Island oak is a tree growing up to 20 metres (66 feet) in height.[5] The mature tree has a grayish to reddish brown trunk with scaly, furrowed bark.[3] The twigs are reddish and covered in woolly hairs. The leathery leaf blades are often concave and are an oblong lance shape or oval with pointed or rounded tips. The edges are smooth or toothed.[5] The upper surfaces are dark green and lightly hairy when new, losing the hairs over time. The undersides are gray-green and coated in woolly hairs, becoming less woolly with age.[3] They are usually 7 to 10 centimetres (2+3⁄4 to 4 inches) long, sometimes up to 12 cm (4+3⁄4 in). The acorn grows singly or in pairs. The cup has thick scales and woolly hairs and is up to 3 cm (1+1⁄8 in) wide. The nut is up to 3.5cm with a rounded tip.[3][5]
This species is a relict. Though it is now limited to the islands, it was once widespread in mainland California, as evidenced by the many late Tertiaryfossils of the species found there.[5] Recently, it was found that there was a high genetic variability across many of the Q. tomentella populations, but this variation was not evenly distributed.[8]
The species is threatened by overgrazing from nonnative ungulates. The most rapid declines have occurred on Guadalupe Island.[1] The trees there are apparently no longer reproducing.[9]Feral goats have been abundant on the island for at least 150 years. The animals have eliminated much of the native vegetation and caused extensive soil erosion. Fenced enclosures have been helpful in the early recovery of some of the local flora.[10]
^"Quercus tomentella". Inventory of Rare and Endangered Plants. California Native Plant Society. 2013.
^Ashley, M.V., J. R. Backs, L. Kindsvater and S. T. Abraham. 2018. Genetic variation and structure in an endemic island oak, Quercus tomentella and mainland canyon oak, Quercus chrysolepis. International Journal of Plant Science 179