Sorbus

Sorbus is a genus of trees and shrubs in the subfamily Maloideae of the family Rosaceae.

The genus is divided into two main and three or four small subgenera:

• Sorbus subgenus Sorbus, the rowans, with compound leaves usually hairless or thinly hairy below; fruit carpels not fused; type species Sorbus aucuparia (European rowan). Distribution: cool-temperate Northern Hemisphere.

• Sorbus subgenus Aria, the whitebeams, with simple leaves usually strongly white-hairy below (hence the name, from German Weissbaum, 'white tree'); fruit carpels not fused; type species Sorbus aria (Common whitebeam). Distribution: temperate Europe & Asia.

*Sorbus subgenus Micromeles, an indistinct group of a few east Asian species (e.g. Sorbus alnifolia, Korean whitebeam) with narrow leaves; doubtfully distinct from and often included in subgenus Aria. Distribution: temperate northeast Asia.

• Sorbus subgenus Cormus, with compound leaves similar to subgenus Sorbus, but with distinct fused carpels in the fruit; just one species, Sorbus domestica (Service tree). Distribution: warm-temperate Europe.

• Sorbus subgenus Torminaria, with rather maple-like lobed leaves with pointed lobes; fruit carpels not fused; just one species, Sorbus torminalis (Wild service tree). Distribution: temperate Europe.

• Sorbus subgenus Chamaemespilus, a single shrubby species Sorbus chamaemespilus with simple, glabrous leaves and pink flowers with erect sepals and petals. Distribution: mountains of southern Europe.

• Hybrids are common in the genus, including many between the subgenera; very often these hybrids are apomictic (self-fertile without pollination), so able to reproduce clonally from seed without any variation. This has led to a very large number of microspecies, particularly in western Europe (including Britain) and parts of China.

All species in the genus are also occasionally known by the confusing name mountain ash.

Referenced By