Column: Reed canary grass – terror of the wetlands
Published 5:11 pm Thursday, August 4, 2005
We've all heard about the problems imported water hyacinth is causing in Florida's waterways. Its aggressive growth is choking slow moving rivers and streams and in many cases completely blocking them off. It also crowds out all the other native aquatic vegetation. Up here in the northland an equally infamous wetland invader is purple loosestrife. It, too, grows aggressively and crowds out the natural vegetation of our shallow marshes and ponds. There's another invader wreaking havoc in our wetlands that has received much less publicity. It's reed canary grass and it is even more devastating to wetland ecosystems than purple loosestrife.
Reed canary grass, or R.C.G. as biologists contemptuously call it, is a cool season, perennial grass. It's a whopper, averaging six to seven feet tall in a good quality wetland. It spreads aggressively, forming dense sod and thick top growth. No other plants can break through the sod and those with the audacity to try are quickly shaded out. It's one of the first plants to sprout in the spring so its towering stems have a jump start on everything else. By May and early June when most plants are just getting a start in life, R.C.G. has matured and is already forming seed heads.
It spreads by both seed and rhizome. Rhizomes are sprouts that run an amazing distance sideways underneath the soil surface, sending up shoots all along the way. The rhizome sprouts are supplemented by millions of seeds that drop each year to not only form new plants, but create a tremendous seed bank in the soil for generations to come. R.C.G. crowds and shades out everything in its path. If the rhizomes are blocked by a stream or pond, no problem, seeds drop onto the water and bob happily downstream or ride wind blown wavelets to continue the relentless onslaught. The monotypic habitat formed by R.C.G. is of no use to anything. A large stand of reed canary grass is a biological desert. No plants, insects, birds, reptiles or animals can tolerate its impenetrable, claustrophobic mass.
There is a species of reed canary grass native to the U.S. but it pretty much behaves itself. The bad R.C.G. was brought over from Eastern Europe and Asia starting way back in the 1800s because of its vigorous growth. It was, and still is in certain circles, highly acclaimed for erosion control and livestock forage. Until recently it was being planted by everyone from farmers to wildlife managers and highway departments. Now that its detrimental effects are known professionals have pretty much abandoned it but private land owners are still playing a role in its spread.
Like so many alien species that take a liking to foreign soils, R.C.G. is very difficult to control and all but impossible to eradicate from an area. Herbicides work to a degree on mature plants but have to be used in very strong concentrations. This, of course, poses hazard to the delicate wetland ecosystem. It also takes several applications to kill the rhizomes. This is only an inconvenience to R.C.G., though, as the vigorous seeds in the soil bank pop right up the following spring. If you pull the plants or plow them under, each broken rhizome sends up more shoots and the disturbed soil encourages new seed growth. About the only way to eliminate a stand of R.C.G. is to bulldoze off the top soil and remove it from the area. Bulldozers, loaders and dump trucks don't work so swell in swamps, though.
I have a new idea I'm going to try. Last spring I was jawing the fat with a native seed collector out in Minnesota. He said where marsh betony grows, aggressive grasses like big blue stem are noticeably thinned out. Marsh betony is a native, parasitic plant that gets its nourishment from the roots of other plants. He speculates that if the reed canary grass was killed or even just regularly mowed and then marsh betony heavily planted the betony just might win out. Betony isn't aggressive and is certainly the lesser evil. He graciously gave me a pound of betony seed to experiment with. How's that for a cool project? Carpe diem.