Cyperus lupulinus, the Great Plains flatsedge, is a plant species native to North America. It is widespread across southeastern Canada and the central and northeastern United States as far west as Wyoming, Colorado and New Mexico, with more isolated populations reported in Washington (Asotin County), Idaho (Idaho County) and Oregon (Wallowa County). It grows in open, sun-lit locations such as fields, prairies, roadsides, farms, etc.