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:Water Stargrass

Scientific Name:Heteranthera dubia

Native or Non-native:Native

Illustration:Links to Water Stargrass collage

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Water stargrass can be found in non-tidal freshwater areas of tributaries, and in streams, lakes and ponds. Water stargrass is found in many parts of Chesapeake Bay as well as in some rivers and reservoirs. It grows primarily in clay or calcareous soils, but also in gravel streams and rivers. Water stargrass can tolerate moderately eutrophic waters. A terrestrial form of water stargrass with waxy cuticle can also be found when low water levels strand plants on shore.

Water stargrass has grass-like leaves with no distinct midvein. Leaves are arranged alternately on freely-branching stems, with the basal parts of the leaf forming a sheath which wraps around the stem. In summer, water stargrass produces striking, yellow star-like flowers that protrude well above the water surface. The terrestrial form also produces flowers, but branching of stems is reduced or absent and leaves are small or leathery.

Ecological Significance:
​Unlike other bay grasses, water stargrass also has a terrestrial form that develops when low water levels strand the plant (the origin of its other common name, mud plantain). Water stargrass is sometimes eaten by waterfowl, and also provides habitat for micro/macro invertebrates which are in turn eaten by other organisms such as fish and waterfowl.

Similar Species:
​TThe leaves of water stargrass are similar in appearance to those of the Naiads (Najas spp.), though the leaves of water stargrass are much longer.

Reproduction of water stargrass is by sexual and asexual means. During sexual reproduction yellow flowers arise from a six-lobed spathe with a long thread-like tube. Flowers that do not reach the water surface remain closed and self-pollinate. Seeds are produced over the winter months and germinate in spring. Asexual reproduction occurs throughout the growing season by creating new plants from broken stem fragments. Water stargrass becomes dormant in winter, and stems and broken stem tips remain in the sediment until spring.

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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