Quercus turbinella

Illustrator: John Myers

Copyright: Flora of North America Association

Shrubs or small trees, evergreen or subevergreen, to 4 m. Bark light gray or brown, scaly. Twigs brown to gray, 1-3 mm diam., usually tomentulose, sometimes glabrous, becoming glabrate. Buds brown, round to ovoid, 1-2 mm, minutely pubescent. Leaves: petiole 1-4 mm. Leaf blade elliptic or ovate, (1.5-)20-30 × (5-)10-15(-20) mm, thick, leathery, base cordate or rounded, margins planar or slightly crisped-undulate, coarsely 3-5-toothed or very shallowly lobed on each side, teeth spinose with spines 1-1.5 mm, secondary veins 4-8 on each side, apex acute or obtuse; surfaces abaxially yellow or reddish, usually glaucous, minutely stellate-puberulent, adaxially grayish, glaucous, or yellowish glandular, glabrous or sparsely and minutely stellate-pubescent. Acorns solitary or several, on axillary peduncle 10-40 mm; cup hemispheric or shallowly cup-shaped, 4-6 mm deep × 8-12 mm wide, covering 1/4-1/2 nut, scales tightly appressed, ovate, moderately tuberculate, grayish or yellowish puberulent; nut light brown, ovoid, to 20 × 11 mm, minutely puberulent or glabrate. Cotyledons distinct.

Phenology: Flowering spring.
Habitat: Dry desert slopes, often in juniper and pinyon woodlands
Elevation: 800-2000 m

Distribution

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Ariz., Calif., Colo., N.Mex., Nev., Tex., Utah, Mexico (Baja California, Sonora, and probably n Chihuahua).

Discussion

Formerly, California populations of what here is referred to as Quercus john-tuckeri have been included in the concept of Q. turbinella. Quercus john-tuckeri has subsessile fruit and noncordate leaf bases as opposed to the consistently pedunculate fruit and strongly cordate leaf bases of Q. turbinella. The two species seem to be no more closely related to each other than each might be to other southwestern oaks, and Q. john-tuckeri shares at least as many characteristics with Q. berberidifolia as with Q. turbinella. Thus, treatment of these two taxa as varieties of the same species is inappropriate.

Quercus turbinella forms putative hybrid swarms with Q. gambelii (see treatment), as well as with Q. grisea.

Selected References

Tucker, J. M. 1961b. Studies in the Quercus undulata complex. II. The contribution of Q. turbinella. Amer. J. Bot. 48: 329-339.

Lower Taxa

None.