Sorbus is a genus of over 100 species of trees and shrubs in the rose family, Rosaceae. Species of Sorbus ( s.str.) are commonly known as rowan or Sorbus aucuparia. The genus used to include species commonly known as whitebeam, Torminalis and Cormus domestica that are now classified in other genera (see below). The genus Sorbus, as currently circumscribed, includes only the pinnate leaved species of former subgenus Sorbus.
Sorbus is not closely related to the true ash trees which belong to the genus Fraxinus, although the leaves are superficially similar.
Genus
As treated in its broad sense, the genus was traditionally divided into several subgenera, but this treatment was found to be
Paraphyly, 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 name
Sorbus retained only for the rowans. Additionally, it was recognised that despite a comparably large genetic distance between them, the genera
Sorbus (sensu stricto),
Aria, Chamaemespilus and
Torminalis have interbred extensively, in various combinations, which lead to the recognition of an additional five intergeneric hybrid genera.
[Rushforth, Keith (2018). The Whitebeam problem, and a solution. Phytologia 100(4): 222-247. 21 December 2018.]
- Sorbus ( Sorbus)
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now genus rowan 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; the type is Sorbus aucuparia (European rowan). Distribution: cool-temperate Northern Hemisphere.
- Sorbus ( Aria)
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now genus Aria and its intergeneric hybrids (see below), the whitebeams, with simple leaves usually strongly white-hairy below (hence the name, from German Weissbaum, 'white tree'); fruit carpels not fused; the type is Aria edulis (common whitebeam). Distribution: Europe, Maghreb and western Asia.
- Sorbus ( Micromeles)
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now genus Micromeles, a group of east Asian species with narrow leaves; sometimes previously included in subgenus Aria. Distribution: temperate and tropical east Asia.
- Sorbus ( Cormus)
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now genus Cormus, with compound leaves similar to subgenus Sorbus, 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, see Apfelwein.
- Sorbus ( Torminaria)
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now genus Torminalis, with rather maple-like lobed leaves with pointed 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 the Caucasus and Mount Lebanon ranges.
- Sorbus ( Chamaemespilus)
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now genus Chamaemespilus, 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.
Intergeneric hybrid genera
Uses
Ornamental trees
Sorbus species are cultivated as ornamental trees for parks and gardens and as avenue trees, and have given rise to several
cultivars. The following, of mixed or uncertain parentage, have gained the Royal Horticultural Society's Award of Garden Merit:
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'Eastern Promise'
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'Leonard Messel' named for Leonard Messel of Nymans in Sussex.
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'Wisley Gold'
Gallery
File:Punetav pihlapuu.jpg|Red rowan
File:Rowan in the garden of Eastern Siberia.jpg|Rowan in the garden of Eastern Siberia
Lijsterbes (Sorbus). 31-03-2024 (d.j.b.) 02.jpg|New leaf from one Sorbus opens up.
Further reading
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Price, D.T. 2007. One-way introgressive hybridisation between Sorbus aria and S. torminalis (Rosaceae) in southern Britain. Watsonia. 26: 419–431.
