A big plant is invading Waterloo Region, and it’s causing big problems says John Kemp, founder of the Giant Hogweed Mitigation Project Community.
“Giant Hogweed is definitely a growing problem this year. We’ve taken the data that’s been collected since 2010, and we determined that the population is growing about five times per year,” Kemp says.
“That means that this year is five times worse than last year, and next year will be 25 times worse than last year. The year after that, it will be 125 times worse. It’s a scary problem.”
Giant Hogweed is an invasive plant, native to the Caucasus region between Southwestern Asia and Europe. It is in the carrot and parsley family, closely related to Cow Parsnip, which is the only member of the hogweed genus native to North America.
Giant Hogweed was first introduced in the early 1900s. Ontario’s first confirmed record of the plant was in 1949. It grows to an enormous size, producing large umbrella shaped clusters of white flowers.
Today, it is scattered across southern and central Ontario with populations ranging in size from one to thousands of plants.
Kemp says Giant Hogweed is a dangerous invader.
“It’s the damage to humans, that’s the real problem. If you get the sap from the plant on your skin, it removes the ability of your skin to protect you from sunlight. It takes about six hours to do this damage to skin and you may not even notice anything happening,” Kemp says.
Giant Hogweed sap contains toxins which can increase the skin’s sensitivity to sunlight and may result in severe burns and blisters and temporary or permanent blindness if it comes in contact with the eye.
“Once you are exposed to even moderate sunlight, you will get a full burn where you will blister. This can take months to heal. You can be permanently marked or discoloured. Sometimes you will get a sunburn on that same spot for years," Kemp says.
Giant Hogweed is also an ecological threat as it competes with native plants for space, sun, and nutrients.
In 2019, the Giant Hogweed Mitigation Project Community was introduced, a Facebook group dedicated to raising awareness and helping with efforts to remove the invasive plant.
The group was established to share information about Giant Hogweed along the shores of the Grand River and its tributaries. The premise is that everyone, ‘as a community, can arrest the spread of this hazardous and poisonous plant and keep the riverbanks friendly and safe’.
Kemp encourages people to spread the word and recommend the Facebook group to help raise awareness and build community.
The primary task is to safely locate the plants with landowners and volunteers. Removal will be dealt with by trained personnel later. Hunt events occur in mid April through mid May, according to the Facebook group page.
“I first found out about Giant Hogweed in 2012. I was looking for information about poisonous plants for Scouts. At that time, Scouts could obtain a badge after they had learned about poisonous plants and how to avoid them," Kemp says.
Kemp says he discovered that Giant Hogweed likes to grow in damp or wet environments where the seeds are moved predominantly by humans, and then secondly, by currents in the water.
Since the mitigation program began, Kemp continues to meet with hunters, fishers, canoeists, and kayakers by attending their general meetings and making presentations.
“We probably have about 500 people watching for Giant Hogweed and about 10 who are actually removing it,” Kemp says.
“Often, the property owner does not even know that it is dangerous to humans.”
Kemp says the largest Giant Hogweed he has seen to date was 15 ft tall.
But Kemp says Hogweed and Giant Hogweed are different plants.
Also, not to be confused with the native plant, more commonly known as Cow Parsley, Giant Hogweed is considered its ‘alien relative’ and is extremely dangerous.
From April until November, Kemp says Giant Hogweed can really pose a danger between April and November.
“The seeds land and float down stream and begin growing in other locations. That’s what we are dealing with right now. It’s not just one seed landing, it’s literally billions of seeds,” Kemp says.
“One plant can produce about 21,000 seeds.”
Kemp says mitigation takes a four-visit approach.
“We find them, take them out, go back at the end of April, and then check again in early June. When they are ‘bolting’, they shoot up three and a half inches daily with a strange pod on top, looking like something from an alien movie,” Kemp says.
“And the fourth visit is in July, when the flowers are out, and the plants are at least six ft. tall up to 15 ft. tall with a glorious white flower on top, and that’s when we can find them again. The plants will die because when it makes a flower, it goes to seed, and it dies.”
Kemp says the important thing is to capture the seeds to prevent spread.
“Right now, it’s tough and it’s a problem. I think the key is to get everyone looking at the shorelines in April. That’s when the plants are big enough to see and are obvious. Then we can dig them up, mark the spot, and come back later to see if there is any more growth,” Kemp says.
“By collecting information about the location and quantity of the plants, we can determine the source of the seeds and then plan the best methods for control. Our goal is to help each other in this battle.”
To learn how to identify and control invasive plants on your property, see the list of guides provided by the Ontario Invasive Plant Council here.
For more information about the Giant Hogweed Mitigation Project Community Facebook group visit here.
