Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Elodea canadensis
(Canadian pondweed)

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Datasheet

Elodea canadensis (Canadian pondweed)

Summary

  • Last modified
  • 08 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Preferred Scientific Name
  • Elodea canadensis
  • Preferred Common Name
  • Canadian pondweed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae
  • Summary of Invasiveness
  • E. canadensis is a submerged aquatic species of slower flowing rivers, native to North America. It has been intentionally introduced into areas outside of its native range as an ornamental aquarium species. This...

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Pictures

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PictureTitleCaptionCopyright
Elodea canadensis (Canadian pondweed); habit and habitat. USA.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit and habitat. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit and habitat. USA.
HabitElodea canadensis (Canadian pondweed); habit and habitat. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit and habitat. USA.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit and habitat. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit and habitat. USA.
HabitElodea canadensis (Canadian pondweed); habit and habitat. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit, showing leaves and stem. USA.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit, showing leaves and stem. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit, showing leaves and stem. USA.
HabitElodea canadensis (Canadian pondweed); habit, showing leaves and stem. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
Copyright©GBNNSS/Crown Copyright/British Waterways
Elodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
HabitElodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.©GBNNSS/Crown Copyright/British Waterways
Elodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
Copyright©GBNNSS/Crown Copyright/British Waterways
Elodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.
HabitElodea canadensis (Canadian pondweed); habit, close view, showing stem and leaves. UK.©GBNNSS/Crown Copyright/British Waterways
Elodea canadensis (Canadian pondweed); close-up, showing leaves and stem. USA.
TitleLeaves
CaptionElodea canadensis (Canadian pondweed); close-up, showing leaves and stem. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); close-up, showing leaves and stem. USA.
LeavesElodea canadensis (Canadian pondweed); close-up, showing leaves and stem. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); close-up, showing leaves. USA.
TitleLeaves
CaptionElodea canadensis (Canadian pondweed); close-up, showing leaves. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); close-up, showing leaves. USA.
LeavesElodea canadensis (Canadian pondweed); close-up, showing leaves. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); close-up of leaves and leaf base. USA.
TitleLeaves
CaptionElodea canadensis (Canadian pondweed); close-up of leaves and leaf base. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); close-up of leaves and leaf base. USA.
LeavesElodea canadensis (Canadian pondweed); close-up of leaves and leaf base. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit. Note hand for scale. USA.
TitleHabit
CaptionElodea canadensis (Canadian pondweed); habit. Note hand for scale. USA.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); habit. Note hand for scale. USA.
HabitElodea canadensis (Canadian pondweed); habit. Note hand for scale. USA.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Elodea canadensis (Canadian pondweed); plant parts: (A) aquatic habit; (B) submerged leaf arrangement in whorls of three, rarely four leaves; (C) male flower; (D) female flower, note petals narrower than sepals.
TitlePlant parts
CaptionElodea canadensis (Canadian pondweed); plant parts: (A) aquatic habit; (B) submerged leaf arrangement in whorls of three, rarely four leaves; (C) male flower; (D) female flower, note petals narrower than sepals.
Copyright©NOVARTIS (amended from Ciba-Geigy Monocot Weeds Vol.3)
Elodea canadensis (Canadian pondweed); plant parts: (A) aquatic habit; (B) submerged leaf arrangement in whorls of three, rarely four leaves; (C) male flower; (D) female flower, note petals narrower than sepals.
Plant partsElodea canadensis (Canadian pondweed); plant parts: (A) aquatic habit; (B) submerged leaf arrangement in whorls of three, rarely four leaves; (C) male flower; (D) female flower, note petals narrower than sepals.©NOVARTIS (amended from Ciba-Geigy Monocot Weeds Vol.3)

Identity

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Preferred Scientific Name

  • Elodea canadensis Rich. in Michx. (1803)

Preferred Common Name

  • Canadian pondweed

Other Scientific Names

  • Anacharis alsinastrum Bab.
  • Anacharis canadensis (Michx.) Planch.
  • Elodea ioensis Wylie
  • Elodea planchonii Casp.
  • Udora canadensis (Michx) Nutt.

