Polygonum aviculare |
Polygonum argyrocoleon |
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birdweed, common knotgrass, common knotweed, doorweed, dooryard knotweed, knotgrass, knotweed, lowgrass, pigweed, prostrate knotweed, renouée des oiseaux, yard knotweed |
Persian knotweed, silver sheath knotweed |
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Habit | Plants green or bluish green, green after drying, sometimes whitish from powdery mildew, homophyllous or heterophyllous. | Plants green, heterophyllous. | ||||||||||||||||||||||||||||
Stems | prostrate to erect, branched, flexuous, 5–200 cm. |
erect or decumbent, branched mostly from base, not wiry, 15–100 cm. |
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Leaves | ocrea 3–15 mm, proximal part cylindric or ± funnelform, distal part silvery, hyaline, soon disintegrating into persistent fibers or nearly completely deciduous; petiole 0.3–9 mm; blade green to gray-green, narrowly elliptic, lanceolate, elliptic, obovate, or spatulate, 6–50(–60) × 0.5–22 mm, margins flat, apex acute, obtuse, or rounded; stem leaves 1–4 times as long as adjacent branch leaves; distal leaves overtopping flowers. |
ocrea 4–8 mm, proximal part cylindric, distal part soon disintegrating into curly or straight fibers; petiole 0–1.5 mm; blade bluish green, lanceolate or linear-lanceolate, 15–50 × 2–8 mm, margins flat, apex acute; stem leaves 2.1–4 times as long as branch leaves; distal leaves abruptly reduced and not overtopping flowers (shorter than or equaling flowers). |
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Inflorescence(s) | axillary; cymes uniformly distributed or aggregated at tips of stems and branches, 1–6(–8)-flowered. |
axillary and terminal, spikelike; cymes aggregated at tips of stems and branches, 4–6-flowered, bracts inconspicuous. |
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Pedicels | enclosed in or exserted from ocreae, 1.5–5 mm. |
enclosed in ocreae, 1–2 mm. |
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Flowers | closed or semi-open; perianth 1.8–5.5 mm; tube 20–57% of perianth length; tepals overlapping or not, green or reddish brown with white, pink, or red margins, petaloid, not keeled, oblong to obovate, often cucullate in fruit; midveins branched or unbranched, thickened or not; stamens 5–8. |
closed; perianth 1.8–2.4 mm; tube 10–22% of perianth length; tepals overlapping, green or white, usually with pink, rarely red or white, margins, petaloid, not keeled, oblong to obovate, cucullate; midveins usually unbranched; stamens 7–8. |
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Achenes | enclosed in or exserted from perianth, light to dark brown, ovate, (2–)3-gonous, 1.2–4.2 mm, faces subequal or unequal, apex not beaked, edges slightly concave, dull, usually coarsely striate-tubercled, sometimes obscurely tubercled; late-season achenes common or not, 2–5 mm. |
enclosed in perianth, brown, ovate, 3-gonous, 1.3–2.3 mm, faces subequal, slightly concave, apex not beaked, with concave edges, shiny, smooth; late-season achenes unknown. |
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Polygonum aviculare |
Polygonum argyrocoleon |
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Phenology | Flowering May–Oct. | |||||||||||||||||||||||||||||
Habitat | Fields, gardens, disturbed sites, often in saline soils | |||||||||||||||||||||||||||||
Elevation | 0-1200 m (0-3900 ft) | |||||||||||||||||||||||||||||
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; nearly worldwide
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AZ; CA; CO; FL; ID; LA; MA; MO; NC; NM; NV; TX; UT; VT; WV; c Asia [Introduced in North America]
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Discussion | Subspecies 7+ (6 in the flora). Polygonum aviculare is a taxonomically controversial polyploid complex of selfing annuals. Although members of the complex have been considered inbreeders, they possess some structures that make cross pollination possible. Cleistogamous and chasmogamous flowers, heterostyly, protandry, and the capacity to secrete nectar suggest an ancestral mixed-mating system. Isoenzyme studies showed that the complex has an allopolyploid origin (P. Meerts et al. 1998) and has evolved as a swarm of inbreeding lines (“Jordanons”) (J. Gasquez et al. 1978). The six subspecies included here have been treated variously (T. Karlsson 2000; M. Costea and F. J. Tardif 2003). Complex intergradation patterns among them make their recognition at the species level impractical. Multivariate analysis and isoenzyme studies show that populations with intermediate characteristics may occur (Meerts et al. 1990, 1998). Except for subsp. boreale, which occurs in Greenland and Labrador, all subspecies are partially sympatric and their distributions have been influenced greatly by humans. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 556. | FNA vol. 5, p. 560. | ||||||||||||||||||||||||||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||||||||||||||||||||||||||
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Name authority | Linnaeus: Sp. Pl. 1: 362. (1753) | Steudel ex Kunze: Linnaea 20: 17. (1847) | ||||||||||||||||||||||||||||
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