How to Identify Itchy-Rash Plants

Identify weeds causing skin rashes, burning sensations

Poison ivy in a field
John Burke/ Getty Images

Itchy-rash plants are the plant kingdom's answer to yellow jackets, mosquitoes, and the like. As if it were not bad enough that you have to watch out for the burning sting that yellow jackets can inflict while you are going about your business in the yard, there is a weed (stinging nettle) that can also burn you and cause itching. And while those who fail to practice mosquito control are doomed to suffer itchy stings, we all know the skin rashes caused by poison ivy are no picnic, either.

What you may not know is that you can also come down with an itchy rash from contact with lesser-known noxious weeds that commonly grow in the yard.

Yes, there is a skin rash just waiting to happen when you step out into your yard. Learn to identify the plants in question. Once you know what they look like, you can eradicate them (or, at least, avoid them). 

Illustration of common itchy rash plants
Illustration: Catherine Song. © The Spruce, 2018

Plants That Cause a Burning Rash: Stinging Nettles

Stinging nettles can't swoop in on you and deliver a burning sting, as yellow jackets can. But if you accidentally run through a patch of these plants in short pants, your legs will feel a bit like a swarm of tiny yellow jackets just attacked your unsuspecting appendages. 

The Big Three of the Itchy World: Poison Ivy, Poison Oak, and Poison Sumac

Do you depend on the rhyme, "Leaves of three, let them be!" to identify poison ivy and poison oak? You should not. It is true that poison ivy has three leaves (as does poison oak), but these itchy-rash plants are far from being the only weeds with three leaves. Moreover, the rhyme is quite useless for poison sumac identification, because poison sumac's leaf is shaped like a feather. So instead of relying on rhymes, learn to identify these plants properly.

Lesser-Known Plants That Cause Itchy Rashes: Ragweed, Giant Hogweed

You are not still blaming your fall allergies on goldenrod plants, are you? It is widely recognized now that the ragweeds (both the giant variety and common ragweed) are the worst culprits behind hay fever in the autumn. What is not so widely known is that the ragweeds can also cause skin rashes if you touch them. Once you learn what ragweed looks like, remove it from your property (while wearing gloves, a long-sleeved shirt, etc.) so that you do not accidentally brush up against it while performing yard maintenance.

The story of the arrival of giant hogweed (Heracleum mantegazzianum) to North America is a common one. Like Japanese knotweed (Polygonum cuspidatum), for example, it was discovered growing in its native Asia by Western plant explorers, who found it highly ornamental. They brought it back with them, first to the U.K., then to the U.S. Only after it had escaped into the wild in its new homelands did people start to realize what a potent enemy they had let in. In fact, the potency of giant hogweed is indicated in its genus name: Heracleum is an allusion to Heracles, the famously powerful hero of Greek mythology. This weed may, in fact, be the worst of the itchy-rash plants. It can cause not only rashes but even blindness.

The New Myth About Poinsettias

As if these weeds were not bad enough for your health, even some highly-valued plants, such as Christmas poinsettias, can cause rashes and make you itch (or worse). People have read countless stories on the web about how it is a myth that anyone eating a poinsettia leaf will surely die from it. Is that truly a myth? Yes. But here is the problem: As a result of becoming aware of this myth, people have let their guard down altogether about poinsettias. As so often happens, the busting of one myth spawns another. The new myth surrounding poinsettias is that they are totally harmless for everyone. That is simply false.