International Common Names

  • English: American duckweed; Canadian elodea; Canadian waterweed; common elodea; ditch weed; elodea; oxygen weed; water thyme; waterweed
  • Spanish: broza del Canada
  • French: elodee du Canada
  • Portuguese: estrume-novo

Local Common Names

  • Cuba: elodea
  • Germany: Kanadische Wasserpest
  • Italy: elodea; peste d'acqua
  • Japan: kanadamo
  • Netherlands: waterpest
  • South Africa: Kanadese waterpes
  • Sweden: vattenpest

EPPO code

  • ELDCA (Elodea canadensis)

Summary of Invasiveness

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E. canadensis is a submerged aquatic species of slower flowing rivers, native to North America. It has been intentionally introduced into areas outside of its native range as an ornamental aquarium species. This species has a wide ecological tolerance and grows relatively fast, but prefers neutral to calcareous open water that is not turbid or strongly affected by environmental influences such as water turbidity or wind fetch. E. canadensis is a perennial, overwintering in the deeper water, reproducing asexually. Disturbance increases the dispersal of numerous propagules and the vigorous re-growth is enhanced through changes in availability of nutrients. E. canadensis is considered a pioneer species, rapidly colonising new areas, however, it is often later replaced by other aquatic weeds such as E. nutallii. E. canadensis can form dense mats which can interfere with recreational activities, navigation and port infrastructure. In addition to this, the dense mats outcompete native plant species and therefore decrease the biodiversity in an area. It also accentuates the accumulation of finer and organic silts which enhances its growth further as nutrients are released. Control of this species is complicated and loss of fragments should be minimised to prevent further spread. E. canadensis is considered a serious weed in Australia and as a principal weed in Denmark, England, Germany, Italy, New Zealand, The Netherlands, Norway, Poland, Sweden and parts of the USA.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Monocotyledonae
  •                     Order: Hydrocharitales
  •                         Family: Hydrocharitaceae
  •                             Genus: Elodea
  •                                 Species: Elodea canadensis

Notes on Taxonomy and Nomenclature

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Historically there has been much confusion in the classification of the species of the genus Elodea (Family Hydrocharitaceae). However, Cook and Urmi-König (1985), in the latest revision of the genus, recognise five species of Elodea, all of them from the New World: E. potamogeton (Bert) Espinosa and E. callitrichoides (Rich.) Caspary are endemic to South America, while E.bifoliata St. John, E. canadensis and E. nuttallii grow in North America.

The name E. canadensis Michx. is universally accepted for this common, widespread waterweed. Four varieties are recognised by Missouri Botanical Gardens (2014), var. angustifolia (Muhl.) Farw., var. gigantea Hort. In Bailey, var. latifolia (Casp.) Asch. & Graebn and var. planchonii Farw. ITIS (2014), however, does not recognise any of these.

Description

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E. canadensis is a dioecious, perennial, submerged aquatic macrophyte with elongated flexuous stems and long internodes which are clothed with whorls of sessile, minutely-serrate leaves and rooted from their nodes typically in mud substrates. The middle and upper leaves, typically three per whorl, are elliptic, approximately 2-5 mm wide; leaves in the upper whorls grow closely together. In autumn, turions or short densely-leaved resistant stems develop then break off to float around the waterbody before they sink to the bottom where they rest until they regrow in spring. Male flowers are pedunculate by the elongate, filiform base of the floral tube, not released from the plant at anthesis; sepals 3.5-5.0 mm long, petals 5 mm long. The staminate spathe has a pedunculate base, inflated, 7 mm long, 4 mm wide. The female flower stalk is approximately 15 cm long; sepals and petals 2-3 mm long. Petals white. Pistillate spathe cylindrical. Female flowers are common, male flowers are absent in Europe and apparently rare elsewhere. Seed buds mostly without stems, sometimes with short stems and seeds are glabrous.

Distribution

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E. canadensis originates from North America, but now occurs throughout the USA. The plant was introduced to the UK in the mid-1800s and has spread eastwards in Western Europe with the apparent exception, so far, of Iberia and northern Scandinavia. It is widespread in Australia and New Zealand, but has, so far, been recorded in only a few Asiatic countries.

