giant hogweed toronto

One of Canada's most dangerous plants was just spotted in Toronto

A poisonous ornamental plant that, while pretty, can literally burn your skin off is giving hikers in Toronto's Don Valley a reason to be more cautious than usual this summer, with Metrolinx warning that Giant hogweed has been found near Evergreen Brickworks.

Thought to be one of the most dangerous plants in Canada, Giant hogweed looks a lot like Queen Anne's Lace or Valerian, but way, way bigger, with flower heads that can grow up to one metre wide.

It's also significantly more dangerous than similar plants with white flower clusters thanks to its toxic, skin-burning sap.

"The clear watery sap of Giant hogweed contains toxins that can cause severe dermatitis (inflammation of the skin). You can get severe burns if you get the sap on your skin and the skin is then exposed to sunlight," reads the provincial government's invasive species information portal.

"Symptoms occur within 48 hours and consist of painful blisters. Purplish scars may form that last for many years. Eye contact with the sap has been reported (in the media and by various websites) to cause temporary or permanent blindness."

The province notes that any claims of permanent blindness caused by Giant hogweed are purely anecdotal, but that doesn't mean there aren't any serious threats associated with the invasive plant. Who wants purple bruises that last for years?

Metrolinx, which operates the GO regional transit network, announced on Friday that staff had recently found and removed some Giant hogweed that had been growing alongside train tracks near Evergreen Brickworks.

The GO Train operator is warning people to stay on the designated trails when enjoying Toronto's natural landscape and to stay away from rail corridors (if they haven't already learned to), where the plant is known to prefer growing, in addition to roadsides, ditches, streams and open woodlands.

Giant hogweed has the potential to spread readily, producing up to 120,000 winged seeds per plant when they die.

Like fellow non-native flora including Common burdock and Purple loosetrife, the proliferation of Giant hogweed could have serious impacts on our local ecosystem, choking out other types of plant life and harming native wildlife.

If you spot something you believe to be Giant hogweed in Toronto, you can call 311 to report the sighting, but be careful not to touch the stuff. Those who accidentally touch the weed are advised to wash their hands immediately and get out of the sun. It usually takes about 15 minutes for the blisters to start appearing once exposed to sunlight.

Lead photo by

Jon Sullivan

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