The Nature Conservancy of Canada is urging people to document sightings of giant hogweed.
The towering, three-metre green plant, which has large white flowers, has been spreading in southern Ontario and elsewhere in Canada.
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.
The conservancy is asking people to document sightings of the invasive plant through apps such as iNaturalist.