California black oak

Quercus californica (Torrey) Cooper; Q. tinctoria W. Bartram var. californica Torrey

Trees , deciduous, to 25 m. Bark dark brown to black, ridges broad, irregular. Twigs brown to red-brown, (1.5-)2-3.5 mm diam., glabrate. Terminal buds chestnut brown, ovoid, 4-10 mm, glabrous or with scales ciliate on margins. Leaves: petiole 10-60 mm, glabrous to densely pubescent. Leaf blade ovate or broadly elliptic to obovate, 60-200 × 40-140 mm, base cordate to obtuse, occasionally rounded, margins with 7-11 lobes and 13-45 awns, lobes acute to distally expanded, separated by deep sinuses, apex acute; surfaces abaxially glabrous with small axillary tufts of tomentum to densely pubescent, adaxially glabrous to minutely pubescent, veins raised on both surfaces. Acorns biennial; cup saucer-shaped to deeply bowl-shaped, 13-27 mm high × 20-28 mm wide, covering 1/2-2/3 nut, outer surface glabrous to sparsely puberulent, inner surface 1/3 to completely pubescent, scales more than 4 mm long, attenuate or acuminate to acute, smooth, occasionally tuberculate near base of cup, tips loose, especially at margin of cup; nut oblong to broadly ellipsoid, 21-34 × 14-22 mm, puberulent, especially at apex, scar diam. 5.5-10.5 mm. 2 n = 24.

Flowering late spring. On slopes and valleys of hills and mountains; 300-2400 m; Calif., Oreg.

The abundant crops of acorns from Quercus kelloggii were at one time an important food source for Native Americans.

The species reportedly hybridizes with Quercus agrifolia (= Q. × ganderi C. B. Wolf) and Q. wislizeni (= Q. × morehus Kellogg).