Rhus diversiloba. The old adage, "If it has three (leaves), let it be" definitely applies as this common sumac family shrub has caused more than one hiker much suffering. Leaves start out green in the spring and turn bright red in the fall. Inhabits a variety of niches from coastal headland to elevations of around 4500 feet. It is much less vine-like than the eastern poison ivy, growing in large bunches, but poison oak is equally as poisonous as its eastern relative to those not immune to its nasty rash-causing effects.