Habitat
Western poison oak occurs only on the Pacific Coast of North America, where it is common, and ranges from southern Canada to the Baja California peninsula. It is one of California's most prevalent woody shrubs, but also climbs, vine-like, up the sides of trees, and can be found growing as single stems in grassland, often as part of early stage succession where woodland has been removed, and serving as a nurse plant for other species.
The plant often occurs in California oak woodlands and Douglas-fir (Pseudotsuga) forests. The vine form climbs far up the trunks of coast redwoods, potentially killing smaller trees.
It is found in damp, semishady areas near running water and also thrives in direct sunlight, requiring water only in early spring. Any trail leading to a waterfall on California's coast may likely be home to western poison oak; it can also be found in some inland mountain ranges, such as the Cascades.
The plant toxin produced by members of the genus Toxicodendron, called urushiol, is known for causing an uncomfortable, and sometimes painful, skin reaction. Urushiol is the main component of the oily resin that is found on the stems and leaves of poison ivy and several other related species. It causes contact dermatitis — an immune-mediated skin inflammation (Kalish et al., 1994) — in four-fifths of humans.
The active components of urushiol have been determined by Billets (1975) to be unsaturated congeners of 3-heptadecylcatechol with up to three double bonds in an unbranched C17 side chain. In poison ivy, these components are unique in that they contain a -CH2CH2- group in an unbranched alkyl side chain.
Deer species and other animals feed on the leaves of the plant — which are rich in phosphorus, calcium and sulfur, while bird species utilize the plant structure for shelter. These animals do not seem to demonstrate any sort of reaction to urushiol. Furthermore, poison oak for example is widely distributed in western North America, inhabiting both forests and chaparral biomes.
Read more about this topic: Toxicodendron Diversilobum
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