Technical Abstract: There are seven North American and three introduced European Glyceria species growing in western North America, yet distinguihsing among the species is challenging. As contaminants in annual ryegrass grass seed lots, the introduced species G. declinata and G. fluitans are undesirable domestically, while North American species are undesirable in seed grown for international trade. In order to distinguish between the western North American and introduced European Glyceria species we designed PCR, Taqman SNP, and DNA sequencing assays. The PCR assays are co-dominant markers in which a larger sized amplification product is detected in G. declinata, G. fluitans, and G. fluitans-like G. occidentalis than is detected among the other species. The Taqman SNP assay shows VIC hybridization signal for G. declinata and FAM hybridization signal for G. fluitans and G. fluitans-like G. occidentalis. DNA sequencing of the chloroplast trnK region, and the nuclear ribosomal ITS-1 region, provide several SNPs that identify each of the individual species. However, Glyceria occidentalis samples contain chloroplast and ITS-1 sequences identical to either G. leptostachya or G. fluitans, thus currently cannot be distinguished with DNA markers.