Persicaria amphibia
Persicaria bungeana
amphibious bistort, r enouée amphibie, water knotweed, water smartweed
prickly smartweed
prostrate to ascending or erect, simple or branched, ribbed, glabrous or strigose to hirsute.
ascending to erect, ribbed or obscurely so, glabrous or glandular-pubescent distally;
prickles 1–1.5 mm.
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 brownish, cylindric, 8–14 mm, chartaceous, base inflated or not, without prickles, margins truncate, ciliate with bristles 2–4 mm, surface with appressed bristles along veins;
petiole 0.5–1.5 cm;
blade lanceolate to narrowly elliptic, 5–12.5 × 1.5–3.5 cm, base acute, margins entire, antrorsely ciliate, apex acute acuminate, rarely obtuse, faces glabrous or pubescent and, usually, with antrorse prickles along midvein abaxially and adaxially.
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.
racemelike, uninterrupted or interrupted proximally, 20–45 × 5–10 mm;
peduncle 20–40 mm, usually stipitate-glandular at least proximally;
ocreolae usually overlapping, sometimes not overlapping proximally, margins eciliate.
ascending, 0.5–1.5 mm.
mostly ascending, 2–3 mm.
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.
2–4 per ocreate fascicle;
perianth pale green, often tinged red, glabrous, accrescent, not becoming blue and fleshy in fruit;
tepals 5, connate 1/4–1/3 their length, petaloid, elliptic to broadly elliptic, 3–4 mm, apex obtuse;
stamens 8, filaments distinct, free;
anthers pink, ovate;
styles 2, connate to middle.
included, dark brown, biconvex, (2–)2.2–3 × (1.5–)1.8–2.6 mm, shiny or dull, smooth or minutely granular.
included, black, biconvex, 2.5–3 × 2.3–2.8 mm, dull, rugose.
= 66, 132.
Persicaria amphibia
Persicaria bungeana
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.)
Persicaria bungeana is a weed of soybean fields (R. N. Andersen et al. 1985). It is not known how or when it was introduced into the midwestern United States.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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