Here is a tree in a lovely park in Silver Springs, Maryland. What stood out is how the lower section of the tree trunk has a nice bunch of Virginia Creeper on it but higher up, the tree is all covered with poison ivy.

The base of the tree is a mix of neither plant. This tree is in a pretty well-cared for park, so any ground level poison ivy would be noticed by the staff, but the climbing vine higher up? It probably started behind the tree, out of sight, then move around front to get more sunlight.