Annuals (perhaps persisting), 15–70(–100+) cm. Leaves on proximal ¹/2–³/4+ of each stem; blades of undivided cauline leaves ± linear to filiform, margins entire or denticulate, midribs usually prickly-setose. Heads in race-miform to spiciform arrays. Involucres 6–9(–13+) mm. Phyl-laries usually erect in fruit. Florets 6–12(–20+); corollas yellow (sometimes abaxially bluish), usually deliquescent. Cypselae: bodies pale brown, ± flattened, elliptic to oblanceolate, 2.5–3.5 mm, beaks ± filiform, (2–)5–6 mm, faces 5–7-nerved; pappi white, 5–6 mm. 2n = 18.

Flowering Aug–Oct. Disturbed sites; 10–1500 m; introduced; Ont., Que.; Ala., Ariz., Ark., Calif., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Mo., Nebr., Nev., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Oreg., Pa., S.C., Tenn., Tex., Va., Wash., W.Va., Wis.; Europe; introduced also in Mexico.