Myriophyllum heterophyllum (broadleaf watermilfoil)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Latitude/Altitude Ranges
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Uses List
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Myriophyllum heterophyllum Michaux, 1803
Preferred Common Name
- broadleaf watermilfoil
International Common Names
- English: American water-milfoil; variable watermilfoil
Local Common Names
- Germany: Verschiedenblaettriges Tausendblatt
- Netherlands: Ongelijkbladig vederkruid
- USA: variable-leaf water milfoil
- MYPHE (Myriophyllum heterophyllum)
Summary of InvasivenessTop of page
M. heterophyllum is an aquatic plant native to southeast USA. It is considered invasive throughout New England and northwest USA and as an emerging invader in Europe because of its tendency for uncontrolled growth and subsequent formation of dense mats of submergent vegetative material throughout the water column and at the water surface. These mats prevent water flow, reduce sunlight, reduce oxygen availability, and impede swimming, boating and fishing. M. heterophyllum is banned from sale in some New England states and Washington state.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Haloragidales
- Family: Haloragidaceae
- Genus: Myriophyllum
- Species: Myriophyllum heterophyllum
Notes on Taxonomy and NomenclatureTop of page
Common names include variable-leaf watermilfoil, two-leaf watermilfoil and broad-leaf watermilfoil. The exact origins of these names are not known, but are presumed to be North American. In the aquarium trade, M. heterophyllum may be sold as ‘myrio’, ‘foxtail’, or ‘parrotfeather’.
DescriptionTop of page
M. heterophyllum is an aquatic plant that has submerged vegetation with emergent flowering spikes. Plants hermaphroditic, occasionally monoecious. Stem stout, to 100 cm; internodes crowded. Submerged leaves 4- or 5-whorled or scattered, pectinate, oblong in outline, (1.5-)2-4 × 1-3 cm; segments in 5-12 pairs, filiform, 0.5-1.5 cm. Inflorescence a terminal spike of 4-whorled flowers, 5-35 cm, in monoecious plants lowermost flowers female, uppermost ones male; bracts persistent, eventually reflexed, lanceolate to oblong or obovate, 4-18 × 1-3 mm, margin sharply serrulate; bracteoles ovate, ca. 1.2 × 0.6 mm, margin serrate. Petals 1.5-3 mm. Stamens 4. Fruit 4-loculed, subglobose, 1-1.5 mm; mericarps with 2 finely tuberculate ridges abaxially, apex beaked (Flora of China Editorial Committee, 2012).
Plant TypeTop of page Aquatic
DistributionTop of page
The distribution of M. heterophyllum is generally known, but not documented in detail. Aiken (1981) lists its distribution in North America as ‘…Virginia to Florida, northward to Ontario and Michigan, and westward to Missouri and Texas’. The species is generally considered as native to the eastern part of the USA, except the northeastern region. It is considered non-native and invasive in New England, where it appears to have been introduced circa 1932 via escape from cultivation with subsequent spread via vegetative propagules (Les and Mehrhoff, 1999). Since its initial introduction to New England, it has spread throughout the region and is the most common invasive aquatic plant in New Hampshire (Thum and Lennon, 2009). It is not clear if M. heterophyllum was historically native to the mid-Atlantic region (Delaware, Maryland, New Jersey, New York, Pennsylvania and Virginia). For example, it is treated as a non-native invasive species in New York and eastern Pennsylvania, but is considered an extremely rare native and threatened species in nearby Delaware. Part of the confusion regarding its historical status (native/non-native) in northeastern USA may result from confusion with the closely related species M. pinnatum, which is considered native along the eastern coast from Florida through eastern Massachussetts (Aiken, 1981). M. heterophyllum is also considered non-native in western USA: while it is not clear when it was first introduced here, its recent spread in the region - especially in Washington state - is causing concern among water resource managers. Two causes for concern include the possible misidentification of M. heterophyllum with the closely-related, morphologically similar, and endemic western watermilfoil, M. hippuroides, and the potential for hybridization between the two species.
