Weed of the Month: Eastern Poison Ivy

Animals such as cats, dogs, and horses are not sensitive to poison ivy, but can transfer the irritating urushiol oil to humans.

Photo: University of Kentucky's College of Agriculture, Food, and Environment

Common name: Eastern Poison Ivy
Scientific name: Toxicodendron radicans (L.) Kuntze

Life Cycle: Perennial
Origin: North America
Poisonous: Severe skin irritant to sensitive humans

Eastern poison ivy, frequently called poison ivy, occurs in much of the eastern United States. It is a woody perennial that can grow as a low shrub, trailing vine, or climbing vine. As a climbing vine, it can grow several yards and often reaches into the tops of trees. It will grow in a wide range of habitats, such as pastures, fence rows, and the edge of woods.

Poison ivy roots are fibrous from a taproot (the main root that grows vertically downward) and long subterranean rhizomes (rootstalks). Vines are woody and light brown or grayish and frequently have aerial roots on them. Poison ivy’s easiest identifying characteristic is a trifoliate (having three leaves) compound leaf. Leaflets are shiny, typically 2 to 4 inches in length, and pointed at the tip. Leaves turn a bright red or reddish-yellow in the fall and produce greenish to grayish white berries in late summer to early fall. Reproduction is by seeds, rootstalks, and stems that root when they come into contact with the soil. Berries are spread by birds.

All parts of the poison ivy plant, both live and dead, contain urushiol oil and might cause acute dermatitis to humans sensitive to the oil. Fumes from burning poison ivy plants might also transmit the oil. Animals such as cats, dogs, and horses are not sensitive to poison ivy, but can transfer the oil to humans.

Poison ivy plants in pastures usually grow low to the ground, and mowing is not an effective control tactic. Cutting the vines and removing plants from fences or trees does not offer long-term control since the poison ivy plant will regrow from root buds or rhizomes. The most effective control is by herbicidal sprays. Several herbicide products are available to control poison ivy. Consult your local Cooperative Extension Service personnel for herbicidal control in your area.

William W. Witt, PhD, professor emeritus in UK’s Plant and Soil Sciences, provided this information.

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