Plants (50-)90-150 cm. Leaves: petiole 3.5-4.5(-8) cm, glandular-pubescent; leaflet blade oblanceolate to rhombic, 2.5-4.5 × 1.2-2.5 cm, margins serrulate-denticulate, apex acute, surfaces glabrate to glandular-pubescent. Racemes 5-20 cm (10-40 cm in fruit); bracts trifoliate, 10-25 mm. Pedicels purple, 8-15 mm, glabrous. Flowers: sepals green, lanceolate, 3.5-5 × 0.8-1.2 mm, glandular-pubescent; petals purple or white, oblong to ovate, 7-14 × 3-4 mm; stamens purple, 8-30 mm; anthers 1-2 mm; gynophore purple, 10-14 mm in fruit; ovary 6-10 mm; style 1-1.2 mm. Capsules 45-95 × 3-4 mm, glandular-pubescent. Seeds reddish brown to black, 1.4-1.6 × 1-1.2 mm, rugose to tuberculate. 2n = 34, 36.

Flowering late spring-late summer. Disturbed roadsides, vacant lots, waste areas, railroads; 0-200 m; introduced; Ala., Fla., Ga., La., Miss., N.Y., N.C., Okla., Pa., S.C., Tex.; Old World tropics; introduced also in Mexico, West Indies, Central America, South America.

The C₄ photosynthetic pathway has been reported from Gynandropsis gynandra (S. K. Imbamba and L. T. Tieszen 1977). This species is sometimes grown as an ornamental. B. S. Barton (1836, p. 317) provided a detailed and accurate illustration of the flower, obviously drawn from life; this indicates that the species was cultivated (perhaps escaped) in Pennsylvania at that time. In some tropical countries, it is cultivated as a potherb (K. Waithaka and Chweya 1991; J. A. Chweya and N. A. Mnzava 1997). It is also used medicinally. The fresh plant has a peculiar odor that is sometimes described as similar to burning Cannabis.