serrata Thunb.) B477, S409, K88 Q. glauca Thunb. B478, S410, K88

Section II. Species Accounts

Quercus

727

1 cm

1 cm

B

A

728

Quercus

New Trees

1 cm

Section II. Species Accounts

Quercus graciliformis C.H. Mull.

Quercus

Chisos Oak, Slender Oak

(Subgen. Quercus, Sect. Lobatae) Tree to 8–10 m. Bark dark grey and broken into sections, giving a rough appearance. Branches slender and pendulous. Branchlets yellowish, brown or deep reddish brown, largely glabrous, though the apices may be pubescent. Leaves largely deciduous, 4.5–9 × 1–2.5 cm, lanceolate to elliptic or obovate, largely glabrous, upper surface glossy dark green with slight sheen, lower surface glossy and with occasional tufts of tomentum in the vein axils, five to seven secondary veins on each side of the midrib, margins with eight to ten teeth or shallow lobes (rarely entire), terminating in spiny bristles (one to nine in total), apex acute to attenuate; petiole 1–2 cm long, glabrous or with a few hairs. Cupule saucer- or bowl-shaped, 0.7–1 × 0.4–0.6 cm, outer surface glabrous or with a few hairs, inner surface uniformly pubescent; scales acute and appressed, sometimes tuberculate at the base of the cupule. Acorn ovoid to ellipsoid, with one-quarter to one-third of its length enclosed in the cupule, 0.9–1.8 cm long, stylopodium prominent. Fruiting in the second year (USA). Nixon 1997, Melendrez 2000. Distribution USA: Texas (Chisos Mts.). Habitat Dry rocky canyons between 0 and 1650 m asl. USDA Hardiness Zone 6. Conservation status Critically Endangered. Quercus graciliformis suffers ongoing habitat disturbance, degradation and loss. Illustration Nixon 1997.

Quercus graciliformis is a small tree with graceful, slender, drooping branches, as its name suggests, and has a summer flush of paler leaves. Despite being confined as a native to a very limited area in Texas, it seems to flourish almost everywhere it is cultivated, although it is possibly intolerant of alkaline soils (Melendrez 2000). Sternberg (2004) considers that it is not likely to be hardy beyond Zone 8, but Melendrez (2000) indicates that it is very cold-tolerant, and a nice-looking specimen at the JC Raulston Arboretum is flourishing in Zone 7 conditions. Received as a small plant in 2000, this had reached 3 m by 2004 (JC Raulston Arboretum collection database). A specimen seen at the Hoyt Arboretum in Portland, Oregon in 2004 is also growing fast (7 m tall after six years, in 2004), but is unfortunately leaning. At the Hillier Gardens there are trees raised from acorns collected by Guy Sternberg in 1996 from plants at the Texas A&M University. The best is now 6.2 m high (2008), with a straight trunk, and seems to be growing very fast; although these specimens show some atypical characters, this may be a response to cultivation rather than evidence of hybridity (A. Coombes, pers. comm. 2007). Similar rapid growth has been reported from France, even when trees are growing on apparently inhospitable sites (Lamant 2004). At Arboretum de la Bergerette, one specimen grown from the Sternberg collection mentioned above is ‘a superbly shaped pyramidal tree’; in 2006 it had grown to ‘around 9 m tall in eight years, virtually evergreen and completely impervious to cold and drought’ (S. Haddock, pers. comm. 2006), and by 2008 it had reached 12.5 m (A. Coombes, pers. comm. 2008). Q. gramuntia (NOW Q. ilex L.) B484, K88

Quercus gravesii Sudw.

Chisos Red Oak, Graves Oak

(Subgen. Quercus, Sect. Lobatae) Tree to 13–15 m, 0.9 m dbh. Bark dark greyish black to black, with flat ridges separated by narrow fissures. Variable in size and form, dependent on growing conditions, sometimes large and massive, sometimes small and pendulous. Branchlets pale brown or dark reddish brown, glabrous, with white lenticels. Leaves deciduous, 4.5–14 × 2–12 cm, ovate to elliptic, upper surface glossy, glabrous except for a few hairs near the base and along the midrib, lower surface with small axillary tufts of hair along the midrib and veins or glabrous, four to six secondary veins on each side of the midrib, margins with three to five triangular lobes, terminating in spiny bristles (9–20 in total), apex obtuse or acute, rarely attenuate or falcate; petiole 0.5–2.5 cm long, minutely pubescent. Infructescence 1–3 cm long with one to two (to five) cupules. Cupule turbinate or deeply cup-shaped, 0.7–1.2 × 0.4–0.8 cm, outer surface glabrous or with a few hairs, inner surface glabrous or pubescent; scales acute with appressed tips. Acorn ovoid to ellipsoid, rarely subglobose, with one-third to

Figure 83 (opposite). Quercus gravesii: habit with acorns.

729

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Quercus

New Trees

half of its length enclosed in the cupule, 0.9–1.6 cm long, stylopodium prominent; stellate tomentum around apex and in longitudinal bands down acorn. Fruiting in the second year (USA). Nixon 1997. Distribution USA: Texas (Chisos, Davis and Glass Mts.). Habitat Dry wooded hillsides. USDA Hardiness Zone 7. Conservation status Least Concern. Illustration Nixon 1997; NT728. Taxonomic note Very variable in the wild, sharing similarities with both Q. buckleyi and Q. kelloggii in different parts of its range (Melendrez 2000).

Quercus gravesii is a small red oak, perhaps most notable for its excellent autumn colour. Sternberg (2004) writes of it painting the hillsides red in the Big Bend National Park, Texas – but as an interesting counterpoint, Melendrez describes how the colour varies between golden-yellow and scarlet in different parts of its range. He also mentions that it occurs on both limestone and igneous rocks in the wild (Melendrez 2000), and Sternberg (2004) considers that on a hot, dry alkaline site it might survive cold winters successfully. This appears to be the case at Kruchten in western Germany, where it tolerates the mildly alkaline soil without signs of chlorosis and has reached 1.8 m in five years of growth. These trees, grown from a Jablonski collection in New Mexico in 2000, have stunning scarlet-red autumn colour in late November (E. Jablonski, pers. comm. 2006). The species is also successful in central and southern England. A tree at Kew planted out in 1978 is now c.10 m tall (UK champion), with heavy spreading branches that form a rounded, though sparse, crown. This specimen showed no signs of attractive colouring in mid-November 2005, when the leaves were still green. A 1987 collection made by Guy Sternberg has reached 6 m at Thenford House. At Thierry Lamant’s arboretum in Dept. Loiret, France, one tree has achieved a stunning growth rate of 5 m in five years (Lamant 2004).

Quercus griffithii Hook. f. & Thomson ex Miq.

(Subgen. Quercus, Sect. Quercus)

Tree to 25 m. Crown oblong in outline. Bark grey or reddish brown with deep longitudinal fissures. Branchlets covered with yellowish grey pubescence. Leaves deciduous, 10–20 × 4–10 cm, obovate to elliptic, upper surface shiny mid-green, glabrous but for the hairs along the midrib, lower surface bluish green, densely covered in grey or golden hairs, with a fringe along the veins, 12–18 secondary veins on each side of the midrib, margins serrulate with 5–15 rounded or acute lobes, apex acuminate; petiole 0.5–1 cm long and shaggy greyish brown. Pistillate cupules solitary or in fascicles of two to three. Cupule cup-shaped, 1.2–1.5 cm diameter; scales ovate to triangular. Acorn ellipsoid to ovoid, with one-third to half of its length enclosed in the cupule, 1.5–2 cm long, stylopodium broad. Flowering January to April, fruiting September to November (China). Huang et al. 1999, Menitsky 2005. Distribution BHUTAN; CHINA: Guizhou, Sichuan, Xizang, Yunnan; INDIA: Sikkim and northeast; LAOS; MYANMAR; SRI LANKA; THAILAND; VIETNAM. Habitat Mixed forest between 700 and 2800 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Huang et al. 1999, Menitsky 2005; NT691. Taxonomic note May be synonymous with Q. aliena Blume var. acutiserrata Maxim. ex Wenzig (Huang et al. 1999).

Quercus griffithii is represented in cultivation at the time of writing by a few young seedlings from recent collections; the only older specimens seen in research for the current work are plants at Quarryhill and Kew raised from SICH 1105. This collection was made at 2930 m in Yunnan in 1992, from an old tree growing on a grazed hillside with Rhododendron and other oaks. At Quarryhill it has made a nice tree, reaching 10 m, with ascending to spreading branches. The tree at Kew is now 2 m tall but looks as if it is struggling, with numerous dead twigs and the suggestion that it has lost its leader on at least one occasion. The species is clearly not very hardy in northern Europe, although a succession of milder winters may enable it to develop a trunk before a hard winter coppices it back. In the mild conditions of Brittany, for example, a specimen derived from the Wuliang Shan, Yunnan has reached 4 m in the garden of Brigitte Fourier, Morbihan. At Chevithorne Barton a 3 m specimen was cut to the ground in the winter of 2005–2006 but was producing vigorous new shoots of bright

Section II. Species Accounts

Quercus

731

copper-red new leaves in late summer 2006. A plant at Starhill Forest Arboretum is cut to the ground annually, but the hot summers there enable it to send out shoots of 2 m or more each year. The leaves are bold and handsome, and despite the difficulty of finding a good spot for it, this is clearly a species worth persevering with, especially if high-altitude provenances can be found.

Quercus grisea Liebm.

(Subgen. Quercus, Sect. Quercus)

Grey Oak

Shrub or tree, usually to 10 m (US champion 16.6 m, 1.8 m dbh). Bark fissured, with shaggy plates, light or dark grey. Branches spreading, forming a rounded crown. Branchlets yellowish grey with sparse or dense stellate tomentum when young. Leaves deciduous or sub-evergreen, (1.5–)2.5–3.5(–8) × 1.5–3(–4) cm, oblong to ovate or elliptic, upper surface dull green with profuse stellate tomentum, lower surface dull greyish or yellowish green and with minute, interlocking stellate hairs, 6–10 secondary veins on each side of the midrib, margins somewhat revolute, entire or with three to five shallow mucronate teeth near the apex, apex acute to obtuse; petiole 0.3–1 cm long. Infructescence 1.2–1.6 cm long with one to two cupules. Cupule deep and goblet- or cup-shaped, 0.8–1.5 × 0.4–1 cm; scales ovate to oblong, proximal scales tuberculate; reddish brown, appressed. Acorn ovoid to ellipsoid, with half of its length enclosed in the cupule, 1.2–1.8 cm long, stylopodium short. Flowering April, fruiting August to October (USA). Nixon 1997, Sternberg 2004. Distribution MEXICO: Aguascalientes, Chihuahua, Coahuila, Durango, Guanajuato, Jalisco, Nuevo León, San Luis Potosí, Sonora, Veracruz, Zacatecas; USA: Arizona, New Mexico, Texas. Habitat Between 1500 and 2200 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Nixon 1997; NT698, NT731.

In the United States this species, with its attractive sub-evergreen blue-grey foliage, is considered to be a rapid grower in cultivation (Melendrez 2000, Sternberg 2004). As it is a white oak, unenthusiastic growth is perhaps to be expected in areas with cool summers. Young trees at Ettelbruck are putting on good growth, but specimens in southern England seem to do less well. The largest observed for the present work, at the Hillier Gardens, is just over 5 m tall after several decades (planting date unrecorded,

Plate 471. Quercus grisea in Texas making a picturesque medium-sized tree, appreciating the evident warmth. Image E. Jablonski.

732

Quercus

New Trees

but prior to 1980), and has formed a rather scrappy-looking bushy dome. Younger plants there also seem to be slow-growing. It will probably do best in warmer areas on acidic soil, although it shows no chlorosis at pH 6.9 (E. Jablonski, pers. comm. 2006). It has not apparently suffered winter damage in Luxembourg or western Germany. Q. haas (NOW Q. robur L. subsp. robur) B511, K88 Q. hartwissiana Steven B478, K89

Quercus hemisphaerica Bartram ex Willd. (Subgen. Quercus, Sect. Lobatae)

Upland Laurel Oak, Darlington Oak

Tree to 35 m, 2.1 m dbh. Branchlets pale brown or dark reddish brown with white lenticels, glabrous. Leaves evergreen or late deciduous, 3–12 × 1–4 cm, ovate to elliptic or oblanceolate, rarely falcate, both surfaces largely glabrous, though occasional tufts of tomentum on the lower surface, 5–10 secondary veins on each side of the midrib, margins entire or with a few shallow lobes or teeth near the apex and one to four bristles, apex acute to acuminate; petiole 0.1–0.6 cm long and glabrous. Cupules one to two, sessile or with a peduncle to 0.5 cm long, saucer- or bowl-shaped, 1.1–1.8 × 0.3–1 cm, outer surface minutely pubescent, inner surface partially pubescent; scales acute to obtuse, sometimes distinctly tuberculate. Acorn broadly ovoid, with one-quarter to one-third of its length enclosed in the cupule, 0.6–1.6 cm long, stylopodium prominent. Flowering March, fruiting October to November of the following year (USA). Nixon 1997, Sternberg 2004. Distribution USA: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Virginia. Habitat Sand hills, stream banks and hillsides between 0 and 150 m asl. Usually on dry, sandy soils. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997; NT7, NT732. Taxonomic note Very similar to Q. laurifolia, but flowers two weeks later when the two grow together.

Plate 472. The small glossy leaves of Quercus hemisphaerica are evergreen or tardily deciduous, and form a dense shady canopy. Image P. de Spoelberch.

This species seems to be well established in cultivation, potentially forming a large tree that may branch low down into several stiffly ascending trunks to make a wide crown; this can appear as a rather dull dark green mass (although flushing bronzered). Old leaves take on red tints in the autumn, but this is essentially an evergreen tree. In southeastern parts of the United States it is widely planted as a street tree; one somewhat more compact selection of it is marketed as ‘Darlington’ – a reference to a provenance in South Carolina (not a cultivar) (Dirr 1998). Another version of this name seems to be Q. laurifolia ‘Darlingtoniana’, attached to recently distributed plants (A. Coombes, pers. comm. 2008). A specimen at the Hillier Gardens is currently approximately 10 m high and seems to be the largest in the United Kingdom at the time of writing, although a younger one (1984 accession) at Kew is catching up, now being c. 8 m tall. At Starhill Forest Arboretum it is sub-evergreen, and has so far survived two winters, despite its southern origins. It appears to be intolerant of alkaline soils. Q. ×heterophylla F. Michx. B489, K89 Q. ×hickelii A. Camus B530, K89 Q. ×hispanica Lam. B479, S410, K89 Q. hypoleucoides A. Camus B482, K90 Q. iberica (NOW Q. petraea subsp. iberica (Steven ex M. Bieb.) Krassiln.) B501, K90 Q. ilex L. B482, S410, K90 Q. ilex var. ballota (NOW Q. rotundifolia Lam.) B483, K90 Q. ilicifolia Wangenh. B484, K90 Q. imbricaria Michx. B485, S410, K90

Section II. Species Accounts

Quercus incana Bartram

Quercus

(Subgen. Quercus, Sect. Lobatae)

Bluejack Oak

Tree, usually to 10 m, occasionally to 17 m, 0.7 m dbh, often forming thickets with thin, irregular crowns. Bark dark brown or black, becoming thick and corky, but broken into square plates. Branchlets brown or reddish brown and tomentose. Leaves deciduous (or semi-evergreen), 3–10 × 1.2–3.5 cm, ovate to elliptic or obovate, upper surface glossy and with sparse hairs along the midrib, lower surface densely tomentose and with longer (sometimes reddish) hairs in vein axils, 6–12 secondary veins on each side of the midrib, margins entire with one apical bristle, or occasionally a couple of weak lobes, apex acute to obtuse; petiole 0.2–1 cm long and tomentose. Cupules one (to two), sessile; saucer- or bowl-shaped, 1–1.8 × 0.4–0.8 cm, outer surface minutely pubescent, inner uniformly pubescent; scales acute to obtuse, tips tightly appressed. Acorn ovoid to subglobose, with one-quarter to one-third (rarely half) of its length enclosed in the cupule, 1–1.7 cm long, stylopodium prominent. Flowering March to April, fruiting September to October of the following year (USA). Nixon 1997, Sternberg 2004. Distribution USA: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Texas, Virginia. Habitat Barrens, hammocks, dunes and upland ridges between 0 and 250 m asl. Typically on well-drained, sandy soils. USDA Hardiness Zone ~5. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004. Cross-references B485, K90.

Bean (1976b) believed this species to be not in cultivation in Britain, and although it is now represented here it is unlikely to become widely grown. It seems to require hot summers and does not prosper in the cool climate of northern Europe: all the specimens seen in England have the appearance of being there against their wishes. Perhaps the most contented-seeming is a 4.2 m tree (2008) at the Sir Harold Hillier Gardens, in a sunny site on sandy soil with shelter behind it. Grown from a collection made in 1993 in Bienville Co., Louisiana, and planted in 1999, it is doing comparatively well. Slightly taller trees at Chevithorne Barton (4.5 m in 2008, planted in 1992, from Mallet Court Nursery) lack distinct leaders, and form a tangled top that looks more like an Elaeagnus than an oak. The general failure to thrive in northern Europe is regrettable, because the dense grey pubescence of Quercus incana is immediately recognisable and makes the tree distinct and attractive. The grey pubescence gives interesting colour effects as the bronze flush of new growth or the red autumn tints develop below it. It is much more impressive in the warm parts of the United States (Sternberg 2004). Plants of Q. incana have recently been distributed in continental Europe as Q. pumila Walter – a shorter, shrubby species (A. Coombes, pers. comm. 2008), which is in cultivation at the Hillier Gardens and elsewhere.

Q. infectoria G. Olivier B486, S411, K90 Q. infectoria var. boissieri (NOW Q. infectoria subsp. veneris (A. Kern.) Meikle) K91

Quercus insignis M. Martens & Galeotti

(Subgen. Quercus, Sect. Quercus)

Tree to 30 m, 1.3 m dbh. Branchlets covered in dense, yellow to red tomentum; in the second year, becoming glabrous, glaucous or grey and with prominent white lenticels. Leaves deciduous, 10–20(–28) × 4–9(–10) cm, elliptic to obovate, thick and hard, upper surface shiny and glabrous, lower surface dull and tomentose, 18–20 secondary veins on each side of the midrib, margins entire or undulate, very rarely dentate, apex acute; petiole 0.8–1.5(–2.5) cm long, densely tomentose. Cupules one to four, sessile; saucer-shaped, 4–8 × 2–3 cm, often contracted at the base; scales large, free, golden-tomentose, broad and triangular at base of cupule, narrow and inward-curving at margins, tomentose or almost glabrous, tips appressed or spreading. Acorn ovoid to globose, with half to two-thirds of its length enclosed in the cupule, 3–5 cm long, to 12 cm diameter, stylopodium short; basal scar prominent, and golden, silky hairs at apex. Fruiting July to August (Costa Rica). Muller 1942. Distribution COSTA RICA; GUATEMALA; HONDURAS; MEXICO: Jalisco, Oaxaca, Veracruz; PANAMA. Habitat Cloud forest between 900 and 2000 m asl. USDA Hardiness Zone (9–)10. Conservation status Near Threatened (IUCN); endangered in Mexico, due to habitat loss. Illustration NT35, NT698.

733

734

Quercus

New Trees

According to Rodriguez-Coombes et al. (2004), Quercus insignis is one of the most spectacular trees in Mexico, but it is threatened by forest clearance for coffee cultivation. This should serve as a hint that it is a very tender species – not surprising for a primarily Central American tree with only limited occurrence in Mexico. It has grown happily outside for several years in the collection of Michel Duhart, Arboretum Chocha, near Ustaritz, in the Pyrénées Atlantiques, France (A. Coombes, pers. comm. 2006), and Thomas Methuen-Campbell has a 1.5 m specimen in similar coastal conditions at Penrice Castle in south Wales – although this is protected in winter (A. Coombes, pers. comm. 2008). In general, however, where it has been tried outside in the United Kingdom it barely survives. Showing what it can do, there is a most impressive specimen in the Temperate House at Kew, touching the roof seven years after planting in 1998. This was grown from material collected by Allen Coombes (no. 221) near Huatusco, Veracruz in 1995. Its large bold foliage, flushed bronze when young (with new shoots being produced even in winter), would be good reason enough to try to grow it, but the most exciting character of this species is the huge size of the acorns, which can be an extraordinary 10–12 cm across (excluding the cupule). Another unusual feature is that the hypocotyl emerges from the base of the acorn – a distinction otherwise known only in Q. alnifolia and Q. aucheri from the eastern Mediterranean (A. Coombes, E. Jablonski, pers. comms. 2006).

Q. ithaburensis Decne. B495 Q. ×jackiana C.K. Schneid. K91

Quercus laceyi Small

Q. kelloggii Newb. B486, S411, K91 Q. ×kewensis Osborn B487, S411, K92

(Subgen. Quercus, Sect. Quercus)

Lacey Oak

Syn. Q. breviloba Sarg. f. laceyi (Small) Trel.

Plate 473. Quercus laceyi has a limited natural distribution and is rare in gardens. Image E. Jablonski.

Tree to 5–8(–10) m, shrubby in poor habitats. Bark grey, broken into flat, narrow ridges with deep intervening fissures. Branches erect, spreading. Branchlets initially covered with stellate tomentum, later reddish brown, glabrous. Leaves deciduous, (2–)4–9(–21) × (2–)5–9(–12) cm, obovate or elliptic, immature leaves covered with dense white stellate tomentum, mature leaves largely glabrous, six to nine secondary veins on each side of the midrib, margins entire or with up to six shallow (or rarely deep) lobes, apex rounded; petiole 0.3–1.2 cm long. Infructescence 1(–3) cm long with one to two cupules. Cupule saucer-shaped, 1–1.8 × 0.4–0.7 cm; scales somewhat tuberculate, covered with easily detachable hairs. Acorn oblong, one-quarter to one-third of its length enclosed in the cupule, 1–2 cm long, with a short stylopodium. Flowering April, fruiting October (USA). Nixon & Muller 1992, Nixon 1997. Distribution MEXICO: Coahuila, Nuevo León; USA: Texas (Edwards Plateau). Habitat Woodland, canyons, along streams in limestone hills between 350 and 2200 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Nixon 1997; NT734.

As a white oak of southern origin, Quercus laceyi cannot be expected to thrive in northern Europe, and it is indeed very rare here. In the United States, however, Sternberg (2004) notes that it is hardy to Zone 6, its tolerance to colder conditions facilitated by its becoming deciduous. He also comments that this results in good yellow to red

Section II. Species Accounts

Quercus

autumn colour. At Starhill Forest Arboretum one young plant is surviving, but struggling. The leaves are small and neat, with a few rounded lobes, and are mid-green with a hint of glaucescence. Allen Coombes (pers. comms. 2006, 2008) reports that a young tree at the Hillier Gardens has attractive pink new foliage; it put on good growth during the hot summer of 2006, and is now 2.4 m tall. At Arboretum de la Bergerette it suffers from dieback (S. Haddock, pers. comm. 2006), but has reached 4 m (A. Coombes, pers. comm. 2008). Q. laevis Walter B487, K92 Q. lamellosa Sm. B488, S411, K92

Quercus lancifolia Schltdl. & Cham.

(Subgen. Quercus, Sect. Quercus)

Tree to 35 m, 0.75 m dbh. Branchlets initially covered with fawn-coloured tomentum, later grey or buff with pale lenticels. Leaves deciduous, 7–15 × 1.5–5 cm, oblanceolate to ovate, leathery, glabrous, upper surface glossy green and glabrous, lower surface with scattered stellate tomentum and tufts of hair in vein axils, 10–14 secondary veins on each side of the midrib, margins with small bristle-tipped teeth, apex acute; petiole 2–2.5 cm long and glabrous. Infructescence 1–2 cm long with one to two cupules. Cupule saucer-shaped, 1.5–2 cm diameter; scales blunt and appressed. Acorn ovoid, with one-quarter to one-third of its length enclosed in the cupule, 1.8–4.5 cm long, stylopodium prominent. Standley 1922, Trelease 1924. Distribution GUATEMALA; MEXICO: Chiapas, Veracruz. Habitat Montane evergreen forest between 700 and 2000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated.

Apparently first introduced by Allen Coombes in 1995 from collections (Coombes 249, 250) made in Puebla, this southern species has not performed particularly well in cultivation. The largest at the Hillier Gardens had grown to 2.5 m by 2002, but two others at this location had reached no more than 1.5 m in the same time. A plant at Chevithorne Barton has reached 1.8 m but looks very unhappy, with twiggy stunted growth; when seen in 2005 it showed very short extension growth, and it was further damaged by the 2005–2006 winter. At Shaun Haddock’s Arboretum de la Bergerette Quercus lancifolia died in the cold winter of 2002–2003, along with the other Mexican species Q. planipocula and Q. uxoris (Lamant 2004).

Quercus laurifolia Michx.

Swamp Laurel Oak

(Subgen. Quercus, Sect. Lobatae) Tree to 40 m, 2.1 m dbh. Bark dark brown and moderately smooth in young trees; at maturity, black and divided by deep furrows into broad, flattened ridges. Branchlets yellowish or reddish brown and glabrous. Leaves (largely) deciduous, 3–12 × 1.5–4.5 cm, rhombic or broadly elliptic to ovate, immature leaves with tufts of hair in the abaxial vein axils, mature leaves glabrous, 8–10 secondary veins on each side of the midrib, margins entire or with some shallow lobing, apex obtuse or rounded and tipped with a bristle; petiole 0.1–0.5 cm long and glabrous. Cupule solitary and sessile; shallow and saucer-shaped to deep and bowlshaped, 1.1–1.7 × 0.3–0.9 cm, outer surface minutely pubescent, inner partially pubescent; scales acute or attenuate, tips appressed. Acorn ovoid or globose, with one-quarter to half of its length enclosed in the cupule, 0.8–1.6 cm long, stylopodium prominent. Fruiting September to October of the following year (USA). Nixon 1997, Sternberg 2004. Distribution USA: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Virginia. Habitat Floodplains, riverbanks and terraces between 0 and 150 m asl. Typically on sandy soils. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT698. Cross-references B502, K92.

Quercus laurifolia is well represented in European collections, and was introduced as long ago as 1786 according to Krüssmann (1986). Although none of the specimens observed for the present work are very old, among them are some impressive

735

736

Quercus

New Trees

trees, one at Kew planted in 1972 being 10 m tall and as much wide, while another at the Hillier Gardens is about 12 m tall. This compares with older trees of 15 m at Stanage Park, Powys and at Winkworth Arboretum (Johnson 2003). At the Trompenburg Arboretum, despite the high water-table there, it has not done so well, perhaps because it has been given too shaded a site. It is a handsome tree with a rounded crown developing from very dense branches, with a good red flush in spring (G. Fortgens, pers. comm. 2005), and again in summer. In the southern United States it is a popular shade tree and is said to be both flood- and shade-tolerant (Sternberg 2004), but to need acidic soil (Hillier & Coombes 2002).

Quercus laurina Bonpl.

(Subgen. Quercus, Sect. Lobatae)

Syn. Q. malinaltepecana Trel., Q. treleaseana A. Camus Tree to 40 m, 0.5 m dbh. Bark grey, smooth above, becoming rough and flaky at the base with longitudinal furrows developing in time. Branchlets yellow-tomentose; in the second year, coffee-coloured with yellow lenticels. Leaves deciduous, 3.3–14.5 × 1–5 cm, elliptical to lanceolate, rigid and leathery, juvenile leaves covered in simple reddish hairs, mature leaves glossy dark green and glabrous, except for tufts of hairs in the vein axils, 5–13 secondary veins on each side of the midrib, margins entire or with one to three teeth or serrations at the apex, apex acute or attenuate; petiole 0.8–3.6 cm long with abundant yellow tomentum. Infructescence 0.2–1.2 cm long with one to three cupules. Cupule hemispheric, 1–1.7 × 0.7–1 cm; scales woody and glabrous or with short hairs. Acorn ovoid, with half of its length enclosed in the cupule, 1.5–2 cm long, stylopodium prominent. Flowering April, fruiting June to November (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution MEXICO: Distrito Federal, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Oaxaca, Puebla, Querétaro, Tlaxcala, Veracruz. Habitat Pine-oak forest between 1500 and 3200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Romero Rangel et al. 2002; NT698.

Quercus laurina appears to be exceedingly scarce in cultivation, the only specimen seen for the current work being one at Chevithorne Barton. This has done well and has reached 7 m (2008), making a nicely upright, almost fastigiate tree with stiffly ascending branches. Its only fault lies in its very dull dark green foliage. There are some good trees at Hackfalls in New Zealand, according to Allen Coombes (pers. comm. 2006).

Q. ×leana Nutt. B488, S411, K92 Q. leucotrichophora A. Camus B489, S411, K93 Q. liaotungensis (NOW Q. wutaishanica Mayr) K93

Quercus longinux Hayata

Q. libani G. Olivier B490, S411 Q. ×libanerris Boom B468, K93 Q. lobata Née B492, K94 Q. lodicosa O.E. Warb. & E.F. Warb. B490

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis longinux (Hayata) Schottky Shrub or tree to 15 m. Branchlets glabrous, with oblong lenticels. Leaves evergreen, 6–8 × 2–2.5 cm, lanceolate to oblong, upper surface bright green, lower surface farinose or with simple hairs, seven to nine secondary veins on each side of the midrib, margins upper half serrate, apex acuminate to caudate; petiole 1–2 cm long and glabrous. Cupule bowl-shaped, 0.8 × 1–1.2 cm, outside greyish brown-tomentose; scales in six to ten rings. Acorn ellipsoid to ovoid, with about half of its length enclosed in the cupule, 1.7–2.2 cm long. stylopodium short but persistent. Flowering March to May, fruiting September to November (Taiwan). Liao 1996a, Huang et al. 1999, Menitsky 2005. Distribution TAIWAN. Habitat Broadleaved evergreen forest between 300 and 2500 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Liao 1996a, Huang

Section II. Species Accounts

Quercus

et al. 1999, Menitsky 2005. Taxonomic note Menitsky (2005) considers this taxon a subspecies of Q. glauca Thunb. The varieties of Q. longinux recognised by Liao (1996a) are not recognised in Flora of China (Huang et al. 1999) or the Fagales Checklist (Govaerts & Frodin 1998).

The only older plants of Quercus longinux known in cultivation at present are at Tregrehan, grown from acorns collected by Tom Hudson in 1989 and now 3 m tall. As with so many of these newly introduced oaks, flowering and fruiting are needed to confirm their identity. It was also collected in Taiwan by Allen Coombes in 2003.

Quercus ×look Kotschy

(Subgen. Quercus, Sect. Cerris)

Quercus ×look was thought to be a naturally occurring hybrid between Q. libani and Q. ithaburensis subsp. macrolepis (Hedge & Yaltirik 1994, Menitsky 2005). The Fagales Checklist (Govaerts & Frodin 1998) treats it as a synonym of Q. ithaburensis subsp. ithaburensis, but Michael Avishai, of the Jerusalem Botanical Gardens, considers it to be a good species in its own right and has sent seed from Israel (A. Coombes, pers. comm. 2006). The resultant seedlings are growing in several collections. A tree attributable to this taxon has grown in the Dijon Botanic Garden for over 40 years (F. Picard, pers. comm. via A. Coombes 2008). It was the parent of a tree growing at Arboretum Waasland, Belgium, which in turn was the source of a good young specimen at Thenford House, and another at the Arboretum Günther Diamant, Duisburg, Germany (E. Jablonski, pers. comm. 2006). These are both growing with great vigour, reaching 10–12 m and 14 m respectively by 2006, and producing annual new growth of over 1 m. The deeply but regularly dissected dark green leaves are attractive, and are semi-evergreen. Q. ×ludoviciana Sarg. B492, S412, K94 (but the clone distributed for many years in Europe as Q. ×ludoviciana, illustrated in Krüssmann (1986), is Q. nigra ‘Beethoven’: A. Coombes, pers. comm. 2006) Q. lusitanica Lam. K94 Q. lyrata Walter B494, K95

Quercus macranthera Fisch. & C.A. Mey. ex Hohen.

Caucasian Oak

(Subgen. Quercus, Sect. Quercus)

This species was described by Bean (B493, S412) and Krüssmann (K96).

Quercus macranthera subsp. syspirensis (K. Koch) Menitsky This subspecies forms a small tree, 7–10 m, with leaves 5–10(–12) × 3–5 cm with five to nine short regular lobes. The leaves are dark green and glabrous or sparsely pubescent above and densely covered with yellowish brown stellate pubescence below; the petiole is tomentose, 0.5–2 cm long. The cupule is 1.5 cm diameter, light brown with ovate-lanceolate scales, and covers one-third to half of the acorn. Subsp. syspirensis differs from the typical subspecies in that the stipules persist only on the terminal bud rather than on all buds. Subsp. macranthera is generally larger in all parts, and is found in the Caucasus and northern Iran. Hedge & Yaltirik 1994. Distribution TURKEY. Habitat Oak-pine woodland on dry slopes between 1000 and 1900 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Ertas 1995.

As seen in the United Kingdom, plants of this subspecies might well be named ‘uninspirensis‘; those observed for the present work are really rather dull and uninteresting in appearance. The largest is a specimen of 5.3 m (2008) at the Hillier Gardens,

737

738

Quercus

New Trees

from TURX 124, collected in 1991 in Zonguldak Province, Turkey, which appears to be growing steadily. In mitigation of this view, however, Eike Jablonski (pers. comm. 2006) points out that it is a slow-growing tree, suitable for small gardens and rockgarden planting. Q. macrocarpa Michx. B494, S412, K96 Q. macrocarpa var. oliviformis (NOW Q. macrocarpa Michx. var. macrocarpa) K96 Q. macrolepis (NOW Q. ithaburensis subsp. macrolepis (Kotschy) Hedge & Yalt.) B494, S412, K96

Quercus mexicana Bonpl.

Q. macrolepis var. vallonea (NOW Q. ithaburensis subsp. macrolepis (Kotschy) Hedge & Yalt.) B495 Q. margaretta (Ashe) Small K96 Q. marilandica (L.) Münchh. B495, S413, K97 Q. mas (NOW Q. petraea (Matt.) Liebl. subsp. petraea) B501, K97

(Subgen. Quercus, Sect. Lobatae)

Syn. Q. rugulosa M. Martens & Galeotti

Plate 474. Several Mexican red oaks, including the tolerant Quercus mexicana, have remarkable pachydermatous bark when young – a lovely feature. Image J. MacEwen.

Tree 3–15 m, 1 m dbh. Bark dark grey, smooth or wrinkled when young, becoming coarser and flaking in plates with age. Branchlets with stellate pubescence, though quickly glabrous, greyish brown with small lenticels. Leaves deciduous, (2–)3–9(–12) × 1.5–3.5(–4.2) cm, elliptical to lanceolate or oblong, leathery, upper surface dull green with sparse stellate pubescence which quickly erodes, lower surface pale green with dense stellate pubescence giving a distinctive spotted appearance, midrib elevated, 6–12 secondary veins on each side of the midrib, margins entire and retuse, apex acute to rounded; petiole 0.2–0.8 cm long and pubescent. Infructescence 0.5–0.8 cm long with one to two cupules. Cupule hemispheric, 1–1.3 cm diameter; scales thin and pubescent. Acorn ovoid, with one-third to half of its length enclosed in the cupule, 0.9–1.5 cm long, stylopodium short. Fruiting July to January (Mexico). Romero Rangel et al. 2002. Distribution MEXICO: Coahuila, Distrito Federal, Hidalgo, México, Nuevo León, Puebla, Querétaro, San Luis Potosí, Tamaulipas, Tlaxcala, Veracruz. Habitat Oak and pine-oak forest and eroded areas between 2230 and 3200 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration Romero Rangel et al. 2002; NT698, NT738.

Quercus mexicana is well established in cultivation in Europe and North America, and seems to be tolerant of a wide range of conditions, being surprisingly hardy even in Illinois (Sternberg 1995). One of the largest seen is a fruiting specimen at Arboretum Trompenburg, which has exceeded 10 m in steady growth since 1992 (van Hoey Smith 2001; G. Fortgens, pers. comm. 2006), despite difficulties in getting an anchor down in the wet soil there and the concomitant effects of wind-blow. There is a nice, but also leaning specimen, of about 7 m (in 2004), in the Hoyt Arboretum in Portland, Oregon, growing fast from a 1998 accession. In the United Kingdom the largest specimens observed are at the Hillier Gardens, where trees grown from Frankis 168, collected in 1991, are now (2008) up to c.13 m tall. Vigorous new growth from a slightly gawky tree seems to be typical of the species, and unless very securely staked and in full sun it has a tendency to lean. It would seem to be an ideal species for dry, sunny gardens in Mediterranean climates, and its slightly hoary, dull green leaves will assort well with many typical Mediterranean plants. Leaves on new shoots in summer are brownish red. Q. michauxii Nutt. B504, K97

Section II. Species Accounts

Quercus mongolica Fisch. ex Ledeb.

Quercus

739

Mongolian Oak

(Subgen. Quercus, Sect. Quercus)

Quercus mongolica subsp. mongolica Tree to 30 m, 1 m dbh. Crown irregular. Bark grey or black with deep longitudinal fissures. Branchlets glabrous, reddish or purplish brown with sparse lenticels. Leaves deciduous, (5–)7–19(–23) × (2–)3–11 cm, obovate, largely glabrous, though there may be some hairs along the veins, (5–)10–18 secondary veins on each side of the midrib, margins with (5–)7–10 rounded lobes on each side of the leaf, apex truncate, mucronate or cuspidate; petiole 0.2–0.8 cm long and glabrous. Infructescence 0.5–2 cm long with four to five cupules, though typically only one or two are fertile. Cupule cup-shaped, 0.8–1.5 × 1.2–1.8(–2.8) cm, outside densely or sparsely grey-pubescent; scales triangular to ovate with bulbous bases and narrow apices, some tuberculate. Acorn narrowly ovoid to ellipsoid, with one-third to half of its length enclosed in the cupule, 1.5–2.4 cm long, stylopodium persistent. Flowering May to June, fruiting September to October (China). Huang et al. 1999, Menitsky 2005. Distribution CHINA: Gansu, Hebei, Heilongjiang, Henan, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan; NORTH KOREA; RUSSIAN FEDERATION; SOUTH KOREA. Habitat Mixed forest between 200 and 2500 m asl. USDA Hardiness Zone 4. Conservation status Least Concern. Illustration Huang et al. 1999, Menitsky 2005; NT698. Taxonomic note Quercus mongolica, when treated in its broadest sense as in Flora of China (Huang et al. 1999), is a widespread and variable species. However, three recognisable forms of it are in cultivation. Typical Q. mongolica (for example, subsp. mongolica, Govaerts & Frodin 1998) occurs in northeast China, Korea and eastern Russia (incl. Sakhalin), and is described above. The taxon known commonly as var. grosseserrata (Blume) Rehder & E.H. Wilson, but correctly as subsp. crispula (Blume) Menitsky, also occurs in northeast China, Korea and eastern Russia, but in Japan as well, and was described by Bean (B496, S413) and Krüssmann (K97). It differs from typical Q. mongolica in that the leaf lobes are sharp and pointed. Subsp. crispula also appears to retain its leaves for longer (for example, at the Sir Harold Hillier Gardens in October 2005, the leaves of Q. mongolica subsp. mongolica were dry and brown while those of subsp. crispula were still green). Quercus wutaishanica (incl. Q. liaotungensis, Govaerts & Frodin 1998) of northwest China has smaller leaves (7–16.5 × 3.5–7.5 cm) and flatter cupule scales. Its leaves are also green in October (for example, at Kew). It is probable that the comparatively small sample of collections seen in cultivation do not accurately reflect the continuum of variation seen in the wild.

Quercus mongolica subsp. mongolica is not nearly as common in European cultivation as its sister taxon subsp. crispula, young plants at the Hillier Gardens being the only ones seen in research for this work. As noted above, the broad, round-toothed leaves are distinctive. Several trees labelled Q. liaotungensis are growing well at the Morton Arboretum, from collections made in 1990 by arboretum staff in the Pangquangou Nature Protection Area, Luliang Shan, Shanxi, China. These are making broad trees with good central leaders, up to 7–8 m in height. Their foliage is characteristic of the broad Q. mongolica concept. As an oak for cold winter climates, Q. mongolica is ideal. At Starhill Forest Arboretum in central Illinois it is the first oak to break in spring, but the new leaves are not affected by frost (G. Sternberg, pers. comm. 2006). Q. montana Willd. (WAS Q. prinus B504, K101)

Quercus morii Hayata

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis morii (Hayata) Schottky Tree to 30 m, 1 m dbh. Bark reddish brown and scaly. Branchlets thick and glabrous or with web-like hairs when young; lenticels conspicuous. Leaves evergreen, 6–10 × 2.5–4 cm, oblong to obovate, glabrous or covered with silky hairs when young, 8–11 secondary veins on each side of the midrib, margins upper half serrate, apex caudate; petiole 1.5–3 cm long and glabrous. Infructescence 2–3 cm long with one to two cupules. Cupule cup-shaped to campanulate, 1.4–1.8 × 1.5–2 cm, outside brown-pubescent, inside brown-tomentose; scales in seven to eight rings. Acorn ovoid to cylindrical, with about half of its length enclosed in the cupule, 1.5–2.5 cm long, stylopodium persistent. Flowering April to May, fruiting October to November of the following

Plate 475. Quercus morii is growing well at Tregrehan. Image J. Grimshaw.

740

Quercus

New Trees

year (Taiwan). Liao 1996, Huang et al. 1999, Menitsky 2005. Distribution TAIWAN. Habitat Broadleaved evergreen forest between 750 and 2600 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Liao 1996a, Huang et al. 1999; NT698, NT739.

This Taiwanese endemic oak was first introduced by the Edinburgh Taiwan Expedition of 1993 (under ETE 11), but it may not have become established: there are none at any of the Scottish botanic gardens, and one from this introduction at the Sir Harold Hillier Gardens has proved to be Quercus glauca. Allen Coombes gathered acorns in Taiwan in 2003 and distributed material to other collections. At the Hillier Gardens the seedlings have grown very slowly and have not yet been planted (A. Coombes, pers. comm. 2006). This contrasts with the situation at Tregrehan, where a seedling grown from acorns supplied by the Taiwan Forestry Department has grown 2 m within the first two years after planting in 2004 (T. Hudson, pers. comm. 2006).

Quercus muehlenbergii Engelm. (Subgen. Quercus, Sect. Quercus)

Chinkapin (Chinquapin) Oak, Yellow Chestnut Oak

Syn. Q. brayi Small, Q. prinoides Willd. var. acuminata (Michx.) Gleason

Plate 476. Quercus muehlenbergii scarcely qualifies as a ‘new tree’, having been introduced to England in 1737, but it has never done well there. Its magnificence is greatly appreciated in the United States. Image E. Jablonski.

Tree to 30 m, occasionally to 45 m, to 2.1 m dbh, though in drier areas forming a shrub to 3 m. Bark thin, fissured and flaking, pale grey to creamy white. Branches spreading. Branchlets pale brown, minutely pubescent; becoming grey and glabrous in the second year. Leaves deciduous, 2–4 × (1–)1.5–2.5 cm, ovate to obovate, leathery, upper surface dark green and glabrous, lower surface glaucous and covered with minute six- to ten-rayed stellate hairs, (9–)10–14(–16) secondary veins on each side of the midrib, margins regularly undulate and dentate (or with shallow lobes), teeth/lobes rounded to acuminate and pointing towards the apex, apex acute to acuminate or apiculate; petiole 1–3 cm long. Infructescence 1–1.5 cm long with one to three cupules. Cupule shallow, hemispheric, 0.8–2.2 × 0.4–1.2 cm; scales tuberculate, closely appressed, with short, grey pubescence. Acorn oblong to ovoid, with one-quarter to half of its length enclosed in the cupule, 1.5–3 cm long, stylopodium prominent. Flowering April to May, fruiting September to October (USA). Nixon 1997. Distribution CANADA: Ontario; MEXICO: Coahuila, Nuevo León, Tamaulipas, Veracruz; USA: Alabama, Arkansas, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin. Habitat Mixed deciduous forest, woodland, thicket between 0 and 2300 m asl. In western part of range, often restricted to north-facing slopes and river valleys. Generally prefers limestone or other calcareous soils. USDA Hardiness Zone 4. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT740. Cross-references B505, S415, K98. Taxonomic note This species is closely related to the Dwarf Chinkapin Oak Q. prinoides, and is regarded by some as the arborescent phase of that species (Clark 1994). The spelling muehlenbergii is correct, despite Clark’s arguments for muhlenbergii : the taxonomic code requires ‘ü’ to be written ‘ue’ in a scientific name.

Despite being described by Melendrez (2000) as ‘one of America’s most regal oaks’, and possessing the widest range of any temperate oak in North America, Quercus muehlenbergii is poorly known in Europe and was barely afforded a comparative note by Bean (1976b) – although it was first introduced to England in 1737 (Forest 2004). A tree in Kensington Gardens was 20 m tall in 1981 (Mitchell 1983), but the current UK champion is a ‘supine’ 10 m specimen at Syon House, Middlesex (Johnson 2003). There are small, young trees across the river at Kew, and others at the Hillier

Section II. Species Accounts

Quercus

741

Gardens are doing well, but as a white oak it presumably prefers warmer summers than southern England can provide. It seems to thrive in central Europe, some individuals at Ettelbruck reaching up to 2.4 m in five years. Its qualities for the eastern United States are very amply treated by Sternberg (2004) and Clark (1994), but its wide range enables appropriate selections to be made for different environments. Melendrez (2000) particularly recommends seed from desert provenances for plantings in the drier southwestern states. It is also noted for its tolerance of alkaline soils (Clark 1994, Sternberg 2004). Fine specimens can be seen in most of the arboreta and collections of the eastern United States, including a particularly lovely grove at Longwood Gardens, Pennsylvania. Q. myrsinifolia Blume B497, S413, K98

Quercus myrtifolia Willd.

(Subgen. Quercus, Sect. Lobatae)

Myrtle Oak

Shrub or small tree to 12 m. Bark thin and smooth, becoming dark and slightly furrowed near the ground. Branches short and spreading, with the twigs intricately interlaced. Branchlets slender, dark reddish brown with persistent pubescence, rarely glabrous. Leaves evergreen or semi-evergreen, 1.5–5(–7) × 1–2.5(–3.5) cm, elliptic to obovate (rarely spathulate), upper surface glabrous and glossy, lower surface glabrous except for tufts of tomentum in the vein axils (and sometimes small reddish spots), six to eight secondary veins on each side of the midrib, margins entire and revolute, but with one to four bristles, apex obtuse to rounded; petiole 0.1–0.5 cm long and generally glabrous. Cupules one to two, sessile or with peduncle to 1.6 cm; saucer-shaped, 0.8–1.4 × 0.4–0.7 cm, outer surface minutely pubescent, inner surface pubescent; scales acute and tightly appressed. Acorn ovoid to globose, with one-quarter to one-third of its length enclosed in the cupule, 0.9–1.4 cm long, stylopodium prominent and elongated. Flowering March, fruiting August to September of the following year (USA). Nixon 1997. Distribution USA: Alabama, Florida, Georgia, Mississippi, South Carolina. Habitat Dunes, sand hills and oak scrub between 0 and 100 m asl. USDA Hardiness Zone 7. Conservation status Least Concern. Illustration Nixon 1997. Cross-reference K98.

This is a species from the Coastal Plain of the southeastern United States and is only ever likely to have a marginal existence in northern Europe, or even further north in its native country. There are a few representatives in the Hillier Gardens, the largest of which (2–2.5 m) were collected by Sir Harold Hillier in 1983. They are small trees with a shrubby head, but the neat, glossy dark green leaves are attractive. Q. nigra L. B497, S413, K98

Quercus oblongifolia Torr.

Sonoran Blue Oak

(Subgen. Quercus, Sect. Quercus) Tree to 10 m, 0.45 m dbh. Crown spreading, rounded, with wide-spreading branches. Bark with small, fissured, square plates, pale grey. Branchlets pale brown with stellate tomentum, though soon largely glabrous. Leaves evergreen, (2–)3–6(–8) × (0.5–)1–2.5(–3) cm, oblong to elliptic or lanceolate, upper surface dull blue-green or glaucous with sparse ephemeral stellate tomentum, lower surface with dense, loose glandular tomentum, 7–8(–10) secondary veins on each side of the midrib, margins entire and undulate, though with occasional teeth towards the apex, apex acute to rounded; petiole 0.2–0.5 cm long. Infructescence 0.8–1.5 cm long with one to two cupules. Cupule cup-shaped, 1–1.3 × 0.6–0.8 cm; scales acute, tuberculate towards the base of cup, grey-pubescent. Acorn ovoid or oblong, with one-third of its length enclosed in the cupule, 1.2–1.7 cm long, stylopodium short. Flowering April, fruiting August to October (USA). Nixon 1997. Distribution MEXICO: Chihuahua, Coahuila, Durango, Sonora; USA: Arizona, New Mexico, Texas. Habitat High grasslands, woodlands and canyons between 1300 and 1650 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Nixon 1997; NT741.

Plate 477. Bluish green foliage is characteristic of Quercus oblongifolia, valued in the southern United States for its tolerance of harsh conditions. Image E. Jablonski.

742

Quercus

New Trees

Appreciated in the southern United States for its blue-green foliage, and tolerant of heat, drought and alkaline soil (Texas Native Trees 2008), this should be an ideal small or medium-sized white oak for gardens in the dry southern and southwestern United States. Pyramidal when young, it becomes crooked and picturesque with age. It is a favourite of Sean Hogan (pers. comm. 2006), in whose Portland garden a young tree is growing at a rate of 60 cm or more each year. It is grown in European collections, the largest at the Hillier Gardens being over 5 m tall (planting date uncertain, but prior to 1980).

Quercus obtusata Bonpl.

(Subgen. Quercus, Sect. Quercus)

Tree to 20 m, 0.6 m dbh. Branchlets reddish grey or black with some stellate tomentum. Leaves deciduous, (4–)6–17(–22) × (2–)3–8(–11) cm, thick and leathery, obovate to elliptic, immature leaves reddish and with dense yellowish stellate tomentum, mature leaves upper surface lustrous green with sparse stellate and simple hairs, particularly at the base of the midrib, lower surface yellowish green with short stellate tomentum, 7–12 secondary veins on each side of the midrib terminating in a robust marginal mucro, margins revolute and dentate with three to nine teeth towards the apex, apex obtuse or rounded; petiole 0.3–1.5 cm long and glabrous. Infructescence 3–6 cm long with one to three (or more) cupules. Cupule hemispheric, 1.2–1.8 × 0.7–1 cm; scales pubescent, acute with a swollen base. Acorn globose, with one-third of its length enclosed in the cupule, 0.6–2 cm long, stylopodium short. Flowering April to May, fruiting August to October (Mexico). Gonzalez & Labat 1987, Romero Rangel et al. 2002. Distribution MEXICO: Distrito Federal, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Veracruz, Zacatecas. Habitat Pine-oak forest, mesophytic montane forest and xerophytic scrub between 620 and 2580 m asl. USDA Hardiness Zone 8. Conservation status Least Concern. Illustration Gonzalez & Labat 1987, Romero Rangel et al. 2002.

The only specimens of Quercus obtusata traced in the United Kingdom are at the Hillier Gardens, grown from Coombes 257, collected in Hidalgo in 1995. The best of these is now just over 2 m tall, but growing well and forming a straight leader with spreading branches. At Arboretum de la Bergerette a tree from the same collection has done much better, now being approximately 6.2 m tall (2008) (S. Haddock, pers. comms. 2006, 2008). Its comparatively hairy leaves are quite distinctive among other smaller-leaved Mexican species, and are a good red when young (A. Coombes, pers. comm. 2006).

Quercus oglethorpensis W.H. Duncan

Oglethorpe Oak

(Subgen. Quercus, Sect. Quercus) Tree to 25 m. Bark pale grey or light brown and scaly; epicormic shoots from the trunk are frequent. Branchlets initially covered with stellate hairs, later reddish brown and largely glabrous. Leaves deciduous, 5–15 × 2–4.5 cm, elliptic to oblanceolate, immature leaves with short-stalked red glands above and sparse stellate hairs below, mature leaves dark glossy green above, yellowish green and thinly covered in stellate hairs below, three to eight secondary veins on each side of the midrib, margins entire or with a few teeth towards the apex, apex rounded, obtuse or acute; petiole 0.2–0.7 cm long. Infructescence with one to two cupules. Cupule turbinate, 1 × 0.8 cm; scales pale brown-pubescent and closely appressed. Acorn ovoid, with onethird of its length enclosed in the cupule, 0.9–1.1 cm long, stylopodium short. Flowering April (USA). Coombes & Coates 1995, Nixon 1997. Distribution USA: Georgia, Louisiana (?), Mississippi, South Carolina. Habitat Alluvial woodland and pasture between 0 and 200 m asl. USDA Hardiness Zone 5. Conservation status Endangered. Quercus oglethorpensis has a restricted range and is threatened by chestnut blight and poor seed viability. Illustration Coombes & Coates 1995, Nixon 1997; NT743.

A fascinating, discursive account of General James Oglethorpe and the oak that obliquely commemorates him through its occurrence in Oglethorpe Co., Georgia has been given by Coombes & Coates (1995 in The New Plantsman, reprinted 1996 in the Journal of the International Oak Society). Although the authors of this account

Section II. Species Accounts

Quercus

A

B

1 cm

1 cm

were somewhat pessimistic about the chances of this white oak in northern Europe, it must be said that, while not flourishing in the same way as some of the new Mexican introductions, Quercus oglethorpensis is making reasonable trees in southern England, and is growing steadily though slowly in Luxembourg (E. Jablonski, pers. comm. 2006); also at Arboretum de la Bergerette, where it has achieved 4 m in 10 years with no twig dieback (S. Haddock, pers. comm. 2006). Coombes & Coates recorded, in 1995, that the biggest specimens at the Hillier Gardens were 3.5 m tall, but the largest there now (the UK champion, grafted on Q. robur in 1978) is 8.9 m tall (2008), and seedlings from 1989 have reached 5 m. The new growth, especially from

Figure 84 (above). Quercus oglethorpensis: habit (A); acorn (B).

743

744

Quercus

New Trees

the many epicormic shoots on trunk and branches, often fails to ripen in the cool English summers, and there is much annual dieback of smaller shoots, giving a somewhat unshaven appearance to what would otherwise be a more respectable tree. In the warmer summers of the eastern United States Q. oglethorpensis fares much better, even as far north as Illinois (Coombes & Coates 1995, Sternberg 2004). Exemplifying this are several specimens at the Morton Arboretum which have made rounded crowns as broad as they are high (8–9 m) and look very happy, with dense canopies of glossy dark green leaves. They are very densely branched, with minimal twig dieback. Q. oxyodon Miq. B498, S413, K99

Quercus pagoda Raf.

(Subgen. Quercus, Sect. Lobatae)

Cherry-bark Oak

Syn. Q. falcata Michx. var. pagodifolia Elliott Tree to 40 m, 2.7 m dbh. Bark smooth at first, then with flaky or scaly ridges, resembling that of the Black Cherry (Prunus serotina Ehrh.), hence its common name. Branchlets yellowish brown and pubescent. Leaves deciduous, 9–30 × 6–16 cm, ovate to elliptic or obovate, immature leaves flat and covered with yellowish stellate tomentum, mature leaves puckered along the midrib, upper surface glossy and glabrous or with sparse stellate hairs along the midrib, lower surface pale and tomentose, 6–10 secondary veins on each side of the midrib, margins with 5–11 shallow triangular or falcate lobes, terminating in spiny bristles (10–25 in total), apex acute; petiole 2–5 cm long, glabrous or pubescent. Cupules one to two and sessile or with a peduncle to 1 cm long; saucer- or cup-shaped, 1–1.8 × 0.3–0.7 cm, outer surface minutely pubescent, inner surface pubescent; scales acute with tightly appressed tips. Acorn subglobose, with one-third to half of its length enclosed in the cupule, 0.9–1.5 cm long with a short, button-like stylopodium. Flowering March, fruiting October of the second year (USA). Nixon 1997, Sternberg 2004. Distribution USA: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia. Habitat Poorly drained valley floors and slopes between 0 and 300 m asl. USDA Hardiness Zone 5. Conservation status Least Concern. Illustration Nixon 1997; NT744. Cross-references B474, K87 (in both cases, as Q. falcata var. pagodifolia).

Plate 478. Quercus pagoda is one of the best red oaks for areas with acidic soil, growing vigorously into a shapely tree. Image J. Grimshaw.

Quercus pagoda is a massive, fast-growing timber tree when in favourable conditions, which would seem to be rich, fertile but lime-free ground with adequate moisture (Sternberg 2004), and it is very curious that it is not better known in European collections. It was briefly described by Bean (1976b) under its synonym, but with no indication that it was then in cultivation in the British Isles; Krüssmann, however, commented (1986) that it was introduced to cultivation in 1904. The UK champion, at Syon House, Middlesex, is 22 m tall (Johnson 2003). The planting date of this specimen is unknown, but a beautiful young tree at the Sir Harold Hillier Gardens, planted in 1989, is already 14.5 m high (2008) with a fine straight trunk, and Michael Heathcoat Amory records rapid growth from his trees in Devon. The specimen at the Hillier Gardens was notable, when observed in October 2005, for the irregularity of the lobing of the leaves, which were broad and comparatively shallow in the first flush, but much narrower with neater, smaller lobes in later growth. Quercus pagoda should be planted wherever other red oaks thrive and there is room for a magnificent tree. The name reflects its tapering, pagoda-like shape when young or, alternatively, the outline of its leaves.

Section II. Species Accounts

Quercus palmeri Engelm.

Quercus

(Subgen. Quercus, Sect. Protobalanus)

745

Palmer Oak

Shrub or small tree to 4.5 m. Branchlets rigid, reddish brown and pubescent. Leaves evergreen, 2–3(–5) × 2–4 cm, elliptic to ovate or orbicular, leathery and brittle, upper surface dark greyish green with fascicled erect and twisting hairs, lower surface glaucous and waxy, but covered with golden-brown glandular hairs, 5–8(–12) secondary veins on each side of the midrib, each terminating in a spine, margins crisped and rarely entire (but more frequently so when mature), apex broadly rounded to subacute; petiole 0.2–0.5 cm long, glabrous or pubescent. Infructescence with one to two cupules. Cupule turbinate or saucer-shaped, 1–3.5 × 0.7–1 cm; scales appressed and embedded, often tuberculate and densely golden-tomentose. Acorn oblong to fusiform, with one-third to half of its length enclosed in the cupule, 2–3 cm long, with a button-like stylopodium. Flowering June, fruiting September (USA). Nixon 1997. Distribution MEXICO: Baja California; USA: Arizona, California, Nevada, New Mexico, Utah. Habitat Dry thickets, chaparral and mountain canyons between 700 and 1800 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Nixon 1997.

A member of section Protobalanus, Quercus palmeri is an evergreen shrub or occasionally a small tree. Nixon (2002) says that its leaves are ‘among the spiniest of any oak species’ and that it forms virtually impenetrable thickets. Apparently slow-growing in the wild, it seems to be capable of rapid growth in more favourable garden conditions, adding 1 m or more in a year (Melendrez 2000). It is not common in cultivation, but there is a good specimen at Thenford House. Planted in 1998, this is now 2.4 m tall, increasing by about 30 cm per annum, with a somewhat lax and sparse appearance (M. Heseltine, pers. comm. 2006). Q. palustris Münchh. B498, S414, K99

Quercus parvula Greene (Subgen. Quercus, Sect. Lobatae)

Santa Cruz Island Oak, Coast Oak

Shrub 1–3 m (var. parvula) or tree to 17 m (var. shrevei, var. tamalpaisensis). Leaves evergreen, 3–16 cm long, oblong, lanceolate or ovate, upper surface olive-green and glabrous, lower surface dull olive-green and glabrous, six to eight secondary veins on each side of the midrib, margins entire, rarely dentate, apex acute to acuminate; petiole 0.2–1 cm long. Cupule bowl-shaped, 1.2–1.5 × 0.6–1 cm, tomentose inside; scales flat, rather thin. Acorn barrel-shaped to ovoid with an abruptly tapered apex, 3–4.5 cm long. Flowering in late spring, fruiting the year after flowering (USA). Tucker 1993. Distribution USA: California. Var. parvula occurs on Santa Cruz Is. and in a few sites in Santa Barbara Co.; var. shrevei (C.H. Mull.) Nixon from the Santa Lucia Mts. north to the San Francisco Bay Area; var. tamalpaisensis S.K. Langer in the vicinity of Mt. Tamalpais. Habitat Woodland and chaparral in canyons and on slopes below 1000 m asl. USDA Hardiness Zone 8. Conservation status Endangered. Illustration NT745. Taxonomic note This species is often confused with Q. wislizeni A. DC. (Bean: B521) and was treated as a synonym of it by Nixon (1997). However, it can be distinguished by its larger leaves (3–16 cm vs. 2–5 cm long), distinctive leaf undersides (dull olive-green vs. shiny yellow-green) and acorns (abruptly tapered vs. gradually tapered). Quercus parvula is more typical of wetter areas in the coastal fog belt; in contrast, Q. wislizeni is typical of arid slopes in the interior. While hybrids of the two species do occur naturally (in the San Francisco Bay Area), the characters that distinguish the species do not change when they are grown together outside their native habitats, and interspecific hybridisation is not uncommon in oaks (Nixon 2002).

Quercus parvula is in cultivation in specialist oak collections, and has reached 3.6 m after 10 years of growth at the Hillier Gardens. A similarly sized specimen at Chevithorne Barton was fruiting heavily in August 2006, with clusters of acorns on the previous year’s shoots. The cupule almost entirely covers the acorn. The leaves are a glossy dark green, with sparse and irregular teeth. This is perhaps not a prepossessing tree, with evergreen foliage reminiscent of several Mexican species, but it is interesting as

Plate 479. Quercus parvula, fruiting heavily in Michael Heathcoat Amory’s remarkable oak collection at Chevithorne Barton in Devon, in August 2006. Image J. Grimshaw.

746

Quercus

New Trees

one of few Californian red oaks, and if judged by the limited sample seen, is vigorous and hardy in cultivation. Q. phellos L. B502, S414 Q. pedunculiflora Q. phillyreoides (NOW Q. robur L. subsp. pedunculiA. Gray B502, S415, K100 flora (K. Koch) Menitsky) B511, K99 Q. petraea (Matt.) Liebl. B499, S414, K100

Quercus planipocula Trel.

(Subgen. Quercus, Sect. Lobatae)

Tree to 12 m, 0.4 m dbh. Branchlets with dense yellow tomentum when young; glabrous or partially tomentose when woody. Leaves deciduous, 15–21 × 7–11 cm, elliptic to ovate, upper surface with yellow stellate hairs or glabrous and dark green, lower surface yellow and velvety, 12–16 secondary veins on each side of the midrib, margin entire, sinuate or with occasional bristles, apex acute or acuminate; petiole pinkish, 1–1.4 cm long, glabrous or tomentose. Infructescence with one to two cupules. Cupule saucer-shaped, 2–2.5 cm diameter; scales thin and blunt, light brown to grey. Acorn round to ovoid, with one-third to half of its length enclosed in the cupule, 1.5–2 cm long with a stylopodium. Fruiting in the second year (Mexico). Trelease 1924, Gonzalez & Labat 1987. Distribution MEXICO: Guerrero, Jalisco, Michoacán, Nayarit, Sinaloa. Habitat Pine-oak forest between 680 and 1960 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Nixon 1997.

This Mexican endemic is apparently rare in cultivation, but seems to be to growing quite well at Chevithorne Barton, where there is a 3.5 m specimen (2008), and has done very much better in the mild climate of southwest France, where one tree has reached 6 m in Michel Duhart’s collection near Ustaritz (A. Coombes, pers. comm. 2006). Both of these individuals came from Coombes 184, collected in 1995 in Nayarit, Mexico at only 1020 m – rather a low altitude from which to hope for hardiness in a Mexican species (A. Coombes, pers. comm. 2006). Also from Nayarit is a tree at Tregrehan that was planted in 1998 and is now 4 m tall (T. Hudson, pers. comm. 2008). The mature leaves are a dull dark green, but when young flush crimson below yellow hairs, giving a striking and attractive appearance. At this stage the leaves are velvety to touch but, as in most oaks, the pubescence wears off as the leaves mature. Q. polycarpa (NOW Q. petraea subsp. iberica (Steven ex M. Bieb.) Krassiln.) K101

Quercus polymorpha Schltdl. & Cham. (Subgen. Quercus, Sect. Quercus)

Net-leaf White Oak, Monterrey White Oak

Tree to 20 m or slightly more. Branchlets reddish or greenish brown and tomentose, though soon glabrous with pale lenticels. Leaves sub-evergreen, 5–10(–15) × 3–6(–8) cm, elliptic or ovate, upper surface dark or light green, glossy, glabrous though tomentose when young and with impressed veins, lower surface light green to glaucous with prominent raised veins, largely glabrous, but tomentose and with erect golden hairs when young, 10–12(–14) secondary veins on each side of the midrib, margins entire or with prominent serrations in upper third of leaf, apex rounded, acuminate or retuse; petiole 1.5–2.5 cm long. Infructescence 0.5–1 cm long with one to two cupules. Cupule hemispheric or funnel-shaped, 1.2–2 × 1–1.3 cm; scales acute, grey-pubescent, appressed. Acorn ovoid to ellipsoid, half of its length enclosed in the cupule, yellow-tomentose, 1.4–2.5 cm long with a short stylopodium. Flowering October (USA). Muller 1942, Nixon 1997. Distribution GUATEMALA; MEXICO: Chiapas, Hidalgo, Nuevo León, Oaxaca, Puebla, San Luis Potosí, Tamaulipas, Veracruz; USA: Texas. Habitat Dry, tropical forest, cloud forest, pine-oak woodland, gallery forest, between 400 and 2450 m asl. USDA Hardiness Zone 7. Conservation status Near Threatened. Illustration Nixon 1997.

This widespread but principally Mexican white oak is most frequently represented in collections throughout our area by small young plants only, but in suitable condi-

Section II. Species Accounts

Quercus

747

tions it has the potential to make a fine tree. Seedlings observed at the Cistus Nursery in Portland, Oregon showed considerable variation in the degree of toothing on the leaves. All, however, demonstrated the spectacular red-pubescent new growth that makes this species very desirable. It is not successful in the cool English summers of the Hillier Gardens but is flourishing in Shaun Haddock’s collection in southern France (A. Coombes, pers. comm. 2006). Demonstrating the white oaks’ preference for hot summers, a specimen at the JC Raulston Arboretum is 7 m tall, dbh 12 cm. Planted in 1999, it has formed a single straight trunk with spreading branches, and when observed in June 2006 was just starting the year’s second flush of new growth.

Q. Pondaim Group K101 (a group of unnamed seedlings of Q. pontica × Q. dentata) Q. pontica K. Koch B503, S415, K101 Q. prinoides Willd. B504, S415, K101 Q. prinus L. (NOW Q. michauxii Nutt.; OR, in cultivation, most probably Q. montana Willd.) B504, K101 Q. pubescens Willd. B505, K102 Q. pubescens subsp. anatolica (NOW Q. pubescens subsp. crispata (Steven) Greuter & Burdet) K102 Q. pubescens subsp. palensis (NOW Q. pyrenaica Willd.) B505, K102

Quercus rugosa Née

Q. pungens Liebm. K102 Q. pyrami (NOW Q. ithaburensis subsp. macrolepis (Kotschy) Hedge & Yalt.) K103 Q. pyrenaica Willd. B506, S415, K103 Q. ×rehderi Trel. K103 Q. reticulata (NOW Q. rugosa Née, NT747) B507, S415, K103 Q. ×richteri Baen. B499, K104 Q. ×robbinsii Trel. K104 Q. robur L. B507, S416, K104 Q. ×rosacea Bechst. S414, K106 Q. rubra L. B512, S417, K106 Q. ×rudkinii Britton K107

(Subgen. Quercus, Sect. Quercus)

Net-leaf Oak

Syn. Q. reticulata Bonpl. Shrub or tree (5–)10–30 m, 1 m dbh. Bark with small, thin, flaky scales. Branchlets brown, turning grey with age; tomentose, glabrous or pubescent. Leaves evergreen, 8–10 × 3–5(–7) cm, obovate, elliptic or fiddleshaped, usually concave at the apex, upper surface dark green and lustrous with sparse stellate pubescence, lower surface dull glaucous or with dense brown tomentum, reticulate veins raised and prominent, 8–10(–12) secondary veins on each side of the midrib, margins revolute, crisped or flat with mucronate teeth near the apex, apex broad and rounded; petiole ~0.7 cm long. Infructescence 3–6 cm long with one to three cupules. Cupule cup- or saucer-shaped, 1.5 × 0.9 cm; scales spreading, brown and tomentose. Acorn ovoid to elliptic, with half to three-quarters of its length enclosed in the cupule, 0.7–2 cm long, stylopodium short. Flowering November, fruiting July to September (Mexico). Nixon 1997, Romero Rangel et al. 2002. Distribution MEXICO: Aguascalientes, Chiapas, Coahuila, Colima, Distrito Federal, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Sonora, Veracruz, Zacatecas; USA: Arizona, New Mexico, Texas. Habitat Pine-oak and tropical deciduous forest between 1800 and 2900 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997, Romero Rangel et al. 2002; NT698, NT747. Cross-references B507, S415, K103 (all as Q. reticulata).

Considered to be the most widely distributed Mexican oak, Quercus rugosa is usually a medium-sized tree with a rounded crown; its dark green rugose leaves with a paler undersurface are ruggedly handsome. According to Sean Hogan (pers. comm. 2005) it ‘works wonderfully in a garden’, although it may be shrubby, and in Hogan’s

Plate 480. With a wide distribution in Mexico, Quercus rugosa is correspondingly variable. Image G. Fortgens.

748

Quercus

Plate 481. The distinctive oak from La Siberica, Nuevo León, is generally thought to belong in Quercus rugosa, but may perhaps be Q. greggii. Image J. Grimshaw.

New Trees

experience it is hardy to below –18 ºC. Warm Mediterranean climates may suit this white oak best; in most parts of England trees are slow-growing (2 m in 15 years at Chevithorne Barton, then cut to the ground in the 2005–2006 winter), but in the mildest parts of the United Kingdom and France it fares better. At Tregrehan a specimen planted in 1990 is 6 m tall, and has attractive, plated bark (T. Hudson, pers. comm. 2006). In France there are two good examples at the university campus of Saint-Martind’Hères, Grenoble, the largest of which is fruiting and was 9 m tall, 34 cm dbh in 2004 (Lamant 2004). Seedlings from a Jablonski collection made in New Mexico in 2000 have been hardy so far in Luxembourg, although becoming completely deciduous in winter, and have reached 1.6 m. It seems to thrive in the hot, humid summers of the North Carolina Piedmont, with a 5.5 m specimen doing well at the JC Raulston Arboretum, but the winters of central Illinois are too much for it. At Starhill Forest Arboretum it is cut to the ground each winter and survives only through annual shoots from the base. An oak from Nuevo León known unofficially as La Siberica Form (see Plate 481) has been associated with Q. rugosa, but it is by no means certain that it belongs to this species; Allen Coombes (pers. comm. 2008) believes that it may represent Q. greggii (A. DC.) Trel. It is well known to aficionados of Mexican trees in the United States, and was perhaps first discovered by John Fairey and Carl Schoenfeld, of Peckerwood Garden and Yucca Do Nursery, respectively (Ward 2004). La Siberica is a village at 2500 m, and its oak differs from the typical Q. rugosa in having fewer marginal teeth and a paler indumentum on the undersurface of the leaves; it may also form a smaller tree when fully grown. Sean Hogan and his late partner Parker Sanderson have planted it as a street tree as part of their famous and exciting experiment in community horticulture on Portland’s Northeast 11th Avenue, and it grows well in such conditions of full sun with a little extra irrigation in summer. American collectors have recognised distinct populations of other oaks in Nuevo León that deserve further investigation. One of these is known as La Encantada Form, described as being a stately evergreen with small narrow leaves, taking its name from the village of La Encantada (2100 m). Another, with elliptic leaves on a small tree, is known as Pinal de Amoles Form (Ward 2004). It is clear that Mexico will continue to produce much to excite oak enthusiasts in the future. Q. ×runcinata (DC.) Engelm. B489, K107

Quercus rysophylla Weath.

Loquat-leaf Oak

(Subgen. Quercus, Sect. Lobatae) Tree to 15 m, possibly much more in cultivation. Bark dark and rough, forming chunky blocks that are palesurfaced at first, smoother above. Branchlets initially greenish, ridged, with brown stellate tomentum and silky hairs, later greyish brown, glabrous, with small pale lenticels. Leaves evergreen, 14–20 × 4–7 cm, lanceolate to ovate with an auriculate base, upper surface glossy and rugose with prominent sunken veins, lower surface largely glabrous, but with some pubescence along the midrib, immature leaves pinkish red, veins prominent, 15–20 secondary veins on each side of the midrib, margins undulate and revolute, entire or with shallow bristle-tipped teeth towards the apex, apex acute; petiole 0.5 cm long, glabrous. Cupule c.1 cm; scales obtuse, golden, appressed. Acorn with half of its length enclosed in the cupule, c.1.5 cm long, stylopodium short. Standley 1922, Trelease 1924. Distribution MEXICO: Hidalgo, Nuevo León, Querétaro, Veracruz. Habitat Dry, tropical forest, cloud forest, pine-oak woodland, gallery forest, between 400 and 2100 m asl. USDA Hardiness Zone 7. Conservation status Near Threatened. The known populations are small and fragmented.

Section II. Species Accounts

Quercus

749

Illustration NT694, NT749. Taxonomic note When published, the spelling rysophylla was used, but this has often been ‘corrected’ to rhysophylla (including in Govaerts & Frodin 1998), and other orthographic variants have appeared. Asked to adjudicate before we went to press, Rafaël Govaerts decided (October 2008) that the original spelling should stand.

Of all the trees in this book, Quercus rysophylla is the one that has made the greatest impression on me (JMG) wherever it has been seen, and if only one ‘new tree’ were to be grown, this should perhaps be it. Fortunately – as it is of limited occurrence in the wild – it is now well established in cultivation and is regularly offered by the nursery trade as grafted specimens. The large, leathery, bullate leaves are its distinctive feature and are held in dense clusters at the ends of the shoots; in some individuals the late flush is a fabulous red, but in others it is less intense. Seed was first received at the Hillier Gardens in 1978 from a collection made by Lynn Lowrey, who was responsible for promoting its use (with Q. canbyi and Q. polymorpha) in the southern United States, especially Texas (Pickens 1999). Another early introduction to the United Kingdom was a collection made in 1979 in Nuevo León by Sir Harold Hillier (Hillier 622), but it has since been collected on several other occasions. It is fitting that the finest individual seen in the research for New Trees is at the Hillier Gardens, on sandy soil near Brentry House, raised from Hillier 622 and now a great dense pillar 17.6 m tall (in 2008) and still growing vigorously. It is magnificent in all respects, even down to the deep layer of leaf litter around it, where the reddish brown persistent leaves are attractive in their own right. The bark is also good. There is another specimen from the same collection at Kew, which has made a fine tree of 10 m. In warmer climates it may perform still more impressively; Lamant (2004) mentions that at Arboretum Chocha, near Ustaritz, a tree planted in 1992 had attained a height of 12 m, dbh 22 cm, and was 6 m through at the time he wrote. Rapid, straight growth seems to be a feature of the species, although one specimen at the Hoyt Arboretum had its top bowed by snow and has continued to lean. It is said by Hillier & Coombes (2002) to require lime-free conditions, but in central Ireland it grows well in soils of pH 7.5–7.8 (J. Ravensberg, pers. comm. 2006). A comparison of the performance in cultivation of Q. rysophylla and Q. polymorpha, which grow together in the wild, is an instructive lesson in the differences between red and white oaks. As Q. rysophylla becomes more familiar, selections are being made and propagated either by grafting or as cuttings. ‘Maya’ is said to be a good selection, made by M.M. Bömer, with particularly fine red new leaves, and foliage suitable for the cutflower market (J. Ravensberg, pers. comm. 2006). Many trees grown from gardencollected seed are hybrids with other red oaks, and care should be taken to obtain the ‘real thing’. One specimen found in 1992 by Allen Coombes at Karaca Arboretum in Turkey in 2002 is apparently a hybrid with Q. falcata; this has been propagated by Pavia Nursery, Belgium and named Q. ‘Zehra’. Some of the plants distributed from Peckerwood Garden, Texas derive from a naturally occurring hybrid between Q. rysophylla and Q. sartorii (A. Coombes, pers. comm. 2007).

Plate 482. Quercus rysophylla is an outstanding species, with bold evergreen foliage, flushing a strong red at least twice a year. It should be planted where an impressive evergreen tree is required. Image J. De Langhe.

750

Quercus

New Trees

Q. sadleriana R. Br. ter. B513, K107

Quercus salicina Blume

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis salicina (Blume) Oerst., Q. stenophylla (Blume) Makino Tree to 18 m, though often shrubby in cultivation. Branchlets greenish yellow and minutely pubescent, though glabrous in time. Winter buds brown and green, 0.3–0.8 cm long, resembling those of Fagus. Leaves evergreen, 3.5–17 × 1.5–3.5 cm, narrowly oblong-lanceolate to linear, immature leaves bronze-pink and glossy; mature leaves blue-grey to silvery white on the lower surface; 8–14 secondary veins on each side of the midrib, margins sharply serrated in the upper half, with erect or incurved teeth, apex long and acuminate; petiole 0.5–2 cm long, longitudinally grooved and slightly pubescent; stipules prominent, to 0.7 cm long, persisting for 6–14 months. Infructescence 0.5 cm long with one to two cupules. Cupule shallowly cup-shaped, 1.2 × 0.5 cm; scales in six to eight rings. Acorn rounded, with half to two-thirds of its length enclosed in the cupule, 1–2 cm long, stylopodium umbonate, surrounded by several faint rings. Flowering March to May, fruiting September to October (Japan). Muir 1996. Distribution JAPAN (incl. Ryukyu Is.); NORTH KOREA; SOUTH KOREA. Quercus salicina has been reported from Taiwan (Liao 1996), but those plants represent the closely related Q. stenophylloides (Huang et al. 1999). Habitat Montane evergreen to deciduous forest between 300 and 1000 m asl. Often on limestone hills. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Muir 1996; NT750.

Plate 483. Quercus salicina – one of the hardier members of subgenus Cyclobalanopsis – makes a broad dome of evergreen foliage, each leaf waxy-white underneath. Image K. Camelbeke.

Quercus salicina has been in cultivation in Europe for some time (Muir 1996, 1997), but has been confused with Q. glauca Thunb. As Muir has explained, the presence of a good specimen of this tree at Tortworth in Gloucestershire was persistently overlooked by W.J. Bean and his editorial successors; planted in about 1890, it reached 12.5 m tall, with a dbh of 41 cm (Johnson 2003), but has recently died. Further material has been introduced from Japan and Korea in recent decades, and the species can be regarded as being well established, in British gardens at least. It forms a rather bushy, round crown that can be as wide as it is tall, growing steadily and increasing in width as much as in height. Muir (1996) recorded that trees at the Hillier Gardens (dating from about 1977) were ‘nearly 3 m tall’, but the tallest has now reached 10.8 m (2008). The foliage is attractive, the silvery glaucous undersurface contrasting well with the dark green above, and Michael Heathcoat Amory (pers. comm. 2006) notes that the new growth is pink. As Muir commented, it has proven itself as a hardy tree in the Cotswolds and elsewhere in the United Kingdom, and deserves to be more widely planted. It dislikes lime, as presumably do other related species (Hillier & Coombes 2002).

Q. ×sargentii Rehder K107

Quercus sartorii Liebm.

(Subgen. Quercus, Sect. Lobatae)

Sartor’s Oak

Syn. Q. huitamalcana Trel. Tree to 20 m. Branchlets greenish brown or black with small brown lenticels; occasional stellate hairs or flaky scales present. Leaves sub-evergreen, 9–13 × 2.5–5 cm, elliptic to lanceolate, upper surface shiny black-green and glabrous, lower surface dull, glabrous or with a few tufts of hair in vein axils and along the midrib, 8–12 secondary veins on each side of the midrib, each terminating in a bristle of up to 0.5 cm, margins entire or with a few shallow teeth, apex acute; petiole 1.5–4 cm long and glabrous. Infructescence 0.5–0.7 cm long with (one to) two to five cupules. Cupule turbinate to hemispherical, 1.5 × 0.5 cm; scales obtuse and appressed with golden pubescence. Acorn round to ovoid, with half of its length enclosed in the cupule, stylopodium short. Fruiting August to September (Mexico). Trelease 1924. Distribution MEXICO:

Section II. Species Accounts

Quercus

751

Hidalgo, Puebla, Oaxaca, Tamaulipas, Veracruz. Habitat Between 1300 and 2000 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT751. Taxonomic note Quercus sartorii Liebm. should not be confused with Q. sartorii Botteri ex A. DC., a synonym of Q. acutifolia.

Michael Heathcoat Amory’s notes on his oak collection record that Quercus sartorii is a ‘bit delicate’, but when seen in October 2005 some of his trees of this species were growing well, the largest then approximately 5 m in height after ten years’ growth (currently 7 m tall: A. Coombes, pers. comm. 2008) – although another individual in a more exposed situation was less happy. At the Hillier Gardens, the largest specimen of Coombes 248, from Puebla, collected in 1995, is 8.7 m tall (2008) and also thriving, and there is another good tree at Wisley. In Illinois, Sternberg (1995) found it to show early promise of being winter-hardy; in such Zone 5 conditions, it is deciduous. The new foliage on late summer shoots is red. Q. ×saulii C.K. Schneid. K107 Q. ×schochiana Dieck B489, K107

Quercus schottkyana Rehder & E.H. Wilson

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis glaucoides Schottky, Q. glaucoides (Schottky) Koidzumi Tree to 20 m. Branchlets greyish green or brown and tomentose, later glabrous. Leaves evergreen, 5–12 × 2–5 cm, elliptic to obovate or oblanceolate, leathery, upper surface green, lower surface glaucous with tawny tomentum on the veins and midrib, 8–12 secondary veins on each side of the midrib, margins serrated for upper two-thirds, apex acuminate to caudate; petiole 0.5–2 cm long. Infructescence 1.5–2 cm long with 8–14 cupules, though only one to two mature. Cupule bowl-shaped, 0.6–0.8 × 0.8–1.2 cm, outside tawnytomentose, inside with pale brown silky hairs; scales in six to eight rings. Acorn ellipsoid to ovoid, with onethird to half of its length enclosed in the cupule, 1–1.4 cm long, stylopodium short but persistent. Flowering May, fruiting October (China). Huang et al. 1999. Distribution CHINA: Guizhou, Sichuan, Yunnan. Habitat Broadleaved evergreen forest between 1500 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Huang et al. 1999; NT698. Taxonomic note Menitsky (2005) considers this taxon a subspecies of Q. glauca Thunb. Flora of China recognises the species as Cyclobalanopsis glaucoides, with Q. schottkyana and Q. glaucoides as synonyms (Huang et al. 1999). However, the epithet ‘glaucoides’ already exists in Quercus for a Mexican species (Q. glaucoides M. Martens & Galeotti) and Q. glaucoides (Schottky) Koidzumi is a later homonym. The Chinese species must therefore be referred to as Q. schottkyana when included in Quercus.

Quercus schottkyana is one of the few recently introduced Chinese species to rival the Mexicans for beauty and vigour, with the potential to become a very large tree. Perhaps the first introductions to our area are those from the SICH expeditions of 1998 and 1992, and trees from these are growing well at Wakehurst and Quarryhill, but there have also been several later introductions. At Quarryhill a tree from SICH 1142 (collected as Cyclobalanopsis glaucoides) was 5 m in height in 2004, branching from near the base to form a dense mass of foliage. A straight-stemmed specimen of 10 m (2008) is growing at Chevithorne Barton. The evergreen leaves are narrow and strongly toothed, with a distinctly yellow petiole in all the examples observed for the current work. On emergence the young leaves can be most beautiful, flushed reddish

Plate 484. Shiny new leaves on Quercus sartorii expand from a hairy start, but darken as they mature. Image K. Camelbeke.

752

Quercus

New Trees

bronze and covered with a dense sheen of silvery hairs, just as are many members of the Lauraceae, and this similarity is enhanced by the young leaves of the oak hanging downwards. The coloration of the new shoots is rather variable, however, and some specimens produce only plain green shoots. Q. semecarpifolia Sm. B513, S417, K107 Q. shumardii Buckley B514, S417, K108 Q. shumardii var. schneckii (Britton) Sarg. K108

Quercus sinuata Walter

Bastard Oak, Durand Oak

(Subgen. Quercus, Sect. Quercus) Syn. Q. durandii Buckley Shrub or tree, usually to 20 m, occasionally to 26 m, 1 m dbh. Branchlets pale grey and glabrous or minutely pubescent. Leaves deciduous, (2.5–)3–12(–14) × (1.5–)2.5–6 cm, oblong to oblanceolate, upper surface dull green and glabrous, lower surface silvery or dull green with minute eight- to ten-rayed stellate hairs or glabrous, 7–11 secondary veins on each side of the midrib, margins entire or irregularly dentate or with sinuous lobes, apex rounded, but rarely attenuate and three-lobed; petiole 0.2–0.5 cm long. Infructescence short with (one to) two cupules. Cupule saucer-shaped, 0.8–1.5 × 0.2–0.8 cm; scales ovate and flat, grey with red margins. Acorn ovoid to oblong, with one-eighth to one-quarter of its length enclosed in the cupule, 0.7–1.5 cm long, stylopodium short. Flowering March, fruiting October (USA). Muller 1942, Nixon 1997. Distribution MEXICO: Coahuila, Nuevo León, Tamaulipas; USA: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Texas. Habitat Oak woodlands, scrubland and along streams between 0 and 600 m asl. Typically on limestone. USDA Hardiness Zone 5–6. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT752. Taxonomic note There are two varieties of Q. sinuata: var. sinuata is a tree to 20 m with a solitary trunk, leaves 5–12 cm long and acorns 1.2–1.8 cm long. It has a marked preference for low, wet areas between 0 and 400 m asl and is found in the southeastern United States. Var. breviloba (Torr.) C.H. Mull. (Bigelow Oak) is a multistemmed shrub or tree to 5 m, leaves 3–6 cm long and acorns 0.7–1.2 cm long. It occurs in oak woodland and scrub between 200 and 600 m asl, from the Edwards Plateau south into Mexico. The two varieties meet along streams in central Texas, where they produce a range of intermediate forms (Nixon 1997).

Plate 485. A large old tree of Quercus sinuata at Waco, Texas. The species has a wide distribution in the southeastern United States. Image E. Jablonski.

This southern white oak is currently represented in European arboreta by young plants grown from acorns distributed through the International Oak Society or from personal collections in the United States. Among these are seedlings of North Carolina origin at Ettelbruck, which have reached 1.5 m in six years and are very hardy there (E. Jablonski, pers. comm. 2006). Quercus sinuata is grown in American arboreta also, but although mentioned by Sternberg (2004) it appears not to be common in cultivation there. A tree in the JC Raulston Arboretum, accessioned as a 30 cm plant in 2000, was c. 3 m in 2006, growing well, with vigorous new shoots some 60 cm long in June. Q. stellata Wangenh. B515, K108 Q. stenophylla (NOW Q. salicina Blume, NT750) K108

Quercus stenophylloides Hayata

(Subgen. Cyclobalanopsis)

Syn. Cyclobalanopsis stenophylloides (Hayata) Kudô & Masam. Tree to 17 m. Branchlets slender, grey and glabrous. Leaves evergreen, 7–12 × 1.5–3.5 cm, elliptic to oblong or lanceolate, leathery, the lower surface glaucous with prostrate hairs and prominent veins, 11–13 secondary veins on each side of the midrib, margins with short bristle-like teeth, apex acuminate to caudate; petiole 1.5–2 cm long and glabrous. Infructescence 2–2.5 cm long with six to seven cupules. Cupule cup-shaped, 1–1.5

Section II. Species Accounts

Quercus

× 1.2 cm, outside and inside grey-velvety; scales in six to eight rings. Acorn ellipsoid, with half of its length enclosed in the cupule, 1.7–2 cm long, stylopodium persistent, three-ringed. Flowering April to May, fruiting September to October of the following year (Taiwan). Liao 1996a, Huang et al. 1999. Distribution TAIWAN: central and northern provinces. Habitat Broadleaved evergreen forest between 1100 and 2600 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Liao 1996a, Huang et al. 1999.

Quercus stenophylloides is a member of the Cyclobalanopsis group, and notable for the silvery white undersides to its leaves (Muir 1996). It is rare in cultivation, and its hardiness may be questionable. The oldest seems to be at Tregrehan, grown from TH 002, collected in Taroko Gorge, Taiwan in 1989, and now (2008) over 6 m tall. In addition it has been introduced by a team from the Royal Botanic Garden Edinburgh, in 1993, although a specimen from ETE 161 planted against the greenhouse wall at Inverleith has died (M. Gardner, pers. comm. 2006). It was also collected more recently by Allen Coombes, in 2003, and young plants from this source have been distributed to several gardens (A. Coombes, pers. comm. 2006). Among these, one at Thenford House was cut back by the 2005–2006 winter, although it resprouted in 2006. An internet search on Q. stenophylloides principally yielded the information that the acorns of this and other species are an important dietary item for Asiatic Black Bears in Taiwan (Hwang et al. 2002), which suggests that collectors should proceed to fruiting trees with some caution. Q. suber L. B515, S417, K108 Q. suber var. occidentalis (NOW Q. suber L.) B516, K109

Quercus subspathulata Trel.

(Subgen. Quercus, Sect. Quercus)

Tree to 15 m, 0.5 m dbh. Branchlets purplish or brownish grey and glabrous with yellow lenticels. Leaves deciduous (or sub-evergreen), 6–24 × 3–11 cm, obovate to subspathulate, leathery, upper surface slightly glossy and glabrous, lower surface waxy glaucous with stellate tomentum along the midrib, 8–16 secondary veins on each side of the midrib, margins slightly revolute with 5–10 sinuous lobes on each side, apex obtuse or rounded; petiole 0.4–1.5 cm long and glabrous. Infructescence with one to three cupules. Cupule hemispheric, 1.1–1.5 × 0.7–0.9 cm; scales acute and tomentose. Acorn ovoid, with one-quarter of its length enclosed in the cupule, ~2.5 cm long, stylopodium short. Trelease 1924. Distribution MEXICO: Chihuahua, Jalisco, Sonora. Habitat Pine-oak forest, between 1500 and 1600 m asl. USDA Hardiness Zone 9. Conservation status Vulnerable, due to habitat loss.

Quercus subspathulata is another species very scarce in cultivation. So far it has been slow-growing at both Chevithorne Barton and the Hillier Gardens, and Michael Heathcoat Amory records that it suffers from dieback. At both locations it derives from Coombes 431, collected in Puebla in 1997, and the trees were about 1.5 m tall in 2006. In the warmer conditions of La Bergerette, however, it does better, and the best specimen there has reached 6 m (A. Coombes, pers. comm. 2008).

Quercus texana Buckley

Texas Red Oak, Nuttall’s Oak

(Subgen. Quercus, Sect. Lobatae) Syn. Q. nuttallii E.J. Palmer Tree to 25 m, 2 m dbh. Branchlets reddish brown or grey and glabrous. Leaves deciduous, 7.5–20 × 5.5–13 cm, ovate to elliptic or obovate, upper surface glabrous, lower surface glabrous except for conspicuous tufts of tomentum in vein axils, five to seven secondary veins on each side of the midrib, margins with 4–11 oblong or distally expanded lobes, terminating in spiny bristles (9–24 in total), apex acute; petiole 2–5 cm long and glabrous. Cupule solitary and sessile; thin and goblet-shaped with a pronounced constriction at the base, 1.5–2.2 × 1–1.6 cm, outer surface glabrous, inner surface pubescent; scales acute with appressed tips. Acorn

753

754

Quercus

New Trees

broadly ovoid to ellipsoid, with one-third to half of its length enclosed in the cupule, 1.5–2.6 cm long, stylopodium persistent. Flowering March, fruiting August to October of the following year (USA). Muller 1942, Nixon 1997. Distribution USA: Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Tennessee, Texas. Habitat Floodplains between 0 and 200 m asl. USDA Hardiness Zone 5. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT698, NT754. Cross-reference K109. Taxonomic note The name Q. texana is often used erroneously for Q. buckleyi and Q. gravesii, and the narrow application of Q. texana Buckley to this taxon, which scarcely occurs in Texas, has been much bemoaned (Nixon 1997, Lamant & Sternberg 2000) and is not always accepted: Sternberg (2004), for example, uses the name Q. nuttallii.

Plate 486. Trees of the Quercus texana New Madrid Group produce deep burgundy-red growth in spring. Later flushes are a lighter red, as here, and their autumn colour is also good. Image J. Grimshaw.

The confusion over the nomenclature of three red oaks all of which have borne the name Quercus texana causes problems for dendrologists visiting arboreta, where any of the three may bear a label with that name! The tree at Kew thus marked is from a collection made in Louisiana by a team from the Morton Arboretum, and is correctly identified. It is currently about 8 m tall, from accession in 1986, and has formed a rounded, small tree with attractive, deeply lobed, toothed foliage. Sternberg (2004) notes that the leaves turn a good red, but often rather late in the season, and that they may be caught by frost before turning. With its wide range in the lower Mississippi valley this is an adaptable tree, and populations in southern Illinois are particularly hardy. Acorns collected from an isolated tree in New Madrid, Missouri have given uniform progeny with outstanding red autumn colour, but which also flush purple before turning green. Their leaves are relatively coarsely lobed for this species. These trees have been given the name ‘New Madrid’ by Guy Sternberg (pers. comm. 2006), but as the name applies to numerous seedlings, New Madrid Group is to be preferred. With their comparatively northern provenance, they are very hardy. The species is closely related to Q. palustris (Sternberg 2004), but is considered to be a more useful plant for landscaping in the southeastern United States (Dirr 1998).

Q. thomasii (NOW Q. robur L. subsp. brutia (Ten.) O. Schwarz) B511, K109 Q. tlemcenensis (NOW Q. faginea subsp. broteroi (Cout.) A. Camus) B474

Quercus tomentella Engelm.

Channel Islands Oak

(Subgen. Quercus, Sect. Protobalanus) Tree to 20 m. Bark thin and reddish brown, divided into large scales. Branches spreading to form a rounded crown. Branchlets reddish brown or greyish green, rigid and densely tomentose. Leaves evergreen, (3–)7–10 (–20) × 2.5–4 cm, oblong to lanceolate or elliptic, leathery, upper surface glossy dark green and sparsely stellate-tomentose, lower surface densely tomentose with white hairs and a pilose midrib, 8–10(–12) secondary veins on each side of the midrib, margins strongly revolute, crenate to dentate (rarely entire) with mucronate teeth, apex rounded or acute; petiole 0.3–1 cm long with rusty hairs. Infructescence with a solitary (rarely paired) cupule. Cupule cup-shaped, 1.5–3 × 0.4–0.8 cm; scales deeply embedded in whitish brown tomentum, with only the elongated apices visible. Acorn ovoid, with one-quarter to one-third of its length enclosed in the cupule, 2–3 cm long, stylopodium persistent. Flowering May to June (USA). Nixon 1997. Distribution MEXICO: Baja California, Guadalupe Is.; USA: California (Channel Is.). Habitat Lower parts of steep canyons and ridge tops between 100 and 650 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable, due to habitat degradation and loss. Illustration Nixon 1997.

Despite its origin on frost-free offshore islands, and having been described by Lamant (2004) as ‘famous for lack of hardiness’, Quercus tomentella is proving to be fully hardy in southern England and is making good growth at both Chevithorne Barton and the Sir Harold Hillier Gardens. At the latter, a specimen from Coombes 445, collected in 1997 from plants in Santa Barbara Botanic Garden that originated on Santa Cruz Island, was 7.9 m tall by October 2008. Acorns collected at Rancho Santa

Section II. Species Accounts

Quercus

755

Ana gave the hybrid Q. tomentella × Q. chrysolepis. In France there is a fine specimen in Stéphane Brame’s collection at Villeneuve le Comte, Dept. Seine et Marne (Lamant 2004). The hard-textured, glossy, dark green leaves are rather holly-like with their marginal spines.

