Polygonum ramosissimum |
Polygonum majus |
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bushy knotweed, yellow knotweed, yellow-flower knotweed |
large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
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Habit | Plants yellowish green or bluish green, (dark brown to black after drying in subsp. prolificum), heterophyllous or homophyllous. | Herbs. | ||||
Stems | erect, usually profusely branched in distal 1/2, not wiry, 10–100(–200) cm. |
erect, green, simple or branched, ± wiry, 15–60 cm, usually papillose-scabridulous. |
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Leaves | 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. |
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. |
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Inflorescences | axillary or axillary and terminal, spikelike; cymes uniformly distributed or crowded toward tips of branches, 2–5-flowered. |
axillary and terminal, spikelike, elongate; cymes spaced along branches, 2–5-flowered. |
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Pedicels | enclosed in or exserted from ocreae, 1–6 mm. |
exserted from ocreae, reflexed, 0.5–1 mm. |
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Flowers | 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). |
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. |
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Achenes | 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. |
enclosed in perianth, black, elliptic, 3.5–5 mm, faces subequal, shiny or dull, smooth or striate-tubercled. |
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Polygonum ramosissimum |
Polygonum majus |
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Phenology | Flowering May–Aug. | |||||
Habitat | Dry plains, meadows, sometimes on serpentine | |||||
Elevation | 500-2000 m (1600-6600 ft) | |||||
Distribution |
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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CA; CO; ID; NV; OR; UT; WA; WY; BC
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Discussion | 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. 551. | FNA vol. 5, p. 570. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | P. coarctatum var. majus, P. douglasii subsp. majus | |||||
Name authority | Michaux: Fl. Bor.-Amer. 1: 237. (1803) | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) | ||||
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