Poison Ivy: Hairy Vine

There are almost as many ways to climb trees as there are species of vines. Grapevines have curly tendrils that grab branches, while Virginia creepers use little suction-cups. Asian bittersweet corkscrews its way round and round the tree trunk. But poison ivy’s method of ascent is unique.

Poison ivy gets to the top by growing thread-like rootlets all along the length of its stems. At first the rootlets appear as little patches that look like tufts of fuzzy hair. The furry roots secrete a glue-like substance which virtually cements the vine to tree or wall. As the main stem ages, more and more rootlets grow, forming a thick pelt of what looks like auburn fur, making a poison ivy vine look more like a mammal than a plant. The wiry little roots dig their way into every tiny crevice in the bark, and hold on tight.

Some vines get incredibly fuzzy, like a big furry snake.

If you tried to loosen a poison ivy vine’s grip on a tree trunk (don’t) you’d discover that it’s so tightly welded to the tree that often the bark comes off with the vine. But the vine, brown and inconspicuous, often goes unnoticed when trees are cut up for firewood, which is not good–tiny droplets of urushiol (the chemical that causes the itch) are carried by the smoke, and breathing it in can be really, really bad for your lungs.

So anyway, with all those sticky little rootlets clinging to the tree trunk, poison ivy doesn’t need to corkscrew itself around the tree for support. It goes straight up.

All vines are by definition parasitic: they derive benefits at the expense of a host organism. Most vines are harmful to the trees that support them, and some vines, like Asian bittersweet, are lethal—they literally strangle their host, especially if the tree they’re spiraling around is a young sapling. But poison ivy tends to prefer older, mature trees to climb, so that the fuzzy roots can grab the bark more easily.

Poison ivy has minimal impact on the trees that host it. It’s far less destructive a parasite than are Asian bittersweet, grapevines, and many other vines. Not all bad.

For more fun with poison ivy, please check out my children’s book Leaflets Three, Let It Be! The Story of Poison Ivy.