European Frogbit (Hydrocharis morsus-ranae, or EFB) was first identified in Cobbossee Lake in 2018. The plant itself is free floating and grows best in slow-moving water, such as coves and marshes. In the winter, EFB produces small seed structures called turions that drop to the bottom of the lake to lay dormant until spring, when it will grow a new plant. 

EFB sends out runners which produce new connected plants that tangle together into a dense web that is impossible to boat or swim through. Management of this plant currently relies on manual removal by both FOCW staff and volunteers.

FOCW removing EFB from Cobbossee Lake

EFB is easily pulled by hand, and volunteers and shorefront owners can pull the plants once positively identified to help reduce the spread. Plants should be disposed of away from water bodies. For information about EFB identification or tips on removal, reach out to

FOCW removing EFB Monmouth Boat Launch

Additional Resources:


Maine DEP

Invasive Species Centre


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