Canadians cautioned to look out for toxic giant hogweed

Canadians cautioned to look out for toxic giant hogweed

The plant has been discovered in the Atlantic Provinces, Quebec, Ontario and B.C.

The Nature Conservancy of Canada (NCC) is urging people across the country to be on the look out for giant hogweed, a tall, green plant with white flowers that is one of the most dangerous plants in the country due to its serious threat to human health.

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.

In British Columbia, it has been originating in the Lower Mainland area and moving inwards from there, according to Richard Klaski, program director for the Canadian Rockies Nature Conservancy of Canada.

“Down there it’s wetter, damper,” Klaski explained. “It does really well along streams and moist areas, meadows and stuff.”

Clerks said that, for the most part, in the Kootenays so far the only place it has been officially recorded is in New Denver in the West Kootenays. However, people in this region may confuse it with another plant that grows regionally and looks very similar to hogweed, called Cow Parsnip which grows in moist areas, avalanche paths and along streams, particularly in higher elevations.

Cow Parsnip forms an umbrella-like shape, with a white flower head, large leaves and it grows to about five or six feet tall.

“So basically if anyone thinks they have hogweed, take a picture of it with somebody standing beside it for scale,” Klaski said, “because the giant hogweed is 12 to 15 feet tall so it’s humungous. So Cow Parsnip, that looks a lot like it, is only shoulder height, waist height usually. Maybe in the best places it might get up to six feet tall.”

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 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.

“You are sharing that information with plant experts, biologists, different folks and you’re really doing people a favour because what you’re doing is you’re showing where this plant is potentially spreading or where an infestation may grow and then people can also comment and confirm whether or not that’s giant hogweed or not,” explains Andrew Holland, national media relations director with Nature Conservancy in an interview with the Townsman.

“So it’s a really useful app that more and more municipalities are relying on, invasive plant and invasive species councils and others — it’s kind of like citizen science, and so it’s a way people can really help out, keep tabs on these things so it can be managed.”