As treated in its broad sense, the genus was traditionally divided into several subgenera, however, this treatment was found to beparaphyletic, comprising two disparate lineages within the Malinae subtribe. Consequently, each of the former subgenera have since been elevated into genera in their own right, with the genus nameSorbus retained only for the rowans. Additionally, it was recognised that despite a comparably large genetic distance between them, the generaSorbus (sensu stricto),Aria, Chamaemespilus andTorminalis have interbred extensively, in various combinations, which lead to the recognition of an additional fiveintergeneric hybrid genera.[2]
Sorbus (Sorbus)
now genusSorbus s.s., are commonly known as the rowan (primarily in the UK) or mountain-ash (in Ireland, North America and the UK), with compound leaves usually hairless or thinly hairy below; fruit carpels not fused; thetype isSorbus aucuparia (European rowan). Distribution: cool-temperateNorthern Hemisphere.
Sorbus (Aria)
now genusAria and its intergeneric hybrids (see below), the whitebeams, with simple leaves usually strongly white-hairy below (hence the name, from GermanWeissbaum, 'white tree'); fruit carpels not fused; the type isAria edulis (common whitebeam). Distribution: Europe,Maghreb and western Asia.
Sorbus (Micromeles)
now genusMicromeles, a group of east Asian species with narrow leaves; sometimes previously included in subgenusAria. Distribution: temperate and tropical east Asia.
Sorbus (Cormus)
now genusCormus, with compound leaves similar to subgenusSorbus, but with distinct fused carpels in the fruit; just one species,Cormus domestica (true service tree). Distribution: North Africa, warm-temperate Europe, western Asia. Used to flavour some apple wines, seeApfelwein.
Sorbus (Torminaria)
now genusTorminalis, with rather maple-like lobed leaves withpointed lobes; fruit carpels not fused; just one species (wild service tree). Distribution: warm-temperate Europe, south to the mountains of North Africa and east to theCaucasus andLebanon ranges.
Sorbus (Chamaemespilus)
now genusChamaemespilus, monotypic, with a single shrubby species, false medlar. Has simple, glabrous leaves and pink flowers with erect sepals and petals. Distribution: mountains of southern Europe.
Sorbus species are cultivated as ornamental trees for parks and gardens and as avenue trees, and have given rise to severalcultivars. The following, of mixed or uncertain parentage, have gained theRoyal Horticultural Society'sAward of Garden Merit:[3]
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