Persicaria hydropiperoides

(Michaux) Small

Fl. S.E. U.S., 378. 1903.

Common names: Swamp smartweed renouée faux-poivre-d’eau
Basionym: Polygonum hydropiperoides Michaux Fl. Bor.-Amer. 1: 239. 1803
Synonyms: Persicaria opelousana (Riddell ex Small) Small Persicaria paludicola Small Polygonum hydropiperoides var. adenocalyx (Stanford) Gleason Polygonum hydropiperoides var. asperifolium Stanford Polygonum hydropiperoides var. breviciliatum Fernald Polygonum hydropiperoides var. bushianum Stanford Polygonum hydropiperoides var. digitatum Fernald Polygonum hydropiperoides var. opelousanum (Riddell ex Small) W. Stone Polygonum hydropiperoides var. psilostachyum H. St. John Polygonum opelousanum Polygonum opelousanum var. adenocalyx Stanford
Treatment appears in FNA Volume 5. Treatment on page 585. Mentioned on page 574, 582, 583, 586, 587, 588.

Plants perennial, 1.5–10 dm; roots also often arising from proximal nodes; rhizomes often present. Stems decumbent to ascending, usually branched, without noticeable ribs, glabrous or obscurely strigose distally. Leaves: ocrea brown, cylindric, 5–23 mm, chartaceous, base inflated, margins truncate, ciliate with bristles (2–)4–10 mm, surface glabrous or strigose, not glandular-punctate; petiole 0.2–2 cm, glabrous or strigose; blade without dark triangular or lunate blotch adaxially, broadly lanceolate to linear-lanceolate, 5–25 × 0.4–3.7 cm, base tapered or acute, margins antrorsely appressed-pubescent, apex acuminate, faces glabrous or appressed-pubescent along midveins and sometimes on faces, usually punctate abaxially. Inflorescences terminal, sometimes also axillary, erect, uninterrupted or interrupted proximally, 30–80 × 2–5 mm; peduncle 10–30 mm, glabrous or strigose; ocreolae overlapping distally, often not overlapping proximally, margins ciliate with bristles to 2(–3) mm. Pedicels ascending, 1–1.5 mm. Flowers bisexual or unisexual and staminate, 2–6 per ocreate fascicle, homostylous; perianth roseate proximally, roseate, white, or greenish white distally, not glandular-punctate or sometimes glandular-punctate with punctae on tubes and inner tepals, scarcely accrescent; tepals 5, connate ca. 1/3–1/2 their length, obovate, 2.5–4 mm in bisexual flowers, 1.5–2.5 mm in staminate flowers, veins prominent or not, not anchor-shaped, margins entire, apex obtuse to rounded; stamens 8, included or exserted in staminate flowers; anthers pink or red, elliptic to ovate; styles 3, connate near middle. Achenes included or apex exserted, brown to brownish black or black, 3-gonous, 1.5–3 × 1–2.3 mm, shiny, smooth.

Phenology: Flowering Jun–Nov.
Habitat: Wet banks and clearings, shallow water, marshes, moist prairies, ditches
Elevation: 0-1500 m


V5 1195-distribution-map.gif

B.C., N.B., N.S., Ont., Que., Ala., Alaska, Ariz., Ark., Calif., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., Wash., W.Va., Wis., Mexico, Central America, South America.


The extreme variability in Persicaria hydropiperoides is reflected in its extensive synonymy. Among the segregates most often recognized in floras and checklists is P. opelousana, which C. B. McDonald (1980) showed to be broadly sympatric and highly interfertile with P. hydropiperoides. Consistent with this conclusion, R. S. Mitchell (1971) found that P. hydropiperoides and P. opelousana are unique among native North American smartweeds in consistently possessing multicellular plate-glands on the abaxial surface of their leaves. Such glands also are found on P. maculosa, an introduced European species.

Herbarium specimens of Persicaria hydropiperoides sometimes are misidentified as P. maculosa, especially when the roots are missing. The former species may be distinguished reliably by its achenes all trigonous (trigonous and biconvex achenes are mixed in the inflorescences of P. maculosa) and bristles on the margins of the ocreae that average longer. M. L. Fernald (1922c) reported hybrids with P. robustior from Nova Scotia.

Selected References


Lower Taxa

Harold R. Hinds† +  and Craig C. Freeman +
(Michaux) Small +
Polygonum hydropiperoides +
Swamp smartweed +  and renouée faux-poivre-d’eau +
B.C. +, N.B. +, N.S. +, Ont. +, Que. +, Ala. +, Alaska +, Ariz. +, Ark. +, Calif. +, Conn. +, Del. +, D.C. +, Fla. +, Ga. +, Idaho +, Ill. +, Ind. +, Iowa +, Kans. +, Ky. +, La. +, Maine +, Md. +, Mass. +, Mich. +, Minn. +, Miss. +, Mo. +, Nebr. +, N.H. +, N.J. +, N.Y. +, N.C. +, N.Dak. +, Ohio +, Okla. +, Oreg. +, Pa. +, R.I. +, S.C. +, S.Dak. +, Tenn. +, Tex. +, Vt. +, Va. +, Wash. +, W.Va. +, Wis. +, Mexico +, Central America +  and South America. +
0-1500 m +
Wet banks and clearings, shallow water, marshes, moist prairies, ditches +
Flowering Jun–Nov. +
Fl. S.E. U.S., +
Weedy +  and Illustrated +
Persicaria opelousana +, Persicaria paludicola +, Polygonum hydropiperoides var. adenocalyx +, Polygonum hydropiperoides var. asperifolium +, Polygonum hydropiperoides var. breviciliatum +, Polygonum hydropiperoides var. bushianum +, Polygonum hydropiperoides var. digitatum +, Polygonum hydropiperoides var. opelousanum +, Polygonum hydropiperoides var. psilostachyum +, Polygonum opelousanum +  and Polygonum opelousanum var. adenocalyx +
Persicaria hydropiperoides +
Persicaria sect. Persicaria +
species +