Phragmites are probably Ontario’s worst invasive species


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Feral pigs are the latest entry on Ontario’s invasive species list.

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Supposedly, feral pigs are a thing and enough of a threat that they’ve managed to make their way onto the invasive species list. The only pigs I’ve ever seen are those in a barn. And I saw seemingly happy pigs on a tractor-trailer, obviously unaware of what awaited them.

Feral pigs will never reach the level of concern for Phragmites, which many experts say are Ontario’s worst invasive species. Phragmites is everywhere, spreading like wildfire, knocking out a host of native plants and animals in its wake.

The problem with Phragmites is that they quickly turn a forest, grassland or wetland, filled with plant diversity, into a monoculture where nothing else grows. Birds and wildlife that once depended on their host plants for food and shelter are disappearing as quickly as Phragmites are advancing.

Phragmites came to Canada a long time ago when we started trading with Europe and other parts of the world. As shipping traffic increased, so did the arrival of Phragmites.

For a short while, gardeners weren’t bothered by Phragmites, as they had a few positive attributes. Phragmites grew rapidly and gave instant privacy. Its shimmering white plumes, appearing in the fall, sway back and forth in the wind. And Phragmites loved poor soils where little else grew. It performed particularly well in wet and swampy places.

In addition to the ecological threat posed by phragmites, the weed is becoming a serious nuisance in cities. Its aggressive roots penetrate drain pipes and slabs in the field. Stem growth is so rapid that fire hydrants and traffic signs are quickly buried. Phragmites are so thirsty that, like willows, they make less water available to others. Phragmites roots are known to lift concrete sidewalks.

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Perhaps the greatest danger of Phragmites is that when frozen, their stems dry out and become highly flammable.

Phragmites are not easy to eliminate. Cutting it will do no good as it spreads mainly through its roots. Phragmites have a growth habit like raspberries or sumac, with new shoots appearing near existing parent plants.

Burning Phragmites in a controlled burn makes sense, but it won’t kill the extensive root system left behind. Glyphosate herbicide is effective when applied in the spring or fall when growth is active. Repeat applications will likely be required.

Conservation authorities have found that the most effective method of eradicating Phragmites is a three-phase approach where spraying, mowing and burning are undertaken over a period of two or three years.

You and I can do our part to reduce the spread of Phragmites by cleaning our shoes and bicycle tires when we leave an infested area. If we are cleaning Phragmites stems, roots or seeds, it is important to properly dispose of garden waste rather than composting it or moving it to other areas.


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