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amphibious bistort, r enouée amphibie, water knotweed, water smartweed

Carey's smartweed, renouée de Carey

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. Plants annual, 3–15(–20) dm; roots also rarely arising from proximal nodes; rhizomes and stolons absent.
Stems

prostrate to ascending or erect, simple or branched, ribbed, glabrous or strigose to hirsute.

erect, branched distally, ribbed distally, hirsute proximally, stipitate-glandular distally, usually smooth proximally.

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 brownish to reddish brown, cylindric, 8–20 mm, chartaceous, base inflated or not, margins truncate, ciliate with bristles 2–7 mm, surface strigose to hirsute, not glandular-punctate, rarely stipitate-glandular;

petiole (0.1–)0.5–1.5 cm, hirsute, leaves sometimes sessile;

blade without dark triangular or lunate blotch adaxially, narrowly lanceolate, 6–18 × 1–3.5 cm, base tapering, margins antrorsely strigose, apex acuminate to attenuate, faces sparingly hirsute abaxially and adaxially, veins often hirsute, sometimes stipitate-glandular.

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 and axillary, nodding or drooping, usually interrupted, 10–100 × 5–10 mm;

peduncle 20–50 mm, stipitate-glandular;

ocreolae overlapping or not overlapping proximally, margins eciliate or ciliate with bristles to 1.3 mm.

Pedicels

ascending, 0.5–1.5 mm.

ascending to spreading, 1–4 mm.

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.

(1–)2–8 per ocreate fascicle, homostylous;

perianth roseate or purple, glabrous, not glandular-punctate, scarcely accrescent;

tepals 5, connate in proximal 1/3, obovate, 2.4–3.2 mm, veins prominent or not, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 5 (or 8), included;

anthers pink, elliptic;

styles 2, connate to middle.

Achenes

included, dark brown, biconvex, (2–)2.2–3 × (1.5–)1.8–2.6 mm, shiny or dull, smooth or minutely granular.

included, dark brown to black, biconvex, 1.8–2.5 × 1.5–2 mm, shiny, smooth.

2n

= 66, 132.

Persicaria amphibia

Persicaria careyi

Phenology Flowering Jun–Sep. Flowering Jul–Oct.
Habitat Shallow water, shorelines of ponds and lakes, banks of rivers and streams, moist prairies and meadows Low thickets, swamps, bogs, moist shorelines, clearings, recent burns, cultivated ground
Elevation 0-3000 m (0-9800 ft) 0-300 m (0-1000 ft)
Distribution
from FNA
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
[WildflowerSearch map]
[BONAP county map]
from FNA
CT; DE; FL; IL; IN; KY; MA; MD; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VA; VT; WI; NB; ON; QC
[WildflowerSearch map]
[BONAP county map]
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.)

An infusion made from entire plants of Persicaria careyi was used by the Potawatomi as a cold remedy and febrifuge (D. E. Moerman 1998).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 5, p. 583. FNA vol. 5, p. 592.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria
Sibling taxa
P. arifolia, P. bicornis, P. bungeana, P. capitata, P. careyi, P. chinensis, P. glabra, P. hirsuta, P. hydropiper, P. hydropiperoides, P. lapathifolia, P. longiseta, P. maculosa, P. meisneriana, P. minor, P. nepalensis, P. orientalis, P. pensylvanica, P. perfoliata, P. punctata, P. robustior, P. sagittata, P. setacea, P. virginiana, P. wallichii
P. amphibia, P. arifolia, P. bicornis, P. bungeana, P. capitata, P. chinensis, P. glabra, P. hirsuta, P. hydropiper, P. hydropiperoides, P. lapathifolia, P. longiseta, P. maculosa, P. meisneriana, P. minor, P. nepalensis, P. orientalis, P. pensylvanica, P. perfoliata, P. punctata, P. robustior, P. sagittata, P. setacea, P. virginiana, P. wallichii
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 Polygonum careyi
Name authority (Linnaeus) Gray: Nat. Arr. Brit. Pl. 2: 268. (1822) (Olney) Greene: Leafl. Bot. Observ. Crit. 1: 24. (1904)
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