Sp. Pl. 2: 987. 1753.
Plants 10–80 (–200) cm; nodal spines 0. Leaves: petioles 20–100 (–140+) mm; blades suborbiculate to ± pentagonal or deltate, 4–12 (–18+) × 3–10 (–18+) cm, sometimes palmately 3–5-lobed, abaxial faces green, hirtellous. Burs 10–30+ mm. 2n = 36.
Phenology: Flowering Jul–Oct.
Habitat: Damp or seasonally wet, often alkaline, soils, waste places, margins of agriculture
Elevation: 10–2000 m
Alta., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask., Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo., Mexico, Central America, South America, widely in Old World
Recognition of a dozen or more taxa (treated as species, subspecies, varieties, and/or forms) has been proposed for plants treated together here as Xanthium strumarium. Bases for the various taxa mostly involved subtle differences in the burs.