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The 411 on Giant Hogweed, the Invasive Plant That Can Cause Severe Burns and Blisters

The toxic plant has now spread to even more states across the U.S.

What’s 14 feet tall, green, hairy, and covered in toxic sap? It may sound like a monster, but this scary beast is actually giant hogweed, a towering, invasive plant whose sap can cause painful burns, scarring, and possibly even blindness.

Originally from the the Caucasus mountain region of Eurasia, researchers just confirmed the presence of this federally listed “noxious weed” in Virginia for the first time. The state now joins Maine, Massachusetts, Vermont, Connecticut, New York, Pennsylvania, North Carolina, Michigan, Illinois, Washington, and Oregon as hosts to this non-native plant.

Naturalists intentionally brought the species here in the early 1900s, as its size and enormous flowers made it desirable for ornamental planting. However, the average giant hogweed produces a whopping 20,000 seeds that can fall 30 feet from the plant and travel even farther through wind or water. Translation: It didn’t take long for this species to spread out of control — and start injuring unsuspecting gardeners.

Why Giant Hogweed Is Dangerous

The danger of giant hogweed stems from its sap, which is present on all parts of the plant. Toxic chemicals in it called furanocoumarins cause severe burns when exposed to UV light from the sun. Even when the painful blisters subside, permanent scarring can remain.

“The more sap you touch, the greater damage it causes,” Naja Kraus, the New York Department of Environmental Conservation’s Giant Hogweed Program Coordinator, tells GoodHousekeeping.com. “Once you get it on you, it makes your skin unable to protect itself from the sun.”

The reaction — called phytophotodermatitis — is similar to how some antibiotics you take make your skin more sensitive to UV light. “It basically fuses your DNA in that area,” Kraus explains.

One 17-year-old boy recently went to the hospital with second- and third-degree burns after he accidentally chopped down a giant hogweed plant as part of his summer landscaping job. Alex Childress of Spotsylvania County, Virginia, didn’t notice anything unusual until he went to take a shower that evening.

“I started rubbing my face,” he told People. “I thought it was just a little bit of skin at first, but then big chunks of my face were falling off.” Childress stayed in the Virginia Commonwealth University’s burn center for two days, and now must avoid the sun for up to six months.

While other news reports warn of blindness as another side effect, Kraus says she hasn’t encountered a verified case in her 11 years with the Giant Hogweed Program, but their hotline has received more than enough calls reporting the painful burns.

How to Identify Giant Hogweed

If you encounter a plant that resembles giant hogweed in your backyard, the first step is to verify it. Giant hogweed doesn’t grow to 14 feet overnight; the seedlings and saplings start out much smaller. It’s only after three to five years — when the plant gains enough energy from its roots — that it rockets in growth and begins to produce early-summer white flowers one to two feet across, as well as five-foot-wide lobed, jagged leaves.

Anything with smaller blooms (like Queen Anne’s lace) is probably an imposter. Two other similar looking species include the very benign native plant cow parsnip, which only grows to about six feet, and Angelica, which has compound leaves and smooth stems.

The easiest way to identify giant hogweed is to look for purple blotches and white hairs on the stem. If the plant has both those qualities, there’s a strong chance it’s the real thing. Keep an eye out in open sites with lots of light and moist soil, as well as partially shaded areas along streams, rivers, and roads as well as in fields, forests, and yards.

You should also watch out for wild parsnip. It’s in the same family and produces the same toxic sap, but doesn’t grow as tall. Look for yellow flowers and grooved stems.

What to Do If You See It

The first step is report it to your local authority, like the Department of Environmental Conservation or an extension service.

The agency may remove it or advise you on how to do it yourself safely wearing protective gear. Experts may recommend manual methods of control — like cutting the roots — or applying an herbicide. In addition to posing a public health risk, this species poses an ecological hazard as well by reducing plant diversity and causing soil erosion, Kraus says.

What to Do If the Sap Gets on Your Skin

If you inadvertently brush up against any part of giant hogweed, you might notice the skin reaction within 15 minutes. Dark, painful blisters will form within two days, and the purplish or brown scars and sensitivity to sunlight can last for years.

