Shasta knotweed

Subshrubs. Stems prostrate to as-cending, brown, branched, gnarl-ed, not wiry, 5-40 cm, glabrous. Leaves ± uniformly distributed, articulated to ocreae, basal leaves caducous or persistent, distal leaves not reduced in size; ocrea 3-5 mm, glabrous, proximal part cylindric, distal part membranous, deciduous with leaves; petiole 0-0.5 mm; blade 1-veined, without pleats, lanceolate to elliptic, 5-25 × 2-5 mm, coriaceous, margins revolute, smooth, apex acute. Inflorescences axillary; cymes in distal axils, 2-6-flowered. Pedicels enclosed in or slightly exserted from ocreae, erect, 2-4 mm. Flowers open or semi-open; perianth 5-9 mm; tube 7-15% of perianth length, tepals partially overlapping, uniformly pink or white, petaloid, ovate to ovate-round, apex rounded; midveins with numerous branched lateral veins; stamens 8. Achenes enclosed in or slightly exserted from perianth, brown, narrowly ovate, 3-4 mm, faces subequal, shiny, smooth.

Flowering Jul-Sep. Rocky or gravelly slopes; 2100-3400 m; Calif., Nev., Oreg.

Polygonum shastense may be cultivated in rock gardens in rock crevices with favorable water regime and shaded in summer.