Fall Knotweed

Herbs. Stems erect, green, divar-icately branched, not wiry, 5-50 cm, usually papillose-scabrid-ulous, rarely glabrescent. Leaves uniformly distributed, articulated to ocreae, basal leaves usually caducous, distal leaves abruptly reduced to bracts, articulated to ocreae; ocrea 8-12 mm, papillose-scabridulous, proximal part cylindric, distal part disintegrating into a few persistent fibers; petiole 0.1-2 mm; blade 1-veined, not pleated, linear to lanceolate, 35-60 × 1-3 mm, margins flat or narrowly revolute, smooth or papillose-denticulate, apex acute, mucronate. Inflorescences axillary and terminal, spikelike, dense; cymes crowded, ± overlapping at branch tips, 2-5-flowered. Pedicels enclosed in or slightly exserted from ocreae, erect to spreading, 0.5-2 mm. Flowers open or semi-open; perianth 3-5 mm; tube 9-17% of perianth length; tepals overlapping, uniformly pink or white, petaloid, oblong-obovate, cucullate, navicular in distal 1/ 4, apex rounded; midveins branched; stamens 8. Achenes enclosed in perianth, black, narrowly elliptic or elliptic-lanceolate to narrowly ovate, 3-5 mm, faces subequal, shiny, smooth to striate-tubercled.

B.C.; Calif., Idaho, Mont., Oreg., Wash., Wyo.

Flowering Jun-Oct.

Moist to dry, open rocky places, including serpentine; 10-2000m.

Polygonum douglasii Greene subsp. spergulariiforme (Meisner ex Small) J. C. Hickman; P. emaciatum A. Nelson