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Tree to 10 m. Bark thick and light grey-brown with broad ridges separated by narrow fissures. Branches thick, set at right angles to the trunk, forming a broad, irregular crown. Branchlets pale brown with sparse or dense stellate tomentum. Leaves sub-evergreen, (2–)3–6(–8) × (0.5–)1–2(–2.5) cm, oblong to elliptic, rarely lanceolate or ovate, grey or blue-green to glaucous, upper surface glabrous, lower surface with dense glandular tomentum that easily rubs off, though persistent at the base of the midrib, 7–8(–10) secondary veins on each side of the midrib, margins usually entire or with irregular teeth towards the apex, apex acute to rounded; petiole 0.2–0.6 cm long. Infructescence ~0.6 cm long with one to two cupules. Cupule cup-shaped, 1–1.5 × 0.8–1 cm; scales swollen and tuberculate near the base, grey and pubescent. Acorn ovoid to oblong, with one-third of its length enclosed in the cupule, 1.5–2.5 cm long, stylopodium short. Flowering April to May, fruiting September to November (USA). Nixon 1997. Distribution MEXICO: Baja California; USA: southern California (incl. Santa Catalina Is.). Habitat Oak woodland and the margins of chaparral between 50 and 1200 m asl. USDA Hardiness Zone (8–)9. Conservation status Vulnerable, due to habitat degradation and loss. Illustration Nixon 1997; NT698. Taxonomic note This species is closely related to Q. oblongifolia.
This characteristic oak of southern California is rare in cultivation. Young plants are struggling at both Arboretum de la Bergerette and Ettelbruck, losing their leaves and suffering some dieback each year (E. Jablonski, S. Haddock, pers. comms. 2006). The best specimen observed for the current work is one of some 4 m at Chevithorne Barton, apparently thriving. This is strange, considering its native habitat of the hot, dry hillsides south of Los Angeles, and its genealogy as a white oak. However, Nixon (2002) points out that Quercus engelmannii is a member of the subsection Glaucoideae, whose species are principally found in areas with summer rainfall. The main flush produces leaves that are typically rather rounded, without teeth, but in secondary flushes they are neatly toothed.