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large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed

Habit 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.

Polygonum majus

Phenology Flowering May–Aug.
Habitat Dry plains, meadows, sometimes on serpentine
Elevation 500-2000 m (1600-6600 ft)
Distribution
from FNA
CA; CO; ID; NV; OR; UT; WA; WY; BC
[WildflowerSearch map]
[BONAP county map]
Source FNA vol. 5, p. 570.
Parent taxa Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia
Sibling taxa
P. achoreum, P. argyrocoleon, P. austiniae, P. aviculare, P. bidwelliae, P. bolanderi, P. californicum, P. cascadense, P. douglasii, P. engelmannii, P. erectum, P. fowleri, P. glaucum, P. heterosepalum, P. hickmanii, P. humifusum, P. marinense, P. minimum, P. nuttallii, P. oxyspermum, P. paronychia, P. parryi, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
Synonyms P. coarctatum var. majus, P. douglasii subsp. majus
Name authority (Meisner) Piper: Fl. Palouse Reg., 63. (1901)
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