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dotted knotweed, dotted smartweed, renouée ponctuée, water smartweed

knotweed

Habit Plants annual or perennial, 1.5–12 dm; roots also often arising from proximal nodes; rhizomes often present. Trees, shrubs, vines, or herbs, perennial or annual, homophyllous (heretophyllous in some species of Polygonum); root fibrous or a solid taproot, rarely tuberous.
Stems

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

usually prostrate to erect, sometimes scandent, not scapose, rarely with recurved spines (some species of Persicaria), glabrous or pubescent, sometimes glandular;

nodes usually swollen;

branches free (adnate to stems distal to nodes and appearing to arise internodally in Polygonella);

tendrils absent (except in Antigonon and Brunnichia).

Leaves

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 (persistent in Coccoloba and sometimes more than 1 year in Antigonon and Polygonella), basal or basal and cauline, rarely cauline only, mostly alternate;

ocrea present, persistent or deciduous, cylindric to funnelform, chartaceous, membranous, coriaceous, or, rarely, foliaceous or partly so;

petiole present or absent, rarely articulate basally (Fagopyrum, Fallopia, Polygonella, Polygonum), rarely with extrafloral nectaries (Fallopia, Muehlenbeckia);

blade simple with entire margins, rarely undulate or lobed.

Inflorescences

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, racemelike, paniclelike, cymelike, or, rarely, capitate, comprising simple or branched clusters of compound inflorescences;

bracts absent;

peduncle spreading to erect, sometimes absent;

clusters of flowers subtended by connate bracteoles forming persistent membranous tube (ocreola), awnless.

Pedicels

ascending, 1–4 mm.

Flowers

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.

usually bisexual, sometimes bisexual and unisexual on same plant, rarely unisexual only, 1–20+ per ocreate fascicle, often with stipelike base distal to articulation;

perianth often accrescent in fruit, often greenish, white, pink, yellow, red, or purple, usually unwinged and unkeeled (winged or, sometimes, keeled in Fallopia, rarely keeled in Polygonum), campanulate or urceolate, sometimes membranous, indurate, or fleshy in fruit, rarely developing raised tubercles proximally (Rumex), glabrous or pubescent, sometimes glandular or glandular-punctate;

tepals 2–6, usually in 2 whorls, distinct or connate proximally and forming tube, petaloid or sepaloid, monomorphic or dimorphic;

nectary a disk at base of ovary or glands associated with bases of filaments;

stamens usually (1–)6–9, staminodes rarely present;

filaments distinct, or connate basally and sometimes forming staminal tube, free or adnate to perianth tube;

pistils (2–)3(–4)-carpellate;

ovary 1-locular (sometimes with vestigial partitions proximally);

ovule 1, orthotropous or, rarely, anatropous, placentation basal or free-central;

styles 1–3, erect to spreading or recurved, distinct or connate proximally;

stigmas peltate, capitate, fimbriate, or penicillate.

Achenes

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

yellowish, brown, red, or black, homocarpic (sometimes heterocarpic in Polygonum), winged or unwinged, usually 2–3-gonous, sometimes discoid, biconvex, or spheroidal, rarely 4-gonous.

Seeds

embryo usually straight or curved, rarely folded.

2n

= 44.

Persicaria punctata

Polygonaceae subfam. Polygonoideae

Phenology Flowering Jun–Nov.
Habitat Shallow water, shores, marshes, floodplain forests
Elevation 0-1500 m (0-4900 ft)
Distribution
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]
Mainly temperate regions of North America
Discussion

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.)

Genera 28, species ca. 850 (16 genera, 160 species in the flora).

Morphological (K. Haraldson 1978; L.-P. Ronse Decraene and J. R. Akeroyd 1988; Ronse Decraene et al. 2000; Hong S. P. et al. 1998) and molecular (A. S. Lamb Frye and K. A. Kron 2003) data provide support for separation of Persicaria from Polygonum. Further studies are needed to elucidate the relationships of allied genera, particularly Aconogonon, Bistorta, and Koenigia with Persicaria, and Fallopia and Polygonella with Polygonum.

