What is Duckweed?

A common native aquatic plant that is visible during summer months is duckweed. But what is all that bright green stuff, and is it good or bad?

image of small duckweed plants
Photo of individual duckweed plants

Duckweed is a small, aquatic plant that grows on the surface of waterbodies. Duckweed usually grows in standing water and is more widespread during the warmest months of the year. This aquatic plant is not rooted in the lake bottom, so it moves easily when the wind blows it or there is current in the water. Duckweed can form a bright green “blanket” over the surface of small waterbodies, which some find unappealing. Despite its looks, this native plant benefits wildlife and poses no human or environmental health risks. Duckweed is a great food source for ducks and geese, and it can help prevent unwanted algae blooms.

Even with its benefits, there may be areas where duckweed is unwanted. Although duckweed is difficult to control because it regrows easily, there are two primary methods to manage duckweed. A licensed applicator can apply aquatic herbicide to control duckweed growth. You can also physically skim the water’s surface to remove duckweed. The Nine Mile Creek Watershed District does not participate in duckweed control because duckweed does not impair water quality. Check with your city about any local rules before applying herbicide. A permit from the Minnesota Department of Natural Resources (MnDNR) may also be required to apply herbicides. Learn more about MnDNR regulations: https://www.dnr.state.mn.us/shorelandmgmt/apg/regulations.html.

Learn more about duckweed!

Duckweed Fact Sheet