Syst. Nat. 2: 291. 1821.
Plants densely pubescent, trichomes appressed, stellate mixed with simple ones. Stems simple or few from base, (2–)3–8(–11) dm. Basal leaves (withered by flowering): blade oblanceolate, (2.5–)3.5–8(–10) cm, base cuneate or attenuate, apex obtuse. Cauline leaves: blade apex acute or obtuse. Fruiting pedicels appressed to rachis, (4–)5–9(–12) mm. Flowers: sepals 2–2.5 mm; petals narrowly obcordate, (4–)5–6.5(–8) mm (lobes oblong, (1–)1.5–3 × 0.5–1.5 mm); filaments white, median pair 2–3.3 mm, lateral pair 0.3–1 mm; anthers 0.5–1 mm. Fruits (4–)5–8.5(–10) × (2–)2.5–4 mm; valves obtuse at both ends, trichomes sometimes with unequal rays; style 1–4 mm, sparsely pubescent basally. Seeds slightly flattened, narrowly margined, 1–2.3 mm diam. 2n = 16.
Phenology: Flowering May–Sep.
Habitat: Flood plains, meadows, waste places, railroad embankments, woodlands, grasslands, roadsides, fields, stream banks, pastures, hillsides, forest floor
Elevation: 0-2800 m
Introduced; B.C., Man., N.B., Ont., Que., Sask., Ariz., Calif., Colo., Conn., D.C., Idaho, Ill., Ind., Iowa, Kans., Maine, Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Utah, Vt., Va., Wash., W.Va., Wis., Wyo., Europe, Asia.