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July 2009  Poison Ivy

“Leaves of three, leave it be” an old saying that is supposed to help us avoid Poison Ivy. However, what is just as important is to recognize the many other plants that also have the three leaflet configuration.

 In most of Western North Carolina, as well as along the Greenway, one finds the Kudzu growing rampant over fence, bush and tree. It has three leaflets quite similar to Poison Ivy. But one notes the thinner leaf and the red hairs along the stem. Kudzu teeth are more rounded instead of pointed, and the underside of the leaf is a lighter green.

 The Tick Trefoils and the Wild Beans also have three leaflets. They are usually smaller, more delicate plants than PI, and are readily recognized when in flower or seed.

The small clovers and the bush clovers also have three leaflets. As does Sorrel and Alfalfa.

 

Other vines such as the Butterfly Pea, Hog Peanut, Dewberry, Wild Strawberry and Blackberry are among those with leaflets three. The last three have sharply toothed leaves which aids in identification.

 

In shaded areas we find the lovely trilliums and Jack-in-the-pulpit with their three large leaves outstanding for their perfect circular arrangement.

 Even among the trees and shrubs we find the pattern of three leaflets. The Prairie Rose usually has but three leaflets, and the Bladdernut, the Fragrant Sumac and Wafer Ash all comply.

So what other features do we look for to really avoid this plant that drives many folks slightly crazy with a seven day itch?

 The Poison Ivy plant can be shrub-like in that, with its woody stems, it can stand upright along the forest floor or along a path.

 It can take on a vine-like appearance and climb up a large tree truck, stretching out its stems like limbs to gain some sunlight. As it gets larger and healthier the climbing portion thickens and develops black hairs all along the main stem. These hair-rootlets cling to the bark and hold it in place allowing the plant to reach the full height of the tree, which may be 40 to 50 feet up. Eventually the leafy parts may completely cover and shield the top of the tree from the sun, thus killing it.

 Its greenish flowers in April-May are in small bunches growing from the leaf axils. The fruit are small gray or whitish berries, that develop in August to October, and are much loved by many species of birds.

This year poison ivy is especially large with rampant growth. Perhaps it's catching up for the drought years.

 All parts of the plant: stem, leaves, flowers, fruit and the roots hold the oils responsible for the skin rash that many humans get. When the leaves fall off in the fall the woody stem remains upright along the ground, or sticking out from the tree. The tiny buds are pointy, brownish, and slightly hairy.

 Poison Ivy (Rhus radicans) and Poison Oak (Rhus toxicodendron) are similar plants. Leaf shapes are somewhat diagnostic. Poison Oak leaves are usually lobed, or more coarsely toothed and will be found more often in the Piedmont and eastern parts of North Carolina than here in the mountains. Growth is very similar.

Accidentally burning the plant parts that might be still clinging to a piece of wood, can release the oils into the water vapor coming off in the smoke and can irritate nose and throat tissues. It behooves us to learn to recognize Poison Ivy. It's not a friendly plant.