Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Monochoria vaginalis
(pickerel weed)



Monochoria vaginalis (pickerel weed)


  • Last modified
  • 16 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Monochoria vaginalis
  • Preferred Common Name
  • pickerel weed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae

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M. vaginalis seedling.
CaptionM. vaginalis seedling.
Copyright©Chris Parker/Bristol, UK
M. vaginalis seedling.
SeedlingM. vaginalis seedling.©Chris Parker/Bristol, UK
Young flowering plant of M. vaginalis in Bhutan.
TitleYoung flowering plant
CaptionYoung flowering plant of M. vaginalis in Bhutan.
Copyright©Chris Parker/Bristol, UK
Young flowering plant of M. vaginalis in Bhutan.
Young flowering plantYoung flowering plant of M. vaginalis in Bhutan.©Chris Parker/Bristol, UK
Flowering plants in rice.
TitleFlowering plants
CaptionFlowering plants in rice.
CopyrightJohn Terry
Flowering plants in rice.
Flowering plantsFlowering plants in rice.John Terry
Dense infestation of M. vaginalis in rice, Bhutan.
TitleInfestation in rice crop
CaptionDense infestation of M. vaginalis in rice, Bhutan.
Copyright©Chris Parker/Bristol, UK
Dense infestation of M. vaginalis in rice, Bhutan.
Infestation in rice cropDense infestation of M. vaginalis in rice, Bhutan.©Chris Parker/Bristol, UK


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Preferred Scientific Name

  • Monochoria vaginalis (Burm.f) C.Presl. (1827)

Preferred Common Name

  • pickerel weed

Other Scientific Names

  • Gomphima vaginalis Rafin. (1836)
  • Monochoria junghuhniana Hassk. (1852)
  • Monochoria linearis Miq. (1859)
  • Monochoria ovata Kunth (1843)
  • Monochoria pauciflora Kunth (1843)
  • Monochoria plantaginea Kunth (1843)
  • Pontederia linearis Hassk. (1842)
  • Pontederia pauciflora Bl. (1827)
  • Pontederia plantaginea Roxb. (1832)
  • Pontederia vaginalis Burm. F. (1768)

International Common Names

  • Spanish: monocoria

Local Common Names

  • Bangladesh: Panee kachu
  • Cambodia: Chrach
  • Indonesia: Etjeng padi
  • Indonesia/Java: Bengok
  • Japan: Konagi
  • Korea, DPR: Mooldalgebi
  • Malaysia/Peninsular Malaysia: Chacha layar; Keladi agas; kelayar
  • Nepal: Piralay
  • Philippines: Biga-bigaan; Gabi-gabi
  • Taiwan: Ya-she-tsau
  • Thailand: Ka-kiad; Phak-khait
  • Vietnam: Rac mác lá thon

EPPO code

  • MOOVA (Monochoria vaginalis)

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Monocotyledonae
  •                     Order: Pontederiales
  •                         Family: Pontederiaceae
  •                             Genus: Monochoria
  •                                 Species: Monochoria vaginalis

Notes on Taxonomy and Nomenclature

Top of page M. vaginalis is very variable and for this reason may be misidentified. Backer and Bakhuizen van den Brink Jr (1968) note that "Specimens with few-flowered inflorescences and small, often narrow, proportionally long leaves have wrongly been described as varieties or even separate species. They are either young or weak, or were collected in deep water".

Three varieties of M. vaginalis (Burm. F.) C. Presl. (1827) have been recognized (Gopal, 1987): var. minor Miq. (1859); var. plantaginea (Roxb.) Solms. (1883); and var. pauciflora (Bl.) Merr. (1917).

A variety of M. vaginalis was described by Ohwi (1965) as M. vaginalis (Burm. F.) Presl var. plantaginea Roxb. Solms-Laub (= Pontederia plantaginea Roxb. and Monochoria plantaginea Roxb. Kunth.). This has been recorded in Japan, Korea and China (Holm et al., 1977) and is described as having long-petioled basal leaves, shorter petioles on leaves attached to a stem or axis, a (3-7)-flowered inflorescence and purplish-blue flowers.

M. vaginalis is occasionally cited as a native of tropical Africa, as well as Asia (e.g. Holm et al., 1977). However, in the Flora of West Tropical Africa (Hutchinson et al., 1968), earlier references to M. vaginalis var. plantaginea in the region are concluded to be erroneous and instead are re-categorized as M. brevepetiolata.