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

Asia

ChinaPresentIntroducedHolm et al., 1979; Lia et al., 2009
IndiaPresentIntroducedHolm et al., 1979; Q-bank, 2014
MalaysiaPresentIntroducedRevilla et al., 1991
Saudi ArabiaPresentIntroducedMohamed and Al-Shehri, 2010
SingaporePresentIntroducedRevilla et al., 1991
TaiwanPresentIntroducedQ-bank, 2014
ThailandPresentIntroducedRevilla et al., 1991

Africa

EgyptPresentIntroducedHolm et al., 1979
MauritiusPresentIntroducedHolm et al., 1979
South AfricaWidespreadIntroducedSpicer and Catling, 1988; Invasive Species South Africa, 2014

North America

CanadaPresentPresent based on regional distribution.
-AlbertaWidespreadNativeHaag, 1979; Spicer and Catling, 1988; Alberta Biodiversity Monitoring Institute, 2014
-British ColumbiaWidespreadSpicer and Catling, 1988; E-Flora, 2014
-ManitobaWidespreadGodfrey and Wooten, 1997
-New BrunswickPresentUSDA-NRCS, 2014
-Nova ScotiaPresentUSDA-NRCS, 2014
-OntarioWidespreadSpicer and Catling, 1988
-QuebecWidespreadSpicer and Catling, 1988
-SaskatchewanWidespreadGodfrey and Wooten, 1997
MexicoPresentHolm et al., 1979; USDA-NRCS, 2014
USAPresentPresent based on regional distribution.
-AlabamaWidespreadNativeGodfrey and Wooten, 1997
-AlaskaPresentNativeAlaska Plant Materials Center, 2014; USDA-NRCS, 2014
-ArizonaWidespreadNativeGodfrey and Wooten, 1997
-ArkansasWidespreadNativeWesterdahl and Getsinger, 1988
-CaliforniaWidespreadNativeAnderson, 1981
-ColoradoWidespreadNativeWesterdahl and Getsinger, 1988
-ConnecticutWidespreadNativeWesterdahl and Getsinger, 1988
-DelawareWidespreadNativeWesterdahl and Getsinger, 1988
-FloridaWidespreadNativeWesterdahl and Getsinger, 1988
-GeorgiaWidespreadThomaston, 1978
-HawaiiPresentNativeHolm et al., 1979
-IdahoWidespreadNativeWesterdahl and Getsinger, 1988
-IllinoisWidespreadNativeWesterdahl and Getsinger, 1988
-IndianaWidespreadNativeWilley et al., 1974
-IowaWidespreadNativeMitzner, 1978
-KansasWidespreadNativeWesterdahl and Getsinger, 1988
-KentuckyWidespreadWesterdahl and Getsinger, 1988
-LouisianaWidespreadWesterdahl and Getsinger, 1988; Aquatic plant species in Louisiana, 2014
-MaineWidespreadNativeGodfrey and Wooten, 1997
-MarylandWidespreadGodfrey and Wooten, 1997
-MassachusettsWidespreadLawrence, 1976
-MichiganWidespreadNativeNichols et al., 1989
-MinnesotaWidespreadNativeWesterdahl and Getsinger, 1988
-MississippiWidespreadNativeWesterdahl and Getsinger, 1988
-MissouriWidespreadWesterdahl and Getsinger, 1988
-MontanaWidespreadNativeWesterdahl and Getsinger, 1988
-NebraskaWidespreadNativeWesterdahl and Getsinger, 1988
-NevadaWidespreadNativeWesterdahl and Getsinger, 1988
-New HampshireWidespreadNativeWesterdahl and Getsinger, 1988
-New JerseyWidespreadNativeWesterdahl and Getsinger, 1988
-New MexicoWidespreadNativeGodfrey and Wooten, 1997
-New YorkWidespreadNativePeverly and Johnson, 1979; Peverly and Kopka, 1991
-North CarolinaWidespreadNativeWesterdahl and Getsinger, 1988
-North DakotaWidespreadNativeWesterdahl and Getsinger, 1988
-OhioWidespreadNativeQuinn et al., 1977
-OklahomaWidespreadGodfrey and Wooten, 1997
-OregonWidespreadNativeWesterdahl and Getsinger, 1988
-PennsylvaniaWidespreadNativeGodfrey and Wooten, 1997
-Rhode IslandWidespreadNativeWesterdahl and Getsinger, 1988
-South CarolinaWidespreadWesterdahl and Getsinger, 1988
-South DakotaWidespreadNativeWesterdahl and Getsinger, 1988
-TennesseeWidespreadNativeWesterdahl and Getsinger, 1988
-TexasWidespreadWesterdahl and Getsinger, 1988
-UtahWidespreadNativeWesterdahl and Getsinger, 1988
-VermontWidespreadNativeWesterdahl and Getsinger, 1988
-VirginiaWidespreadNativeGodfrey and Wooten, 1997
-WashingtonWidespreadNativeWood, 1990
-West VirginiaWidespreadNativeGodfrey and Wooten, 1997
-WisconsinWidespreadNativeSimsiman, 1974
-WyomingWidespreadNativeWesterdahl and Getsinger, 1988

