Plants sparsely to densely hispid, glabrous, or glabrate. Stems (3-)4-10(-12) dm, pubescent or, rarely, glabrate. Basal leaves: petiole (1.5-)3-10(-17) cm; blade broadly cordate to narrowly cordate-ovate, (1.5-) 3-12(-18) × (1-)2-8(-12) cm, base cordate, often pubescent. Cauline leaves similar to basal, petiole shorter (distal sessile); blade (proximal opposite, distal alternate), smaller distally. Fruiting pedicels (7-)10-15 mm, glabrous or pubescent. Flowers: sepals (5-)6-9 (-10) × 1-2 mm; petals (15-)17-25(-30) × 5-10 mm, claw 5-10 mm; filaments 5-8 mm; anthers oblong, 2-3 mm; gynophore relatively slender, 7-18 mm. Fruits 3-4.5(-5) × 2-3(-3.5) cm, strongly latiseptate; valves each rounded basally and apically; replum glabrous or sparsely ciliate; style 4-10 mm. Seeds grayish brown, (6-)7-10(-12) × 5-9 mm. 2n = 30. Flowering Apr-Jun. Roadsides, waste grounds, railroad embankments, thickets, woods, pasture margins; 0-1000 m; introduced; B.C., Man., N.S., Ont., Que.; Calif., Conn., Del., Idaho, Ind., Ky., Md., Mass., Mich., N.Y., Ohio, Oreg., Pa., R.I., Utah, Vt., Wash.; Europe; introduced also in South America (Argentina). Lunaria annua is cultivated for its attractive flowers but especially for the infructescences, which are used in dry bouquets after removal of the fruit valves and seeds.