Polygonum heterosepalum, common name dwarf desert knotweed or oddsepal knotweed, is a plant species native to the Great Basin Desert in southwestern Idaho, northern Nevada, northeastern California, and southwestern Oregon. It has been reported from 1 county in California (Modoc), 4 in Nevada (Washoe, Humboldt, Elko and Lander), 4 in Idaho (Owyhee, Twin Falls, Elmore and Gooding), and 5 in Oregon (Lake, Malheur, Harney, Grant and Crook). The species occurs in dry, open sites in sagebrush plains and pine woodlands.