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:  
Scientific Name:

Common Name:Slender Pondweed

Scientific Name:Potamogeton pusillus

Native or Non-native:Native

Illustration:Slender Pondweed collage

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Slender pondweed grows in fresh to slightly brackish water. It grows in soft, fertile mud substrates and quiet to gently flowing water. Slender pondweed occurs in many ponds, lakes and both tidal and non-tidal waters in the Mid-Atlantic.

The leaves of slender pondweed are fine, narrow, linear and grass-like, and are arranged alternately on slender, branching stems. Leaf blades of slender pondweed are entire and have pointed tips and can have a purplish tint. The leaf bases are free of stipules and usually contain two small translucent glands. Slender pondweed has a root-rhizome system.

Ecological Significance:
Like all other pondweeds, slender pondweed is considered an important food for waterfowl. It's ability to colonize a wide range of habitats make it one of the more common species in Maryland. Slender pondweed is also a good habitat for fish.

Similar Species:
Slender pondweed is similar in appearance to sago pondweed (Stuckenia pectinata), widgeon grass (Ruppia maritima) and horned pondweed (Zannichellia palustris). However, slender pondweed only overlaps in distribution with horned pondweed. Slender pondweed has slightly wider and longer leaves.

Slender pondweed reproduces asexually and sexually. Asexual reproduction is by buds, which are dense aggregations of leaves that eventually drop off and over-winter to form new plants in spring. Smooth-leaved winter buds form axillary along branches and at terminal ends of stems. Sexual reproduction is by late summer flowering. These flowers occur in whorls of 3 to 5 on terminal or axillary spikes. Fertilization takes place underwater, producing smooth seeds with rounded backs.

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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