Gray oak

Quercus undulata Torrey var. grisea (Liebmann) Engelmann, Trans. St. Louis Acad. 3: 393. 1877

Large shrubs or moderate trees , deciduous or subevergreen, to 10 m. Bark gray, fissured. Twigs gray, 1-2 mm diam., sparsely or densely stellate-tomentulose or tomentose when young. Buds dark red-brown, ovoid to subglobose, 1-2 mm, stellate hairs causing yellowish color, at least on outer scales; stipules persistent, 1-4, subulate, pubescent, at base of terminal buds. Leaves: petiole 3-10 mm. Leaf blade oblong to elliptic or ovate, (15-)25-35(-80) × (7-)15-30(-40) mm, thick and leathery, base cordate or rounded, margins minutely revolute, entire or dentate with mucronate teeth, secondary veins 6-10 on each side, branched, apex acute, sometimes obtuse, rarely rounded; surfaces abaxially dull gray-green or yellowish, minutely stellate-pubescent with interlocking hairs, secondary veins very prominent, adaxially dull green, very sparsely and minutely stellate-pubescent, secondary veins slightly raised. Acorns solitary or paired, subsessile or on peduncle 0-30 mm; cup from deeply goblet- to deeply cup-shaped, 4-10 mm deep × 8-15 mm wide, enclosing to 1/2 nut, scales broadly ovate to oblong, proximal scales slightly or markedly tuberculate and whitish canescent, tips closely appressed, red-brown, thin, glabrate; nut light brown, ovoid to narrowly ovoid or ellipsoid, 12-18 × 8-12 mm. Cotyledons connate.

Flowering spring. Igneous or dolomitic slopes, oak woodlands, juniper woodlands, desert chaparral; usually above 1500 m; Ariz., N.Mex., Tex.; Mexico (Sonora, Chihuahua, and Durango).

Some of the specimens referred to Quercus endemica by C. H. Muller should be placed in Q . grisea .

Numerous hybrids between Quercus grisea and other white oaks, including Q . gambelii , Q . mohriana , Q . arizonica , and numerous species in northern Mexico, have been reported. In the Hueco and Quitman mountains of trans-Pecos Texas, putative hybrids of Q . grisea × Q . turbinella Greene occur.