Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Polygonum hydropiper
(marsh pepper)



Polygonum hydropiper (marsh pepper)


  • Last modified
  • 02 August 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Preferred Scientific Name
  • Polygonum hydropiper
  • Preferred Common Name
  • marsh pepper
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae

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Young P. hydropiper plants.
TitleYoung plants
CaptionYoung P. hydropiper plants.
Copyright©Chris Parker/Bristol, UK
Young P. hydropiper plants.
Young plantsYoung P. hydropiper plants.©Chris Parker/Bristol, UK


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Preferred Scientific Name

  • Polygonum hydropiper L. (1753)

Preferred Common Name

  • marsh pepper

Other Scientific Names

  • Persciaria hydropiper (L.) Spach
  • Persicaria hydropiper (L.) Opiz

International Common Names

  • English: marshpepper smartweed; redshank; smartpepper; water pepper; water willow
  • Spanish: Persicaria picante; pimenta-de-agua; pimienta de agua; resquemona
  • French: curage; persicaire acre; poivre d'eau; renouee poivre d'eau
  • Chinese: pinyin; shui-liao
  • Portuguese: persicaria mordaz

Local Common Names

  • Algeria: felfel el ma
  • Bangladesh: bishkatali; pakurmal; panimarich
  • Denmark: bidende pileurt
  • Egypt: qeddab; qordaab; qordeyb
  • Finland: katkeratatar
  • Germany: Knoeterich; Pfefferknoeterich; Pfeffer-Knoterich; Wasserpfeffer; Wasserpfeffer-Knoterich
  • Hungary: borsus keserufu
  • India: bishkatal; packurmul
  • Italy: erba pepe; idropepe; pepe b'acqua; poligono pepe-acquatica
  • Japan: yanagitabe; yanagitade
  • Mexico: chillo
  • Netherlands: waterpeper
  • Norway: vasspepar
  • Paraguay: caatai
  • Poland: rdest ostrogorzki
  • Saudi Arabia: fulful el ma; zangabil et kilab
  • Sweden: bitterblad; bitterpillort
  • Yugoslavia (Serbia and Montenegro): dvornik papreni; dvornik tankoklasni

EPPO code

  • POLHY (Polygonum hydropiper)

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Polygonales
  •                         Family: Polygonaceae
  •                             Genus: Polygonum
  •                                 Species: Polygonum hydropiper

Notes on Taxonomy and Nomenclature

Top of page The genera Polygonum and Persicaria are commonly combined as Polygonum, and together contain about 300 species. The generic name means 'many angles or joints', either with reference to the often angled lower stem with its swollen nodes or the frequently triangular fruits. Hydropiper means water-pepper, a reference to its aquatic or semi-aquatic habitat and the sharply peppery taste of all parts of the shoots.

The 2n chromosome number of P. hydropiper is 20 (Holm et al., 1997).


Top of page P. hydropiper is an annual herb which normally reproduces only by seed.

The plant has a taproot that may grow to over 1 m deep, although it is usually much shorter.

The main stem is often procumbent at the base, and may root from the lower nodes. It commonly branches at the lower nodes to produce several erect or ascending stems, 15-80 cm tall. The stems are smooth and hairless to very finely hairy, swollen at the nodes, green to red or light brown, and are surrounded above each node by cylindrical membranous ochreas which are 0.5-1 cm long with bristly tips. The stems normally branch towards their tips.

The single leaves have short stalks which taper into slender finely hairy glandular blades 4-10 cm long. Emerging leaves are rolled downwards at the edges. Modified stipules known as ochreae sheath the stem above the junction of stem and petiole. In P. hydropiper these are about 5 mm long with a fringe of hairs about the same length.

Inflorescences occur at the tips of all branches and in the upper leaf axils. Each is a slender (often nodding) spike of well-spaced green to pink flowers, 2-4 mm long, the outer parts of which are covered with dark glands.

Fertilized flowers develop into hard, usually triangular (also flattened), 2-3.5 mm long, dark dull brown to black fruits which remain enclosed in the dried flowers.

The seedlings exhibit epigeal germination. The hypocotyl is slender, green and about 1 cm long, and the cotyledons oval, green, and about the same length. The juvenile leaves are rolled downwards at the margins as they emerge, and are slender, green, and 1-2 cm long.


