University of Illinois Extension

Poison Ivy Control

Poison ivy (Toxicodendron radicans) can be a nightmare, said a University of Illinois Extension horticulture educator.

“It can cause skin irritation if the plant resins--urushiols--come in contact with the skin,” said Barbara Bates. “The rash and accompanying itching is an allergic reaction.

“Not all persons are allergic, but most are and some will develop the allergy over time. To those who are sensitive, even the leafless winter and early-spring stems should be avoided.”

Despite its name, poison ivy is not a true ivy like English ivy, she noted. It is a woody vine in the same family as sumac, cashews, and magnolias. Native to North America, it often grows as an under-story shrub or vine.

Photo of poison ivy (1)“Poison ivy is very shade tolerant, but it is very adaptable and can be found in almost any habitat--sun or shade, wet or dry,” Bates explained. “It is easily spread by birds who feed on the fruits. The fruits are whitish-gray berries that grow in clusters and ripen in the fall. The clusters of fragrant white flowers appear late in the spring.”

While it is a vine, poison ivy may grow as a groundcover, spreading by underground roots. It may also grow as a vine, clinging by aerial roots, vertically up tree trunks or on structures such as fences or utility poles.

“Once it establishes itself in a vertical growth habit, lateral branches reach out horizontally several feet and blend with tree or shrub branches at upper body level,” she said. “Recognition of the leaves and observation of hairy vines on tree trunks can help avoid contact.

“The rhyme ‘leaves of three, not for me,’ is a good thing to remember, but know that there are many plants with leaves bearing three leaflets.”

Poison ivy has compound leaves with three leaflets connected at a central point, all of relatively equal size. The leaflets are longer than wide but size varies based on growing conditions. New leaves emerge with a red tinge, turn dark green in summer, and change to a rich, red color in the fall.

Leaflets have few to no teeth on the margins and are arranged alternately on the stem. Stems have wiry hairs and are brown to gray. Stems can become quite large in diameter--up to several inches--and densely hairy.

“Poison ivy can be confused with several other woody species, including box elder, some brambles, fragrant sumac, and Virginia creeper,” said Bates. “To differentiate, look for green to red stems arranged opposite to each other on box elder. Brambles (Rubus) have red to purplish mature stems armed with thorns and leaves with regularly toothed margins. Fragrant sumac has three glossy green leaflets of unequal size, with regularly-spaced rounded teeth on the leaf margins. The stems are softly hairy, but do not cling or climb.

Photo of poison ivy (2)“Virginia creeper has five to seven leaflets emanating from a central point.”

The three methods recommended for controlling poison ivy are digging or grubbing; severing the vine and then treating the re-growth with a herbicide; or applying a herbicide to individual leaflets.

“Always wear protective clothing when working around poison ivy,” Bates noted. “If your hands become infected, you can spread the irritant to other parts of your body. Contact with clothes or pets that have picked up the sap can cause a reaction.

“Smoke from burning leaves or vines, even after they have dried, can cause lung and throat irritation. See a doctor if this happens.”

Bates said that when pulling the poison ivy plant, be sure to remove the entire root so the plant will not re-sprout.

“If the vines are growing vertically, sever them at the base and carefully pull them down using a rake and dispose of them,” she said. “Glyphosate, a non-selective systemic herbicide, should be applied to new sprouts that arise.

“Glyphosate should only be applied to actively growing foliage. Several repeat applications may be necessary. Always read and follow the instructions on the label.”