Phragmites Australis

European Reed in North America

Phragmites australis (pron: Frag-my-teez) is a tall perennial grass found in wetlands throughout temperate and tropical regions of the world. It was originally thought the species had just one genus, but the aggressive expansion of this species in North America led to an eventual separation between the nativePhragmites australis, and the invasive strand. Scientists are now referring to the invasive Phragmites australis as European Reed, or simply Phragmites.

Native Common Reed was documented in North America as early as 1820 with 37 collections to follow and by 1950 its range was established as widespread across Canada. Invasive European Reed was not collected until 1910, and by 1950 had only three localized populations: Nova Scotia, St. Lawrence River, and southwestern Ontario and all three were established in port towns. The different distribution patterns strongly suggested the European Reed was introduced (copy pictures from Naturalist article – or Link to article).

Once established the Phragmites can expand several meters a year to quickly crowd out native vegetation and dominate an area. The invasion can facilitate its own growth by reproducing in two ways; sexual and clonal. Sexual reproduction is by seeds; each inflorescence can contain up to 1000 viable seeds that can be dispersed by wind, animal or flowing water and remain viable for 2-5 years. Sexual reproduction allows European Reed to colonize new sites. Clonal reproduction is by rhizome growth beneath the surface and is an important invasive characteristic of the species. Rhizome buds grow horizontal and vertical shoots that develop the reed bed and allows above ground biomass to accumulate into dense monoculture stands (700-1400g/m2). Rhizomes will also secrete a toxic chemical into the soil that destroys the structural proteins of neighbouring species (allelopathy) and allows the stand to easily dominate the native plant community.

Dominant, monoculture stands of Phragmites exert a myriad of negative effects on the local ecology. Above ground biomass can alter nutrient cycling in the system by blocking sunlight and reducing photosynthesis in native species. Water is transpired at a faster rate through Phragmites stands which can lower water levels. Rhizomes and roots grow many meters into the ground and can absorb significant volumes of water and interrupt ground water flow. The structural proteins of Phragmites decompose at a much slower rate than native species, and this can deplete the ecosystem of essential nutrients. Loss of habitat for native species will reduce local biodiversity, and extensive stands of Phragmites can block access to the shore for both wildlife and people.

Phragmites & the Lake Huron Coast

The invasive, non-native Phragmites was first identified on the shores of Lake Huron in the early 2000s. The Coastal Centre undertook a preliminary field survey to record its occurrence in southern Bruce County where it appeared to be most prevalent in 2007. It did a more extensive survey in 2011 for the are from Sarnia to Tobermory. The Centre also began some trials to better understand possible control options. Mechanical measures such as cutting, smothering with black plastic sheets, and the removal and bagging of seed heads were tried, as well as chemical applications of herbicide applied manually to the stalks of the plant. Herbicide use was the most effective option, but there are always concerns about using chemical herbicides in sensitive ecosystems, and our coastal areas are considered to be sensitive environments.

The Coastal Centre’s Board considered this issue and developed a position statement on the use of herbicides in coastal environments. The use of chemical herbicides near Lake Huron was a concern, and if it was going to be used, the following considerations need to be made: Long term plan needs to be developed; Need a ‘Letter of Opinion’ from the Ministry of Natural Resources; Need to use an Ontario Licensed herbicide applicator trained in working within sensitive ecosystem, and working with Phragmites; Targeted sites need to be field-checked by an experienced biologist to identify rare and at-risk species and flag these areas as exclusion areas for herbicide use.

In recent developments, the Ontario Ministry of Natural Resoureces 
has developed a set of Best Management Practices for Phragmites 
control. It can be downloaded at MNR.

Invasive Phragmites has become so extensive in southwestern Ontario that eradication is not realistically possible. The best we can hope for is to control its spread, and manage its occurrence in sensitive coastal habitats. Control can be costly, and requires an ongoing commitment.

Early detection and early control provides the advantage of being the easiest, least costly approach. Small stands can be controlled through manual efforts. For dense, monoculture stands it is important to take the time to create a realistic long term management plan that brings together all the affected stakeholders and addressed all the potential impacts to native ecosystems. And then gather the funds required to complete the plan.

For more information on Phragmites or other invasive species, start at the The Lake Huron Centre For Coastal Conservation website