Perennials; (caudex simple or branched, with some persistent petiolar remains); sparsely to moderately pubescent, trichomes bulbous-based, simple and long-stalked, forked, (to 2 mm), these often mixed with fewer 3-rayed, stalked stellate ones. Stems simple or few from base (caudex), erect, unbranched distally, (0.6-) 1.7-4.5(-5) dm, (usually pubescent throughout, rarely subglabrate, coarsely hirsute, trichomes simple, mixed with forked ones). Basal leaves: petiole 0.5-2(-3) cm, (ciliate); blade oblanceolate to obovate, (1-)2-5(-9) cm × (5-)8-18(-22) mm, margins entire or repand to dentate, (ciliate), apex obtuse, surfaces pubescent or glabrous, trichomes simple and forked, sometimes mixed with 3-rayed stellate ones. Cauline leaves 3-6 (or 7); blade oblong, 1-3(-6) cm × 2-7(-15) mm, base not auriculate, margins entire or dentate, (ciliate or not), apex obtuse, surfaces pubescent as basal leaves or glabrous. Racemes simple, (dense). Fruiting pedicels ascending to erect, 5-10 mm, (pubescent or glabrous). Flowers: sepals (purple), oblong, (5-)6-8 × 1.5-2 mm, lateral pair saccate basally; petals purple or pink, spatulate, (10-)12-15(-16) × (3-)4-5 mm, apex obtuse; filaments (4-)5-8 mm; anthers narrowly oblong, 1.2-1.8 mm. Fruits erect or nearly so, slightly torulose, (3-)4.5-6 cm × 1.5-2 mm; valves each with prominent midvein; ovules 24-30 per ovary; style 0.5-1 mm. Seeds narrowly winged distally or not winged, oblong, 1.8-2.2 × ca. 1 mm; wing ca. 0.1 mm wide. 2n = 32.

Flowering Apr-May. Moist granitic soil, rocky hillsides, chaparrals, steep banks; 500-1000(-1400) m; Calif., Oreg.

Arabis oregana is known from Napa and Siskiyou counties (California) and Jackson County (Oregon).