Hippuris vulgaris

Mare's Tail

NATIVE TO MAINE

Habitat: Mare’s tail grows in the emergent to submersed plant community, generally in muddy substrates, along damp shores and in shallow, quiet waters of ponds and streams. This plant may occur in fresh or brackish water, and prefers non-acidic conditions.

Description: The simple, unbranched stems of mare’s tail emerge along stout, spongy, creeping rhizomes. Ribbon-like leaves (length 1 to 10 cm) are entire, and attached at the base (with no leaf stem). The leaves occur in whorls of 6 to 12 leaves per whorl, with whorls more closely spaced toward the growing tip. The top part of the stem often emerges from the water. The emergent leaves are linear, with blunt, hard tips. The submersed leaves are generally more elongate, more flaccid and sometimes paler than the emergent leaves. Tiny inconspicuous flowers occur in the axils of the middle and upper leaves.

This is the only aquatic plant native to Maine with blade-shaped leaves occurring in whorls of more than three leaves. This feature may cause this plant to be confused with two of the invasive plants on Maine’s watch list: hydrilla and Brazilian elodea. Unlike both hydrilla (with its conspicuously serrated leaves) and Brazilian elodea (with its finely serrated leaves), the leaves of mare’s tail are entire (smooth edged). Also, both hydrilla and Brazilian elodea branch freely along the stem as they grow. Mare’s tail may branch at the base where it emerges from the rhizome, but otherwise grows throughout the season as simple, unbranched stems.

Origin and Range: Mare’s tail is native to many parts of the US, including parts of New England. Based upon its status in other New England states, mare’s tail is believed to be rare in Maine.

Annual Cycle: Mare’s tail is a perennial, stems emerging anew from stout rhizomes each spring. Flowers occur from June through September, however sexual reproduction (propagation by seed) is considered to be rare. The primary means of reproduction is asexual, through rhizome division and spread.

Value to the Aquatic Community: Mare’s tail offers habitat and food to various species of fish and invertebrates.

Look Alikes: May be confused with hydrilla, Brazilian elodea, common waterweed, and slender waterweed. The emergent tips of mare’s tail may be confused with the flowering emergent spikes of some watermilfoil species.