Charlotte Kidd, M. Ed. is a writer, professional gardener, garden designer and garden coach in Southeastern Pennsylvania. She does horticultural programs for the Pennsylvania Horticultural Society, the Philadelphia International Flower Show and Longwood Gardens. She’s a member of the Society of Environmental Journalists and the Garden Writers Assoc. Contact her at

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Is THIS Poison Ivy?
by Charlotte Kidd    

Several weeks ago, poison ivy horticulturist Umar Mycka and I were driving to Longwood Gardens to do training about poison ivy. “Look at that,” said Mycka, pointing to the right. I saw a tall privet hedge overhanging a public sidewalk by half. He'd spotted huge leaves of poison ivy waving from deep inside the shrub.

The woman hurrying by might well have gotten a swipe of urushiol, poison ivy oil, as her left arm brushed against the leaves. I imagined her a day later, mystified by an outbreak of a red, itchy rash and oozing blisters. She would probably lament, “What is THIS? And how DID I get it?” It's poison ivy dermatitis, aka Toxicodendron dermatitis.

When was the last time you got the poison ivy rash? Did you see it coming? If not, read on. If you maybe recognized it, read on for what to do when you've been exposed.

This poison ivy seedling blends in well with the vinca in a Philadelphia garden.

The standard warning — Leaves of three, let it be- still holds true. There's much more though, explained Mycka at the first 2013 Philadelphia Poison Ivy Conference in late March. Overall, the most common poison ivy is the species and a subspecies of the robust, ubiquitous Eastern climbing poison ivy. On the East Coast and in the South we're way too familiar with this Eastern species (Toxicodendron radicans ssp. radicans). Low-growing Rydberg's poison ivy (Toxicodendron rydbergii) makes its home westward and up north. Experts talk about a new natural hybrid in New England — a cross between Eastern and Rydberg's. They won't be sure until those plants are DNA-tested.

Photo by Umar Mycka
By autumn, these Eastern climbing poison ivy leaves are as large as a hand.

Also, poison ivy leaves look different depending on their age and species, Mycka explains. Most are leaflets of three. Very mature vines can have leaflets of five and seven, he adds. Some leaflet edges are notched. Others are smooth. Some are ovate-shaped. Others are lobed. Some have a dull surface. Others are shiny! During summer, the leaves can be light green, dark green or in between. In the fall, they turn a come-hither orange, copper or scarlet. Beware! They're just as toxic to touch then.

It's no wonder we're confused. “But the poison ivy you showed us yesterday didn't look like that,” my gardening staff complains all season long. “You're right,” I agree. “Poison ivy takes lots of forms. Just stay away from anything with three leaves. And tell the rest of us so we'll steer clear too.”

If I have a can of red paint, I spray around the leaves to mark the spot. If it's a small spot, I'll apply an herbicide. A month later I'll return wearing latex gloves and carrying plastic bags with lots of newspaper to carefully pull out dead but still potent leaves, stems and roots. Plant parts go in plastic bags for disposal in landfill garbage (not yard waste).

Call professional poison ivy removers if you feel daunted, there's an abundance or if you get the poison ivy rash easily.


Poison ivy sprouts from a seed likely eaten by a bird. Easy-to-remove seedlings have a red stem. Sometimes young leaves are reddish.

The poison ivy leaf has three leaflets that join at a node. Two small leaflets connect opposite each other. The large leaflet with a long stalk (petiole) joins them at a right angle. Young poison ivy leaflets can have notched, jagged edges. Older leaves tend to be smooth-edged, Mycka has found. The leaf variations sparked his curiosity at the age of 8. He's studied poison ivy since, educating people about identification and removing it by hand without using herbicides.

In late March, this Eastern climbing poison ivy thrives on the top of a wall on a cemetery path.

Anyone walking on the sidewalk by this tree could brush against this young Eastern climbing poison ivy vine.


About 75 to 85 percent of North Americans have an allergic reaction to urushiol, the poison ivy oil, which is in all plant parts. Urushiol begins to penetrate the skin within minutes after it touches our skin. By 8 hours, the oil binds completely to the skin. Poison ivy dermatitis — skin inflammation — sets in. Unbearable itching, a red rash, blistering, oozing and scaling can occur. The misery can linger from a week to a month.

This Eastern climbing poison ivy root contains urushiol too.

Photo by Umar Mycka
Don't be deceived by poison ivy's brightly colored autumn leaves. They have urushiol too.


Prevention is the first defense, experts agree. Pay attention to the plants around you and avoid those that look anything like poison ivy.

Act fast if your skin touches poison ivy. Gently swab skin with alcohol. Or wash the area with dish or laundry detergent or shampoo and lots of water. Wash and rinse several times to remove as much oil as possible, advises Eric Boman, Department of Emergency Medicine, York Hospital, and doctor of wilderness medicine in York, Pa.

Launder exposed clothing, gloves, hats and shoes with an effective detergent. Clean tools including handles with alcohol or detergent and water.

Treating the rash is a medical problem. For a serious rash, contact your doctor immediately. For a small limited inflammation, several experts recommended the over-the-counter product Zanfel™. Bowman says Zanfel seems to have ingredients that slough off and wash away some urushiol-bound skin. “Benedryl may help with itch,” he adds. “Expect the rash to last several days.”


To help with poison ivy plant identification, biologist Tara Johnson's iPhone app Rash Plants is available for $.99 at iTunes.

In early June Umar Mycka organized Poison Ivy Identification Week. All sorts of details and information about poison ivy are on his website is

For clever, common-sense information to help identify and share stories about poison ivy, see Jon Sach's website

Photos by Charlotte Kidd unless otherwise noted.


Posted: 07/01/13   RSS | Print


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