Annual or perennial herbs, rarely shrubs. Stems erect. Leaves opposite or rarely whorled, compound, lobed, or simple leaves. Heads solitary, in corymbs or panicles, radiate or discoid. Outer florets ligulate, neuter or pistillate, usually yellow; central florets perfect or rarely functional staminate, (4-)5-lobed, yellow or brownish orange. Achenes linear-oblong to ellipsoid, 3- or 4-angled or compressed, sometimes winged. Pappus of up to four usually barbed awns and/or bristles, or absent.
About 240 species distributed worldwidely, especially North and South America; four species, one of which is represented by three varieties, in Taiwan.
Sherff, E. E. 1937. The Genus Bidens, parts I & II. Field. Mus. Nat. Hist., Bot. Ser. 16: 1-709.
