Brazilian Elodea (Egeria densa) (also called Brazilian Waterweed, Anacharis)

Leafy stalk of the Brazilian elodea with a small, white flower
Photo from the Wisconsin DNR.

Description

Appearance

Brazilian elodea is a submersed aquatic plant that can be rooted or free floating. This green plant has a bottle-brush appearance and can grow nine to 15 feet tall. Upon reaching the surface of the water, the leafy branches create dense mats.

Leaves and Stem

Leaves are approximately one inch long and a quarter-inch wide. They’re arranged in whorls (multiple leaves radiating from a single node) of four to six around the stem, and have very small “toothed” or serrated edges that require a magnifying glass to see. Stems will grow until they reach the surface of the water, up to 15 feet tall.

Flowers

Flowers are small, about one inch wide, and white with three petals. They grow on short stalks above the water, and bloom in spring and summer.

Roots

Roots are slender, and white or pale in color. It produces adventitious roots (arising from a part of the plant other than the root) from multiple places on the stem.

Biology

Brazilian elodea is a perennial plant. Native populations contain both male and female plants, however only male plants have been reported in the United States. No seeds are produced in United States populations. It spreads primarily by vegetative fragmentation—a small piece of the stem breaks off from the parent colony and disperses. Stem fragments can take root, or grow as free-floating mats. The plant can overwinter as dormant shoots or semi-dormant shoots until temperatures are ideal for growth.

Origin and Spread

Brazilian elodea is native to South America. It is commonly imported and sold by the aquarium and water garden trades (often sold as “Anacharis”), leading to the potential for illegal release into the wild. The first report of Brazilian elodea in the United States was in New York in 1893. The species is most prevalent in the southern and eastern United States, with few established populations in the Midwest. The only known Minnesota infestation was discovered in 2007, in Powderhorn Lake (Hennepin County), but was successful eradicated. No known infestations exist in Minnesota today. Refer to the infested waters list for current distribution.

Don't be fooled by these look-alikes

Brazilian elodea looks similar to many native, beneficial aquatic plants found in Minnesota lakes and rivers, but can be distinguished based on the number of leaves and the leaf structure.

Look-alikes:

 

Regulatory Classification

Brazilian elodea (Egeria densa) is a regulated invasive species in Minnesota, which means it is legal to possess, sell, buy and transport, but it may not be introduced into a free-living state, such as being released or planted in public waters.

 

Threat to Minnesota Waters

Invasive species cause recreational, economic and ecological damage—changing how residents and visitors use and enjoy Minnesota waters.

Brazilian elodea impacts:

  • Dense mats at the water’s surface inhibit water recreationists.
  • Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
  • Provides unsuitable shelter, food, and nesting habitat for native animals.

 

What you should do

People spread Brazilian elodea primarily through the illegal release of aquarium or water garden plants into public waters. To avoid spreading Brazilian elodea and other ornamental plants, build water gardens away from public waters and areas prone to flooding. Inspect and rinse aquatic plants to remove seeds, snails, and other hitchhikers. Do not dispose of unwanted aquatic plants or animals in or near public waters. Refer to Habitattitude for alternatives to release.

Whether or not a lake is listed as infested, Minnesota law requires water recreationists to:

  • Clean watercraft of all aquatic plants and prohibited invasive species.
  • Drain all water by removing drain plugs and keeping them out during transport.
  • Dispose of unwanted bait in the trash.
  • Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.

Report new occurrences of Brazilian elodea to the DNR immediately by contacting your DNR Invasive Species Specialist or log in and submit a report through EDDMapS Midwest.

 

Control Methods

Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit from the DNR. Talk to a DNR specialist for more information.

Mechanical control can be done by cutting or pulling the plant by hand or with equipment such as rakes or cutting blades. Take care to remove all plant fragments to prevent fragmentation.

Herbicide control can be done using fluridone. Endothall and diquat have also been successful in combination with some copper compounds.

 

Resources