Plants (sometimes glaucous), glabrous throughout. Stems (0.9-)1.5-5.5(-8) dm. Basal leaves not rosulate; petiole 0.5-3 cm; blade oblanceolate, spatulate, or obovate, 1-5 cm × 4-23 mm, base attenuate or cuneate, margins entire, repand, or coarsely dentate, apex rounded. Cauline leaves: blade oblong, (0.5-)1.5-4 (-8) cm × (2-)5-15(-25) mm, apex rounded, obtuse, or subacute. Fruiting pedicels straight or slightly upcurved, (5-)9-13(-15) mm. Flowers: sepals (1.5-) 2-3(-3.3) × 1-1.5 mm; petals (2.4-)3-4.5(-5) × (0.8-) 1.1-1.7 mm, narrowed to clawlike base (ca. 1 mm), apex obtuse or emarginate; filaments (1-)1.5-2.2 mm; anthers 0.3-0.5 mm. Fruits obovate or suborbicular, (0.6-)0.9-2 cm × (5-)7-20 mm, base obtuse or rounded, apex deeply emarginate, notch ca. 5 mm deep; wings broad throughout, 1-1.5 mm wide basally, 3.5-5 mm wide apically; ovules 6-16 per ovary; style 0.1-0.3 mm. Seeds (1.2-)1.6-2(-2.3) × 1.1-1.3 mm, concentrically striate. 2n = 14. Flowering Mar-Aug. Roadsides, fields, waste places, lawns, gardens, railroad tracks, stream banks, bluffs, thickets, slopes, floodplains, woods; 0-2000 m; introduced; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia. Thlaspi arvense is a cosmopolitan weed of Eurasian origin. Cattle feeding on it develop tainted milk.

Plant: Annual; caudex 0; stem 1-5 dm; branches 0-many Leaves: simple; basal few, 2-6 cm, short-petioled, oblanceolate, shed early; upper cauline sessile, wavy-margined to dentate, base lobed, clasping stem INFLORESCENCE: raceme Flowers: bisexual; sepals 4, free, 1.5-2 mm, green or purple-tinged; petals 3-4 mm, 1-2 X sepals, white; 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: capsules with 2 deciduous valves, 1-1.5 cm wide, widely oblong to round, winged; tip notch 1.5-2.5 mm; pedicel spreading to upcurved, 7-15 mm, slender; Seed 2-8 per chamber, ± 2 mm, striate; wing 0; embryonic root at edges of both cotyledons Misc: Disturbed areas, fields, roadsides; < 500 m.; May-Aug