Phragmites australis (Phragmites) is an alien, invasive plant with origins in Europe that has found its way to Ontario and is spreading rapidly throughout the province.

Phragmites is an aggressive spreading grass capable of reaching heights greater than 5 m and densities of over 200 plants per square meter. It typically colonizes new sites from seeds that can be dispersed up to 10km by wind, or by plant parts such as rhizomes (underground root network), stolons (horizontal stalks that root at each node), and stems floating in water. Human activities, particularly those that disturb the soil are a major contributor to the rapid spread of this plant.

In 2005, Phragmites was recognized as Canada’s worst invasive plant by scientists at Agriculture and Agri-Food Canada. Unlike our native Phragmites, this invasive strain out-competes all native vegetation and once established can expand into massive stands void of other plants and wildlife.

Phragmites was first recorded on the Saugeen Bruce Peninsula more than 20 years ago. It can be found in many areas, including along the Lake Huron shoreline, inland lakes and wetlands, and along roadside ditches. The largest infestation can be found in Oliphant and the western shores of the Fishing Islands, where it now covers approximately 100 hectares. Extensive work is ongoing to combat this population, led by the Oliphant Fishing Islands Phragmites Community Group.

Loss of Habitat

Monoculture stands of Phragmites replace natural habitat and food supplies for various wildlife species, including Species at Risk. Phragmites stalks are rigid and tough, and do not allow for wildlife or humans to easily navigate among them. Species like turtles can be found exhausted or dead within large stands of Phragmites as they become too tired to navigate through it.

Loss of Biodiversity and Species Richness

Phragmites significantly reduces biodiversity by displacing native plants and animals once it develops into a monoculture (i.e. 100% Phragmites) stand. Only the edges of these areas are used by native species while the interior is effectively a dead zone.

Changes in Hydrology

Phragmites lowers water levels through high evapotranspiration rates resulting in the dewatering of shallow isolated pools. Evapotranspiration is the process by which water is transferred from the land to the atmosphere by evaporation from the land surface and transpiration from plants. The dead plant stalks are resistant to decay and over time a thick layer of dead plant material can build up and fill in open ponds.

Changes in Nutrient Cycling

Phragmites does not break down as easily as native plant species and therefore significantly alters nutrient cycling, nutrient levels, and availability in a system. It outcompetes native plants for available nutrients and is capable of sending roots downward several meters to obtain required nutrients and water.

Economic and Social Impacts

Phragmites has many negative social and economic impacts. It can impede drainage leading to reduced crop production. It can block sight lines at intersections creating driving hazards. Along infested shorelines it may reduce property values, recreational opportunities, and aesthetic enjoyment.

Increased Fire Hazard

The high percentage of dead stalks within a stand are highly combustible, especially during the dormant season when conditions are dry.

To learn more about the negative impacts or Phragmites please refer to:

Ontario Phragmites Working Group
Great Lakes Phragmites Collaborative
Ministry of Natural Resources & Forestry

The Saugeen Peninsula hosts a variety of globally rare and significant habitats, including coastal wetlands, fens, and meadow marshes that are susceptible to Phragmites invasion. These areas support an abundance of wildlife, including many species at risk such as:

• Black Tern

• Least Bittern

• Snapping Turtle

• Houghton’s Goldenrod

Invasive species pose a major threat to these areas, as the World Conservation Union lists invasive species as the second most significant threat to biodiversity, after habitat loss. Controlling Phragmites and preventing its spread is critical to restoring and preserving the habitats that the species listed above, and many more, rely on.

Since Phragmites has no natural controls to keep it in check, human intervention is required. Phragmites can be controlled using either mechanical or chemical control options.

Mechanical Control

For Phragmites growing on dry land or shallow water (<30cm), the spading technique is used. This involves using a sharpened spade to sever the phragmites stem below the soil surface. This forces the rhizome to expend energy, eventually exhausting the plants energy supply.

The cut-to-drown method is used when Phragmites is growing in water and involves cutting each Phragmites stem as close to the lakebed as possible. With the correct minimum water depth (>30 cm), this technique can effectively drown the plant by limiting the supply of oxygen to the lower part of the plant and preventing photosynthesis. Cutting is completed either by hand using manual cutters and hedge trimmers, or using large amphibious machines known as Truxors.

Mechanical methods are best used on small or sparse stands. While effective, these methods are labour-intensive and require ongoing efforts over multiple years to see long-term results.