To minimize the damage, immediately wash the affected area with soap and water and contact your physician ASAP if you experience a reaction. A GP may prescribe topical or oral steroids to reduce the severity and help it heal faster. Cover your skin to protect it from sunlight for the next few days.

“When it’s blistered, just wearing a long-sleeve shirt isn’t enough,” Kraus says. “You actually have to wrap it with an ace bandage or wear sun-protective clothing. You can’t get any UV rays on it at all.” You’ll want to protect the burned area from sunlight for the next few years as well to reduce scarring.

While these side effects certainly sound scary, avoiding them is as easy as learning to identify this species — and steering clear when you see it. “People are often very frightened when they hear about giant hogweed,” Kraus says. “It’s really important to realize that it’s a plant. It can’t move. The only way you can burned by giant hogweed is to touch it.”

Giant hogweed is an enormous invasive plant whose sap can cause painful burns and scarring. It's found in New England, the Mid-Atlantic, and Northwest regions of the country.

Giant Hogweed

Common Name: Giant Hogweed
Scientific Name: Heracleum mantegazzianum Sommier & Levier
Legal Status: Prohibited – Eradicate

All above and below ground parts of the plant must be destroyed. Additionally, no transportation, propagation, or sale of this plant is allowed. Failure to comply may result in an enforcement action by the county or local municipality. Minnesota Noxious Weed Law.

Background

Giant hogweed is a perennial plant native to the Caucasus region of Asia which includes Armenia, Azerbaijan, Georgia, and part of Russia. It was originally introduced to the US as a novelty ornamental which escaped cultivation. Giant hogweed has not yet been discovered in Minnesota but is established in Wisconsin.

Description

  • Deeply cut leaves up to five feet across.
  • Produces a flowering stalk 10-15 feet tall with large clusters of tiny white flowers 2½ feet across.
  • Stalks are two inches in diameter and hollow with purple mottling.
  • Stems and leaves are covered in coarse white hairs.
  • Contact with the sap in the presence of sunlight can produce painful, burning blisters.
  • Cow parsnip (Heracleum maximum) is a similar native look-alike. The leaves are less deeply cut and are between 2-2 ½ feet across. The flowers are also white but flat-topped and no larger than one foot wide. The stem is usually green, but it can have purple marks that are not spots. For photos and more information to compare cow parsnip and giant hogweed, visit Invasive Species Council of Metro Vancouver, and New York State Department of Environmental Conservation.

Habitat

Giant hogweed can be found growing in yards, ditches, disturbed areas, pastures, open wooded areas, and along stream banks. It thrives in sunny locations and is also somewhat shade tolerant.

Means of spread and distribution

It spreads by seed that can be moved by wind, water, wildlife, and humans. Seeds can remain viable in the soil for up to 10 years.

Giant hogweed is a serious public health hazard and can negatively impact soil dynamics, fisheries, and outcompete native plants. When giant hogweed displaces native riparian plants, stream bank erosion increases and streams can become overloaded with silt.

Prevention and management

  • Management of giant hogweed requires careful handling and appropriate personal protective equipment. For all management methods, it is important to monitor the site for several years after treatment for newly germinating seedlings or resprouting roots.
  • Removing plants by hand is difficult, and dangerous considering the toxic nature of the plant’s sap. Mowing can be a good management tool, if repeated throughout the season and over several years, or in coordinated conjunction with herbicide application.
  • Well-timed herbicide application can be effective, but numerous applications are usually required. If using herbicide treatments, check with your local University of Minnesota Extension agent, co-op, or certified landscape care expert for assistance and recommendations.
  • Grazing cows and pigs, apparently unaffected by the plant’s sap, can help to manage but not eliminate the plants.

Toxicity

Contact with the sap and exposure to sunlight can produce painful, burning blisters that can leave scars. Sap coming into contact with the eyes can cause temporary or permanent blindness. Appropriate protective clothing including gloves, goggles and long sleeve shirts should be worn and contact with the stems should be avoided. If sap comes in contact with skin, avoid exposure to sunlight, immediately wash skin with soap and water, and seek medical attention.

Common Name: Giant Hogweed