Can be herbaceous, shrub or tree. Usually annual, some perennial. Flowers various, petals sometimes partly united, but only at base. Monocotyledon, stems are triangular unlike grasses, no ligules present, usually found in moist environments. Members of this family are among the world's worst weeds, especially problematic in rice.
Vegetative parts are red, especially undersides of leaves and often reddish streaks along stem.
Cotyledons are linear in shape. Flowers are inconspicuous and in clusters or spikes, often in the leaf axils, subtended by green bractlets. Seeds are black with a distinctive metallic sheen. The thistles are in this family. Often seedlings will be a rosette.