Top of page P. hydropiper is most commonly reported from the USA, China, India, Taiwan and Japan. It is more common in the Northern Hemisphere, but also occurs in Argentina, Australia, Brazil, Chile and New Zealand. Although very widespread throughout temperate and tropical regions, P. hydropiper appears to be absent from Africa. However, this may be a false assumption based on lack of referenced recordings from that continent.

It is present all across Europe, with the exception of the Balearic and Faeroe Islands, Iceland and Spitzbergen (Chater and Webb, 1993).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes


BangladeshPresentHolm et al., 1997
BhutanPresentParker, 1992
ChinaWidespreadWang, 1990; Holm et al., 1997
-GuangdongPresentXiang, 2002
-LiaoningPresentZheng et al., 2007
-ShanghaiPresentWang and Chu, 2007
-ZhejiangPresentGuo et al., 2005
IndiaPresentHafliger and Wolf, 1988; Holm et al., 1997
-AssamPresentSaikia and Sarma, 1996
-MeghalayaPresentNeogi and Rao, 1982
IndonesiaPresentHafliger and Wolf, 1988; Holm et al., 1997
IranPresentZehzad and Azimzadeh, 1997
JapanWidespreadNumata and Yoshikawa, 1975; Hafliger and Wolf, 1988; Holm et al., 1997
JordanPresentHolm et al., 1997
Korea, DPRPresentHafliger and Wolf, 1988; Holm et al., 1997
Korea, Republic ofPresentPark et al., 2005
MalaysiaPresentHolm et al., 1997
NepalPresentHolm et al., 1997
PhilippinesPresentHafliger and Wolf, 1988
TaiwanPresentHolm et al., 1997

North America

CanadaPresentHafliger and Wolf, 1988
MexicoPresentHafliger and Wolf, 1988; Holm et al., 1997
USAWidespreadLorenzi and Jeffery, 1987; Hafliger and Wolf, 1988; Holm et al., 1997
-AlabamaPresentUSDA, 1970
-AlaskaPresentUSDA, 1970
-ArizonaPresentUSDA, 1970
-ArkansasPresentUSDA, 1970
-CaliforniaPresentUSDA, 1970
-ColoradoPresentUSDA, 1970
-ConnecticutPresentUSDA, 1970
-DelawarePresentUSDA, 1970
-HawaiiPresentUSDA, 1970
-IdahoPresentUSDA, 1970
-IllinoisPresentUSDA, 1970
-IndianaPresentUSDA, 1970
-IowaPresentUSDA, 1970
-KansasPresentUSDA, 1970
-KentuckyPresentUSDA, 1970
-LouisianaPresentUSDA, 1970
-MainePresentUSDA, 1970
-MarylandPresentUSDA, 1970
-MassachusettsPresentUSDA, 1970
-MichiganPresentUSDA, 1970
-MinnesotaPresentUSDA, 1970
-MississippiPresentUSDA, 1970
-MissouriPresentUSDA, 1970
-MontanaPresentUSDA, 1970
-NebraskaPresentUSDA, 1970
-NevadaPresentUSDA, 1970
-New HampshirePresentUSDA, 1970
-New JerseyPresentUSDA, 1970
-New MexicoPresentUSDA, 1970
-New YorkPresentUSDA, 1970
-North CarolinaPresentUSDA, 1970
-North DakotaPresentUSDA, 1970
-OhioPresentUSDA, 1970
-OklahomaPresentUSDA, 1970
-OregonPresentUSDA, 1970
-PennsylvaniaPresentUSDA, 1970
-Rhode IslandPresentUSDA, 1970
-South CarolinaPresentUSDA, 1970
-South DakotaPresentUSDA, 1970
-TennesseePresentUSDA, 1970
-TexasPresentUSDA, 1970
-UtahPresentUSDA, 1970
-VermontPresentUSDA, 1970
-VirginiaPresentUSDA, 1970
-WashingtonPresentUSDA, 1970
-West VirginiaPresentUSDA, 1970
-WisconsinPresentUSDA, 1970
-WyomingPresentUSDA, 1970

Central America and Caribbean

El SalvadorPresent
HondurasPresentHolm et al., 1997

South America

ArgentinaPresentHolm et al., 1997
BrazilPresentHafliger and Wolf, 1988; Holm et al., 1997
ChilePresentHolm et al., 1997
ColombiaPresentHafliger and Wolf, 1988


