Polygonum ramosissimum |
Polygonum marinense |
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bushy knotweed, yellow knotweed, yellow-flower knotweed |
Marin knotweed |
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Habit | Plants yellowish green or bluish green, (dark brown to black after drying in subsp. prolificum), heterophyllous or homophyllous. | Plants often reddish tinged, heterophyllous, subsucculent. | ||||
Stems | erect, usually profusely branched in distal 1/2, not wiry, 10–100(–200) cm. |
prostrate to ascending, branching from base, not wiry, 15–40 cm. |
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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. |
ocrea 4–6 mm, proximal part funnelform, distal part silvery hyaline, soon disintegrating, leaving almost no fibrous remains; petiole 2–5 mm; blade often reddish tinged, elliptic to obovate or oblanceolate; 20–35 × 9–16 mm, margins flat, apex rounded; stem leaves (1.3–)2–2.6(–3.5) times as long as branch leaves; distal leaves overtopping flowers in distal part of inflorescence. |
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Inflorescences | axillary or axillary and terminal, spikelike; cymes uniformly distributed or crowded toward tips of branches, 2–5-flowered. |
axillary; cymes in most leaf axils, 1–4-flowered. |
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Pedicels | enclosed in or exserted from ocreae, 1–6 mm. |
mostly exserted from ocreae, 2–4 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). |
semi-open; perianth 3–3.5(–4) mm; tube 18–25% of perianth length; tepals overlapping, green, margins white or pink, petaloid, not keeled, broadly rounded, cucullate; midveins unbranched; 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. |
exserted from perianth, brown, ovate, 3-gonous, 2.8–3.4(–4) mm, faces subequal or evidently unequal, apex not beaked, edges straight, shiny, minutely roughened; late-season achenes uncommon, 4.5–5 mm. |
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2n | = 60. |
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Polygonum ramosissimum |
Polygonum marinense |
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Phenology | Flowering Apr–Oct. | |||||
Habitat | Coastal salt and brackish marshes, swamps | |||||
Elevation | 0-10 m (0-0 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
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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.) |
Of conservation concern. The origin and taxonomic affinities of Polygonum marinense are uncertain. T. R. Mertens and P. H. Raven (1965) suggested a relationship with P. oxyspermum C. A. Meyer & Bunge or the Mediterranean P. robertii Loiseleur-Deslongchamps. Polygonum marinense may be confused with P. ramosissimum. It can be distinguished by its subsucculent texture, funnelform ocreae, leaves rounded at the apices, and semi-open flowers. Marin knotweed is known from fewer than 15 locations in Marin, Napa, Solano, and Sonoma counties; it is threatened by coastal development. (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. 552. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | Michaux: Fl. Bor.-Amer. 1: 237. (1803) | T. R. Mertens & P. H. Raven: Madroño 18: 87. (1965) | ||||
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