Rowan

Sorbus subgenus Sorbus
Sorbus aucuparia - European Rowan
Sorbus americana - American mountain ash
Sorbus cashmiriana - Kashmir Rowan
Sorbus commixta - Japanese Rowan
Sorbus decora - Showy mountain ash
Sorbus glabrescens - White-fruited Rowan
Sorbus hupehensis - Hubei Rowan
Sorbus matsumurana
Sorbus sargentiana - Sargent's Rowan
Sorbus scalaris - Ladder Rowan
Sorbus sitchensis - Sitka mountain ash
Sorbus vilmoriniana - Vilmorin's Rowan
Plus several other species
Sorbus subgenus Aria

The rowans are plants of the Family Rosaceae, in the Genus Sorbus, Subgenus Sorbus. They are native throughout the cool temperate regions of the northern hemisphere, with the highest species diversity in the mountains of western China and the Himalaya, where numerous apomictic microspecies occur.

Rowans are mostly small deciduous trees 10-20 m tall, though a few are shrubs. The leaves are arranged alternately, and are pinnate, with (8)-11-35 leaflets. The flowers are borne in dense corymbs; each flower is creamy white, and 5-10 mm across with five petals.

The fruit is a small pome 4-8 mm diameter, bright orange or red in most species, but pink, yellow or white in some Asian species. The fruit are soft and juicy, which makes them a very good food for birds, particularly waxwings and thrushes, which then distribute the rowan seeds in their droppings. Rowan is used as a food plant by the larvae of some Lepidoptera species - see list of Lepidoptera which feed on Sorbus.

The best known species is the 'Rowan Clark' Sorbus aucuparia, a small tree typically 4-12 m tall growing in a variety of habitats throughout northern Europe and in mountains in southern Europe and southwest Asia. Its berries are a favourite food for many birds and are a traditional wild-collected food in Britain and Scandinavia. It is one of the hardiest European trees, occurring to 71° north in Vardø in arctic Norway, and has also become widely naturalized in northern North America.

North American native rowans include the American mountain ash Sorbus americana and Showy mountain ash Sorbus decora in the east and Sitka mountain ash Sorbus sitchensis in the west.

The greatest diversity of form as well as the largest number of species is in Asia, with very distinctive species such as Sargent's Rowan Sorbus sargentiana with large leaves 20-35 cm long and 15-20 cm broad and very large corymbs with 200-500 flowers, and at the other extreme, Small-leaf Rowan Sorbus microphylla with leaves 8-12 cm long and 2.5-3 cm broad. While most are trees, the Dwarf Rowan Sorbus reducta is a low shrub to 50 cm tall. Several of the Asian species are widely cultivated as ornamental trees.

For other Sorbus species, see whitebeam (Sorbus subgenus Aria) and the genus article Sorbus.