Egeria densa

Brazilian Elodea

BRAZILIAN WATER-WEED, GIANT WATER-WEED, ANACHARIS

NOT NATIVE TO MAINE - INVASIVE

Habitat: Brazilian elodea is found in the submersed plant community. It may grow in substrates of sand, mud or stone to depths of 6.5 meters. A buoyant plant, most of its biomass is produced near the water surface. Infestations of Brazilian elodea may occur in large dense rooted stands and drifting mats.

Description: Brazilian elodea is a rooted, submersed perennial with bright green leaves, densely arranged in whorls of 4 to 6 leaves on slender, brittle stems. (Note: the lower leaves may be opposite or in whorls of 3 leaves.) The leaves are finely-toothed (teeth seen with magnification only), strap-shaped with a pointed tip, 1 to 3 cm long, and up to 5mm wide. (Having more than 3 leaves per whorl, and leaves more than 1 cm in length help to distinguish this plant from Maine’s native waterweeds.) Branches form irregularly along the stems in areas where two whorls appear to be joined (known as “double nodes”). The small flowers (averaging 2 cm in diameter) have three white petals and a yellow center, and emerge just above or at the surface on slender stalks projecting from leaf axils near the stem tips. The slender roots are pale and un-branched. Unlike hydrilla, Brazilian elodea does not produce tubers.

Origin and Range: Brazilian elodea is native to South America. It has been widely distributed in the US (usually under the name “anacharis”) as an aquarium plant and a “beneficial” oxygenator for water nurseries. Brazilian elodea is currently present many parts of the US including the nearby states of New Hampshire, Massachusetts, Vermont and New York.

Annual Cycle: Brazilian elodea prefers moderate water temperatures, therefore optimum growth occurs in the spring and fall. During the summer and winter, growth may slow, or cease completely. When water temperatures become extreme, plants will die back to the roots. Areas on the stems known as “double nodes” play an important role in food storage and reproduction. Adventitious roots and branches are both produced from double nodes on the stem. If a Brazilian elodea fragment does not have a double node, it can not grow into a new plant. Regeneration of plant fragments containing a double node is the only means for reproduction. Only male flowers are present on plants found in the US, therefore no seeds are produced.

Impacts: Infestations of Brazilian elodea reduce the abundance and diversity of native plants and may cause a decline in water quality. Dense stands restrict water movement and trap sediments, and may alter the natural bathymetry, storage capacity of the waterbody. Dense beds also interfere with navigation and traditional recreational uses.

Look Alikes: May be confused with hydrilla, American waterweed, slender waterweed, common water starwort and mare's tail.