Sp. Pl. 2: 794. 1753.
Annuals or biennials, 10–140(–200) cm. Stem bases soft to hard, herbaceous, often hollow. Leaves: blades of mid cauline spatulate or oblong to obovate or lanceolate, 6–35 × 1–15 cm, bases auriculate, auricles deltate to lanceolate, ± straight, acute, margins usually pinnately (often runcinately) lobed, lobes ± deltate to lanceolate, not constricted at bases, terminals usually larger than laterals, entire or dentate. Peduncles usually glabrous, sometimes stipitate-glandular. Involucres 9–13+ mm. Phyllaries usually glabrous, sometimes tomentose and/or stipitate-glandular. Corollas: ligules ± equaling tubes. Cypselae dark brown, mostly oblanceoloid, 2.5–3.5+ mm, ribs 2–4 on each face, faces transversely rugulose or tuberculate across and between ribs; pappi 5–8 mm. 2n = 32, 36.
Phenology: Flowering (Apr–)Jul–Oct (year-round in south).
Habitat: Disturbed sites, gardens, roadsides, along streams
Elevation: 0–2000 m
Introduced; Greenland, St. Pierre and Miquelon, Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., 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.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo., Europe, introduced also in Mexico, West Indies, Bahamas, Central America, South America, Africa, Asia, Pacific Islands (New Zealand), Australia.