Patwary et al. (1989) suggest interspecific hybridization between Monochoria vaginalis and Monochoria hastata Solms. in populations grown in Bangladesh. They identified two distinct morphological types of each species and from morphological and cytological observations suggested that M. vaginalis type II (2n = 52) is an allotetraploid derived from M. hastata type I (2n = 28) X M. vaginalis type I (2n = 24). They also suggest that M. hastata type II (2n = 80) is an autoallohexaploid hybrid of M. vaginalis type II X M. hastata type I.


Top of page M. vaginalis is a fleshy, tufted, annual or perennial herb with a glabrous, shiny appearance and a short rhizome. It is an aquatic herb, forming rosettes and spreading by short stolons.

It is 10-50 cm tall and stemless. Older plants often form large clumps, but these are not connected. Leaf size and shape is highly variable. In young plants without lamina, the leaves are 2-12.5 cm long and 0.5-10 cm wide. In somewhat older plants, the leaves are floating, linear or lanceolate and in still older plants, are ovate-oblong to broadly ovate, sharply acuminate with a heart-shaped or rounded base, shiny, deep-green, and with longitudinal veins. The petioles are soft and hollow, usually less than 30 cm in length and growing from buds at the base; leaf sheaths are twisted together at the base and slightly reddish when young.

The inflorescence is spicate, 3-6 cm long, basally opposite the sheath of the floral leaf with a large bract arising from a thickened bundle on the leaf stalk, about two-thirds of the way up the stalk from the base. The flowers are pedicelled, bisexual, choripetalous, in racemes, initially inside the sheath of the apical leaf and recurved after anthesis. Flowers number from 3-25 and open simultaneously or from top to bottom in quick succession, with six violet or lilac petals which are spreading at flowering and later spirally contorted. Pedicels are 4-25 mm long and the perianth 11-15 mm long. The stamens are six in number, one with a lateral, obliquely erect tooth. The ovary has a long style, and the capsule (of about 1 cm in size) splits between the partitions into three valves. Seeds are numerous and longitudinally ribbed. (After Holm et al, 1977; Pancho and Soerjani, 1978; Soerjani et al., 1987.)

The distinguishing characteristics of M. vaginalis are the spike-like inflorescence opposite the floral leaf, and the one stamen with a lateral, oblique, erect tooth.


Top of page The geographical distribution of M. vaginalis shown in the map is incomplete. This species has been recorded in Korea and Japan, through the Pacific Islands (including Hawaii), to the mainland of South-East Asia and across into India (Holm et al., 1977). However, specific references to some locations (for example, the individual Pacific Islands) were not found and therefore are not included in the map.

Similarly, few detailed references were found on its distribution within individual countries, though its occurrence is acknowledged to be widespread. For example, M. vaginalis is said to occur throughout Indonesia (Soerjani et al., 1987); at a wide range of altitudes and probably in all districts of Bhutan (Parker, 1992); throughout India, from Kashmir to Assam (Kaul, 1986) and in East, Central and South China, as well as Hebei, Shaanxi, Gansu, Sichuan, Guizhow and Yunnan provinces (Wang, 1990).

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.


Top of page A native of Asia, M. vaginalis is a plant of subaquatic to aquatic conditions (Ampong-Nyarko and De Datta, 1991) and is locally abundant (Pancho and Soerjani, 1978). It can occur in areas with a pronounced dry season, and is typically found in sunny sites in swamps, marshes, open wet places, along ditches and in all types of inundated rice (Soerjani et al., 1987). In Java it occurs from 0-700 m elevation in freshwater pools, mudflats in rivers, ditches, ricefields, and along canal banks (Backer and Bakhuizen van den Brink Jr, 1968). In Fiji it grows in shallow water, swampy ground, open drains, ricefields, or in very wet soils (Parham, 1958).

With the exception of its recorded incidence in taro in Hawaii, all references to its occurring as a weed concern paddy rice in tropical Asia and the Pacific Islands (Holm et al., 1977).

Habitat List

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Host Plants and Other Plants Affected

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Plant nameFamilyContext
Oryza sativa (rice)PoaceaeMain

Biology and Ecology

Top of page Relatively little is known of the biology of M. vaginalis (Holm et al., 1977).

