Leaves of Three
First published on garden.org on March 29, 2007, by Suzanne DeJohn
Springtime in the South -- when gardeners' thoughts turn to tulips and trilliums, bluebirds and bluebells. And for some of us, poison ivy. If you've ever had to endure the maddeningly itchy rash, you're not alone. Four out of five people develop skin lesions upon exposure to poison ivy, or more specifically to urushiol (oo-roo-shee-all), the oil contained in the sap. Approximately 350,000 cases of poison ivy-related dermatitis are reported each year. (I don't know about you but I get poison ivy every summer and I've never reported it to anyone except my long-suffering husband, so I'm betting that the number of actual cases is much, much higher.) On the misery index, poison ivy rivals toothaches and long lines at the DMV.
Identifying Poison Ivy
The National Park Service Public Health Program, on the other hand, suggests avoiding alcohol because it will spread the urushiol, and instead suggests washing with soap and cold water (cold water because hot water will open the skin's pores, allowing the urushiol to enter).
With some hundreds of thousands of cases of poison ivy reported each year, and likely millions of unreported ones, you'd think researchers would have a definitive answer on something as simple as the alcohol vs. soap question. But I suppose we'll each have to figure out what works best. Keep a stash of rubbing alcohol, soap, or purchased poison ivy treatment and some disposable gloves with your gardening supplies for poison ivy triage. If you can do the initial washing outdoors, you'll avoid bringing the oil into the house. Of course, the practicality of this will depend on how much clothing you need to remove and/or the proximity of your neighbors.
If you need to get rid of poison ivy in a small area, you can try smothering it by covering the area with newspapers or cardboard and a thick layer of mulch. You'll have to keep an eye on it to make sure the vines don't find a way out. If you're not allergic you can try pulling young vines with gloved hands, but know that repeated exposure can lead to an allergic response even if you've never had one before. Poison ivy holds the honor as the only plant I'll treat with glyphosate herbicide. I can't smother it because the vines are everywhere, and I'd likely end up in the hospital if I tried. I certainly can't pull it out. Used judiciously, glyphosate herbicide is probably the safest treatment.
If it seems like there's more poison ivy around than ever before, you may be right. Poison ivy prefers "edge habitats" -- disturbed areas near woodlands. With development reaching further and further into previously wooded areas, poison ivy is finding a perfect niche where civilization meets wilderness. Other woody weeds, such as Japanese honeysuckle, are also thriving.
The proliferation of poison ivy may be yet another negative impact of global warming. Duke University researchers conducted a six-year study using growth chambers to assess the impact of elevated atmospheric carbon dioxide (a leading cause of global warming) on poison ivy growth. They discovered that higher carbon dioxide levels increased photosynthesis, water use efficiency, and growth of poison ivy -- more so than for other woody plants. And the plants produce an even more toxic form of urushiol under these conditions, too. When it comes to the impact on my everyday life, the other ramifications of global warming -- melting polar ice caps, rising sea levels -- are relatively remote. The threat of more vigorous and more toxic poison ivy really hits home.
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