Q. trojana Webb B516, S418, K109

Quercus turbinella Greene

Sonoran Scrub Oak, Scrub Live Oak

(Subgen. Quercus, Sect. Quercus) Shrub or tree, 5–10 m, occasionally to 20 m. Bark grey, fissured and scaly. Branchlets greyish brown, tomentose to glabrous. Leaves evergreen or partially deciduous, (1.5–)2–3 × 1–1.5(–2) cm, elliptic to ovate, leathery, upper surface glaucous or yellowish and glandular, glabrous or with minute stellate pubescence, lower surface yellowish or reddish and glaucous with minute stellate pubescence, four to eight secondary veins on each side of the midrib, margins with three to five coarse teeth or shallow lobes on each side of the midrib, apex acute to obtuse; petiole 0.1–0.4 cm long. Infructescence 1–4 cm long with one to three cupules. Cupule hemispheric or cup-shaped, 0.8–1.2 × 0.4–0.6 cm; scales ovate, partially tuberculate and covered in greyish or yellowish pubescence. Acorn ovoid, with one-quarter to half of its length enclosed in the cupule, ~2 cm long, stylopodium small. Flowering April, fruiting July (USA). Nixon 1997. Distribution MEXICO: Baja California, Chihuahua, Sonora; USA: Arizona, California, Colorado, New Mexico, Nevada, Texas, Utah. Habitat Dry desert slopes in juniper/pinyon woodland between 800 and 2000 m asl. USDA Hardiness Zone ~5. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT755.

Accounted the hardiest of the American evergreen oaks by Sternberg (2004), Quercus turbinella is a species well adapted to its arid hillside habitat, often forming little more than a prickly bush. It was recommended by Melendrez (2000) as an attractive species suitable for planting in cold, dry areas; it thrives in Denver Botanic Gardens, Colorado (A. Coombes, pers. comm. 2008). At Ettelbruck it is hardy but slow-growing, and snow pressure can be a problem for the thin flexible stems (E. Jablonski, pers. comm. 2006). A plant in shade at Chevithorne Barton has reached approximately 3 m.

Plate 487. Quercus turbinella, seen here in Arizona, is perhaps the coldhardiest of the American evergreen oaks, but needs a hot summer to grow successfully. Image E. Jablonski.

756

Quercus

New Trees

In European collections generally, however, it is rare. In cultivation in North America it hybridises freely with the most disparate-seeming partners, including Q. robur (Sir Harold Hillier Gardens database), and is a parent of several wild hybrids. Q. ×turneri Willd. B517, S418, K109 (N.B. Q. ×turneri A. DC. = Q. ×hispanica Lam.)

Quercus undulata Torr.

(Subgen. Quercus, Sect. Quercus)

Specimens labelled as Quercus undulata appear in several oak collections. The name has been rather loosely applied to a complex of white oak hybrids from the southwestern United States, but should refer only to Q. gambelii × Q. grisea. All members of the complex have Q. gambelii Nutt. as one parent, but six other species (Q. arizonica, Q. grisea, Q. havardii, Q. mohriana, Q. muehlenbergii and Q. turbinella) are also involved. The complex includes not only the F1 hybrids, but also a series of other intermediates formed from backcrossing with one of the parent species (Tucker 1961, Tucker et al. 1961, Tucker 1963, 1970, 1971). The F1 hybrids typically have foliage intermediate between Q. gambelii and the other parent species (exemplar leaves are illustrated by Tucker 1961). Backcrossing features in the parentage of many cultivated specimens, however, and these may therefore not demonstrate typical F1 morphology. It is also possible that cultivated specimens of any of the seven parent species may actually have a hybrid origin. A number of selections have been made from the complex, and some are being propagated, especially by Pavia Nursery, Belgium. Q. utahensis (NOW Q. gambelii Nutt.) B518

Quercus uxoris McVaugh

(Subgen. Quercus, Sect. Lobatae)

Tree to 25 m, 1 m dbh. Branchlets covered in thick golden tomentum, which erodes later; lenticels prominent. Leaves deciduous, (10–)15–26 × (3.5–)6–10 cm, ovate or obovate to elliptic, leathery, juvenile foliage with glandular hairs and stellate pubescence, hairs dense and golden on the lower surface and sparse on the upper surface, mature leaves largely glabrous or with stellate hairs on the veins of the lower leaf surface, 11–14 secondary veins on each side of the midrib, margins revolute, with 10–14 teeth on each side of the midrib, lateral veins terminating in a bristle, apex acuminate to attenuate; petiole (0.8–)1.2–3 cm long. Infructescence 1–4 cm long with one to several cupules. Cupule saucer-shaped, 2–2.2 × 0.8 cm; scales grey and triangular. Acorn ovoid, with one-quarter to one-third of its length enclosed in the cupule, 1.8–3 cm long, stylopodium small. Muller & McVaugh 1972, Gonzalez & Labat 1987. Distribution MEXICO: Colima, Guerrero, Jalisco, Michoacán, Oaxaca. Habitat Pine-oak or oak forests in steep valleys between 900 and 2500 m asl. USDA Hardiness Zone (9–)10. Conservation status Vulnerable. The range of Q. uxoris has not been fully documented and the rate of forest clearance is alarming. Illustration Gonzalez & Labat 1987.

Introduced from Jalisco by Allen Coombes in 1995, Quercus uxoris has proved to be too tender to grow outside at Chevithorne Barton, but is maintained under glass there (M. Heathcoat Amory, collection notes). Neither has it survived with Shaun Haddock in southern France. It has distinctively long leaves with long-acuminate tips.

Q. vacciniifolia Kellogg B468, K109 Q. variabilis Blume B519, S418, K109 Q. velutina Lam. B519, S418, K110

Q. virgiliana (NOW Q. pubescens Willd. subsp. pubescens) B506, K110

Section II. Species Accounts

Quercus virginiana Mill.

Quercus

757

Southern Live Oak

(Subgen. Quercus, Sect. Quercus) Tree (rarely shrub) to 35 m, 4 m dbh, trunk stubby and often buttressed, with wide-spreading branches forming a dense rounded crown. Bark dark reddish brown, rough and gnarled, furrowed with square plates. Branchlets pale yellow or grey and minutely pubescent. Leaves evergreen or partially deciduous, (1–)3.5–9(–15) × (1.5–)2–4(–8.5) cm, obovate to oblanceolate, upper surface dark or light green and glossy, glabrous or with a few stellate hairs, lower surface white to glaucous with a dense covering of minute stellate hairs, 6–9(–12) secondary veins on each side of the midrib, margins minutely revolute, entire or with one to three irregular teeth on each side of the leaf, apex obtuse to rounded or acute; petiole 0.1–1(–2) cm long. Infructescence 1–2 cm long with one to three cupules. Cupule hemispheric or goblet-shaped, 0.8–1.5 × 0.8–1.5 cm, base often constricted; scales whitish grey and keeled, tips red and acute. Acorn ovoid or barrel-shaped, with one-third to half of its length enclosed in the cupule, 1.5–2.5 cm long, stylopodium short. Live oak seedlings form a swollen underground tuber and may reproduce clonally, particularly when young. Flowering April, fruiting September (USA). Nixon 1997. Distribution USA: Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Virginia. Habitat Evergreen woodland and scrub on the Coastal Plain between 0 and 200 m asl. USDA Hardiness Zone 7. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT757. Cross-reference K111.

The Live Oak of the American South is a splendid tree with wide-spreading branches that can live to great age: one estimated to be 1200 years old is known at Lewisburg, Louisiana (Landry 2005). It is strongly associated with many of the fine old gardens and parks of the southern states, although there are some who feel that due to a lack of imagination in the horticultural and landscaping trades it has been over-planted and forms almost a monoculture in some places (Ware 1995a). Sternberg (2004) illustrates some magnificent examples, and discusses its cultural and horticultural significance in considerable detail. Its characteristic hoary appearance comes from it often being draped with Spanish Moss Tillandsia usneoides (Ellis 1996), an association that may supply a clue to the poor performance of this oak in areas with cooler, less humid summers. Despite its occurrence as far north as Virginia – and Sternberg (2004) emphasises that for success in such northern areas, northern provenances must be used – Quercus virginiana has never been much use in Europe, where it misses the steamy warmth of its native habitat. The two trees at Chevithorne Barton (the only ones traced in England) are very unhappy-looking, with stunted growth. Michael Heathcoat Amory records that although one had reached 1.8 m in six years it was still 1.8 m at nine years. By 2008, when 12 years old, it had achieved 2 m, and the other 2.3 m (A. Coombes, pers. comm. 2008). The species is a calcifuge (Hillier & Coombes 2002).

Quercus vulcanica Boiss. & Heldr. ex Kotschy

Kasnak Oak

(Subgen. Quercus, Sect. Quercus) Tree to 30 m, 1.6 m dbh. Branchlets yellowish or reddish brown with short silky hairs, later glabrous. Leaves deciduous, 9–17 × 5–10 cm, obovate, upper surface yellowish or grey-green, glabrous or with some single and stellate hairs particularly by midrib, lower surface with appressed stellate or grouped hairs, seven to eight secondary veins on each side of the midrib, margins with four to seven deep, regular, acute or rounded lobes with shallow secondary lobing, apex obtuse to rounded or acute; petiole 0.8–3.5 cm long, pubescent. Infructescence short with one to three cupules. Cupule hemispheric, 1.4–1.8 × 1–1.3 cm, grey-brown; scales flat, appressed,

Plate 488. The classic shade tree of the American South is Quercus virginiana, surrounding elegant homes and planted in allees. Image JC Raulston Arboretum.

758

Quercus

New Trees

1 cm

1 cm

B A

Figure 85 (above). Quercus vulcanica: habit (A); acorn (B).

tomentose. Acorn ovoid, half to two-thirds of its length enclosed in cupule, ~2 cm long, stylopodium short. Flowering June, fruiting September (Turkey). Hedge & Yaltirik 1994. Distribution TURKEY. Habitat Mixed oak and conifer woodland between 1300 and 1800 m asl. USDA Hardiness Zone 6. Conservation status Near Threatened. Illustration A plate of Q. vulcanica from T. Kotschy’s Die Eichen Europas und des Orients (1858–1862) is fortuitously reproduced (p. 496) in the excellent history of botanical art Garden Eden: Masterpieces of Botanical Illustration, by H. Walter Lack (2001), which would repay its place on any plantsman’s shelf. NT758.

Section II. Species Accounts

Quercus

759

The field notes of the Flanagan & Pitman Expedition to Turkey (1990) describe Quercus vulcanica as ‘a magnificent species with outsize leaves’. The collection by this team under TURX 82 came from near Egridir in Isparta Province, and the specimen at Kew that derives from it already deserves the adjective ‘magnificent’. It is forming a columnar tree, currently approximately 8 m tall and growing very fast, and has every chance of being one of the great trees of Kew in the future. Closely related to Q. frainetto, but endemic to Anatolia, Q. vulcanica shares the deeply lobed leaves of that more familiar species, but the leaves have distinctly velvety-feeling pubescence on their lower surfaces. Although the sample is limited, Q. vulcanica may not always be so successful: at Chevithorne Barton a small and very slow-growing individual suffers badly from mildew, while at the Hillier Gardens another small specimen is attempting to reorganise itself after losing its top. At Arboretum Trompenburg it is doing well from a 1987 collection in Turkey (G. Fortgens, pers. comm. 2006); at Ettelbruck, where it is not affected by mildew, it grows slowly but steadily (E. Jablonski, pers. comm. 2006). Dirk Benoit at Pavia Nursery, Belgium has propagated a distinct clone with particularly deeply lobed leaves and named it ‘Kasnak’, after the region of Turkey where the species grows (Jablonski 2006).

Q. warburgii (NOW Q. ×warburgii A. Camus; Q. wislizeni A. DC. B521, K111

Quercus xalapensis Bonpl.

OR

Q. ‘Warburgii’) B520, S418, K111

(Subgen. Quercus, Sect. Lobatae)

Tree to 35 m, 0.7 m dbh. Branchlets dark brown with yellow tomentum, quickly glabrous, then black with conspicuous white lenticels. Leaves deciduous, 10–15 × 4–8 cm, ovate to lanceolate, immature leaves upper surface glossy, but with some stellate tomentum and rusty hairs on the midrib, lower surface with dense rusty stellate tomentum on the veins, spreading onto the lamina, mature leaves upper surface glabrous and somewhat glossy, lower surface shiny and largely glabrous, but with rusty tufts of hair in the vein axils, 6–10 secondary veins on each side of the midrib, margins serrate with five to seven shallow teeth, teeth often bristle-tipped and better developed towards the apex, apex acute; petiole 2–3 cm long and glabrous or minutely pubescent. Infructescence to 1 cm long with one to two cupules. Cupule hemispheric; scales loose, grey-green with a reddish apex, blunt and pubescent. Acorn round to ovoid, with half of its length enclosed in the cupule, silky, 2 cm long, stylopodium small. Flowering March to April (Mexico), fruiting in the following year. Trelease 1924. Distribution MEXICO: Hidalgo, San Luis Potosí, Tamaulipas, Veracruz. Habitat Between 1300 and 1800 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable, due to habitat degradation and loss.

This species is included here on the strength of a specimen at Kew identified by Jan De Langhe and David Gardner as Quercus aff. xalapensis, having originally been donated by James Russell as Q. polymorpha, collected under J. Russell 433 in Xalapa Botanic Garden in 1983. This tree is approximately 10 m tall, with a wide-spreading but open crown, producing long new shoots each year. It certainly fits the description of Q. xalapensis, a red oak (Q. polymorpha is a white oak), and its attractiveness suggests that it might usefully be sought again in Mexico, preferably from higher altitudes. Specimens from Xalapa Botanic Garden have always proved tender at the Hillier Gardens. The related species Q. skinneri Benth., from Nicaragua northwards to southern Mexico, does well at Tregrehan, producing attractively bronze-flushed new growth.

Plate 489. The handsome Quercus skinneri from Central America, here photographed at Tregrehan, is extremely rare in cultivation. Image J. Grimshaw.

760

Quillaja

New Trees

QUILLAJACEAE (formerly ROSACEAE)

QUILLAJA

Plates 490 (below, top), 491 (below). The flowers of Quillaja saponaria are followed by distinctive fruits composed of five follicles. Images R. Unwin.

Molina

Quillaja comprises three to four species in southern Brazil, Peru, Argentina and Chile, of which only Q. saponaria is in cultivation. They are evergreen trees or shrubs, with caducous stipules. The leaves are simple, alternate and spirally arranged; leathery, and with shallowly toothed margins. Inflorescences are terminal and axillary, paniculate and few-flowered. The flowers may be hermaphrodite or unisexual; they are 5-merous, with a fleshy, five-lobed nectary disc in the centre. The fruit is a leathery, dehiscent follicle; each flower produces five follicles, which are partially fused at the base. The numerous seeds are winged (Zardini 1973, Pennington et al. 2004).

Quillaja saponaria Molina

Quillay, Soap Tree

Tree to 15 m, dbh 1 m. Bark smooth, light brown. Branchlets pubescent. Leaves leathery, 2–4 × 1–2.5 cm, elliptic, glabrous, lustrous and yellowish green, margins entire or with small, irregular teeth, apex obtuse to acute; petiole to 0.2 cm long; stipules small and caducous. Inflorescences axillary with (one to) three to five flowers, or terminal with three flowers; the central flower is hermaphrodite, while the lateral flowers are staminate. Flowers 0.1–0.15 cm diameter; sepals broadly triangular, tomentose; petals white, spathulate, alternating with sepals; stamens 10 in two whorls; nectary disk yellowish green, conspicuous. Follicles ~1.3 × 0.5–0.6 cm, leathery and tomentose, dehiscent via two valves; the five follicles arranged in the form of a star. Flowering October to January (Chile); the dry fruits remain attached to the tree for a long time. Rodríguez R. et al. 1983. Distribution CHILE: Limarí Province to Bío-Bío Province. Habitat Occurs in a variety of habitats, both dry and humid, warm and cold. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT760, NT760.

Quillaja saponaria derives its specific name from the high content of saponins in its bark, traditionally a soap substitute but now also a component of fire extinguisher foam (Mabberley 1997a), and used as an expectorant (Chevallier 1996). It is not an outstandingly beautiful tree, forming a dense mass of dark, glossy green foliage, but the creamy white flowers are not unattractive and the persistent five-lobed fruits are interesting and ornamental. They resemble a Star Anise fruit (Illicium). The tree can grow as a single-stemmed specimen, or it may have several stiffly upright stems. There is a fine individual at Tregrehan, multistemmed in form, which exceeded 10 m after only 15 years. Johnson (2007) reports on several other trees in the United Kingdom, including a 6 m specimen in Dundee and one of 4 m in Essex, suggesting that it is not particularly tender. It is cultivated and is in commerce in the western United States. The freely produced seed is probably the best means of propagation. It seems to be tolerant of a range of soil conditions (Hillier & Coombes 2002).

Section II. Species Accounts

Rehderodendron

761

STYRACACEAE

REHDERODENDRON

Hu

The five recognised species of Rehderodendron are found in southwest China, Myanmar and Vietnam. They are deciduous or semi-evergreen trees, with winter buds enclosed in scales. The leaves are alternate with serrate or serrulate margins; stipules absent. Inflorescences are axillary, usually below the current leaves, and paniculate or racemose. Flowering occurs before or as the leaves emerge. The flowers are hermaphrodite and 5-merous; the calyx tubular, 5- to 10-ribbed, the corolla campanulate, divided almost to the base, and there are 10 stamens, five long and five short. The fruit is a woody, indehiscent capsule with 5–10 prominent ribs and a short beak; each fruit has one to three fleshy seeds (Hwang & Grimes 1996). Discussing Rehderodendron is difficult because its diversity is poorly understood, both in the wild and in horticulture. Enthusiasts in southern England and in western North America grow a range of accessions from China and Vietnam for which no precise identifications are as yet available, and which cannot therefore be discussed in any meaningful way! Determinations will require flowering and fruiting material. One of the exciting aspects of these ‘unknown’ species is that some are precocious-flowering, the floral display appearing before the leaves unfurl – offering the promise of a stunning spectacle when the trees mature. The only well-known Rehderodendron is R. macrocarpum, which makes a solid, wide-limbed tree whose masses of white flowers are succeeded by red, sausage-shaped fruits. It deserves the adjective ‘magnificent’ (as applied, for example, by Hillier & Coombes 2002), its only slight demerit being that the flowers appear with the foliage and are thus somewhat obscured. At the David C. Lam Asian Garden there are a number of plants derived from cuttings taken from seedlings of a Rehderodendron collected by Steve Hootman on the Daliang Shan, Sichuan in 1995, under his numbers SEH 98 and SEH 126. These have been grown under the label R. aff. macrocarpum and have made fine trees, currently up to 5–6 m high, each derived from different numbered individual seedlings. They are now flowering, and produce spectacular rose-coloured capsules. The flowers are smaller and fewer in number in the raceme than in familiar specimens of R. macrocarpum, but agree in their typical exserted stamens, and in flowering as the leaves develop. They almost certainly fall within the range of variation of R. macrocarpum, but may possibly equate to the concept of R. mapienense Hu, now sunk into R. macrocarpum. The specific epithet mapienense derives from Mabian, a region of southern Sichuan (P. Wharton, pers. comm. 2008). Styracaceae in general were great favourites of the late Peter Wharton’s, and his comments on Rehderodendron were among the last e-mails received from him in May 2008. He also wrote about

Plate 492. Steve Hootman’s collection of Rehderodendron from Sichuan produced fruits at the David C. Lam Asian Garden in Vancouver in 2006, but its identity is still in doubt. It may be R. macrocarpum, or another species (D. Justice, pers. comm. 2008). Image P. Wharton.

762

Rehderodendron

Plate 493. The foliage of the Vietnamese Rehderodendron kwangtungense is handsome in its own right. Image J. Grimshaw.

New Trees

R. indochinense H.L. Li: ‘We [the David C. Lam Asian Garden] have a young plant of this species derived from a collection made on the southwestern side of the main Fan Si Pan peak, near Sapa, northern Vietnam. This collection is derived from a large leaning riverside tree (23 m, 60 cm dbh) at 1480 m in a gorge of the Nam Bon river. The conspicuous red-brown barrel-shaped woody seed capsules are very distinctive, some reaching 10 × 5 cm. The impressive ovate-oblong leaves were also on average considerably larger (22 × 15 cm) than described in the Flora of China. The hardiness and the quality of the flowers of this species are at present unknown. I suspect [it] will thrive in regions with reasonable summer heat, moderate winters and ample ground moisture. The fall colour was quite a respectable clear yellow’ (pers. comm. 2008). It seems certain that any newly introduced Rehderodendron will require similar conditions to those enjoyed by R. macrocarpum, and most Styracaceae, namely a moist acidic soil and a warm, sheltered site. Propagation is by seed, which is formed only after cross-pollination, so it is important to plant groups of any collection; or by cuttings, though these need care to make a good specimen (Wharton et al. 2005). R. hui (NOW R. kwangtungense Chun, NT762) K113

Rehderodendron kwangtungense Chun Syn. R. hui Chun Tree to 15 m, 0.2 m dbh. Bark grey. Branchlets smooth. Leaves 7–16 × 3–8 cm, elliptic to oblong, both surfaces glabrous, or with some tomentum on veins, 7–11 secondary veins on each side of the midrib, margins remotely serrate, apex acute to acuminate; petiole 1–1.5 cm long. Inflorescences racemose, ~7 cm long with six to eight flowers. Calyx with dense grey-yellow pubescence, corolla lobes ovate, 2–2.5 cm long, slightly uneven. Capsule hard, woody, cylindrical, obovoid to ellipsoid, 4.5–8 cm long, 3- to 10-ribbed, smooth or slightly pubescent. Flowering March to April, fruiting July to September (China). Hwang & Grimes 1996. Distribution CHINA: Guangdong, Guangxi, Hunan, Yunnan. Habitat Dense forest between 100 and 1300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT762, NT762. Crossreference K113 (as R. hui). Taxonomic note Rehderodendron kwangtungense is similar to R. macrocarpum but differs in its precocious flowering and slightly larger corollas (to 1.8 cm long in R. macrocarpum), and in the stamens being equal to or shorter than the corolla (slightly longer in R. macrocarpum).

Plate 494. Rehderodendron kwangtungense in flower. Image J. Grimshaw.

Rehderodendron kwangtungense was described by Krüssmann (1986) as being the ‘most decorative species’ of the genus, but also as being not in cultivation. Unfortunately it has to be said that this may still be true, as a number of plants at Tregrehan thought to be this species turned out to be Halesia macgregorii when they flowered (T. Hudson, pers. comm. 2007). It is closely related to R. macrocarpum. Another tree at Tregrehan, originating in northern Vietnam, is now flowering, however, and appears to fit all the key characters of R. kwangtungense – although this species is not recorded from Vietnam by Hwang & Grimes (1996). There seems to be a very high level of diversity of Rehderodendron in northern Vietnam, with all the Chinese species except R. gongshanense Y.C. Tang being found in close proximity in a number of locations within the Hoang Lien Son mountains, and it is conceivable that other undescribed taxa could be present, in this region and in the neighbouring trans-border forests close to Yunnan (P. Wharton, pers. comm. 2008). R. macrocarpum Hu B523, S419, K113

Section II. Species Accounts

Rhus

763

ANACARDIACEAE

RHUS

L.

Sumacs The taxonomy of the genus Rhus is in disarray. At least seven segregate genera have been described, from the well-known and long-accepted Cotinus Mill. (Smoke-bush), to the less frequently adopted Toxicodendron Mill. (Poison-ivy). If accepted, these would reduce the number of species from about 200 (by which count Rhus is the largest genus in the Anacardiaceae) to just 35. However, allocation of species of Rhus into the segregate genera is confused. For example, R. lancea has been placed in both Toxicodendron and Searsia F.A. Barkley. In addition, because many new combinations have not yet been made, many Rhus species do not have valid names in the new, segregate genera (Barkley 1937, 1961, Brizicky 1963, Barkley 1965, Miller et al. 2001). Considering, then, the uncertainty as to the generic limits of Rhus, the following account utilises a broad concept of the genus. Rhus species are small to medium-sized, deciduous or evergreen trees, shrubs or climbers, with sap that may be poisonous (Toxicodendron) or not (Rhus). The branches are either numerous and slender, or of limited number, in which case they are thick, often pubescent and reminiscent of deer antlers. Winter buds are naked. The leaves are alternate, simple, trifoliate, or imparipinnate and then with a winged or terete rachis. Rhus is dioecious, though occasional bisexual flowers occur in the inflorescences. Inflorescences can be compact, terminal thyrses or lateral or terminal spikes. The individual flowers are unimpressive. The fruit is a red, slightly compressed drupe covered with glandular or mixed simple and glandular hairs, though in Toxicodendron the fruit is greenish white or yellowish white without glandular pubescence (Barkley 1937, Brizicky 1963, Ohwi 1965). Rhus is probably most familiar to gardeners in the form of the sumacs, R. typhina and its allies, while in the woods of North America the poison-ivies can add an element of hazard to the most innocuous walk, and render the genus notorious. Taken as a whole, however, Rhus provides many useful ornamental trees with bold pinnate leaves, some of which – such as R. chinensis and R. verniciflua – are reasonably well known in cultivation, though others – like R. wallichii, described below – are not. The name Rhus javanica regularly appears in horticulture, but the taxonomy associated with it is extremely confusing. The name was first published by Linnaeus, but his species has since been transferred into the genus Brucea J. Mill. (Simaroubaceae). The same name was also published by Thunberg for a species of Rhus that has now been placed in synonymy with R. chinensis Mill. (Chandra & Mukherjee 2000). The name ‘Rhus japonica’ was never validly published, but appears on some cultivated plants introduced into the United Kingdom that seem also to be referable to R. chinensis. The larger, tree-forming species should be given sites in good soil with plenty of sun, and will do best in areas with hot summers.

Plate 495. Rhus wallichii is one of a group of SinoHimalayan species of Rhus with large leaves. This is Bill McNamara’s collection M 0066 from Nepal, seen at Quarryhill. Image H. Higson.

764

Rhus

Plate 496. Rhus lancea is a very useful tree for hot, dry areas. The three long, narrow leaflets are distinctive. Image A. Coombes.

New Trees

Many species of Rhus are shrubby, including a large number of trifoliolate species in Africa, of which R. lancea is one of the largest. Several South African species are in cultivation and commercially available in the United Kingdom, though it is not known how well established they are. These include: R. glauca Thunb., a shrub up to 8 m, whose leaves start out a very glossy green, although the ‘varnish’ causing this dries out to a greyish powdery layer; R. incisa L. f., which is smaller, with pinnatifid leaflets that are white-woolly below; R. krebsiana C. Presl ex Engl., a shrub from the Drakensberg with unexceptional leaves; R. leptodictya Diels, which can reach 8 m, with elongated leaflets that have toothed margins (largely coming from the Highveld, it can withstand considerable frost: Coates Palgrave 1990); and R. magalismontana Sond., with broad leaflets (another shrub from the old Transvaal). All produce small yellowish green flowers in (usually) short panicles. Another species commercially available at present is R. integrifolia (Nutt.) Brewer & S. Watson, a chaparral shrub from southern California, where it is known as Lemonade Berry as the fruits are said to produce a lemonade-flavoured beverage if steeped in water. Although tolerant of dry conditions, it is frost-tender (Wikipedia 2008a). Rhus integrifolia, other Californian or Mexican species, and the South Africans mentioned above, should be given sunny, well-drained sites in mild areas if they are to have much chance of surviving. Quite different, and coming from damp forests, R. ambigua Lavallée ex Dippel is a climbing species from eastern Asia, that turns brilliant red in autumn (Crûg Farm Plants 2007–2008), but this should be regarded with caution as it appears to be an Asian poison-ivy, as its alternative name Toxicodendron orientale Greene suggests. None of the poison-ivies should be sold without a clear health warning, and care should be taken with any unfamiliar species of Rhus, as they may have inflammatory sap or allergenic pollen. Rhus can be rooted from cuttings, or grown from seed.

R. aromatica Aiton B943, K198 R. chinensis Mill. B944, K198 R. copallina L. B944, K198 R. coriaria L. B945, K198 R. coriaria f. humilior (NOW R. coriaria ‘Humilior’) B945 R. diversiloba Torr. & A. Gray B948, K198 R. glabra L. B946, K198

Rhus lancea L. f. Syn. Searsia lancea (L. f.) F.A. Barkley

Willow-leaved Sumac, Karee

Shrub or small tree to 8–12 m, trunk to 0.15 m dbh or larger in cultivation; branches somewhat pendent, as in a willow. Bark dark reddish brown with a sweet, spicy scent; breaking into a number of irregular plates with age. Densely branched; branches slender, glabrous and dull or shiny reddish brown, with prominent lenticels. Leaves evergreen, trifoliate, leaflets linear-lanceolate and sometimes falcate, 2.7–24 × 0.4–1.8 cm, the lateral leaflets usually shorter than the central leaflet; the leaves leathery, upper surface dark green, lower surface pale green, margins entire, apex acute to emarginate; midrib distinct; petiole distinct, 3–4 cm long and with flattened margins. Dioecious. Inflorescence a lateral or terminal panicle, to 11 cm long. Flowers yellow and sweetly scented. Fruit a slightly compressed drupe, 0.4–0.5 cm long, greenish white to brown

Section II. Species Accounts

Rhus

and brittle. Schonland 1930, Barkley 1961. Distribution BOTSWANA; NAMIBIA; SOUTH AFRICA; ZAMBIA; ZIMBABWE. Habitat Mixed savannas and bushveld, typically near permanent water sources. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Coates Palgrave 1990; NT764.

In the northern hemisphere Rhus lancea is the best known of the South African species, and with its narrow dark green leaflets on somewhat weeping branches has a very distinctive appearance. The bark is also attractive. In South Africa it is valued as a drought- and heat-tolerant, frost-hardy species and is recommended for barrier plantings and as a street tree (Stern 2002), and it seems to have been introduced to the southwestern United States for these same qualities of tolerance to adverse conditions. Jacobson (1996), in whose book North American Landscape Trees it is the only South African representative, records its date of introduction as c.1916. In the southwestern United States it is not only well established (and generally valued) as a landscape tree, but has become naturalised, and could pose a threat to natural ecosystems, especially desert washes. Its pollen is said to be allergenic (Arizona Board of Regents 2001–2006). It is also grown further north, into Oregon, but is hardy only down to –10 ºC (Jacobson 1996), although it can resprout from the base if the top is killed (Hogan 2008). It is rare in Europe. Cuttings taken by Allen Coombes at the JC Raulston Arboretum were introduced to the Hillier Gardens in 1992; these died out, but it has since been reintroduced there, and new plants are becoming established.

R. michauxii Sarg. B946, K199 R. orientale (Greene) C.K. Schneid. B949, K199 R. potaninii Maxim. B947, S477, K199 R. ×pulvinata Greene B946, K199 R. punjabensis Brandis B947 P. punjabensis var. sinica (Diels) Rehder & E.H. Wilson K199 R. radicans L. B947, K199 R. radicans var. rydbergii (Small) Rehder B948, K200

Rhus wallichii Hook. f.

R. succedanea L. B949, K200 R. sylvestris Siebold & Zucc. B952, K200 R. toxicodendron L. B949, K200 R. trichocarpa Miq. B949, K200 R. trilobata Torr. & A. Gray B944, K200 R. typhina L. B950, K200 R. typhina f. laciniata (NOW R. typhina ‘Dissecta’) B951 R. verniciflua Stokes B951, S477, K201 R. vernix L. B952, K201

Himalayan Sumac

Syn. Toxicodendron wallichii Kuntze Tree to 15 m. Branches sparse, robust, coated in ferruginous pubescence, ridged, with prominent leaf scars. Young stems and immature leaves densely tomentose. Leaves deciduous, 20–60 cm long, imparipinnate, leaflets 7–15, ovate-oblong, 2.7–24 × 0.4–1.8 cm, upper surface dark green, lower surface pale green and with ferruginous tomentum, margins entire, apex acuminate; rachis tomentose, without wings; petiole distinct, 8–20 cm long. Dioecious. Inflorescence an axillary or terminal panicle, densely tomentose, much shorter than the leaves. Flowers insignificant, dirty white. Fruit a globose drupe, 0.5–0.7 cm long, ferruginous, tomentose. Flowering and fruiting May to November (India). Chandra & Mukherjee 2000. Distribution INDIA: Himachal Pradesh, Uttar Pradesh, West Bengal; NEPAL. Habitat Montane forest, between 1950 and 2300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Chandra & Mukherjee 2000; NT3, NT763.

The only specimens of Rhus wallichii traced in our research are at Quarryhill, grown from seed collected by Bill McNamara in 1993 from small trees growing at 2035 m in Nepal (M 0066). When seen in 2004 they were 6–7 m tall, forming attractive multistemmed, open-crowned trees, bearing foliage only at the tips of the shoots. The

765

766

Rhus

New Trees

multistemmed habit may in part have been caused by their having frozen to the base when young, and resprouted (W. McNamara, pers. comm. 2004). The big pinnate leaves of R. wallichii are somewhat reminiscent of those of Juglans, but the leaflets are much larger than would be expected in a walnut; they emerge a strong red in colour. The inflorescences of many small dirty white flowers are dull, but the fruiting panicles are not unattractive.

SALICACEAE

SALIX

L.

Syn. Chosenia Nakai, Toisusu Kimura

Willows

Plate 497. Female catkins among the developing leaves of Salix amygdaloides. This is an extremely hardy and tolerant tree. Image D. Mullen.

The genus Salix comprises approximately 400 species and has an almost worldwide distribution (it is absent from Australia and Antarctica), though there is a greater diversity of species in the northern temperate zone. Salix species are dioecious woody plants; most are erect trees or shrubs, often with pendulous branches, although a significant minority are prostrate shrubs that occur beyond the treeline in the Arctic or in alpine areas. Terminal buds are usually absent; winter buds with one scale. The leaves are deciduous, alternate or rarely opposite, and remarkably variable. They range in size from 25 cm long (S. magnifica) to only 1 cm long (S. serpyllifolia); they may be thin or leathery, hairy or glabrous, with shapes ranging from lanceolate to circular. Considerable leaf variation occurs within species, and leaves of juvenile shoots are often completely different from those of mature branches. Hybridisation, which is extremely common in Salix, further extends the range of leaf variation. Stipules are present in most species. Inflorescences (catkins) are erect and are produced either before the leaves emerge (precocious), during leaf emergence (coetaneous) or afterwards (serotinous); floral bracts are entire. The flowers have no perianth, and one to two nectaries. The fruit is a two-valved capsule containing numerous seeds surrounded by hairs (Argus 1986, Newsholme 1992, Fang et al. 1999). Phylogenetic studies based on DNA have demonstrated that the genera Chosenia and Toisusu should be included in Salix (Azuma et al. 2000b). The vast array of willows provides trees and shrubs for all areas of the garden and arboretum, and some species are used in the production of a range of commercial items, from cricket bats to biomass fuel. Much horticultural interest focuses on those with coloured stems in winter, usually grown as coppice or pollards, or those with handsome male catkins in early spring, again often pruned to achieve vigorous new shoots with abundant inflorescences. As larger trees, willows are usually relegated to the damper

Section II. Species Accounts

Salix

edges of the arboretum, although they do not necessarily need particularly damp conditions. There is good coverage of Salix in Bean (1981b), but essential reading is Christopher Newsholme’s Willows: The Genus Salix (1992). Propagation is either by seed, sown as soon as it ripens, or by hardwood cuttings in winter. Although these are notoriously easy to root, best results are achieved by taking cuttings in autumn to enable good early callus formation; when growth resumes in spring, shoot and root growth is then in balance. S. acutifolia Willd. B268, K277 S. aegyptiaca L. B253, K278 S. alba L. B254, K278 S. alba f. argentea (NOW S. alba var. argentea Wimm.) B255 S. alba var. calva (NOW S. alba var. coerulea (Sm.) Koch) B255

Salix amygdaloides Andersson

S. alba var. vitellina (L.) Stokes B256 S. ×alopecuroides Tausch K279 S. alpina Scop. B288, K279 S. ×ambigua Ehrh. B297 S. amplexicaulis (Bory & Chaub.) C.K. Schneid. B294

Peach-leaf Willow

Shrub or tree 4–20 m, often with two to three trunks. Bark reddish brown, deeply furrowed. Branchlets slender, brittle, yellowish brown or grey; buds yellowish brown and glabrous. Leaves deciduous, 6–15 × 1.5–3 cm, ovate to lanceolate, upper surface largely glabrous, lower surface glabrous and thickly glaucous, 7–15 secondary veins on each side of the midrib, margins glandular-serrate, apex acuminate to caudate; petiole 0.7–2.1 cm long, yellowish, glabrous to tomentose; stipules minute, caducous, conspicuous and kidney-shaped on sprout shoots. Inflorescences coetaneous, borne on leafy axillary branchlets, though accompanying leaves deciduous after flowering. Staminate catkins 3.8–6 cm long, on branchlets 1–2 cm long, bracts tawny, stamens three to seven per flower. Pistillate catkins 2.5–9 cm long, on branchlets 0.4–3.5 cm long, flowers sparse. Capsule brown, ~0.3 cm long. Flowering April to May (USA). Argus 1986, Newsholme 1992. Distribution CANADA: Alberta, British Columbia, Manitoba, Ontario, Quebec, Saskatchewan; USA: Arizona, Colorado, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Texas, Utah, Washington, Wisconsin, Wyoming. Habitat Wetlands, including marshland and dune slacks, by rivers and lakes. USDA Hardiness Zone 3. Conservation status Not evaluated. Illustration Argus 1986, Newsholme 1992, Sternberg 2004; NT766. Cross-reference K279.

Salix amygdaloides can be a large, multistemmed tree or can be coppiced to maintain it as a large shrub. As a very hardy tree, at both extremes of temperature, it is a valuable landscaping species for much of west-central North America. It has a slightly pendulous habit, with yellow twigs, and the big glossy leaves have pale undersides – making it, as Sternberg (2004) says, attractive on windy days. It appreciates good conditions of soil and water abundance (Newsholme 1992), but will grow in hot situations in the deserts of the southwestern United States if groundwater is within reach (Sternberg 2004). The catkins are long, but being yellowish green are inconspicuous among the developing leaves. S. apoda Trautv. B277, K279 S. appendiculata Vill. B307, K280 S. arbuscula L. B256, K280 S. arbutifolia Pall. B258 S. arctica Pall. K280 S. arctica var. petraea Andersson B259 S. arenaria L. K280 S. atrocinerea Brot. K280

S. aurita L. B259, K280 S. babylonica L. B260, K280 S. ×balfourii E.F. Linton B281, K280 S. bebbiana Sarg. B308, K281 S. bicolor (NOW S. schraderiana Willd.) B292, K281 S. ×blanda Andersson K281 S. bockii Seem. B262, K281

767

768

Salix

New Trees

S. ×boydii E.F. Linton K281 S. breviserrata Flod. B288, K282 S. caesia Vill. B264, K282 S. ×calliantha J. Kerner B268, K282 S. ×calodendron Wimm. B306, K282 S. canariensis Buch B308 S. candida Fluegge ex Willd. B265, K283 S. caprea L. B265, K283 S. caprea var. coaetanea (NOW S. caprea var. sphacelata (Sm.) Wahlenb.) B266, S484 S. caspica Pall. K283 S. ×cernua E.F. Linton B277 S. cinerea L. B266, K283 S. cinerea subsp. oleifolia (Sm.) Macreight B267 S. cordata (NOW S. adenophylla Hook.) B267, K283 S. ×cottetii Lagger ex Kern. B300, K284 S. daphnoides Vill. B267, K284 S. daphnoides var. pomeranica (NOW S. daphnoides subsp. pomeranica K. Koch) B268, K284 S. ×dasyclados Wimm. B306, K284 S. decipiens Hoffm. B273 S. discolor Muhl. B269, K284 S. ×doniana Sm. B294, K284 S. ×ehrhartiana Sm. B286, K284 S. elaeagnos Scop. B270, K284 S. elbursensis Boiss. B295

Salix humboldtiana Willd.

S. elegantissima K. Koch K284 S. ×erdingeri J. Kerner B268, K285 S. eriocephala Michx. K285 S. ×erythroflexuosa Rag. K285 S. exigua Nutt. B270 S. fargesii Burkill B271, K285 S. ×finnmarchica Willd. B288, K285 S. foetida Schleicher ex Lam. B257, K285 S. fragilis L. B272, S484, K286 S. ×friesiana Andersson B298 S. furcata (NOW S. fruticulosa Andersson) B283 S. gilgiana Seem. B295 S. ×gillotii A. Camus & E.G. Camus K286 S. glabra Scop. B274, K286 S. glauca L. B274, K286 S. glauca var. acutifolia (Hook.) C.K. Schneid. K286 S. glaucosericea Flod. B274, K286 S. gooddingii Ball B289 S. gracilis Andersson K287 S. gracilistyla Miq. B275, K287 S. ×grahamii Borrer ex Baker B277, S484, K287 S. hastata L. B276, K287 S. hegetschweileri Heer B292, K288 S. helvetica Vill. B282, K288 S. herbacea L. B277, S484, K288 S. hibernica Rech. f. K288 S. hookeriana Barratt B278, K288

Chilean Willow

Syn. S. chilensis Molina Tree to 18 m, 0.2–0.8 m dbh; of upright, almost fastigiate habit, but when in leaf the crown becomes pendulous. Bark greyish, thick and deeply furrowed. Branchlets slender, ribbed and grey. Leaves deciduous, 3–10(–15) × 0.5–1.5 cm, linear-lanceolate, vivid green to silver and glabrous on both surfaces, lateral veins indistinct, margins serrate, apex acuminate; petiole 0.1–0.15 cm long, slightly pubescent; stipules absent, or small and caducous. Inflorescences coetaneous, pendulous, borne on leafy axillary branchlets 5–7 cm long. Staminate catkins 3–10 × 0.6–1 cm, bracts tawny, stamens five to eight per flower. Pistillate catkins shorter. Capsule brown, 0.4–0.5 cm long. Flowering September to November, fruiting October to December (Chile). Rodríguez R. et al. 1983, Newsholme 1992. Distribution ARGENTINA; BOLIVIA; BRAZIL; CHILE; COLOMBIA; COSTA RICA; ECUADOR; EL SALVADOR; GUATEMALA; HONDURAS; MEXICO; NICARAGUA; PANAMA; PERU. Naturalised across the Caribbean and in Australia. Habitat Wetlands by rivers, lakes and estuaries, between 0 and 600 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Rodríguez R. et al. 1983; NT769. Taxonomic note Newsholme (1992) maintains S. chilensis as distinct from S. humboldtiana, though he suggests that it may be a hybrid, with S. humboldtiana and the European S. alba (introduced into Argentina in the early-twentieth century) as the parents.

Section II. Species Accounts

Salix

769

1 cm

A 1 cm

B

1 cm

C

Salix humboldtiana is bluntly described by Newsholme (1992) as ‘rather coarse, without any special ornamental quality’, and he says that it is very susceptible to frost. It is regarded as an invasive weed in Australia and in parts of the Caribbean (Global Compendium of Weeds 2007). With all this encouragement it is improbable that it would be widely planted even if material became available. It is however well established at Benmore, from a collection made in Chile (Región X) in 1997 by M. Gardner and A. Newton (no. 46). The denigrated Australian weed is apparently principally a fastigiate male clone, ‘Pyramidalis’, spreading vegetatively (Weeds Australia 2008).

Figure 86 (above). Salix humboldtiana: habit (A); inflorescence (B); capsules opening to release seeds (C).

770

Salix

Plate 498. Salix scouleriana, growing in Washington State. The broad, glossy leaves give it horticultural appeal. Image D. Brastow.

New Trees

S. humilis Marshall B269, K288 S. hylematica C.K. Schneid. K289 S. integra Thunb. B295, S485, K289 S. interior Rowlee B271, K289 S. irrorata Andersson B279, K289 S. japonica Thunb. B279, K289 S. jessoensis Seem. B280, K289 S. kangensis Nakai B269 S. kinuyanagi Kimura B311, K289 S. kitaibeliana Willd. K289 S. koreensis Andersson B280 S. koriyanagi Kimura B295, K289 S. laggeri Wimm. K289 S. lanata L. B281, K289 S. lanata × S. repens B282 S. ×lanceolata Sm. K290 S. lapponum L. B282, K290

S. lapponum var. daphneola Tausch K290 S. lasiandra Benth. B283, K290 S. lasiolepis Benth. B279, K290 S. ×laurina Sm. K291 S. lindleyana Andersson B283, K291 S. lucida Muhl. B284, K291 S. lutea (NOW S. rigida Muhl. var. mackenziana (Raup.) Cronq.) B300 S. mackenziana (NOW S. rigida Muhl. var. mackenziana (Raup.) Cronq.) B300 S. magnifica Hemsl. B284, K291 S. matsudana Koidz. B284, K291 S. medwedewii Makino K291 S. melanostachys Makino K291 S. ×meyeriana Rostk. B286, K291 S. microstachya Turcz. ex Trautv. B312, K291 S. mielichoferi Sauter B290, K291 S. missouriensis Bebb B300 S. miyabeana Seem. B295, K291 S. ×mollissima Ehrh. B286, S485, K292 S. ×moorei F.B. White K292 S. moupinensis Franch. B287, K292 S. myrsinites L. B287, K292 S. myrtilloides L. B288, K292 S. nakamurana var. yezoalpina (Koidz.) Kimura B288 S. nigra Marshall B289, K293 S. nigra var. falcata (Pursh) Rehder K293 S. nigricans (NOW S. myrsinifolia Salisb.) B289, S485, K293 S. nipponica Franch. & Sav. B310 S. nivalis Hook. K293 S. ×ovata Ser. S484 S. oxica Dode K293 S. pedicellata Desf. B308, K293 S. pentandra L. B290, K294 S. petiolaris Sm. B291, K294 S. petrophila Rydb. K294 S. phylicifolia L. B292, S485, K294 S. planifolia Pursh B292 S. polaris Wahlenb. B278, K294 S. ×pontederana Willd. B294, K294 S. pulchra (NOW S. daphnoides Vill. ‘Pulchra’) B292, K294

Section II. Species Accounts

S. purpurea L. B293, K294 S. purpurea subsp. amplexicaulis (Bory & Chaub.) C.K. Schneid. K295 S. purpurea f. gracilis (NOW S. purpurea var. gracilis C.K. Schneid.) B293 S. purpurea subsp. lambertiana Sm. K295 S. purpurea var. lambertiana (NOW S. purpurea subsp. lambertiana Sm.) B293 S. purpurea var. sericea (Ser.) K. Koch K295 S. pyrenaica Gouan B295, K295 S. pyrifolia Andersson B296, K295 S. pyrolifolia Ledeb. K295 S. rehderiana C.K. Schneid. B302, K296 S. ×reichardtii A. Kern. B266 S. reinii Franch. & Sav. ex Seem. B274

Salix scouleriana Barratt ex Hook.

Salix

771

S. repens L. B296, K296 S. repens subsp. argentea (NOW S. arenaria L.) B297 S. repens var. fusca (L.) Wimm. & Grab. B297, S486 S. reptans Rupr. K296 S. reticulata L. B298, K296 S. retusa L. B299, K296 S. rigida Muhl. B300 S. rosmarinifolia L. B297, K297 S. rotundifolia Trautv. K297 S. ×rubens Schrank B272, K297 S. ×rubra Huds. B301, K297 S. sachalinensis Fr. Schmidt B302, K297 S. ×sadleri Syme B278 S. safsaf Forsk. K297 S. ×salamonii Carrière K297 S. salviifolia Brot. K297 S. saximontana Rydb. K297 S. schwerinii E. Wolf B311

Nuttall Willow, Scouler’s Willow

Shrub or tree 3–18 m, though usually under 10 m. Branchlets brown, pubescent to glabrous. Leaves deciduous, 3–8 × 2–3 cm, elliptic to obovate, immature leaves covered with silky hairs, mature leaves with upper surface glossy and glabrous, lower surface glaucous and densely tomentose, margins entire, glandular (rarely serrate), apex acute to rounded; petiole 0.5–1.5 cm long, reddish brown, velvety; stipules tiny. Inflorescences precocious, borne on leafy axillary branchlets. Staminate catkins 1.5–4 cm long, bracts tawny, stamens two per flower. Pistillate catkins 1.5–5 cm long, flowers sparse. Capsule 0.5–1 cm long, covered in silky hairs. Newsholme 1992. Distribution CANADA: Alberta, British Columbia, Manitoba, Saskatchewan, Yukon; MEXICO: Coahuila, Sonora; USA: Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, Wyoming. Habitat From dry forest and meadows to wet forest and swamps, between 90 and 3400 m asl. USDA Hardiness Zone 3. Conservation status Not evaluated. Illustration Newsholme 1992; NT770, NT771.

Any tree that occurs from Alaska to Mexico must have application as a landscaping species, and it is valued as such in the western half of North America: an exceptionally hardy and tough tree. Its horticultural value is enhanced by the reddish twigs and a good display of male catkins in spring, followed by attractive glossy leaves with glaucous undersides (Newsholme 1992, Sternberg 2004). It accepts most soil types, and is capable of tolerating some shade in woodland conditions (Sternberg 2004).

S. ×sepulcralis Simonk. B303, S486, K298 S. ×sericans Tausch ex Kern. B305 S. sericea Marshall B307, K298

S. ×seringeana Gaud. B270 S. serpyllifolia Scop. B299, K298 S. silesiaca Willd. B307, K298 S. ×simulatrix F.B. White B278, K298

Plate 499. The leaves of Salix scouleriana have reddish hairs on their undersides. Image D. Brastow.

772

Salix

New Trees

S. sitchensis Bong. K298 S. ×smithiana Willd. S486, K298 S. starkeana Willd. B308, K299 S. ×stipularis Sm. K299 S. ×subalpina Forbes B309 S. subopposita (NOW S. repens L. var. subopposita (Miq.) Seem.) B298, K299 S. syrticola Fernald K299 S. ×tetrapla Walker ex Sm. B290, K299 S. triandra L. B309, K299 S. triandra var. hoffmanniana (Sm.) Bab. B309 S. tristis (NOW S. occidentalis Walt.) B269, S484

S. ×tsugaluensis Koidz. B295, K299 S. udensis Trautv. & C.A. Mey. B302 S. urbaniana Seem. B258 S. uva-ursi Pursh B310, K299 S. variegata Franch. B262 S. vestita Pursh K299 S. viminalis L. B310, K299 S. vulpina Andersson B308 S. waldsteiniana (NOW S. arbuscula L. var. erecta Andersson) B258, K300 S. wilhelmsiana Bieb. B312, K300 S. ×wimmeriana Gren. & Godr. B294, K300 S. xerophila Flod. K300 S. yezoalpina Koidz. K300

LAURACEAE

SASSAFRAS

J. Presl

There are three species of Sassafras: S. albidum (from eastern North America), S. tzumu (China) and S. randaiense (Taiwan). All are very similar, and Flanagan’s comment that the best character by which to distinguish them is their country of origin is not inappropriate, although he also provides a key (Flanagan 1998). They are large or medium-sized deciduous trees, which flower in spring as the leaves emerge. Terminal buds are large and covered in silky hairs. The leaves are alternate, papery, and fragrant when crushed; they may be entire (then pinninerved) or two- to three-lobed (then triplinerved). The genus is dioecious, though hermaphrodite flowers occur in S. tzumu. Inflorescences are lax, pendulous terminal racemes with deciduous bracts at the base. The flowers are usually fragrant and have a yellow perianth tube with six lobes. Staminate flowers have nine fertile stamens in three whorls inserted on the throat of the perianth tube; an additional whorl of staminodes is also present in the Asian species. Pistillate flowers have six staminodes (in two whorls) or twelve staminodes (in four whorls). The fruit is a dark blue, ovoid drupe with a shallow cupule at the base (Rohwer 1993a, Liao 1996b, van der Werff 1997, Flanagan 1998, Li et al. 2005). Sassafras albidum has long been a valuable commodity for the aromatic compounds it contains, used in the manufacture of a range of pharmaceutical and edible products, including the curious beverage sold in North America as root beer. Most such uses are now prohibited as it has been found that the active component, safrole, is a potential carcinogen; it is also an ingredient in the manufacture of the psychoactive drug ‘Ecstasy’ (and others) (Wikipedia 2009). These aromatic properties quickly brought S. albidum to the attention of early colonists in North America, and Bean (1981b) states that it was introduced to Britain in the 1630s. It remains a reasonably familiar species in cultivation, but in cool maritime climates seldom achieves great size. It is noted for

Section II. Species Accounts

Sassafras

773

its flamboyant autumn colours, but the curiously shaped leaves are of interest at all times. The same characters are also to be found in the Asian species. Sassafras tzumu was briefly described by Bean (1981b) and was apparently introduced by E.H. Wilson, but its persistence in cultivation was tenuous. For many years the only known individual was a fine old tree attributed to the species at Wakehurst Place, but this blew down in 1987, and as recently as 1998 Mark Flanagan could find no other reference to S. tzumu in cultivation. In the past few years, however, it has become quite widely cultivated, and can now be seen in many collections in our area. Seed obtained from a commercial source in 1990 has resulted in quite large bushy trees at Tregrehan that are very attractive, but most individuals in cultivation are still small. The young foliage flushes pinkish bronze and turns red in autumn. The species seems to be as hardy as S. albidum. All Sassafras require fertile, acidic or neutral soil and will perform best in warm gardens. Propagation is usually easy from root cuttings (though apparently not so for S. randaiense – see below); or naturally produced root suckers can be detached. S. albidum (Nutt.) Nees B334, S489, K309 S. albidum var. molle (Raf.) Fernald B334, K309

Sassafras randaiense (H. Lév.) Yang Tree to 12 m or more, and 0.7 m dbh. Branchlets robust, glabrous, reddish brown with lenticels and prominent leaf scars. Leaves deciduous, alternate, 10–15(–16) × 3–6(–7.5) cm, rhombic to ovate, entire or with two to three lobes (lobed leaves only on infertile branchlets), upper surface green and glabrous, lower surface glaucous and glabrous, midrib prominent on both surfaces, seven to eight secondary veins on each side of the midrib, apex acute; petiole 3–5 cm long. Inflorescences terminal or subterminal, racemose and ~3 cm long. Flowers unisexual; staminate flowers with a short (~0.4 cm long), six-lobed perianth tube that is pubescent inside, nine fertile stamens in three whorls. Fruit globose, ~0.6 cm diameter, with a shallow cupule. Flowering February, fruiting October (Taiwan). Liao 1996b, Flanagan 1998, Li et al. 2005. Distribution TAIWAN. Habitat Evergreen broadleaved forest, between 900 and 2400 m asl. USDA Hardiness Zone 9. Conservation status Vulnerable, due to habitat loss, and suffers from poor regeneration due to seed predation. Illustration NT773.

Sassafras randaiense has a very limited existence in cultivation, following its introduction from Taiwan by Mark Flanagan and Tony Kirkham in 1992. As recounted in their book (Flanagan & Kirkham 2005), they found the species growing as an understorey to Taiwania cryptomerioides near Chilan Shan, Taiwan, but the trees were not fruiting. The seed they brought home was a gift from the Taipei Botanic Garden and the Taiwan Forestry Research Institute. Resulting seedlings were distributed to mild gardens in the British Isles, including Mount Usher (where it now thrives: M. Flanagan, pers. comm. 2007), as well as being planted in the Evolution House at Kew and outside at Wakehurst Place (where it did not survive). The only outdoor specimens seen in our research are at Tregrehan, and these have rocketed up as single-stemmed, very straight trees, reaching 8 m when seen in 2005. The foliage is less lobed than might be expected in Sassafras, being more deltoid

Plate 500. Foliage of Sassafras randaiense in the Evolution House at Kew. This fast-growing tree from Taiwan is evidently not very hardy, surviving outdoors only in the mildest gardens. Image J. Grimshaw.

774

Sassafras

New Trees

in outline, but it has an attractive spring flush and good autumn colours of yellow and reddish orange, and when seen against a dark background the pale yellow-green flowers are quite conspicuous (T. Hudson, pers. comms. 2005, 2007). The bark remains green for several years before becoming corky from the base upwards. A tree in the greenhouse at the Savill Garden, Windsor grew up to 10 m very fast but was impossible to propagate (including by root cuttings), and had to be removed (M. Flanagan, pers. comm. 2007). S. tzumu (Hemsl.) Hemsl. B334, K309

ARALIACEAE

SCHEFFLERA

J.R. Forst. & G. Forst.

Umbrella Trees

Plate 501. Schefflera rhododendrifolia has proven itself hardy outdoors in the British climate. This is Edward Needham’s specimen in his sheltered Cornish garden, but it also thrives in Scotland. Image R. Lancaster.

The World Checklist of Araliaceae (Frodin et al. 2003) lists 582 species of Schefflera, and many new species are still to be described. The genus occurs in all of the tropical and subtropical regions of the world, but it is less well represented in Africa. Schefflera are usually small trees or shrubs, though woody climbers and perennial herbs are known. They are evergreen, unarmed and hermaphrodite, or with both male and hermaphrodite flowers on the same plant. The leaves are palmately compound (rarely unifoliolate) and the leaflets are entire to serrate; stipules are united with the petiole. Flowers are arranged in umbels, heads or racemes, which in turn are arranged in panicles or compound racemes; the inflorescences bear deciduous or persistent bracts. The flowers are pedicellate (pedicel not articulated below flower), with an entire or five-toothed calyx, 5–11 valvate petals and 5–11 stamens. The fruit is a globose or ovoid drupe, with (4–)5–11 seeds (Ohashi 1993c, Xiang & Lowry 2006). The genus has been shown to be polyphyletic by several studies, and should be restricted to species from the southwestern Pacific area. The Asian species form a distinct clade, however, so should bear the same generic name, once the appropriate revisions have been made (see Xiang & Lowry 2006). Only a few years ago the idea of a hardy Schefflera would have been considered almost absurd – The New RHS Dictionary of Gardening (Huxley et al. 1992) advising that ‘In colder areas they may be cultivated in the intermediate to hot glasshouse …’ Less than two decades later though, they are ‘must-have’ plants, without which, apparently, no garden is complete. Some are, indeed, making a genuine impact, and the enthusiasm of the moment will no doubt lead to the testing of a wide range of possibilities, from which survivors will emerge. Hardy scheffleras were pioneered by introductions of the late Edward Needham some 20 years ago, in whose sheltered Cornish garden S. delavayi, S. rhododendrifolia and S. taiwaniana have formed impressive specimens, admired by many. Cuttings from

Section II. Species Accounts

them were gently passed around the horticultural community, and these clones have now entered commerce. In consequence these three species have become the best known and are the most tested; all have proved to be reliably hardy in many parts of the British Isles, and can therefore be expected to grow successfully in coastal western Europe and the Pacific Northwest. More recently, the potential of the genus has been most extensively explored by Bleddyn and Sue Wynn-Jones of Crûg Farm Plants in Gwynedd. Perceiving the possibilities, they have made Schefflera a priority on their collecting trips, and it is no coincidence that in the RHS Plant Finder 2008–2009, of 29 entries for taxa available in British nurseries (some of which are indubitably tender species for indoor cultivation), 18 are offered exclusively by Crûg Farm. The genus has been less readily available in North America, although numerous species are now in cultivation there. The ease with which they are grown from seed and cuttings is likely to ensure that they continue to be distributed widely. With their exceptionally handsome palmate to digitate leaves, and distinctive outlines, it is no wonder that Schefflera species have caught the imagination of the gardening public as well as garden designers, bringing new shapes and forms into horticulture. Although they are grown principally as foliage plants, their inflorescences can also be quite ornamental. The individually small flowers are succeeded by round fruits that are usually blackish purple like those of their relatives Hedera L. and Fatsia Decne & Planch., but can occur in a variety of colours (Wynn-Jones 2005). When ripe these are both decorative and monetarily valuable. In the wild, many if not most species of Schefflera are pioneers, colonising open, disturbed places and forming the best-looking plants in such sites. Examples seen in forest conditions are usually drawn and scrawny (B. Wynn-Jones, pers. comm. 2008). In consequence they should not be considered to be shade plants, and even in the woodland garden should be given a sunny site – though where sunlight is very intense (as in the Pacific Northwest) some high light shade may be appropriate. Ample moisture is necessary for success, however, and it is important not to be tempted into planting them in a hot sunny place that may become dry; all Schefflera come from moist areas. A sheltered warm site with good soil and water supplies is optimal. Poor drainage must be avoided, and they do not like clay soils (B. Wynn-Jones, pers. comm. 2008). It is probably wise to grow young plants in pots for a couple of years before planting out, to ensure that they have a woody base from which regrowth could occur should they be badly frosted, and to protect them against cold winds and heavy frost when young. Wind at any time is damaging, to the large-leaved species especially, so these should be sited in sheltered places. Late frost can be a danger to new shoots – but this problem is not exclusive to Schefflera. It is important to bear in mind that few of these species have been really comprehensively tested in gardens, and their true tolerances will only become apparent in future years. In the United States, at least, Strawberry Root Weevil (Otiorhynchus ovatus) is damaging to the foliage of Schefflera (D. Hinkley, pers. comm. 2008), and it is possible that other Otiorhynchus weevils could be a nuisance elsewhere. A selection of reasonably well-tested Asian species are described in full below, but there are many other species worthy of consideration and investigation, either

Schefflera

775

Plate 502. The inflorescences and the fruiting panicles of Schefflera can be spectacular, erupting from the centre of the shoot. This is Schefflera delavayi. Image R. Maurer.

776

Schefflera

New Trees

currently in cultivation, or as yet un-introduced, from high altitudes in mountains across the tropics and subtropics. Northern Vietnam, especially Fan Si Pan and its surroundings, has been a particularly rich source of material for the Wynn-Joneses, but some introductions have as yet been only tentatively identified and will probably not be confirmed until they flower. Among these are several taxa that seem to form a closely related group, whose identities are by no means certain. These include S. aff. brevipedicellata HWJ 1870, a shrubby species to 2 m; and S. aff. enneaphylla HWJ 1018, a shrub to 3 m in the wild, and notable for its extra false-whorl of leaflets overlapping the primary leaflets, giving a multilayered effect. Young plants of the latter have not proven very vigorous in pots under cover at Colesbourne, Gloucestershire, and emerging leaves were burnt during hot weather in May 2008. An expedition in 2000 led to the collection of another of this group, identified as S. fantsipanensis Bui BSWJ 8228, which has been written up (Wynn-Jones 2005) under the name S. hoi (Dunn) R. Vig. var. fantsipanensis (Bui) C.B. Shang. This forms a single-stemmed small tree to 5 m, on open slopes as well as in forest, from about 2000–2400 m asl, and has survived for several years at Crûg Farm. Another taxon with an extra ring of leaflets, collected in 1999 as HWJ 622, has been identified as S. gracilis (Miq.) R. Vig., but the World Checklist of Araliaceae restricts this name to a climbing species from Borneo. On Fan Si Pan this plant occurred only up to 2200 m but it has tolerated –11 ºC at Crûg Farm, and has survived outside for several winters there (Wynn-Jones 2005). In Dan Hinkley’s garden near Seattle the same taxon has flowered and fruited in its second year, when only 45 cm high; the effect is quite ornamental, but does not bode well for the development of a good plant (D. Hinkley, pers. comm. 2008). In the wild it is a low shrub to 1.5 m. Also found in the Fan Si Pan area is a different group of scheffleras, related to S. alpina (see below), and the Wynn-Joneses have seen other species on the mountain as well, seed of which they have not yet been able to obtain (B. Wynn-Jones, pers. comm. 2008). From southern Vietnam comes S. aff. lenticellata BSWJ 9762 (introduced in 2003), a robust shrub or small tree with heavily lenticellate green stems. (Much of the information for this paragraph derives from the Crûg Farm Plants online database (2007–2008) or personal communications with Bleddyn Wynn-Jones.) The milder the garden, the wider the range of options in Schefflera, as several species tolerate cold temperatures but only a few degrees of frost. These include S. arboricola (Hayata) Merr. from Hainan and Taiwan (frequently grown as a long-suffering houseplant, often in the form of variegated cultivars), and the Philippine cloud-forest semi-climbing shrub S. microphylla Merr. These are severely damaged at only –5 ºC (Wynn-Jones 2005). The New Zealand S. digitata J.R. Forst & G. Forst. is also not very hardy, but in practically frost-free situations can develop into a fine specimen; the largest recorded in the British Isles was 15 m tall, measured at Ashbourne House Hotel, Co. Cork in 1987, and there is a 9 m tree at Tresco Abbey on the Isles of Scilly (Johnson 2007). A very beautiful plant of S. bodinieri (H. Lév.) Rehder from Guizhou, with long narrow leaflets, grows in the Temperate House at Kew, and enthusiasts are itching to try it outside. No doubt further introductions will appear, but it should be noted that identification can be difficult – inadequate descriptions supplementing the problems associated with variability and the occurrence in some species of distinct juvenile and adult foliage. The ease with which Schefflera can be propagated is very helpful in building up a stock with which to experiment. Cuttings root very readily but suitable material, especially of the larger species, can be sparse and difficult to manage: for the brave,

Section II. Species Accounts

however, one possibility is to decapitate the main stem and take cuttings from the axillary shoots that develop. Seed is generally an easier option, if it is available. Connected only by its family relationship and its initial S, Sinopanax is a monospecific genus comprising S. formosanus (Hayata) H.L. Li, found in Taiwan. This has handsome firm-textured greygreen leaves that are wedge-shaped or rounded in outline, with three to five toothed lobes. It is in cultivation in both the United Kingdom and the United States, in the mild western extremities of each, as might be expected, but needs to be tested further afield. It is hardy at Crûg Farm, but both cutting material and seed are sparse and this has delayed its commercial introduction (B. Wynn-Jones, pers. comm. 2008). Although usually a shrub, 3–4 m tall and broad, it can form a tree to 12 m (Xiang & Lowry 2006). Trevesia palmata (Roxb. ex Lindl.) Vis., known as the Snowflake Tree on account of the regular pattern of its pinnatisect leaflets, is more closely related to Schefflera, and is a magnificent foliage plant – exceptional even within the Araliaceae. From within its huge range, from India through southern China to Vietnam, high-altitude provenances should be sought: a hardy version would be an unparalleled coup for its collector. It is currently rated Zone 10 (Huxley et al. 1992) and is grown outdoors in California and the Mediterranean, as well as under glass in botanic gardens. It would certainly be worth attempting in the mildest parts of our area, but other species from higher altitudes may be more promising (B. Wynn-Jones, pers. comm. 2008).

Schefflera alpina Grushv. & Skvortsova Shrub or tree to 5 m. Leaves evergreen, palmate; leaflets seven to nine, leathery, 8.5–12 × 3.5–4.5 cm, elliptic, upper surface dark green, glabrous, lower surface pale green, somewhat pilose, 10–11 pairs of secondary veins on each side of the midrib, margins entire, revolute, apex acuminate; new growth purple; petiole 25–30 cm long, red. Inflorescences lateral, paniculate, primary axis ~20 cm long; composed of ~10 umbels, each with 10–15 flowers; bracts 4.5 cm long, leathery. Drupe globose to pentagonal, ~0.4 cm diameter, purple, with a persistent style. Grushvitsky & Skvortsova 1975. Distribution VIETNAM. Habitat Montane forest, between 2700 and 2800 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated.

Schefflera alpina has been collected on several occasions from 2000 onwards by varying combinations of the Wynn-Joneses and Dan Hinkley (for example, HWJ 585, HWJ 936, HWJ 31018, BSWJ 8247), from a single specimen located in the upper parts of Fan Si Pan. It is an attractive, rather dainty species, with smallish leaflets that flush a dramatic purplish red and become dark green. Although ‘alpina’ may be a slight exaggeration it is a high-altitude plant, found above 2400 m, and reported to be capable of withstanding –15 ºC (Crûg Farm Plants online database 2007–2008), but Dan Hinkley (pers. comm. 2008) has found that it is apt to produce new growth in autumn that is at risk from frost. Making up another small group are taxa related to S. alpina, including material currently known as S. aff. chapana HWJ 983 that forms a small tree to 7 m in the wild and similarly retains dark purple hues in the new growth. This has also been labelled S. aff. kornasii HWJ 918. From the same area again, around Fan Si Pan, in exposed sites at high altitude, another taxon (currently identified as S. aff. alpina) grows usually as a single-stemmed plant with thick leaves (B. Wynn-Jones, pers. comm. 2008).

Schefflera

777

Plate 503. Sinopanax formosanus is another highly desirable member of the Araliaceae, and grows well in conditions that suit Schefflera. Image J. Grimshaw.

778

Schefflera

New Trees

Schefflera delavayi (Franch.) Harms Tree to 8 m. Leaves evergreen, palmate; leaflets four to seven, papery to leathery, (8–)30–35 × 3–12 cm, elliptic to oblong or lanceolate, upper surface dark green, glabrous, lower surface greyish white or yellowish brown, tomentose, 7–13 pairs of secondary veins on each side of the midrib, margins entire to irregularly dentate (usually pinnately lobed in young plants), apex abruptly acute to acuminate; petiole (10–)15–60 cm long, green. Inflorescences terminal, paniculate, primary axis to 25–80 cm long, greyish white-tomentose; composed of numerous spikes, each to 30 cm long. Flowers small, sessile; calyx five-toothed, tomentose. Drupe globose, 0.3–0.5 cm diameter, with a persistent style. Flowering October to November, fruiting January (China). Xiang & Lowry 2006. Distribution CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Yunnan; VIETNAM. Habitat Evergreen broadleaved forest, between 600 and 3000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT775, NT778.

Plate 504. Schefflera delavayi has become well and widely established in horticulture in the past couple of decades, valued for its dark green foliage on broad, rounded plants. Image R. Maurer.

Schefflera delavayi is one of the species first introduced by Edward Needham from his travels in China, and at his home and in other Cornish gardens it has made substantial, broad, bushy trees (up to 4 m tall by 8 m wide at Tregrehan, for example: Johnson 2007). Later introductions, often from commercial seed collections (S. Hogan, pers. comm. 2008), have spread it more widely in commerce on both sides of the Atlantic, and it looks set to become an important component of milder gardens. With its dark green foliage and long white inflorescences it is quite distinctive. In coastal Washington it grows well but has a tendency to produce an autumn flush of leaves that often gets frosted (D. Hinkley, pers. comm. 2008). In Scotland, a species that may be S. delavayi has done very well and is hardy even in inland Stirlingshire (Hutchinson 2005). In international trade S. delavayi has regrettably become confused with another species that has huge, deeply pinnatisect mature leaves – a quite magnificent plant, but not S. delavayi, in which only juvenile leaves show any sign of deep lobing. Unfortunately this plant appears with some frequency in internet searches for Schefflera delavayi (for example, Nature Products 2000–2008). Whatever it is, it would be worth cultivating! Neither should S. delavayi be confused with Metapanax delavayi (Franch.) J. Wen & Frodin, a species that has wandered between a diversity of genera – Panax, Nothopanax, Acanthopanax, Pseudopanax, Macropanax – before coming finally (one hopes) to rest in the recently described Metapanax (not covered by Flora of China). Metapanax delavayi is a very attractive bushy shrub or small tree with dark green leaves composed of three to five forward-pointing leaflets, resembling a very finely textured Schefflera. In Washington it has proven absolutely hardy since 1996, when Dan Hinkley collected it above Lijiang in Yunnan; he regards it as ‘one of the best evergreen shrubs to come out of China in a long time’ (D. Hinkley, pers. comm. 2008). It is fully hardy in the Pacific Northwest and also in the southeastern United States, from North Carolina southwards (Wharton et al. 2005). The other species in this genus, M. davidii (Franch.) J. Wen & Frodin, is also in cultivation (Heronswood Nursery catalogues 2004, 2005), and in the United States performs in much the same way as M. delavayi, forming a rounded bush, although it is potentially a small tree. Its leaves are simple or have three leaflets.

Schefflera macrophylla (Dunn) R. Vig. Tree to 20 m. Leaves evergreen, palmate; leaflets five to seven, leathery, 20–55 × 8–22(–20) cm, ovate-elliptic, upper surface dark green, becoming glabrous, lower surface densely covered in white or russet indumentum, which also covers the petioles and upper leaf surfaces when young, 8–12 pairs of secondary veins on each

Section II. Species Accounts

Schefflera

779

side of the midrib, margins entire or with inconspicuous teeth, apex acuminate; petiole 45–100 cm long, purple. Inflorescences terminal, paniculate, primary axis to 75 cm long, secondary axes to 40 cm, densely covered in reddish brown stellate hairs; composed of numerous umbels. Flowers small, pedicellate; calyx entire or inconspicuously five-toothed, with dense reddish stellate hairs. Merrill 1924, Xiang & Lowry 2006. Distribution CHINA: southeast Yunnan; VIETNAM. Habitat Montane forest, especially in valleys, between 1900 and 2600 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT779.

‘Dramatic’ is perhaps the best adjective for Schefflera macrophylla, with its long petioles supporting a broadly spreading ‘hand’ of leaflets, and all the new growth and leaf undersides covered in russet or ginger hairs: it inspires lust. It is a spectacular sight in the garden, even as a young plant, or as a mature tree in the mountains of Vietnam. In the forest it becomes a spindly unbranched and non-flowering tree, to 20 m, but in exposed situations it is more compact and floriferous (B. Wynn-Jones, pers. comm. 2008). It was first introduced in 1998 by Tom and Jo Hudson (T. Hudson, pers. comm. 2008), and has been growing well at Tregrehan ever since. It was found by the Wynn-Joneses in 2000 and they have made two collections (BSWJ 8210 and BSWJ 9788), from which have grown the plants currently sold through Crûg Farm. This material was initially identified as S. petelotii Merr. (a much smaller species from lower altitudes in the same general area), and plants were first released under this name in 2007; specimens should be relabelled. It is perhaps too soon to make a balanced assessment of its hardiness. At Crûg Farm, plants have suffered –11 ºC without protection (Crûg Farm Plants online database 2007–2008), but Dan Hinkley (pers. comm. 2008) reports that his collection DJHV 06124 was severely damaged in his Windcliff garden in Washington during the comparatively mild 2007–2008 winter there. A site sheltered from wind will be important. In Vancouver it does well in the David C. Lam Asian Garden. Peter Wharton, in his last communication of information for New Trees, wrote that it is ‘truly a stunning, bold architectural plant. We have several Crûg plants now growing away with fine vigour. The combination of this species with large-leaved Asiatic magnolias and rhododendrons is a classic’ (pers. comm. 2008). A form with silvery undersides to the foliage is known as var. flava Bui, and a similarly large-leaved species, but in which the leaflets are deeply pinnately lobed when young, is S. farinosa (Blume) Merr. Seed of both of these has been collected (B. Wynn-Jones, pers. comm. 2008).

Schefflera rhododendrifolia (Griff.) Frodin Syn. Panax rhododendrifolius Griff., S. impressa (C.B. Clarke) Harms Tree to 20 m. Leaves evergreen, palmate; leaflets (five to) six to seven (to nine), leathery, 12–20 × 3–5 cm, narrowly obovate to elliptic, upper surface glabrous and rugose, lower surface initially covered in greyish white stellate tomentum, but glabrescent, glaucous at maturity, 8–12 pairs of secondary veins on each side of the midrib, margins entire and revolute, rarely serrate or with pinnate lobes in young plants, apex acuminate; petiole to 30 cm long, petiolules stout, 1–2.5 cm long. Inflorescences terminal, paniculate, primary axis to 20 cm long, densely tomentose; flowers in umbels. Flowers small, pedicel 0.5–1 cm long; calyx tiny, inconspicuously five-toothed. Drupe globose, 0.4–0.5 cm diameter, with a persistent style. Xiang & Lowry 2006. Distribution BHUTAN; CHINA: southeast Xizang; INDIA: Sikkim, West Bengal only; NEPAL. Habitat Evergreen broadleaved forest, between 2500 and 3200 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hudson 2004, Hutchinson 2005; NT774.

Plate 505. Since its introduction to commerce Schefflera macrophylla has been widely planted. This specimen, with sumptuous coppery new growth, is in Mark Everson’s garden, Cwmbran, south Wales. Image J. Grimshaw.

780

Schefflera

New Trees

Schefflera rhododendrifolia is best known under its synonym S. impressa – an epithet that boringly refers to the sunken (impressed) appearance of the leaf veins on dried specimens, rather than to the plant’s impressive appearance overall. When young the stem tends to shoot straight up, forming a column composed of the large leaves arranged around the stem, branching only later (or if the top is damaged). It is a perfect choice to bring contrast to a planting of, for example, rhododendrons or other woodland shrubs. The new growth emerges covered in brown stellate hairs, and these remain on the leaf undersides and scattered over other parts as the leaf matures, giving a slightly scurfy look to the otherwise dark green foliage when seen up close. Although Edward Needham’s plants in Cornwall are perhaps the best known to Schefflera enthusiasts, and have been propagated commercially, probably the first attempt to grow this species outside was made by Sir Peter Hutchinson, in Argyll. His plant was collected as a seedling in Nepal in 1965; after a few years in a pot – during which time it ‘looked as if it had strayed out of an airport lounge somewhere’ – it was planted out, and still survives, as a 10 m tree. Having come through the hard winter of 1981–1982 its potential as a hardy plant was revealed (Hutchinson 2005), and a few specimens were propagated and distributed. Since then, S. rhododendrifolia has become an important feature in the gardens where it is established. At Tregrehan, for example, it has shot up, both in the woodland garden (to about 5 m) and against the house (3.5 m). As a tree from comparatively low altitudes in the Himalaya (for example, GWJ 9375, collected at 3000 m on the Singalila Ridge above Darjeeling), its apparent hardiness should not be taken for granted everywhere, but in a sheltered site this species has huge potential. Some variation is evident among plants in cultivation. For example, the original Needham stock has broader, more rounded leaflets than those of GWJ 9375. Dan Hinkley (pers. comm. 2008) has noted, both in the wild and in cultivation (from his collection DJHB 1071, made in northern Sikkim in 2005), that the young leaves can be strongly lobed.

Schefflera taiwaniana (Nakai) Kaneh. Shrub or tree 2–4 m. Leaves evergreen, palmate; leaflets four to nine, papery, (5–)10–15 × (1.5–)2.5–5 cm, narrowly ovate or oblong, both surfaces glabrous, five to seven pairs of secondary veins on each side of the midrib, though largely obscured, margins entire, apex acuminate; petiole glabrous, 10–25 cm long, green to red. Inflorescences terminal, paniculate, primary axis to 25(–30) cm long, sparsely pubescent; composed of numerous racemes or umbels, each with up to six flowers. Flowers small; calyx six-toothed, petals six, stamens six. Drupe globose, 0.5–0.7 cm diameter, with a persistent style. Flowering August to October, fruiting October to November (Taiwan). Ohashi 1993, Xiang & Lowry 2006. Distribution TAIWAN. Habitat Scattered in coniferous forest, between 2000 and 2850 m asl. USDA Hardiness Zone 8–9. Conservation status Lower Risk. Illustration Wynn-Jones 2005; NT781. Taxonomic note An almost identical taxon in Assam, Myanmar and Yunnan is distinguished as S. shweliensis W.W. Sm.

Schefflera taiwaniana is one of the most significant plant introductions of recent years, and certainly the most valuable of the genus in terms of general garden usefulness and adaptability. While its foliage is not as large as that of some of the others, it makes up for this in the elegance of its pose and the many leaflets. In each new shoot the dark green leaves are held outwards on petioles of diminishing length so that they overlap like tiles on a roof; in spring the new growth erupts above them in pale green, with each leaflet furled downwards. It eventually forms a short, branching, small tree that develops a broad, rounded canopy, but it is attractive at all ages. In the garden it is supremely adaptable, bringing tremendous architectural structure to a planting. Judicious trimming will keep it in shape if space is limited. Where it will

Section II. Species Accounts

Schefflera

grow, there is some danger of it becoming as ubiquitous as Fatsia japonica (Thunb.) Decne & Planch. – but S. taiwaniana will always be much more beautiful. The species was first collected by Edward Needham in the early 1990s (T. Hudson, pers. comm. 2008) and this stock has proved to be a great success, in Cornwall and elsewhere, forming good bushy plants to 3 m or more in height. It is particularly elegant, with longer, slightly more undulate leaflets than found in some more recent collections. The majority of stock available in commerce, however, has been distributed from Crûg Farm from gatherings made in Taiwan from 1993 onwards (BSWJ 3575, BSWJ 7096, RWJ 10000, RWJ 10016, RWJ 10064). Of these, RWJ 10016 is the collection from the highest altitude, found at just under 3000 m on Yushan in 2003 – but whatever the altitude of origin, cultivated material of S. taiwaniana all seems to be equally hardy. The species is very variable in many respects, some plants even retaining juvenile lobing into adulthood. It also shows variation in the degree to which it branches from the base, the higher-altitude collections such as RWJ 10016 being most likely to do so. At Crûg Farm it has grown outside for more than 12 years with no problems and fruits heavily, and it is showing equal toughness wherever it has been planted in the United Kingdom (B. Wynn-Jones, pers. comm. 2008). Although doing very well in the Pacific Northwest it (like other scheffleras) is a failure in the southeastern United States, apparently not liking the heat and humidity in summer (D. Hinkley, T. Avent, pers. comms. 2008).

THEACEAE

SCHIMA

Reinw. ex Blume

Schima comprises anywhere between one and thirty species of evergreen trees (rarely shrubs), distributed from the Himalaya through southeastern Asia to New Guinea. The branchlets are covered with white lenticels, while the buds are covered in silky hairs. The leaves are entire, alternate, spirally arranged, and entire to crenate or serrate. Schima flowers are hermaphrodite, axillary and solitary, or rarely three to five flowers are crowded along a short raceme. The flowers are subtended by two or more caducous bracteoles, and have five sepals, basally fused and persistent, five white petals, also basally fused, and numerous stamens. The fruit is a woody, globose or subglobose capsule, which splits for half its length into (four to) five (to six) segments; a stout, central column remains. The seeds are small and kidney-shaped, with a narrow marginal wing (Keng 1994, Stevens et al. 2004, Ming & Bartholomew 2007). Schima species are extremely variable and can be difficult to distinguish. For this reason, Bloembergen (1952) amalgamated all of them into one species, S. wallichii (DC.) Korth. More recent opinions (Prince & Parks 2001, Ming & Bartholomew 2007) suggest that the genus contains numerous species; the truth is probably somewhere in between. The consequence, especially of Bloembergen’s work, which became widely adopted (see, for example, Bean 1981b), is that nomenclature within Schima

781

Plate 506. Schefflera taiwaniana is perhaps the most horticulturally useful of the genus for areas with cool summers. Image J. Grimshaw.

782

Schima

Plate 507. This taxon was collected in Indonesia by Bian Tan of the San Francisco Botanical Garden, as Schima wallichii. Identifying Schima is a nightmare but they are all attractive plants, often flowering at a young age. This was a 45 cm plant in a small pot, covered in buds, grown in North Carolina. Image J. Grimshaw.

New Trees

is a mess. The shoehorning of everything into S. wallichii not only obscured the range of variation in the genus, but resulted in lengthy trinomials (S. wallichii (DC.) Korth. subsp. noronhae (Bl.) Bloembergen var. superba (Gardner & Champ.) Bloembergen, for example) that were very unwieldy and sometimes fragmented into various dubious combinations. The problem is that Schima is both rather uniform in general appearance across the genus and rather variable within species – making the fine points of recognition required by the key in Flora of China, for example, difficult to use. The recent wave of plant-hunting effort in the Sino-Himalaya has resulted in a much wider diversity of Schima in cultivation than ever before, but a rather opaque veil is drawn over them by these nomenclatural and identification difficulties, and ‘Schima sp.’ is how most are noted in garden lists. In view of the difficulties and general confusion associated with the genus it is important that specimens in arboreta are reviewed and re-identified, so far as this is possible. It will probably be necessary to wait for flowers. The descriptions below are provided to help with the identification of plants under various names frequently seen in literature and on labels. A name that has been in circulation for some time is ‘S. yunnanensis’. This appears to have become attached to material collected in 1984 as SBEC 0079, on the SinoBritish Expedition to Cangshan, Yunnan, but has no botanical validity. Detective work by John David (David 2007) suggests that the material in question is S. argentea, a species first introduced by George Forrest and apparently persisting in cultivation from his gathering F 15029 made in 1917. With strongly glaucous undersides to its leaves, S. argentea is a handsome plant. Owing to the taxonomic difficulties now associated with the name S. wallichii, it is difficult to be certain whether this species as narrowly defined is in cultivation. It is found across a wide range in Asia, but is perhaps best known from Nepal (Lancaster 1981, Polunin & Stainton 1984). Seed was collected from Nepalese trees in 1993 by Bill McNamara, but did not germinate (McNamara 2007b). In the David C. Lam Asian Garden in Vancouver there is a tree identified as S. sericans (Hand.-Mazz.) T.L. Ming, grown from PW 107A. This flowered first in September 2006 and has made a very attractive specimen, with abundant, rounded, fragrant flowers (Mosquin 2006). Trees labelled S. noronhae are in cultivation, but with the persistence of Bloembergian nomenclature it is by no means clear if these represent the ‘real thing’, S. noronhae Reinw. ex Blume, a principally tropical species. Hudson (2004) notes that the trees have ‘superior’ flowers, produced in clusters from the terminal axils of each shoot. Whatever name is attached to them, Schima are all horticulturally very interesting, having handsome evergreen foliage that may flush reddish. The fragrant, white ‘fried-egg’ flowers containing a big boss of stamens are often produced through the autumn and winter months as well as in spring. (It should, however, be noted that cultivated plants may flower at different seasons to those in the wild.) With the development of the hybrid genus ×Schimlinia (see p. 784), Schima has taken on even more significance. They need a warm or at least mild climate with ample moisture

Section II. Species Accounts

Schima

783

and humidity to do well, so in our area they are effectively confined to the western coastal fringes of Europe and the Pacific Northwest; they also thrive in the southeastern United States (Hogan 2008). Light open woodland conditions are the most suitable, where young specimens can be planted in light understorey and allowed to quest for the canopy. Like the evergreen magnolias, they have the potential to become very substantial trees when mature. Johnson (2007) records (under the usual miscellany of names and combinations) several specimens in western Britain that are over 10 m tall. The largest of all is a ‘S. wallichii var. khasiana’ measured at 20 m (70 cm dbh) at Trewithen, Cornwall in 2004; a specimen with this name at Logan House, Dumfries & Galloway was 11 m tall in 1993. As with other members of the Theaceae, Schima species require acidic soil. Propagation is either from seed, sown as fresh as possible, and with a cool stratification period, or from cuttings taken in late summer or early autumn (Hogan 2008). Cutting-raised plants can flower well when still small. In locations with marginal conditions it may be best to allow plants to build up some wood in a pot for a few years, but in favourable areas they succeed if planted out while young (McNamara 2007b). S. argentea E. Pritz. ex Diels B337, S489, K310 S. khasiana Dyer B337, S489, K310

Schima superba Gardner & Champ. Syn. S. liukiuensis Nakai Tree 5–20 m. Branchlets glabrous or slightly pubescent. Leaves leathery, 7–13 × 2.5–4(–6) cm, elliptic to oblong, upper surface shiny green, glabrous, lower surface pale green, sparsely pubescent or glabrous, seven to nine secondary veins on each side of the midrib, margins undulate, somewhat crenate, apex acuminate; petiole 1–2 cm long, sparsely pubescent or glabrous. Inflorescences racemes of four to eight flowers, 2–3 cm diameter; pedicel 1–2.6 cm long, glabrous or sparsely pubescent. Bracteoles two, caducous, sepals suborbicular, ~0.3 cm diameter, petals white, obovate, 1–1.5 cm long, stamens 0.5–0.7 cm long, ovary tomentose. Capsule subglobose, 1–2 cm diameter. Flowering June to August, fruiting October to December (China). Ming & Bartholomew 2007. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, Zhejiang; JAPAN: Ryukyu Is.; TAIWAN. Habitat Forests between 800 and 1600 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT783.

The difficulties of identifying Schima are perfectly illustrated by young, vigorously growing trees at Tregrehan labelled S. superba, grown from seed collected in the Jinggang Shan, Jiangxi. They differ from published descriptions in having 10–11 vein pairs, and some have flat, entire leaf margins while others have teeth on the upper half of the leaf. Juvenility may be partly responsible for this variation, and identification will need to be checked once they reach flowering size. Bill McNamara (2007b) collected seed from very tall trees (up to 30 m) identified as S. superba by local botanists in Taiwan in 2004. In the United States a plant known as S. superba var. kankaoensis (Hayata) Keng is in cultivation (for example, at the San Francisco Botanical Garden). This Taiwanese taxon is included in S. superba by Ming & Bartholomew (2007), but maintained as distinct by Li (1976). Material labelled S. wallichii subsp. liukiuensis (Nakai) Bloemb. has been distributed from Chollipo Arboretum, South Korea, and seems to be particularly successful in New Zealand (Clapperton 2008), whence stock has reached the United Kingdom. Its identity needs confirmation, but the trees are very attractive! S. wallichii (DC.) Korth. K310

Plate 508. Potentially forming large forest trees, Schima have handsome glossy evergreen leaves. This specimen is believed to be Schima superba, from Jiangxi, China. Image J. Grimshaw.

784

×Schimlinia

New Trees

THEACEAE

×SCHIMLINIA

Ranney & Fantz

×Schimlinia floribunda is the product of a cross between Schima argentea E. Pritz. ex Diels and Franklinia alatamaha W. Bartram ex Marshall (Ranney et al. 2003).

×Schimlinia floribunda Ranney & Fantz

Mountain Schimlinia

Tree to 4 m (after two growing seasons). Leaves evergreen to semi-evergreen, (8–)11–14 × 2.5–4.5(–5) cm, elliptic to obovate, upper surface dark green and reticulate, lower surface pale green with some stiff bristles, 9–11 secondary veins on each side of the midrib, margins serrate to crenulate, apex short-acuminate; petiole absent. Inflorescences axillary, subracemose, to 5 cm long with one to four flowers; pedicel 0.7–1.5 cm long, pubescent. The hybrid is considerably more floriferous (10–90 flowers per shoot) than either F. alatamaha (2–4 per shoot) or S. argentea (10–15 per shoot). Flowers 4–7 cm wide, fragrant; bracteoles two, caducous, sepals five, suborbicular, ~0.5 cm diameter, petals five, white, 2–2.6 cm long, stamens numerous, bright yellow, 0.4–0.9 cm long, ovary tomentose. Fruit unknown. Ranney et al. 2003. Distribution Does not occur in the wild. The parent taxa originate in China (S. argentea) and the United States (F. alatamaha). The hybrid was originally produced at the Mountain Horticultural Crops Research Station, Fletcher, North Carolina, by a team led by Prof. Tom Ranney. USDA Hardiness Zone 7 (?). Illustration Ranney et al. 2003; NT784.

Plate 509. ×Schimlinia floribunda is an exciting recent bigeneric hybrid, produced in North Carolina, and likely to flourish best in the high heat and humidity of the southeastern United States. Image T. Ranney.

This exciting intergeneric hybrid was produced by deliberate cross-pollination of the parents in 1999 and 2000. The seeds germinated well and the resultant progeny grew extremely fast, some individuals reaching 2 m and flowering within nine months of sowing. They showed characters intermediate between those of the parents (tabulated by Ranney et al. 2003, on which this account is principally based), but were much more floriferous, with several buds in each leaf axil, and with larger flowers than either parent. The plants are evergreen to semi-evergreen, and show clear indications of becoming respectably sized trees. They have yet to be widely tested, however, as there has been very limited distribution to other institutions, and no material has been made available commercially as yet. It should be expected to thrive in the southeastern United States, however, and wherever Franklinia performs well. Previous research efforts (summarised by Ranney et al. 2003, Ranney & Fantz 2006) had attempted crosses between Franklinia and Camellia, which gave rise only to very feeble progeny, and between the American natives Franklinia and Gordonia lasianthus. In this latter case the progeny were vigorous at first but again did not live long. The Franklinia × Gordonia cross was made again in 2002, at the Mountain Horticultural Crops Research Station, and seedlings from this attempt first flowered in 2004. The progeny clearly demonstrated their hybridity, being in many ways intermediate, but with recognisable parental characters as well. The leaves and flowers are generally larger than in either parent, however, and available images suggest that this is a very handsome plant. It is semi-evergreen, with older leaves turning a brilliant scarlet that ‘surpasses a Nyssa’ (T. Ranney, pers. comm. 2008). So far it has performed well, with

Section II. Species Accounts

×Schimlinia

seedlings showing good vigour, reaching heights of up to 3.5 m after two seasons of growth. Progeny of this cross have now been named ×Gordlinia grandiflora Ranney & Fantz. (A full description and comparative table are provided by Ranney & Fantz 2006; see also Plate 11 above, p. 2.) As with ×Schimlinia, it is to be expected that ×Gordlinia will perform best in areas with hot humid summers. These successful crosses give hope of further success with the diversity of material of Asian Schima now available, and perhaps with Polyspora and Pyrenaria. Since some of these thrive better in maritime Europe than Franklinia, one can speculate on all sorts of interesting possibilities for the future.

ANACARDIACEAE

SCHINUS

L.

Syn. Duvaua Kunth

Pepper-trees The 28 species of Schinus are almost entirely restricted to central South America, with a centre of diversity in northern Argentina, though S. molle extends northwards into Mexico (Barkley 1957). Schinus species range from small shrubs to large trees, with evergreen leaves. The resin in the stems and leaves can cause allergic reactions in some people. The branches are slender or thick, glabrous or pubescent. The leaves are extremely variable across the genus: they are simple or compound, small or large, thick and leathery or thin and membranous, and glabrous or pubescent. The leaf margins may be entire, dentate or crenate, and the leaf rachis (in compound leaves) is winged. Schinus is dioecious, though occasional bisexual flowers occur in the inflorescences. The inflorescences are typically paniculate, with moderate to considerable branching. They are glabrous or pubescent, and may, rarely, be spicate. The individual flowers are numerous but unimpressive. The fruit is a drupe with thin, papery skin, ranging from deep red to lilac in colour (Barkley 1944, 1957, 1961). Schinus can be split into two major groups: those with pinnate leaves (for example, S. molle), and those with simple leaves (for example, S. montanus Engl.). The latter group has been separated into a segregate genus, Duvaua Kunth, though the discovery of a simple-leafed form of the typically pinnate S. pearcei Engl. suggests that this distinction is invalid. Schinus molle is the best known of its genus, but merits a place in this work principally to quell optimism over its hardiness. Schinus polygamus, on the other hand, is much hardier, and also earned mild praise from Bean (1981b) for its masses of small flowers. Propagation is easy from seed, and the fruit clusters of S. molle – like the pods of that other hopeless case, Ceratonia siliqua – are very tempting to holidaymakers. S. latifolius Engl. B339

Schinus molle L.

(Peruvian /Brazilian, etc.) Pepper-tree, Mulli

Tree to 20 m, trunk often short and stout; crown broad and much branched. Branches pendulous, slender, brown and glabrous at maturity; exuding white or clear latex when cut. Bark greyish brown, scaly and cracked, very rough. Leaves evergreen, imparipinnate, pale to dark green, 10–30 cm long; leaflets 19–41, sessile, linearlanceolate, 0.8–6 × 0.4–0.8 cm, somewhat membranous, margins entire to coarsely serrate, apex acute and

785

786

Schinus

New Trees

slightly curved; petiole distinct, 2–3 cm long; rachis slightly winged. Dioecious. Inflorescence a lateral panicle or a terminal thyrse, 8–15 cm long and typically longer than the leaves. Flowers inconspicuous. Fruit a drupe, 0.5–0.7 cm diameter, skin shiny and brittle, lavender to pink. Barkley 1944. Distribution ARGENTINA; BOLIVIA; BRAZIL; CHILE; COLOMBIA; ECUADOR; MEXICO; PARAGUAY; PERU; URUGUAY; VENEZUELA. The natural range of S. molle is somewhat difficult to determine as it is widely planted in subtropical regions around the world. Habitat Mixed savannas and bushveld, typically near permanent water sources. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration NT786. Cross-reference K311. Taxonomic note Schinus molle var. areira (L.) DC. (= S. areira L.) is distinguished by Barkley (1957) on the basis of minor leaf variation, and is said to be distributed from Mexico to Chile while the type variety is restricted to central South America. It does not seem helpful, however, to separate a variety based on characters that vary across the species. Another variety, from Peru – var. rusbyi Barkley – is a small tree of only 3 m, with inflorescences somewhat shorter than the leaves and the terminal leaflet absent. This may be worthy of specific rank. The epithet molle is a corruption of the Native American name mulli, and does not indicate softness.

