Polygonum majus |
Polygonum oxyspermum |
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large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
knotweed, sharp-fruit knotweed |
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Habit | Herbs. | Plants green to blue-green, homophyllous. | ||||
Stems | erect, green, simple or branched, ± wiry, 15–60 cm, usually papillose-scabridulous. |
prostrate to ascending, branched at proximal and middle nodes, not wiry, 20–100 cm. |
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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. |
ocrea 6.5–12 mm, proximal part cylindric, pruinose, distal part hyaline, soon disintegrating into brown fibers or nearly completely deciduous; petiole 0–1 mm; blade green to bluish green, elliptic-lanceolate to linear, 10–35 × 1.5–15 mm, margins flat or narrowly revolute, apex acute; middle stem leaves slightly larger than adjacent branch leaves, distal leaves overtopping flowers. |
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Inflorescences | axillary and terminal, spikelike, elongate; cymes spaced along branches, 2–5-flowered. |
axillary, cymes uniformly distributed, 2–7-flowered. |
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Pedicels | exserted from ocreae, reflexed, 0.5–1 mm. |
exserted from ocreae, 2.5–5(–7) mm. |
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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. |
semi-open; perianth 3.5–5.5 mm; tube 28–39% of perianth length; tepals slightly overlapping, green, margins white to pink, petaloid, not keeled, oblong to obovate, not cucullate; veins branched; stamens 8. |
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Achenes | enclosed in perianth, black, elliptic, 3.5–5 mm, faces subequal, shiny or dull, smooth or striate-tubercled. |
exserted from perianth, pale brown to dark brown, ovate, 3-gonous, (3.5–)4.1–5.5(–6.5) mm, faces subequal, apex not beaked, edges straight, shiny, smooth or with fine tubercles especially toward apex; late-season achenes unknown. |
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Polygonum majus |
Polygonum oxyspermum |
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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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ME; NB; NF; NS; PE; QC; Europe |
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Discussion | Subspecies 3 (2 in the flora). The treatment by D. A. Webb and A. O. Chater (1963) of the Polygonum oxyspermum complex is followed here. T. Karlsson (2000) accepted P. raii and P. oxyspermum as distinct species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 570. | FNA vol. 5, p. 554. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | P. coarctatum var. majus, P. douglasii subsp. majus | |||||
Name authority | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) | C. A. Meyer & Bunge ex Ledebour: Index Seminum (Dorpat) 1824: 5. (1824) | ||||
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