18. Polygonum heterosepalum M. Peck & Ownbey, Madroño. 10: 250. 1950.
Dwarf desert knotweed
Herbs, compact, often cushion-like. Stems erect, green or reddish, simple or branched near base, not wiry, 1.5-5 cm, glabrous. Leaves uniformly distributed, dense, not articulated to ocreae, basal leaves persistent or caducous, distal leaves gradually reduced to bracts; ocrea 3-6 mm, glabrous, proximal part cylindric, distal part disintegrating almost to base, with whitish, straight, rigid fibers; petiole absent; blade 3-veined, without pleats, linear to lanceolate, 10-20 × 0.6-2.7 mm, margins revolute, smooth, apex spine-tipped. Inflorescences axillary; cymes in most axils, 2-3-flowered. Pedicels enclosed in ocreae, erect, 0.1-1 mm. Flowers closed; perianth 2.3-2.7 mm; tube 3-7% of perianth length; tepals overlapping, whitish with whitish or pink margins, petaloid, oblong, navicular, dimorphic, outer 2 shorter than inner 3, outer 2 0.8-1.2 mm, inner 2.3-2.7 mm, papillose at base, apex acute or acuminate; midveins unbranched; stamens 5-6. Achenes enclosed in perianth, olive brown, narrowly ovate to ovate-lanceolate, 1.5-2 mm, faces subequal, shiny, smooth.
Flowering Jun-Aug. Dry waste ground, open flats in sagebrush plains, ponderosa pine forests; of conservation concern; 1000-1500 m; Idaho, Nev., Oreg.