Poison Ivy: Leaves of Three, Let It Be

It’s springtime, and as you come out into the yard, the garden, the woods, and the playgrounds, you’ll want to know how to identify Poison Ivy (Toxicodendron radicans), which is also coming out again.

By mid-summer this creeping, crawling tyrant will take over the woodland walking paths, the roadside shoulders, and the sidewalks in many areas of the Eastern United States and elsewhere. It will cover the chain-link fences and the trunks and branches of trees on the edges of woodlands and parking lots. It can climb just about anything; and it can grow independently as a bush, a woodland undergrowth up to 4 feet tall, or a low-lying ground cover in areas that get enough sunlight.

Leaves of Three, Let It Be

This old adage reminds us that poison ivy leaves always occur in threes. Each trio of leaves has its own stem, and the stems can be red or green. The leaves are oblong and pointed, and they may or may not have one or more large notches along their edges. New leaves may be red and glossy, turning matte and green as they mature, and then turning beautiful vibrant red, orange and yellow in the fall. The leaves drop in autumn, but they remain toxic. The brown or gray vines, branches, and roots are alive and noxious all year long. The vines of poison ivy can get very thick, often obscuring the tree that hosts them, and these vines may be covered with red, brown, or gray hairs. Poison ivy produces tiny white flowers in clusters, and then green berries that turn white.

There are no thorns and there are no tiny, serrated saw-tooth edges on the leaves of the poison ivy plant. This will help you to identify it and to distinguish it from wild blackberry or raspberry plants, which also have leaves of three. (All of the photos in this article are poison ivy.)

Urushiol Oil

The roots, branches, vines, berries, flowers, and leaves of poison ivy contain urushiol oil, the active component that causes the infamous rash. This liquid oil, found in the milky sap of the plant, can remain active on any surface for many years. (Dead poison ivy is not dead.) You need a solvent like alcohol to dissolve urushiol oil. Washing with water will not remove it from your skin, your clothes and shoes, your pet, your garden tools and food, or your wild edibles. In fact, washing with water or even with oil-based soap can spread the oil.

Humans are the only animal known to suffer the poison ivy rash. If your pets get into poison ivy, they probably won’t get sick, but they can transfer the oil to you via their fur.

One day after exposure to even a miniscule amount of this oil, a susceptible person develops a terribly itchy rash. At two days, small blisters appear. After four days, large blisters develop, burst, and ooze. Total healing time may take up to 4 weeks.

If any part of the poison ivy plant is burned and the smoke inhaled, the rash can occur in the lungs, being extremely painful and possibly fatal. Smoke carries the urushiol oil, and exposure can lead to a rash that covers your entire body. Mowing, raking, weed-whacking, or hand removal of this plant can also be hazardous.

Eating poison ivy can damage the mucus lining of the mouth and digestive tract, so foragers and gardeners, please take heed. Always be absolutely certain there is no poison ivy (or other poisonous plant) near the wild edible plants that you choose when foraging or the foods that you pick from your garden.

Toddlers and young children may be attracted to the pretty poison ivy leaves or berries that cover the fences of playgrounds. Children may be tempted to swing on the thick Tarzan-like ropes of poison ivy vine that drop straight down from the high branches of trees in the woods. I did this myself as a child, but this is certainly not advisable.

Not everyone reacts to urushiol oil. An estimated 15% to 30% of people are immune to poison ivy, but this immunity may come and go. I haven’t experienced this rash, but now that I’m older and slightly wiser, I’ll err on the side of caution with this plant.

As an interesting side note, poison ivy is a big consumer of carbon dioxide. As CO2 levels have risen, the appearance of poison ivy and its levels of toxicity have also increased. Is poison ivy a natural defense mechanism, nature’s response to human activities? Maybe, maybe not, but food for thought.

Poison Ivy



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2 Responses to Poison Ivy: Leaves of Three, Let It Be

  1. S. Thornhill says:

    Laura – my father always gave us this little warning and growing up in the “hills” of Pennsylvania, I learned to heed it well! Thank you for all the information, I love how you sum up everything all nice and neat and with photos!

    • Laura says:

      Thank you for your kind words, Stacie. A little information goes a long way with poison ivy. Enjoy playing outside this spring. xo

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