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?
Polygonum sawatchense Polygonum sawatchense is a North American species of plants in the buckwheat family. It in the western United States and western Canada, from the Pacific Coast to the western Great Plains, so from British Columbia south to California and east as far as New Mexico, Colorado, Saskatchewan, and the Dakotas.
Eriogonum latens Eriogonum latens is a species of wild buckwheat known by the common name Inyo buckwheat. It is native to the western Great Basin region, in the eastern slopes of the Sierra Nevada and the Inyo Mountains of California and the White Mountains, which extend just into western Nevada. It is an uncommon member of the flora in the sagebrush and woodlands of these mountains, where it grows in granitic sandy soils.