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denseflower knotweed, smooth smartweed

Habit Plants perennial, 3–15 dm; roots also often arising from proximal nodes; rhizomes present.
Stems

decumbent to erect, usually branched distally, without noticeable ribs, glabrous or, rarely, pubescent distally, sometimes glandular-punctate.

Leaves

ocrea light brown, cylindric, 12–23 mm, chartaceous, base inflated, margins truncate, eciliate, surface glabrous, usually obscurely glandular-punctate;

petiole 0.2–2 cm, scabrous;

blade without dark triangular or lunate blotch adaxially, lanceolate, (10–)15–30 × (1.5–)2–5.4 cm, base tapered, margins glabrous or antrorsely strigose, apex acute to acuminate, faces glabrous or scabrous along midveins, sometimes glandular-punctate.

Inflorescences

mostly terminal, sometimes also axillary, erect to slightly nodding, usually uninterrupted, 30–100 × 5–9 mm;

peduncle 10–50 mm, glabrous or scabrid, glandular-punctate;

ocreolae usually overlapping, margins eciliate.

Pedicels

erect to spreading, 2–5 mm.

Flowers

(1–)3–8 per ocreate fascicle, homostylous;

perianth greenish white to white or pink, glabrous, not glandular-puncate or glandular-punctate with punctae ± uniformly distributed, scarcely accrescent;

tepals 5, connate ca. 1/3 their length, obovate, 3–3.6 mm, veins not prominent, not anchor shaped, margins entire, apex obtuse to rounded;

stamens 5–7, included;

anthers pink or red, ovate;

styles 2, connate proximally.

Achenes

included, dark brown to brownish black, biconvex, 2–2.2 × 1.3–1.6 mm, shiny, smooth.

Persicaria glabra

Phenology Flowering Aug–Nov.
Habitat Swamps, wet thickets, marshy shores, frequently in water, mostly on coastal plain of e North America
Elevation 0-300
Distribution
from FNA
AL; AR; DE; FL; GA; KY; LA; MD; MO; MS; NC; NJ; SC; TN; TX; VA; Central America; South America; Asia; ne Africa; Pacific Islands (Hawaii, Philippines)
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Discussion

American plants here included in Persicaria glabra often have been treated as distinct and called P. densiflora. The morphological differences between them and Asian and Pacific P. glabra are minor. Regional tendencies exist but do not appear sufficient to warrant separation of the species (K. L. Wilson 1990b).

An infusion made from pounded whole plants was used by the Hawaiians as a blood medicine (D. E. Moerman 1998).

Persicaria portoricensis Small and Polygonum portoricense Bertero ex Small are superfluous and illegitimate names that pertain here.

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

Source FNA vol. 5, p. 586.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria
Sibling taxa
P. amphibia, P. arifolia, P. bicornis, P. bungeana, P. capitata, P. careyi, P. chinensis, 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 glabrum, P. densiflora, Polygonum densiflorum
Name authority (Willdenow) M. Gómez: Anales Inst. Segunda Enseñ. 2: 278. (1896)
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