Chemical Control

Chemical control using herbicides is the most efficient and cost-effective method of control and is therefore preferred for large, well-established infestations. For dry land sites, glyphosate and imazapyr-based products registered for use in Canada may be used where standing water is not present. For wet sites, the aquatic herbicide Habitat Aqua (active ingredient Imazapyr) is used. Herbicide control is often effective after one or two applications.

If you have a small stand of Phragmites on your property and you are interested in controlling it yourself, this video has all the information you need.

If the stand is too big to control yourself, the SPISC can help! Our crews provide Phragmites control services to treat and kill Phragmites on your land at no cost to you. Both mechanical and chemical control methods are offered free of charge for any landowner on the Saugeen Bruce Peninsula who would like Phragmites controlled on their property.

To sign up for free-of-charge control services, or for more information, click here.

Habitat Aqua is a low-volume, aquatic herbicide developed for the control of invasive or undesirable emergent aquatic vegetation (vegetation growing above the water) and does not impact submergent (underwater) vegetation. It is specifically formulated for use in and around aquatic sites.

Habitat Aqua is applied directly to the foliage of the target plant, where it is readily absorbed and translocated (moved) throughout the plant. In perennial plants, such as invasive Phragmites, the herbicide is translocated into underground or submerged storage organs (e.g. root systems), which not only kills the plant, but also prevents re-growth. This type of herbicide is considered a systemic herbicide.

Habitat Aqua is designed for use in and around standing and flowing water – including lakes, slow moving rivers, streams, ponds, drainage ditches, reservoirs, terrestrial and aquatic sites, seasonal wet areas, and more.

When Habitat Aqua is proposed for use in a wet site, permits must be secured before use.

Herbicides provide the most efficient and effective way to control large stands of Phragmites. If left uncontrolled, Phragmites can have negative environmental, social, and economic impacts. These negative impacts include loss of habitat, biodiversity and species richness, human safety hazards such as fire and sightline hazards, and obstruction of drainage ditches.

The negative impacts posed by uncontrolled Phragmites far outweigh any unintended impacts resulting from control efforts. Care is taken to minimize potential impacts associated with herbicide use. Application is completed as per label directions, at a time of year when impacts to non-target species are minimized, and by fully licensed, trained, and experienced applicators.

Only individuals who are licensed in accordance with Provincial law can apply Habitat Aqua. Use of this product in or immediately adjacent to water bodies must be appropriately authorized and applied in accordance with Provincial Regulations. Approval is required from the Ministry of Environment, Conservation and Parks (MECP) for aquatic herbicide application.

Herbicide application occurs between August 15 and October 15. This timing window allows for optimum control results, while minimizing potential impacts to non-target plants and animals.

For optimum results when using herbicide to control Phragmites, application should occur in the late summer or early fall. During this time, Phragmites plants are actively transferring nutrients to their root systems (rhizomes). This allows systemic herbicides (such as Habitat Aqua) to be translocated as well, directly impacting the root system.

This timing also coincides with reduced activity of native wildlife and dormancy in native vegetation. The breeding and spawning windows for birds, reptiles, amphibians and fish are avoided, and most plants have senesced (i.e. gone to sleep), therefore limiting potential impacts to non-target species.

As a precautionary measure, all surface water systems (i.e. intakes from a lake) for potable uses (i.e. for drinking, cooking, or food preparation) within 1km of an application area must be turned off during application and for a minimum of 48 hours after application. Systems should be flushed for at least 20 minutes before consuming again. Please note: these precautionary measures are only for private water systems drawing directly from the water body to be treated. This does not apply to groundwater wells or other water systems.

Access by people through an application area is restricted until the herbicide has dried on the plant leaves (access restricted for a minimum of 1 hour).

Please note that there is no restriction on the use of water for recreation or domestic purposes (toilets, showers, etc.).

All herbicides available for use in Canada are registered by Health Canada’s Pest Management Regulatory Agency (PMRA). The registration decision can be viewed at the following link: Registration Decision RD2021-03, Imazapyr, Habitat Aqua - Canada.ca

Each pesticide registered for use requires a label. The pesticide label is the primary information source for the safe and effective use of the pesticide. Habitat Aqua’s label is available at the following link: view_label (hc-sc.gc.ca)

Approval is required from the Ministry of Environment, Conservation, and Parks (MECP) for aquatic herbicide application. Questions regarding the review and approval process for Habitat Aqua use can be directed to your Regional MECP Office: https://www.infogo.gov.on.ca//infogo/home.html#orgProfile/-270/en

Additional information about the product is available on the manufacturers website: https://www.better-vegetation-management.basf.ca/en/products/habitat-aqua.html