Duckweeds and Watermeal (Lemna minor, Spirodela polyriza, Wolffia columbiana)

Lesser duckweed illustration Greater duckweed illustration Watermeal illustration


Common names: Lesser duckweed, duck's meat, water lentil.

Location: Ponds and quiet backwaters of lakes and streams; some duckweeds are often found near creek inlets or in ditches. Rarely will duckweed become overly abundant on lakes and large ponds exposed to wind and heavy wave action. Watermeal is often found growing with duckweed.

Description: Tiny, free-floating green plants. Watermeal resembles small grains floating on the water surface; no roots are present. Duckweed typically consists of a leaf or cluster of leaves with small roots that hang down into the water; leaves and stem are not distinguishable from each other.

Hints to identify: From a distance, duckweed is often mistaken for algae; it may form a thick, green blanket on the water surface. Duckweed is not interconnected, as is filamentous algae. Watermeal resembles green cornmeal floating in the water.

Importance of plants: Provide food for waterfowl and marsh birds; support insects that fish eat. However, may shade out larger, submerged plants.

Management strategy: See DNR regulations. Because duckweed and watermeal reproduce rapidly and are small, effective control is difficult. If control is absolutely necessary, try using aquatic herbicides.