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Tree, sometimes a shrub, to 15–20 m, occasionally to 30 m and 2 m dbh. Bark black or dark brown, smooth but warted when young, becoming broken into thick plates separated by deep fissures. Branches spreading, sometimes towards the ground, and forming a tall, domed crown. Branchlets pale reddish brown and pubescent. Leaves evergreen or sub-evergreen, 2.8–9.5 × 1.5–4.5 cm, ovate to oblong or obovate, hard and leathery, upper surface glabrous and glossy, lower surface covered in stellate tomentum, but this is easily rubbed off except for the tufts of tomentum on each side of the midrib at the base of the lamina, reticulate tertiary veins prominent, six to eight secondary veins on each side of the midrib, margins entire and cartilaginous or spinose with up to 13 bristles, apex acute to truncate; petiole 0.3–1 cm long, pubescent. Infructescence 0.6 cm long with one to two cupules. Cupule cup-shaped, 0.7–1.2 × 0.5–7.5 cm, both surfaces somewhat pubescent; scales blunt and appressed. Acorn ellipsoid to oblong, with one-quarter to half of its length enclosed in the cupule, 1–1.8 cm long, stylopodium prominent; ripening in the first year. Flowering April to May, fruiting July to September (USA). Standley 1922, Nixon 1997, Melendrez 2000. Distribution MEXICO: Chihuahua, Coahuila, Durango, Nuevo León, Sonora, Tamaulipas; USA: Arizona, New Mexico, Texas. Habitat Limestone ridges and slopes and along small streams between 150 and 2200 m asl. USDA Hardiness Zone 6. Conservation status Least Concern. Illustration Nixon 1997.
Quercus emoryi is slow-growing in the wild, where it often occurs on rocky ground with little or no topsoil, and is clearly tolerant of hot, dry conditions, as its grey, holly-like leaves suggest. In North America it has proved to be extremely hardy, remaining evergreen in Zone 6–7 conditions (Melendrez 2000). Although Melendrez suggests that it remains slow-growing in cultivation this is somewhat contradicted by young trees at the Hillier Gardens, collected as acorns in New Mexico in 1997 and now up to 3.5 m in height; also by specimens collected there by E. Jablonski in 2000, whose progeny are now 2.0 m at Ettelbruck and show no sign of winter damage (E. Jablonski, pers. comm. 2006). An older tree at the Hillier Gardens, grown in shade, has reached 7 m, but its planting date is not known. The acorns are sweet and are a valued food source for Native Americans, as well as being important to wildlife (Melendrez 2000).