Perennial herbs, often arising from a thick rhizome. Leaves imparipinnate; stipules adnate to petiole. Inflorescence a dense terminal spike or cluster. Flowers bisexual (not in Victoria) or unisexual, monoecious, each flower subtended by 2 or 3 bracteoles. Hypanthium cup-shaped; epicalyx and petals absent; sepals 4; stamens 4–many, rarely 2; ovary superior, surrounded by hypanthium, carpels 1 or 2, rarely 3, 1 ovule per carpel. Fruit of 1 or 2 achenes enclosed in 4-angled, hardened, dry hypanthium, aggregated into a fruiting spike or head.
About 26 species, chiefly in the northern temperate regions; 2 species naturalised in Australia.