In Europe, it is found in Austria, Belgium, France, Germany, Netherlands and Spain (EPPO, 2012, 2014).
Distribution TableTop of page
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/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Introduced||Yu et al., 2002, publ. 2003; EPPO, 2014|
|-Guangdong||Present||Introduced||Flora of China Editorial Committee, 2012; EPPO, 2014|
|-British Columbia||Present||USDA-NRCS, 2008; EPPO, 2014||Potential for confusion with native M. hippuroides|
|-New Brunswick||Present||USDA-NRCS, 2008; EPPO, 2014|
|-Ontario||Present||Native||USDA-NRCS, 2008; EPPO, 2014|
|-Quebec||Present||USDA-NRCS, 2008; EPPO, 2014|
|Mexico||Present||USDA-NRCS, 2008; EPPO, 2014|
|-Alabama||Present||Native||Not invasive||USDA-NRCS, 2008|
|-Arkansas||Present||Native||Not invasive||USDA-NRCS, 2008|
|-California||Unconfirmed record||USDA-NRCS, 2008||No confirmed records appear to exist. Potential for confusion with native M. hippuroides|
|-Connecticut||Present, few occurrences||Introduced||1932||Invasive||Les and Mehrhoff, 1999; USDA-NRCS, 2008; EPPO, 2014|
|-Delaware||Present, few occurrences||Native||USDA-NRCS, 2008||Considered native but very rare. Confusion with other species may complicate account of species here|
|-Florida||Widespread||Native||Not invasive||USDA-NRCS, 2008; EPPO, 2014||Widespread throughout state, but not necessarily abundant|
|-Georgia||Present||Native||Not invasive||USDA-NRCS, 2008||Known from locations throughout the state, but not necessarily abundant throughout|
|-Illinois||Present||Not invasive||USDA-NRCS, 2008|
|-Indiana||Present||USDA-NRCS, 2008||Occurs commonly in northern portion of state|
|-Kentucky||Present||USDA-NRCS, 2008||Very rare species of special concern|
|-Louisiana||Widespread||Not invasive||USDA-NRCS, 2008|
|-Maine||Present, few occurrences||Invasive||USDA-NRCS, 2008; EPPO, 2014|
|-Massachusetts||Present||Invasive||USDA-NRCS, 2008; EPPO, 2014||Prohibited plant in this state|
|-New Hampshire||Widespread||Introduced||Invasive||USDA-NRCS, 2008; Thum and Lennon, 2010; EPPO, 2014|
|-New Jersey||Present||USDA-NRCS, 2008||Historical status of species uncertain and may be complicated by confusion with closely-related milfoils, especially M. pinnatum|
|-New York||Present||USDA-NRCS, 2008||Historical status of species uncertain and may be complicated by confusion with closely-related milfoils, especially M. pinnatum|
|-North Carolina||Present||Native||Not invasive||USDA-NRCS, 2008||Occurs along the eastern portion of the state|
|-North Dakota||Present||USDA-NRCS, 2008|
|-Ohio||Present, few occurrences||Native||Not invasive||USDA-NRCS, 2008||Considered endangered|
|-Oklahoma||Localised||Native||Not invasive||USDA-NRCS, 2008||Found in southeastern portion of state|
|-Pennsylvania||Present||USDA-NRCS, 2008||Considered native and endangered to western portion of state. Considered non-native and invasive in eastern portion of state|
|-Rhode Island||Present||USDA-NRCS, 2008|
|-South Carolina||Widespread||Native||Not invasive||USDA-NRCS, 2008||Common in eastern portions of the state|
|-South Dakota||Present||USDA-NRCS, 2008|
|-Tennessee||Present||Native||Not invasive||USDA-NRCS, 2008|
|-Texas||Present||USDA-NRCS, 2008; EPPO, 2014|
|-Vermont||Localised||Introduced||USDA-NRCS, 2008; EPPO, 2014||Discovered in 2008 in a single location, possibly eradicated after discovery|
|-Virginia||Present||Native||Not invasive||USDA-NRCS, 2008|
|-Washington||Present, few occurrences||Invasive||USDA-NRCS, 2008; EPPO, 2014|
|-West Virginia||Present||USDA-NRCS, 2008|
|-Wisconsin||Present||Native||Not invasive||USDA-NRCS, 2008|
Central America and Caribbean
|Austria||Present||Introduced||DAISIE, 2009; EPPO, 2014|
