Plants annual or biennial (perennial), 30-90 cm, glabrous. Stems erect, usually branched. Leaves (cauline shorter distally); blade ovate to ovate-oblong, pinnatisect (lobes 4-15 pairs, lanceolate-oblong), 3-15 × 3-5 cm, (base attenuate), margins entire or repand to raggedly toothed, surfaces glabrous. Racemes (dense) 20-40 cm; bracts persistent, lanceolate-linear, 3-3.5 mm. Pedicels 2-8 mm. Flowers: sepals persistent, 5(-6), not reflexed in fruit, lanceolate-linear, 2-2.5 mm; petals 5(-6), white, (3.5-)4-6 mm, subrounded-clawed, adaxial ones 3-lobed; stamens 10-14; filaments persistent, 2-3.5 mm, glabrous; intrastaminal nectary-discs papillose; anthers 1-2 mm; placenta entire. Capsules erect, 4-carpelled, cylindric to ovoid-oblong, 8-14 × 4-6 mm, apically 4-toothed, glabrous or ribs papillose. Seeds 1-1.3 mm, dull, finely papillose. 2n = 40. Flowering May-Aug(-Nov). Muddy shores, dunes, waste places, railroad ballasts, roadsides, basic soils; 0-800 m; introduced; B.C., Man., Ont., Que., Sask.; Ark., Calif., Conn., Del., Ill., Kans., Maine, Mass., Mich., N.H., N.J., N.Y., Ohio, Oreg., Pa., Vt., Wash.; s Europe; sw Asia; n Africa; introduced also in South America, s Africa, Australia.