Invasive Phragmites | County of Peterborough

Invasive Phragmites (Frag-MY-tees) is a perennial grass that was introduced to the coastal regions of Canada in the 1800s. The plant spread quickly and aggressively by outcompeting native vegetation for water, sunlight, nutrients and space. By the late 1990s, it had well established roots within the province of Ontario, posing a major threat to our wetlands and shorelines.

Phragmites thrives in wet environments such as wetlands, lakeshores, beaches and even damp fields. It grows in dense populations, with mature plants reaching 5-6 meters in height. Its leaves are blue-green in colour and during growing season its stem is primarily green but turns tan near the base of the plant. Phragmites produces a dark brown/deep purple seed head in the late summer, before turning fluffy in the early fall as the plant begins seed dispersal. It has an extensive root network between plants, containing rhizomes in which it also reproduces.

Invasive Phragmites vs. Native Phragmites

Description	Invasive Phragmites	Native Phragmites
Latin Name	Phragmites australis subsp. australis	Phragmites australis subsp. americanus
Look	Dull, tan or beige stems Blue-green leaves that are darker than the native variety Large, dense seed heads	Shiny, reddish-brown stems Yellow-green leaves Smaller, sparser seed heads
Growth	Grows in stands that can be extremely dense with as many as 200 stems per square metre Stands include both live stems and standing dead stems	Grows in stands that are usually not as dense as the invasive plant Frequently mixed with other plant species
Density	Is so dense that it crowds out other species	Other species have enough light and space to grow in same area
Height	Up to 6 metres	Up to 2 metres
Common locations	Roadside ditches (very common) Wetlands Agricultural lands	Unlikely to be found in roadside ditches Commonly interspersed with other plant species
Leaf sheaths	Dead leaf sheaths stay on stem	Dead leaf sheaths are loose and drop off easily in the winter, leaving bare stems standing in the spring
Stems	Stems break down very slowly, forming a dense thatch	Stems break down quickly

Why Are We Worried About Invasive Phragmites?

Not only is Phragmites blocking sunlight, stealing nutrients and taking up valuable real estate for our native vegetation, it’s also absorbing water within the ecosystem at a faster rate. Because of this, lower water levels are being observed within our wetlands and shorelines, which is directly impacting species at risk that reside and breed within these habitats.

It is important to note that we are not only seeing Phragmites populations near wetlands and bodies of water, it’s succeeding in growing in locations with little to no standing water levels within our road allowance. This is obstructing sightlines for vehicles travelling our road network, encroaching on regulatory and warning signs for motorists, impacting drainage within the ditch, establishing on agricultural land of County farmers and damaging our infrastructure with its extensive rhizome (root) network.

What is Peterborough County doing about Invasive Phragmites?

Peterborough County applied for and received a grant through the Invasive Phragmites Control Fund, coordinated by the Invasive Species Centre and Ministry of Natural Resources. With the funding, we created an application to map the presence of Phragmites throughout the County’s road allowance. We collected attribute details such as population size, density, hydrological conditions and whether it was present on public land, private land, or present on both. Our goal was to be able to visually assess the scale of invasive phragmites populations within our road allowance.

The map-based approach has allowed us to overlay information such as provincially significant wetlands or information from 3rd party working groups that are actively working on phragmites eradication. This will allow Peterborough County to explore methods and required resources to implement a phragmites management program following best management practices.

Additional Resources

For more information about invasive phragmites and up to date best management practices, please visit: Invasive Phragmites – Profile and Resources | Invasive Species Centre

To report a sighting of an invasive species, including Phragmites, please visit: Invasive species in Ontario | ontario.ca

Reddish-purple Seed Head

Phragmites growing through asphalt

Seeds ready for dispersal

Invasive Phragmites Control Fund Sign

Phragmites encroaching on road sign

Rhizomes with root network