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dotted knotweed, dotted smartweed, renouée ponctuée, water smartweed

knotweed, smartweed, tearthumb

Habit Plants annual or perennial, 1.5–12 dm; roots also often arising from proximal nodes; rhizomes often present. Herbs, perennial or annual (sometimes suffrutescent in P. wallichii); taprooted or fibrous-rooted; sometimes rhizomatous or stoloniferous.

ascending to erect, branched, without noticeable ribs, glabrous, glandular-punctate.

erect or, sometimes, prostrate or scandent, simple or branched, glabrous or pubescent, rarely with recurved prickles.


ocrea brown, cylindric, (4–)9–18 mm, chartaceous, base inflated, margins truncate, ciliate with bristles 2–11 mm, surface glabrous or strigose, glandular-punctate;

petiole 0.1–1 cm, glandular-punctate, leaves sometimes sessile;

blade without dark triangular or lunate blotch adaxially, lanceolate to lanceolate-ovate or subrhombic, 4–10(–15) × 0.6–2.4 cm, base tapered or cuneate, margins antrorsely strigose, apex acute to acuminate, faces glabrous or scabrous along midveins, glandular-punctate.

deciduous, mostly cauline, alternate, petiolate or sessile;

ocrea persistent or disintegrating with age and deciduous entirely or distally, usually tan, brown, or reddish, chartaceous or partially to entirely foliaceous, rarely coriaceous proximally and chartaceous distally, glabrous or scabrous to variously pubescent, never 2-lobed distally;

blade lanceolate or ovate to hastate or sagittate, margins entire or, rarely, hastately lobed.


mostly terminal, sometimes also axillary, erect, interrupted, 50–200 × 4–8 mm;

peduncle 30–60 mm, glabrous, glandular-punctate;

ocreolae mostly not overlapping, margins mostly ciliate with bristles to 2 mm.

terminal or terminal and axillary, spikelike, paniclelike, or capitate;

peduncle present.


ascending, 1–4 mm.

present or absent.


2–6 per ocreate fascicle, homostylous;

perianth greenish proximally, white distally, rarely tinged pink, glandular-punctate with punctae ± uniformly distributed, scarcely accrescent;

tepals 5, connate ca. 1/3 their length, obovate, 3–3.5 mm, veins prominent or not, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 6–8, included;

anthers pink or red, elliptic to ovate;

styles 2–3, connate proximally.

bisexual (often functionally unisexual in P. amphibia and P. hydropiperoides), 1–14 per ocreate fascicle, base not stipelike;

perianth white, greenish white, roseate, red, or purple, campanulate or urceolate, rarely rotate, rarely becoming fleshy in fruit, glabrous, sometimes glandular-punctate, accrescent or nonaccrescent;

tepals 4–5, connate 1/4–2/3 their lengths (less than 1/5 their lengths in P. wallichii), petaloid, dimorphic, outer larger than inner;

stamens 5–8, filaments distinct or connate basally, outer ones sometimes adnate to perianth tube, glabrous;

anthers yellow, pink, or red, elliptic to ovate;

styles 2–3, erect to spreading or reflexed, distinct or connate;

stigmas capitate.


included or apex exserted, brownish black, usually 3-gonous, rarely biconvex, (1.8–)2.2–3.2 × 1.5–2.2 mm, shiny, smooth.

included or exserted, brown or dark brown to black, not winged, discoid, biconvex, 2–3-gonous, or spheroidal, glabrous.


embryo curved.


= 10, 11, 12.


= 44.

Persicaria punctata


Phenology Flowering Jun–Nov.
Habitat Shallow water, shores, marshes, floodplain forests
Elevation 0-1500 m (0-4900 ft)
from FNA
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; VA; VT; WA; WI; WV; WY; HI; BC; MB; NB; NS; ON; PE; QC; SK; Mexico; West Indies (Puerto Rico); Central America (Guatemala); South America (Brazil)
[WildflowerSearch map]
[BONAP county map]
Nearly worldwide
[BONAP county map]

N. C. Fassett (1949) proposed a complicated classification for Persicaria punctata with 12 varieties in North America and South America. He also identified numerous specimens that he considered to be morphologically intermediate between various varieties. M. Dalci (1972) documented a wide range of phenotypic and genotypic variation throughout the range of P. punctata and extensive overlap in many of the features used by Fassett to distinguish varieties. Consequently, recognition of varieties does not seem warranted. Persicaria punctata and its close relatives P. robustior and P. glabra are unique among native North American smartweeds in possessing complex glands called valvate chambers in their epidermises. Persicaria punctata is confused most frequently with P. hydropiper; the achenes are diagnostic.

The Chippewa, Houma, and Iroquois prepared decoctions from leaves, flowers, and roots for use as analgesics as well as gastrointestinal, orthopedic, and psychological aids (D. E. Moerman 1998).

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

Species ca. 100 (26 in the flora).

Opinions vary widely about the circumscription and infrageneric classification of Persicaria. The concept employed here generally follows L.-P. Ronse Decraene et al. (2000) and K. Haraldson (1978), with five sections recognized in the flora. Aconogonon and Bistorta, which often are included in Persicaria or in Polygonum in the broad sense, are treated here as separate genera.

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


Key to the Sections of Persicaria

1. Styles exserted, persistent on achenes; inflorescences spikelike, interrupted
sect. Tovara
1. Styles included, rarely exserted, deciduous; inflorescences capitate, paniclelike, or spikelike, uninterrupted or interrupted
→ 2
2. Stems with recurved prickles, scandent or, rarely, ascending to erect
sect. Echinocaulon
2. Stems unarmed, usually erect or ascending, rarely prostrate or decumbent
→ 3
3. Inflorescences capitate; petioles usually winged, auriculate
sect. Cephalophilon
3. Inflorescence spikelike or paniclelike; petioles not winged, not auriculate
→ 4
4. Inflorescences paniclelike; perianths rotate; tepals connate less than 1/ 5 their lengths
sect. Rubrivena
4. Inflorescences spikelike; perianths campanulate; tepals connate 1/ 2/ 3 their lengths
sect. Persicaria
Source FNA vol. 5, p. 586. FNA vol. 5, p. 574.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria Polygonaceae > subfam. Polygonoideae
Sibling taxa
P. amphibia, 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. robustior, P. sagittata, P. setacea, P. virginiana, P. wallichii
Subordinate taxa
P. sect. Cephalophilon, P. sect. Echinocaulon, P. sect. Persicaria, P. sect. Rubrivena, P. sect. Tovara
Synonyms Polygonum punctatum, Polygonum acre var. leptostachyum, Polygonum punctatum var. confertiflorum, Polygonum punctatum var. ellipticum, Polygonum punctatum var. leptostachyum, Polygonum punctatum var. parviflorum, Polygonum punctatum var. parvum Polygonum unranked P.
Name authority (Elliott) Small: Fl. S.E. U.S., 379. (1903) (Linnaeus) Miller: Gard. Dict. Abr. ed. 4, vol. 3. (1754)
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