The photos are disgusting: arms covered in purple welts and oozing blisters. The stories are also horrifying: there is the New Hampshire woman who needed intravenous antibiotics and cortisone shots but still had purple scars and sensitivity to sunlight for months.
Giant hogweed, the culprit, is a nasty plant. If its watery sap gets on your bare skin, and if that sap-covered skin is exposed to sunlight, you can get a chemical burn, complete with blisters and itching. Even after the blisters have healed, you may be scarred and be sensitive to sunlight for months.
With the disgusting pictures and horrifying stories, it’s easy to oversell the threat of giant hogweed. People’s sensitivities to the toxins in its sap vary widely. It’s possible to have a run-in with the plant – complete with exposure to sap and sun – and barely notice the impact.
“It’s kind of like poison ivy,” says Emilie Inoue, state pest survey coordinator for the Vermont Department of Agriculture. “Some people are more sensitive to it.”
Poison ivy, pesky though it may be, is a native to our area, is well established, and has a role in the local ecosystem. Giant hogweed, on the other hand, is native to the area around Armenia and the country of Georgia.
It’s been in Britain long enough to have inspired the 1971 Genesis song “Return of the Giant Hogweed,” perhaps the only rock tune with lyrics that include the words “photosensitize” and “herbicidal.”
It isn’t widespread in our area yet, and with vigilance, it looks as though we can keep it at bay.
Giant hogweed is easiest to identify when it is in bloom, which may happen as early as mid-May or as late as July. It looks like the world’s biggest Queen Anne’s lace plant. The resemblance is not accidental. Both plants are members of the carrot/parsley family.
There is little chance of mistaking Queen Anne’s lace for giant hogweed, though, or vice versa. Giant hogweed can be from 8 to 15 feet tall. It has a large, white, umbrella-shaped flower head, which is made up of smaller flowers – like Queen Anne’s lace – however, the flower head is at least a foot across. Its leaves can be up to five feet long and, while intricate, they are not feathery looking, as are Queen Anne’s lace leaves.
Cow parsnip, a native plant, is frequently mistaken for giant hogweed. In fact, at this time of year, with the plants not full-grown and not in flower, even the experts have a hard time telling them apart. Cow parsnip seldom grows taller than six feet, with flower heads rarely reaching a foot across. Its sap can also burn skin with exposure to sunlight, but it is much less toxic than giant hogweed’s. You can think of it as giant hogweed lite.
Another way to tell hogweed from parsnip is by the stem: purple, splotchy, and covered with white hairs on the hogweed, green and more furry than hairy on the parsnip.
About five years ago, the federal government became concerned about the spread of giant hogweed and put it on its list of noxious plants. Vermont and New Hampshire officials responded in kind so that in both states it is now illegal to grow, move, or transplant giant hogweed. It also means that in both states, the departments of agriculture ask people to report giant hogweed plants and keep track of the sightings.
Inoue reports that the plant has become established in six Vermont counties. In the wild, she says, it is mostly found near rivers. But Tim Schmalz, the plant pathologist for the State of Vermont, says that most of the sightings have been in gardens. “It’s a pretty plant. It’s a spectacular plant,” he says. “People bring it in to re-create Victorian gardens.”
Doug Cygan, with the New Hampshire Department of Agriculture, says there have been six confirmed sightings of giant hogweed in the state, and at all but one of those sites, the plant has been eradicated.
Both states have kept on top of giant hogweed for five years now, and it looks like the plant only exists in isolated pockets that can be eradicated, especially if people continue to report it and continue to get rid of it using the techniques the agriculture departments suggest.
In Vermont, people who believe they have seen giant hogweed can call (802) 241-3544. In New Hampshire, people can report it by calling (603) 271-3488. Those needing help making an ID can call the University of New Hampshire Cooperative Extension between 9 am and 2 pm Monday through Friday, at (877) 398-4769.
And, of course, getting a cutting or other sample of this plant can be painful experience at best, so leave the suspect plant alone until you get more information.