Elodea is a genus of aquatic plants often called the water weeds. Elodea is native to North America and it is also widely used as aquarium vegetation. The introduction of some species of Elodea into waterways in parts of Europe, Australia, Africa, Asia, and New Zealand has created a significant problem, and it is now considered a noxious weed in these areas.
Elodea canadensis, sometimes called American or Canadian water weed/pond weed is widely known as the generic water weed. The use of these names causes it to be confused with similar-looking plants, like Brazilian elodea (Egeria densa) or hydrilla (Hydrilla verticillata). American water weed is an attractive aquarium plant, and is a good substitute for Brazilian elodea. It can be used for science experiments in classrooms as it can show how plants use carbon dioxide with the usage of bromothymol blue(BTB).
The American water weed lives entirely underwater with the exception of small white flowers which bloom at the surface and are attached to the plant by delicate stalks. It produces winter buds from the stem tips that overwinter on the lake bottom. It also often overwinters as an evergreen plant in mild climates. In the fall, leafy stalks will detach from the parent plant, float away, root, and start new plants. This is the American water weed's most important method of spreading, with seed production playing a relatively minor role.
Silty sediments and water rich in nutrients favor the growth of American water weed in nutrient-rich lakes. However, the plant will grow in a wide range of conditions, from very shallow to deep water, and in many sediment types. It can even continue to grow unrooted, as floating fragments. It is found throughout temperate North America, where it is one of the most common aquatic plants.
American water weed is an important part of lake ecosystems. It provides good habitat for many aquatic invertebrates and cover for young fish and amphibians. Waterfowl, especially ducks, as well as beaver and muskrat eat this plant. Also, it is of economic importance as an attractive and easy to keep aquarium plant. It was used as a drug by the Iroquois. The first written record of the Elodea in North America was in 1745 in Le Folklore Botanique De Caughnawaga and was written by Jacques Rousseau.