What is the name of the broad expanse of flat land in the western United States and western Canada  where the species of plant called the Polygonum sawatchense of the buckwheat family be found?
Great Plains The Great Plains (sometimes simply "the Plains") is the broad expanse of flat land (a plain), much of it covered in prairie, steppe and grassland, that lies west of the Mississippi River tallgrass prairie states and east of the Rocky Mountains in the United States and Canada. It embraces
Snake River Plain (ecoregion) The Snake River Plain ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) in the U.S. states of Idaho and Oregon. It follows the Snake River across Idaho, stretching roughly 400 mi from the Wyoming border to Eastern Oregon in the xeric intermontane west. Characterized by plains and low hills, it is considerably lower and less rugged than surrounding ecoregions. Many of the alluvial valleys bordering the Snake River are used for agriculture. Where irrigation water and soil depth are sufficient, sugar beets, potatoes, alfalfa, small grains, and vegetables are grown. Elsewhere, livestock grazing is widespread. Cattle feedlots and dairy operations are found locally.