I just got back from a wonderful Memorial Day trip to Moab, where I had a little brush with some type of poison ivy or poison oak near the Green River in Canyonlands National Park. I do a lot of hiking and mountain biking, and I see a lot of plants with "leaves of three," but I'm never sure which ones are poison oak or poison ivy.
Poison oak and poison ivy plants are great imitators of the plants around them - they can change size, leaf shape, and leaf color depending on where they are growing. If growing among trees, these plants will grow as vines. Among shrubs, they will grow as shrubs, and in open areas, they will grow as small weeds.
About.com guide to walking Wendy Bumgardner has created a couple of excellent photo galleries to help you learn to identify poison oak, poison ivy and poison sumac. Take a look and learn to spot these shape-shifting, irritating plants.
Photo by Wendy Bumgardner