Herbicide eliminated Eurasian water-milfoil, but it won’t kill invasive starry stonewort, officials say
Kal Johnson, chair of the Lagoon City Parks and Waterways Commission (LCPWC), remembers the days when the phone rang off the hook with complaints from people whose boats were caught up in weeds and unable to move through the canals.
“The reason we harvest the weeds is so the canals stay navigable,” said Laura Pye, general manager of development and infrastructure for the Township of Ramara.
Harvesting — completed on a daily basis during business hours — takes place between July and October. Weed management started in 2007 but with few tracking methods.
“We are looking into developing more measurable performance metrics,” Pye said, responding to a December report that shows a steady reduction in the amount of weeds in the canals over the past three years.
Significant changes took place more than a decade ago, according to Johnson.
The LCPWC started working with the company Weeds B Gone, which serves clients along the waterways of southern and central Ontario.
Clean-Flo — an aeration system with compressors that create bubbles to keep the water moving — was installed. In some areas of the lagoons, the muddy bottom eroded to a hard clay surface.
This is a good thing, explained Johnson, because it led to less plant growth as clay harbours fewer nutrients. Oxygenation from the bubbler system is healthier for fish to live in and fewer weeds allows them more space to swim.
Johnson believes the system has saved them hundreds of thousands of dollars in what would otherwise have been used for dredging. It could also prevent the return of blue-green algae, which prefers calm water and high temperatures.
“When you see those bubbles come up, you don’t think that you’re moving the water much, but when you look at the stats and how far that little bubble pushes water around, it really is amazing,” said Johnson.
At the same time, the Clean-Flo system cleans the water, which encourages plant growth, “so we have to harvest,” said Johnson.
The invasive Eurasian water-milfoil was eliminated by the use of herbicide, but there are more invasive species to worry about in Lake Simcoe.
Among its other concerns, removing weeds has been a top priority of the LCPWC. Use of the canals is, after all, Lagoon City’s biggest attraction.
“That spray killed it, but it doesn’t kill the starry stonewort,” said Johnson.
The herbicide killed the water-milfoil but also everything else in the water, which is not ideal.
Earlier this year, Ramara released a notice that it had stopped using herbicides in an effort to improve water quality and long-term sustainability. Johnson is curious and keeps watch for if the water-milfoil returns.
The current problem is with starry stonewort, which acts more like algae, gaining its nutrients from the water, not the ground. This grass-like seaweed, also native to Eurasia, forms dense, impenetrable strands. It displaces other species and blocks smaller fish from shelter in their habitable shallow depths.
“It’s one of the hardest ones to deal with because it’s so heavy,” said Johnson.
He described improvements to the process since an additional harvester was purchased and put to use in 2024.
“It holds over three times what the little harvester held,” he said.
The harvesters bring the weeds to a barge, which transports them to a conveyor that offloads into a bin located at Cedar Lagoon. The harvested weeds are then brought to a licensed disposal facility.
In the early days, Johnson said the goal was to harvest each lagoon twice a day. Now, with the upgraded equipment and increased frequency, it is easier to keep up with the weeds. Staff hired for snow removal are not laid off in the summer as they are trained to operate the harvesters.
“We need to stay as efficient as we can,” Johnson said about plans for 2026.
The starry stonewort, in particular, will propagate where it is cut, and throwing it back in the water if found tangled in boats will only add to its spread. If spotted, it should be disposed of on land away from the water. It is also recommended to call the Invading Species Hotline at 1-800-563-7711.
Residents and visitors can still expect to enjoy clearer waterways than Lagoon City has seen in the past.
There are many directions the LCPWC can choose to focus on. It manages the weeds in the canals, as well as bridges, beaches and parks. With some newer members, Johnson believes the commission will learn what is important to residents during the next campaign and decide from there how to move forward.
The harvesting season will resume the first week of July. More information about routes and times can be found here.