Plate 510. Schinus molle is a popular landscaping tree in hot dry places, but it is not a success in most of our area. Image M. Gardner.

Schinus molle, the Pepper-tree, is a familiar sight in dry, hot parts of the world, whether fringing a golf course in Palm Desert or sheltering a dusty school in the African bush, its long drooping shoots and stubby trunk giving it a very distinctive appearance, while its aromatic foliage and lovely fruits are memorable. It is the sort of tree one can become nostalgic about. For most gardeners in our area, however, it is a tree to be enjoyed in memory only, requiring heat to grow well and harden its shoots, in which case it can tolerate a few degrees of frost. In California it grows through the Central Valley and along the coast, but is subject to damage in the event of a frost – even large old trees being cut to the base in severe conditions. It is grown along the Oregon coast also but has not been successful in Portland, where it fails to ripen its wood, and resprouts from the base each year (S. Hogan, pers. comm. 2008). No doubt other similar outposts can be found away from its strongholds in Mediterranean Europe, but in northern Europe it is really only suited for use as a patio tub tree, despite occasional optimistic assessments that it is merely a ‘little tender’ (Taylor 1990). In his survey of half-hardy trees in Britain and Ireland, carried out during 2006, Owen Johnson (2007) found only one very weak specimen, in Peckham, south London – in ‘as hot and frost-free a garden as any’. In our area its potential weediness is not an issue, but this is a concern in more favourable climates. It is also potentially allergenic, and the fruits – now a regular component in fancy pepper mills – can be mildly toxic. Many medical benefits, however, are claimed for the tree and its essential oils (Taylor 2005). S. polygamus (Cav.) Cabrera B338, K311

S. terebinthifolius Raddi K311

ELAEOCARPACEAE

SLOANEA Figure 87 (opposite). Sloanea sinensis: habit with flowers (A); capsule beginning to open (B); fully open capsule without seeds (C).

L.

There are about 120 species of Sloanea, most of which are found in the New World tropics and Malesia. The genus is absent from Africa, but present in Madagascar. Sloanea species are evergreen trees or shrubs with pubescent buds. Stipules may be large and foliose or small and caducous. The leaves are alternate or clustered at

Section II. Species Accounts

Sloanea

787

C

B

1 cm

A

788

Sloanea

New Trees

the stem apices, and are simple (rarely pinnate in some immature specimens). The margins are entire or serrate and the venation is pinnate. Flowers may be solitary or racemose, and are axillary. They are typically hermaphrodite, 4- or 5-merous and with long pedicels. Sepals are valvate or imbricate and stamens numerous. The petals may resemble sepals or may be distinct; in some taxa they are absent. The fruit is a prickly capsule with a woody or bony outer layer and a leathery inner layer, which detaches when dry. The fruit is valvate and opens to expose one to many pendulous seeds. There is often a large aril or sarcotesta covering half of the seed (Coode 1983, Tang & Chamlong 2005). Although Krüssmann (1986) described two species of Sloanea there is nothing to suggest that they were actually in cultivation when he wrote, and so far as can be ascertained, the genus is represented in horticulture only by S. sinensis. There are 14 species in China, however, and it is conceivable that other species may be introduced in the future, although they are usually from rather low altitudes.

S. hemsleyana Rehder & E.H. Wilson K321

Sloanea sinensis (Hance) Hemsl. Tree (rarely a shrub) to 22 m. Branchlets slender and glabrous, grooved when young. Leaf buds pubescent, later glabrous. Leaves evergreen, simple, grouped towards the stem apices, 6–9(–12) × 3–5 cm, thin and leathery, elliptic to obovate though extremely variable, both surfaces glabrous, major veins prominent beneath, five to seven secondary veins on each side of the midvein, margins entire or sinuous, apex acute or acuminate; petiole 1–3(–4.5) cm long, glabrous; stipules to 0.5 cm long, pubescent and caducous. Flowers solitary, fascicled and hermaphrodite; axillary or in groups at the stem apex, with subtending leaves absent; 4-merous and to 1.2 cm long; petals white, slightly pubescent, divided into (two to) seven to eight segments, stamens 60–80. Fruit a red or brown capsule, 2–4 × 1.5–2.5 cm, with long, densely packed spines and several valves (three to seven), interior red or purple when ripe. Seeds with a yellow aril. Flowering June to October, fruiting August to October (China). Coode 1983, Tang & Chamlong 2005. Distribution CAMBODIA; CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Zhejiang; LAOS; MYANMAR; THAILAND; VIETNAM. Habitat Evergreen forest, between 700 and 1000 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration NT787.

Sloanea sinensis was first introduced by the Guizhou Expedition of 1985 (Russell 1987). It entered commerce as one of Piroche Plants’ ‘Wild Dragon’ assortment in 1995 (Piroche Plants 2002–2005), and has since achieved a degree of ‘take-up’ by other American nurseries, but remains scarce. In Sean Hogan’s garden in Portland, Oregon it has achieved 3.5 m as an understorey plant, but Hogan considers that it is probably not hardy below –6 ºC (pers. comm. 2007). A plant obtained from Piroche in 1999 by the JC Raulston Arboretum was a slender 1.8 m when seen in 2006, its single shoot having sprouted from the base of a stem that had previously been cut down. It was evidently not thriving, and has since been removed. Interest in the plant derives mainly from its evergreen leaves that flush bronze, and the spiny capsules that open to reveal a red or purple interior. It can be grown from seed, which is sometimes commercially available, or propagated by cuttings. A warm, sheltered site with reasonable moisture and fertility would seem to be appropriate.

S. sterculiacea (Benth.) Rehder & E.H. Wilson K321

Section II. Species Accounts

Sophora

789

LEGUMINOSAE (PAPILIONOIDEAE)

SOPHORA

L.

Syn. Edwardsia Salisb.

Kowhais Sophora is a medium-sized genus of approximately 50 species with a broad distribution in subtropical regions of the world. It is particularly diverse around the Pacific Ocean (Hurr et al. 1999), where it is often an important component of island vegetation: S. tetraptera (Kowhai) blossom is the national flower of New Zealand, while S. toromiro (Philippi) Skottsb. (Toromiro) was the only native timber tree suitable for house-building and carving on Easter Island – at one time reduced to a single specimen, and now the subject of intensive conservation action (Maunder et al. 2000). Sophora species are unarmed, small to medium trees and shrubs, or rarely herbs. The leaves are deciduous or evergreen and imparipinnate. The leaflets are entire, small and numerous, or few and large. Stipules are small and caducous. Inflorescences are simple, terminal racemes or panicles. The flowers are yellow and 5-merous; standard petals are broad and erect or reflexed, wing petals are free, and keel petals are overlapping or partially fused. The leguminous fruit is cylindrical or moniliform, rarely winged, and may be fleshy, woody or leathery; the pods are indehiscent or open slowly (Allen & Allen 1981). The formerly large and diverse genus Sophora has been under botanical scrutiny in recent years, and on the basis of morphological, genetic and chemical evidence has been split into three rather distantly related genera, the other two being Calia Teran & Berland. and Styphnolobium Schott (Pennington & Wojciechowski 2008). Calia contains four species of small trees and shrubs from the arid areas of the southwestern United States to central Mexico, including the popular C. arizonica (S. Wats) Yakovlev, and C. secundiflora (Ortega) Yakovlev with purplish flowers. Calia are widely cultivated as ornamentals in arid parts of the southern United States and various selections have been made for foliage qualities (ranging from green to silver) and flower colour. Styphnolobium turns out to be closely related to Cladrastis Raf., which it resembles in being found in both southeastern Asia and the eastern side of North and Central America south to Colombia; its nine members include the familiar S. japonicum (L.) Schott and S. affine (Torr. & A. Gray) Walp. The remnant Sophora (about 50 species) includes the majority of the horticulturally familiar species, including the popular S. microphylla and its relatives S. prostrata and S. tetraptera from New Zealand, and the Chilean taxa. In New Zealand several further species of Sophora have been recognised recently, their identities having previously been lost under the blanket name

Plate 511. The Chilean Sophora cassioides has often been confused with the similar S. microphylla from New Zealand, but S. cassioides does not have a distinct juvenile growth phase. Image R. Hitchin.

790

Sophora

Plate 512. A selection of pods from Sophora cassioides, showing fascinating variation. Image R. Hitchin.

New Trees

of S. microphylla. Each has a recognisable morphology and distinct distribution, raising important conservation concerns regarding the planting of appropriately native kowhais in those areas (Heenan et al. 2001, Heenan 2004). Some are in cultivation under these new names, including S. chathamica Cockayne, S. fulvida (Allan) Heenan & de Lange, the tender S. howinsula (W.R.B. Oliver) P.S. Green (Green et al. 2002), S. longicarinata G. Simpson & J.S. Thomson, and S. molloyi Heenan & de Lange. Cultivars belonging to several of these taxa have been selected in New Zealand but most have not as yet been distributed further afield (Hughes 2002). A selection of S. molloyi, ‘Dragon’s Gold’, has become quite widely available in commerce. This originated from seed collected in the 1950s by R. Veitch of the New Zealand Wildlife Division, on Stephens Island in the Cook Strait – a haunt of the curious tuatara reptiles, which later suggested the name. The clone was selected from this material by Terry Hatch of Joy Plants, Pukekohe, New Zealand (Hughes 2002). It was introduced to the northern hemisphere in 1985 by Graham Hutchins of County Park Nursery, Hornchurch, Essex (Hillier & Coombes 2002). It is usually a compact shrub, but with age can reach 6 m, with fine foliage, each leaf having up to 31 leaflets. Its lemon-yellow flowers are produced in late winter and early spring. Another species not known to be in cultivation, in the northern hemisphere at least, is S. godleyi Heenan & de Lange, but pendulous cultivars have been selected in New Zealand (Hughes 2002). Various cultivars are attributed to S. microphylla in the horticultural literature and nursery catalogues, but in view of the recent segregates these should probably be re-examined. A key to the New Zealand taxa (as wild plants, with a caveat over hybridity in cultivation) is available (Heenan 2004). Sophora are not difficult to grow in good well-drained soil, but need some shelter from cold winds. Propagation is from seed, with abrasion of the testa and a preliminary warm-water soak being advisable; or from cuttings.

S. affinis (NOW Styphnolobium affine (Torr. & A. Gray) Walp.) B386, S494, K325

Sophora cassioides (F. Phil.) Sparre

Pelu

Syn. S. macnabiana (Graham) Skottsb. Shrub or small tree to 16 m; branches sparse and somewhat tortuous. Branchlets covered in ferruginous, silky hairs, later glabrous. Leaves deciduous, imparipinnate, leathery, glabrous above, but with ferruginous hairs below, 4–11 × 1.5–2 cm; leaflets 17–31, subopposite, elliptic to ovate, 0.6–1.1 × 0.3–0.6 cm, apex acute, rounded or slightly notched, margins entire; petiole and rachis contiguous, furrowed above and pubescent; stipules caducous. Inflorescences terminal racemes with three to seven golden-yellow flowers, produced during the emergence of new leaves in spring. Flowers opening widely, with yellow, broadly toothed calyx, petals bright yellow, with standard shorter than wings. Fruit a moniliform legume containing one to six yellow seeds; the swollen seed-bearing portions having four wings with crenulate margins, the pod apex extending into a woody beak to 9 cm long. Flowering August to September (Chile). Gay 1845–1846. Distribution CHILE: from Maule Region south to Chiloé Is.; GOUGH ISLAND (in the middle of the South Atlantic, part of the British Overseas Territory of Saint Helena). Habitat Sandy or loam soils in low-lying areas or hills. Forming pure stands in open forest and shrubland (‘mulga country’), or dominant in mixed vegetation. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT789, NT790. Cross-reference B392. Taxonomic note The taxonomy of this species is complex. It was originally described as Edwardsia macnabiana by Graham (1838, 1839), who based his description on cultivated material in Edinburgh, of unknown origin.

Section II. Species Accounts

Sophora

The species was transferred into Sophora (S. macnabiana (Graham) Skottsb.), but this combination was not validly published. Pelu has also been recognised as S. microphylla subsp. macnabiana (Graham) Yakovlev, but S. microphylla Aiton is now considered to be endemic to New Zealand (Heenan et al. 2001). The correct name for the Chilean Pelu is Sophora cassioides, as established by Heenan (2001).

The confusion of Sophora cassioides with the New Zealand species S. microphylla is perhaps excusable, given that they look very similar and belong to the same section of the genus (Edwardsia). When young, however, S. microphylla has divaricate juvenile growth, later producing mature-phase flowering stems, whereas S. cassioides does not. (There were no moas in Chile!) As mature plants the two differ principally in characters of the leaflets. In S. cassioides these do not usually overlap (though they can do so slightly), are broad in relation to their width, do not taper towards the apex, and are usually glabrous or have only a few appressed hairs. Sophora cassioides forms a small tree with dark green foliage and abundant golden-yellow flowers, followed by attractive four-winged, irregularly shaped fruits. The unselected wild type is sparsely cultivated in our area, but seems to be hardy in southern England and the Pacific Northwest, though usually short-lived. Bean (1981b) records that it was introduced to Britain in 1927 by Harold Comber, but the stock in cultivation has been bolstered by further importations, and seed is freely available in commerce. Sophora cassioides is also cultivated in New Zealand, often under the name S. microphylla ‘Goldilocks’ (New Zealand Plant Conservation Network 2005b) – with risk therefore of contamination of populations of native kowhais. Plants so-labelled are also in cultivation in Europe. Material presumably originating from Gough Island has been distributed as S. tetraptera ‘Goughensis’, but a specimen at the Sir Harold Hillier Gardens acquired in 1989 under this name is S. cassioides. This was 4.2 m tall in 2008, but not looking very healthy. The tree now very widely propagated and sold as S. microphylla Sun King (‘Hilsop’) originated from material received at the Hillier Gardens in 1982 from Chile. It was selected by John Hillier when it began to flower well, but Allen Coombes has convincingly demonstrated that it is a hybrid between S. cassioides and S. macrocarpa (also from Chile), being intermediate in all respects; another such intermediate has occurred more recently at Hillier Nurseries, in an imported batch of Chilean seed (A. Coombes, pers. comm. 2008). Sun King, which is protected by Plant Breeders’ Rights in Europe and holds an Award of Garden Merit from the Royal Horticultural Society, is marketed as a shrub up to 3 m or so, and seems to be hardy in sheltered sites throughout much of the United Kingdom, producing its rich yellow flowers through late spring. The original tree has reached 3.8 m in height, with a spread of 4 m, supported by several principal stems (A. Coombes, pers. comm. 2008).

S. davidii (Franch.) Pavol. B387, K325 S. flavescens Aiton B388, S494, K325 S. japonica (NOW Styphnolobium japonicum (L.) Schott) B388, S494, K325 S. japonica var. pubescens (NOW Styphnolobium japonicum (L.) Schott) B389, K325 S. macrocarpa Sm. B390, K326 S. microphylla Aiton B391, K326

S. microphylla var. longicarinata (G. Simpson & J.S. Thomson) Allan B391 S. moorcroftiana (Benth.) Baker B388 S. prostrata Buchan. B392, K327 S. secundiflora (NOW Calia secundiflora (Ortega) Yakovlev) B390 S. tetraptera J.F. Mill. B390, S494, K327 S. tomentosa L. K327

791

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Sorbus

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1 cm

Section II. Species Accounts

Sorbus

ROSACEAE

SORBUS The familiar subfamily Maloideae in Rosaceae, containing many important fruiting trees and shrubs, has long been a challenge to taxonomists, and species have moved rather freely between genera over the centuries. Generic concepts in the Rosaceae continue to change, and among the casualties is the well-known and very popular genus Sorbus, which was dismembered by Robertson et al. (1991). More recently the Rosaceae as a whole have been thoroughly investigated by Potter et al. (2007) who have proposed a phylogenetically based infrafamilial classification, with good support from morphological and physiological characters. In their paper the subfamily Maloideae is recognised as subtribe Pyrineae within the supertribe Pyrodae, in subfamily Spiraeoideae. The work of Potter and his co-authors shows that the various entities that made up the broad genus Sorbus are in fact quite distantly related within the subtribe (Potter et al. 2007), making recognition as subgenera impossible. The result of these studies is that Sorbus has been redefined to contain only taxa with pinnate leaves (excluding Cormus domestica). This concept was adopted by Hugh McAllister in his monograph The Genus Sorbus (2005a), which is the foundation for the present account, and should be consulted as the primary source for information on the genus. We are also grateful to Hugh McAllister and Keith Rushforth for extensive assistance. The remaining taxa fall into four genera: Aria (Pers.) Host (whitebeams, including three distinct groups), the type species becoming Aria nivea Host (Sorbus aria Wimm. ex Nyman); Chamaemespilus Medik., comprising C. alpina (Mill.) K.R. Robertson & J.B. Phipps (Sorbus chamaemespilus (L.) Crantz, False Medlar) and C. sudetica Roem.; Cormus Spach, including only C. domestica Spach (Sorbus domestica L., Service Tree); and Torminaria Medik., containing only T. torminalis Dippel (Sorbus torminalis Crantz, Wild Service Tree). The principal segregation therefore – for the purposes of New Trees at least – is into the pinnate-leaved rowans, Sorbus s.s., and the nonpinnate whitebeams, Aria. This taxonomy has not met with universal acceptance, however, and some recent authors maintain the segregate genera as subgenera of Sorbus (Aldasoro et al. 2004, Aldasoro et al. 2005). Generic accounts in floras usually refer to the familiar broad genus. It is well to recall, in all of this, that the current standard concept of Sorbus is itself relatively recent: in the first edition of his work, Bean (1914) discussed them all under the generic name of Pyrus! An important factor in accounting for these discrepancies in generic delimitation is hybridisation, which deceptively holds the genera together. Hybridisation between genera is common and widespread in the Rosaceae, and was thought to indicate a close relationship between interfertile genera. The presence in Europe and western Asia of numerous naturally occurring apomictic microspecies of hybrid origin, between Aria, Chamaemespilus, Sorbus and Torminaria (from the Himalaya eastwards the genera are distinct), suggested that they should all be included in one genus for convenience; but this point of view ignores the fact that Sorbus forms hybrids with several other discrete genera in the Rosaceae, including Amelanchier Medik., Aronia Medik. (= Photinia Lindl.), Cotoneaster Medik. and Crataegus L. Robertson et al. (1991) take the view that the high degree of intergeneric hybridisation in Rosaceae is the result of ineffective barriers between genera, rather than an indication of relationships.

Figure 88 (opposite). Sorbus randaiensis: habit with fruits (A); partial inflorescence (B).

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Sorbus

New Trees

The principle of the narrow circumscription of Sorbus advocated by Robertson et al. (1991), Potter et al. (2007) and McAllister (2005a) is adopted here. Principles and practicalities do not always meet, however, and the difficulty of using this approach in a work such as New Trees is that many whitebeams do not have published names in the genus Aria (though see Ohashi & Iketani 1993), and there are no nothogeneric names for the many hybrids between the two genera. Rather than creating a number of new taxonomic combinations without having undertaken the massive study of the complex that is urgently required, possibly introducing unnecessary synonyms thereby, we cover Aria species as an adjunct to this Sorbus account, as either Aria or Sorbus, depending on whether the combination in Aria is available. Much of the introductory material covers both genera. (Within Chamaemespilus, Cormus and Torminaria there are no new introductions to be discussed, so the issue does not arise for these.)

SORBUS

L.

Mountain Ashes, Rowans Plate 513. Sorbus randaiensis is a fertile diploid, needing pollen from another tree to achieve fertilisation. Unless several specimens of it are grown together, seedlings are likely to be hybrids. Image R. Unwin.

The pinnate-leaved genus Sorbus (s.s.), typified by the familiar Rowan Sorbus aucuparia L., comprises over 70 named species ranging across the temperate northern hemisphere, and many more that are as yet unnnamed. They are typically small trees or shrubs, or rarely dwarf rhizomatous shrubs, and have smooth or flaky bark. Dependent on the growth phase of the tree, the shoots may be long (vegetative extension growth) or short (reproductive short shoots, or vegetative short shoots). Buds are shortly ovate to conical, often asymmetrical, with (usually) four bud scales plus one extra larger scale overlapping these at the side. The leaves are imparipinnate and spirally arranged (although sometimes appearing almost whorled on short shoots). All species are deciduous, and many produce spectacular displays of autumn foliage colour. Sorbus is monoecious; the inflorescences are paniculate, flat and corymbose or rarely pyramidal, appearing in spring, and are followed by fruits that ripen mostly from late summer onwards, though some ripen as early as midsummer. The flowers are hermaphrodite, rather small (usually less than 1 cm diameter), and mostly very similar among the species (not described in detail here), with sepals more or less fleshy and persistent, petals white to pink, 10–20 stamens and (two to) three to five carpels. The fruit is a small pome, which may be orange-red or crimson to white; yellow fruits are extremely rare (McAllister 2005a). Sorbus is a justly popular and attractive genus of small trees, valued for their foliage and abundant brightly coloured fruits; seed is frequently collected in the wild, by both amateur and professional collectors, and there is a vast diversity of material in cultivation. Some is named, some is nameable, but much remains unnamed. The key to the diversity of Sorbus – both physical and

Section II. Species Accounts

taxonomic – lies in understanding its reproductive systems. Although complicated, this has great implications for horticulture, and is not merely a botanical curiosity. The basic distinction is between those species that reproduce sexually, through recombination of genes from pollen and ovule in the normal way, and those that reproduce by apomixis, the production of seed without recombination of genes, so that seedlings are genetically identical to the parent tree. A full exposition of Sorbus reproduction is given by McAllister (2005a), from which the following notes have been condensed and modified. Sorbus (and Aria) species that reproduce sexually may be self-compatible, meaning that they do not need to receive pollen from another tree to set viable fruit, or self-incompatible, in which case cross-pollination from another clone is required. The practical consequence for horticulture is that seed of self-incompatible species, unless gathered from a group of several clones of that species, will have been fertilised by pollen from a tree of another species, with the result that the progeny will be of hybrid origin. With some species (for example, S. scalaris and S. esserteauiana), a more or less uniform batch of seedlings hybridised with S. aucuparia is often obtained. Late flowering or isolated individuals of self-incompatible species (for example, S. matsumurana) may fail to produce fruit. Sexual Sorbus are diploids, with a normal number of chromosomes (2n = 34). Apomixis is the production of a seed without a fertilisation event of any kind: the embryo is created through mitosis (in which the genetic complement is not reduced to the haploid level and then fertilised, as would normally happen in a sexually reproducing species). The result is that the seedlings of apomictic species are genetically identical to their parent and can be regarded as a clone. Populations of these clones can form in the wild, although they may comprise only a few individuals. When recognised and named, such entities are known as ‘microspecies’. Most apomictic microspecies are tetraploids, with a doubled complement of chromosomes. In the Maloideae (Sorbus, Cotoneaster, Malus, Crataegus, Amelanchier, etc.), apomicts are pseudogamous: that is, they require pollination and fertilisation of the central fusion nucleus in the embryo sac to stimulate the formation of endosperm and so the seed – though there is usually no fertilisation of the egg cell which develops into the embryo. Most tetraploid Sorbus apomicts are pollen-fertile, but triploid apomicts have limited if any pollen fertility and therefore depend on pollen from neighbouring diploids or tetraploids for seed set. Triploids therefore usually set much less fruit than tetraploids and are rarely widespread in the wild (for example, S. arranensis, S. minima). Fertile pollen from apomictic tetraploids fertilising sexual diploids generates new triploid microspecies. Unreduced female gametes of these triploids (which normally develop into apomictic embryos) may occasionally (up to 10 per cent) be fertilised by normal reduced haploid gametes from diploids and give rise to new tetraploid apomictic microspecies. Fertile diploid species are thus able to cross with apomictic tetraploids to give further apomicts. The initial crosses are apparently quite rare, but the apomicts that result from such events are able to reproduce themselves and form clonal populations. An example of this that has been fully elucidated is the cross that has arisen on several occasions in the British Isles and continental Europe between the tetraploid apomictic whitebeam Sorbus (Aria) rupicola (2n = 68) and the diploid sexual S. aucuparia (2n = 34). One result is the apomictic triploid hybrid microspecies S.

Sorbus

795

796

Sorbus

Plate 514. The Sorbus microphylla aggregate contains several similar microspecies from a wide area of the Sino-Himalaya. They do best in cool, moist conditions. Image K. Camelbeke.

New Trees

arranensis (2n = 51), which exists as a small population on the Isle of Arran, North Ayrshire. Others are S. minima and S. leyana in Wales, and S. lancifolia and S. subpinnata in Norway. All have a rather similar morphology (intermediate between the two parents), but are not identical, and they each have discrete distributions, justifying their recognition as separate microspecies. Some may even cross with a sexual species to produce further new microspecies. Sorbus arranensis, for example, has backcrossed with S. aucuparia to give the apomictic tetraploid S. pseudofennica (the numerous unnamed microspecies of the S. hybrida type have a similar origin), and with Torminaria torminalis (S. torminalis) to give S. intermedia. Such Byzantine relationships contribute to the nomenclatural difficulties of splitting Sorbus s.l. into segregate genera, and the only option at present is to use the generic name Sorbus for all such hybrids. In Europe and western Asia the overall picture seems to be that the variable Aria nivea (S. aria) has several times given rise to (presumably autopolyploid) tetraploid whitebeams that are apomictic (S. rupicola, S. porrigentiformis, S. graeca, etc.). Crosses between these and the diploid S. aucuparia, Torminaria torminalis, Chamaemespilus alpina, and Aria nivea itself, have given rise to over a hundred named apomictic microspecies (Warburg & Kárpáti 1968). Within the pinnate-leaved rowans (Sorbus s.s.), crossing and backcrossing between sexual and apomictic taxa has occurred freely in the Sino-Himalayan region, producing a multitude of apomictic microspecies, each one often with a very limited range. Most are probably represented in the wild by only a handful of individuals, and very few have been collected more than once. The conservation status of such taxa is almost impossible to define. Some genotypes are possibly now represented solely by cultivated trees. In The Genus Sorbus, McAllister (2005a) took the step of naming only those that are established in cultivation or likely to become so, acknowledging that there are very many more in the wilds of the SinoHimalaya that could likewise be described (as has been done in Europe, where some native apomictic microspecies have become common in cultivation: for example, S. intermedia, S. hybrida, S. arranensis, S. lancifolia). While it is useful to have a definitive ‘handle’ for cultivated material, such an approach does not clarify the situation in the wild, for which aggregate names covering a range of microspecies with similar assumed parentage, ploidy and appearance would perhaps be more useful – as in the case of S. microphylla agg. (p. 807). For the gardener, and especially the nurseryman, knowledge as to whether a tree reproduces sexually or by apomixis is very valuable. Apomicts, reproducing themselves perfectly from seed, should always be seed-raised to allow the plant to develop its own natural form, rather than the shape imposed upon it by grafting. To propagate sexual species from cultivated plants it will usually be necessary to resort to grafting onto a suitable stock (unless a breeding group is maintained in isolation) – but genetic diversity will be lost unless several clones are propagated at the same time. For a new collection of an unknown wild Sorbus, practical observation of resulting seedlings will often indicate whether they vary significantly and are therefore probably fertile diploids, or are uniform and probably apomictic. Confirmation can be achieved only via a chromosome count or more advanced DNA research techniques, or alternatively, by raising numbers of seedlings from cultivated plants grown in association with other species (if the seedlings are very uniform the parent is likely to be apomictic; if variable, it is sexual). Identifica-

Section II. Species Accounts

tion of microspecies is likely to be a considerable challenge, and collectors’ numbers should always be retained with any material distributed. Where material does not fit any of the recognised taxa it may be permissible to apply a cultivar name – as in the case of the white-fruited ‘Molly Sanderson’ (see McAllister 2005a) – but the collector’s number is preferable. In addition to the complexities of the breeding systems of these plants, there is an extensive infrageneric classification of Sorbus s.s. McAllister (2005a) recognises two subgenera, easily distinguished by their fruits. In subgenus Sorbus the fruits are orangeor vermilion-red when ripe, with orange flesh, while in subgenus Albocarmesinae the fruits are white, pink or crimson-red, and have white flesh. Each subgenus then has several sections, containing both sexual diploids and apomictic polyploids. A full synopsis is provided by McAllister (2005a). A number of different species in subgenus Albocarmesinae section Discolores (characterised by their pyramidal inflorescences, hard fruits, fleshy sepals in fruit and short styles) have been grown under the name Sorbus hupehensis, two of which have become popular – indeed, outstanding – garden trees. These are the taxa generally known to gardeners as S. hupehensis (or S. hupehensis white-fruited form) and S. hupehensis var. obtusa (or pink-fruited form). Both have Awards of Garden Merit from the Royal Horticultural Society. Research by Hugh McAllister has demonstrated, however, that the name S. hupehensis C.K. Schneid., based on Wilson’s collection W 2082B, is a synonym of S. discolor (Maxim.) E. Goetze. Sorbus discolor is a diploid, sexual species, with a wide range in China, and shows considerable variation. It is rare in cultivation, although it was described by Bean (B421) and Krüssmann (K334). The two so-called S. hupehensis forms are tetraploid microspecies, and their horticultural populations are uniform – despite the six or so supposedly different ‘clonal selections’ of the pink-fruited microspecies! As the placement of S. hupehensis into synonymy with S. discolor left them nameless, new names were necessary, and McAllister (2005a) has described them as S. glabriuscula (white fruits) and S. pseudohupehensis (pink fruits). Several other microspecies allied to them are also excellent garden trees and are described below. A key to the group is provided in the account of S. glabriuscula. The similarly named S. glabrescens (Cardot) Hand.-Mazz. is also a member of section Discolores but is not well understood botanically, and was not described by McAllister (2005a) or by Gu et al. (2003); trees in cultivation under this name are S. glabriuscula. In the garden in northwestern Europe Sorbus are exceptionally useful, ranging in size from small shrubs to small or medium-sized trees, and some are extremely adaptable. Most true Sorbus – and in this they differ from Aria – are not suitable for dry places in warm climates, as they have shallow roots and require an ample supply of moisture through the growing season. (Exceptions to this are species allied to S. cashmiriana, and members of section Discolores – when grown on their own roots!)

Sorbus

797

Plate 515. Sorbus glabriuscula was known to gardeners for many years as S. hupehensis (white-fruited form). Sorbus flowers are all rather similar, and are not described here individually for each species. Image J. Grimshaw.

798

Sorbus

New Trees

In dry gardens the careful preparation of a humus-rich planting site can help. Good aeration is also important, and for this reason they usually do not do well on heavy clay soils. Most, however, are happy on both acidic and alkaline soils (a handful are calcifuge). An interesting discovery by Hugh McAllister is the sensitivity of Sorbus to high nutrient concentrations, especially when young and in pots, although normal potting composts are acceptable. As noted above, Sorbus should wherever possible be raised from seed, as this gives better-looking and thriftier trees than when grafted (though grafting has to be resorted to on occasion). The traditional method in the United Kingdom is to sow seed in pots in autumn and leave them outside in ambient winter temperatures (not in a cold frame, which may warm up too much). This is the usual method for numerous tree species, and works well with many Sorbus. With some, however, and some recent introductions in particular, it tends to give very low germination rates, perhaps because British winters are too short and warm in comparison with those of their native habitat. Hugh McAllister has devised a technique for maximising successful germination, sowing thoroughly cleaned seeds on filter paper in a Petri dish kept in a refrigerator at 0–3 ºC. Regular inspection is needed, and newly germinated seeds are removed and potted up in a low-nutrient medium. Full details are given in The Genus Sorbus. The worst enemies of Sorbus s.l. are diseases caused by fungi or bacteria. Coral-spot Fungus Nectria galligena is perhaps the most harmful, causing shoot dieback, and in serious cases, death. It is most prevalent if the trees are drought-stressed, or where the soil is rich in nitrates. Honey Fungus Armillaria mellea will exact its toll in similar circumstances, and especially on wet clay soils. Fireblight, caused by the bacterium Erwinia amylovora, occasionally a problem in western Europe, is often devastating in North America (Dirr 1998). Sorbus trees tend to be short-lived, but though the central trunk may succumb to various fungi, a plant grown on its own roots may well coppice itself by producing new shoots from the base. As usual, it seems, there is a much wider range of pests and diseases in North America, where heat and humidity in the eastern and southern states make Sorbus largely ungrowable anyway. Borers are among the numerous insect pests (Dirr 1998). Young Sorbus are also particularly tasty to browsing mammals, from voles to deer, and protection should be provided as appropriate. The popularity of the genus means that new collections and horticultural selections regularly become available in the nursery trade. For example, a number of Sorbus selections have been made by Glendoick Gardens in Perthshire and are sold by them as grafted specimens (K. Cox, pers. comm. 2006), under names prefaced by the registered ‘Glendoick‘ name (‘Glendoick Glory’, ‘Glendoick Ruby’, etc.); they are not attributed to species, but are all small trees with attractively coloured fruits. For descriptions of these and other new cultivars nursery catalogues must be consulted; well-established cultivars are largely covered by McAllister (2005a) or Hillier & Coombes (2002). In addition to the principally tree-forming species described below, many smaller shrubby species have been written up by McAllister (2005a), including the following known to be currently in commercial circulation in the United Kingdom: S. apiculata McAll., S. bissetii McAll., S. californica Greene, S. eburnea McAll. (often grown as Harry Smith 12799), S. frutescens McAll. (often grown as Rock 13268, but this is probably in error for Rock 14987), S. monbeigii (Cardot) N.P. Balakr., and S. munda Koehne (often cultivated as S. prattii). Many of these shrubby species are extremely ornamental and deserving of garden space, and a few are particularly worthy of attention. Sorbus gonggashanica McAll. is a multistemmed bush forming a rounded

Section II. Species Accounts

dome up to 3–4 m tall, that in autumn can be covered by abundant clusters of white fruits – a beautiful sight. First introduced by Roy Lancaster (under Lancaster 906, 927, 937 in part, 946 in part, 1007, 1008) from the Gongga Shan (Minya Konka) in 1981, though also collected on other occasions, it is now quite widely grown and much admired. Very closely related to the familiar S. cashmiriana, and sharing its upright shrubby habit, but with pink fruits, is S. rosea McAll. This was introduced from Gilgit, northern Pakistan by the Swedish Expedition to Pakistan of 1983 (SEP 492), and has been widely distributed as ‘Rosiness’ (originally ‘Rosy-Ness’). Unusually in the genus, the flowers are also a soft pink. It is tolerant of dry conditions, and an excellent choice for small gardens. Sorbus macallisteri Rushforth from Arunachal Pradesh is remarkable in several ways – perhaps foremost for being an epiphyte on Abies densa. The leaves have only one or two pairs of virtually untoothed leaflets, set on very slender shoots little more than a millimetre in diameter, and the flowers have only two styles. It shows some similarity to S. kurzii (see below). First collected by Kingdon-Ward in 1938, it has recently been introduced from the Mande La above Dirang Dzong, near to the Bhutan border. It has white fruits and red autumn colour. Most of the species covered below were relatively recently described and are not widely grown (at least under these names), so the horticultural commentary given is often shorter than usual. Most arboreta and many botanical gardens have a good range of Sorbus. In England there are two National Plant Collections for the genus, at Ness Botanic Gardens and in the Granada Arboretum surrounding the Jodrell Bank Science Centre, both in Cheshire. A particularly wide range is maintained in Scotland, in the collections of the Royal Botanic Garden Edinburgh and its satellites, especially at Dawyck. In continental Europe there are good collections at the Arboretum Lenoir, Rendeux, Belgium; the Arboretum of Wageningen University in the Netherlands; the Gothenburg Botanic Garden in Sweden; and the Store Milden Arboretum, Bergen, Norway. In North America Sorbus cultivation is effectively limited to the cooler, moister areas and it is not such a popular genus as it is in Europe, but there are reasonable collections at the Arnold Arboretum and Washington Park Arboretum. An interesting selection of Sorbus s.l. is maintained at the National Clonal Germplasm Repository at Corvallis, Oregon, as part of the collection there of potentially edible plants. An interesting range of well-grown specimens from recent collections is to be found in the Reykjavik and Akureyri Botanic Gardens in Iceland, where many species grow much better than in warmer climates. Reykjavik is probably the only city in the world in which more unusual species can be seen growing commonly in private and public gardens (S. bissetii, S. cashmiriana, S. decora, S. frutescens, for example). This is no doubt partly because in Iceland there is a tradition of propagating trees from seed rather than by grafting, producing much more attractively shaped and longer-lived specimens of these naturally multistemmed species (H. McAllister, pers. comm. 2007). Cross-references to Sorbus will be found on pp. 823–825.

Sorbus

799

Plate 516. Sorbus are an important feature of highaltitude forests across much of Eurasia. Seen here, Sorbus kongboensis enlivens its type locality on the Nam La, Tibet with autumn red, in 1997. Image S. O’Brien.

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Sorbus

New Trees

Sorbus amoena McAll. Shrub or tree to 8 m. Branchlets to 0.3 cm diameter. Buds red, ovate, to 1.5 cm long with reddish brown hairs at the apex. Leaves to 21 cm long, with 12–14 pairs of leaflets. Leaflets 2.7–2.9 × 1.1–1.5 cm, margins serrated in the upper half or three-quarters. Fruit crimson or white with crimson flecks, 1 × 1.2 cm and glabrous; calyx lobes fleshy with a distinct midrib, carpels three to four (to five). Tetraploid apomict. McAllister 2005a. Distribution CHINA: Yunnan (Zhongdian). Habitat Scrub on steep slopes. USDA Hardiness Zone 6. Conservation status Not evaluated.

This species is known only from one collection; its description is necessarily brief therefore, and its natural distribution and variation may be more extensive. It is very closely related to the shrubby Sorbus apiculata McAll., which achieves 5 m and is known only from CLD 310, but differs primarily in its bright crimson fruits (pearly white in S. apiculata). The single collection of S. amoena was made at about 3400 m asl northeast of Zhongdian by the Chungtien, Lijiang & Dali Expedition of 1990 (CLD 311), and more material is needed for both botanical and horticultural study. It is grown in a few collections where seed from the expedition was raised, including Dawyck, Ness and the Hillier Gardens, and is now commercially available in the United Kingdom. McAllister (2005a) notes that it and the related S. apiculata are very drought-tolerant, and that both have good red-orange colour in autumn; he accords it the tribute of considering it to be one of the most beautiful species in the genus. Apparently the area from which these two apomictic microspecies were collected has now been ‘developed’, so both are now likely to exist only in cultivation (D. Patterson, pers. comm. to H. McAllister).

Sorbus arachnoidea Koehne Tree to 12 m. Branchlets stout, shiny, 5–7 mm in diameter. Buds rounded. Leaves 12–21 cm long, with 8–10 pairs of leaflets. Leaflets oblong, 2.5–6 × 1–1.5 cm, margins entire or remotely toothed in upper third to half, apex mucronate, with pale brown hairs persisting on the veins beneath. Stipules stalked, large, leafy, persistent, to 1.5 cm across, clasping the bud and shoot. Flowers pink, in dense corymbs. Fruit 0.8–1 cm, ripening through red to pink then white, persisting only a short time; calyx lobes triangular, pointing forwards; carpels (four to) five, forming a conical protuberance below calyx lobes. Sexual diploid. McAllister 2005a. Distribution BHUTAN; INDIA: Sikkim; NEPAL. Habitat Abies-Rhododendron forest near the treeline and above. USDA Hardiness Zone 6. Conservation status Not evaluated. Cross-reference B435.

Sorbus arachnoidea is common in the shrub zone between the top end of the Abies forest and the Rhododendron moorland from east Nepal to Bhutan. Beer 404, collected in Nepal in 1971, was probably the first introduction, but it has been firmly established in cultivation since the 1980s from Ron McBeath’s collection (no. 1118) from east Nepal in 1981. From Bhutan, KR 1247, 1438, 1447 and 1487 are also in cultivation. It is related to S. insignis, and like that species, is noticeable for its stout shoots and persistent stipules, but the leaves tend to burn off rather than assume good autumn colours (K. Rushforth, pers. comm. 2008). Allied to S. arachnoidea is S. longii Rushforth, which is included in S. arachnoidea by Long (1987) but differs in the more slender shoots and smaller leaves (Rushforth 1991). Sorbus longii was first introduced by Hedegaard in 1977 (under his number 350) to Hørsholm, Denmark, from the Milke Danda ridge, Nepal, and subsequently by Keith Rushforth from Bhutan (KR 1423, 1611). In Bhutan it is the commonest rowan in the forest zone dominated by Abies densa, and is also found in Picea spinulosa and Juniperus recurva forest. The character of the fruits dropping as soon as ripe and the absence of strong autumn colour limit the horticultural desirability of this species (K. Rushforth, pers. comm. 2008).

Section II. Species Accounts

Sorbus

801

Sorbus carmesina McAll. Tree probably to 10–15 m. Branchlets deep red. Buds conical to ovoid, to 1.2 cm long with reddish brown and/or white hairs on the margins and at the apex of the scales. Leaves to 20.5 cm long, with six to seven pairs of leaflets, gradually decreasing in size towards the petiole. Leaflets 4.5–5 × 2–2.4 cm, obovate, upper surface bluish green and glabrous, lower surface somewhat papillose, margins entire or almost so; leaves turning reddish orange or reddish yellow in autumn. Fruit crimson to pink, 0.8 × 0.8 cm and rather hard; calyx lobes very fleshy, carpels (three to) four (to five). Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (Cangshan range). Habitat Scrub on steep slopes. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT801.

Sorbus carmesina is an apomictic microspecies in section Discolores of subgenus Albocarmesinae (see p. 797), very closely related to S. pseudohupehensis, from which it differs only slightly. Its fruits are larger than those of S. pseudohupehensis, ripen later and remain crimson for several months before turning pinkish, and – most importantly from a horticultural viewpoint – the trees fruit every year, unlike the biennial fruiting of S. pseudohupehensis. The autumn leaves are red, but with shades of yellow and orange. It is represented in cultivation by young trees grown from seed collected by Chris Brickell and Alan Leslie (B&L 12545) in the Cangshan range near Dali, Yunnan in 1987, and their derivatives. Its ultimate dimensions are not known, but may be assumed to be about the same as those of S. pseudohupehensis. Like other species of section Discolores it is relatively heat- and drought-tolerant in comparison with other Sorbus, especially when grown on its own roots. It is therefore suitable for warmer areas where even S. aucuparia may fail to thrive.

Sorbus coxii McAll. Tree probably to 10–15 m. Leaves to 13 cm long, with five to eight pairs of similarly sized leaflets. Leaflet margins dentate on upper half on spur shoots. Fruit white flushed with crimson, 0.8–0.9 × 0.8–0.95 cm; carpels (three to) four to five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (east flank of the Lijiang range). Habitat Presumably mountain woodland or scrub. USDA Hardiness Zone 6 (?) Conservation status Not evaluated. Illustration NT25.

Sorbus coxii was named in honour of the Cox family of Glendoick, Perthshire, well known for their hereditary interests in rhododendrons and plant-hunting, and in whose gardens at Glendoick this microspecies was first recognised (by Hugh McAllister in 1998), in the form of two trees presumably originally grown from Forrest 5550, collected in 1910. Sorbus coxii is also in section Discolores, and is similar to S. pseudohupehensis, though the foliage is more green and the leaflets are all of similar sizes. It is also close to S. muliensis (Forrest 22177), and McAllister (2005a) compares the two in tabular form. His conclusion is that they are distinct, but very similar, apomictic microspecies.

Sorbus ellipsoidalis McAll. Tree to 6 m. Branchlets reddish brown, about 0.3 cm diameter. Buds reddish, conical to ovoid, to 1.2 cm long with white hairs on the margins and apices of the scales. Leaves to 28 cm long, with five to seven pairs of leaflets. Leaflets 4.3–5.2(–7) × 1.4–1.7(–2.3) cm, elliptic, upper surface glabrous, lower surface papillose, margins dentate for about half their length. Fruit white, ellipsoid, 0.9 × 0.85 cm; calyx lobes very fleshy, carpels four to five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (Sung-kuei

Plate 517. Sorbus carmesina has great horticultural potential since it fruits reliably every year. As an apomictic tetraploid, it is easily propagated from seed. Image P. Williams.

802

Sorbus

New Trees

[Songgui]). Habitat Presumably mountain woodland or scrub. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a.

As with several members of section Discolores described recently by Hugh McAllister, Sorbus ellipsoidalis was recognised in cultivation. In this case the trees were found growing at Bodnant, Conwy, in 1982, and were confirmed to have come from the collection McLaren C288. When George Forrest died in 1932 his experienced collecting team was kept on for another season through the sponsorship of H.D. McLaren (later Lord Aberconway), and seed gathered in that year is usually attributed to ‘McLaren’s collectors’. Among the seed and specimens they gathered was this tree, and the type specimen at Edinburgh bears the note ‘half way up Sung Kuei Mountain’ (Yunnan). It remains the only collection known, though as a tetraploid apomictic microspecies S. ellipsoidalis is easily propagated from seed. It is closely related to S. glabriuscula (see p. 803), but differs in being more slender in appearance, with narrower leaflets and an elongated (ellipsoid) fruit. A more technical distinction is the presence of a white patch around the micropyle of the seed, about one-quarter the length of the seed (McAllister 2005a). In other regards, with its almost perfectly white ripe fruits, it is very similar to S. glabriuscula – and apparently its equal for garden performance, though with distinctly more delicate foliage. Howick 1960, collected at c. 3990 m on the southwestern side of the Wuming Pass, Sichuan in 1994, is comparable and may become common in cultivation as it too has almost pure white fruits, and similarly delicate foliage.

Sorbus fansipanensis McAll. Plate 518. Sorbus fansipanensis probably requires shelter in a mild garden to do well. This specimen is at Ness Botanic Gardens, grown from KR 2173. Image P. Williams.

Tree to 10 m. Branchlets, petioles and leaf rachises covered in reddish brown hair, particularly when young. Buds reddish, to 1 cm long with reddish brown hairs on the margins and apices of the scales. Leaves almost evergreen, 15–22 cm long, with four to five (to six) pairs of leaflets. Leaflets 4–6 × 1.6–2.3 cm, narrowly oblong to obovate, upper surface bluish green and glabrous, lower surface highly papillose, margins dentate in the upper three-quarters (long shoots) or at the apex only (short shoots). Inflorescence erect and remaining so in fruit. Fruit small, hard and crimson, 0.6 × 0.5 cm; calyx lobes fleshy, carpels three to four (to five). Diploid (2n = 34). McAllister 2005a. Distribution VIETNAM: Lao Cai (Fan Si Pan, Ban Khoang). Habitat Scrub on steep slopes. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration NT802.

This rowan from Fan Si Pan is an interesting species as its leaves remain more or less evergreen, especially in mild climates or over a warm winter. Despite this, and its southern origins, it seems to be surprisingly hardy, surviving well at Ness where it is making single-stemmed small trees 3–4 m tall (grown from KR 2173). Its long-lasting red berries make it attractive through the winter, persisting until at least April in some gardens. A sheltered place in light woodland would probably give the best chances for its success. Also growing on Fan Si Pan are Sorbus pseudovilmorinii or something very similar (McAllister 2005a) (see p. 809), and the exceptionally attractive Sorbus (Aria) subulata (p. 819).

Section II. Species Accounts

Sorbus forrestii McAll. & Gillham Tree to 12 m, though usually less. Branchlets grey. Buds deep red, conical to ovoid with white hairs on the margins and apices of the scales. Leaves to 20 cm long, with seven to nine pairs of leaflets. Leaflets rather widely spaced, ~4 cm long, upper surface glabrous, lower surface highly papillose, margins dentate to entire; leaves turning salmon-pink to orange in autumn. Fruit white with a crimson tint at the calyx, 0.8 × 0.95 cm; carpels three to four (to five). Tetraploid apomict (2n = 68). McAllister & Gillham 1980, McAllister 2005a. Distribution CHINA: Yunnan (Beima Shan). Habitat Mixed thickets. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister & Gillham 1980, McAllister 2005a. Cross-reference S497.

Sorbus forrestii, although another apomictic member of section Discolores, does not resemble the familiar species S. glabriuscula and S. pseudohupehensis and therefore does not feature in the key to their allies (p. 804). It is distinct in its larger white fruits and smaller but more numerous leaflets. It is also smaller-growing in cultivation, and at Ness has reached only 4 m in 40 years (McAllister 2005a), though elsewhere it is faster. Like others, however, it was recognised in cultivation, when in 1972 it was drawn to Hugh McAllister’s attention under the name S. prattii. Research found it to be growing in several British botanical gardens, and a chain of evidence led to its identification with Forrest’s collection (no. 19583) made on the Beima Shan, Yunnan in 1921. The dense crops of white fruit and low bushy habit make it ideal for smaller sites, and it is now widely grown and commercially available throughout our area. Much rarer, and as yet only tentatively distributed beyond Ness and Keith Rushforth’s own collection, is another apomict, S. bulleyana McAll., which differs principally in its more numerous leaflets (9–11 pairs) and ‘pearly pinkish white’ fruits. The solitary tree at Ness is derived from Keith Rushforth’s gathering KR 2809 made in 1993 in the Zhongdian Gorge, Yunnan at 3200 m, which also provided the type specimen. The specimen at Ness is a bit straggly, but the fruits are pretty. From the same seed collection came an anomalous diploid seedling that has been named ‘Keith Rushforth’ (McAllister 2005a).

Sorbus glabriuscula McAll. Syn. S. hupehensis hort. non C.K. Schneid. (white-fruited form), S. glabrescens hort. non (Cardot) Hand.-Mazz. Tree to 8–15 m. Branchlets stiff and stout. Buds red, conical to ovoid, to 1.5 cm long with some reddish brown hairs on the margins and apices of the scales. Leaves 14–26 cm long, with five to eight pairs of leaflets. Leaflets 4–5.5 × 2 cm, obovate, upper surface glabrous, lower surface somewhat papillose, margins toothed for half to two-thirds of their length; leaves turning orange-yellow in autumn. Fruit white flushed with pink at the calyx, 0.75 × 0.8 cm; calyx lobes very fleshy, carpels four to five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (Lijiang range). Habitat Scrub on steep slopes. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT797.

Sorbus glabriuscula is discussed here to establish the unfamiliar new name for a familiar old plant, the white-fruited S. hupehensis of horticulture. The species is comprehensively discussed by McAllister (2005a), who believes that it must have been introduced by George Forrest, although details are a little hazy. Whatever its origins this is a first-class tree, producing its heavy crops of persistent white fruits reliably each year. It appears at its best when planted against a dark background of conifers, where winter sunlight can illuminate the fruits. The first record of it flowering in cultivation is a herbarium specimen collected in Woburn, Bedfordshire in 1931, so it is interesting that good specimens are growing now in adjacent small private gardens in Woburn village, presumably on their own roots (H. McAllister, pers. comm. 2007).

Sorbus

803

804

Sorbus

New Trees

To help clarify the situation regarding the species known in horticulture as S. hupehensis, and their allies, a key is provided below.

Key to Sorbus glabriuscula, S. pseudohupehensis and similar tetraploid apomictic species in section Discolores 1a. Fruits white, occasionally with a pink flush especially at calyx ........................................................ 2 1b. Fruits usually mostly pink or red (can be almost white in S. pseudohupehensis if grown in shade) ................................................. 3 2a. Leaflets elliptic, fruit elongated (longer than broad) ...................................................... S. ellipsoidalis 2b. Leaflets oblong to obovate, fruit more or less round ..................................................... S. glabriuscula 3a. Leaflets more or less equal in size, so leaf outline is parallel-sided, usually not blue-green; fruits comparatively soft, some exceeding 7 × 8 mm ............................... 4 3b. Leaflets increasing in size towards apex, so leaf outline is kite-shaped, usually blue-green; fruits very hard, not exceeding 7 × 8 mm ...................................................... 5

Plate 519. Sorbus muliensis in its autumn colours. The apomictic members of Sorbus section Discolores differ only subtly from each other. Image P. Williams.

4a. Leaflets in seven to eight pairs, oblong, rounded at base; fruit white flushed crimson, seed flattened .......................................................................................... S. coxii 4b. Leaflets in six to seven pairs, oblong-elliptic, cuneate at base; fruit to 8.5 × 9 mm, white heavily flushed crimson, seed globular ............................... S. muliensis 5a. Fruit to 7 mm, white flushed pink at calyx and where exposed to sun; autumn foliage turning from purplish to crimson; often biennial fruiting in UK .......... S. pseudohupehensis 5b. Fruit to 8 mm, crimson becoming paler and more pink; autumn foliage orange and red; fruiting annually ................................................................................ S. carmesina

Sorbus helenae Koehne Plate 520. Sorbus helenae has a distinctive appearance from its large leaves with only a few pairs of wide leaflets, but the broad inflorescence is also characteristic. This is CEE 308, growing at Dawyck. Image D. Knott.

Tree 3–7(–10) m. Branchlets stout, c. 5 mm diameter, with sparse lenticels, glabrous. Buds to 2 cm long, oblong-ovoid, scales green with red and black at apices, glabrous. Leaves to 20 cm long, with two to three pairs of leaflets, the apical pair being the largest. Leaflets leathery, to 9(–11) × 3 cm, upper surface finely rugose with impressed veins, glabrous, lower surface with red-brown pubescence, non papillose, margins finely serrate throughout; stipules dentate, persistent and leafy, 0.7 × 1.1 cm; petiole 2.5–5 cm long, somewhat sheathing at base. Inflorescences to 15 cm across, dense, with branches and pedicels reddish-hairy. Flowers to 0.8 cm diameter, white. Fruit white with pink around calyx lobes, slightly broader than long, to 0.7–0.8 cm diameter; calyx lobes slightly fleshy, carpels five. Sexual diploid (2n = 34). McAllister 2005a. Distribution CHINA: western Sichuan. Habitat Mountain forests. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration NT804.

Sorbus helenae (named after Ernest Wilson’s daughter) is very rare in cultivation. The first successful introduction was by Edward Needham, who collected it from the top of Emei Shan (EN 3088). Grafted plants of this have been distributed to several collections by Keith Rushforth (pers. comm. 2008). Another introduction, also from Emei Shan, was made by the Chengdu Edinburgh Expedition of 1991, under the number CEE 308. This is growing happily at Dawyck, making a good bushy individual (there are a few progeny elsewhere). Seen through rainy spectacles it has a suggestion of a Sambucus – this impression contributed principally by the

Section II. Species Accounts

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large leaves with their broad leaflets. McAllister (2005a) records that S. helenae has brilliant orange-red autumn colour. It deserves to be more widely grown.

Sorbus hypoglauca (Cardot) Hand.-Mazz. Tree to 6 m. Branchlets thick, stiff and to 0.7 cm diameter. Buds 1–2 cm long, conical to ovoid, scales crimson to green with white hairs on the margins and apices. Leaves to 24 cm long, with 8–10 pairs of leaflets. Leaflets leathery, 5.6 × 1.2 cm, upper surface glabrous, lower surface white and densely papillose, margins dentate at apex or to two-thirds of their length; stipules persistent and leafy, 1.7 × 2 cm, lobed and dentate; petiole with glabrous sheathing at base. Inflorescences dense and corymbose, erect, even when in fruit. Fruit white or with a slight crimson flush, broadly turbinate, 0.55–0.75 × 0.8–1 cm; calyx lobes hardly fleshy, carpels five. Sexual diploid (2n = 34). McAllister 2005a. Distribution CHINA: Yunnan. Habitat Open hillsides with Abies and Rhododendron. USDA Hardiness Zone 6. Conservation status Not evaluated.

The pale undersides to the large leaves make Sorbus hypoglauca distinct from all other Sorbus and an interesting species for the collector. The broad inflorescences are reminiscent of those of S. rehderiana but in the latter the stipules are small and caducous. Sorbus hypoglauca fails to score high marks, however, as its autumn coloration is a dull brown and the fruiting corymbs soon break up (McAllister 2005a). It is very rare in cultivation, although grown at Ness, Tregrehan and elsewhere from collections made by Keith Rushforth in the Cangshan, Yunnan in 1993 and 1996 (KR 2733, 2738, 2746, 4047, 4061).

Sorbus khumbuensis McAll. Shrub or tree to 7.5 m. Branchlets slender, reddish brown with grey patches. Buds ~0.7 cm long, conical to ovoid, dark red with reddish brown hairs on the margins and apices. Leaves to 13 cm long, with 12–19 pairs of leaflets. Leaflets 2.1–5.5 × 0.8–1.7 cm, broadly oblong to elliptic, upper surface glabrous, lower surface not papillose, margins dentate to the base; leaves turning reddish pink in autumn. Inflorescences lax with few flowers; flowers pink. Fruit initially dull crimson, but ripening to pink then white, apple-shaped, 0.85 × 1 cm; calyx lobes slightly fleshy with three distinct veins, carpels three to four (to five). Tetraploid apomict (2n = 68). McAllister 2005a. Distribution NEPAL: Khumbu. Habitat BetulaRhododendron forest. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT805.

Sorbus khumbuensis is a member of the S. microphylla aggregate of similar apomictic microspecies (see p. 807), but differs in several ways and has therefore been described and named as a distinct entity within the group. The type and only collection was made by Tony Schilling (Schilling 2341) in the Khumbu area of Nepal in 1978. It has proven to be a successful and easily grown garden tree, apparently tolerating drier conditions than other members of the S. microphylla group. From them it may be distinguished by its 12 to 19 pairs of leaflets, which turn an excellent red in autumn, its pink flowers, and fruits that turn from crimson to almost pure white as they mature (McAllister 2005a). Trees are well established at Wakehurst Place, Ness and other collections, but it deserves to be widely planted and is ideal for a small garden.

Plate 521. Like many apomictic Sorbus taxa, Sorbus khumbuensis has only been collected once. Found by Tony Schilling in Nepal in 1978, it is ideal for a small garden. Image Phytophoto.

806

Sorbus

New Trees

Sorbus kongboensis McAll. Small, spreading tree to 6 m. Buds densely covered with reddish brown hair. Leaves dark green, to 40 cm long, with 11–12 pairs of leaflets. Leaflets 7.5 × 1.7 cm, margins dentate for about three-quarters of their length; leaves turning reddish brown in autumn. Fruit pink, 0.8 × 1.2 cm; carpels three to four (to five). Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Xizang (Kongbo). Habitat Clearings in Abies forest. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT799.

Sorbus kongboensis is a common small tree in southeastern Tibet and is now established in cultivation, although as yet it is not widely grown. Again it is thanks to Keith Rushforth that this species was discovered and introduced (KR 3664). In the wild it has spectacular autumnal coloration, derived from both the fruits – crimson, slowly becoming paler – and the rich red leaves. This red pigmentation is also apparent in the abundant red hairs that cover the buds and young leaves.

Sorbus kurzii (G. Watt ex Prain) C.K. Schneid. Tree to 7.5 m. Branchlets slender. Buds to 0.9 cm long, reddish and ovoid. Leaves to 13 cm long, with four to five pairs of leaflets. Leaflets 1.6–3.5 × 1.2–1.8 cm, broadly oblong to ovate, upper surface glabrous and very shiny, lower surface papillose, margins serrate, at least at the apices. Inflorescences lax with few flowers; flowers greenish white with pink tips. Fruit initially crimson, but ripening to white flushed with pink, five-angled, 0.55–0.75 × 0.55–0.9 cm; carpels (three to) four to five. Sexual diploid (2n = 34). McAllister 2005a. Distribution BHUTAN; INDIA: Sikkim, Arunachal Pradesh; NEPAL. Habitat Mixed scrub, between 3000 and 3300 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a. Cross-reference S498.

For a change, Sorbus kurzii was discovered and named in the nineteenth century, but was introduced to cultivation only in recent years, from eastern Nepal by Ted Millais, and from Bhutan by Keith Rushforth (KR 1501); the latter has also found it in Arunachal Pradesh, slightly extending its previously known range (Keith Rushforth, pers. comm. 2008). It is this stock from Arunachal Pradesh that has become most widely grown and is currently commercially available in the United Kingdom. This is not a very exciting species, with sparse white fruits and rather leathery, rose-like leaves. The leaves are reported to turn a good red colour in autumn, however, and the plant is reasonably drought-tolerant (McAllister 2005a). In the Royal Botanic Garden Edinburgh, where it is represented by EMAK 288, the pearly white fruits set off by the small leaflets in autumn colour are most attractive, but the species probably needs a cool climate to thrive and perform well (H. McAllister, pers. comm. 2007).

Sorbus lingshiensis Rushforth Tree to 6 m. Branchlets 4–5 mm diameter. Buds narrowly conical, to 1.8 cm, with some rufous hairs. Leaves to 9 cm, with six to nine pairs of leaflets. Leaflets ovate-lanceolate to oblong-lanceolate, acute, margins toothed in upper half; stipules caducous, small. Fruit obovoid, 0.8–1 × 0.6–0.8 cm, ripening white with a pink flush; carpels three to four. Sexual diploid. Rushforth 1991, McAllister 2005a. Distribution BHUTAN; CHINA: Xizang. Habitat Betula-Rhododendron forest. USDA Hardiness Zone 6. Conservation status Not evaluated.

Sorbus lingshiensis is related to the S. rehderiana complex, differing in its more slender shoots, fewer leaflets and fewer carpels. It was described from Lingshi in the northwest of Bhutan where it grows with S. rinzenii in low forest dominated by Betula utilis and Rhododendron aeruginosum Hook. f. Similar plants occur in adjacent southeast Tibet. Sorbus lingshiensis was collected under the numbers KR 876 and 878, and has been distributed by John Millais (K. Rushforth, pers. comm. 2008).

Section II. Species Accounts

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807

Sorbus microphylla agg. Shrub or tree to 10 m. Branchlets reddish brown or greyish brown. Buds to 0.8 cm, ovoid to conical, reddish with reddish brown hairs, particularly at scale apices. Leaves to 16 cm long, with 12–14 pairs of leaflets. Leaflets to 2.5 × 0.8 cm, rather variable, but may be pubescent with dentate margins. Inflorescences lax. Flowers small, pink to crimson. Fruit white with some pink, 0.8–1.1 × 0.95–1.2 cm; sepals not fleshy, midrib visible, carpels three to five. Tetraploid apomict (2n = 68). Lu & Spongberg 2003, McAllister 2005a. Distribution BHUTAN; CHINA: northwest Yunnan; INDIA: Sikkim; MYANMAR; NEPAL. Habitat Mountain thickets, between 3000 and 4000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT796, NT807. Cross-references B446, S499.

In describing Sorbus microphylla, Wenzig included material that is now treated as belonging to S. cashmiriana (the type) and S. rufopilosa. Rushforth (1993) lectotypified S. microphylla Wenzig emend Rushforth, making the Thomson specimen from Simla, India (preserved at Berlin) the lectotype. However, this is not in cultivation, and the complex is known to contain many pinkto crimson-flowered Himalayan apomictic microspecies, in which S. rufopilosa is an important diploid parent. Were the pattern of recognising each clonal population as a microspecies to be strictly followed, each of the many entities that fit here could bear a separate name. Such a plethora of species would be unworkable for field botanists and horticulturists alike (apomicts in the living state often being identifiable only in fruit) and McAllister’s approach of treating this group under an aggregate name is wise. Another reason he gives for not naming all these plants is that they tend not to thrive in cultivation, obviating the desirability of attaching an epithet to each and every one. The exception is the easy-to-grow S. khumbuensis (see p. 805), which unlike other members of the group has fruits that turn crimson before becoming pinkish white. The rest of the S. microphylla aggregate have white fruits with varying amounts of pink, but share pink to red flowers. Material has been brought into cultivation on multiple occasions, the first apparently being the collection made by Schilling, Sayers and Bista (SSB 443) in the Langtang valley of Nepal in 1966, followed by a further series of introductions from Nepal during the 1970s, through to Ron McBeath’s gatherings in the Barun Khola in 1981. These collections are maintained in cultivation but seem to thrive only in the cooler wetter parts of the United Kingdom: for example, at Inverewe on the west coast of northern Scotland (McAllister 2005a). A more recent introduction, currently commercially available, was made at 3700 m in northern Sikkim in 2002, by Sally Goddard and Sue and Bleddyn Wynn-Jones (GWJ 9252), who describe it as ‘wonderfully neat’ (Crûg Farm Plants 2007–2008).

Sorbus muliensis McAll. Tree to 10 m. Branchlets reddish brown. Buds ovoid to conical, reddish with reddish brown hairs, particularly at the scale apices. Leaves to 23 cm long, with six to seven pairs of leaflets. Leaflets to 4.6 × 1.6 cm, elliptic to oblong, dentate towards the apex. Inflorescences pyramidal. Flowers white. Fruit white flushed with crimson, 0.85 × 0.9 cm; sepals very fleshy, carpels four to five. Tetraploid apomict (2n = 68). McAllister

Plate 522. One of the Sorbus microphylla aggregate, in autumn, at Benmore. The smaller Sorbus often make bushy little trees that are of great garden value. Image R. Unwin.

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New Trees

2005a. Distribution CHINA: western Sichuan (near Muli town). Habitat Mountain thickets. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT804.

This apomictic microspecies is closely related to Sorbus pseudohupehensis and S. coxii and is rather similar in appearance to both, with the same high horticultural merits. Botanical differences are set out in the key provided for this group (p. 804), but a useful horticultural distinction between S. muliensis and S. pseudohupehensis is that S. muliensis fruits every year (S. pseudohupehensis can become biennial-fruiting), and the larger, softer fruits ripen slightly later than those of S. pseudohupehensis. It may also be slightly hardier than S. pseudohupehensis (McAllister 2005a). Once again, the species was recognised from a single surviving grafted tree at the Royal Botanic Garden Edinburgh, in this case grown from Forrest 22177, collected near Muli in 1922 – often described as the best Sorbus in the garden, fruiting heavily and attractively every year.

Sorbus olivacea McAll. Tree to 10 m. Buds ~1.1 cm, red with reddish brown hairs on the margins and apices of the scales. Leaves whitish green, to 26 cm long, with five to six (to seven) pairs of leaflets. Leaflets to 6.3 × 2.3 cm, elliptic to oblong, slightly papillose beneath. Fruit hard, 0.7–0.8 × 0.7–0.9 cm, white flushed with pink or crimson in full sun; carpels (three to) five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Sichuan (Xichang Co.). Habitat Mountain forests. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT808.

Plate 523. Sorbus olivacea, introduced from China in 1992 as SICH 1162, is recognisable by its unusual pallid foliage – especially the undersides of the leaves. Image P. Williams.

Sorbus olivacea is rather more distinct than other members of section Discolores, having unusually coloured leaves that make it quite conspicuous. The upper surfaces are a soft grey-green and the lower surfaces pale, so the whole tree has a pallid shimmer that will be greatly appreciated in the landscape as it becomes better known. The fruits are white, flushing pink or even red where exposed to the sun, and the tree at Ness, when leafless and covered in fruit, is extremely attractive illuminated by winter sunshine (H. McAllister, pers. comm. 2007). Like S. muliensis before it, it too is from Muli Co., Sichuan, having been collected at 2850 m there by the 1992 SICH team (Fliegner, Staniforth, Howick & McNamara: SICH 1162, as S. oligodonta). Under the number SICH 1482 (1994 expedition) is a similar taxon from Xichang Co., differing in minor details, which is another as yet unnamed apomictic microspecies (McAllister 2005a).

Sorbus parvifructa McAll. Tree to 15 m. Branchlets slender. Buds ~1 cm, ovoid to conical, reddish brown with white hairs on the margins and apices of the scales. Leaves to 18 cm long, with 8–11(–14) pairs of leaflets. Leaflets to 4 × 0.9 cm, very papillose beneath. Fruit hard, to 0.7 × 0.5 cm, soft pink; sepals very fleshy, carpels five with white-hairy apices. Sexual diploid (2n = 34). McAllister 2005a. Distribution CHINA: Xizang (Bomi Co.). Habitat Wet, mixed deciduous-coniferous woodland. USDA Hardiness Zone 7. Conservation status Not evaluated.

Sorbus parvifructa is a sexual diploid member of section Discolores and as such can be expected to vary slightly, and to form hybrids when grown in proximity to other species. It was first spotted as fallen fruits by Hugh McAllister, on an expedition with Keith Rushforth on the Showa La of southeastern Tibet in 1997, and immediately recognised as a distinct species. Seed was introduced under the numbers KR 5731–5735. The high number of leaflets and very small pink, slightly elongated fruits are its points

Section II. Species Accounts

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809

of distinction within the section. As yet it has not been widely grown, but it should make an interesting specimen. It is certainly very vigorous; a young plant donated by Hugh McAllister has gained 50 cm in its first growing season at Colesbourne Park, Gloucestershire.

Sorbus pseudohupehensis McAll. Syn. S. hupehensis hort. non C.K. Schneid. (pink-fruited form), S. hupehensis var. obtusa C.K. Schneid., S. laxiflora Koehne, S. oligodonta hort. non (Cardot) Hand.-Mazz., S. wilsoniana hort. non C.K. Schneid. Tree to 15 m. Branchlets deep red. Buds ~1.2 cm, conical to ovoid with reddish brown and/or white hairs on the margins and apices of the scales. Leaves to 17.5 cm long, with five to seven pairs of leaflets. Leaflets to 4.4 × 1.7 cm, gradually decreasing in length towards the stem, obovate, bluish green glaucous above, papillose beneath; in autumn, leaves turning dark chocolate then brilliant red colour. Inflorescences pyramidal. Fruit very hard, 0.7 × 0.8 cm, white flushed with crimson; sepals very fleshy, carpels four to five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (Lijiang). Habitat Mountain thickets. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration McAllister 2005a. Cross-references B431–432 (as S. hupehensis), K335 (as S. hupehensis var. obtusa).

As discussed above (pp. 797, 804), Sorbus pseudohupehensis has long been known as S. hupehensis (pink-fruited form) or as S. hupehensis var. obtusa, and still appears in some recent literature as S. oligodonta (Wharton et al. 2005), but should now be known under its new name. It is an extremely familiar tree, widely grown for its bluegreen leaves and persistent pinkish fruits that give a wonderful display long into the winter after the tree has dropped its red autumn plumage. As with S. glabriuscula, this is seen best against a dark background. It can develop the unfortunate habit of becoming biennial-fruiting, like some apples; a number of its allies are more reliable in this regard, and have equally good effect, but are not likely to supplant it in popularity. So-called selections such as ‘Pink Pagoda’ are identical to every other member of the microspecies. As with all apomictic Sorbus, it should be grown from seed to ensure the most attractively shaped and vigorous trees. Its origin is believed to have been seed gathered in the Lijiang range of Yunnan by George Forrest in the early 1920s, but it is not now attributable with certainty to any particular collection (McAllister 2005a).

Sorbus pseudovilmorinii McAll. Shrub or small tree to 7.5 m. Branchlets slender, reddish brown. Buds ~0.8 cm, conical to ovoid, deep red with reddish brown hairs on margins and apices of scales. Leaves to 15 cm long, with 10–14 pairs of leaflets. Leaflets to 2.3 × 0.7 cm, elliptic, margins finely dentate in upper third or half, apex apiculate, not papillose beneath. Inflorescences lax. Fruit apple-shaped, 0.85 × 1.1 cm, initially bright crimson (rarely white), gradually becoming paler, until white with crimson flecks, reddish brown hairs at base; sepals fleshy, carpels three to five. Sexual diploid (2n = 34). McAllister 2005a. Distribution CHINA: Guizhou (Fan Jin Shan), southeast Sichuan, southeast Xizang, northwest Yunnan; VIETNAM: Lao Cai (Fan Si Pan). Habitat Mountain forests or scrub. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT809.

Sorbus pseudovilmorinii is named for its similarity to the wellknown and very popular S. vilmorinii, a tetraploid apomict that comes true from seed. This seems to have been introduced to the Vilmorin nursery at Les Barres, France by Abbé Jean Delavay in 1889, and it is probable that all cultivated

Plate 524. Sorbus pseudovilmorinii, seen here at Tullynally Castle, Co. Westmeath, is one of the best rowans for general garden use, giving heavy crops of brightly coloured berries. Image J. Grimshaw.

810

Sorbus

New Trees

plants derive from that introduction – sadly usually seen as ungainly grafted specimens. It was as S. vilmorinii that Forrest collected numerous herbarium specimens and seeds of a similar tree in western China during his last expedition (1930–1932), but a survivor at Borde Hill, West Sussex was much later discovered to be a fertile diploid and thus not referable to S. vilmorinii. More gatherings from a wide area of western China began to be made available after the area became more accessible to western visitors from 1980 onwards, and it is now apparent that this diploid species has a huge range in western China. The type specimen is from a tree in cultivation at Ness collected in the Cangshan, Yunnan by the Sino-British Expedition to China in 1981, as SBEC 974. Material has been repeatedly collected since then, and the species is widely represented in collections, at least throughout the British Isles. Being a sexual diploid it is very variable. A group at Tullynally Castle, Co. Longford grown from seed collected by Thomas Pakenham, seen in full fruit in September 2006, showed this very well, their fruits ranging from deep magenta-pink to almost white, and with much variation in the shape of the trees. If, among such seedling batches, an outstanding individual is found, it may be propagated by grafting or by cuttings taken in summer. However, as the species flowers later than many others, groups of seedling trees produce seed that comes almost wholly true, so this sexual species can also be propagated by seed. Pure white-fruited clones are known and may be confused with S. koehneana, although on close inspection they vary in many respects, as tabulated by McAllister (2005a). The best forms of this small tree are exceptional, and as it is tolerant of drier conditions than S. vilmorinii it should be grown more widely. The autumn foliage is a good red.

Sorbus randaiensis (Hayata) Koidz. Plate 525. Sorbus species are noted for their brilliant autumn colours. Seen here in full glory is the remarkably hardy Sorbus randaiensis at Dawyck. Image R. Unwin.

Large shrub or tree to 8 m. Branchlets reddish brown. Buds ~1.8 cm, conical, red, sticky, with obscure reddish brown hairs on margins and apices of scales. Leaves to 20 cm long, with 7–10 pairs of leaflets. Leaflets leathery, to 6 × 1.1 cm, ovoid to lanceolate, margins finely dentate, apex acuminate, upper surface glossy green, lower surface not papillose. Inflorescence a flattened corymb. Fruit spherical, 0.85–1.1 × 0.85–1.1 cm, orange-red and shiny; sepals slightly fleshy, carpels three to four. Sexual diploid (2n = 34). Lu & Spongberg 2003, McAllister 2005a. Distribution TAIWAN. Habitat Mountain forests, between 2100 and 4200 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration McAllister 2005a; NT792, NT794, NT810. Cross-references B418, K338.

Sorbus randaiensis is a member of subgenus Sorbus, section Commixtae, and as such it has orange fruits suggestive of the familiar rowans. These can be produced in huge abundance, and when so clad, from about August onwards, the tree is a striking sight. In the wild it grows in the transition zone between coniferous forests and subalpine scrub, and can be rather shrubby, but some individuals form shapely trees (field notes to ETOT 84, ETE 230). Although it was described in 1913, the authenticity of specimens in cultivation was always in doubt (see Bean 1981b), and genuine material was not introduced until 1981, through the botanic

Section II. Species Accounts

Sorbus

811

gardens seed exchange system from the Taiwanese Forestry Commission (McAllister 2005a). Before then, narrow-leaved forms of S. commixta seem to have been cultivated under this name (More & White 2003), and the tall old trees in the West Sussex gardens of Borde Hill (16 m in 2003) and Leonardslee (10 m in 2003, TROBI) and in Westonbirt are probably really S. commixta. Some of these misidentified trees have had cultivar names applied, such as S. commixta ‘Dodong’ (A. Coombes, pers. comm. 2008). In recent years S. randaiensis has been collected regularly in Taiwan, by both European and American collectors, and it is now well established in cultivation. It would appear to be easy to grow, but Dan Hinkley (pers. comm. 2007) reports that in the Seattle area it is prone to sudden collapse. In southern England it leafs out in early spring but seems to be unaffected by later frosts (Flanagan & Kirkham 2005).

Sorbus rinzenii Rushforth Tree to 6 m. Branchlets 1.5–2.5 mm on extension shoots, to 4 mm on fruiting spurs. Leaves 9–19 × 3–5 cm, with (9–)11–14 pairs of leaflets. Leaflets to 3 × 0.7 cm, oblong, apex rounded, margins serrate with acuminate teeth in upper two-thirds, white-pilose. Stipules foliaceous, oblong, serrate on outer margin, 11 × 3.5 mm on flowering shoots, persisting. Flowers white. Fruit globose, 8.5–12 × 7–9 mm, ripening white or pink, fading to white; carpels four to five. Sexual diploid. Rushforth 1991. Distribution BHUTAN; INDIA: northern Sikkim; NEPAL: eastern. Habitat Mountain forests, c. 4000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated.

Sorbus rinzenii is a small tree in the S. microphylla alliance. It shares many characteristics with S. rufopilosa, including being a sexual diploid, but is larger in all parts, with large persistent stipules and leaflets up to 3 cm long that are toothed to more than half their length (McAllister 2005a). It comes from the drier area of northwestern Bhutan, where it was collected by Keith Rushforth in 1985, and also occurs in northern Sikkim and eastern Nepal at c. 4000 m, from where it was introduced by the Kew-Edinburgh-Kanchenjunga Expedition in 1989 (KEKE 627). It tolerates drier conditions than S. rufopilosa, and is more widely grown.

Sorbus rubescens McAll. Shrub or small tree to 8 m. Branchlets reddish brown. Buds ~0.8 cm, ovoid, reddish with reddish brown hairs on margins and apices of scales. Leaves to 20 cm long, with 11–14 pairs of leaflets. Leaflets to 2.5 × 0.5 cm, ovoid to elliptic, margins dentate. Inflorescences lax. Flowers pale pink. Fruit apple-shaped, 0.95–1.1 cm, white tinged with red, occasionally crimson; sepals fleshy at base only, carpels (three to) four to five. Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Yunnan (Zhongdian). Habitat Mountain forest or scrub. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration McAllister 2005a; NT811.

Sorbus rubescens is another species described from cultivation with quite a historic trail behind it. Its introduction is attributable to T.T. Yu’s collection (no. 13815) made near Zhongdian in 1937. A tree was grown at Wisley, from where seed was distributed; it returned to Ness from the Washington Park Arboretum, courtesy of the late Brian Mulligan (McAllister 2005a). It represents another apomict from the Zhongdian area, and may have S. filipes as one parent, contributing the pink flowers. The epithet rubescens indicates its tendency to flush red in some of the otherwise white fruits. It is a slow-growing, rather shrubby tree, but apparently reasonably tolerant of dry conditions. With its abundant crops of fruit it is horticulturally desirable, and is suitable for smaller gardens. Sorbus filipes Hand.-Mazz. is probably a complex of similar apomictic taxa, found in the mountains of Yunnan east across southeastern Tibet to Bhutan and possibly

Plate 526. Sorbus rubescens – the epithet rubescens (‘turning red’) alluding to the colour change that may be undergone by some of the otherwise mostly white fruits. Image P. Williams.

812

Sorbus

New Trees

Sikkim. They are characterised by their slender, shrubby habit and long narrow leaves with up to 17 pairs of leaflets. The flowers are deep pink or crimson and are followed by white or pink-flushed fruits (McAllister 2005a). Some occur only as shrubs, 1–2 m in height, with wand-like stems, but occasional tree forms are seen. To date, only apomictic tetraploids are known.

Sorbus rufopilosa C.K. Schneid. Tree to 10 m. Branchlets thin and delicate. Leaves to 8 cm long, with 10–17 pairs of leaflets. Leaflets to 1.5–2 × 0.4–1.1 cm, ovate, margins with few, large teeth. Inflorescences lax. Flowers pale pink. Fruit 0.95 × 0.9 cm or smaller, white flushed with pink; sepals not fleshy, midrib clearly visible, carpels three to four (to five). Sexual diploid (2n = 34). Lu & Spongberg 2003, McAllister 2005a. Distribution BHUTAN; CHINA: Guizhou, Sichuan, southeast Xizang, northwest Yunnan; MYANMAR; NEPAL. Habitat Montane forest with Abies, Picea and bamboos, between 2700 and 4000 m asl. USDA Hardiness Zone 6. Conservation status Not evaluated. Illustration NT812.

Sorbus rufopilosa and the related S. rinzenii Rushforth are sexual diploids allied to S. microphylla and share many of the same characters, such as the comparatively long, narrow leaves composed of numerous small leaflets, and pink-flushed flowers succeeded by white and pink fruits. The reddish hairs from which S. rufopilosa takes its name are conspicuous on the young foliage. Although an attractive plant it needs high rainfall and constant moisture to thrive and prosper, but when doing well it is exceptionally beautiful (McAllister 2005a). It has been introduced on several occasions from Nepal (for example, Binns, Mason & Wright 98, collected in 1979) and Bhutan (Sinclair & Long 5674, collected in 1984). Plate 527. Sorbus rufopilosa is a diploid allied to the S. microphylla aggregate, and to thrive it has similar requirements of abundant moisture and cool summers. Image R. Unwin.

Sorbus rushforthii McAll. Tree to 6 m. Buds ~1.5 cm, ovoid to conical, reddish with reddish brown hairs at the apex and white hairs on the scale margins. Leaves to 21 cm long, with (seven to) eight to nine pairs of leaflets. Leaflets 3.7–4.1 × 1.4–1.5 cm, elliptic to oblong, margins dentate in the upper third. Fruit hard, 0.75–0.9 × 0.75–0.95 cm, pale pink with deeper pink around the calyx; carpels (two to) three to four (to five). Tetraploid apomict (2n = 68). McAllister 2005a. Distribution CHINA: Xizang (Kongbo, Pome). Habitat Along streams in dry scrub. USDA Hardiness Zone 6. Conservation status Not evaluated.

This species is named in honour of Keith Rushforth, whose long-standing interest in Sorbus has led to the introduction of many interesting taxa, by no means all of which have been named. He has collected it (and other similar but probably distinct microspecies) on several occasions in the area of southern Tibet north of the great bend in the Yarlung Tsangpo, but the type collection was made in company with Hugh McAllister, from near Pasum Tso (the ‘Turquoise Lake’). The young trees in cultivation have so far fruited every year and seem to be similar in horticultural qualities to related species. Their performance as mature trees for comparison with earlier introductions

Section II. Species Accounts

will be assessed over the next few years. It is interesting that each of Rushforth’s collections from five locations (Milling, Pé, Gyala, Nyima La and Showa) lying within about 80 km of the top of the Yarlung Tsangpo Gorge seems to represent a different microspecies, that from Showa being particularly notable in having very numerous leaflets like S. parvifructa (which grows in the same valley).

Sorbus wallichii (Hook. f.) T.T. Yu Syn. S. wattii Koehne Tree to 10 m. Immature shoots and leaves densely white-tomentose. Buds ~1 cm, ovoid, reddish brown with white hairs. Leaves to 15 cm long, with four to eight (to nine) pairs of leaflets. Leaflets to 4.6–5 × 1.1–1.9 cm, margins dentate in the upper half, lower surface papillose. Stipules large, 1 × 1 cm with ~6 teeth. Inflorescences erect, even in fruit. Fruit elliptic, 0.7 × 0.7 cm, shiny crimson; sepals fleshy, carpels three to four. Sexual diploid (2n = 34). McAllister 2005a. Distribution BHUTAN; CHINA: Yunnan; INDIA: Arunachal Pradesh, Assam, Sikkim; MYANMAR; NEPAL; VIETNAM: Ha Giang. Habitat Low-altitude forest. Often an epiphyte. USDA Hardiness Zone 9. Conservation status Lower Risk.

Contrary to the usual view that rowans are a hardy breed of mountaineers, Sorbus wallichii is a tree from rather low altitudes, growing in subtropical laurel-oak forest over much of the southern flank of the eastern Himalaya, sometimes as an epiphyte. In consequence it is not very hardy, and is only suitable for mild, sheltered sites. McAllister (2005a) records a long-established tree at Ventnor Botanic Garden on the Isle of Wight, and notes that specimens of KR 1272 from Bhutan have survived –7 ºC. It is rare in cultivation, but collections made by Keith Rushforth in Yunnan and Vietnam are also being grown (K. Rushforth, pers. comm. 2008). The white-hairiness of the young growth is unique and makes it sound very tempting, but trees seen at Ness are rather thin and straggly.

Sorbus wilsoniana C.K. Schneid. Tree to 10 m. Branchlets thick and stiff. Buds large, ovoid and very sticky. Leaves to 25 cm long, with seven pairs of leaflets. Leaflets leathery, to ~8.3 cm long. Stipules large, leafy and persistent. Inflorescences large. Fruit subglobose, 0.8 × 0.8 cm, shiny crimson; carpels (three to) four to five. Sexual diploid (2n = 34). Lu & Spongberg 2003, McAllister 2005a. Distribution CHINA: Guangxi, Guizhou, western Hubei, Hunan, Jiangxi, western Sichuan, Yunnan. Habitat Mixed forests, between 1300 and 3300 m asl. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT814. Cross-references B426, K814.

Sorbus wilsoniana is very similar and closely related to the well-known and popular S. sargentiana, differing only in being slightly smaller in all parts, and having up to five carpels per fruit (three to four in S. sargentiana) (McAllister 2005a). It is an equally good garden tree, sharing its characteristic strong autumn colours and big orange clusters of fruits. It was introduced early in the twentieth century (though perhaps not by Wilson – Plantae Wilsonianae records that his collections were made of flowering specimens only: Sargent 1913); this stock seems, however, to have died out. It was reintroduced in 1985 through the Shanghai Botanic Garden seed list, the material having originated in Hunan (McAllister 2005a), and since then it has been collected on several other occasions, notably by expeditions to Sichuan (SICH 1233, 2100, 2215). Field notes indicate that it grows in mixed, rather open woodland over a range of altitudes, some of them quite low (SICH 2100, for example, was gathered at 1650 m in Tianquan Co. in 2001). The species is now quite widespread in cultivation, and freely available in the nursery trade.

Sorbus

813

814

Sorbus

New Trees

1 cm

B

C

A

D

E

H F

G

Section II. Species Accounts

ARIA

Aria / Sorbus

815

(Pers.) Host

Syn. Sorbus subgen. Aria Pers., Sorbus subgen. Micromeles (Decne.) J.B. Phipps, K.R. Robertson & Spongberg

Whitebeams Aria contains numerous species, ranging from tall trees to shrubs, often with smooth, pale bark. It is characterised by ovoid, conical buds with many spirally arranged scales and simple, toothed, or more or less lobed leaves which often have a persistent white or greyish tomentum beneath. In the leaf the lateral veins run straight out to the leaf margin (craspedodromous) or bend just before reaching the margin, forming a loop (camptodromous). Inflorescences are paniculate or corymbose. The flowers are white, 2- to 5-merous, and with a campanulate hypanthium. The fruits (pomes) are often red but may be yellowish, greenish or russet-coloured. The calyx may or may not persist on the fruit. In the species with persistent calyx lobes the fruits are never softly fleshy. Throughout Aria the fruit flesh is heterogeneous, giving a dryish granular texture, and when ripe the fruits taste sweet without the bitterness found in the fruits of almost all species of Sorbus s.s. The type species of the genus is Aria nivea Host, best known as Sorbus aria (L.) Crantz, the Whitebeam. In addition to the basic distinction of the leaf shapes and fruit characters, in most cases the two genera can also be distinguished by the form of their buds, and so can be told apart in winter – Sorbus having mostly elongated ovate-conical buds, one scale extending most of the length of the bud and usually few scales evident, while in Aria the buds are usually less elongated and have several bud scales evident on the surface, but no one scale extending the full length of the bud. The apomictic microspecies of hybrid origin are intermediate, with more deeply lobed leaves than in species of Aria, and those that have leaves with free pinnae have a terminal leaflet larger than, and of a different shape from, any of the free pinnae, distinguishing them from species of Sorbus, in which the terminal leaflet is more or less the same size as the laterals. As a native genus Aria is confined to the Old World, with no representatives in North America, but occurring through temperate Eurasia from the western seaboard of Europe and North Africa to Japan. In the east of this range it is represented by a number of A. nivea-like, large-leaved, rather ill-defined diploid species in the Himalaya and western China, and a few species that form a link with those that used to be assigned to Sorbus subgenus Micromeles. The breeding systems in Aria are just like those in Sorbus s.s., as outlined above. Aria as now interpreted includes species previously placed in Sorbus subgenus Micromeles. These have sometimes been considered sufficiently distinct to be placed in the separate genus Micromeles Decne., on the basis of their inferior ovaries and deciduous calyces (Kovanda & Challice 1981) as well as their general appearance. However, Robertson et al. (1991) argued that the heterogeneous flesh of the fruits in all species of both groups, and lack of consistency in the distribution of other characters (including those used by Kovanda & Challice), made it impossible to maintain the separation of Micromeles, even at the subgeneric level. Several familiar species (A. megalocarpa, A. folgneri, A. hemsleyi) show characters of both groups. It is clear that modern phylogenetic studies of both Sorbus s.l. and Aria s.l. are long overdue, but at present we have only morphology and cytology to work with.

Figure 89 (opposite). Sorbus tamamschjanae: four leaves of varying shape, from the same tree (A–D). Sorbus wilsoniana: leaf with stipule (E). Sorbus (Aria) hajastana: three leaves of varying shape, from the same tree (F–H).

816

Aria / Sorbus

New Trees

Hugh McAllister, who kindly supplied text that forms most of this introduction to Aria, recognises three groups of species that appear to represent the most natural divisions within the genus. No infrageneric classification is as yet available in Aria. Plate 528. Sorbus hajastana is a typical whitebeam, with white-hairy undersides to the simple leaves, and red fruits. No combination has been published for it in the genus Aria, within which it belongs to Group A. Image R. Unwin.

* Fourteen new taxa from Britain and Ireland have been described in 2009 (Rich & Proctor 2009, Rich et al. 2009).

Group A Equating to Sorbus subgenus Aria Pers. section Aria (Pers.) Dumortier European and west Asiatic species related to Aria nivea (Sorbus aria), with fruits that are wholly red when ripe and seeds that are round in cross-section. The embryos of these seeds contain germination inhibitors as they do not germinate on excision. Almost all have leaves that are white-tomentose beneath. This group occurs from western Europe to the Caucasus, is the only group found in this area, and does not appear to overlap in distribution with the other two groups. Within the group, diploids (only A. nivea, possibly S. umbellata and Chamaemespilus alpina) are sexual and polyploids apomictic. Apomicts have hybridised with A. nivea, S. aucuparia, Torminaria torminalis and Chamaemespilus alpina to produce a vast range of apomictic microspecies (100 named in Flora Europaea), which are often grouped with the pure aria types under Sorbus subgenus Aria or treated as the arranensis and latifolia aggregates. New taxa within this group are described regularly, with every crag, gorge and ridge in some areas supporting distinct microspecies. The Avon Gorge near Bristol in southwestern England is the most intensively studied sorbiferous part of the world, with nine native and four introduced taxa growing on its limestone cliffs (Rich & Houston 2006). Five of the natives are British endemics, three of these known only from the Avon Gorge, including White’s Whitebeam S. whiteana T.C.G. Rich & L. Houston, described in 2006. The abundance and diversity of such local taxa seems to depend somewhat on research effort (Avon Gorge is under the beady eyes of researchers from the universities of Bristol and Cardiff, for example).*

Group B Equating to Sorbus subgenus Aria Pers. section Micromeles (Decne.) Rehder OR subgenus Micromeles (Decne.) J.B. Phipps, K.R. Robertson & Spongberg, in part Himalayan and east Asiatic species with usually more or less spherical fruits that never become uniformly red or orange, the skin of the fruit often containing much chlorophyll when ripe, and which may be densely covered with lenticels (russeted), thereby resembling an apple or pear (Malus or Pyrus) rather than fruit of European species of Group A. The seeds are always laterally flattened and radially elongated, as in Cormus, and the embryos germinate on excision. All species that have been examined are diploid and sexual. The concept of this grouping is new and it needs refinement, as it probably contains elements from different lineages (H. McAllister, K. Rushforth, pers. comms. 2008), but this will require further study. Species with white-tomentose leaf undersides mostly have persistent calyces and free carpel apices (these were formerly referred to subgenus Aria), while those with more or less glabrous leaf undersides mostly have deciduous calyces and fused carpel apices (and were formerly referred to Micromeles); both craspedodromous and camptodromous venation are found in this latter subgroup.

Section II. Species Accounts

The existence, however, of species with a mixture of characters of these two subgroups makes it impractical to maintain separation between them: A. megalocarpa has a persistent calyx but more or less glabrous leaf undersides and fused carpel apices, for example, while A. hemsleyi has deciduous calyces but white-tomentose leaf undersides. (As pointed out by Robertson et al. (1991), Malus and Pyrus include species with and without deciduous calyces, and in some species of Malus leaves on long shoots have craspedodromous venation while short-shoot leaves have camptodromous venation.)

Group C Equating to Sorbus subgenus Aria Pers. section Alnifoliae (T.T. Yu) Aldasoro, Aedo & C. Navarro OR subgenus Micromeles (Decne.) J.B. Phipps, K.R. Robertson & Spongberg, in part For example, Aria alnifolia, A. folgneri, A. japonica, A. yuana, A. zahlbruckneri. East Asiatic species with oblong fruits that become a distinctive translucent red or orange on ripening, the seeds of which are pear-shaped and round in cross-section, and the embryos of which contain germination inhibitors and do not germinate on excision. Calyx lobes are persistent or deciduous; leaf venation craspedodromous. All species that have been examined are diploid and sexual. The distribution of this group overlaps with that of Group B but no hybrids between them have been reported from the wild. (Hybrids between A. nivea and A. alnifolia have been found in cultivation: H. McAllister, pers. comm. 2008.) Aldasoro et al. (2004) provided the first published recognition of it as a natural species grouping, and combinations in Aria are available for most species (Ohashi & Iketani 1993). Aria alnifolia is considered to be one of the few sorbi to be a success in the cooler parts of the United States (Jacobson 1996, Dirr 1998). Adding the evidence from A. yuana, it seems that these members of former subgenus Micromeles are among the best options for Sorbus s.l. in American horticulture. All appear to be totally self-incompatible, so that single isolated trees bear only small fruits that are much less attractive than the large fruits they produce if cross-fertilised. They should therefore always be planted in groups containing more than one clone, with spacing to ensure that at least two clones can be grown to maturity. One option might be to graft two clones to a single stock, to ensure a free-fruiting specimen. The protean diversity of Aria and its hybrid derivatives in Europe and southwestern Asia makes a comprehensive account almost impossible in a book of this nature; there is an almost endless pool of local taxa available to be brought into cultivation, each with its own alluring name, although perhaps not really very distinct. The value of these trees in the garden and landscape is undoubted, though they often fall just short of the first rank. Their prime moment is often the unfurling of the leaves in spring, when the white undersides show to best advantage on the whitebeams, and some Asian species (Micromeles) flush with effective red or bronzed new growth. Their autumn efforts are variable. Most of the allies of Aria nivea and its derivatives are disappointing then, but the Asian species can colour very well. Described more fully below, though with abbreviated cultivation notes, S. hajastana, S. takhtajanii and S. tamamschjanae are drought-tolerant small trees from eastern Turkey and Armenia, initially introduced to cultivation through seed sent to Ness

Aria / Sorbus

817

818

Aria / Sorbus

Plate 529. Sorbus tamamschjanae, seen here in flower at Kew in May 2008, was introduced to Britain by the Armenian botanist Dr Eleonora Gabrieljan. Image J. Grimshaw.

