Wild Ideas: Poison ivy, the sneaky plant

Measles make you bumpy 

And mumps’ll make you lumpy 

And chicken pox’ll make you jump and twitch 

A common cold’ll fool ya 

And whooping cough can cool ya 

But poison ivy, Lord’ll make you itch!! 

 – “Poison Ivy,” by Jerry Lieber and Mike Stoller 

As a kid growing up in Virginia, I learned early to spot the trio of shiny leaves – “leaves of three, let it be” – that spelled disaster if I touched it. Already prone to contact dermatitis, when I brushed up against poison ivy (Toxicodendron radicans) I could expect my reward would be a persistent rash that itched and oozed, leading to sleepless nights and misery for weeks in the hot, humid days of summer. And even if I was careful, my dog wasn’t. Impervious to urushiol, the oily substance that triggers the itch, all my dogs have been happy to share it with me.

Poison ivy leaves appear to be growing out of a black locust, but a closer look reveals the branch came from huge intertwined poison ivy vines.
Pam Owen | Rappahannock News
Poison ivy leaves appear to be growing out of a black locust, but a closer look reveals the branch came from huge intertwined poison ivy vines.

Urushiol is also found in other native plants in the Toxicodendron genus, including Poison Oak and Poison Sumac, but poison ivy is more pervasive and a shape shifter. It takes the form of a shrub when no upright support is available, often blending into Virginia’s subtropical tangle of plants along forest edges. When trees are available, T. radicans can wrap its hairy vines around them, growing several inches thick as it climbs up the tree. Being the only native vine that’s hairy, at least it’s easier to spot in that form.

According to the Poison Ivy, Oak, and Sumac Information Center, the name “poison ivy” was coined by Captain John Smith in 1609, and the earliest public records of the plant date back to that era. Not an ivy at all, it is actually in the pecan plant family (Anacardiaceae). Although it doesn’t produce tasty nuts, T. radicans is important to an array of wildlife that feed on its flowers and, in the fall and through the winter, on its whitish berries.

Rhymes that help to spot poison ivy

“Leaves of three, let it be.” “One, two, three? Don’t touch me.” “Longer middle stem, stay away from them.” “Hairy vine, no friend of mine.” “Raggy rope, don’t be a dope!” “If it’s got hair, it won’t be fair.” “Berries white, run in fright” or “berries white, danger in sight.”

Source: Wikipedia

Unlike some other plants and animals that are becoming extinct as temperatures rise globally, T. radicans is quite happy with increased carbon dioxide in the atmosphere and the rise in heat it causes. Duke University scientists who dispersed carbon dioxide into the air in test plots in Duke Forest at levels similar to those predicted to occur on Earth in 2050 found that poison ivy grew 149 percent faster and produced a concentration of urushiol that was 153 percent higher than vines grown in control plots.

There are a variety of ways to combat contact with urushiol. On family apple-picking outings in the western Piedmont, I usually brought back rashes along with apples until an orchard owner sent me down to her spring with a bar of lye soap to scrub myself before going home. While lye soap can remove urushiol, there are other substances available that are kinder to the skin. Jewelweed, a common native plant, was likely used by native people before Europeans arrived but seems to have had a rebirth in popularity and is now easy to find in soap form. Tecnu, a manufactured product, also works well for me. Whatever the stripper, it should be used as soon as possible after exposure.

A variety of remedies are also available for getting rid of the rash after the fact, although I’ve never found any to be particularly useful other than to relieve the itch a bit. As the Information Center points out, “Everyone appears to react slightly different to all the remedies.”

I’ve had a lot of discussions over the years about how many people are allergic to poison ivy. Sources vary, but the range seems to be from 15 to 50 percent. According to most sources, the allergic reaction seems to come down to the frequency and concentration of exposure – the more contact, the more our immune systems are likely to react. Only contact with urushiol can cause the rash, so if the oil can be thoroughly removed in time, a rash won’t occur. If urushiol is removed after the rash appears (not a pleasant process), the rash will not spread. Burning poison ivy is bad idea because breathing in the smoke can cause an allergic reaction in the lungs, according to a National Institute for Occupational Safety and Health pamphlet, “Protecting Yourself from Poisonous Plants” (cdc.gov/niosh) which offers suggestions on dealing with exposure to urushiol.

While it’s good to remember that the tri-leafed stems of poison ivy help in identifying it, there are other plants with similar structure, and its leaves are not always shiny or red and can be a lovely matte green – and the plant can take surprising forms. I was reminded of that one day when my brother and I, walking down around one of the lower ponds, saw a branch over our heads that we couldn’t easily identify. I took hold of the branch to get a closer look at the leaves.

The branch was more than 10 feet long and appeared at first glance to be growing out from a 30-foot tree. It had lovely smooth, gray bark and three leaflets on each stem, with the main stem longer than the one with the other two leaflets. I thought of poison ivy but dismissed it because the branch seemed to be coming from the tree.

While I was looking at the leaves, my brother tracked back to the tree and found it came from one of several thick, intertwining poison ivy vines wrapped around the tree and extending more than 30 feet up to near the crown. The leaves that were left on the tree, a Black Locust, were barely discernible through the thick foliage of the poison ivy. Fortunately, I had not touched the leaves, and the bark of the branches is less likely to have urushiol than the rest of the plant, but I still scrubbed my hands with jewelweed soap when I got back to the house.

So, keep your eyes peeled, think before you touch any plant, and keep the jewelweed soap, Tecnu, or both handy. It’s going to be a long, hot summer.

Pam Owen
About Pam Owen 341 Articles
Writer, editor, photographer, and passionate nature conservationist living in Rappahannock County, in the Blue Ridge Mountains of Virginia. Two favorite quotes: By E.O. Wilson, who coined the term "biodiversity," "Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction”; by Douglas Adams, “I love deadlines. I love the whooshing sound they make as they pass by.”