|Belgium||Present||Introduced||DAISIE, 2009; EPPO, 2011; EPPO, 2014|
|France||Present||Introduced||EPPO, 2011; Lebreton, 2013; EPPO, 2014||EPPO Reporting Service No. 2011/180. First found in July 2011|
|Germany||Localised||Introduced||Invasive||Hussner, 2005; EPPO, 2007; EPPO, 2014||First recorded in North Rhine-Westphalia in 1979. Found in eastern Germany since 1960 spreading west|
|Greece||Absent, invalid record||EPPO, 2014|
|Hungary||Absent, unreliable record||EPPO, 2014|
|Netherlands||Present||Introduced||Invasive||EPPO, 2011; Q-bank, 2013; EPPO, 2014|
|Spain||Present||Introduced||Cirujano et al., 1997; EPPO, 2014|
|Sweden||Absent, no pest record||EPPO, 2014|
|UK||Eradicated||Introduced||Stace, 1991; EPPO, 2014|
History of Introduction and SpreadTop of page
Although native to eastern North America, M. heterophyllum is not considered native to northeastern USA. The first recorded observation of the species in northeastern USA was from Bridgeport, CT in 1932. Les and Mehrhoff (1999) presume the original introduction can be attributed to escape from cultivation, with subsequent spread by vegetative propagules escaping cultivation. Recent genetic analyses suggest that M. heterophyllum may have been independently introduced to northeastern USA on several occasions (R Thum, Grand Valley State University, USA, personal communication, 2010).
Very little is known about the history of introduction to western USA. The Washington State Noxious Weed Control Board (2007) claims that only four populations of M. heterophyllum have been found in the state, all within private lakes, while the Aquatic Plant Monitoring project at the University of Washington has 5 locations listed throughout the state of Washington as having M. heterophyllum (see http://www.ecy.wa.gov/programs/eap/lakes/aquaticplants/).
In Europe, M. heterophyllum was first recorded in Germany in the 1960s, but details regarding its introduction and spread are lacking (Hussner, 2005). The species is also reportedly naturalized in Spain (Cirujano et al., 1997). It was first reported from France, in a private pond in Haute-Vienne department, in 2011 (Lebreton, 2013).
M. heterophyllum has also been reported in China (Yu et al., 2002), but details regarding its history and spread are lacking.
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|China||Yu et al. (2002, publ. 2003)||Possibly from USA|
|Connecticut||USA||1932||Escape from confinement or garden escape (pathway cause)||Yes||Les and Mehrhoff (1999)||Has spread throughout northeastern USA|
|Germany||Circa 1960s||Yes||Hussner (2005)||Possibly from USA|
|Spain||Yes||Cirujano et al. (1997)||Possibly from USA|
|Washington||USA||Washington State Noxious Weed Control Board (2007)|
Risk of IntroductionTop of page
M. heterophyllum is a popular plant in the aquarium and water gardening trades and can readily be obtained from any number of aquatic plant vendors under a variety of names. Plants genetically confirmed as M. heterophyllum have been purchased from a variety of vendors under a variety of common names (myrio, foxtail, and parrotfeather) and scientific names of (M. heterophyllum, M. pinnatum, M. tuberculum, M. aquaticum and M. simulans). Once escaped from an aquarium or cultivated pond, M. heterophyllum is capable of spreading through vegetative fragments. As such, it can be moved around by any number of water and animal vectors and may be commonly transported among water bodies on boats and boat trailers. Seeds may also be dispersed by animal vectors.
EPPO (2012) considers M. heterophyllum to have the potential to become invasive across Europe, 'especially in shallow lakes and channels.'
