What is European Frog-bit?
European frog-bit (EFB) is an herbaceous, free-floating, freshwater plant that grows into 4-8 inch rosettes with heart shaped leaves. The flowers have three white petals and a yellow center. European frog-bit can form daughter plants connected by horizontal floating stems. Depending on location, EFB plants can exist as scattered rosettes interspersed among emergent and floating vegetation or they can grow into dense mats of interconnected rosettes.
View of single EFB rosette
Two EFB flowers
Horizontal view of newly germinated EFB plants
Growth & Reproduction
European frog-bit flowers from mid- to late-summer. After a female flower is fertilized, a round, green fruit begins to develop and ripen underwater. Once ripe, internal pressure causes the fruit to split, releasing the seeds. Seeds sink to the lakebed where they remain until germination in the following growing season.
EFB rosette with fruits
EFB seeds pre- and post germination
In addition to sexual reproduction, EFB can reproduce asexually. Clonal daughter plants are produced throughout the growing season from buds at the tips of horizontal stems. European frog-bit can also produce modified buds, called turions, that detach from the plant and sink to the lakebed. Turions remain on the substrate overwinter until conditions warm and they float to the surface. Turions produce new EFB plants in the spring and summer.
EFB rosette with turion
EFB rosettes germinating from turions
European frog-bit can form dense, entangled, floating mats that cover the surface of the water. These mats have the potential to impact the human use of waterbodies by clogging navigation and irrigation channels and hindering recreational and commercial activities. These mats also have the potential to reduce light, dissolved gas, and nutrient availability in the water column below, and there is concern this can negatively impact native flora and fauna and lead to negative social, economic, and environmental impacts.
A large mat of EFB in St. Clair Flats, MI
A large mat of EFB in Lake Erie, MI
EFB among water lillys in Alpena, MI
Habitat & Ecology
European frog-bit can be found in wetlands associated with lakes, rivers, and streams, as well as artificial waterbodies such as canals, channels, ditches, and ponds. Within wetlands, it can colonize the emergent, floating, and submerged vegetation zones. In Great Lakes Coastal Wetlands, EFB is often associated with cattail and common reed, which shelter it from wind and wave action. European frog-bit often occurs in nutrient rich waters, but may establish in areas of varying water quality. You may commonly find EFB in manmade waterbodies with stagnant water or Great Lakes Coastal Wetlands intermixed with emergent vegetation.
EFB intermixed with a common reed stand
EFB growing along edge of cattail stand
EFB mat growing across a drainage pond
European frog-bit was first documented outside of cultivation in North America in Ontario in 1939. It has since been recorded in Ontario, Quebec, New York, Vermont, Ohio, Michigan, Maine, Pennsylvania, and Washington state. Within North America, EFB seems to be tolerant of a wide range of climatic conditions, making it a high risk species for further spread.
North American Spread of EFB from 1950 to 2020
Map updates in one-year intervals and slows down in 2010, at the start of targeted EFB monitoring in many regions.
Documented occurrences of EFB as of 04 February 2021
How it Spreads
European frog-bit's free-floating habit allows it to drift with waters natural flow between connected waterbodies. European frog-bit and its reproductive structures are also capable of spreading between waterbodies by accidental transportation via boat trailers and recreational equipment. Wildlife may contribute to EFB spread by becoming entangled in EFB rosettes or seeds and turions passing through the digestive tracts of waterfowl. It is also possible that EFB can be introduced through the improper disposal of plants in the water garden and aquarium trade.
How to Report
If you think that you have encountered EFB, make sure to take one or several photos, note the location, date, and time of the observation and report to:
-EGLE Aquatic Invasive Species Program EGLE-WRD-ANC@michigan.gov 517-284-5593
- Or -
-Use the Midwest Invasive Species Information Network (MISIN) online reporting tool
- Or -
-Download the MISIN smartphone app and report from your phone http://www.misin.msu.edu/tools/apps/#home
What You Can Do
By becoming informed and sharing information about EFB, you can help change public awareness and perception of this invasive aquatic species. If you recreate in areas that have known EFB populations or have the potential to have populations, be sure to keep an eye out and report occurrences. Make sure to decontaminate watercraft, trailers, and gear to prevent the further spread of this species.