[agduvnsz] Poison ivy

Poison ivy has leaves of three.
If it has thorns, it's not poison ivy.
If the leaves have tiny jagged edges all the way around, it's not poison ivy.  (It might be wild strawberry.)

Finally, in each group of three, the side leaves are often asymmetrical on their own.  (It might be -- is supposed to be -- symmetrical with the other side leaf, though various damage might prevent that.)  Others have described this asymmetry as mitten-shaped leaves, though it struck me more as derpy: as if nature couldn't be bothered to design a nice-looking symmetrical leaf.