Perennials; (short-lived, caudex simple or few-branched); (glaucous), usually glabrous throughout, (except sepals pubescent, sometimes also petioles). Stems branched, 2.2-12(-15) dm. Basal leaves rosulate (in juvenile plants); petiolate (petioles usually glabrous, rarely ciliate); blade obovate to spatulate, 3.5-10 cm, margins entire. Cauline leaves: blade broadly oblong to ovate or suborbicular, 2.5-10 cm × 10-35 mm, (smaller distally), base amplexicaul, margins entire. Racemes ebracteate, (lax). Fruiting pedicels divaricate-ascending, (straight), 5-10 mm. Flowers: calyx subcampanulate; sepals yellow-greenish proximally, purple distally, oblong, 6-8 mm, not keeled, (with subapical tuft of hairs); petals purple or brownish (claw yellow-green), 8-12 mm, blade 1-3 × 0.5-0.8 mm, margins not crisped, claw 6-10 mm, wider than blade; stamens in 3 unequal pairs; filaments (distinct): abaxial pair 6-8 mm, lateral pair 4-6 mm, adaxial pair 7-10 mm; anthers (all) fertile, 3.5-5 mm; gynophore 0.3-1 mm. Fruits descending, smooth or slightly torulose, arcuate, flattened, 5-13(-15) cm × 2-2.5 mm; valves each with prominent midvein; replum straight; ovules 50-82 per ovary; style 1.5-3.5 mm; stigma entire. Seeds oblong, 2.2-3 × 1.4-1.8 mm; wing 0.1-0.4 mm wide, continuous.

Flowering May-Jul. Openings in pine forests, oak woodland; 400-1700 m; Calif.

Streptanthus longisiliquus is known from Butte, Shasta, and Tehama counties.