BelgiumPresentHolm et al., 1997
CroatiaPresentVukelic and Baricevic, 2000
FinlandPresentHolm et al., 1997
FrancePresentHafliger and Wolf, 1988
GermanyPresentHolm et al., 1997
IrelandPresentHolm et al., 1997
ItalyPresentHafliger and Wolf, 1988; Holm et al., 1997
NetherlandsPresentHolm et al., 1997
PolandPresentHolm et al., 1997
PortugalPresentHolm et al., 1997
RomaniaPresentHolm et al., 1997
Russian FederationPresentHafliger and Wolf, 1988; Holm et al., 1997
SwitzerlandPresentHolm et al., 1997
UKPresentHafliger and Wolf, 1988
Yugoslavia (former)PresentHolm et al., 1997


AustraliaPresentHafliger and Wolf, 1988; Holm et al., 1997
-New South WalesPresentHnatiuk, 1990
-QueenslandPresentHnatiuk, 1990
-TasmaniaPresentHnatiuk, 1990
-VictoriaPresentHnatiuk, 1990
-Western AustraliaPresentHnatiuk, 1990
New CaledoniaPresentMacKee, 1985
New ZealandPresentHafliger and Wolf, 1988; Holm et al., 1997


Top of page P. hydropiper is a warm or wet season annual herb, occurring wherever there is moist soil or standing water. It grows on poorly drained agricultural land, along creek, river, canal and stream banks, in marshes and swamps, in poorly drained hollows, and in seasonally flooded areas.

The species grows well in most soils including silts, peats, loams and sands, and whilst tolerating a wide range of pH frequently grows better in more acid situations (Holm et al., 1997).

Hosts/Species Affected

Top of page P. hydropiper is also a common weed in other (especially irrigated) crops, vegetables, pastures and gardens, as well as wasteland and roadsides. It is especially common and pervasive where the soil is damp or waterlogged.

Biology and Ecology

Top of page P. hydropiper is an annual herb which reproduces mainly by seed, although broken stems may root at the nodes and grow into new plants.

In temperate climatic zones, it germinates as the soil and water warm up in spring, flowers during the summer, and produces fruits from mid summer until killed by the frost in autumn or winter (Holm et al., 1997). Timson (1966) has shown it to be self-pollinating and phenotypically variable. Individual plants produce 385-3300 seeds, each weighing 1-2.5 mg (Datta and Banerjee 1973).

Dormancy characteristics and germination requirements vary between seed lots. In the USA, Justice (1941) showed that stratification of fresh seeds at 2-4°C for 18 weeks improved the otherwise low germination to over 90%, whilst in Japan, Nakamura (1970) demonstrated that removal of the seed coat, alternating temperatures and light all stimulated increased germination. Germination was stimulated by far-red and red light, but not by gibberellic acid. Seeds from tropically adapted plants may show different germination requirements.

The fruits float in water, and are distributed by irrigation, flood and drainage waters and by human activities including contamination of crop and pasture seed, in soil and plant trash and by boats and fishing gear equipment. They are also likely to be eaten by water birds and may be carried either externally or internally by water buffalo, pigs, aquatic birds and other wildlife to new water bodies (Holm et al., 1997).

Seed dormancy may be prolonged, but probably varies significantly between collections. Seeds have survived from 4 to 36 months underwater (Shull, 1914; Comes et al., 1978), 6 months in sand (3% germination) and loam (66% germination) (Timson, 1966), and up to 50 years in field soil (Darlington, 1951).

As with most other plants, the degree of stem branching increases as plant density declines, and stomata occur primarily on the undersides of the leaves (Timson, 1966). Some genotypes have purplish seedlings (used to garnish white fish in Japan), and the degree of anthocyanin pigmentation varies with light intensity, temperature (greatest at 5-10°C) and plant age, and increases as nitrogen levels fall (Miura and Iwata, 1979, 1981).

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Gastrocyanea atrocyanea Herbivore Leaves

Notes on Natural Enemies

Top of page No significant natural enemies have been recorded for P. hydropiper.


