Tridax

Perennials [annuals], 10-40[-80+] cm. Stems procumbent to ascending. Leaves basal and/or cauline; opposite; petiolate [sessile]; blades deltate, lanceolate, lance-ovate, or ovate, often pinnately or palmately lobed, ultimate margins coarsely toothed to subentire, faces glabrate, hirsute, scabrellous, or strigillose. Heads radiate [discoid], borne singly [in ± cymiform arrays]. Involucres cylindric to hemispheric, 4-8 mm diam. Phyllaries persistent, 11-15+ in 2-3+ series (outer usually shorter, more herbaceous, the inner often scarious). Receptacles convex to conic, paleate (paleae ± persistent, lance-linear, scarious, weakly conduplicate, often apically toothed). Ray florets [0-]3-8[-13], pistillate, fertile; corollas pale yellow [white or purplish]. Disc florets [20-]40-80+, bisexual, fertile; corollas yellowish [whitish or purplish], tubes shorter than cylindric or funnelform throats, lobes 5, usually deltate [sometimes rays 0 and corollas of peripheral florets ± bilabiate]. Cypselae obconic to obpyramidal, 3-, 4-, or 5-angled, densely piloso-sericeous [glabrous, villous]; pappi [sometimes wanting in rays] persistent, of [10-]20[-40], plumose [ciliate], setiform scales. x = 10.