Canadian Waterweed

Canadian Waterweed Plant Information

Canadian Waterweed grows in the following 47 states:

Alaska, Arizona, Colorado, Connecticut, District Of Columbia, Idaho, Illinois, Indiana, Kansas, Kentucky, Maryland, Minnesota, Mississippi, Montana, Nebraska, New Hampshire, New Mexico, North Carolina, Oklahoma, Pennsylvania, South Carolina, South Dakota, Utah, Vermont, Wisconsin, Wyoming, Oregon, West Virginia, Alabama, Arkansas, California, Delaware, Florida, Iowa, Maine, Massachusetts, Michigan, Missouri, Nevada, New Jersey, New York, North Dakota, Ohio, Rhode Island, Tennessee, Virginia, Washington

Elodea canadensis (American or Canadian Waterweed or Pondweed) is a perennial aquatic plant, or submergent macrophyte, native to most of North America. It has been introduced widely to regions outside its native range and was first recorded from the British Isles in about 1836.

Native to most of North America. Widely introduced to regions outside its native range such as Ireland and the British Isles (female plants only).
Ireland: County Galway found at several sites along the Eglinton Canal, County Galway County Down. and from the Lagan Canal near Lisburn, Ireland.
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 are bright green, translucent, oblong, 6-17mm long and 1-4mm broad, borne in whorls of three (rarely two or four) round the stem. It lives entirely underwater, the only exception being the small white or pale purple flowers which float at the surface and are attached to the plant by delicate stalks.
It is dioecious, with male and female flowers on different plants. The flowers have three small white petals; male flowers have 4.5-5mm petals and nine stamens, female flowers have 2-3mm petals and three fused carpels. The fruit is an ovoid capsule, about 6mm long containing several seeds that ripen underwater. The seeds are 4-5mm long, fusiform, glabrous (round), and narrowly cylindrical. It flowers from May to October.
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 10-25C and moderate to bright lighting.
It is closely related to Elodea nuttallii, which generally has narrower leaves under 2mm broad. It is usually fairly easy to distinguish from its relatives, like the Brazilian Egeria densa and Hydrilla verticillata. These all have leaves in whorls around the stem; 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.
It is frequently used as an aquarium plant. Propagation is by cuttings.
It is an invasive species in Europe, Asia, Africa, and Australia. It was introduced into County Down, Ireland in about 1836, and appeared in Great Britain in 1841, spreading through both countries in ponds, ditches and streams, which were often choked with its rank growth.
Other common names for this plant include Anacharis (an older name for the genus Elodea), water thyme, common elodea, and ditch moss.
This articleincorporates text from a publication now in the public domain:Chisholm, Hugh, ed. (1911). "article name needed". Encyclopdia Britannica (11th ed.). Cambridge University Press.

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