New Trees

Botanic Gardens by Dr Eleanora (Nora) Gabrieljan of Yerevan, Armenia, who named them (H. McAllister, pers. comm. 2007). They were distributed to other botanical gardens in Britain from Ness, and all three may be seen in the collections of Kew and Edinburgh, for example. Sorbus armeniaca Hedl., S. kusnetzovii Zinserl. and S. subfusca Boiss. are whitebeams from the same general area also occasionally found in botanical gardens. All do well in the British Isles, and while not particularly outstanding, could be grown where smallish, slow-growing whitebeams are required, for their attractive red fruits and leaves with white undersides. Allen Coombes has made us aware of an interesting range of Aria species (or hybrids) being cultivated commercially in Hungary and evidently valued as good ornamentals and street trees. The following taxa were offered by the nursery Alsótekeresi Faiskola Kft. of Balatonvilágos, Hungary, in their 2006–2007 catalogue (the brief descriptions are derived from this source): S. bakonyensis Jáv. (a small, bushy tree with orange-red fruits); S. bodajkensis nom. nud. (a medium-sized, robust tree suitable for landscaping or as a street tree); S. borbasii Kárpáti (bushy, with early-ripening purplish fruits; can be grown as a hedge); S. borosiana Kárpáti ‘Alba Regia’ (a state-approved selection, forming a small tree with very dark green leaves for landscaping; the fruits sweet and delicious); S. decipientiformis Kárpáti ‘Vállus’ (also a state-approved selection, forming a slender conical tree, again with delicious fruits); S. degenii Jáv. (a Hungarian native, allied to Torminaria torminalis and producing edible fruits); S. eugenii-kellerii Kárpáti (a small tree native to the Vértes Mountains of western Hungary, producing ‘marvellous little vermilion apples’); S. ‘Hainburg’ (selected near Hainburg, Austria; medium-sized, very tolerant of calcareous soils and dry conditions); and S. incana Hedl. (a small, thick-crowned tree of hybrid origin, from Scandinavia). Several of these are in cultivation at Wageningen in Holland, from where they have been distributed over many years through the botanic gardens seed exchange. Some are growing well at Ness, near Liverpool (H. McAllister, pers. comm. 2008), where the Sorbus form a National Plant Collection. Another, for the whole group, is at the Jodrell Bank Science Centre, Cheshire. There are also National Plant Collections of British Sorbus maintained by Lord Ridley at Blagdon, Northumberland and by Glyndwr Marsh at Cadnam, Hampshire, while Aria and Micromeles collections are maintained by the East Durham & Houghall Community College, Durham, and at Winkworth Arboretum, Surrey. TROBI includes records on a number of taxa belonging to Aria Group A in cultivation in British arboreta, mostly represented by solitary specimens in the Sir Harold Hillier Gardens. Their names are noted here, but information on them will have to be sought in regional floras: S. adamii Kárpáti, S. barthae Kárpáti, S. danubialis (Jáv.) Kárpáti, S. latissima Kárpáti, S. leptophylla E.F. Warb., S. pseudobakonyensis Kárpáti, S. semi-incisa Borbás, S. simonkaiana Kárpáti, S. thaiszii (Soó) Kárpáti, S. zolyomii (Soó) Kárpáti. A further selection is cultivated in the Netherlands, according to the catalogue of Plantentuin Esveld (2004–2006), which mentions the following (not all of which are offered by the nursery): S. dacica Borbás, S. dubia Hedl., S. pontica Zaik., S. pseudolatifolia Boros, S. redliana Kárpáti, S. retroflexis (author not traced), S. stankovii Juz., and S. taurica Zinserl. No doubt a more diligent search of arboretum catalogues would reveal many further names.

Section II. Species Accounts

An attractive species of unknown origin is S. croceocarpa P.D. Sell, a member of the S. latifolia group with small, weakly lobed leaves and bright orange-yellow fruits in autumn. This has become widely naturalised in Britain. All of the named and some of the un-named native British Sorbus species are in cultivation at Ness, where S. hibernica and S. porrigentiformis from the Menai Straits in northern Wales are particularly attractive as heavy-fruiting small versions of A. nivea that (being apomictic) can be propagated by seed. Also particularly promising horticulturally are slow-growing small trees from southern Europe of apomictic tetraploid origin, including, for example, S. aff. graeca from Sicily and the Sierra de Cazorla in Andalucia, southern Spain. Like the Armenian microspecies noted above, these are very heat- and drought-tolerant. In the mountains of China and northern Vietnam many interesting Aria taxa are to be found, mostly attributable ‘in old money’ to Micromeles. These are proving to be of great interest to collectors visiting the area and are trickling into cultivation. Their taxonomy is extremely uncertain, however, and names should probably not be taken as definitive. One of the best is a taxon identified as S. subulata (J.E. Vidal) T.H. Nguyên & Yakovlev (syn. S. verrucosa Rehder var. subulata J.E. Vidal) and described as being a small tree with arching branches, bearing neat, heavily veined leaves on long petioles and crops of yellowish orange fruits. The leaves emerge glossy bronze and stay that colour for a long time; in autumn they turn good shades of orange and red (Crûg Farm Plants 2007–2008). It was introduced by Keith Rushforth in 1992 and has made 5 m in Devon. It has done well in northern Wales, and also for Dan Hinkley in Indianola, Washington. In an e-mail sent from northern Vietnam (to JMG, in October 2006), Hinkley wrote: ‘It is absolutely lovely in new leaf, rather red-copper and one of the earliest to leaf out. I offered it through Heronswood for some time but only under a collection number (HWJ 99579, collected 1999; HWJ 3925, 2003). It grows nearby here in Sa Pa; the fruit are a bitch to clean and as usual with Sorbus, very few seed inside each fruit.’ On reading this Hugh McAllister wrote (pers. comm. 2006): ‘I agree with this comment if you try to clean seed from hard fruits – it is best to let them ripen and soften in a polythene bag before trying to extract the seeds.’ Several other northern Vietnamese species are noted for their attractive spring flush. Sorbus aff. granulosa, HWJ 1041, collected from a large tree at 1900 m, has excellent bronze-red new leaves and turns good colours in autumn. Sorbus ligustrifolia (A. Chev.) J.E. Vidal is a small tree to 8 m or more, often shrubby, from exposed ridge-tops, with small, thickened leaves that are evidently well adapted to this habitat, and also flush bronze. It was first introduced by Keith Rushforth in 1994. Although distributed as S. aff. ligustrifolia, the collection HWJ 984 probably fits in this species. Another in this group from northern Vietnam, and extending just into Yunnan at Pingbian, is S. brevipetiolata T.H. Nguyên & Yakovlev. This small tree to 10 m is allied to S. caloneura but differs in having very short petioles. It was first introduced from Vietnam by Keith Rushforth (under KR 2169a) in 1992, and from Yunnan in 1996 (under KR 4285) from the Da Wei Shan, and is in cultivation at Ness and Tregrehan. The parent trees of another introduction (BSWJ 11771), which had been felled by local people clearing forest for crops, had reached about 8 m and bore strongly ‘corrugated’ leaves and greenish brown lenticellate fruits. Keith Rushforth (pers. comm. 2007) reports that these fruits are

Aria / Sorbus

819

Plate 530. Sorbus croceocarpa is a hybrid whitebeam, of unknown origin but with considerable effect in autumn. Image J. Grimshaw.

820

Aria / Sorbus

Plate 531. An extraordinary unidentified Aria with enormous leaves and fruits, collected from the Mangshan, Hunan, and now in cultivation. Image A. Coombes.

New Trees

very tasty when bletted. A species allied to A. megalocarpa but with even larger fruits has been collected in the Mangshan, Hunan by several travellers there (see Plate 531). From China come A. aronioides (Rehder) H. Ohashi & H. Iketani and A. thomsonii (Hook. f.) H. Ohashi & H. Iketani, lumped together by Aldasoro et al. (2004) as Sorbus thomsonii, although they are quite different in appearance and are maintained as distinct by Gu et al. (2003). Aria aronioides seems to have first been introduced as SICH 407 in 1988 (illustrated p. xvi). Three trees derived from seed collected from a small specimen of this growing at Kew have been in cultivation at Ness for many years. Two have formed neat upright single-trunked trees of over 6 m. The flowers are greenish white and not showy, and neither are the greenish fruits. Under some conditions the foliage can develop brilliant autumn coloration like that of a Nyssa, the leaves being also very similar in proportion (H. McAllister, pers. comm. 2007). Aria thomsonii was introduced from Arunachal Pradesh in 2005 (K. Rushforth, pers. comm. 2008). A remarkable (and baffling) diversity of cultivated material was displayed and discussed at the Sorbus: Micromeles & Aria Sections Workshop held at Wisley in September 2008, organised by the Royal Horticultural Society Woody Plant Committee. The day emphasised the fascination these trees hold for gardeners, but also highlighted how much remains to be learnt about them! All Group A whitebeams related to the European A. nivea are much more tolerant of sunny dry sites than most rowans, and in Europe and southwest Asia they are often to be found on dry limestone slopes – an ecological distinction that draws attention to the differences between the two genera. The Asian species are also apparently more adaptable than most rowans, being more tolerant of clay soils and of more southern and low-altitude origin, although often from areas with moist climates – but doing reasonably well on thin soils too. As usual, however, they will all perform much better where conditions are more benign. In general, the remarks on cultivation for Sorbus given above apply to Aria as well.

Sorbus hajastana Gabrieljan

Plate 532. Sorbus hajastana, at Benmore. Many of the Eurasian whitebeams in Aria Group A form small rounded trees, that are pleasant enough without being very exciting. Image R. Unwin.

Tree to 10 m. Branchlets smooth, glabrous, with a few lenticels. Buds hairy, 0.7–0.75 cm long. Leaves 7.5–10 × 6.5–7.5 cm, ovate to rounded, upper surface glabrous, lower surface white-tomentose, eight to nine secondary veins on each side of midrib, craspedodromous, margins double-serrate to shallowly lobed, apex acute; petiole 1.3–2 cm long, pubescent. Inflorescence corymbose, pubescent. Flowers white, hermaphrodite; hypanthium turbinate, sepals deciduous, petals glabrous, 0.5 cm long. Fruit orange, 0.9–1.1 × 0.7–0.9 cm, covered with lenticels. Flowering May to June, fruiting July to September (Caucasus). Aldasoro et al. 2004. Distribution ARMENIA; AZERBAIJAN; GEORGIA. Habitat Mountain slopes, forest margins, between 1700 and 2300 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration More & White 2003; NT814, NT816, NT820. Taxonomic note A tetraploid apomictic microspecies, or more likely an aggregate of similar microspecies, very like S. graeca and behaving similarly in cultivation (H. McAllister, pers. comm. 2007).

One of the species named and introduced by the famous Armenian botanist Nora Gabrieljan (as noted above), Sorbus hajastana is grown in a number of British collections. It is an unremarkable small whitebeam, forming a rounded, bushy small tree.

Section II. Species Accounts

Aria / Sorbus

821

Aria hemsleyi (C.K. Schneid.) H. Ohashi & H. Iketani Syn. Sorbus hemsleyi (C.K. Schneid.) Rehder, Micromeles hemsleyi C.K. Schneid. Shrub or tree 7–10 m or more. Branchlets dark reddish brown, smooth and glabrous with a few lenticels. Buds glabrous, 0.7–1 cm long. Leaves 9.5–13.5 × 5–7 cm, ovate to lanceolate, upper surface glabrous, lower surface sparsely hairy, 10–14 secondary veins on each side of the midrib, craspedodromous, margins double-serrate, apex short-acuminate; petiole 1.2–2 cm long, glabrous. Inflorescence paniculate, glabrous. Flowers white, hermaphrodite; hypanthium turbinate, sepals acute and persistent, petals glabrous, 0.4 cm long. Fruit green with reddish or yellowish tints, 0.7–0.9 × 0.7–1 cm, covered with lenticels. Flowering May to July, fruiting July to October (China). Gu et al. 2003, Aldasoro et al. 2004. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Yunnan, Zhejiang; NEPAL. Habitat Evergreen broadleaved forest, between 900 and 3200 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration Spongberg 1991; NTxvi, NT821.

Aria hemsleyi is now well established in cultivation and proving itself to be an adaptable, easily grown and very attractive small tree – though it can become much larger in the wild (C. Crosbie, pers. comm. 2008). Its narrow leaves are greyish dark green above and nicely white below; they are held more or less upright on stiffly ascending branches, creating a pleasant shape overall. The leaves turn yellow in autumn. Its first introduction seems to have been from collections made in Hubei by the Sino-American Botanical Expedition in 1980 (SABE 1317, 1342), but it has been gathered on numerous later occasions as well, including, for example, the Kew expedition to Sichuan in 1994 (SICH 1464). (SICH 718, from 1991, had been identified as A. hemsleyi, but has now been determined to be A. pallescens.) Planted at Wakehurst Place, specimens from SICH 1464 are now up to 8 m tall or more (TROBI, measured in 2005). Most individuals in cultivation are probably descended from the SABE stock, however. Strangely, Spongberg (1991) considered A. hemsleyi to be ‘more of a botanical curiosity than a promising ornamental’, but this assessment now seems pessimistic, especially as it seems to grow well in western and northeastern North America. In the United Kingdom the name ‘John Bond’ has been attached to a clone selected in the early 1990s at Bridgemere Nurseries by Chris Sanders, out of a batch raised by David West from seed supplied to Roy Lancaster, from the original SABE trees at the Arnold Arboretum. This had a neater, more upright habit than others of the batch and was chosen to be planted at Wisley to commemorate John Bond’s service to the Woody Plant Trials Subcommittee, and was named in his honour on that occasion (R. Lancaster, C. Sanders, pers. comms. 2008). It is now in commercial production, perpetuating the memory of a great plantsman who was for many years the highly respected Keeper of the Gardens in Windsor Great Park. Plants distributed from Heronswood Nursery (c. 2001) as S. henryi Rehder under Eric Hammond’s number EDHCH 97163, gathered in Sichuan, may be A. hemsleyi, within which S. henryi is included by Flora of China – although Stephen Spongberg records a dissenting view and maintains its distinction. Material shown at the Sorbus Workshop at Wisley in September 2008, however, was judged to resemble A. pallescens. Sorbus xanthoneura Rehder is another name lumped under A. hemsleyi in Flora of China, which is not very reliable on Sorbus (H. McAllister, pers. comm. 2008), and specimens may be found under this name (for example, KR 161 from Emei Shan, which does not match the usual view of A. hemsleyi) (K. Rushforth, pers. comm. 2008).

Plate 533. Aria hemsleyi, with ascending branches bearing brightly whitebacked leaves, is one of many good trees introduced by the Sino-American Botanical Expedition in 1980. It belongs to Aria Group B. Image P. de Spoelberch.

822

Aria / Sorbus

New Trees

Sorbus takhtajanii Gabrieljan Tree to 7 m. Branchlets smooth, glabrous, with a few lenticels. Buds hairy, 0.5–0.7 cm long. Leaves 6.5–8.5 × 4.5–5.5 cm, rhombic to elliptical, upper surface glabrous, lower surface white-tomentose, six to seven secondary veins on each side of the midrib, craspedodromous, margins lobed, apex acute; petiole 1.5–2 cm long, pubescent. Inflorescence corymbose and pubescent. Flowers white, hermaphrodite; hypanthium shallowly turbinate, sepals acute and persistent, petals 0.5 cm long. Fruit orange or reddish, 1.1–1.2 × 0.9–1.1 cm, covered with lenticels. Flowering May to July, fruiting August to September (wild plants). Aldasoro et al. 2004. Distribution ARMENIA; AZERBAIJAN; IRAN; TURKEY. Habitat Mountain slopes and forest margins, between 1200 and 2200 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration More & White 2003.

Sorbus takhtajanii is represented in several British arboreta and is reasonably distinct on account of its dark green leaves with a bright white underside. The leaves are strongly toothed in their upper half. It is one of the Armenian species whose introduction is described above. All of them have proved to be relatively slow-growing, having champions of no more than 4–5 m (TROBI) as yet.

Sorbus tamamschjanae Gabrieljan

Plate 534. At the Arnold Arboretum, Aria yuana has flourished and grown into shapely trees since its introduction by the SABE team in 1980. Image R. Lancaster.

Shrub or tree to 8 m. Buds ovate, 0.4–0.6 cm long. Leaves 2.5–9 cm long, ovate, upper surface dark green, lower surface greyish white-pubescent, margins deeply lobed to almost pinnate at the leaf base and on immature shoots, apex subobtuse. Inflorescence 4–11 cm diameter, with 25–60(–90) flowers. Flowers 1.5–1.8 cm diameter. Fruit orange, 1.2 cm diameter, no lenticels. Gabrieljan 1972. Distribution ARMENIA; TURKEY: eastern Anatolia. Habitat Open mixed forest or scrub, between 1500 and 2600 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated. Illustration More & White 2003; NT814, NT818, NT825. Taxonomic note This species is almost certainly the Armenian equivalent of S. arranensis, probably the result of hybridisation between one of the local tetraploids of the Aria aggregate (S. hajastana, S. takhtajanii, or perhaps even S. subfusca) and Armenian S. aucuparia (H. McAllister, pers. comm. 2007).

The deeply lobed leaves of Sorbus tamamschjanae make it recognisable among the Armenian species (see p. 817), but it cannot be said to be particularly exciting.

Aria yuana (Spongberg) H. Ohashi & H. Iketani Syn. Sorbus yuana Spongberg Tree to 15 m. Branchlets reddish brown to purple or black, smooth, with a few lenticels. Buds glabrous, 0.6–1 cm long. Leaves 8.5–11 × 6–7 cm, elliptic to broadly ovate, both surfaces usually glabrous or with whitish hairs in the vein axils of the lower surface, 11–14 secondary veins on each side of the midrib, craspedodromous, margins double-serrate or with shallow lobes, apex short-acuminate; petiole 2.3–2.5 cm long, glabrous. Inflorescences terminal, to 20 cm diameter, corymbose, glabrous. Flowers white, hermaphrodite; sepals acute, persistent. Fruit reddish, 1–1.4 × 0.7–1.2 cm, sparsely covered with small lenticels. Flowering April to June, fruiting July to September (China). Gu et al. 2003, Aldasoro et al. 2004. Distribution CHINA: Hubei, Shaanxi, Sichuan. Habitat Forest margins, steep slopes, between 2000 and 2400 m asl. USDA Hardiness Zone 5–6. Conservation status Not evaluated (IUCN), but considered to be rare by Flora of China. Illustration Wharton et al. 2005; NT822.

Aria yuana was one of the trophies of the 1980 Sino-American Botanical Expedition, collected in the Shennongjia Forest District of Hubei (SABE 1555) and later named after Professor T.T. Yu (1908–1986), who had a long and brilliant career in botany and horticulture. If it is to be given a vernacular name in English it should therefore be Yu’s Whitebeam, not the strange ‘Yuan Whitebeam’ already in use by some (Wharton et al. 2005). It is a truly notable introduction, but has still not been widely distrib-

Section II. Species Accounts

Aria / Sorbus

uted beyond botanical gardens on both sides of the Atlantic. It is best known from the specimens in the Arnold Arboretum grown from the original seed, now forming shapely trees that have so far avoided fireblight and other diseases and problems of sorbi in North America, as well as proving fully hardy in Massachusetts (Spongberg 1991). They branch freely above the base, the branches ascending stiffly to form neatly shaped conical crowns. The leaves are attractive throughout the summer, being strongly ribbed and dark green with a pale underside, then turning golden-yellow in time to partner the richly red fruits in autumn. The flowers are also a good feature, being abundantly produced and a good clean white. The species is self-incompatible and needs a friend for fertilisation, but in the absence of pollination is capable of producing small, infertile parthenocarpic fruits that are still attractive. When a group of clones are grown together, as at the Arnold Arboretum, or at Ness where there are several specimens raised from seed supplied by Stephen Spongberg, the fruits are much larger and more spectacular (and contain fertile seed) (H. McAllister, pers. comm. 2007). Aria yuana deserves to be widely planted. When first collected it was thought to be A. zahlbruckneri, to which it is evidently closely related but from which it differs in having larger, broader leaves with less regularly toothed margins, and larger fruits (Gu et al. 2003). This and related species could conceivably hybridise with other species grown nearby, so seedlings should be checked with care.

A note on cross-references for Sorbus s.l. Because of the confusing taxonomic situation resulting from the acceptance of several still-conjoined genera in place of a single monolithic Sorbus, our usual cross-references to accounts in Bean (1981b) and Krüssmann (1986) are given here under their names in Sorbus s.l. To clarify their current position, so far as is possible, members of Sorbus s.s. are identified with ‘(Sorbus)’. Species that should be placed in Aria but for which no combination has yet been published are indicated by ‘(Aria)’. Where an alternative name in another genus is available, however, it is provided in full. Where a taxon is of intergeneric hybrid origin, or its affiliations are unclear, no attribution to a current genus is given.

S. alnifolia (Siebold & Zucc.) K. Koch (Aria alnifolia Decne.) B404, S495, K331 S. alnifolia var. submollis Rehder B405, K331 S. americana Marshall (Sorbus) B406, S495, K331 S. anglica Hedl. B406, K331 S. anglica subsp. austriaca (G. Beck) Hayek B407 S. aria (L.) Crantz (Aria nivea Host) B407, S495, K331 S. aria f. cyclophylla (Beck) Javorka B409 S. aria f. incisa (Reichenb.) Javorka B409

S. aria f. longifolia (Pers.) Rehder B409, K332 S. ×arnoldiana Rehder (Sorbus) K332 S. arranensis Hedl. B447, K332 S. aucuparia L. (Sorbus) B411, K332 S. aucuparia subsp. glabrata (NOW S. aucuparia L.) B412 S. aucuparia f. integerrima (NOW S. aucuparia ‘Integerrima’) B412, K332 S. aucuparia var. lanuginosa Beck B412 S. aucuparia subsp. praemorsa (Guss.) Nym. B412 S. aucuparia subsp. sibirica (Hedl.) McAll. B412

823

824

Sorbus

New Trees

S. austriaca Hedl. (Aria austriaca Beck ex Hedl.) K333 S. bristoliensis Wilmott B440, S499, K333 S. caloneura (Stapf) Rehder (Aria caloneura (Stapf) H. Ohashi & H. Iketani) B414, K333 S. cashmiriana Hedl. (Sorbus) B414, K333 S. chamaemespilus (L.) Crantz (Chamaemespilus alpina (Mill.) K.R. Robertson & J.B. Phipps) B415, K333 S. chamaemespilus var. sudetica (NOW Chamaemespilus sudetica M. Roem.) K333 S. commixta Hedl. (Sorbus) B416, S496, K333 S. commixta var. rufoferruginea (NOW S. commixta Hedl.) B417 S. cuspidata (NOW S. vestita (Wall. ex G. Don) S. Schauer) (Aria) B418, S496, K334 S. decipiens (Bechst.) Hedl. K334 S. decora (Sarg.) C.K. Schneid. (Sorbus) B420, K334 S. decora var. groenlandica (C.K. Schneid.) G.N. Jones B421 S. devoniensis E.F. Warb. B440, K334 S. discolor (Maxim.) E. Goetze (Sorbus) B421, K334 S. domestica L. (Cormus domestica Spach) B423, S496, K334 S. domestica f. pomifera (Hayne) Rehder B423, K334 S. domestica f. pyrifera (Hayne) Rehder B423, K334 S. eminens E.F. Warb. B461 S. epidendron Hand.-Mazz. (Aria epidendron (Hand.-Mazz.) H. Ohashi & H. Iketani) B424, K334 S. esserteauiana Koehne (Sorbus) B425, K334 S. filipes Hand.-Mazz. (Sorbus) K335 S. folgneri (C.K. Schneid.) Rehder (Aria folgneri (C.K. Schneid.) H. Ohashi & H. Iketani) B426, S497, K335

S. foliolosa (Wall.) Spach (Sorbus) B428 S. glomerulata Koehne (Sorbus) B429 S. gracilis (Siebold & Zucc.) K. Koch (Sorbus) B430, K335 S. graeca (Spach) Kotschy (Aria) B460 S. harrowiana (Balf. f. & W.W. Sm.) Rehder (Sorbus) B434 (included in S. insignis), K335 S. hedlundii C.K. Schneid. (Aria) B419 S. hibernica E.F. Warb. (Aria) B461 S. himalaica Gabrieljan (Sorbus) B462 S. ×hostii (Jacq.) K. Koch B430, K335 S. hupehensis (NOW S. glabriuscula McAll., NT803; S. pseudohupehensis McAll., NT809) B431, K335 S. hybrida L. B433, S497, K335 S. insignis (Hook. f.) Hedl. (Sorbus) B434, K335 S. intermedia (Ehrh.) Pers. B436, S497, K336 S. japonica (Decne.) Hedl. (Aria japonica Decne.) B437, K336 S. karpatii Boros B441 S. keissleri (C.K. Schneid.) Rehder (Aria keissleri (C.K. Schneid.) H. Ohashi & H. Iketani) B438, K336 S. ×kewensis Hensen (Sorbus) B449 S. koehneana C.K. Schneid. (Sorbus) B439, K336 S. lanata (D. Don) Schau (Aria) B420, K336 S. lancastriensis E.F. Warb. (Aria) B461 S. lancifolia Hedl. apud Dahl. B447, K337 S. latifolia (Lam.) Pers. B439, S499, K337 S. leyana Wilmott B447 S. matsumurana (Makino) Koehne (Sorbus) B444, K337 S. megalocarpa Rehder (Aria megalocarpa (Rehder) H. Ohashi & H. Iketani) B444, K337 S. megalocarpa var. cuneata Rehder B445 S. meinichii (Hartm.) Hedl. B445, K337 S. meliosmifolia Rehder (Aria meliosmifolia (Rehder) H. Ohashi & H. Iketani) B445, K337

Section II. Species Accounts

S. minima Hedl. B447, K337 S. mougeotii Soy.-Willem. & Godr. B407, S495, K337 S. neglecta Hedl. K338 S. pallescens Rehder (Aria pallescens (Rehder) H. Ohashi & H. Iketani) B447, K338 S. paucicrenata (Ilse) Hedl. K338 S. ×pekinensis Koehne B420 S. pluripinnata (NOW S. scalaris Koehne) K338 S. pohuashanensis (NOW S. aucuparia L.) B448, K338 S. porrigentiformis E.F. Warb. (Aria) B461 S. poteriifolia Hand.-Mazz. (Sorbus) B449, K338 S. prattii Koehne (Sorbus) B451, K338 S. prattii var. subarachnoidea (NOW S. munda Koehne) K338 S. prattii var. tatsiensis (NOW S. prattii Koehne) K338 S. pygmaea hort. (NOW S. poteriifolia Hand.-Mazz.) K338 S. pseudofennica E.F. Warb. B434 S. pseudovertesensis Boros B441 S. reducta Diels (Sorbus) B452, K339 S. rehderiana Koehne (Sorbus) B462, K339 S. rhamnoides (Decne.) Rehder (Aria rhamnoides (Decne.) H. Ohashi & H. Iketani) S500, K339 S. rufoferruginea (NOW S. commixta Hedl.) K339 S. rupicola (Syme) Hedl. (Aria) B461, K339 S. sambucifolia (Cham & Schltdl.) Roem. (Sorbus) B452, K339 S. sargentiana Koehne (Sorbus) B453, S500, K339 S. scalaris Koehne (Sorbus) B454, S500, K339 S. scopulina Greene (Sorbus) B421, K339 S. serotina (NOW S. commixta Hedl.) K339 S. setschwanensis (C.K. Schneid.) Koehne (Sorbus) B439, S498

Sorbus

S. sitchensis Roem. (Sorbus) B455, K339 S. sitchensis var. grayii (NOW S. occidentalis (S. Watson) Greene) B455 S. ×splendida Hedl. K340 S. subcuneata Wilmott B442 S. subpinnata Hedl. K340 S. subsimilis Hedl. K340 S. thuringiaca (Ilse) Fritsch K340 S. teodorii Liljefors B445 S. thibetica (Cardot) Hand.-Mazz. (Aria thibetica (Cardot) H. Ohashi & H. Iketani) B455, S500 S. ×thuringiaca (Ilse) Fritsch B457, S501 S. tianschanica Rupr. (Sorbus) B458, K340 S. torminalis (L.) Crantz (Torminaria torminalis Dippel) B459, S501, K340 S. torminalis var. caucasica Diapulis S501 S. umbellata (Desf.) Fritsch B460, K340 S. umbellata var. cretica (Lindl.) C.K. Schneid. K340 S. ursina (NOW S. foliolosa (Wall.) Spach) B461 S. ursina var. wenzigiana (NOW S. foliolosa (Wall.) Spach) B462 S. ×vagensis Wilmott B443 S. vestita (Wall. ex G. Don) S. Schauer (WAS S. cuspidata) (Aria) B418, S496, K334 S. vexans E.F. Warb. (Aria) B461 S. vilmorinii C.K. Schneid. (Sorbus) B463, K341 S. wattii (NOW S. wallichii (Hook. f.) T.T. Yu, NT813) B429 S. wilmottiana E.F. Warb. (Aria) B461 S. xanthoneura (see Aria hemsleyi (C.K. Schneid.) H. Ohashi & H. Iketani, NT821) K341 S. zahlbruckneri C.K. Schneid. (Aria zahlbruckneri (C.K. Schneid.) H. Ohashi & H. Iketani) B428, S497, K341

825

Plate 535. Sorbus tamamschjanae (p. 822) is believed to be of hybrid origin, from a cross between a member of Aria s.s. and S. aucuparia. Such hybrids join the two genera deceptively and make unravelling of nomenclature difficult. Image R. Unwin.

826

Styrax

New Trees

STYRACACEAE

STYRAX

L.

Snowbells, Storax There are about 130 species of Styrax, occurring in eastern Asia, North and South America and the Mediterranean. They are evergreen or deciduous trees with several winter buds at each node, each with one outer scale. The leaves are alternate, petiolate, glabrous to stellate and with sub-entire to serrate margins; they often vary greatly in size on the shoot, the uppermost frequently being much larger than those below. Inflorescences are axillary or terminal, solitary or several per fascicle; individual inflorescences may be racemose, cymose, paniculate or even single-flowered. The flowers are hermaphrodite and typically 5-merous; the calyx cup-like, with (two to) five (to seven) teeth or lobes, the corolla white or pink, campanulate, 5- to 7-lobed, the lobes reflexed or not; with (8–)10(–13) stamens, usually all of equal length. The fruit is a fleshy drupe or a dry capsule, which may be dehiscent (and then three-valved) or indehiscent; with one (to two) hard seeds per locule (Gonsoulin 1974, Spongberg 1976, Hwang & Grimes 1996, Fritsch 1997, Huang et al. 2003). Styrax, together with other members of the Styracaceae, is the subject of ongoing scientific research by Peter W. Fritsch and his associates, based at the California Academy of Sciences, San Francisco. Their work has greatly improved our understanding of the genus and family (Fritsch et al. 2001, Huang et al. 2003, Fritsch 2004); where possible, the accounts below follow their views. Styrax – described by Tom Hudson (2004) as having ‘poise and style’ – is an upand-coming genus in horticulture, many newly introduced species having recently joined the rather few that are well known. Of these, only S. japonicus is really widely grown, and this is the only species in which cultivars have been selected. Amongst the varied assortment of cultivars with different growth habits or flower colour, ‘Sohuksan’ (syn. ‘Emerald Pagoda’), selected by J.C. Raulston from seedlings of a collection made in South Korea in 1985, is generally acclaimed to be the finest, having larger flowers than normal, and larger, darker leaves, and seeming to be more heattolerant than others. Dirr (1998) considered it to be one of Raulston’s best introductions. ‘Crystal’ came from the same collection. Styrax grandiflorus Griff. is a synonym of S. japonicus, occasionally found on labels. Styrax obassia is also quite frequently grown, especially in North American collections (P. Fritsch, pers. comm. 2008), but most others are rather rare. The pendulous, usually five-pointed, usually white corollas are very characteristic of the genus, and have given rise to the popular name ‘snowbells’, especially for S. japonicus. Styrax in general seems to be quite variable, and varieties have been recognised in several of the species described in the present work. Significant ones are mentioned briefly below. There is much local endemism, especially in the southeastern United States and adjacent Mexico (from where future introductions might be expected), as well as in populations stretching into South America (Fritsch 1997). The growth habit varies considerably, from quite small and shrubby to trees of a size useful in forestry, such as S. tonkinensis. (As the genus is so scantily known in horticulture, we bend our usual rules slightly here to include descriptions of some of the

Section II. Species Accounts

A

Styrax

1 cm

B

smaller species.) After much discussion Styrax is now accepted (Nicolson & Steyskal 1976) to be of masculine gender, resulting in most names ending in –us, rather than the familiar feminine -a or the occasionally seen neuter -um. Most arboreta have a small representation of Styrax, but a comprehensive assortment is harder to find. J.C. Raulston built up a good collection, which he wrote about (Raulston 1991, 1992), and the current plantings at the JC Raulston Arboretum remain reasonably diverse. On the West Coast the University of California Botanical Garden at Berkeley and the San Francisco Botanical Garden grow a selection of taxa, including some Mexican species apparently not much grown elsewhere. Further north, the

Figure 90 (above). Styrax grandifolius: habit with flowers (A); infructescence (B).

827

828

Styrax

Plate 536. A good form of Styrax hemsleyanus is in cultivation under the name S. huanus. Image N. Macer.

New Trees

University of British Columbia Botanical Garden has an interesting assemblage of Asian species, and these also feature strongly in private collections in southwestern England, such as that of Tom Hudson at Tregrehan. None of the essentially Mexican taxa, or those from further south in Latin America, are widely grown in our area. Styrax platanifolius, with two subspecies in cultivation, is described below. Styrax ramirezii Greenm., potentially a tree to over 20 m, with a wide range in Mexico, is grown in the San Francisco Bay Area but is probably not hardy further north; it has large evergreen leaves and smallish flowers, of white or pink. Styrax glabrescens Benth., ranging from northeastern Mexico to Costa Rica, is another evergreen, with trees to 30 m. It survived in the JC Raulston Arboretum for 10 years until lost to a late freeze (T. Lasseigne, pers. comm. 2007), and has grown in Berkeley since 1991. Raulston (1992) recorded that a mysterious ‘S. globosus’ was being cultivated by Yucca Do Nursery in Texas, but this was in fact S. lanceolatus P.W. Fritsch (P. Fritsch, pers. comm. 2008). It is not known if it has persisted in cultivation. Several poorly known Asian species are also grown in our area, including S. macrocarpus W.C. Cheng from Guangdong and Hunan, which has large leaves uniquely preceded by solitary flowers opening on the bare branches – although this has not done well at Tregrehan, and probably requires greater warmth in summer. The smaller S. rugosus Kurz, from India, Myanmar and Yunnan, also attempted at Tregrehan, is another that has not been successful there. Material grown as S. huanus Rehder is more promising. The taxon has been sunk into S. hemsleyanus (Huang et al. 2003), differing from it principally in being heavily pubescent, but otherwise falling completely within the range of variation expected in a Styrax species (P. Fritsch, pers. comm. 2008). At his home in Cornwall the late Edward Needham had a fine specimen labelled S. huanus, collected by himself in China, and propagations from this are being grown elsewhere in that county. It is a ‘good thing’, according to Tom Hudson (pers. comm. 2007). If the example of the few familiar species can be used as a guide, cultivation requirements for the genus include warmth but not great heat, shelter but not deep shade, and a moist acidic soil. In the British Isles summers tend to be on the cool side for them, and they need as much warmth as possible. Some, including S. japonicus, can tolerate full sun in cooler climates, but in general they are prone to sunburn where light intensity is too great. In eastern North America light shade is advised for S. japonicus in areas covered by Zones 7–8 (Dirr 1998), and the heat and humidity of the lowland southeastern United States are too much for most potentially hardy species (Raulston 1991). In all areas most require ample summer moisture, though taxa from Mediterranean climates need a dry summer. Propagation is by cuttings taken in early summer, but it can be difficult to get them through the following winter. The seed has a double dormancy so patience is required (Huxley et al. 1992, Dirr 1998). S. americanus Lam. B514, K367 S. americanus f. pulverulentus (Michx.) Perkins K367

Styrax calvescens Perkins Syn. S. dasyanthus Perkins var. cinerascens Rehder Shrub or tree 5–15 m, 0.15 m dbh. Branchlets sparsely covered in brown stellate tomentum. Leaves leathery, 3–8 × 1.5–4.5 cm, elliptic to obovate, upper surface sparsely covered with grey stellate tomentum, lower surface densely covered with grey stellate tomentum, six to seven secondary veins on each side of the mid-

Section II. Species Accounts

rib, margins minutely serrate towards the apex, apex acute to acuminate; petiole 0.1–0.3 cm long. Inflorescences terminal or axillary, racemose or paniculate; pedicels 0.5–1 cm long. Flowers numerous, 1–1.5 cm long; calyx five-toothed, covered with yellowish grey tomentum, corolla tube 0.3 cm, lobes 1 cm, oblong, stamens shorter than corolla. Fruit obovoid, ~0.8 cm long, densely stellate-tomentose. Flowering March to June, fruiting July to August (China). Hwang & Grimes 1996. Distribution CHINA: southern Henan, western Hubei, Hunan, Jiangxi, Zhejiang. Habitat Forest margins, between 500 and 1200 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996. Cross-reference B515 (as S. dasyanthus var. cinerascens).

Bean (1981b) noted that this taxon (which he called Styrax dasyanthus var. cinerascens) had been introduced from the Lushan Botanic Garden in the 1930s as S. philadelphoides; not only was it not that species, however, but – he commented – the material received was itself very variable in its degree of pubescence. It was distributed by Hillier Nurseries as both S. philadelphoides and S. serrulatus (Hillier & Coombes 2002), but is now known to be S. serrulatus (A. Coombes, pers. comm. 2008). It is not clear if any material from this introduction persists in cultivation, and the plant is evidently rare. A specimen growing in the JC Raulston Arboretum, labelled as S. calvescens, lacks the tomentose indumentum supposedly diagnostic for the species, but is correct in terms of leaf size and the paired flowers in the leaf axils.

Styrax confusus Hemsl. Syn. S. philadelphoides Perkins Tree 2–8 m, 0.12 m dbh. Branchlets densely covered in brown stellate tomentum. Leaves leathery, 4–14 × 2.5–7 cm, oblong to obovate or elliptic, both surfaces sparsely covered with stellate tomentum, five to seven secondary veins on each side of the midrib, margins serrulate, apex acute to short-acuminate; petiole 0.1–0.3 cm long. Inflorescences terminal, racemose, 4–10 cm long, with three to eight flowers; pedicels 1–1.5 cm long. Flowers ~1.5 cm long; calyx five-toothed, 0.5–0.8 cm long, densely covered in yellowish grey tomentum, corolla tube 0.3–0.4 mm, lobes 1.2–2 cm, lanceolate to oblong. Fruit subglobose to ovoid, 0.8–1.5 cm diameter, densely stellate-tomentose. Flowering April to June, fruiting September to November (China). Hwang & Grimes 1996. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Zhejiang. Habitat Sparse, montane forest, between 100 and 1700 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996, Hudson 2004. Taxonomic note In addition to typical S. confusus, two varieties are recognised: var. microphyllus Perkins has a short calyx, 0.3–0.4 cm long, and flowers from September to October; var. superbus (Chun) S.M. Hwang has flowers ~2.2 cm long.

Styrax confusus is a very attractive tree-forming species, now well established though still scarce in gardens, with many examples being as yet rather small. It is well worth growing for its relatively large leaves and showy racemes, bearing several white flowers in early summer. When seen at the JC Raulston Arboretum in May 2006 it was just finishing flowering but had evidently been very beautiful. Two specimens were noted, one labelled S. confusus and the other S. philadelphoides, but they seemed to be identical. The latter plant was 5.5 m tall, developing faintly striated bark on its trunk. S. dasyanthus Perkins B515, K368 S. dasyanthus var. cinerascens (NOW S. calvescens Perkins, NT828) B515

Styrax faberi Perkins Shrub 1–2 m. Branchlets densely villose. Leaves papery, 4–11 × 3–3.5 cm, elliptic to obovate, both surfaces sparsely covered with grey or brown stellate pubesence, five to six secondary veins on each side of the midrib, margins serrulate, apex acuminate; petiole 0.1–0.2 cm long. Inflorescences terminal, racemose, 3–4 cm long, with three to five flowers; pedicels 0.8–1.5 cm long. Flowers 1.2–1.5(–2) cm long; calyx fivetoothed, membranous, corolla tube 0.3–0.4 cm, lobes 0.5–1.5 cm, lanceolate to oblong, membranous. Fruit

Styrax

829

830

Styrax

New Trees

subglobose to obovoid, 0.6–0.8 cm long, densely covered in grey stellate tomentum. Flowering April to June, fruiting August to October (China). Hwang & Grimes 1996. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Zhejiang; TAIWAN. Habitat Forest undergrowth or hillside scrub, between 100 and 600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996.

The shrubby Styrax faberi has been quite widely cultivated and is available commercially in Europe, but is seldom seen. As it comes from rather low altitudes in southern and eastern China it is unlikely to be particularly hardy.

Styrax formosanus Matsum. Shrub 2–3 m, or larger tree to at least 9 m. Branchlets densely brown-tomentose. Leaves deciduous, papery, 2–5(–7) × 1.5–2.5 cm, elliptic to rhomboid, both surfaces sparsely covered with brown stellate tomentum, three to five secondary veins on each side of the midrib, margins coarsely serrate towards the apex, rarely two- to four-lobed, apex caudate to acuminate; petiole 0.3–0.4 cm long, sparsely tomentose. Inflorescences terminal, racemose, 2.5–4.5 cm long, with three to five flowers; pedicels 0.8–1.2 cm long. Flowers 1.2–1.5 cm long, slightly pendulous; calyx obscurely five-toothed, densely grey-tomentose, corolla tube 0.2–0.3 cm, lobes five to six, 0.8–1.1 cm, lanceolate to oblong, membranous, stamens (9–)10(–11), shorter than corolla. Fruit ovoid, ~0.6 cm long, rugose. Flowering April to May, fruiting May to June (Taiwan). Hwang & Grimes 1996, Huang et al. 2003. Distribution TAIWAN. Habitat Forest thickets, between 500 and 1300 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996; NT28, NT830. Taxonomic note Styrax formosanus is closely related to S. japonicus, but differs in having imbricate corolla lobes in bud (valvate in S. japonicus). In addition to typical var. formosanus there is also var. hirtus S.M. Hwang, with dense stellate pubescence on petioles and pedicels.

Plate 537. Styrax formosanus is closely related to the familiar S. japonicus, with which it shares an abundance of scented white flowers. It is a Taiwanese endemic. Image N. Macer.

Although Styrax formosanus is described by Flora of China as a shrub, plants in cultivation under this name are indubitable single-stemmed trees. A specimen planted at Tregrehan in 1998 was 5 m tall in 2007 (Johnson 2007) and producing wide-spreading branches. Unlike some species it is proportionate in its leaf-to-flower ratio, producing masses of flowers, with a good jasmine scent that wafts about (T. Hudson, pers. comms. 2005, 2007). The white flowers contrast well with the very dark green of the leaves. The brown hairs are conspicuous, especially on new growth. Although said by Flora of China to occur over a wide area of southern China, it is considered by Huang et al. (2003) to be endemic to Taiwan, and all the material traced in cultivation seems to come from there. An early collection was apparently that made by Tony Kirkham and Mark Flanagan under the number ETOT 121, in 1992. This was gathered from 9 m tall trees at 1900 m on Taipingshan, growing in company with Chamaecyparis formosensis and Alnus formosana in remnant forest on humus-rich soil. It was in commerce by the late 1990s, and further gatherings in northern Taiwan by Sue and Bleddyn Wynn-Jones (BSWJ 6786, 6797) have widened its availability. The same collectors have also introduced material from Taipingshan (BSWJ 6823), as S. formosanus var. hayataianus. This varietal name is attached by Flora of China to S. suberifolius, which should have densely stellate-tomentose leaf undersides and a single locule in the ovary (compared to S. formosanus in which the stellate hairs are much sparser and the ovary is three-locular). The parent plant of BSWJ 6823 was silvery-pubescent on the undersides of the leaves, but this feature has still to appear

Section II. Species Accounts

Styrax

on the as-yet unflowered plants of this gathering (B. Wynn-Jones, pers. comm. 2008), so to date its identity remains unconfirmed.

Styrax grandifolius Aiton

Big-leaf Snowbell

Shrub or tree to 9 m. Branchlets blackish brown with some stellate hairs. Leaves 4–10(–20) × 2.5–7(–12) cm, elliptic to ovate or obovate, upper surface glabrous, lower surface silvery grey, densely to finely tomentose, margins entire or minutely serrate towards the apex, apex acute to acuminate; petiole 0.4–0.9 cm long, pubescent. Inflorescences terminal, racemose, 5–15 cm long, with 5–20 flowers, or sometimes flowers solitary. Flowers ~2 cm long; calyx obscurely five-toothed, densely grey-pubescent, corolla tubular, lobes elliptic, downy, stamens as long as corolla. Fruit globose, 0.7–0.9 cm diameter, tomentose. Flowering March to April (USA). Spongberg 1976, Gonsoulin 1974. Distribution USA: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, Missouri, North Carolina, South Carolina, Tennessee, Texas, Virginia. Habitat Woodland on wet or preferably well-drained sandy soils. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration Gonsoulin 1974; NT827. Cross-reference K368.

Styrax grandifolius has more potential than presence in gardens, at least in the southeastern United States, where it tolerates the summer heat better than most other Styrax (Raulston 1991, 1992). Images available on the internet suggest that its inflorescences are often partly concealed by the developing large leaves, but that when in full flower it is an attractive sight. Raulston (1992) noted that it performs much better in cultivation than in the wild, flowering being enhanced by improved light. It seems unlikely to be a great success in areas with cooler summers. S. hemsleyanus Diels B515, S505, K368

Styrax hookeri C.B. Clarke Syn. S. hookeri var. yunnanensis Perkins, S. macranthus Perkins, S. perkinsiae Rehder, S. shweliensis W.W. Sm., S. yunnanensis hort. (nom. inval.) Shrub or tree to 10 m. Branchlets with grey-brown stellate hairs when young, becoming glabrescent with age. Leaves papery to thickly so; two basal leaves on each branchlet, more or less opposite, other leaves alternate, 6–8(–12) × 3–4(–6) cm, oblong to narrowly elliptic, upper surface with sparse stellate hairs, lower surface glabrous to sparsely or more extensively stellate-hairy, especially hairy on the veins and in the vein axils, five to seven secondary veins on each side of the midrib, margins glandular-serrate, apex acuminate to caudate, base rounded to variably cuneate; petiole < 1 cm long. Inflorescences pseudoterminal, when sometimes racemose with two to three (to six) flowers, or axillary, when one- to three-flowered; pedicels 0.2–1.3 cm long. Flowers to 2.5 cm long; calyx lobes irregularly two- to three-toothed, densely covered with grey and orange to brown stellate hairs, corolla to 1.9 cm, white or pink, tube 0.3–0.4 cm, lobes four (to five), 1.1–1.8 cm, obovate to obovate-elliptic; stamens 8–10. Fruit ovoid, to 2 cm diameter, with yellow-grey stellate hairs. Flowering April to July, fruiting October to November (China). Hwang & Grimes 1996, Huang et al. 2003. Distribution BHUTAN; CHINA: Guangxi, Guizhou, Sichuan, Xizang, Yunnan; INDIA: Sikkim to Arunachal Pradesh; MYANMAR; NEPAL. Habitat Open woodlands, forest edges on mountain slopes, between 700 and 3350 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996. Cross-reference B519 (as S. shweliensis). Taxonomic note The wide range and variability of S. hookeri has led to a number of synonymous taxa being described (Huang et al. 2003). The invalid name S. yunnanensis, occasionally applied in horticulture, appears to belong here.

As Styrax shweliensis, S. hookeri was introduced from Yunnan in 1919 by George Forrest (F 18249) (Bean 1981b). It has not become widely grown under any name, but there are several old specimens in Cornish gardens. The largest, though with a broken top, growing at Caerhays, was measured at 8 m (31 cm dbh) by Owen Johnson in 2006. More recent introductions include KR 1714 from Bhutan, also established in Cornwall, and there are stocks labelled S. yunnanensis in the Netherlands (Plantentuin Esveld 2006–2008). As a large-flowered species related to S. japonicus it deserves attention, but may be hardy only in milder areas.

831

832

Styrax

New Trees

S. japonicus Siebold & Zucc. B516, K368 S. langkongensis (NOW S. limprichtii Lingelsh. & Borza, NT832) B519

Styrax limprichtii Lingelsh. & Borza Syn. S. langkongensis W.W. Sm. Shrub 1–2.5(–6) m. Branchlets densely covered with greyish yellow or yellow-brown stellate tomentum when young, glabrescent later. Leaves papery, 3.5–7(–9.5) × 2–4.5 cm, elliptic to obovate, upper surface stellatepubescent, lower surface densely covered with white stellate tomentum with scattered orange or brown hairs especially on the veins, five to six secondary veins on each side of the midrib, margins serrulate towards the apex, apex acute to acuminate, base rounded to broadly cuneate; petiole 0.1–0.3 cm long. Inflorescences borne on current season’s shoots, lateral or pseudoterminal, the latter 1–2 cm long with two to three (to four) flowers; pedicels 0.3–0.4 cm long. Flowers 1.5–2.0 cm long; calyx with white appressed hairs externally, densely yellow-brown to orange tomentose inside, teeth rather uneven; corolla to 1.4 cm, tube 0.4 cm, lobes five, 0.9–1.1 cm, elliptic to ovate-elliptic. Fruit globose, 1–1.5 cm diameter, rugose, densely pubescent, splitting by way of three valves. Flowering March to April, fruiting August to October (China). Hwang & Grimes 1996, Huang et al. 2003. Distribution CHINA: southern Sichuan, northwest Yunnan. Habitat Forests between 1700 and 2400 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996, Hudson 2004. Cross-reference B519 (as S. langkongensis).

With Styrax limprichtii, horticultural experience and botanical records are again divergent, the low shrub in the wild becoming much taller in gardens (up to c. 6 m), though remaining multistemmed through the production of suckers. It is, however, capable of flowering when only 30–60 cm tall, and is an ideal species for small gardens. The abundant flowers contrast well with the light green foliage, and like its relative S. wilsonii it fruits prolifically (Hudson 2004; T. Hudson, pers. comm. 2007). It seems able to tolerate drier conditions than most species, occuring in the wild on dry banks (T. Hudson, pers. comm. 2007), and has a limited presence in British gardens. S. obassia Siebold & Zucc. B517, S505, K368 S. officinalis L. B518, S505, K368

S. officinalis var. californica (NOW S. redivivus (Torr.) L.C. Wheeler, NT833) B519

Styrax platanifolius Engelm. ex Torr. Shrub to 3 m. Branchlets glabrous to densely covered in white stellate pubescence, sometimes somewhat glaucous, with a few brown stellate hairs at the base. Leaves papery, 4.5–9(–12) × 4–9(–11.5) cm, rounded to broadly ovate, upper surface glabrous or pubescent, lower surface glabrous or densely covered with white stellate hairs, five to six secondary veins on each side of the midrib, margins sometimes lobed or coarsely toothed towards the apex, apex rounded to obtuse; petiole 0.6–2 cm long. Inflorescences pseudoterminal, 2–5 cm long, with one to seven flowers; pedicels 0.4–0.9 cm long. Flowers ~1.5–2 cm long; calyx glabrous or densely covered in white stellate pubescence, teeth scattered, to 1 cm long; corolla to 2.1 cm, lobes five (to six), elliptic. Ovary densely covered in short stellate pubescence. Fruit globose, c.1 cm diameter, splitting by way of three valves, hairs greyish. Fritsch 1997. Distribution MEXICO: Coahuila, Tamaulipas; USA: Texas. Habitat Woodlands in desert mountains. USDA Hardiness Zone 8. Conservation status Not evaluated (IUCN), but generally rather rare (Fritsch 1997). Illustration Gonsoulin 1974.

Styrax platanifolius exists as a number of scattered small populations in Texas and adjacent Mexico, with five subspecies having been described (Fritsch 1997). Of these, only subsp. mollis and subsp. youngiae appear to be in cultivation in our area, but the Texan subsp. platanifolius (which lacks any white stellate hairs), subsp. stellatus (Cory) P.W. Fritsch and subsp. texanus (Cory) P.W. Fritsch could conceivably appear in collections of native plants.

Section II. Species Accounts

Styrax

833

Styrax platanifolius subsp. mollis P.W. Fritsch Subsp. mollis differs from subsp. youngiae by having soft stellate hairs that do not entirely cover the lower leaf surface, and from subsp. stellatus in that the arms of each stellate hair are up to 0.8–1 mm long (0.4 mm in subsp. stellatus), and in its disjunct range. Flowering April (Mexico). Fritsch 1997. Distribution MEXICO: Coahuila, Tamaulipas. Habitat Wooded canyons, between 1200 and 1400 m asl, in the northern Sierra Madre Oriental, and Chihuahuan desert mountains. USDA Hardiness Zone 8–9. Conservation status Not evaluated (IUCN). Rare (Fritsch 1997).

This plant is known in cultivation only from material collected in 1991 by John Fairey of Yucca Do Nursery, Hempstead, Texas, grown for example in the University of California Botanical Garden at Berkeley and the San Francisco Botanical Garden.

Styrax platanifolius subsp. youngiae (Cory) P.W. Fritsch

Young’s Snowbell

In subsp. youngiae the lower surface of the leaf is completely covered and hidden by white stellate hairs, and the upper is more sparsely stellate-pubesccent (glabrous in subsp. texanus). Flowering April to May, fruiting July to September (Mexico). Fritsch 1997. Distribution MEXICO: Coahuila; USA: Texas. Habitat Mountain slopes and canyons, between 900 and 2000 m asl, in the Davis Mountains and eastern slopes of Chihuahuan desert mountains. USDA Hardiness Zone 7–8. Conservation status Not evaluated (IUCN). Rare (Fritsch 1997). Illustration Gonsoulin 1974; NT833.

Subsp. youngiae was cultivated for many years at the JC Raulston Arboretum, the longest survivor being an accession from Yucca Do Nursery obtained in 1993. This made a bushy plant of about 1.2 m tall, but was moved to avoid construction work and did not really recover (V. Tyson, pers. comm. 2008). When seen in 2006 it was a struggling shrub, and it has since been removed. With their rather few flowers and short stature, these taxa are not among the cream of the genus, and are probably of botanical interest only, but considering their rarity in the wild as well as in cultivation any remaining plants should be carefully conserved.

Styrax redivivus (Torr.) L.C. Wheeler

California Snowdrop Bush

Syn. S. officinalis var. redivivus (Torr.) R.A. Howard, S. officinalis var. californicus (Torr.) Rehder Shrub to 4 m. Branchlets with white or yellowish brown stellate hairs, bark exfoliating when older. Leaves 3–7.5(–11.5) × 2.5–6.6(–8.5) cm, broadly elliptic to obovate to almost orbicular, upper surface glabrous or with sparse stellate pubescence, lower surface paler, glabrous to densely covered in greyish stellate hairs, with some yellow to brown hairs, especially on the veins, margins entire, apex rounded to bluntly acute, base truncate or rounded to cordate or cuneate; petiole 0.3–1.4 cm long, variably hairy. Inflorescences pseudoterminal, shortly racemose, with one to six flowers. Flowers held on short pedicels that widen from base to apex; calyx with obscure, unequal teeth; corolla with 4–10 (usually 6) lobes, 1.6–2.6 cm long, pure white; filaments to 9 mm, anthers 4–6 mm; ovary densely stellate-pubescent, style pubescent at base or nearly throughout its length. Fruit globose, 1.2–1.4 cm diameter. Flowering March to April (USA). Gonsoulin 1974, Spongberg 1976, Fritsch 1996a, Hickman 1996. Distribution USA: California. Habitat Dry woodland and chaparral in the foothills of the Sierra Nevada, between 150 and 1500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration Gonsoulin 1974; NT834. Cross-reference B519 (as S. officinalis var. californicus).

The taxonomic status of Styrax redivivus has been much disputed, it having long been considered to belong within S. officinalis, as a variety of that Mediterranean species (see, for example, Bean 1981b). They have now been shown to be distinct species, on both genetic and morphological grounds, with S. redivivus being most closely

Plate 538. Styrax platanifolius subsp. youngiae is perhaps more of botanical than horticultural interest, but as it is rare both in the wild and in cultivation it should be looked after carefully in the few gardens where it grows. Image JC Raulston Arboretum.

Section II. Species Accounts

Styrax

835

related to the S. platanifolius group (Fritsch 1996a, 1996b). Fritsch (1996a) provides a key to the three taxa, adapted here. 1a. Stalked stellate hairs on vegetative parts (where present) white or tawny; pedicels 8–17 mm, of equal thickness throughout; corolla lobes widely spreading; pollen pale yellow; Mediterranean Basin .................................................... S. officinalis 1b. Stalked stellate hairs on vegetative parts (where present) golden-yellow to dark brown; pedicels 4–9 mm, widening from base to apex; corolla lobes moderately spreading; pollen orange-yellow; North America ...................................................... 2 2a. Larger undehisced capsules 7–10 mm, hairs on capsule greyish; pedicel 1.3–2.3 times length of calyx; leaves often coarsely lobed or irregularly undulate; Mexico (northeastern), USA (Texas) ......................................... S. platanifolius 2b. Larger undehisced capsules 11–15 mm, hairs on capsule brownish; pedicel 0.5–1.4 times length of calyx; leaves entire; USA (California) ........................... S. redivivus

The superficial similarities between the Californian Snowdrop Bush and its Mediterranean equivalent S. officinalis are remarkable, but it is good that the various unfeasible explanations of their linkage as varieties of each other can now be laid to rest. Styrax redivivus is a lovely member of the California chaparral and dry woodland flora, combining beautifully with Cercis occidentalis both in the wild and in gardens (S. Hogan, pers. comm. 2007), and brings Styrax into the reach of those with hotter drier gardens than tolerated by most others of the genus. It is summer-dormant, flushing out as the winter rains arrive, and is not tolerant of any combination of heat and humidity (S. Hogan, pers. comm. 2007). Summer watering should be avoided. It is appreciated by gardeners in California but not widely grown elsewhere.

Styrax serrulatus Roxb. Tree 4–12 m, 0.25 m dbh. Branchlets densely covered with brown stellate tomentum. Leaves papery, 5–14 × 2–4(–5.5) cm, ovate or oblong to lanceolate, glabrous or with sparse stellate tomentum, five to seven secondary veins on each side of the midrib, margins serrate or rarely entire, apex acuminate; petiole 0.3–0.5 cm long. Inflorescences terminal, racemose or paniculate, 3–10 cm long, with numerous flowers; pedicels 0.3–0.8 cm long. Flowers 1–1.3 cm long; calyx densely yellow-tomentose, five-toothed, corolla tube 0.2–0.3 cm, lobes 0.7–0.9 cm, oblong to lanceolate, stamens shorter than corolla. Fruit ellipsoid to ovoid, 0.8–1.6 cm long, densely covered with grey-brown tomentum. Flowering March to May, fruiting June to November (China). Hwang & Grimes 1996. Distribution BHUTAN; CHINA: southern Guangdong, southern Guangxi, Hainan, southeast Xizang, southern Yunnan; INDIA; LAOS; MALAYSIA: Malay Peninsula; MYANMAR; NEPAL; TAIWAN; THAILAND; VIETNAM. Habitat Forests between 500 and 1700 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Hwang & Grimes 1996. Taxonomic note The name S. serrulatus is sometimes incorrectly given as a synonym of S. japonicus.

The wide natural range of this plant is not matched by its presence in cultivation, where it is extremely scarce. Two specimens have grown in the Hillier Gardens since the 1970s and seem to be correctly named, the larger one currently 5 m tall with a spread of about 8 m, with several stems (A. Coombes, pers. comm. 2008). The species has also been in cultivation at the JC Raulston Arboretum since 1994, when it was received from Sonoma Horticultural Nursery, California. When seen in May 2006 it was a somewhat sparse multistemmed bush, 2.5 m tall, and had just finished flowering. S. shiraianus Makino B519, K368 S. shweliensis (NOW S. hookeri C.B. Clarke, NT831) B519, K369

Plate 539 (opposite). The Californian Snowdrop Bush, Styrax redivivus, is a beautiful small tree from the chaparral of the lower slopes of the Sierra Nevada. Image Phytophoto.

836

Styrax

New Trees

Styrax suberifolius Hook. & Arn. Tree 4–20 m. Branchlets covered with reddish or greyish brown stellate tomentum. Leaves leathery, 5–15(–18) × 2–5(–8) cm, elliptic or oblong to lanceolate, upper surface glabrous or with tomentum along the midrib, lower surface densely covered in brown stellate tomentum, 5–12 secondary veins on each side of the midrib, margins usually entire, apex acuminate and often slightly curved; petiole 1–1.5(–2) cm long, four-angled. Inflorescences terminal or axillary, racemose or paniculate, 6–12 cm long with numerous flowers; pedicels 0.1–0.3 cm long. Flowers 1–1.5 cm long; calyx densely covered with yellow-grey tomentum, corolla tube 0.3 cm, lobes four to five, to 1.0 cm, oblong to lanceolate, stamens 8–10, shorter than corolla. Fruit ovoid to globose, 1–1.8 cm diameter, densely brown-tomentose, dehiscing by way of three valves. Flowering March to May, fruiting August to November (China). Hwang & Grimes 1996. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; MYANMAR; TAIWAN; VIETNAM. Habitat Between 300 and 3000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996. Taxonomic note In addition to typical S. suberifolius there is var. hayataianus (Perkins) Mori, with greyish white tomentum on the underside of the leaf (see discussion under S. formosanus above, p. 830).

Yet another extremely scarce species in cultivation is Styrax suberifolius, of which a few examples grow at Tregrehan and in the University of British Columbia Botanical Garden. When seen in 2005 the trees at Tregrehan were about seven years old and were up to 8 m tall, having developed very straight unbranched trunks with spreading branches. The bark, like that of many Styrax, is finely striated with darker lines over a rich brown ground – a lovely detail worthy of close inspection. The Tregrehan trees, of Yunnan origin, have bloomed, but the flowers have only a slight scent (T. Hudson, pers. comm. 2005).

Styrax tonkinensis (Pierre) Craib ex Hartwich Tree 6–30 m, 0.6 m dbh. Branchlets covered with stellate tomentum, becoming glabresecent. Leaves papery to leathery, 5–18 × 4–10 cm, elliptic to ovate, upper surface glabrous or with some hairs along the veins, lower surface densely covered in grey stellate tomentum, five to six secondary veins on each side of the midrib, margins entire or apically serrate, apex short-acuminate, base rounded to cuneate; petiole 0.5–1.5 cm long. Inflorescences axillary, when 3–5 cm long, with one to seven flowers, or pseudoterminal, when racemose or paniculate, 3–20 cm long, with 6–23 flowers; pedicels 0.5–1 cm long. Flowers 1.2–1.5 cm long; calyx white-hairy, with irregular small teeth; corolla tube 3–4 mm, lobes five, 10–15 mm, ovate to lanceolate, membranous. Fruit subglobose, 1–1.2 cm diameter, grey stellate-tomentose, splitting by way of three valves. Flowering May to June, fruiting August to October (China). Hwang & Grimes 1996, Huang et al. 2003. Distribution CAMBODIA; CHINA: Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Yunnan; LAOS; THAILAND; VIETNAM. Habitat Forests between 100 and 2000 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Hwang & Grimes 1996.

Resin obtained from various species of Styrax has a long history of use in medicine and as incense. Once obtained from the Mediterranean S. officinalis, these resins are now mostly obtained from S. benzoin Dryander and other Asian species, including S. tonkinensis, and are a surprisingly valuable commodity. In 1996 the trade in ‘gum benzoin’ was worth US$5.2 million to Singapore alone (Kashio & Johnson 2001). Another important use of S. tonkinensis is as a plantation and agroforestry tree, for its rapid growth and quick yield of wood for fuel and pulpwood (Pinyopusarerk 1994). As a natural pioneer, germinating in disturbed forest, S. tonkinensis is ideally suited to plantation conditions, and exhibits at least some hardiness. It is not common in cultivation, but a few trees are growing in the milder parts of our area. At the David C. Lam Asian Garden in Vancouver it flowered profusely at a young age (Wharton et al. 2005), but at Tregrehan, though growing fast to 10 m, it has yet to flower (T. Hudson, pers. comm. 2007). In Cornwall it can be semi-evergreen in a mild winter,

Section II. Species Accounts

Styrax

and with its large leaves requires a sheltered site (Hudson 2004). Plants labelled as S. tonkinensis have been grown at the JC Raulston Arboretum for some time but are almost certainly misidentified (M. Weathington, pers. comm. 2008). S. veitchiorum (NOW S. odoratissimus Champ. ex Benth.) B520, K370 S. wilsonii Rehder B520, K370

TAXODIACEAE

×TAXODIOMERIA In China there is at present a phenomenal interest in Taxodium, with trees being planted by the millions in the southeast to beautify developing urban areas there (Creech et al. 2008). In China and in the southeastern United States the genus is being actively researched and bred, resulting in new clonal selections with superior form and tolerances. ‘Zhongshansha 302’, for example, is a cultivar of a Chinese-bred hybrid between two varieties of Taxodium distichum (L.) Rich., var. distichum and var. mexicanum Gordon (syn. T. mucronatum Ten.). Selected for its straight growth, lack of ‘knees’ and tolerance of alkalinity and salty soil, it has been released into American commerce as a joint venture between SFA (Stephen F. Austin State University) Mast Arboretum, Nacogdoches, Texas and Nanjing Botanic Garden, under the name Nanjing Beauty, and is probably the precursor of a series of superior clones (Creech 2007a, 2007b). A few years earlier, in 2003, there were reports from China of a new intergeneric hybrid between Taxodium distichum var. mexicanum and Cryptomeria japonica (Zhang et al. 2003a), supposedly created in the 1970s by the late Prof. Ye Pei-Zhong by deliberate hybridisation, using a tree of the Taxodium growing in Nanjing as maternal parent and the local Cryptomeria japonica (Thunb. ex L. f.) D. Don (often known in China by the invalid name C. fortunei Hooibr.) as the male. This gave rise to a handful of surviving seedlings, which were propagated and distributed. Further multiplication took place in Shanghai post-1975, and the resulting trees were claimed to fare better there than either of the parents or similar conifers, being almost evergreen and with considerable salt tolerance. In consequence they were described as ×Taxodiomeria peizhongii Z.J. Ye, J.J. Zhang & S.H. Pan. The characters used to define the hybrid were rather weak, however, and the trees resembled Taxodium distichum var. mexicanum in most respects, although they were stated to be less fertile (Zhang et al. 2003a). The announcement was greeted with much interest, including enthusiastic articles in the horticultural press (see, for example, Hecker 2004), only for cold water to be poured on the situation by a paper published in 2006 (Ling et al. 2006) demonstrating that no trace of Cryptomeria genes were to be found in supposedly hybrid material investigated. This confirmed the view of British conifer experts who had already concluded that there was no evidence of hybridity in the material illustrated and described in 2003 (A. Coombes, pers. comm. 2008), and in July 2006 the Royal Horticultural Society Advisory Panel on Nomenclature and Taxonomy concurred with this view. Repeated attempts to recreate the cross, by Prof. Xu in Nanjing, have failed (Creech et al. 2008). Despite this, a patent application for ×Taxodiomeria peizhongii ‘Dongfangshan’ by the Shanghai Forestry Station was approved by the US Patent

837

838

×Taxodiomeria

New Trees

Office in 2007 (PP17,767) (see US Patent Office 2007). The lengthy and curiously worded description submitted with the application (the plant is said, for example, to be ‘semi-indeciduous’) adds nothing new to that published by Zhang et al. (2003a). Dr David Creech (pers. comm. 2008) has seen the purported hybrid trees and is not convinced that they are anything but a Taxodium. In a recent article, Creech and co-authors also mention a suspect record from Soviet Russia, of Metasequoia × Taxodium, that has never been independently confirmed (Creech et al. 2008). A further intriguing conifer hybrid was reported by Frank Callahan (to JMG, pers. comm. 2004), who recalled seeing hybrids between Metasequoia and Sequoia in California, but said that they had not survived long as they were ‘confused’ between being evergreen or deciduous (undecideduous, perhaps). Controlled crosses should be attempted between these two redwood genera.

TAXACEAE

TAXUS

L.

Yews

Plate 540. Taken on the Dochu La, Bhutan in 1985, this photograph shows Taxus wallichiana var. wallichiana in fruit – but there are no significant morphological characters that would easily distinguish it from T. baccata. Image P. de Spoelberch.

Taxus are evergreen trees and shrubs with reddish brown, flaky bark. They are typically dioecious, though the shrubby T. canadensis is monoecious. The branchlets are irregularly alternate, greenish yellow when young, reddish brown later. The leaves are flexible, two-ranked, sessile or shortly petiolate, the stomata in two pale-coloured strips on the lower surface. Both male and female cones are solitary and axillary; the male (pollen) cones globose, pedunculate, with 6–14 microsporophylls; the female (seed-bearing) structures (cf. cones) subsessile, bearing several overlapping bracts at the base, with one ovule per structure. The ovule is partially enclosed in a red or orange (yellow in some cultivars) fleshy aril, open at the apex (Hils 1993, Fu et al. 1999d). The taxonomy of Taxus has always been and remains challenging (death may be certain – Taxus is anything but), and recently renewed medicinal interest in the genus (see below) has brought forth a number of new species and systematic interpretations. The number of recognised species varies widely from one account to another, largely due to the relative paucity of gross morphological characters by which taxa can be delimited. Taxus species are currently defined largely by geography, and most cultivated yews can be identified with certainty only when their provenance is known. Farjon (2001) recognises 10 species, but given the difficulty in separating even these there is some merit in following Pilger (1903), who treated all yews as subspecies of T. baccata. The extraordinary recent review by Spjut (2007), recognising 24 species and 55 subspecific taxa, is probably best ignored; it includes six newly described species, and specieslevel recognition for a number of horticulturally significant trees such as the Irish Yew, T. baccata ‘Fastigiata’. Recent studies of the T. wallichiana complex (Gao et al. 2007, Möller et al. 2007, Shah et al. 2008) have found some useful morphometric attributes by which to distinguish entities among Asian species, but only at the cost of measuring a lengthy suite of characters in the minutest detail.

Section II. Species Accounts

Taxus

Identification through criteria of geography is always unsatisfactory, but in Taxus it seems to be essential. In his review of the Taxaceae in cultivation, Cope (1998) noted that while most species have clearly disjunct ranges, the distributions of the Asian yews overlap. Here the characters traditionally used for identification are bud scales and leaf apices, but these are variable, any differences being very slight – only to be perceived through a detailed study of a large range of material – and even then identification is by no means certain (Möller et al. 2007). To compound the problem, there are considerable differences between dried and fresh material (Shemluck et al. 2003). There is at present no serious study setting out an opinion on comparative points of difference for all species, and trying to collate various authors’ views from a literature survey seems futile. In consequence, we feel, we can only advise horticulturists to accept names that are currently attached to plants, and, where provenance is known, ensure that it is scrupulously recorded. In view of all this, the accounts below give only minimal descriptions. (We are very non-yew.) In our notes on plants in cultivation their identification has been taken in good faith, and cross-references are given with the caution of caveat lector. It is perhaps useful to note that identification of named cultivars is also a nightmare (Dirr 1998). Expeditions made in the early 1990s by Rob Nicholson and Melvin Shemluck were an important source of authenticated wild-origin Taxus material. Nicholson (first of the Arnold Arboretum, then Smith College Botanic Garden) and Shemluck (of Quinsigamond Community College, Massachusetts) went in search of specimens to be tested for taxol content by the National Cancer Institute (USA) and private pharmaceutical companies, and living material was propagated from each of their collections, resulting in over 300 new documented Taxus clones in cultivation. Their travels took them to many areas where yews occur, and material of many of the taxa (or should that be Taxi?) they found has been introduced to botanic garden collections. Taxols are cancer-inhibiting compounds found in yew bark, of great importance (especially paclitaxcel) in the pharmaceutical industry. Although they can be partly synthesised artificially, they are still extracted from plant tissue, and overexploitation of wild trees has led to T. wallichiana becoming threatened in many parts of its range (Gao et al. 2007). Since 1995 all Asian species of Taxus have been included on CITES Appendix 2, controlling their movement around the world. In consequence it is illegal to transfer any parts of these plants across international borders without CITES certification (with the exception of cultivated specimens of the familiar T. cuspidata). The value of yews in the landscape, in all their shades and shapes, is undisputed. In western Europe T. baccata is unrivalled, but in much of North America and continental Europe it is replaced by the hardier T. cuspidata and hybrids T. ×media (T. baccata × T. cuspidata) and T. ×hunnewelliana (T. canadensis × T. cuspidata). In the southeastern United States these commoner yews do not tolerate the heat and humidity, so Asian species and the native T. floridana have been investigated for wider use (Dirr 1998). Propagation is by seed – but hybrids occur, adding to confusion – or by cuttings. T. baccata L. B561, S508, K281 T. brevifolia Nutt. B568, S508, K288 T. canadensis Marshall B568, K288 T. celebica (NOW T. sumatrana (Miq.) de Laub., NT841) B569, K289

T. cuspidata Siebold & Zucc. B569, S509, K289 T. cuspidata f. latifolia (NOW T. cuspidata var. cuspidata) K290 T. cuspidata var. nana Hort. ex Rehder B569

839

840

Taxus

New Trees

T. cuspidata f. thayerae (NOW T. ×media Rehder) B570

Taxus floridana Nutt. ex Chapm.

Florida Yew

Distribution USA: Florida. Habitat Moist, shaded valleys in broadleaved forest, between 15 and 30 m asl. USDA Hardiness Zone 7. Conservation status Critically Endangered. The Florida Yew exists only along the eastern side of the Apalachicola River, where it is threatened by fungal disease and the extraction of water from underground aquifers. Illustration Elias 1980; NT840. Cross-reference K291.

Plate 541. Taxus floridana is useful in the southern United States as it is tolerant of summer heat and humidity. This young plant was photographed in South Carolina, at Woodlanders Nursery. Image J. Grimshaw.

Despite its narrow natural range, where it is presumably a relict population related to T. globosa (see p. 841), the Florida Yew seems to be quite adaptable, and is found in collections throughout milder areas on both coasts of the United States. It grows outdoors at the Arnold Arboretum, though discolouring to brown in winter (R. Nicholson, pers. comm. 2008). It is considered to have potential for use in the southeastern states as a replacement in the landscape for T. baccata, T. cuspidata and T. ×media, which do not tolerate heat and humidity (Dirr 1998). In the United Kingdom it does well where grown; at the Hillier Gardens, for example, there is a respectable specimen of 4.2 m.

Taxus fuana Nan Li & R.R. Mill

Western Himalayan Yew

Syn. T. wallichiana in part Distribution AFGHANISTAN; CHINA: Xixang; INDIA; NEPAL: western; PAKISTAN. Habitat Forest, between 1800 and 3400 m asl. USDA Hardiness Zone 7 (?). Conservation status Vulnerable (IUCN); also included on CITES Appendix 2.

The yews of the Himalayan chain have traditionally been treated as Taxus wallichiana (see, for example, Farjon 2001), but in 1997 a new taxon – T. fuana – was described, on morphological evidence, and said to occupy the range indicated above. This position was adopted by Fu et al. (1999d) in Flora of China; Farjon (2001), however, while accepting the species as valid, considered it to occur only in southwestern Tibet. To complicate matters further, Spjut’s (2007) research has unearthed the prior name T. contorta Griff., but it remains to be seen whether others will concur and adopt this name (much the oldest) for the Western Himalayan Yew. Recent investigations using morphological and molecular data from a large sample of material have shown that T. fuana is distinct from both T. baccata (to which the yews of the western Himalaya have been ascribed) and T. wallichiana; each also occupies a discrete distribution (Shah et al. 2008). As so often in Taxus, even in this case where morphological characters are well supported by DNA evidence, the visible recognition characters remain rather tenuously distinct, though the species are separable when a large sample is compared. Taxus fuana has, on average, 13.3 leaves per cm of a two- to three-yearold branch, compared with 9.9 in T. wallichiana and 11.5 in T. baccata. The leaves are also straighter, longer and narrower (mean length 32.4 mm, mean width 1.8 mm, compared to a curved 28.7 mm long, 2.3 mm wide in T. wallichiana). Their mean length to width ratio is 13.8, indicating that they are the longest and narrowest of any in the complex, and they have the lowest mean number of stomatal bands (7.7). The differences are tabulated by Möller et al. (2007) and Shah et al. (2008), for those who really want to know, but the principal distinction, once again, is distribution. All yews growing west of central Nepal, to the Afghan border, are attributable to T. fuana. From eastern Nepal eastwards they can be ascribed to T. wallichiana s.l., see p. 842). What happens in central Nepal is not entirely clear, but the two taxa seem

Section II. Species Accounts

Taxus

to remain distinct even though there is a transition zone where they overlap (Möller et al. 2007). Taxus baccata is not known to occur further east than Iran. As it seems that T. fuana is indeed a valid species, it is safe to say that it is in cultivation in gardens across our area, exemplified by trees grown from gatherings made in northern Pakistan (EPAK 146, collected in 1995) and Himachal Pradesh, India (H&M 1912, 1838, from 1994).

Taxus globosa Schlecht.

Mexican Yew

Distribution GUATEMALA; MEXICO: Hidalgo, Nuevo León, Oaxaca, Querétaro, San Luis Potosí, Tamaulipas, Veracruz. Habitat Humid canyons and montane, pine or fir forest, between 1000 and 2850 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk/Near Threatened. Cross-reference K291.

In their review of the natural history and chemical compounds of Taxus globosa, Shemluck et al. (2003) rehearse the usual difficulties associated with identifying yews, but report that of the New World species, T. globosa is most similar to T. floridana. This species pair, though widely disjunct, share similarly soft-textured, tapered leaves, of comparable length and width (20–30 mm long or more, 1.5–2 mm wide), each tipped with an apiculus, though the mucro is better defined in T. floridana than in T. globosa. The undersides of the leaves of T. globosa are more or less uniform in colour, with two dark green marginal lines, and are matt between the veins, whereas in T. floridana they are glossier. On average there are six to eight stomatal lines in T. floridana and eight to nine in T. globosa. Shemluck and his co-authors also note that the aril of T. globosa is fatter and rounder than in any other yew, sometimes having a truncated distal end. In general, T. globosa has the highest taxol levels of any species investigated, including T. brevifolia, and it is suggested that plantation culture of selected clones could be a viable source of revenue. Taxus globosa has been collected in Mexico on several occasions by American groups, with participants including Eduardo Estrada, Rob Nicholson and Melvin Shemluck with John Fairey and Carl Schoenfeld, and also by private expeditions, with the result that it is well established in cultivation in the United States and has a slender presence in Europe. It is commercially available from several West Coast nurseries and was described by Dan Hinkley (Heronswood Nursery catalogues, 1999 onwards) as forming ‘dense rotund masses’ of dark green foliage with a ‘hint of blue-green’, but whether it has advantages over any other yew remains to be seen. It is certainly not adapted to dry conditions, growing in moist forests in the wild. T. ×hunnewelliana Rehder K291 T. ×media Rehder B570, S509, K291

Taxus sumatrana (Miq.) de Laub.

Tropical Asian Yew

Syn. T. celebica (Warb.) H.L. Li Distribution INDONESIA: Sulawesi (Celebes), Sumatra; PHILIPPINES. Habitat Humid, subtropical forest and montane forest, between 1400 and 2300 m asl. USDA Hardiness Zone 8. Conservation status Lower Risk (IUCN), but threatened by forest clearance (Nicholson 1998); included on CITES Appendix 2. Crossreference B569 (but this refers to mixed material of mainland origin). Illustration NT842.

The name Taxus sumatrana has at times been very widely applied to Asian yews – for example by de Laubenfels (1988), who included under it all but T. cuspidata – but Farjon (2001) used it only to refer to yews occurring in Indonesia and the Philippines.

841

842

Taxus

Plate 542. Taxus sumatrana, collected in the Philippines by Rob Nicholson and Mel Shemluck, is now established in cultivation. Image R. Nicholson.

New Trees

The recent studies on the T. wallichiana group (see below) included a very small sample of Philippine, Sulawesi and Taiwanese material; although this did fit within the wider picture of T. wallichiana, the sample was insufficient to allow firm conclusions (Möller et al. 2007), and we follow Farjon’s geographical delimitation here. Material collected by Nicholson and Shemluck from the Philippine islands of Luzon and Mindanao, and therefore permissibly identified as T. sumatrana, is in cultivation outdoors in areas of the United States with mild climates, and elsewhere under glass (for example, at the Royal Botanic Garden Edinburgh). The 25 clones that have been propagated include material from Mount Pulog, Luzon (labelled by the population identifiers Pulog 1 to Pulog 7) and from Mount Apo on Mindanao (Apo 8 to Apo 25) (R. Nicholson, pers. comm. 2008). One of their collections from Mindanao (Apo 14) is grown outdoors at Quarryhill, where it was looking somewhat sunburnt when seen in 2004. Nicholson (1998) has pointed out that yews are shade-dependent for germination, raising concerns that populations are unlikely to survive where even selective felling opens up the canopy. There are many other stocks of yews in cultivation under this name, dating back to collections made by Wilson (for example, W 4053) in Sichuan. Others include Townsend & Bridger’s (HONX 68) from Honshu (currently growing at Kew and elsewhere), and material sent from Wishan in Taiwan by the Forest Research Institute of Taiwan (Kew). No doubt there are many more – including stock labelled T. celebica. Plants offered for sale as T. sumatrana by Heronswood Nursery c.1999–2000 were raised by Dan Hinkley (pers. comm. 2008) from seed from a Japanese Index Seminum. None of the above should be considered T. sumatrana in the strict geographical circumscription given by Farjon, however; they are most likely to be members of the T. wallichiana complex.

Taxus wallichiana Zucc.

Sino-Himalayan Yew

Syn. T. baccata subsp. wallichiana (Zucc.) Pilg., T. chinensis var. yunnanensis (W.C. Cheng & L.K. Fu) L.K. Fu, T. yunnanensis W.C. Cheng & L.K. Fu

The comparatively simple geographical distinction between Taxus fuana and T. wallichiana in the main Himalayan chain has been dealt with above, but it is within the T. wallichiana complex that things become really complicated. Perhaps due to the persistent effects of glacial refugia and rather limited genetic exchange between populations, yews ascribable to T. wallichiana growing east of central Nepal tend to form rather distinct populations, at least when their DNA is considered (Gao et al. 2007); morphologically, they remain very difficult to distinguish. Within T. wallichiana, Fu et al. (1999d) recognised three varieties – vars. wallichiana, chinensis and mairei – even though the characters used to separate them were as woolly as usual. Their validity has been more or less confirmed by recent studies investigating their morphology (using 27 separate characters), DNA and biogeography,

Section II. Species Accounts

Taxus

843

but still it is difficult to pin down morphological characters that can reliably separate the taxa (Gao et al. 2007, Möller et al. 2007). In addition, yews from the Hengduan mountains of Yunnan show characters that do not fit any of the three recognised varieties, and the position of isolated populations needs further consideration. Full details of the investigations, and the complete range of morphological measurements used, are provided by Gao et al. (2007) and Möller et al. (2007).

Taxus wallichiana var. wallichiana Distribution CHINA: Sichuan, Yunnan, Xizang; INDIA: Arunachal Pradesh, Assam, Manipur, Sikkim; MYANMAR; NEPAL; VIETNAM. Habitat Broadleaved and mixed forest, often in association with bamboos, between 2000 and 3500 m asl. USDA Hardiness Zone 7. Conservation status Data Deficient (IUCN); but included on CITES Appendix 2. Illustration NT838, NT843. Cross-references B570, K294.

Var. wallichiana occurs from central Nepal to western China as a geographically disjunct metapopulation. Outliers fitting the morphological template of var. wallichiana grow with var. mairei in southern and eastern China and southern Vietnam, but these may reflect variation in the population of the latter. As defined by Möller et al. (2007), var. wallichiana has a mean leaf density of 10 per 2 cm, mean leaf length to width ratio 10.4 (i.e. longish leaves of medium width), and a high number of stomatal bands (mean 13.2). The definable distribution of var. wallichiana makes it possible for some collections, at least, to be confidently ascribed here. Schilling 2056, for example, grown in several British arboreta, came from mixed forest in the Dudh Kosi valley of eastern Nepal in 1975 (T. Schilling, pers. comm. 2004), east of the distribution of T. fuana; Philippe de Spoelberch’s collection from the Dochu La, Bhutan in 1985 fits here as well. Gatherings from southwestern Sichuan and western Yunnan can also be reliably identified as var. wallichiana.

Taxus wallichiana var. chinensis (Pilg.) Florin Syn. T. cuspidata var. chinensis (Pilg.) C.K. Schneid., T. chinensis (Pilg.) Rehder var. chinensis Distribution CHINA: Chongqing, Hubei, Shaanxi, Sichuan; VIETNAM. Habitat Forest and bamboo groves, between 1100 and 2700 m asl. USDA Hardiness Zone 7 (?). Conservation status Lower Risk (IUCN); but included on CITES Appendix 2.

Var. chinensis can be categorised as having densely placed leaves (mean 12.1 per 2 cm), with a mean length to width ratio of 6.4 (i.e. longish, wide leaves) and a high number of stomatal bands (mean 12.0). It is principally found in the mountains surrounding the Sichuan Basin in west-central China, but trees with chinensis characters also occur in northern Vietnam (Möller et al. 2007). Plants named T. chinensis are recommended by Yucca Do Nursery, Hempstead, Texas (Yucca Do online catalogue 2008), as rapidly growing, heat-tolerant yews.

Taxus wallichiana var. mairei (Lemée & H. Lév.) L.K. Fu & Nan Li Syn. T. speciosa Florin, T. chinensis var. mairei (Lemée & H. Lév.) W.C. Cheng & L.K. Fu Distribution CHINA: southern Anhui, Fujian, southern Gansu, northern Guangdong, northern Guangxi, Guizhou, western Henan, western Hubei, Hunan, Jiangxi, southern Shaanxi, Sichuan, eastern Yunnan, Zhejiang; VIETNAM. Habitat Coniferous and mixed forest, between 100 and 3500 m asl, though usually lower than var. chinensis. USDA Hardiness Zone 7 (?). Conservation status Not evaluated (IUCN), but as for var. chinensis. Cross-references B570, K294.

Plate 543. This yew growing at 2500 m between the Arun and Tamur Rivers in eastern Nepal, photographed in November 1984, can be safely identified as Taxus wallichiana var. wallichiana because its locality is documented (Søndergaard 1985). Image J.R.P. van Hoey Smith.

844

Taxus

New Trees

Var. mairei has comparatively widely spaced leaves (mean 9.4 per 2 cm), with a mean length to width ratio of 8 (i.e. long and wide leaves) and a high number of stomatal bands (mean 12.7). It has a wide range in central and southern China, meeting var. chinensis along the western and southern edges of the Sichuan Basin and in northern Vietnam (Möller et al. 2007). The epithet mairei is attached to plants grown quite widely throughout our area. Specimens seen in the United States are attractive and were flourishing, both at Heronswood and at the JC Raulston Arboretum. It is probable that many specimens grown as T. celebica (see Bean: B569), T. sumatrana and T. wallichiana belong here.

TELOPEA

PROTEACEAE

R. Br.

Waratahs

Plate 544. The bright pinkish red flowers of Telopea oreades appear in spring. It is remarkably hardy, and could be planted more widely in areas with maritime climates. Image J. Grimshaw.

Telopea is endemic to Australia, the five species being found in New South Wales, Victoria and Tasmania. Waratahs are multistemmed shrubs or small trees, usually with a lignotuber. The leaves are simple, with entire, dentate or lobed margins. The inflorescence is a terminal head surrounded by red or pink bracts. The flowers are in pairs; they are 4-merous and usually red. The perianth is tubular and strongly incurved in bud, splitting to expose the conspicuous, curved style, and bearing the anthers on the perianth segments. The fruit is a woody follicle that curves backwards away from the stem. It opens until almost flat to release the numerous winged seeds (Crisp & Weston 1987, 1995, 2002). The waratahs are spectacular flowering shrubs and small trees that clearly have considerable but unrealised potential for garden use within our area. Perhaps people have been scared off by their exotic looks. The genus has recently been thoroughly reviewed from a horticultural standpoint by Jeff Irons (2006), in an article that is essential reading for anyone wishing to grow these plants. It gives exceptionally thorough cultivation advice, including a league table of palatability to gastropods (a major problem), and detailed recommendations for fertilising plants in pots. Like all members of the Proteaceae, Telopea prefer relatively infertile, well-drained acidic soils, forming masses of fine roots to extract any available nutrients. A mulch of leaf mould is very beneficial. They will do best in areas with high summer rainfall. Propagation is from seed sown in heat, or by cuttings (see Irons 2006). As with many slightly marginal species, it is wise to allow seedlings to develop some bulk (and in this case, a lignotuber) in a pot before planting them out. Irons’ article is remarkably encouraging on the prospects for growing waratahs outside in our area, citing specimens of four of the five species established in the open ground in the British Isles. The hardiness of

Section II. Species Accounts

Telopea

T. truncata has been recognised for many years, and it is a mystery that this species is so seldom seen. Telopea oreades (described below) and T. mongaensis are perhaps not quite as hardy, but worthy of attempt in milder, moister parts. Telopea mongaensis is more shrubby than the others as it produces suckers; its inflorescences, however, are just as attractive. It is very rare in cultivation but plants are known to grow outside in Devon (Irons 2006). The most magnificent species, T. speciosissima, is indubitably the most tender, although Irons mentions one specimen growing against a boilerhouse wall in Kirkcudbrightshire, southern Scotland. In the wild it would seldom experience a frost below –4 ºC; hardier provenances could be sought, but even without this, such a tolerance would make it eligible for many coastal areas in western Europe and the Pacific coast (as it is in California). Hybrids between the different species have been developed in Australia, to combine the floral effect of T. speciosissima with the hardiness of others: ‘Burgundy’, for example, is the product of T. oreades × T. speciosissima, and is said to be hardy to –7 ºC (Irons 2006).

Telopea oreades F. Muell.

Gippsland Waratah

Shrub or tree to 12 m; highly branched. Leaves narrowly obovate to spathulate, papery, 11–28 × 1.5–6 cm, secondary veins indistinct above, distinct but not raised below, margins entire, apex acuminate. Inflorescences numerous, 5–8 cm diameter, each with 36–60 flowers; bracts inconspicuous, 1.5–7.5 cm long, pink or green with hairy apices. Flowers pink to crimson outside and deep red inside; perianth 2.8–3.6 cm long, tubular, style incurved. Follicle 5–7 cm long. Flowering August, fruiting October to December (New South Wales). Crisp & Weston 1987, 1995, 2002. Distribution AUSTRALIA: New South Wales (southeastern coastal ranges and in the Monga Valley), Victoria (East Gippsland). Habitat Temperate rain forest and wet eucalypt forest, between 200 and 1200 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Irons 2006. Cross-reference S509.

This species has been in cultivation since 1910, when it was introduced to Ludgvan Rectory in western Cornwall by the Revd A.T. Boscawen, and has grown at Wakehurst Place since 1968. As Clarke (1988) records, it has suffered from frost there in the past, but it can be expected to tolerate temperatures of –12 ºC without harm (Irons 2006). It is becoming more frequently grown in southwestern Britain, where it is commercially available, but could be tried more widely, even away from the coast. A 3 m specimen at Tregrehan, planted in 2002, was flowering beautifully when seen in April 2008. T. mongaensis Cheel S509 T. speciosissima R. Br. K390

T. truncata (Labill.) R. Br. B571, S509, K390

TERNSTROEMIACEAE (or PENTAPHYLACACEAE)

TERNSTROEMIA

Mutis ex L. f.

There are over 90 species of Ternstroemia, distributed across tropical and subtropical Asia, Africa and the Americas. They are evergreen trees or shrubs with alternate, petiolate, entire (rarely serrate) leaves. Ternstroemia flowers are axillary and solitary, though it is not unusual to find several flowers clustered together on leafless branch-

845

846

Ternstroemia

New Trees

lets. They are subtended by two bracteoles, which remain close to the sepals and are persistent or caducous. The flowers are 5-merous; the sepals imbricate, their margins glandular-serrate, the petals imbricate, slightly fused at the base, with 30–50 stamens in one to two (to three) whorls, filaments fused to the base of the petals. The fruit is a berry, which may be indehiscent or irregularly dehiscent, with pendulous seeds. The seeds are kidney-shaped with a red fleshy outer layer (Weitzman et al. 2004, Ming & Bartholomew 2006). Ternstroemia and its allies (for example, Eurya Thunb., Cleyera Thunb.) were previously classified as a subfamily of the Theaceae, but DNA evidence indicates that they should be recognised as a separate family, or in combination with Pentaphylacaceae (Prince & Parks 2001, APG 2003). As a largely tropical genus, Ternstroemia does not impinge much on temperate gardens – with the conspicuous exception of T. gymnanthera. This evergreen shrub or small tree was said by Bean (1981b) to be ‘not of much ornamental value’, but has become an important landscaping evergreen in the southeastern United States, where numerous cultivars have been selected (Dirr 1998). Propagation is by seed or by cuttings taken in late summer. T. gymnanthera (Wight & Arn.) Bedd. B572, K390

Ternstroemia nitida Merr. Plate 545. A handsome evergreen. Although still small, plants of Ternstroemia nitida at Tregrehan are showing considerable promise. Image J. Grimshaw.

Shrub or tree 2–8(–12) m. Bark smooth and greyish brown. Branchlets glabrous and greyish brown. Leaves papery to thin and leathery, 6–10 × 2.5–4 cm, oblong to elliptic or obovate, upper surface dark green, shiny and glabrous, lower surface pale green and glabrous, seven to nine secondary veins on each side of the midrib, margins entire, apex shortly acuminate; petiole 1–1.5 cm long, glabrous. Flowers axillary and solitary, staminate or hermaphrodite; pedicel 1.5–2 cm long. Bracteoles 0.2 × 0.2 cm, sepals ovate to oblong, covered with golden dots, petals obovate, white to pale yellow, 0.5–0.7 cm long, stamens 25–45. Fruit purplish red, ovoid, 1–1.2 cm long. Flowering June to July, fruiting August to September (China). Ming & Bartholomew 2006. Distribution CHINA: Anhui, Fujian, northern Guangdong, northeast Guangxi, eastern Guizhou, Hunan, Jiangxi, southern Zhejiang. Habitat Montane forests, between 200 and 900 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Hudson 2004; NT846.

Ternstroemia nitida is very rare in cultivation, but shows promise of being an attractive evergreen for milder gardens: ‘a first rate foliage shrub’ according to Hudson (2004). Plants grown from seed obtained from the Qingpu Paradise Horticultural Company have grown slowly but steadily at Tregrehan, the growth rate increasing as they become larger, and have reached 1.8 m after about ten years (T. Hudson, pers. comm. 2008). The very handsome broad leaves flush bronze before becoming dark green, and the small flowers are strongly scented. At Tregrehan it grows in semi-shade, which is probably advisable to avoid the leaves being scorched in sunlight.

Section II. Species Accounts

Tetraclinis

847

CUPRESSACEAE

TETRACLINIS

Mast.

The genus Tetraclinis is monospecific, comprising only the species T. articulata.

Tetraclinis articulata (Vahl) Mast. Syn. Callitris quadrivalvis Rich. & A. Rich., Thuja articulata Vahl Shrub or tree to 15 m, trunk straight or contorted, 0.6–1.2 m dbh. Bark thin, greyish. Crown conical or pyramidal. Branchlets flexible, articulated (each section 0.2–0.8 cm long) and dorsiventrally flattened. Leaves scale-like, decussate, appressed, the free section only 1 mm long, slightly dimorphic; the lateral pairs slightly longer than the facial pairs, which they partially overlap. Male strobili solitary, terminal, greenish yellow, 0.1–0.3 cm long with six to eight sporophylls, several adjacent shoots bearing solitary strobili, giving the appearance of a group. Seed cones solitary, terminal, subglobose, 0.8–1.2 cm long, initially glaucous blue, then greyish brown at maturity. Seed scales in two decussate pairs, heart-shaped to ovate, valvate, only the outer scales fertile, two to three seeds per scale; young cones with minute umbo. Seeds lenticular, 0.3–0.5 cm long; wings two, equal, to 0.8 cm long, reddish brown, translucent. The wood is golden-brown to orange-red with an intricate grain pattern, numerous knots and high resin content, highly valued by carpenters and cabinet makers. My desktop pen box is made of it (JMG). Masters 1893, Gardner & Jury 1993, López Lillo & Sánchez de Lorenzo Cáceres 2001. Distribution ALGERIA; MALTA; MOROCCO; SPAIN: Murcia, Sierra de Cartagena. Habitat Rocky slopes, between 0 and 1800 m asl. In Spain Tetraclinis appears to be restricted to limestone regions, while in North Africa it occurs on a variety of acidic and alkaline soils. USDA Hardiness Zone 9. Conservation status Lower Risk (IUCN). Tetraclinis is relatively abundant in North Africa, where scattered populations cover a large area. In Europe, however, it has an extremely limited distribution, and in Malta it is restricted to one site only. Illustration Gardner & Jury 1993; NT847. Cross-reference K294.

