Aquatic Invasive Plants
This information was provided by the LCPOA Environment Committee, December 2020.
These plants can be floating or rooted, underwater or partially above water. They can displace native vegetation, slow down water flow, alter oxygen levels and affect enjoyment of boating, fishing and swimming.
Eurasian Water-Milfoil
Eurasian Water-Milfoil
This familiar aquarium plant was probably first introduced to our continent as aquarium “seaweed” or in the ballast of international ships entering Canadian waters and has now invaded our waterways. This fast growing Eurasian form of Milfoil can interbreed with native forms, creating a more aggressive invasive species.
Eurasian Milfoil prefers water depths of less than 3 metres but can root in up to 10 metres of water and establish itself in a variety of substrates. It forms dense mats that shade other plants and decrease oxygen levels in the fall when they die and begin to decay, which can affect our fish population and is especially harmful to lake trout. Dense stands of this weed can stagnate water, which is an ideal breeding ground for mosquitoes.
Small plant pieces can easily grow into new plants.
Eurasian Milfoil prefers water depths of less than 3 metres but can root in up to 10 metres of water and establish itself in a variety of substrates. It forms dense mats that shade other plants and decrease oxygen levels in the fall when they die and begin to decay, which can affect our fish population and is especially harmful to lake trout. Dense stands of this weed can stagnate water, which is an ideal breeding ground for mosquitoes.
Small plant pieces can easily grow into new plants.
Frequently Asked Questions (FAQ's)
Starry Stonewort
Starry Stonewort
This is another native Eurasian plant that was unintentionally introduced to our Great Lakes from ships’ ballasts and is slowly creeping north towards Lake Clear. Starry Stonewort is actually a micro algae with no true roots, stems or leaves. Each stem or branchlet is actually a single cell.
This aggressive “plant” can form dense mats in shallow water (2 to 10 metres) where it outcompetes native aquatic plants. It is unsuitable as food, shelter or nesting for native fish and wildlife, impedes water flow and makes swimming and boating unpleasant.
Not only is this invasive species brought into lakes by boats and trailers, but since the reproductive cells called oocytes can attach to fur and feathers, animals can also move Starry Stonewort from lake to lake.
This aggressive “plant” can form dense mats in shallow water (2 to 10 metres) where it outcompetes native aquatic plants. It is unsuitable as food, shelter or nesting for native fish and wildlife, impedes water flow and makes swimming and boating unpleasant.
Not only is this invasive species brought into lakes by boats and trailers, but since the reproductive cells called oocytes can attach to fur and feathers, animals can also move Starry Stonewort from lake to lake.
Frequently Asked Questions (FAQ's)
These plants, or cell chains, have bushy, bright green branchlets (branchlike structures) found in whorls, radiating from a single point on what looks like a fine stem. Sometimes single stems look like fishing line, but they have little white knots that look like stars. These are the bulbils or seeds that are deposited in the mud and can survive our cold winters allowing the plant to spread easily. The entire structure can grow up to 2 metres in length.
As with all invasive aquatic species it is imperative that boats and all water equipment are thoroughly and properly cleaned if they have been in another water body. Small fragments and bulbils from Starry stonewort are difficult to see but both could bring the species into our lake.
Recommendations are to spray equipment with high-pressure water, rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds) and dry for at least five days.
Lakes such as Lake Simcoe in Ontario that are already suffering with this infestation have found that no herbicide seems to kill these micro algae. Mechanical harvesting is best. Since there are no roots, the entire mat should be pulled or skimmed from the water. Cutting could cause small fragments to spread.
Recommendations are to spray equipment with high-pressure water, rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds) and dry for at least five days.
Lakes such as Lake Simcoe in Ontario that are already suffering with this infestation have found that no herbicide seems to kill these micro algae. Mechanical harvesting is best. Since there are no roots, the entire mat should be pulled or skimmed from the water. Cutting could cause small fragments to spread.
Other Invasive Aquatic Plants
Fanwort and European Frog-Bit
Fanwort
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European Frog-Bit
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These plants have been found in nearby watersheds. They both are persistent rooted or floating, submerged perennial plants with white to pinkish flowers of 3 petals, which can form large dense mats.
Yellow Iris
Yellow Iris
Originally introduced as an ornamental garden plant, it has been found in wetlands and shallow water throughout southern Ontario. Dense stands can displace native vegetation and can begin to dry up the wetlands. The plant is poisonous if ingested by animals and can cause skin blisters on humans.
Curly Leaved Pondweed
Curly Leaved Pondweed
This plant is a unique and easy to identify rooted plant that can also dominate large areas.
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