Origin:
Native to the United States - spread throughout the western United States, and replaced by Toxicodendron radicans - Poison Ivy - in the eastern half of the country.
Biology:
Perennial, deciduous shrub or vine – may stay under 3 feet tall or mature plants may be as high as 13 feet tall. As a vine it grows up tree trunks to heights of 75 feet, sustaining itself with aerial roots. (Poison ivy never acts as a vine.) The poisons in both poison oak and poison ivy are the milky oils found in the phloem layer of the stems, as well as oils and resins in the leaves and berries. Susceptible persons develop a severe, itching, long-lasting skin rash on contact, and severe reactions if smoke from burning poison oak is inhaled.
Identification:
Shrub or vine, stems woody and either hairless or sparsely hairy, gray to reddish brown. Leaves oak-like and arranged as 3 leaves on a stalk. Shape of leaves varies from lobed to toothed edges, round or oblong. Color is shiny, leathery green turning bright red in autumn, prior to dropping from the plant. Flowers are white and small, in clusters on long stalks. They develop to the fruit, or berries, that are white with 5 black, longitudinal lines on them. Fruit is consumed by birds, which spread the seeds in their droppings.
Characteristicts Important to Control:
Extensive stems and extensive root systems exist. Control with systemic herbicides is best accomplished after full foliage is in place. Physical removal may be successful with very young plants with a single stem, and gloves always should be worn when contacting leaves or stems. Burning poison oak should be done with extreme caution, as smoke that is inhaled may cause severe reactions in humans.
