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Tree to 20 m. Bark thin and reddish brown, divided into large scales. Branches spreading to form a rounded crown. Branchlets reddish brown or greyish green, rigid and densely tomentose. Leaves evergreen, (3–)7–10 (–20) × 2.5–4 cm, oblong to lanceolate or elliptic, leathery, upper surface glossy dark green and sparsely stellate-tomentose, lower surface densely tomentose with white hairs and a pilose midrib, 8–10(–12) secondary veins on each side of the midrib, margins strongly revolute, crenate to dentate (rarely entire) with mucronate teeth, apex rounded or acute; petiole 0.3–1 cm long with rusty hairs. Infructescence with a solitary (rarely paired) cupule. Cupule cup-shaped, 1.5–3 × 0.4–0.8 cm; scales deeply embedded in whitish brown tomentum, with only the elongated apices visible. Acorn ovoid, with one-quarter to one-third of its length enclosed in the cupule, 2–3 cm long, stylopodium persistent. Flowering May to June (USA). Nixon 1997. Distribution MEXICO: Baja California, Guadalupe Is.; USA: California (Channel Is.). Habitat Lower parts of steep canyons and ridge tops between 100 and 650 m asl. USDA Hardiness Zone 8. Conservation status Vulnerable, due to habitat degradation and loss. Illustration Nixon 1997.
Despite its origin on frost-free offshore islands, and having been described by Lamant (2004) as ‘famous for lack of hardiness’, Quercus tomentella is proving to be fully hardy in southern England and is making good growth at both Chevithorne Barton and the Sir Harold Hillier Gardens. At the latter, a specimen from Coombes 445, collected in 1997 from plants in Santa Barbara Botanic Garden that originated on Santa Cruz Island, was 7.9 m tall by October 2008. Acorns collected at Rancho Santa Ana gave the hybrid Q. tomentella × Q. chrysolepis. In France there is a fine specimen in Stéphane Brame’s collection at Villeneuve le Comte, Dept. Seine et Marne (Lamant 2004). The hard-textured, glossy, dark green leaves are rather holly-like with their marginal spines.