14. Polygonum paronychia Chamisso & Schlechtendal, Linnaea. 3: 51. 1828.
Beach or black or dune knotweed
Shrubs or subshrubs. Stems prostrate or ascending, brown, branched, rooting at nodes, not wiry, 10-100 cm, glabrous, covered with remains of lacerate, hyaline ocreae. Leaves crowded at branch tips, articulated to ocreae, basal leaves caducous or persistent, distal leaves not reduced in size; ocrea 15-20 mm, glabrous, proximal part cylindric to funnelform, distal part silvery, entire or slightly lacerate, disintegrating into persistent white-gray curly fibers; petiole 0-0.5 mm; blade 1-veined, without pleats, linear to oblanceolate, (5-)10-20(-33) × 3-8 mm, coriaceous, margins revolute, smooth, apex acute or mucronate. Inflorescences axillary; cymes crowded in distal axils, 2-5-flowered. Pedicels enclosed in ocreae, erect to spreading, 2-5 mm. Flowers semi-open or open; perianth (4.5-)6-10 mm; tube 22-48% of perianth length; tepals partially overlapping, uniformly pink or white, reddish brown when dried, petaloid, oblong-ovate to ± lanceolate, apex rounded; midveins pinnately branched; stamens 8. Achenes enclosed in or slightly exserted from perianth, black, ovate, 4-5 mm, faces subequal, shiny, smooth.
Flowering Mar-Sep. Coastal sands, scrub along coast; 0-50 m; B.C.; Calif., Oreg., Wash.
Polygonum paronychia may be cultivated in rock gardens in open sites with sandy soil.