| Impact Description | Glyceria maxima (reed manna grass) may also be a competitive threat to native species of manna grass. These native species that are listed as threatened or endangered in at least one Great Lake State: G. acutiflora Torr., G. arkansana Fernald, G. borealis (Nash) Batchelder, G. grandis S. Watson, and G. obtusa (Muhl.) Trin. |