M. vaginalis may be an annual in flooded ricefields, but can also grow as a perennial in constantly flooded conditions (Holm et al., 1977). The plant roots in mud, with its upper portions growing above the water. Reproduction is mainly from seed, with occasional new growth from tubers (Pancho and Soerjani, 1978). Flowering can occur throughout the year in the Philippines (Merrill, 1912). M. vaginalis is characterized by prolific seed production: Gupta (1968) suggested that submergence of the fruits after pollination was beneficial for seed development.

Noda and Eguchi (1965) found that seedling emergence is greater in early planted ricefields in Japan and, with early planting, seedling emergence was higher in saturated soils than in dry soils. They also found that the patterns of seed germination varied greatly according to moisture levels. In submerged conditions, the majority of seedlings emerged within a short space of time, the peak germination being between 15 and 25 days. In contrast, in saturated or dried soils, germination occurred gradually throughout the season. Miyahara et al. (1989) studied seedling emergence from buried seed over a 15-year period and found that emergence declined from one year to the next more rapidly in well-drained than in poorly drained soils. Kim and Mercado (1987) suggest that M. vaginalis seeds develop a light requirement for germination when buried for 1 month or longer at depths of greater than 1 cm.

M. vaginalis is a rapidly growing, competitive C3 plant (Ampong Nyarko and De Datta, 1991). Its property of discontinuous germination allows it to evade control.

In Taiwan M. vaginalis produced higher fresh-weight yields in paddy fields than any other weed species (Lin, 1968).

Notes on Natural Enemies

Top of page Waterhouse (1994) has summarized records of natural enemies attacking M. vaginalis in South-East Asia. All are polyphagous, but because M. vaginalis is apparently not a weed in Africa or western Asia, it would be worthwhile to investigate its natural enemies in these areas.


Top of page M. vaginalis is a serious weed in ricefields in east and southern Asia. It is a principal weed of rice in Korea, Malaysia (Sarawak) and the Philippines. It is one of the three most serious weeds of rice in Indonesia, Japan and Taiwan and is a common weed of rice in Cambodia, Sri Lanka, China, India and Thailand (Holm et al., 1977). In Bhutan, it is a major weed of flooded rice, often the most abundant and dominant species and regarded as one of the most important by farmers (Parker, 1992).

With the exception of its recorded incidence in taro in Hawaii, all references to its occurring as a weed concern flooded rice in tropical Asia and the Pacific Islands (Holm et al., 1977). It occurs in all types of rice (except dryland rice) including transplanted, both wet and dry direct-seeded and in deepwater and tidal swamp rice (IRRI, 1989).

M. vaginalis is a rapidly growing, competitive C3 plant (Ampong Nyarko and De Datta, 1991). Its property of discontinuous germination allows it to evade control.

Sattar and Biswas (1991) recorded yield losses in rice of up to 82% at high densities of M. vaginalis. In competition studies in the Philippines, M. vaginalis was less competitive with rice than the other principal weed, the annual grass Echinochloa crus-galli (Lubigan and Vega, 1971). The critical weed population was 60 plants per square metre: a natural stand of 366 plants per square metre reduced rice yield by 35%. Lubigan and Vega (1971) concluded that M. vaginalis does not compete seriously for light and, being shallow rooted, the deeper-rooted rice plants are able to compete more vigorously for nutrients.

M. is reported to be a secondary host for the rice grassy stunt virus, transmitted by the brown planthopper, Nilaparvata lugens (IRRI, 1988) and for Sarocladium oryzae (Deka and Phookan, 1992). It is also a host of rice ragged stunt oryzavirus (RRSV) (Salamat et al., 1987), though it may not act as a reservoir of this virus (Parejarearn et al., 1988).

All parts of M. vaginalis except for the roots are relished as a vegetable (Mabberley, 1990) and it is used locally as a medicine (Burkill, 1935; Mabberley, 1990). The roots are used against stomach and liver ailments and against toothache (Soerjani et al., 1987). It is also used as cattle fodder (Patwary et al., 1989).

Uses List

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Human food and beverage

  • Vegetable

Similarities to Other Species/Conditions

Top of page M. vaginalis is similar in appearance to a related species M. hastata: the latter plant is larger and has a well-developed, branched rhizome, whereas M. vaginalis has a short rhizome. M. hastata has predominantly sagittate or hastate leaves whereas the leaves of M. vaginalis are heart shaped. M. hastata has more flowers in the raceme and, although the flowers of M. vaginalis open nearly simultaneously, those of M. hastata do not. The lower pedicels of flowers on M. hastata are elongated, whereas all pedicels in M. vaginalis are less than 1 cm long. (Holm et al. 1977).

