Polygonum heterosepalum

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.

Polygonum heterosepalum is a short herb up to 5 cm tall, forming mats that seem rather moss-like. Stems are green or red. Leaves are densely packed, narrow up to 3 mm long. Flowers are white, sometimes pink along margins, borne in groups of 2–3 in the axils of the leaves, slightly zygomorphic with some tepals longer than the others.