Eurasian water milfoil, (Myriophyllum spicatum), in the Rideau Canal, downtown Ottawa.

Eurasian Water Milfoil: A Vegetation Invasion

The thick tangles of plants that choke the navigation channel along the Rideau River are an exotic plant species called Eurasian water milfoil. This invading plant thrives in water that has both flow and depth, which are both characteristics of the boat channel.

A mechanical harvester tackles Eurasian water milfoil in the Rideau Canal.

Eurasian water milfoil easily spreads to new areas because its reproduction is not solely dependent on seeds. Fragments carried elsewhere, as by boat propellers and birds, are able to root and keep growing. Also, new plants are able to shoot up from existing roots. The species was found in many sampling sites along the River.

Since 1998, a mechanical harvester has been working to remove the milfoil from the section of the Rideau Canal that passes through downtown Ottawa. Although this provides temporary relief, the fragments are able to quickly recolonize as well as float downstream and colonize elsewhere.

Despite its interference with navigation and swimming, European water milfoil does not seem to have a negative impact on native aquatic plant diversity in the Rideau River. It is not likely to have a negative impact on the animal life in the Rideau River because it provides shelter and food.

Wetland Plants: Beautiful Biodiversity

Although they were not systematically recorded during the Project, wetland plants are an essential element of the landscape of the Rideau River.

Blue iris, Iris versicolor.

Wetland plants grow in areas of transition between primarily aquatic habitat and primarily terrestrial habitat. Wetland plants grow in ground that is very wet or under shallow water. Wetland plants can, however, tolerate water level fluctuations during the growing season. Project researchers concentrated on aquatic plants that grew in water that was at least a half-metre deep.

Among the most common wetland plants are: cattails (species of Typha), blue iris (Iris versicolor), purple loosestrife (Lythrum salicaria) and swamp loosestrife (Decodon verticillatus).

Beauties all, with their flashes of colour and tall grace, their relative height makes them readily visible.

Bypass the supermarket and harvest what nature has to offer you, with the guidance of books from the Edible Wild Plants of Canada series. You can order this title online: Wild Green Vegetables of Canada. Edible Wild Fruits and Nuts of Canada, Edible Garden Weeds of Canada and Wild Coffee and Tea Substitutes of Canada are sold out. Look for all four books in your local library.

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