Aquatic Moss

Species: Fontinalis antipyretica Hedw., common water moss
Family: Fontinalaceae

Common water moss is a dark green underwater plant that attaches to rocks or logs in flowing water, or floats loose or attached in still water. The leaves are sharply pointed, ridged, overlapping, and arranged in 3 rows along the entire length of the stems. The stems grow up to 60 cm long and appear triangular if the leaves are removed. Common water moss does not produce flowers, reproducing by stolons, plant fragments, or spores instead. It is one of only a few truly aquatic mosses in the Pacific Northwest. It is often found dried and dormant above water in the summer.

Aquatic Moss Icon
Leaf: The rather rigid, sharply-pointed leaves are 4 to 9 mm long, broadly lance-shaped to egg-shaped, and have a lengthwise ridge down the back. They are arranged in 3 rows and partly overlap along the entire length of the stem. When removed from the stem, the leaves appear to be folded length-wise down the middle.

Stem: The branching stem is 20 to 60 mm long, conspicuously three-angled (appears triangular in cross section), and entirely covered by the leaves.

Flower: None, produces spores instead.

Fruit: Microscopic spores are produced in smooth capsules that measure 2 to 2.6 mm long. Spores are only produced on plants that are subjected to periods of drying. Fertilization and spore release will only take place above water.

Root: No true roots. Rootlets (rhizoids) attach common water moss to rocks and logs.

Propagation: Mostly by stolons and leafy plant fragments. Infrequently by spores.

Importance of plant: Provides habitat for aquatic insects, larvae, and other microorganisms. Small fish species will nest in it. It is a popular plant for cold water aquariums.

Distribution: In northern North America extending southward to Pennsylvania in the east and Arizona in the west. Also in Europe, Asia, and Africa. In Washington, it is more common west of the Cascade Mountains.

Habitat: Water moss is found attached to rocks or logs in swift flowing water, or floating loose or attached to substrate in still water. It is common in shaded sites and prefers slightly acidic water. It requires water below pH 8.4 where dissolved carbon dioxide is available.

May be confused with: Other moss species, which have leaves that are not ridged or as distinctly 3-rowed as common water moss.

Photographs: Fontinalis sp. closeup

Line Drawings: Not available

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