Complete name: Elodea canadensis Michaux 1803
Taxonomy: Magnoliophyta » Magnoliophyta » Liliopsida » Alismatales » Hydrocharitaceae » Elodea canadensis
Authors: Stephan Gollasch
Last updated: October 30th, 2006

Canadian waterweed, Canada waterweed, Canadian pondweed, Canadian water pest, American waterweed, broad waterweed, common waterweed, water-thyme, oxygen weed.

Anacharis alsinastrum Bab.
Anacharis canadensis (Michx.) Planch.
Anacharis planchonii (Caspary) Rydb.
Anacharis pomeranica (Rchb.) Peterm.
Elodea brandegeeae St. John
Elodea canadensis Michx.
Elodea ioensis Wylie
Elodea latifolia Caspary
Elodea linearis (Rydb.) St. John
Elodea oblongifolia Michx. ex Caspary
Elodea planchonii Caspary
Helodea canadensis Reichb.
Philotria canadensis (Michx.) Britt.
Philotria linearis Rydberg
Philotria planchonii (Caspary) Rydb.
Serpicula verticillata Rostk. & Schmidt

It is an aquatic herb with branching stems 20-30 cm long, which tends to form dense monospecific stands that can cover hundreds of acres. Leaves are oblong-linear in groups of three. Flowers are white or pale purple appear at the water surface. Fruits are capsules less than 1 cm in length.

• Dispersal Mechanisms
  • Dispersed by seeds and fragments via water currents.
• Reproduction
  • It is a dioecious plant flowering from June to August. Pollination occurs near the water surface and pollen is distributed by wind and water currents. Vegetative reproduction by fragments is very common. Mass development has been reported multiple times in the last century.
• Known Predators/Herbivores
  • Preyed upon by a high number of freshwater organisms including fish and birds.
• Resistant Stages (seeds, spores etc.)
  • Unknown.

• Native (EUNIS Code)
  • C1: Surface standing waters, C2: Surface running waters) Shallow lakes, ponds, pools, ditches and streams with slow moving water.
• Habitat Occupied in Invaded Range (EUNIS Code)
  • Surface standing waters, C2: Surface running waters). Shallow lakes, ponds, pools, ditches and streams with slow moving water, up to 3 m water depth. In exceptional cases up to 16 m in depth.
• Habitat Requirements
  • Tolerates pH values from 6.0 to 7.5 and temperatures from 1 to 25 °C.

Accidental release after intentional import for ornamental purposes in aquaria and ponds.

• Native Range
  • North American inland waters.
• Known Introduced Range
  • The first European record was reported from Ireland in 1836. It subsequently became widespread in north and central European countries.
• Trend
  • After a rapid colonization of northern Europe the populations declined due to the introduction of Elodea nuttallii. Today the population is stable.

known distribution area (in CGRS grid squares; in countries; along coast)

	eradicated
	extinct
	not present; eradicated
	native distribution range in CGRS grid squares
	native range
	assumed native range
	infrequent distribution
	key distribution area
	not established

• Ecosystem Impact
  • As it can be very dominant, it competes for nutrients and space with other plants. It can bioaccumulate nutrients and modify the habitat by reducing water movement. The species is known to outcompete other plants.
• Health and Social Impact
  • Unknown.
• Economic Impact
  • During dense blooms, impairs boating, fishing, swimming, and water skiing. Clogging of water intake pipes of power plants and other industries were reported.

• Prevention
  • Should not be released in the wild.
• Mechanical
  • Covering the plants to block light may result in eradication. In reservoirs and lake systems the water level may be lowered in winter with the aim of controlling the population. The success is related to the degree of desiccation, air temperature (at best freezing conditions after drainage), and the presence of snow. As the plant spreads through fragmentation, mechanical controls should only be undertaken during mass developments and when the risk of spread to other water systems is minimal. Using mechanical controls during an ongoing invasion may promote the spread due to fragmentation.
• Chemical
  • Trials were undertaken by using various chemical formulations, such as complexed copper, dipotassium salt and fluridone.
• Biological
  • Recently a fungus (Fusarium sp.) was identified which damaged Elodea in laboratory tests. The enhancement of native or introduced herbivorous fish may pose another biocontrol option. Carp prey upon E. canadensis. However, a risk remains, as most biocontrol species do not selectively prey upon the invader only.

The following contributors have provided records in the DAISIE database for this species.

The following experts registered themselves as having knowledge about this species or its family.

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Bowmer KH, Jacobs SWL, Sainty GR (1995) Indentification, Biology and Management of Elodea canadensis, Hydrocharitaceae. Journal of Aquatic Plant Management 33:13-19

Casper SJ, Krausch HD (1980) Süßwasserflora von Mitteleuropa, Pteridophyta und Anthophyta, 1. Teil. Band 23, Gustav Fischer Verlag, Stuttgart, pp 403

Spicer KW, Catling PM (1988) The biology of Canadian weeds. 88. Elodea canadensis Michx. Canadian Journal of Plant Sciences 68:1035-1051

Catling PM, Wojtas W (1986) The waterweeds (Elodea and Egeria, Hydrocharitaceae) in Canada. Canadian Journal of Botany 64:1525-1541

Cook CDK, Urmi-König K (1985) A revision of the genus Elodea (Hydrocharitaceae). Aquatic Botany 21:111-156

De Winton MD, Clayton JS (1996) The impact of invasive submerged weed species on seed banks in lake sediments. Aquatic Botany 53(1-2):31-45

Denys L, Packet J, Van Landuyt W (2004) Neofyten in het Vlaamse water: signalement van vaste waarden en rijzende sterren. Natuur focus 3(4):120-128

