Water soldier (Stratiotes aloides) is a submerged perennial aquatic invasive plant native to Europe and northwest Asia. In 2008, the only known population in North America was found in the Trent River Ontario, Canada. This infestation was likely established by the use of water soldier as an ornamental plant in aquatic gardens. Stopping the sale and use of water soldier is imperative to preventing its spread.
Water soldier forms dense mats of floating vegetation that displace native aquatic plants and can alter surrounding water chemistry. These mats can also hinder recreational activities such as boating and fishing. Swimmers can become injured with cuts from water soldiers’ sharp serrated leaf edges.
Leaves form in a circular rosette, each about 40 cm long, sword-shaped, bright green, with sharp spines. Leaves are submerged at first to later become buoyant during the summer months. As leaves mature, they become waterlogged causing the plant to sink below the water surface.
Flowers are not always present but are white with three petals, and the fruit is a fleshy berry containing up to 24 seeds.
Manual Control: Small infestations can be managed by hand pulling. Extreme care and proper protection should be used as the serrated edges can cut skin. The use of shade cloth enclosures was reported effective by Ontario’s Invading Species Awareness Program.
Chemical Control: To avoid non-target species chemical applications should occur in the fall while water soldier is actively growing and native plants have gone dormant. NOAA’s Great Lakes Aquatic Nonindigenous Species Information System suggests Diquat herbicide as an effective chemical application.