Poison Oak (Toxicodendron diversilobum)

Poison Oak (Toxicodendron diversilobum) Information

By Ronnie Dauber, Garden Guides Contributor The Poison Oak is native to California, and is one of the two most poisonous plants in North America, the second being Poison Ivy. Anyone touching the leaves or any part of this plant to any degree, regardless of age or culture, can be afflicted with moderate to severe dermatitis. In California where there are ongoing uncontrolled fires, when the Poison Oak is burned it mixes the poisonous fumes with the smoke and turns it into a harmful inhalant causing a serious inflammation of the respiratory mucous membranes among the fire fighters.

General Characteristics

Poison Oak is a member of the Sumac family (Anacardiaceae). It grows as a dense shrub in open sunlight when the Poison Ivy lives in the shaded areas as a ground ivy. The Poison Oak bear petioles each with three leaves 3 1/2 to 10c long, and have scalloped, toothed or lobed edges. They closely resemble the leaves of the Oak Tree except that they follow their family suit and are generally bright green in the spring and turn a yellow-green to reddish in the summer and then a bright red in the fall. The plant s produce small greenish-white flowers in the spring and clusters of ivory-white fruit in the fall giving this plant great eye appeal. It is the urushiol oil that covers the leaves that is poisonous and causes the inflammation.

Growing Conditions

Poison Oak grows as a dense shrub in open sunlight and can adapt to shaded areas, and is reproduced by seeds or creeping rootstocks. It grows around lakes and streams in the midwestern and eastern United States and Canada.

Cultivation and Care

These plants are extremely aggressive and do not require any human intervention to help them to grow. The Poisonous Oak grows in the form of a small bush or shrub and although it prefers sun and moist soil, it can survive heat or drought, sun or shade.

Weed Control Techniques

If Poison Oak or Ivy is discovered in your own yard, the best option is to call a landscaper and have it professionally removed. Other options would be to spray the plants with an herbicide such as Roundup or Ortho Poison Ivy Killer, but you are risking harming surrounding plants. You could manually remove the plants by digging them up including its full root, and disposing of them. Both of these methods will have to be repeatedly many times since the plants grow back very quickly. The poison oil on the dead plants has the same threat as live plants so don't handle them with bare hands just because they are dead. As well, the oil that is transferred to your clothes or equipment used to dig them up does not become less potent because it is off of the plant and the inflamed reaction will be the same as touching the plant. Never burn Poison Oak or Ivy because inhaling the fumes is more dangerous to your health than the skin reaction.

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