It is a medium-sized
deciduous tree growing to 20–30 m tall with a trunk up to 1.5 m diameter. The
bark is smooth and pale grey on young trees, becoming square-cracked and knobbly on old trees. The
buds are pale brown, which readily distinguishes it from the related
Fraxinus excelsior (black buds) even in winter. The
leaves are in opposite pairs or whorls of three, pinnate, 15–25 cm long, with 3–13 leaflets; the leaflets being distinctively slender, 3–8 cm long and 1–1.5 cm broad. The
flowers are produced in
inflorescences which can be male, hermaphrodite or mixed male and hermaphrodite. The male and hermaphrodite flowers occur on all individuals, i.e. all trees are functionally hermaphrodite. Flowering occurs in early spring. The
fruit when fully formed is a
samara 3–4 cm long, the seed 1.5–2 cm long with a pale brown wing 1.5–2 cm long. ==Variation==