How To Identify Poison Ivy

Even bad boys can have a good side; and so it goes with an unwanted inhabitant of many a garden, poison ivy.  The native plant sure knows how to take over a room. For humans, its ornamental qualities are less than desirable. That being said, poison ivy does have its uses. See below.

WHAT IT IS

According to the Centers for Disease Control and Prevention (CDC), poison ivy is one of the most common poisonous plant species found throughout the continental United States. A native of North America, it grows mostly in the eastern and midwestern states where it tends to inhabit forests, fields, and shorelines. More worrisomely, it’s also come to love urban/suburban environments such as road sides and parks. This in turn has led to it taking up residence in many of our backyards. 

Poison ivy is a member of the sumac family, Anacardiaceae, which comprises over 860 known species. Along with poison sumac and poison oak, it is part of the genus toxicodendron, whose toxic properties produce contact dermatitis in affected individuals. 

A TOXIC RELATIONSHIP

So what makes toxicodendron so toxic? The culprit is urushiol, an oily resin with allergenic properties. Urushiol is found in every part of toxicodendron, including dead or dormant plants. When poison ivy, poison oak or poison sumac are bumped, damaged or even burned, they release urushiol as a means of protection.

In fact, research shows that only a small amount of exposure can cause an allergic rash. And by small amount, that means just 1 nanogram or one billionth of a gram. There is even evidence that urushiol can remain on a surface for up to five years. The take-away? I’d say avoid these plants altogether.

On a good note, apparently about 10 to 15 percent of the human population is immune to poison ivy and its cousins, and therefore will never experience the rash. And poison ivy is less common outside the U.S., although it can still be found here and there around the globe. 

HOW TO IDENTIFY POISON IVY

A common adage says ‘Leaves of three, let it be’, while another counsels ‘Leaves of three, run and flee’. I prefer the latter, having suffered from major breakouts throughout my lifetime in the garden. That being said, poison ivy is a chameleon when it comes to appearance. it can be downright hard to identify. Compare the photo below to the two above. You’ll see what I mean.

The truth is poison ivy has so many variations it can baffle even the most seasoned horticulturalist. Take for instance its make-up. It can be a creeping groundcover, or a woody vine (referred to as a liane) which, once it scales a tree, can put on 20 feet of growth in just one season. And full sun can cause it to take on a shrub form.

And while most of us know to look out for a plant with three leaves, from that point on, things can get murky. Poison ivy has a compound leaf, which means that what presents as a single leaf is actually three. Additionally, its leaves can be shiny or dull, and their size and shape can vary greatly. Some leaves are toothed, while others are deeply lobed. And in some rare instances, poison ivy can have five leaves instead of three. 

Poison ivy taking on fall color

Look for bright green leaves during the growing season and bright red ones in the fall.

HERE’S THE RUB

The good news is that, according to the U.S. Food & Drug Administration (FDA), poison ivy rashes are not contagious and therefore cannot be spread from person to person. However, it is possible to pick up the rash from toxins stuck to clothing, tools or other items including pets (see below.) And contrary to common thought, the rash occurs only where the oil has touched the skin. So rubbing or scratching won’t spread it. What may seem like a spreading rash is actually the toxin’s effects appearing gradually over time.

Photo credit/medicinenet.com

Always wash your skin and clothes after coming into contact with poison ivy. This is essential to removing all traces of urushiol. And use cold water, not hot. Hot water thins the oil and helps it dissipate more quickly.

CAN ANIMALS GET POISON IVY?

According to the Pet Poison Helpline, the answer is rarely. Usually, their long protective coats prevent the plant oils from ever reaching their skin. However, animals can carry the toxin on top of their fur, so don’t let your pet rub against you if you think he or she’s been in contact. Try bathing yours with a colloidal oatmeal shampoo while wearing gloves to eliminate the urushiol.

My cat, Squeaky

IT’S GOOD FOR SOMETHING

Before you decide to remove that patch on your slope, you might want to think again. Like kudzu, poison ivy is great at erosion control, especially on coastlines where it acts as a stabilizer for sandy soil. (It’s a big player along the Eastern coastline.) Moreover, it provides valuable food for many species of wildlife, who eat its fruit, stems and leaves.  And it also functions as a protective shelter for small mammals.

Small animals like rabbits like to feed on poison ivy

WHAT TO DO ABOUT IT

As with most unwanted plants, the best way to eliminate them is to get to know their seedlings and start early. As poison ivy matures, however, it may require years of patient digging to totally eliminate its root structure.  You can apply an herbicide like glyphosate to the plant’s roots, leaves or vines. However, be sure to wear eye protection and gloves when chopping down vines. And never use a chain saw, which can spread the toxins by air.

 

 

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About carole funger

I'm a landscape designer and Maryland Master Gardener living in the Washington, DC area. I blog about new trends in horticulture, inspiring gardens to visit and the latest tips and ideas for how to nurture your own beautiful garden. Every garden tells a story. What's yours?

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