Leaves of three, let it be …or so the saying goes. While this piece of conventional wisdom is intended to help you avoid members of the Toxicodendron genus — poison ivy, poison oak, and poison sumac — it's not entirely accurate. If you carefully avoid all three-leaved plants, you'll waste a whole lot of time avoiding harmless look-alike species, and you may even miss some beneficial food sources (the blackberry bush, for example). Additionally, the “leaves of three” rule doesn't apply to poison sumac, which will still give you a rash despite having more than three leaves per stem.

After looking at the illustration above, you may think it's relatively easy to identify these three species. In the real world, it's much harder — Poison-Ivy.org has some good information if you'd like to study it before testing your knowledge. We created a 14-question quiz with images of poison oak, poison ivy, and poison sumac mixed in with several similar yet harmless plant varieties. Give it a shot, and see how good you are at spotting these rash-inducing plants.

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If you got 100%, congratulations, you're on your way to becoming an expert at Toxicodendron identification! If you misidentified safe plants as poison varieties, you would've carefully avoided them for no good reason, but no harm done otherwise. If you incorrectly identified poison ivy, poison oak, or poison sumac as a safe plant, you'd likely be covered in an irritating rash right now. Want to find out where you went wrong? Click here for the answer key, which identifies all the plants shown in this quiz.

Even if you came into contact with the poison plants in the quiz above, it's possible to remove the invisible urushiol oil they produce from your skin before it causes a rash, but you'll need to act quickly. Check out our previous article, Never Get a Poison Ivy Rash Again.

Written by Patrick McCarthy