“Leaves of Three, Leave it Be.” Easy Right? Well, Not Really.

Leaves of three, leave it be. This common phrase is taught to children all over Michigan. It’s a convenient rhyme meant to steer you away from touching poison ivy and getting a rash. However, this concept is not quite as clear-cut as it seems. There are several other native plants (yes, even though you may hate it, poison ivy is native) that have leaves in configurations similar enough to poison ivy to cause confusion. There is also the fact that it’s not only the leaves you have to avoid, the stems and roots contain the same oily resin. Besides, what do you do in the winter when the leaves fall off the plants? Poison ivy can both creep along the forest floor and climb woody structures like trees. Do you think you’d be able to spot the climbing kind without its leaves?

Well, unless you want to test it in a real life experiment you might want to take a look at this article from Michigan State University Extension on how to identify the plant.

Identifying poison ivy isn’t always easy to do

Don’t spoil your summer fun by coming in contact with poison ivy; learn to identify it so you can avoid it.

Poison ivy is a plant you should learn to identify so that you can avoid it. An oily resin called urushiol, which is found in all parts of the plant, is what causes skin rashes when people come in contact with it. People vary in their sensitivity to poison ivy, but may become more sensitive after repeated exposure to it. One common misconception is that the poison ivy rash itself is contagious. The fluid in the blisters of a poison ivy rash does not contain urushiol and won’t cause the rash to spread. You won’t get poison ivy unless you come in contact with the oil still on someone’s skin or clothing.

Urushiol is easily transferred to clothing, skin, tools or pet’s fur. If contaminated objects aren’t cleaned, contact with the oil on them can cause skin reactions much later. Poison ivy should never be burned as the smoke from burning poison ivy contains the oil and can irritate lungs and nasal passages as well as skin and eyes. See the Michigan State University Extension Bulletin E2946 for more information on how to control poison ivy.

Poison ivy is a very widespread and prolific plant, frequently appearing along the edge of roadways, paths and other disturbed areas. One reason for its wide distribution is due to the fact that its berries are eaten by birds and deer. Over 60 species of birds have been documented to eat poison ivy berries. The seeds are not digested, but pass through the intestinal tract to be deposited throughout the active ranges of animals that eat them. Unlike humans, the animals eating the berries do not become sensitized to the volatile oils and do not experience allergic reactions to the plant.

Poison ivy can be a bit of a chameleon. It looks similar to several common backyard plants including Virginia creeper and boxelder. The leaves of poison ivy may be shiny or dull and the leaf margins may be toothed or wavy, or have no teeth at all. The leaves may be hairy, or have no hairs at all. Its appearance can vary greatly, but in all cases it has compound leaves that consist of three leaflets. The leaflets are 2-5 inches long, green during the growing season and turning scarlet red in fall. The leaves are arranged in an alternate pattern on the stem. The terminal (end) leaflet has a longer stalk than the lateral (side) leaflets.

Poison ivy Poison ivy Poison ivy with flowers
Poison ivy leaves showing variation in appearance. The picture to the right shows poison ivy flowers. Photo credits: Mark Czarnota, University of Georgia, Bugwood.org (left); David Cappaert, Michigan State University, Bugwood.org (middle); and Catherine Herms, The Ohio State University, Bugwood.org (right)

Poison ivy flowers in spring and produces dense clusters of white berries that ripen from late summer through fall and persist through the winter. Poison ivy can take the form of an erect shrub or climbing vine or grow in large colonies along the ground. Poison ivy has aerial rootlets that it uses to attach to the bark of trees. The rootlets have a hairy appearance. Twigs of poison ivy may be covered with fine hairs. The bark of poison ivy is gray.

Poison ivy roots Poison ivy berries
Left, Poison ivy aerial roots. Right, Poison ivy berries in fall. Photo credits: Joseph LaForest, University of Georgia, Bugwood.org (left) and Ohio State Weed Lab Archive, The Ohio State University, Bugwood.org (right)

Virginia creeper, like poison ivy, has brilliant red fall color. Virginia creeper is a vine, closely related to grapes. Its leaves have five leaflets, although very young plants may have some leaflets that appear in threes. The leaves are arranged in an alternate pattern on the stem. It produces small clusters of greenish flowers in spring that mature to blue berries in fall. Although it clings to trees like poison ivy, unlike the distinctly hairy looking aerial roots of poison ivy, Virginia creeper adheres to trees and walls with small, circular pads on the ends of tendrils.

Virginia creeper Virginia creeper blueberries
Left, Virginia creeper has five leaflets and tendrils with circular pads that adhere to trees and walls. Right, Blueberries of Virginia creeper. Photo credits: John Cardina, The Ohio State University, Bugwood.org (left) and James H. Miller, USDA Forest Service, Bugwood.org (right)

Young seedlings of the boxelder tree superficially resemble poison ivy. Boxelder seedlings grow to become large trees with green twigs and alternate compound leaves with three to seven leaflets. Boxelder is in the maple family, and is sometimes known as ash-leafed maple. Boxelder has yellow fall color, lacks the hairy aerial rootlets and does not have berries. The fruits are the typical maple seeds called samaras.

Boxelder leaves
Boxelder leaves. Photo credit: Paul Wray, Iowa State University, Bugwood.org


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