The U.S. Department of Agriculture has put this plant near the top of its Federal Noxious Weed list. Officials in Washington are asking residents to be on the lookout for it so they can eradicate it. In New York a hotline has been set up so residents can easily report sightings, and crews in several states are seeking it out and destroying it. To date it has been reported in Connecticut, Maine, Maryland, Massachusetts, Michigan, New York, New Hampshire, Ohio, Oregon, Pennsylvania, Washington and Vermont.

The plant is the giant hogweed (Heracleum mantegazzianum), originally from central Asia. Since its discovery it has spread all over the world, because as a specimen plant it is a knockout. White flowers nearly 3 feet in diameter bloom on top of stalks that can reach 15 feet tall. The tropical looking compound leaves grow 3-5 feet across and up to 9 feet long on purple spotted stalks. People naturally want to touch it because it is so unusual, and that is what makes this plant is so dangerous.

The plant’s clear, watery sap works with moisture and sunlight in a reaction called phytophotodermatitis. People coming into contact with the sap develop large, painful blisters that resemble severe sunburn. Some have had to be hospitalized for intravenous antibiotics and cortisone injections and have taken a month or more to heal. Once the blisters heal, scars resembling cigarette burns remain. Children who have used the hollow stems as pea shooters have developed painful blisters around their mouths, and others who have used them as telescopes have been permanently blinded by the burning sap.

Doug Cygan, Invasive Species Coordinator with the NH State Department of Agriculture says, “It’s by far the worst plant pest when it comes to human health.” In New Hampshire, state officials have begun surveying and mapping sites where giant hogweed grows. So far it has been found in Grafton, Sullivan and Rockingham Counties, with unconfirmed reports of four injuries from the sap.

Officials warn those who think they’ve found a giant hogweed plant to stay away from it, keep pets and livestock from grazing on it, and make sure children and pets don’t play around it. There are reports of people getting burned by playing with cats and dogs who’ve gotten the sap on their fur.

NH residents who suspect they have found giant hogweed should call the Cooperative Extension’s Family, Home & Garden Education Center’s Info Line at 1-877-398-4769, Monday-Friday, 9 AM -2 PM, prepared to describe the plant and its location. All parts of the plant contain toxic sap, and it is recommended that people do not touch the plant while trying to identify it. Instead, wait for confirmation from a state inspector. For more information and photos, click here.

Resources include the University of New Hampshire Cooperative Extension Service, the State of New York Department of Environmental Conservation, and the U.S. Department of Agriculture.

NOTE: I’m getting asked repeatedly where folks should report their giant hogweed sightings. It’s important that you contact the extension service or department of agriculture in your state. To find that information simply go to Google or any other search engine and type “Reporting giant hogweed in XXXXXXXX” where XXXXXXXX is the name of your state. Once you do this you’ll find a wealth of information, including photos and how to identify this plant. More often than not I’m told, what people are seeing is cow parsnip or another look alike. Please do your homework and try your best to make an accurate identification before contacting the authorities in your state.