poison ivy

1. A North American shrub or vine (Toxicodendron radicans syn. Rhus radicans) that has compound leaves with three leaflets, small green flowers, and whitish berries and that causes a rash on contact.
2. A skin rash caused by contact with this plant.

A general name applied to certain species of the genus Toxicodendron, previously known as Rhus, in the sumac family (Anacardiaceae). Toxicodendron radicans is the poison ivy of eastern North America; T. diversiloba is the poison oak of California. These plants are natives of North America. Both cause ivy poisoning, an annoying and often painful dermatitis. Toxicodendron radicans, the most widespread species, is extremely variable. It has a bushy or climbing habit and three-foliolate leaves which are smooth and glossy or hairy and are entire, toothed, or lobed. Poison ivy bears white fruits whereas the nonpoisonous sumacs bear red fruits. See also Hypersensitivity; Sapindales.

You can look, but you'd better not touch. England knew ivy, but nothing so irritating. In 1784 the first volume of Memoirs of the American Academy of Arts and Sciences described Hedera or Poison Ivy as producing "inflammations and eruptions." The name Hedera did not stick, but poison ivy did.

Only the name was new in 1784. Captain John Smith, for one, had known of the plant in 1624 when he published his Generall Historie of Virginia, though he mentioned it in regard to Bermuda. To him poison seemed too strong a word: "The poysoned weed is much in shape like our English Ivy, but being but touched, causeth rednesse, itching, and lastly blisters, the which howsoever after a while passe away of themselves without further harme, yet because for the time they are somewhat painfull, it hath got itselfe an ill name, although questionlesse of no ill nature."

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Poison ivy (Toxicodendron radicans) (credit: Walter Chandoha)

Either of two North American species of white-fruited woody vines or shrubs of the sumac, or cashew, family. The species found in eastern North America (Toxicodendron radicans) is abundant; a western species, known as poison oak, is less common. Both species are sometimes classified as genus Rhus. A key identifier is leaves with three mitten-shaped leaflets. Contact with urushiol, an oil produced by the plant, can cause severe inflammation and blistering of human skin. Urushiol may be carried from the plant on clothing, shoes, tools, or soil; by animals; or by smoke from burning plants. Because urushiol is nonvolatile, a reaction may result from wearing clothing a year or more after its contact with the plant.

For more information on poison ivy, visit Britannica.com.

Poison ivy is a poisonous plant, though the term is also used for the rash urushiol-induced contact dermatitis, caused by contact with it. It is not a true ivy, which are species of the genus Hedera.

Poison ivy may also refer to:

• Poison Ivy (comics), a villain and enemy of Batman in the DC Comics universe.
• Poison Ivy (musician), co-founder of the band The Cramps.
• Ivy Lee, a pioneer in public relations and an employee of John D. Rockefeller's (nickname from the United Mine Workers)
• Poison Ivy, a 1937 novel by Peter Cheyney
• Poison Ivy (film), a 1992 US film.
  • Poison Ivy II: Lily, a 1996 sequel to the 1992 film
  • Poison Ivy: The New Seduction (aka Poison Ivy 3: Violet), a 1997 US film
  • Poison Ivy: The Secret Society, the 2008 fourth film in the Poison Ivy series
• "Poison Ivy" (Law & Order episode)
• "Poison Ivy" (Gossip Girl episode)
• "Poison Ivy" (song), a 1959 Leiber/Stoller song.
• Poison Ivy (1985 film), a 1985 NBC made-for-television movie.
• "Poison Ivy", a Faster Pussycat song from the 1989 album Wake Me When It's Over
• "Poison Ivy", a song from the album Lines, Vines and Trying Times by the Jonas Brothers

See also

• Ivy

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