Persicaria hydropiper |
Persicaria bicornis |
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common smartweed, marsh-pepper smartweed, marshpepper knotweed, mild water-pepper, renouée poivre-d'eau, smartweed, water-pepper, water-pepper smartweed |
pink 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, 2–18 dm; roots also rarely arising from basal nodes; rhizomes and stolons absent. |
Stems | decumbent to ascending or erect, branched, without noticeable ribs, glabrous, glandular-punctate. |
ascending to erect, rarely decumbent, branched, ribbed, glabrous or appressed-pubescent to spreading-pubescent distally, stipitate-glandular or, rarely, without stipitate-glands. |
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, cylindric, 6–20 mm, chartaceous, base inflated, margins truncate, eciliate or ciliate with bristles to 1 mm, surface glabrous or scabrous proximally, eglandular; petiole 0.1–1.5(–2.3) cm, glabrous or appressed-pubescent; blade sometimes with dark triangular or lunate blotch adaxially, linear-lanceolate to ovate-lanceolate, 2.3–13(–18) × (0.4–)1–2.3 cm, base tapered to cuneate, margins antrorsely scabrous, apex acute to acuminate, faces glabrous or appressed-pubescent along midveins, glandular-punctate abaxially. |
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, erect, uninterrupted, 8–60 × 10–18 mm; peduncle 8–60(–70) mm, glabrous or pubescent, usually stipitate-glandular; ocreolae overlapping, margins eciliate or ciliate with bristles to 0.8 mm. |
Pedicels | ascending, 1–3 mm. |
ascending, 1.5–5 mm. |
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. |
2–11 per ocreate fascicle, heterostylous; perianth pink, glabrous, not glandular-punctate, accrescent; tepals 5, connate ca. 1/4–1/3 their length, obovate to elliptic, 3–4.6 mm, veins prominent, not anchor-shaped, margins entire, apex obtuse to rounded; stamens 6–8, included or exserted; anthers pink or red, elliptic; styles 2(–3), included or exserted, connate at bases. |
Achenes | included or apex exserted, brownish black, biconvex or 3-gonous, 1.9–3 × 1.5–2 mm, dull, minutely roughened. |
included or apex exserted, brownish black to black, discoid or, rarely, 3-gonous, 1 side usually slightly concave and other with central hump, (2–)2.2–2.9 × 2–2.8(–3) mm, shiny, smooth. |
2n | = 20. |
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Persicaria hydropiper |
Persicaria bicornis |
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Phenology | Flowering May–Nov. | Flowering Jun–Oct. |
Habitat | Shorelines of lake and ponds, banks of streams and rivers, fens, forested wetlands, pastures, occasionally waste ground | Moist, disturbed places, permanent and ephemeral wetlands, ditches, cultivated fields, shorelines of ponds and reservoirs |
Elevation | 0-1500 m (0-4900 ft) | 50-1600 m (200-5200 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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AR; CO; IA; IL; KS; LA; MO; NE; NM; OK; SD; TX; WY
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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.) |
Persicaria bicornis is a characteristic smartweed of permanent and ephemeral wetlands and moist, disturbed sites in the Great Plains. It often has been included in P. pensylvanica but can be distinguished readily by its heterostylous flowers. The achenes, which usually bear an obscure or prominent hump in the center of one face, also are diagnostic. This hump often ruptures the side of the perianth on fruiting herbarium specimens. Persicaria bicornis also has leaf blades that are on average narrower than are those of P. pensylvanica, and populations exhibit less variation in perianth color. As in P. pensylvanica, flowers with three styles and trigonous achenes are produced very rarely. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 5, p. 590. | FNA vol. 5, p. 589. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria | Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria |
Sibling taxa | ||
Synonyms | Polygonum hydropiper, Polygonum hydropiper var. projectum | Polygonum bicorne, P. longistyla, Polygonum longistylum |
Name authority | (Linnaeus) Spach: Hist. Nat. Vég. 10: 536. (1841) | (Rafinesque) Nieuwland: Amer. Midl. Naturalist 3: 201. (1914) |
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