Invasive Phragmites. Why this plant is a problem.European Common Reed (Phragmites australis) is invading Canadian wetlands, threatening their biodiversity and integrity. So-called “Phrag” can reach over 3 m in height, forming dense, shady, impenetrable stands that are like trying to walk through wicker furniture. This excludes native plants and also reduces habitat for wetland birds, amphibians and reptiles. Phrag is a clonal grass with perennial roots, but annual shoots. Consequently, it is capable of regenerating rapidly from control efforts that only tackle the above-ground part of the plant and it is challenging to eradicate once it becomes established.
What about herbicide management solutions?Because tackling the shoots has little effect (GBF note: Selective cut method does help control Phragmites in water, where herbicides illegal) , the most successful treatment method is to spray the plant with herbicide in autumn to kill the roots, and then to mow, burn, or flatten the shoots later that winter to eliminate the standing dead plant litter and open up the canopy for native plants to recolonize. Typically, the major source of colonists is the seedbank: the repository of seeds resting dormant in the soil and waiting for the right conditions to sprout. Of course, there are concerns (including by GBF) that using herbicides in a wetland may have undesirable side effects. Although the herbicide used in Phrag control is only meant to affect adult plants, we wanted to test whether there was a risk that the herbicide application would affect the seedbank . To test this, we looked at soil samples from sites that had been sprayed with a 5% glyphosate solution and from an adjacent area that was not sprayed: our control plot. Both plots were located in Big Creek National Wildlife Area, in Long Point, Ontario.
- We also thought the density of Phrag might influence the kind of vegetation that sprouts from the seedbank, because really dense stands would have less exposed soil for seeds to land in. Alternatively, the less dense Phrag patches might let more of the herbicide slip through the canopy to land on the soil, potentially affecting germination rates. To test the effect of Phrag density, we collected samples from high and low density Phrag patches in both the areas that were sprayed with herbicide and our untreated control patches. We washed the soil from the collected seeds and planted them in germination trays in the University of Waterloo greenhouse with 12 hours of light per day and daily watering.
GBF note: What you can do:
In Ontario, there are NO approved herbicides to use over water. GBF teaches non-chemical treatment, or selective cutting which is necessary to help Georgian Bay coastal wetlands.
1. Learn more about and how you can help stop invasive Phragmites, in your own community.
2. Email us at firstname.lastname@example.org if you want to be a Phragbuster.
3. Visit our Community Phragbuster page. Find and work with others in your community, or promote your group's efforts and get more volunteers. Join one or register your group