Polygonum argyrocoleon |
Polygonum nuttallii |
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Persian knotweed, silver sheath knotweed |
Nuttall's knotweed |
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Habit | Plants green, heterophyllous. | Herbs. |
Stems | erect or decumbent, branched mostly from base, not wiry, 15–100 cm. |
spreading to erect, sometimes zigzagged, purplish, simple or branched, wiry, (5–)10–35 cm, papillose-scabridulous. |
Leaves | 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). |
evenly distributed or crowded at branch tips, articulated to ocreae, basal leaves persistent, distal leaves gradually reduced to bracts; ocrea 3–4 mm, papillose-scabridulous, proximal part funnelform, distal part finely lacerate; petiole 0.1–2 mm; blade 1-veined, not pleated, linear to narrowly oblong-elliptic, 8–30 × 1–4(–7) mm, margins narrowly revolute, never touching along midrib, smooth, apex acute, mucronate, ± glaucous adaxially. |
Inflorescence(s) | axillary and terminal, spikelike; cymes aggregated at tips of stems and branches, 4–6-flowered, bracts inconspicuous. |
axillary and terminal, spikelike, dense; cymes mostly congested toward tips of branches, 2–3-flowered. |
Pedicels | enclosed in ocreae, 1–2 mm. |
enclosed in ocreae, erect to spreading, 2–3 mm. |
Flowers | 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. |
semi-open or closed; perianth 1.8–2.4 mm; tube 25–33% of perianth length; tepals overlapping, greenish, white, or pink with pink margins, petaloid, oblong, cucullate, navicular in distal 1/4, apex rounded; midveins unbranched; stamens 8. |
Achenes | 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. |
enclosed in perianth, black, elliptic to ovate, 1.8–2.3 mm, faces subequal, shiny, smooth. |
Polygonum argyrocoleon |
Polygonum nuttallii |
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Phenology | Flowering May–Oct. | Flowering May–Oct. |
Habitat | Fields, gardens, disturbed sites, often in saline soils | Dry prairies, open knolls in lower mountains, open sites in lowland and montane zones, sandy soil |
Elevation | 0-1200 m (0-3900 ft) | 800-1100 m (2600-3600 ft) |
Distribution |
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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OR; WA; BC
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Discussion | C. L. Hitchcock (1964) suggested that Polygonum nuttallii is but a small-flowered form of P. spergulariiforme. Although morphologically similar, P. nuttallii differs from P. spergulariiforme in some respects, including its wiry, purplish stems, short and funnelform ocreae, adaxially glaucous leaves, longer bracts, shorter fruiting perianth, and achenes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 5, p. 560. | FNA vol. 5, p. 570. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia |
Sibling taxa | ||
Synonyms | P. intermedium, P. douglasii subsp. nuttallii | |
Name authority | Steudel ex Kunze: Linnaea 20: 17. (1847) | Small: Mongr. Amer. Sp. Polygonum, 132, plate 53. (1895) |
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