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Washington State Department of Ecology > Water & shorelines > Freshwater studies > Lake water quality > Aquatic Plant Guide home > Submersed Plants > Limosella aquatica

Aquatic Plant Identification Manual for Washington's Freshwater Plants

Submersed Plants

Species: Limosella aquatica L., Water-mudwort
Limosella acaulis Sesse´ & Mocino, mat mudwort
Family: Scrophulariaceae

Mudworts are small members of the snapdragon family found in shallow water and along shorelines. They grow in clusters of narrow leaves up to 12 cm tall with tiny flowers borne individually on short stalks. Each clump of plants is connected by horizontal runners (stolons), much the way strawberry plants are joined. Water mudwort leaves usually have a distinct flattened, spoon-shaped blade. Mat mudwort leaves may be narrow along the entire length, or may be flattened slightly toward the tip. Mat mudwort tends to form cushion-like mats.
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Leaf: Leaves arise from the plant base with transparent stipules located at the base of the leaf stalks. Water mudwort: the spoon-shaped to oval blades are 5-30 mm long and 2-8 mm wide; the leaf stalks (to 10 cm long) are generally distinct from the blade. Mat mudwort: the linear to spoon-shaped leaf is 1-6 cm long and 0.5-2 mm wide; the leaf-stalk is not differentiated from the leaf blade.

Stem: An upright stem is lacking. Stolons connect individual clumps of plants. Water mudwort: leaf stalks may look like stems to an untrained person.

Flower: Flowers occur singly on stalks much shorter than the leaves and have 5 small sepals and petals which are fused together at the base. Water mudwort: dull white or purplish petals (about 2 mm long) with pointed tips. Mat mudwort: white to lavender petals (2-3 mm long) with rounded tips. 

Fruit: The ball-shaped or oval capsule is 3-5 mm long and contains many tiny seeds.

Root: Many fibrous roots emerge from the plant base and sometimes rise above the lower leaf bases giving the plant a woven appearance.

Propagation: Seeds, stolons. 

Importance of plant: Water mudwort has occasionally been cultivated for aquaria. Mat mudwort is on Washington's rare plant "watch" list.

Distribution: Water mudwort: North America, Eurasia. Mat mudwort: North America.

Habitat: Shallow still or slowly flowing waters. Muddy or sandy shorelines and areas with fluctuating water levels. Lakeshores subject to daily water level fluctuations.

May be confused with: Other small tufted plants, including small spikerush species (Eleocharis spp.), awlwort (Subularia aquatica), quillwort (Isoetes lacustris), water lobelia (Lobelia dortmanna), flowering quillwort (Lilaea scilloides), and lilaeopsis (Lilaeopsis occidentalis). A combination of stolon presence, leaf shape, and flower characteristics will distinguish them. 

Photographs: Limosella aquatica plant 
Line Drawings: None available

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