Annuals; (not glaucous), glabrous or sparsely to moderately hirsute. Stems erect, unbranched or branched distally, 1.7-12 dm, usually hirsute basally. Basal leaves soon withered; blade lyrate, margins sinuate-pinnatifid. Cauline leaves petiolate (median 0.3-2 cm) or (distal) sessile; blade lanceolate to oblong or oblanceolate, 2-13.5 cm × 3-35 mm (smaller distally, base sometimes subauriculate), margins dentate. Racemes without a terminal cluster of sterile flowers, (considerably elongated in fruit). Fruiting pedicels ascending to strongly reflexed, (slender or thickened), 4.5-8 mm, glabrous or sparsely pubescent. Flowers: sepals usually erect, rarely ascending to spreading, oblong, 6-9 × 1.5-2 mm, (not saccate or urceolate); petals (erect), usually white to creamy white, rarely pinkish, (narrowly lanceolate), 7-13 mm, blade 3-5 × 1-1.5 mm, channeled, crisped, claw linear-oblanceolate, 4-8 × 1-1.7 mm; filaments tetradynamous, (erect), median pairs 5-7 mm, lateral pair 3-5 mm; anthers narrowly oblong, equal, 1.5-2.5 mm. Fruits erect, (straight), terete, 3.8-7.7 cm × 1.4-2 mm; valves each with obscure midvein, (glabrous or sparsely pubescent); ovules 44-58 per ovary; style 1-3.5 mm; stigma subentire. Seeds (brown), 1.3-1.8 × 0.9-1.2 mm. 2n = 28.

Flowering Mar-May. Serpentine grounds, roadsides, gumbo clay slopes, open hillsides, grassy fields; of conservation concern; 100-800 m; Calif.

Caulanthus flavescens is distributed primarily from Monterey and San Benito counties north to Napa and San Joaquin counties.