Persicaria amphibia |
Persicaria sect. Persicaria |
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amphibious bistort, r enouée amphibie, water knotweed, water smartweed |
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Habit | Plants perennial, 2–12 dm in terrestrial plants, to 30 dm in some aquatic plants; roots also sometimes arising from proximal nodes; rhizomes or stolons usually present. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | prostrate to ascending or erect, simple or branched, ribbed, glabrous or strigose to hirsute. |
ascending to erect or, rarely, prostrate, usually branched, sometimes simple, unarmed. |
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Leaves | ocrea tan to dark brown, cylindric or flared distally, 5–50 mm, chartaceous or, sometimes, foliaceous distally, base inflated, margins truncate to oblique, glabrous or ciliate with hairs 0.5–4.5 mm, surface glabrous or appressed-pubescent to hirsute, not glandular-punctate; petiole 0.1–3(–7) cm, glabrous or appressed-pubescent to hirsute, leaves sometimes sessile; blade without dark triangular or lunate blotch adaxially, ovate-lanceolate to elliptic or oblong-lanceolate, 2–15(–23) × 1–6(–8) cm, base usually tapered to acute or rounded, rarely cordate, margins antrorsely scabrous, apex acute to acuminate, faces glabrous or sparingly strigose, midveins glabrous or strigose, not glandular-punctate. |
ocrea chartaceous, rarely foliaceous distally, margins eciliate or ciliate; petiole not winged, not auriculate; blade sometimes with dark triangular or lunate blotch adaxially, lanceolate to narrowly elliptic, base tapered, acute, rounded, or cordate, margins entire. |
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Inflorescences | terminal, ascending to erect, uninterrupted or interrupted proximally, 10–150 × 8–20 mm; peduncle 10–50 mm, glabrous or strigose to hirsute, often stipitate-glandular; ocreolae overlapping except sometimes proximal ones, margins ciliate with bristles to 1 mm. |
terminal or terminal and axillary, spikelike, uninterrupted or interrupted. |
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Pedicels | ascending, 0.5–1.5 mm. |
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Flowers | bisexual or functionally unisexual, some plants having only staminate flowers, others with only pistillate flowers, 1–3(–4) per ocreate fascicle, heterostylous; perianth roseate to red, glabrous, not glandular-punctate, slightly accrescent; tepals 5, connate ca. 1/3 their lengths, obovate to elliptic, 4–6 mm, veins prominent, not anchor-shaped, margins entire, apex rounded to acute; stamens 5, included or exserted; anthers pink or red, elliptic; styles 2, included or exserted, connate 1/2–2/3 their length. |
homostylous or heterostylous, articulation swollen or not; perianth campanulate; tepals 4–5, connate 1/4–2/3 their length; stamens 5–8; styles deciduous, 2–3, included or exserted (exserted syles and stamens in heterostylous species), spreading. |
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Achenes | included, dark brown, biconvex, (2–)2.2–3 × (1.5–)1.8–2.6 mm, shiny or dull, smooth or minutely granular. |
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2n | = 66, 132. |
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Persicaria amphibia |
Persicaria sect. Persicaria |
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Phenology | Flowering Jun–Sep. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Shallow water, shorelines of ponds and lakes, banks of rivers and streams, moist prairies and meadows | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 0-3000 m (0-9800 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AK; AR; AZ; CA; CO; CT; DC; DE; 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; PE; QC; SK; YT; SPM; Mexico; South America; Ont ; Eurasia; Africa
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Nearly worldwide; especially n temperate regions |
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Discussion | Persicaria amphibia is widespread in the Northern Hemisphere and naturalized in Mexico, South America, and southern Africa. It is highly polymorphic and the most hydrophytic of the native North American smartweeds (R. S. Mitchell 1976). In recent decades, botanists have tended to follow Mitchell (1968) in recognizing two endemic, intergrading North American varieties. Studies by G. Turesson (1961) and Mitchell (1968, 1976) have shown that phenotypic extremes in the species are part of a cline of nearly continuous morphological variation that is strongly correlated with submergence, but also with some genetic integrity. Formal recognition of varieties is even less tenable when Eurasian elements also are considered. Aquatic-adapted plants, which bloom in water or are sometimes stranded on land, have been called var. stipulacea (although that epithet may not be the oldest one available for the taxon). They produce ovoid-conic to short-cylindric inflorescences 10–40(–60) mm, prostrate aerial stems, and leaf blades that are glabrous with acute to rounded apices. Terrestrial forms of this ecotype usually are spreading-pubescent and often bear ocreae that are foliaceous, green, and flared distally, characters found only in North American plants (R. S. Mitchell 1968). Terrestrial-adapted plants, referred to var. emersa, bloom on moist soil and produce short- to elongate-cylindric inflorescences 40–110(–150) mm, spreading or erect aerial stems, and leaf blades that are appressed-pubescent with acute to acuminate apices. They produce ocreae that are entirely chartaceous and not flared distally. Emergent and terrestrial plants of this ecotype exhibit less phenotypic plasticity and a lower frequency of heterostyly than do plants of the aquatic ecotype (R. S. Mitchell 1968). R. S. Mitchell and J. K. Dean (1978) and H. R. Hinds (2000) recognized var. amphibia, the Eurasian element, as introduced in New York and New Brunswick, respectively. These plants are morphologically intermediate between the North American ecotypes and often indistinguishable from North American plants (Mitchell and Dean). The Meskwaki and Ojibwa used leaves, stems, and roots as a drug to treat a variety of maladies, the Potawatomi used roots to treat unspecified ailments, and the Lakota and Sioux used plants for food (D. E. Moerman 1998). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Species ca. 60 (16 in the flora). Members of sect. Persicaria frequently grow in moist or inundated habitats. Many have evolved responses to submergence that allow them to survive extended periods of inundation (R. S. Mitchell 1976). Hybridization often is implicated for the taxonomic difficulties in the section. However, J. Timson (1965) concluded that, at least among annual European species, hybridization is rare due to autogamous breeding systems. Mitchell (1971) demonstrated the usefulness of leaf morphology in distinguishing major groups among the native North American smartweeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 583. | FNA vol. 5, p. 581. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria | Polygonaceae > subfam. Polygonoideae > Persicaria | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Synonyms | Polygonum amphibium, P. amphibia var. emersa, P. amphibia var. stipulacea, P. coccinea, P. hartwrightii, P. muhlenbergia, Polygonum amphibium var. emersum, Polygonum amphibium subsp. laevimarginatum, Polygonum amphibium var. natans, Polygonum amphibium var. stipulaceum, Polygonum coccineum, Polygonum coccineum var. pratincola, Polygonum coccineum var. rigidulum, Polygonum emersum, Polygonum hartwrightii, Polygonum natans | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Linnaeus) Gray: Nat. Arr. Brit. Pl. 2: 268. (1822) | unknown | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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