Annuals. Stems unbranched or branched distally, (0.8-)2-8 (-10) dm, densely to moderately hirsute basally, trichomes simple, to 2.5 mm, often mixed branched ones, (glabrescent distally). Basal leaves withered by anthesis. Cauline leaves: blade lanceolate, narrowly oblong, or linear-lanceolate, (0.8-)1.5-5.5(-7) cm × 1-10(-20) mm, base sagittate or minutely auriculate, margins entire or, rarely, remotely denticulate, (often subciliate), apex acute, surfaces pubescent, trichomes primarily simple. Fruiting pedicels ascending, 4-14(-17) mm. Flowers: sepals 2-3.5 × 0.5-1 mm; petals pale yellow, (2.5-) 3-4(-6) × 1-2 mm; filaments 1.5-3 mm; anthers ca. 0.5 mm. Fruits pyriform to narrowly so, 3.5-5(-7) × 2-4(-5) mm, apex acute; valves each often with obscure midvein, margin narrowly winged; style 1-3.5 mm. Seeds reddish brown or brown, 0.8-1.4(-1.5) × 0.5-0.6 mm. 2n = 40. Flowering May-Jul. Farms, fields, meadows, prairies, roadsides, forest margins, open woods; 0-2500 m; introduced; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Ala., Ariz., Calif., Colo., Conn., Del., D.C., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia; n Africa; introduced also in South America.

Plant: Annual 3-10 dm; stem simple to ± branched above; hairs simple, spreading, below also forked, stellate Leaves: generally cauline, sessile, oblong to lanceolate, ± entire; tip acute to acuminate; lower leaf hairs as on stems INFLORESCENCE: raceme, elongate Flowers: bisexual; sepals 4, free; petals (0)4, free, petals 4-5 mm, pale 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 simple or 2-lobed Fruit: capsule, 5-8 mm, obovate; pedicel spreading to ascending, 1-1.5 cm, slender; style 2-2.5 mm, beak-like; Seed 2 rows per chamber, ± longer than wide, plump Misc: Grainfields, roadsides, hillsides; < 1000 m.