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FNA | Family List | FNA Vol. 7 | Brassicaceae | Boechera

100. Boechera subpinnatifida (S. Watson) Al-Shehbaz, Novon. 13: 389. 2003.

Arabis subpinnatifida S. Watson, Proc. Amer. Acad. Arts 20: 353. 1885

Perennials; long-lived; sexual; caudex woody (often with persistent, crowded leaf bases). Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 1-4(-5) dm, densely pubescent proximally, trichomes short-stalked, 2-6-rayed, 0.1-0.2 mm, sparsely pubescent distally. Basal leaves: blade narrowly oblanceolate, 1-4(-5) mm wide, margins prominently dentate to subpinnatifid (leaf margins of sterile shoots often entire), ciliate near petiole base, trichomes (simple or 2-rayed), 0.4-0.6 mm, surfaces densely pubescent, trichomes short-stalked, (2-)4-9-rayed, 0.05-0.2 mm. Cauline leaves: (10-) 20-60, often concealing stem throughout; blade auricles 0.5-3 mm, surfaces of distalmost leaves moderately to sparsely pubescent. Racemes 8-30-flowered, usually unbranched. Fruiting pedicels reflexed, strongly recurved, 5-15 mm, pubescent, trichomes appressed, branched. Flowers divaricate-ascending to pendent at anthesis; sepals pubescent; petals usually purple, rarely lavender, 9-14 × 1.5-3 mm, glabrous; pollen ellipsoid. Fruits pendent, not appressed to rachis, not secund, straight to slightly curved, edges parallel, (3.5-)5-8 cm × (1.6-)2-3 mm; valves pubescent throughout; ovules 24-42 per ovary; style 0.5-1 mm. Seeds uniseriate, 2.5-3.5 × 1.5-2.2 mm; wing continuous or at both ends, 0.4-0.8 mm wide. 2n = 14.

Flowering Mar-May. Rock outcrops, talus, gravelly soil, often in sagebrush-grassland communities; 800-2400 m; Calif., Idaho, Nev., Oreg., Utah.

Originally thought to be restricted to northern California and adjacent Oregon, Boechera subpinnatifida is a sexual species that recently has been found in central Idaho, northern Nevada, and northwestern Utah. It appears to intergrade with both B. puberula and B. retrofracta, and species boundaries within this complex need further study.


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