Polygonum sawatchense |
Polygonum erectum |
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Johnston's knotweed, knotweed, sawatch knotweed |
devil's shoestring, erect knotweed, renouée dressée, upright knotweed, wireweed |
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Habit | Herbs. | Plants light green or yellowish, heterophyllous. | ||||
Stems | erect, green to brownish, simple or branched from base, not wiry, 4–50 cm, glabrous or papillose-scabrid-ulous. |
erect to ascending, sparingly branched in distal 1/2, not wiry, 15–75 cm. |
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Leaves | uniformly distributed, articulated to ocreae, basal leaves persistent or caducous, distal leaves abruptly or gradually reduced to bracts; ocrea 4–10 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part lacerate or disintegrating into a few persistent fibers; petiole 0.1–2 mm; blade 1-veined, not pleated, linear or narrowly oblong to oblanceolate, 8–45 × 2–8(–12) mm, margins revolute or flat, smooth or papillose-denticulate, apex acute, mucronate, rarely obtuse. |
ocrea 7–12 mm, proximal part cylindric, distal part usually persistent, with strong veins, margins entire or lacerate, silvery, later disintegrating into ± persistent brown fibers; petiole 1–5 mm; blade light green or yellowish, elliptic to obovate, 30–60(–80) × (8–)10–25 mm, margins flat, apex obtuse; stem leaves 1.5–3.5(–4) times longer than branch leaves; distal leaves overtopping flowers in distal part of inflorescence. |
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Inflorescences | axillary or axillary and terminal, spikelike, elongate; cymes widely spaced along branches, 2–4-flowered. |
axillary; cymes in axils of most leaves and toward tips of stems and branchs, 1–5-flowered. |
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Pedicels | enclosed in or exserted from ocreae, erect, 1–4 mm. |
mostly exserted from ocreae, 3–7 mm. |
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Flowers | closed or at least some open; perianth (2.5–)4 mm; tube 20–40% of perianth length; tepals overlapping, greenish or reddish, sometimes flushed with purple, with white or pink margins, sepaloid or petaloid, oblong or oblong-elliptic, cucullate, navicular, apex rounded; midveins unbranched or with few branches at base; stamens 3–8. |
closed; perianth 2.8–3.8(–4.2) mm; tube 20–37% of perianth length; tepals overlapping, green with yellowish, rarely whitish green, margins, sepaloid, not keeled, oblong to obovate, cucullate; midveins branched, moderately to heavily thickened; stamens 7–8. |
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Achenes | enclosed in perianth, black, elliptic or ovate, 2.5–3.3 mm, faces subequal, shiny, smooth. |
enclosed in perianth, brown to tan, ovate, 3-gonous, 2.3–3.5 mm, faces subequal, ± concave, apex not beaked, edges concave, dull, striate-tubercled; late-season achenes uncommon, 4–5 mm. |
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Polygonum sawatchense |
Polygonum erectum |
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Phenology | Flowering May–Oct. | |||||
Habitat | Dry, waste ground | |||||
Elevation | 10-300 m (0-1000 ft) | |||||
Distribution |
AZ; CA; CO; ID; MT; ND; NE; NM; NV; OR; SD; UT; WA; WY; AB; BC; SK
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AL; AR; CO; CT; DC; DE; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; TN; VA; VT; WA; WI; WV; WY; AB; ON; QC; SK
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Discussion | Subspecies 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Polygonum erectum was cultivated in the midwest by Native Americans for its starchy seeds (C. M. Scarry 1993). It was formerly confused with P. achoreum (T. R. Mertens and P. H. Raven 1965). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 568. | FNA vol. 5, p. 550. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | Small: Bull. Torrey Bot. Club 20: 213, plate 156. (1893) | Linnaeus: Sp. Pl. 1: 363. (1753) | ||||
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