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Poison Ivy Toxicodendron radicans (Rhus radicans)


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Poison Ivy, ground level
credit: SWMNPoliSciProject/CCSA

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Alternate name: Eastern Poison Ivy

Family: Anacardiaceae, Cashew view all from this family

Description Poison ivy (older synonyms are Rhus toxicodendron and Rhus radicans), is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it. The plant is not a true ivy (Hedera).

Poison ivy can be found growing in any of the following three forms:as a trailing vine that is 10-25 cm tall (4 to 10 inches); as a shrub up to 1.2 m tall (4 feet); as a climbing vine that grows on trees or some other support.

Poison ivy grows throughout much of North America, including the Canadian Maritime provinces, Quebec, Ontario, Manitoba, and all U.S. states east of the Rockies, as well as in the mountainous areas of Mexico up to around 1,500 m (4,900 ft) (caquistle or caxuistle is the Nahuatl term), and is normally found in wooded areas, especially along edge areas. It also grows in exposed rocky areas and in open fields and disturbed areas. It can grow as a forest understory plant, although it is only somewhat shade tolerant. The plant is extremely common in suburban and exurban areas of New England, the Mid-Atlantic, and southeastern United States. Similar species, poison oak, and Toxicodendron rydbergii are found in western North America. Poison ivy rarely grows at altitudes above 1,500 m (4,900 ft), although the altitude limit varies in different locations. The plants can grow as a shrub up to about 1.2 metres (3.9 ft) tall, as a groundcover 10–25 cm (3.9–9.8 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.

Warning All parts of this plant contain volatile oil that can cause severe skin inflammation, itching, and blistering on direct contact or if borne by sooty smoke. Washing thoroughly with soap or swabbing with alcohol immediately on exposure removes the oil irritant. The berries are poisonous if eaten.

Habitat Mountains, Cities, suburbs & towns, Swamps (fresh & salt), Beaches & shorelines, Canyons & valleys, Watersides (fresh), Fields.

Range Southwest, Eastern Canada, Great Lakes, Mid-Atlantic, Texas, New England, Florida, Plains, Southeast.