Japanese mountain ash

Description

Sorbus commixta, is a species of flowering plant in the family Rosaceae, native to Japan, Sakhalin (in the Russian Far East), and the Korean island of Ulleungdo. The specific epithet commixta means "mixed or mingled together". It is a small to medium-sized deciduous tree growing to 7–10 m (23–33 ft) tall, rarely 18 m (59 ft), with a rounded crown and brownish to silvery-grey bark. The leaves are 20–30 cm (8–12 in) long, and pinnate. The leaves consist of 11–17 leaflets, each 4–7 cm (2–3 in) long and 1–2.5 cm broad, with an acuminate apex and serrated margins; they change to a deep purple or red in autumn. The flowers are 6–10 mm in diameter, with five white petals and 20 yellowish-white stamens; they are produced in corymbs 9–15 cm (4–6 in) in diameter in late spring to early summer. The fruit is a bright orange to red pome 7–8 mm in diameter, maturing in autumn. Plants from Hokkaidō, the Kuril Islands and Sakhalin are sometimes distinguished as Sorbus commixta var. sachalinensis, with larger leaflets up to 9 cm long. Outside its native range, it is grown as an ornamental tree, hardy in zones 5-9. It grows best in moist, well-drained soil, in full sun. A number of cultivars have been selected, the most popular being 'Embley' (with fastigiate branching) and 'Serotina' (flowering later in early summer). 'Embley' has gained the Royal Horticultural Society's Award of Garden Merit. Sorbus is a genus of over 100 species of trees and shrubs in the rose family, Rosaceae. Species of Sorbus 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.