Arabis suffrutescens S. Watson, Proc. Amer. Acad. Arts 17: 362. 1882; A. dianthifolia Greene; A. duriuscula Greene

Perennials; long-lived; sexual or apomictic; caudex woody. Stems usually 1 per caudex branch, arising from center of rosette, elevated above ground surface on woody base, 1-4(-5) dm, usually glabrous proximally, rarely pubescent, trichomes short-stalked, 2-rayed, 0.1-0.3 mm, glabrous distally. Basal leaves: blade narrowly oblanceolate, 1.5-6 mm wide, margins entire, not ciliate or, rarely, with simple trichomes to 0.7 mm, surfaces glabrous or sparsely to densely pubescent, trichomes short-stalked, 2-6-rayed, 0.07-0.4 mm. Cauline leaves: (4-)6-12, sometimes concealing stem proximally; blade auricles 0.5-2 mm, surfaces of distalmost leaves glabrous. Racemes 6-12-flowered, usually unbranched. Fruiting pedicels reflexed, usually abruptly recurved at base, otherwise straight, 4-18 mm, glabrous. Flowers pendent at anthesis; sepals glabrous; petals purple or whitish with rose tips, 4.5-6 × 2-2.5 mm, glabrous; pollen ellipsoid or spheroid. Fruits reflexed to closely pendent, sometimes appressed to rachis, often secund, straight to somewhat curved, edges undulate (not parallel), 3-7(-8) cm × 3-5(-6) mm; valves glabrous; ovules 20-30 per ovary; style 0.4-1.2 mm. Seeds uniseriate, 2.5-5.5 × 1.8-3.5 mm; wing continuous, 0.8-1.5 mm wide.

Flowering Jun-Aug. Rocky slopes and gravelly soil, often with sagebrush; 1800-3000 m; Calif., Idaho, Nev., Oreg., Wash.

Boechera suffrutescens is recognizable by its prominently suffrutescent habit and wide (greater than 3 mm), reflexed fruits. Both sexual and apomictic collections are known; further study is needed to determine whether they truly are conspecific. The taxon previously known as Arabis suffrutescens var. horizontalis appears to be of hybrid origin; it is treated here as a distinct species (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison).