Although this particular rhizome is that of bamboo, the rhizomes of reed would look identical. These roots allow for maximum density and can grow as deep as six feet. Photography by Armin Kübelbeck.
What is common reed? Common reed is a type of grass often found in marshes and surrounding bodies of water. This grass can grow up to fifteen feet high and is found in dense clusters due to its rhizomes. A rhizome is plant stem that projects both the stems and the roots. This part of the common reed is submerged in water. They are tall but relatively hollow, making them a poor food source. Where does common reed come from? Common reed has variations that are native to North America. These variations are now very uncommon and hard to distinguish. The variation that has overwhelmed the native Maryland common reed is native to Europe and parts of Asia. In Europe, nearly half of their herbivores primarily consume common reed, whereas less than half that amount would eat it, at all, in the United States.
Why is common reed so harmful? Common reed dramatically reduces biodiversity. It smothers many native species, including cattails, arrow arum, wild rice, pond weed, pickerel weed, and many more. Although muskrat, ducks, and various other species will still consume common reed, they would consume far more of the species common reed is replacing. Those species can shelter nearly five times the number of species that common reed can shelter.
Because common reed has rhizomes, it grows deeper into the water than the native species which can alter the hydrology of the entire ecosystem. With roots so deep, areas that previously flooded can no longer hold that water. This can reduce the amount of water in seasonal ponds and pools, drastically reducing the number of killifish and other small aquatic species in the ecosystem. This reduced flooding can also alter the salinity of the soil by preventing salt and fresh water from meeting. Brackish habitats contain many sensitive species which will dramatically suffer from the altered salinity of their habitat. These thick, deep roots can also block the sun from reaching parts of the water, preventing any potential growth. The density of its growth and connected roots increase the chance and severity of wildfire. After fires, common reed recovers more quickly than most species. The biologically diverse area that existed before a fire could become entirely covered with common reed which allow room for little else to grow.
How is it controlled? Since these rhizomes are tough, long, and so far underground, they are very difficult to control. Although they can be cut down this is a difficult strategy. They often grow back and it is difficult to cut them down without spreading more seeds in the process. This is often a means for temporary management rather than removal. Although burning can harm other species more than it harms common reed, when done properly it is incredibly effective. Since each individual root is connect to such a vast number of stalks, controlled burnings are the most efficient way to kill common reed. Herbicides are effective in controlling reed, forcing them to be used often despite effects on other species. Other options include grazing, mowing, and smothering the plant.