Perennials, 30-60(-100+) cm. Leaf blades ovate to lanceolate, 30-350+ × 20-120+ mm, margins usually crenate to serrate, sometimes coarsely toothed or somewhat lobed (then mostly toward bases), faces hispid to hirtellous or ± scabrous, gland-dotted. Heads radiate, borne in corymbiform to paniculiform arrays. Peduncles 1-8(-12+) mm. Phyllaries: outer 5(-6) lanceolate to broadly ovate, 3-5 mm, inner 5(-6) ± orbiculate, 4-6 mm. Pistillate florets 5(-6); corolla laminae ovate to oblong or orbiculate, 1-2+ mm. Disc florets 15-35+. Cypselae ± obovoid, 3-4+ mm; pappus-like enations 0 or 2(-4), erect to spreading, ± subulate or threadlike, fragile, 0.3-0.6+ mm. 2n = 72. Flowering May-Sep. Glades and barrens, prairies, disturbed sites; 10-500 m; Ala., Ark., Conn., Ga., Ill., Ind., Iowa., Kans., Ky., La., Mass., Mich., Minn., Miss., Mo., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis. As evidenced by the synonymy, Parthenium integrifolium as here circumscribed has been variously partitioned by other taxonomists. For the present, I see no justification for segregating species from, or for formal recognition of infraspecific taxa within P. integrifolium.