Cascade knotweed

Herbs. Stems spreading to erect, zigzagged, green, simple or branched from base, wiry, 5-12(-15) cm, glabrous. Leaves uniformly distributed, articulated to ocreae, basal leaves persistent, distal leaves abruptly reduced to bracts; ocrea 2-5 mm, glabrous, proximal part funnelform, distal part lacerate; petiole essentially absent; blade 1-veined, not pleated, oblanceolate to obovate, 5-20 × 2-5 mm, margins revolute, never touching along midrib, sparsely papillose-denticulate, apex rounded or apiculate. Inflorescences axillary and terminal, spikelike, dense; cymes congested at tips of stems and branches, 3-5-flowered. Pedicels enclosed in ocreae, erect to spreading, 2-3 mm. Flowers open; perianth 2-2.5 mm; tube 12-25% of perianth length; tepals overlapping, uniformly white, petaloid, oblong to obovate, cucullate, navicular in distal 4, apex rounded; midveins unbranched; stamens 8. Achenes enclosed in or exserted from perianth, black, ovate to ovate-oblong, 1.8-2.1 mm, faces subequal, shiny, smooth.

Flowering Jun-Sep. Dry, usually rocky slopes, often on serpentine; 1600-1800 m; Oreg.