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bristly lady's-thumb, oriental lady's thumb, oriental lady's-thumb smartweed

Habit Plants annual, 3–8 dm; roots also often arising from proximal nodes; rhizomes and stolons absent.
Stems

decumbent to ascending, branched, without noticeable ribs, glabrous.

Leaves

ocrea hyaline to brownish, cylindric, 5–12 mm, chartaceous, base sometimes inflated, margins truncate, ciliate with bristles 4–12 mm, surface glabrous or strigose, not glandular-punctate;

petiole 0.1–0.3(–0.6) cm, glabrous, leaves sometimes sessile;

blade without dark triangular or lunate blotch adaxially, ovate-lanceolate to linear-lanceolate, 2–8 × 1–3 cm, base tapering to cuneate, margins antrorsely strigose, apex acute to acuminate, faces glabrous or sparingly strigose along veins abaxially, glabrous or strigose along midvein and margins adaxially, not glandular-punctate.

Inflorescences

terminal, sometimes also axillary, erect, uninterrupted, 10–40(–80) × 3–7 mm;

peduncle 10–50 mm, glabrous;

ocreolae overlapping, margins ciliate with bristles (0.5–)1–4(–6) mm.

Pedicels

ascending, 1–2 mm.

Flowers

1–5 per ocreate fascicle, homostylous;

perianth pinkish green proximally, roseate distally, glabrous, not glandular-punctate, scarcely accrescent;

tepals 5, connate ca. 1/3 their length, obovate, 2.2–2.8 mm, veins not prominent, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 5, included;

anthers yellow, elliptic to ovate;

styles 3, connate proximally.

Achenes

included, dark brown to black, 3-gonous, 1.6–2.3 × 1.1–1.6 mm, shiny, smooth.

Persicaria longiseta

Phenology Flowering May–Oct.
Habitat Floodplain forests and woodlands, shorelines of ponds, moist roadsides, waste places
Elevation 0-300 m (0-1000 ft)
Distribution
from FNA
AL; CT; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; NE; NJ; NY; OH; PA; SC; TN; TX; VA; VT; WI; WV; BC; NB; ON; e Asia [Introduced in North America; introduced also in Europe]
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[BONAP county map]
Discussion

Persicaria longiseta is morphologically similar to another Asian species, P. posumbu (Buchanan-Hamilton ex D. Don) H. Gross (= P. caespitosa). Its spread in the United States since its introduction near Philadelphia in 1910 was summarized by A. K. Paterson (2000).

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

Source FNA vol. 5, p. 592.
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. glabra, P. hirsuta, P. hydropiper, P. hydropiperoides, P. lapathifolia, 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 longisetum, P. caespitosa var. longiseta, Polygonum caespitosum var. longisetum
Name authority (Bruijn) Kitagawa: Rep. Inst. Sci. Res. Manchoukuo 1: 322. (1937)
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