Shoreline Plants  

 
Species: Equisetum fluviatile L., water horsetail, swamp horsetail
Family: Equisetaceae

Water horsetail commonly grows in dense colonies along shorelines or in shallow water. These slender, dark green plants lack flowers and true leaves. They can be recognized by their hollow, rough-textured, corrugated, jointed stems. At each joint, the plants have a whorl of tiny, black-tipped scales. Some water horsetail plants produce whorls of long, thin-jointed branches. Spores are produced in cones at the stem tip. Horsetails are the direct descendents of the giant horsetails that formed primeval forests 300 million years ago.
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Leaf: Leaves are reduced to whorls of 4-9 mm-long black-tipped scales at regular joints along the stem. Also sometimes produces whorls of long thin green branches.

Stem: Dark green, hollow, jointed stem grows to 1 m high and 1 cm in diameter with 10-30 longitudinal ridges that give it a corrugated appearance. The stem readily pulls apart at the joints. The hollow part of the stem is at least 3/4 of the total diameter of the stem, making the stem easy to crush. Fertile and sterile stems look alike.

Flower: No flowers; instead, cone-like spore-producing structures develop at the ends of the fertile stems.

Fruit: Produces spores instead of fruit.

Root: Creeping rhizomes, often with deep roots.

Propagation: Mainly spreads by rhizomes; spores are also produced.

Importance of plant: Historically used by both Europeans and Native Americans for scouring, sanding, and filing because of the high silica content in the stems. Early spring shoots were eaten. Medicinally it was used to treat kidney ailments. Rootstocks and stems are eaten by waterfowl. Horsetails absorb heavy metals from soil, and are often used in bioassays for metals.

Distribution: Northern Hemisphere

Habitat: Shallow water, marshes, bogs, and streams. 

May be confused with: Horsetails are distinct from other plants, but various species are often difficult to tell apart. Water horsetail has similar fertile and sterile stems, while other species can have two different stem types. Water horsetail has weak, hollow stems with thin walls that can be easily collapsed, and usually grows in deeper water than other horsetails. Most often confused with marsh horsetail (E. palustre) which has fewer (5-10) stem ridges.

Photographs: Equisetum fluviatile

Line Drawings: Equisetum sp. 


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