22. Oxalis oregana Nuttall in J. Torrey and A. Gray, Fl. N. Amer. 1: 211. 1838.
Oxalis acetosella Linnaeus subsp. oregana (Nuttall) D. Löve; O. oregana var. smalliana (R. Knuth) M. Peck; O. oregana var. tracyi Jepson; O. smalliana R. Knuth
Herbs perennial, acaulous, rhizomes present, <fleshy-thickened, densely scaly>, stolons absent, bulbs absent. Leaves basal, <clustered at rhizome tips>; petiole 5–15(–21) cm, <sparsely to densely villous, hairs rusty>; leaflets 3, green, broadly obcordate, 10–30(–40) mm, lobed 1/5–1/4 length, <lobes apically convex>, surfaces sparsely villous, oxalate deposits absent. Inflorescences 1-flowered; scapes (6–)11–25 cm, glabrous or sparsely villous. Flowers heterostylous; sepal apices without tubercles; petals white to deep pink, usually with yellow spot sub-basally and prominent purple veins, (8–)15–25 mm. Capsules ovoid, 6–8(–12) mm, glabrate.
Flowering Feb–Sep. Douglas fir, mixed fir, cedar-spruce, mixed conifer, and hemlock-maple forests, maple woodlands, alder glens, Gaultheria thickets, stream banks; 10–800(–1000) m; B.C.; Calif., Oreg., Wash.
Oxalis oregana has sometimes been treated as a disjunct geographical taxon of the European O. acetosella Linnaeus (see comments under 21. O. montana).