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garden knotweed, garden smartweed, Himalayan knotweed, Kashmir plume

hairy smartweed

Habit Plants perennial, 3–9 dm; roots also often arising from proximal nodes; rhizomes present.
Stems

decumbent to ascending or erect, branched, without noticeable ribs, brownish-hirsute on internodes.

Leaves

ocrea brown to reddish brown, cylindric, 6–12 mm, chartaceous, base sometimes inflated, margins truncate, eciliate or ciliate with bristles 4–7.5 mm, surface hirsute, not glandular-punctate;

petiole 0.1(–0.3) cm, hirsute, leaves sometimes sessile;

blade without dark triangular or lunate blotch adaxially, ovate to lanceolate, (2–)4–8 × (0.5–)1–2.5 cm, base rounded to cordate, margins strigose to hirsute, apex acute to acuminate, faces sparingly hirsute abaxially and adaxially, midvein usually hirsute abaxially.

Inflorescences

mostly terminal, erect, interrupted proximally, usually uninterrupted distally, 20–80 × 4–8 mm;

peduncle 30–60 mm, hirsute or, sometimes, nearly glabrous distally;

ocreolae overlapping distally, usually not overlapping proximally, margins ciliate with bristles 0.4–1.5(–2) mm.

Pedicels

ascending, 1–2 mm.

Flowers

1–3 per ocreate fascicle, homostylous;

perianth white to pink, glabrous, not glandular-punctate, nonaccrescent;

tepals 5, connate in proximally 1/3, obovate, 1.5–2 mm, veins not prominent, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 5, included;

anthers red, elliptic to ovate;

styles 3, connate proximally.

Achenes

included or apex exserted, dark brown to brownish black, 3-gonous, 2–2.5 × 1.3–1.8 mm, shiny, smooth.

2n

= 20.

Persicaria wallichii

Persicaria hirsuta

Phenology Flowering Jun–Oct.
Habitat Sandy soils, open areas in savannahs, pond margins, ditches, often in shallow water
Elevation 0-100 m (0-300 ft)
Distribution
from FNA
CA; MA; OR; BC; Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; FL; GA; MS; NC; SC
[BONAP county map]
Discussion

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.)

C. B. McDonald (1980) showed that Persicaria hirsuta is closely related to P. setacea and P. hydropiperoides. Hybrids between P. hirsuta and P. setacea have been produced experimentally but appear to be rare in the wild. Although geographically sympatric, the two species generally occupy different habitats. Experimental crosses between P. hirsuta and P. hydropiperoides were unsuccessful (McDonald).

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

Source FNA vol. 5, p. 581. FNA vol. 5, p. 587.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Rubrivena Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria
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. punctata, P. robustior, P. sagittata, P. setacea, P. virginiana
P. amphibia, P. arifolia, P. bicornis, P. bungeana, P. capitata, P. careyi, P. chinensis, P. glabra, 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
Subordinate taxa
P. wallichii var. wallichii
Synonyms Polygonum polystachyum, Aconogonon polystachyum, Pleuropteropyrum polystachyum, Reynoutria polystachya, Rubrivena polystachya Polygonum hirsutum
Name authority Greuter & Burdet: Willdenowia 19: 41. (1989) (Walter) Small: Fl. S.E. U.S., 379. (1903)
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