Sorbus porrigentiformis, GREY-LEAVED WHITEBEAM, is described and illustrated. It is a neoendemic with obovate leaves and fruits wider than long, and it is widespread in south-west England and South Wales. It was originally broadly circumscribed, but it has now been split into at least 11 constituent parts. It is a cornerstone species for Sorbus speciation in Britain. It may have originated from S. aria × S. rupicola or from an ancestral taxon in Central Europe.Sorbus porrigentiformis E.F.Warb., GREY-LEAVED WHITEBEAM (Plate 1044), in its broad sense is the most problematic group of Sorbus L. in Britain (see, e.g., , and it is still being resolved into its constituent parts. English plants with obovate leaves and fruits wider than long were first separated from S. aria (L.) Crantz, COMMON WHITEBEAM, and S. rupicola (Syme) Hedl., ROCK WHITEBEAM, by Hedlund (1914) who included them in his new species S. porrigens Hedl., widely distributed across Europe and Asia Minor. Willmott (1939) typified S. porrigens with a Turkish specimen, and it is no longer accepted as a European taxon (Kurtto et al., 2018). Warburg (1952Warburg ( , 1957 noted that there were distinct morphological differences between the plants in Britain and those in Asia Minor; he separated the British material as S. porrigentiformis, including both triploids and tetraploids, noting that additional subdivisions might be necessary following further studies.After a series of such studies (

Sorbus subcuneata, SOMERSET WHITEBEAM, is described and illustrated. This narrow endemic species from coastal Devon and Somerset is endangered. Details of its discovery, historical taxonomic treatment and reproductive biology are provided.

Sorbus aucuparia subsp. aucuparia, ROWAN or MOUNTAIN ASH, is described and illustrated. Details of its distribution, genetic variability, cultural history and use by humans and animals are provided.

Sorbus eminens, ROUND-LEAVED WHITEBEAM is a tetraploid member of Sorbus subgenus Aria. The complex taxonomic history is summarised. This species is characterised by the large, unlobed, roundish leaves (sometimes likened in shape to a tennis ball) with rounded bases and few veins and usually acuminate, outwardly directed teeth, and large red fruits which are wider than long.

SummarySorbus avonensis, AVON WHITEBEAM, is described and illustrated. It was originally treated as a triploid hybrid to cover plants of S. aria (diploid) × S. porrigentiformis (tetraploid) parentage, but after the discovery of more identical trees in 2014–2016, it is now treated as a species. It is endemic to the Avon Gorge, England where a population of c. 47 trees is known.