Island Oak
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The Island Oak (Quercus tomentella), also known as Island Live Oak or Channel Islands Oak, is an oak in the section Protobalanus. Island Oak is native to six islands off the coast of California, Santa Rosa, Santa Cruz, Anacapa, Santa Catalina, San Clemente, and Guadalupe islands. The first five islands are Channel Islands of California; Guadalupe Island is located to the west of Mexico (Baja California).
Island Oak is usually less than 20 meters in height. Its bark is usually gray and becomes furrowed with age. The species is named for the dense hairs found on the undersides of its leaves. Leaves, which are evergreen, are usually 5-8 cm in length, oblong to oblong-obvate in shape, with a toothed margin, deeply indented. Acorns take 2 years to mature and are saucer- to bowl-shaped with a rounded tip, and large in size (cup 20-30 mm wide, 6-8 mm deep, nut 20-35 mm).
Many native populations of Island Oak are in need of immediate restoration due to severe impacts of grazing by non-native herbivores. The National Park Service has classified Island Oak as a species of special environmental concern.
Fossils of Island Oak have been found in mainland California; the youngest known fossils are two to ten million years old and were found near St. Mary's College, somewhat near the Oakland hills. The oldest known fossils are 30 to 60 million years old and were found in the Mojave desert. Island Oak is no longer native to mainland California, and is thought to be a relict of a climate that was warmer and wetter than today's. However, it will grow readily in mainland California if planted and regularly watered.
Island Oak can hybridize with all other members of the section Protobalanus, although its natural range overlaps only with Quercus chrysolepis, the Canyon Live Oak.
References
- Nixon, K. et al. (1998). [Quercus tomentella]. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Vulnerable (VU B1+2ce v2.3)
- [Flora of North America - Quercus tomentella]
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