The Genus Betula. A taxonomic revision of birches.

‘Long-awaited’ is an apt expression for this book, which has not only been long-delayed, but much-needed as a contemporary review of the whole genus Betula, from both botanical and horticultural perspectives. Curtis’s Botanical Magazine Monographs, published by Kew, are a series of authoritative monographs, which continue the tradition of the oldest scientific journal in the world, blending botanical accuracy with horticultural information and fine illustration. The Genus Betula is no exception, filled with many photographs, as well as paintings by Josephine Hague and line drawings by Andrew Brown. The authors, Kenneth Ashburner and Hugh McAllister, worked together on Genus Betula for many years before Kenneth’s death in 2010, after which Hugh completed the book. However, it is still very much a joint production bringing together decades’ worth of birch study in many remote places. One of the results of this is the arboretum at Stone Lane Gardens, Ashburner’s former home in Devon, where groves of birch saplings from the same collection were planted together. This gives a unique opportunity to study natural variation. The diversity of Betula is perhaps surprising. Occuring throughout the cooler parts of the northern hemisphere, 45 species are recognised here; a mixture of familiar trees and shrubby species. Although often attractive in the wild, with nice autumn colour, most of the small species are of ‘botanical interest only’, seldom performing well in gardens. Of the taller trees, it is clear there are many possibilities for bringing new characters to the garden, such as with the Vietnamese B. insignis var. fansipanensis with purple-flushed new growth, and for selecting superior cultivars. This book will also remind gardeners of the existence of the species that are seldom planted, such as the B. grossa, for which there are no current suppliers in the UK. In these times when tree diseases are prevalent we need as much diversity as possible. Although The Genus Betula is mainly a botanical book that discusses birches from a taxonomic and biological view, for the horticulturist there is a chapter on cultivation, reminding us of their shallow-rooted nature and the desirability of planting birches young. Each species has a note on its merits or demerits in cultivation. A chapter on birch cultivars by Paul Bartlett, who runs Stone Lane Gardens, is useful but a fuller description of each would have been welcome, and they are not illustrated, which is a pity. However, this is still a very useful book and will be a standard reference for years to come. -- John Grimshaw, * Garden Design Journal *