This book contains an account of 52 native or naturalised Sorbus taxa in Britain and Ireland (44 species and 8 hybrids). 43 of the taxa are native, 35 of which are endemic to Britain and two to Ireland. The monograph is based on morphological and molecular taxonomic studies coupled with extensive field work, during which 22 new trees have been described. It is the result of over ten years collaborative work between the National Museum Wales, Royal Botanic Gardens Kew and the Universities of Bristol, Exeter and Oxford. The introduction covers the history of Sorbus research, reproductive biology and ecology, interpretation of the characters, keys to all taxa and 14 regional keys. The taxonomy, history, distribution, biology and ecology and each Sorbus taxon is described, with an assessment of its conservation status and notes to help with identification.