Brazilian Elodea is actually not in the genus Elodea, which
gave it the common name. Instead its in the genus Egeria, which
is closely related. Its native to south america and has been indroduced
to the United states and become a problem plant. It is known in the Aquairum
plant industry as "Anacharis."
In fact, its one of the most common aquarium plants in use today.
Brazilian Elodea is generally more of a problem in the northern US than
it is in the south. This is of course, speaking relative to its more invasive
densa is a plant that looks very similar to three other invasive
plants - Hydrilla verticillata and
Elodea canadensis. There are however
some easy ways to tell the difference. First of all, Egeria has the largest
leaves of any of them, growing up to 1/2 inch in diameter and 3/4 to 5/4
inches long. Unlike Elodea, which is much smaller and has whorls of 3
(rarely 4), Egeria has whorls of from 4-6, but never 3. Hydrilla usually
has whorls of 5. Finally, while Elodea and Egeria have smooth leaves,
Hydrilla's feels rough to the touch. This is because there are small teeth
on the midrib. With this information, you should be able to distinguish
these three major noxious aquatic plants.
Brazillian Elodea does not handle the hot summers of the south as well
as Hydrilla. Because of this, it is not nearly as problematic a species
as Hydrilla or Egeria.