James CS, Eaton JW, Hardwick K (1999) Competition between three submerged macrophytes, Elodea canadensis Michx, Elodea nuttallii (Planch.) St. John and Lagarosiphon major (Ridl.) Moss. Hydrobiologia 415:35-40

Josefsson M, Andersson B (2001) The Environmental Consequences of Alien Species in the Swedish Lakes Malaren, Hjalmaren, Vanern and Vattern. Ambio 30(8):514-521

Kahkonen MA, Pantsar-Kallio M, Manninen PKG (1998) Analysing heavy metal concentrations in the different parts of Elodea canadensis and surface sediment with pca in two boreal lakes in Southern Finland. Chemosphere 35(11):2645-2656

Karjalainen H, Stefansdottir G, Tuominen L, Kairesalo T (2001) Do submersed plants enhance microbial activity in sediment? Aquatic Botany 69(1):1-13

Kleiven E, Dolmen D (1999) Vasspest Elodea canadensis Michx i Molandsvatnet, Arendal. Elodea canadensis Michx in Molandsvatnet, Arendal, South Norway. Blyttia 57:117-119

Kohler A (1995) Neophyten in Fließgewässern - Beispiele aus Süddeutschland und dem Elsaß. Schriftenreihe für Vegetationskunde (Sukopp-Festschrift) 27:405-412

Kohler A, Sipos V, Sonntag E, Penksza K, Pozzi D, Veit U, Björk S (2000) Makrophyten-Verbreitung und Standortqualität im eutrophen Björka-Kävlinge-Fluss (Skane, Südschweden). Limnologica 30:281-298

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Kozhova OM, Izhboldina LA (1993) Spread of Elodea canadensis in Lake Baikal. Hydrobiologia 259:203-211

Luther H (1951) Verbreitung und Ökologie der hoheren Wasserpflanzen im Brackwasser der Ekenas-Gegend in Südfinnland. II. Spezieller Teil. Acta Bot. Fenn. 50:1-370

Mal TK, Adorjan P, Corbett AL (2002) Effect of copper on growth of an aquatic macrophyte, Elodea canadensis. Environmental Pollution 120(2):307-311

Ozimek T, van Donk E, Gulati RD (1993) Growth and nutrient uptake by two species of Elodea in experimental conditions and their role in nutrient accumulation in a macrophyte-dominated lake. Hydrobiologia 251:13-18

Preston CD, Pearman DA, Dines TD (2001) New Atlas of the British and Irish Flora Oxford University Press

Riis T, Sand-Jensen K, Vestergaard O (2000) Plant communities in lowland Danish streams: species composition and environmental factors. Aquatic Botany 66(4):255-272

Roerslett B, Berge D, Johansen SW (1984) Mass invasion of Elodea canadensis in a mesotrophic, South Norwegian lake - impact on water quality. Proceedings of the Congres of International Association of Theoretical and Applied Limnology 22 (2):2920-2926

Roerslett B, Berge D, Johansen SW (1986) Lake enrichment by submersed macrophytes: A Norwegian whole-lake experience with Elodea canadensis. Aquatic Botany 26(3-4):325-340

Seehaus A (1992) Die Ausbreitung von Elodea nuttallii (Planch.) St. John in der Leinaue südlich von Hannover im Zeitraum von 1973 bis 1991. Floristische Rundbriefe 26(2):72-78

Simpson DA (1990) Displacement of Elodea canadensis Michx. by Elodea nuttallii (Planch.) St. John in the British Isles. Watsonia 18:173-177

Slynko YV, Koreneva JG, Rivier IK, Papchenkov VG, Scherbina GH, Orlova MI, Therriault TW (2002) The Caspian-Volga-Baltic invasion corridor. In: Leppakoski, E, Gollasch S, Olenin S (eds) Invasive Aquatic species of Europe - distribution impacts and management. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp 399-411

Tremp H (2001) Standörtliche Differenzierung der Vorkommen von Elodea canadensis Michx. und Elodea nuttallii (Planch.) St. John in Gewässern der badischen Oberrheinebene. Berichte des Instituts für Landschafts- und Pflanzenökologie 10:19-32

Van de Weyer K, Wahrenburg P, Wiegleb G (1990) Die Makrophytenvegetation im Einzugsgebiet der Ruhr. 1. Die Fließgewässervegetation und ihre Bedeutung für Naturschutz und Landschaftspflege. Decheniana 143:141-159

Vöge M (1980) Elodea nuttallii (Planch.) St. John im Öjendorfer See in Hamburg. Kieler Notizen 12:7

Wallentinus I (2002) Introduced marine algae and vascular plants in European aquatic environments. In: Leppakoski E, Gollasch S, Olenin S (eds) Invasive Aquatic species of Europe - distribution impacts and management. Kluwer Academic Publishers, Dordrecht, The Netherlands. ppm 27-52

Weber-Oldecop DW (1977) Elodea nuttallii (Planch.) St. John, eine neue limnische Phanerogame der deutschen Flora. Archiv für Hydrobiologie 79:397-403

Weidema IR (2000) Introduced species in the nordic countries. Nordic Council of Ministsers, Copenhagenm. Nord 13, pp 242

Wells RD, de Winton MD, Clayton JS (1997) Successive macrophyte invasions within the submerged flora of Lake Tarawera, Central North Island, New Zealand. New Zealand Journal of Marine and Freshwater Research 31:449-459

Wolff P (1980) Die Hydrillae (Hydrocharitaceae) in Europa. Göttinger Floristische Rundbriefe 14:33-56