''Elodea canadensis'' (American waterweed or Canadian waterweed or pondweed) is a
perennial
A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...
aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...
, or submergent
macrophyte, native to most of
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
.
[Flora of North America]
''Elodea canadensis''
/ref>[Plants of British Columbia]
''Elodea canadensis''
/ref>[Jepson Flora]
''Elodea canadensis''
/ref> It has been introduced widely to regions outside its native range and was first recorded from the British Isles
The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...
in about 1836.
Distribution
The native range of the species lies within North America, but it has been introduced in many parts of the world either intentionally or not. Europe has been particularly affected with the first record dating back as far as 1836. Since then, the species' presence has been confirmed in all continental European countries.
Records of the species' presence in Ireland include: County Galway
Galway ( ; ga, Gaillimh, ) is a City status in Ireland, city in the West Region, Ireland, West of Ireland, in the Provinces of Ireland, province of Connacht, which is the county town of County Galway. It lies on the River Corrib between Lo ...
, found at several sites along the Eglinton Canal, County Galway,
County Down. and from the Lagan Canal near Lisburn
Lisburn (; ) is a city in Northern Ireland. It is southwest of Belfast city centre, on the River Lagan, which forms the boundary between County Antrim and County Down. First laid out in the 17th century by English and Welsh settlers, with ...
, Northern Ireland
Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
.
Description
Young plants initially start with a seedling stem with roots growing in mud at the bottom of the water; further adventitious roots are produced at intervals along the stem, which may hang free in the water or anchor into the bottom. It grows indefinitely at the stem tips, and single specimens may reach lengths of 3 m or more.
The leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are bright green, translucent, oblong, 6–17 mm long and 1–4 mm broad, borne in whorls of three (rarely two or four) round the stem.flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s which float at the surface and are attached to the plant by delicate stalks.These stalks, or hypanthea, are the lower part of the petals joined to form a floral tube. This floral tube can be up to 30 centimeters (12 inches) in length while only 1/25 inch (one millimeter) in width. for a length to width ratio of 300 fold. However, according to Wilie this ratio can sometimes be as much as ''one thousand fold,'' dioecious
Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
, with male and female flowers on different plants. The flowers have three small white petals; male flowers have 4.5–5 mm petals and nine stamens, female flowers have 2–3 mm petals and three fused carpels. The fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
is an ovoid capsule, about 6 mm long containing several seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s that ripen underwater. The seeds are 4–5 mm long, fusiform, glabrous (round), and narrowly cylindrical. It flowers from May to October.[Huxley, A., ed. (1992). ''New RHS Dictionary of Gardening''. Macmillan .]
It grows rapidly in favorable conditions and can choke shallow ponds, canals, and the margins of some slow-flowing rivers. It requires summer water temperatures of 10–25 °C and moderate to bright lighting.Elodea nuttallii
''Elodea nuttallii'' is a species of waterweed known by the common name western waterweed or Nuttall's waterweed. This is a perennial aquatic plant which is native to North America where it grows submersed in lakes, rivers, and other shallow wat ...
'', which generally has narrower leaves under 2 mm broad. It is usually fairly easy to distinguish from its relatives, like the Brazilian ''Egeria densa
''Egeria densa'', the large-flowered waterweed or Brazilian waterweed, is a species of '' Egeria'' native to warm temperate South America in southeastern Brazil, Argentina, Chile and Uruguay. It is considered a problematic invasive species due t ...
'' and ''Hydrilla verticillata
''Hydrilla'' (waterthyme) is a genus of aquatic plant, usually treated as containing just one species, ''Hydrilla verticillata'', though some botanists divide it into several species. It is native to the cool and warm waters of the Old World in ...
''. These all have leaves in whorls around the stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
; however, ''Elodea'' usually has three leaves per whorl, whereas ''Egeria'' and ''Hydrilla'' usually have four or more leaves per whorl. ''Egeria densa'' is also a larger, bushier plant with longer leaves.[Native Freshwater Plants]
American Waterweed
Cultivation and uses
It is frequently used as an aquarium
An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...
plant. Propagation is by cuttings.[Hiscock, P. (2003). ''Encyclopedia of Aquarium Plants'' Interpret Publishing, United States and Canada .]
It is an invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
in Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, and Oceania
Oceania (, , ) is a region, geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern Hemisphere, Eastern and Western Hemisphere, Western hemispheres, Oceania is estimated to have a land area of ...
. It was introduced into County Down
County Down () is one of the six counties of Northern Ireland, one of the nine counties of Ulster and one of the traditional thirty-two counties of Ireland. It covers an area of and has a population of 531,665. It borders County Antrim to the ...
, Ireland in about 1836, and appeared in Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
in 1841, spreading through both countries in ponds, ditches and streams, which were often choked with its rank growth.[Flora of NW Europe]
''Elodea canadensis''
Other common names for this plant include ''Anacharis'' (an older name for the genus ''Elodea''), water thyme, common elodea, and ditch moss.
Gallery
Image:ElodeaCanadensisFlowering.jpg, Ditch with a dense colony of flowering plants
Image:Elodea canadensis nf.jpg, Illustration showing leaf and flower detail
Image:ElodeaLeaffaceupcells.jpg, Leaf cells at 450x magnification
References
{{Taxonbar, from=Q159760
Hydrocharitaceae
Freshwater plants
Flora of North America
Plants described in 1803
Dioecious plants