Trees, often suckering, deciduous, rarely half-evergreen. Bark deeply furrowed. Leaves alternate, usually oblique at base; margins serrate or crenate, usually with small secondary teeth forming on primary teeth; venation pinnate; stipules free, deciduous. Inflorescence racemose or clustered, 3–15-flowered, produced before the leaves on lateral shoots. Flowers bisexual, rarely unisexual; perianth 4–8-lobed, c. 3 mm long; stamens equal in number to and opposite perianth lobes, usually exserted; ovary compressed, sometimes stipitate. Fruit a single seeded samara or a dry flattened winged nutlet. Seeds ovate; embryo straight; endosperm absent.
About 30 species in the Northern Hemisphere, 5 naturalised in Australia.