Agricultural Sciences

Poison Ivy -- A Wildlife Food -- One Of First Plants To Change Color

UNIVERSITY PARK, Pa. -- Avoiding poison ivy gets easier in the fall because later this month or early next -- before most plants show autumn colors -- poison ivy's leaves will turn a brilliant red.

Unlike humans, many animals don't have adverse reactions to poison ivy, according to an expert in Penn State's College of Agricultural Sciences. "In fact, for woodpeckers, warblers, vireos and many other birds, poison ivy's berries are a preferred food," says Jim Finley, professor of forest resources. "Deer, black bears, muskrats and rabbits eat the fruit, stems and leaves. For these animals, poison ivy's eye-catching early-fall color will act as a food marker rather than a poison warning."

Human reactions to poison ivy are most common in the summertime but can occur at any time of the year. Most people are not allergic upon first contact, but repeated contact can cause itching, swelling, blistering and even numbness to about 85 percent of those exposed. "Any direct contact with poison ivy -- or even indirect contact such as touching clothing, tools or a pet's fur that have come into contact with leaves -- can elicit an allergic reaction," warns Finley.

Poison ivy is usually a vine (sometimes, it appears as a small upright single- or multiple-stem shrub), with leaflets clustered in groups of three. The leaves may appear shiny or dull and often are pointed at the tips. The edges of each leaflet may be smooth or have a few coarse notches, but are not serrated. In the summer, leaves and berries are green. In the fall, the berries turn white and the leaves red. All parts of this plant are poisonous and remain so even after it is dead.

"Look for poison ivy around the edges of open fields, woodlots and trails," says Finley. "The vines often climb trees, fences and stone walls." Don't try to rip poison ivy vines out of the ground, even with gloves, he advises. "If you have only a few scattered vines, you could try digging them up with a shovel after a rain, when the soil is moist," Finley says. "Don't use a weed whacker. Urushiol, the oil of the plant that causes the allergic reaction, could get on your clothing, exposed parts of your body or neighboring plants."

Never burn poison ivy. Poison ivy smoke can cause a severe allergic reaction in the lungs. "Short of using a broadleaf herbicide, which also would be effective," says Finley, "repeatedly amputating the vine at its source is the best method of controlling poison ivy."

Reactions to poison ivy range from mild to severe and typically last at least 10 days. Once the itching or blistering begins, the rash has already spread and will be difficult to control. To stop the rash before it spreads, shower with cold water (hot water will open your pores and let the oil in) immediately after contact and before any symptoms appear. Regardless of your previous contacts with poison ivy, never assume immunity. Sensitivity can develop at any age after any number of contacts.

More information about poison ivy is available in the free publication Weed Identification #21: Poison Ivy. To request this or any other free publication, contact the Pennsylvania Forest Stewardship Program by calling toll free (800) 235-WISE, e-mailing or writing to Forest Stewardship Program, Forest Resources Extension, The Pennsylvania State University, 7 Ferguson Building, University Park, PA 16802.


EDITORS: Contact Jim Finley at 814-863-0401 or

Writer: Elizabeth Webster 814-863-0401


Jeff Mulhollem 814-863-2719 814-863-9877 fax #251

Last Updated March 19, 2009