WASHINGTON – It’s poised at Maryland’s borders, 15 feet tall with sap that causes skin to blister and burn in sunlight.
The giant hogweed is not part of the axis of evil — but it is the Invader of the Month.
The Maryland Invasive Species Council gave that dubious honor to the hogweed, whose scientific name is Heracleum mantegazzianum. It has been found in Pennsylvania and Washington, D.C., and officials fear it could migrate into the state and become a public health hazard.
It is related to carrots and parsley, but the white-flowered hogweed can grow up to 20 feet high with 5-foot-wide leaves. While carrot and parsley leaves can cause rashes in people sensitive to them, the sap of the giant hogweed makes skin more sensitive to ultraviolet radiation and causes severe burns and blisters, said Alan Tasker, coordinator of the U.S. Department of Agriculture’s Federal Noxious Weed Program.
“It really reduces your resistance to sunlight, so you get some really bad sunburn,” he said.
Simply brushing the plant is probably safe. Skin has to come into contact with the sap to be damaged, he said.
“It seems to have almost a physical reaction under the skin when the sunlight hits it,” he said.
A native of southwest Asia, the giant hogweed might have been brought to the United States in the early 20th century as an ornamental plant for gardens or for its oval fruits, which are used as a spice in Iranian cooking.
“People with garden clubs or other sorts of groups like that don’t know the problems with the plant and say, ‘Oh, this is dramatic,’ and want to plant it,” Tasker said.
The giant hogweed has invaded other countries as well. One resident of England, where it lines waterways, made a website that rates locations based on the size and number of the plants. And in the 1970s, the British rock group Genesis wrote a song about the plant, “The Return of the Giant Hogweed.”
Because the plant is classified as a noxious weed, the U.S. Department of Agriculture forbids bringing it into the country or transporting it between states.
The heaviest known hogweed infestations in the United States are in western New York and western Pennsylvania, Tasker said. Maryland officials are concerned because some giant hogweed has been found in eastern Pennsylvania near Delaware. If the plant is found along the upper Susquehanna River, the seeds could float into Maryland, Tasker said.
“If it’s near a stream or if it floods it can travel tremendous distances,” he said.
The Maryland Department of Agriculture will hold a workshop May 20 for people to learn how to identify and dispose of the giant hogweed, said department spokeswoman Sue DuPont.
Tasker said the Pennsylvania Department of Agriculture has a program to eradicate the giant hogweed. Pennsylvania spot treats the leaves with herbicide and treat seedlings for several years after the taller plants are killed because the seeds last in the soil, he said.
The giant hogweed is the second of Invader of the Month identified by the Maryland Invasive Species Council, a group of public and private representatives that includes everything from state agencies to nurseries. Tasker said the council has identified about 24 species that it plans to highlight as an Invader of the Month.
Last month’s invader, the first in the series, was the hemlock woolly adelgid, an insect that sucks the sap from young hemlock trees, causing the needles to dry up. The state Agriculture Department is releasing beetles to eat the adelgids, which have been a problem in Garrett County, but does not yet know if that will control them, DuPont said.