|Poison ivy during autumn|
|Poison ivy in spring, Ottawa, Ontario|
|Toxicodendron radicans range map in North America|
Toxicodendron radicans, commonly known as eastern poison ivy or poison ivy, is an allergenic Asian and Eastern North American flowering plant in the genus Toxicodendron. The species is well known for causing urushiol-induced contact dermatitis, an itchy, irritating, and sometimes painful rash, in most people who touch it. The rash is caused by urushiol, a clear liquid compound in the plant's sap. The species is variable in its appearance and habit, and despite its common name, it is not a true ivy (Hedera), but rather a member of the cashew and pistachio family (Anacardiaceae). T. radicans is commonly eaten by many animals, and the seeds are consumed by birds, but poison ivy is most often thought of as an unwelcome weed. It is a different species from western poison ivy, Toxicodendron rydbergii, which has similar effects.
poison ivy (countable and uncountable, plural poison ivies)
- Any of three ivy-like species of Toxicodendron, known for their ability to cause an itching rash and blistering for most people, through urushiol, an oil that is a skin irritant.
The name is often spelled "poison-ivy" to indicate that it is not a true ivy or Hedera.
- (ivy-like plant producing skin irritant): Toxicodendron orientale (Asian poison ivy), Toxicodendron radicans (eastern poison ivy), Toxicodendron rydbergii (western poison ivy)
- leaves of three, let it be
- poison oak
- poison sumac