Submersed Plants

Species: Scirpus subterminalis Torrey, water bulrush
Family: Cyperaceae

Unlike other bulrush species (Scirpus spp.) common in the Pacific Northwest that have stout emergent stems, water bulrush grows mostly underwater and has limp, weak, underwater stems and leaves. The green, hair-like leaves and long, round stems grow completely underwater except for the flower spike, which rises above the water surface. The solitary flower spikes are short, light brown in color, and appear to grow out of the side of the stem.

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Leaf: The long, very narrow, green leaves (approximately 0.5 mm wide and up to 1m long) are limp, grass-like, and originate in a bundle at the base of the plant. The leaf tips often float on the water surface. 

Stem: The slender, limp, round stem is 20-140 cm long and less than 1 mm wide.

Flower: The flowers are arranged in dry, solitary, light brown spikes 6-13 mm long and 4-7 mm wide and are located at or near the stem tips. The individual flowers are hidden behind pointed scales that are 4-6 mm long. What appears to be a continuation of the stem above the flower spike is really a modified bract. The flowering spikes emerge above the water surface. Water bulrush blooms July to August.

Fruit: Small achenes (2.5-3.5 mm) are hard, three-sided with a prominent tip, and contain one seed.

Root: Delicate, slender rhizomes grow partly or completely below the sediment surface.

Propagation: Rhizomes and seeds.

Importance of plant: The seeds of many bulrush species are among the most important foods for North American ducks. The stems and roots are eaten by muskrats and geese.

Distribution: Northern North America. In Washington, water bulrush is most common west of the Cascade Mountains.

Habitat: Water bulrush is found in the quiet shallow water of ponds, lakes, and marshes and typically grows in water 0.5-1 m deep.

May be confused with: Water celery (Vallisneria americana) and bur-reeds (Sparganium spp.), which have much broader leaves (usually 0.5-1 cm wide). Spreading rush (Juncus supiniformis) which has flowers that occur in clusters at the stem tips. Sedges and other members of bulrush family, none of which have the long, submersed, hair-like leaves and the solitary flower spike of water bulrushes. 

Photographs: Photograph of a herbarium specimen of Scirpus subterminalis 

Line Drawings: None available 

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