“Leaflets of three, leave them be.” If you’ve tramped through a prairie, a woodland or any kind of untamed area, you’re familiar with this saying and the native plant it’s referring to. Poison ivy, Toxicodendron radicans, is a member of the cashew family. (Yes, that means cashews, eaten raw, would be poisonous but handling and treatment have rendered these quite palatable.) Poison ivy is notorious for the itchy rash it causes and readily spreads to other parts of the body.
Just so you know, poison oak and poison sumac do not grow in this part of the Midwest, so don’t worry about finding these during your hikes. Being able to identify poison ivy so you can show it a healthy respect, however, is necessary to giving it a wide berth.
Each leaf of poison ivy consists of 3 leaflets, arranged triangularly. The two leaflets forming the base of the triangle will often be shaped like mittens, with serrations on both sides of the center leaflet. Seedlings of the native boxelder resemble poison ivy but can be distinguished from poison ivy by the leaf attachment to the stem. Boxelder will have opposite leaves; poison ivy alternate leaves.
Poison ivy produces ¼-inch sized fruits that birds eat and “plant” in new locations. It is extremely adaptable, growing in the shade of wooded areas but can also create stands in the glaring sun of graveled roadsides.
All parts of the poison ivy plant contain urushiols, the oily compounds responsible for the reaction in humans. Most animals do not react to poison ivy, but pets walking through poison ivy can retain the compounds on their fur, posing a problem for us when we pet them. Urushiols are slow to break down, so touching dead roots, stems, or leaves, even years later, will still cause problems. Washing skin with an over-the-counter soap (found at pharmacies) neutralizes the harmful compounds.
Eradicating poison ivy is best done with herbicides labeled for use on brushy plants. Persistence will be necessary as it is unlikely one herbicide treatment will be enough to take care of it. Be sure to wear chemical-resistant gloves, long sleeves and long pants when working in areas where poison ivy is present. Clothing should be washed separately from the rest of the family laundry.
Oddly enough, some people who have never had a reaction to poison ivy can develop one as they age. The opposite is true too—some people who have always reacted to poison ivy can develop a tolerance to it over time. Regardless, one thing that should never, ever be done is to burn poison ivy. The rash that it causes on skin can develop on the inside of lungs, rendering difficulty in breathing and potentially causing death.