Korean mountain ash alder

Description

Alniaria alnifolia (Syns. Sorbus alnifolia and Aria alnifolia), also called alder-leafed whitebeam, Korean whitebeam, or Korean mountain ash, Chinese: pinyin: shui yu hua qiu; lit. 'water elm rowan', is a species of whitebeam native to eastern Asia in eastern and northern China, Taiwan, Korea and Japan. Alniaria alnifolia is a medium-sized deciduous tree growing to 10–20 m tall with a trunk up to 30 cm diameter and grey bark; the crown is columnar or conic in young trees, becoming rounded with age, with branches angled upwards, and slender shoots. The leaves are green above, and thinly hairy with white hairs beneath, 5–10 cm long and 3–6 cm broad, simple, usually unlobed (but see varieties, below), broadest near the base, with serrated margins and an acute apex. The autumn colour is orange-pink to red. The flowers are 10–18 mm diameter, with five white petals and 20 yellowish-white stamens; they are produced in corymbs 4–8 cm diameter in late spring. The fruit is a globose pome 8–15 mm diameter, bright red, with a dimple at the apex; they are mature in mid autumn. It has sometimes been placed in a separate genus of its own as Micromeles alnifolia, differing from other whitebeams in the deciduous sepals on the fruit (persistent in other whitebeams), but genetic evidence places it close to Sorbus aria. It is occasionally grown as an ornamental tree in northern Europe, primarily for its autumn colour. The cultivar 'Skyline' has been selected for its fastigiate growth. Sorbus is a genus of over 100 species of trees and shrubs in the rose family, Rosaceae. Species of Sorbus (s.l.) are commonly known as whitebeam, rowan (mountain-ash) and service tree. The exact number of species is disputed depending on the circumscription of the genus, and also due to the number of apomictic microspecies, which some treat as distinct species, but others group in a smaller number of variable species. Recent treatments classify Sorbus in a narrower sense to include only the pinnate leaved species of subgenus Sorbus, raising several of the other subgenera to generic rank. Sorbus is not closely related to the true ash trees which belong to the genus Fraxinus, although the leaves are superficially similar.