Keep an eye out for Giant Hogweed

Tall giant hogweed plant - Nature Conservancy of Canada (wings)

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

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 can grow up to five 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. A key feature to look for to identify this plant is purple prickly stems.

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

This plant has been spreading in Canada with documented occurrences in the Atlantic Provinces, Quebec, 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.

“A single plant can produce thousands of seeds per year 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, outcompeting our native vegetation,” said Andrew Holland, national media relations manager for NCC.

Holland 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 and determine management plans and ways to remove and control infestations. 

Holland also encourages people to report it by using the iNaturalist.ca 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.