HabitatTop of page
Gerber and Les (1996) found M. heterophyllum to be associated with water bodies that had higher pH and calcium levels relative to other species of milfoils in Michigan and Wisconsin. Thum and Lennon (2010) found M. heterophyllum to be associated with higher order lakes - large, low elevation lakes with relatively high pH, alkalinity and conductivity - in its introduced range in New Hampshire, USA. However, it is not clear whether these relationships hold true across different geographic areas where the species occurs, or among distinct genetic lineages of M. heterophyllum.
Habitat ListTop of page
|Coastal areas||Present, no further details||Harmful (pest or invasive)|
|Coastal areas||Present, no further details||Natural|
|Mud flats||Present, no further details||Harmful (pest or invasive)|
|Mud flats||Present, no further details||Natural|
|Irrigation channels||Present, no further details||Harmful (pest or invasive)|
|Irrigation channels||Present, no further details||Natural|
|Lakes||Principal habitat||Harmful (pest or invasive)|
|Reservoirs||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Natural|
|Ponds||Principal habitat||Harmful (pest or invasive)|
Biology and EcologyTop of page
Reproduction may occur through asexual vegetative propagation and also sexual reproduction (seed production). Asexual vegetative propagation is thought to be the dominant mode of reproduction in introduced populations (e.g. Washington State Noxious Weed Control Board factsheet) (http://www.nwcb.wa.gov/). The emergent flowers are wind-pollinated.
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Means of Movement and DispersalTop of page
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
|Economic/livelihood||Positive and negative|
|Environment (generally)||Positive and negative|
Economic ImpactTop of page
In general, aquatic invasive weeds in the USA cost about $110 million annually (Pimentel et al., 2000). In the specific case of M. heterophyllum, it has been associated with up to a 40% decrease in property values in New Hampshire (Halstead et al., 2003) in addition to costs associated with control.
Environmental ImpactTop of page
M. heterophyllum is highly competitive and able to outcompete other aquatic plants. It forms dense mats of submergent vegetative material throughout the water column and at the water surface, which can prevent water flow, reduce sunlight and reduce oxygen availability. The resulting low oxygen conditions can harm or kill aquatic organisms (EPPO, 2012).
Social ImpactTop of page
M. heterophyllum forms dense stands in water bodies, which have negative effects on boating, swimming and aesthetics.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Highly mobile locally
- Fast growing
- Has high reproductive potential
- Reproduces asexually
- Has high genetic variability
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Monoculture formation
- Negatively impacts animal health
- Negatively impacts livelihoods
- Negatively impacts aquaculture/fisheries
- Negatively impacts tourism
- Reduced amenity values
- Transportation disruption
- Negatively impacts animal/plant collections
- Competition - monopolizing resources
- Competition - shading
- Rapid growth
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
Uses ListTop of page
- Wildlife habitat
- Pet/aquarium trade
Detection and InspectionTop of page
Morphological keys (such as Aiken, 1981) are available but rely mostly on characters of flowers and fruits, which may not be present, as M. heterophyllum rarely flowers. It can best be recognised by its dense underwater growth and undivided, serrate emergent leaves (Q-bank, 2015).
Similarities to Other Species/ConditionsTop of page
M. heterophyllum may be confused with any number of Myriophyllum species. In general, Myriophyllum are distinguished by characters of flowers and fruits, which may not be present. Vegetative material of M. heterophyllum may especially be confused with closely related species M. humile, M. farwelli, M. pinnatum, M. laxum, and M. hippuroides. However, misidentifications with more distantly related species also occur (Aiken, 1981; Thum et al., 2006), especially M. verticillatum.
Genetic identifications using the nuclear ribosomal DNA internal transcribed spacer regions (ITS) have become common (Moody and Les, 2002; Thum et al., 2006). However, further work on the reliability of these markers based on much larger sample sizes is needed.
Prevention and ControlTop of page
Measures include mechanical harvesting, hand harvesting, suction harvesting, blanketing – a large blanket is placed over the population, limiting light and stressing the plants, ‘drawdown’ – water is drawn down in a reservoir area and milfoil beds are exposed to dry substrate, heat, cold, ice, etc. (Massachusetts Department of Conservation and Recreation http://www.mass.gov/dcr/).
