Plants annual or perennial herbs, prostrate or erect to floating or scrambling. Leaves opposite, entire. Inflorescences sessile or pedunculate, bracteate, heads or short spikes, axillary, solitary or clustered.Flowers bisexual, solitary in the axil of a bract, bibracteolate, bracts persistent but the perianths falling with the fruits; bracteoles persistent or not; tepals 5, free, equal or unequal, glabrous or furnished with smooth or denticulate hairs; stamens 2-5, some occasionally without anthers; filaments distinctly united at the base into a cup or tube, usually alternating with large and dentate or laciniate to very small pseudostaminodes, these rarely absent; ovaries with a single pendulous ovule; styles short; stigmas capitate. Fruits indehiscent utricles, thin-walled or sometimes corky; seeds ± lenticular.
Alternanthera has about 150 species, most of which are native to the tropics and subtropics of the New World but several species have sprea to become pantropical weeds.
Modified from the published treatment for greater consistency with other descriptions in OpenHerbarium.
Key to the species of Somaliland and Somalia; Pakistan.