Don't touch: Giant plant causes blindness, third-degree burns

Toxic sap from giant hogweed can burn human skin; plant spotted in new state

Image shows a giant hogweed plant from michigan.gov
Image shows a giant hogweed plant from michigan.gov

It’s called giant hogweed, and well, not to be alarming, but it’s pretty scary. Have you heard of it?

The sap from the invasive plant contains something called glucosides, which react with the sun’s ultraviolet rays and can severely burn the skin, causing blisters or temporary blindness.

And giant hogweed has now been spotted for the first time in Virginia, according to the Associated Press.

“Giant” is right: These plants can grow up to 14 feet tall, with thick leaves stretching 2 to 5 feet across. About 30 plants were discovered in Clarke County, reads a Facebook post put up within the past week, by the Massey Herbarium at Virginia Tech University.

Today I helped ID VA’s first giant hogweed population! Its sap causes severe burns. One plant was found in Clarke...

Posted by VT Massey Herbarium on Tuesday, June 12, 2018

Officials are forming a plan to respond to the discovery, said Debra Martin, a program manager with the Virginia Department of Agriculture and Consumer Services.

So, what’s going on? Tell me again how this plant is so dangerous.
Giant hogweed is grown in the wild. Just by touching the plant, people can get third-degree burns and go temporarily blind. Like we mentioned, sap from the hogweed contains toxic chemicals. When those chemicals come into contact with human skin, a reaction can sometimes take place, making someone’s skin extremely light-sensitive. It can also cause a reaction that leads to painful, dark-colored blisters that come with scars.

What else should I know? How can I avoid it?
Well, giant hogweed (despite having an ugly name) is actually kind of pretty. The white flowers on top look a little bit like Queen Anne’s Lace, and sit kind of like an umbrella over the rest of the plant. Be aware of what this invasive plant looks like, so that you can steer clear. You don’t want to touch it at all -- but above all else, you definitely don’t want to get sap in your eye, because that’s what leads to long-term light sensitivity and blindness. Also, be aware that a toxic reaction can start as soon as 15 minutes after having contact with the plant.

What if I think I spot the plant?
“Remember that giant hogweed is very similar to the widespread species cow parsnip,” which is native to Virginia, the Massey Herbarium said on Facebook. “So if you think you have found giant hogweed, there's a really good chance it's actually cow parsnip.”

If you’re still unsure, check this plant identification guide and snap some clear photos. Then, check with your extension office. You’re unlikely to find any more hogweed in Virginia, an updated Facebook post from the Herbarium said Wednesday.

I prepared a specimen of the giant hogweed from Clarke County yesterday! Look at the giant leaves--very distinctive! The...

Posted by VT Massey Herbarium on Wednesday, June 20, 2018

What can I do?
Awareness is key. Of course, if you think you’ve touched the plant and you’re having a reaction, call your doctor. You could also soak a compress in a mixture of aluminum acetate, which is available at most pharmacies, if you think you’ve come into contact with the hogweed. This provides some relief for skin irritations. And if the sap gets in your eyes, rinse them out as soon as you can, put on sunglasses and call your doctor.

Is it anywhere other than Virginia?
Giant hogweed has previously been found in Michigan, Illinois, Maine, New York, Pennsylvania, Oregon and Washington. It was first discovered in Wisconsin in 2004.

Tell me more about the plant itself.
It’s part of the carrot family. Its real name is heracleum mantegazzianum. Giant hogweed is one of three plants defined in Virginia as a Tier 1 noxious weed, and it is heavily regulated. The plants spread when birds or waterways carry the seeds to new locations. These can grow for 10 years once they’re dropped off, according to published reports. The plant is a native of the Caucasus region of Eurasia, between the Black and Caspian seas. It was brought to the United Kingdom and to the United States in 1917 as an ornamental plant. It can grow to as high as 20 feet. Giant hogweed is fast-growing and is known to invade roadsides, the edges of forests and empty lots, the AP said.

And a fun fact?
The AP says giant hogweed is listed as a prohibited species, meaning the plant isn’t widespread and so far has been found only in isolated spots -- but it's likely that it would spread, if it's not controlled. If necessary, the DNR can even obtain a court order to eradicate it.

And now you know.

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