94. Boechera serpenticola Windham & Al-Shehbaz, Harvard Pap. Bot. 11: 82. 2006.
Perennials; long-lived; (cespi-tose); sexual; caudex woody. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 0.5-1.8 dm, densely pubescent proximally, trichomes short-stalked, 5-8-rayed, 0.1-0.2, sparsely to moderately pubescent distally. Basal leaves: blade narrowly oblanceolate, 1-2 mm wide, margins entire, ciliate along petiole, trichomes (branched), to 0.5 mm, surfaces densely pubescent, trichomes short-stalked, 5-8-rayed, 0.1-0.2 mm. Cauline leaves: 4-14, rarely concealing stem proximally; blade auricles 0.1-0.5 mm, surfaces of distalmost leaves densely pubescent. Racemes 10-20-flowered, unbranched. Fruiting pedicels divaricate-descending or horizontal, nearly straight, 3-7 mm, pubescent, trichomes appressed, branched. Flowers ascending at anthesis; sepals pubescent; petals purple, 6-8 × 1.5-2.5 mm, glabrous; pollen ellipsoid. Fruits usually divaricate-descending or horizontal, rarely widely pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 3-4.5 cm × 2.5-3 mm; valves sparsely pubescent to glabrate; ovules 20-24 per ovary; style 1.5-2 mm. Seeds uniseriate, 2-2.5 × 1.5-1.8 mm; wing continuous, to 0.2 mm wide.
Flowering Mar-Jun. Serpentine ridges and talus; ca. 1100 m; Calif.
Boechera serpenticola has been confused with B. subpinnatifida but is easily distinguished by its entire (versus subpinnatifid to dentate) leaves, shorter (6-8 versus 9-14 mm) petals, and longer (1.5-2 versus 0.5-1 mm) styles. It is known only from Shasta and Trinity counties in north-central California.