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Poison Ivy

 

 by Cynthia (Sid) Taylor

Anyone who frequents the woods should learn to recognize poison ivy and poison oak. For the susceptible individuals the dermatitis resulting from contact with the oils (urushiol compounds) can be a very unpleasant and debilitating experience.

Common in our area in moist woods is Poison ivy, Toxicodendron radicans (syn. Rhus radicans). Its range is broad in North America. It ranges from Nova Scotia to British Columbia; south to Florida, Texas and Arizona.

Not so common in our area is Eastern poison oak, Toxicodendron toxicarium (syn. Toxicodendron. pubescens and Rhus toxicodendron). It grows in dry, scrubby habitats in Levy and Marion Counties.

Its range is chiefly coastal plains. It ranges from New Jersey and Maryland south to Florida, (Levy and Marion Counties); Tennessee to eastern Oklahoma south to Alabama and Texas. Toxicodendron radicans and Toxicodendron toxicarium both have alternate, trifoliate leaves, having three leaflets per leaf blade (petiole). They can also be distinguished by their differing growth habits.

Poison ivy is a climbing or trailing vine. The stem can reach the diameter of 10 cm or 4 inches. The leaves can be up to 30 cm or 12 inches long and 12 cm or 4 3/4 inches wide. Dangling aerial roots develop. The leaflets are lobed, coarsely toothed, with pointed tips. The leaf surfaces are lustrous above and pale below. The fruit clusters are white, glabrous (without hairs) and should NOT be handled due to the toxic oil present.

Poison oak appears 'oak-like' having scalloped edges to the lobed leaflets. The leaf blades are shorter than the leaflets themselves. It grows erect as a smallish shrub, not vine-like, or ivy-like. The flowers grow on a very short stalk, and are pubescent (hairy).

One must come into direct contact with the oil of Toxicodendron to be effected by the skin irritating compound urushiol. Petting an animal's fur that has brushed against the plant can cause a reaction.

In addition, clothing or tool surfaces can retain the oil residue for up to a full year. Allergic individuals have had eruptions of dermatitis in their esophagus from breathing the smoke of burning brush piles containing poison ivy or poison oak.

Urushiols are oil soluble. Washing as soon as possible with a NON-oil based soap (without tallow) is a good preventative to breaking out. Scrub under the fingernails to remove potential oil. Exposed clothing should be laundered immediately and by itself.

Toxicodendron radicans frequently grows adjacent to Virginia creeper or Woodbine (Parthenocissus quinquefolia) of the Grape family. The usual distinction is the five leaflets of the Virginia creeper. Be aware - poison ivy has an aberrant form of five leaflets also.

A person's allergic reaction can vary through out ones life. Regardless of ones susceptibility, we should all avoid contact with these plants. The first allergic eruption can be the most severe. Give these plants a wide berth. It is wise to become aware of both species to help yourself and others to avoid contact with them. Encourage others to learn to recognize the plant.

Happy woods stomping, but stay out of the Toxicodendron!

 

Coile, Nancy C. Poison-ivy (Toxicodendron radicans (L.) Kuntze) and its Relatives in Florida Fla. Dept of Agric. & Consumer Services, Division of Plant Industry: Gainesville, FL. Botany circular No. 31, March/April 1996

Duncan, Wilbur H. Woody Vines of the Southeastern United States. University of Georgia Press: Athens, GA 1975

Godfrey, R.K., and J.W. Wooten. Trees, Shrubs, and Woody Vines of Northern Florida and Adjacent Georgia and Alabama. University of Georgia Press: Athens, GA. 1981 (illustrations used)

Grimm, Carey. The Illustrated Book of Wildflowers and Shrubs. Stackpole Books: Harrisburg, PA. 1993

Nelson, Gil. The Shrubs & Woody Vines of Florida. Pineapple Press: Sarasota, FL. 1996

Radford, Albert E., H. E. Ahles and C. R. Bell. Manual of Vascular Flora of the Carolinas. University of North Carolina: Chapel Hill, NC. 1964

 

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