Poison ivy (Toxicodendron radicans) is a nuisance plant that grows throughout the continental United States. It grows in almost any type of soil, in both the shade and the sun. While it is most commonly found as a trailing vine, it can also form an upright shrub, and can climb trees, boulders, or walls to heights of 15 meters (50 feet). Its seeds are an important winter food for many types of birds.

Poison ivy's oil causes an itchy, blistering rash in most people who come in contact with it. All parts of the plant contain the oil, although the leaves are the most easily bruised and are therefore the most likely to cause the rash. The oil is sticky and will cling to (and be spread on) skin, clothing, tools, and animal fur. It is also spread in smoke when the plant is burned. In fact, irritation...