Published on Mon, 06/25/2018 by Nature Conservancy of Canada

Look out for and report Giant hogweed: Nature Conservancy of Canada raises awareness about dangerous plant

While summer is arriving, another sign of better weather brings a troublesome and dangerous plant called giant hogweed.

Giant hogweed is one of Canada’s most dangerous plants as it poses a real human health concern.

The Nature Conservancy of Canada (NCC) is urging people across the country to document sightings of the towering green plant. Giant hogweed is one of Canada’s most dangerous plants as it poses a real human health concern.

The non-native plant usually grows up to four to six metres in height. It features large clusters of white flowers at the top. It grows along streams, roadsides, ditches, in open fields and woodlands.  

The not-for-profit land conservation group says the plant is visible now and flowering so it is easy to identify.

The plant’s clear, toxic sap can cause rashes, blistering, third-degree burns and temporary and even permanent blindness if it touches the body and is then exposed to the sun.  

Infestations have been spreading in Canada with discoveries in the Atlantic Provinces, Quebec, across Ontario and BC.    It has been found in many urban centres such as Greater Toronto and Ottawa. 

Giant hogweed was brought to Canada from Eastern Europe and Asia in the 1940s as a decorative, horticultural plant. This invasive plant is spreading around the world and now occurs in Europe, Australia, New Zealand and the United States.

Nature Conservancy of Canada national conservation biologist Dan Kraus says one issue is that people think it would be an interesting garden addition, and move it from garden to garden or collect the seeds and plant them. 

“A single plant can produce thousands of seeds and it can spread quickly. The seeds are dispersed when they fall into rivers and streams, and can be dispersed short distances by the wind.  Because it’s a tall perennial, giant hogweed can take over large areas along rivers and streams, shade out all of our native vegetation and actually nothing can grow under it sometimes,” said Kraus. “In Europe, dense stands of Giant Hogweed along rivers have caused erosion and it has been identified as a serious threat to salmon spawning habits in Great Britain.”

Kraus urges people to not take a specimen of the plant or touch it, as contact with it can cause burning of the skin, as well as other complications. He says people who find giant hogweed should have it removed professionally by people wearing protective gear.  People may also contact their local municipality along with provincial invasive plant and species councils who take records of sightings. 

Kraus also encourages people to report it by using the app. By downloading the app on your phone, it allows you to take a picture of a species and share it with plant experts who can help identify it.  The app will automatically map it as well so people can see where giant hogweed is spreading.


The Nature Conservancy of Canada (NCC) is the nation's leading not-for-profit private land conservation organization, working to protect our most important natural areas and the species they sustain. Since 1962, NCC and its partners have helped protect more than 1.1 million hectares (2.8 million acres), coast to coast.

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tall_giant_hogweed_plant_-_nature_conservancy_of_canada.jpgTall giant hogweed plant - Nature Conservancy of Canada photo3.67 MB