Reed Canary Grass — A Formidable Enemy

By Mary Meier
Nachusa Grasslands volunteer

To identify reed canary grass stewards pull back the blade from the sheath to look at the ligule. The membrane is a translucent white, about 1/8-1/4 inch long, rounded at the top, and often folded over. The ligule lacks any hairs.

Each May, Nachusa Grasslands’ staff and stewards usually dread the appearance of one of our major weed adversaries, reed canary grass (Phalaris arundinacea — RCG). This year, however, we may welcome the opportunity to attack the invaders, if and when we are released from our “stay at home” restrictions. The prospect of heading out into the field laden with herbicide backpacks is very appealing right now.​

​What is reed canary grass? RCG is a coarse, cool-season perennial grass with erect hairless stems that grow from 2 to 6 feet tall. Densely clustered single flowers at the top of each plant change from green to purple to tan in late spring. Shiny dark brown seeds form during the summer months and shatter easily. Reproduction takes place both by seed dispersal and underground rhizomatous roots that create a thick, impenetrable mat just under the soil. Seeds can float down waterways and also spread via animals, humans, or machines. For example, Nachusa’s bison and deer populations may brush up against the plants and then carry the seeds in their fur.

All the green grass seen in this pond (mid-April) is reed canary grass.

​Where does reed canary grass grow? The plants thrive in moist areas, including marshes, swamps, prairies, meadows, fens, stream banks, and swales. It is especially abundant in disturbed wetlands, but can also appear in high quality native habitat.
 
How did reed canary grass arrive in northern Illinois? Since the 1800s, agronomists have encouraged planting RCG for forage and erosion control. Some states prohibit selling the seeds, but Illinois does not. A native species actually exists, but it is almost impossible to distinguish from the more aggressive Eurasian variety. At Nachusa Grasslands we strive to eradicate all occurrences of RCG in order to diminish its ecological threats.

See the thick thatch created by the grass?

​Why does reed canary grass cause problems in our natural areas? RCG forms large monocultures, crowding out native species and building up a tremendous seed bank that germinates year after year. The thick thatch that forms from rhizomes and collapsed stems is especially problematic, as it prevents more desirable seeds from germinating. RCG, therefore, reduces native plant and insect diversity, while providing little shelter or food for wildlife.

Restoration technicians, Tyler Pellegrini and Amanda Contreras, backpack spray with post-emergence grass herbicide.

How do we manage reed canary grass at Nachusa Grasslands? Spraying grass herbicide is our main approach. The staff and stewards treat RCG with Intensity, a post-emergence grass herbicide (1% clethodim). Even though clethodim does not kill the plants’ roots, it helps set back the grasses and allows sedges and forbs to move in. Around waterways and high-quality natural areas, the crew uses the same formula with extra caution to reduce overspraying.

Amanda wades through deep water to treat the reed canary grass along a steep bank.

​What are some other reed canary grass control methods? Research and experience show that burning and mowing can actually stimulate regrowth of RCG but may also be useful in removing thatch prior to overseeding. Digging up rhizomes is labor-intensive and disturbs the soil, so other weeds may then invade the site. In small patches, cutting off the seed heads and disposing them off-site can be effective when combined with herbicide application. Covering with shade cloths is another option for large infestations.
 
As with all weed management projects, best practices depend on overall goals and objectives, the size, distribution, and location of RCG infestations, willingness to use herbicides, and available human and equipment resources. In addition, every method requires follow-up monitoring, treatment, and establishing native species as we strive to extirpate this very challenging invasive species.

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Mary Meier has been a dedicated volunteer at Nachusa since 2002. She is currently an officer for Friends of Nachusa Grasslands, an Autumn on the Prairie festival organizer, and a member of the social media team. Along with her husband Al, she stewards the Dot and Doug Wade Prairie Unit, which is about half restoration and half remnant.