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Washington State Department of Ecology > Water & shorelines > Freshwater studies > Lake water quality > Aquatic Plant Guide home > Shoreline Plants > Elatine triandra

Aquatic Plant Identification Manual for Washington's Freshwater Plants

Shoreline Plants  

Species: Elatine triandra Schkuhr, mudwort or three-stamen waterwort
Family: Elatinaceae

This small, smooth-looking annual plant is typically found growing along the shorelines of lakes, ponds, and slow-moving streams. The plants are light green and have matted, prostrate stems with delicate, upright branches. The leaves are oblong and oppositely arranged with tiny notches at the tips. Minute flowers occur at the leaf bases. Several other species of Elatine occur in the Northwest; details of the tiny seeds must be examined to distinguish them.
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Leaf: The oppositely-arranged, linear to spatula-shaped smooth-edged leaves are 5 to 12 mm long and have notched tips.

Stem: The somewhat thickened or fleshy prostrate matted stem ranges from 2 to 10 cm long and has upright branches.

Flower: Stalkless, minute flowers occur singly at the base of the leaves. Each flower has 3 to 4 sepals and petals.

Fruit: Fruits are 3- or 4-celled capsules with each cell containing 7 or 8 seeds. The seeds are straight or slightly curved and are characterized by tiny yet distinctive longitudinal rows of minute indentations on their surfaces. The number and arrangement of these indentations are used to distinguish species of mudwort.

Root:  Fibrous roots. Roots may also form at the nodes along the prostrate stems of aquatic forms of mudwort.

Propagation: By seeds, often distributed by waterfowl.

Importance of plant: Usually considered beneficial in stabilizing shorelines.

Distribution: Western United States.

Habitat: Mudwort grows along the shorelines of lakes, ponds, and slowly moving water and is adapted to fluctuating water levels.

May be confused with: California waterwort (Elatine californica), which has tiny, but showier flowers at the ends of short stalks, each with four sepals and four petals, and seeds that are distinctly J- or U-shaped. May also be confused with water starwort (Callitriche spp.) which sometimes has tiny rosettes of leaves at the ends of the stems and no sepals or petals, or pigmy weed (Crassula aquatica formerly known as Tillaea aquatica) which has fleshy opposite leaves joined at the base and no notch at the leaf tip.

Photographs: Elatine sp.

Line Drawings: None available

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