There is also a lot of Poison Oak--a close cousin of Poison Ivy--growing on some of the trails. Leaf shape is somewhat variable, but the leaves always grow in clusters of 3 with the middle leaf on a long stem. The leaves are somewhat shiny on top, and turn red in the fall. Remember the saying"Leaves of three--don't touch me". Poison Oak, Poison Ivy, and Poison Sumac are all closely related, and contain the same irritant oil; if you are sensitive to one you are sensitive to all three.