The definitive guide for how to identify poison ivy, treat poison ivy rashes, and remove this bothersome plant.
Don't let the beautiful red fall leaves deceive you.
If you spend any amount of time in the outdoors, you probably know the saying, “Leaves of three, let ‘em be,” as well as you know those menacing leaves of three. Poison ivy, along with poison oak and poison sumac, might cause more misery than any other plant in North America; up to three out of every four people are sensitive to it. Poison ivy thrives in a wide range of places and is growing faster – and more potent – than ever before.
Once you’ve experienced a poison ivy rash, you won’t likely forget it. Inflamed red streaks form on the affected area, accompanied by a maddening desire – no, need – to scratch, made worse by the knowledge that scratching is the absolute worst thing you can do. Soon, small watery blisters form, popping and weeping. Contrary to common belief, these will not spread the poison ivy rash. Rashes on your face, between your fingers and toes, under your arms, or yes, in your groin, can also cause painful swelling. Hang in there; it’s going to be a rough week or two, possibly more.
All of this misery is thanks to a resinous oil, called urushiol, found throughout the plant – in its leaves, stems, berries and roots, pretty much everywhere. Poison ivy produces urushiol as waterproofing, not for defense; humans, lucky as we are, are the only species “blessed” with sensitivity to the stuff. Deer snack on the leaves, birds devour the berries (and incidentally, spread new plants, neatly fertilized, wherever they take a “comfort stop”), and dogs and cats roll happily in poison patches – and then bring the oil home to us.
A little bit of urushiol goes a long way; enough to coat the head of a pin can have up to 500 people scratching in misery. It travels easily, transferring to Fido’s fur, your boots, your jacket, even the rake handle you used during last fall’s cleanup, then to you. Most times, you won’t even know you’ve been exposed to poison. That is, until the itching starts.
Urushiol is also incredibly stable, surviving up to five years, possibly longer, before it breaks down. This can make disposal tricky. Bag it up and send it to the landfill, or bury it deep – very deep. Don’t try to compost poison ivy green waste, and definitely do not burn it: Urushiol easily survives the temperatures generated in most brush and leaf fires. Worse, it permeates the smoke as a fine airborne mist. Breathing oil-laced smoke can be fatal, causing a reaction inside your lungs, sending you to the emergency room. Woodcutters beware.
Oddly enough, urushiol itself is harmless; your own immune system creates all the misery. Once the oil soaks into your skin, your immune system identifies it as an invader, producing histamines to protect itself from attack. Instead, they betray your body, attacking the oil-soaked skin, creating the itching rash, blisters and swelling we all dread. The reaction can happen within one to four days after exposure, and can last up to three weeks.
Now for some good news. If you know you’ve been exposed to urushiol, you can wash it off with lots of cold water. Don’t waste time; you only have a half hour or so before it soaks into the skin. You can also try an over-the-counter soap formulated to denature urushiol. Do NOT take a hot shower. Hot water opens the pores in your skin, allowing the oil to soak in even faster – and that’s the last thing you want.
Sometimes you just can’t avoid an allergic reaction, but there are a few things you can do to ease the rash a bit. Oatmeal baths, Calamine lotion and other remedies can offer some relief. Stems of wild impatiens (Impatiens capensis), also known as touch-me-nots or jewelweed, contain a gel similar to aloe, which can also soothe poison rash. Interestingly, studies using purified impatiens gel showed no apparent benefits, but I can tell you from personal experience, the raw gel helps.
While most antihistamines won’t relieve the reaction, sedating types like Benadryl can help you fall asleep. Anyone who has ever had a poison rash can tell you what a blessing that can be. A bad rash will keep you up for hours. A hot shower can also provide some temporary relief and help you get to sleep.
Most poison rashes will fade on their own within three weeks, with no medical attention, but severe cases may need professional care. Dr. Pamela Weaner, a primary care physician practicing in Pennsylvania, offers this advice: “Seek medical attention if the rash is widespread and symptoms are not controlled by home remedies, there is swelling in affected area like genitals and face, and signs of secondary bacterial infection like pus and fever.” Your doctor will likely administer a steroid treatment for the oil reaction. Antibiotics may also be needed to fight secondary infections. Seek medical attention if you have difficulty breathing after burning leaves, brush or firewood.
