THE ISSUE:  Common/European frogbit   

Common/European frogbit (Hydrocharis morsus-ranae) is an aquatic annual native to Europe and Northern Africa.  It invades rivers, lakes, reservoirs, and wetlands. It establishes particularly well when sheltered from currents and waves. Common frogbit is typically free-floating but when water is less than 2 feet deep it can root in soil. It spreads very quickly forming large dense mats of vegetation that interfere with native ecosystems, recreation, and irrigation.  

Common frogbit leaves look like small lily pads (1/2-2 ¼” in diameter), with a round heart shape. Leaves are yellowish green on the top and purple on the bottom. Flowers are small, white, have 3 petals (½” in diameter), and have yellow centers. Its ability to spread vegetatively by stolons and fragmentation allows this weed to spread very quickly. 

Integrated Pest Management (IPM) Options: 

• Prevention— Learn to identify this plant. Remove all vegetation from boats and recreational equipment before transporting to a new body of water. Never dispose of aquarium contents in bodies of water. Report sightings to local authorities. 

• Mechanical— When small infestations are present hand removal can be effective. Remove as much plant material as possible. This weed can reproduce from broken fragments.   

• Cultural— Water drawdown during the winter or in the spring can help to control populations in small bodies of water.   

• Chemical—Consult with local authorities before attempting to control this weed with herbicides. Special care should always be taken when using herbicides near bodies of water. Always read and follow herbicide label directions!

Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou County. 208-547-3205 [email protected]