Annuals. Trichomes of leaves primarily 3- or 4-rayed, some-times mixed with 5-rayed ones, 2-rayed trichomes primarily on stem and pedicels. Stems erect, often branched distally, (ribbed), (0.7-)1.5-10(-15) dm. Basal leaves (withered by fruiting), similar to cauline. Cauline leaves: (median and distal) shortly petiolate or sessile; blade (lanceolate, linear, or elliptic-oblong, (1-)2-7(-11) cm × (2-)5-12 (-23) mm, base cuneate) margins usually subentire or denticulate, rarely sinuate-dentate, (apex acute or obtuse). Racemes considerably elongated in fruit. Fruiting pedicels divaricate or ascending, slender, much narrower than fruit, 5-13(-16) mm. Flowers: sepals oblong, 1.8-3.2 mm, lateral pair not saccate basally; petals yellow, narrowly spatulate, 3-5.5 × 1.5-2 mm, claw 1.5-3.5 mm, apex rounded; median filaments 2-3.5 mm; anthers oblong, 0.5-0.7 mm. Fruits suberect or divaricate-ascending, linear, straight, somewhat torulose, (1-)1.5-2.5(-4) cm × 1-1.3 mm, 4-angled, not striped; valves with prominent midvein, pubescent outside, trichomes 3-5-rayed, densely pubescent inside; ovules (20-)30-55 per ovary; style cylindrical, slender, 0.5-1.5 mm; stigma entire or slightly 2-lobed, lobes as long as wide. Seeds oblong, 1-1.5 × 0.4-0.6 mm; not winged. 2n = 16. Flowering Jun-Aug. Dry stream beds, moist areas, waste ground, fields, pastures, disturbed ground; 0-3000 m; introduced; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ark., Calif., Colo., Conn., D.C., Fla., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia; n Africa.