The best way to deal with a poison rash is to avoid contact in the first place, and for that, identification is key. As the saying goes, poison ivy always has compound leaves with three leaflets. However, so do many other plants. With poison ivy, there are a few other details to look for: The center leaflet always has a longer stalk, the leaves will always be staggered on the stem, and the long leaf petioles will resemble miniature celery stalks. Be very careful getting close enough to see these details. The leaves will also either be teardrop shaped or toothed like holly or oak leaves. They are actually rather handsome, with a deep glossy green, flaring to yellow, orange and red in early autumn. Poison ivy berries are also distinct, resembling small, loose clusters of tiny, waxy white grapes.
The plant itself grows in a variety of patterns. Usually, it will climb walls, trees, poles and posts – but not always. Poison ivy can also sprawl across the ground or tumble over sand dunes like a ground cover. It even grows as a shrubby bush. Vines also form aerial branches, turning poles into a fair impression of leafy Christmas trees, disguising posts as bushes, and hiding their own leaves among the branches of the trees they’re climbing. Be careful of those low-growing branches, especially if they look different from the rest of the tree.
So how do you identify poison ivy after it loses its leaves? Identification may actually be easier in the winter, if you know what to look for.
First, you need to know how poison ivy climbs. It grips its support with tiny aerial rootlets all along the stem. This provides two clues for identification. Poison ivy vines either grow straight up, or zigzag back and forth as they climb. They don’t spiral up a tree trunk. As a vine ages, it also produces so many rootlets that it starts looking hairy or woolly.
Second, poison ivy’s aerial branches stretch horizontally out into space before sweeping upwards at the tip. They don’t branch very much, which makes whatever the vine is growing on begin to look like a bottlebrush or artificial Christmas tree.
Poison ivy likes to live on the edge – literally. It prefers tree lines, fencerows, roadsides, creek sides, even the cracks between sidewalks and walls. It takes advantage of disturbed places like vacant lots, field edges and construction sites. As we continue to develop new land into fields and subdevelopments, abandoning old sites to decay, poison ivy grows with us, claiming new territory at a terrifying rate.
If that sounds bad, the situation is worse. We are feeding poison ivy, fueling its expansion with increasing levels of atmospheric carbon dioxide. Poison ivy is bigger, greener, and more potent than ever before. Urushiol is twice as strong in today’s poison ivy as it was 50 years ago. And the rate is accelerating.
Are we doomed to scratch ourselves to death? No. Poison ivy can be removed safely with a little planning, effort and extra-careful handling. The trick is to physically remove it whenever possible, even though that means handling the stuff. Herbicides may seem like a tempting solution, but most don’t work well against poison ivy’s waxy leaves; the ones that do work tend to kill desirable plants as well, in addition to contaminating groundwater and soil. Dead vines are still capable of delivering plenty of rashes. Physical removal makes more sense in the long run.
Small, first-year vines are the easiest to remove. You’ll need a garden hose, cold water and some garbage bags. Soak the ground at the base of the vine with the hose set to a slow trickle for at least an hour before you do anything. You want the soil to be absolutely saturated. Next, turn the bags inside out and stick them on your arms like oversized gloves. The garbage bags must stay between your skin and the vine at all times. With one hand, grasp the base of the vine and slowly begin pulling it out of the soil. Did I say slowly? I meant slower than that.
At the same time, use the hose, set to a sharp stream, to wash the soil away from the roots. With care, you can pull the entire vine and be sure it won’t come back. Miss a section of root, and you can pull it all over again in a few weeks. Once the vine is out of the soil, carefully ball it up and pull the garbage bags off your arms and over the bundle of misery. Tie the bags shut, and send them out with the trash. Wash your arms and legs down with lots of cold water, just in case you made contact with the vine.
Meadows filled with a lot of vines require a different angle. You can mow poison ivy safely, as long as you use a riding mower that mulches the clippings back into the turf. Wear long pants and closed-toe shoes while you mow, and wash the mower deck down thoroughly when you are finished. Do NOT weed whack poison patches – unless you enjoy flaying the skin from your legs with your fingernails. A more elegant solution is to pasture goats in the area to be cleared of poison; they absolutely relish the stuff. Whichever method you choose, plan on maintaining it for an entire season, until the ivy’s roots give up and die from exhaustion.
