Greenough Harbour Community

The GHPA Board Minutes for the Apr 5 2023 meeting are now available under the Resources tab.

Dangers of The Giant Hogweed

It’s a dangerous world out there, with Wild Parsnips, Posion Ivy, and another invasive and very toxic species to be aware of – the Giant Hogweed!  Giant Hogweed is a huge, toxic plant that can burn skin and cause permanent blindness.

Contact with the weed’s clear, watery sap can be very dangerous, Jeff Muzzi, Renfrew County ’s forestry manager and weed inspector. “What it does to you is pretty ugly,” said Mr. Muzzi. “It causes blisters. Large blisters and permanent scarring. What’s left over looks like a scar from a chemical burn or fire.” Even a tiny trace of sap applied to the eye can singe the cornea, causing temporary or permanent blindness, he added. The chemicals in the sap, furocoumarins, are carcinogenic and teratogenic, meaning they can cause cancer and birth defects. The weed’s sap, which is found all over the plant, bonds chemically with human skin when exposed to sunlight and, within 48 hours, leads to inflammation, red colouring and itching, weeping blisters and eventually black and purplish scars.

Hogweed Burn3 Hogweed Burn1 Hogweed Burn2

Photos above courtesy of

Native to the Caucasus Region and Central Asia, it was brought to Europe and North America as a botanical curiosity in the 19th and 20th centuries and has spread rapidly. It typically grows on riverbanks, ditches and roadsides. While the weed is on the federal government’s official noxious weeds list, there is apparently no national or provincial strategy in place to stop its spread. A 2005 study of the plant’s spread in Canada said it was likely to continue for the next 25 to 100 years “with worsening ecological, economic and health effects.”

Here are some other pictures of the Giant Hogweed:

Giant Hogweed3 Giant Hogweed2

Giant Hogweed Leaves Have Jagged Edges As Shown Below

Hogweed Leaves


The plant grows to about 1 to 5.5 meters high, with jagged leaves as above growing as much as 1 meter on width. The stems are hollow, ridged and purple splotched with course white hairs with a diameter of about 4-10 cm at the base. The flowers as in the above pictures are white compound umbrel 80 cm. or more across made up of 4-12 smaller (14-40 cm) flat round units.

If exposed, wash the affected area immediately, get out of the sun and seek medical attention. DO NOT TRY TO ERADICATE USING A WEED WACKER!

The pdf below should be downloaded and printed off for reference.

Download (PDF, 704KB)