Top of page P. hydropiper is a competitive weed in a great many crops, especially in irrigated crops, in rice, and in other crops grown on poorly drained soils (Holm et al., 1997). It grows well in poorly drained pastures, and, being very unpalatable, reduces the value of the grazing. The species is allelopathic to rice (Holm et al., 1997).


Top of page The purplish seedlings of P. hydropiper are used as a relish with fish dishes in Japan, and the dried leaves as a condiment in South-East Asia (Holm et al., 1997). Macerated plants are used as a fish poison in India. It is also used for the treatment of haemorrhoids and as a diuretic. (Holm et al., 1997).

Extracts from P. hydropiper have significant biocidal properties, for example, against nematodes (Sukul, 1970).

Similarities to Other Species/Conditions

Top of page There are very many species within the Polygonum/Persicaria complex, many of which occur in wet soils and are generally similar in appearance. to P. hydropiper. The species require a good local flora for accurate separation and identification.

One of the closest in appearance in Europe, is P. mite Schrank (= Persicaria laxiflora (Weihe) Opiz) which differs in lacking the biting taste, and in having glossy achenes. Others mostly have denser inflorescences including P. persicaria (qv), P. lapathifolium and P. nepalense (qv). Hafliger and Wolf (1988) and Parker (1992) illustrate these and a number of other weedy species and show distinguishing features, including, for example, the ochreae.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control

Plants should be hand-pulled or mechanically controlled before flowering. They must be either uprooted or buried, as simply breaking the stem will result in resprouting at the soil surface.

Chemical Control

Little work has been conducted on the chemical control of P. hydropiper, although significant literature is available for Polygonum species of dryland sites.

In Korea, Park et al. (1995) showed that cyhalofop + bentazone and cyhalofop + pendimethalin gave good control of a dryland rice weed mixture which included this species, whilst Seong et al. (1991) obtained similarly good control with sequential applications of butachlor or benthiocarb [thiobencarb] followed by bentazone + quinclorac.

In New Zealand pastures, Sanders et al. (1994) obtained good kill of P. hydropiper with thifensulfuron.

Biological Control

No biological control has been attempted against P. hydropiper (Julien 1992), although the beetle Gastrophysa atrocyanea has been shown to damage this species in trials against Rumex japonicus (Xiaoshui, 1991).


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Chater AO; Webb DA, 1993. 2. Polygonum L. In: Tutin TG, Burges NA, Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA, eds. Flora Europaea Volume 1 Psilotaceae to Platanaceae 2nd edition. Cambridge, UK: Cambridge University Press, 91-97.

Comes RD; Bruns VF; Kelley AD, 1978. Longevity of certain weed and crop seeds in fresh water. Weed Science, 26(4):336-344

Datta S; Bannerjee A, 1973. Weight and number of weed seeds. Proceedings of the 4th Asian-Pacific Weed Science Society Conference, 1:87-91.

Guo ShuiLiang; Huang Hua; Chao Ke; Zhu YiJun, 2005. On caloric values and ash contents of ten weed species in Jinhua suburb and its adaptive significances. Bulletin of Botanical Research, 25(4):460-464.

Hafliger TJ; Wolf M, 1988. Dicot Weeds. 1. Basle, Switzerland: CIBA-GEIGY Ltd.

Hnatiuk RJ, 1990. Census of Australian Vascular Plants. Australian Flora and Fauna Series Number 11. Canberra, Australia: Australian Government Publishing Service.

Holm LG; Doll J; Holm E; Pancho JV; Herberger JP, 1997. World Weeds: Natural Histories and Distribution. New York, USA: John Wiley & Sons Inc.

Holm LG; Pancho JV; Herberger JP; Plucknett DL, 1991. A Geographic Atlas of World Weeds. Malabar, Florida, USA: Krieger Publishing Company.

Julien MH ed., 1992. Biological Control of Weeds. A World Catalogue of Agents and their Target Weeds, 3rd edition. Wallingford, UK: CAB International.

Justice O, 1941. A Study Of Dormancy in seeds of Polygonum. Memoirs of Cornell University Agricultural Experimental Station, 253.

Lorenzi HJ; Jeffery LS(Editors), 1987. Weeds of the United States and their control. New York, USA; Van Nostrand Reinhold Co. Ltd., 355 pp.

