Life Cycle: Submerged aquatic perennial
Leaves: Leaves are bright green, sessile, whorled, and occur in groups of 3-6. Upper leaves are 15-40 mm in length and 2-5 mm in width. Lower leaves are opposite and scale-like.
Flower: White, glossy, and wrinkled flowers emerge on the surface to 1.5 inches from the water. Flowers have three petals.
Stems: Like the leaves, stems are bright green in color. They can easily break off and can root on nodes.
Found in: Submerged in water generally 1-2 meters deep, particular to warmer waters but will overwinter.
Native to: Brazil, Argentina, and Uruguay
Prevention: Often these plants are introduced when contents of aquariums are not disposed of properly. Always dispose of aquarium items in a sealed bag. Once established, it spreads easily through fragmentation, so it is important to clean, drain, dry boats, waders, boots, and all angling gear before entering another water body.
Impacts: Creates dense mats that make recreating more difficult. These mats can also clog water intakes, allows the plant to outcompete native aquatic vegetation, and alters habitat. Contributes to reduced water quality through surplus of nutrients and oxygen uptake.
Native lookalikes: American waterweed (Elodea canadensis), can distinguish between the two because Elodea canadensis has dark spots on leaves, and leaves are longer and less wide.
In Montana: Not present in Montana.
Sources: COC AIS book, http://www.invadingspecies.com/brazilian-elodea/, http://fieldguide.mt.gov/speciesDetail.aspx?elcode=PMHYD02010#:~:text=Brazilian%20Waterweed%20is%20native%20to,(DiTomaso%20and%20Healy%202003).
For Map Building:
In Montana: not present
States in US: Puerto Rico, Alabama, Arizona, Arkansas, California, Connecticut, Delaware, Florida, Georgia, Hawaii, Illinois, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Mississippi, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Utah, Vermont, Virginia, and Washington.
Source: USFWS, 2018: fws.gov
Hand pulling: Removal by hand or other mechanism is not recommended as it can cause further growth and spread fragments to reproduce. Removing and destroying any fragments of the plant off boats or other exposed equipment can prevent the spread.
Mechanical: Diver assisted dredging of small infestations (<2 acres) can be effective. Bottom barriers can be utilized to prevent the growth in a small area. Barriers need to be cleaned often to prevent any growth on the sedimentation that occurs on top of the barrier. In sparse populations, dewatering (drawdown) in the fall can be effective at killing plants that are exposed to the cold temperatures.
Biological control: Grass Carp (Ctenopharyngodon Idella) has been used to control Brazilian waterweed in other states; however, it is not a biological control option in Montana.
King County Noxious Weed Control Program