Toxicodendron radicans foliage

Warning: this is a noxious weed in Ontario. Toxicodendron radicans, known in English as "poison ivy" and in French as sumac grimpant, herbe à puce, bois de chien, or sumac vénéneux, is a woody vine native to much of North America. It's important to be able to recognize its characteristic leaves, with three leaflets, because it contains urushiol, an oil which causes a horrible itchy rash in many people. (When we were kids, my sister actually decided to try rubbing it on her arm to see if she really would get a rash. She sure regretted that.) Because of its allergenic properties for humans, poison ivy is considered a noxious weed in Ontario.

Although few people will deliberately plant poison ivy, it is one of the top twenty plants in terms of providing food for birds and mammals according to American Wildlife & Plants: A Guide to Wildlife Food Habits by Alexander C. Martin, Herbert S. Zime, and Arnold L. Nelson (New York: Dover, 1961). I like Sara Stein's suggestion, in Noah's Garden, of planting poison ivy in areas where vandalism is a problem; it would not only deter vandals but feed birds as well.

I photographed this poison ivy in Purdon Conservation Area.