Central America and Caribbean

BelizePresentHolm et al., 1979
CubaPresentIntroduced Invasive Oviedo Prieto et al., 2012
Puerto RicoPresentIntroducedHolm et al., 1979

South America

ArgentinaPresentIntroducedHolm et al., 1979
ChilePresentIntroducedMissouri Botanical Garden, 2008
EcuadorPresentIntroducedMissouri Botanical Garden, 2008

Europe

AustriaWidespreadIntroducedWychera et al., 1990
BelgiumWidespreadIntroducedSculthorpe, 1971
BulgariaPresentIntroducedDandy, 1980
Czechoslovakia (former)WidespreadIntroducedAdamec and Ondok, 1992
DenmarkPresentIntroduced1870Sculthorpe, 1971
EstoniaPresentIntroduced1905NOBANIS, 2014
FinlandPresentIntroduced1884Dandy, 1980; NOBANIS, 2014Extremely common in southern and central Finland and still expanding its range
FranceWidespreadIntroducedSculthorpe, 1971
GermanyPresentIntroduced1859Sculthorpe, 1971; Krausch, 1987; NOBANIS, 2014
GreeceWidespreadIntroducedBoliotes, 1984
HungaryWidespreadIntroducedKeresztes and Horvath, 1977
IrelandWidespreadIntroducedSculthorpe, 1971; NOBANIS, 2014
ItalyPresentIntroducedHolm et al., 1979
LatviaWidespreadIntroduced1872NOBANIS, 2014
LithuaniaWidespreadIntroduced1884Stepanaviciene, 2000; NOBANIS, 2014
NetherlandsWidespreadIntroducedvan Oostsroom, 1973; Best, 1979
NorwayWidespreadIntroduced1925Rorslett, 1995; NOBANIS, 2014
PolandWidespreadIntroduced1859Dandy, 1980; NOBANIS, 2014
PortugalPresentIntroducedDandy, 1980
RomaniaPresentIntroducedDandy, 1980
Russian FederationWidespreadIntroducedSculthorpe, 1971
-Central RussiaPresentIntroducedDandy, 1980
-Russia (Europe)PresentIntroduced1880Dandy, 1980
-SiberiaWidespreadIntroducedSculthorpe, 1971; Kozhova and Izhboldina, 1993
SpainWidespreadIntroducedPalet et al., 1991
SwedenWidespread1871Sculthorpe, 1971; NOBANIS, 2014
SwitzerlandWidespreadIntroducedSher-Kaul et al., 1995
UKWidespreadIntroducedSculthorpe, 1971First reported in Scotland in 1854
UkrainePresentIntroducedKharchenko et al., 2008
Yugoslavia (former)PresentIntroducedDandy, 1980

Oceania

AustraliaWidespreadIntroducedMitchell, 1978; Burdon and, 1986; Royal Botanic Gardens Sydney, 2008
-New South WalesWidespreadIntroducedRipper Madin, 1984
-South AustraliaPresentIntroducedRoyal Botanic Gardens Sydney, 2008
-TasmaniaWidespreadIntroducedSculthorpe, 1971
-VictoriaWidespreadIntroducedSculthorpe, 1971
New ZealandWidespreadIntroducedForsyth and Howard-Williams, 1983; Coffey and Clayton, 1987

