Toxic giant hogweed spreading in Canada


It can cause third-degree burns and even permanent blindness – and it’s spreading.

Giant hogweed is cutting a wider swath in B.C. and Ontario, and the Nature Conservancy of Canada is urging people across the country to document sightings of the­ towering green plant with large umbels of white flowers.

Dan Kraus, a biologist with the conservancy, says the invasive species likely arrived in Canada in the 1940s as an ornamental plant and can now be found in the Atlantic provinces, Quebec, Ontario and B.C.

Its clear sap can cause blistering third-degree burns and even permanent blindness if it touches the body and is then exposed to the sun, through a phototoxic reaction.

Kraus says there is also a concern about a loss of native biodiversity, as giant hogweed is an aggressive plant that can outcompete native plants and spread — especially when it grows near rivers and streams and its seeds are carried downstream.

He says the conservancy is asking people to document sightings of the invasive plant through apps such as iNaturalist, which helps scientists understand how the plants are spreading and identifies areas they need to be eradicated.


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