Thlaspi californicum S. Watson, Proc. Amer. Acad. Arts 17: 365. 1882; T. alpestre Linnaeus var. californicum (S. Watson) Jepson; T. glaucum (A. Nelson) A. Nelson subsp. californicum (S. Watson) Munz; T. montanum Linnaeus var. californicum (S. Watson) P. K. Holmgren

Stems (0.5-)1-1.2(-0.2) dm. Basal leaves: petiole differentiated from blade, 0.8-1.8 times longer than blade; blade spatulate to obovate, 5-7(-8) mm wide, base cuneate. Cauline leaves 2-5. Racemes lax. Fruiting pedicels strongly ascending to divaricate-ascending, forming an angle 15-70º with rachis. Flowers: petals white, 6-8 × 1.6-2.5 mm. Fruits not winged, elliptic, 0.7-10.5 × 2.7-4 mm, 2.2-3.2 times as long as wide, apex acute; style (1.3-)1.5-2(2.4-) mm. Seeds 2-6 per fruit.

Flowering May-Jun. Serpentine rock outcrops; of conservation concern; ca. 800 m; Calif.

Subspecies californica is known from one population at Kneeland Prairie in Humboldt County. It was recognized by Holmgren as a variety of Thlaspi montanum, whereas R. C. Rollins (1993) treated it as T. californicum. In my opinion, the differences in fruit apex and size between this taxon and Noccaea fendleri are rather small and do not seem to justify its recognition as an independent species.