Shoreline Plants  

 
Species: Eleocharis acicularis (L.) R. & S., needle spike-rush
Eleocharis parvula (R. & S.) Link, small spike-rush
Family: Cyperaceae

These green, grass-like perennial herbs can be recognized by the oval-shaped, brownish-flowering spikes at the tips of smooth, round stems. These spike-rush species grow individually or in clumps along shorelines or in shallow water, sometimes forming ankle-high turf-like mats. Needle spike-rush often looks hair-like when growing underwater. Several other spike-rush species also occur in Washington, some growing to waist height.
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Leaf: Small, inconspicuous leaves are located at the stem base. Needle spike-rush: several needle-like square-tipped leaves with pale reddish basal sheaths. Small spike-rush: leaves have membranous sheaths at the base of the stems. 

Stem: Round, green, solid (not hollow) stems turn brown in fall. Needle spike-rush: stems measure 2-15 cm tall. Small spike-rush: stems measure 1-10 cm tall.

Flower: Flowers are in round or oval spikes at the tips of stems and are arranged spirally. Each flower is protected by a scale-like bract. Needle spike-rush: flower scales are green down the center and brown on the sides with 3-15 flowers per spike. Small spike-rush: flower scales are green to brown, and reddish brown on the sides with 2-9 flowers per spike.

Fruit: The achenes are about 1mm long. Needle spike-rush: egg-shaped, white to pale gray or yellowish achene. Small spike-rush: straw-colored, 3-angled achene.

Root: Needle spike-rush: slender, branching rhizomes and stolons. Small spike-rush: slender, inconspicuous rhizomes and fibrous roots.

Propagation: By seeds and division of plants connected by rhizomes.  

Importance of plant: Seeds and stems are important food for waterfowl and mammals. Spike-rushes provide habitat for amphibians and fish and help stabilize shorelines.

Distribution:  Needle spike-rush: Northern hemisphere. Small spike-rush: Europe, North America, and northern South America.

Habitat: Adapted to fluctuating water levels. Needle spike-rush: marshes, shallow water of lakes, ponds, and stream beds. Small spike-rush: wet saline flats, marshes, and alkaline lakes.

May be confused with: Each other; refer to technical keys to distinguish species of Eleocharis. Spike-rush species may also be confused with grasses and small rushes (Juncus spp.) or sedges (Carex spp.), which all lack the solitary flower spikes at the stem tips. Sedges also generally have wedge-shaped stems. 

Photographs: Eleocharis acicularis, Eleocharis parvula

Line Drawings: Eleocharis acicularis, Eleocharis sp. 


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