Plants sparsely to densely hirsute basally, trichomes simple, to 1.5 mm, these mixed with fewer, forked, stalked ones, sparsely pubescent distally. Stems usually ascending, prostrate, or decumbent, rarely erect, (0.4-)1-4.5(-6) dm. Basal leaves: petiole (0.3-)1-2.5(-3.5) cm; blade (1.5-)2.5-10(-15) cm, margins pinnatifid to pinnatisect; lobes 3-8(-12) on each side, ovate, oblong, or linear, (0.1-)0.6-2(-3) cm × (0.5-)1-3(-6) mm, shorter than terminal, margins entire, dentate, or pinnatifid. Cauline leaves: (proximal) petiolate or (distal and bracts) sessile; blade similar to basal, smaller and less divided distally. Fruiting pedicels erect to ascending, straight, (4-)6-17 (-35) mm, pubescent. Flowers: sepals 2.5-4 × 0.7-1.5 mm, glabrous or pubescent; petals obovate to spatulate, 3-6 × 1.5-4 mm, not clawed; filaments 2.5-4 mm; anthers 0.5-0.6 mm. Fruits narrowly linear, (25-) 30-60(-70) × 1.5-2(-3) mm, length 13-46 times width; valves 2, thin-leathery, smooth, usually pubescent or puberulent, rarely glabrescent, trichomes simple, retrorse; septum incomplete or absent; ovules 30-70 per ovary; style (0.3-)0.8-2.5(-4) mm. Seeds dark brown, 1.2-1.6 × 0.7-1 mm. 2n = 16.

Flowering Mar-May. Roadsides, fields, hillsides, grassy pastures, sandy washes, sage scrub, chaparral, ravines, beaches, gravel flats; 0-1200 m; Calif.; Mexico (Baja California).

Tropidocarpum gracile is known from central and coastal to southernmost California.