Shrub Species of the World's Boreal Forests

World Boreal Trees

Terminology | Pictorial

Toxicodendron radicans
Poison Ivy
Anacardiaceae (Sumac Family)

A climbing vine or erect or trailing shrub, growing up to a height of 2 m.


Poison Ivy Distinguishing Features - Leaves: alternate, on long stalks, palmately compound, three leaflets, around 5 - 10 cm long, generally glossy, wavy-edged or slightly toothed, sometimes slightly lobed; young leaves, green, often with a reddish cast. Flowers: off-white with a yellowish or greenish tinge, 3 mm wide, in loose clusters 2.5 - 7.5 cmlong at lower leaf axils; flowering May to July. Fruit: white, berrylike, 6 mm wide, clustered.


Native to North America and Asia; introduced in Europe; common around lakes, swamps, and rivers; in a wide variety of other habitats; also common along roadsides and trails, in areas of waste ground, in thickets, in open woods, and old fields; prefers rich soil with good drainage and plenty of water.


All parts of the Poison Ivy plant contain volatile pale yellow oil called "urushiol" that can cause severe skin inflammation, itching, and blistering on direct contact with the skin. Urushiol itself is not poisonous. However, urushiol which remains on your skin for more than five minutes or so will begin to be absorbed and metabolized. The metabolites bind with skin proteins, forming new structures. In a good majority of the human population, the immune system sees these structures as foreign and attacks them. It is this immune response, or allergic reaction, which causes the itching, inflammation, and blistering of the skin. These symptoms generally appear in less than two days. After a few more days, when all of the alien structures have been destroyed, along with much of the surrounding tissue, the rash begins to heal.

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