Polygonum majus |
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large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
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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 |
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Phenology | Flowering May–Aug. |
Habitat | Dry plains, meadows, sometimes on serpentine |
Elevation | 500-2000 m (1600-6600 ft) |
Distribution |
CA; CO; ID; NV; OR; UT; WA; WY; BC
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Source | FNA vol. 5, p. 570. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia |
Sibling taxa | |
Synonyms | P. coarctatum var. majus, P. douglasii subsp. majus |
Name authority | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) |
Web links |
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