cityscape Why Everyone Can Relax About A Huge Blistering Plant Called Giant Hogweed

The GTA's scariest botanical invader is on its way out, thanks to aggressive action by the municipality and TRCA.

A severely toxic plant called Giant Hogweed, despite seasonal media attention, is really not a widespread problem in the GTA according to experts. At least, not any more.

After a five-year-long removal effort, the plant has now been almost completely eradicated in the city. And that’s a good thing.

The 20-foot plant is so scary because when its clear and watery sap touches human skin, “photodermatitis” occurs—a reaction that causes the affected skin to become hyper-sensitive to sunlight and blister intensely as a result. It’s “poison ivy on steroids,” says Gord MacPherson, associate director of restoration at the Toronto Region Conservation Authority.

After contact with the dangerous/terrifying/oddly impressive plant, blisters can last for up to a few months and skin can remain sensitive to sunlight for up to a year.

Pause. If you’re about to Google image search “Giant Hogweed blisters,” just don’t. We already did. It’s not pretty.

Five years ago, Giant Hogweed sightings were higher than normal in Toronto with about 50 plants spotted in the Don Valley.

“It’s really been in the news a lot lately and people assume that it’s abundant and that it’s a new arrival,” says Peter Kotanen, associate professor in the department of ecology and evolutionary biology at UTM, who reassures us that this isn’t the case. “It’s still a fairly scarce species. It’s not like we’re overrun with it.”

While it hasn’t happened in Ontario, it is fairly easy for Giant Hogweed to become abundant, as it is in parts of Europe, including the Czech Republic.

MacPherson says there are now only about six known Giant Hogweed sites in the GTA. The plant is mostly found on roadsides and forest edges and near streams. They’re “in our green spaces more than any place else,” he says. “It’s really not that widespread.”

In other words, there’s no need for a hazmat suit to do your Saturday gardening—the stuff rarely shows up in Toronto’s backyards.

The TRCA and the City of Toronto have worked hard to eradicate the relatively small number of heinously toxic Giant Hogweeds in Toronto. The removal process involves either removing the plant altogether, fencing off the surrounding area or installing a caution sign nearby. Sometimes pesticide is used to control the spread of seeds.

“When it’s found, our municipality is pretty aggressive about taking care of it,” says MacPherson. “The reality is that you don’t need to be scared.”

Facts about Giant Hogweed

Giant Hogweed is often mistaken for Cow Parsnip or Queen Ann’s Lace. (In reality it towers over those plants, standing around 20-feet tall.)

It was likely imported to North America from Asia as a garden plant.

The sap does not affect pets, but if you touch sap that has been on your pet, it’s likely you will become affected.

If met with a human eyeball, Giant Hogweeed’s terrifying sap can cause blindness.