|EAST LANSING, Mich. — If poison ivy had a middle name, it would be “variable.” It can grow as an upright shrub or as a climbing or sprawling vine. You can run into it in the woods, on the shore of your favorite lake, in a park or in your own backyard. Its leaflets vary in shape, with margins that may be smooth, toothed and/or lobed, and leaves may be glossy or dull or something in between.
The only advice on identification that you can rely on to be true every time is the old rhyme “Leaflets three, let it be,” said Mary McLellan, Extension Master Gardener program coordinator at Michigan State University.
“The one thing that you can count on is that leaflets occur in groups of three alternately along the stem,” she said.
Avoiding contact with any plant with leaflets in groups of three is no guarantee against poison ivy poisoning, however. The plant oil that causes the itching, inflammation, swelling and blister formation in sensitive individuals can be easily transferred to clothes, tools, other objects or pets. It’s also present in the smoke from burning poison ivy.
“Direct contact with the plant is the usual route of exposure, but it’s not the only one,” McLellan said. “Touching something that has touched poison ivy and picked up the oil or encountering smoke from burning plants can also cause poisoning.”
People vary in their sensitivity to poison ivy. Even people who know they’ve been exposed to it without developing symptoms should try to avoid it - sensitivity can develop with repeated exposure.
All parts of the plant contain and secrete the oil that causes poisoning, and it’s present all year round, McLellan explained. This makes controlling poison ivy difficult.
“In the home grounds, it’s often involved with landscape plants, having grown from seeds deposited by birds that ate the waxy white berries,” she observed. “Digging up the plants presents the risk of poisoning, and unless you get all the roots, may not be effective. Herbicides are an option, but if vines are growing up through other plants, it may be impossible to treat the vines without damaging the other plants, too. If you do successfully kill it, you can either remove it - carefully! - or allow it to decompose in place.”
Any tools used around poison ivy should be cleaned with alcohol. Skin that’s come in contact with the plant should be washed with alcohol or a strongly alkaline soap such as yellow laundry soap or naphtha - ordinary hand soap is too mild to remove the oil completely. Clothing that may be contaminated with the oil should be washed in hot water with an alkaline detergent. The person handling the clothing should assume he/she has picked up some of the oil and clean skin with alcohol or alkaline soap to avoid being poisoned.
This farm news was published in the April 12, 2006 issue of Farm World.