Wiry knotweed

Polygonum coarctatum Douglas ex Meisner var. majus Meisner in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 101. 1856; P. douglasii Greene subsp. majus (Meisner) J. C. Hickman

Herbs. Stems erect, green, simple or branched, ± wiry, 15-60 cm, usually papillose-scabridulous. Leaves uniformly distributed, articulated to ocreae, basal leaves often caducous, distal leaves abruptly reduced to bracts, articulated to ocreae; ocrea 5-12 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part lacerate or disintegrating into fibers; petiole 0.1-2 mm; blade 1-veined, not pleated, linear to narrowly oblong or lanceolate, 15-70 × 2-8 mm, margins revolute, papillose-denticulate, apex acute or mucronate. Inflorescences axillary and terminal, spikelike, elongate; cymes spaced along branches, 2-5-flowered. Pedicels exserted from ocreae, reflexed, 0.5-1 mm. Flowers open or semi-open; perianth (3.5-)4-5 mm; tube 9-17% of perianth length; tepals overlapping, uniformly white to pink, petaloid, oblong to oblong-obovate, cucullate, navicular in distal 1/ 4, apex rounded; midveins unbranched or with short lateral branches; stamens 8. Achenes enclosed in perianth, black, elliptic, 3.5-5 mm, faces subequal, shiny or dull, smooth or striate-tubercled.

Flowering May-Aug. Dry plains, meadows, sometimes on serpentine; 500-2000 m; B.C.; Calif., Colo., Idaho, Nev., Oreg., Utah, Wash., Wyo.