Recently, Lake Superior has become host to another unwelcome visitor: the invasive Phragmites, an aggressive reed which is tall, perennial, and chokes wetland habitats. While they’ve posed major problems in the lower Great Lakes for some time, the spread of Phragmites have only lately become problematic in Lake Superior. (photo credit: Ontario Phragmites Working Group)
What’s the problem?
To identify the problem with Phragmites, it’s important first to differentiate between native and invasive versions of the species. The americanus subspecies is relatively benign; it’s the spread of australis which is frustrating scientists and environmental organizations. The Michigan Department of Environmental Quality published a table differentiating between the two subspecies.
- can grow to 20 ft high
- has dull/tan stems
- has bluish-green leaves that are flat and stiff
- leaves persist throughout winter
- appears in dense monocultures
Invasive Phragmites cause ecological, economic, and social impacts, including:
- threats to coastal and interior wetlands
- reducing plant diversity by out-competing other species
- destroying wildlife habitat
- drying of marsh soils through increased evaporation and trapping sediment
- reducing property value by impairing land use (i.e. swimming, hunting, fishing, shoreline views)
- creating potential fire hazard due to dry biomass during winter (source: Michigan DEQ)
How does Phragmites spread?
Phragmites reproduce through seeds and rhizomes. Rhizomes are underground, horizontal stems growing up to 60 ft long and more than 6 ft per year. Because they can penetrate underground more than 6 ft, they become resilient and persistent by accessing groundwater, and surviving both dry and wet conditions.
The quickest spread of Phragmites occurs when rhizomes are fragmented and grow new plants. Phragmites also spread with seeds germinated from mature plants during spring. A mature plant can produce up to 2,000 seeds, but viability is low where water depths extend beyond 2 inches.
What is being done to control Phragmites?
As part of a combined, long-term management strategy, any number of the following treatments and control methods can be applied to fight the spread of Phragmites. Herbicide is considered the primary method of control, followed by one or more followup methods:
- prescribed fire, or
- mechanical treatment (mowing), or
- water level management (flooding), or
- grazing by livestock, or
- smothering with black plastic
The methods are intended for long-term management and monitoring, employed over several seasons to control the aggressive reeds. The Michigan DEQ estimates that they can successfully control Phragmites for 1-2 years without additional application. However, the reeds can recover 3 years after treatment if follow-up management isn’t applied.
The Michigan DEQ states that there are no current biological controls being used in North America for Phragmites. While there are no commercially available biological methods, some insect species and microorganisms in Europe have reportedly attacked Phragmites. The Michigan DEQ goes on to suggest that Cornell University is currently researching the use of these species as biological controls in North America. However, a 2016 publication from researchers from Louisiana State University, University of Rhode Island, and the University of Florida suggests evidence that biological controls for invasive Phragmites would also have negative effects for native Phragmites as well.
What can I do?
Learn more about Phragmites in the Great Lakes Basin at www.greatlakesphragmites.net. This site provides resources for landowners, public officials, and land managers. These include brochures, videos, documents, fact sheets, management guidelines, mapping tools, and more. The site also helps connect stakeholders with regional resources for Phragmites management, both state and provincial.
If you live in Ontario, the Ontario Phragmites Working Group provides EDDMapS Ontario (Early Detection and Distribution Mapping System), a digital tool which is used to report and track invasive species across Ontario. You can also call 1-800-563-7711, or email email@example.com with sightings.