History of Introduction and Spread

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The following extract is taken from NOBANIS, (2011) - ‘Elodea canadensis was first observed in Europe in 1836, in an Irish pond, where it had already been established for some time. It has been introduced to a large number of European countries and was first reported in Scotland in 1854, in Germany near Berlin in 1859 and also in Poland at about this time. The first report of E. canadensis in Scandinavia is from Denmark in 1870, Sweden in 1871 and Finland in 1884. In Finland E. canadensis was intentionally planted in the Botanical Garden of the University of Helsinki (Hintikka 1917), from which it spread with water and birds to the entire country. Although E. canadensis was first observed in Norway near Oslo in 1925, it did not begin to spread to other areas until the 1960s. E. canadensis was observed for the first time in the European part of Russia in 1880, in Latvia in 1872, in Lithuania in1884 and in Estonia in 1905.’

The introduction of the closely related and invasive E. nuttallii into Europe resulted in the displacement of E. canadensis from many localities where it had become well established (Simpson, 1990; Thiébaut et al., 1997; Barrat-Segretain, 2001; Larson, 2007). 

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Australia 1876 Yes Council of Heads of Australasian Herbaria (2014) First recorded in Tasmania
Ireland USA 1836 Yes DAISIE (2014)
New Zealand 1868 Aquaculture (pathway cause) Yes THOMSON (1922)

Habitat

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E. canadensis can grow in a range of habitats, but prefers quiet ponds, lakes and slow-moving water with a peaty or muddy silt substrates. E. canadensis is a common species in nutrient rich, or eutrophic, relatively quiet or slower water flows of many inland freshwater bodies (ponds, lakes, ditches, irrigation channels) and is often associated with organic-rich muds.

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial ‑ Natural / Semi-naturalWetlands Secondary/tolerated habitat Productive/non-natural
Freshwater
 
Irrigation channels Principal habitat Harmful (pest or invasive)
Lakes Secondary/tolerated habitat Productive/non-natural
Reservoirs Secondary/tolerated habitat Productive/non-natural
Rivers / streams Principal habitat Productive/non-natural
Ponds Principal habitat Harmful (pest or invasive)

Biology and Ecology

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Genetics

As exotic populations in Europe appear to only reproduce vegetatively, depending on the number of different introductions, the genetic diversity is likely to be small. Molecular studies are however, needed, however, to clarify this issue. 

Reproductive Biology

E. canadensis is an aggressively competitive weed, which spreads mainly by vegetative plant fragments, but also to some extent by seeds. Over-wintering buds and fragments of the brittle branches are easily detached by waves, currents, foraging animals and boat traffic. New roots develop quickly on the nodes of these fragments which are carried downstream to form new stands. This method of propagation gives E. canadensis a considerable advantage over annual species and resulted in its rapid spread throughout Europe following its introduction from North America (Holm et al., 1997; NOBANIS, 2011). Sexual reproduction in the field is believed to be very rare because of infrequent flowering and the differing abundance of the two sexes in nature. In Europe, only female flowers occur, making sexual reproduction impossible, so that spread occurs entirely by vegetative fragments. When both pistillate and staminate flowers are present at a site, the reproductive structures are pushed from the spathe, raised to the water surface by thread-like hypanthia and anthesis and pollination occur. At dehiscence the anthers open explosively and pollen is scattered over the water where it drifts to the stigmas.

Physiology and Phenology

Perennation is by densely leaved crowded apices or turions. During autumn, apices cease to elongate and come to bear tightly clustered dark green leaves, which contain much starch and are slightly more cuticularized than the normal foliage leaves. These apices may be liberated when the parent stems disintegrate and sink to the bottom, or remain attached throughout winter. The apices remain dormant until spring, when the leaves expand, adventitious roots develop from the lower nodes, the axis elongates and a new plant is formed. E. canadensis begins to grow during the spring season in temperate zones as the temperature rises to between 10-15°C. At ambient light levels, shoot biomass increases with temperature up to 28°C; root biomass shows an opposite tendency (Barko et al., 1982). Growth of this species is greatly stimulated under eutrophic conditions (Hughes, 1976; Barko and Smart, 1983; Kraush, 1987).

