Common Reed Grass
Phragmites australis ssp. australis

Name and Family

Common reed grass, Phragmites australis ssp. australis, is a member of the grass family (Poaceae). The plant is also commonly called phragmites, although it is important to note that there is both a native and invasive variety of phragmites.

Native vs. invasive subspecies

Native: Phragmites australis ssp. australis
Invasive: Phragmites australis ssp. americanus

On Prince Edward Island, both native and invasive varieties of phragmites exist. The native variety is a plant that has been established on PEI for hundreds if not thousands of years, provides shelter and nutrients to native wildlife, and does not outcompete native vegetation. The invasive variety is relatively new to the island, arriving within the past few decades. Where the invasive variety grows, it spreads very quickly, excluding native vegetation and reducing the availability of native wetland ecosystems for native wildlife. 

Most coastal phragmites populations can be anticipated to be native. Currently, there are three genetically confirmed patches of invasive phragmites on PEI, with two prospective, unconfirmed sites.

While the two plants have some very similar characteristics, here are some morphological traits you can use to distinguish between the two plants.

This is not an exhaustive list of distinguishing features. For additional information, we recommend reviewing the following paper: https://www.cambridge.org/core/journals/invasive-plant-science-and-management/article/morphological-traits-for-rapid-and-simple-separation-of-native-and-introduced-common-reed-phragmites-australis/47377F16AD751AD37DE80D6CAF0C2642

History

Common reed grass (Phragmites australis ssp. australis) is an invasive perennial grass that is native to Eurasia. It is not known for certain how it was moved to North America, but it likely arrived on the Atlantic coast accidentally via ballast materials in the late 1700s – early 1800s. (Swearingen, J. and K. Saltonstall. 2010)

Since establishing in North America, Phragmites australis ssp. australis has spread throughout continental U.S. and to most provinces in Canada. It prefers to grow in standing water but will tolerate growing in dryer areas.

Identification Guide

Here are some key features that may help positively identify common reed grass and distinguish it from its native relative:

Phragmites australis ssp. australis (Invasive):

  • Grows in dense stands and crowds out other species
  • Grows to be ~5 m tall, a much more robust plant than the native phragmites
  • Lower stems are tan or beige-coloured
  • Leaves are arranged alternately and are a blue-green colour
  • The panicle inflorescence (seed head) is larger and more full than the native subspecies’
  • Begins growing earlier in the spring and grows later into the fall than the native subspecies

Phragmites australis ssp. americanus (Native):

  • Grows in a more scattered manner, mixed in with other native wetland species
  • Typically reaches 2 m in height
  • Lower stems are red
  • Leaves are yellowish-green, smaller than invasive phragmites’, and distributed predominantly on the same side of the stem
  • The panicle inflorescence (seed head) is smaller and more sparse

What it does in the ecosystem

Invasive common reed grass (phragmites) is a fast-growing and quickly spreading invasive plant. It invades primarily wetland ecosystems and rapidly chokes out and outcompetes native species for space and nutrients.

The plant grows to be very tall (up to 15ft.) and can shade out other native species easily. The word phragmites comes from the Greek word “phragma” which means fence. It certainly earns this name, as common reed grass forms dense monoculture stands that create imposing barriers. These barriers are not only physical, but also ecological, and even chemical. Common reed grass alters water movement and sedimentation. It creates a fire hazard in the dry season due to the buildup of dead material. As the grass dominates an ecosystem, it removes habitat not only for other plants, but also for the birds, fish, and amphibians that depend on native plants for food and shelter. Chemical barriers are created by common reed grass’s allelopathic ability, meaning that it changes the soil chemistry to prevent or reduce native plant competition. 

For humans, common reed grass infestation affects our ability to take part in recreational activities like boating and fishing by changing and blocking shorelines. From a safety standpoint, tall fences of common reed grass can block sightlines for vehicles, and block access to key public infrastructure like fire hydrants. 

Management

First and foremost, determine whether you are dealing with the native or the invasive species of common reed grass. The native species does not require management. Check out our factsheet for a list of discriminating features. Once this determination is made, begin thinking about which management strategy will work best for your time and labour constraints. Think also of how your management will affect neighbouring organisms and their habitat. Often, multiple control methods are used simultaneously.

Consider how common reed grass reproduces. It produces seed heads in midsummer. You should monitor the population’s flowering and plan to conduct management before they go to seed. If planning to manually cut common reed grass, it is recommended that you do so when the plant reaches maximum height, just before it goes to seed. In aquatic environments, it is recommended that the plant be cut at the soil level, which will effectively drown the plant as new shoots fail to break the surface. On land, cutting should be done below soil level to ensure the rhizome is properly severed. Using a spade, cut the plant at a 45-degree angle a few inches below the soil surface and remove the aboveground parts. Return to the site regularly to continue management of any new growth.

In wet environments where water levels can be controlled, flooding is an effective way to stress and reduce populations of common reed grass. The plant appears to be intolerant to changing water levels. Chemical control in such environments is not often a viable option, so alternative measures such as flooding and cutting often must be implemented. When working in or within 15m of a waterbody, one must obtain a Watercourse, Wetland and Buffer Zone Activity Permit from the PEI Department of Environment, Energy, and Climate Action. This permit should be applied for a minimum of six weeks before work commences.

As common reed grass can regrow from left-behind roots and seeds, multiple years of treatment will likely be necessary to completely eradicate an infestation. One way to decrease regrowth may be to remove the accumulated dead reed grass from the area. Making competition for common reed grass by replanting the area with competing native grasses will apply an additional stressor.  It is important to collect, bag, and properly dispose of all removed invasive plant material to prevent potential regrowth, especially any root pieces and seed heads. Clean all equipment and clothing of all plant parts before moving on to prevent inadvertent spread. 

References

OIPC_BMP_Phragmites_April302021_D10_WEB.pdf (ontarioinvasiveplants.ca)

LS-MgmtPlan.pdf (greatlakesphragmites.net)

Final-Phragmites-2021.pdf (ontarioinvasiveplants.ca)

(PDF) The biology of Canadian weeds. 129. Phragmites australis (Cav.) Trin. ex Steud. (researchgate.net)

https://www.cambridge.org/core/journals/invasive-plant-science-and-management/article/morphological-traits-for-rapid-and-simple-separation-of-native-and-introduced-common-reed-phragmites-australis/47377F16AD751AD37DE80D6CAF0C2642

Are hybrid Phragmites becoming invasive? An investigation of potential hybridization among native and invasive Phragmites in Ontario, Abagail Warren and Joanna Freeland, Department of Biology, Trent University

Status of the common reed, Phragmites australis, in Prince Edward Island. Presented to the Atlantic Society of Fish & Wildlife Biologists, Gaelic College, Cape Breton, NS, Oct. 28th 2015 by Rosemary Curley, Nature PEI.