Leymus arenarius is an invasive grass of coastal beaches and dunes where it appears to be spreading quickly and outcompeting the native flora. Leaves are conspicuously blue in color and they stand out clearly from the green leaves of the native American dune-grass (Ammophila breviligulata Fernald). It appears to spread vegetatively from the point of colonization to form clones. It competes with and poses a threat to native plants along the Lake Michigan shoreline, including several species of conservation concern (Elymus lanceolatus, Calamovilfa longifolia, Salix cordata, Cirsium pitcheri, Solidago simplex, Solidago ohioensis, Euphorbia polygonifolia).

Leymus arenarius has been known in Wisconsin for about 30 years and appears to have increased rapidly in the most recent decline of Lake Michigan water level, beginning in about 1998. Many sites have been invaded in Manitowoc County and the map should be amended to show recent collections from Door County. In Wisconsin it appears to be restricted to the Lake Michigan shoreline, but there is no obvious reason that it cannot spread to the Lake Superior shore as well.

Link to comparison of Leymus arenarius and Elymus lanceolatus.