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

Key
1. Tendrils present; plants vines
→ 2
1. Tendrils absent; plants trees, shrubs, or herbs, rarely vinelike shrubs
→ 3
2. Perianths pink to purple or, rarely, white or yellow, membranous; pedicels not 3-winged
Antigonon
2. Perianths green to greenish yellow, indurate; pedicels 3-winged, 1 wing more prominent and becoming greatly expanded in fruit
Brunnichia
3. Plants trees or shrubs; tubes of pistillate flowers becoming fleshy in fruit
Coccoloba
3. Plants herbs, subshrubs, or, rarely, vinelike shrubs; tubes of pistillate flowers rarely becoming fleshy in fruit
→ 4
4. Tepals 6
→ 5
4. Tepals 3, 4, or 5
→ 7
5. Flowers unisexual; outer 3 tepals of pistillate flowers each with apex ending in stout spine
Emex
5. Flowers bisexual or, rarely, unisexual; outer 3 tepals each without apex ending in stout spine
→ 6
6. Achenes winged; inner tepals of fruiting perianths nonaccrescent; stamens (6-)9
Rheum
6. Achenes unwinged; inner tepals of fruiting perianths usually accrescent; stamens 6
Rumex
7. Herbs annual; tepals 3 [4]; stamens (1-)3[-5]
Koenigia
7. Herbs perennial or annual, or shrubs; tepals 4-5; stamens 3-8
→ 8
8. Tepals 4; achenes lenticular, winged; leaves mostly basal
Oxyria
8. Tepals 4 or 5; achenes 3-gonous, discoid, biconvex, spheroidal, or 4-gonous, unwinged or essentially so; leaves cauline or basal and cauline, rarely mostly basal
→ 9
9. Branches adnate to stems, appearing to arise internodally
Polygonella
9. Branches not adnate to stems, not appearing to arise internodally
→ 10
10. Plants shrubs, vinelike; flowers unisexual, tubes of pistillate flowers becoming fleshy in fruit
Muehlenbeckia
10. Plants herbs or, if shrubs, not vinelike; flowers bisexual or, rarely, unisexual, if unisexual then tubes of pistillate flowers not becoming fleshy
→ 11
11. Outer tepals winged or keeled
→ 12
11. Outer tepals unwinged and unkeeled
→ 13
12. Outer tepals winged (keeled in F. ciliondis and, usually, F. convolvulus); ocreae chartaceous, tan to brownish, glabrous or scabrous to variously pubescent, never 2-lobed distally
Fallopia
12. Outer tepals keeled; ocreae often hyaline, silvery, glabrous, 2-lobed distally
Polygonum
13. Leaves mostly basal, some cauline; inflorescences terminal, spikelike; stems simple
Bistorta
13. Leaves cauline; inflorescences terminal and axillary or axillary; stems usually branched, rarely simple
→ 14
14. Achenes strongly exserted; perianths nonaccrescent; tepals distinct
Fagopyrum
14. Achenes included or exserted; perianths accrescent or nonaccrescent; tepals connate to 2/3 their lengths. [15. Shifted to left margin.—Ed.]
→ 15
15. Ocreae often hyaline, silvery, glabrous, 2-lobed distally, often disintegrating into fibers or completely
Polygonum
15. Ocreae chartaceous, usually tan, brown, or reddish, rarely silvery, glabrous or scabrous to variously pubescent, never 2-lobed distally, often tearing with age
→ 16
16. Inflorescences spikelike, paniclelike, or capitate; tepals 4 or 15, connate 1/ 2/ 3 their length (less than 5 their length in P. wallichii); stamens 5-8
Persicaria
16. Inflorescences racemelike or paniclelike; tepals 5, connate ca. 1/ 4 their length; stamens 8
Aconogonon
Source FNA vol. 5, p. 586. FNA vol. 5, p. 479.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria Polygonaceae
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
Aconogonon, Antigonon, Bistorta, Brunnichia, Coccoloba, Emex, Fagopyrum, Fallopia, Koenigia, Muehlenbeckia, Oxyria, Persicaria, Polygonella, Polygonum, Rheum, Rumex
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
Name authority (Elliott) Small: Fl. S.E. U.S., 379. (1903) Eaton: Bot. Dict. ed. 4, 30. (1836)
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