Publication: Torreya 19: 224. 1919.
selected vouchers: WTU
Notes: FNA24: "Glyceria ×occidentalis has hitherto been considered an uncommon native species that grows along lakes, ponds, and streams, and in marshy areas of western North America. It differs from other species in the region primarily in its longer lemmas and anthers. Studies of chloroplast DNA in western North American species of Glyceria demonstrated that, contrary to C.L. Hitchcock's (1969) conclusion, G. fluitans is present in western North America, and that all specimens being identified as G. ×occidentalis had cpDNA resembling that of G. leptostachya or G. fluitans; there was no distinctive G. ×occidentalis cpDNA (Whipple et al. [in press]). This strongly suggests that G. ×occidentalis is a series of reciprocal hybids, and probably backcrosses, between G. fluitans and G. leptostachya. As the key indicates, G. ×occidentalis is intermediate between its two putative parents. The cpDNA study also confirmed that G. declinata is distinct from G. ×occidentalis (see discussion under that species)."