In 2024, a new population of water soldier was found in Lake Simcoe. Being the largest known population of water soldier in North America, the significance of Lake Simcoe as the largest inland lake in southern Ontario, and the lake’s role as a vital source of drinking water for 500,000 residents, a working group, co-chaired by the Invasive Species Centre and Ontario Federation of Anglers and Hunters, was formed to take collaborative action.

The overall goals of the working group are to:

Monitor and map this population of water soldier
Work towards the restoration of Lake Simcoe by developing and executing an integrated pest management plan
Raise awareness about water soldier and its impacts
Prevent the spread of water soldier in Lake Simcoe and beyond

What Is Water Soldier

Water soldier is an invasive aquatic plant that grows in shallow water along shorelines, wetlands, and slow-moving rivers. Originally introduced as an ornamental plant for water gardens, it has spread into natural waterways where it can quickly establish and expand.

It looks similar to an aloe plant, with long, narrow, triangular leaves that grow in a rosette (circular cluster). The leaves are bright green and have sharp, serrated edges, which can easily cut skin if handled without gloves. Water soldier can float on the water’s surface or grow fully submerged, depending on the time of year.

During the growing season, it forms dense patches of vegetation that can crowd out native plants and take over nearshore areas.

Water soldier is listed as a prohibited species under the Ontario Invasive Species Act. This means it is illegal to import, possess, transport, grow, buy, sell, or release the plant in Ontario.

How to Identify Water Soldier

Cluster of water soldier: The plant forms dense mats of floating and submerged vegetation.

Leaves:

The leaves of this plant are 40 cm long and shaped like thin swords.

The leaves form a large circle and are bright green in colour.

Leaf close-up: Sharp, serrated leaves can easily cut skin.

Flower: Some populations of water soldier produce small, white, three-petaled flowers in the summer. However, it’s important to note that populations in Ontario have rarely been found to produce flowers.

Where you might find water soldier: This plant prefers slow-moving waters rather than fast-moving waters, shallow waters, or waters that fluctuate in level. It is often found in back bays and along shorelines and can be lightly anchored in soft, muddy sediments.

Why It’s a Concern & What’s Being Done

Water soldier grows quickly, forming dense mats in shallow water that can limit recreational activities such as swimming, boating, and fishing. Its sharp, serrated leaves can also pose a safety risk to people and pets. By crowding out native plants and blocking sunlight, it can reduce biodiversity and impact local ecosystems, as well as recreation and shoreline use.

Water soldier was first detected in Cook’s Bay in summer 2024, near Young Harbour, after a member of the public reported the sighting – highlighting the importance of community reports. The Lake Simcoe Water Soldier Working Group, made up of federal and provincial ministries, Indigenous communities, municipalities, conservation authorities, and environmental organizations, is working together to monitor, map, and manage the infestation.

Management approaches depend on the size and location of the population, and may include hand removal for small patches, mechanical harvesting for larger areas, and targeted herbicide treatments where appropriate. Timing is important to reduce the spread and protect native species. Control efforts are guided by Ontario’s Water Soldier Prevention and Response Plan.

There are also opportunities from time to time for residents of the Lake Simcoe area to learn more about this population and how you can help prevent the spread through events such as workshops and site visits. Visit our events calendar to learn more.

This is a multi-year effort, and continued monitoring, management, and community awareness will be important to limit further spread within the lake.

Lake Simcoe Water Soldier Working Group:

How Water Soldier Got to Lake Simcoe

Water soldier is not native to Ontario and is unlikely to spread long distances on its own. Most introductions are linked to human activity, particularly through water gardens and ponds where the plant has been intentionally added. From there, it can enter nearby waterways through improper disposal, flooding events, or accidental movement on boats, trailers, or equipment.

Although this is the first time water soldier has been detected in Lake Simcoe, it is already present in other parts of the province. Established populations are being actively managed in the Trent-Severn Waterway and the Bay of Quinte, and it has also been found in places like Red Horse Lake.

The population in Cook’s Bay is considered a separate introduction and is unlikely to be connected to previously managed populations, including the one that was removed from the Black River.

How You Can Help!

Know the law

Water soldier is listed as a prohibited species under the Ontario Invasive Species Act. This means it is illegal to import, possess, transport, grow, buy, sell, lease, or release the plant in Ontario.

Clean, Drain, Dry your boat and gear

Cleaning, draining, and drying your boat and equipment is one of the most effective ways to prevent the spread of water soldier and other invasive species.

In Ontario, cleaning and draining your watercraft (motorized or non-motorized), trailer, vehicles entering the water, and other equipment is required by law before entering or leaving any waterbody:

- remove or open drain plugs to allow water to drain from the boat or boat equipment
- take reasonable precautions to remove all aquatic plants (weeds), animals and algae from any boat, boat equipment, vehicle or trailer

It’s even better if you can allow everything to dry completely in the sun or clean your boat from top to bottom with hot water or pressurized water.

Learn how to identify and report water soldier

If you see water soldier outside of Cook’s Bay, please report it online to EDDMapS or iNaturalist or call the Invading Species Awareness Hotline at 1-800-563-7711. A good report includes clear photos and location coordinates.

Safely manage small populations

Plants and small populations can be controlled by hand pulling or with a rake. Gloves should always be worn when handling water soldier plants to prevent injury from the serrated edges on the leaves. The best time of year for hand pulling is in the early summer before water soldier produces turions (dormant winter buds), which can be released from the plant during these activities.

What to keep in mind when planning to manage water soldier: In Ontario, the beds of most waterbodies, including Lake Simcoe, are provincial Crown land. According to the Public Lands Act, a person can remove invasive aquatic plants, including water soldier, by mechanical means or by hand without a permit if you:

are the waterfront property owner or conducting work on behalf of the property owner
minimize the removal of native aquatic vegetation (e.g., wild rice)
dispose of the plants/material you remove on dry land to prevent it from re-entering the water
use, operate or store any wheeled or tracked machinery/equipment on dry land, or on a barge or vessel
only use mechanical devices (e.g., rake, cutter bar) or your hands to remove plants, and do not dredge the bed of the waterbody
do not carry out work during fish spawning season or during the time of other critical fish life stages, as set out in the In-water Work Timing Window Guidelines.

If you cannot meet all of the prescribed rules, or want to conduct control or removal activities outside of the timing window guidelines, you will need a work permit to remove water soldier. Learn more here. Please note that these guidelines do not apply to federal lands and water bodies (e.g., the Trent-Severn and Rideau Canal waterways), and certain isolated or offline water bodies on private lands.

Refer to Parks Canada’s See It, Pull It video to learn how to safely remove water soldier.

Other Ways You Can Help

Here are a few more simple ways you can help stop the spread:

Do not include water soldier in water gardens or ponds. If you already have water soldier, dispose of it properly by removing it from the water and placing it on dry land where it cannot re-enter a waterbody or by sealing it in a bag and placing it in the garbage. Never compost or release it into natural areas.