Minnesota Profile - Western Poison Ivy (Toxicodendron rydbergii)

Appearance: "Leaflets three, let it be" is old and still good advice. Each compound leaf has three slightly wavy and toothed blades, or leaflets. In spring the leaflets have a glossy, reddish tint, which becomes deep green. In the fall they turn bright yellow or red. Round green berries appear in midsummer and turn waxy white by the fall; they can remain on the plant stubble all winter. Plants grow 4 inches to 4 feet tall.

Range: Poison ivy grows well almost anywhere in the state. It likes sunshine and drier soil, but grows in moist shade too. It thrives in disturbed ground such as roadside ditches. It is common along fences and utility wires, where it springs from seeds in bird droppings.

Human Contact: A clear, colorless oil called urushiol causes poison ivy dermatitis. It courses through all parts of the plant except pollen. The urushiol released through a pinprick in a leaf is enough to cause a rash in 80 to 90 percent of humans. If the plant burns, the urushiol travels in smoke, which can also cause dermatitis. Anyone inhaling the smoke should immediately seek medical attention.

Urushiol can remain potent on objects for a long time. For example, a rake handle dropped on poison ivy probably has enough urushiol to cause a reaction when touched months later.

An itchy rash and blisters can develop a few hours or days after contact. The rash and sores contain only body serum and are not contagious. Rashes that seem to spread are simply developing over time. Seek medical attention if the itch is intense or if the rash covers more than one-quarter of the body or develops on sensitive areas such as the face.

Prevention: Learn to identify the plant in all stages, and avoid contact. If skin touches the plant, wash with plenty of water within 15 minutes to dilute the urushiol. Do not use soap: It can spread the urushiol. Rubbing alcohol sloshed (not rubbed) over exposed areas within several hours of contact can neutralize the urushiol. (Rinse off with water.)

Management: Birds and other animals eat its berries without apparent ill effect. Poison ivy propagates by seed and underground runners. More persistent than invasive, it can be controlled along paths and other disturbed places with a systemic woody brush killer such as Roundup. Patches may pop up again if animal droppings contain seeds.

Susan Carol Hauser, author of Outwitting Poison Ivy, The Lyons Press, 2001