Toxicodendron Diversilobum

Toxicodendron diversilobum, western poison oak or Pacific poison oak (syn. Rhus diversiloba) is in the Anacardiaceae family (the sumac family) and is a plant best known for its ability to cause allergic rashes and itching after contact. Western poison oak is found only on the Pacific Coast of the United States and of Canada.

It is extremely common in that region, where it is the predominant species of the genus; the closely related Atlantic poison oak (T. pubescens) occurs on the Atlantic Coast.