Title: Guide to Trees Introduced into Southern Africa
Authors: Braam van Wyk; Hugh Glen
Publisher: Penguin Random House South Africa (Struik Nature)
Cape Town, South Africa 2016
ISBN 9781775841258 / ISBN 978-1-77584-125-8
Softcover, 15 x 21 cm, 464 pages, 1900 photographs
Guide to Trees Introduced into Southern Africais intended primarily as a manual to identify cultivated alien trees in southern Africa. Such non-native trees are predominantly associated with places of human habitation, notably home gardens, parks and other open spaces in towns and cities. This guide has been compiled as a companion volume to Field Guide to Trees of Southern Africa (2013, Struik Nature), one of the most popular books for the identification of trees native to the subcontinent. Hence the present book follows the same easy-to-understand group recognition approach adopted in the former. Readers familiar with using one of the two books will therefore be able to switch between them with ease. For both field guides, there is the added advantage of a complementary volume that presents the background botanical information required for tree identification, namely How to Identify Trees in Southern Africa (2007, Struik Publishers).
With southern Africa's exceptionally rich native tree flora of about 2,100 species, most tree identification books for the subcontinent have hitherto neglected the identification of those cultivated trees introduced from other parts of the world. However, it is estimated that at least 2,000 alien tree species are being cultivated in the region. By far the majority were introduced because they possess one or more properties valued by humans. For example, several tree species from cool-temperate parts of the northern hemisphere have been introduced to compensate for the general lack of native trees that can tolerate the extreme winter cold on the South African Highveld. Since the 1970s, efforts to promote the preferential cultivation of trees indigenous to southern Africa have to some extent overshadowed the immense importance of alien trees. In any case, so-called indigenous trees in cultivation are strictly speaking also aliens if they are grown outside their natural range, as is often the case.
Alien trees in general have unfortunately also acquired a bad reputation in our region because of the invasive tendencies of a relatively small number of species. In South Africa, several trees once popular in gardens have been declared alien invaders and are now subject to legal control and various restrictions. However, trying to curb the spread of most of the more common naturalised alien species through legislation is, in our opinion, a futile if not unjust (towards land owners) exercise. Once naturalised in a new region, alien plants become part of the local biodiversity and can still be immensely useful by providing a range of ecological services. Some people even dub the disdain with which these species are viewed as 'green xenophobia'. Perhaps the best long-term solution for containing the spread of well-established alien invaders is to put in place specific biological control measures for each species to ensure that numbers are being kept in check.
Cold-hardiness zones and distribution of cultivated trees
Map: Cold-hardiness zones of southern Africa
The naming of cultivated plants
How to use this book
Guide to the species accounts
Key to the groups
Glossary of terms
Bibliography and contact addresses