Big, Beautiful and Blister Inducing, Giant Hogweed Shows Its True Colors Around Vermont | Environment | Seven Days | Vermont's Independent Voice

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Big, Beautiful and Blister Inducing, Giant Hogweed Shows Its True Colors Around Vermont

Local Matters


Published July 20, 2011 at 10:53 a.m.

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Giant hogweed is often described as Queen Anne’s lace on steroids. Its leaves can extend three feet in diameter; the plant’s thick stalks, topped with feathery flowers that open like umbrellas, can grow up to 15 feet tall. In short, the plant can take your breath away — and if you’re not careful, your eyesight, too.

“It’s an impressive and very charismatic-looking plant,” says Tim Schmalz, a plant pathologist with the Vermont Agency of Agriculture, Food and Markets. “When you see it, you understand why a Victorian gardener would be interested in having one up against the house.”

Apparently, the Victorians weren’t especially fond of their groundskeepers. Schmalz warns that giant hogweed has a light-sensitive sap that, when transferred to human skin and exposed to sunlight, can cause painful burns, blisters and lasting scars. Inhaled, the sap can cause respiratory problems. Contact with the eyes can lead to blindness.

With the plant in bloom all over the state, Schmalz has fielded numerous phone calls about giant hogweed from Vermont gardeners, farmers, landscapers and other outdoor enthusiasts. Its ill effects aren’t as easily transmitted as, say, poison ivy’s; the sap is in the stalks, not on the leaves. But Schmalz warns that anyone who weed-whacks or cuts down these plants without wearing a long-sleeved shirt, pants and protective eyewear is “playing with fire.”

Once a popular showpiece in ornamental gardens, giant hogweed is in the same plant family as carrots, parsley, dill and cilantro, and is often mistaken for cow parsnip or purple angelica, which are smaller and more common in Vermont. Also known by its Latin name, Heracleum mantegazzianum, the invasive species is now listed as a noxious weed. It’s against the law to sell or transport it anywhere in New England.

Giant hogweed thrives in what Schmalz calls “waste places,” i.e., land that’s not actively managed or under cultivation, such as ditches and roadsides. Its seeds don’t drift in the air like dandelion seeds but float easily on water, allowing the weed to spread along the banks of rivers and streams.

According to Schmalz, giant hogweed can also be found in New Hampshire, Massachusetts, Maine and Québec. Some states, including New York, have active management and eradication plans. For years, the Vermont Agency of Agriculture tracked the plant’s spread but no longer does so, as it’s now considered “widely distributed but not very abundant” in Vermont.

Poison parsnip, a member of the same plant family, is in bloom now, too, Schmalz adds. This wild version of the parsnips you can buy in the supermarket also has flowers that resemble those of Queen Anne’s lace, but they are yellow rather than white. It has the same dangerous phytophotosensitive sap, too, that burns the skin, though not as dramatically as giant hogweed.

Schmalz says he’s puzzled by the recent flurry of phone calls about giant hogweed. The plant has been on the agency’s radar for several years and doesn’t appear to be spreading.

“It’s dangerous, but just walking by the plant along the sidewalk won’t make you sick,” Schmalz adds. “It’s not some Friday the 13th horror-movie kind of thing.”

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