Print this Article
Wednesday, Aug. 8, 2007 03:47 am

Controlling poison ivy

Leaves of three, let it be; leaves of four, eat some more

Untitled Document Controlling and eradicating poison ivy can be a challenge, but for many people elimination of this noxious plant is imperative because it can cause nightmarish rashes and itching. Not everyone is sensitive to the plant’s resins, but in some the allergy develops over time and even the leafless winter and early-spring stems can set off a reaction.
Poison ivy (Toxicodendron radicans) is a woody vine in the same family as sumac, cashews, and magnolias, not a true ivy like English ivy. Native to North America, it often grows as an understory shrub or vine. “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,” says Barbara Bates, a University of Illinois Extension horticulture educator. “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.”
Although it is a vine, poison ivy may grow as a ground cover, spreading by underground roots. It may also grow as a vine, clinging by aerial roots, up tree trunks or such structures as fence posts and 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,” Bates says. “Recognition of the leaves and observation of hairy vines on tree trunks can help avoid contact.”
Remember the rhyme “leaves of three, let it be.”
Poison ivy has compound leaves consisting of three leaflets, all of relatively equal size, connected at a central point. The leaflets are longer than they are wide, but their size varies, depending on growing conditions. New leaves emerge with a red tinge, turn dark green in summer, and change to a rich red in the fall. Leaflets have few to no teeth on the margins and are arranged alternately on the stem. Stems, which are brown to gray and have dense wiry hairs, can grow to a diameter of several inches. “Poison ivy can be confused with several other woody species, including box elder, some brambles, fragrant sumac, and Virginia creeper,” Bates says. “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. 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 regrowth with a herbicide; and applying a herbicide to individual leaflets. “Always wear protective clothing when working around poison ivy,” Bates says. “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.”
When pulling the poison ivy plant, Bates warns, be sure to remove the entire root so that 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 says.
For more information about the University of Illinois Extension’s Sangamon-Menard unit, go to