Common Frogbit

A flowering plant belonging to the genus Hydrocharis in the family Hydrocharitaceae. In North America, it is referred to as Common Frogbit or European Frogbit to distinguish it from the related American Frogbit (Limnobium spongia).
In 1932 this plant was introduced into a pond in the Arboretum of the Central Experimental Farm in Ottawa. The seeds came from Switzerland. The species grew without incident until 1939, when it was seen growing in nearby sections of the Rideau River.
By 1952 this plant had spread to the Ottawa River. By 1982 it had spread to the Great Lakes. Since its introduction in Ottawa, European frogbit has become one of the dominant plants in many eastern-Ontario wetlands, and has reduced native plant biodiversity.