Poison Ivy: Identification and Control
Kevin W. Bradley
State Extension Weed Scientist
Division of Plant Sciences
Although poison ivy (Toxicodendron radicans) is easily identified and should be avoided, countless people experience an uncomfortable
Poison Ivy: Identification and Control
Kevin W. Bradley
State Extension Weed Scientist
Division of Plant Sciences
Although poison ivy (Toxicodendron radicans) is easily identified and should be avoided, countless people experience an uncomfortable introduction to the species. A mere touch of the foliage can result in a blotching of the skin and burning water blisters, which cause the flesh beneath to swell and itch intensely. Symptoms may become evident within a short time after exposure, or they may take a few days to appear. Usually, exposure leaves no scars, and general health is not impaired.
All parts of the plant, including stem and roots, contain and secrete a nonvolatile oil called urushiol, which affects the skin. Because the oil is insoluble in water, washing with water alone merely spreads the oil to other areas and increases the discomfort. However, washing with a strong alkali soap such as yellow laundry soap or naptha will relieve the discomfort. Alcohol will dissolve and remove the oily substance from the skin, and, if applied soon enough, will prevent irritation.
Burning poison ivy after it has been cut or grubbed out and dried can be hazardous because smoke can cause the same symptoms. Inhaling the smoke can result in serious consequences.
Poison ivy can be found as a low-growing shrub, can grow as a trailing vine along the ground, or can occur as a vine that climbs to the top of the tallest tree. Aerial rootlets enable the vine to attach itself to other plants or objects nearby. Poison ivy is a perennial with woody rhizomes, which are underground creeping roots, so control of this species can be difficult.
The leaves of poison ivy are readily identifiable and help to distinguish it from most other weed species. The leaves are compound, with three leaflets that occur alternately along the stem. Leaflets may have smooth, scalloped or irregularly toothed margins (Figure 1), but typically the lateral two leaflets have irregularly toothed outer leaf margins and smooth, untoothed inner leaf margins. The leaf surface may or may not have a waxy or oily appearance. Leaves can occur in a variety of colors on the same plant, but leaflets typically have a greenish-red cast when they first emerge in the spring, then turn dark green throughout the summer, and eventually turn red, orange or yellow in the fall.
The fruit of poison ivy is a smooth, greenish-white berry with a waxy appearance. It grows in clusters the size of small currants. Each berry contains a single seed. Birds and other wildlife feed on the berries and consequently spread poison ivy in their droppings.
Although poison ivy is relatively easy to identify, other weedy species have similar characteristics. Fragrant sumac (Rhus aromatica) with three leaflets is commonly confused with poison ivy. However, this species differs in that both fruit and leaves may be hairy.
Virginia creeper (Parthenocissus quinquefolia), also called woodbine, is found throughout Missouri. An aggressive vine, it will grow to the top of the tallest tree. It can be readily identified and distinguished from poison ivy by the five leaflets making up the compound leaf. Neither Virginia creeper nor fragrant suma