Whether they are called invasive, nonnative alien, exotic, or nonindigenous, introduced species are those that evolved elsewhere and have been purposely or accidentally relocated . While some species have invaded habitats on their own (e.g., migrating wildlife, plants and animals rafting on floating debris), human exploration and colonization have dramatically increased the diversity and scale of invasions by exotic species. Introduced species often find no natural enemies in their new habitat and therefore spread easily and quickly.

There are a wide range of wetland invaders, some of the more problematic species in the CLOCA jurisdiction include:

• Native to Europe
• Brought to North America by settlers in the early 1800’s
• Used extensively in flower gardens
• Mature plants can produce in excess of 2 million seeds annually
• Competes with and displaces native wetland vegetation
• Seeds are hardy and can remain dormant in the seed bank for many years
• Biological control is available for large infestations
• Mechanical control is successful by removing entire plant during flowering before seed set

Biocontrol was implemented in Cranberry Marsh with the release 5000 Galerucella beetles in 1999, to learn more on the release see Cranberry Marsh Restoration – Purple Loosestrife control.

• Originally from Europe and Asia
• Introduced to the Ottawa Region in 1938 as a horticultural species
• Looks similar to American frog-bit (Limnobium spongia)
• Forms dense mats on the surface of open water thereby reducing native biodiversity
• Reproduces both sexually and asexually, the latter being more dominant
• Few methods of control, removal by hand is a temporary solution
• Plants are spread to new waterbodies through boat propellers and other aquatic equipment
• European fro-bit is commonly sold as a water garden plant

• Large member of the Graminae family
• Can reach heights of 5 m
• Dominates marsh areas and displaces native vegetation
• Aggressive and resistant plant
• Chemical and mechanical controls are available but often repeat procedures are required

• Thought to be introduced in the late 1800’s with not positive ID until 1942
• Submersed, rooted plant that is one of the most widely distributed non-native aquatic species in North America
• Thrives in disturbed areas
• Reproduces both sexually and asexually
• Can interfere with boating, fishing and swimming
• Prevention is the best tool for stopping further spread – check & clean recreational equipment
• Research is ongoing for a biocontrol method

For additional information on invasive species see Forests and Streams sections.

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