The Trouble With Poison Ivy

Ronald Strahan, Koske, Thomas J.

LSU AgCenter, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A, 10B, 11

Poison Ivy

Poison Ivy leaves

Virginia Creeper

Anyone cleaning out overgrown areas or even just weeding this spring should beware. Poison ivy (Toxicodendron radicans) may be growing among the plants you are handling. Gardeners and landscapers often come into contact with poison ivy and many contract a bothersome rash as a result. It pays to be able to identify this plant and avoid it.

Poison ivy is a tall climbing vine that is leafless in winter (deciduous). As it climbs tree trunks, wood fences or other flat structures the stem produces many small roots that cling to the surface. This is a good identifiable characteristic of the vine in case you can't easily see the leaves. Plants are very common along fences, at the base of trees and seedlings are often found in garden beds.

Poison ivy has a characteristic compound leaf consisting of three leaflets (Hence the saying, "Leaves of three, let it be"). The leaves are 2 to 4 inches long and dull or glossy green with pointed tips. The middle leaflet is generally larger than the two laterals. The margins of the leaflets are variable, appearing irregularly toothed, lobed or smooth. The leaves are arranged alternately on the stems. Young foliage is often shiny or oily-looking with a reddish tint.

Mature poison ivy vines growing up trees flower and produce a white fruit which is readily eaten by birds. The birds spread the seeds through their droppings creating the wide occurrence of this plant. New seedlings of poison ivy are easily overlooked. They may have a reddish tint to their foliage and will appear upright. As they get older they will begin to vine and grow up nearby shrubs or trees. It is easy to come into contact with young poison ivy seedlings when weeding flower beds, so you need to be observant.

Another common vine in our area, Virginia creeper (Parthenocissus quinquefolia), is a non-poisonous vine that is often mistaken for poison ivy. It has five leaflets radiating from one point of attachment on mature leaves, which distinguishes it from poison ivy which has three. The leaflets also have a different marginal appearance.

The agents in poison ivy responsible for causing the dermatitis are various catechols. They are found in every part of the plant including the leaves, stems, flowers and even pollen. They can survive burning, and if poison ivy is burned contact or breathing of the smoke would be dangerous for people who are allergic. A significant portion of people are allergic to these catechols, and sensitivity can change over time. Just because you were not allergic to poison ivy as a child does not mean you are not allergic as an adult.

It is best to avoid poison ivy altogether, but if you do realize you have come into contact with it prompt washing may reduce the reaction. Wash with running water without using soap (soap can remove the natural oils protecting the skin and increase penetration of the catechols). There are special cleansers available at local drug stores that can be used (generally in the section with calamine lotion, a common treatment for poison ivy rashes), and you might want to keep these on hand if you have had problems in the past. Lotions are also available that, when applied to the skin beforehand, protect the individual from the catechols should contact occur.

In controlling poison ivy, one of the most important things to do is to periodically check your landscape carefully for seedling or vines. Look for the three leaflet leaves in out of the way areas, under shrubs, along back fences and by trees.

Three methods can be effective in eradicating poison ivy in landscapes. The first is hand pulling or digging out when the soil is moist; getting out as much of the roots as possible. Use long gauntlet rubber gloves available at local hardware stores or dishwashing gloves when handling the vines. Place the plants into a plastic bag, seal it (in consideration for trash collectors) and throw it away. Be sure to wash your gloves with soap and water after handling poison ivy.

The second is to carefully spray the foliage with a systemic herbicide. This is only possible when the spray will not get on the foliage of desirable plants. If needed, nearby desirable plants can be covered with plastic sheets or bags to protect them while you do the spraying. Be sure to wet the foliage of the poison ivy vine thoroughly. Systemic herbicides are absorbed by the foliage and enter the plants circulatory system which sends the material into the vines roots killing them as well. Glyphosate (Roundup, Eraser, Hi-Yield Killzall, and other brands) or triclopyr (Brush-B-Gon, Brush Killer and other brands) are commonly recommended for poison ivy control. Herbicides that contain combination of dicamba (banvel) and 2,4-D also work well. Once the vine dies it may be removed. The dead leaves still contain the catechols and should be handled cautiously with gloves.

The third method is for larger established vines growing up in trees or intertwined in the landscape. Spraying the vine foliage is not practical in these situations because of the potential to injure desirable trees and surrounding landscape plants. Poison ivy control in sensitive areas can best be achieved by the cut vine method. Cut off the vine a few inches from the ground with loppers and immediately treat the fresh cut stump with undiluted triclopyr (Greenlight Cut Vine and Stump Killer). The vine in the tree or landscape will die because it has no root system. The treated stump will die because the herbicide gets absorbed by the freshly cut surface and translocates to the roots. Applying the herbicide to the fresh cut is necessary because it prevents the stump from resprouting. This method is very effective and may be used any time of the year.

Getting poison ivy off your property will probably take repeated herbicide applications. Older vines in neighboring yards may continue to drop seeds in your landscape. Watch out for this unwelcome plant and be prompt and aggressive in your efforts to control it. Be persistent and frequent with your efforts.

3/19/2005 2:15:59 AM
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