Erhard and Gross (2006) suggested that the production by both of allelochemicals that interfere with the growth of cyanobacteria and algae by E. canadensis and the closely related E. nuttallii could at least play some role in the success of these two species as invasives.

Environmental Requirements

E. canadensis has a wide climatic tolerance, present from Alaska to Puerto Rico, though it may be less common as the extremes of its range, being predominant in temperate areas of North America and Europe. Pip and Simmons (1986) in Canada and Sheldon and Boylen (1977) in the USA, studied the maximum depths at which a number of submerged aquatic plants were found and the maximum recorded for any species was 12-14 m for Elodea. In North America it has been recorded in neutral to slightly alkaline inland waters and in fresh to slightly brackish coastal waters (Holm et al., 1997).

Riis et al. (2012), compared the effects of temperature and light availability on the growth and morphology of E. canadensis, Egeria densa and Lagarosiphon major and suggested that, in general, subject to variations due to timing of introductions, E. densa will dominate warmer, shallower waters, L. major will dominate in colder, clear-water lakes, whilst E. canadensis will continue its role as a pioneer species which is rapidly replaced by the two taller species after their arrival.

Climate

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ClimateStatusDescriptionRemark
C - Temperate/Mesothermal climate Preferred Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C
Cf - Warm temperate climate, wet all year Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
65 55

Air Temperature

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Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -1 4

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Conductivity (µmhos/cm) 200 1000 Optimum 2000 tolerated
Depth (m b.s.l.) 1 Optimum 3 (-12) tolerated
Dissolved oxygen (mg/l) Optimum metabolism creates range of 40-250%
Hardness (mg/l of Calcium Carbonate) 20 300 Optimum <20 - >400 tolerated
Salinity (part per thousand) 0 Optimum 0.05 seawater tolerated
Velocity (cm/h) 0 700 Optimum 0-20 cm/sec
Water pH (pH) 7 8.5 Optimum 8.5-10 tolerated
Water temperature (ºC temperature) 10 25 Optimum 4-28 tolerated but probably temperature adaptive

Notes on Natural Enemies

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The snails Lymnea peregra and Bithynia spp. are natural herbivores of E. canadensis. Populations of these species can expand enormously if not controlled by natural predators and under such circumstances snails can serve as a biological control agent. However, Pieczynska (2003) studied the damage inflicted on a population of E. canadensis by the snail L. stagnalis and concluded that although the snail caused a substantial reduction in biomass and severe damage to E. Canadensis, the plant fragments remaining after grazing showed a high capacity to regenerate new plants.

Means of Movement and Dispersal

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Natural Dispersal

E. canadensis is spread locally downstream along rivers, streams and channels.

Vector Transmission

Pieces of fragment may become attached to water animals, mammals, fish or birds and transferred locally. 

Accidental Introduction

Accidental spread of E. canadensis may also occur via attachment of fragments to fishing nets or boats.

Intentional Introduction

E. canadensis was intentionally introduced into countries outside of its native range as an ornamental aquarium species.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Fisheries Yes
Flooding and other natural disasters Yes
Garden waste disposal Yes
Hitchhiker Yes Yes
Internet sales Yes
Ornamental purposes Yes Yes
Pet trade Yes Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Aquaculture stockFragments with stocking/or nets Yes Yes
Floating vegetation and debrisErratic, flood events Yes
Land vehiclesOn wheels, tracks or in attached mud etc. Yes
Pets and aquarium speciesCasual introductions and discarded material Yes
Water Yes

