Shoreline Plants  

Species: Hippuris vulgaris L., common mare's-tail
Family: Hippuridaceae

Common mare's-tail looks like a robust green bottlebrush growing in patches primarily in the shallow areas of streams, ponds, and lakes or on wet muddy shores when water levels drop. This plant is characterized by unbranched stems, abundant whorled leaves, and inconspicuous flowers. The leaves and stems vary in form depending on whether they are growing underwater or are emergent. The underwater plant portions are limp, flexible, and have very long leaves. Emergent portions are stiff and erect, with short narrow leaves.

Leaf:  Arranged in whorls; 6-12 stalkless, smooth-edged leaves per whorl. Two types: submersed leaves are soft, pale green, and measure up to 5 cm long and 3 mm wide. Emergent leaves are dark green, stiffer, and smaller. In deeper water only the submersed leaf form may be present.

Stem: The unbranched stem is hollow, up to 1 m long, and forms roots at the nodes. The stem is erect when emergent; limp when submersed; and can form creeping rhizomes.

Flower: Small, inconspicuous flowers are located at the leaf bases. The flowers which lack petals and sepals, are reduced to a tiny rim.

Fruit: Tiny (mature fruit about 2 mm long), nut-like, located at leaf bases.

Root: Fibrous. Arising from lower portion of stems and rhizomes.

Propagation: Seeds, rhizomes. Will regrow from stem cuttings.

Importance of plant: Seeds and sometimes vegetation eaten by waterfowl and shorebirds. Provides shelter for small animals. Sometimes used in ornamental ponds or cool-water aquariums.

Distribution: Occurs in cooler regions of North and South America, Eurasia, and Australia. It is one of the few aquatic plants found in arctic pools and lakes.

Habitat: At the edges of lakes, ponds, and streams in fresh, usually shallow water, though it will grow in water up to 2 m deep.

May be confused with:  Horsetails (Equisetum spp.) and parrotfeather (Myriophyllum aquaticum). Horsetails have corrugated, distinctly jointed stems. Parrotfeather has divided feather-like leaves rather than simple, narrow leaves. Submersed mare’s-tail plants may be confused with members of the oxygen plant family (Hydrocharitaceae), but mare’s-tail has more leaves per whorl. A closely related plant, mountain mare’s-tail (H. montana) is found in high elevation wet meadows or on mossy banks. It is more terrestrial, smaller (to 10 cm), and has shorter leaves (to 10 mm long) than common mare’s-tail.

Photographs: Hippuris vulgaris

Line Drawings: None available

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