Perennials; long-lived; (cespi-tose); apomictic; caudex woody. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 1-2.5 dm, glabrous or sparsely pubescent proximally, trichomes short-stalked, 2-5-rayed (rarely, some simple), 0.4-0.6 mm, glabrous distally. Basal leaves: blade oblanceolate, 2.5-6 mm wide, margins entire, ciliate proximally, trichomes (simple), surfaces densely pubescent, trichomes short-stalked, 4-7-rayed, 0.3-0.5 mm. Cauline leaves: 3-12, often concealing stem proximally; blade auricles 0.5-2 mm, surfaces of distalmost leaves usually glabrous, sometimes margins ciliate. Racemes 12-25-flowered, usually unbranched. Fruiting pedicels ascending to divaricate-descending, straight, 2-6 mm, glabrous. Flowers ascending at anthesis; sepals pubescent; petals purple, 5-6 × 1.5-2 mm, glabrous; pollen spheroid. Fruits ascending to divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 2-3.7 cm × 2-2.8 mm; valves glabrous; ovules 56-80 per ovary; style 0.1-0.3 mm. Seeds uniseriate, 1-1.5 × 0.8-1 mm; wing distal or continuous, 0.05-0.1 mm wide.

Flowering Jun-Sep. Granitic ledges and talus slopes; 2700-3400 m; Calif.

Boechera peirsonii is an apomictic species of unknown origin; although previously treated as a variety of Arabis (B.) breweri, it is quite distinct from that taxon (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). All known collections come from the San Bernardino Mountains of southern California, ca. 200 km distant from the nearest populations of B. breweri.