Erect or scandent shrubs or vines; monoecious. Leaves opposite, deciduous or persistent, petiolate, margins entire, toothed or lobed. Inflorescences paniculate, corymbose or pyramidal, with sterile flowers present or with only fertile flowers. Fertile flowers bisexual; sepals 4 or 5, valvate, inconspicuous, enlarged in sterile flowers, united at base, adnate to ovary and forming hypanthium; petals 4 or 5, reflexed, free or united, valvate, deciduous during anthesis, usually ovate, rarely spathulate, white, pink, blue or yellow; stamens 8 or 10, rarely up to 20, free, filaments as long or longer than petals; styles free or united at base; stigma capitate or decurrent along style; ovary 2–4(–5)-celled, ovules numerous, pendent, erect or horizontal. Sterile flowers with 3–5 enlarged petaloid sepals, few in number, arranged on the periphery of inflorescence. Fruit a capsule with apical interstylar dehiscence, hemispherical or turbinate; seeds ellipsoidal, fusiform, obovoid or urceolate, winged or unwinged.
c. 29 species from eastern Asia and south-east North America, Central America and western South America; 1 species naturalised in Australia.