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This remarkable evergreen hybrid oak was raised at Kew in 1914 from acorns gathered from Q. wislizenii, an evergreen species from California. Three plants were raised and it was soon evident from their foliage and rate of growth they were not of pure parentage. The leaves are 11⁄2 to 31⁄2 in. long, 3⁄4 to 13⁄4 in. wide, oblong-ovate in main outline, but with the margins cut into five or six triangular lobes 1⁄8 to 1⁄2 in. deep, each lobe and the apex having a mucronate tip, the base subcordate or truncate, dull green and glabrous above, shining green with loose stellate hairs on the midrib and stalk beneath, the latter 1⁄4 to 1⁄2 in. long. Young shoots slightly furnished at first with stellate hairs, bright brown. The tree is evergreen, its branching slender, dense and erect; the largest example in 1932 was about 28 ft high and growing vigorously. Acorns 3⁄4 to 1 in. long, 1⁄2 in. wide, taking two years to reach maturity like those of Q. wislizenii.
The mother tree is standing in the Oak collection at Kew and it is fairly certain that its female flowers were fertilised by wind-blown pollen from a large Turkey oak (Q. cerris) growing some forty yards away. The angular lobing of the leaves of Q. × kewensis is very suggestive of the Turkey oak and so is its fine network of veins on the undersurface. But the dull grey-green beneath the leaves of the Turkey oak and the very characteristic thread-like stipules that surround its buds disappear in the hybrid, which is also quite evergreen.
The original tree at Kew now measures 30 × 5 ft (1972).
There are two examples at Kew, measuring 30 × 5 ft and 50 × 41⁄4 ft, both in the Oak Collection by the Thames (1972–3).