ISSUE 20  |  Landscaping 101

Landscaping 101: How to Kill Poison Ivy

May 21, 2015 1:30 PM

BY Michelle Slatalla

Poison ivy was making enemies as early as the 17th century. Upon discovering it in the New World, Captain John Smith noted in 1623, “The poysoned weed is much in shape like our English Ivy, but being but touched, causeth rednesse, itching, and lastly blisters.”

The redness, itching, and blisters are the main reasons that 400 years later gardeners are still trying to get rid of the vine (touching the oily substance called urushiol on the plant’s leaves and stems causeth more than 70 percent of us to break out in a painful rash).

But Toxicodendron radicans is not an easy plant to kill. To get rid of poison ivy, you have to dig out or kill its roots as well as its stems and leaves. The last time I tried this, I ended up with a prescription for prednisone and instructions from my doctor to go home and sterilize my Felco pruners.

There’s a better way to kill poison ivy in your garden. Here’s how:

Leaves of Three, I Hate Thee

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Above: Photograph by Virens via Flickr.

The first step to getting rid of poison ivy is identifying it. It’s tougher to ID than you might think. Yes, it has clusters of three leaves. Yes, the leaves are pointed and–if mature–have ridges along their edgeth, as John Smith might say. This much is known.

But poison ivy also can look a lot like poison oak, or like furry raspberry leaves (which you don’t want to kill), and is frequently mistaken for Virginia creeper (which has five-leaf clusters).

If you’re not sure if you have poison ivy, put on a pair of heavy gloves and snip off a cluster of leaves to examine more closely. Photos abound on the Internet. If you’re still not sure, take the leaves to your local nursery to get a positive ID.

Learn Its Tricks


toxicodendron_radicans-h-zell-wikimediaAbove: Photograph by H. Zell via Wikimedia.

Poison ivy likes dappled sunlight but also lurks in shady spots. It will climb tree trunks, attach itself to a fence or wall, and run rampant in moderate climates along the Eastern Seaboard.

In a wooded area, it will intertwine itself with other low-growing plants, such as ferns, which makes it harder to kill without hurting its neighbors. But don’t give up.

Pick Your Poison

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Above: Photograph by Bmerva via Wikimedia.

You have two choices when it comes to killing poison ivy: a natural method or a chemical poison. Both will work, but chemicals may work faster. For more on the pros and cons of DIY natural weed killer versus a chemical herbicide such as Roundup, see Landscaping 101: Homemade Weed Killer.

Natural Born Killers

Gardenista, homemade weed killer, vinegarAbove: Photograph by Justine Hand. For more, see Landscaping 101: The Pros and Cons of Homemade Weed Killers.

If you want to avoid chemicals, you have a few choices:

Manual Labor: Put on long sleeves and pants, tape your pants and shirt cuffs to prevent skin exposure, pull on a pair of heavy gloves, and dig out as much poison ivy as you can. The trick is to get the roots, which means digging down a few inches–at least 6–beneath roots and then reaching in to pull them out. This job is easier if the ground is soft; try it after a rainy spell. Be warned that you will inevitably overlook a few little roots. Watch for new growth and pull it out as soon as possible to weaken the plant, or at least to try to break its spirit.

Boiling Water: I am a big fan of pouring a kettle of boiling water onto weeds to kill them. This works best if the plant you want to kill is growing in a crack in a path or next to the driveway or somewhere other than a garden bed full of desirable plants. Boiling water will kill anything it touches. Caveat: when it comes to poison ivy, the underground roots will survive a dousing. After the boiled leaves and stems die back, new growth will emerge. As soon as you see it, pour on more boiling water. Over time, the rate of new growth will slow.

toxicodendron-radicans-esculapio-wikimedia

Above: Photograph by Esculapio via Wikimedia.

Smothering: You can cover a patch of poison ivy with a plastic tarp or big piece of cardboard to kill it. Afterward, check the perimeter of the treated area for new growth; underground roots that were outside the jurisdiction of the tarp may send up shoots.

Potions: The main ingredients in DIY homemade weed killer are salt, vinegar, water, and dish soap (which helps to broadcast the spray farther). Justine investigated the pros and cons of homemade weed killers–some of which are not as “natural” as you might think–and offers a comprehensive report at Gardening 101: Pros and Cons of Homemade Weed Killers.

Chemical Warfare

The two most commonly used chemical herbicides in the war against poison ivy are Roundup and Brush-B-Gone, whose respective active ingredients are glyphosate or triclopyr. These are chemicals I don’t use in my garden, but if I had a backyard overrun by poison ivy and small children tromping through it, I might feel differently. If you spray chemical herbicides on poison ivy, it will die fast. As with other methods, watch for new growth and spray again immediately.

Dispose of the Body

Above: After you cut, pull out, or dig up poison ivy, do not put it in your compost pile. Do not touch it with bare hands. Do not burn it (it can release harmful, irritating fumes). Instead, bag it in plastic and dispose of it as trash (unless you live in a municipality that offers an alternate plan).

After you finish killing poison ivy, strip off your gardening clothes–gloves too–and put them into the clothes washer on a hot setting. Hose down or clean off your shoes or boots before wearing them again (urushiol can remain active on the surface of clothing and shoes for as long as five years).

Weed warriors, unite. For more suggestions, see: