Thlaspi montanum Linnaeus var. siskiyoense P. K. Holmgren, Mem. New York Bot. Gard. 21(2): 84. 1971

Stems (0.6-)0.7-1.6(-2.4) dm. Basal leaves: petiole differ-entiated from blade, (1.7-) 2-3.6(-4) times longer than blade; blade ovate to oblong, 4-8(-9) mm wide, base cuneate. Cauline leaves 2-6. Racemes lax to compact. Fruiting pedicels horizontal or slightly descending, forming an angle 80º or more with rachis. Flowers: petals white, 3.8-6 × 1.2-2.2(-2.9) mm. Fruits often strongly winged, obovate to obdeltate, (4-)4.8-7(-8) × (3-)3.5-5.5(-6) mm, 1-2 times as long as wide, apex truncate to strongly emarginate; style (0.8-)1-2 mm. Seeds 2-4 per fruit. 2n = 14.

Flowering Apr-Jun. Moist, open rocky serpentine slopes; 300-500 m; Oreg.

Subspecies siskiyouensis is known from Curry, Douglas, and Josephine counties.