Physaria alpestris

Perennials; caudex usually simple, rarely branched, (ces-pitose); (silvery) pubescent throughout, trichomes several- rayed, rays (1- or) 2-bifurcate, (low-umbonate, tubercles rel-atively few, small). Stems several from base, decumbent to ascending, (unbranched), 0.5-1.5 dm. Basal leaves: (petiole slender); blade obovate, 3-5 cm (width 10-20 mm, base tapering abruptly to petiole), margins entire, (apex rarely slightly acute). Cauline leaves: blade oblanceolate, 0.5-1.5 cm (width 3-5 mm), margins entire. Racemes subcorymbose. Fruiting pedicels (divaricate, straight), 5-10 mm. Flowers: sepals oblong, 8-10 mm; petals spatulate, 12-14 mm. Fruits didymous, mostly highly inflated (strongly flattened at least in 1/2 toward replum), 14-18 × 14-18 mm, (papery, basal sinus slightly notched, apical open, shallow); valves (retaining seeds after dehiscence), evenly pubescent; replum lanceolate, 7-10 mm, width 1.5-2.5 mm, as wide as or wider than fruit, apex acute to acuminate); ovules 8-10 per ovary; style 5-7 mm. Seeds flattened, (2-3 mm). 2n = 48-52, 52, 64, 67-70.

Flowering May-Jun. Alpine scree, rocky ridges, talus slopes, volcanic sands and gravel, serpentine gravel, granitic slopes, mountain shrub, subalpine fir, and whitebark pine communities; (700-)1300-2400 m; Wash.