The more serious weed, Eichhornia crassipes (water hyacinth) is in the same family as M. vaginalis and bears some resemblance. Eichhornia crassipes differs in being more robust (up to 1 m tall), with larger and more numerous flowers which are borne on a separate stalk, rather than appearing laterally on leaves. Eichhornia crassipes occurs as a free-floating aquatic plant on lakes and ponds.

Prevention and Control

Top of page Seed germination and seedling growth of M. vaginalis are encouraged by submergence and in rice this weed is therefore not controlled by irrigation. It is not difficult to remove by hand, but requires persistence to remove successive flushes of germination (Parker, 1992).

The pattern of seed germination varies according to moisture levels (Noda and Eguchi, 1965). In submerged conditions, the majority of seedlings emerge within a short space of time, with a germination peak 15-25 days after shedding. Under these circumstances, a single weeding or herbicide treatment after the germination flush could give season-long control. In saturated or dry soils, however, germination can occur throughout the season, so that a single weeding would be less effective and season-long control would be required.

In a study in the Philippines, Krock et al. (1988) found that mats of the aquatic fern Azolla used to suppress weeds in rice were particularly effective for the control of M. vaginalis.

This weed is usually controlled by butachlor, but requires a full dose of the herbicide (Parker, 1992). Other herbicides to which it is sensitive include bensulfuron, bentazone, butralin, chlomethoxyfen, cinmethylin, 2,4-D, glyphosate, MCPA, oxadiazon, oxyfluorfen, paraquat, pendimethalin, piperophos and pretilachlor. It is most sensitive to quinclorac and thiobencarb, but resistant to fenoxaprop (Ampong-Nyarko and De Datta, 1991), and propanil rarely gives good results (Soerjani et al., 1987). In greenhouse trials, it was highly susceptible to pyributicarb (Tsukuda et al., 1993).


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Ampong-Nyarko K; Datta SK de, 1991. Handbook for weed control in rice. Manila, Philippines: International Rice Research Institute.

Backer C; Bakhuizen van den Brink R, 1968. Flora of Java, Volume 3. Groningen: Wolters-Noordhoff NV.

Burhan H; Sozzi D; Zoschke A, 1989. Setoff for weed control in rice: practical experience from Indonesia. Proceedings, 12th Asian-Pacific Weed Science Society Conference Taipei, Taiwan; Asian-Pacific Weed Science Society, No. 1:127-131

Burkill IH, 1935. A Dictionary of the Economic Products of the Malay Peninsula, Volumes 1 and 2. London, UK: Governments of the Straits Settlements and Federal Malay States, Crown Agents for the Colonies.

Deka AK; Phookan AK, 1992. Some common weed hosts of Sarocladium oryzae in Assam, India. International Rice Research Newsletter, 17(6):25

Gopal B, 1987. Biocontrol with arthropods. Water hyacinth., 208-230; [2 fig., Aquatic Plant Studies No. 1].

Gupta S, 1968. Flowering process and curvature behaviour of the inflorescence in Monochoria vaginalis Presl. Tropical Ecology, 9:234-238.

Holm LG; Pancho JV; Herberger JP; Plucknett DL, 1979. A geographical atlas of world weeds. New York, USA: John Wiley and Sons, 391 pp.

Holm LG; Plucknett DL; Pancho JV; Herberger JP, 1977. The World's Worst Weeds. Distribution and Biology. Honolulu, Hawaii, USA: University Press of Hawaii.

Hutchinson J; Dalziel JM, 1968. Flora of West Tropical Africa, 2nd edn. Millbank, London: Crown Agents for Overseas Governments and Administrators.

IRRI, 1988. Annual Report for 1987. Los Ba±os, Philippines: International Rice Research Institute.

IRRI, 1989. Weeds Reported in Rice in South and South East Asia. Manila, Philippines: International Rice Research Institute.

Jiang RC; Xue G; Lou YL; Du JR, 1989. Field trials of oxyfluorfen, a herbicide used for control of weeds in rice field in Jiangsu Province. Jiangsu Agricultural Sciences, No. 5:22-24

Kaul MK, 1986. Weed Flora of Kashmir Valley. Jodhpur, India: Scientific Publishers, 422 pp.

