''Elodea canadensis'' (American waterweed or Canadian waterweed or pondweed) is a
perennial
In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
aquatic plant
Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...
, or submergent
macrophyte
Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...
, native to most of
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
.
[Flora of North America]
''Elodea canadensis''
/ref>[Plants of British Columbia]
''Elodea canadensis''
[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 an archipelago in the Atlantic Ocean, 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 Hebrides, Inner and Outer Hebr ...
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 ( ; , ) is a City status in Ireland, city in (and the county town of) County Galway. It lies on the River Corrib between Lough Corrib and Galway Bay. It is the most populous settlement in the province of Connacht, the List of settleme ...
, 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 t ...
, Northern Ireland
Northern Ireland ( ; ) is a Countries of the United Kingdom, part of the United Kingdom in the north-east of the island of Ireland. It has been #Descriptions, variously described as a country, province or region. Northern Ireland shares Repub ...
.
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 (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
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
Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s which float at the surface and are attached to the plant by delicate stalks.These stalks, or hypanthia, 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 one article, this ratio can sometimes be as much as ''one thousand fold,'' dioecious
Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...
, 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
The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the filamen ...
, female flowers have 2–3 mm petals and three fused carpel
Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more ...
s. The fruit
In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering.
Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...
is an ovoid capsule, about 6 mm long containing several seed
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s that ripen underwater. The seeds are 4–5 mm long, spindle-shaped and smooth. 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 light levels.stem
Stem or STEM most commonly refers to:
* Plant stem, a structural axis of a vascular plant
* Stem group
* Science, technology, engineering, and mathematics
Stem or STEM can also refer to:
Language and writing
* Word stem, part of a word respon ...
; however, ''Elodea'' usually has three leaves per whorl, whereas ''Egeria'' and ''Hydrilla'' usually have four or more. ''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 (: 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. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...
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 is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
in Europe
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
, Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
, Africa
Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
, and Oceania
Oceania ( , ) is a region, geographical region including Australasia, Melanesia, Micronesia, and Polynesia. Outside of the English-speaking world, Oceania is generally considered a continent, while Mainland Australia is regarded as its co ...
. 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 552,261. 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 north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...
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:Canadian Pond Weed Leaf Tip.jpg, Close up image of the leaf tip
References
{{Taxonbar, from=Q159760
Hydrocharitaceae
Freshwater plants
Flora of Northern America
Plants described in 1803
Dioecious plants
Taxa named by André Michaux