Western Poison Oak

Toxicodendron diversilobum, Anacardiaceae

This deciduous perennial has highly variable growth habits: vine, ground cover, shrub. Its compound leaves have three leaflets. The terminal leaflet ranges in size from 1/3 to 5 inches long by 1/3 to 3 inches wide. Lateral leaflets may be half as long. Leaves appear shiny bright green or red in spring then turn dull green or dusty red in summer. The leaves are very resinous. They can be confused with blackberry leaves which also have three leaflets. However, western poison oak leaves and branches lack any spiny or hairy projections, and the leaflets tend to have more rounded tips.