European Reed Canary Grass

Invasive species April 2024

European Reed Canary Grass (Phalaris arundinacea). Reed Canary Grass (RCG) originated in Europe, Asia, and Canada. It is unclear if there was a native strain of RCG in Illinois. The native and European strains of RCG are hard for botanists to tell apart with the naked eye but easy for ecologists to separate. See that wetland over there that is completely covered with RCG? Yeah, that’s the European strain.

At one time, Reed Canary Grass was sold to farmers to improve wet pastures and hay meadows. Nearly a century ago, botanists like Charles Deam of Indiana were warning that RCG was taking over wetlands and wiping out almost all native plants. Since only a few species of insects feed on RCG, this meant a drastic loss of native insects, along with a decline in the total number of insects. RCG makes a thick mat of grass that makes a very covered, dark, and damp aboveground environment. This differs greatly from the much more open, sunny sedge meadow with wide travel spaces between tussocks, or even the somewhat thicker wet prairie habitat, especially after a fire burns off the duff. 

Due to the lack of Midwestern fires in the last 70 years, RCG carpets have created wetlands that support very few animals. Only a few insects feed on RCG, causing a drastic reduction in the number and variety of insects living there. This, in turn, affects the food chain, leading to a decline in the populations of reptiles, amphibians, fish, and birds, which rely on insects as a food source. The changed habitat also results in many of these species disappearing. 

What can be done? Well, there’s certainly good news in the control of RCG. A new grass herbicide, Clethodim, has been a game changer. Clethodim is a grass-specific herbicide that has shown that many native plants can survive for several decades in a carpet of RCG. However, it’s important to note that while Clethodim is effective, it’s not a permanent solution. The natives eventually die out, but they may be hanging on as tiny plants that are hard to see in the mass of RCG.

Once, we were dependent on Aquaneat (glyphosate formulated for use in wetlands). We would burn the wetland between fall and early spring when the RCG was dormant. Then, sometimes, there would be a window of a week or two when the RCG would be up and about 3 or more inches tall, and the native grasses, sedges, and wildflowers that were surviving (in areas that hadn’t been overrun for too long) were still in the ground dormant. Spray the whole area down with glyphosate, and it was an instant native wetland (of the species that were still hanging on). 

Sometimes, you would wait year after year for the right conditions (not flooded too deep or natives not up yet) to spray glyphosate. If you gave up on waiting for ideal conditions, your spray would kill all the plants in the wetland, and you would have a very hard time restoring a healthy wetland afterward.

Now we have Clethodim, a grass herbicide that only kills grasses and even seems to hurt Eurasian grasses more than many native grasses (although it will kill native grasses, especially at high rates or when a good soaking is applied). Clethodim is sold over the counter at many farm supply stores. The only downside is that it is not licensed for use over water, although damp ground is okay. Sometimes, you have to wait for the water to go away before spraying an area. It’s important to follow the instructions on the label and use protective gear when applying Clethodim.

Burning dormant RCG meadows is still the first step. This removes the leaf litter and allows you to get good spray coverage of the RCG. It is still ideal to spray before native grasses emerge from the ground, but it is not critical. If native grasses are barely up, they usually aren’t killed by Clethodim. Also, since Clethodim will not harm native sedges or wildflowers in your wetland, you can spray at non-ideal times and keep the vast majority of remaining native plants. Our native wetlands have relatively few native grasses (please don’t shoot me, all you botanists), so you can eliminate carpets of RCG with often the loss of just bluejoint grass, which often recovers from the seed bank or adjacent areas. Even more important is that when you spot spray to clean up the isolated clumps of RCG, you can do it without killing off the wildflowers and sedges growing alongside the RCG. Clethodim is effective from spring through June and in the fall but seems to be less effective in mid-summer.