Commenting on the biogeographical interest of Tetraclinis articulata, and its timber properties, most authors are prompt to mention that it is only very marginally hardy in the British Isles (Dallimore & Jackson 1966, Rushforth 1987a, Hillier & Coombes 2002), and Bean (1981b) omits it altogether. Such caution is appropriate, as this tender tree is suited only to the very mildest parts of our area. Just two were seen in the research for the current work – one a small specimen in shade at Logan, the other a healthy-looking 2 m tree at Mount Usher. Occasionally, however, it has reached a more respectable size. In the 1920s there was an individual of ‘15 feet by 12 feet’ at Rostrevor House, Co. Down (Moore 1929) (this seems to have been the most successful British example to date). Tetraclinis is cultivated in the San Francisco Bay Area, and would appear to be ideal for the hotter, drier parts of California and the Mediterranean, as it is extremely drought-tolerant, but not for anywhere cooler and damper.

RUTACEAE

TETRADIUM

Lour.

Tetradium was revised by Hartley (1981), who expanded it to include all the hardy species of Euodia J.R. Forst. & G. Forst. (Horticultural references have generally used Euodia, or the orthographic variant Evodia – as reflected in the cross-references below.) It is now a genus of nine species, distributed from the Himalaya east to Japan and

Plate 546. The developing cones of Tetraclinis articulata are covered in glaucous wax, which disappears as they mature. The extremely small leaves are an adaptation to its arid habitat. Image S. Knees.

848

Tetradium

Plate 547. Tetradium glabrifolium is now well established in cultivation on both sides of the Atlantic, although it thrives best in areas with warm summers. Image N. Macer.

New Trees

the Philippines, and south to Indochina, the Malay Peninsula, Sumatra and Java. They are evergreen or deciduous trees or shrubs with naked buds. The leaves are opposite, imparipinnate (rarely paripinnate) and are dotted with oil glands. Inflorescences are terminal only or terminal and in the axils of the uppermost pair of leaves; corymbose to paniculate with numerous flowers. The flowers are unisexual (rarely hermaphrodite) and the trees dioecious; flowers 5- or 4merous, with valvate sepals, persistent in fruit, petals hooked at the apex, and the same number of stamens as petals. The fruit is a follicle containing one or two glossy seeds, the follicles in groups of one to four or one to five, the seeds remaining attached to the follicle (Hartley 1981, Flanagan 1988). A key to the cultivated species has been produced by Flanagan (1988). Mark Flanagan’s article (1988) on species of Tetradium in cultivation gives a comprehensive picture of their status in British gardens during the 1980s, which can be updated here. Flanagan’s main point – applicable across the genus – is that the various species are very variable, so that it is wise to take the broad view and not attempt to split off local variants. The four species he described at the time appear to have remained a quartet, with no new additions. Two are described below, T. glabrifolium and T. ruticarpum; the plant of T. fraxinifolium (Hook.) T.G. Hartley at Benmore that he mentioned, of possibly dubious identity and of unknown origin, has since died. The fourth species, T. daniellii, has always been the most common, and can be distinguished from the other three by the absence of conspicuous oil glands on the non-glaucous leaf undersides (Flanagan 1988). As Flanagan put it, T. daniellii is ‘not in the first rank of ornamental trees [but is] a useful and subtly attractive plant’, and it is probably fair to say the same of the others. The foliage is handsome but the prime moment of all members of the genus comes when the fruits ripen to bright red, held in broad corymbs at the tips of the branches. For all species a good light open site should be chosen, but they are not fussy about soil types. As members of a largely tropical family, Tetradium would be expected to thrive best in warm conditions but they seem to be very adaptable. Propagation is by seed, or by semi-ripe cuttings in summer (Wharton et al. 2005). Tetradium is very similar to Phellodendron, especially in vegetative characters, but has exposed axillary buds whereas in Phellodendron the buds are hidden at the base of the petiole and are only visible after leaf fall. In addition, the fruit of Tetradium is follicular, while that of Phellodendron is a drupe. Phellodendron has recently been revised (Ma et al. 2006) and only two species – P. amurense Rupr. and P. chinense C.K. Schneid. – are now recognised, without varieties. These are most easily distinguished by their fruiting panicles, those of P. chinense being compact with short branches while in P. amurense the branches are longer, making the panicles much more open in shape. The revision of Phellodendron did away with a complex set of varieties and

Section II. Species Accounts

‘species’, including P. insulare Nakai, which referred to material from Korean islands distributed in recent years from Chollipo Arboretum (now placed in P. amurense). Euodia baberi (NOW T. ruticarpum (A. Juss.) T.G. Hartley, NT850) S233 Euodia bodinieri (NOW T. ruticarpum (A. Juss.) T.G. Hartley, NT850) K54 Euodia daniellii (NOW T. daniellii (Benn.) T.G. Hartley) B145, S233, K54 Euodia fraxinifolia (NOW T. fraxinifolium (Hook.) T.G. Hartley) K54

Tetradium glabrifolium (Champ. ex Benth.) T.G. Hartley Syn. Euodia glauca Miq., E. meliaefolia Hance ex Walp. Shrub or tree to 20 m. Branchlets finely pubescent to glabrous. Leaves imparipinnate, 14–38 cm long; leaflets (3–)5–19, ovate to lanceolate, 4–15 × 1.7–6 cm, papery, oil glands inconspicuous, upper surface glabrous or with appressed hairs on the midrib, lower surface glaucous, glabrous or with appressed hairs on the midrib, 8–18 secondary veins on each side of the midrib, margins entire to almost crenulate, apex acuminate; petiolule 0.3–1.5 cm long; rachis glabrous or finely pubescent. Inflorescences 9–19 cm long, finely pubescent or glabrous; pedicels 0.1–0.4 cm long. Flowers mainly 5-merous (occasionally 4-merous); sepals finely pubescent to glabrous, petals green to yellow to white, 0.3–0.4 cm long. Follicles in groups of four to five (rarely one to three), sparsely or densely pubescent, three-sided, 0.35–0.5 cm long. Seeds black, one per follicle, paired with an aborted seed, attached to the follicle via a strip of tissue. Hartley 1981, Chang & Hartley 1993. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hong Kong, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang; INDIA: Assam, Sikkim, West Bengal; INDONESIA: Sumatra; JAPAN: Honshu, Kyushu, Ryukyu Is., Shikoku; MALAYSIA: Malay Peninsula; MYANMAR; PHILIPPINES; TAIWAN; THAILAND; VIETNAM. Habitat Evergreen forest, between 0 and 2000 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Wharton et al. 2005; NT848. Taxonomic note Ohba (1999) distinguished Japanese plants as var. glaucum (Miq.) T. Yamaz., on the grounds that the follicles are glabrous, though conspicuously tuberculate.

Writing in the immediate aftermath of the Great Storm of 1987, Flanagan (1988) bemoaned the loss of a fine tree of Tetradium glabrifolium at Wakehurst Place, grown from Wilson 247 and thought to be the only one in the country. Another large specimen, presumably of similar vintage, survives at Rowallane, Co. Down, however, where it was 12.7 m with two trunks in 2000 (TROI). It has been reintroduced since that time, and now seems to be well established in cultivation on both sides of the Atlantic, and commercially available, in the United Kingdom at least. A specimen growing at the University of British Columbia Botanical Garden since 1988 has formed an attractive, round-crowned tree that is as wide as it is tall (about 5 m in both directions) (Wharton et al. 2005). It is said to require a hot summer to do well, and in the absence of this growth is apt to occur later in the year. The new growth can be tinged with reddish brown. In Vancouver flowering occurs from summer into late autumn, and is much appreciated by bees (Mosquin 2005), with leaf fall in December. Flanagan (1988) noted that the old tree at Wakehurst Place occasionally coloured well (to a rich coppery red) but this seems to be unusual, the principal display coming generally from the bright red stems of the infructescence. Material was collected in Taroko, Taiwan in 1999 by Bleddyn and Sue Wynn-Jones (BSWJ 6882), and has been available from Crûg Farm. Euodia glauca (NOW T. glabrifolium (Champ. ex Benth.) T.G. Hartley, NT849) B145, S233, K55 Euodia henryi (NOW T. daniellii (Benn.) T.G. Hartley) B146, S233, K55 Euodia hupehensis (NOW T. daniellii (Benn.) T.G. Hartley) B145, S233, K55 Euodia officinalis (NOW T. ruticarpum (A. Juss.) T.G. Hartley, NT850) K55

Tetradium

849

850

Tetradium

New Trees

1 cm

C 1 cm

A B

1 cm

Tetradium ruticarpum (A. Juss.) T.G. Hartley Syn. Euodia baberi Rehder & E.H. Wilson, E. bodinieri Dode, E. officinalis Dode, E. rutaecarpa A. Juss. Figure 91. Tetradium ruticarpum: habit with infructescence (A); detail of stem with petiole bases (B); capsule releasing seeds (C).

Shrub or tree to 10 m (possibly more). Branchlets finely pubescent to glabrous. Leaves imparipinnate, 15–40 cm long; leaflets (3–)5–13, elliptic to ovate or rarely lanceolate, 4.5–17 × 2–8 cm, papery, oil glands conspicuous, upper surface largely glabrous, but with dense pubescence on the midrib, lower surface partially glaucous, sparsely to densely pubescent, 9–17 secondary veins on each side of the midrib, margins entire or irregularly crenulate, apex acuminate; petiolule 0–0.9 cm long; rachis finely pubescent. Inflorescences 2.5–18 cm long,

Section II. Species Accounts

Tetradium

851

finely to densely pubescent; pedicels 0–0.4 cm long. Flowers mainly 5-merous (occasionally 4-merous); sepals finely to densely pubescent, petals green to yellow to white, 0.3–0.5 cm long. Follicles in groups of one to five, glabrous or sparsely pubescent, subglobose, 0.35–0.6 cm long. Seeds black, one per follicle, paired with an aborted seed, attached to follicle via a strip of tissue. Hartley 1981, Chang & Hartley 1993. Distribution BHUTAN; CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang; INDIA: Assam, Sikkim; MYANMAR; NEPAL; TAIWAN. Cultivated in Japan. Habitat Mid-altitude forest. USDA Hardiness Zone 7. Conservation status Not evaluated. Illustration NT23, NT850, NT851. Cross-references S233 (as Euodia baberi), K55 (as E. ruticarpa). Taxonomic note By orthographic mutation, Roy Lancaster’s introduction L 594, under the name T. baberi, has become T. faberi on some labels.

Tetradium ruticarpum was apparently not successfully introduced by the earlier generation of plant collectors in China (Flanagan 1988), but recent expeditions have more than made up for the omission and it is now to be found in many collections across our area. It is frequently labelled T. baberi, although this combination seems never to have formally been made from Euodia baberi. The name T. baberi is particularly associated with Roy Lancaster’s collection (L 594) made on Emei Shan in 1980, which contends for priority with the introduction made by the SABE team from Hubei in the same year (SABE 1947), that has also been widely distributed. Given its broad range it is not surprising that collections of T. ruticarpum have come from diverse areas, including Taiwan (BSWJ 3541, for example, made in 1996). Tetradium ruticarpum grows rapidly and well, flowering when young. It enjoys the heat of the eastern United States, as evidenced by vigorous trees seen at the JC Raulston Arboretum (planted in 1996 and up to 8 m in 2006), but is also happy with cooler summer conditions. At Tregrehan it has shot up to nearly 10 m in eight years. It can be expected to make a broad-crowned rather than tall tree, however (T. Hudson, pers. comm. 2005). As with T. fraxinifolium, the young leaves are reddish brown but expand to a deep green, that admirably sets off the pale inflorescences. The red fruits are very handsome. Euodia velutina (NOW T. daniellii (Benn.) T.G. Hartley) B145, S233, K55

CUPRESSACEAE

THUJA

L.

Arborvitae Five species are recognised within Thuja, including two in North America (T. occidentalis and T. plicata), one in Japan (T. standishii) and one in Korea (T. koraiensis). The fifth species, T. sutchuenensis, of central China, was thought to be extinct but was recently rediscovered (Xiang et al. 2002). Thuja species are generally small evergreen trees or shrubs (though T. plicata can reach 50 m), with a broadly conical crown and billowing branches. The bark splits longitudinally, the ridges of the resulting fissures peeling off in long strips. Major branches are sparse, often pendent, sometimes rooting into the ground on contact; branchlets are dorsiventrally flattened and fan-shaped. The leaves are scale-like, keeled, appressed, decussate, partially decurrent and dimorphic; lateral pairs are falcate, partially overlapping facial pairs, which may have conspicu-

Plate 548. The fruits of Tetradium ruticarpum persist after the foliage has fallen, extending its season of interest into the winter. Image P. de Spoelberch.

852

Thuja

New Trees

ous glands, and the foliage is strongly scented. Male strobili are terminal, on lateral branchlets, with 6–10 microsporophylls; though technically solitary, the strobili are generally present on several adjacent branchlets, forming a cluster. Female cones are terminal and solitary, on lateral branchlets, and roughly ovoid, opening in the first year. Seed scales occur in two to six decussate pairs, of which only the middle two or three pairs are fertile; the seeds are lenticular, one or two per scale, with two narrow, lateral wings (Fu et al. 1999e). Thuja and its close relative Thujopsis Siebold & Zucc. are part of the Cupressoid clade, with affinities to Chamaecyparis (Gadek et al. 2000). Thuja is an important and familiar constituent of the garden and park, whether as one of the numerous selections of T. occidentalis suitable for the smaller site (or the closely related Platycladus orientalis (L.) Franco – still widely known as Thuja, although it differs in several important respects: see Morgan 1999), or as the magnificent huge tree that T. plicata can become, even in apparently poor, dry conditions. They have generally been comprehensively covered in the standard dendrological literature. An important recent introduction, however, is Thuja ‘Green Giant’ (Green Giant Arborvitae). This cultivar was first produced at the Hørsholm Arboretum in Denmark by crossing the North American Thuja plicata with the Japanese T. standishii. Material was sent to the US National Arboretum, where it proved to have exceptional horticultural qualities, and clones were distributed through the arboricultural community (US National Arboretum 1999). Thuja ‘Green Giant’ grows exceptionally fast (almost 1 m per year) and can reach 18 m, though it retains its tight, uniform, pyramidal habit. The bark becomes thick and fibrous with age. Major branches are densely packed, thick and horizontal or ascending; branchlets are rather coarse. The foliage is fragrant, dark green, lustrous above, pale below, and develops a bronze tint where exposed to winter sunshine. The cones are 1.0–1.5 cm long, green to brown, and persistent; the cone scales have a spine at the apex (US National Arboretum 1999, Advanced Tree Technology 2000–2008). Thuja ‘Green Giant’ has a number of advantages. It has no serious pests or diseases and can tolerate a variety of soil types and climates (USDA Hardiness Zones 5–8). Furthermore, its fast growth rate and uniform habit make it particularly suitable for hedging, and it is being promoted as an alternative to ×Cuprocyparis leylandii. It is being marketed in the United States under the name Green Rocket Hybrid Cedar (Advanced Tree Technology 2000–2008).

Thuja koraiensis Nakai

Korean Arborvitae

Shrub or small tree to 10 m (or more in cultivation), 0.8 m dbh. Bark smooth, reddish brown, becoming greyish brown, flaky and fissured in older trees. Crown conical or domed, rather open. Branchlets glaucous, then green. Leaves densely crowded, dimorphic; lateral pairs equal to or shorter than the facial pairs, facial pairs 0.2–1.5 cm long, obtuse; lower surface with a conspicuous covering of glaucous stomata bands; leaves releasing a strong smell of almonds when crushed. Male strobili subglobose, 0.2–0.3 cm long, with 6–10 microsporophylls. Seed cones dark brown, globose to ovoid, 0.7–1 × 0.6–0.8 cm. Seed scales in four pairs, valvate, only the middle two pairs fertile, the apical pair narrow and elongated. Seeds ellipsoid, 0.4 × 0.1 cm; wings two, equal, 1–1.5 cm wide, translucent. Fu et al. 1999e, Farjon 2005c. Distribution CHINA: Jilin; NORTH KOREA; SOUTH KOREA. Habitat Valleys and mountain ridges, between 700 and 1800 m asl. USDA Hardiness Zone 5. Conservation status Data Deficient (IUCN). Illustration Fu et al. 1999e; NT246, NT853. Cross-references B586, S512, K295.

Thuja koraiensis was discussed by Bean (1981b), but without provision of a technical description, allowing us to include this sometimes extremely attractive species in our account. The word ‘sometimes’ is used deliberately here, as it can be a rather undistinguished low shrub, in the wild as well as in cultivation, and such plants have

Section II. Species Accounts

Thuja

little horticultural merit. Examples of recently introduced material with this habit can be seen at the Morris Arboretum, collected (as cuttings) by the 1989 US National Arboretum expedition to Korea (NEKG 117), at 1300 m in the Taebaek Mountains. The field notes relate that it formed an ‘attractive ground cover’ below a mixed canopy. Other specimens make attractive columnar trees, resembling T. plicata but with sparser branching and much less vigour. All show some glaucescence on the undersides of the shoots, but this varies enormously in extent. The most familiar stock in cultivation, derived from Wilson 9244, shows a moderate degree of glaucescence on columnar trees (to c.15 m at Hergest Croft, planted in 1925). At Kew, a young tree planted near the Orangery has minimal glaucescence and is a somewhat dull olive-green. This was grown from seed collected in 1989 at 750 m in the Mount Soraksan Nature Reserve, South Korea by the Kirkham, Flanagan & Boyce Expedition to Korea (KFBX 56). At the other end of the scale are the wonderfully glaucous specimens growing in the Netherlands at the University of Utrecht Botanic Garden and Von Gimborn Arboretum, which deserve a cultivar name as the bluest of all Thuja. Commercially available plants in Europe, while glaucous, do not match the quality of these, but are apparently of tree form. American nurseries sell plants under the (illegitimate) names ‘Glauca’, ‘Glauca Nana’ and ‘Glauca Prostrata’, but it is not clear if these are different or merely nomenclatural variants for the same bushy clone. Thuja koraiensis seems to be amenable to a diversity of sites and conditions, but even the true tree-forming specimens are slow-growing compared with T. plicata. The foliage has a particularly pleasant aroma – ‘rich fruit cake with plenty of almonds’, according to Mitchell (1972). T. occidentalis L. B578, S510, K295 T. occidentalis f. gaspensis (NOW T. occidentalis L.) K298 T. occidentalis f. mastersii (NOW T. occidentalis L.) B580 T. orientalis (NOW Platycladus orientalis (L.) Franco) B581, S511, K305 T. orientalis f. flagelliformis (NOW Platycladus orientalis (L.) Franco) B582 T. plicata Donn ex D. Don B584, S511, K308 T. standishii (Gordon) Carrière B586, S512, K310 T. sutchuenensis Franch. K310

MALVACEAE (formerly TILIACEAE)

TILIA

L.

Lindens, Lime-trees, Basswoods Estimates of the number of Tilia species range from 20 to 40; the genus is currently under review by Donald Pigott, whose most recent publication puts the number of species at 22 (Pigott 2006). They are distributed across the temperate (and rarely subtropical) northern hemisphere. Tilia are large deciduous trees, with a noted ability to coppice, and sometimes with a tendency to produce shoots at the base. The leaves

853

Plate 549. Cultivated in the Netherlands, this exceptionally glaucous form of Thuja koraiensis is a treeforming clone. The species can be shrubby or arborescent. Image J. Grimshaw.

854

Tilia

New Trees

1 cm

B 1 cm

A C 1 cm

Section II. Species Accounts

are alternate, petiolate, often heart-shaped and asymmetric, subtended by caducous stipules. Inflorescences are cymose and very distinctive, as the peduncle is fused to the upper surface of an elongated bract. The flowers are hermaphrodite, ~1 cm diameter, 5-merous, white, cream or yellow, and strongly scented, the sepals boat-shaped, with hair-covered nectaries on the upper surface, the petals strap-shaped, with numerous stamens. The fruit is a small, woody, indehiscent, nut-like drupe, containing one to three seeds (Jones 1968, de Jong 1992b, Pigott 1997, Tang et al. 2007). The family Tiliaceae, together with Bombacaceae and Sterculiaceae, has been merged with the Malvaceae (APG 2003). The Common Linden Tilia ×europaea is well known as one of the most valuable and magnificent trees in cultivation, often the tallest and most distinctive in the landscape, and scenting the air with delicious fragrance. It is unfortunate that it has developed a poor image derived from the problem of honeydew falling from aphids onto cars parked below. This negative connotation has also, it seems, passed unfairly into association with the rest of the genus, at least in the eyes of the general public. Fortunately, Tilia are commonly planted in arboreta, and much valued by dendrologists. In 2005 the Belgian Dendrology Society held a Tilia Study Day at Arboretum Wespelaar, which resulted in a trilingual series of articles in their yearbook (Belgische Dendrologie Belge 2005 2006), including an article that is the foundation for the present account (Grimshaw 2006). The yearbook also includes many illustrations of the range of species and cultivars in the genus. Donald Pigott’s forthcoming monograph Lime-trees and Basswoods: A Monograph of the Genus Tilia (in prep.), based on decades of study of both wild and garden material, is keenly awaited, and will clarify what has become a taxonomically muddy genus. The taxonomy of the American lindens is particularly controversial, between one and four species being recognised. Hardin (1990) took the step of combining all American and Mexican species into T. americana, with four varieties. Pigott’s as yet unpublished classification, using rather different criteria, will take a different view but unfortunately has not been brought out in time for us to adopt it here. In the meantime the nomenclature we use follows Jones (1968), as in Pigott’s paper on Tilia chromosomes (Pigott 2002) and the latter’s account for the European Garden Flora (Pigott 1997). The centre of Tilia distribution is without doubt eastern Asia, throughout China and from Manchuria to South Korea and Japan. Within this area 16 taxa are currently recognised by Pigott, where the Flora of China treatment recognises 19 species and numerous varieties. It is clear that most species of Tilia show considerable natural variation – an observation that is often obscured by the limited range of material in general cultivation, often propagated from a single clone. Many Asian lindens were introduced by plant collectors in the late-nineteenth and early-twentieth centuries, and were described by Bean (1981b), although often already rare by that time. In some cases a few individuals or a limited number of clones from these collections have persisted to the present day. In many other cases more material has been introduced, in the current wave of plant exploration in China, and several once-rare species such as T. tuan are now much more regularly planted. No Tilia species feature on the IUCN Red List 2007, but this should not encourage complacency. As Pigott (2006) has pointed out, the survival of T. endochrysea is threatened by forest clearance, and this must apply equally to species such as T. nobilis whose range seems to be rather restricted.

Tilia

855

Plate 550. The neat leaves of Tilia amurensis subsp. taquetii are smaller and more pointed than those of subsp. amurensis. Image J. Grimshaw.

Figure 92 (opposite). Tilia nobilis: habit with flowers (A); branchlet with fruits (B); detail of underside of leaf (C).

856

Tilia

New Trees

Tilia are very promiscuous, and garden-collected seed is likely to be of hybrid origin. In the absence of wild-collected seed, therefore, growers must resort to vegetative propagation, either by grafting or by layering – though it would be useful if a range of clones could be propagated, to maintain diversity. Many hybrids have been named, and some are very fine ornaments to the arboretum, including ‘Alan Mitchell’, T. mongolica × T. tomentosa (Muir 1995–1996); and ‘Harold Hillier’, ‘T. insularis’ (probably T. japonica ‘Ernest Wilson’) × T. mongolica. There is considerable potential in the genus for the enterprising breeder to create some very beautiful hybrids, combining good foliage and floral characters. A number of selections of the common and important landscaping species T. cordata, T. platyphyllos and T. tomentosa have been made in recent years, especially in North America and continental Europe, and should be considered when planting these species. For further information on these and other recent cultivars see Dirr (1998), Jacobson (1996) and van den Berk (2002). In general Tilia are very tolerant of a wide range of conditions, but some do prefer a hotter summer than that usually experienced in the British Isles, resulting in better growth in continental Europe and North America. The genus is well represented in most arboreta, and in Britain there are National Plant Collections at Peasmarsh Place, East Sussex and at Thorp Perrow, North Yorkshire.

T. americana L. B594, S513, K394 T. americana var. vestita (Döll) V. Engl. B594

Tilia amurensis Rupr. Syn. T. insularis Nakai Tree to 25 m, 1 m dbh. Bark grey. Branchlets slender, initially with tangled white stellate indumentum, later glabrous. Leaves 7–8 × 6–7 cm, circular, upper surface dull green, glabrous, lower surface pale green, initially with white stellate indumentum, which erodes leaving tufts of brown hair in the vein axils, four to five secondary veins on each side of the midvein, base cordate, margins serrate (teeth uneven, often blunt), apex acute; petiole slender, glabrous, 2–3.5 cm long. Inflorescences 3–5 cm long, with 15–25 flowers; bracts 3–7 × 0.5–1 cm, elliptic, glabrous, usually stalked. Sepals broad-lanceolate, 0.5–0.6 cm long; petals 0.6–0.7 cm long; stamens ~20; ovary tomentose. Fruit ellipsoid to obovoid, 0.5–0.8 cm long, pointed, covered in reddish brown indumentum. Flowering July (China). Pigott 1997, Tang et al. 2007. Distribution CHINA: Heilongjiang, Jilin, Liaoning; NORTH KOREA; RUSSIAN FEDERATION: northeast Siberia; SOUTH KOREA. Habitat Mixed coniferous forests, between 1300 and 1400 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006; NT856. Cross-references K395; also B600, S514, K397 (all as T. insularis).

Plate 551. In western Europe, new growth of Tilia amurensis from northern provenances is apt to be frosted, but material from South Korea breaks bud later. Image K. Camelbeke.

Tilia amurensis is a widespread species in far-eastern Asia, ranging from Siberian Manchuria to Korea, principally as subsp. amurensis. In cultivation the nominate subspecies has a bad reputation for emerging early and being badly frosted, leading to the view that there is no good reason to plant it (de Spoelberch 2006). Provenance may however play a part in this, as at Kew a specimen collected in Sakhalin by the Expedition to Sakhalin and Ussuri (ESUS 127) of 1994 is struggling, apparently for this reason, whereas others from Korea are doing much better (BECX 451, for example, collected in Gangwon-do in 1982), as they come into leaf later. Tilia amurensis subsp. amurensis has in fact been in cultivation for over 100 years, a tree at the Arnold Arboretum, received from Saint

Section II. Species Accounts

Petersburg, having been planted in 1900 (Pigott 2002), and there have been regular reintroductions as well – but it is not commonly grown, at least under this name. A particularly hairy form from Jilin has been recognised as T. amurensis var. araneosa C. Wang & S.D. Zhao, and is maintained as distinct by Tang et al. (2007). The population of T. amurensis on the Korean island of Ullungdo has been named T. insularis (see Bean and Krüssmann: B600, S514, K397), on the basis of very minor characters, but fits within the range of T. amurensis (Pigott 2000). In European horticulture and literature the name T. insularis is apparently almost exclusively attached to an exceptional clone producing very abundant large inflorescences, the parent tree of which grows at Kew (accession number 29-76801). This derives from a collection made by Ernest Wilson in Japan in 1919 and sent to the Arnold Arboretum, from where the Kew tree was received in 1924. Pigott (2008) has demonstrated, however, that this specimen is in fact a representative of T. japonica, having five staminodes (absent in T. amurensis). Wilson did collect Tilia on Ullung-do in 1919, and the confusion seems to have arisen when his gatherings there and in Japan were conflated at the Arnold Arboretum. The Kew tree has been extensively propagated and the clone is found in collections across Europe as a grafted tree, always labelled T. insularis. Since it is now considered to be a representative of T. japonica, a distinctive moniker was desirable, and ‘Ernest Wilson’ has been applied as a cultivar name (Grimshaw 2008).

Tilia amurensis subsp. taquetii (C.K. Schneid.) Liou & Li Syn. T. koreana Nakai This subspecies has smaller leaves (4–5 × 3.5–4 cm) than in typical T. amurensis; the leaves have a truncate or emarginate base and an acuminate apex, giving a birch-like appearance, and reddish stellate hairs on the stems (as opposed to white stellate hairs in subsp. amurensis). Pigott 1997, Tang et al. 2007. Distribution CHINA: Heilongjiang, Jilin, Liaoning; RUSSIAN FEDERATION; SOUTH KOREA. Habitat Forests. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration NT855.

The smaller, daintier-leaved subsp. taquetii is still rare in cultivation but deserves to be more widely cultivated. A vigorous young tree seen at Harry Hay’s garden in Surrey was 3 m tall in 2005, grown from seed collected on Jirisan in Jeollanam-do, South Korea in 1994 and distributed by the Chollipo Arboretum. Elsewhere in the garden is another specimen from the same source in 1996, but originating from the Taebaek Mountains (H. Hay, pers. comm. 2008).

Tilia caroliniana Mill. Tilia caroliniana subsp. caroliniana, from the southeastern United States, has never been a great success in British gardens, although repeated introductions have kept it in cultivation. It seems to need hot humid summers to thrive, and can be damaged by frost if the wood is insufficiently ripened (D. Pigott, pers. comm. 2008). It was described by Bean (B595). Relationships and variation within the T. caroliniana complex will be fully discussed by Pigott (in prep.), which should be consulted when available.

Tilia

857

Plate 552. The famously floriferous Tilia at Kew, long known as T. insularis, has been re-identified as Tilia japonica and been given the cultivar name ‘Ernest Wilson’. Image J. Grimshaw.

858

Tilia

New Trees

Tilia caroliniana subsp. floridana (Small) A.E. Murray This generally poorly understood and rather variable subspecies has leaves with rounded lobes at the base, though the lobes are unequal (lobes not rounded in subsp. caroliniana). The leaf undersides are usually covered with pale, stellate hairs (brown hairs in subsp. caroliniana), but may be glabrous. The inflorescences are small, with the cymes usually not exceeding the bracts. The backs of the sepals are sparsely covered with grey, stellate indumentum. West & Arnold 1956. Distribution USA: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Texas, Virginia. Habitat Unknown. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006. Cross-reference K396.

Tilia caroliniana subsp. floridana has a limited presence in British cultivation from collections made by Donald and Sheila Pigott in 2000, close to the type locality in Jackson Co. in the Florida Panhandle; Donald Pigott (pers. comm. 2007) does not know of any other introductions to the United Kingdom. A specimen growing under this name in the National Botanic Garden of Belgium at Meise was obtained from Pavia Boomkwekerij, Deerlijk, Belgium, where material had in turn been received from the Arnold Arboretum (De Meyere 2006; National Botanic Garden of Belgium accessions list). It is more widely grown in the eastern United States, and trees so-labelled were seen at the Arnold Arboretum and the Morton Arboretum in 2006 – the 15 m tree at the Morton containing the nest of a Cedar Waxwing (Bombycilla cedrorum) at the time. It presumably requires a warm, moist position in cultivation. Neither it nor subsp. caroliniana are discussed in any detail by the standard American authors (Dirr 1998, Jacobson 1996, Sternberg 2004).

Tilia chinensis Maxim. Syn. T. laetevirens Rehder & E.H. Wilson Tree to 30 m. Bark smooth, grey. Buds large. Branchlets glabrous or variably pubescent. Leaves (5–)7–13 × (4.5–)6–9 cm, broadly elliptic or orbicular to ovate-orbicular, upper surface glabrous, lower surface with dense stellate indumentum, seven to nine secondary veins on each side of the midvein, base usually oblique, truncate or cordate or rounded, margins serrate, apex more or less acuminate; petiole 3–8 cm long, usually sparsely pilose. Inflorescences with one to three flowers; bracts 4–12 × 1–2 cm, glabrous above, hairy below, sessile or with stalk to 0.5 cm. Sepals narrowly ovate, 0.6–0.7 cm long, outer surface stellate-pubescent, inner surface stellate-pubescent or glabrous in the centre; petals 0.8–0.9 cm long, glabrous; stamens numerous; staminodes five, smaller than petals; ovary pubescent, five-angled. Fruit globose, 1–1.4 × 0.8–0.9 cm, five-angled, tomentose. Flowering June to July, fruiting August to October (China). Forest 1983, Tang et al. 2007. Distribution CHINA: Gansu, Henan, Hubei, Shaanxi, Sichuan, Xizang, Yunnan. Habitat Forests between 1800 and 3100(–3900) m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006. Cross-references B601 (as T. intonsa), S514, K395.

Tilia chinensis is an extremely variable species from central and western China, where it is a big tree, forming a rounded, spreading crown. The leaves are dull green above, the underside covered in brown hair with the green showing through. The extent of this indumentum is variable and is not a significant taxonomic character, although the Flora of China treatment uses it to distinguish infraspecific taxa. Within T. chinensis Flora of China maintains var. investita (V. Engl.) Rehder, with fewer hairs on the leaf underside, though with tufts of hair in the leaf axils, and var. intonsa (E.H. Wilson) Y.C. Hsu & R. Zhuge (see Bean: B601), with longer, dense tomentum on the twigs (said to be glabrous in var. chinensis); but it is likely that these are merely extremes of a continuum. Tilia chinensis is infrequent in arboreta – either persistent from early introductions, as in the case of the British champion at Westonbirt (15 m, 32 cm dbh) (Johnson 2003), and sometimes concealed under names such as T. intonsa, or from more recent expeditions. Young trees from SICH 1125, collected at 2900 m in Muli

Section II. Species Accounts

Tilia

859

Co. in 1992, are doing well at Kew and have already flowered. It has also been collected in Yunnan, by the Pigotts and by expeditions from Edinburgh. Dirk Benoit of Pavia Boomkwekerij has found it difficult to propagate, as it will not ‘take’ on stocks of either T. cordata or T. platyphyllos (Benoit 2006) – which probably explains why the trees labelled T. intonsa at Colesbourne mentioned by Bean (1981b) and Clarke (1988) are both T. platyphyllos, the failure of the scion having passed unnoticed.

Tilia chingiana Hu & W.C. Cheng Syn. T. breviradiata (Rehder) Hu & W.C. Cheng Tree to 15 m. Bark smooth, grey. Branchlets glabrous or minutely pubescent initially. Leaves 5–10 × 4–9 cm, broadly ovate, upper surface glabrous, lower surface with patchy stellate indumentum, eroding to leave only a few hairs in the vein axils, six to seven secondary veins on each side of the midvein, base obliquely truncate or cordate, margins serrate, apex acuminate or acute; petiole 2.5–4 cm long, sparsely pubescent to glabrous. Inflorescences 5–8 cm long, with 4–10 flowers; bracts 7–9 cm long, narrowly oblanceolate, pubescent on both surfaces, usually stalked. Sepals lanceolate, ~0.5 cm long, outer surface pubescent; petals ~0.7 cm long; stamens numerous; staminodes five, petaloid, smaller than petals; ovary pubescent. Fruit globose, ~0.9 cm long, tomentose. Flowering June to July (China). Forest 1983, Tang et al. 2007. Distribution CHINA: Anhui, Jiangsu, Jiangxi, Zhejiang. Habitat Forests. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration Forest 1983, Belgische Dendrologie Belge 2005 2006; NT859. Cross-references S516, K395.

The eastern Chinese species Tilia chingiana is not well known in gardens, although seed collected in the Lushan, Jiangxi was received from China in 1938 by Lord Rosse. Three specimens grown from this seed persist at Birr Castle, Co. Offaly, the largest of which had reached 11.5 m by 2002 (Johnson 2003). Trees derived from this introduction are found elsewhere as well (a specimen at the Hillier Gardens, for example, was measured at 12.5 m in 2008) and are the source of material recently distributed commercially in the United Kingdom and Europe (D. Pigott, pers. comm. 2005). The species has also been reintroduced by Donald and Sheila Pigott, from Guling, also in the Lushan, in 1996. The leaves are ovate, with hairs only in the vein axils of the lower surface, distinguishing it from several other Chinese species in which the underside of the leaf is hairy all over. The leaves can sometimes achieve huge size on vigorous young shoots. It seems to be hardy and easy to grow, and will flower in late July and early August, thus continuing the season into later summer. T. cordata Mill. B596, S513, K395

Tilia dasystyla Loud. Tilia dasystyla subsp. dasystyla Tree 20–25 m. Bark grey, becoming rough and ridged. Branchlets green, glabrous or with a few stellate hairs. Leaves 4.8–8.2 × 4.7–8 cm, circular, upper surface dark green, glossy, lower surface pale green, dull, clusters of light brown hair in vein axils, approx. eight secondary veins on each side of the midvein, base cordate, margins serrate (teeth small, acute), apex acute; petiole glabrous, 2.5–4 cm long. Inflorescences with two to four flowers; bracts 5–7 × 1–1.5 cm, yellowish green, elliptic, glabrous, waxy, stalked, characteristically stiff and

Plate 553. Tilia chingiana in Harry Hay’s garden in Surrey. New growth on young specimens of Tilia can be very vigorous, producing abnormally large leaves – adding to the identification problems in this challenging genus. Image J. Grimshaw.

860

Tilia

New Trees

B 1 cm

A 1 cm

C

D

recurved. Flowers 1.2–1.5 cm diameter. Fruit spherical, obovate or spindle-shaped, to 1 cm diameter, densely tomentose. Pigott 1997, Pigott & Francis 1999. Distribution UKRAINE: Crimea. Habitat Cliffs and scree slopes to wooded hills, between 120 and 860 m asl. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006; NT860. Cross-references B609, K395 (in part).

Figure 93 (above). Tilia dasystyla. Subsp. dasystyla: leaf (A); flower (B). Subsp. caucasica: flower (C); leaf (D).

Tilia dasystyla subsp. dasystyla occurs only in the Crimea (and possibly Turkey), where it can grow to 20–25 m (Pigott & Francis 1999). It has small, circular, rather thick leaves that are a shining dark green and are held poised above the stems. The flower bracts are a shining, rather waxy, yellow-green. Despite a long history in the literature,

Section II. Species Accounts

Tilia

861

and frequent nomenclatural presence, it is actually quite rare in horticulture. Many earlier examples are apparently a single clone, with unusually large leaves that have long-tipped marginal teeth. Material obtained from botanic gardens should be checked for signs of hybridity, but the 10 m specimen at the National Botanic Garden of Belgium at Meise, grown from seed from Yalta Botanic Garden, appears to be correct. Verified material has recently been reintroduced from several localities in the Crimea by Donald and Sheila Pigott, and is in cultivation in public and private gardens in the United Kingdom – for example at Kew, where it is growing steadily and already flowering.

Tilia dasystyla subsp. caucasica (V. Engl.) Pigott Syn. T. begoniifolia Steven Subsp. caucasica has larger leaves (6.6–12.6 × 5.2–10.6 cm) than in typical T. dasystyla, and they are non-glossy, with more pronounced marginal teeth. The floral bracts are also larger (7.6–14 × 1–2.6 cm), pale green (not yellowish green), not waxy, largely flat, though often with undulate margins. Pigott 1997, Pigott & Francis 1999. Distribution AZERBAIJAN; GEORGIA; IRAN. Habitat Beech forest. USDA Hardiness Zone 6–7. Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006; NT860, NT861. Cross-references B609, K395 (in part).

As with subsp. dasystyla, subsp. caucasica has been in cultivation since the nineteenth century, but confusion over nomenclature makes it difficult to track older examples of either accurately. Subsp. caucasica is still rare in horticulture, although it was reintroduced from Iran in 1972 by Roy Lancaster and Ann Ala (A&L 16), and later from Georgia by the Pigotts. The larger leaves are not glossy and droop from the twigs – the former name T. begoniifolia was very apt. Specimens from A&L 16 are growing well at Kew and at the Hillier Gardens, making straight trunks with wide-spreading branches and giving promise of forming very large trees.

Plate 554. Tilia dasystyla subsp. caucasica A&L 16, from the Caspian Forest in Iran, seen here at Kew. Image J. Grimshaw.

Tilia endochrysea Hand.-Mazz. Tree to 20 m. Bark grey with smooth ridges, separated by darker grey fissures. Branchlets bright green, glabrous or minutely pubescent. Leaves in two ranks, 7–14 × 5–11 cm, broadly to narrowly ovate to almost triangular, upper surface dark, shiny green, glabrous, lower surface pale green or glaucous, glabrous or covered with rusty stellate hairs, five to six secondary veins on each side of the midvein, base oblique-cordate or truncate, margins entire to sparsely dentate, often three-lobed near the apex, apex rounded or obtuse to acute; immature leaves crimson with pale green stipules; petiole glabrous, 2.5–6 cm long. Inflorescences 9–16 cm long, with 8–32 flowers, strongly pubescent; bracts 6–13 × 1.5–3 cm, oblong, glabrous above, glabrous to densely tomentose below, stalked. Sepals long-ovate, 0.6–0.8 cm long, outer surface tomentose, inner surface filled with long hairs; petals strap-shaped, 1–1.2 cm long; stamens ~40; staminodes five, petaloid, slightly shorter than petals; ovary white-tomentose. Fruit globose, initially fleshy, splitting via five valves. Flowering July to August (China). De Jong 1993, Pigott 2006, Tang et al. 2007. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Hunan, Jiangxi, Zhejiang. Habitat Mixed evergreen and deciduous broadleaved forest, in valleys with well-drained soils. Typical climate of mild winters and warm, wet summers. USDA Hardiness Zone 8 (?). Conservation status Not evaluated. Illustration Belgische Dendrologie Belge 2005 2006, Pigott 2006; NT25, NT861.

Tilia endochrysea is a primitive species in the genus, with the peduncle joined to the bract only at its base, and a dehiscent fruit. It is extremely rare in cultivation, having apparently been introduced only once, and represented by a single clone. The few trees known (in private collections, at Kew, and in the Cambridge University Botanic

Plate 555. The mature foliage of Tilia endochrysea is strikingly bicoloured (see also the new growth, in Plate 41, p. 25). Image J. Grimshaw.

862

Tilia

New Trees

Garden) are derived from scion wood collected by Donald and Sheila Pigott in the Wuzhi Shan, Guangdong in 1993 (Pigott 2006). The clone has striking foliage features, the leaves opening a dark crimson and becoming dark green above with dense grey-white stellate hairs below, but variability was noted in the wild population. Seed from the same area sadly failed to germinate. Young plants have so far proved hardy in British conditions, usually breaking bud late enough to avoid significant frost damage, but in northwestern England it has been defoliated by strong wind (Pigott 2006).

T. ×euchlora K. Koch B596, S513, K395 T. ×europaea L. B597, S514, K395 T. ×flaccida Host K396 T. ×flavescens Döll B596, K396 T. henryana Szysz. B599, S514, K397 T. heterophylla Vent. B600, K397 T. heterophylla var. michauxii (NOW T. heterophylla Vent.) K397 T. insularis (NOW T. amurensis Rupr., NT856; but trees in cultivation across Europe are usually T. japonica ‘Ernest Wilson’, NT857) B600, S514, K397 T. intonsa (NOW T. chinensis var. intonsa (E.H. Wilson) Y.C. Hsu & R. Zhuge) B601, S514, K397 T. japonica Simonk. B601, S524, K397 T. ×juranyana Simonk. K397 T. kiusiana Makino & Shiras. B602, S515, K397 T. mandschurica Maxim. B610, K397 T. maximowicziana Shiras. B602, S515, K397 T. maximowicziana var. yesoana (Nakai) Tatewaki S515 Plate 556. Tilia mexicana is proving to be surprisingly successful in British gardens, from an collection made in Nuevo León in 1991 by the Compton, d’Arcy and Rix team. Image J. Grimshaw.

Tilia mexicana Schlecht. Small to medium-sized tree resembling T. caroliniana, distinguished from it by Hardin (1990) only on account of its disjunct distribution (200 km separating populations of caroliniana in Texas and mexicana in Coahuila) – somewhat supported by the villose pubescence of its twigs, peduncles and pedicels, but the hair type is very variable in the Mexican populations. Leaves unequal at base, with reddish brown hairs. Cymes large, usually exceeding the length of the accompanying bracts; dense covering of stellate hairs on outsides of sepals. Hardin 1990. Distribution MEXICO: Chihuahua, Coahuila, Durango, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nuevo León, Oaxaca, Puebla, San Luis Potosí, Sinaloa, Tamaulipas, Veracruz. Habitat Moist, montane forest, between 770 and 2600 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT862.

At present the name Tilia mexicana stands for all Mexican lindens, whose range of variation has yet to be fully explored and evaluated (D. Pigott, pers. comm. 2008). From the limited sample available in cultivation, plants seem to be surprisingly hardy. Seed was collected by the British team of James Compton, John d’Arcy and Martyn Rix in the Sierra Madre Oriental near Saltillo, Nuevo León in 1991. This has given rise to several specimens in British gardens that are growing steadily, including on heavy clay in James Compton’s garden in Wiltshire (J. Compton, pers. comm. 2008), and it is

Section II. Species Accounts

Tilia

currently commercially available in the United Kingdom from the same provenance. It has also been collected in three localities by Donald and Sheila Pigott. The elongated leaves with their reddish hairs are very attractive. T. miqueliana Maxim. B603, S515, K397 T. ×moltkei C.K. Schneid. B603, S515, K398 T. mongolica Maxim. B604, S515, K398

T. monticola (NOW T. heterophylla Vent.) K398 T. neglecta (NOW T. americana L.) K398

Tilia nobilis Rehder & E.H. Wilson Tree 4–12 m. Branchlets glabrous. Leaves (5.5–)10–14(–17) × (5–)7–8(–13) cm, nearly circular, upper surface glabrous, lower surface glabrous or with tufts of hair in vein axils, six to eight secondary veins on each side of the midvein, base oblique-cordate, truncate or rounded, margins serrate, apex acuminate or short-caudate; petiole glabrous, 4–10 cm long. Inflorescences as long, or longer than accompanying bract, with three to five flowers; bracts 8–16 × 1.5–2.5 cm, oblanceolate to oblong, largely glabrous, sessile or short-stalked. Sepals glabrous or sparsely pilose outside, margins densely hairy; petals oblanceolate, glabrous; stamens 30–45; staminodes spathulate; ovary tomentose. Fruit nearly globose, ~1 cm long, yellow-tomentose, five-angled. Flowering June to July, fruiting August to October (China). De Jong 1993, Tang et al. 2007. Distribution CHINA: Sichuan, Yunnan. Habitat Forests between 1800 and 2500 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT854. Cross-references S516, K398.

As recorded in the rather full account given by Clarke (1988), Tilia nobilis is best known to western dendrologists from Emei Shan, Sichuan. Roy Lancaster (1989) describes a 12 m tree growing by a path, from which he (L 521) and Keith Rushforth (KR 226) took scion wood. From these collections it has become well established in UK gardens, although so far in very small numbers. It seems to grow slowly but steadily, and has big, rounded leaves with prominent veins and very short stellate hairs. The inflorescence bract is very large, and proportionally the flowers appear quite small, although they are followed by massive fruit. Interestingly, it is an octoploid, 2n = 328 (Pigott 2002). It is to be hoped that this intriguing tree will go on to develop to full potential in cultivation and become more widely available in the nursery trade. T. oliveri Szysz. B604, S516 T. ×orbicularis (Carrière) Jouin B606, S517, K398 T. paucicostata Maxim. B605 T. ‘Petiolaris’ (NOW T. tomentosa ‘Petiolaris’) B605, S516, K398 T. platyphyllos Scop. B607, S517, K398 T. tomentosa Moench B609, S517, K399

Tilia tuan Szysz. This extremely variable Chinese linden has been covered by the standard dendrological authorities (see Bean and Krüssmann: B610, S518, K399), but its morphological diversity has led to a proliferation of names for insignificant variants. The species is recognisable by its strongly asymmetric leaves, dull dark green or greyish green above, grey-hairy below, with tufts of hairs in the vein axils. The most frequently encountered named variant is T. tuan var. chenmoui (W.C. Cheng) Y. Tang (often found as T. chenmoui W.C. Cheng), which was introduced by Donald and Sheila Pigott from its type locality in the Jizu Shan, Yunnan in 1993. Seedlings were planted at the

863

864

Tilia

New Trees

Cambridge University Botanic Garden and distributed to other collections (D. Pigott, pers. comm. 2005). It is maintained at varietal rank by Flora of China, but Donald Pigott views it as indistinguishable within the variation of the species. It is said to differ from var. tuan in having strongly toothed leaves (vs. entire or few-toothed leaves in var. tuan) and few-flowered inflorescences (three to six flowers), with stalked bracts that are 12–16 cm long (Tang et al. 2007). Tilia tuan var. chinensis (Szysz.) Rehder & E.H. Wilson is also recognised by Tang et al. (2007), as sharing dentate margins with var. chenmoui but differing in its more numerous flowers (16–22 per inflorescence), and shorter (8–12 cm) sessile bracts. Pigott (1997) distinguishes it by its hairy twigs and buds. Var. chinensis was said to have been collected by Ernest Wilson, but Bean (1981b: B610) was unable to report on authentic specimens in the United Kingdom, and neither can we. T. ×varsaviensis Kobendza K399

TAXACEAE

TORREYA

Arn.

Syn. Tumion Raf.

Nutmeg-yews, Stinking Cedars, Torreyas The five species of Torreya occur in China (T. grandis, T. jackii), Japan (T. nucifera) and the United States (T. californica, T. taxifolia). They are dioecious (rarely monoecious) evergreen trees and shrubs with distinctive large plum-like ‘fruits’. The branches are in whorls; branchlets nearly opposite or whorled. Leaf arrangement is decussate or opposite, two-ranked; the leaves are green, leathery, linear to lanceolate, the apex sharply acuminate, the base twisted, the lower surface with two distinct whitish bands of stomata. Male (pollen) cones are axillary, solitary, short-pedunculate, with four to eight whorls of four microsporophylls. The seed-bearing structures (cf. cones) are axillary and sessile, each bearing two pairs of decussate bracts. There are two ovules per structure, though one usually aborts. The surviving ovule develops into a drupe-like fruit, with the woody seed completely enclosed within a fleshy aril; the seed matures in the autumn of the second year (Hils 1993, Fu et al. 1999d). Torreya is an interesting and not unattractive genus whose members can form tall, single-stemmed trees, but are often seen as somewhat scruffy bushes of no particular merit. The large, green plum-shaped fruits are a surprising feature in autumn. The most widely tolerant seems to be T. californica, which is growable across large areas of maritime northern Europe and the Pacific Northwest. It does well throughout much of southern Britain, flourishing and even self-sowing in the cool dry limestone conditions of Colesbourne, Gloucestershire. The only other species that is regularly collected and relatively frequently planted is T. nucifera, which seems to require a hot and preferably humid summer to perform at its best – for example, in the eastern United States – although there are a few reasonable specimens in Europe. It is said to require an acidic soil (Huxley et al. 1992). In addition to the taxa described below,

Section II. Species Accounts

Torreya

865

T. jackii, from northern Fujian, northeastern Jiangxi and southern Zhejiang, has been in cultivation in the United States since 1994, when cuttings were collected from a tree in Nanjing Botanic Garden by a NACPEC expedition to Wudang Shan. It is grown by the Arnold Arboretum and the US National Arboretum, with material under glass and (at the latter institution at least) outdoors (R. Olsen, pers. comm. 2008). The Chinese taxa are surprisingly poorly known in western horticulture, and more material is needed. Propagation of Torreya is from seed, which can take two winters to germinate, or from cuttings as for Taxus, but plants from cuttings may not form monopodial trees. T. californica Torr. B612, S518, K312 T. fargesii (NOW T. grandis var. fargesii (Franch.) Silba, NT866) K312

Torreya grandis Fortune ex Lindl. Torreya grandis was described by Bean (B612, S518) and Krüssmann (K312). Farjon (2001) recognised four varieties within T. grandis – var. grandis, var. fargesii (Franch.) Silba, var. jiulongshanensis Z.Y. Li, Z.C. Tang & N. Kang and var. yunnanensis (W.C. Cheng & L.K. Fu) Silba – though only var. grandis appears to be established in cultivation. Var. jiulongshanensis and var. yunnanensis are both narrow-range endemics. Flora of China (Fu et al. 1999d) uses a different taxonomy, recognising two species (T. grandis and T. fargesii), each with two varieties.

Torreya grandis var. grandis Syn. T. grandis var. dielsii Hu (var. ‘dickii’ of Krüssmann 1985b), T. grandis var. merrillii Hu, T. grandis var. sargentii Hu Shrub or tree to 25 m, 0.5(–2) m dbh. Bark yellowish grey or greyish brown with longitudinal fissures. Leafy branchlets oblong to obovate in outline, 4–13 × 2.5–7.5 cm, branchlet itself glabrous, green, becoming yellowish green, light brownish yellow or pale brown with time. Leaves (0.7–)1.1–2.5(–4.5) × 0.2–0.4 cm, linear to lanceolate, usually straight, upper surface glossy green, lower surface with prominent midrib and stomatal bands, apex cuspidate, margins flat or very slightly revolute; petiole absent or to 0.1 cm. Male cones columnar to ovoid, 0.5–0.8 cm long. Seed ellipsoid to ovoid, 2–4.5 × 1.2–2.5 cm; aril pale green to purplish brown with white powdery bloom when ripe. Fu et al. 1999d. Distribution CHINA: south Anhui, north Fujian, northeast Guizhou, west Hunan, south Jiangsu, north Jiangxi, Zhejiang. Habitat Forest between 200 and 1400 m asl. USDA Hardiness Zone 7–8. Conservation status Lower Risk. Illustration Van Gelderen & van Hoey Smith 1996, Fu et al. 1999d; NT865.

Bean (1981b) recorded that Torreya grandis had been introduced by Robert Fortune in 1855, but that only two specimens were known. The one at Borde Hill, West Sussex, recorded by Bean as being 8.8 m in 1968, had shrunk to 6 m when measured in 1995 by Owen Johnson (TROBI), and its record is marked ‘doubtful’. The other specimen, at Kew, was 7.6 m in 1970 and only 8 m in 2001 when re-measured by Johnson. There have been several more recent introductions, however, and some of the plants seen are looking promising. At Arboretum Trompenburg there is a vigorous young tree forming a shapely specimen of about 6 m tall, that was fully clad in foliage to the ground when observed in 2005. This was obtained from M. Decalut of Arboretum Waasland, Belgium in 1994. In several European arboreta there are plants grown from

Plate 557. Torreya grandis var. grandis, seen here thriving at Arboretum Trompenburg. Now available in commerce, it is likely to be grown more widely, in arboreta accross our area. Image J.R.P. van Hoey Smith.

866

Torreya

New Trees

wild-origin seed since 1995, by the German nursery Allerweltsgrün Niehues in Köln, from where it is still available. Collections have also been made by North American expeditions, from which young plants are established in the Arnold Arboretum and elsewhere. At the Morris Arboretum specimens obtained from the Arnold in 1994 are doing well, having reached 1.9 m by 2006, with good straight stems and leaders. The species is currently commercially available from several sources in North America, where it is recommended as being tolerant of heat and shade (Camellia Forest Nursery 2007–2008) as well as preferring moist alkaline soil (Piroche Plants 2000–2005). The seeds of T. grandis are used for their oil and in medicinal preparations, both in China and the West – including, for example, a herbal remedy recommended for cleansing the colon and expelling ‘unwanted guests’ (Blessed Herbs 2004–2008); the less squeamish might use the term ‘vermifuge’ …

Torreya grandis var. fargesii (Franch.) Silba Syn. T. fargesii Franch. Var. fargesii differs from var. grandis in having two longitudinal grooves on the upper leaf surface (absent in var. grandis). Also, in var. fargesii the midvein on the lower surface is narrower than the marginal bands (the section of leaf outside the stomatal bands), while in var. grandis the midvein and marginal bands are of approximately similar size. Fu et al. 1999d. Distribution CHINA: possibly south Anhui, west Hubei, northwest Hunan, Jiangxi, south Shaanxi, Sichuan, northwest Yunnan. Habitat Coniferous, mixed and broadleaved forests between 1000 and 3400 m asl. USDA Hardiness Zone 7–8. Conservation status Vulnerable. Illustration Fu et al. 1999d.

Torreya grandis var. fargesii is curiously unknown in cultivation. Arrowhead Alpines (2000–2008) of Fowlerville, Mississippi sell a plant under the name T. yunnanensis ‘Rock’, but mention that it probably belongs to T. grandis var. fargesii. The implication on their website is that it originated as a collection made by Joseph Rock. T. grandis var. ‘dickii’ (NOW T. grandis Fortune ex Lindl. var. grandis, NT865) K312 T. grandis var. merrillii (NOW T. grandis Fortune ex Lindl. var. grandis, NT865) K312 T. grandis var. sargentii (NOW T. grandis Fortune ex Lindl. var. grandis, NT865) K312 T. jackii Chun K313

Torreya taxifolia Arn.

T. nucifera (L.) Siebold & Zucc. B612, S518, K313 T. nucifera var. igaensis (NOW T. nucifera (L.) Siebold & Zucc.) K313 T. nucifera var. macrosperma (NOW T. nucifera (L.) Siebold & Zucc.) K313 T. nucifera var. radicans (NOW T. nucifera (L.) Siebold & Zucc.) K313

Florida Torreya, Stinking Cedar

Tree to 13(–18) m, 0.8 m dbh. Branchlets spreading to pendulous, yellowish green, yellowish brown or grey. Leaves 1.5–3.5 × 0.3 cm, linear to lanceolate, lower surface with two shallow, greyish bands of stomata; leaves emit a foetid smell when crushed. Male cones pale yellow, 0.5–0.7 cm long. Seed 2.5–3.5 cm (including aril); aril dark green, but purple-streaked, glaucous. Hils 1993. Distribution USA: Florida & Georgia (Apalachicola River valley). Habitat Cool, shady wooded slopes and ravines, between 15 and 30 m asl. USDA Hardiness Zone 6–7. Conservation status Critically Endangered (IUCN); Federally Listed as Endangered Species in the United States since 1984. Illustration Van Gelderen & van Hoey Smith 1996; NT867. Cross-reference K313.

Torreya taxifolia is effectively a relict species, marooned since the last glaciation (with its distant relative Taxus floridana) on the low sandy bluffs of the Apalachicola River valley in the Florida Panhandle. It was formerly reasonably abundant there, and

Section II. Species Accounts

formed good trees, whose wood was valued for items such as shingles and fence posts. In the mid-twentieth century the already reduced and stressed population became infected with a number of fungal pathogens, including Phytophthora cinnamomi and species of Physalospora and Macrophoma, which result in death of the shoots (but which can be cured with fungicide) (Esser 1993, Georgia Plant Conservation Alliance 2008). All the mature trees of T. taxifolia there are now long gone and the plant persists in the wild only as resprouting coppice stumps – of which there are probably fewer than 1000 individuals. Only one fertile tree is known, which has produced ‘approximately eight’ seeds since it was located, and no wild seedlings have been recruited for decades (Schwartz 2005). Not surprisingly, therefore, the species is of great conservation concern, with both official and unofficial efforts being directed at it. In particular, it has become a focus species in the debate over ‘assisted migration’ in the face of global warming (McLachlan et al. 2007, Nijhuis 2008). All participants in the debate are clear that T. taxifolia is confined to the Apalachicola area only by climatic circumstances, not through an inability to grow elsewhere. This is abundantly proven by the fact that the most important remaining population of the Florida Torreya is now at the Biltmore Estate, Asheville, North Carolina, where it was introduced as an ornamental in 1896–1897 and again in 1939, when about a dozen trees were planted. It has thrived there, with mature trees up to 15 m, and the population includes numerous self-sown seedlings. This is currently the most important source of seed for distribution to individuals and institutions (Torreya Guardians 2008). The species also does well in the western states. For example, two broad, bushy specimens (grown from cuttings!) were shown to me (JMG) in the obscure location of Hawthorne Park, Medford, Oregon in 2004 by Frank Callahan, who recalled that they had been received from the US National Arboretum in about 1990. The species is established in many European collections, principally as small trees or seedlings, although it has reached 3 m at Chyverton, Cornwall (TROBI). The officially favoured method of conservation is through traditional ex situ methods, with populations being maintained in botanic gardens and regulated collections. Atlanta Botanical Garden and other bodies in Georgia (where it is a native plant, as a few individuals grow within 200 m of the Florida–Georgia state line) are playing an important part in establishing orchards of different clones collected from the wild (Bailo et al. 1998, Georgia Plant Conservation Alliance 2008). The alternative view is that wild or semi-wild populations should be established further north in the Appalachian Mountains, where it can grow in a more suitable climate. To this end, an informal group known as the Torreya Guardians has been created, which actively promotes the planting of populations of T. taxifolia on private land outside the species’ natural range (Torreya Guardians 2008). This has raised howls of disapproval from

Torreya

867

Plate 558. The leaves of Torreya taxifolia are indeed yew-like, but have a sharp tip. This tree is the subject of a difference of opinions on how best to save it from extinction. Image J. Grimshaw.

868

Torreya

New Trees

conservationists, who principally fear the risk of it becoming an invasive species in an area where it is not native (Schwartz 2005), but has kindled debate on how species with naturally or artificially restricted ranges, threatened by climatic change (or other phenomena), should be treated. There will be many such cases in the near future, for which integrated active management will be required.

PINACEAE

TSUGA

(Endl.) Carrière

Syn. Hesperopeuce (Engelm.) Lemmon

Hemlocks

Plate 559. Specimens of Tsuga chinensis var. chinensis SICH 1761 are flourishing at Kew, and began producing cones at an early age. Image A. Farjon.

Nine species are recognised in the genus Tsuga, found in North America and Asia. Most are exclusively monopodial, including the largest, the American T. heterophylla, but others may be multistemmed or forked, and this is commonly the case with the Asian species. Young trees look more alike, with their conical form and drooping terminal shoots. The bark is generally scaly, and develops longitudinal cracks in later life. The branchlets are initially soft and bright green, in stark contrast with the dark mature foliage. The buds are not resinous, or only slightly so. The needle-like leaves are spirally arranged, on small pegs (pulvini), and twisted at the base; they are short, linear or ovate, entire or denticulate, with considerable variation in apex shape. The male strobili are solitary and grow from axillary buds on second-year shoots in the outer crown. They are very small, 0.3–0.6 cm long, subglobular, and change from reddish to yellow to reddish purple. The cones are sessile or with a short peduncle and are distributed across the entire crown; they are erect at pollination, but become pendulous; cones are green to greenish purple, and mature in one year. The seed scales are peltate or orbicular, petiolate, more or less persistent, and open to release the seeds. There are two seeds on each seed scale, and the bract scales are small, rhombic and included. The seeds are partially enclosed in a membranous cup, which extends to form a persistent wing (Farjon 1990). The hemlocks are an important small genus of beautiful conifers, whose elegant outlines and dark foliage give them great value for the garden and landscape where their requirements of well-drained but moist

Section II. Species Accounts

Tsuga

acid soil can be met. Unfortunately, in the northeastern United States at least, Tsuga are ravaged by the Hemlock Woolly Adelgid (Adelges tsugae), which has decimated the native and horticultural population of T. canadensis, and also affects T. caroliniana. A resistant replacement has been sought, and may have been found in T. chinensis (see below). Much valuable information on the Hemlock Woolly Adelgid is available on the internet, with the latest findings on its control, including biological methods. Several other pests can cause problems with these species – in particular, the Elongate Hemlock Scale (Fiorinia externa), often found together with the adelgid, and causing further debilitation and death of infested trees. T. blairinghemii (NOW T. diversifolia (Maxim.) Mast.) K315 T. calcarea (NOW T. dumosa (D. Don) Eichl.) K316 T. canadensis (L.) Carrière B622, S519, K316 T. canadensis f. microphylla (NOW T. canadensis (L.) Carrière) B623 T. caroliniana Engelm. B624, S520, K320

Tsuga chinensis (Franch.) E. Pritz.

Chinese Hemlock

Syn. T. formosana Hayata Tree to 50 m, 1.5–2 m dbh. Bark orange-brown with grey-green flakes, becoming grey-brown and very scaly in older trees. Crown broad, conical or flat-topped. Branchlets slender, finely grooved between the slightly swollen pulvini, yellowish brown, minute pubescence in the grooves, later glabrous; vegetative buds not resinous. Leaves dark, glossy green, (0.6–)1–2(–2.7) × 0.18–0.3 cm, linear, apical margins denticulate, emarginate or entire. Male strobili 0.3–0.5 cm long, yellow with a hint of purple. Female cones ovoid to oblong, 1.5–2.5 × 1.3–2.2 cm, light green, turning shiny brown later; pedunculate or sessile, deciduous after shedding. Seed scales nearly circular, 0.8–1.2 × 0.8–1 cm. Bract scales transversely rhombic, 0.1–0.2 cm long, included. Seeds light brown, ovoid to triangular or oblong, wings ovate, 0.6–0.7 × 0.35 cm, light yellow and transparent. Farjon 1990, Fu et al. 1999c. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Xizang, Yunnan, Zhejiang; TAIWAN. Habitat Occurs in mixed mesophytic forest and, rarely, in montane coniferous forest, at altitudes of between 600 and 3200 m asl. USDA Hardiness Zone 6. Conservation status Lower Risk. Illustration Farjon 1990, Fu et al. 1999c, Aiello 2006; NT868, NT870. Cross-references B625, S520, K320. Taxonomic note Flora of China (Fu et al. 1999c) recognises five varieties of T. chinensis: var. chinensis, var. formosana (Hayata) H.L. Li, var. forrestii (Downie) Silba (recognised as T. forrestii Downie by Farjon 2001), var. patens (Downie) L.K. Fu & Nan Li, and var. robusta W.C. Cheng & L.K. Fu, differing in the colour and diameter of the shoots, and in cone characteristics. Of these, Farjon (2001) accepts only T. chinensis var. robusta – but adds T. chinensis var. oblongisquamata W.C. Cheng & L.K. Fu, which Fu et al. (1999c) treat as T. oblongisquamata (W.C. Cheng & L.K. Fu) L.K. Fu & Nan Li, though acknowledging its closeness to T. chinensis.

Tsuga chinensis was briefly described by Bean (1981b), with the comment that it was ‘not in general cultivation’. In view of its emerging importance in eastern North America, however, as an apparently Woolly Adelgid-resistant substitute for T. canadensis and T. caroliniana, it is treated here in full. It was first introduced by Wilson from Hubei in 1902, and until recently was principally represented in cultivation by specimens from this collection (and perhaps later Wilson collections for the Arnold Arboretum). An original specimen at Bodnant, Conwy was 18 m tall, 65 cm dbh in 1990 (Johnson 2003), and there are survivors in the United States from Wilson collections (for example, at the Arnold). A shapely, straight tree (12 m tall, 50 cm dbh) at the Scott Arboretum of Swarthmore College, Pennsylvania, however, was imported from Hillier & Sons in 1938 (A. Bunting, pers. comm. 2007). Recent reintroductions have brought new genetic diversity. Wilson noted that it was a denser, shorter tree in Hubei than in Sichuan (Sargent 1916), and in Taiwan it

869

870

Tsuga

New Trees

1 cm

C

D

E

F

B

H

A

G 1 cm

J

Section II. Species Accounts

Tsuga

871

can be up to 50 m tall (ETOT field notes). It has been collected by British expeditions in Sichuan (SICH 1761, in 1996) and Taiwan (ETOT 63, 100, in 1992). NACPEC teams have also collected it on several occasions during the 1990s and more recently, resulting in a large number of accessions throughout North American arboreta, regarded as important for their assumed adelgid resistance (Aiello 2006). In 2005 it was collected in Gansu, at the northern edge of its range, with hopes of extra hardiness (Aiello 2006). All these introductions are still young, but most seem to be growing well, and material has been released to commerce within the United States. In 2005, plants from the 1996 SICH 1761 collection were up to 2.2 m at Kew, while at Wakehurst Place a tree from ETOT 63 was 2 m tall and already fruiting, although it appeared rather unhappy, perhaps because it was planted in full sun. Light shade, as as minimum, seems to be useful for T. chinensis, at least when young. A recent study of the biogeographic and phylogenetic relationships of Tsuga species (Havill et al. 2008) has found that material attributed to T. chinensis from Taiwan (i.e. var. formosana) groups with the Japanese T. sieboldii rather than with T. chinensis. On the other hand, material from Ullung-do, identified as T. sieboldii, groups with the other Japanese species, T. diversifolia. It is clear that further investigation of these populations is needed. Tsuga forrestii (or T. chinensis var. forrestii) has supposedly been represented in cultivation since its original introduction (by Forrest) by a tree at Borde Hill, West Sussex, and propagations from it (Bean 1981b). One of these descendants, however, at the Sir Harold Hillier Gardens, was recently identified by Aljos Farjon as T. dumosa (A. Coombes, pers. comm. 2008), as was a more recent introduction originally identified as T. forrestii, the 1992 SICH 1123 collection from near Muli, Sichuan. A tree grown at Ness Botanic Gardens from seed collected near Lijiang, Yunnan, by Pan Chih Kang of the Chinese Academy of Forestry in 1980/81, thought to be possibly T. forrestii, also seems to be T. dumosa (H. McAllister, M. Frankis, K. Rushforth, pers. comms. 2008). True T. forrestii does not seem to be in cultivation, but its distinctness is upheld by Havill et al. (2008). T. crassifolia (NOW T. mertensiana subsp. grandicona Farjon) K321 T. diversifolia (Maxim.) Mast. B626, S521, K321 T. dumosa (D. Don) Eichl. B626, S521, K321 T. formosana (NOW T. chinensis (Franch.) E. Pritz. var. formosana (Hayata) H.L. Li OR var. chinensis) K321 T. forrestii Downie (OR T. chinensis var. forrestii (Downie) Silba) B625, K321 T. heterophylla (Raf.) Sarg. B628, S521, K322 T. ×jeffreyi (NOW T. mertensiana subsp. mertensiana var. jeffreyi (A. Henry) C.K. Schneid.) B630, K322

T. longibracteata (NOW Nothotsuga longibracteata (W.C. Cheng) Hu ex C.N. Page) K322 T. mertensiana (Bong.) Carrière B629, S522, K322 T. mertensiana f. glauca (Beissn.) Rehder B629 T. patens (NOW T. chinensis (Franch.) E. Pritz. var. patens (Downie) L.K. Fu & Nan Li OR var. chinensis) K322 T. sieboldii Carrière B630, S522, K323 T. tschekiangensis (NOW T. chinensis (Franch.) E. Pritz. var. chinensis) K323 T. yunnanensis (NOW T. dumosa (D. Don) Eichl.) B627, K323

Figure 94 (opposite). Tsuga relatives. Nothotsuga longibracteata: branch with seed cones (A); cone (B); lower leaf surface (C). Tsuga chinensis var. chinensis: upper leaf surface (D); branch with seed cones (H); lower leaf surface (E); branch with seed cones (J). Pseudotsuga sinensis var. wilsoniana: lower leaf surface (F); branch with seed cones (G).

872

Ulmus

New Trees

A

1 cm

1 cm

1 cm

C

B

Section II. Species Accounts

Ulmus

873

ULMACEAE

ULMUS

L.

Elms Ulmus comprises 20–45 species, distributed across the temperate northern hemisphere and into subtropical Asia and Central America. Elms are deciduous or evergreen trees, or rarely shrubs. The branches may be more or less smooth, or have two flat opposite corky wings or longitudinal corky layers. The leaves are in two distinct rows; they have pinnate venation and each vein extends to the leaf margin, where it terminates in a tooth; the margins are serrate or double-serrate. There are two stipules at each node, membranous and caducous, leaving a pair of scars at the leaf base. Inflorescences are fascicled, racemose or cymose. The flowers are hermaphrodite and/or unisexual, pedicellate, appearing in spring before the leaves, or rarely in autumn or winter; the perianth is campanulate, four- to nine-lobed, the tepals membranous, the number of stamens equal to the number of tepals. Floral characters are generally not significant in elm taxonomy, and are poorly reported in the literature. The fruit is a flat, usually more or less circular samara, with the seed in the centre or towards the apex; samaras are usually notched at the apex (Sherman-Broyles et al. 1997, Fu et al. 2003). Most interest in elms, dendrological or otherwise, focuses on their effect in the landscape as magnificent umbrageous trees – Tennyson’s ‘immemorial elms’, or the iconic English Elm, as described by H.J. Elwes (in Elwes & Henry 1913): ‘Its true value as a landscape tree may be best estimated by looking down from an eminence in almost any part of the valley of the Thames, or of the Severn below Worcester, during the latter half of November, when the bright golden colour of the lines of elms in the hedgerows is one of the most striking scenes that England can produce.’ There is much beauty in their detail too: And whoever wakes in England Sees, some morning, unaware, That the lowest boughs and the brushwood sheath Round the elm-tree bole are in tiny leaf

Plate 560. Elms have special value for their magnificence in the landscape. This is one of the Ulmus davidiana var. davidiana trees at the Morton Arboretum, grown from seed obtained from China in 1980, as part of the research programme conducted at the Morton by Dr George Ware. Image J. Grimshaw.

(R. Browning, Home-thoughts, from Abroad) All the mystery and magic of spring is captured in that word ‘unaware’. Even before the leaves appear, the flush of flowers and the bright green of the samaras are welcome sights as the days begin to lengthen. In their eclectic way, Elwes & Henry (1913) left the elms to the end of their magisterial if randomly arranged work, allowing them longest to study them, but even in books produced in a different order, Ulmus remains the last great dragon in the way of a dendrological survey. The modern view of the genus revolves around Dutch elm disease (see below), which colours all perspectives on it in the pallid yellowish

Figure 95 (opposite). Ulmus bergmanniana: habit with fruits (A); leaf underside (B); cluster of fruits (C).

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Ulmus

New Trees

green and brown of a stricken tree. So many trees have been lost – and with them not only their own aesthetic but the important wildlife habitats they represented. This is not the place to mourn their loss, however, but to look forward to options for their replacement. Many of the complications associated with innumerable European taxa have effectively been swept away with the trees, but the taxonomy of the genus remains controversial and infrageneric affinities are unclear for many species. The highly reduced flowers and fruits yield little taxonomic information, and interspecific hybridisation is common (Wiegrefe et al. 1994). In addition, many elms reproduce asexually, allowing clones to survive indefinitely. The problem is exemplified by the case of the British elms, which comprise anywhere between one and six species and additional hybrids, depending on taxonomic viewpoint (Armstrong & Sell 1996). A sensible current view is that there are a limited number of species (U. glabra, U. minor, U. procera) with one frequent hybrid (U. ×hollandica) and several to many distinct clones of uncertain origin that are probably best treated as cultivars (Coleman 2002). A basic guide to the currently most widely accepted names of recognised Ulmus species and the synonymy associated with them is provided by Buchel (2000), but this does not include all names used by Bean (1981b) and other authors. Some synonyms – for example, U. carpinifolia (now U. minor) and U. japonica (now U. davidiana var. japonica) – are frequently used in the literature by breeders referring to certain genetic entities within the specific pool, and in such cases the name used by the breeder is also given in the accounts below. As is well known, Dutch elm disease (DED), caused by fungi of the genus Ophiostoma, O. novo-ulmi being the most virulent, is carried from tree to tree by bark beetles of the genera Scolytus (in Europe, and as an alien in North America and Australasia) and Hylurgopinus (in North America). The attractiveness of particular species to the beetle is an important aspect in transmission of the disease. For example, the European White Elm (U. laevis) is not favoured by the beetle, probably because of the presence of a triterpene (alnulin) in the bark (Martín-Benito et al. 2005), and therefore often survives unscathed in areas ravaged by DED, although it is extremely sensitive to the disease if inoculated (Heybroek 2000). Infection can also enter trees through interconnected roots – a pathway that may have been responsible for the rapid demise of many American street elms – and via contaminated tools and machinery. Death is caused by the tree’s vascular system becoming blocked, by the fungus and by gels and tyloses produced by the tree itself in reaction to the infection. Originating in Asia, where Ulmus species are largely resistant, first Ophiostoma ulmi and then O. novo-ulmi spread through the elm populations of Europe and North America in the twentieth century, resulting in the death of millions of trees. In Britain and continental Europe the ease with which the disease spread, and the almost total annihilation of mature elms from the landscape, is often ascribed to the fact that many of the trees were of clonal origin (or at least of limited genetic diversity); in North America, however, where most elms were genetic individuals grown from seed, it spread just as rapidly and was equally devastating in its effects on the landscape. A third species of fungus, O. himal-ulmi, was discovered in the Himalaya in 1993; there it is in balance with native elms, but it is potentially virulent as a source of disease in European and American species (Brasier 2000). Innumerable reviews have been published on the subject of DED, as an internet search will reveal, but a particularly authoritative and well-illustrated account is provided by an excellent website (www.dutchelmdisease.

Section II. Species Accounts

org) hosted by the University of Amsterdam (Universiteit van Amsterdam 2008). Another good source of information on DED and many other aspects of the biology of Ulmus is The Elms (Dunn 2000), the proceedings of an International Elm Conference held at the Morton Arboretum in Illinois. For those who read Dutch, a further resource is De iep of olm, karakterboom van de Lage Landen (The Elm, Characteristic Tree of the Low Countries) (Goudzwaard et al. 2008). Dutch elm disease is a complex problem, and challenges anyone working with elms in any way. The response to the epidemic of O. novo-ulmi, in its European and North American races, has been intense and sustained, from research into its pathology to attempts to breed and select resistant cultivars. The devastation to countryside and cityscapes caused by the loss of the elms has provoked a huge emotional response which continues to spur efforts to find replacements, especially in North America – even to the extent that clones with the same growth habit as U. americana are the stated aim of some breeding programmes (Ware 2000). The history of efforts to breed DED-resistant elms has recently been comprehensively reviewed by Mittempergher & Santini (2004), and the following account is largely based on this work. Mittempergher & Santini identify six major centres of activity, three on each side of the Atlantic. In Europe, work started in the Netherlands in 1928 after the first outbreak of DED caused by O. ulmi, and resulted in the release of some cultivars that were resistant to that species, but not to the later-arriving O. novo-ulmi. This programme, transferred to the Dorschkamp Research Institute, Wageningen, continued to select and release elms until 1992 when it was terminated on the retirement of its leader, Hans Heybroek, and from it came the cultivar ‘Nanguen’ (Lutèce), which promises to be the best replacement (to date) for Europe’s native elms. In Italy Lorenzo Mittempergher has directed the elm-breeding work of the Istituto per la Protezione delle Piante (Institute of Plant Protection), based in Florence, focusing on making selections

Ulmus

875

Plate 561. Elm breeders have turned to Asian species to find genetic resistance to Dutch elm disease. Among them is Ulmus chenmoui. Image F. Picard.

876

Ulmus

Plate 562. The original Ulmus davidiana var. japonica ‘Morton’ (Accolade) has resisted Dutch elm disease for over 80 years, and has been extensively used in breeding work. Image K. Bachtell, Morton Arboretum.

New Trees

suitable for Mediterranean conditions, while in Spain a team led by Luis Gil at the Universidad Politécnica in Madrid is also seeking suitable cultivars for local use. In the United States, work by the US Department of Agriculture Agricultural Research Service (USDA/ARS) was begun in 1937, when U. americana started dying. Work has continued to the present day under the leadership of Alden J. Townsend, and by 2004, 11 clones had been released to the market from this programme – an indication of the long-term commitment needed when breeding big forest trees. An important step taken in this project (by the late Frank S. Santamour, Jr.) was to incorporate U. parvifolia into breeding work. At the University of Wisconsin, Madison, elm-breeding started in 1958 and continued until 2002, when it was terminated following the death of the long-term project leader Eugene Smalley. One goal was to seek resistant U. americana, the other to breed new entities from the Eurasian gene pool. The U. americana work resulted in the release of a group of six clones known collectively as American Liberty, but these have not proved to be as reliable as other selections. The Eurasian elm project, which involved acquiring material from Japan, and China shortly after it ‘opened up’ in the 1980s, was much more successful, producing ‘Sapporo Autumn Gold’ as its first release. The starting point for the ongoing programme at the Morton Arboretum, at Lisle near Chicago, was the recognition in 1972 of the resistant qualities of an exceptional tree already growing in the collection, later named ‘Morton’ (Accolade). This became the foundation of the breeding work commenced and continued by George H. Ware and his team, which has resulted in the accumulation at the Arboretum of the finest collection of elms in North America, if not anywhere. They have sought out and incorporated into the breeding programme many formerly (and often still) obscure Ulmus species from China. On both continents, other smaller and shorter-lived projects have resulted in the release of various cultivars in all categories. Successful releases from the main research institutes have complicated genetics, built up over decades of breeding and testing, and it is important that resources of knowledge and material are not jeopardised by cessation of funding – as, for example, in the cases of the University of Wisconsin and the Dorschkamp Research Institute (Mittempergher & Santini 2004). For those with an interest in planting elms, the more or less resistant cultivars resulting from these programmes are effectively almost the only possibilities to consider, as DED has wiped out of the picture most native species and most of the old clones (with the notable exception of U. laevis), and the Asian species are very rare in commerce, especially in Europe. In taking account of these resistant cultivars we treat them here in groups according to the principal origin of their genetics (rather than their place of raising): see below, alphabetically within the sequence of accounts, ‘Asian elm hybrids and selections’ and ‘European elm hybrids and selections’. Many selections have two names, the usual cultivar name (for example, ‘Morton’), and a selling name (Accolade) often rendered in the form of a vernacular name (for example, Accolade Elm). The urge to develop resistant elms led to a surge in interest in the Asian species during the 1980s and 1990s, and a number of species have been collected by both European and American

Section II. Species Accounts

breeders for research into their resistance and for use in breeding work (see, for example, Ware 1995c). These form the core of the accounts that follow, in the usual way, but it is probable that most of them will be seldom available to the ordinary grower. The Morton Arboretum has been especially active in obtaining material from the seed lists of Chinese botanic gardens and the Chinese Academy of Forestry, as well as via specially commissioned collections. In addition to the species described or crossreferenced below, the following taxa are or have been in cultivation there (Ware 2000, Morton Arboretum online catalogue 2008): U. changii W.C. Cheng, U. elongata L.K. Fu & C.S. Ding, U. harbinensis S.Q. Nie & G.Q. Huang, U. lanceifolia Roxb. ex Wall., U. microcarpa L.K. Fu, U. prunifolia W.C. Cheng & L.K. Fu, U. pseudopropinqua Wang & Li, and U. sukaczevii Andronov (probably a form of U. glabra). In many cases the sample of natural variation of a species in cultivation is very limited, small numbers of clones having been grown from the original accession. The Morton Arboretum is the International Cultivar Registration Authority (ICRA) for Ulmus, reflecting the long and sustained programme of research on the genus carried out there. In Europe collections are maintained by some research institutions, but there is not much interest in planting elms among the wider public, as reflected by the paucity of entries in recent editions of the RHS Plant Finder. In the United Kingdom, one exception to this is in West Sussex, where the Brighton & Hove City Council maintain the National Plant Collection of Ulmus, comprising over 100 taxa distributed throughout their area (see the Council website for updated information on all aspects of this remarkable community conservation effort: Brighton & Hove City Council 2008). Another important project was initiated in 2001 by the Hampshire and Isle of Wight Branch of the charity Butterfly Conservation. The White-letter Hairstreak butterfly Satyrium w-album is dependent on elm as its larval food plant and has become a rare species in consequence of the loss of most of the mature elms in southern England. The Butterfly Conservation project aims to assess the potential of various elms, mostly hybrids, for their suitability for the butterfly and as landscape specimens, and has established a significant trial of new elm selections. A preliminary report is available (Brookes 2006), and assessment continues. In France, extensive trials of elms for disease resistance have been carried out by the Institut National de la Recherche Agronomique (INRA), with trial plantations in the Bois de Vincennes and elsewhere, from which much valuable information has been derived and which have led to the propagation and promotion of some of the most important new ‘European’ cultivars (Pinon & Cadic 2007). Although mature elms have essentially disappeared from the landscape across most of Europe and North America, they are not entirely gone. There are certain enclaves of varying size where DED has limited impact – for example, the area around Brighton in the United Kingdom, as noted above, where good populations of mature trees are defended by strenuous monitoring and control measures, and similarly protected populations of trees in Minneapolis and other cities in Minnesota (Stennes 2000). DED is absent from the Canadian province of Alberta (Alberta Government 2001–2008), where again there are rigorous controls in place. The elms of the Isle of Wight and the Channel Islands are also not affected (S. Andrews, pers. comm. 2008). In Europe elms

Ulmus

877

Plate 563. The first shoots of recovery? A young plant of Ulmus ‘Nanguen’ (Lutèce) in the Butterfly Conservation trial of elms in Hampshire – the closest match so far, among new hybrid elms, for the old European taxa. Image Butterfly Conservation.

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Ulmus

Plate 564. The stately presence of Ulmus americana has largely disappeared from the cityscapes of North America since the onset of Dutch elm disease but some individuals, like this one in Illinois, have escaped it – through resistance or good luck. Image J. Grimshaw.

New Trees

remain very common in the form of regenerating suckers from the roots, persisting in woodland and hedgerows and sometimes developing into quite respectable trees – before the beetle eventually, apparently inevitably, finds them. These populations act as a genetic reservoir for the trees, from which they may regenerate should there ever come a time when they are able to escape the disease – but also for the pathogen and the beetles, as dead and dying trees are left standing and unattended to. Dutch elm disease can be kept at bay on isolated or valued specimens by the use of systemic fungicides, usually by injection or infusion, which is much cheaper than the cost of removing a large mature elm tree and is thus a wise course for the preservation of trees in gardens and arboreta (Stipes 2000, Stennes 2000). Vigorously applied sanitary measures, including prompt removal of any infected material, severing of root unions between infected and healthy trees and the banning of imported elm timber for firewood, offer the only practical hope for control of the disease in larger populations – and authorities must be constantly vigilant. According to press reports, 370 mature elms were killed in Brighton in 2005, for example (see Brookes 2006). Dutch elm disease is only the most severe of the pests and diseases that afflict Ulmus; Dirr (1998) was heretical enough to ask why elms have been ‘treated like royalty when they are so fallible’, going on to provide an alarming catalogue of other problems that can beset them. Among the worst, though principally affecting American native species, is the disease elm yellows, caused by a phytoplasma vectored by piercing insects, that causes rootlet death and progresses to kill the phloem and cambium. Also sometimes called ‘phloem necrosis’, it has been responsible for huge die-offs of U. americana in the past, and poses a continuing threat to that species even where DED is controlled (Sinclair 2000). In America it is of extremely rare occurrence in cultivated Eurasian taxa, but it is present in Italy, and although it seems to be of limited significance in native taxa it could be problematic in hybrids involving Asian species, which show greater susceptibility (Mittempergher 2000). A suite of insect pests feed on the leaves, including Japanese Beetle Popillia japonica, Elm Leaf Beetle Xanthogaleruca (Pyrrhalta) luteola, Elm Leafminer Kaliofenusa ulmi, cankerworms and weevils, causing unsightly defoliation and consequent debilitation. There are variations in the resistance of different clones to these pests, which must be taken into account when breeding and selecting new cultivars (Miller 2000). Elm Leaf Beetle is a particularly serious problem in North America and has unfortunately been introduced to Europe, although it is at present unknown in Britain (A. Brookes, pers. comm. 2008). All these factors have implications for the success of newly planted elms and (particularly in North America) it will be advantageous to make local enquiries to find out which cultivars succeed best in a given area. With the unparalleled abundance of arboreta undertaking research and extension work in the United States, this information is much more readily available there than it is in Europe. In general, however, elms are tolerant of many growing conditions, though most require good drainage to be successful. It should also be remembered that ample space is required for these big, densely shady trees; one may imagine cases in which the demise of an elm too close to a house or shading a field could

Section II. Species Accounts

Ulmus

actually have been a very welcome event. Fertile clones can produce masses of seedlings that may be a nuisance, and they hybridise easily, as evidenced by the breeding work. Swarms of hybrid seedlings are potentially able to invade wild habitats, as they have in Spain and Italy, where the native U. minor Mill. has met with U. pumila (Collin et al. 2000). The Butterfly Conservation trial in Hampshire (Brookes 2006) found that small, young specimens established much better than large specimens (over 4 m) supplied as bare-root standards, which required staking until they were properly established, by which time the smaller trees had overtaken them. Propagation of selected elms is by cuttings, either of hardwood taken in winter and rooted with basal heat in a cool atmosphere, or as softwood in summer. Hormonal rooting preparations can be advantageous in both cases (Beckett & Beckett 1979, Mittempergher et al. 1991). We shall probably never see the old, elm-dominated landscapes again, but the new hybrids give glimmers of hope that we will in the future be able to enjoy majestic elms in many places where they have been absent for some decades now. The lessons of the past must, however, be heeded. We must not depend solely on a few clones to supply our landscapes with elms – or any other genus of tree. Diversity must be maintained. U. alata Michx. B657, K405

Ulmus americana L.

American Elm, (American) White Elm

Ulmus americana was described by Bean (B638) and Krüssmann (K405). Formerly one of the most important street and landscape trees in North America, it was very badly hit by DED, and it is nostalgia for this beautiful species that has driven the quest there for DED-resistant elms. The lesson of the effect of planting monocultures of street trees has not really taken root, however; as Dirr (1998) points out, a limited palette of urban trees is still dominant across much of North America, each species in turn becoming plagued by problems. As a genetically variable natural species, U. americana varies in its susceptibility to DED, and any survivors in generally disease-stricken areas should be regarded with particular interest (Sternberg 2004). A number of surviving clones have been selected and named, but their degree of resistance varies. Lists and brief descriptions are provided by several sources (for example, Dirr 1998, Jacobson 1996, Warren 2000). There is consensus, however, that two introductions from the US Department of Agriculture Agricultural Research Service are the most resistant. ‘Valley Forge’ is the best of all in this respect, closely followed by ‘New Harmony’ from the same source (see Townsend 2000 for the history of the USDA/ARS releases of DED-resistant elms). Named in 1922, before DED became a major problem, ‘Princeton’ from the Flemer family nursery in Princeton, New Jersey was selected on account of its fine growth habit and resistance to damage by the Elm Leaf Beetle. Fortuitously, however, it proved also to be not very susceptible to DED, and has retained its place in the nursery trade and planting lists. All the above-mentioned clones have the classic, desirable vase-shape with arching branches expected of an all-American elm. ‘Princeton’ has recently achieved some fame as the elm selected for planting in an avenue at Highgrove House by HRH The Prince of Wales. Notwithstanding this

879

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Ulmus

New Trees

distinction, as Brookes (2006) has also observed, U. americana was never a great success in the British climate even in pre-DED times (Elwes & Henry 1913), not least because its foliage was more vulnerable to leaf-feeding invertebrates than that of native or archaeophytic elms. U. angustifolia (NOW U. minor Mill. subsp. angustifolia (Weston) Stace) B639 U. angustifolia var. cornubiensis (NOW U. minor Mill. subsp. angustifolia (Weston) Stace) B639 U. angustifolia × U. glabra B640

Asian elm hybrids and selections

Plate 565. The foliage of Ulmus davidiana var. japonica ‘Morton’ (Accolade) is apparently not tasty to Scolytus beetles (carriers of Dutch elm disease) or the Elm Leaf Beetle – a very valuable double resistance. Image K. Bachtell, Morton Arboretum.

Having co-evolved with Ophiostoma, the Asian elms possess a varying degree of resistance to DED, both between and within the species, and it is this potential resistance that makes them so interesting and attractive to many breeders. Two taxa (U. davidiana var. japonica and U. pumila) have been the principal parents of cultivars released to the trade, but U. davidiana var. davidiana, U. macrocarpa and U. szechuanica are also under investigation at the Morton Arboretum for their value as parents (Ware 2000). The following account has been drawn up using several sources (Jacobson 1996, Dirr 1998, Smalley & Guries 2000, Townsend 2000, Ware 2000, Warren 2000, van den Berk 2002), which should be consulted for more detailed information than can be given here. Most of these cultivars are very poorly known in Europe. The botanical entity currently recognised as U. davidiana var. japonica has long been grown as two species, U. japonica and U. wilsoniana (see p. 884), and trees ascribed to any of these three names are extremely important in breeding programmes. The first clue to the importance of this parentage was the recognition in 1972 of the qualities of a U. japonica × U. wilsoniana hybrid growing at the Morton Arboretum which had excellent form and appearance, approaching the shape of the ideal U. americana, and was also resistant to DED and the Elm Leaf Beetle. This beautiful tree, planted in 1924 and still standing (see Plate 561, p. 876), 18 m tall (75 cm dbh) in 2008 (K. Kim, pers. comm. 2008), was named ‘Morton’ and has achieved wide planting under the selling name Accolade. Twenty metres seems to be about its maximum height, and it is noted for its smallish, deep green leaves. Although still considered to be one of the best in itself, for its double resistance (to DED and Elm Leaf Beetle), ‘Morton’ has also been an important parent of elms released by the Arboretum. Crossed with U. pumila it has produced ‘Morton Red Tip’ (Danada Charm) and ‘Morton Glossy’ (Triumph). It was also a parent of ‘Morton Stalwart’ (Commendation) – a complex hybrid, interesting for incorporating European genes from its other parent, a seedling from a cross between U. pumila and U. minor (as U. carpinifolia). Dirr (2007), however, finds the three stablemates ‘Morton Stalwart’, ‘Morton Glossy’ and ‘Morton Vanguard’ to be ‘ugly’, on account of their ‘wild’ growth and splaying branches. Moreover, in trials at the University of Minnesota, ‘Morton Red Tip’ was judged the worst of 17 cultivars for breakage, owing to its narrow crotch angles and trapped bark (Giblin & Gillman 2006). Other selections attributable to U. davidiana var. japonica are ‘Prospector’, released by USDA/ARS, and ‘Discovery’ and ‘Jacan’ from the Morden Research Station,

Section II. Species Accounts

Ulmus

Manitoba, all of which are hardy, well-shaped trees, resistant to DED and the beetle. ‘Prospector’ is a parent of ‘Patriot’, the other parent of which is ‘Urban’ (see p. 887), so this has particularly complex genetics. Also released by USDA/ARS, ‘Patriot’ grows very rapidly to form a narrowly vase-shaped crown, and is resistant to DED and elm yellows, but suffers damage from Elm Leaf Beetle. Ulmus pumila has been weighed in the balance across North America and generally found to be wanting in several ways – principally for its brittleness and the propensity for its leaves to be skeletised by insects. Denounced by Michael Dirr (1998) as ‘one of the world’s worst trees’, that ‘does not deserve to be planted anywhere’, and generally best left in the wild, it is on the other hand very hardy, and resistant to both DED and elm yellows. Numerous selections of the species have been named, but its greatest significance is as an extremely important parent in breeding, contributing hardiness and disease resistance to some of the most valued hybrid elms. One of the first was ‘Sapporo Autumn Gold’ – a valued flagship of the University of Wisconsin programme. Remarkably, this widely planted clone arose from the first batch of seed received at Wisconsin in 1958, sent by Prof. Nobuku Takahashi from the Hokkaido University Botanical Gardens in Sapporo. It proved to be a hybrid between U. pumila and U. davidiana var. japonica, as was a sister seedling, ‘Cathedral’. ‘Sapporo Autumn Gold’ has been very widely planted across North America and Europe, and makes a good tree with a rounded crown of smallish leaves. It is expected to reach 15–18 m in height (Dirr 1998), and many trees in Britain are now approaching this stature (TROBI). It will be interesting to see how big they get. It does not look like the classic European elms, so is not a substitute for them in the landscape – but as long as this is not the aim it is an excellent choice, as it appears to be fully resistant to DED. It can turn golden in autumn, but the leaves are more often yellowish green and not always very persistent once they have turned. ‘New Horizon’ is another clone of this parentage from the University of Wisconsin, with a more upright shape and a denser crown of larger leaves. It and the similar ‘Rebona’ (again of the same origin and parentage) have been widely planted, including in Europe where they are marketed by the German nursery Conrad Appel KG, Darmstadt, as part of their Resista series (which also includes ‘Sapporo Autumn Gold’). All seem to be very resistant to DED and other problems. ‘New Horizon’ is expected to reach maximum size below 16 m and have a compact shape. On winter-wet soil in Hampshire it has performed poorly, dying back severely each winter, but in good, well-drained soil it flourishes (Brookes 2006). ‘Morton Plainsman’ (Vanguard) also shares the U. pumila × U. davidiana var. japonica parentage, but was raised in Chicago.

Ulmus bergmanniana C.K. Schneid.

Bergmann Elm

Tree to 26 m. Bark greyish white to dark grey or greyish brown, longitudinally fissured. Branchlets purplish grey to pale brown, glabrous or pubescent, not winged. Leaves deciduous, 6–18 × 3–8.5 cm, elliptic to oblong or ovate, upper surface glabrous and often scabrous, lower surface densely hirsute when young, later hairs remaining in the vein axils only, (15–)17–26 secondary veins on each side of the midrib, margins doubleserrate, apex caudate to acuminate; petiole 0.1–1.3 cm long, glabrous or pubescent. Inflorescences produced on second-year branches; fascicled cymes. Perianth campanulate, four- to six-lobed, margins ciliate. Samaras tan to light brown, broadly obovate to circular, 1.2–1.8 × 1–1.6 cm, largely glabrous, perianth persistent.

881

Plate 566. Ulmus ‘Sapporo Autumn Gold’ is a highly resistant hybrid that has been widely planted in England, but it has a very different shape to the native elms. Image D. Sanford.

