Arabis koehleri Howell, Fl. N.W. Amer., 44. 1897; A. arbuscula Greene; A. koehleri var. stipitata Rollins

Perennials; long-lived; sexual; caudex woody (with persistent, peg-like leaf bases). Stems usually 1 per caudex branch, arising from center of rosette, elevated above ground surface on woody base, 0.8-4.5 dm, pubescent proximally, trichomes stalked, 2-4-rayed, to 0.5 mm, mixed with simple ones, to 1 mm, glabrous distally. Basal leaves: blade narrowly oblanceolate, 1-3 mm wide, margins entire, ciliate proximally, trichomes (simple), to 1 mm, surfaces moderately to sparsely pubescent, trichomes stalked, 2-4-rayed, 0.1-0.3(-0.5) mm. Cauline leaves: 3-17(-30), rarely concealing stem; blade auricles 0.5-2.5 mm, surfaces of distalmost leaves glabrous. Racemes 6-20(-35)-flowered, usually unbranched. Fruiting pedicels divaricate-ascending to horizontal, straight, 10-18 mm, glabrous or sparsely pubescent, trichomes spreading, simple and 2-rayed. Flowers ascending at anthesis; sepals pubescent; petals deep purple to magenta, 8-12 × 2.5-4 mm, glabrous; pollen ellipsoid. Fruits divaricate-ascending to widely pendent, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 5-7.5 cm × 1.8-2.5 mm; valves glabrous; ovules 58-94 per ovary; style 0.05-0.2 mm. Seeds uniseriate, 1.3-1.8 × 1.2-1.5 mm; wing continuous, 0.1-0.2 mm wide.

Flowering Apr-May. Serpentine and limestone outcrops; 100-500 m; Calif., Oreg.

Boechera koehleri var. koehlerei is in the Center for Plant Conservation’s National Collection of Endangered Plants.