Thlaspi bursa-pastoris Linnaeus, Sp. Pl. 2: 647. 1753

Plants mostly sparsely to densely pubescent, trichomes sessile, 3-5-rayed, stellate (base of plant often mixed with much longer, simple ones). Stems (0.2-)1-5 (-7) dm. Basal leaves: petiole 0.5-4(-6) cm; blade oblong or oblanceolate, (0.5-)1.5-10(-15) cm × 2-25(-50) mm, base cuneate or attenuate, apex acute or acuminate. Cauline leaves: blade narrowly oblong, lanceolate, or linear, 1-5.5(-8) cm × 1-15(-20) mm, base sagittate, amplexicaul, or, rarely, auriculate. Fruiting pedicels usually straight, (0.3-)0.5-1.5(-2) cm, glabrous. Flowers: sepals green or reddish, 1.5-2 × 0.7-1 mm (margins membranous); petals (1.5-)2-4(-5) × 1-1.5 mm; filaments 1-2 mm; anthers to 0.5 mm. Fruits (0.3-)0.4-0.9(-1) cm × (2-)3-7(-9) mm, base cuneate, apex emarginate or truncate; valves each with subparallel lateral veins; style 0.2-0.7 mm. Seeds brown, 0.9-1.1 × 0.4-0.6 mm. 2n = 32.

Flowering and fruiting Jan-Oct. Roadsides, gardens, fields, barren gravel, pastures, plantations, lawns, orchards, cultivated ground, waste areas, vineyards, mountain slopes; 0-2800 m; introduced; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., 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; n Africa; introduced also in Mexico, West Indies, Central America, South America, Atlantic Islands, Pacific Islands, Australia.

According to M. Coquillat (1951), Capsella bursa-pastoris is the second most common weed on earth, after Polygonum aviculare.