The walls of giant grasses growing on our roadsides and in ditches may be impressive but they aren't natural. In fact, they are down-right invasive.
Over the last two centuries Indiana has lost 85% of its wetlands. Many of the remaining wetlands have been dramatically altered, degraded by soil disturbance, increased sedimentation, nutrient loading and salinization from road salt. These changes are bad for our native plants, but good for common reed.
Common reed (Phragmites australis) is an invasive perennial grass ranging in heights of 3-15 feet. Its leaves are wide, smooth and flat with large, showy and feathery flowers that vary from a wheat color to grayish-purple when in fruit. Dense stands are found in open wetland habitats, alongside rivers, shores of lakes and ponds and even in the polluted soils along roadsides and ditches. Huge colonies form quickly, but not from seeds. Instead, common reed relies on rhizomes, a horizontal stem that grows beneath the surface and sprouts new roots and shoots from underground, to invade our natural communities. A stand of common reed can extend its boundaries by as much as 50 feet within one season. In Indiana, most of these impenetrable stands are found in the northwestern counties.
Common reed competes with native wetland plants, and it plays to win. Once introduced, it will overtake a marsh community quickly by crowding out native vegetation, changing marsh hydrology, altering wildlife habitat and increasing fire potential. Its high biomass blocks light to other plants and occupies all the growing space below ground quickly turning a once diverse plant community into a phragmites monoculture. Once established, it spreads like a thick blanket, smothering native vegetation and filling in shallow open water.
Although there is evidence that common reed is native to the Midwest, this native strain has long been displaced by a European strain - one more invasive than the phragmites found in the past. The aggressive, invasive varieties can be distinguished from the native strains by a variety of characteristics, including darker leaves, much more rigid stems and dense seedheads.
Control of this invasive grass is quite difficult. According to Indiana's Aquatic Invasive Profile for Common Reed, cutting, disking, plowing and dredging will hinder the spread, but will not eradicate it. Burning does not eliminate the plant as well as the rhizomes are not affected by fire. In fact, burning may help regenerate new plants more quickly.
The best method to eradicate common reed is through the application of a systematic herbicide that will attack the rhizomes and kill the plant. The stewards at the Kankakee Sands Restoration Project have found success in killing phragmites through a foliar application of 1.5 - 3% Rodeo. Before applying any kind of herbicide, please take the proper precautions to protect yourself and the surrounding area of overexposure. When spraying stands near water, only herbicides labeled for phragmites should be used.
Of course, preventing the spread of common reed elsewhere is ideal. By rinsing off plant fragments, mud and debris from boats, clothing and equipment prior to leaving any body of water will decrease transportation of common reed and other aquatic invasive species elsewhere. If signs of an invasion are already clear, make sure to begin eradication as soon as possible.February 20, 2013