Shoreline Plants  

 
Species: Alisma gramineum Lej., narrowleaf water-plantain, and Alisma triviale Pursh (also called Alisma plantago-aquatica L. by American authors), American water plantain
Family: Alismataceae

These perennial plants typically grow on wet soil or in shallow water. Look for parallel veined leaves rising from the plant base. The small white or occasionally pink flowers occur on delicate stalks arranged in whorls around the main flower stalk. Stiff leaves generally stand above the water surface, but young plants often have ribbon-like underwater leaves. Narrowleaf water-plantain has narrow leaves and grows to 0.5 meters high. American water-plantain has broad, oval-shaped leaves and grows to 1.2 meters high. American water-plantain has frequently been known as common water-plantain (A. plantago aquatica), a species found in Europe.
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Leaf: Leaves with parallel-looking veins arise from the plant base and are stiff when raised above the water. Submersed leaves may be ribbon-like and flexible. Narrowleaf: To 50 cm long including the stalk, narrow blade to 7 cm long, 8 mm to 2 cm wide. American: To 45 cm long including the stalk, oval-shaped blade to 15 cm long, 10 cm wide.

Stem: What appear to be stems are actually long leaf stalks. The stem is a bulb-like fleshy corm, usually buried in sediment.

Flower: White to pinkish individual flowers to 7 mm across; each has 3 sepals and 3 petals. They occur in whorls on slender branches arranged around a central flower-stalk. The whorls form a cone-shaped outline. Narrowleaf: stalks to 20 cm long, about same length as leaves. American: stalks to 1.2 m long, much longer than leaves.

Fruit: Dry, brown, flattened, oval-shaped achenes are arranged in a ring on small, flat receptacles. Narrowleaf: edge of achene with a ridge and 2 groves. American: edge of achene with 1 grove.

Root: Many, fibrous, arising from the corm.

Propagation: Seeds, or division of corms.

Importance of plant: Food and habitat for waterfowl, fish, and wildlife. Historical medicinal uses, and corms were stored for human food.

Distribution: Narrowleaf: Mainly in the Northern Hemisphere. American: Nearly worldwide.

Habitat: Marshy areas and along shorelines; occasionally completely submerged.

May be confused with: Various species of duck potato (Sagittaria spp.). The achenes of duck potato are arranged in a ball rather than a ring. Often the leaves of duck potato are arrow-shaped. When growing submersed it is easily confused with tapegrass (Vallisneria americana) or submersed forms of bur-reed (Sparganium spp.).

Photographs: Alisma gramineum (narrowleaf water-plantain), Alisma triviale (American water-plantain)

Line Drawings: Alisma triviale


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