Daniel Gill, Merrill, Thomas A. | 8/25/2006 11:54:19 PM
By Dan Gill
LSU AgCenter Horticulturist
Anyone cleaning out overgrown areas or even just weeding should beware. Poison ivy may be growing among the plants you are handling.
Plants are very common along fences and at the base of trees, and seedlings are often found in garden beds.
Recognizing Poison Ivy
Poison ivy (Toxicodendron radicans) is a tall-climbing, deciduous vine.
Because it’s decidous, now is a good time to look for it, since it will be leafless later on in the year.
As poison ivy 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.
Poison ivy has a characteristic compound leaf consisting of three leaflets – Hence the saying, "Leaves of three, let it be." The leaves are 2 inches to 4 inches long and dull green or glossy green with pointed tips. The margins of the leaflets are variable, appearing irregularly toothed, lobed or smooth. Young foliage often is shiny with a reddish tint.
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.
If poison ivy is burned, the catechols survive, and contact with 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.
While it goes without saying that it is best to avoid contact with poison ivy altogether, if you realize you have come into contact with it, prompt washing may reduce the reaction. Wash with running water, but don’t use soap, since 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 if you’ve come into contact with poison ivy. You might want to keep these on hand if you have had problems in the past. Lotions also are available that, when applied to the skin beforehand, protect an individual from the catechols if contact with poison ivy occurs.
Controlling Poison Ivy
In controlling poison ivy, one of the most important things is to periodically check your landscape carefully for seedlings 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 your landscape.
The first is hand pulling or digging it out when the soil is moist; getting out as much of the roots as possible. Use long-gauntlet rubber gloves, which are 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 plant’s circulatory system, which sends the material into the vine’s roots and kills 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 a combination of dicamba (banvel) and 2,4-D also work well.
When you use a herbicide, the vine may be removed once it dies. But keep in mind the dead leaves and vine still contain the catechols and should be handled cautiously with gloves.
The third method of removing poison ivy really applies to larger, established vines that are 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. This method involves cutting off the vine a few inches from the ground with loppers and then immediately treating the fresh-cut stump with undiluted triclopyr (Greenlight Cut Vine and Stump Killer). The vine up in the tree or shrubs will die because it has been cut off from its 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 sprouting again. This method is very effective and may be used any time of the year.
Getting poison ivy off your property probably will take repeated herbicide applications – particularly since 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.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.