Plants annual, biennial, or perennial herbs or subshrubs to shrubs, 1-120(-400) cm tall. Stems more or less erect, usually branched. Leaves alternate, usually cauline, sometimes in rosettes, petiolate or sessile; blade variously shaped, sometimes 1(-2) pinnately lobed, margins entire or toothed, surfaces, at least the lower, usually hairy and gland-dotted. Capitula usually radiate, sometimes ± disciform, usually in corymbose or paniculate synflorescences, sometimes in glomerules; involucres ± hemispheric, 3-8(-12) mm in diameter; phyllaries 10(-16), deciduous, usually free, usually in 2 distinct series; outer phyllaries 5(-8), herbaceous to scarious; inner phyllaries 5-8, ± scarious to membranous; florets without a pappus; corollas ochroleucous or white; ray florets, pistillate, 5(-8), fertile, tubes stout, glandular, lamina oblong to reniform or orbiculate; disk florets 12-60+, functionally staminate, funnelform. Achenes black, oblanceoloid to obovoid or pyriform, often obcompressed, shed with their subtending phyllary and 1-2 disk florets, sometimes with 1-3 pappuslike enations that grow from the top. x = 9.
There are about 17 species of Parthenium. They are native to warm temperate and tropical regions of the Americas but some have been introduced to similar regions elsewhere.
Modified from the account in Flora of North America for use in OpenHerbarium.
GBIF records include introduced and cultivated plants. Consequently, the distribution shown often differs from statements about a taxon's native distribution.