Annuals; glabrous. Stems few to several from base, prostrate or decumbent, branched, (0.2-)0.4-3(-4.6) dm. Basal leaves rosulate; petiole (0.3-)0.6-2.5(-3.2) cm; blade spatulate to oblanceolate or linear, pinnatifid or lobed (lobes 3-9 pairs, ovate to oblong), (0.7-)1.3-5.2(-6) cm × 3-8 mm, margins (of lobes) entire. Cauline leaves: petioles 0.1-0.5 cm; blade obovate to spatulate or oblanceolate, (0.6-) 1-1.8(-2.3) cm × 2-8(-14) mm, base attenuate-cuneate, not auriculate, margins dentate-sinuate to crenate or entire. Racemes (corymbose to subcapitate), slightly elongated in fruit; rachis glabrous. Fruiting pedicels divaricate to horizontal, straight or slightly sigmoid, (terete), (2.7-)3-4.4(-5) × 0.2-0.3 mm, glabrous. Flowers: sepals obovate-oblong, 1-2 × 0.6-1 mm; petals yellow (rarely creamy white at early anthesis), spatulate, (1.8-)2-2.8(-3) × 0.6-1 mm, claw 0.5-1 mm; stamens 6; filaments (median pairs) 1.2-2 mm, (glabrous); anthers 0.4-0.5 mm. Fruits usually narrowly to broadly ovate, rarely suborbicular, (2.2-)2.5-3.8(-4.2) × (1.6-)2.2 3.2(-3.5) mm, apically divergently winged, apical notch 0.2-0.6 mm deep; valves thin, smooth, moderately reticulate-veined, usually glabrous, rarely pubescent; style 0.7-1.6 mm, exserted beyond apical notch. Seeds ovate, 1-1.6 × 0.6-0.9 mm. 2n = 32.

Flowering Mar-Jun. Sagebrush communities, open mesas, sandy flats and deserts, alluvial fans, dry valley floors, floodplains, washes, alkaline flats, roadsides, playa margins; 600-1600 m; Calif., Nev.; Mexico (Baja California).

The slightly smaller-fruited form of Lepidium flavum, recognized by C. L. Hitchcock (1936) and R. C. Rollins (1993) as var. felipense, does not merit recognition.