Toxicodendron diversilobum

Toxicodendron diversilobum is extremely variable in growth habit and leaf appearance. It grows as a dense 0.5–4 m (1.6–13.1 ft) tall shrub in open sunlight, a treelike vine 10–30 feet (3.0–9.1 m) and may be more than 100 feet (30 m) long with an 8–20 cm (3.1–7.9 in) trunk, as dense thickets in shaded areas, or any form in between. It reproduces by spreading rhizomes and by seeds.
  T. diversilobum foliage at Samuel P. Taylor State Park, California
The plant is winter deciduous, so that after cold weather sets in, the stems are leafless and bear only the occasional cluster of mature fruit. Without leaves the stems may sometimes be identified by occasional black marks where its milky sap may have oozed and dried.
The leaves are divided into three (rarely 5, 7, or 9) leaflets, 3.5 to 10 centimetres (1.4 to 3.9 in) long, with scalloped, toothed, or lobed edges. They generally resemble the lobed leaves of a true oak, though tend to be more glossy. Leaves are typically bronze when first unfolding in February to March, bright green in the spring, yellow-green to reddish in the summer, and bright red or pink from late July to October.White flowers form in the spring, from March to June. If they are fertilized, they develop into greenish-white or tan drupes.Botanist John Howell observed that the toxicity of T. diversilobum obscures its merits:
"In spring, the ivory flowers bloom on the sunny hill or in sheltered glade, in summer its fine green leaves contrast refreshingly with dried and tawny grassland, in autumn its colors flame more brilliantly than in any other native, but one great fault, its poisonous juice, nullifies its every other virtue and renders this beautiful shrub the most disparaged of all within our region."Toxin qualitiesEdit
Main article: Urushiol-induced contact dermatitis
Toxicodendron diversilobum leaves and twigs have a surface oil, urushiol, which causes an allergic reaction. It causes contact dermatitis – an immune-mediated skin inflammation – in four-fifths of humans. However, most, if not all, will become sensitized over time with repeated or more concentrated exposure to urushiol.
The active components of urushiol have been determined 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.
ReactionsEdit
  Urushiol-induced contact dermatitis from poison oak
Toxicodendron diversilobum skin contact first causes itching; then evolves into dermatitis with inflammation, colorless bumps, severe itching, and blistering. In the dormant deciduous seasons the plant can be difficult to recognize, however contact with leafless branches and twigs also causes allergic reactions.
Urushiol volatilizes when burned, and human exposure to T. diversilobum smoke is extremely hazardous, from wildfires, controlled burns, or disposal fires. The smoke can poison people who thought they were immune. Branches used to toast food over campfires can cause reactions internally and externally.
Urushiol is also found in the skin of mangos, posing a danger to people already sensitized to T. diversilobum when eating the fruit while it is still in the rind.

Toxicodendron Diversilobum

Toxicodendron diversilobum

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