Movement control is through inspection of boats and boat trailers on public waterbodies, also signs posted to inform boaters of the risks of transporting milfoil. Wash stations are available at some boat launches to provide a means of ridding milfoil fragments from boats.
Monitoring and Surveillance
ReferencesTop of page
EPPO, 2007. EPPO reporting service no. 2007/085. EPPO reporting service no. 2007/085. Paris, France: European and Mediterranean Plant Protection Organization, unpaginated. http://archives.eppo.org/EPPOReporting/2007/Rse-0704.pdf
EPPO, 2011. EPPO Reporting Service. EPPO Reporting Service. Paris, France: EPPO. http://archives.eppo.org/EPPOReporting/Reporting_Archives.htm
EPPO, 2012. Myriophyllum heterophyllum (Haloragaceae). Invasive Alien Plants. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/INVASIVE_PLANTS/iap_list/Myriophyllum_heterophyllum.htm
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Flora of China Editorial Committee, 2012. Flora of China Web. Cambridge, USA: Harvard University Herbaria. http://flora.huh.harvard.edu/china/
Halstead JM; Michaud J; Hallas-Burt S; Gibbs JP, 2003. Hedonic analysis of effects of a nonnative invader (Myriophyllum heterophyllum) on New Hampshire (USA) lakefront properties. Environmental Management, 32(3):391-398.
Hussner A, 2005. Distribution of alien aquatic plants in the river Erft (North Rhine-Westphalia). (Zur Verbreitung aquatischer Neophyten in der Erft, Nordrhein-Westfalen.) Frankfurter Geobotanische Kolloquie, 19:55-58.
Lebreton A, 2013. Myriophyllum heterophyllum Michaux [Haloragaceae] in Haute-Vienne (Limousin, France), and the situation of this invasive plant in France and in Europe. (Myriophyllum heterophyllum Michaux [Haloragaceae] en Haute-Vienne (Limousin, France), et situation de cette plante invasive en France et en Europe.) Bulletin OEPP/EPPO Bulletin, 43(1):180-192. http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2338
Les DH; Mehrhoff LJ, 1999. Introduction of nonindigenous aquatic vascular plants in Southern New England: a historical perspective. Biological Invasions, 1(2/3):281-300. http://www.springerlink.com/(yqxryu55evlqoi4524ps0d45)/app/home/contribution.asp?referrer=parent&backto=issue,18,19;journal,25,26;linkingpublicationresults,1:103794,1
Q-bank, 2013. Comprehensive databases of quarantine plant pests and diseases. http://www.q-bank.eu/
Stace C, 1991. New Flora of the British Isles. Cambridge, UK: Cambridge University Press.
Thum RA; Lennon JT, 2010. Comparative ecological niche models predict the invasive spread of variable-leaf milfoil (Myriophyllumheterophyllum) and its potential impact on closely related native species. Biological Invasions, 12(1):133-143. http://www.springerlink.com/content/x065475764481jnh/?p=b8eb71c07ab345d1a474d1e523242c58&pi=12
OrganizationsTop of page
Europe: DAISIE - Delivering Alien Invasive Species Inventories for Europe, Web-based service, http://www.europe-aliens.org
France: European and Mediterranean Plant Protection Organisation (EPPO), OEPP/EPPO, 1 rue Le Notre, 75016 Paris, http://www.eppo.org/
USA: MVLMP (Maine Volunteer Lake Monitors), 24 Maple Hill Road, Auburn, ME 04210, http://www.mainevolunteerlakemonitors.org
ContributorsTop of page
01/06/09 Original text by:
Ryan Thum, Grand Valley State University Grand Valley State University, Annis Water Resources Institute, 224 Lake Michigan Center, 740 West Shoreline Drive, Muskegon, MI 49441, 616-331-3989, USA
Matthew Zuelig, Grand Valley State University, Annis Water Resources Institute, 224 Lake Michigan Center, 740 West Shoreline Drive, Muskegon, MI 49441, 616-331-3989, USA
Distribution MapsTop of page
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