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European frog-bit (Hydrocharis morsus-ranae)
A free-floating annual aquatic herb in the Frog’s Bit family. Can dramatically affect native aquatic life and limit recreational activities.
European frog-bit is Prohibited (Red counties)
Other names for this plant include:
- Common names: common frogbit
- Invades shallow, quiet, or slow-moving water; edges of lakes, rivers, and streams; swamps, marshes, and ditches.
- Forms large colonies of dense, floating mats that can dramatically affect native aquatic life and limit recreational activities.
Classification in Wisconsin: Prohibited
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for European frog-bit was based upon this literature review developed by the department.
Leaves: Usually floating; resemble tiny water lilies; kidney-shaped with long stems; 0.5-2.25” in diameter; smooth; often dark purple beneath; lateral veins are arching and make a 75-90 degree angle with the midvein; tissue containing airpockets are located mostly along the midvein. Lower leaf surfaces are dark purple in color.
Flowers: White; cup-shaped; three petals with yellow dots at base; bloom mid-summer.
Fruits & seeds: Rarely produces seeds and instead relies on vegetative reproduction.
Roots: Long, cord-like stolons form large floating mats of connected plants. It also forms turions.
Similar species: Often confused with American frog-bit (Limnobium spongia), a species whose leaves have lateral veins that make a 30-80 degree angle with the midvein, and whose leaf tissue contains large air pockets throughout.
Currently, there have not been reports of European frog-bit in WI. Have you seen it? Send us a report.
Mechanical: Other than hand-pulling, there are no known control methods.
View European frog-bit pictures in our photo gallery!
Sources for content:
- Czarapata, Elizabeth; Invasive Plants of the Upper Midwest: an illustrated guide to their identification and control. University of Wisconsin Press. 2005. Pg. 146
- Global Invasive Species Database: European frogbit.
- Invasive Plant Atlas of New England: European frogbit
- European Frog-bit (Hydrocharis morsus-ranae) A Technical Review of Distribution, Ecology, Impacts, and Management Wisconsin DNR publication SS-1048
Links for More Information