Economic Impact

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Both E. canadensis and the closely related E. nuttallii have the potential to develop into dense submerged beds. This prevents the use of water for recreational and professional purposes (Larson, 2003), navigation and port infrastructure (CPS-SKEW, 2008). The plant can also clog and impede drainage waterways. Water flow in irrigation channels may slow and become blocked, reducing water supply to irrigation fed crops, such as rice in Asiatic countries and cotton in the USA. In Australia, Elodea is one of the main problems in 8000 km of canals and irrigation channels which feed the farm areas of Victoria (Bill, 1969). Mehta et al. (1973) reported that about 1500 ha of the Chambal irrigation system was infested with aquatic weeds, causing a reduction in the water carrying capacity by as much as 80%. Elsewhere, infestations have been reported to reduce water flow in canals and streams by up to 80%, this in turn may interfere with water traffic, disturb hydroelectric and urban water supplies, limit recreational water use and change the aquatic environment. Blockage of larger channels may inhibit ship movements, thus affecting trade. Submerged plants in general, have been proven to interfere with fishing operations, causing loss of revenue (Dutta and Gupta, 1973). In New Zealand a number of submerged aquatic weeds including E. canadensis cause considerable losses to hydropower stations (Howard-Williams, 1993).

Environmental Impact

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E. canadensis can from dense monospecific stands which can outcompete native plants for both space and nutrients resulting in a decrease in biodiversity and potentially local extinctions (DAISIE, 2014; NOBANIS, 2014). Changes to invertebrate communities have also been reported (RAFTS, 2009). Species of Elodea are also known to accumulate metals from the sediment and release them into the waterbody (RAFTS, 2009).

Social Impact

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E. canadensis can form large and dense stands that interfere with boating, fishing and thereby adversely affect recreation activities.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Is a habitat generalist
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Reproduces asexually
Impact outcomes
  • Conflict
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Modification of hydrology
  • Modification of natural benthic communities
  • Modification of nutrient regime
  • Modification of successional patterns
  • Monoculture formation
  • Negatively impacts cultural/traditional practices
  • Negatively impacts livelihoods
  • Negatively impacts aquaculture/fisheries
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
  • Transportation disruption
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - shading
  • Competition - smothering
  • Competition - strangling
  • Filtration
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Highly likely to be transported internationally illegally

Uses

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Although E. canadensis frequently occurs as a noxious weed, in warmer climates it is important to fish as a direct food source and for shade/shelter and as food for many birds, including ducks, coots, geese, grebes, swans, marsh birds, shore birds and game birds (Sculthorpe, 1971).

Uses List

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Animal feed, fodder, forage

  • Fodder/animal feed

Environmental

  • Wildlife habitat

General

  • Ornamental
  • Pet/aquarium trade

Materials

  • Manure
  • Mulches

Similarities to Other Species/Conditions

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Identification of E. canadensis in its vegetative form can be confused with E. nuttallii and with another member of the Hydrocharitaceae family, Hydrilla verticillata, which both have similar habits within the USA.

Distinction between E. canadensis and E. nuttallii is possible from inflorescences: E. nuttallii has sessile male flowers, which are released at anthesis and female flowers with a shorter floral tube (up to 9 cm). E. nuttallii can also occur as a common waterweed in the same geographic regions as it is rapidly expanding its distribution, but it is not yet as widespread, though is found in similar conditions and often seems to grow slightly more vigorously. The identification of both species is however sometimes confused and misidentifications occur. E. canadensis is characterised by a flat elongate leaf blade and a leaf length to width ratio of 3:1, whereas E. nuttallii has a ratio of 6:1 and typically has an obvious twist of at least half a turn along the length of the leaf blade. In some countries, the perceived occurrence of the two species of Elodea has been further confused because E. nutallii, introduced to Britain in 1939, has displaced E. canadensis in many European waterways (Barrat-Segretain et al., 2002).

Distinction between E. canadensis and H. verticillata is easy after flowering, when H. verticillata forms short branchlets on the internodes and subterranean tubers on the rootstocks (Godfrey and Wooten, 1997). Holm et al. (1997) suggest that H. verticillata may be distinguished in the vegetative stage by its conspicuously toothed leaves, while confusion with Egeria densa is avoided by the fact that the latter has leaves in whorls of four or five, not three.

Prevention and Control

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Prevention

Vehicles, boats, equipment and clothing should all be checked for fragments of the plant to prevent E. canadensis from being spread into new locations (RAFT, 2009).

