Polygonum douglasii |
Polygonum ramosissimum |
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Douglas' knotweed, renouée de Douglas |
bushy knotweed, yellow knotweed, yellow-flower knotweed |
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Habit | Herbs. | Plants yellowish green or bluish green, (dark brown to black after drying in subsp. prolificum), heterophyllous or homophyllous. | ||||
Stems | erect, green, simple or branched, not wiry, 5–80 cm, glabrous or sparsely papillose-scabridulous. |
erect, usually profusely branched in distal 1/2, not wiry, 10–100(–200) cm. |
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Leaves | uniformly distributed, articulated to ocreae, basal leaves caducous, distal leaves abruptly reduced to bracts; ocrea 6–12 mm, glabrous or minutely papillose-scabridulous, proximal part cylindric, distal part hyaline, lacerate; petiole 0.1–2 mm; blade 1-veined, not pleated, linear, narrow-oblong, or oblanceolate, 15–55 × 2–8(–12) mm, margins revolute, smooth or papillose-denticulate; apex acute to mucronate. |
ocrea 6–12(–15) mm, proximal part cylindric, distal part silvery, soon disintegrating into persistent brown fibers; petiole 2–4 mm; blade variable, light yellowish green to bluish green, proximal often caducous, narrowly elliptic, lanceolate, or oblanceolate, rarely ovate, 8–70 × 4–18(–35) mm, margins flat, apex acute to acuminate or obtuse; distal leaves, either overtopping or shorter than or equaling flowers. |
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Inflorescences | axillary and terminal, spikelike, elongate; cymes widely spaced along branches, 2–4-flowered. |
axillary or axillary and terminal, spikelike; cymes uniformly distributed or crowded toward tips of branches, 2–5-flowered. |
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Pedicels | mostly exserted from ocreae, reflexed, 2–6 mm. |
enclosed in or exserted from ocreae, 1–6 mm. |
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Flowers | closed; perianth 3–4.5 mm; tube 20–28% of perianth length; tepals overlapping, green to tannish with white or pink margins, petaloid, oblong, cucullate, navicular, apex rounded; midveins usually branched, rarely unbranched; stamens 8. |
closed; perianth (2–)2.2–3.6(–4) mm; tube 20–38% of perianth length; tepals overlapping, greenish yellow with greenish yellow or yellow, rarely pink or white, margins, petaloid or sepaloid, not keeled, elliptic to oblong, cucullate; midveins thickened or not; stamens 3–6(–8). |
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Achenes | enclosed in perianth, black, elliptic or oblong to ovate, 3–4(–4.5) mm, faces subequal, shiny or dull, smooth or minutely striate-tubercled. |
enclosed in or exserted from perianth, dark brown, ovate, 3-gonous, 1.6–3.5 mm, faces subequal, concave, apex not beaked, edges straight, shiny or dull, usually smooth to roughened, sometimes uniformly or obscurely tubercled; late-season achenes common, 4–15 mm. |
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Polygonum douglasii |
Polygonum ramosissimum |
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Phenology | Flowering Jun–Oct. | |||||
Habitat | Dry, often disturbed places, rock outcrops, sandy ground | |||||
Elevation | 300-3000 m (1000-9800 ft) | |||||
Distribution |
AZ; CA; CO; IA; ID; MI; MN; MT; NE; NH; NM; NV; NY; OR; SD; UT; VA; VT; WA; WY; AB; BC; MB; ON; QC; SK; YT
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AR; AZ; CA; CO; CT; DE; 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; NS; NT; ON; PE; QC; SK
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Discussion | Five taxa that have been included in Polygonum douglasii (E. Murray 1982; J. C. Hickman 1984; J. T. Kartesz and K. N. Gandhi 1990) are treated here as distinct species: P. austiniae, P. majus, P. nuttallii, P. sawatchense, and P. spergulariiforme. Hickman noted extensive intergradation and numerous intermediate specimens among those sympatric elements, but qualitative or quantitative characters allow reliable discrimination in most cases (M. Costea and F. J. Tardif 2005), and species are here circumscribed similar to C. L. Hitchcock (1964). Greene described var. latifolium as having leaf blades and achenes broader than those of var. douglasii. C. L. Hitchcock (1964) recognized the former, but the characters used to distinguish it appear to vary continuously, and reliable separation is not possible. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 2 (2 in the flora). Polygonum ramosissimum exhibits considerable morphological complexity and is similar in difficulty to the P. aviculare complex. Further research is necessary to understand the infraspecific variability of this species (M. Costea and F. J. Tardif 2003b). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 567. | FNA vol. 5, p. 551. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | P. douglasii var. latifolium, P. emaciatum, P. montanum, P. tenue var. commune, P. tenue var. latifolium | |||||
Name authority | Greene: Bull. Calif. Acad. Sci. 1: 125. (1885) | Michaux: Fl. Bor.-Amer. 1: 237. (1803) | ||||
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