Arabis polyantha Greene, Leafl. Bot. Observ. Crit. 2: 80. 1910; A. macdougalii Rydberg

Perennials; usually short-lived; sexual; caudex not woody. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 2.5-9 dm, densely pubescent proximally, trichomes short-stalked, 2-6-rayed, 0.1-0.7 mm, similarly pubescent distally. Basal leaves: blade oblanceolate, 1.5-7 mm wide, margins entire or shallowly dentate, ciliate at petiole base, trichomes to 0.9 mm, surfaces densely pubescent, trichomes short-stalked, 5-10-rayed, 0.1-0.25 mm. Cauline leaves: 16-42, concealing stem proximally; blade auricles 0.5-1.5 mm, surfaces of distalmost leaves pubescent. Racemes 17-96-flowered, usually unbranched. Fruiting pedicels reflexed, abruptly recurved at base, otherwise straight, 7-13 mm, pubescent, trichomes appressed, branched. Flowers descending at anthesis; sepals pubescent; petals white, 6-9 × 1-2.5 mm, sparsely pubescent abaxially; pollen ellipsoid. Fruits strongly reflexed, usually ap-pressed to rachis, sometimes somewhat secund, straight, edges parallel, 3.5-7.2 cm × 1.2-1.5 mm; valves densely pubescent; ovules 74-110 per ovary; styles 0.05-0.2 mm. Seeds uniseriate, 0.9-1.2 × 0.7-1 mm; wing continuous, 0.05-0.1 mm wide.

Flowering late Apr-early Jun. Rocky, gravelly, and sandy slopes in open areas; 900-2500 m; Idaho, Mont., Oreg., Wash.

Boechera polyantha is closely related to B. retrofracta, but is easily distinguished by densely pubescent fruits and scattered trichomes on abaxial petal surfaces.