Horticulture and Crop Science
2001 Fyffe Court, Columbus, OH 43210-1096
Jane C. Martin
Anyone who has ever experienced the blisters, swelling, and extreme itching from an unfortunate encounter with poison ivy, learns quickly to avoid it whenever possible. It grows in non-cultivated sites, such as along stream banks, roadways, fencerows, and woodlands. It can even make an appearance in your ornamental shrub or perennial borders. Therefore, knowing how to identify and control it are the best defenses against accidental contact.
The best way to identify poison ivy (Rhus radicans) is by its characteristic compound leaf consisting of three leaflets. The leaflets are two to four inches long, 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 positioned alternately on the stems. In contrast, Virginia Creeper, a non-poisonous vine often mistaken for poison ivy, has five leaflets radiating from one point of attachment.
Poison ivy can be found in one of three forms; as an erect woody shrub, a trailing shrub running along the ground, or a woody vine. The vine is usually seen growing on trees or other objects for support. It has aerial roots along the stem that give it the appearance of a "fuzzy rope." Yellowish-green flowers occur in compact clusters in leaf axils, and are produced in June or July. The waxy, berry-like fruit is grayish-white, with distinct lines marking the outer surface, and is about three-sixteenths of an inch in diameter.
|Poison Ivy--Rhus radicans|
There are three methods that can be effective in eradicating poison ivy in ornamental beds. They include hand pulling or grubbing; severing the vine and then treating the regrowth with an herbicide; or applying an herbicide to individual leaflets.
Hand pulling is most successful when the soil is moist. The roots can be dug and pulled out in long pieces. Care should be taken to remove the entire root because the plant can resprout from sections of root left in the ground. Avoid skin contact by wearing gloves while you work and washing clothing and gloves immediately after. The washing machine should be rinsed thoroughly afterward to eliminate the possibility of contaminating other clothing.
Vines growing on trees can be difficult to pull out of the ground because their roots may be entangled with the tree's roots. Sever the vine at the base and carefully pull it out of the tree. Glyphosate (eg., Roundup or Ortho's Kleeraway Grass & Weed Killer), a non-selective, translocated herbicide, can be applied to the new shoots that will soon emerge from the base of the old plant. This herbicide is most effective if applied to actively growing foliage two weeks on either side of full bloom, in early summer.
Another herbicide that may be used is triclopyr (eg., Ortho's Brush-B-Gon Poison Ivy Killer). Poison ivy is difficult to control even with herbicides. Neither glyphosate nor triclopyr will provide complete control from a single application, and repeat applications to treat regrowth may be necessary. Other herbicide brands or formulations may be found at your local garden center. Be sure to read the label to ensure that poison ivy is listed on the label, then follow the manufacturer's directions.
|Poison Ivy--Rhus radicans|
When poison ivy is found in the midst of your prized ornamental plants, special care should be taken to eliminate it. Paint the individual leaflets with a non-selective herbicide like glyphosate to avoid harming desirable plants.
The blistering rash caused by poison ivy is the direct result of contact with the oily toxicant, known as "urushiol." Urushiol is found in resin ducts within the plant's phloem. These ducts are found throughout the plant, including the roots, stems, bark, leaflets and certain flower parts. The plant has to be crushed, broken, or in some way injured to release the resin. The injury may be something as little as an insect chewing on the plant.
Once urushiol is released, it can find its way to your skin by direct contact with the plant and then spread by touching other parts of the body. Because the sticky, oily substance is easily transmitted, there are indirect ways to contact it, for instance, from the fur of the family pet, garden tools, garden gloves, clothing, golf balls or other objects that have come in contact with an injured plant. Contrary to popular belief, the rash from poison ivy cannot be transmitted from touching the oozing blisters.
If you know you have contacted poison ivy, wash the area as soon as possible with soap and cool water. Warm water may cause the resin to penetrate the skin faster. Because urushiol can penetrate in a matter of minutes, you may still get a rash, but at least you have contained the infected area. A visible reaction, redness and swelling may be apparent within 12 to 24 hours. Contact your family physician or pharmacist for recommendations for effective non-prescription medication.
One additional caution is that people can contract a rash by exposure to smoke of burning poison ivy; be careful not to burn wood with the poison ivy vine attached to it. Take extreme caution to avoid inhaling smoke or contact of smoke with skin and clothing.
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Hecht, Annabel. (1986). The itch of the great outdoors. FDA Consumer. June. pp. 22-24.
Martin, Jane. (1995). Leaflets Three, Let it Be. Ohio State University Extension Publication. Buckeye Yard and Garden Line. July 7, BYGL #14.
Schwartz, David, M. (1986). Leaflets three. Country Journal. August. pp. 42-49.
Smith, Elton, M. (1983). Poison Ivy Control. The Ohio State University. Home Yard and Garden Facts, HYG-1015-83.