Submerged Aquatic Vegetation (SAV) Identification Key

​​The bay grass key was designed to allow you to identify most species of bay grasses found in Maryland. Although bay grasses are notoriously difficult to identify using standard taxonomic keys, the flexible format of the Internet allows us to combine detailed pictures, simple line drawings and text messages in a stepwise sequence that makes identifying bay grasses simple. You may find it useful to have a clear metric ruler with millimeters marked, a magnifying glass, and a Ziploc plastic bag to help you in the process of identifying your plant.

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Common Name:  
or
Scientific Name:



Common Name:South American Elodea

Scientific Name:Elodea densa

Native or Non-native:Non-native


Illustration:


Link to larger illustration:

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Family:Hydrocharitaceae

Distribution:
South American Elodea (Egeria Densa) is an invasive submerged aquatic plant that originally came from South America, and is often referred to as Brazilian Waterweed. This aquatic plant is now found throughout the United States due to its potential for fast growth and rapid spreading. It is a freshwater plant that can grow in lakes, ponds, streams, and ditches. It is not common in Maryland but it is known from a few locations.

Recognition:
South American Elodea is a rooted plant with a many-branched stem. It has many leaves, which are longer than they are wide. The leaves have finely toothed margins and are grouped in whorls of ~4. The stem and leaves are bright green, and the many branches of the plant gives it a bushy appearance.

Ecological Significance:
Since it can grow and spread at such a high rate, South American Elodea can end up displacing native species and taking over areas, which lowers biodiversity and can have negative effects on the ecology. Another issue that it can cause is that if too much of the plant grows in one stream it can change the flow of the water which also can impact the ecology inside and around that stream.

Similar Species:
South American Elodea is easily confused with Hydrilla and Common Waterweed because they all have whorled, green leaves with a somewhat bushy appearance. The easiest way to tell the difference between these plants is the amount of leaves per whorl, as South American Elodea usually has four while Hydrilla has 5 and Common Waterweed generally has 3.

Reproduction:
The main method of reproduction for the plant is vegetative, meaning that new plants can grow from broken off fragments of another plant. Even though the plant does have male and female flowers, there have been no recorded cases of seed germination in the United States, and the only way the plant has been seen to reproduce has been through vegetative reproduction.



Print out a complete version of the key in PDF format (Adobe Acrobat file 18MB)

For permission to reproduce individual photos, please contact Mike Naylor

The text and photos used in this key were produced through a collaborative effort among the following partners.

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