Control

Cultural Control

The drying out of lakes, ditches, ponds and irrigated fields is widely used, but is satisfactory only in countries with a prolonged dry season, or elsewhere in habitats which are easily drained (Surber, 1949; Clark, 1954; Walker, 1959). The technique has been moderately successful in the rice fields of tropical countries in eradicating E. canadensis and other submerged macrophytes. It is often supplemented by ploughing the dry soil with disks to a depth of about 25 cm. Effective removal by mechanical means is possible if the growth of the weed is in a reasonably early stage, e.g. pre-emptive control. Modifying the channel environment, however small a change and wherever possible, all helps to reduce aquatic plant growth. Demonstrated effects include reducing direct sunlight by correctly-orientated marginal shade from vegetation, or even artificial materials near the water surface or also reducing in the light penetration of water (Dawson, 1986). Environmental changes may include manipulation of water flow periodic or regular brief increases in water flow to washout out less stable vegetation or substrates, restructuring or reshaping channel shape, etc. (Dawson and Brabben, 1991; Bolton and Dawson, 1992). Restricting nutrient availability for example, the use of salt-rich water for secondary irrigation in Australia, is also likely to severely restrict the growth of freshwater plants.

Where submerged aquatic weeds cause blockage of penstock intake screens in New Zealand, the three methods commonly used for preventing such blockage are floating booms at an angle across the current to collect floating weed masses and concentrate them at a single site on the shore, mechanical screen cleaners on the intake screens, or lake draw-downs in summer to desiccate weed masses and in winter to freeze kill weed masses in shallow water (Howard-Williams, 1993).

Physical/Mechanical Control

In North America and Western Europe, special barges are used which cut the weeds and remove them from the water, alternatively, cutting machines are mounted on boats or tractors. These are used to cut the weeds in streams and small rivers letting the cut plant material float downstream (Westlake and Dawson, 1986). Mechanical mowing and rolling are widely practised in the control of weeds in irrigation ditches (Dunk and Tisdall, 1954; Seaman, 1958).

Chemical Control

Controlling aquatic weeds with herbicides has progressed most in the USA, Western Europe, Australia and New Zealand. A datasheet on control for the UK is available (Newman, 2005). In tropical countries, the use of herbicides is far more limited. For submerged plants, a number of chemicals were used but many are now prohibited in the USA (IARC, 2014) and elsewhere. Bensulfuron methyl has given fair control of E. canadensis in Australian irrigation channels (McCorkelle et al., 1990). An overview of chemical control methods published by the US Army Corps of Engineers, Waterways Experiment Station, lists dichlobenil, diquat alone and diquat with complexed copper as 'excellent' methods; and acrolein, Endothall [endothal] demethylalkylamine salts and fluridone as 'good' methods (Westerdahl and Getsinger, 1988).

Glomski et al. (2005) established that diquat gives excellent control of E. canadensis, even at low concentrations. Diquat is often used as the herbicidal component of gels that carry the herbicide into direct contact with the weed (Barratt, 1978; Chandrasena et al., 2012).

Biological Control

Control by aquatic herbivores has been investigated in numerous countries (NAS, 1976). Species tested include Tilapia melanopleura, T. mossambica and the Chinese grass carp, Ctenopharyngodon idella. Since the latter is an exotic species, introduction is only allowed when the species can be confined to a particular waterbody and, therefore, investment in fences is a prerequisite. Nevertheless, several successful examples of control are known from Western Europe and the USA (Stott et al. 1971; Willey et al., 1974; Mitzner, 1978; Fowler, 1984).

References

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Organizations

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Netherlands: European Weed Research Society - EWRS, Postbus 29, NL-6865 ZG Doorwerth, http://www.ewrs.org

UK: Centre for Ecology and Hydrology - CEH, CEH Wallingford, Maclean Building, Crowmarsh Gifford, Walingford, Oxfordshire, http://www.ceh.ac.uk/

UK: Environment Agency, National Customer Contact Centre PO Box 544, Rotherham S60 1BY, http://www.environment-agency.gov.uk/

Contributors

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02/10/2014 Updated by:

Ian Popay, Landcare Research, New Zealand

14/01/2008 Updated by:

Hugh Dawson, CEH Wallingford, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK

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