Information about poison ivy, oak, sumac and the skin rashes they cause
This shows that, below a certain size, the vine does not grow the hairy roots that attach to vertical surfaces, so the smaller branch is bare and the larger is hairy.
The hairy vine is the most common way to spot the plant when the leaves are gone. But notice how branches are going in all directions, many without any hairs at all.
This is just here because the vine is easier to see on the white birch (though I have not found lots of cases of poison ivy climbing white birches).
Typical urban wall heavily infested with poison ivy. (However, there were many birds living in and around this giant vine.)
Here is poison ivy climbing the trunk of a dead tree, sending out shoots in all directions.
A poison ivy "explosion" where the vine has reached the top of a vertical form, then sent out branches in every direction, looking for sun or for the next place to grab onto.
The seeds are easier to see in winter, as they hide under leaves in summer. They are great bird food, but are not edible for humans!
Here are poison ivy vines growing on cut firewood. Handling this firewood, and worse, burning it, are great ways to get a rash in winter. Breathing the smoke is very dangerous.
This giant 6-inch vine, cut off in March, is oozing a great deal of sap from inside the outer bark. This sap is where the oil is that causes the rash. (You can run afoul of the sap in the summer; this just shows that you are not safe from it in winter.)
It is very difficult to spot a growth of ground growing poison ivy in winter since there are no hairy roots. I only knew this plant was poison ivy because I had been to this spot many times in summer.