882

Ulmus

New Trees

Flowering and fruiting February to April (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Anhui, Gansu, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Shanxi, Sichuan, Yunnan, Zhejiang. Habitat Forests between 1500 and 2600 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003; NT872. Cross-reference K405.

Ulmus bergmanniana var. lasiophylla C.K. Schneid. This variety differs from typical U. bergmanniana in that the undersides of the leaves are densely covered in curved or crisped hairs. Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Gansu, Shaanxi, northwest Sichuan, southeast Xizang, northwest Yunnan. Habitat Forests between 2100 and 2900 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003.

Ulmus bergmanniana has grown at Kew for some years, but accession details are not recorded. The current specimen was measured at 8 m in 2001 (TROBI), but there is also a record of a 10 m tree in 1990. Material of both varieties of U. bergmanniana was obtained by the Morton Arboretum from China in 1995 (Morton Arboretum online database) and both are growing there for comparison. To the inexperienced eye there is not much difference between them, as the leaf undersides are hairy in both, but the hairs are denser in var. lasiophylla, in some specimens at least. At the Morton Arboretum a specimen of var. bergmanniana was forming a narrowly vase-shaped 7 m tree when observed in 2006, and var. lasiophylla was forming a broad column about 8 m tall. The latter tree showed heavy insect damage to the leaves. Curiously, specimens of both varieties from the same introduction seen in the same year in the Chicago Botanic Garden, not very far away, were forming rounded trees. The species seems to be resistant to DED but is very susceptible to the Elm Leafminer (Smalley & Guries 2000), and while not suffering much from Elm Leaf Beetle in Oklahoma (Sunshine Nursery 2008), has been considered to be moderately to highly preferred by this insect in research carried out at the Morton Arboretum (Miller 2000). It is very hardy (Shirazi & Ware 2004).

U. campestris (nomen ambiguum) B641 U. canescens Melville B641, K405 U. carpinifolia (NOW U. minor Mill. subsp. minor) B642, K405

Ulmus castaneifolia Hemsl. Syn. U. multinervis W.C. Cheng

U. carpinifolia var. italica (A. Henry) Rehder K406 U. carpinifolia var. suberosa (Moench) Rehder B643, K406

Chestnut-leaved Elm, Multinerved Elm

Tree to 20 m, 0.5 m dbh. Bark pale grey to blackish brown with a thick corky layer, longitudinally fissured. Branchlets thick, initially white to reddish brown, not winged, later dark brown to grey with yellowish lenticels. Leaves deciduous, 8–15 × 3.5–6.5 cm, oblong to elliptic or obovate, upper surface smooth or scabrous, densely hirsute when young, later largely glabrous except for hairs on the secondary veins, lower surface densely pubescent with prominent tufts in the vein axils, 16–35 secondary veins on each side of the midrib, margins double-serrate, apex long-acute to cuspidate; petiole 0.1–1.2 cm long, densely pubescent. Inflorescences produced on second-year branches; fascicled cymes. Perianth four- to five-lobed, margins ciliate or glabrous. Samaras tan, oblong to obovate, 1.6–3 × 1–1.6 cm, glabrous, perianth persistent; seed positioned towards the apex. Flowering and fruiting February to April (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Yunnan, Zhejiang. Habitat Broadleaved forests between 500 and 1600 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003; NT883.

Section II. Species Accounts

Ulmus

883

The leaves of Ulmus castaneifolia do indeed resemble those of a chestnut (Castanea), and with their numerous veins have quite a distinct look. Details of its introduction are unknown, but there is a specimen at Kew, of 11 m in 2001 (Johnson 2003). It is in cultivation elsewhere in the United Kingdom as well, including several individuals in Calderstones Park, Liverpool, one of which is the British champion, measured by Owen Johnson at 13 m (45 cm dbh) in 2004 (TROBI), when Johnson noted that all were in excellent health and growing well while other elms nearby had been reduced to sucker growth. Its resistance to DED has been confirmed by Smalley & Guries (2000), but it can be badly damaged by Elm Leaf Beetle (Miller 2000). It was among the species obtained by the Morton Arboretum from China in 1995, and now has a limited presence in North American cultivation, even being commercially available. A 6 m specimen at the Chicago Botanic Garden was developing heavily ridged bark when seen in 2006, and had strong spreading branches from low down on its trunk.

Ulmus chenmoui W.C. Cheng

Chenmou Elm, Langya Mountain Elm

Tree to 20 m, 0.5 m dbh. Bark greyish brown, breaking into irregular oblong flakes. Branchlets densely pubescent when young, without wings or a corky layer. Leaves deciduous, 6–18 × 3–10 cm, broadly obovate to oblong or elliptic, scabrous, upper surface densely hirsute and pubescent along the midrib, lower surface densely pubescent, 15–21 secondary veins on each side of the midrib, margins double-serrate, apex shortly caudate to acuminate; petiole 1–1.5 cm long, densely villous. Inflorescences produced on second-year branches; fascicled cymes. Perianth four-lobed, margins glabrous. Samaras obovate, 1.5–2.5 × 1–1.7 cm, glabrous, perianth persistent; seed positioned in centre or towards the apex. Flowering and fruiting March to April (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Anhui, Jiangsu. Habitat Forests between 100 and 200 m asl. USDA Hardiness Zone 4–5. Conservation status Endangered, due to habitat loss/ degradation, wood extraction and poor regeneration. Illustration Fu & Xin 2000, Fu et al. 2003; NT875.

Ulmus chenmoui is well established in cultivation and is available commercially in North America, but is not commonly planted anywhere except in research collections. This may change, however, as it is a handsome tree with classic elm features and seems to possess good resistance to DED (less so to elm yellows) (Mittempergher 2000), and limited susceptibility to Elm Leaf Beetle (Miller 2000). The Morton Arboretum obtained wild-collected seed from Anhui in 1995, and from Hangzhou Botanical Garden in 1998, and the species is growing well there, although a 5 m specimen seen in 2006 had heavy insect damage to the foliage. It is in cultivation in Europe, principally for research purposes, but also in private collections such as the arboretum of Verrièresle-Buisson, near Paris, owned by the Vilmorin family (F. Picard, pers. comm. 2008). In the Bois de Vincennes, 13 trees received from the Dorschkamp Research Institute were planted in 1980 by the Institut National de la Recherche Agronomique, but most were killed by drought on the gravelly soil. (J. Pinon, pers. comm. via A. Brookes 2008). The heavily ridged, corky bark is one of the features of the tree as it matures (F. Picard, pers. comm. 2008). The largest specimen in the United Kingdom is at the Hillier Gardens, measured at 8.3 m in 2008. The species has recently been hybridised by the Istituto per la Protezione delle Piante in Florence; its progeny (clones FL 509 and FL 522) are under assessment in Italy and the United Kingdom.

Plate 567. The large, strongly veined leaves of Ulmus castaneifolia are distinctive. It seems to possess a good degree of resistance to Dutch elm disease. Image T. Kirkham.

884

Ulmus

New Trees

U. coritana (NOW U. minor var. plotii Mill.) B643 U. coritana var. angustifolia Melville B643

Ulmus davidiana Planch.

U. coritana var. rotundifolia Melville B643 U. crassifolia Nutt. B644, K407

David Elm

Ulmus davidiana var. davidiana Syn. U. davidiana var. mandshurica Skvortsov Shrub or tree to 15 m, 0.3 m dbh. Bark pale grey to grey, longitudinally fissured. Branchlets pubescent when young, sometimes with an irregularly fissured corky layer. Leaves deciduous, 4–9(–10) × 1.5–4(–5.5) cm, broadly obovate to elliptic, upper surface sparsely hirsute when young, lower surface densely pubescent when young, later glabrous with tufts of hair in the vein axils, 12–22 secondary veins on each side of the midrib, margins double-serrate, apex caudate-acuminate to acuminate; petiole 0.5–1(–1.7) cm long, pubescent. Inflorescences produced on second-year branches; fascicled cymes. Perianth four-lobed, margins glabrous. Samaras tan, obovate, 1–1.9 × 0.7–1.4 cm, densely pubescent over the seed, perianth persistent; seed positioned in centre or towards the apex. Flowering and fruiting March to May (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Hebei, Henan, Liaoning, Shaanxi, Shanxi. Habitat Slopes, valleys and wetlands, below 2300 m asl. USDA Hardiness Zone 3–4. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003; NT873. Cross-reference K407 (as U. davidiana). Taxonomic note The more widespread U. davidiana var. japonica (Rehder) Nakai, as defined by Flora of China (Fu et al. 2003) (syn. U. japonica Rehder, U. wilsoniana C.K. Schneid., U. propinqua Koidz.), is widely cultivated, and was described by Bean and Krüssmann: B650, K410 (as U. japonica); B660, K413 (as U. wilsoniana). It differs from typical U. davidiana in that its bark is blackish and the samaras are glabrous. Owing to its wider geographical range (China, Japan, Korea, Mongolia, Siberia), it can found flowering/fruiting from February to May. Many elm experts maintain three separate species in this complex.

Whatever the taxonomic viewpoint adopted for it, the Ulmus davidiana complex is extremely important in the search for DED-resistant elms. One of the best selected clones, ‘Morton’ (Accolade), is a hybrid between U. davidiana var. japonica and U. wilsoniana – the latter recently sunk into U. davidiana var. japonica (Fu et al. 2003), so the hybrid now fits entirely within the new definition of U. davidiana var. japonica, as do several other named cultivars (discussed on p. 880). Ulmus davidiana var. davidiana is much less familiar in horticulture than these taxa, but shows great potential. It is said to have been introduced to cultivation in 1895, but only one specimen is recorded by TROBI, a 7 m tree with spreading branches planted in 1965 at Stanmer Park, Essex (Johnson 2003). When he measured this in 2002, Owen Johnson noted that it was ‘smothered in pink flowers’. Var. davidiana has only a sparse representation in other European collections, but there are wild-origin trees from China and South Korea at Edinburgh. Seed was obtained by the Morton Arboretum from the Botanical Garden of Forestry, Harbin, China in 1980, under the name U. davidiana var. mandschurica, and the resultant trees are now magnificent specimens there, up to about 12 m in 2006 and forming dense dark crowns, either rounded or vase-shaped. The leaves are quite small but a deep glossy green – described by George Ware (2000) as ‘a splendidly meritorious attribute’. Many seedlings from the Morton trees have been distributed in the Midwestern states, and it seems to be very suitable for propagation from seed (Ware 2000). Although the degree of resistance to DED varies slightly between clones, in general the U. davidiana complex is perhaps the most promising of all for the selection and breeding of new cultivars (Smalley & Guries 2000).

U. ×diversifolia Melville B652 U. ×elegantissima Horwood B653, K407

U. elliptica (NOW U. glabra Huds.) B644, K407

Section II. Species Accounts

Ulmus

885

European elm hybrids and selections Paralleling the situation in North America, the quest in Europe is ultimately to find replacements for the great towering elms that were so dominant a feature in the landscape, with their characteristics of shape, colour and value for wildlife, as well as to some extent their timber. There are grounds for optimism but it seems inescapable that – with the unusual exception of the European White Elm U. laevis – for the foreseeable future almost all elms widely planted in Europe will have genes from Asian species in their background. The important review by Mittempergher & Santini (2004) is the basis for the following account, with further information from multiple sources (Jacobson 1996, Dirr 1998, Smalley & Guries 2000, Townsend 2000, Ware 2000, Warren 2000, van den Berk 2002, Brookes 2006, Pinon & Cadic 2007). The earliest research into DED and resistance to it was conducted by a remarkable team of Dutch ladies working at the Willie Commelin Scholten Phytopathologisch Laboratorium in Baarn, in the Netherlands. Their early selections of native U. minor, ‘Christine Buisman’ and ‘Bea Schwarz’, proved susceptible to the fungus Nectria cinnabarina and unsatisfactory in other ways, and new criteria for selections were defined. Native elms were still the source of breeding material, however, and although the clones ‘Commelin’ and ‘Groeneveld’, released in the early 1960s, were excellent in many ways and resistant to Ophiostoma ulmi, they were not resistant to O. novo-ulmi which shortly afterwards began to ravage Europe in the second wave of the disease, and they are now seldom seen. In 1938 the Dutch team crossed the Himalayan U. wallichiana with U. glabra ‘Exoniensis’, and from the progeny selected a particularly resistant seedling. This became the parent and grandparent of all the clones released from the Dorschkamp Research Institute (to which the research project transferred after 1956). The first trio of releases, spectacularly ill timed in 1973 at the height of the devastation by O. novoulmi, were named after early Dutch botanists, ‘Dodoens’, ‘Lobel’ and ‘Plantyn’, followed in 1983 by ‘Clusius’. These were initially hailed as the saviours of the elm, with good shape and many useful characters as landscape trees (including tolerance of seaside conditions) but time has shown them to be variably resistant to DED. They remain in limited circulation, however, and were formerly planted quite freely (especially the first three), so that they are not infrequent in parks and arboreta. Two later releases from Dorschkamp are, by contrast, proving to be first-rate resistant trees. ‘Columella’ (1989) was named after the Roman writer Lucius Junius Moderatus Columella (AD 4–70), whose work De Re Rustica is an important source of information on all aspects of Roman farming and countryside practice. (His lesser work De Arboribus makes him the first author of a book solely on trees.) As his writings contain numerous mentions of elms this is an appropriate tribute, and it is pleasingly coincidental that ‘Columella’ is also rather fastigiate, forming a narrowly columnar tree. Although purists may not care to see such shapes in the landscape, it makes an excellent street or avenue tree, growing rapidly, and has been found to be wind-resistant in Holland and southern England (Brookes 2006). ‘Columella’ was a seedling

Plate 568. Ulmus ‘Dodoens’ was one of a trio of elm cultivars marketed in the early 1970s as resistant to Dutch elm disease. This specimen, growing at Kew, was covered in samaras in March 2005. Image J. Grimshaw.

886

Ulmus

Plate 569. Hans Heybroek (left), long-time elm breeder at the Dorschkamp Research Institute, inspecting a nursery crop of one his creations, Ulmus ‘Columella’, in the company of Ronnie Nijboer. Image Butterfly Conservation.

New Trees

from a self-pollination of ‘Plantyn’. It has distinctively shaped, somewhat in-rolled leaves, said to be a recessive character derived from U. glabra ‘Exoniensis’ (Mittempergher & Santini 2004). In response to the summer drought of 2006 in England, however, many trees shed their leaves in early August, and some later died – a failing acknowledged by the tree’s originator, Hans Heybroek (H. Heybroek, pers. comm. via A. Brookes 2008). Potentially the most useful elm to emerge from the Dutch research is ‘Nanguen’, known usually as Lutèce (from the Roman name for Paris, reflecting its adopted nationality and principal trial ground) but originally seedling no. 812. Ironically, the Dutch did not promote this clone as they feared, erroneously, that it would succumb to Coral Spot Fungus Nectria cinnabarina, as one of its parents did (‘Bea Schwarz’). Thus the rights to it were ultimately sold to the French Institut National de la Recherche Agronomique. It was trialled for many years in the Bois de Vincennes, where at a spacing of 4 × 4 m it reached an average 12.5 m (22 cm dbh) in 20 years (Pinon & Cadic 2007), and has since been widely planted in France. It was released commercially in 2002. It seems to be entirely resistant to current strains of DED, and has gained top marks in the Butterfly Conservation trial in Hampshire, described there as being ‘an unqualified success’ (Brookes 2006). It has the genetic potential to make a very large tree, quite of the stature of the old European elms, and is very fast-growing, with broad leaves. The Hampshire trials suggest that it is tolerant of summer drought and winter waterlogging, and it appears to be wind-resistant once established. Another clone (no. 762) originating from the Dutch breeding programme but adopted by the French INRA is ‘Wanoux’ (Vada), which is slightly more upright and more vigorous, achieving an average 14 m (24 cm dbh) in the Bois de Vincennes trials. It is an open pollinated seedling from ‘Plantyn’, and has the look of a traditional European elm (Pinon & Cadic 2007), but is only available wholesale from the Lemonnier and Minier nurseries in France. These two cultivars currently offer the best substitute for northern Europe’s native elms. The Italian project directed by Lorenzo Mittempergher at the Istituto per la Protezione delle Piante in Florence has had slightly different goals, seeking elms suitable for Mediterranean countries and resistant to the different suite of pests and pathogens found there. ‘San Zanobi’ and ‘Plinio’ were the first two releases from this work (in 2001), derived from two different clones of U. pumila crossed with ‘Plantyn’. ‘San Zanobi’ in particular shows great promise of being a large, but narrow-outlined tree, growing very fast when young; it was the most vigorous clone in the Butterfly Conservation trials, putting on over a metre of growth each year (Brookes 2006). ‘Plinio’ is also fast-growing, and can be expected to form a very broad crown. ‘Arno’ and ‘Fiorente’ are the latest cultivars to be released (Santini et al. 2007), the latter derived from a crossing of U. pumila and native U. minor, the two species that are also the foundation of the Spanish programme. More releases are planned soon in Italy, featuring Asian species other than U. pumila (A. Santini, pers. comm. via A. Brookes 2008). Breeding using European elms as parents has also been conducted in the United States, resulting in some very complex genetics. ‘Frontier’, U. minor var. minor (recorded as U. carpinifolia) × U. parvifolia, forming a broadly oval canopy and noted for its good red autumn colour, was a USDA/ARS introduction in 1990. It has excellent DED resistance but is moderately susceptible to Elm Leaf Beetle. ‘Pioneer’ is one

Section II. Species Accounts

Ulmus

of the few modern hybrid elms to be derived entirely from European parents, being the progeny of U. glabra × U. minor (U. carpinifolia) and therefore attributable to U. ×hollandica. It forms a rounded crown, casting dense shade, but is not as resistant to DED as many other selections. ‘Homestead’ (USDA/ARS, introduced 1984), ‘Regal’ (University of Wisconsin, 1983), and ‘Urban’ (USDA/ARS, 1976) all derive from crossings of U. pumila with (‘Commelin’ × (U. pumila × U. minor ‘Hoersholmiensis’)). They are all resistant to DED but susceptible to Elm Leaf Beetle, and have received mixed reviews on the merits of their growth form and performance. Many specimens of ‘Urban’, for example, were blown over in gales where used in a shelterbelt in the west of England, because of their poorly developed root structure (Rouse 1989). The search for resistance in native European elms continues with, for example, the Ancient Tree Hunt in the United Kingdom, launched in 2004 by the Woodland Trust and the Tree Register of the British Isles, which has this as one of its goals. Professor David Bellamy’s Conservation Foundation is also committed to the discovery and propagation of old, seemingly resistant, elms. It should be remembered, however, that the most likely cause of survival is isolation rather than resistance. Any hopeful discoveries should be subject to rigorous testing, using the protocols developed by breeders on both sides of the Atlantic, and extensive trialling. Unhappily, neither of these projects has a programme of inoculation with the causal fungus to verify the resistance of trees (A. Brookes, pers. comm. 2008). Soberingly, in France over 300 clones from all the European species were tested by inoculation by the agricultural and environmental research company Cemagref, and not one was found to have a worthwhile resistance to DED (Pinon et al. 2005).

Ulmus gaussenii W.C. Cheng

Gaussen Elm, Hairy Elm, Anhui Elm

Tree to 25 m, 0.8 m dbh. Bark dark grey to black, scabrous, longitudinally fissured. Branchlets densely pubescent for first one to two years, with yellowish brown lenticels, sometimes with paired corky wings. Leaves deciduous, 3–11 × 1.8–5.5 cm, oblong to obovate or elliptic, upper surface densely hirsute and scabrous, lower surface densely pubescent when young, hair remaining on the veins at maturity, 8–10 secondary veins on each side of the midrib, margins serrate or double-serrate, apex obtuse-acuminate to acute; petiole 0.4–0.8 cm long, pubescent. Perianth campanulate, four- to five-lobed, pubescent, margins ciliate. Samaras circular, 1.8–2.8 × 1.7–2.7 cm, pubescent, perianth persistent; seed positioned in centre. Flowering and fruiting March to April (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Anhui. Habitat Riverbanks in limestone mountains, covering 10 ha in the Langya Hills (IUCN 2008). USDA Hardiness Zone 4–5. Conservation status Critically Endangered, with fewer than 30 specimens known in the wild, due to habitat loss/degradation, wood extraction and poor regeneration. Illustration Fu & Xin 2000, Fu et al. 2003.

Ulmus gaussenii is extremely rare both in the wild and in cultivation, but some hope is offered by the note in Flora of China that it is cultivated around Nanjing (Fu et al. 2003). Material obtained from China in 1995 is maintained at the Morton Arboretum and a few other American institutions, and has been commercially available from Sunshine Nursery, Clinton, Oklahoma, where the proprietor Steve Bieberich maintains a good collection of Ulmus. There it has been found to be only slightly damaged by Elm Leaf Beetle (Sunshine Nursery 2008). A young tree seen at the Morton Arboretum in 2006 was 3.5 m tall and already beginning to form heavy longitudinal plates on its bark. The leaves flush reddish, but quickly become a dull mid-green. U. glabra Huds. B644, K407 U. glabra f. cornuta (David) Rehder B646

U. glabra subsp. montana (NOW U. glabra Huds.) B645 U. glabra f. nitida (Fries) Rehder K406

887

888

Ulmus

New Trees

Ulmus glaucescens Franch. Ulmus glaucescens var. lasiocarpa Rehder

Hairy-fruited Glaucescent Elm

Shrub or tree to 18 m. Bark longitudinally fissured. Branchlets glabrous or pubescent, without wings or a corky layer. Leaves deciduous, 2.5–5 × 1.5–3 cm, elliptic to ovate, though shape extremely variable, both surfaces pubescent with tufts of hair in the forkings of the secondary veins, but never in the vein axils, 6–12(–14) secondary veins on each side of the midrib, margins serrate or double-serrate, apex acuminate; petiole 0.3–0.8 cm long, pubescent. Inflorescences produced on second-year branches; fascicled cymes. Perianth campanulate, four-lobed, glabrous or margins ciliate. Samaras tan, elliptic to obovate, 2–2.5 × 1.5–2 cm, densely pubescent when young, with scattered hairs when mature, perianth persistent; seed positioned in centre or towards the apex. Flowering and fruiting March to May (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Hebei, Henan, Nei Mongol, Ningxia, eastern Qinghai, Shanxi. Habitat Along river and mountain slopes, between 2500 and 2600 m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Taxonomic note Ulmus glaucescens var. glaucescens does not appear to be in cultivation. It has glabrous samaras and occurs in Gansu, Hebei, Henan, Liaoning, Nei Mongol, Ningxia, eastern Qinghai, Shaanxi, Shandong and Shanxi.

Interest in Ulmus glaucescens stems principally from its apparent tolerance of arid conditions, but it is extremely rare in cultivation. It forms part of the research collection at the Morton Arboretum, and is grown by Sunshine Nursery in Oklahoma (where it can suffer heavy damage from Elm Leaf Beetle); there is also a specimen at the Mount Lofty Botanic Garden near Adelaide, South Australia (Wikipedia 2008b). All these are derived from seed sent from the Beijing Botanical Garden. Horticulturally, U. glaucescens is probably most desirable for its very attractive bark, which is mottled in grey and fawn, with reddish brown lenticels. The specimen observed at the Morton Arboretum in 2006 was multistemmed, with a dense canopy of scabrid dull green leaves. U. ×hollandica Mill. B647, K408 U. japonica (NOW U. davidiana var. japonica (Rehder) Nakai) B650, K410

Ulmus laciniata (Trautv.) Mayr

Manchurian Elm, Cut-leaf Elm

Tree to 27 m, 0.5 m dbh. Bark dark greyish brown to grey, longitudinally fissured. Branchlets reddish brown to greyish brown or grey, pubescent when young, no wings. Leaves deciduous, 7–18 × 4–14 cm, obovate to obtriangular, upper surface sparsely hirsute, lower surface pubescent, 10–17 secondary veins on each side of the midrib, margins deeply double-serrate, ciliate, apex truncate or rarely rounded, often with one to three caudate lobes on each side; petiole 0.2–0.5 cm long, pubescent or glabrous. Inflorescences produced on second-year branches; fascicled cymes. Perianth campanulate, five-lobed, margins glabrous to ciliate. Samaras tan or pale green, elliptic to circular, 1.5–2 × 1–1.4 cm, glabrous, perianth persistent; seed positioned in centre or slightly towards the base. Flowering and fruiting April to May (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Hebei, Heilongjiang, Henan, Jilin, Liaoning, Nei Mongol, Shaanxi, Shandong; JAPAN; NORTH KOREA; RUSSIAN FEDERATION: eastern Siberia; SOUTH KOREA. Habitat Between 700 and 2200 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003; NT889. Cross-references B646, K410.

Ulmus laciniata is a relative of the Wych Elm U. glabra, and could be expected to develop the same large stature, but it is proving to be difficult to grow except in sheltered, humid sites (Heybroek 1993). At the University of Oxford’s Harcourt Arboretum there are several specimens grown from seed received from the Moscow Botanical Garden in 1981, but they are currently only about 3 m tall (P. Newth, pers. comm. 2008). A specimen at the Hillier Gardens planted in an exposed location in 1982 died in 2007. The species shows some resistance to DED, but is very susceptible to the Elm

Section II. Species Accounts

Ulmus

889

1 cm

1 cm

B

A

Leafminer (Miller 2000, Smalley & Guries 2000) and Elm Leaf Beetle (Mittempergher & Santini 2004, Sunshine Nursery 2008), so in consequence its usage is very limited. This is regrettable, because the lobed and toothed leaves are extremely striking. They are produced only on vigorous shoots as the growing season progresses. Smalley & Guries (2000) record that there were numerous importations of U. laciniata into the

Figure 96 (above). Ulmus laciniata: habit (A); fruits (B).

890

Ulmus

New Trees

United States from the 1950s onwards, enabling research into its qualities of pest and disease resistance, but it had had a limited presence in cultivation since its introduction to the Arnold Arboretum in 1905. A 1995 accession at the Morton Arboretum, originating in Liaoning Province, was a small bushy specimen 2.5 m tall in 2006. Although not recognised by Ohwi (1965), a localised form from near Nikko in central Honshu, Japan has been named U. laciniata var. nikkoensis Rehder, and was described by Krüssmann (1986: K410). It too is extremely rare in cultivation, but a tree at the Morton Arboretum grown from a 1984 accession is exceptionally attractive, and looks remarkably like a cherry tree! It was 8–9 m tall in 2006, forming a vase-shaped crown on three principal branches. No insect damage was apparent. The leaves are red on emergence, then slowly fading through bronze to green, and although toothed are not lobed. U. laevis Pall. B650, K410

Ulmus lamellosa C. Wang & S.L. Chang

Mottled-bark Elm, Hebei Elm

Syn. U. taihangshanensis S.Y. Wang

Plate 570. Several of the Asian elms have attractive bark – at least when young. This is Ulmus lamellosa, seen at the Morton Arboretum. Image J. Grimshaw.

Shrub or tree 8–12 m. Bark grey or greyish white, peeling in irregular flakes around reddish brown lenticels. Branchlets brown to greyish brown, glabrous, no wings, sometimes with a corky layer. Leaves deciduous, 5–10 × 2.5–5.5 cm, obovate, upper surface scabrous, densely hirsute, lower surface scabrous and densely pubescent when young, 9–10 secondary veins on each side of the midrib, margins serrate or double-serrate, apex caudate to cuspidate; petiole 0.3–0.8 cm long. Inflorescences produced at the same time as the leaves. Perianth campanulate, six-lobed, pubescent. Samaras scattered at the base of branchlets, ± circular, 2.5–3.5 × 2–2.7 cm, densely pubescent, perianth persistent; seed positioned in centre. Flowering and fruiting March to May (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Hebei, Henan, Nei Mongol, Shanxi. Habitat Mountain ravines, at c.1200 m asl. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003; NT890.

The bark of Ulmus lamellosa is a distinctive and ornamental feature, with light grey plates flaking off between rings of reddish brown or darker lenticels. It ought to be widely grown for this reason alone, but also has a nice rounded, shade-giving crown of dull green leaves that flush red and turn yellow in autumn, and seems, in addition, to be reasonably resistant to DED and not too badly attacked by insects. It is not tolerant of wet soils, however (Ware 1995c). It was introduced to the Morton Arboretum from China in 1990 and 1995, and was collected by the Sino-Scottish Expedition to Northwest Yunnan in 1995 (no. 205), from which source it is cultivated at the Royal Botanic Garden Edinburgh. It must have been introduced to the West earlier than this, however, as the University of British Columbia Botanical Garden received a plant from a cultivated source in 1983. There are a few other specimens scattered across our area, including individuals at the Strona Arboretum in Poland and at Arboretum Wespelaar. At Wespelaar a tree obtained in 1993 from Arboretum Waasland, NieuwkerkenWaas, also in Belgium, has flourished, and is described by Koen Camelbeke (pers. comm. 2008) as a ‘really very handsome elm’ with a good shape, that has (so far) been free of disease. U. macrocarpa Hance B651, K410

Section II. Species Accounts

Ulmus parvifolia Jacq.

Ulmus

Lace-bark Elm, Chinese Elm

This autumn-flowering species was described by Bean (B651) and Krüssmann (K411); we discuss it here too, however, as it has become very important in the fight against DED, to which it is largely resistant. Michael Dirr (1998) rates it extremely highly (and has personally been responsible for several selections), considering it to be one of the great landscape trees for a diversity of purposes. Its common name comes from its exfoliating bark, which can be very ornamentally coloured or relatively drab. It is very variable in all its characteristics, including leaf retention and hardiness, and suitability for geographical area should be borne in mind when choosing between clones. The standard sources provide lists of cultivars. Four that were selected for special mention by Warren (2000), and have also received general approval from Dirr (1998) and Jacobson (1996), are: ‘Emer I’ (sold as Athena), originating in Georgia and noted for outstanding bark and a rounded crown of dark green leaves (that unfortunately turn an unpleasing brown in autumn); ‘Emer II’ (sold as Allee), also from Georgia, highly rated for its excellent bark and good autumn colour, but with a more upright crown shape; and ‘A. Ross Central Park’ (sold as Central Park Splendor) – one of the hardiest clones, selected from an old tree in New York’s Central Park, with a broadly vase-shaped crown and good bright green leaves that turn yellow, although with dull bark. On ‘Dynasty’ opinions differ, Warren and Jacobson considering it to be a useful, fast-growing cultivar with good shape and decent autumn colour, though dull bark, but Dirr dissenting, claiming that it ‘borders on a boondoggle’ and citing poor shape and its boring bark as reasons not to grow it. With such a range of cultivars available in North America, it is unfortunate that European nurseries currently seem to offer only dwarfish and/or variegated clones. Opinions on these are best kept private. U. plotii (NOW U. minor Mill. var. plotii Mill.) B652, K411 U. procera Salisb. (OR U. minor Mill. var. vulgaris Richens) B653, K412 U. procera var. australis (A. Henry) Rehder K412

U. pumila L. B655, K412 U. pumila f. androssowii (NOW U. ×androssowii R. Kam.) K412 U. pumila var. arborea Litvin. K412 U. rubra Muhl. B656, K413 U. serotina Sarg. B656, K413

Ulmus szechuanica W.P. Fang

Sichuan Elm, Red-fruit Elm

Tree to 18 m, 0.8 m dbh. Bark dark grey, greyish brown or greyish black, scabrous, longitudinal fissures somewhat irregular. Branchlets grey, pubescent when young, with pale yellow lenticels, no wings, sometimes with a fissured corky layer. Leaves deciduous, 2–9 × 1.7–5.5 cm, obovate to elliptic, upper surface pubescent along the midrib when young, sparsely pubescent along secondary veins when young, 9–19 secondary veins on each side of the midrib, margins double-serrate, apex acute to acuminate; petiole 0.5–1.2 cm long, glabrous or pubescent. Inflorescences produced on second-year branches; fascicled cymes. Perianth campanulate, fourlobed, glabrous. Samaras tan, ± circular, 1.1–1.6 × 0.9–1.3 cm, glabrous, perianth persistent; seed positioned in centre. Flowering and fruiting February to March (China). Fu & Xin 2000, Fu et al. 2003. Distribution CHINA: Anhui, Jiangsu, Jiangxi, central Sichuan, Zhejiang. Habitat Forests. USDA Hardiness Zone 4–5. Conservation status Not evaluated. Illustration Fu & Xin 2000, Fu et al. 2003.

This elm is of interest to the breeding project at the Morton Arboretum because of its similarity in shape to U. americana, and has been used for artificial crosses there (Ware 2000). It seems to be reasonably DED-resistant (Smalley & Guries 2000), and specimens at Sunshine Nursery, Oklahoma showed no signs of damage by Elm Leaf

891

892

Ulmus

New Trees

Beetle, but some insect had caused heavy leaf damage to trees seen at the Morton Arboretum in June 2006. The leaves are glossy dark green above but paler below, and can look somewhat sombre, making it appear rather dull. Material was first received at the Morton in 1984, and one tree from this had reached about 10 m in height by 2006; further accessions came in 1995. It is hardy, but has rather fragile wood, so is subject to wind damage. It needs a well-drained site (Ware 1995c). A specimen originating as seed from Shanghai Botanic Garden has grown at the Hillier Gardens since 1993 and is now 4.4 m tall; another forms part of the elm collection at Brighton. U. wallichiana subsp. xanthoderma Melville & Heybroek B660 U. wilsoniana (NOW U. davidiana var. japonica (Rehder) Nakai) B660, K413

U. thomasii Sarg. B657, K413 U. villosa Brandis ex Gamble B657, K413 U. wallichiana Planch. B659, K413 U. wallichiana var. tomentosa Melville & Heybroek B660

CUNONIACEAE

WEINMANNIA

L.

Weinmannia is the largest genus in the Cunoniaceae, with 150–160 species, ranging from Central and South America to the Indian Ocean (Comores, Madagascar and the Mascarenes), Malesia and the South Pacific (Bradford 1998, Bradford et al. 2004). Most species are found in tropical montane forest, though several occur in the southern temperate zone. Weinmannia are canopy trees, shrubs, or rarely, epiphytes or stranglers. Branches develop from axillary buds, but in some species the apical bud aborts, producing dichotomous branching. The leaves are opposite and decussate, and may be simple or imparipinnate, though the terminal leaflet may be missing. There is great variation in leaf and leaflet size across the genus. The petiole and/or rachis may be winged, and stipules are always present. Flowers are densely clustered along racemes that are grouped into partial inflorescences; rarely, racemes develop directly on the main stem. Partial inflorescences may also be grouped together. The flowers can be hermaphrodite or unisexual and are rather uniform. They are white, cream or pink, 4- or 5-merous, and may be fragrant or not. The capsules are also rather uniform, leathery, dehiscent and with two valves, and the seeds have long hairs (Allan 1961, Bradford 1998, Hopkins 1998a). Weinmannia is best known in temperate horticulture in the form of W. trichosperma, whose handsome pinnate foliage is a great asset in mild, moist gardens. The milder and moister it is, the better this Chilean species grows; W. racemosa (described below) from New Zealand, by contrast, has not yet been very successful, even in similar conditions. Weinmannia pinnata L., which has a wide range from Mexico to Brazil, is in cultivation at the University of California Botanical Garden at Berkeley, but would probably need protection in winter elsewhere in our area. All Weinmannia species can be propagated from seed or by cuttings.

Section II. Species Accounts

Weinmannia racemosa L. f.

Weinmannia

893

Kamahi

Tree to 25 m, 1.2 m dbh. Branchlets pale grey and glabrous. Leaves evergreen and leathery, simple, 2–10 × 1–4 cm, elliptic to ovate, upper surface dark green and glossy, lower surface glabrous, with major veins slightly raised, six to nine secondary veins on each side of the midvein, margins coarsely serrate, apex obtuse; petiole to 2 cm long, pubescent on upper surface; stipules ligulate, caducous. Juvenile leaves simple, threelobed or trifoliolate; leaves of reversion shoots up to five-foliolate. Inflorescence terminal, composed of two racemes; vegetative growth may continue from between the racemes. Flowers hermaphrodite, up to 1.2 cm long, pedicellate, petals white or pale pink, styles 0.3–0.4 cm long and persistent. Fruit a capsule to 0.5 cm long. Flowering December to January, fruiting January to April (New Zealand). Allan 1961, Wardle 1966, Hopkins 1998a, 1998b. Distribution NEW ZEALAND: North Is., South Is., Stewart Is. Habitat Weinmannia racemosa is one of the most abundant of all New Zealand trees and occurs in a variety of habitats, between 0 and 1100 m asl. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Salmon 1996, Hopkins 1998b; NT893. Cross-references B751, K457. Taxonomic note Two species of Weinmannia occur in New Zealand and they can be difficult to distinguish. Weinmannia sylvicola Sol. ex A. Cunn. differs from W. racemosa in that the branchlets and pedicels are typically pubescent, the adult leaves are mostly trifoliolate and the juvenile leaves have up to 10 leaflets. The former occurs only on North Is. (Allan 1961, Wardle 1966). It is cultivated in Tasmania (from where seeds have been distributed: K. Gillanders, pers. comm. 2008) and in California, and elsewhere under glass.

Despite its abundance in New Zealand, Weinmannia racemosa is a rare plant in most of our area, probably because it is not hardy in any but the mildest of conditions. In principle it would seem very well suited to western coasts of Europe and North America, especially in moist sheltered places, but unlike its Chilean cousin W. trichosperma, no large plants of it have been traced. It has not become established at either Logan or Tregrehan, where it might have been expected to thrive, and although present in various other collections this is only as recent plantings. It is in commerce in the United Kingdom, sometimes under its Maori name Kamahi, applied in the form of a cultivar name. It is, however, established in California: for example, at the San Francisco Botanical Garden. With its upright, conspicuous inflorescences of pinkish white flowers held above the foliage it is distinctive and attractive, and worth trying where it has a sporting chance. W. trichosperma Cav. B750, K457

Plate 571. Weinmannia racemosa, seen here in the wild in New Zealand, has not yet become established in apparently suitable British gardens. Image S. Toomer.

894

Widdringtonia

New Trees

CUPRESSACEAE

WIDDRINGTONIA

Endl.

Cypress Pines, African Cedars/Cypresses Widdringtonia comprises four species endemic to southern Africa, of which W. nodiflora is the most widespread, stretching from the Cape to Mount Mulanje in southern Malawi. The remaining three species are isolated in the Clanwilliam (W. cedarbergensis) and Willowmore (W. schwarzii) districts of South Africa and on Mount Mulanje (W. whytei Rendle). Widdringtonia are generally small evergreen trees or shrubs, with fragrant wood. Their habit is extremely variable and depends on environmental and human factors. Initially, the young plants are conical or pyramidal; they may remain this shape, or, more frequently, develop a wide, flat-topped crown in maturity. Widdringtonia nodiflora is often coppiced by fire, and then develops into a large, multistemmed shrub. As in many Cupressaceae, there are two leaf forms: the juvenile leaves are spirally arranged and needle-like, the mature leaves scalelike, decussate or alternate, and appressed; the lateral and facial pairs are similar, with sharp, acute apices. The male strobili are terminal and solitary on short, lateral branchlets, with (five to) six (to seven) decussate microsporophylls. The female cones are axillary, solitary or in whorls of four (rarely five or six) on elongated shoots; they are roughly globose, valvate, often rather resinous, and mature in one year, though cones at varying stages of development can be found on a single tree at any time of the year. The seed scales are arranged in a whorl of four (occasionally five to six); they are thick and woody, with a smooth or warty external face. Each scale bears several seeds, which are released after fires; smoke may stimulate germination. The seeds are ovoid or three-angled, with a dark, papery wing; their dark colouring may protect them from predation by birds, by camouflaging them against recently burnt ground (Masters 1904, Palmer & Pitman 1972, Coates Palgrave 1990, Pauw & Linder 1997, Glen 2000, Farjon 2005c). Botanising in the embarrassingly rich flora of southern Africa is a daunting prospect for those used to lesser diversity, and amid the plethora of unfamiliar families it is reassuring to have no doubts over the identification of Widdringtonia – the only native conifers south of the Zambesi, with the exception of the solitary Juniperus procera in Zimbabwe. Unlike Juniperus, however, the affinities of Widdringtonia lie with other Gondwanan conifers, it being closely related to Diselma Hook. f. (Tasmania) and Fitzroya Lindl. (South America). Although in many areas it forms part of the fire-maintained fynbos community, the genus has an uncomfortable relationship with fire: a blaze is essential for seed survival and germination, but is the main cause of mortality in mature trees. This interesting little genus is an inevitable temptation to collectors, and as seed is regularly available from South Africa, young plants occasionally appear in the gardens of those interested in South African plants in general: seedlings of W. cedarbergensis, for example, have been sold in recent years by Pine Cottage Plants, Devon – a nursery specialising in Agapanthus! Unfortunately, in the British Isles at least, their chances of developing into a significant tree are slim if judged by past experience; Tom Hudson

Section II. Species Accounts

Widdringtonia

895

(pers. comm. 2005) regards them as hopeless cases. They have a greater chance of success in areas with a defined Mediterranean climate, where frosts are light. In our area this effectively means a limited area of northern California and adjacent Oregon, though possibly also some sheltered sites in southeastern England. Excessive wetness should be avoided at all times, and watering should probably be sparse in summer to avoid root rot, but they are not difficult to grow as potted specimens. Propagation from seed is easy and does not require a conflagration.

Widdringtonia cedarbergensis J.A. Marsh

Clanwilliam Cedar /Cypress

Shrub or small tree to 20 m, though typically 5–7 m, trunk massive and gnarled, 0.9–1.2 m dbh. Bark thin, fibrous, reddish grey, soon flaking. Crown initially conical, later rather broad and open. Juvenile leaves 1–2 × 0.1–0.2 cm; mature leaves 2–4 mm long, acute. Male strobili 1–2 mm long. Female cones axillary, usually clustered or in whorls of four, subglobose, valvate, 2.5–3.8 cm diameter. Seed scales in a single whorl of four, reddish brown inside, dark brown outside, rough and woody with a warty external face. Seeds with three corners, extremely resinous, wing inconspicuous. Coates Palgrave 1990, Pauw & Linder 1997, Farjon 2005c. Distribution SOUTH AFRICA: Western Cape (Clanwilliam district: Cederberg mountains). Habitat Mist-cloaked mountains and cliffs, between 915 and 1980 m asl. In its natural environment it can tolerate shallow, infertile soils, and experiences regular summer droughts and winter snow and frosts. USDA Hardiness Zone 9. Conservation status Endangered. Illustration Coates Palgrave 1990; NT895. Cross-reference K324. Taxonomic note The recently suggested English name Clanwilliam Cypress is more accurate, but has to compete against the hallowed vernacular Cedar – from which the whole Cederberg range takes its name.

Clanwilliam Cedars are the subject of intensive investigation by South African botanists, foresters and conservationists (Manders et al. 1990, Mustart 1993). Pollen analysis and historical records suggest that the species’ range was significantly larger in the past, but the main stands of it were ruthlessly exploited for their timber by European settlers in the Cape, and few mature trees now remain. Re-establishment is proving to be very slow and difficult, even with heavy input of finances and management. Plants face various threats, including seed predation by birds and rodents, grazing of seedlings, low seed yields and illegal timber extraction; fire, however, remains the chief concern. Due to their high resin content cedars burn incredibly fast, and can even explode! Yet fire is essential for seed release and seedling establishment. Rigorous management of the Cederberg area, with routine, controlled burning, may be the only way to save Widdringtonia cedarbergensis, and attempts are ongoing (see, for example, Plantzafrica 2003, Global Trees Campaign 2008). It is recommended for cultivation in South Africa, though not for planting too near a braai (barbecue) area … It is also used as a Christmas tree there (Plantzafrica 2003). It is not surprising that such an interesting tree should attract the attention of horticulturists, and young plants appear occasionally in British gardens. There is a shapely individual of 1.2 m (2008) in Christine Battle’s arboretum at Upton Cheyney in Gloucestershire, for example, planted in 2006. No old specimens are known, however, and Johnson (2007) notes that a bush growing at Pine Lodge gardens in Cornwall is unlikely to make a tree. It is established in California: for example, in the botanic gardens around San Francisco. W. cupressoides (NOW W. nodiflora (L.) Powrie, NT896) K324

Plate 572. Widdringtonia cedarbergensis is the subject of long-running conservation efforts to re-establish viable wild populations in the Cederberg mountains, South Africa. Image J. Grimshaw.

896

Widdringtonia

New Trees

Widdringtonia nodiflora (L.) Powrie Syn. W. cupressoides (L.) Endl., W. nodiflora var. dracomontana (Stapf) Silba

Mountain Cedar /Cypress, Sapree-wood

Shrub or small tree to 9 m; usually multistemmed, each stem developing from a swollen, subterranean base up to 3.5 m wide; rarely forming a monopodial tree to 40 m. Bark thin, grey, peeling in longitudinal strips to reveal a reddish inner layer. Crown (in the absence of fire) dense, narrow, columnar or conical. Juvenile leaves glaucousgreen, 1–2.5 × 0.2 cm; mature leaves dark green, 1–1.2 × 0.5 mm, obtuse; mature leaves on terminal branchlets narrow, oblong. Male strobili 2–4 mm long. Female cones usually clustered or in whorls of four, globose, valvate, 1.5–2 cm diameter, glaucousgreen though dark brown at maturity. Seed scales in a single whorl of four, dark brown, woody, smooth, slightly wrinkled or with a few small warts; each scale bearing multiple seeds, these accumulating in the (often resinous) cones until the branches that bear the cones are killed; the seeds are then released to colonise the charred ground. Seeds blackish brown, ovoid, wing conspicuous, ~0.4 cm long, reddish. Coates Palgrave 1990, Pauw & Linder 1997, Farjon 2005c. Distribution LESOTHO; MALAWI: Mt. Mulanje; MOZAMBIQUE; SOUTH AFRICA: Eastern Cape, Free State, Gauteng, KwaZulu-Natal, Mpumalanga, Western Cape; ZIMBABWE. Habitat Fire-prone ericaceous scrub and grasslands, often on the margins of montane forest, to 2590 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. This species is becoming increasingly rare in South Africa due to fire damage and wood collection. Large trees are restricted to the most inaccessible locations. Illustration Coates Palgrave 1990; NT896. Taxonomic note There is considerable confusion as to the identity of the cedars of Mt. Mulanje (‘Mulanje Cedar’). Some consider them an endemic species (W. whytei Rendle), while others lump them into W. nodiflora. Pauw & Linder (1997) have shown that there are two taxa on the mountain, each with a distinct habit: W. whytei forms a broad, layered crown and does not coppice.

Plate 573. Widdringtonia nodiflora growing at Kirstenbosch. Widdringtonia is the only genus of conifer native to southern Africa – adding to its interest to growers. Image J. Grimshaw.

With its wide range – extending away from the winter-rainfall area of the Western Cape where it grows in the fynbos, into the summerrainfall area of eastern South Africa, and then northwards – Widdringtonia nodiflora at least offers a variety of provenances for experimentation. It is probable that most collections have been made from accessible populations in the Cape, but these are least likely to result in success in northern conditions; seed should be sought from its highest elevations, in the Drakensberg of eastern South Africa. Once again, though the species has often been tried, and is successful in California, there are no significant specimens outdoors in northern Europe.

Widdringtonia schwarzii (Marloth) Mast.

Willowmore Cedar

Small or large tree to 37 m, trunk straight and massive. Bark thin, fibrous, reddish grey, soon flaking. Crown slender and conical or columnar. Branchlets with densely packed mature leaves appear thread-like. Juvenile leaves glaucous-green, 1–2 × 0.2 cm; mature leaves 1–1.5 mm long, acute, with a dorsal gland; mature leaves on terminal branchlets, ovate. Male strobili 1–2 mm long. Female cones axillary, usually clustered or in whorls of four, subglobose, valvate, ~2 cm diameter. Seed scales dark brown, rough and woody, with a warty external face. Seeds flattened, with a conspicuous wing, ~0.4 cm long, reddish brown. Coates Palgrave 1990, Pauw & Linder 1997, Farjon 2005c. Distribution SOUTH AFRICA: Eastern Cape (Baviaanskloof and Kouga mountains). Habitat South-facing mountain slopes with poor soils, at c. 910 m asl. USDA Hardiness Zone 9. Conservation status Vulnerable. Illustration Coates Palgrave 1990. Cross-reference K324.

This narrow endemic, rejoicing in the Afrikaans name Baviaanskloofseder, comes from a summer-rainfall area and may thus be slightly more adaptable than the preceding two species discussed. In Oregon it grows well for Sean Hogan in his Portland garden, and he recommends some summer irrigation. The story behind the collection of this material is amusing: when Hogan and the late Parker Sanderson sought permission to

Section II. Species Accounts

Widdringtonia

take seed they met with incomprehension and were repeatedly asked how many trees they wanted, by an official who could not grasp that they were requesting only a pinch of seed. They did eventually get their permit, however, and some seeds (S. Hogan, pers. comm. 2007; Cistus Nursery online catalogue). Among the seedlings raised was one with particularly glaucous young growth which is now propagated clonally and sold under the name ‘Drakensberg Blue’. As specimens mature, this foliage contrasts well with the reddish bark. Widdringtonia schwarzii is evidently happy in dry Californian and Oregonian conditions, and could probably be tried in hot dry sites in Europe, especially in the current climate, but the only large specimen recorded by TROBI is one at Mount Congreve, Co. Waterford, that had reached 2.5 m in 1974.

ARAUCARIACEAE

WOLLEMIA

W.G. Jones, K.D. Hill & J.M. Allen

The discovery of the genus Wollemia, comprising the single species W. nobilis, in a gorge not far west of Sydney, Australia, is the most remarkable and exciting botanical story of recent times. The similarity between extant and fossilised leaves of Wollemia has earned it the status of a living fossil – but it also qualifies as a ‘new tree’!

Wollemia nobilis W.G. Jones, K.D. Hill & J.M. Allen

Wollemi Pine

Tree to 40 m, trunk to 1.2 m dbh. Bark reddish brown, peeling in small, thin scales; in mature plants, bark deep, soft and spongy, with distinctive nodules to 1.5 cm long. Crown slender and columnar, but trees often branch from the base. Shoots terminated by a resting bud that is usually covered by a heavy white resinous secretion, sometimes called the ‘polar cap’. Major branches rather short, arching upwards or horizontal. Branches composed of distinctive repetitive growth units, in which the leaves are initially small and scalelike, gradually increasing in length; these units giving the stems a modular appearance. Juvenile leaves distichous, dark green above and glaucous below, 0.3–8 × 0.2–0.5 cm, linear to narrowly triangular, apex obtuse. Adult leaves in four rows, decurrent, leathery, dull light green to dark green, 0.3–4 × 0.4–0.8 cm, no distinct midrib, apex rounded. Male strobili terminal on first-order leafy shoots, 10 × 2 cm, microsporophylls numerous (over 500 per strobilus), dark reddish brown. Female cones terminal on first-order leafy shoots, often on branches above those bearing male strobili; cones sessile, globular to ellipsoid, 12.5 × 10 cm, green, turning brown later, shedding bract scales. Bract-scale complexes are formed, from fusion of the seed scales and the bracts, such that the component parts are indistinguishable. These complexes are numerous (over 300 per cone), flattened, roughly rhombic, 1.2–1.7 × 1.4–2.2 cm, with a conspicuous recurved point, each bearing one seed. Seeds pale brown, rectangular to cuneate, 0.7–1.1 × 0.5–0.7 cm including a narrow, circumferential wing. Jones et al. 1995. Distribution AUSTRALIA: New South Wales (Wollemi National Park). Habitat Known from a single almost inaccessible sandstone gorge system in the Blue Mountains, where the trees grow in acidic soils alongside a permanent stream. USDA Hardiness Zone 8–9. Conservation status Critically Endangered. Fewer than 100 mature trees of Wollemia are known to exist in the wild, and their genetic diversity is extremely low. They are threatened by fire, poor regeneration, competition with other trees, and pathogens. Illustration Jones et al. 1995, Farjon 2001, Pastoriza-Piñol 2007, and many others; NTxi, NT20, NT898, NT900. Taxonomic note The taxonomic affinities of Wollemia are relatively unambiguous; the broad leaves with no central midrib and the large female cones with fully fused bract-scale complexes clearly place these plants in the Araucariaceae. Unique features of Wollemia are the bark (sometimes likened to bubbling molten chocolate), and the terminal placement of the male strobili and female cones. Phylogenetic studies of the Araucariaceae suggest that Wollemia is sister to Agathis (Gilmore & Hill 1997).

897

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Wollemia

New Trees

Plate 574. Wollemia is proving to be much hardier than expected, perhaps partly due to the fact that it undergoes proper winter dormancy, with the apical bud protected under a resinous secretion often referred to as the ‘polar cap’. Image T. Kirkham.

Perhaps no other tree has generated such a frenzy of hype as Wollemia nobilis, whose Lazarus-like career has brought it straight from the age of the dinosaurs to the age of celebrity. Newspaper and magazine articles galore, scientific journals and a book (Woodford 2000) have covered it on paper, and at the time of writing it featured on ‘about’ 54,800 websites (according to Google, June 2008 – though for comparison, it should be noted, Quercus robur generated 1,030,000 hits!), including ‘the official home of the Wollemi Pine’ (www.wollemipine.com) (Wollemi Pine 2004–2008). A particularly useful website, however, is that provided by the Botanic Gardens Trust, Sydney, Australia (Botanic Gardens Trust 2008), and the very informative Wollemi Pine Recovery Plan (see below) is also available online (New South Wales Department of Environment and Conservation 2006). These and the accounts by Jones et al. (1995) and Pastoriza-Piñol (2007) have provided the basis of the following discussion. The tale of the plant’s discovery in 1994 by the adventurous David Noble of the New South Wales National Parks and Wildlife Service has been frequently recounted, and need only be briefly recapitulated here. While exploring a gorge in the Wollemi Wilderness – a particularly remote and rugged tract of the Wollemi National Park (which appropriately derives its name from an Aboriginal word meaning ‘look around’ or ‘watch your step’) – Noble came across a small group of trees that he did not recognise and collected a fragment for identification. Further specimens were collected, the species was quickly described and information about it was released, triggering intense interest worldwide. Not the least extraordinary part of the story was that this tree, promptly if inaccurately dubbed the ‘Wollemi Pine’, was growing within 200 km of Sydney. There were not very many specimens, however, and even after the location of another group in 1994 and a third in 2000, all within 2–3 km of each other in the same canyon system, there are still fewer than 100 adult individuals known in the wild, plus 200–300 juveniles. The largest tree (known as King Billy) is 40 m high, and estimated to be over 1000 years old, but the range of size classes in the population suggests some recruitment from seed. They also regenerate vegetatively, from meri-

Section II. Species Accounts

stems below the bark, and are capable of coppicing. The ultimate potential size for the species is unknown. Their native habitat is warm temperate rainforest in the bottom of the gorge, where there is a small stream. Owing to the extreme rarity and interest of the trees, access to the gorge where they occur is very strictly controlled and its location is kept secret, not only for fear of damage by human intruders but also to prevent contamination by alien fungi and parasites. A programme for management of the species, the Wollemi Pine Recovery Plan, is being implemented by the New South Wales Government Department of Environment and Climate Change (New South Wales Department of Environment and Conservation 2006). Not long after its discovery, the New South Wales National Parks and Wildlife Service, together with the Royal Botanic Gardens, Sydney, took the decision to propagate and distribute Wollemia commercially under licence, nationally and internationally, as a method of safeguarding its future survival. This innovative process provides collectors and horticulturists with a much sought-after tree while also raising funds for conservation of wild Wollemia and other threatened Australian plants. Much of the financing of the Recovery Plan (estimated at up to AUS $1,336,000) is expected to be derived from this income. Seed and propagating material were collected on early visits to the site, and the first tree to be publicly unveiled was planted in the Royal Botanic Gardens, Sydney in 1998. Seedlings were presented to Kew in 1997, and there was a specimen growing happily (unlabelled) in the Temperate House well in advance of its ‘first planting’ there by Sir David Attenborough in 2005, outside the Orangery. The contract for the commercialisation of Wollemia was awarded to the Queensland Forestry Institute and Birkdale Nursery in 1999, and later that year they received 500 plants from the Royal Botanic Gardens, Sydney. From these, approximately half a million young plants have been produced, mostly as cuttings, and these in turn have been made available worldwide through selected nursery partners, starting in 2006 – at premium prices. A young Wollemia of approximately 50 cm in a three-litre pot cost £97 on first release in the United Kingdom (though the price in continental Europe was much cheaper, at €97!), and at the time of writing trees up to 180 cm tall were available in the United Kingdom for £1000 (Wollemi Pine 2004–2008). These small individuals generally available represent the second wave of the introduction, however, which started with an auction of the ‘Wollemi Pine Collectors Edition’, comprising almost 300 plants grown by the Royal Botanic Gardens, Sydney from cuttings of known, named parent trees in the gorge. The auction was conducted by Sothebys in October 2005, in the gardens, and achieved the expected press coverage. Bidding was brisk and the second lot, of two specimens propagated from the Bill Tree and the de Carvalho Tree, was acquired for Worcester College, Oxford via an earlymorning telephone bid (E. Wilson, pers. comm. 2006). Now planted permanently in the college grounds, these two trees are among the very select group of ‘originals’ in Britain. Another auctioned specimen reached Tregothnan, Cornwall, where in 2008 it became the first plant outside Australia known to have produced female cones (Tregothnan 2008); specimens at Kew had earlier produced male cones (T. Kirkham, pers. comm. 2008). Import regulations prevented American collectors from taking part in the auction, and the first commercial plants were released there in 2007, though it had been growing in a few arboreta prior to this (S. Hogan, pers. comm. 2008). The introduction of Wollemia is in many ways reminiscent of those celebrated conifer introductions in the 1840s and ’50s, of Sequoia and Sequoiadendron, which

Wollemia

899

900

Wollemia

Plate 575. David Noble, pictured here with the first specimen of Wollemia nobilis to be planted outside at Kew. The epithet nobilis is a nice pun, conveying ‘noble’ in the dictionary sense, but with obvious reference also to the discoverer of this remarkable tree. Image T. Kirkham.

New Trees

also sold for celebrity prices, or that of Metasequoia in 1948. Whether Wollemia will perform so well, and stand to be recognised as the tree of the 2000s, remains to be seen. When work started on New Trees in 2004 there were no specimens growing outdoors in our area, and there was some discussion as to whether it should be on our list for inclusion. The first tree at Kew, planted near the Orangery in 2005 and enclosed in a cage for its protection, is now (in 2008) over 2 m tall, exceeding the top of the cage and threatening to escape at the sides. It has shown no evidence of any perturbation by winter weather, although temperatures have not fallen below –5 ºC. Others have now been planted, in large numbers it seems, in gardens and collections throughout western Europe, and the story seems to be that they are surviving winters well both in Europe and in parts of eastern North America. At Plant Delights Nursery, Raleigh in North Carolina a specimen planted in February 2007 has withstood –10 ºC on numerous occasions over two winters, and has tolerated fierce summer temperatures over 40 ºC with equanimity. This individual is now one metre tall; a second, however, planted at the same time but in a drier situation, has grown much more slowly (T. Avent, pers. comm. 2008). In addition, in 2008 Tony Avent planted an allee of Wollemia at Juniper Level Botanic Garden, adjacent to Plant Delights Nursery. Plants are surviving as far north as Washington DC, although several have been lost at the US National Arboretum, perhaps because they were planted too late in the season and did not have time to become established (R. Olsen, pers. comm. 2008). The apparent hardiness of Wollemia has come as a surprise to most gardeners – perhaps principally due to the stereotypical image of sunbaked Australia, rather than through rational analysis of its habitat. The Wollemi Pine Recovery Plan provides a chart of air temperatures for one year of monitoring at the primary site and demonstrates that mean winter temperatures there are somewhere around 5–7 ºC, with actual minima in the three midwinter months hovering around zero. Summer maxima are at around 30 ºC, with mean summer temperatures between 15 and 20 ºC (New South Wales Department of Environment and Conservation 2006). This is not very different to temperatures experienced in maritime western Europe. Beyond the current temperate climate in Wollemi National Park, and any ancestral hardiness ‘left over’ from earlier times, an important factor in its hardiness must be that it has a definite dormancy, the terminal bud shutting down when conditions are unsuitable for growth and being protected to some extent by the resinous exudate of the ‘polar cap’. In production in Australia potted plants seem to require an acidic medium (less than pH 6), and in the wild the soil is pH 4.5. At Evenley Wood, Northamptonshire Tim Whiteley (pers. comm. 2008) has specimens growing on both acidic (pH 5.5) and alkaline (pH 8) soil, and reports no difference in vigour. The Worcester College specimens, however, are in soil of about pH 7–7.2 (planted out in 2006), and by early summer 2008 were looking decidedly unhappy, with poor growth and yellowish foliage. After treatment to reduce the pH they responded extremely quickly, re-greening and producing normal shoots within a couple of weeks (E. Wilson, pers. comm. 2008) – suggesting that any apparent tolerance of alkalinity may be shortlived. In general, plants of Wollemia respond well to fertilisers, and can grow surprisingly

Section II. Species Accounts

Wollemia

fast in cultivation. Yet another point of interest with this remarkable species is that it is the only member of the Araucariaceae to have two forms of mycorrhizal association, wild specimens having been found to have both arbuscular mycorrhizae and ectendomycorrhizae (Botanic Gardens Trust 2008). Cultivated specimens are often sold with a sachet of mycorrhizal inoculant, to be deployed on planting. Other fungal associations are less happy. In cultivation Wollemia is susceptible to diseases caused by Botryosphaeria fungi, and to dieback or root rot from infection by the aggressive water-borne pathogen Phytophthora cinnamomi, common in Australia (as well as having a very broad range elsewhere), spores of which can be carried on shoes – which is one reason why access to the native trees is so carefully restricted. Unfortunately it seems that wild trees have already been infected, possibly via unauthorised visitors (New South Wales Department of Environment and Conservation 2006). Its detractors may say that it looks like a fake Christmas tree made out of plastic seaweed (perhaps to be decorated with dinosaur models, as suggested by Tony Avent in the 2008 Plant Delights Nursery catalogue), but Wollemia nobilis is a remarkable tree with a potential that is as yet almost totally unexplored.

CUPRESSACEAE

XANTHOCYPARIS

Farjon & Hiep

Golden-cypresses Xanthocyparis is the most recently described conifer genus, X. vietnamensis having been discovered in northern Vietnam in 1999 (Farjon et al. 2002, Farjon 2005c). DNA and morphological studies indicated that its closest relative was the North American Nootka Cypress, Chamaecyparis nootkatensis, which was subsequently transferred into Xanthocyparis (Farjon et al. 2002, Little et al. 2004), and the close relationship between these two remains undisputed. They are medium-sized to large evergreen trees, X. nootkatensis reaching 30 m tall, with a remarkably regular, conical crown, while X. vietnamensis reaches 15 m at most, with an irregular or flat-topped crown. The bark peels into stringy, longitudinal strips. Branching is rather irregular, and the primary branches are often pendulous; the leader shoot is pendent. The juvenile leaves are linear and the mature leaves are scale-like. This is rather common in the Cupressaceae; in X. vietnamensis, however, juvenile, mature and transitional leaves may all occur on branches of the mature tree, and this feature occurs naturally in only a few other taxa (for example, Callitris macleayana (F. Muell.) F. Muell., and Juniperus chinensis) – though it may also result from mechanical damage such as coppicing. Juvenile leaves are radially arranged in alternate whorls of four, while transitional leaves are decussate. The mature leaves are decussate and strongly dimorphic in shape and size, with the lateral pair flattened and arranged on a plane. This characteristic, common in the Cupressaceae, results in the leaf-covered branchlets appearing to be bilaterally flattened. The male strobili are terminal and solitary, on lateral branchlets with small, mature scale leaves. The female cones are terminal and solitary, on lateral

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Xanthocyparis

Plate 576. Xanthocyparis vietnamensis has the unusual feature of producing juvenile growth even on mature trees – just visible in the background here, with mature-phase growth seen in front. Image J. Grimshaw.

New Trees

branchlets with regular scale leaves. The cones are roughly spherical, mature in two years, and change from blue-green to purplish brown. The seed scales are arranged in two (or rarely three) decussate pairs, fused at the base. The scales have a prominent, central umbo, and at maturity open to release the seeds. The seeds are flattened and have two lateral wings. The two species of Xanthocyparis can be easily separated by their distinct habits and by the mixture of leaf types on mature branches of X. vietnamensis; in reality, confusion is anyway unlikely, as X. vietnamensis is virtually unknown in cultivation while X. nootkatensis is extremely common. Hardly had the genus Xanthocyparis been erected than arguments began over its name. Little et al. (2004) claimed that X. nootkatensis had previously been placed in the genus Callitropsis Oerst. (non Callitropsis Compton), and that in consequence this name had priority over Xanthocyparis, rendering the genus Xanthocyparis Farjon & Hiep illegitimate if it contains X. nootkatensis. However, the combination Callitropsis nootkatensis was not validly published by Oersted in 1865 (who only suggested in a footnote that the Nootka Cypress might belong here), and the combination Callitropsis nootkatensis (D. Don) Florin was only made in 1979. The name Callitropsis in Oersted’s rather confused sense had lain completely forgotten until resurrected by Florin, and then by Damon Little and his colleagues; in the meantime, however, the name Callitropsis had been applied by Compton in 1922 to a genus of conifers endemic to New Caledonia (now correctly Neocallitropsis). On its ‘rediscovery’, Callitropsis should have been regarded as a nomen confusum (and indeed nomen ambiguum), and should have been abandoned. Instead, Little (2006) picked it up and ran with it, insisting on its priority over Xanthocyparis and adopting it (on the grounds of the inclusion within it of C. nootkatensis) as the generic name for his segregation of American Cupressus from Eurasian Cupressus, resulting in the publication of 19 new names in Callitropsis for the American cypresses and X. vietnamensis (see also pp. 290–291) – the name Callitropsis for these trees has already become widely adopted by botanists and gardeners in North America (D. Hinkley, pers. comm. 2007). A proposal to conserve the name Xanthocyparis over Callitropsis (Mill & Farjon 2006) was quickly submitted to the Committee for Vascular Plants of the International Association of Plant Taxonomists (the body that adjudicates on matters of disputed botanical nomenclature). This panel decided in favour of Xanthocyparis (Brummitt 2007), on the grounds that Callitropsis has most widely been used in Compton’s sense, as a name for the New Caledonian Neocallitropsis, and for the sake of stability in the nothogeneric name of the Leyland Cypress, which can now become ×Cuprocyparis (a relatively small change from the familiar ×Cupressocyparis). The result is that Xanthocyparis must be used for any genus including the Nootka Cypress – there are times when it is easiest to take refuge in vernacular names – unless this reverts to its original name, Cupressus nootkatensis D. Don, as some would suggest. If anyone holds a strong enough view that the American cypresses are indeed distinct from the Eurasian taxa, the way is now open to make

Section II. Species Accounts

Xanthocyparis

all of them Xanthocyparis, including ×C. leylandii. As mentioned on p. 292, however, several authors consider that the two golden-cypresses are best recognised as Cupressus (Silba 2005, Xiang & Li 2005, Rushforth 2007).

Xanthocyparis nootkatensis (D. Don) Farjon & Harder

Nootka Cypress

Syn. Cupressus nootkatensis D. Don, Chamaecyparis nootkatensis (D. Don) Spach, Callitropsis nootkatensis (D. Don) Florin

This well-known species was described in detail by Bean (B596) and Krüssmann (K83), under the name Chamaecyparis nootkatensis (D. Don) Spach.

Xanthocyparis vietnamensis Farjon & Hiep

Vietnamese Golden-cypress

Syn. Callitropsis vietnamensis (Farjon & Hiep) D.P. Little, Cupressus vietnamensis (Farjon & Hiep) Q.P. Xiang & J. Li Tree to 15 m, trunk straight and slender, to 0.5 m dbh. Bark smooth and purplish brown to reddish brown, becoming soft, fibrous and greyish brown in older trees. Crown initially pyramidal, later spreading, irregular or flat-topped. Major branches long, spreading horizontally. Foliage branches numerous and drooping; those with juvenile leaves bushy, not flattened and sparsely branched; those with mature leaves rounded in outline, flattened and with up to four orders of branching. Juvenile leaves green above and with two whitish bands below, arranged in whorls of four, decurrent, monomorphic, free distal section 15–20 × 1.5–2 mm, linear, apex acute; stomata in six to seven rows, within the abaxial whitish bands, parallel to the leaf axis. Mature leaves green, decussate, dimorphic, imbricate, 1.5–3 × 1–1.3 mm, lateral leaf pairs slightly longer than facial leaf pairs, conduplicate, initially decurrent then spreading, margins denticulate, apex acute; facial leaves narrow, ovate-rhombic, keeled, margins minutely denticulate, apex acute or acuminate; stomata inconspicuous, mainly adaxial, covered in wax. Male strobili terminal and solitary, ovoid, 2.5–3.5 × 2–2.5 mm, green to yellowish brown. Seed cones solitary or in groups of two to three, subglobose, 9–11 × 10–12 mm, cone green, ripening to dark brown, persistent after seed dispersal. Seed scales in two (or rarely three) decussate pairs, valvate, outer surface smooth then furrowed, inner surface reddish brown and with faint grey or whitish seed scars, one to three seeds per scale; umbo prominent, 1–2.5 mm long. Seeds eight to nine per cone, reddish brown and ovoid, 4.5–6 × 4–5 mm including wings; seed wings two, lateral, 0.5–1 mm wide, membranous. Farjon et al. 2002, Farjon 2005c. Distribution VIETNAM: Ha Giang (locally in the Bat Dai Son mountain system). Habitat On limestone ridges in montane cloud forest, between 1060 and 1180 m asl. The climate is subtropical, but wet most of the year. Xanthocyparis vietnamensis grows in thin pockets of soil. USDA Hardiness Zone 9 (?). Conservation status Critically Endangered. This species is restricted to only a handful of sites in a 50 km2 area, with an estimated 560 trees, and is prized for its hard, fragrant, yellow-brown timber (IUCN 2007). Illustration Farjon et al. 2002, Cribb 2004, Luu & Thomas 2004, Farjon 2005c; NT902. Taxonomic note Despite the stance of both Farjon and Little that Xanthocyparis is a distinct genus, however interpreted, it is clear that there are several botanists who believe the two species belong in Cupressus, resulting in a regrettable plethora of publications: Cupressus vietnamensis Q.P. Xiang & J. Li (2005), which has priority; C. vietnamensis (Farjon & Hiep) Silba (2005); C. vietnamensis (Farjon & Hiep) Rushforth (2007).

The importance of the discovery of a strange, stunted-looking conifer on a limestone ridge in northern Vietnam, by an expedition in1999 comprising Phillip Cribb, Leonid Averyanov and Nguyen Tien Hiep, was not at first appreciated, and it took a second, unconnected collection in the same year for the species to be recognised as new (Cribb 2004). Its distinctness triggered the creation of the genus Xanthocyparis and the taxonomic dispute that followed. In subsequent years it has been visited in its very limited range by several groups and material has been brought into cultivation. These limestone crags are home to a remarkable diversity of plants, and growing with Xanthocyparis vietnamensis are representatives of up to seven other genera of gymnosperms: Amentotaxus, Nageia, Pinus, Podocarpus, Pseudotsuga, Taxus and Tsuga (Rushforth 2007). Whether the Xanthocyparis is a relict of a cooler climate in

903

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Xanthocyparis

New Trees

the area or truly adapted to a tropical existence is unclear, but this will have great bearing on the chances of its success in cultivation. In the United Kingdom material collected in 2002 on the Northern Vietnam First Darwin Expedition (nos. 140, 141, 142), and by T.Q. Thao in 2003, grown at the Royal Botanic Garden Edinburgh as part of the International Conifer Conservation Programme, has been passed to a few selected institutions and gardens for safekeeping. When seen in the greenhouses in Edinburgh in 2005 plants were showing the remarkable combination of adult and juvenile foliage for which the species is renowned. Under glass they have grown well, but it is not yet known whether the species will be hardy in our area – or whether its diminutive stature in the wild is a result of its environment or its genes. It is not apparent whether it is currently in cultivation in North America.

ULMACEAE

ZELKOVA

Figure 97 (opposite). Zelkova schneideriana: branch from the outer crown, with small leaves and fruits (A); branch from the inner crown, with large leaves (B); with fruits (C).

Spach

The six species of Zelkova occur in temperate Eurasia, with three species in the Mediterranean and western Asia, and three species in eastern Asia (Denk & Grimm 2005). Zelkovas are deciduous trees with smooth bark. Unlike the elms, the branchlets are never corky or winged. The leaves are in two distinct rows; they have pinnate venation and each vein extends to the leaf margin, where it terminates in a tooth. There are two stipules at each node, though these are caducous, leaving a pair of scars at the leaf base. Zelkova is polygamous. Staminate flowers are clustered in the lower leaf axils of young branchlets; the perianth is campanulate, with four to six (to seven) lobes, and the stamens are short. Pistillate and hermaphrodite flowers are solitary, or rarely in clusters of two to four, in the upper leaf axils of young branchlets, the perianth with four to six lobes. The fruit is a scarcely fleshy drupe with a dorsal keel; the perianth and stigma are persistent (Ainsworth 1989, Andrews 1994, Fu et al. 2003). Zelkova is one of the minor but important genera of trees, possessing few species but among them a handful of arboretum essentials. The magnificent Z. carpinifolia and Z. serrata are long established and well known (Andrews 1994), but Z. schneideriana shows signs of becoming an equally fine tree. The most recent addition to the genus is Z. sicula G. Di Pasquale, G. Garfì & Quézel, known only from a tiny population with limited genetic diversity in southeastern Sicily, where it was discovered in 1991. There it grows as a deciduous shrub, 2–3 m tall, with small, rounded, crenate leaves that are hairy on both sides. It is in cultivation in Italian botanic gardens and also at the National Botanical Conservatory of Brest, France (IUCN 1995–2006). Several cultivars of Z. serrata have made an appearance in recent decades, especially in the United States, including ‘Flekova’ (Green Vase) which is particularly commended by Dirr (1998), ‘Spring Grove’, ‘Urban Ruby’ and ‘Village Green’. These vary somewhat in growth habit, vigour and autumnal colouring, and ‘Flekova’ and ‘Village Green’ are considered resistant to Dutch elm disease (DED) (van den Berk 2002), which may be an important consideration. Unfortunately, as close relatives of

Section II. Species Accounts

Zelkova

A

B

C

5 mm

1 cm

905

906

Zelkova

New Trees

the elms, Zelkova are susceptible to many of the same problems of disease and foliage pests as Ulmus. They can be killed by DED if infected, but there is some evidence that they are less attractive to the Scolytus beetles that carry the fungus, and that infection is by no means always fatal (Andrews 1994). Damage to the foliage from the Elm Leaf Beetle and other insects can, however, be quite severe. They seem to grow well in any reasonable soil. Propagation is from seed or as cuttings, with selected cultivars being grafted onto seedling Z. serrata. Z. abelicea (Lam.) Boiss. B776, S528, K465 Z. carpinifolia (Pall.) K. Koch B777, S528, K465

Zelkova schneideriana Hand.-Mazz. Tree to 35 m, 0.8 m dbh; crown densely branched. Bark purplish red to grey, scaly and peeling. Branchlets grey or greyish brown, covered with whitish pubescence. Leaves thickly papery, 3–10 × 1.5–4 cm, ovate to elliptic-lanceolate, upper surface greenish brown and strigose, lower surface green to reddish purple and densely pubescent, 8–15 secondary veins on each side of the midrib, margins serrate to crenate, apex acuminate to acute; petiole 0.3–0.7 cm long, pubescent; stipules linear to lanceolate, to 0.9 cm long. Staminate flowers solitary or in clusters of two to three; pistillate and hermaphrodite flowers usually solitary. Drupe pea-green, subsessile, 0.2–0.4 cm diameter, covered in an irregular network of ridges. Flowering April, fruiting September to November (China). Fu et al. 2003. Distribution CHINA: Anhui, Fujian, southern Gansu, Guangdong, Guangxi, Guizhou, southern Henan, Hubei, Hunan, Jiangsu, Jiangxi, southern Shaanxi, southeast Sichuan, southeast Xizang, Yunnan, Zhejiang. Habitat Along streams, between 200 and 1100(–2800) m asl. USDA Hardiness Zone 5. Conservation status Not evaluated. Illustration Andrews 1994, Valder 1999, Fu et al. 2003; NT905, NT907. Cross-references S529, K467. Taxonomic note Zelkova schneideriana appears to be closely related to Z. serrata, differing in its densely grey-white pubescent new shoots (glabrous or sparsely pubescent in Z. serrata) and in its much hairier leaves. Both differ from the other Chinese species, Z. sinica, in having smaller, rough-surfaced drupes (0.5–0.7 cm in Z. sinica, with a smooth surface) (Fu et al. 2003). Richard Olsen has drawn attention to Ohwi’s (1965) tentative linking of Z. serrata var. stipulacea Makino from Honshu with Z. schneideriana: var. stipulacea has ‘leaves pilose on both surfaces’, suggesting that there is variability in this feature in Z. serrata. It could be that Z. schneideriana is in fact a western expression of Z. serrata.

Zelkova schneideriana was discovered in western China by that interesting character, the Austrian botanist Heinrich Handel-Mazzetti, whose explorations in China are often overlooked by anglophones in favour of the more accessible tales of Wilson, Farrer, Forrest, Kingdon-Ward et al. (although his account of his travels is now available in English: Winstanley 1996). He named it in honour of his colleague Camillo Schneider, with whom he had travelled in China (1913–1915) and who was responsible for the naming of many Chinese discoveries. Handel-Mazzetti and Schneider did not, however, introduce seed of Z. schneideriana. The earliest introduction attributed to Z. schneideriana was of seed presented to the Bureau of Plant Industry of the US Department of Agriculture by the director of the Sun Yat-Sen Tomb and Memorial Park Commission, Nanjing, China on 16 April 1934 and given the accession number PI 105331. Originally received as Z. serrata, it was identified as Z. schneideriana by the late US National Arboretum taxonomist Frederick G. Meyer in 1973 (USNA herbarium specimen F.G. Meyer s.n. 19 Sept. 1973), and by research geneticist Frank Santamour, Jr., and confirmed by Stephen Spongberg in 1986 (US National Arboretum records, via R. Olsen, pers. comm. 2009). From this has grown a beautiful, round-crowned tree at the Glenn Dale Plant Introduction Station, Maryland, noted for its magnificent red autumn display. By the late 1980s several further specimens had been planted in the Washington DC area, including what is now a nice tree in the grounds of the US Capitol (R. Olsen, pers. comm. 2009).

Section II. Species Accounts

Elsewhere the early introductions of Z. schneideriana are somewhat obscure. According to Andrews (1994) it was growing in France in the Arboretum National des Barres by 1965, but no earlier records can be traced. New material began to arrive from China in the late 1970s, and most trees in cultivation derive from introductions made in this period, specimens now being found in collections across our area. Among the first known in the United Kingdom were grown by Harry Hay in his Surrey garden, from Chinese seed received in 1977. The young trees did well at first, then died back and resprouted as multistemmed coppices. By 1993 they were 6 m tall, but in the 1990s most succumbed to inundation in a very wet winter: the sole survivor has three stems and is now 8 m tall (Andrews 1994; H. Hay, pers. comm. 2008). Kew also received seed in 1977, from Nanjing, and trees from this were 7 m and 8 m tall in 2001 (TROBI). Similarly, the US National Arboretum received seed from the Chinese Academy of Forestry in 1981, and the oldest specimen at the Arnold Arboretum was accessioned in 1979. A NACPEC expedition introduced seed from Hubei in 1994, from which trees are growing in several American collections, including the Morris Arboretum where it does well. The finest seen in the research for New Trees was a specimen of about 12 m (53 cm dbh) in 2006, at the JC Raulston Arboretum (planting date unknown), forming a good rounded crown from four principal vertical stems. The British champion was 10 m (28 cm dbh) in 2006, growing at the Royal Horticultural Society’s garden Rosemoor, in Devon (TROBI). In arboreta, where it is grown as a specimen in the open it is most often seen as a dome-shaped tree with wide-spreading limbs – sometimes wider than tall – but it is evident that in woodland conditions it can develop a much taller, narrower shape (Valder 1999). The foliage is a dullish green through the summer. It can turn a fabulous red in autumn, perhaps especially in North America, but does not invariably do so: at Arboretum Wespelaar it does not colour well, and Koen Camelbeke (pers. comm. 2008) also comments that it is ‘one of those plants that one goes by without paying any attention to it’. Many, however, would disagree with this, and consider Z. schneideriana a very worthy new tree.

Z. serrata (Thunb.) Makino B778, S529, K467 Z. sinica C.K. Schneid. B779, S529, K467 Z. ×verschaffeltii (Dipp.) G. Nicholson K467

Zelkova

907

Plate 577. The autumn colours of Zelkova schneideriana PI 105331 at Glenn Dale, Maryland are superb. Image R. Olsen.

Section III. Appendices Appendix 1. Focus Arboreta In the research for this book many arboreta were visited, to observe and make notes on the trees, and information was also obtained in correspondence and conversation with owners and curators. To enable comparison of growing conditions, data relating to a selection of important arboreta across our area are presented below. These details have mostly been provided by representatives of the arboreta, and are believed to be accurate at the time of going to press. Sources of meteorological information vary, depending on the availability of records; some was supplied from local weather stations. In cases where details are not supplied, this is because no data were available. The Arnold Arboretum of Harvard University Harvard University and the City of Boston: 125 Arborway, Boston, Massachusetts 02130, USA Tel. +1 (0)617 524 1718 (ext. 100), E-mail [email protected], Website www.arboretum.harvard.edu

The Arnold Arboretum comprises 107 ha of varying terrain, from low-lying, marshy areas to several distinct hills and ridges. The soils are also considerably variable, including silts, sands and clays. The arboretum was founded in 1872 when the President and fellows of Harvard College became trustees of part of the estate of a wealthy New England merchant, James Arnold. Charles Sprague Sargent was appointed director, and with landscape architect Frederick Law Olmsted, developed the road and pathway system and delineated the grounds, on land in the Jamaica Plain area of Boston previously given to Harvard by Benjamin Bussey. Specialist collections of Acer, Carya, conifers, Fagus, Magnolia, Quercus, Rosaceae. Catalogue available online. Altitude 15–79 m. Zone 6. Rainfall 1102 mm. January mean temp. 1.3 °C; July mean temp. 19.3 °C, July mean max. temp. 23.1 °C.

Bedgebury, The National Pinetum The Forestry Commission: Bedgebury Pinetum, Goudhurst, Kent TN17 2SL, UK Tel. +44 (0)1580 211044, E-mail [email protected], Website www.forestry.gov.uk/bedgebury

Started in 1925 as a partnership between the Forestry Commission and Kew, since 1965 the Pinetum has been managed by the Forestry Commission. It comprises 130 ha of gently rolling landscape with lakes, streams, a very rich native flora and fauna, and one of the most important conifer collections in the world. In addition to the botanical collection there are old forestry trial plots of various species. There are nine different soil types, pH 3.5 to 6.5 (average 4.5), and they are particularly nutrient deficient. The emphasis has always been on conifer species and cultivars but there are also fine examples of broadleaf trees and shrubs. Conservation of conifers has become important, and many of the new plantings are from collections from the wild by Bedgebury staff. National Plant Collections of Chamaecyparis lawsoniana cultivars, ×Cuprocyparis leylandii, Juniperus, Thuja, Taxus. A list of taxa cultivated is available online (see www.bedgeburypinetum.org.uk).

Plate 578 (opposite). Acacia (Vachellia) caven. Elqui Valley, Monte Grande, Chile. Image M. Gardner.

910

Appendix 1. Focus Arboreta

Altitude c.130 m. Zone 8–9. Some meteorological data from Cranbrook, Kent (92 m) (Weatherbase 2008). Rainfall 680 mm. January mean 3 °C, absolute min. –18.4 °C (January 1940) (Bedgebury records); July mean 16 °C, July mean max. 21 °C, absolute max. 32 °C (in past five years).

New Trees

Altitude 15–137 m. Zone 8. Rainfall 2400 mm. January mean min. 1.9 °C, absolute min. –13.9 °C (2006); July mean max. 21.9 °C, absolute max. 29.6 °C.

Chicago Botanic Garden National Botanic Garden of Belgium State-owned: Domein van Bouchout, Nieuwelaan 38, B-1860 Meise, Belgium Tel. +32 (0)2 260 09 20, E-mail offi[email protected], Website www.botanicgarden.be

This 92 ha estate has gently undulating terrain with two small lakes and a stream forming a valley through the centre. The soil is an alkaline loam over clay. Belgium’s previous national botanic garden was in Brussels, but increasing urbanisation limited growth of the garden, so in 1938 the Belgian government purchased the current site, the Bouchout estate in Meise, from the royal family. In 1939 the first buildings and greenhouses were set up and the first plants were moved from Brussels to Meise. Specialist collections of Acer, Magnolia, Quercus. Catalogue available online (www.br.fgov.be/RESEARCH/ COLLECTIONS/LIVING/LIVCOL/index.html). Altitude 33 m. Zone 8. Rainfall 780 mm. January mean 2.6 °C, January mean min. –0.3 °C, absolute min. –20.2 °C (1981); July mean 17.1 °C, July mean max. 21.6 °C, absolute max. 38.8 °C (June 1947).

Chicago Horticultural Society: 1000 Lake Cook Road, Glencoe, Illinois 60022, USA Tel. +1 (0)847 835 5440, Website www.chicagobotanic.org

Situated in northern Cook Co., the Chicago Botanic Garden comprises 156 ha of gently rolling hills. Half of it is landscaped and the rest includes natural woodland, lakes and the Skokie River. Soils are primarily heavy silt-clays. Originally leased by the Chicago Horticultural Society in 1965, the garden was opened to the public in 1972. Landscaping began in 1967 and continues to this day. There is an extensive collection of cultivated, native and aquatic plants. Specialist collections of Amelanchier, Cornus (non-bracted), Ginkgo, native Quercus, Salix, Thuja plicata. Catalogue available online; printed copies available at the Plant Information Desk (Visitor Center) and in the Library (Regenstein Education Building). Altitude 200–210 m. Zone 5. Rainfall 930 mm. January mean –4 °C, January mean min. –8 °C, absolute min. –27 °C (January 1982); July mean 24 °C, July mean max. 28 °C, absolute max. 41 °C (July 1995).

Dawyck Botanic Garden

Benmore Botanic Garden

Royal Botanic Garden Edinburgh: Stobo, Peebles, The Borders EH45 9JU, UK

Royal Botanic Garden Edinburgh: Dunoon, Argyll PA23 8QU, UK

Tel. +44 (0)1721 760 254, E-mail [email protected], Website www.rbge.org.uk

Tel. +44 (0)1369 706261, E-mail [email protected], Website www.rbge.org.uk

This garden extends over 25 ha of north-facing slopes above the River Tweed, on soils derived from glacial drift, so stony, free-draining and acidic. Dawyck has benefited from over 300 years of sustained tree planting, including many first introductions. The historic tree collection includes many fine conifers from North America and Asia (particularly China and Japan). Dawyk became a regional garden of the Royal Botanic Garden Edinburgh in 1978, and has many new plantings of shrubs, deciduous trees and conifers, particularly from cool temperate areas of the northern hemisphere. Specialist collections of Betula, Cotoneaster, Sorbus, Spiraea. National Plant Collections of Larix, Tsuga. Catalogue available online.

Benmore comprises the south-, east- and west-facing slopes of the Eachaig valley in western Scotland, with acid to strongly acid soil (to pH 3.9). Tree plantings date back to the 1820s; the famous avenue of Sequoiadendron giganteum was planted in 1863. Since becoming a regional garden of the Royal Botanic Garden Edinburgh in 1928, the collection’s diversity and wild-origin status has risen. Plants from the Sino-Himalaya and temperate rain-forest regions of the world have been targeted, resulting in phytogeographic plantings from Bhutan, Chile, Japan and Tasmania. Specialist collections of Abies, Cephalotaxus, Picea, Nothofagus, Rhododendron. Catalogue available online.

Altitude 200–210 m. Zone 8. Rainfall 1000 mm. January mean 3.4 °C, January mean min. –0.6 °C, absolute min. –19.2 °C

Section III. Appendices

Appendix 1. Focus Arboreta

(December 1995); July mean 14.6 °C, July mean max. 19.8 °C, absolute max. 29.8 °C (July 2006).

Hergest Croft

Royal Botanic Garden Edinburgh

Tel. +44 (0)1544 230160, E-mail [email protected], Website www.hergest.co.uk

Royal Botanic Garden Edinburgh: 20A Inverleith Row, Edinburgh EH3 5LR, UK Tel. +44 (0)131 5527171, Website www.rbge.org.uk

Founded as a physic garden in 1670, the Royal Botanic Garden relocated to its third and present site at Inverleith, north of the city centre, in 1820. The site comprises 32 ha of undulating land with a sandy, acidic soil. It has 1.5 ha of glass, including an elegant Temperate Palm House, built in 1858, which is still the tallest in Britain. The Garden is funded by the Scottish Executive Environment and Rural Affairs Department, and through scientific research and education, explores and explains the world of plants. Specialist collections of conifers, Ericaceae (particularly Rhododendron), Gesneriaceae, Umbelliferae, Zingiberaceae. Catalogue available online.

911

Mr Lawrence Banks: Hergest Estate, Kington, Herefordshire HR5 3EG, UK

Hergest Croft comprises 30 ha of hilly land with neutral soil. The collection was started in 1895 by William Hartland Banks, though some specimens date back to the 1860s. W.H. Banks bought extensively from Veitch’s Nursery from 1900 onwards, but also from Vilmorin and Chenault’s Nurseries in France. He also received plants from Werrington and Caerhays (UK). Richard Banks, whose special interests were Acer and Betula, subsequently extended the collection, with many plants coming from Hillier Nurseries. Since 1985 the arboretum has been cared for by Lawrence and Elizabeth Banks, and it has new plant accessions from China and elsewhere, from many contemporary collectors. National Plant collections of Acer, Betula, Zelkova.

Altitude 20–40 m. Zone 9. Rainfall 637 mm. January mean min. 0.7 °C, absolute min. –15.5 °C ; July mean max. 19 °C, absolute max. 27 °C.

Altitude 195–260 m. Zone 8. Rainfall 1000 mm. Temperature records are not kept, but in general winters are mild and summers cool. Winter temperatures below –5 °C are unusual, and the summer maximum rarely exceeds 27 °C.

National Botanic Gardens of Ireland – Glasnevin

The Sir Harold Hillier Gardens

State-owned: Glasnevin, Dublin 9, Ireland

Hampshire County Council: Jermyns Lane, Ampfield, Romsey, Hampshire SO51 0QA, UK

Tel. +353 (0)1 804 0300, E-mail [email protected], Website www.botanicgardens.ie

Glasnevin covers 19.5 ha of gently undulating terrain, including higher ground and the low-lying floodplain of the Tolka River. The soil is a shallow loam over gravel. Established by the (Royal) Dublin Society in 1795, aided by grants from the Irish Parliament, the gardens are Ireland’s premier botanical and horticultural institution. A public institution since 1878, they are now managed by the Office of Public Works. Since the early 1990s there has been major restoration and rejuvenation of the gardens, improving the Victorian glasshouses and constructing a new Library and National Herbarium building and Visitor Centre. A satellite arboretum at Kilmacurragh, Co. Wicklow is also managed by the National Botanic Gardens. Specialist collections of Acer, Arbutus, Cupressaceae, Ericaceae, Ilex, Pinaceae, Quercus, Rosaceae, Salix, Taxaceae. Catalogue available online. Altitude c. 20 m. Zone 9. Rainfall 724 mm. January mean min. 1.7 °C, absolute min. –19.6 °C (January 1982); July mean max. 19.3 °C, absolute max. 27.8 °C.

Tel. +44 (0)1794 368787, E-mail [email protected], Website www.hilliergardens.org.uk

The Hillier Gardens (often called the Hillier Arboretum) were founded in 1953 by the late Sir Harold Hillier as a private arboretum surrounding his residence, Jermyn’s House. The Hillier family have been nurserymen around the nearby town of Winchester since 1864. The garden has been a charitable trust since 1977, with Hampshire County Council as sole trustee. The soil is mostly neutral on London clay, with an acidic area of Bagshot sand. The collection contains around 12,000 taxa, and is one of the most comprehensive anywhere, with both cultivars and wild-origin material. Twelve National Plant Collections, including Carpinus, Cornus, Corylus, Lithocarpus, Metasequoia, Pinus, Quercus (depository for the International Oak Society). A herbarium is maintained, with all specimens digitised. Catalogue available online. Altitude 27–60 m. Zone 9. Rainfall 750 mm. January mean 3.8 °C, January mean min. 1.0 °C; July mean 16.5 °C, July mean max. 21.1 °C.

912

Appendix 1. Focus Arboreta

New Trees

Howick Hall Gardens & Arboretum

Royal Botanic Gardens, Kew

Lord (Charles) Howick: Howick Hall, Alnwick, Northumberland NE66 3LB, UK

Royal Botanic Gardens, Kew: Richmond, Surrey TW9 3AB, UK

Tel. +44 (0)1665 577285, E-mail [email protected], Website www.howickhallgardens.org.uk

Tel. +44 (0)208 332 5000, E-mail [email protected], Website www.kew.org

Howick, near the Northumberland coast, has one of the United Kingdom’s largest collections of wild-origin plants, growing over an area of approximately 26 ha. Opened to the public in 2006, it accommodates a large number of seed-grown trees, arranged according to their country of origin. The collection was begun in 1985 and now includes over 11,000 trees, with a strong emphasis on the native trees of China and Japan. Although one of the youngest arboreta in the United Kingdom, Howick presents a huge diversity of species, many of which are recent introductions of known wild origin. Collections have been made during overseas expeditions, often in conjunction with Quarryhill Botanical Garden or the Royal Botanic Gardens, Kew. No catalogue available, but accessions may be found via the Asian Plant Database (see www.quarryhillbg.org/asianplantdatabase.html). Altitude c. 40 m. Zone 8. Rainfall 651 mm. January mean min. 1.3 °C; July mean max. 17.9 °C.

JC Raulston Arboretum North Carolina State University (NCSU): 4415 Beryl Road, Raleigh, North Carolina 27606, USA Tel. +1 (0)919 515 3132, Website www.ncsu.edu/jcraulstonarboretum

The JC Raulston Arboretum comprises 10 ha of gently rolling terrain on the boundary between the Piedmont Plateau and the Coastal Plain. Soils are brown sandy loam underlain by red clay; pH 5.0–6.0. The arboretum was founded in 1976 by the late Dr J.C. Raulston, a renowned plantsman and professor of horticultural science at NCSU, to educate horticulture students and evaluate new plants for southern landscapes. Originally called the NCSU Arboretum, it was renamed the JC Raulston Arboretum in 1997. Today it is a nationally acclaimed garden, with one of the largest and most diverse collections of landscape plants in the southeastern United States. Specialist collections of Acer palmatum, Aesculus, Cercis, conifers, Ilex, Magnolia, Quercus (Mexican spp.), Styracaceae. Catalogue available online. Altitude c.140 m. Zone 7b. Rainfall 1120 mm. January mean min. –1.2 °C; July mean max. 31.5 °C.

The Royal Botanic Gardens, Kew evolved from two royal estates, a small botanic garden being founded in 1759. Part of the landscape, several buildings and some surviving trees date to this period. Greatly developed by Sir Joseph Banks between 1771–1820, and reinvigorated by Sir William Hooker and his son Sir Joseph in the nineteenth century, Kew became recognised as one of the great botanic gardens of the world. Its Herbarium, with over 7 million specimens, is one of the largest in the world, and also maintains an unrivalled collection of botanical art. Molecular research is carried out in the Jodrell Laboratory, and the Millennium Seed Bank is housed at Wakehurst Place. A strong emphasis is placed on the need for conserving the world’s flora. The garden covers 121 ha on a flat site, on generally sandy soil near the Thames, much of it comprising the Arboretum, filled with a great diversity of trees. Most recent plantings are of documented wild origin. The gardens, with their fine buildings and glasshouses, were designated a UNESCO World Heritage Site in 2002, and were further enhanced for tree-lovers in 2008 by the opening of the Rhizotron and Xstrata Treetop Walkway, giving a new view of treetops and tree roots. No catalogue, though some basic accession data available (www.rbgkew.org.uk/epic). Altitude 6 m. Zone 9. Rainfall 627 mm. January mean min. 1.7 °C, absolute min. (1985–2004) –12.0 °C (January 2000); July mean max. 23.3 °C, absolute max. 38.1 °C (August 2003).

