Not every plant in Muskoka is friendly.
Once considered a garden ornamental, giant hogweed is now referred to as an invasive species, a flowering plant that is spreading throughout the region, said Don Chadwick, road maintenance and weed inspector for the District Municipality of Muskoka.
“It’s spread around Gravenhurst, Bala, Dwight, Port Carling,” said Chadwick. “I’m sure it’s spreading (even further) – it has been for the last 50 years.”
The pesky plant, which has been compared to cow parsnip, can grow upward of 5.5 metres, has white, umbrella-shaped flower heads, pointed leaves that can grow about 12 inches in width, and a thick, hair-covered stem speckled with red or purple dots.
It also excretes a poisonous sap that can cause severe burns if it comes in contact with human and animal skin. The clear, watery sap causes photo dermatitis, making skin extremely sensitive to light, resulting in severe blistering, scarring and even blindness if it comes into contact with the eyes.
“It came from Asia,” explained Chadwick. “People probably liked the way it looked and brought it to the U.K., then to Canada.”
And now it’s difficult to get rid of it. Removing the plant requires full-body covering, including goggles, and a sharp, serrated knife to cut the stem. The seed heads and flowers, along with the rest of the plant, need to be bagged and sent to a landfill to prevent spreading.
According to InvadingSpecies.com, it may take several years to completely eradicate an infestation of it.
According to a letter dated Oct. 31, 2002, and distributed by the Ministry of Food and Agriculture, the Weed Control Act does not apply to nuisance weeds, such as poison ivy, ragweed and giant hogweed.
“The purpose of the Weed Control Act is to protect horticultural and agricultural land from noxious weeds … the act does not refer to the protection of human health as a reason for controlling noxious weeds,” adds the letter.
Therefore, according to Chadwick, weed inspectors are not mandated to remove giant hogweed.
Jan McDonnell, natural heritage biologist for the Ministry of Natural Resources in Bracebridge, said most hogweed is found on private property, making it “up to the private landowner to remove and control” the plant, though reporting any sightings to the Invading Species Hotline is a good step.
The hotline is a part of the Invading Species Awareness Program, a joint endeavor between the Ministry of Natural Resources and the Ontario Federation of Anglers and Hunters.
McDonnell said hogweed not only negatively affects humans and animals, but also poses a threat to the environment.
“It’s a very aggressive and invasive plant,” she said. “One worry is that it grows so well here that it replaces native vegetation – this plant can really take over areas.”
Eradication of hogweed is being handled mostly through public education, said McDonnell, though identifying the plant does not seem to be a problem.
She said the flowers look similar to Queen Anne’s lace, but “giant hogweed is huge – it can easily be twice as tall as a human … and the flower heads are huge, at least a couple feet in diameter.
“People usually ask, ‘How do I know if I have the plant?’ The answer is the size. Nothing grows bigger that’s native to Ontario, unless it’s a tree,” she said.
If you come into contact with giant hogweed sap, avoid sunlight, wash immediately with soap and water, and seek medical attention.
For more information on identifying or removing giant hogweed, call the Invading Species Hotline at 1-800-563-7711, or visit InvadingSpecies.com or WeedInfo.ca.