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European frog-bit leaves and flower

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.


Regulated areas of European frog-bit
European frog-bit is Prohibited (Red counties)

Other names for this plant include:

  • Common names: common frogbit

Ecological threat:

  • 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!


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Last revised: Monday December 11 2017