Western Poison Oak is a deciduous shrub, ground cover, or vine, found along the Pacific Coast of North America that is important to be identified and avoided by those who are allergic to it. The plant produces a toxic oil called urushiol that can cause a severe reaction in the form of a red rash accompanied by swelling and blisters. The leaves grow in sets of three off the stem and are scalloped and wavy and shaped much like an oak leaf. The top side of the leaf often appears glossy green in the growing season with seasonal colors of yellow, red and brown. Whitish-green flowers appear in the spring with light green berries throughout the summer and into the fall.