pondweed, oxygenweed, yankeeweed
Species commonly cultivated
Elodea canadensis Michx. (North America)
E. nuttallii (Planchon) St. John (North America)
Elodea canadensis is widely distributed on most continents, while E. nuttallii is established in Europe and Asia.
Elodea canadensis is a serious weed in more than 45 countries around the world, where it obstructs waterways and irrigation. This species is prohibited in several countries, including Australia and New Zealand.
Annual or perennial. Stems elongate, some ascending and others stoloniferous and close to substrate, unbranched adventitious roots produced from basal nodes. Leaves in whorls of 3-8, regularly spaced along stem, condensed near apex, sessile; leaf blade linear to obovate; margin entire with fine serrations. Inflorescence axillary; spathe of two united bracts. Flowers unisexual; male flowers solitary, floating on water surface, attached to long threadlike pedicel or abscising; female flowers solitary, subsessile but appearing long-pedicellate, opening at water surface; sepals 3; petals 3 (rudimentary or absent in male flowers). Dispersal by seeds, stem fragments or resting turions.
still waters of lakes, streams, and rivers, especially artificial impoundments