The Giant Hogweed Mitigation Project has confirmed 1,700 reports of giant hogweed in the Grand River watershed this summer, prompting the rare Charitable Research Reserve to warn people about the importance of avoiding the plant.
Watery sap excreted from the plant can cause severe skin inflammation and when exposed to sunlight can result in burns.
"Hogweed propagates along the river system, as its seed are generally spread by flood waters," Tom Woodcock, planning ecologist for rare Charitable Research Reserve, said.
"At rare, we see the plants growing almost exclusively in the active floodplain. Throughout the years we have watched numbers grow exponentially on our property, requiring increasing effort and staff time to control, which takes away from other duties, including control of other invasive plants."
Containment can be difficult due to re-infection from downstream sources, Woodcock said.
Each plant is capable of spreading up to 50,000 seeds that can travel for three days.
Ideally, hogweed is removed as seedlings but in cases of growth, seed heads can be removed from mature plants.
So far this year, rare has dealt with over 1,000 plants.
"The larger they get, the more protective equipment and precautions are necessary," Woodcock said.
"Professional control should be sought to deal with hogweed on a property. The volunteer run Giant Hogweed Mitigation Group has been the main voice attempting to raise the alarm of hogweed infestation in the Grand River drainage. We've been working with them to attempt to document populations and raise awareness of the need for control."
Woodcock reiterates that on rare property hogweed doesn't appear near trails or where the public typically is.
As for his advice for people who are out and about, avoid it.
"Stay away, it can cause significant burns," he said.
"Report sightings to the appropriate municipality and if it's on your property, seek professional removal."
Hogweed can be documented using the apps iNaturalist, EDDMapS and through the Invasive Species Center.
