Poison Oak, the hikers bane. I have seen people in absolute misery after being exposed. This plant is native to the West Coast of North America and is wide spread. It can take weeks to heal the skin irritations and people have been hospitalized. But sensitivity varies widely. Some people develop a tolerance and can walk right through a patch of it with no problems. But my wife is so sensitive that when I am around it, she can get it from my clothes.
In Southern California, as the weather warms up and thing dry out, Poison Oak starts putting on a show. It has fall like colors in late spring and early summer.
Latin Toxicodendron diversilobum