Old, established vines require more effort – and a paper suit and face shield – for removal. Vines with a single trunk can be carefully girdled in midspring, when the bark slips easily from the wood. Cut a 3-inch-wide collar of bark from the trunk with a very sharp pocketknife. Remove the strip of bark all the way around the trunk. The vine won’t die that first season, but it will die over the winter. Once it has died, suit up and pull down as much of the dead vine as you can, bagging it up for the trash.
Vines with multiple trunks will take more work and care. Use pruners or long-handled loppers to sever each trunk. Do NOT use a saw or power tool, as they will splatter oil-laced sap everywhere. Remove as much of the top growth as you can; there’s no need to wait until it dies and dries. The roots will try to grow back, so be prepared to repeat the process.
It bears repeating to go get a cold shower immediately each time you think you may have been exposed to poison ivy. Remember, you only have a half-hour window to avoid a reaction.
One final note: Some people advocate desensitizing oneself by eating (!) small amounts of poison ivy each day, beginning when the very first leaves appear in spring. This takes months of very low doses, does not always produce the desired results, and can cause hives, rashes and itching in a certain, very unpleasant location. This method is not recommended.
Poison ivy can be found just about anywhere outdoors, and it’s growing faster and stronger all the time. The reaction it produces in most people has been described as the worst itch imaginable, and can drive you to distraction. All is not lost; we can take back lost ground. Leaves of three, don’t let them be.
The plant family Anacardiaceae is a large, mostly tropical and subtropical group, containing about 650 different species, including cashews, pistachios and mangoes. However, five species of the genus Toxicodendron are of special interest in North America. All 48 of the contiguous United States host at least one species. Incidentally, Toxicodendron translates, quite literally, to ‘poison tree.’
• Poison Oak (T. pubescens), also known as Atlantic poison ivy, grows well across the Southeastern United States, from Virginia to Florida, and west to Texas and Kansas. It forms an upright bush, reaching a height of 3 to 4 feet, and the leaves are deeply lobed, resembling white oak. It prefers dry, sandy conditions.
Pacific Poison Oak (T. diversilobum) grows along the Pacific Coast, from British Columbia into Mexico. It grows as a bush, climbing vine or thickets. The variable leaves can have scalloped, toothed or lobed edges, and resemble glossy oak leaves. It can be found in forests, grasslands and scrublands.
• Western Poison Ivy (T. rydbergii) stretches across the continent. It grows from Newfoundland to the Yukon Territory and south through Mexico. In the United States, it can be found practically everywhere, except in Alaska, Hawaii, California and the Deep South. It typically grows as a shrub, occasionally forming a climbing vine. It grows in a wide range of soil conditions, from bony and thin soils to deep, rich soils, tolerating acid and basic conditions, as well as variable sun exposures and occasional flooding.
• Eastern Poison Ivy (T. radicans) grows from Ontario and Nova Scotia to Guatemala, and from the East Coast to the Midwestern states. It can be a groundcover, shrub or climbing vine. It tolerates a wide range of soils, slight salinity, droughty soils and wet soils, growing well in edge conditions such as roadsides, waterways and tree lines. Its three-part leaves can have smooth, toothed or lobed edges, often confused with poison oak.
• Poison Sumac (T. Vernix) differs from the rest of the ‘poison’ family in that it does not bear three-part leaves, but rather forms compound leaves similar to black walnut or tree-of-heaven (Ailanthus), bearing seven to 11 leaflets. It grows in scattered territories between the Atlantic and Mississippi shores, and west into Texas. It grows as a shrub or small tree in swamps and bogs. Many people confuse it with staghorn sumac (Rhus typhina), which is much more widespread and visible. Staghorn sumac does not cause poison rash, and its red berries and cones can produce a dye, and even a drink much like pink lemonade. Poison sumac, on the other hand, bears white berries, as do all four poison ivy/oak species.
Andrew Weidman lives in Lebanon, Pennsylvania, where he has spent much time afield, doing his best to avoid poison ivy, more or less successfully.
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