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Article from New Trees by John Grimshaw & Ross Bayton
'Quercus turbinella' from the website Trees and Shrubs Online (treesandshrubsonline.
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Shrub or tree, 5–10 m, occasionally to 20 m. Bark grey, fissured and scaly. Branchlets greyish brown, tomentose to glabrous. Leaves evergreen or partially deciduous, (1.5–)2–3 × 1–1.5(–2) cm, elliptic to ovate, leathery, upper surface glaucous or yellowish and glandular, glabrous or with minute stellate pubescence, lower surface yellowish or reddish and glaucous with minute stellate pubescence, four to eight secondary veins on each side of the midrib, margins with three to five coarse teeth or shallow lobes on each side of the midrib, apex acute to obtuse; petiole 0.1–0.4 cm long. Infructescence 1–4 cm long with one to three cupules. Cupule hemispheric or cup-shaped, 0.8–1.2 × 0.4–0.6 cm; scales ovate, partially tuberculate and covered in greyish or yellowish pubescence. Acorn ovoid, with one-quarter to half of its length enclosed in the cupule, ~2 cm long, stylopodium small. Flowering April, fruiting July (USA). Nixon 1997. Distribution MEXICO: Baja California, Chihuahua, Sonora; USA: Arizona, California, Colorado, New Mexico, Nevada, Texas, Utah. Habitat Dry desert slopes in juniper/pinyon woodland between 800 and 2000 m asl. USDA Hardiness Zone ~5. Conservation status Least Concern. Illustration Nixon 1997, Sternberg 2004; NT755.
Accounted the hardiest of the American evergreen oaks by Sternberg (2004), Quercus turbinella is a species well adapted to its arid hillside habitat, often forming little more than a prickly bush. It was recommended by Melendrez (2000) as an attractive species suitable for planting in cold, dry areas; it thrives in Denver Botanic Gardens, Colorado (A. Coombes, pers. comm. 2008). At Ettelbruck it is hardy but slow-growing, and snow pressure can be a problem for the thin flexible stems (E. Jablonski, pers. comm. 2006). A plant in shade at Chevithorne Barton has reached approximately 3 m. In European collections generally, however, it is rare. In cultivation in North America it hybridises freely with the most disparate-seeming partners, including Q. robur (Sir Harold Hillier Gardens database), and is a parent of several wild hybrids.