Kim JS; Mercado BL, 1987. Viability and emergence of buried seeds of Echinochloa glabrescens, Monochoria vaginalis and Cyperus difformis. Proceedings, 11th Asian Pacific Weed Science Society Conference Taipei, Taiwan; Asian Pacific Weed Science Society, No. 2:469-476

Kröck T; Alkämper J; Watanabe I, 1988. The contribution of Azolla to weed control in rice crops. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz, Sonderheft 11:349-355.

Li D, 1987. An investigation on paddy field weeds in Fujian. Journal of Fujian Agricultural College, 16(4):267-277

Lin C, 1968. Weeds found on cultivated land in Taiwan. Volumes 1 and 2. Taipei, Taiwan: College of Agriculture, National Taiwan University.

Lubigan R; Vega M, 1971. The effect of different densities and durations of competition of Echinochloa crusgalli (L.) Beauv. and Monochoria vaginalis (Burm. f.) Presl. on the yield of lowland rice. Weed Science Report 1970-71. Los Ba±os, Philippines: University of the Philippines, 19-23.

Mabberley DJ, 1990. The Plant Book: a Portable Dictionary of the Higher Plants. Cambridge, UK: Cambridge University Press.

Merrill E, 1912. A Flora of Manila. Publication 5. Manila, Philippines: Bureau of Science.

Miyahara M; Morita H; Takabayashi M, 1989. Survival of seeds of major annual weeds buried in cultivated soil for 15 years under different soil moisture conditions and cultivation types in paddy fields of Southern Japan. Proceedings, 12th Asian-Pacific Weed Science Society Conference Taipei, Taiwan; Asian-Pacific Weed Science Society, No. 1:57-66

Moody K; Lubigan RT; Munroe CE; Paller EC, 1984. Major weeds of the Philippines. Weed Science Society of the Philippines. Los Ba±os, Laguna, Philippines: University of the Philippines.

Noda K; Eguchi S, 1965. Studies on ecology of weeds on arable lands: 1. Emergence patterns of annual representative weeds which are commonly found on the paddy rice fields of south-western Japan. Bulletin of the Kyushu Agricultural Experimental Station, 11:153-170.

Ohwi J, 1965. Flora of Japan. Smithsonian Institution, Washington, DC, 418.

Pancho JV; Soerjani M, 1978. Aquatic weeds of Southeast Asia. A systematic account of common Southeast Asian aquatic weeds. Aquatic weeds of Southeast Asia. A systematic account of common Southeast Asian aquatic weeds., 130 pp.; [260 X 180 mm].

Parejarearn A; Chettanachit D; Balaveang W; Disthaporn S, 1988. Rice ragged stunt virus (RSV) in aquatic weed Monochoria vaginalis. International Rice Research Newsletter, 13(2):22

Parham J, 1958. The Weeds of Fiji. Bulletin 35. Suva, Fiji: Department of Agriculture.

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

Patwary MU; Haque MM; Zaman MA, 1989. Polyploidy in Monochoria hastata Solms. and M. vaginalis Prest. grown in Bangladesh. Cytologia, 54(3):505-511

Ranjit JD; Bhattarai AN, 1988. Crop Weeds and their Control in Nepal. Kathmandu, Nepal: Winrock International/USAID.

Salamat GZ Jr; Parejarearn A; Hibino H, 1987. Weed hosts of ragged stunt virus. International Rice Research Newsletter, 12(4):30

Sattar SA; Biswas JC, 1991. Effect of density of pickerel weed (Monochoria vaginalis) on transplanted rice (Oryza sativa). Indian Journal of Agricultural Sciences, 61(8):567-570

Sharifi MM, 1990. First report of Monochoria vaginalis in Iran. International Rice Research Newsletter, 15(4):30

Soerjani M; Kostermans AJGH; Tjitrosoepomo G, 1987. Weeds of Indonesia. Jakarta, Indonesia: Balai Pustaka, 716 pp.

Tsukuda K; Murakami M; Morinaka H; Tsuzuki K; Ichizen N; Konnai M; Takematsu T, 1993. Herbicidal and phytotoxic properties of pyributicarb, a new paddy herbicide, and its movement in soil. Weed Research (Tokyo), 38(3):175-181

Wang Z, 1990. Farmland weeds in China: a collection of coloured illustrative plates. Beijing, China: Agricultural Publishing House.

Links to Websites

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Distribution Maps

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