Annuals; puberulent. Stems simple from base, erect, (paniculately) branched beyond base or distally, 2-6 dm. Basal leaves (soon withered, often before anthesis); not rosulate; blade dentate to pinnatifid. Cauline leaves shortly petiolate to subsessile; blade narrowly oblanceolate to linear, 1-3.3 cm × 1-4 mm, base attenuate, not auriculate, margins entire. Racemes (often paniculate), considerably elongated in fruit; rachis glabrous or puberulent, trichomes straight, cylindrical. Fruiting pedicels divaricate-ascending to horizontal, straight, (terete), 2-3.5 × 0.1-0.15 mm, puberulent adaxially. Flowers: sepals oblong, 0.7-0.8 × 0.3-0.4 mm; petals (rudimentary), white, linear, 0.4-0.6 × 0.05-0.1 mm, claw absent; stamens 4, median and lateral; filaments 0.6-0.8 mm; anthers ca. 0.2 mm. Fruits orbicular to broadly elliptic, 1.8-2 × 1.7-1.8 mm, apically not winged, apical notch 0.05-0.1 mm deep; valves thin, smooth, not veined, sparsely pilose; style ca. 0.1 mm, equaling apical notch. Seeds oblong, 1-1.2 × 0.7-0.8 mm.

Flowering May-Jun. Waste places, disturbed sites; 0-600 m; introduced, Calif.; e Europe; w Asia.

Lepidium pinnatifidum apparently has not become a serious weed of the Californian flora.