MacKee HS, 1985. Les Plantes Introduites et Cultivees en Nouvelle-Caledonie. Volume hors series, Flore de la Nouvelle-Caledonie et Dependances. Paris, France: Museum Nationelle d'Histoire Naturelle.

Miura H; Iwata M, 1979. Effect of nitrogen, phosphorous and potassium on anthocyanin content of the seedlings of Polygonum hydropiper L. Journal of the Japanese Horticultural Society, 48: 91-98.

Nakamura S, 1970. Germination of Polygonum hydropiper L. seeds. Bulletin of the Faculty of Agriculture, Yamaguti University, 21:78-83.

Neogi B; Rao RR, 1982. Weed flora of various hill agro-ecosystems in Meghalaya, north-eastern India. Australian Weeds, 2(1):9-15

Numata M; Yoshizawa N, 1975. Weed flora of Japan. Japan Association for the Advancement of Phyto-Regulators. Tokyo, Japan: Zenkoku Noson Kyoiku Kyokai.

Park SungJun; Cho NamKi; Kang YoungKil; Song ChangKhil; Cho YoungIl, 2005. Effects of split nitrogen application on the density of creeping bentgrass. Journal of the Korean Society of Grassland Science, 25(2):119-124.

Park TS; Park JE; Ryu GH; Lee IY; Lee HK; Lee JO, 1995. Effective weed control in direct-seeded rice under dry fields. Korean Journal of Weed Science, 15(2):99-104

Parker C, 1992. Weeds of Bhutan. Weeds of Bhutan., vi + 236 pp.

Roy B; Popay I; Champion P; James T; Rahman A, 1998. An illustrated guide to common weeds of New Zealand. An illustrated guide to common weeds of New Zealand., vi + 282 pp.

Saikia LR; Sarma SK, 1996. Phytosociological investigation of the rice field weeds of Duliajan (Assam). Indian Journal of Forestry, 19(1):40-44; 8 ref.

Sanders P; Rahman A, 1994. Evaluation of thifensulfuron for control of some pasture weeds. Proceedings of the forty seventh New Zealand plant protection conference, Waitangi, New Zealand, 9-11 August 1994 [edited by Popay, A. J.] Rotorua, New Zealand; New Zealand Plant Protection Society, 62-67

Seong KY; Lee CW; Oh YJ; Park RK; Kwon YW, 1991. The systematic application of herbicides for dry-drill seeding of rice. Research Reports of the Rural Development Administration, Rice, 33(2):41-45

Shull G, 1914. The longevity of submerged seeds. Plant World, 17:329-337.

Sukul NC, 1970. Nematocidal properties of two species of polygonaceous plants. Proceedings of the Zoological Society of Calcutta., 23(2):139-146

Timson J, 1996. Polygonum hydropiper L. Journal of Ecology, 54:815-821.

USDA, 1970. Selected Weeds of the United States. Agriculture Handbook No. 366. Washington DC, USA: United States Department of Agriculture, 324-325.

Vukelic J; Baricevic D, 2000. Development of vegetation in localities of pedunculate oak dieback in Croatia. In: Glasnik za ?umske Pokuse, 37 [ed. by Vukelic, J.\Anic, I.]. 277-293.

Wang LiCheng; Chu JianJun, 2007. Species association between Solidago canadensis and other plants. Journal of Shanghai Jiaotong University - Agricultural Science, 25(2):115-119.

Wang ZR, 1990. Farmland Weeds in China. Beijing, China: Agricultural Publishing House.

Xiang MM, 2002. Pathogenic fungi from the weeds in fields in Guangdong province. Journal of South China Agricultural University, 23(1): 41-44.

Xiaoshui W, 1991. Gastrophysa atrocyanea (Col: Chrysomelidae), an agent for biological control of the dock, Rumex japonicus (Polygonaceae) in China. Tropical Pest Management, 37(4):383-386

Zehzad B; Azimzadeh R, 1997. Recognition and biology of aquatic and semi-aquatic weeds in irrigation systems of paddy fields in Guilan province. Applied Entomology and Phytopathology, 64(1/2):11; Pe30-Pe39.

Zheng DongMei; Wang QiChao; Zhang ZhongSheng; Zheng Na; Zhang XiuWu, 2007. Transfer of mercury in soil-plant system of Wuli River, Huludao City. China Environmental Science, 27(5):676-680.

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