Weeds

Poison Oak

Poison Oak
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Poison oak (Toxicodendron diversilobum) is a woody plant that is native to North America and is abundant west of the Cascade and Sierra Mountains. It can be found in diverse environments; open areas as well as forested areas. Poison oak tends to grow as a shrub
3-10 feet tall in open areas or a woody vine in shaded areas. Vines will develop rootlets (short woody hairs) that will enable the plant to climb up and attach itself to trees, fences, etc. Initially plants grow from seeds but extend their territory through a lateral root system
that produces shoots that grow into new plants.
Poison oak produces small pale-green flowers that emerge from slender stalks at the base of the leaves. Flowers produce small, white, pumpkin-shaped fruit in the late summer to early fall. The fruit is soft with deep grooves (resin canals) and is surrounded by a papery covering. Within the fruit is a stony seed.
Poison oak is most identifiable by its leaf arrangement and shape. Leaves are produced in groups of three leaflets from a common stem (occasionally leaflets are in groups of five, seven or nine) and are about 1 – 4 inches long. Two of the leaves emerge opposite from each other with the third continuing out from the stem between them. Often, the two bottom leaves are less symmetrical than the third and tend to be more deeply lobed on the side closest to the stem (furthest away from the third leaf). However, poison oak leaves can look very different from plant to plant. Some leaves have softly lobed edges while others are more jagged. Leaves can be either smooth, have a blistered appearance, dull, glossy, or have fine hairs. Young leaves tend to emerge shiny green or red with green, turning a glossy green in summer and orange, red, and brown in the fall. Vines and shrubs both lose their leaves each fall.