European Frog bit – Hydrocharis morsus-ranae

European Frog-bit (Hydrocharis morsus-ranae) is a free floating aquatic plant that is usually found in marshes, ditches and swamps. This plant originates from Europe and Asia and was introduced in North America in 1932 for horticultural purposes in an aquatic/ornamental pond in the Ottawa region. Because of its ability to reproduce both vegetatively (primary mode of reproduction) and sexually, it has since spread to many tributaries and wetlands along the St. Lawrence River, southwest to Lake Ontario and northeast to Quebec City, as well as in the northeastern United States.

Hydrocharis morsus-ranae - © Photo : Kriss de Niort - Forum FAAXAAL

Hydrocharis morsus-ranae

© Photo : Kriss de Niort - Forum FAAXAAL

Rapid growth in the summer months results in dense floating vegetative mats that block light and nutrients to native plants that grow below the water's surface. In environments such as wetlands, the European frog-bit becomes the dominant species by displacing other native aquatic flora.

Eventually, these dense vegetative mats break away and decompose at the bottom of the body of water, thus contributing to the depletion of dissolved oxygen necessary for survival of fish and other organisms.

Once it has become established, the European frog-bit can hinder aquatic recreational activities such as swimming and boating and is spread very quickly via recreational boats, waterfowl or by water currents and waterways.

Because of its reproductive capacity and ability to spread quickly, proliferation of this invasive plant is difficult to control.

While methods such as removal by hand provide short term results, prevention of accidental release remains the best means of controlling its spread. This can be achieved by either over-wintering plants indoors or, at the end of the season, discarding them in the garbage.

For more detailed information on this invasive aquatic plant, contact:

Global Invasive Species Database;

Ontario Federation of Anglers and Hunters;

Ontario's Invading Species Awareness Program.