Reed canary grass is a major threat to natural wetlands. It outcompetes many native species by reducing available area, sunlight and nutrients. They grow in large, monoculture stands, reducing biodiversity. It also presents a major challenge in wetland mitigation efforts. The rhizomes of the grass can form dense mats along with dead stems that prevent native seeds for germinating. This species of grass is hard to control because of its persistent rhizome system, and its ability to grow both vegetatively and sexually.