Persicaria hydropiperoides(Michx.) Small

swamp smartweed

WFO wfo-0000488422 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Persicaria hydropiperoides, photographed by Kahio Tiberio Mazon
fig. a Kahio Tiberio Mazon, CC0 1.0 / 2022-02-26 / obs. 180950846
Persicaria hydropiperoides, photographed by Ruth Gutiérrez Oliveros
fig. b Ruth Gutiérrez Oliveros, CC0 1.0 / obs. 147187213
Persicaria hydropiperoides, photographed by Ryan Sorrells
fig. c Ryan Sorrells, CC BY 4.0 / obs. 140198776
Persicaria hydropiperoides, photographed by Eduardo Luis Beltrocco
fig. d Eduardo Luis Beltrocco, CC BY 4.0 / obs. 126313618
Persicaria hydropiperoides, photographed by Liliana Ramírez-Freire
fig. e Liliana Ramírez-Freire, CC BY 4.0 / obs. 125629985
Persicaria hydropiperoides, photographed by Ruth Gutiérrez Oliveros
fig. f Ruth Gutiérrez Oliveros, CC0 1.0 / obs. 111563279
Persicaria hydropiperoides, photographed by Ruth Gutiérrez Oliveros
fig. g Ruth Gutiérrez Oliveros, CC0 1.0 / obs. 102840705
Persicaria hydropiperoides, photographed by Dan Johnson
fig. h Dan Johnson, CC BY 4.0 / obs. 101874361

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 89 botanical countries

Regions where Persicaria hydropiperoides is native: Azores, Alabama, Alaska, Arizona, Arkansas, British Columbia, California, Connecticut, Delaware, District of Columbia, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Northwest, Mexico Southeast, Mexico Southwest, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Brunswick, New Hampshire, New Jersey, New York, North Carolina, North Dakota, Nova Scotia, Ohio, Oklahoma, Ontario, Oregon, Pennsylvania, Québec, Rhode I., South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, Washington, West Virginia, Wisconsin, Argentina Northeast, Argentina Northwest, Argentina South, Bahamas, Belize, Bolivia, Brazil North, Brazil Northeast, Brazil South, Brazil Southeast, Brazil West-Central, Cayman Is., Chile Central, Chile North, Chile South, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Galápagos, Guatemala, Honduras, Juan Fernández Is., Nicaragua, Panamá, Paraguay, Peru, Puerto Rico, Suriname, Uruguay, Venezuela AlabamaAlaskaArizonaArkansasBritish ColumbiaCaliforniaConnecticutFloridaGeorgiaIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMexico CentralMexico GulfMexico NortheastMexico NorthwestMexico SoutheastMexico SouthwestMichiganMinnesotaMississippiMissouriNebraskaNew BrunswickNew HampshireNew JerseyNew YorkNorth CarolinaNorth DakotaNova ScotiaOhioOklahomaOntarioOregonPennsylvaniaQuébecSouth CarolinaSouth DakotaTennesseeTexasVermontVirginiaWashingtonWest VirginiaWisconsinArgentina NortheastArgentina NorthwestArgentina SouthBelizeBoliviaBrazil NorthBrazil NortheastBrazil SouthBrazil SoutheastBrazil West-CentralChile CentralChile NorthChile SouthColombiaCosta RicaCubaDominican RepublicEcuadorEl SalvadorGuatemalaHondurasNicaraguaPanamáParaguayPeruPuerto RicoSurinameUruguayVenezuela AzoresDelawareDistrict of ColumbiaRhode I.BahamasCayman Is.Galápagos
Native distribution of Persicaria hydropiperoides, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows. Regions too small to draw at this scale are marked with a dot.
RegionTDWG codeContinent
Alabama ALA NORTHERN AMERICA
Alaska ASK
Arizona ARI
Arkansas ARK
British Columbia BRC
California CAL
Connecticut CNT
Delaware DEL
District of Columbia WDC
Florida FLA
Georgia GEO
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Kansas KAN
Kentucky KTY
Louisiana LOU
Maine MAI
Maryland MRY
Massachusetts MAS
Mexico Central MXC
Mexico Gulf MXG
Mexico Northeast MXE
Mexico Northwest MXN
Mexico Southeast MXT
Mexico Southwest MXS
Michigan MIC
Minnesota MIN
Mississippi MSI
Missouri MSO
Nebraska NEB
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New York NWY
North Carolina NCA
North Dakota NDA
Nova Scotia NSC
Ohio OHI
Oklahoma OKL
Ontario ONT
Oregon ORE
Pennsylvania PEN
Québec QUE
Rhode I. RHO
South Carolina SCA
South Dakota SDA
Tennessee TEN
Texas TEX
Vermont VER
Virginia VRG
Washington WAS
West Virginia WVA
Wisconsin WIS
Argentina Northeast AGE SOUTHERN AMERICA
Argentina Northwest AGW
Argentina South AGS
Bahamas BAH
Belize BLZ
Bolivia BOL
Brazil North BZN
Brazil Northeast BZE
Brazil South BZS
Brazil Southeast BZL
Brazil West-Central BZC
Cayman Is. CAY
Chile Central CLC
Chile North CLN
Chile South CLS
Colombia CLM
Costa Rica COS
Cuba CUB
Dominican Republic DOM
Ecuador ECU
El Salvador ELS
Galápagos GAL
Guatemala GUA
Honduras HON
Juan Fernández Is. JNF
Nicaragua NIC
Panamá PAN
Paraguay PAR
Peru PER
Puerto Rico PUE
Suriname SUR
Uruguay URU
Venezuela VEN
Azores AZO AFRICA

Not drawn on the map: Juan Fernández Is.. We hold no public-domain boundary for this region, so it is listed rather than guessed at.

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Flowering 330 in flower of 372 examined

Peak flowering in Nov. Each bar is the share of Persicaria hydropiperoides observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 330 of 372 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 2 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Also published as 13 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Persicaria hydropiperoides var. hydropiperoides
  • Persicaria hydropiperoides var. setaceum (Small) Gleason
  • Polygonum barbatum Wall.
  • Polygonum hydropiperoides Michx.
  • Polygonum hydropiperoides f. leucochranthum A.H.Moore
  • Polygonum hydropiperoides f. strigosum (Small) Stanford
  • Polygonum hydropiperoides var. asperifolium Stanford
  • Polygonum hydropiperoides var. bushianum Stanford
  • Polygonum hydropiperoides var. digitatum Fernald
  • Polygonum hydropiperoides var. macerum Stanford
  • Polygonum hydropiperoides var. macounii Small
  • Polygonum hydropiperoides var. sanibelense Stanford
  • Polygonum hydropiperoides var. strigosum Small

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. USDA PLANTS Database. common name, checklist symbol POHY2. public domain. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.