Invasives: Control Measures on Clear Lake

Despite its name, Clear Lake has water quality concerns. The little lake in Minnesota is infested with two invasive species.

They are Curly leaf pondweed and Eurasian watermilfoil and are common across the state.

Clear Lake, 2005. (Credit: Christopher Aloi via Creative Commons)

According to the Minnesota Department of Natural Resources, Curly leaf pondweed:

• has small teeth visible along the edge of its leaf;

• begins growing in early spring;

• and appears reddish-brown in the water.

Curly leaf pondweed. (Credit: Robert Mohlenbrock, Global Invasive Species Database, U.S. Department of Agriculture)

Eurasian watermilfoil:

• forms in thick underwater stands of tangled stems;

• can create floating canopies that crowd out other aquatic plants;

• and establishes new colonies quickly.

Eurasian milwaterfoil. (Credit:

In response to the infestation, the Waseca Lakes Association is planning to chemically treat Clear Lake with herbicides and rein in the two species. Officials say removing the invasives completely isn’t possible and are instead opting to control them the best they can.

Though Eurasian watermilfoil can strangle some subsurface plants, according to the University of Wisconsin – La Crosse, Curly leaf pondweed can benefit some ecosystems if its levels are properly maintained.