Annuals. Trichomes of leaves 2-rayed, mixed with fewer 3-rayed ones. Stems erect, unbranched or branched basally, (0.4-)1.5-4.5(-7) dm. Basal leaves (often withered by fruiting), similar to cauline. Cauline leaves: (proximal and median) petiolate and (distal) sessile, (petiole (0.3-) 0.5-2(-3) cm); blade [linear, narrowly oblanceolate, elliptic, or oblong, (1-)2-8(-11) cm × (2-)5-12(-17) mm, base attenuate], margins sinuate or coarsely dentate to denticulate or repand, (distal) entire or denticulate, (apex acute). Racemes considerably elongated in fruit. Fruiting pedicels divaricate, stout, as wide as fruit, 2-4(-6) mm. Flowers: sepals linear-oblong, 4-6 mm, lateral pair not saccate basally; petals yellow, narrowly oblanceolate to spatulate, 6-8 × 1.5-2 mm, claw 3-6 mm, apex rounded; median filaments 4-6 mm; anthers narrowly oblong, 0.8-1.3 mm. Fruits widely spreading to divaricate-ascending, narrowly linear, straight or curved upward, somewhat torulose, (2-)3-8(-10) cm × 1.5-2 mm, 4-angled, not striped; valves with prominent midvein, pubescent outside, trichomes 2-rayed and, fewer, 3-rayed, often glabrous, sometimes pubescent inside; ovules (40-)50-80(-90) per ovary; style cylindrical or subclavate, stout, 1-4 mm, sparsely pubescent; stigma slightly 2-lobed, lobes as long as wide. Seeds oblong, 1.1-1.5 × 0.6-0.7 mm; not winged or, rarely, winged distally. 2n = 16. Flowering Apr-Jun. Disturbed sites, roadsides, fields, waste places, barren hillsides, brush communities, pastures; 0-2100 m; introduced; B.C., Ont., Que.; Ala., Ariz., Ark., Calif., Colo., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Mich., Miss., Mo., Mont., Nebr., Nev., N.J., N.Mex., N.Y., N.C., Okla., Oreg., Pa., Tenn., Tex., Utah, Va., Wash., W.Va., Wyo.; Eurasia; n Africa; introduced also in South America, Australia.

Plant: Annual; stems 1-few, 5-50 cm Leaves: linear to narrowly oblanceolate; most hairs 2-branched; basal 5-15 cm, generally deeply toothed Flowers: bisexual; sepals 4, free; petals 5-10 mm, light yellow; stamens generally (2,4)6, generally 4 long, 2 short; ovary 1, superior, chambers generally 2, septum membranous, connecting 2 parietal placentas, style 1, stigma 2-lobed Fruit: capsule with 2 deciduous valves, stiffly spreading, 4-10 cm, 1-1.5 mm wide, ± round, narrowed between seeds; pedicel 2-7 mm, ± = fruit width; style 1-5 mm; Seed 1.2-1.7 mm, 0.5-0.8 mm wide; wing 0; 1-2 rows per chamber Misc: Fields, disturbed areas; 0-2000 m.