Lepidium didymum Linnaeus, Syst. Nat., ed. 12, 2: 433. 1767; Senebiera didyma (Linnaeus) Persoon; S. pinnatifida de Candolle.

Herbs annual or rarely biennial, fetid, 10-45(-70) cm tall, glabrous or pilose with straight trichomes to 1 mm. Stems procumbent or erect, usually several from base, branched above. Basal leaves not rosulate, pinnatisect or bipinnatisect, 4-10 cm; lateral lobes 2-7(-10) on each side of rachis, variable in size, entire, dentate, or incised, acute. Middle cauline leaves similar to basal ones, 1.5-3.5(-4.5) × 0.5-1.2 cm, progressively smaller and less divided upward, shortly petiolate to subsessile; lobes lanceolate to oblong or elliptic, entire to serrate or incised. Racemes terminal or lateral and leaf opposed. Fruiting pedicels slender, ascending to divaricate or slightly reflexed, straight or recurved, 1.5-2.5(-4) mm, glabrous or pubescent. Sepals ovate, 0.5-0.7(-0.9) mm, ascending to spreading, glabrous or pubescent. Petals white, elliptic to linear, 0.4-0.5 mm. Stamens 2 or rarely 4, median; filaments white, dilated at base, 0.3-0.6 mm; anthers ovoid, 0.1-0.2 mm. Fruit 1.3-1.7 × 2-2.5 mm, didymous, compressed, emarginate at apex and base; valves subreniform, semicircular, or suboblong, prominently reticulate or rugose, rounded on back; style absent, sometimes obsolete, included in apical notch. Seeds oblong, curved, finely reticulate, 1-1.2 × 0.7-0.8 mm. Fl. Mar-Jun. 2n = 32.

Presently treated by Ihsan Al-Shehbaz as Lepidium didymum Linnaeus.

Roadsides, waste areas, fields; near sea level to 1000 m. Anhui, Fujian, Guangdong, Hubei, Jiangsu, Jiangxi, Shandong, Sichuan, Taiwan, Xinjiang, Yunnan, Zhejiang [native to South America; naturalized elsewhere].