Alien Invaders: Phragmites

The Suspect
European Common Reed
Phragmites australis australis

Known Whereabouts
Phragmites australis americanus, the native subspecies of common reed, has historically grown in wetlands throughout the temperate zones in Canada. The European common reed, Phragmites australis australis was likely introduced during the European colonization of the Americas and is now found virtually wherever the native subspecies grows in addition to habitats unsuitable for the native reed. Today, the European reed is more widespread in Canada than the native species and can be found in marshes, fens, and along riverbanks and roads. It can survive in both fresh and brackish water.

Description
Tall perennial grass, 2-5 m in height, stems up to 2.5 cm in diameter. Stems terminate in a dense, 30 cm long seedhead. Roots grow to a depth of 1 m.

Reed stand

Reed stand

Seedhead

Seedhead


The following table can help you distinguish the two subspecies:

Trait Native Common Reed European Common Reed
Leaf sheaths Easily removable, shed in autumn Hard to remove, stay on year-round
Stem colour at base (summer) Red to chestnut Tan
Stem colour at base (winter) Light chestnut to light brown/grey Tan
Stem texture Smooth, glossy Rough, dull
Stem flexibility Flexible Rigid
Leaf colour Yellow-green Yellow-green to dark green/grey
Flowering season July-August August-September
Seedheads Small, sparse Large, dense
Rhizomes Partially submerged in water Fully submerged in water

Crimes
The European subspecies grows aggressively, displaces many native plants, reduces biodiversity and degrades wetlands. The European reed even has the ability to release toxins from its root system, which prohibits the growth of plants in the surrounding area.

The native reed grows in drier environments and its root masses (rhizomes) are not completely submerged in water. Conversely, the rhizomes of the water-loving European reed are totally submerged. As it grows, the reed stand must expand outwards into the water, filling in critical aquatic habitat and lowering the water table. The European reed grows in much higher densities than the native species with stands containing up to 200 stems/m². Large stands of reeds can restrict the movement of aquatic vertebrates, such as turtles, limiting their available shelter, nesting areas and protection from predators. Other species may disappear entirely from the wetland as the aquatic plants on which they rely are replaced by invasive reeds.

Over time, invasive reeds may become the only remaining vegetative species in the wetland rendering it unsuitable for most naturally occurring species. Due to its aggressive nature, the European common reed has been considered the highest priority invasive species in Canada by Agriculture and Agri-Food Canada.

Phragmites

Stop The Spread!
We recommend that you remove European reeds as soon as you find them on your property or in roadside ditches. The best way to remove them involves both chemical and physical methods. It is very difficult to control reed growth because in addition to having wind-dispersed seeds, new stems can grow from rhizome fragments. Thus, simply cutting down the reeds will not stop the plant from reproducing and may even promote the growth of new individuals. Likewise, a controlled burn will only destroy the above-ground material and leave the rhizomes intact.

While the use of herbicides* is generally frowned upon, chemicals are highly effective in controlling the common reed. However, you may require permits to apply the herbicide so we recommend using a licenced professional. To minimize the impact of the herbicide on the surrounding vegetation, the chemical should be applied directly (e.g. with a sponge or paint brush) to the green leaves or cut stems of young reeds. Effective herbicides include glyphosate-based (e.g. Credit, Roundup) and imazapyr-based (e.g. Polaris, Habitat) brands. Glyphosate-based herbicides should be applied in August or September while Imazapyr-based herbicides are applied earlier (June-September) and are typically longer lasting.

Physical removal of the reeds can commence at least 2 weeks after the herbicide treatment. Hand pulling is time consuming and is ineffective as rhizome fragments are often left behind. A combination of mowing and disking is recommended. Reed stands should be mowed annually, after the ground has frozen. This will allow for new growth to be visible and treatable. Rhizomes are best removed by disking, although this method may initially result in new growth through the spread of rhizome fragments. Thus, reed removal should be continued annually.

Finally, here are 5 tips to reduce the spread of the European common reed:

  1. Clean equipment after mowing/cutting the reed
  2. Clean up plant clippings to prevent rhizomes from spreading
  3. Do NOT compost the clippings – seeds may germinate
  4. Limit the disturbance of the soil from removal sites
  5. Use both chemical and physical control; repeat annually

*Only certified professionals may apply imazapyr-based herbicides and the application of any herbicides in non-private
wetlands may require community or government approval.

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