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false water pepper, false water-pepper smartweed, mild waterpepper, renouée faux-poivre-d'eau, swamp smartweed, water-pepper

garden knotweed, garden smartweed, Himalayan knotweed, Kashmir plume

Habit Plants perennial, 1.5–10 dm; roots also often arising from proximal nodes; rhizomes often present.
Stems

decumbent to ascending, usually branched, without noticeable ribs, glabrous or obscurely strigose distally.

Leaves

ocrea brown, cylindric, 5–23 mm, chartaceous, base inflated, margins truncate, ciliate with bristles (2–)4–10 mm, surface glabrous or strigose, not glandular-punctate;

petiole 0.2–2 cm, glabrous or strigose;

blade without dark triangular or lunate blotch adaxially, broadly lanceolate to linear-lanceolate, 5–25 × 0.4–3.7 cm, base tapered or acute, margins antrorsely appressed-pubescent, apex acuminate, faces glabrous or appressed-pubescent along midveins and sometimes on faces, usually punctate abaxially.

Inflorescences

terminal, sometimes also axillary, erect, uninterrupted or interrupted proximally, 30–80 × 2–5 mm;

peduncle 10–30 mm, glabrous or strigose;

ocreolae overlapping distally, often not overlapping proximally, margins ciliate with bristles to 2(–3) mm.

Pedicels

ascending, 1–1.5 mm.

Flowers

bisexual or unisexual and staminate, 2–6 per ocreate fascicle, homostylous;

perianth roseate proximally, roseate, white, or greenish white distally, not glandular-punctate or sometimes glandular-punctate with punctae on tubes and inner tepals, scarcely accrescent;

tepals 5, connate ca. 1/3–1/2 their length, obovate, 2.5–4 mm in bisexual flowers, 1.5–2.5 mm in staminate flowers, veins prominent or not, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 8, included or exserted in staminate flowers;

anthers pink or red, elliptic to ovate;

styles 3, connate near middle.

Achenes

included or apex exserted, brown to brownish black or black, 3-gonous, 1.5–3 × 1–2.3 mm, shiny, smooth.

Persicaria hydropiperoides

Persicaria wallichii

Phenology Flowering Jun–Nov.
Habitat Wet banks and clearings, shallow water, marshes, moist prairies, ditches
Elevation 0-1500 m (0-4900 ft)
Distribution
from FNA
AK; AL; AR; AZ; CA; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; VA; VT; WA; WI; WV; BC; NB; NS; ON; QC; Mexico; Central America; South America
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; MA; OR; BC; Asia
[WildflowerSearch map]
[BONAP county map]
Discussion

The extreme variability in Persicaria hydropiperoides is reflected in its extensive synonymy. Among the segregates most often recognized in floras and checklists is P. opelousana, which C. B. McDonald (1980) showed to be broadly sympatric and highly interfertile with P. hydropiperoides. Consistent with this conclusion, R. S. Mitchell (1971) found that P. hydropiperoides and P. opelousana are unique among native North American smartweeds in consistently possessing multicellular plate-glands on the abaxial surface of their leaves. Such glands also are found on P. maculosa, an introduced European species.

Herbarium specimens of Persicaria hydropiperoides sometimes are misidentified as P. maculosa, especially when the roots are missing. The former species may be distinguished reliably by its achenes all trigonous (trigonous and biconvex achenes are mixed in the inflorescences of P. maculosa) and bristles on the margins of the ocreae that average longer. M. L. Fernald (1922c) reported hybrids with P. robustior from Nova Scotia.

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

Varieties 2 (1 in the flora).

Persicaria wallichii is an ornamental that escapes infrequently in the flora area. A population in Nova Scotia apparently was ephemeral. Plants with leaf blades sparsely to densely pubescent abaxially and pedicels glabrous are var. wallichii, to which naturalized North American plants appear to be referable. Plants with leaf blades brownish-tomentose abaxially and pedicels usually pubescent are var. tomentosa S. P. Hong, which may be in cultivation in North America.

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

Source FNA vol. 5, p. 585. FNA vol. 5, p. 581.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Rubrivena
Sibling taxa
P. amphibia, P. arifolia, P. bicornis, P. bungeana, P. capitata, P. careyi, P. chinensis, P. glabra, P. hirsuta, P. hydropiper, 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. 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
Subordinate taxa
P. wallichii var. wallichii
Synonyms Polygonum hydropiperoides, P. opelousana, P. paludicola, Polygonum hydropiperoides var. adenocalyx, Polygonum hydropiperoides var. asperifolium, Polygonum hydropiperoides var. breviciliatum, Polygonum hydropiperoides var. bushianum, Polygonum hydropiperoides var. digitatum, Polygonum hydropiperoides var. opelousanum, Polygonum hydropiperoides var. psilostachyum, Polygonum opelousanum, Polygonum opelousanum var. adenocalyx Polygonum polystachyum, Aconogonon polystachyum, Pleuropteropyrum polystachyum, Reynoutria polystachya, Rubrivena polystachya
Name authority (Michaux) Small: Fl. S.E. U.S., 378. (1903) Greuter & Burdet: Willdenowia 19: 41. (1989)
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