Les Barres – L’Arboretum National des Barres Ecole Nationale du Génie Rural des Eaux et des Forêts: L’Arboretum National des Barres, 45290 Nogent-sur-Vernisson, France Tel. +33 (0)2 38 97 62 21, Website www.arboretumdesbarres.com

The domaine of Les Barres was acquired in 1821 by Philippe André de Vilmorin, of the French nursery dynasty, remaining in the family until 1921 when it was donated to the French state. Many important collections made in China in the late-nineteenth and early-twentieth centuries by French collectors and others were planted, and form the core of the 35 ha botanical arboretum. The adjoining 300 ha are plantations where forestry research

Section III. Appendices

is carried out. Specialist collections of Abies, Acer, Crataegus, Picea, Pinus. Altitude 150 m. Zone 8. The following meteorological data from Sully-sur-Loire (118 m) (Weatherbase 2008). Rainfall 640 mm. January mean 3 °C, absolute min. –15 °C; July mean 18 °C, July mean max. 22 °C, absolute max. 40 °C.

Logan Botanic Garden Royal Botanic Garden Edinburgh: Port Logan, Stranraer, Dumfries & Galloway DG9 9ND, UK Tel. +44 (0)1776 860231, E-mail [email protected], Website www.rbge.org.uk

Comprising 10 ha of gently undulating land at Scotland’s most southerly tip, underlain with a neutral to acidic loam soil, Logan is unrivalled as the country’s most exotic garden. A colourful walled garden of tree ferns, palms and borders contrasts with a woodland area with Gunnera bog and collections of southern-hemisphere trees and shrubs. Since 1969, when it became a regional garden of the Royal Botanic Garden, many new wildcollected trees and shrubs have been planted, particularly from New Zealand, Chile and Tasmania. Specialist collections of Azara, Eucalyptus, Eucryphia, Rhododendron, Weinmannia. Catalogue available online. Altitude 25–40 m. Zone 9. Rainfall 1000 mm. January mean 6 °C, January mean min. 3 °C, absolute min. –10.5 °C (December 1995); July mean 16.9 °C, July mean max. 21.1 °C, absolute max. 27.7 °C (July 2006).

Appendix 1. Focus Arboreta

913

Altitude 76 m at highest point. Zone 6b. Rainfall 1090 mm. January mean 0.5 °C, January mean min. –5 °C; July mean 25.6 °C, July mean max. 30 °C.

The Morton Arboretum Private, Not for Profit organisation: 4100 Illinois Route 53, Lisle, Illinois 60532-12, USA Tel. +1 (0)630 968 0074, E-mail [email protected], Website www.mortonarb.org

The Morton Arboretum covers 690 ha of level terrain, including glacial uplands and the floodplain of the DuPage River. The underlying soils are silty-loam to clay. Established in 1922 by Joy Morton (1855–1934), owner of the Morton Salt Company, the arboretum has extensive plant collections, gardens, lakes, natural woodlands and restored prairie, and an award-winning children’s garden. A complete revitalisation of the central visitor area was completed in 2005. The arboretum features notable collections of Chinese, Appalachian, Ozarkian and Midwestern plants of wild-collected origin. Specialist collections of Acer, Malus (crabapples), Quercus, Ulmus. Catalogue available online, and printed. Altitude 201–245 m. Zone 5a. Rainfall 920 mm. January mean –5.6 °C, January mean min. –9.8 °C, absolute min. –32 °C (January 1982); July mean 16.9 °C, July mean max. 22.9 °C, absolute max. 40.5 °C (July 1934).

Mount Usher Gardens The Morris Arboretum of the University of Pennsylvania

Mrs Madelaine Jay: Ashford, Co. Wicklow, Ireland

University of Pennsylvania: 100 E. Northwestern Avenue, Philadelphia, Pennsylvania 19118, USA

Tel. +353 (0)404 40205 / +353 (0)8723 01678, E-mail [email protected], Website mountushergardens.ie

Tel, +1 (0)215 247 5777, E-mail [email protected], Website www.morrisarboretum.org

The 64 ha Morris Arboretum includes 37 ha of public gardens with a varied terrain, ranging from floodplain to ridge top. Soils are well drained and largely acidic, but for an alkaline pocket above limestone. Founded in 1887 as the private estate of John and Lydia T. Morris, the Morris Arboretum of the University of Pennsylvania was established in 1932 as a university-administered arboretum and public garden for research, education and horticultural display. It became the official Arboretum of the Commonwealth of Pennsylvania in 1988. Specialist collections of Acer, conifers, Hamamelis, Ilex, Magnolia, Rosa. A printed catalogue is available.

Mount Usher Gardens are laid out over 9 ha of land in the valley of the River Vartry in Co. Wicklow, on a rich alluvial soil. Created from 1868 by the Walpole family, Mount Usher is Ireland’s finest Robinsonian garden. The planting includes over 5000 species from all over the world, including many rare, tender exotics and a number of Irish champion trees, such as a renowned Pinus montezumae which dates from c.1900. Specialist collections of Eucryphia, Nothofagus. Catalogue available at reception. Altitude 25 m. Zone 8. Rainfall 900 mm. Jan. mean 9 °C, Jan. mean min. –3 °C, absolute min. –6 °C (March 2004); July mean 21 °C, July mean max. 26 °C, absolute max. 29 °C (July 2006).

914

Appendix 1. Focus Arboreta

Quarryhill Botanical Garden Private, Not for Profit organisation: 12841 Sonoma Highway, Glen Ellen, California 95442, USA Tel. +1 (0)707 996 3166, E-mail [email protected], Website www.quarryhillbg.org

Quarryhill comprises 9 ha of garden on a west-facing slope of the Mayacamas Mountains. The soils are acidic, derived from volcanic rock. Founded in 1987 by Jane Davenport Jansen (1940–2000), the collection consists largely of wild-origin plants (over 90%) grown from seed collected on annual expeditions to Asia – primarily China, but also Japan, Taiwan, India and Nepal. Accessions may be found via the Asian Plant Database (www. quarryhillbg.org/asianplantdatabase.html), which also lists holdings of Asian plants in many other collections. Altitude 60–90 m. Zone 9. Rainfall 900–1000 mm. January mean min. 2 °C, absolute min. –10 °C (December 1990); July mean max. 27 °C, absolute max. 42 °C (July 2006).

New Trees

mainly from warm temperate areas, and the garden’s fertile soil, sheltered aspect and favourable climate have allowed many exotic species to reach record sizes. Many of the recent accessions are wild-collected and of known source, and the emphasis is on conservation of rarer species. Direction is presently provided by a small steering committee led by representatives from the Royal Botanic Gardens, Kew, who monitor the nature and extent of current planting, within the surrounding historical landscape. Specialist collections of Aceraceae, Araliaceae, Ericaceae, Flacourtiaceae, Hamamelidaceae, Lauraceae, Magnoliaceae, Pinaceae, Podocarpaceae, Styracaceae, Theaceae. A printed catalogue is available. Altitude 50 m. Zone 9. Some meteorological data from Falmouth, Cornwall (60 m) (Weatherbase 2008). Rainfall 1150– 1200 mm (Tregrehan data). January mean 6 °C, January mean min. 4 °C; July mean 15 °C, July mean max. 19 °C.

Trompenburg Arboretum

Starhill Forest Arboretum

Stichting Arboretum Trompenburg: Honingerdijk 86, 3062 NX, Rotterdam, The Netherlands

Guy and Edie Sternberg: 12000 Boy Scout Trail, Petersburg, Illinois 62675, USA

Tel. +31 (0)10 2330166, E-mail [email protected], Website www.trompenburg.nl

E-mail [email protected], Website www.starhillforest.com

Trompenburg Arboretum occupies 8 ha of flat, formerly cultivated polderland along the River Maas, with shallow, humus-rich clay soil and a high water-table. Formerly the private property of the van Hoey Smith family, Trompenburg dates back (in part) to 1820, when pastures were transformed into a naturalistic parkland. Since then its are has been extended, in 1870, 1970, 1996 and 2001. The collection of trees and shrubs began in the 1920s. Trompenburg has been managed by the Stichting Arboretum Trompenburg since 1985. Specialist collections of dwarf conifers, Fagus, Ilex, Quercus, Rhododendron. Catalogue: see Trompenburg Arboretum, Green Oasis in Rotterdam, by J.R.P. van Hoey Smith (2001).

Starhill Forest extends over approximately 20 ha of gently rolling land with silt-loam to clay-loam soils (pH 6.5). Founded in 1976 by Guy and Edie Sternberg, Starhill holds one of the most comprehensive collections of oak (Quercus) in North America. Specialist collections of Quercus and other Fagaceae; also of Acer, Anacardiaceae, Betulaceae, Juglandaceae, Pinaceae, Ulmaceae. Catalogue unavailable, but online photograph albums may be viewed. Altitude c.180 m. Zone 5. The following meteorological data from Springfield, Illinois (181 m) (Weatherbase 2008). Rainfall 800 mm. January mean –2 °C, January mean min. –7 °C, absolute min. –23 °C; July mean 25 °C, July mean max. 31 °C, absolute max. 38 °C.

Altitude 1.2 m below sea-level. Zone 7–8. Rainfall 850 mm. Jan. mean 3 °C, Jan. mean min. 1 °C, absolute min. –18 °C (1963); July mean 17 °C, July mean max. 21 °C, absolute max. 31 °C.

Tregrehan Garden

United States National Arboretum

Mr T.C. Hudson: Tregrehan House, Par, Cornwall PL24 2SJ, UK

United States Department of Agriculture (USDA): 3501 New York Avenue, N.E., Washington DC 20002, USA

E-mail [email protected], Website www.tregrehan.org

Tel. +1 (0)202 245 2726, Website www.usna.usda.gov

Over 15 ha of sloping land on acidic, free-draining loam, Tregrehan displays a botanical collection built up by the Carlyon family over the past 160 years. The plants are

Situated largely on the floodplain of the Anacostia River, the 180 ha US National Arboretum has a diverse terrain and soil profile. The arboretum was founded by an

Section III. Appendices

Appendix 1. Focus Arboreta

915

Act of Congress on 4 March 1927, for the ‘purposes of research and education concerning tree and plant life’. The primary focus has been to support ornamental plantbreeding work in the USDA, serving as a repository for research plants and germplasm collected by USDA scientists. The grounds were officially opened to the public in 1948, and the collections are now visited by 450,000 people a year. Specialist collections of Acer, Buxus, azaleas, dwarf conifers, Ilex, Magnolia. The accessions database is not available to the general public, but individual accessions can be identified at the plant locator kiosk.

the whole collection was databased, and in 2001–2003 coordinates were added for every accession, allowing accurate mapping. Highlights include the Heather garden and the Rhododendron and Tsuga forests. Specialist collections of Acer, Betula, conifers (esp. Tsuga), Ericaceae (esp. Rhododendron), Euonymus, Fraxinus, Laburnum, Magnolia, Syringa. Catalogue available online.

Altitude 3–73 m. Zone 7a. Rainfall 1100 mm. January mean 1.3 °C , January mean min. –3.8 °C, absolute min. –23.3 °C (January 1982); July mean 25.5 °C, July mean max. 31.4 °C, absolute max. 40 °C (July 1954, August 1997).

Wakehurst Place

University of British Columbia Botanical Garden

Situated on the Sussex High Weald, Wakehurst Place comprises approximately 210 ha of woodland, meadows, wetlands and landscaped gardens along a steep-sided valley, running down to a reservoir. The site has been managed by Kew on behalf of the British government since 1965, when the estate was bequeathed to the National Trust by Sir Henry Price. The climate and topography at Wakehurst, and its existing collections – originally made by Gerald Loder and Sir Henry Price – greatly increased Kew’s scope to expand and develop collections that did not grow well in London. The temperate tree and shrub collections are planted out in a phytogeographical arrangement, and there are important collections of southern-hemisphere plants. Specialist collections of Betula, conifers, Nothofagus, Rhododendron. No catalogue, though some basic accession data are available (www.rbgkew.org.uk/epic).

University of British Columbia: 6804 Southwest Marine Drive, Vancouver, British Columbia V6T 1Z4, Canada Tel. +1 (0)604 822 9666, E-mail [email protected], Website www.ubcbotanicalgarden.org

The garden (about 44 ha) is located on the western edge of the city of Vancouver, to the southwestern side of Point Grey Peninsula, atop cliffs that descend to the Strait of Georgia. The original botanical garden began in 1912 at Colony Farm, Essondale, just east of Vancouver. John Davidson was appointed provincial botanist, and built up a collection of over 9000 species. In 1916 the collection was moved to the Point Grey campus and Davidson became the first director of the UBC Botanical Garden. This is now an academic unit within the Faculty of Land and Food Systems. Specialist collections of Acer, Cornus, Eucalyptus, Lauraceae, Magnoliaceae, Rhododendron, Sorbus, Styracaceae. Catalogue available online.

Altitude 3 m. Zone 7. Rainfall 803 mm. January mean 2.8 °C, January mean min. –0.6 °C, absolute min. –24.8 °C; July mean 17.4 °C, July mean max. 21.6 °C, absolute max. 36.8 °C.

Royal Botanic Gardens, Kew: Selsfield Road, Ardingly, Haywards Heath, West Sussex RH17 6TN, UK Tel. +44 (0)1444 894000, E-mail [email protected], Website www.kew.org

Von Gimborn Arboretum

Altitude 133 m at highest point. Zone 6–7. Some meteorological data from Horsham, West Sussex (51 m) (Weatherbase 2008). Rainfall c. 820 mm (Wakehurst data). January mean 4 °C, January mean min. 2 °C, normal annual min. –5 to –8 °C (Wakehurst data); July mean 16 °C, July mean max. 22 °C, absolute max. 37.6 °C (Wakehurst data).

University of Utrecht: Velperengh 13, 3941 BZ, Doorn, The Netherlands

Warsaw Agricultural University Arboretum at Rogów

Tel. +31 (0)30 2531826, Website www.bio.uu.nl/botgard/

Warsaw Agricultural University: PL-95-063 Rogów, Poland

This arboretum extends over 27 ha of low-lying, flat ground with a sandy soil. Founded in 1924 by Max von Gimborn, who specialised in conifers, it was adopted after his death in 1964 by the University of Utrecht, when new collections were added. In the late 1980s

Tel. +48 (0)468748136, E-mail [email protected], Website arboretum.sggw.pl

Altitude 76 m. Zone 8b. Rainfall 1226 mm. January mean min. 1.2 °C; July mean max. 20.4 °C.

The Rogów Arboretum consists of 54 ha of woodland on acidic, often podzolic soils. It was established in 1925 as a research and training site for scientists and students

916

Appendix 1. Focus Arboreta

of the Forestry Faculty of Warsaw Agricultural University. The main objective was to assess the usefulness for Polish forest economy of different foreign tree species. To achieve this goal, numerous forestry trial plots were established, with a small number of specimen trees and shrubs planted in between. The collection became significant only after World War II, when permanent staff were employed for the first time and a nursery and greenhouse were constructed. Specialist collections of Acer, Araliaceae, conifers, Sorbus, Stewartia. Catalogue available online. Altitude 185–196 m. Zone 6b. Rainfall 600 mm. January mean –3.2 °C, January mean min. –6.1 °C, absolute min. –34 °C (February 1929); July mean 17.3 °C, July mean max. 22.9 °C, absolute max. 36.2 °C (August 1992).

Washington Park Arboretum University of Washington Botanic Gardens: 2300 Arboretum Drive East, Seattle, Washington 98112, USA Tel. +1 (0)206 543 8616, E-mail [email protected], Website www.uwbotanicgardens.org

Washington Park occupies a site of 93 ha in a shallow valley with a north-south trending axis; the soils are extremely variable. The arboretum was established in 1934 through an agreement between the University of Washington and the City of Seattle. A large tract of cityowned park land known as Washington Park was selected and made available. Under the agreement, the City of Seattle manages all park functions and the University is charged with the design, creation and management of the arboretum and botanic garden plant collection. The Arboretum Foundation was established in 1935 and has been an active support group since that time. Specialist collections include Abies, Acer, Betula, Ilex, Magnolia, Nothofagus, Pinus, Quercus, Sorbus. Printed catalogue available. For more information online, see Arboretum website (depts.washington.edu/wpa/collection.htm). Altitude 6–50 m. Zone 8. Rainfall 945 mm. January mean 4.5 °C, January mean min. 1.8 °C, absolute min. –18 °C (January 1950); July mean 18.5 °C, July mean max. 24 °C, absolute max. 37.8 °C (July 1994).

Arboretum Wespelaar Foundation Arboretum Wespelaar: Grote Baan 63, 3150 Haacht-Wespelaar, Belgium Tel. +32 (0)16 608641, E-mail [email protected], Website www.arboretumwespelaar.be

New Trees

Arboretum Wespelaar extends over 15 ha of largely flat land with heavy, poorly drained, loam soil; acid soils predominate, though there are some neutral pockets (pH 3.4–7.6). The Arboretum Foundation was established in 2001 to manage the botanical collections of Philippe de Spoelberch and the adjacent private garden, Herkenrode (10 ha). The tree collections at Wespelaar and Herkenrode were begun in 1985 and 1965, respectively. The arboretum contains around 2800 specimens of trees and shrubs, including many rare species collected in their natural habitat, as well as numerous cultivars and selections. Specialist collections of Acer, Betula, Carpinus, Fagus, Fraxinus, Ilex, Lindera, Liquidambar, Magnolia, Quercus, Styrax, Tilia. Catalogue available online. Altitude 8–14 m. Zone 6–7b. Rainfall 900 mm. January mean 2.3 °C, January mean min. –4.4 °C, absolute min. –19 °C (January 1985); July mean 19.3 °C, July mean max. 30.8 °C, absolute max. 44 °C (August 2003).

Westonbirt, The National Arboretum The Forestry Commission: Westonbirt, Tetbury, Gloucestershire GL8 8QS, UK Tel. +44 (0)1666 880220, E-mail [email protected], Website www.forestry.gov.uk/westonbirt

Westonbirt is planted over 250 ha of largely flat ground, with soils varying from acid loam to base-rich clay-loam. Since 1956 the arboretum has been owned and managed by the Forestry Commission. The basic layout was established in one phase between 1854 and 1881, under the guidance of its creator Robert Staynor Holford and his son Sir George Holford. Apart from some single genus collections in Silk Wood, most subsequent development has been carried out within this original framework. In addition to its botanical value, the arboretum, owing much to the influence of nineteenth-century landscape design, has many identifiably ‘Picturesque’ elements – possibly resulting from Robert Holford’s known appreciation of the work of W.S. Gilpin. National Plant Collection of Acer. Catalogue available online (www.thewestonbirtmap.org.uk). The National Arboreta managed by the Forestry Commission also include Bedgebury, the National Pinetum in Kent (see above), home of the most complete collection of conifers in the world. Altitude 130 m. Zone 7. Rainfall 850 mm. January mean 4.1 °C, January mean min. 1.3 °C, absolute min. –12.9 °C (January 1999); July mean 16.4 °C, July mean max. 21.3 °C, absolute max. 32.6 °C (August 1995).

Appendix 2. Collectors’ References Many collectors’ references are cited throughout New Trees, often in the form of an initial or acronym associated with a serial number. To help decipher these the following list is provided, but further references are also available in the annual editions of The RHS Plant Finder (for example, Lord 2008). We are very grateful to Susyn Andrews for her help in compiling this list. There is occasional variation in the form in which such references are cited, as different institutions use different forms (for example, W&H and WAHO both relate to collections made by Roger Warner and Lord Howick). Collection numbers are an important part of the data associated with wild-origin material, and should never be discarded from labels or records.

ACE Alpine Garden Society Expedition to China, 1994.

ECEH Eric Hammond (formerly of Heronswood Nursery). Chile, 2000.

A&L Ann Ala, Roy Lancaster. Iran, 1972.

EDHCH Eric Hammond. China, 1997.

B&L See BRLL. BB Bruce Bartholomew.

EHOK RBG Kew Expedition to Hokkaido, 1997.

BECX RBG Kew: I. Beyer, Charles Erskine, Jill Cowley. South Korea, 1982.

EMAK RBG Edinburgh Expedition to Makalu, 1991.

BRLL Christopher Brickell, Alan Leslie. (Also B&L.)

EN Edward Needham.

BSWJ Bleddyn and Sue Wynn-Jones. (Crûg Farm Plants. For a comprehensive list of Wynn-Jones collections, see Crûg Farm Plants 2007–2008.) BWJ Bleddyn Wynn-Jones (collecting alone). CBS NACPEC Expedition to Changbai Shan, Jilin, China, 1997. (Correctly, the reference is NACPEC 97 (CBS).) CDR James Compton, John d’Arcy, Martyn Rix. CEE Chengdu Edinburgh Expedition, 1991. CH Peter Cox, Steve Hootman. CLD Cangshan, Lijiang, Dali Expedition, 1990. (Sometimes CLDX.) DAP Dendrological Atlas Project. DJH Daniel J. Hinkley. (Suffix indicates collection area. For example: DJHB, Bhutan; DJHC, China; DJHJ, Japan; DJHS, Sikkim; DJHT, Taiwan; DJHV, Vietnam.)

ENEP RBG Edinburgh Nepal Expedition, 2001. EPAK RBG Kew Expedition to Pakistan, 1995. ESUS RBG Kew Expedition to Sakhalin & Ussuri, 1994. ETAZ RBG Kew Expedition to Tasmania, 2002. ETE RBG Edinburgh Expedition to Taiwan, 1993. ETOT RBG Kew Expedition to Taiwan, 1992. F George Forrest. (Occasionally also used for collections by Reginald Farrer.) FAWA Aljos Farjon, A. Watt. FLSX RBG Kew: H. Fliegner, John Simmons Expedition to Iran, 1977. FRJA Aljos Farjon. (Kew records format.) GCCE Glasnevin Central China Expedition, 2002.

Ulmus laciniata

918

Appendix 2. Collectors’ References

New Trees

G&K Martin Gardner, Sabina Knees. Chile, 1990.

KR Keith Rushforth.

SBG Shanghai Botanic Garden.

KSW

SCHL Tony Schilling.

GSE RBG Edinburgh Gaoligong Shan Expedition, 1996.

KW Frank Kingdon-Ward.

GUIZ RBG Kew Expedition to Guizhou, 1985. GWC Guy Clapperton. GWJ Sally Goddard, Bleddyn and Sue Wynn-Jones. H Lord (Charles) Howick. (Usually used in combination: H&M, etc.) HLJ NACPEC Expedition to Heilongjiang, China, 1993. H&M Lord (Charles) Howick, Bill McNamara. HONX RBG Kew Expedition to Honshu, 1996. HWJ Dan Hinkley, Bleddyn and Sue Wynn-Jones. Vietnam, 1999. HWJK D. Hinkley, Bleddyn and Sue Wynn-Jones, Jamaica Kincaid. Eastern Nepal, 2002. ICE Instituto de Investigaciones Ecologicas Chiloé & RBG Edinburgh, 1996. JCRA JC Raulston Arboretum. JR James Russell. KE (USNA-led) Korean Expedition – Southwest Coast & Islands, 1985. (Also sometimes KSW.) KEKE RBG Kew & Edinburgh Kanchenjunga Expedition, 1989. KFBX RBG Kew: Tony Kirkham, Mark Flanagan, Peter Boyce. Expedition to South Korea, 1989.

See KE.

L Roy Lancaster.

SCN RBG Edinburgh Sichuan Expedition, 1992.

LUSE Ludlow, Sherriff, Elliot. Himalaya, 1947.

SEP Swedish Expedition to Pakistan, 1983.

MAWAX Araucaria Expedition, Chile, 1998.

SICH (RBG Kew-led) Expeditions to Sichuan. (Successive numbering for nine expeditions, 1988–2003.

MBMX Bill McNamara, Michael Maunder. Expedition to Japan, 1989. MF Maurice Foster. NA US National Arboretum (accession prefix). NACPEC North American China Plant Exploration Consortium (a group of collaborating institutions, mostly from the eastern United States). NACPEC 97 (CBS) NACPEC Expedition to Changbai Shan, Jilin, China, 1997. NEKG (USNA-led) Expedition to Korea – Northeast, 1989. NJM Nick Macer. NWKNW (USNA-led) Expedition to Korea – Northwest, 1984.

SOJA Bill McNamara, Michael Maunder. Southern Japan, 1989. SOKU RBG Kew Expedition to Shikoku (Ray Townsend, Mark Bridger), 1999. SSC Schilling, Sayers, Bista. 1966. TH Tom Hudson. THD Tom Hart Dyke. TNL Philip Thomas, Nan Li, 1999. TURX RBG Kew Expedition to Turkey (M. Flanagan, M. Pitman), 1990. UCEXC Universidad de Chile, RBG Edinburgh. Expedition to Southern Chile, 1998. USDA US Dept. of Agriculture.

PCH MEX G. Pattison, P. Catt, M. Hickson. Mexico, 1995.

USNA US National Arboretum.

PI USDA Plant Introduction.

VERA M. Sparrow, P. Brewster, Expedition to Veracruz, 1993.

PW Peter Wharton. QPH QingPu Paradise Horticultural Co. (commercial branch of Shanghai Botanic Garden). RC Robert (Bob) Cherry. RMcB Ron McBeath. RWJ Crûg–Rickard’s Ferns Joint expedition to Taiwan, 2003.

W E.H. Wilson. (Also WILS.) WAHO Roger Warner, Lord (Charles) Howick. United States, 1986. (Also WH, W&H.) WAPE John Watson, Stephen Pern. WD NACPEC Expedition to Wudang Shan, Northwestern Hubei, China, 1994.

KGB Kunming/Gothenburg Expedition, 1993.

SABE Sino-American Botanical Expedition, 1980.

KNW (USNA-led) Expedition to Korea – Northwest Coast and Islands, 1984.

SAS Stephen A. Spongberg.

WILS / Wilson See W.

SBEC Sino-British Expedition to the Cangshan, 1981.

WSYUS Widrlechner, Schutzki, Yukhnovsky, Sviatetsky. Ukraine, 1999.

WH / W&H See WAHO.

Appendix 3. Sources of Material for Line Drawings Dried specimens are all from the Herbarium of the Royal Botanic Gardens, Kew and are indicated by their collector’s reference (for example, Turrill 1569). Living specimens at Kew are identified by their accession number (for example, Kew 1992-608).

Figure 1. Rosaceous fruits. Pyrus communis subsp. mamorensis (A) Kew 1993-3514, Long Ashton Research Station, Morocco. Malus toringo (B) Kew 1998-321, Townsend & Bridger HONX 55, Honshu. Sorbus sp. sect. Discolores (C) Kew 1979-6681, Lady O’Neill of the Maine 255, Yunnan, grown as S. forrestii. Aria aronioides (D) Kew 1988-5048, SICH 407, Sichuan; Aria hemsleyi (E) Kew 1996142, Fliegner, Erskine, Howick & McNamara SICH 1464, Sichuan; Sorbus tamamschjanae (F) Kew 1982-8156, Gabrieljan 01, Armenia. Crataegus pseudoheterophylla (G) Kew 19774289, Fliegner & Simmons 497, Iran. Malus coronaria var. platycarpa (H) Kew 1986-8284, Long Ashton Research Station, USA. Crataegus meyeri (J) Kew 1968-80055, Botanic Garden of the Academy of Science, Armenian SSR 768, Armenia. Pyrus elaeagnifolia (K) Kew 1986-1632, Long Ashton Research Station. Malus rockii (L) Kew 1986-1590, Long Ashton Research Station, China. Crataegus mexicana (M) Kew 1977-6981, Brenan 433, Chiapas. Pyrus phaeocarpa (N) Kew 1986-8415, Long Ashton Research Station, China. Figure 2. Nothofagus ×leonii: cupule with seeds. Kew 1995-1503, Departamento de Silvicultura, Universidad de Chile, Chile. Figure 3. Styrax formosanus: single flower (A) Wilson 10008; habit with flowers (B) Wilson 10209; infructescence (C) Price 459; calyx and persistent style after the corolla has fallen (D) Wilson 10209.

branchlet (C) Turrill 1569, Bulgaria, leaf underside (G) Turrill 1569, Bulgaria. Abies forrestii: cone rachis (D) Hurst 1050, cult. UK, branchlet with male strobili (E) Kew 0000958, cult. UK, seed (R) Hurst 1050, cult. UK. Abies chensiensis: leaf underside (F) Kew H1420, cult. UK. Abies durangensis: leaf underside (J) Little 17869, Durango. Abies sibirica: leaf underside (K) Korotkij 132, Transbaikal. L Abies forrestii var. georgei: leaf underside (L) Farjon 488, Yunnan. Abies cilicica: seed scale, upper surface without seeds (M), upper surface with two seeds (N), lower surface with bract scale (P); seed (Q). All Davies 16464, Turkey. Figure 6. Abies durangensis: habit with seed cones (A); seed scale, lower surface with bract scale (B), upper surface with two seeds (C); winged seed (D). All Kew 1992-608, Royal Veterinary & Agricultural University, Horsholm 430, Chihuahua. Figure 7. Acacia pataczekii: habit with flowers (A) Chase 16092, cult. Royal Botanic Gardens, Kew; fruit (B) Cameron s.n., Tasmania. Acacia spectabilis: habit with flowers (C) Hadley 2552, New South Wales; fruit (D) Smith & Everist 813, Queensland. Figure 8. Acer, branchlets with fruit. Acer cordatum (A) Ching 2268, Fujian; Acer oblongum var. itoanum (B) Furuse 5641, Ryukyu Is.; Acer laevigatum var. salweenense (C) Forrest 17903; Acer fabri (D) Taam 765, Guangdong; Acer calcaratum (E) Hansen & Smitinand 12861, Thailand.

Figure 4. Betula insignis: seed cone (A); single fruit (B). Kew 1999-1193, Simmons, Fliegner & Russell GUIZ 82, Guizhou.

Figure 9. Acer morifolium: habit with inflorescences (A) Furuse 10459, Kyushu, habit with fruits (B) Furuse 10886, Kyushu; lobed leaf (C) also Furuse 10886, Kyushu.

Figure 5. Abies morphology. Abies homolepis: habit with cone (A) Kew 1969-11616, unknown origin; cone Hatfield s.n., cult. UK. Abies pinsapo var. marocana: branchlet (B), leaf underside (H) All Kew 1984-8258, Arnold Arboretum 020, Morocco. Abies borisii-regis:

Figure 10. Acer, branchlets with fruit. Acer caudatifolium (A); Acer rubescens (B); Acer pseudosieboldianum subsp. takesimense (C); Acer Lancaster 962, grown as Acer sikkimense var. metcalfii (D); Acer sieboldianum (E). All from Hergest Croft.

Acacia spectabilis

920

Appendix 3. Sources of Material

Figure 11. Ackama rosifolia: flowering shoot (A); single flower (B). Both Calder 1959, New Zealand). Pair of fruits (C) Melville & Moore 5200, New Zealand. Figure 12. Branchlets with fruit: Afrocarpus falcatus (A) Fourcade 3319, South Africa, Podocarpus latifolius (C) Acocks 8997, South Africa. With male strobili: Afrocarpus falcatus (B) Fourcade 3319, South Africa, Podocarpus latifolius (D) Stauffer & Esterhuyzen 5121, South Africa. Figure 13. Alangium chinense: habit with flower buds (A); lobed leaf (B); flowers opening (C). All Kew 1985-3641, Sino-American Exp. to China SABE 1703, Hubei. Fruits (D) Chow 99, Anhui. Figure 14. Alnus fauriei: habit w. male catkins and seed cones (A) Kew 1995-3343, Howick 18/12, Japan. Alnus pendula: habit w. mature and immature seed cones (B); immature seed cone (C); mature seed cone (D). All Kew 1989-8239, Kirkham, Flanagan & Boyce 125, South Korea. Figure 15. Alnus trabeculosa: habit with seed cones and immature catkins Kew 1999-158, Forest Tree Breeding Centre, Honshu. Figure 16. Amentotaxus argotaenia: habit with female cones (A) Taam 594, Guangdong; habit with male strobili (B) Taam 552, Guangdong; detail of stem (C) Tsang 20351, Guangdong. Figure 17. Banksia integrifolia var. monticola: (A) habit w. inflorescence, flowers in bud; (B) inflorescence w. open flowers; (C) spent inflorescence,dead flowers, immature follicles; (D) single leaf. All Kew 2002-10, Hardman & Jackson 4, New South Wales. Figure 18. Betula insignis: habit w. immature catkins. Kew 1999-1193, Simmons, Fliegner & Russell GUIZ 82, Guizhou. Figure 19. Bretschneidera sinensis: flowering shoot. Henry 11651, Yunnan. Flower details from photograph (Ronse de Craene et al. 2002). Figure 20. Callitris endlicheri: habit with female cones (A); detail of male strobili (B). All Kew 1999-2115, Farjon 413, New South Wales.

Figure 21. Camptotheca acuminata: inflorescence w. some open flowers (A) Fang 2409, Sichuan; habit w. immature inflorescence (B) Bullock 231, Jiangxi; infructescence (C) Henry 13433, Yunnan. Figure 22. Carpinus rankanensis: habit with seed ‘cones’ and detail of leaf underside. All Kew 1992-4147, Kirkham & Flanagan ETOT 122, Taiwan. Figure 23. Celtis tetrandra: habit w. fruits and detail of leaf underside. All Kew 1965-28007, Les Barres Arboretum 280. Figure 24. Chamaecyparis obtusa var. formosana: habit with female cones (A) Kew 1995-2195, Kirkham & Flanagan ETOT 115, Taiwan. Thuja koraiensis: underside of branchlet (B); detail of branchlet and female cone (C). All Kew 1980-6356, Wilson 9244, South Korea. Calocedrus formosana: detail of branchlet with female cones (D) Kew 19952912, Kirkham & Flanagan ETOT 10, Taiwan. Chamaecyparis obtusa var. formosana: detail of branchlet with female cones (E) Kew 1995-2195, Kirkham & Flanagan ETOT 115, Taiwan.

New Trees

Figure 30. Crataegus baroussana: habit with flowers (A); fruits (B). All Kew 19858523, Rushforth 534, Coahuila. Figure 31. Cupressus dupreziana var. dupreziana: habit (A) Kew 1998-166, Pawluk 278, Algeria; seed cone (B) HanburyTenison 1963, Algeria. Figure 32. Dipentodon sinicus: habit with infructescences (A); inflorescence (B); unopened capsule (C); remains of capsule after dehiscence (D). All cultivated material, donated by Tom Hudson, Tregehan. Figure 33. Elaeocarpus hookerianus: dentate juvenile leaves (A) Melville 20311, New Zealand; adult foliage with fruit (B) Melville 20326, New Zealand; divaricate juvenile growth habit (C) Melville 20311, New Zealand. Elaeocarpus decipiens: flowering shoot (D) Xiang 222, Yunnan. Figure 34. Eucalyptus chapmaniana: habit with flowers (A); detail of flower with calyptra (B); capsules (C); juvenile foliage (D). All Kew 1998-8117, Hill 1413, Victoria.

Figure 25. Choerospondias axillaris: habit w. inflorescences (A) Schilling 789, Nepal; fruit (B) McClure 9753, Hainan.

Figure 35. Eucalyptus archeri: habit with flowers (A), fruits (B); detail of capsule mouth (C). All Kew 2003-2176, Hart Dyke 94, Tasmania.

Figure 26. Cinnamomum japonicum: habit (A) Kew 1989-4003, McNamara & Maunder 398, Kyushu. Inflorescence (B); single flower (C); infructescence (D). All Oldham 702, Kyushu.

Figure 36. Eucalyptus neglecta: habit with flower buds and details of capsules. All Kew 1966-36422, Hill H72/10, Victoria.

Figure 27. Cornus hongkongensis var. melanotricha: flowering branch, with detail of hairs in the vein axils of the lower leaf surface. Cultivated material, Hillier Gardens. Figure 28. Corylus fargesii: habit with fruits (A) Dallimore 42, Sichuan; catkins (B) Bean 136, cult. UK; fruit cluster (C) Cheng & Hira 745, Hubei-Sichuan border. Figure 29. Craibiodendron yunnanense: habit with flowers (A); detail of a flower (B). Both Forrest 15592, Yunnan. Capsule viewed from above (C), viewed from the side (D) Forrest 21068, Yunnan.

Figure 37. Eucalyptus stellulata: habit with fruits and flower buds, with detail of capsules. All Kew 1972-4180, Forest Research Institute, Canberra 7826, New South Wales. Figure 38. Exbucklandia populnea: habit with open fruit capsules (A) Garrett 579, Thailand; three-lobed leaf (B) Garrett 338, Thailand; bract with immature inflorescences (C) Gamble 2860A, Bhutan; inflorescence (D) Kew 000-69-50132, cult. UK. Figure 39. Ficus johannis subsp. afghanistanica: habit with immature fruits. GreyWilson & Hewer 1286, Afghanistan.

Section III. Appendices

Figure 40. Fraxinus lanuginosa: habit (A); infructescence (B). Both Kew 20052129, Kirkham, Coode-Adams, Howick & McNamara EHOK 112, Hokkaido. Figure 41. Glochidion puberum: habit with flowers (A) Wilson 838, Hubei; habit with fruits (B) Chang 4979, Anhui; fruit opening (C) Henry 3050, Hubei. Figure 42. Hedycarya arborea: habit with flowers (A); fruit cluster (B). All Cheeseman s.n., New Zealand. Single fruit (C) Buxton 439634, New Zealand. Figure 43. Hymenosporum flavum: habit w. flowers (A) Melville 3655, Queensland; open capsules after seed release (B) Pickard & Coveny 1211, New South Wales. Figure 44. Ilex nothofagifolia: habit (A); corky growths on stem (B). All cultivated material, Westonbirt, Foster 94116A, Yunnan. Male flower (C) Cox & Hutchinson 424, Assam; fruits (D) Kingdon-Ward 6878, Myanmar. Figure 45. Ilex spinigera: habit w. fruits. Cultivated material, Valley Garden, Windsor Great Park, Ala & Lancaster 18, Iran. Figure 46. Juglans sigillata: nuts in various perspectives, one in transverse section. Material supplied by the China National Tree Seed Corporation in 2005. Figure 47. Juniperus bermudiana: habit with female cones or ‘berries’. Kew 19784443, Philips 424, Bermuda. Figure 48. Chinese conifers. Cathaya argyrophylla: detail of stem (A) Fu 8012, Sichuan; habit with seed cone (B) Liu 15207, Sichuan. Keteleeria evelyniana: seed cone (C) Farjon 497, Yunnan. Habit with male strobili (D); detail of stem (E). Both Forrest 17788, Yunnan. Figure 49. Larix sibirica: habit w. seed cones (A) and after leaf fall (B); leaf lower surface (C), upper surface (D). All Kew 1969-13285, Gothenburg Botanic Garden, Siberia. Larix potaninii: habit w. seed cones (E) Zhao 112491, Sichuan; gall cone (F) Forrest 6745, Tibet. Leaf lower (G) and upper (H) surface CLD 90, Yunnan. Figure 50. Lepidothamnus intermedius: juvenile habit (A) Cheeseman s.n., New Zealand; adult habit with female cones (B) unlabelled specimen, New Zealand.

Appendix 3. Sources of Material

Halocarpus biformis: branchlet exhibiting both juvenile and adult foliage (C) Hector 83, New Zealand. Figure 51. Lindera praetermissa: habit with leaves (A) Forrest 10667, Yunnan; with flowers (B) Manberg & Bulley 1905, Yunnan.

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fruits (B). Myrceugenia planipes: habit with flowers (C). All material cultivated at the Royal Botanic Garden Edinburgh, supplied by Martin Gardner. Figure 62. Nothofagus gunnii: habit w. cupules (A) Hemsley 6447, Tasmania; cupule w. seeds (B) Burns 327, Tasmania.

Figure 52. Liquidambar acalycina: habit with immature fruits. Kew 1981-8314, Sino-American Expedition to China SABE 1950, Hubei.

Figure 63. Osmanthus fragrans: habit (A); inflorescence (B). Kew 1925-63901, Pirie 639, cult. France. Fruits (C) Furuse 10651, Kyushu.

Figure 53. Lithocarpus variolosus: habit with female inflorescences (A), with male inflorescences (B); detail of stem with lenticels (C). All Kew 1991-31, Howick & McNamara 1482, Sichuan. Lithocarpus dealbatus: infructescence (D) Wenger 398, Mizoram.

Figure 64. Pennantia corymbosa: mature habit with inflorescences (A) Melville 5438-a, New Zealand; fruits (B) van Balgovy 4459, New Zealand; immature habit (C) Melville 5438-b, New Zealand.

Figure 54. Maddenia wilsonii: fruiting stem, with detail of leaf venation. All Kew 1983-4459, Wilson 909, China. Figure 55. Maesa montana: habit with flowers (A) Hancock 478, Yunnan; fruits (B) Henry 9464, Yunnan. Figure 56. Magnolia laevifolia: flowering shoot and leaves. Cultivated material donated by Peter Catt. Figure 57. Magnolia zenii hybrid: branchlet with fruit. Cultivated material donated by John Gallagher. Figure 58. Malus ×dawsoniana: habit with flowers and fruit. All Kew 19861563, Long Ashton Research Station 156, unknown origin. Figure 59. Maytenus magellanica: habit with fruits (A) Vervoorst 5409, Argentina, with flowers (B) Goodall 840, Argentina; detail of capsule with a seed (C) Vervoorst 5409, Argentina. Lithraea caustica: habit with flowers (D); fruit (E). Hohenarber 548, Chile. Aextoxicon punctatum: habit with flowers (F) Comber 556, Chile; fruit (G) Gardner & Knees 4702, Chile. Figure 60. Melliodendron xylocarpum: habit with flowers (A) from photograph taken at the University of British Columbia Botanical Garden; single leaf (B) Chun 30408, Guangdong. Figure 61. Chilean myrtles. Blepharocalyx cruckshanksii: habit with flowers (A);

Figure 65. Persea lingue: leaf (A) Kostermans 576. Persea palustris: habit with fruits (B) Fernald & Long 13614. Persea thunbergii: habit with inflorescences, showing caducous bracts at base of inflorescence (C); and single flower (D). Wilson 6614. Figure 66. Picea martinezii: habit w. seed cones (A); detail of stem w. leaves (B). All Kew 1984-5355, Priest 108, Chihuahua. Figure 67. Pinus brutia: habit with immature cone (A) Kew 2002-2798, Flanagan & Pitman 54, Turkey. Pinus strobiformis: seed cone (B) Little 17865, Durango. Pinus massoniana: winged seed (C) Wilson 4073, Sichuan. Pinus cembroides: seed (D); seed scale, upper surface (E), lower surface (F). Bailey et al. 1976, Texas. Pinus maximartinezii: seed scale, side view (G) Farjon & Mejía 338, Zacatecas. Pinus pseudostrobus var. apulcensis: seed scale, side view (H) Hughes 1322, Puebla. Pinus armandii var. mastersiana: seed scale, side view (J) Wilson 9763, Taiwan. Figure 68. Pinus engelmannii: leaf fascicle (A); stem w. male strobili (B); detail of stem, showing reflexed cataphylls and fascicle sheaths (C). All Kew 1969-9242, Hunt 591, Durango. Pinus maximinoi: winter bud (D) Stead & Styles 395, Oaxaca. Figure 69. Pinus pseudostrobus var. pseudostrobus: habit (A); leaf fascicle (B). All Kew 1984-2269, Russell 429, Veracruz. Seed cone (C) Stead & Styles 613, Nuevo León.

922

Appendix 3. Sources of Material

Figure 70. Platanus mexicana: habit w. inflorescences (A) Pringle 8107, Veracruz; single leaf (B) Marquez & Yong 357, Veracruz. Figure 71. Polylepis australis: inflorescence (A); habit with inflorescences (B); single leaf (C); fruits (D). All Kew 19771159, Hjerting 509, Argentina. Figure 72. Populus purdomii: habit w. infructescence (A); detail of stem (B); detail of leaf veins (C). All Kew 1973-6401, Forestry Commission, Alice Holt 076, China. Figure 73. Prumnopitys ferruginea: branchlet with male strobili (A) Kirk 81, New Zealand; branchlet w. female cone (B) Melville 6792, New Zealand. Figure 74. Prunus sogdiana: flowering stems (A) cultivated material donated by Tim Whiteley; branchlet with leaves (B) Vašák s.n., Tajikistan. Figure 75. Pseudopanax ferox: adult habit with fruit (A) Kew 1969-50838, of unknown origin; juvenile leaf (B) Kirk 3/ 77, New Zealand; juvenile habit (C) from a photograph. Figure 76. Pterocarya macroptera: stem with infructescence (A); single leaf (B). All Kew 1979-1589, Chinese Academy of Forestry and Arboriculture 161, Gansu. Fruit of var. macroptera (C) Potanin 1885, Gansu; of var. insignis (D) SICH 1751, Sichuan; of var. delavayi (E) Forrest 22236, Yunnan. Figure 77. Pyrus korshinskyi: habit w. fruits (A); habit w. fruits, leaves removed (B). All Kew 1949-15208, Arboretum Kórnickie 152, Turkmenistan. Figure 78. Quercus rysophylla: habit (A); acorn (B). All Kew 1981-2212, Hillier 622, Nuevo León. Figure 79. Acorns of Quercus insignis (A) Rivera 2020, Costa Rica; Q. spinosa (B) Henry 5981, Hubei; Q. schottkyana (C) Henry 9299, Yunnan; Q. texana (D) Stevens 1978, Texas; Q. laurina (E) Sparrow & Brewster 34, Veracruz; Q. mexicana (F) Hartweg 431, Mexico; Q. laurifolia (G) Palmer 8487, Louisiana; Q. engelmannii (H) Epling 1932, California; Q. rex (J), viewed also from above (K) Henry 12665, Yunnan; Q. morii (L) Wilson

9700, Taiwan; Q. fusiformis (M) Palmer 1280, source unknown; Q. conspersa (N) Hinton 10729, source unknown; Q. candicans (P) Hinton 10673, Guerrero; Q. mongolica (Q) Wilson 10564, North Korea; Q. rugosa (R) Hinton 12390, Michoacán; Q. grisea (S) Metcalfe 756, Mew Mexico; Q. agrifolia var. oxyadenia (T) Warner & Howick 345, California; Q. castanea (U) Hinton 13437, Michoacán; Q. brantii (V) Rustam 1575, Iraq. Figure 80. Quercus affinis: habit (A); acorn (B). Kew 1996-649, Sparrow & Brewster 88, Hidalgo). Figure 81. Quercus aquifolioides: habit (A, B) Kew 1988-8819, Erskine, Fliegner, Howick & McNamara SICH 376, Sichuan. Leaves with varying degrees of spinescence, from the same tree (C); acorn (D). Zhao 112925, Sichuan. Figure 82. Quercus gilva: habit w. male inflorescences (A) Wilson 191, Kyushu; branchlet w. acorns (B) Arch 755, Japan. Figure 83. Quercus gravesii: habit with acorns Kew 1972-3975, Walker 440, Texas. Figure 84. Quercus oglethorpensis: habit (A) Kew 1990-363, Adams 028, Georgia; acorn (B) Duncan 5532, Georgia. Figure 85. Quercus vulcanica: habit (A) Kew 1994-814, Flanagan & Pitman 82, Turkey; acorn (B) Cosson 18, Turkey. Figure 86. Salix humboldtiana: habit (A) Kew 1998-602, Russell 198, Chile; inflorescence (B) Nee 35505, Chile; capsules opening to release seeds (C) Nee 31720, Chile. Figure 87. Sloanea sinensis: habit with flowers (A) Tutcher 611, Hong Kong; capsule beginning to open (B) Sino-British Expedition to Cangshan 0040, Guizhou; fully open capsule without seeds (C) Steward et al. 837, Guizhou. Figure 88. Sorbus randaiensis: habit with fruits (A); partial inflorescence (B. All Kew 1994-3526, Kirkham & Flanagan ETOT 84, Taiwan. Figure 89. Sorbus (Aria) tamamschjanae: leaves of varying shape, from the same tree (A–D) Kew 1982-4, Gabrieljan 01, Armenia. Sorbus wilsoniana: leaf with

New Trees

stipule (E) Kew 2004-245, Kirkham, Ruddy, Flanagan & McNamara SICH 2215, Sichuan. Sorbus (Aria) hajastana: leaves of varying shape, from the same tree (F–H) Kew 1980-6346, Liverpool University Botanic Garden 023, Armenia. Figure 90. Styrax grandifolius: habit with flowers (A) Chapman, s.n., Florida; infructescence (B) Palmer 8745. Figure 91. Tetradium ruticarpum: habit w. infructescence (A); detail of stem with petiole bases (B); capsule releasing seeds (C). All Kew 1985-8304, Sino-American Expedition to China SABE 1947, Hubei. Figure 92. Tilia nobilis: habit w. flowers (A) Wilson 3585, Sichuan; branchlet w. fruits (B) Wilson 2327, Sichuan; detail of leaf underside (C) Wilson 3585, Sichuan. Figure 93. Tilia dasystyla subsp. dasystyla: leaf (A); flower (B). Kew 1997-4972, Pigott 92-18, Crimea. Subsp. caucasica: flower (C); leaf (D). Kew 1977-330, Ala & Lancaster 033, Iran. Figure 94. Tsuga relatives. Nothotsuga longibracteata: branch with seed cones (A) from a photograph, China Red Data Book of Endangered Plants (p. 125). Cone (B); lower surface of leaf (C). Both Steward et al. 675, Guizhou. Tsuga chinensis var. chinensis: upper surface of leaf (D); branch with seed cones (H). Kew 20001388, Kirkham, Flanagan, Howick & McNamara SICH 1761, Sichuan. Lower surface of leaf (E); branch w. seed cones (J). Kew 1996-1018, Simmons, Erskine, Howick & McNamara SICH 771, Sichuan. Pseudotsuga sinensis var. wilsoniana: lower surface of leaf (F); branch w. seed cones (G). Kew 1995-2268, Kirkham & Flanagan ETOT 7, Taiwan. Figure 95. Ulmus bergmanniana: habit with fruits (A) Wilson 320, Hubei. Leaf underside (B); cluster of fruits (C). Maximowicz 66, Hunan. Figure 96. Ulmus laciniata: habit (A) Furuse 43194, Japan; fruits (B) Arnold Arboretum 4569-1, Japan. Figure 97. Zelkova schneideriana: branch from outer crown, w. small leaves and fruits (A); branch from inner crown, w. large leaves (B); w. fruits (C). Kew 1977-6615, Nanjing Botanic Garden 011, Jiangsu.

Glossary and Abbreviations Further definitions and illustrations are provided by M. Hickey and C. King in their outstanding book The Cambridge Illustrated Glossary of Botanical Terms (2000), from which many of the definitions given here are derived or have been adapted. In the definitions that follow, terms given in underlined type are themselves defined within the list. (See also the endpapers of this book, for illustration of some terms.) In some cases where definitions of related terms may be found helpful, these are indicated (‘Cf.’). Abbreviations and acronyms used in collectors’ references are explained in Appendix 2 (pp. 917–918). abaxial (especially of surface of a leaf) Lower; facing away from the axis. (Cf. adaxial.) abscission Shedding of a part of a plant (e.g. leaf, flower) due to old age or stress. achene Small, dry, indehiscent fruit that has a single seed (as in e.g. Polylepis). acicular Needle-shaped. acorn Fruit of Quercus; a single-seeded nut, set in a woody cupule. actinomorphic Radially symmetrical. Applied to flowers with multiple lines of symmetry passing through their centre (e.g. Malus). (Cf. zygomorphic.) acuminate Narrowing gradually to a point. acute Sharply pointed. adaxial (especially of surface of a leaf) Upper; facing towards the axis. (Cf. abaxial.) adherent In close contact with a different part, but not fused to it. adnate Fused with a different part by having grown together. (Cf. connate.) allopatric With a different distribution to that of another taxon. (Cf. sympatric.) alluvial Sediments deposited by rivers, or soils derived from such material. alternate Attached singly along the axis, not in pairs or whorls. amphistomatic With stomata on both sides of the leaf. amplexicaul (of leaf) With a base that clasps the stem but does not entirely surround it. androdioecious With only male or only hermaphrodite flowers on individual plants. androecium Collective name for the male sex organs in a flower (e.g. the stamens). anther Pollen-producing structure of flower, at the tip of the filament; part of a stamen.

anthesis Flowering period; when flower fully open and pollen beginning to be shed. apex (pl. apices) Tip. apical At the apex. apiculate With a short, sharp point. apocarpous Flower in which the carpels are not fused together (e.g. many Magnolia spp.). (Cf. syncarpous.) apomict Taxon that reproduces only or regularly by apomixis. apomixis Reproduction without fertilisation, usually by the asexual production of seeds (agamospermy) (as in e.g. Citrus, Sorbus). Includes vegetative reproduction (stolons, rhizomes, suckers, etc.) (as in e.g. Ulmus). apophysis The exposed tip of a seed scale in a mature, closed conifer cone. Particularly significant in the genus Pinus. appressed Lying flat against an object. apud (after name(s) of the author(s) of a plant name) Literally, ‘in the writings of’. Usually used where the name was published by one author or authors in the work of another. aril Fleshy outgrowth produced at the base of a seed (as in e.g. Taxus). Often acts to attract animal seed-dispersal agents. aristate Bearing a stiff awn. archaeophyte A non-native plant introduced to an area in ancient times (pre-1500 AD, in the United Kingdom). article (in Casuarinaceae) Portion of branchlet between each whorl of leaves. articulated Jointed. asl Above sea-level. assurgent Curving or growing upwards. attenuate Gradually narrowing. auricle Small lobe or ear-like appendage. auriculate With one or more auricles.

Metric – Imperial Conversion

1 inch = 25.4 mm 1 foot = 30.48 cm = 0.3048 m 1 metre = 39.37 inches

0 °C = 32 °F °F = 9 × (°C) + 32 _______ 5 5 × (°F – 32) °C = ___________ 9

Prunus sogdiana

924

Glossary and Abbreviations

authority The author(s) of a plant name. The names of these authors are stated directly after the plant name, often abbreviated. For example, Quercus L. (L. = Carl Linnaeus); Rhus wallichii Hook. f. (Hook. f. = Joseph Hooker, filius, i.e. son of William Hooker). Standard reference for the abbreviations: Brummitt & Powell (1992). autopolyploid State of increased ploidy resulting from doubling of the normal two sets of chromosomes in a single species. awn Bristle. axil Angle between the upper side of a leaf and the stem. axillary Situated in an axil. backcross Cross between hybrid and one of the parent species. berry Fleshy, indehiscent fruit with seed(s) immersed in pulp. bifid Divided, up to halfway, into two parts. bilateral symmetry See zygomorphic. bisexual See hermaphrodite. bletted (of fruit) Softened into edibility, by frost or fungi. bloom Bluish or greyish waxy substance on leaves or fruits. brachyblast A short, lateral, flower-bearing shoot in Magnolia (primarily in species formerly in Michelia). bract Reduced leaf, often subtending flower or inflorescence. bract scale (in female cones of Pinaceae) Papery structures that subtend the seed scales. Derived from modified leaves, and may be included (e.g. Tsuga) or exserted (e.g. Pseudotsuga). In other conifer families, bract scale and seed scale are fused. bracteole Small bract. Typically borne on pedicel of a flower. branchlet Small branch or twig, usually less than a year old. bud Immature shoot, protected by scales, that develops into leaves and/or flowers. bud scale Reduced, scale-like leaf partially enclosing a bud. bullate Puckered; with blister-like swellings on the surface. buttress roots Roots produced from the stem above ground that gradually fuse with the main stem, providing additional mechanical support. buttressed (of stem) With buttress roots. caducous Falling off early. caespitose Tufted. calcareous Relating to lime- or chalk-rich soils or water. calcicole (of a plant) Growing on soil containing lime. calcifuge (of a plant) Avoiding soil containing lime (i.e. usually growing on acidic soil). calyptra Cap-like structure that covers some flowers. Derived from fused-together petals and/or sepals. In Eucalyptus, for example, flowers may have either a single calyptra (sepals and petals), or an inner one (petals) and an outer (sepals). calyx (pl. calyces) Outer whorl of the perianth. Composed of several sepals. cambium Meristematic (actively dividing) cells in the stem responsible for stem expansion (secondary growth). campanulate Bell-shaped. camptodromous Pattern of leaf venation whereby the lateral veins bend just before reaching the margin, forming a loop. (Cf. craspedodromous.) capitate Head-like. capitulum (pl. capitula) Literally, ‘head’; (in plants) head-like inflorescence of sessile (or almost sessile) flowers surrounded by ring of bracts (involucre). Typical of daisies, Asteraceae.

New Trees

capsule Dry, dehiscent fruit; formed from syncarpous ovary. carpel Female reproductive organ of a flower. Composed of ovary, style and stigma. Typically, several carpels are fused together in each flower (syncarpous). The number of them can be of taxonomic significance; it can often be assessed by counting the stigma branches, or the chambers in the fruit. cartilaginous Firm and tough, but flexible; gristly. cataphyll A reduced leaf. In Pinus, cataphylls are scale-like, non-photosynthetic leaves, that line the stem. caudate With a long, tail-like appendage. cauliflory Production of flowers directly on the trunk and stems (as in e.g. Cercis), rather than at stem apex. cauliflorous Exhibiting cauliflory. CBD Convention on Biological Diversity. chaparral Dense vegetation consisting of low, scrubby trees and shrubs, often with small leaves and spines. chartaceous Paper-like. ciliate Fringed with long hairs. CITES Convention on International Trade in Endangered Species of Wild Fauna and Flora. clone Organism arising via vegetative or asexual reproduction. clonal reproduction Reproduction without the exchange of genetic material; asexual reproduction. coetaneous The production of flowers/inflorescences during leaf emergence. (Cf. precocious, serotinous.) compound Made up or consisting of two or more similar parts (e.g. a compound leaf is a leaf with several leaflets). concolorous Having the same colour throughout. conduplicate (of leaves) Folded once lengthwise. cone Term used here primarily to indicate the seed-bearing (female) structure of a conifer (‘conifer’ = ‘cone-producer’); otherwise known as a strobilus. A number of flowering plants produce cone-like seed-bearing structures, including Betulaceae and Casuarinaceae. cone scale A scale in a cone. In Pinaceae this term generally refers to the seed scale, while in other conifer families it refers to the combined complex of bract and seed scale. connate Fused together with a similar part. (Cf. adnate.) convex Having a rounded surface. cordate Heart-shaped (i.e. with two equal lobes at the base). coriaceous Leathery. corolla The inner whorl of the perianth. Composed of free or united petals, often showy. corymb Unbranched inflorescence with lateral flowers, the pedicels of which are of different lengths, making the inflorescence appear flat-topped. corymbose In form of corymb. cotyledon The leaf/leaves of an embryo plant (‘seed leaves’), that may emerge from the seed and become photosynthetic, or may remain within the seed. craspedodromous Pattern of leaf venation whereby the lateral veins run straight out to leaf margin. (Cf. camptodromous.) crenate With rounded teeth at the edge. crenulate With small, rounded teeth at the edge. crisped Curled or crumpled. Critically Endangered IUCN Red List conservation category: ‘facing an extremely high risk of extinction in the wild’.

Glossary and Abbreviations

crustaceous Somewhat hard, elastic; resembling a hard crust or shell. cultivar (cv., cvs) Cultivated variety; cultivated plant selected for feature(s) that is/are useful and/or appealing to growers, that is clearly distinct, uniform and stable in its characteristics, and remains so when propagated. A cultivar is indicated by single quotation marks around the name (e.g. Quercus rysophylla ‘Maya’). For the rules on naming a cultivar, see the International Code of Nomenclature for Cultivated Plants. cultivar group See Group. cuneate Wedge-shaped. cupular Cup-shaped; relating to the cupule. cupule Cup-shaped structure formed from coalescent bracts. Typical of Fagaceae and Nothofagaceae. May be dehiscent (as in e.g. Castanea) or indehiscent (as in e.g. Quercus). cusp A pointed end; curves meeting in a point. cuspidate Ending abruptly in a sharp point. cyme Branched, determinate inflorescence with a flower at the end of each branch. cymose In the form of a cyme. Data Deficient IUCN Red List conservation category: ‘there is inadequate information to make a direct or indirect assessment of its risk of extinction based on its distribution and/or population status’. dbh Diameter (of trunk) at breast height. Breast height is defined as 4.5 feet (1.37 m) above the ground. decurrent Running down, as when a leaf extends along a stem. decussate Leaf arrangement where the leaves are in opposite pairs, each pair at right angles to the preceding pair (as e.g. the scale leaves of Cupressaceae). deflexed Bent or turned downwards. dehiscent Opening naturally. (Cf. indehiscent.) deltoid Triangular. dentate With evenly triangular teeth at the edge. (Cf. crenate, teeth rounded; serrate, teeth saw-like.) denticulate Minutely (triangularly) toothed. determinate A form of inflorescence in which the terminal flower is the first to open, preventing further extension of the inflorescence axis. (Cf. indeterminate.) dichasium A type of cyme with lateral branches on both sides of the main axis. dichotomous Forked, dividing into two. digitate Hand-like; palmate. dimorphic Occurring in two forms. dioecious With male and female flowers on separate plants. dioecy The condition of being dioecious. discoid Flat and circular. disjunct Discontinuous; (of a distribution pattern) the range is split into two or more distinct areas. distal Situated away from point of attachment. (Cf. proximal.) distichous Arranged in two vertical ranks. divaricate Widely spreading, greatly divergent. Many trees and shrubs from New Zealand have a divaricating form, particularly when young, whereby the stems become interlaced, producing a ‘wire-netting’ effect. divergent Spreading from the centre. DNA Deoxyribose nucleic acid, the principal genetic material.

925

domatia Cavity or tuft of hairs that acts as a shelter for insects or other creatures. dorsiventral flattening Where a structure is flattened from top to bottom rather than from side to side. drupe A fleshy, dehiscent or indehiscent fruit with one to several seeds, each enclosed in a hard endocarp (the stone). ellipsoid An elliptic solid. emarginate Notched at the apex. Endangered IUCN Red List conservation category: ‘considered to be facing a very high risk of extinction in the wild’. endemic (of a plant or an animal) Found in a native state only within a defined region or country. endocarp Innermost layer of the fruit wall. Can be membranous and indistinguishable from the other layers of the fruit wall, or may be hard, woody and distinctive (see drupe). entire With an unbroken margin. epicalyx Whorl of sepal-like organs just outside the true calyx. epicarp Outermost layer of the fruit wall; the ‘skin’ on fruits such as apples and plums. epicormic (of shoot) Growing out from trunk or major branches. epidermis Outermost layer of cells (e.g. covering leaves). epimatium Expanded, fleshy, seed-bearing bract scale enclosing the seed in Podocarpaceae. epiphyte Plant growing on trees but not parasitic on the host. epistomatic Possessing stomata only on upper side of leaf. equisetoid Resembling the growth of an Equisetum (horsetail). ex (appearing before the author(s) of a plant name) Indicates the author who published the plant name validly. For example, Quercus floribunda Lindl. ex A. Camus: ‘ex’ denotes that the latter author (Aimée Camus) published the name validly; the name had been used previously by the former author (John Lindley), but had not been validly published by him. exserted Protruding; pushed out. Extinct IUCN Red List conservation category: ‘there is no reasonable doubt that the last individual [of taxon] has died’. Extinct in Wild IUCN Red List conservation category: ‘known only to survive in cultivation, in captivity or as a naturalised population (or populations) well outside the past range’. extrafloral Outside the flower. Used to describe nectaries situated on vegetative parts of a plant. extrapetiolar Outside the petiole. Used to describe stipules that are attached to the stem, rather than to the petiole. F1 A first-generation hybrid between two individuals. F2 The second generation of progeny from an original hybridisation event; derivatives from the F1 generation. facial pair In the Cupressaceae, the scale leaves are arranged in alternating pairs (see decussate). The pair comprising the upper and lower leaves are the facial pair. (Cf. lateral pair.) falcate Sickle-shaped. family A group of genera more closely related to each other than to genera in other families. Names of families are identified by the suffix ‘-aceae’ (e.g. Myrtaceae), with a few traditional exceptions (e.g. Leguminosae). farinose Covered with fine powder. (Cf. mealy.) fascicle Close cluster or bundle; reduced short shoot of Pinus.

926

Glossary and Abbreviations

fascicle sheath Cluster of membranous bud scales at the base of the fascicle in Pinus. fastigiate (of a tree or shrub) Narrow in form, with ascending branches held more or less parallel to the trunk. ferruginous Rust-coloured. filament (in a plant) Stalk of a stamen, supporting the anther. filiform Thread-like. fimbriate Fringed, with edge dissected into long narrow lobes. flabellate Fan-shaped. flush Coordinated growth of leaves or flowers. Such new growth is often a different colour to mature foliage. fluted Channelled or grooved. foliose Leaf-like. follicetum Body made up of several follicles. follicle Dry, dehiscent fruit containing numerous seeds, derived from a single carpel. form (f.) Lowest taxonomic rank (forma) into which an organism is normally classified. Usually showing minor differentiation in only one character and not forming distinct populations. fusiform Spindle-shaped; a gradually tapering rod. fynbos Extremely biodiverse vegetation in the Western Cape of South Africa, dominated by short, finely branched shrubs. galbulus The fruit of Juniperus; a modified cone that becomes fleshy as it matures. gallery forest Thin strip of forest adjacent to a river, in an otherwise unwooded landscape. garrigue Short Mediterranean scrubland. genus (pl. genera) A group of species more closely related to each other than to species in other genera. generic Of genus. germplasm Seed. glabrous Lacking hairs, smooth. glabrescent Becoming hairless. glandular Bearing glands. glaucescent Becoming glaucous; (incorrectly) slightly glaucous. glaucous Grey-blue, often from superficial layer of wax (bloom). globose, globular Spherical or globe-shaped. Group (or cultivar group) Collective name for a number of cultivars within a genus or species with similar characteristics. A very useful modern concept enabling the naming of many similar plants without the need to provide a cultivar name for each: so, for seed-raised plants that come nearly true from seed (as e.g. Quercus texana New Madrid Group); or for the progeny of a repeatable hybridisation; or for variants of a species that cannot be maintained as distinct entities by taxonomists but have horticultural merit and need to be distinguished. ‘Group’ is always included in the name. Named cultivars may be selected from within a cultivar group. gymnocarpy Bare seeds protruding from the cone, in Juniperus, due to insect damage. gynoecium The female sex organs in a flower (e.g. carpels). herbarium A collection of preserved plant specimens; also, the building in which such specimens are housed. herbarium specimen A plant specimen preserved (usually by drying or pickling) and maintained to provide information for botanists, particularly taxonomists. hermaphrodite Having both male and female parts in a single flower; bisexual.

New Trees

hesperidium Type of berry in which the flesh is divided into segments, with tough and leathery outer skin (as in e.g. Citrus). heteroblasty Production of different leaf forms at different ages. Very common in New Zealand native plants (e.g. Elaeocarpus hookerianus) and many Araliaceae. hilum Scar on seed, from its point of attachment in the ovary. Particularly prominent on the large seeds of Aesculus. hirsute Covered in rough, coarse hairs. hyaline Thin, colourless, translucent. hybrid Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies). hybrid swarm A group or population of hybrids that exhibit a range of characters between those of the parents. hybrid vigour Increased expression of characteristics in hybrids, when compared with the parent taxa. hypanthium Cup-shaped or tubular structure at the base of a flower (‘floral cup’), formed by enlargement of the receptacle and/or the bases of the floral parts. hypogynous With ovary situated below floral parts (inferior). hypostomatic With stomata only on lower side of leaf. IDS International Dendrology Society, sponsors of this book. ILDIS International Legume Database & Information Service. imbricate Overlapping. imparipinnate Odd-pinnate; (of a compound leaf) with a central rachis and an uneven number of leaflets, due to the presence of a terminal leaflet. (Cf. paripinnate.) included (botanical) Contained within another part or organ. indehiscent Not opening naturally; remaining closed at maturity. (Cf. dehiscent.) indeterminate A form of inflorescence in which the outer or lower flowers open first, and the inflorescence axis continues to grow. (Cf. determinate.) Index Seminum Seedlist issued by a botanic garden for exchange purposes. indigenous Native to an area; not introduced. indumentum A covering of hairs or scales. inflorescence Flower-bearing part of a plant; arrangement of flowers on the floral axis. infra- Below the rank of. As in ‘infrageneric’, ‘infraspecific’, referring to subdivisions of these taxa. infructescence Fruit-bearing part of a plant; derived from an inflorescence. INRA Institut National de la Recherche Agronomique (French National Institute for Agricultural Research). interfertile Capable of interbreeding with another species or species to give hybrids. intergeneric (of hybrids) Formed by fertilisation between species of different genera. internode Section of stem between two nodes. interspecific (of hybrids) Formed by fertilisation between different species. introgression Incorporation of genes from one species into the genotype of another, through repeated hybridisation, or repetitive backcrossing between a hybrid and one of its parents. involucre A ring of bracts surrounding an inflorescence. involute Rolled inwards at margins (i.e. towards upper surface).

Glossary and Abbreviations

IPNI International Plant Names Index. Database of plant names and associated details. IUCN World Conservation Union (formerly the International Union for the Conservation of Nature). karst Landscape area formed by the dissolution of limestone by water, with much exposed rock. Karst areas are usually rather arid due to the free-draining conditions. keel petal (in the flowers of some legumes) The two front petals, fused together to form a keel-like structure. keeled With a prominent ridge. key (of fruit) Vernacular English term for winged samaras (as in e.g. Acer, Fraxinus, Ulmus) lamina Leaf blade. lanceolate Lance-shaped; broadest in middle, tapering to point. lateral pair (in Cupressaceae) The pair of lateral scale leaves. (Cf. facial pair.) latex Colourless or milky sap produced by some plants (e.g. many Apocynaceae, Euphorbiaceae, Moraceae). laurisilva Humid, subtropical forest with high preponderance of Lauraceae; characteristic forest of Macaronesian islands. lax Loose or open. lectotype Specimen or illustration chosen to serve as the type specimen for a taxon, in cases where one was not designated by the original author. leaflet Leaf-like segment of a compound leaf. Least Concern IUCN Red List conservation category: ‘does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.’ ‘Lower Risk’ was formerly used, and many tree species are still so-categorised in the Red List. legume Two-valved fruit formed from a single carpel, widely known as a ‘pod’, typical of most members of the legume family (Leguminosae). The word has come to be used as much for members of the family as for their distinctive fruits. lenticel Pore on the stem. lenticellate Bearing lenticels. lenticular Lens-shaped. liana Woody climber growing from ground into canopy. lignotuber Woody tuber developed in the axils of the cotyledons or the first few leaf pairs. Common in Eucalyptus, where they provide a means for regeneration after a fire. ligulate Tongue-shaped. linear Strap-shaped. lobe Division of a leaf or other object. lobed Bearing lobes. locule Compartment of the ovary. loculicidal (of dehiscent fruit) Splitting between the locules. (Cf. septicidal.) lomentum Fruit derived from a single carpel, which splits into one-seeded sections (as in e.g. Sophora). Lower Risk See Least Concern. lustrous Smooth and shiny. Macaronesia The subtropical islands of the north Atlantic: the Azores, Canary Islands, Cape Verde Islands and Madeira. Malesia Floristic region including the Malay Peninsula, Indonesia, the Philippines and New Guinea. mallee Multistemmed growth form of many Eucalyptus species, in which numerous stems arise from ground level from an individual plant (from the lignotuber).

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maquis Tall Mediterranean drought-resistant shrubland. matorral Scrub vegetation, composed of low-growing woody plants, derived by degradation of Mediterranean forest. mealy Covered with coarse, flour-like powder. (Cf. farinose.) medial Relating to the middle or median. -merous Having a specified number of parts. In plants, usually refers to floral parts: so, a ‘5-merous’ flower has five sepals, five petals, five (or ten) stamens, etc. mesa Flat-topped, steep-sided mountain, often in arid areas. mesic (of habitat or site) Moderately moist. (Cf. xeric.) mesocarp Middle layer of the fruit wall, in between the epicarp and the endocarp; the ‘flesh’ of fruits such as plums. mesophytic (of a plant) Growing in moist (mesic) habitats. metapopulation ‘Population of populations’, usually referring to scattered populations of the same species. microspecies Species distinguished on the basis of minute differences of morphology. Generally used only for species that reproduce via apomixis (e.g. Sorbus). microsporophyll Pollen-producing scales in the male cones of conifers. midrib, midvein Central and principal vein in a leaf. moniliform Like a string of beads. monoecious With male and female flowers on the same plant. monoecy The condition of being monoecious. monograph Taxonomic account of a single genus or family. monomorphic Occurring in one form. monophyletic (of a group of taxa) With a single ancestor; part of a natural lineage, believed to reflect evolutionary relationships accurately (n. monophyly). (Cf. paraphyly, polyphyly.) monopodial With simple stem/axis, extending by growth of the apical bud and bearing lateral branches. (Cf. sympodial.) monoseed With a single seed. Many junipers in Juniperus section Sabina produce monoseed cones. monospecific (of a genus) Including only one species (as e.g. Aextoxicon). montane Of mountains. morphology The visible form of an organism. morphometric From the measurement of shape. mucro Short, straight point. mucronate Bearing a mucro. mutation Novel characteristic, arisen as a result of a spontaneous genetic change mutant Individual with a mutation. mycorrhiza (pl. mycorrhizae) Beneficial fungus associated with the roots of a plant. Different forms of association occur (e.g. arbuscular, ectendo-, endomycorrhizae), depending on how the fungus and the plant roots interact. nectary Gland or surface from which nectar is secreted. Near Threatened IUCN Red List conservation category: ‘does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying or is likely to qualify for a threatened category in the near future’. node Point on a stem where one or more leaves are borne. nomen ambiguum (nom. ambig.) (of plant name) Name whose application is ambiguous, which could cause confusion. nomen illegitimum (nom. illeg.) (of plant name) Illegitimate name, published with some contravention of the International Code of Botanical Nomenclature and therefore invalid.

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Glossary and Abbreviations

nomen nudum (nom. nud.) (of plant name) Name published without a description and therefore invalid. notho- (prefixed to the name of a taxon) Denotes hybrid origin. Hence nothogenus, nothospecies, nothovar. nut Dry, indehiscent, single-seeded fruit with woody outer wall. nutlet Small nut. Term may also be applied to an achene or part of a schizocarp. ob- (prefixed to technical term) Inverse of. oblanceolate Inversely lanceolate; broadest towards apex. oblate Almost globose, but flattened at apices; subglobose. obtuse Blunt. open pollinated Pollinated without control. Where plants are open pollinated, unexpected hybrids may occur. orbicular Circular. ovary Lowest part of the carpel, containing the ovules; later developing into the fruit. ovate Egg-shaped; broadest towards the stem. ovoid Egg-shaped solid. ovule Structure inside ovary, that when fertilised becomes a seed. palmate Roughly hand-shaped; (of a leaf) divided partially or fully to the base, with all the leaflets arising from the tip of the petiole (as in e.g. Aesculus). panicle A much-branched inflorescence. paniculate Having the form of a panicle. papillae Small protuberances on surface of petal or leaf, sometimes hair-like in appearance. papillose Bearing papillae. páramo Vegetation above the treeline in tropical South America, mostly grasslands and scrub. paraphyletic (of a taxon, usually at generic or family level) With a common ancestor, but some of the other descendants of that ancestor are excluded from the taxon, for subjective reasons of the taxonomist (n. paraphyly). Such a classification is therefore not ‘natural’. (Cf. monophyly, polyphyly.) paripinnate Even-pinnate; (of a compound leaf) with a central rachis and an even number of leaflets (no terminal leaflet). (Cf. imparipinnate.) pectinate Comb-like. pedicel Stalk of a single flower. pedicellate Borne on pedicel. peduncle Stalk of inflorescence. pedunculate With a peduncle. pendent Hanging. peltate Disc-shaped and attached at centre of lower surface to a stalk (e.g. leaf of Nasturtium, Tropaeolum majus). perfect (botanical) All parts present and functional. Usually referring to both androecium and gynoecium of a flower. perhumid Always moist or wet. Usually referring to tropics. perianth Calyx and corolla. Term used especially when petals and sepals are not easily distinguished from each other. perular scale Basal scales in a leaf bud. petal Single segment of the corolla. Often brightly coloured and an attractant for pollinators. petaloid Petal-like. May refer to sepals or stamens modified into a petal-like form. petiole Leaf stalk. petiolate Bearing a petiole. petiolule Stalk of a leaflet in a compound leaf.

New Trees

phenology The seasonal timing of events in the life cycle of a plant or animal, and the study thereof. phloem Sap-carrying vascular tissue. phototropism A plant’s response to light: shoots growing towards it, roots away. phyllichnia (in Casuarinaceae) Longitudinal ridges on articles. phyllode A petiole taking on the form and functions of a leaf (as in e.g. Acacia). phylloid Leaf-like. pilose Softly hairy. pinna (botanical) Primary division of a compound leaf. pinnate (of a compound leaf) With leaflets/veins along each side of a central rachis/midrib. pinnatifid (of a leaf) Dissected into large teeth or lobes that reach no more than halfway to the midvein. pinnatinerved Leaf venation with a pinnate arrangement. pinnatisect (of a leaf) Dissected into large teeth or lobes that reach nearly to the midvein (i.e. not completely pinnate). pinnule Secondary division of a compound leaf. pioneer species Early colonists of disturbed areas. pistillate Female, referring to female plants (dioecy) or flowers (monoecy), or the female parts of a hermaphrodite flower. plicate Folded more than once lengthwise. ploidy Number of chromosomes. podzol A soil characterised by a superficial layer of raw humus above a generally grey layer of mineral soil, depleted of iron sesquioxides and aluminium. pollen Small grains that contain the male reproductive cells. Produced in the anther. pollination Act of placing pollen on the stigma. Various agents may initiate pollination, including animals and the wind. polygamous With unisexual and bisexual flowers on same plant. polyphyletic (of a taxon) Including entities descended from different ancestors and evolutionary lineages, grouped usually as a result of superficial similarities (n. polyphyly). The grouping is therefore not ‘natural’. (Cf. monophyly, paraphyly.) pome Fleshy fruit with leathery core. Typical of Rosaceae subfamily Maloideae (e.g. Malus). precocious The production of flowers/inflorescences prior to leaf emergence. (Cf. coetaneous, serotinous.) propagule Vegetative structure that can become detached and give rise to a new plant. prostrate Lying flat. protologue Text of first publication of a taxon’s name. proximal Situated towards point of attachment. (Cf. distal.) pruinose Covered with a waxy bloom (as found on a plum). puberulent Minutely pubescent. pubescence Hairiness. pubescent Covered in hairs. pulvinus (pl. pulvini) Enlarged portion of petiole or rachis. punctuate Marked with dots, depressions or glands. pyrene Stone of a drupe, consisting of the seed and the surrounding endocarp. pyriform Pear-shaped. raceme Unbranched inflorescence with flowers produced laterally, usually with a pedicel. racemose In form of raceme.

Glossary and Abbreviations

rachis Central axis of an inflorescence, cone or pinnate leaf. rachilla (pl. rachillae) Secondary axis in an inflorescence. radial symmetry See actinomorphic. ramiflory Production of flowers directly on the branches. Included within cauliflory. ramiflorous Exhibiting ramiflory. receptacle Enlarged end of a flower stalk that bears floral parts; (in some Podocarpaceae) fleshy structure bearing a seed, formed by fusion of lowermost seed scales and peduncle. reflexed Folded backwards. relict species Species that has survived unchanged from a previous age (a ‘living fossil’), or become geographically isolated from related species due to a change in circumstances. reniform Kidney-shaped. resin canal Minute tubes containing resin-producing cells, in the leaves and wood of conifers. resin gland Small gland on leaf or other surface exuding resin. reticulate Arranged in a net-like manner. retuse Slightly notched at apex. revolute Rolled downwards at margin. rhizome Persistent horizontal subterranean stem bearing roots and shoots. rhizomatous Having or resembling a rhizome. rhombic Diamond-shaped. rhomboid Diamond-shaped solid. rugose Wrinkled. sagittate Arrowhead-shaped. samara Dry, indehiscent, winged fruit, usually with a single seed (as in e.g. Acer, Fraxinus, Ulmus. Also called a ‘key fruit’. sarcotesta Fleshy outer coat on a seed (as in e.g. Ginkgo). scabrous Rough to the touch, as a result of minute projections. scabrid Slightly less rough. scarious Thin, dry and membranous. schizocarp Dry fruit that breaks up into sections at maturity. sclereid Hard, thick-walled cell; part of the sclerenchyma, the support tissue in plants. Individual sclereids also occur in the flesh of Pyrus fruits, giving their characteristic gritty texture. sclerophyllous With tough, leathery, usually evergreen leaves. Typical of trees and shrubs from warm, dry climates. section (sect.) Subdivision of a genus. seed scale (in female cones of Pinaceae) Seed-bearing structure. In other conifer families, the seed scale and the bract scale are fused together. self-coppicing (of vigorous tree or shrub: e.g. Corylus) Producing new stems at ground level without having been damaged. sensu lato (s.l.) In the broad sense. sensu stricto (s.s.) In the narrow sense. sepal Single segment of the calyx. Protects the flower in bud. septicidal (of fruit) Splitting along the partitions (septa), rather than along the walls of the locules. (Cf. loculicidal.) serotinous The production of flowers/inflorescences after leaf emergence; (of cones/dry fruits) closed until scorched by fire (as in e.g. Banksia, Pinus). (Cf. coetaneous, precocious.) serrate With saw-like teeth at edge. serrulate Minutely serrate. sessile Lacking a stem or stalk. setose Bristly. simple (of a leaf) Unlobed or undivided. sinuate (of a flat leaf) With margins that wind strongly inwards and outwards.

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sinus Recess between two lobes or teeth on leaf margin. s.l. Abbreviation of sensu lato. In the broad sense. s.n. Abbreviation of sine numero. Without a number. s.s. Abbreviation of sensu stricto. In the narrow sense spathulate Spatula-shaped. species (sp., pl. spp.) Division of a genus; group of plants or animals with similar characters, all more closely related to each other than to any other similar group. specific Of species. spicate Spike-like. spike Inflorescence in which flowers sessile on the main axis. spinose Spiny. sp. nov. Abbreviation of species nova. A newly discovered species, for which no epithet has been formally published. sporophyll Specialised leaf or structure derived from a leaf that bears spore-producing bodies. The seed scale of a conifer cone is a megasporophyll, while the scales in a male conifer cone are microsporophylls. SSC Species Survival Commission (of the IUCN). stamen Male reproductive organ of flower. Usually composed of an anther and a filament. staminal ring Ring of stamens. staminate Male, referring to male plants (dioecy) or flowers (monoecy), or the male parts of a hermaphrodite flower. staminode Sterile or abortive stamen. Can be petaloid or converted into a nectary. standard petal (in the flowers of some legumes) Large, upper petal; also known as ‘vexillum’. stellate Star-shaped. stigma (in a flower) The part of the carpel that receives pollen and on which it germinates. May be at the tip of a short or long style, or may be reduced to a stigmatic surface at the apex of the ovary. stipitate Having a stalk (stipe), or borne upon one. stipule An outgrowth arising at the base of the petiole. Often paired. May be foliose or spinose, caducous or persistent. stipulate Bearing stipules. stoma (pl. stomata) Small pores on the leaves (and young stems) that allow for gas exchange. stratify (horticultural) Expose seeds to cold weather to promote germination. strangler An epiphytic vine or tree whose roots extend down the trunk of a supporting tree and coalesce around it, eventually strangling it. striated Bearing fine longitudinal stripes, grooves or ridges. strigose Bearing stiff hairs or bristles. strobilus Cone. Used here to indicate male, pollen-producing structure in conifers, which may or may not be cone-shaped. style Generally an elongated structure arising from the ovary, bearing the stigma at its tip. stylopodium Persistent remains of the style at tip of an acorn. sub- (prefixed to tech. term) Beneath; less than; approximately. subspecies (subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.

930

Glossary and Abbreviations

subulate Awl-shaped. symbiotic (of two organisms) Dissimilar but closely associated, living together in a mutually beneficial manner. sympatric With the same distribution as another taxon (or with overlapping distribution). (Cf. allopatric.) sympodial With stem/axis terminating (perhaps after the production of a flower), and growth continuing via lateral branches. (Cf. monopodial.) syncarpous Flower in which the carpels are fused together to form a single unit. (Cf. apocarpous.) synonym (syn.) (botanical) An alternative or former name for a taxon, usually considered to be invalid (often given in brackets). Synonyms arise when a taxon has been described more than once (the prior name usually being the one accepted as correct), or if an article of the International Code of Botanical Nomenclature has been contravened, requiring the publishing of a new name. Developments in taxonomic thought may be reflected in an increasing list of synonyms, as generic or specific concepts change over time. taiga Region of sparse coniferous forest in northern latitudes. taxon (pl. taxa) Group of organisms sharing the same taxonomic rank (family, genus, species, infraspecific variety). taxonomy Classification, usually in a biological sense. tepal Perianth segment. Petal/sepal of a flower in which the two structures cannot be differentiated (as in e.g. Magnolia). terete Like a slender, tapering cylinder. ternate In threes. terrestrial Growing in the ground. thyrse Mixed inflorescence in which main axis indeterminate but secondary axes determinate. thyrsoid In form of thyrse. Tibet Traditional English name for the formerly independent state known to its people as Bod, now the Tibet (Xizang) Autonomous Region of the People’s Republic of China. The name Xizang is used in lists of Chinese provinces. tomentum Dense layer of soft hairs. tomentose With tomentum. trichome Hair-like growth from epidermis. May be glandular. trifoliate With three leaves or leaflets. trifoliolate With three leaflets. trinerved Three-nerved, with the veins (nerves) all arising from near the base of the leaf. triplinerved Three-nerved, with the two lateral veins (nerves) arising from the midrib above the base of the leaf. TROBI Tree Register of the British Isles. TROI Tree Register of Ireland. trullate Trowel-shaped. truncate Appearing as if cut off. tuber Underground storage organ derived from root or stem. tubercle Small tuber; small, rounded projection or protruberance. tuberculate Bearing tubercles. turbinate Spinning-top shaped; inversely conical; obconical. tylose An obstruction of a connective vessel (xylem or phloem) caused by the intrusion of part of another cell. type specimen A herbarium specimen cited in a taxonomic account to define a particular species or other taxon. umbel Inflorescence in which pedicels all arise from same point

New Trees

on peduncle. May be flat-topped (as in e.g. Umbelliferae) to spherical (as in e.g. Araliaceae). umbellate In form of umbel. umbellaster Basic inflorescence unit in Eucalyptus; a group of flowers (with terminal bud ending in a flower) more or less arising from one point. May derive from cyme, thyrse or panicle. umbilicate Having a small depression; resembling the human belly-button (umbilicus). umbo Boss or protuberance, particularly that in centre of apophysis of pine seed scale. umbonate Bearing an umbo. undulate Wavy. unicellular Single-celled. unifoliolate Having one leaflet, thus appearing to have simple (not compound) leaves. unisexual Having only male or female organs in a flower. urceolate Urn-shaped. USDA United States Department of Agriculture. USDA Hardiness Zone Defined in USDA Plant Hardiness Zone Map, which divides the North American continent into ten zones, each representing an area of winter hardiness for plants, based on average annual minimum temperatures. USNA United States National Arboretum. valvate (of similar parts of a plant: e.g. petals) Meeting without overlapping; (of dehiscent fruit) opening via valves. variety (var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare, minor variants more usefully ranked as forms. venation Pattern of veins (nerves), especially in a leaf. vernalisation The priming of a plant response (e.g. germination, flowering) by exposure to low temperatures in winter. vernation Arrangement of a leaf in its bud. vesicle Small bladder or sac. vicariants Similar, usually related, taxa found in similar habitat, but in distant locations. villous Covered in long, shaggy hairs. viscid Sticky. Vulnerable IUCN Red List conservation category: ‘facing a high risk of extinction in the wild’. whorl Arrangement of three or more organs (leaves, flowers) around a central axis. whorled Arranged in a whorl. wing petal (in flowers of some legumes) The two lateral petals. winter bud Vegetative buds developed in the autumn and persisting through winter until spring, when they burst. WLTM Would Like To Meet. × (multiplication sign) Placed before an epithet, indicates a hybrid; between two parents, denotes a cross between them. xeri-adapted Adapted to tolerate dry conditions. xeric (of habitat or site) Arid. (Cf. mesic.) xerophytic (of a plant) Growing in arid (xeric) habitats. Xizang See Tibet. xylem Vascular tissue carrying water and minerals from roots. zoopharmacognosy Self-medication by animals. zygomorphic Bilaterally symmetrical. Term applied to flowers with a single line of symmetry passing through the centre (e.g. Salvia). (Cf. actinomorphic.)

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— (1945). Studies in the Lauraceae. VI. Preliminary survey of the Mexican and Central American species. Journal of the Arnold Arboretum 26: 365–434. Allen, O.N. & Allen, E.K. (1981). The Leguminosae: A Source Book of Characteristics, Uses and Nodulation. London: Macmillan. Allnutt, T.R., Courtis, J.R., Gardner, M. & Newton, A.C. (1997). Genetic variation in wild Chilean and cultivated British populations of Podocarpus salignus D. Don (Podocarpaceae). Edinburgh Journal of Botany 58: 459–473. American Chestnut Cooperators’ Foundation (1997– 2008). Genus Castanea. At (accessed 22 March 2008). American Horticultural Society (1998–2008). American Horticultural Society (AHS) Plant Heat Zone Map. At (accessed 22 November 2008). Anagnostakis, S.L. (1992). Chestnuts and the introduction of Chestnut Blight. 83rd Annual Report of the Northern Nut Growers Association, Inc.: 39–42. — (2001). The effect of multiple importations of pests and pathogens on a native tree. Biological Invasions 3: 245–254. Anderson, J. (2002). A plantsman’s view of the future plant collection at Inverewe. The Caledonian Gardener 2002: 61–65. Andresen, J.W. (1966). A multivariate analysis of the Pinus chiapensis-monticola-strobus phylad. Rhodora 68: 1–24. Andrews, S. (1986). Corynocarpus laevigatus. The Kew Magazine 3: 125–126. — (1990). FSA Contributions 1: Aquifoliaceae. Bothalia 24: 163–166. — (1991). Aquifoliaceae. In: A.J.C. Grierson & D.G. Long (eds), Flora of Bhutan, vol. 2 (part 1), pp. 104–111. Edinburgh: Royal Botanic Garden Edinburgh.

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Zheng, H., Wu, Y., Ding, J., Binion, D., Fu, W. & Reardon, R. (2004). Invasive Plants of Asian Origin Established in the United States and their Natural Enemies, Vol. 1. Washington, DC: USDA Forest Service.

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Zielinski, Q.B. (1965). Taxonomic status of Pyrus fauriei Schneider (Rosaceae). Baileya 13: 17–19.

Index of Tree Names This index covers names of all the trees described in this book, including synonyms, and names of all trees mentioned in discussion. Taxa that appear in New Trees in the form of cross-references to the works of Bean and Krüssmann but are not otherwise mentioned are not listed again here. Tree genera treated by Bean and Krüssmann but from which there have been no recent introductions (and which therefore are not discussed in New Trees) are indicated below: ‘No NT accounts’. Information on these genera should be sought in Bean and Krüssmann, or elsewhere. In cases where a name change has occurred that could render a cross-reference difficult to find, the new name is included in this index, directing you to the crossreference: so, if seeking Paraserianthes lophantha, you will find it indexed under that name and be directed to its cross-reference under the old name Albizia lophantha (p. 129 above), and thence to its description in Krüssmann (1985a). Using the index and the cross-references together should enable information to be found on the majority of trees cultivated in our area. Text in bold type indicates that the taxon is described in a full account above. Page numbers in italic type indicate illustrations. Page numbers in roman type indicate taxa mentioned in discussion but not fully described, or synonyms, or cross-references.

Abies 43, 426, 465, 535, 562, 584, 671, 800 — alba 46, 47, 55 — balsamea 46 — borisii-regis 44, 46, 46 — bornmuelleriana 56 — cephalonica 46, 56 — chayuensis 52 — ×chengii 47 — chensiensis 44, 47 subsp. chensiensis 47 subsp. salouenensis 47, 48 subsp. yulongxueshanensis 47, 48 — cilicica 44 — colimensis 45 — concolor 50 — delavayi 43, 48 subsp. delavayi 49 var. fabri 48 subsp. fansipanensis 49 var. faxoniana 48 var. forrestii 48, 52 var. georgei 48 var. motuoensis 48 var. nukiangensis 48, 49 — densa 49, 50, 799, 800

Abies continued — durangensis 44, 45, 50, 51 var. coahuilensis 51 var. durangensis 51 — equi-trojani 56 — ernestii var. salouenensis 47 — fabri 43, 48, 49 — fansipanensis 48 — fargesii 43, 48 var. faxoniana 48 var. sutchuenensis 60 — firma 46, 54 — flinckii 45 — forrestii 43, 44, 48, 49, 52 var. ferreana 52 var. forrestii 52 var. georgei 44, 48, 52 var. smithii 52 — fraseri 46 — grandis 50 — guatemalensis 20, 45, 53 var. ixtepejiensis 53 var. jaliscana 45, 53, 53 var. longibracteata 53 var. rushforthii 53 var. tamaulipensis 53 — hickelii var. oaxacana 56

Abies continued — homolepis 44, 53 var. umbellata 53 — koreana 43, 45 — magnifica 45, 54 var. shastensis xi, 42, 54 var. xanthocarpa 54 — marocana 57 — mexicana 45 — nebrodensis 19, 55, 55 — nordmanniana 56 subsp. equi-trojani 56, 56 subsp. nordmanniana 56 — pinsapo 43, 57 var. marocana 44, 45, 57 var. pinsapo 57 var. tazaotana 57, 57 — procera 45, 54 — religiosa 45 var. emarginata 45 — rolii 52 — sachalinensis 58, 570 var. gracilis 58 var. mayriana 32, 58 var. nemorensis 58 var. sachalinensis 58 — sibirica 44, 59, 59

Nomenclatural novelty

New name published in this work: Magnolia ×foggii Figlar, nothosp. nov., p. 489.

