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Don't spread this new invasive aquatic plant!

2021 08 28 bowles frogbit2By Bob Bowles -- Several hours spent monitoring lakes, rivers and creeks in North Simcoe has made me realize roadside ditches, creeks and small streams are being choked out by a new invasive aquatic plant native to Europe.

European frogbit (Hydrocharis morsus-ranae) was unfortunately brought to the Central Experimental Farm in Ottawa in 1932 for possible commercial use as an ornamental plant. In 1939, it was found in the Rideau Canal and has since spread to several rivers, lakes and inland waters.

I first observed it in 2015 in Stony Lake in the Kawartha Lakes region, where it now chokes out some areas. In 2018, I observed it in Canal Lake, east of Brechin.

It was just a matter of time before it reached Lake Simcoe, but I was amazed this August to find large mats choking ditches around Mara Point and creeks like Barnstable Creek, Waiman Creek and Murphy Creek in Ramara Township. It is starting to establish itself in Mill Creek and Broughs Creek in Orillia, Oro-Medonte and Severn.

It has a well-developed root system that normally does not anchor the plant in substrate but rather floats free, sometimes putting down roots 50 centimetres long. It spreads by stem fragments, seeds, winter buds and runners, and is carried by boats, recreation and wildlife. 

Plants form a rosette (six centimetres across) and wide leaves the size of a Canadian dollar coin with rounded apex and heart-shaped bases. Leaves are green above and purple-red beneath. Flowers two centimetres wide have three white petals and a yellow centre.2021 08 28 bowles frogbit1

Plants grow quickly into large tangles that deplete oxygen levels, impact fish communities and aquatic wildlife, crowd out other plants, and restrict recreation like boating and swimming. It prefers slow-moving waters like ditches and creeks with mud bottoms. Care must be taken when moving recreational equipment to new areas to prevent the spread of this invasive plant.

The Robert L. Bowles Nature Centre, founded by June Crinnion and Michael Elmer, is a nature and wellness centre in Ramara, named after Lake Simcoe Living Nature Detective Bob Bowles to honour his role in protecting and caring for the environment. For more information, go to

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