Persicaria hydropiper |
Persicaria nepalensis |
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common smartweed, marsh-pepper smartweed, marshpepper knotweed, mild water-pepper, renouée poivre-d'eau, smartweed, water-pepper, water-pepper smartweed |
Nepalese knotweed, Nepalese smartweed |
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Habit | Plants annual, 2–8(–10) dm; roots also often arising from proximal nodes; rhizomes and stolons absent. | Plants annual, 3–5 dm; roots also often arising from proximal nodes. |
Stems | decumbent to ascending or erect, branched, without noticeable ribs, glabrous, glandular-punctate. |
decumbent to ascending, glabrous except for fleshy, retrorse, whitish hairs at nodes. |
Leaves | ocrea brown, cylindric or funnelform, (8–)10–15 mm, chartaceous, base inflated, margins truncate, ciliate with bristles 1–4 mm, surface glabrous or strigose, usually glandular-punctate; petiole 0.1–0.8 cm, glandular-punctate, leaves sometimes sessile; blade without dark triangular or lunate blotch adaxially, lanceolate to narrowly rhombic, (1.5–)4–10(–15) × 0.4–2.5 cm, base tapered or cuneate, margins antrorsely strigose, apex acute to acuminate, faces glabrous or scabrous along midveins, glandular-punctate, sometimes obscurely so adaxially. |
ocrea brownish or hyaline, cylindric to funnelform, 4–10 mm, chartaceous, base inflated or not, margins oblique, eciliate, surface glabrous or with bristlelike hairs proximally; petiole 0.1–3 cm, winged to base, leaves sometimes sessile; blade ovate-deltate, 1.5–5 × 1–4 cm, base rounded to truncate, margins glabrous or scabrous, apex acute, faces pilose and glandular-punctate abaxially, glabrous adaxially. |
Inflorescences | terminal and axillary, erect or nodding, interrupted or uninterrupted distally, 30–180 × 5–9 mm; peduncle (0–)10–50 mm, sometimes absent on axillary inflorescences and flowers thus enclosed in ocreae, glabrous, glandular-punctate; ocreolae not overlapping or overlapping distally, margins eciliate or ciliate with bristles to 1 mm. |
terminal and axillary, 5–10 × 5–10 mm; peduncle 2–20 mm, apex stipitate-glandular; ocreolae overlapping, margins eciliate. |
Pedicels | ascending, 1–3 mm. |
mostly ascending, 0.1–1 mm, flowers sometimes sessile. |
Flowers | 1–3(–5) per ocreate fascicle, homostylous; perianth greenish proximally, white or pink distally, glandular-punctate with punctae ± uniformly distributed, scarcely accrescent; tepals 4–5, connate ca. 1/3 their length, petaloid, obovate, 2–3.5 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. |
1–2 per ocreate fascicle; perianth white to pink or lavender, urceolate, glabrous, scarcely accrescent; tepals 4(–5), oblong to broadly elliptic, 2.5–3 mm, apex acute to obtuse; stamens (5–)8, filaments distinct, free; anthers purplish black, elliptic; styles 2, connate proximally. |
Achenes | included or apex exserted, brownish black, biconvex or 3-gonous, 1.9–3 × 1.5–2 mm, dull, minutely roughened. |
included, dark brown to black, biconvex, 1.5–2 × 1–1.5 mm, dull, minutely punctate. |
2n | = 20. |
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Persicaria hydropiper |
Persicaria nepalensis |
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Phenology | Flowering May–Nov. | Flowering Jul–Oct. |
Habitat | Shorelines of lake and ponds, banks of streams and rivers, fens, forested wetlands, pastures, occasionally waste ground | Disturbed sites, gravel bars in lowland zone |
Elevation | 0-1500 m (0-4900 ft) | 0-900 m (0-3000 ft) |
Distribution |
AK; AL; AR; 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; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; BC; MB; NB; NF; NS; ON; PE; QC; SPM; Europe; nw Africa; Pacific Islands (Hawaii, New Zealand); Australia [Introduced in North America; introduced also in Asia]
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CT; FL; MA; NY; PA; BC; Asia [Introduced in North America; introduced also in Europe, Africa] |
Discussion | All parts of Persicaria hydropiper have an acrid, pepperlike taste. The plants have a long history of medicinal use in Europe, and the oily exudate produced in multicellular glands can cause skin irritation, hence the common name smartweed (R. S. Mitchell and J. K. Dean 1978). Some Native American tribes used P. hydropiper as a drug to treat a variety of ailments, and the Cherokee and Iroquois consumed it as food (D. E. Moerman 1998). Herbarium specimens of Persicaria hydropiper often are misidentified as P. punctata. In addition to its minutely roughened and dull achenes, P. hydropiper differs from P. punctata frequently in bearing flowers enclosed in the ocreae, the inflorescences thus appearing somewhat leafy. By contrast, inflorescences of P. punctata generally appear terminal and leafless. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 5, p. 590. | FNA vol. 5, p. 579. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria | Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Cephalophilon |
Sibling taxa | ||
Synonyms | Polygonum hydropiper, Polygonum hydropiper var. projectum | Polygonum nepalense |
Name authority | (Linnaeus) Spach: Hist. Nat. Vég. 10: 536. (1841) | (Meisner) H. Gross: Bot. Jahrb. Syst. 49: 277. (1913) |
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