The invasive, exotic species that is causing the most trouble this year is quackgrass. Also known as couch grass, Elymus repens (Agropyron repens) is a difficult plant to control. It is naturalized throughout the world and is an important forage grass in many places. It does provide food for birds and at least one butterfly, as it produces lots of seed.
Why is it a problem? It is problematic because it takes the niche of native plants. Native plants also produce seed and can be home to butterflies. But native plants mesh together to form an environment to support a variety of wildlife while quackgrass forms a mesh of roots that limits what else can grow. This grass is successful because it is a cool season grass, which means it comes up early in the spring and sets its seed before other plants can compete. In fact our other big invasive, exotic species is western brome, a cool season annual. So, quackgrass comes up early in the spring (the early warm springs that we have been having do to climate change don’t help,) sets its seed and grows by rhizomes– underground roots forming a mat that prevent everything else from growing. To just pull them up, without getting the root mass, is counter-productive as it simply creates more plants. Each broken piece of root has the possibility of becoming a plant.
This last work day we chose a small area that was covered with quackgrass and nothing else. We dug up every root we could find, in some cases going more than a foot down because sand had buried the roots quite deeply. This was not an easy job. We will be watching to see how much resprouts and whether or not other, more desirable plants are able to colonize the area. In the meantime it is a bit blank and desolate looking. We also did not smooth the sand, thinking that a rough surface might gather more sand.
We have a couple of other approaches to try. We can cut the seed heads to limit the seed. We can interplant marram grass, a grass that is notorious for outcompeting its rivals. Marram grass is almost always in a stand by itself. The erosion control areas in Loyola Park a bit north of the dune have marram grass and some residual quackgrass so we will watch those areas carefully to see which species wins out.