Trees or shrubs, with brown or black buds. Leaves deciduous, opposite or in whorls of three, imparipinnate. Flowers small, in dense panicles (often decussate) or in fascicles, unisexual or bisexual. Calyx 4-fid or lacking. Corolla 4-lobed or lacking. Stamens 2, usually purple. Ovary 2-locular, with 2 anatropous ovules in each locule. Stigma more or less 2-lobed. Fruit a samara.