Giant hogweed now serious health hazard across Canada

A University of Guelph researcher is attempting to solve thorny problem: how to get rid of giant hogweed, the invasive species that has become a serious health hazard as it continues its spread across the country, most recently being confirmed for the first time in Eastern Ontario.

“It’s this big, impressive plant with this huge flower span,” says University of Guelph student Meghan Grguric, who has been studying giant hogweed as part of her master’s in plant science. “It’s beautiful in a scary way. You know it’s dangerous just by looking at it.”

The sap from giant hogweed can cause severe skin irritation, painful blisters and up to third degree burns upon exposure to sunlight. Reports from the United States and the U.K. have revealed that children have suffered severe burns from the plant, with one girl in Derby, U.K., recently hospitalized after unwittingly brushing up against a plant while playing Pokemon Go. The chemical in the plant’s watery sap which causes the blistering requires bright light in order to react with skin, leaving people who have come in contact with it forced to stay indoors for periods of up to three years.

Despite wearing protective clothing, Grguric herself has suffered burns to her wrist and calf – something she laments but sees as fascinating from a scientific perspective. “The ability of these plants to hurt you is just so interesting,” says Grguric, whose research aims to investigate various methods for dealing with the scourge, including injecting herbicides directly into the plant and successive to reduce the spread of seeds. So far, Grguric has found the plant to be relatively impervious to traditional herbicides. “Basically, you spray it, you kill off what’s there, and new seedlings pop up a few months later.”

Giant hogweed reproduces readily, with a single plant able to give off up to 50,000 seeds which can remain viable in the ground for up to 15 years. Native to Asia and southern Russia and first arriving in Canada in the 1940s, the plant has now been found in approximately 500 locations across the province of Ontario, having made its way into BC, Quebec and the Atlantic Provinces, growing along roadsides, in ditches and near streams and woodlands. The plant blooms in mid-August, with huge flower clusters similar in appearance to Queen Anne’s-Lace. The plant’s stem thick stem is covered with purplish spots and thick hairs that are filled with sap, which can also come from the base of the stem.

The Ontario government offers a hotline for residents to report a giant hogweed sighting and warns landowners against attempting to remove the plant on their own, instead recommending that they hire a professional exterminator.

Grguric sees the task ahead as a challenge, realistically hoping to find effective ways of controlling the further spread of the species. “There is no way we can eradicate it. All we can do is control it to the best of our abilities,” she says. “Once an invasive species gets in, you can’t really eradicate it, unless you are tackling it very early at the source.”

Below: Giant hogweed, Don’t Touch!

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