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South African Journal of Science

On-line version ISSN 1996-7489
Print version ISSN 0038-2353

S. Afr. j. sci. vol.118 n.3-4 Pretoria Mar./Apr. 2022

http://dx.doi.org/10.17159/sajs.2022/12782 

BOOK REVIEW

 

A new revision of Agapanthus

 

 

Brian W. van Wilgen

Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa Email: bvanwilgen@sun.ac.za

 

 

 

BOOK TITLE: The genus Agapanthus
AUTHOR: Graham Duncan
ISBN: 9781842467237 (hardcover, 256 pp)
PUBLISHER: Kew Publishing, London, UK; GBP50.00
PUBLISHED: 2021

Agapanthus is a genus of plants in the family Amaryllidaceae, where it is the only genus in the subfamily Agapanthoideae. The genus includes eight species, with four subspecies recognised under Agapanthus inapertus. These plants are endemic to southern Africa; all eight species are found in South Africa, and three species also occur in Lesotho (two species), eSwatini (two species) and southern Mozambique (one species). One might be forgiven for wondering how it could be possible to fill over 240 pages on a description of just eight species, but this book offers much more than just a revision of a small genus of plants. The taxonomic account is presented at the end of the book, and occupies about a third of the pages. Agapanthus are also globally popular garden plants. The different species show an extraordinary propensity for hybridising in cultivation, giving rise to at least 625 recognised cultivars, of which 155 (90 deciduous and 65 evergreen) are covered in a further third of the book. The selection is intended to portray 'some of the better recommended cultivars, and for which a reasonably good chance exists of their being obtained in the nursery trade from at least one outlet'. Each cultivar is also rated in terms of its hardiness with respect to cold temperatures.

The book is a testament to the difficulties encountered in unravelling the identity of species. Agapanthus species have proved to be difficult in this regard because of the paucity of unique characters that could be used to separate them, as well as the extraordinarily high level of morphological plasticity that exists in some species depending on the conditions found at the sites where they grow. The genus has also been ping-ponged back and forth between its own family Agapanthaceae and a subfamily in the Amaryllidaceae many times since 1836. Frances Leighton's treatment of the genus in 1965, in which 10 species were recognised1, has stood as the only comprehensive account of the genus for over half a century.

The taxonomic treatment provides a comprehensive description of each species' characteristics and distinguishing features, phenology, distribution, habitat and conservation status. The reader is also introduced to a new species (A. pondoensis), which was first collected in 1953, but considered to be a subspecies of A. praecox - 65 years were to pass before the author was able to collect further material and confirm its status as a separate species. Judging by the photographs of its habitat (sheer cliffs alongside spectacular waterfalls), it is no wonder that it remained unstudied for so long. The taxonomic text is complemented by many colour photographs of each species in its natural habitat, as well as distribution maps and superb full-page colour plates by the artist Elbe Joubert.

The remaining third of the book is made up by chapters addressing the history of discovery and classification, cultivation and propagation, ecology and conservation, and biology. Together these chapters cover just about everything that is known about where these plants come from, how they live, reproduce and die, and how they are faring in the modern world. Many of the species are not yet under threat in their native habitats, as they are fairly widely distributed and grow in relatively inaccessible sites. The exception is A. walshii, which is classified as Endangered due to its restricted range, expanding human settlements, invasive alien acacias and changing fire regimes.

This book is a welcome addition to the growing South African botanical literature. Graham Duncan is to be congratulated on an impressive volume, which is in line with his earlier treatments of the genus Lachenalia (published by Kew Publishing in 2012), and of the family Amaryllidaceae (published by Umdaus Press in 2017). I would recommend this book unreservedly to naturalists and gardeners, as well as to collectors of Africana.

 

Reference

1. Leighton FM. The genus Agapanthus LHéritier. J S Afr Bot. 1965;supplementary volume 4.         [ Links ]

 

 

PUBLISHED: 29 March 2022

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