Poison Ivy : A Variable Pest - Indiana Yard and Garden - Purdue Consumer Horticulture

Poison Ivy : A Variable Pest

Rosie Lerner, Purdue Consumer Horticulture Specialist
Released 17 June 1999

Perhaps you’ve heard of the old saying? “Leaves of three, let it be?” Excellent advice for those who are sensitive to the poison ivy plant.

A Perplexing Plant

Poison ivy, Toxicodendron radicans, is generally a woody plant with three leaflets; that is, each individual leaf is subdivided into three leaf-like structures. But that’s where the generalizing ends. Poison ivy can be a vine growing up the side of a tree or building. Poison ivy also can be a self-supported shrub. The edges of the leaflets can be smooth, toothed or lobed. Leaves can be variable even on the same plant!

The flowers are no help in identification, because they are greenish and small and are not generally noticeable. Late in summer and fall, white-gray, waxy berries will ripen. Poison ivy often has outstanding red fall foliage.

Look Alikes

Boston ivy, Parthenocissus tricuspidata, is often mistaken for poison ivy. When Boston ivy is young, the foliage is three-parted. As the plant matures, the leaves are then lobed much like maple leaves. Other plants also may have three leaflets and add to your confusion, so if there is any doubt, it is always best to proceed with caution.

The “Poison” in Poison Ivy

The offending chemical in poison ivy is contained in oil throughout the plant, including leaves, stems, fruit, roots and flowers, and is present throughout the year. For those who are sensitive to the oil, handling tools, pets, clothing or other items that have been in contact with the plant may be enough to cause a skin reaction. People become more sensitive to the oil as they are in contact with it. People who have always believed themselves to be “immune” can become sensitive if repeatedly exposed to the oil. According to the American Medical Association’s Handbook of Poisonous Plants, if you suspect you’ve been in contact with poison ivy, wash the area with plain water immediately. (Contact your physician for information on how to treat a reaction to poison ivy.)


Apparently, birds can eat the berries without harm but in so doing, they spread the plants by seed. Once established, the woodiness of the plant makes it difficult to control. Repeated cutting of the plant back to the ground may eventually starve the plant. However, each time you cut you are potentially exposing yourself to the oil. Small plants can be dug up and discarded. However, if any portion of the root system is left behind, the plant will likely resprout.

Several herbicides are available for control of poison ivy. Keep in mind, though, that any herbicide that will kill poison ivy, will also kill any desirable plants. So if the poison ivy is growing among shrubs and trees, chemical controls must be applied directly to the poison ivy plant and not to any of the other plants. In some cases, it may be worth sacrificing some desirable plants to eliminate the poison ivy. Some of the products that are commonly available for poison ivy control include brush killers (often a formulation of 2,4-D) and glyphosate (Roundup or Kleenup). Of these two types of chemicals, the glyphosate is less likely to give off vapors that can damage other plants nearby. Repeated applications may be necessary to completely eliminate the plant. Be extremely cautious when applying such chemicals, and always read the label directions before applying any pesticide.

No matter what control method you use, be careful to avoid exposing your skin to the plant. Wear gloves, long pants, socks and shoes, and a long-sleeved shirt. NEVER burn poison ivy! The smoke from burning the plant contains particles that can cause serious injury to the eyes, skin and respiratory tract.

Last updated: 10 April 2006


Share This Article
Disclaimer: Reference to products is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in these articles assumes full responsibility for their use in accordance with current directions of the manufacturer.
Indiana Yard and Garden – Purdue Consumer Horticulture - Horticulture & Landscape Architecture, 625 Agriculture Mall, West Lafayette, IN 47907

© 2024 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Indiana Yard and Garden – Purdue Consumer Horticulture

If you have trouble accessing this page because of a disability, please contact Indiana Yard and Garden – Purdue Consumer Horticulture at homehort@purdue.edu | Accessibility Resources