Poison Oak Western (along the Pacific coast) grows to 6-foot-tall clumps or vines up to 30 feet long; Eastern (from New Jersey to Texas) grows as a low shrub; Oak-like leaves, usually in clusters of three Clusters of yellow berries

How to spot Poison Oak

Poison oak is a deciduous shrub that is quite common throughout the mountains and valleys of California, Oregon and Washington. As a rule Poison Oak is not found above 5,000 feet of elevation. In shady canyons and riparian habitats it commonly grows as a climbing vine with roots that cling to the trunks of oaks and sycamores. A National Park Employee told me that it is not uncommon for these vines to stretch from a source of water quite far up the side of a mountain! Poison oak also forms dense thickets in chaparral and coastal sage scrub, particularly in central and northern California. It regenerates readily after disturbances such as fire and trail maintenance. The old adage "Leaves of Three, let it be" has been shortened from its original form. Most of us omit "berries white, a poisonous sight". Poison Oak has male and female plants and flowers in the late Spring. Interestingly, in the early part of Spring the leaves appear shiny and waxy. During late Summer, the leaves turn various shades of red and yellow. The rash from Poison Oak can be caused when there are leaves on the plant and more importantly when there are no leaves because the urushiol resin is found in the stems and roots of the plant.

These images illustrate the changing colors of poison oak throughout the season.