Water Pepper

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.

Plants annual, 2-8(-10) dm; roots also often arising from proximal nodes; rhizomes and stolons absent. Stems decumbent to ascending or erect, branched, without noticeable ribs, glabrous, glandular-punctate. 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. 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. Pedicels ascending, 1-3 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. 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. Achenes included or apex exserted, brownish black, biconvex or 3-gonous, 1.9-3 × 1.5-2 mm, dull, minutely roughened. 2n = 20.

Erect, 30-45 (-50) cm high with tufted roots branched from base or above, or sometime simple, annual to perennial herb. Stem glabrous, brown, sometimes shining. Leaves 1.5-8 (-10) x 0.4-1.5 (-2) cm, linear lanceolate to lanceolate, acuminate, margin ciliate, surface glabrous or scabrous or slightly pubescent beneath on the midrib and reddish punctate gland-dotted on both surfaces, petiole 0.2-0.4 cm long. Ochreae 0.25-1.5 (-2.0) cm long, glabrous, ciliae at the mouth of ochrea 1-4 mm long. Inflorescence 3-7 cm long, lax, flowers ± distant, erect, not drooping pedunculate raceme; peduncles 1.0-6.5 cm long. Flowers 1.0-2.0 mm across, pedicellate; pedicel 0.5-1.25 mm long. Ochreolae 1.0-2.0 mm long, ovate, dentate-entire, gland-dotted. Tepals 5, pink, 1.0-3.0 x 0.75-1.5 mm, obovate, obtuse, red gland-dotted. Stamens 6, filaments long, unequal. Ovary 0.5-1.5 x 0.5-0.75 mm, trigonous, elliptic with 3 or sometimes 2 styles united in the upper half, then free; stigma capitate. Nuts 2.5-3.5 (-4) x 1.5-2.0 mm, mostly trigonous, sometimes biconvex within the same raceme, dark brownish, pubescent.

N. Africa, Europe, Himalaya, India, east to China and Japan, Malaysia, N. America.

introduced; St. Pierre and Miquelon; B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Ala., Alaska, Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; introduced also in Asia; nw Africa; Pacific Islands (Hawaii, New Zealand); Australia.

Distribution: Widely distributed in N. W. Africa, Temperate Asia, Pakistan, India, extending to far east up to Japan, N. America.

900-2300 m

Fl. Per.: April-September.

Flowering May-Nov.

Shorelines of lake and ponds, banks of streams and rivers, fens, forested wetlands, pastures, occasionally waste ground; 0-1500m.

A fairly common and widespread species, grows in ditches, on banks and moist shady places from plains to 2000 m. Easily recognized by its red glandular punctate leaves and red glandular perianth and interrupted racemes. Nuts are variable. Trigonous and biconvex nuts are sometimes found within the same raceme.

Polygonum hydropiper Linnaeus, Sp. Pl. 1: 361. 1753; P. hydropiper var. projectum Stanford

Polygonum hydropiper L., Sp. Pl. 361. 1753; Hook. f., Fl. Brit. Ind. 5: 39. 1886; excl. var. eglandulosa Hook.f.; Kitamura, Pl. W. Pak. & Afgh. 44. 1964; D.A.Webb & Chater in Tutin et al., Fl. Europ. 1:79. 1964; Coode & Cullen in P.H.Davis, Fl. Turk. 2: 274. 1966; Schiman-Czeika & Rech. f. in Rech. f., Fl. Iran. 56: 60. 1968; R.R.Stewart, Ann. Cat. Vasc. Pl. W. Pak. & Kashm. 1: 206. 1977; P. korrense Nakai in Bot. Mag. Tokyo 33: 6. 1919; Nakai in Mor. Enum. Pl. Cor. 132. 1922.