Eleocharis acicularis - needle spikerush

Family: Cyperaceae
Wetland Indictor Status: OBL

General Species Description

Eleocharis acicularis is the smallest spikerush. It has stems that stand 3 - 12 cm tall. It is rhizomatous, can be annual or perennial, and has very small stems (1 mm thick) that look grasslike of hairlike, and have a single terminal inflorescence. It often forms thick mats.


The leaves are reduced to thin scale-like sheaths that can be purple or green.


The flower is a single spike at the end of each stem that is 2.5 to 7 mm long. It is wider than the stem and it's bristles give the spike a white appearance during flowering. The spikes have less than 15 flowers. Each flower has a scale that is green in the middle and red along the sides. They flower from June to August.


The fruit is a small, dry, yellow-white achene.


Acicularis grows in wet meadows and along muddy edges of pools and streams. It prefers areas where the water is present throughout the season. Lemna and Scirpus species are often found with Eleocharis.


This species is found all the way around the north pole and is common in our area from low to moderate elevations.

Similar Species

Eleocharis species are easily distinguished by the single spike at the end of a slender shoot. Acicularis is most easily confused with Eleocharis obtusa. Obtusa, however, is four times as large and has up to 80 flowers per spike. Eleocharis palustris has only 30 flowers per spike, but is up to a meter tall. Plantago lanceolata can look like an Eleocharis species, but is easily discernable due to it's large basal leaves.

Ecological Value

The fruit, stems, and rhizomes are all eaten by birds, and mammals eat the roots. Birds also use the stems and rhizomes as nesting materials.

Human Value

Eleocharis acicularis can be used to help curb erosional processes because it forms such dense mats.


Cooke, Sarah Spear, ed. A Field Guide to the Common Wetland Plants of Washington and Northwestern Oregon. 1997. Seattle Audubon Society. Seattle, Washington. Guard, B. Jennifer. Wetland Plants of Oregon and Washington. 1995. Lone Pine Publishing. Vancouver, B.C., Canada.

This page was created by: Braden Hanna, August 1998

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