Quercus brantii

960

Index of Tree Names

Abies continued — sibirica continued subsp. semenovii 60 subsp. sibirica 59 — spectabilis 50 — tacanensis 53 — veitchii 60 var. sikokiana 60, 60 — vejarii 46, 61, 61 var. macrocarpa 61 subsp. mexicana 45 — yuana 52 — zapotekensis 53 Abrophyllum 213 Abutilon No NT accounts Acacia 11, 27, 35, 63 — baileyana 64 ‘Purpurea’ 64 — caven 64, 65, 908 — dealbata 64, 65, 182 subsp. subalpina 7, 65 — floribunda 66 — genistifolia 66 — karroo 63, 66, 66 — melanoxylon 64 — natalitia 66 — nilotica 63 — obliquinervia 66 — paradoxa 64 — pataczekii 62, 67, 67 — pycnantha 64 — rubida 68 — spectabilis 62, 68, 68 — truncata 66 — ulicifolia 66 Acaciella 63, 64 Acaena 645 Acanthopanax 778 No NT accounts NOW Eleutherococcus Acca No NT accounts Acer 16, 69 — amplum 89 subsp. amplum 89 subsp. bodinieri 81, 89 subsp. catalpifolium 89 subsp. tientaiense 89 — barbatum 105 — ×bornmuelleri 78 — buergerianum 72 — caesium subsp. giraldii 85 — calcaratum 75, 78 — campbellii 71, 74, 81, 84, 107 subsp. campbellii 76 var. fansipanense 76 subsp. flabellatum 76, 85 var. yunnanense 76, 85 subsp. sinense 110 subsp. wilsonii 76, 115

Acer continued — campestre 78 — capillipes 82, 92 — cappadocicum 76, 89 subsp. divergens 83 subsp. lobelii 88 — carpinifolium 71 — caudatifolium 79, 79, 80, 104, 108 ‘Variegatum’ 80 — caudatum 70 subsp. ukurunduense 113 — ceriferum 71, 80 — chapaense 76, 81 — cinnamomifolium 82, 83 — ‘Cinnamon Flake’ 76 — cissifolium 71 — ×conspicuum 74, 81 ‘Candy Stripe’ 82 ‘Elephant’s Ear’ 82, 82 ‘Phoenix’ 82 ‘Silver Cardinal’ 82 ‘Silver Vein’ 82 — cordatum 75, 82 var. dimorphifolium 82 — coriaceifolium 82, 83 — ×coriaceum 78 — craibianum 78 — davidii 71, 73, 74, 81, 90 George Forrest Group 74 subsp. grosseri 86, 90 ‘Karmen’ 74 ‘Serpentine’ 74 — distylum 70 — duplicatoserratum 83 var. chinense 84 — elegantulum 84, 84 var. macrurum 84 — fabri 75, 83, — ×freemanii 85 ‘Armstrong’ 85, 85 Autumn Blaze 85 Autumn Fantasy 85 Celebration 85 ‘Celzam’ 85 ‘DTR102’ 85 ‘Elegant’ 85 ‘Jeffersred’ 85 ‘Marmo’ 85 — fenzelianum 76 — fulvescens 88, 89 — Gingerbread 76 — ginnala 73 — ‘Ginzam’ 76 — ‘Girard’ 76 — glabrum 71 — grandidentatum 105 — griseum 72, 76, 77 — heldreichii subsp. trautvetteri 113

New Trees

Acer continued — ×hillieri 76 ‘Summergold’ 76 ‘West Hill’ 76 — hookeri 109 — hyrcanum 86 subsp. hyrcanum 87 subsp. intermedium 86 subsp. keckianum 86 subsp. reginae-amaliae 73, 86, 87 subsp. sphaerocarpum 86 subsp. stevenii 86, 87 subsp. tauricola 87 — insulare 79 — japonicum 71, 73, 101, 109 — jingdongense 100 — kawakamii 79 — kweilinense xii — laevigatum 71, 82, 83 var. salweenense 75 — Lancaster 962 90, 108 — laurinum 73, 87, 100 — leucoderme 105 — longipes 88 subsp. amplum 89 subsp. catalpifolium 89, 90 subsp. firmianioides 89, 90 ‘Gold Coin’ 90 subsp. longipes 88, 89, 89 — macrophyllum 72, 73 — mandschuricum 72 — maximowiczianum 76, 95 — metcalfii 90 — microsieboldianum 101 — miyabei 76 — mono 98 — monspessulanum 72, 78, 91 subsp. ibericum 91 subsp. monspessulanum 91 subsp. turcomanicum 92, 92 — morifolium 74, 92, 93 — morrisonense H.L. Li 104 — morrisonense Hayata 79 — negundo 71, 94 subsp. californicum 95 var. texanum 95 subsp. interius 95 subsp. mexicanum 94, 94 subsp. negundo 94 — nigrum 105 — nipponicum 70 — oblongum 95 var. concolor 95 var. itoanum vi, 75, 96 var. latialatum 95 var. oblongum 95

Acer continued — obtusifolium 97 — olivaceum 84 — oliverianum 76, 96 subsp. formosanum 96, 96 subsp. oliverianum 107 — opalus 78 — osmastonii 78 — palmatum 71, 73, 81, 84, 97, 98, 101, 109 subsp. amoenum 97 subsp. matsumurae 97 subsp. palmatum 97 var. pubescens 83, 84 — pauciflorum 98 — pectinatum subsp. forrestii 85 ‘Sirene’ 74 subsp. laxiflorum 88 subsp. maximowiczii 90 subsp. taronense 111 — pensylvanicum 71, 73, 81, 82 ‘Erythrocladum’ 73 — pentaphyllum 72 — pictum 98 subsp. dissectum 91 subsp. macropterum 99 subsp. mayrii 91 subsp. okamotoanum vii, 99, 99, 100, 102 subsp. tricuspis 91 — pilosum 72, 100 var. pilosum 100 var. stenolobum 100 — pinnatinervium 88, 88, 100 — platanoides 72, 89 subsp. turkestanicum 113 — ×pseudoheldreichii 100 ‘Blagdon’ 101 — pseudoplatanus 54, 72, 73, 78 ‘Atropurpureum’ 101 — pseudosieboldianum 73, 101 subsp. pseudosieboldianum 101, 101, subsp. takesimense 34, 102, 102, 108 — pubipalmatum 98 — pubinerve 102, 103 — pycnanthum iii, 103, 104 — ‘Red Flamingo’ 82 — robustum 80 — rubescens 74, 82, 104, 105, 108 — rubrum 8, 73, 85, 103, 104 — saccharinum 73, 85 — saccharum 72, 105, 700 subsp. floridanum 106 subsp. grandidentatum 106

Index of Tree Names

Acer continued — saccharum continued subsp. leucoderme 106 subsp. nigrum 70, 106 subsp. saccharum 106 subsp. schneckii 106 subsp. skutchii 105, 106, 106 — schneiderianum 107 — ×schwerinii 113 — serrulatum 96 — shirasawanum 73, 102, 109 — sieboldianum 73, 108, 109 — sikkimense 11, 109 subsp. metcalfii 90 — sinopurpurascens 69, 110, 110 — stachyophyllum 71, 111 subsp. betulifolium 111 subsp. stachyophyllum 111 — stenolobum var. megalophyllum 100 — sterculiaceum 72 subsp. franchetii 85 subsp. thomsonii 112 — takesimense 102 — tataricum subsp. aidzuense 77, 85 subsp. ginnala 85 subsp. semenovii 107 — tegmentosum 74 ‘Joe Witt’ 74 — tenellum 112 — tetramerum 111 — tonkinense 76, 76, 112 subsp. kwangsiense 112 subsp. liquidambarifolium 112 subsp. tonkinense 112 — tschonoskii subsp. koreanum 113 — wardii 4, 71, 113, 113 — ‘White Tigress’ 74, 74 — wuyuanense 102 — yui 69, 76 Ackama 115 — rosifolia 114, 115 Acradenia No NT accounts Actinodaphne pedunculata 557 Adenodaphne 467 Adinandra 116 — drakeana 116 — hemsleyi 116 — millettii 116, 116 Aesculus 117 — ×arnoldiana 118 — assamica 118 — ‘Autumn Splendor’ 118 — ×bushii 118, 118 — californica 117

Aesculus continued — flava 119 — glabra 118 — hippocastanum 117 — indica ‘Sydney Pearce’ 9 — ×marylandica 119, 119 — ×mississippiensis 118 — parviflora 117 — pavia 118 — turbinata 117 — wangii 117,118 Aextoxicon 120 — punctatum 120, 120, 444, 515 Afrocarpus 121 — falcatus 121, 121, 122 — gaussenii 121 — gracilior 6, 121, 641 — mannii 121, 644 Afrocrania 261 Agathis 123, 897 — australis 123, 123 Ailanthus 124 — altissima 124, 249 var. sutchuenensis 125 var. tanakae 124, 125 Akania 175 Alangium 125 — chinense 4, 126, 126, 127 — platanifolium 126 ‘Macrophyllum’ 126 var. macrophyllum 126 Albizia 128 — coreana 128, 129 — garrettii 129 — julibrissin 128, 129 ‘Summer Chocolate’ 128 — kalkora 128, 129 — lebbeck 128 Alcimandra 473 — cathcartii 482 Alectryon 130 — excelsus 130, 130 Aleurites No NT accounts Allocasuarina 131, 222 — duncanii 131, 132 — littoralis 132 — monilifera 132 — torulosa 132 — verticillata 132 Alniphyllum 132 — fortunei 133, 133 — pterospermum 133 Alnus 26, 133, 135, 163 — acuminata 135, 136 subsp. acuminata 136 subsp. arguta 137, 137 subsp. glabrata 137 — cordata 135 — fauriei 134, 138

Alnus continued — ferdinandi-coburgii 135, 136, 138 — firma var. multinervis 143 var. sieboldiana 144 — formosana 135, 139, 140, 830 — glutinosa 136 — henryi 139, 139 — hirsuta 140, 141, 142 f. inokumae 140 — ×hybrida 143 — incana subsp. rugosa 144 subsp. tenuifolia 144 — inokumae 140, 140 — japonica 136, 142 — jorullensis 135, 136 — lanata 136, 141 — mandshurica 141 — maritima 139 var. formosana 139 — matsumurae 142, 142 — ×mayrii 142 — maximowiczii 135 — nitida 139 — pendula 134, 135, 143, 143 — rubra 136 — sieboldiana 26, 135, 144 — trabeculosa 144, 145 — viridis 136 subsp. fruticosa 139, 146 subsp. sinuata 144 Alseodaphne breviflora 553 Altingia 457 Amelanchier 793, 795 No NT accounts Amentotaxus 146, 672, 903 — argotaenia 147, 148, 148 — formosana 21, 148 — yunnanensis 148 Amomyrtus 148 — luma 149 — meli 149, 149 Amygdalus 657 Angophora 275, 324 — hispida 275 Annona No NT accounts Aralia 149 — bipinnata 150 — echinocaulis 150, 150 — elata 150 — foliolosa 150 — fragrans 150 — leschenaultii 150 — stipulata 150 Araucaria 151 — angustifolia 22, 152 — araucana 20, 49, 53, 151, 152

961

Araucaria continued — bidwillii 152, 153 — cunninghamii 152, 382 var. papuana 153 — excelsa 153 — heterophylla 151, 153, 153 — hunsteinii 152 Arbutus 154 — andrachne 154 — ×andrachnoides 154 — arizonica 155 — canariensis 154 — glandulosa 155 — ×reyorum ‘Marina’ 154, 154 — menziesii 155 — occidentalis 155 — texana 156 — ×thuretiana 154 — unedo 154 — xalapensis 33, 155, 156, 156 var. texana 156 Arceuthos 414 Arctostaphylos No NT accounts Argania No NT accounts Aria 793, 794, 815 — alnifolia 817 — aronioides xvi, 820 — austriaca 824 — caloneura 824 — epidendron 824 — folgneri 815, 817, 824 — hemsleyi xvi, 815, 817, 821, 821 ‘John Bond’ 821 — japonica 817, 824 — keissleri 824 — megalocarpa 815, 817, 824 — aff. megalocarpa ex Mangshan 820, 820 — meliosmifolia 824 — nivea 793, 796, 815, 816, 817, 819, 820 — pallescens 821, 824 — rhamnoides 825 — thibetica 825 — thomsonii 820 — yuana 23, 817, 822, 822 — xanthoneura 825 — zahlbruckneri 817, 823, 825 Aristotelia No NT accounts Armeniaca 657 Aromadendron 473 Aronia 793 Asimina No NT accounts Athrotaxis No NT accounts Austrocedrus 186 No NT accounts — chilensis 449 Austrotaxus No NT accounts

962

Index of Tree Names

Banksia 156 — canei 158 — ericifolia 158 — grandis 158 — integrifolia 158, 160 subsp. compar 158, 159 subsp. integrifolia 159 subsp. monticola viii, 157, 159 — marginata 160, 160 — menziesii 158 — praemorsa 158 — robur 158 — serrata 158 — speciosa 158 — spinulosa 158 Bauhinia No NT accounts Beilschmiedia 160 — berteroana 161 — erithrophloia 161 — miersii 19, 161, 161 — tarairi 161 — tawa 161 Bencomia 646 — caudata 646 Berberis 2 No NT accounts Betula 26, 135, 163, 577 — alnoides 167 — ×alpestris 170 — apoiensis 165 — ×aurata 165 — austrosinensis 169 — bomiensis 168 — calcicola 165, 168, 169 — chichibuensis 166, 166 — chinensis 163 — cordifolia 163, 167 — cylindrostachya 167 — delavayi 163, 168, 168 var. microstachya 168 var. polyneura 168 — divaricata 171 — fargesii 163 — globispica 163 — gynoterminalis 168 — ‘Hergest’ 164 — ×hybrida 165 — insignis 41, 162, 164, 169, 169 — japonica 164 — jinpingensis 170 — jiulungensis 168 — kenaica 171 — lenta 18, 170 f. lenta 170 f. uber 18, 170, 171 — litwinowii 164 — luminifera 167 — mandshurica 164 — medwediewii 163

Betula continued — ×obscura 165 — occidentalis 172, 173 — papyrifera 163, 167, 172 var. cordifolia 167 — pendula 164, 165, 172 ‘Golden Beauty’ 165 — platyphylla 164, 165 — populifolia 165 ‘Whitespire Senior’ 165 — potaninii 168, 169 — procurva 164 — pubescens 164, 165 — raddeana 164 — ‘Royal Frost’ 164 — saposhnikovii 164 — schmidtii 163 — szechuanica 164 — tianschanica 172 — turkestanica 164 — uber 18, 170 — ×utahensis 172 — utilis 170, 661, 806 ‘Fascination’ 164 var. jacquemontii 164 ‘Wakehurst Place Chocolate’ 164 Bischofia 173 — javanica 173 — polycarpa 173, 173 Blepharocalyx 174 — cruckshanksii 174, 175, 524 ‘Heaven Scent’ 175 Bretschneidera 175 — sinensis 176, 177 Broussonetia No NT accounts Brucea 763 Bucklandia 365 Bucklandia populnea 367 Buddleja 2, 178 — cordata 178, 178, 179 subsp. ovandensis 179 subsp. tomentella 179 — davidii 178 — delavayi 179 Bumelia No NT accounts NOW Sideroxylon Bursaria No NT accounts Buxus No NT accounts Caldcluvia 115 No NT accounts Calia 789 — arizonica 789 — secundiflora 789 Calodendrum No NT accounts Callistemon 180 — glaucus 181 — viminalis 180, 180, 181, 181 Callitris 182 — endlicheri 183, 184, 184

New Trees

Callitris continued — macleayana 901 — oblonga 184, 185 — oblonga subsp. corangensis 184 subsp. oblonga 184 subsp. parva 184 — preissii 182, 185, 185 — quadrivalvis 847 — rhomboidea 184, 185, 186 ‘Golden Zero’ 186 — verrucosa 185 Callitropsis 290, 291, 302, 902 — nootkatensis 902, 903 — vietnamensis 903 Calocedrus 186, 672 — decurrens 186, 187 — formosana 186, 187, 187, 187, 246 — macrolepis 186 var. formosana 187 Camellia 188, 648, 682, 784 — acutiserrata 197 — albogigas 194 — amplexifolia 189 — April Series 189 — assimilis 190 — brevissima 190 — brevistyla 190 var. rubida 190 — ‘Buttermint’ 195 — caudata 190 — chekiangoleosa 191, 191 — chrysanthoides 189 — costei 191 — crapnelliana 188, 192, 192 — crassicolumna 189 — crassissima 191 — cucphuongensis 189 — drupifera 192 — dubia 191 — edithae 193 ‘Jiuqu’ 193 ‘Momudan’ 193 — euryoides 189 — flavida 189 — fluviatilis 189 — forrestii 193, 193 — fraterna 189 — furfuracea 194 — gaudichaudii 189 — granthamiana 194, 194 — grijsii 189 var. shensiensis 196 — henryana 197 — ×hiemalis 197 — impressinervis 189 — indochinensis 189 — japonica 189, 191, 196, 197

Camellia continued — kissii 195, 195 — lanceolata 188 — liberistamina 191 — lucidissima 191 — lutchuensis 195, 195 var. minutiflora 196 — lutescens 195 — mairei 189 — maliflora 197 — membranacea 190 — minutiflora 196 — multibracteata 192 — oblata 194 — obtusifolia 190 — octopetala 192 — oleifera 189, 190, 192 — parafurfuracea 194 — parvilapidea 190 — percuspidata 190 — petelotii 189, 191 — polypetala 194 — ptilophylla 196 — pubescens 196 — puniceiflora 190 — reticulata 189 — salicifolia 189 — sasanqua 189, 190, 193, 197 — sasanqua × C. oleifera ‘Mason Farm’ 189 ‘Survivor’ 189 ‘Winter’s Joy’ 189 — scariosisepala 197 — semiserrata 189 — sinensis 189, 196, 394 — spectabilis 682 — suaveolens 194 — subacutissima 191 — synaptica 189 — taliensis 648 — transarisanensis 189 — transnokoensis 195, 196 — triantha 190 — trichoclada 189 — truncata 193 — uraku 197 — ×vernalis 197 ‘Dawn’ 197 — vietnamensis 192 — wabiske 197 — wardii 189 — xylocarpa 189 — yunnanensis 196, 197 Camptotheca 198 — acuminata 198, 199, 200 — lowreyana 198 ‘Katie’ 198 Cannabis 227 Carpinus 200 — betulus 202, 203, 210

Index of Tree Names

Carpinus continued — caroliniana 202 subsp. virginiana 202, 202 — cordata 203 var. chinensis 203, 203 var. mollis 203 — coreana 211 var. major 211 — fangiana 201, 203, 210 — fargesiana 204 — fargesii 212 — henryana 205 var. henryana 205 var. simplicidentata 205 — kawakamii 205 — laxiflora var. macrostachya 212 — londoniana 206 — monbeigiana 206, 206 — omeiensis 207 — orientalis 210 — polyneura 207 — pubescens 209 — rankanensis 39, 208, 209, 210 — ×schuschaensis 210 — shensiensis 210 — stipulata 212 — tropicalis 203 — turczaninowii 211 var. coreana 211, 211 var. ovalifolia 207, 212 var. stipulata 212 — viminea 212, 212, 976 Carpodetus 213 — arboreus 213 — serratus 213, 213, 549 Carpolepis 520 Carrierea No NT accounts Carya 214 — carolinae-septentrionalis 215 — cathayensis 214 — ovata 215 var. australis 215 var. mexicana 214 — pallida 215, 215 — tomentosa 214 Caryopitys 579 Cassia No NT accounts Castanea 216 — crenata 217 — davidii 217 — dentata 217, 218 — mollissima 217, 218, 304 — pumila 217 — sativa 216, 217 — seguinii 216, 217 Castanopsis 218, 463, 465 — carlesii 218, 218, — chinensis 220

Castanopsis continued — concolor 219 — cuspidata 218, 221 var. sieboldii 220 — delavayi 218 — fargesii 218 — orthacantha 218, 219, 219 — platyacantha 218 — sclerophylla 220, 220 — sieboldii 218, 220 ‘Angyo Yellow’ 221, 221 var. lutchuensis 221 — tibetana 218 — wattii 221 Castanospermum australe 382 Casuarina 131, 222 — cunninghamiana 222, 222, 382 — equisetifolia 222, 223 — glauca 222 Catalpa 248 No NT accounts — bignonioides 248 — ×galleana 248, 249 — speciosa 248 Cathaya 223 — argyrophylla x, 223, 224, 425 — nanchuanensis 223 Cedrela No NT accounts Cedrus 225, 535 — atlantica 226 — deodara 225 — libani 225 subsp. libani 225, 226 subsp. stenocoma 17, 225, 226, 226 Celtis 226 — australis 227 — choseniana 227 — edulis 228 — georgiana 231 — jessoensis 228, 229 — julianae 229 — labilis 231, 233 — laevigata var. reticulata 230 — occidentalis 227 — sinensis 227, 228, 230, 231 ‘Green Cascade’ 230, 231 var. japonica 230 — tenuifolia 231 — tetrandra 231, 232, 233 — trinervia 231, 233 — vandervoetiana 233 — yunnanensis 231, 233 Cephalotaxus 234, 672 — fortunei 234, 235, 236, 237 — harringtonii 234, 235, 236, 237 var. koreana 235 var. sinensis 236 var. thailandensis 235

Cephalotaxus continued — koreana 235 — mannii 235 — sinensis 234, 236, 237 — wilsoniana 237, 237 Cerasus 657 Ceratonia 237 — oreothauma 237 — siliqua 237, 238, 238, 785 Ceratopetalum 238 — gummiferum 238, 239, 239 ‘Albery’s Dwarf’ 239 ‘Christmas Snow’ 239 ‘Magenta Star’ 239 ‘White Christmas’ 239 ‘Wildfire’ 239 — succirubrum 238 Cercidiphyllum No NT accounts Cercis 240 — canadensis 240, 241 var. canadensis 241, 243 ‘Forest Pansy’ 240 var. mexicana 241, 241, 242 ‘Sanderson’ 242 var. texensis 241, 242 ‘Oklahoma’ 242 ‘Texas White’ 242 ‘Traveller’ 242, 242 — chinensis 240, 241, 243, 244 ‘Avondale’ 240 — chingii 241, 243, 243 — chuniana 241, 243 — gigantea 241, 244, 244 — glabra 240, 241, 244, 245 — likiangensis 243 — occidentalis 240, 241, 835 — orbiculata 241 — racemosa 241 — reniformis 242 — siliquastrum 240 — yunnanensis 244 Ceuthostoma 131 Chamaecyparis 245, 290, 852 — formosensis 247, 830 — hodginsii 245 — lawsoniana 247 — nootkatensis 245, 302, 902, 903 — obtusa 247 var. formosana 246, 247, 247 — thyoides 247 — taiwanensis 247 Chamaemespilus 793, 794, 796 — alpina 793, 816, 824 — sudetica 793, 824 Chamaepericlymenum 261

963

Chilopsis 248 No NT accounts — linearis 248, 249 ×Chitalpa 248 — ‘Minsum’ 249 — ‘Morning Cloud’ 248, 249 — tashkentensis 248, 249 ‘Pink Dawn’ 248, 249, 249 — Summer Bells 249 Chionanthus No NT accounts Choerospondias 249 — auriculata 249 — axillaris 250, 251 var. japonica 251 Chorisia No NT accounts Chosenia 766 No NT accounts NOW Salix Chrysolepis No NT accounts Cinnamomum 251 — camphora 252, 253 — chekiangense 253 — glanduliferum 252 — insularimontanum 253 — japonicum 253, 253, 255, 256 — jensenianum 252 — micranthum 254 — parthenoxylon 252, 253, 254 — pedunculatum 253 — porrectum 254 — tamala 252 — tenuifolium 253 — verum 252 — wilsonii 254 Citrus 256 — ×aurantium Grapefruit Group 8, 256 — cavaleriei 257, 258 — ‘Eustis’ 257 — ichangensis 257 — ×junos 259 — limettioides 257 — ×limon 257 ‘Meyer’ 257 — reticulata 258 — tachibana 257, 257, 258 — trifoliata 257 Cladrastis 789 No NT accounts Clethra 259 — alnifolia 259 — poilanei 260 — pringlei 260 ‘White Water’ 259, 260 Cleyera 846 Cliftonia No NT accounts Cormus 793, 794 — domestica 793, 824 Cornus 261 — alba 261 — alternifolia 261

964

Index of Tree Names

Cornus continued — amomum subsp. obliqua 270 — angustata 266 — canadensis 261 — capitata 261, 264, 266, 267, 270 subsp. angustata 266 subsp. brevipedunculata 264 subsp. emeiensis 264, 269 var. mollis 266 ‘Mountain Moon’ 264 ‘Yoko’ 264 — chinensis 15, 263, 265, 265 f. jinyangensis 265 — Constellation 263 — controversa 261 — ‘Eddie’s White Wonder’ 263 — elliptica 264, 265, 266, 266, 270 ‘Elsbry’ 267 Empress of China 267 ‘First Choice’ 267 — emeiensis 269, 270 — florida 261, 263, 267 subsp. florida 267 var. pringlei 267, 268 subsp. urbiniana 267, 267 ‘Pringle’s Blush’ 268 ‘Pringle’s White’ 268 — fordii 271 — hongkongensis 263, 263, 264, 265, 268, 268 subsp. elegans 269 subsp. ferruginea 269 subsp. gigantea 268, 269 subsp. hongkongensis 269 subsp. melanotricha 262, 269 subsp. tonkinensis 268, 269 — ‘KN30-8’ 263 — kousa 263 subsp. angustata 266 — mas 261 — monbeigii 270 — ‘Norman Hadden’ 263 — nuttallii 263 — omeiense 269 ‘Summer Passion’ 269 — ‘Ormonde’ 263 — poliophylla 270 — quinquenervis 270 — ‘Porlock’ 263 — ‘Rutcan’ 263 — ‘Rutgan’ 263 — ×rutgersensis 263 — ×rutgersiensis 263 — sanguinea 261 subsp. australis 264

Cornus continued — schindleri 270 subsp. poliophylla 271 — sericea 261 subsp. occidentalis 270 — Stellar Pink 263 — ‘Summer Passion’ 269, 270 — Venus 263 — volkensii 263 — walteri 271 — wilsoniana 271, 271 Corokia cotoneaster 549 Corylus 272 — avellana 272 ‘Contorta’ 272 — colurna 272 — fargesii 273, 274, 274 — ferox var. tibetica 274 — maxima 272 ‘Purpurea’ 272 — ‘Red Majestic’ 272 — ‘Te Terra Red’ 272 — yunnanensis 274 Corymbia 275, 324 — citriodora 275, 275 subsp. variegata 275 — ficifolia 3, 275, 328 Corynocarpus 276 — laevigatus 276 ‘Aureus’ 276 Cotinus 763 No NT accounts Cotoneaster 2, 793, 795 No NT accounts — horizontalis 400 Craibiodendron 277 — yunnanense 277, 278 Crataegus 279, 793, 795 — ambigua 281 — apiifolia 284 — baroussana 281, 281, 282 var. baroussana 282 var. jamensis 281 — calpodendron 285 — chlorosarca 284 — chungtienensis 283, 283 — engelmannii 283 — jozana 284 — laevigata 280 — ×lavallei 280, 285 — marshallii 284, 285 — ×media 280 ‘Paul’s Scarlet’ 280 ‘Rubra Plena’ 280 — mexicana xvi, 280, 285, 286 — meyeri xvi, 286 — monogyna 279, 280, 281, 286, 288 — persica 286 — pseudoheterophylla xvi, 287, 287

New Trees

Crataegus continued — pseudoheterophylla cont’d subsp. pseudoheterophylla 288 subsp. turcomanica 288 subsp. turkestanica 288 — pubescens var. / f. stipulacea 285, 286 — scabrifolia 284 — ×sinaica 281 — stipulacea 285, 286 — stipulosa 285 — taurica 286 — ucrainica 286 Crinodendron No NT accounts Cryptocarya 288, 444 — alba 288, 289, 289, 630 — rubra 289 Cryptomeria No NT accounts — fortunei 837 — japonica 837 Cunonia No NT accounts Cunninghamia No NT accounts Cupressus 245, 290, 302, 415, 902 — arizonica 292 var. arizonica 292, 293 var. glabra 292, 293, 302, 303 var. montana 293 var. nevadensis 293 var. stephensonii 292, 293 — assamica 300 — atlantica 296 — austrotibetica 292, 293 — bakeri 294, 294 subsp. bakeri 294 subsp. matthewsii 294 — cashmeriana 299, 300 — chengiana 294 var. chengiana 295 var. jiangensis 295, 295 var. kansouensis 294, 295 var. wenchuanhsiensis 294 — corneyana 299, 300 — darjeelingensis 300 — duclouxiana subsp. austrotibetica 293 — dupreziana 295 var. atlantica 292, 296 var. dupreziana 25, 291, 295, 296 — fallax 294 — funebris subsp. tonkinensis 293 — gigantea 297, 297 — goveniana 298 var. abramsiana 298, 298 var. goveniana 298

Cupressus continued — goveniana continued var. pigmaea 298 — guadalupensis var. forbesii 297 — himalaica 299, 299 var. darjeelingensis 299, 300 — lusitanica 299, 301, 303 — macnabiana 290, 301 — macrocarpa 292, 301, 626 — nootkatensis 902, 903 — sargentii 290, 301, 301 — sempervirens 292, 296, 301 var. atlantica 296 var. dupreziana 296 — tonkinensis 293 — torulosa 297, 299 ‘Corneyana’ 299 var. corneyana 299 var. torulosa 293 — vietnamensis 903 ×Cupressocyparis 302, 902 — notabilis 302 — ovensii 303 ×Cuprocyparis 302, 902 — leylandii 292, 302, 303, 852, 903 — notabilis 302, 302 — ovensii 303 Cuttsia 213 Cyclobalanopsis 465, 691, 692 — gilva 726 — glaucoides 751 — longinux 736 — morii 739 — salicina 750 — stenophylloides 752 Cyclocarya paliurus 676, 678 Cyrilla No NT accounts Dacrycarpus cinctus 640 — compactus 640 — cumingii 640 — dacrydioides 640 — imbricatus 642 — kinabaluensis 642 — steupii 645 — vieillardii 645 Dacrydium 387 No NT accounts — bidwillii 387 — biforme 387 — intermedium 446 — kirkii 388 Dalbergia 303 — hupeana 304, 304 Daphniphyllum 305 — chartaceum 305 — glaucescens 306 var. oldhamii 306

Index of Tree Names

Daphniphyllum continued — himalayense var. macropodum 305 subsp. himalayense 305 — humile 305 — kengii 306, 307 — longiracemosum 305 — macropodum 305 var. humile 305 Humile Group 305 — oldhamii 306 — pentandrum 306 — teijsmannii 307 — teysmanii 305, 307, 307 Davidia No NT accounts Dendriopoterium 646 — menendezii 646 Dendrobenthamia 261 Dendropanax 526 No NT accounts Diospyros 308 — austroafricana 309 subsp. microphylla 309 — cathayensis 308, 309 — duclouxii 309 — ebenum 308 — glaucifolia 310 — japonica 310 — kaki 308 — lotus 308, 309 — lycioides 309 — morrisiana 309 — oldhamii 309 — oleifera 310 — palmeri 309 — rhombifolia 311, 311 — texana 309 — virginiana 308, 310 — whyteana 309 — wilsonii 309, 309 — xiangguiensis 309 Dipentodon 312 — sinicus 312, 312, 313 Dipteronia No NT accounts NOW Acer Disanthus No NT accounts Diselma 894 No NT accounts Docynia No NT accounts Dodecadenia No NT accounts Dombeya No NT accounts Drimys 120, 314 — brasiliensis 314 — confertifolia 314 — granadensis 314, 315 var. chiriquiensis 314 var. granadensis 314, 315 var. grandiflora 314, 315 var. mexicana 314, 315 var. peruviana 314 var. uniflora 314

Drimys continued — winteri 314, 315 Ducampopinus 579 Dugandiodendron 473 Duvaua 785 Edwardsia 789 — macnabiana 790 Elaeagnus 120, 687, 733 Elaeocarpus 315 — angustifolius 316 — decipiens 316, 317, 318, 321 Little Emperor 317 ‘MonProud’ 317 — dentatus 317, 319 — ellipticus 317 — glabripetalus 315 — grandis 316 — hookerianus 213, 317, 318, 319, 549 — japonicus 319 — lacunosus 316 — reticulatus 320, 320 — sylvestris 316, 317, 321 Eleutherococcus 526 No NT accounts Elmerrillia 473 Embothrium No NT accounts Emmenopterys No NT accounts Engelhardtia 321 — chrysolepis 322 — fenzelii 322 — formosana 322 — roxburghiana 322, 322 — spicata 321 Eriobotrya 322 — cavaleriei 323 — deflexa 323, 323 ‘Bronze Improved’ 323 — elliptica 323 — japonica 322 Erythrina No NT accounts Eucalyptus 4, 35, 36, 275, 324, 531 — acaciiformis 331 — albida 331 — aggregata 358 — amygdalina 331 — apiculata 344 — approximans 343 subsp. approximans 330 subsp. codonocarpa 330 — archeri 332, 333 — badjensis 330 — barberi 330 — bicostata 341 — blakelyi 334, 334 — blaxlandii 330 — bridgesiana 329, 334 — brookeriana 334

Eucalyptus continued — camaldulensis 335, 335 subsp. camaldulensis 335 var. obtusa 335 subsp. simulata 335 — camphora 336, 336 subsp. camphora 336 subsp. humeana 336 subsp. relicta 336 — chapmaniana 327, 337, 337 — cinerea 337 — coccifera 330 — cosmophylla 330 — crenulata 338 — croajingolensis 356 — cypellocarpa 338 — dalrympleana 358 — deanei 330 — debeuzevillei 354 — delegatensis 338 subsp. tasmaniensis 338, 339 — divaricata 342 — elliptica 339, 355 — fasciculosa 330 — fastigata 340, 340 — formanii 330 — fraxinoides 340 — globulus 341, 357 subsp. bicostata 341 subsp. globulus 341 subsp. maidenii 341 subsp. pseudoglobulus 341 — goniocalyx 330 — gregsoniana 325, 341, 341 — gunnii 332, 342, 349, 352 subsp. divaricata 342 subsp. gunnii 342 — kitsoniana 330 — kybeanensis 325, 342, 342 — lacrimans 325, 343, 343 — laophila 343 — latiuscula 349 — leucoxylon 344 subsp. bellarinensis 344 subsp. connata 344 subsp. leucoxylon 330, 344, 345 subsp. megalocarpa 345, 345 subsp. pruinosa 330, 344, 345 ‘Rosea’ 345 subsp. stephaniae 344 — ligustrina 330 — macarthurii 345, 346 — macrorhyncha 346 subsp. cannonii 346 subsp. macrorhyncha 346

965

Eucalyptus continued — mannifera 324, 339, 347, 347 subsp. elliptica 339, 347 subsp. gullickii 347 subsp. maculosa 347 subsp. mannifera 347 subsp. praecox 347, 355 — melliodora 347, 348 — mitchelliana 348, 360 — moorei 348, 349, 360 var. nana 349 — morrisbyi 349 — neglecta 330, 349, 350 — nicholii 331, 351 — nitens 326, 326, 352, 352, 357 — nitida 330, 360 — nova-anglica 330, 352 — obliqua 353 — olsenii 330 — oreades 353 — ovata 336 — paliformis 330 — parviflora 330 — parvula 353 — pauciflora 342, 354, 360 subsp. acerina 354 subsp. debeuzevillei 342, 354, 355 subsp. hedraia 354 var. nana 341 subsp. niphophila 342, 343, 354, 355 subsp. parvifructa 354 subsp. pauciflora 354 — petiolaris 344 — praecox 347, 355 — pulchella 332, 345, 351 — radiata 356, 356 subsp. sejuncta 356 — regnans 325, 356, 357 — remota 357 — risdonii 357 — robertsonii 356 — rodwayi 358 — rubida 358, 359 subsp. barbigerorum 359 subsp. canobolensis 359 subsp. rubida 359 subsp. septemflora 359 — salicifolia 331 — saligna 359 — sideroxylon 328, 360, 360 var. rosea 360 subsp. sideroxylon 360 subsp. tricarpa 360 — stellulata 13, 360, 360, 361 — stricta 330 — sturgissiana 330 — subcrenulata 362, 362

966

Index of Tree Names

Eucalyptus continued — tenuiramis 362 — viminalis 363 subsp. cygnetensis 363 subsp. viminalis 363 — willisii 330 — yarraensis 330 — youmanii 330 Eucommia No NT accounts Eucryphia 120, 363 — ×hybrida 364 — jinksii 363, 365 — lucida 364 — milliganii 364, 364 subsp. milliganii 364 subsp. pubescens 364 subsp. pubescens ‘Pink Whisper’ 364 — moorei 365 — wilkiei 363, 363, 365 Euodia 847 — baberi 850 — bodinieri 850 — glauca 849 — meliaefolia 849 — officinalis 850 — rutaecarpa 850 Eugenia No NT accounts Euonymus 2 No NT accounts Euptelea No NT accounts Eurya 846 Euscaphis No NT accounts Exbucklandia 365 — populnea 366, 367, 367 — tonkinensis 367 Fagus 164, 368 — grandifolia 368, 369 subsp. grandifolia 369 subsp. mexicana 369 — japonica 369 var. multinervis 368, 369 — orientalis 56 — sylvatica 9, 368 ‘Black Swan’ 368 Fatsia 526, 775 — japonica 781 Ficus 371 — afghanica 372 — auriculata 372 — benjamina 219, 371, 390 — carica 371, 372, 373 subsp. carica 372 var. afghanica 372 — elastica 3, 371, 490, 493 — geraniifolia 372 — aff. heterophylla 9 — johannis 372 subsp. afghanistanica 370, 372 ‘Silver Lyre’ 372, 372

Ficus continued — johannis continued subsp. johannis 372 — lacor 372 — palmata 372 — roxburghii 372 Firmiana No NT accounts Fitzroya 894 No NT accounts — cupressoides 20, 53 Fokienia 245 No NT accounts — hodginsii 236 Fortunearia No NT accounts Fortunella 256, 258 Franklinia 19, 25, 784, 785 No NT accounts — alatamaha 18, 784 Fraxinus 373 — americana 375 — chinensis 373, 376 var. acuminata 376 subsp. chinensis 376 subsp. rhynchophylla 376 — cuspidata 376 var. macropetala 377 — excelsior 375 ‘Atlas’ 375 ‘Westhof’s Glorie’ 375 — japonica 376 — lanuginosa 374, 377, 377 var. serrata 377 — macropetala 376 — paxiana 375 — pennsylvanica 375 — rhynchophylla 376 — sargentiana 376 — sikkimensis 375 Fremontodendron No NT accounts Gevuina No NT accounts Ginkgo No NT accounts Gleditsia No NT accounts Glochidion 379 — fortunei 379 — puberum 379, 380 — triandrum 379, 379, 381 — wilsonii 379 Glyptostrobus No NT accounts ×Gordlinia grandiflora 2, 785 Gordonia 648 — hainanensis 649 — lasianthus 784 — yunnanensis 648 Grevillea 381 — juniperina subsp. sulphurea 383 — manglesii subsp. manglesii 382 subsp. ornithopoda 382 — robusta 382, 382 Greyia No NT accounts

New Trees

Griselinia No NT accounts Gymnelaea cunninghamii 527 — lanceolata 527 Gymnocladus No NT accounts Gymnostoma 131 Hagenia 383, 645 — abyssinica 383, 383 Hakea No NT accounts Halesia 384, 520 — carolina 384, 385 Monticola Group 385 — diptera 384 — macgregorii 384, 384, 385, 385 — monticola 384 — parviflora 384, 385 — tetraptera 384 Halleria 386 — lucida 386, 386 Halocarpus 387 — bidwillii 387 — biformis 387, 387, 445 — kirkii 388, 388 Hamamelis No NT accounts — subaequalis 544 Hedera 775 Hedycarya 388 — angustifolia 388 — arborea 388, 389, 389 — dorstenioides 388 Hemiptelea No NT accounts Heptacodium No NT accounts — miconioides 2 Hesperopeuce 868 Heteromyrtus 174 Hippophae No NT accounts Hoheria No NT accounts Houpoëa 473 Hovenia No NT accounts Humulus 227 Huodendron 390 — biaristatum 390, 390 — tibeticum 391, 391 Hymenosporum 391 — flavum 391, 392, 393 Hypericum No NT accounts Idesia No NT accounts Ilex 393 — aquifolium 319, 393, 406 var. caspia f. spinigera 404 — ×attenuata 397 ‘Fosteri’ 398 ‘Longwood Gold’ 398 — bioritsensis 394, 395, — buergeri 396, 396 var. buergeri 396 var. rolfei 396 — canariensis 394 — cassine 397 — chinensis 402

Ilex continued — clemensiae 393 — colchica 406 — dipyrena 399 — elmerrilliana 399 — fargesii subsp. fargesii 398 subsp. melanotricha 399 — ficoidea 395 — formosana 394 — forrestii 397 var. glabra 397 — goshiensis 398 — hayatana 398, 398 — hookeri 398 — hyrcana 404 — intricata var. oblata 400 — kingiana 399 — limii 399, 399 — lonicerifolia 394 — maximowicziana 394 — mitis 399, 400 — nothofagifolia 400, 401 — oldhamii 402 — opaca 397 — paraguariensis 394 — pernyi var. veitchii 395, 396 — purpurea 402, 403 — rubra 403 — scandens 393 — shennongjiaensis 404, 404 — spinigera 404, 405 Illicium 406, 760 — anisatum 407 — floridanum 407 ‘Album’ 407 — henryi 407 — lanceolatum 407, 407, 408 — majus 408 — mexicanum 407 ‘Aztec Fire’ 407 — parviflorum 408 ‘Florida Sunshine’ 408 ‘Forest Green’ 409 — simonsii 409, 409 — ‘Woodland Ruby’ 407 — yunnanense 409 — verum 407, 410 Itoa 410 — orientalis 410, 410 — stapfii 410 Juglans 411, 766 — ailantifolia 411 — boliviana 412 — cinerea 412 — elaeopyren 412, 413 — guatemalensis 412 — major 412, 412 var. major 412 — mandshurica 411, 412, 414

Index of Tree Names

Juglans continued — microcarpa 413 var. major 412 — mollis 412 — neotropica 5, 412 — nigra 8, 411, 412 — olanchana 412 — regia 411, 414 — ×segreziensis 411 — sigillata 38, 413, 413 Juniperus 290, 292, 414 — angosturana 420 — bermudiana 416, 417 — brevifolia 418 — cedrus 418, 419 — chinensis 901 — communis 414 var. depressa 419 var. nipponica 422 var. saxatilis 419 — deppeana 417 ‘McFetters’ 417 — distans 423 — excelsa subsp. polycarpos 420, 423 — foetidissima 419, 420 — formosana 417 — glaucescens 420 — indica 424 — komarovii 420 — osteosperma 417 — oxycedrus 418 — ×pfitzeriana 420 — pingii 421 var. carinata 421 var. wilsonii 421 ‘Loderi’ 421 — potaninii 423 — procera 29, 400, 414, 415, 421, 422, 540, 894 — pseudosabina 417, 419, 424 — recurva 800 — rigida var. conferta 419 — sabina var. davurica 419 — scopulorum 417 — semiglobosa 423 — squamata 421 — tibetica 1, 423 — virginiana 280, 418, 424 var. silicicola 424, 424 ‘Brodie’ 424 var. virginiana 424 Kalopanax No NT accounts Keteleeria 424, 536 — davidiana 426 var. formosana 426, 426 — evelyniana 425, 427 — fortunei 426 Kmeria 473

Knightia 427 — excelsa 428, 428 Koelreuteria 428 — bipinnata 428, 429, 429 — elegans 428, 430 subsp. elegans 430 subsp. formosana 430 — henryi 430 — integrifoliola 429 — paniculata 428, 429 ‘Coral Sun’ 429 ‘Fastigiata’ 429 ‘Rose Lantern’ 429 ‘September’ 429 Laburnum No NT accounts Lagerstroemia 431 — ‘Arapaho’ 433 — chekiangensis 433 — ‘Cheyenne’ 433 — fauriei viii, 431, 432, 432, 435 ‘Fantasy’ 433 ‘Townhouse’ 431, 433 — indica 431, 432, 433 — limii 433, 433, 435 — ‘Muskogee’ 433 — ‘Natchez’ 433 — speciosa 432 — subcostata 432, 435 — ‘Tuscarora’ 433 Lagunaria No NT accounts Larix 224, 435, 577 — ×czekanowskii 441 — decidua 436, 442 — ×eurolepis 436 — gmelinii 59, 435, 436, 441 — griffithii 436, 437, 438, 439 var. speciosa 437 — himalaica 436, 436, 438, 439 — kaempferi 436 — kongboensis 436, 438, 439 — laricina 435, 436 — lyallii 436 — ×marschlinsii 436, 437 — mastersiana 436, 439 — occidentalis 436 — potaninii 434, 436, 437, 438, 440 var. australis 437, 440 var. chinensis 440 var. himalaica 438 var. macrocarpa 440, 441 var. potaninii 440 — principis-rupprechtii 436, 437 — russica 441 — sibirica 434, 435, 436, 441, 441, 574 var. sukaczewii 441, 442

Larix continued — speciosa 436, 437 — sukaczewii 441 Laurelia 442 — novae-zelandiae 442, 443, 443 — sempervirens 442, 443 — serrata 442, 443 Laureliopsis 442 — philippiana 443 Laurocerasus 657 Laurus No NT accounts — azorica 553 Legrandia 443 — concinna 18, 443, 444 Leitneria No NT accounts Lepidothamnus 444 — fonkii 444 — intermedius 444, 445, 446 — laxifolius 444, 445 Leucadendron No NT accounts Leucaena 446 — glauca 447 — leucocephala 446, 447, 447 subsp. glabrata 447 subsp. ixtahuacana 447 subsp. leucocephala 447 Leucospermum No NT accounts Libocedrus 186, 448 — bidwillii 448, 448 — formosana 187 — plumosa 448, 449 Ligustrum No NT accounts Limlia 459 Lindera 2, 449 — aggregata 451, 452 — angustifolia 454 — benzoin 451 — cercidifolia 455 — chienii 452 — communis 452 — erythrocarpa 449, 453, 453 — floribunda 453 — glauca 451, 454, 454, 454 var. salicifolia 454 — heterophylla 455 — neesiana 451 — obtusiloba 455 — praetermissa 450, 455 — pulcherrima 455, 455 subsp. pulcherrima 455, 456 subsp. thomsonii 455, 456 — reflexa 456 — rubronervia 451 — salicifolia 451 — sericea 456 var. glabrata 456 — strychnifolia 441

967

Liquidambar 457 — acalycina iv, 23, 457, 457, 458, 459 ‘Burgundy Flush’ 458 — formosana 457 var. monticola 457 Monticola Group 458 — macrophylla 457 — orientalis 457 — styraciflua 457, 458 Liriodendron 474 No NT accounts — chinense 2 Lithocarpus 459 — brevicaudatus 460 — chinensis 220 — cleistocarpus 460 — confinis 460, 462 — corneus 461, 465 — dealbatus 460, 461, 462, 464, 465 subsp. leucostachyus 462 — densiflorus 459, 460, 699 f. attenuato-dentatus 460 var. echinoides 460 — edulis 460 — garrettianus 465 — glaber 460 — hancei 462, 463 — harlandii 460 — henryi 460 — kawakamii 461, 463 — konishii 460 — lepidocarpus 460 — pachylepis 460 — pachyphyllus 460 — paniculatus 460 — ‘pathsapsis’ 460 — polystachyus 460 — truncatus 460 — uvariifolius 461, 463 — variolosus 460, 462, 464, 465, 465 — xylocarpus 460 Lithraea 466 — caustica 466, 466, 515, 630 Litsea 467 — aciculata 467 — aestivalis 467 — calicaris 467 — cubeba 468, 468 — glaucescens 468, 469 — japonica 469 — javanica 467 — neesiana 467 — parvifolia 467 — zeylanica 467 Lomatia No NT accounts Loropetalum No NT accounts Luculia No NT accounts

968

Index of Tree Names

Luma 444 — apiculata 175, 444 Lyonia 277 Lyonothamnus No NT accounts Maackia No NT accounts — chinensis 304 Machilus 550 — bracteata 552 — breviflora 553 — grijsii 557 — thunbergii 557 Maclura No NT accounts Macropanax 778 Maddenia 469 — hypoleuca 471 — wilsonii 2, 470, 471 Maesa 471 — argentea 473 — formosana 473 — henryi 473 — hupehensis 473 — japonica 471 — martinii 473 — montana 471, 472, 473 Magnolia xi, 11, 12, 16, 17, 19, 473 — acuminata var. subcordata 485 — ×alba 479, 483 — amoena 480 — aromatica 480, 480 — biondii 481, 481, 506 — campbellii 475 — cathcartii 482 — cavaleriei 483, 483, 500 — champaca 479, 483 — chapensis 484 — conifera 481, 484 var. chingii 484 — cylindrica 485, 485, 486, 505 — dandyi 500 — dealbata 498 — decidua 475, 486 — delavayi 476 — denudata 475, 485 — dianica 494 — doltsopa 475, 476, 489, 501 — duclouxii 486 — ernestii 487, 487 — figo 475, 488, 489 var. crassipes 488, 488 var. figo 488, 489 ‘Port Wine’ 488 ‘Purple Queen’ 488 Skinneriana Group 488 ‘Stubbs Purple’ 488 — floribunda 476, 489, 489 — ×foggii 489 ‘Allspice’ 490, 490

Magnolia continued — ×foggii continued ‘Jack Fogg’ 490 ‘Picotee’ 490 — fordiana 490, 505 var. calcarea 490 var. fordiana 490, 504 var. forrestii 490 var. kwangtungensis 490 — foveolata 473, 491, 491 var. cinerascens 491 — fraseri var. pyramidata 502 — fulva 491 var. calcicola 492 var. fulva 492 — grandiflora 475, 476, 485, 491, 502, 503, 504 — grandis 25, 492 — guatemalensis 478 — ingrata 492 — insignis 475, 476, 485 — kwangtungensis 493, 493 — lacei 479, 479 — laevifolia 10, 475, 477, 478, 494, 495, 504 ‘Michelle’ 495 ‘Summer Snowflake’ 495 ‘Velvet and Cream’ 495 — lanuginosa 495 — lotungensis 496, 496, 504 — macclurei 497 var. sublanea 497 — macrophylla 475, 498 var. ashei 498 var. dealbata 478, 498, 498 var. macrophylla 498 — martinii 492, 498 — maudiae 474, 496, 499, 500 var. hunanensis 500 var. maudiae 499 var. platypetala 500 ‘Touch of Pink’ 500 — mediocris 497 — megaphylla 494, 500 — montana 479 — moto 493 — nitida 475, 496, 504 — obovata 493, 501 — odora 479 — omeiensis 496 — opipara 501 — ovoidea 484 — ‘Pegasus’ 485 — platypetala 500 — schiedeana 478, 503 — sharpii 478 — sieboldii 485 var. sinensis 502 — sinica 475, 478, 502

New Trees

Magnolia continued — tamaulipana 478, 503, 503 ‘Bronze Sentinel’ 503 — virginiana 475 var. australis 487 — ×wieseneri 504 — xanthantha 492 — yunnanensis 494, 504 — yuyuanensis 476, 490, 491, 504, 505 — zenii 23, 505 hybrid 506 ‘Pink Parchment’ 506 Mallotus 507 — apelta 507, 507 — castanopsis 507 — japonicus 507 — paxii 507 — tenuifolius 507 Malus 2, 508, 683, 795, 817 — ‘Adirondack’ 509 — asiatica 513 — baccata 513, 514 var. himalaica 513 — brevipes 510, 510 — ‘Comtesse de Paris’ 509 — coronaria var. platycarpa xvi — ×dawsoniana 510, 511 — doumeri 511 — ‘Evereste’ 509 — ×floribunda 510 — fusca 510 — honanensis 512 — ‘Indian Magic’ 509 — kansuensis 512 — kirghisorum 512, 513 — mandschurica 510 — niedwetzkyana 509 — ‘Princeton Cardinal’ 509 — pumila 508, 510, 513 — rockii xvi, 508, 513 — sieversii 509 var. kirghisorum 512 — sikkimensis 513 — ‘Snowcloud’ 509 — toringo xvi — Wedding Bouquet 510, 510 — yunnanensis 512 Manglietia 473, 474 — aromatica 480 — chingii 484 — conifera 484 — decidua 486 — duclouxii 486 — fordiana 490 — forrestii 491 — glaucifolia 484 — grandis 492 — hookeri 493 — insignis 493

Manglietia continued — megaphylla 500 — moto 493 — ovoidea 484, 485 — sinica 502 — yuyuanensis 504 Manglietiastrum 473 — sinicum 502 Maytenus 514 — boaria 514, 516 — chubutensis 514 — disticha 514 — magellanica 515, 516 — senegalensis subsp. europaeus 514 Mearnsia 520 Melaleuca 180, 181 No NT accounts — decussata 181 — gibbosa 181 — lanceolata 181 — squamea 181 — uncinata 181 Melia No NT accounts — azederach 182 Meliosma 13, 516 — oldhamii 517 — pinnata subsp. arnottiana var. oldhamii 517 — simplicifolia 517 subsp. pungens 517, 518 subsp. rigida 517, 517, 518 Melliodendron 518, 680 — xylocarpum 518, 519, 520 Meryta 526 Mespilus No NT accounts Metapanax 526, 778 — davidii 668, 778 — delavayi 778 Metasequoia 838, 900 No NT accounts Metrosideros 520 — angustifolia 520, 521 — carminea 521 — diffusa 521 — excelsa 521 — kermadecensis 521 ‘Variegata’ 521 — lucida 521 — umbellata 520, 521, 521, 522 Michelia 473, 474 — ×alba 479 — amoena 488 — calcicola 492 — cathcartii 482 — cavaleriei 483 — champaca 483 — chapensis 484 — chingii 499

Index of Tree Names

Michelia continued — compressa 484 — crassipes 488, 489, 495 — doltsopa 486 — figo 488 — floribunda 489 — ×foggii 489 — foveolata 491 — fulva 491 — ingrata 492 — lanuginosa 495 — macclurei 497 — martinii 498 — maudiae 499 — opipara 501 — sinensis 487 — skinneriana 488 — szechuanica 487 — tsoi 484 — velutina 495 — wilsonii 487 — xanthantha 492 — yunnanensis 494, 495 Microbiota 415 Microcitrus 256 Micromeles 815 et seq. — hemsleyi 821 Microstrobos No NT accounts Mimosa kalkora 129 Morus No NT accounts Myoporum 522 — laetum 522, 523, 523 Myrceugenia 523 — chrysocarpa 525, 525 — lanceolata 525 — leptospermoides 525 — ovata 525 var. nannophylla 525 — pinifolia 525 — planipes 524, 525, 630 Myrsine No NT accounts Myrtus communis 525 — lechleriana 149 Nageia 639, 672, 903 — fleuryi 639, 639, 641 — formosensis 639, 641, 644 — motleyi 644 — nagi 639, 644 — wallichiana 645 Nemopanthus 393 Neocallitropsis 902 No NT accounts Neolitsea 468 — aurata 468 — sericea 468 Neopanax 525, 667 — arboreus 526 — colensoi 526 — laetus 526, 526

Nestegis 527 — apetala 527 — cunninghamii 527, 527, 528 — lanceolata 527, 528 — montana 527 — sandwicensis 527 Nicodemia 178 Notelaea No NT accounts Nothaphoebe 528, 559 — cavaleriei xiii, 528, 528 Nothofagus 317, 444, 529, 555 — alessandrii 531, 532, 534 — alpina 531, 531, 532 — ×dodecaphleps 531, 532 — ×eugenanana 531 — fusca 531 — glauca 533 — gunnii 530, 533, 533 — ×leonii 16, 533, 534 — menziesii 534 — menziesii × N. obliqua 534 — nervosa 531 — nitida 535, 535 — obliqua 531, 532, 534 — procera 531 — pullei 531 Nothopanax 778 No NT accounts — laetus 526 Nothotsuga 535 — longibracteata 535, 536, 536, 870 Nyssa 536, 784, 820 — leptophylla 537 — ogeche 537, 538 — sinensis 537 — sylvatica 537, 538 var. sylvatica 538 var. ursina 537, 538, 538, — ursina 538 Ocotea foetens 553 Olea 539 — africana 540 — chrysophylla 540 — europaea 539 subsp. cuspidata 539, 540, 540 subsp. cerasiformis 539 subsp. europaea 539 var. europaea 539 var. oleaster 539 var. sylvestris 539 subsp. guanchica 539 subsp. laperrinei 540 subsp. maroccana 540 — ferruginea 540, 541 — tsoongii 541 — yuennanensis 539, 541 Osmanthus 541 — aurantiacus 543

Osmanthus 527 — delavayi 543 — fragrans 2, 542, 543, 543 f. aurantiacus 543 ‘Fudingzhu’ 543 var. semperflorens 543 — heterophyllus 543 Ostrya No NT accounts Ostryopsis No NT accounts Oxydendrum No NT accounts Pachylarnax 473 Padus 657 — virens 665 Paliurus No NT accounts Panax 150, 778 — rhododendrifolius 779 Papuacedrus 186 Parakmeria 473 — lotungensis 496 — yunnanensis 494, 504 Paramanglietia 473 — aromatica 480 Paramichelia 473 Paraserianthes lophantha 129 Parasitaxus ustus 645 Parkinsonia No NT accounts Parrotia 544 — persica 544, 545 — subaequalis 25, 544, 545 Parrotiopsis No NT accounts Pasania 459 Paulownia 546 — catalpifolia 546 — elongata 546 — fortunei 546, 547 — ×henanensis 547 — kawakamii 547 — ×taiwaniana 547, 547 — tomentosa 546, 547 var. tsinlingensis 547 Pennantia 549 — baylisiana 549 — corymbosa 548, 549 Pentapanax leschenaultii 150 Perrottetia 312 Persea 528, 550, 559 — americana 550, 551, 551 — borbonia 552, 552, 555, 556 var. humilis 556 var. pubescens 552 — bracteata 552 — breviflora 553 — grijsii 557 — humilis 556 — ichangensis 550 — indica 553 — japonica 558 — liebmannii 555 — lingue 444, 554, 555

969

Persea continued — meyeriana 556 — palustris 554, 556, 556 — pedunculata 557, 557 — podadenia 555 — thunbergii 550, 554, 557 — velutina 557 — yunnanensis 552, 553 Persica 657 Peumus 558 — boldus 558, 558, 629 Phellodendron 848 No NT accounts — amurense 848, 849 — chinense 848 — insulare 849 Phillyrea 561 Phoebe 251, 529, 559 — chekiangensis 561 — formosana 559, 560 — forrestii 560 — sheareri 560 Photinia 444, 793 Phyllanthus 379 Phyllocladus No NT accounts Picconia 561 — azorica 561, 561 — excelsa 561 Picea 562, 584, 671 — abies 562, 564, 574 — asperata 567, 573, 576 var. retroflexa 577 — aurantiaca 578 — balfouriana 572 — breweriana 564 — chihuahuana 563, 564, 565, 565, 575 — crassifolia 566, 567 — engelmannii 567, 586 subsp. engelmannii 567 subsp. mexicana 567 — farreri 24, 564, 568, 568 — ×fennica 577 — glauca 574 — jezoensis 569 subsp. jezoensis var. jezoensis 569, 569 var. komarovii 569, 570 subsp. hondoensis 569, 570 — koraiensis 570 var. koraiensis 571 var. nenjiangensis 570 var. pungsanensis 570 — koyamae 570 — likiangensis 563, 571 subsp. balfouriana 571, 572, 572 var. balfouriana 572 var. hirtella 571, 572, 573

970

Index of Tree Names

Picea continued — likiangensis continued subsp. likiangensis 571, 572, 573 var. likiangensis 571 var. linzhiensis 571, 573 var. montigena 571, 572, 573 var. purpurea 571 var. rubescens 571, 572, 573 — linzhiensis 571, 572, 573 — ×lutzii 574 ‘Machala’ 574 — ×mariorika 574 — martinezii 563, 563, 565, 566, 574, 575 — maximowiczii 575, 576 var. senanensis 576 — mexicana 567 — meyeri 576, 577 — montigena 571, 572, 573 — obovata 59 — omorika 564 — pungens 566 — purpurea 571, 572 — retroflexa 577 — schrenkiana 566, 578 subsp. tianschanica 578, 578 — sitchensis 574, 586 — smithiana 566 — spinulosa 800 — torano 566 Pieris 277, 317 Pilgerodendron 186 No NT accounts — uviferum 20, 53 Pimenta 174 Pinus 16, 237, 579, 672, 902 — amamiana 585, 586 — apulcensis 616 — aristata 607 — arizonica 587 var. arizonica 587, 588 var. cooperi 587 var. stormiae 587 — armandii 588, 610, 628 var. armandii 588, 590 var. dabeshanensis 588, 589 var. mastersiana 580, 582, 588, 589, 589 — australis 613 — ayacahuite 620 var. brachyptera 619 var. novogaliciana 619 var. veitchii 620 — balfouriana 607 subsp. balfouriana 607 subsp. austrina 607

Pinus continued — bhutanica 579, 590 var. ludlowii 590 — brutia 580, 591 var. brutia 592 f. kruepericola 591 var. densifolia 591 var. eldarica 592, 592 var. pendulifolia 592, 593 var. pityusa 592, 593 var. stankewiczii 593 — bungeana 326, 581, 582, 585 — catarinae 618 — cembroides 580, 593, 594, 605, 611 var. bicolor 604 subsp. cembroides 594 ‘Peña Nevada Gold’ 595 var. edulis 599 subsp. lagunae 594, 595 subsp. orizabensis 612 — chiapensis 595 — culminicola 596, 605, 618 — dabeshanensis 589 — densata 597, 597 var. densata 597 var. pygmaea 597 — devoniana 598 — discolor 604, 605 — durangensis 581, 598, 599 — echinata 600 — edulis 582, 599 ‘Juno’ 600 — elliottii 600, 613 var. densa 600 var. elliottii 600 — engelmannii 601, 601, 602 var. blancoi 601 ‘Glauca’ 602 — eremitana 627 — estevezii 616 — fenzeliana 628 var. dabeshanensis 589 — flexilis 620 var. reflexa 620 — gerardiana 581, 582 — gordoniana 598 — halepensis 606 — ×hayatana 609 — henryi 602, 603, 622 — hwangshanensis 603, 604, 626 subsp. transfluminea 603 — johannis 594, 596, 604, 612, 618 — juarezensis 618 — kesiya 585, 604, 605 — krempfii 581, 582

New Trees

Pinus continued — kwangtungensis 628 — lambertiana 579, 586 — leiophylla 582, 605 subsp. chihuahuana 606 subsp. leiophylla 606 — longaeva 606, 607 — longifolia 613 — luchuensis 603, 626 — lumholtzii 582, 584 — luzmariae 612 — martinezii 598 — massoniana 465, 580, 603, 607, 608 var. hainanensis 608 var. shaxianensis 607, 608 — maximartinezii 580, 586, 608 — maximinoi 585, 601 — merkusii 579, 585 — michoacana 598 cornutata 598 — monophylla 581, 618 — montezumae 598 — monticola 586, 596 — morrisonicola 609 — mugo subsp. rotundata 627 — nelsonii 582, 610, 610, 612 — nigra subsp. laricio 586 — oaxacana 616 — oocarpa 584, 611 var. oocarpa 611 var. trifoliata 612 — orizabensis 594, 610, 612 — orthophylla 627 — palustris 582, 602, 613, 613, 623 — parviflora 628 — patula 584, 585 — peuce 596 — pinaster 613 subsp. escarena 614 subsp. hamiltonii 614 var. maghrebiana 614 var. mesogeensis 614 subsp. pinaster 614 subsp. renoui 613, 614 — pinceana 609, 614, 615 — pinea 581, 610 — ponderosa 588 var. arizonica 587 — praetermissa 584 — pseudostrobus 615 var. apulcensis 580, 616 var. estevezii 616 var. pseudostrobus 584, 616, 617 — quadrifolia 618 — radiata 532, 582, 626 — reflexa 620

Pinus continued — remota 618 — rigida 619 subsp. serotina 619 — rzedowskii 609 — serotina 619 — ×sondereggeri 623 — squamata 581, 582, 585 — strobiformis 580, 584, 619 ‘Vanderwolf’s Pyramid’ 620 — strobus 586, 595, 596 var. chiapensis 595 — stylesii 584 — sylvestris 574, 579, 582, 586, 597, 603, 621 var. hamata 621 var. mongolica 621, 621, 622 var. sylvestris 621, 622 — tabuliformis 597, 622 var. densata 597 subsp. henryi 602 var. henryi 602, 622 var. mukdensis 622, 622 var. tabuliformis 622, 623 var. umbraculifera 622, 623 — taeda 2, 600, 619, 623 ‘J.C. Raulston’ 625 ‘Little Albert’ 625 ‘Nana’ 625 NCSU Dwarf Group 624, 625 — taiwanensis 603, 604, 625 var. damingshanensis 603 var. taiwanensis 625 — tecunumanii 584 — thunbergii 586 — torreyana 579, 582, 583, 626 subsp. insularis 627 var. insularis 627 subsp. torreyana 626, 627 — uyematsui 609, 610 — veitchii 620 — wallichiana 582, 590, 591 var. bhutanica 590 — wangii 627 subsp. kwangtungensis 628, 628 subsp. varifolia 628 var. varifolia 628 subsp. wangii 628 — wincesteriana 598 — yunnanensis ix, 462, 585, 597, 628, 629 var. tenuifolia 628, 629 Pistacia No NT accounts Pitavia 629 — punctata 629, 630

Index of Tree Names

Pittosporum 630 — adaphniphylloides 633 — angustifolium 633 — anomalum 631 — brevicalyx 632 ‘Golden Temple’ 23, 632, 632 — crispulum 631 — dallii 631 — daphniphylloides 632 var. adaphniphylloides 633 var. daphniphylloides 631, 633 — erioloma 631 — heterophyllum 631 — huttonianum 633 — illicioides 631 — kirkii 631 — lineare 631 — michiei 631 — napaulense 631 — obcordatum 631 — omeiense 631 — parvilimbum 631 — phillyreoides 634 — pimeleoides 631 — rhombifolium 631 — subulisepalum 631 — tenuifolium 630 — tobira 630 — truncatum 631 — undulatum 631 — viridiflorum 631 Plagianthus No NT accounts Planera No NT accounts Platanus 581, 634 — gentryi 635 — ×hispanica 635 — kerrii 634, 635 — lindeniana 637 — mexicana 635, 636, 637 ‘Alamo’ 637 var. interior 637 — occidentalis 635 — orientalis 634, 635 — racemosa var. wrightii 637 — rzedowskii 634, 635, 637 Platycarya No NT accounts Platycladus No NT accounts — orientalis 852, 853 Podocarpus 121, 638, 672, 903 — acutifolius 639 — brassii 641 — chinensis var. chinensis 643 — chingianus 643 — ‘County Park Fire’ 639 — cunninghamii 639, 641 — drouynianus 641 — elatus 640, 641

Podocarpus continued — elongatus 642 — ensiculus 641 — falcatus 121 — ferrugineus 655 — forrestii 643 — hallii 639 — henkelii 638, 641, 642 — latifolius 122, 641, 642, 642 — lawrencei 639 — macrophyllus 643 var. angustifolius 643 var. chingii 643 var. macrophyllus 643 var. maki 643 var. piliramulus 643 — matudae 14, 644, 644 var. jaliscanus 644 var. matudae 644 var. reichei 644 — milanjianus 639, 642 — nakaii 644 — nivalis 639 — nubigenus 639 — parlatorei 20, 53, 640 — reichei 644 — salicifolius 645 — salignus 639 — spicatus 655 — totara 639 Poliothyrsis No NT accounts Polylepis 645 — australis 645, 646, 646, 647 — pauta 646 — tomentella 646 — tarapacana 645 Polyscias 667 Polyspora 648, 785 — axillaris 648 — chrysandra 648 — hainanensis 648, 649 — yunnanensis 648 Pomaderris No NT accounts Poncirus 256 — trifoliata 257, 259 Populus 577, 649 — angustifolia 649 — balsamifera subsp. trichocarpa 654 — ×canadensis 651 — ciliata 652, 652 var. ciliata 652 — davidiana 654 — deltoides 651 — ×euramericana 651 — glauca 653, 653 — ilicifolia 649 — jacquemontiana 653 — lasiocarpa 649, 651 — nigra 649, 651

Populus continued — purdomii 650, 654, 654 var. rockii 654 — szechuanica 654 — tremula 112 — trichocarpa 651 — wilsonii 653 Protea No NT accounts Prumnopitys 655 — andina 655 — ferruginea 18, 655, 656 — spicata 655 — standleyi 645 — taxifolia 645 Prunus 2, 657, 683 — africana 20, 659 — alabamensis 665 — armeniaca var. mandschurica 662 — ‘Benigasa’ 658 — ‘Beni-yutaka’ 658 — cerasifera 666 subsp. divaricata 660, 666 — cerasoides var. campanulata 659 — Chocolate Ice 13, 13, 658 — clarofolia 662 — cuthbertii 665 — domestica 657 subsp. insititia 661 subsp. italica 661 subsp. syriaca 661 — dulcis 657 — elliptica 317 — Fragrant Cloud 658 — ‘Hanagasa’ 658 — himalaica 657, 660, 661 — jamasakura 659, 661, 665 — ×kanzakura 659 ‘Atami-zakura’ 659 ‘Kanzakura’ 659 ‘Usu-kan-zakura’ 659 — ‘Kanzan’ 658 — ×kobuki-zakura 659 — laurocerasus 117, 502 — ‘Matsumae-benigasa’ 658 — ‘Matsumae-beni-yutaka’ 658 — ‘Matsumae-fuki’ 13, 13, 658 — ‘Matsumae-hanagasa’ 658 — ‘Matsumae-shizuka’ 658 — ‘Matsumae-usugasanesomei’ 658 — obtusata 667 — padus 139 — ×persicoides 659 — pensylvanica var. mollis 662 — Pink Parasol 658 — pseudocerasus 659, 661 — pumila subsp. besseyi 659

971

Prunus continued — ‘Royal Burgundy’ 658, 658 — rufa 660, 661 — salicifolia 663 — serotina 663 subsp. capuli 663 subsp. eximia 663 subsp. hirsuta 663, 665 subsp. serotina 663 subsp. virens 663, 663, 665 var. rufula 665 — serrula 660, 661 — serrulata 658 — ‘Shizuka’ 658 — sogdiana xv, 657, 664, 665, 666 — spinosa 657 — ×subhirtella 659 — takesimensis 657, 657, 666 — trichantha 662 — ×yedoensis 658 Pseudolarix No NT accounts — amabilis 435 Pseudopanax 525, 526, 667, 778 — arboreus 526 — chathamicus 668 — crassifolius 668 — ‘Cyril Watson’ 670 — discolor 670 — ferox 668, 668, 669 — laetus 526 — lessonii 670 ‘Black Ruby’ 670 ‘Gold Splash’ 670 ‘Nigra’ 670 ‘Purpureus’ 670 — ‘Rangatira’ 670 — ‘Sabre’ 670 — ‘Trident’ 670 Pseudotaxus No NT accounts Pseudotsuga 45, 224, 671, 903 — brevifolia 672 — flahaultii 673 — forrestii 672, 674 — guinieri 672 — lindleyana 671, 672 — macrocarpa 671, 672 — macrolepis 672, 673 — menziesii 671, 672, 673 subsp. glauca 672, 673 var. caesia 672 var. glauca 672 var. glauca 672 var. menziesii 672 var. oaxacana 672 — sinensis 672, 673 var. brevifolia 672, 674

972

Index of Tree Names

Pseudotsuga continued — sinensis continued var. gaussenii 674 var. sinensis 674 var. wilsoniana 671, 672, 674, 870 — wilsoniana 674 Psidium No NT accounts Ptelea No NT accounts Pterocarya 674 — delavayi 677 — forrestii 677 — fraxinifolia 676 — hupehensis 676 — insignis 678 — macroptera xiv, 675, 676, 677 var. delavayi 675, 676, 677 var. insignis 675, 677, 678 var. macroptera 675, 677, 678 — ×rehderiana 676 — rhoifolia 676 — stenoptera 676, 678 ‘Fernleaf’ 676 — tonkinensis 676, 678, 678 Pteroceltis No NT accounts Pterostyrax 679 — burmanicus 679 — corymbosus 520, 679, 679, 681 — hispidus 679, 680, 681 — leveillei 681 — psilophyllus 680, 681 Pygeum 657 Pyrenaria 682, 785 — hirta 682 — spectabilis 24, 682, 682 Pyrus 683, 793, 817 — betulifolia 685 — boissieriana 684 — bretschneideri 684, 684 — calleryana 683, 684, 687, 688 ‘Bradford’ 683 ‘Chanticleer’ 683 ‘Fauriei’ 688 — communis 684, 685 subsp. caucasica 685, 686, 686 subsp. communis 685 subsp. gharbiana 685, 686 subsp. longipes 685, 686 subsp. mamorensis xvi, 685, 687 subsp. sativa 685 — cordata 685 — cossonii 686 — elaeagnifolia xvi, 6, 687 subsp. kotschyana 687 White Sails 687

Pyrus continued — fauriei 687, 688 Korean Sun 688 ‘Westwood’ 688 — korshinskyi 683, 688, 689 — longipes 686 — phaeocarpa xvi, 690, 690 f. globosa 690 — pyrifolia 685 — regelii 688 — salicifolia ‘Pendula’ 687 — syriaca subsp. glabra 688 Quercus 16, 237, 304, 460, 465, 691 — acerifolia 700, 700 — acherdophylla 701 — acuta 696 — acutifolia 701, 751 — affinis 12, 702, 702 — agrifolia 703 var. oxyadenia 698, 703 — alamarensis 712 — alba 692 — aliena var. acutiserrata 730 — alnifolia 734 — aquifolioides 703, 705 — arizonica 707, 707, 756 — argyrotricha 696 — aucheri 708, 708, 734 — austrina 709 — baloot 709 — berberidifolia 696 — brantii 698, 710, 710 — brayi 740 — breviloba f. laceyi 734 — buckleyi 711, 711, 730, 754 — canbyi 712, 749 — candicans 698, 713, 713 — candolleana 715 — castanea 698, 714 — cedrosensis 696 — cerris 692 — championii 696 — chenii 701 — chrysolepis 755 — coccifera 708, 710, 714 subsp. rivas-martinezii 714 — cocciferoides 715 — coccinea 719 — coccolobifolia 696 — conspersa 698, 715 — cornea 465 — cornelius-mulleri 696 — crispipilis 696 — cubana 696, 725 — cupreata 696 — daimingshanensis 696 — delavayi 696

New Trees

Quercus continued — dentata 716, 721 subsp. yunnanensis 716, 716 — depressa 696 — deserticola 716 — dilatata 722 — dolicholepis 707, 717 — durandii 752 — durifolia 717 — eduardii 718 — ellipsoidalis 9, 718, 719 ‘Hemelrijk’ 719 — emoryi 719 — engelmannii 698, 720 — eugeniifolia 720 — sp. nov. aff. eugeniifolia 720, 721 — fabri 721, 722 — faginea subsp. broteroi 754 — falcata 749 var. pagodifolia 744 — fimbriata 704, 707 — floribunda 722 — frainetto 759 — franchetii 697, 723 — fusiformis 693, 698, 723 — galeottii 725 — gambelii 756 — garryana 724 var. breweri 724 var. fruticosa 724 var. garryana 724 var. semota 724 — geminata 724 — georgiana 692, 725 — germana 725, 726 var. lemmonii 726 — gilliana 704, 706 — gilva 692, 726, 727 — glauca 695, 737, 750, 751 — glaucoides (Schottky) Koidz. 751 — glaucoides M. Martens & Galeotti 751 — graciliformis 711, 729 — gravesii 711, 712, 728, 729, 754 — greggii 696, 748 — griffithii 691, 730 — grisea 698, 708, 731, 731, 756 — guyavifolia 704, 704, 707 — havardii 696, 756 — hemisphaerica 7, 732, 732 ‘Darlington’ 732 — hinckleyi 696 — hintoniorum 696 — hirtifolia 696 — hondae 696

Quercus continued — huitamalcana 750 — ilex 703 — incana 733 — infectoria subsp. veneris 710, 733 — insignis 35, 698, 733 — intricata 696 — invaginata 696 — ithaburensis subsp. ithaburensis 737 subsp. macrolepis 718, 737, 738, 747 — john-tuckeri 696 — jonesii 696 — kelloggii 730 — laceyi 734, 734 — laeta 696 — lamellosa 17, 692 — lancifolia 735 — laurifolia 698, 732, 735 ‘Darlingtoniana’ 732 — laurina 698, 736 — liaotungensis 739 — libani 710, 737 — liboensis 30, 695, 696 — liebmannii 696 — longinux 736 — longispica 704, 706, 706 — ×look 737 — macranthera 737 subsp. macranthera 737 subsp. syspirensis 737 — malacotricha 716 — malinaltepecana 736 — mexicana 698, 738, 738 — microphylla 696 — miquihuanensis 696 — mohriana 696, 756 — mongolica 698, 739 subsp. crispula 721, 739 subsp. grosseserrata 739 subsp. mongolica 739 — monimotricha 704, 706, 707 — morii 698, 739, 739 — muehlenbergii 2, 740, 740, 756 — multinervis 696 — myrtifolia 741 — nigra ‘Beethoven’ 737 — nuttallii 753, 754 — oblongifolia 720, 741, 741 — obtusata 742 — oglethorpensis 742, 743 — oleoides 725 — oxyodon 695 — pacifica 696 — pagoda 744, 744 — palmeri 745 — palustris 754

Index of Tree Names

Quercus continued — pannosa 704, 707 — parvula 745, 745 var. parvula 745 var. shrevei 745 var. tamalpaisensis 745 — peduncularis 696 — pentacycla 696 — petraea subsp. iberica 732, 746 — planipocula 735, 746 — polymorpha 746, 749, 759 — potosina 696 — prinoides 740 var. acuminata 740 — pseudosemecarpifolia 23, 704, 706, 707 — pumila 696, 733 — pungens 696 — rehderiana 704, 706 — repanda 696 — reticulata 747 — rex 696, 698 — rhysophylla 749 NOW Q. rysophylla (q.v.) — robur 635, 743, 898 subsp. brutia 711, 754 subsp. pedunculiflora 746 — rotundifolia 732 — rubra 8, 692 — rugosa 698, 747, 747 La Encantada Form 748 La Siberica Form 748, 748 Pinal de Amoles Form 748 — rugulosa 738 — rysophylla 694, 695, 696, 714, 748, 749 ‘Maya’ 749 — salicina 750, 750 — sapotifolia 696 — sartorii Botteri ex A. DC. 751 — sartorii Liebm. 749, 750, 751 — schottkyana 698, 751 — semecarpifolia 61, 704, 706 — senescens 704, 706 — serrata 726 — sessilifolia 696 — shumardii 712 var. acerifolia 700 — sinuata 752, 752 var. breviloba 752 var. sinuata 752 — skinneri 759, 759 — spinosa 698, 704, 706, 707, 717 — stenophylla 750 — stenophylloides 750, 752 — suber 691

Quercus continued — subspathulata 753 — taliensis 715 — texana 698, 711, 712, 753 ‘New Madrid’ 754, 754 New Madrid Group 754 — tinkhamii 696 — tomentella 692, 754 — treleaseana 736 — tuberculata 696 — tungmaiensis 696 — turbinella 755, 755, 756 — undulata 756 — uxoris 735, 756 — vaseyana 696 — vexans 715 — virginiana 723, 725, 757, 757 — vulcanica 757, 758 ‘Kasnak’ 759 — wislizeni 745 — wutaishanica 739 — xalapensis 759 — yunnanensis 716 — ‘Zehra’ 749 Quillaja 444, 760 — saponaria 760, 760, 760 Racosperma 63 — dealbatum 65 — spectabile 68 Rapanea No NT accounts Raukaua 667 Ravensara 288 Rehderodendron 384, 385, 761 — gongshanense 762 — hui 762 — indochinense 762 — kwangtungense 762, 762, 762 — macrocarpum 761, 761, 762 — mapienense 761 Retrophyllum comptonii 640 — minus 644 — rospigliosii 645 — vitiense 645 ×Rhaphiobotrya 323 — ‘Coppertone’ 323 — ‘Majestic Beauty’ 323 Rhaphiolepis 323 — indica 323 Rhododendron xi, 2, 699, 730, 800 No NT accounts — aeruginosum 806 Rhodoleia No NT accounts Rhus 763 — ambigua 764 — chinensis 763 — glauca 764 — incisa 764 — integrifolia 764 — japonica 763

Rhus continued — javanica 763 — krebsiana 764 — lancea 763, 764, 764 — leptodictya 764 — magalismontana 764 — typhina 763 — verniciflua 763 — wallichii 3, 763, 763, 765 Ribes 586 Robinia No NT accounts Sabina 414 Salix 649, 766 — adenophylla 768 — alba 768 — amygdaloides 766, 767 — arbuscula var. erecta 772 — arenaria 771 — chilensis 768 — fruticulosa 768 — humboldtiana 768, 769 ‘Pyramidalis’ 769 — magnifica 766 — myrsinifolia 770 — occidentalis 772 — repens var. subopposita 772 — rigida var. mackenziana 770 — schraderiana 767 — scouleriana 770, 771, 771 — serpyllifolia 766 Sambucus No NT accounts Sanguisorba 646 Sapindus No NT accounts Sapium No NT accounts Sassafras 772 — albidum 772, 773 — randaiense 772, 773, 773 — tzumu 772, 773 Saxegothaea No NT accounts Schefflera xi, 526, 774 — alpina 776, 777 — aff. alpina 777 — arboricola 776 — bodinieri 776 — aff. brevipedicellata 776 — aff. chapana 777 — delavayi 774, 775, 778, 778 — digitata 776 — aff. enneaphylla 776 — fantsipanensis 776 — farinosa 779 — gracilis 776 — hoi var. fantsipanensis 776 — impressa 779 — aff. kornasii 777 — aff. lenticellata 776 — macrophylla 778, 779 var. flava 779 — microphylla 776

973

Schefflera continued — petelotii 779 — rhododendrifolia 774, 774, 779 — shweliensis 780 — taiwaniana 774, 780, 781 Schima xi, 648, 781, 785 — argentea 782, 784 — liukiuensis 783 — noronhae 782 — sericans 782 — superba 783, 783 var. kankaoensis 783 — wallichii 781, 782, 782 var. khasiana 783 subsp. liukiuensis 783 subsp. noronhae var. superba 782 — yunnanensis 782 ×Schimlinia 782, 784 — floribunda 784, 784 Schinus 785 — areira 786 — molle 785, 786 var. areira 786 var. rusbyi 786 — montanus 785 — pearcei 785 — polygamus 785 Sciadodendron 150 Sciadopitys No NT accounts Searsia 763 — lancea 764 Semiliquidambar 457 Senegalia 63, 64 Sequoia 3, 347, 357, 838, 899 No NT accounts Sequoiadendron ix, 3, 326, 899 No NT accounts Shaniodendron subaequale 544 Sideroxylon No NT accounts Sinojackia No NT accounts Sinopanax formosanus 777, 777 Sinowilsonia No NT accounts Sloanea 786 — sinensis 787, 788 Sophora 789 — cassioides 789, 790, 790 — chathamica 790 — fulvida 790 — godleyi 790 — ‘Hilsop’ 791 — howinsula 790 — longicarinata 790 — macnabiana 791 — macrocarpa 791 — microphylla 789, 790 ‘Goldilocks’ 791 subsp. macnabiana 791

974

Index of Tree Names

Sophora continued — molloyi 790 ‘Dragon’s Gold’ 790 — prostrata 789 — Sun King 791 — tetraptera 789 ‘Goughensis’ 791 — toromiro 18, 789 Sorbus 11, 24, 29, 237, 793, 794 — adamii 818 — amoena 800 — apiculata 798, 800 — arachnoidea 800 — aria 793, 796, 815 — armeniaca 818 — arranensis 795, 796, 816 — aucuparia 794, 795, 796, 801, 816, 822, 825 — bakonyensis 818 — barthae 818 — bissetii 798, 799 — bodajkensis 818 — borbasii 818 — borosiana ‘Alba Regia’ 818 — brevipetiolata 819 — bulleyana 803 — californica 798 — caloneura 819 — carmesina 801, 801, 804 — cashmiriana 797, 799, 807 — chamaemespilus 793 — commixta 811 ‘Dodong’ 811 — coxii 25, 801, 804, 808 — croceocarpa 819, 819 — dacica 818 — danubialis 818 — decipientiformis ‘Vállus’ 818 — decora 799 — degenii 818 — discolor 797 — domestica 793 — dubia 818 — eburnea 798 — ellipsoidalis 801, 804 — esserteauiana 795 — eugenii-kelleri 818 — fansipanensis 802, 802 — filipes 811 — forrestii 803 — frutescens 798, 799 — glabrescens 797, 803 — glabriuscula 797, 797, 802, 803, 804, 809 — ‘Glendoick Glory’ 798 — ‘Glendoick Ruby’ 798 — gonggashanica 798 — graeca 796, 820

Sorbus continued — aff. graeca 818 — aff. granulosa 819 — ‘Hainburg’ 818 — hajastana 814, 816, 817, 820, 820, 822 — Harry Smith 12799 798 — helenae 804, 804 — hemsleyi 821 — henryi 821 — hibernica 818 — hupehensis 797, 803, 809 var. obtusa 797, 809 — hybrida 796 — hypoglauca 805 — incana 818 — insignis 800 — intermedia 796 — ‘Keith Rushforth’ 803 — khumbuensis 805, 805, 807 — koehneana 810 — kongboensis 799, 806 — kurzii 799, 806 — kusnetzovii 818 — lancifolia 796 — latifolia agg. 816, 819 — latissima 818 — laxiflora 809 — leptophylla 818 — leyana 796 — ligustrifolia 819 — aff. ligustrifolia 819 — lingshiensis 806 — longii 800 — macallisteri 799 — matsumurana 795 — microphylla 807 — microphylla agg. 796, 796, 805, 807, 807, 811, 812 — minima 795, 796 — ‘Molly Sanderson’ 797 — monbeigii 798 — muliensis 801, 804, 804, 807, 808 — munda 798, 825 — occidentalis 825 — oligodonta 808, 809 — olivacea 808, 808 — pontica 818 — parvifructa 808, 813 — porrigentiformis 796, 819 — prattii 798, 803 — pseudobakonyensis 818 — pseudofennica 796 — pseudohupehensis 797, 801, 803, 804, 808, 809 ‘Pink Pagoda’ 809 — pseudolatifolia 818 — pseudovilmorinii 802, 809, 809

New Trees

Sorbus continued — randaiensis 792, 794, 810, 810 — redliana 818 — rehderiana 805, 806 — retroflexis 818 — rinzenii 806, 811, 812 — rosea 799 — ‘Rosiness’ 799 — ‘Rosy-Ness’ 799 — rubescens 811, 811 — rufopilosa 807, 811, 812, 812 — rupicola 795, 796 — rushforthii 812 — sargentiana 813 — scalaris 795 — semi-incisa 818 — simonkaiana 818 — stankovii 818 — subfusca 818, 822 — subpinnata 796 — subulata 802, 819 — takhtajanii 817, 822 — tamamschjanae xvi, 814, 817, 818, 822, 825 — taurica 818 — thaiszii 818 — thomsonii 820 — torminalis 793, 796 — umbellata 816 — verrucosa var. subulata 819 — vilmorinii 809, 810 — wallichii 813 — wattii 813 — whiteana 816 — wilsoniana 809, 813, 814 — xanthoneura 821 — yuana 822 — zolyomii 818 Staphylea No NT accounts Stewartia 648 No NT accounts Strobus 579 Styphnolobium 789 — affine 789 — japonicum 789 Styrax 2, 520, 679, 826 — benzoin 836 — calvescens 828 — confusus 829 var. microphyllus 829 var. superbus 829 — dasyanthus var. cinerascens 828, 829 — faberi 829 — formosanus 28, 830, 830, 836 var. formosanus 830 var. hayataianus 830

Styrax continued — formosanus continued var. hirtus 830 — glabrescens 828 — globosus 828 — grandiflorus 826 — grandifolius 827, 831 — hemsleyanus 828, 828 — hookeri 831 var. yunnanensis 831 — huanus 828 — japonicus 826, 828, 830, 831, 835 ‘Crystal’ 826 ‘Emerald Pagoda’ 826 ‘Sohuksan’ 826 — lanceolatus 828 — langkongensis 832 — limprichtii 832 — macranthus 831 — macrocarpus 828 — obassia 826 — odoratissimus 837 — officinalis 833, 835, 836 var. californicus 833 var. redivivus 833 — perkinsiae 831 — philadelphoides 829 — platanifolius 828, 832, 835 subsp. mollis 832, 833 subsp. platanifolius 832 subsp. stellatus 832, 833 subsp. texanus 832, 833 subsp. youngiae 832, 833, 833 — ramirezii 828 — redivivus 833, 834 — rugosus 828 — schweliensis 831 — serrulatus 829, 835 — suberifolius 830, 836 var. hayataianus 836 — tonkinensis 826, 836 — wilsonii 832 — yunnanensis 831 Sundacarpus amarus 640 Swida 261 ×Sycoparrotia No NT accounts Sycopsis No NT accounts Symingtonia populnea 367 Taiwania No NT accounts — cryptomerioides 773 Talauma 473 Tapiscia No NT accounts Tasmannia 314 — lanceolata 315 ×Taxodiomeria 837 — peizhongii 837 ‘Dongfangshan’ 837

Index of Tree Names

Taxodium 837, 838 No NT accounts — distichum 837 var. distichum 837 var. mexicanum 837 — mucronatum 837 — Nanjing Beauty 837 — ‘Zhongshansha 302’ 837 Taxus 20, 234, 235, 655, 672, 838, 865, 903 — baccata 656, 838, 840, 841 ‘Fastigiata’ 838 subsp. wallichiana 842 — brevifolia 841 — canadensis 838 — celebica 841, 842, 844 — chinensis 843 var. chinensis 843 var. mairei 843 var. yunnanensis 842 — contorta 840 — cuspidata 839, 840, 841 var. chinensis 843 — floridana 839, 840, 840, 841, 866 — fuana 840 — globosa 840, 841 — ×hunnewelliana 839 — ×media 839, 840 — speciosa 843 — sumatrana 841, 842, 844 — wallichiana 838, 839, 840, 842 var. chinensis 842, 843 var. mairei 842, 843 var. wallichiana 838, 842, 843, 843 — yunnanensis 842 Telopea 844 — ‘Burgundy’ 845 — mongaensis 845 — oreades 844, 845 — speciosissima 845 — truncata 845 Temu 174 Ternstroemia 845 — gymnanthera 846 — nitida 846, 846 Tetracentron No NT accounts Tetraclinis 847 — articulata 847, 847 Tetradium 847 — baberi 851 — daniellii 848, 849 — faberi 851 — fraxinifolium 848, 851 — glabrifolium 848, 848, 849 var. glaucum 849 — ruticarpum 23, 31, 848, 850, 850, 851

Tetrapanax 526 No NT accounts Thaleropia 520 Thuja 851 — articulata 847 — ‘Green Giant’ 852 — Green Rocket Hybrid Cedar 852 — koraiensis 246, 851, 852, 853 ‘Glauca’ 853 ‘Glauca Nana’ 853 ‘Glauca Prostrata’ 853 — occidentalis 851 — plicata 851, 852, 853 — standishii 851, 852 — sutchuenensis 851 Thujopsis 852 No NT accounts Tilia 164, 853 — ‘Alan Mitchell’ 856 — americana 855 — amurensis 856, 856 subsp. amurensis 855, 856, 857 var. araneosa 857 subsp. taquetii 855, 857 — begoniifolia 861 — breviradiata 859 — caroliniana 857, 862 subsp. caroliniana 857, 858 subsp. floridana 858 — chenmoui 863 — chinensis 858 var. chinensis 858 var. intonsa 858 var. investita 858 — chingiana 859, 859 — cordata 856, 859 — dasystyla 859 subsp. caucasica 860, 861, 861 subsp. dasystyla 859, 860 — endochrysea 25, 855, 861, 861 — ×europaea 855 — ‘Harold Hillier’ 856 — insularis 856, 857 — intonsa 859 — japonica 857 ‘Ernest Wilson’ 856, 857, 857 — kiusiana 205 — koreana 857 — laetevirens 858 — mexicana 862, 862 — mongolica 856 — nobilis 854, 855, 863 — platyphyllos 856, 859 — tomentosa 856 ‘Petiolaris’ 637

Tilia continued — tuan 863 var. chenmoui 863 var. chinensis 864 var. tuan 864 Toisusu 766 Toona No NT accounts Torminaria 793 — torminalis 793, 794, 796, 816, 818, 825 Torreya 146, 864 — californica 864 — fargesii 865 — grandis 864, 865 var. dielsii 865 var. fargesii 865, 866 var. grandis 865, 865, 866 var. jiulongshanensis 865 var. merrillii 865 var. sargentii 865 var. yunnanensis 865 — jackii 864, 865 — nucifera 864 — taxifolia 864, 866, 867 — yunnanensis 866 Toxicodendron 763 — orientale 764 — wallichii 765 Trema 227 Trevesia palmata 777 Trochetiopsis erythroxylon 18 Trochodendron No NT accounts Tsoongiodendron 473 Tsuga 535, 562, 672, 868, 903 — canadensis 869 — caroliniana 869 — chinensis 869, 869 var. chinensis 868, 869, 870 var. formosana 869, 871 var. forrestii 869, 871 var. oblongisquamata 869 var. patens 869 var. robusta 869 — diversifolia 871 — dumosa 871 — formosana 869 — forrestii 869, 871 — heterophylla 868 — lindleyana 672 — oblongisquamata 869 — longibracteata 536 — sieboldii 871 Tumion 864 Tutcheria 682 — spectabilis 682 Ulmus 2, 227, 873, 906 — Accolade 876, 876, 880, 880, 884

975

Ulmus continued — americana 875, 876, 878, 878, 879, 880, 891 American Liberty 876 ‘New Harmony’ 879 ‘Princeton’ 879 ‘Valley Forge’ 879 — ×androssowii 891 — ‘Arno’ 886 — bergmanniana 872, 881 var. bergmanniana 882 var. lasiophylla 882 — carpinifolia 874, 886, 887 — castaneifolia 882, 883 — ‘Cathedral’ 881 — changii 877 — chenmoui 875, 883 — ‘Clusius’ 885 — ‘Columella’ 885, 886 — ‘Commelin’ 885, 887 — Commendation 880 — Danada Charm 880 — davidiana 884 var. davidiana 873, 880, 884 var. mandshurica 884 var. japonica 874, 880, 881, 884 ‘Discovery’ 880 ‘Jacan’ 880 ‘Morton’ 876, 876, 880, 880, 884 ‘Prospector’ 880 — ‘Dodoens’ 885, 885 — elongata 877 — ‘Fiorente’ 886 — ‘Frontier’ 886 — gaussenii 25, 887 — glabra 874, 877, 887, 888 ‘Exoniensis’ 885, 886 — glaucescens 888 var. glaucescens 888 var. lasiocarpa 888 — ‘Groeneveld’ 885 — harbinensis 874 — ×hollandica 874, 887 — ‘Homestead’ 887 — japonica 874, 880, 884 — laciniata 888, 889 var. nikkoensis 890 — laevis 874, 876 — lamellosa 890, 890 — lanceifolia 877 — ‘Lobel’ 885 — Lutèce 875, 877, 886 — macrocarpa 880 — microcarpa 877 — minor 874, 879, 885, 886, 887 subsp. angustifolia 880 ‘Bea Schwarz’ 885, 886

976

Index of Tree Names

Ulmus continued — minor continued ‘Christine Buisman’ 885 ‘Hoersholmiensis’ 887 subsp. minor 882, 886 var. plotii 884, 891 var. vulgaris 891 — ‘Morton’ 876, 876, 880, 880, 884 — ‘Morton Glossy’ 880 — ‘Morton Plainsman’ 881 — ‘Morton Red Tip’ 880 — ‘Morton Stalwart’ 880 — ‘Morton Vanguard’ 880 — multinervis 882 — ‘Nanguen’ 875, 877, 886 — ‘New Horizon’ 881 — parvifolia 876, 886, 891 Allee 891 ‘A. Ross Central Park’ 891 Athena 891 Central Park Splendor 891 ‘Dynasty’ 891 ‘Emer I’ 891 ‘Emer II’ 891 — ‘Patriot’ 881 — ‘Pioneer’ 886 — ‘Plantyn’ 885, 886 — ‘Plinio’ 886 — procera 874 — propinqua 884 — prunifolia 877 — pseudopropinqua 877 — pumila 879, 880, 881, 886, 887

Plate 579. ‘Like that of leaves is a generation of men’ – Homer, The Iliad. Carpinus viminea, leaf and bark. Lushan, Jiangxi. Image P. de Spoelberch.

New Trees

Ulmus continued — ‘Rebona’ 881 — ‘Regal’ 887 — ‘San Zanobi’ 886 — ‘Sapporo Autumn Gold’ 876, 881, 881 — sukaczevii 877 — szechuanica 880, 891 — taihangshanensis 890 — Triumph 880 — ‘Urban’ 881, 887 — Vada 886 — Vanguard 881 — wallichiana 885 — ‘Wanoux’ 886 — wilsoniana 880, 884 Umbellularia No NT accounts — californica 559 Vachellia 63, 64 — caven 64, 65, 908 — karroo 63, 66, 66 Viburnum 2, 699 No NT accounts Weinmannia 892 — pinnata 892 — racemosa 892, 893, 893 — sylvicola 893 — trichosperma 892, 893 Widdringtonia 894 — cedarbergensis 894, 895, 895 — cupressoides 896 — nodiflora 894, 896, 896 var. dracomontana 896

Widdringtonia continued — schwarzii 894, 896 ‘Drakensberg Blue’ 897 — whytei 894, 896 Wollemia 897 — nobilis ix, xi, 20, 25, 897, 898, 900 Woonyoungia 473 Xanthoceras No NT accounts Xanthocyparis 245, 290, 291, 292, 415, 672, 901 — nootkatensis 247, 290, 302, 303, 901, 902, 903 — vietnamensis 2, 290, 901, 902, 902, 903 Yinquania 261 Yulania 473 — ×soulangeana 474 Zanthoxylum No NT accounts Zelkova 227, 904 — carpinifolia 904 — schneideriana 904, 905, 906, 907 — serrata 904, 906 ‘Flekova’ 904 Green Vase 904 ‘Spring Grove’ 904 var. stipulacea 906 ‘Urban Ruby’ 904 ‘Village Green’ 904 — sicula 904 — sinica 906 Ziziphus No NT accounts