Page authors: Don Knoke, David Giblin
Juncus filiformis
thread rush

Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to northern Oregon, east to the northern Great Plains, Great Lakes region, and northeastern North America.

Habitat: Lake shores and coastal bogs to montane marshes and meadows; in Washington, from near sea level to about 5000 feet elevation.

Flowers: June-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Wind


Somewhat tufted perennial with widespread rhizomes, the stems terete, about 1 mm. in diameter, 5-30 cm. tall.


Sheaths tight, truncate to rounded, usually with a vestige of a blade.


Inflorescence apparently lateral, the involucral bract terete, erect, sharp-pointed, at least half as long as the stem and sometimes exceeding it; inflorescence a tight to open panicle up to 2 cm. long, 7- to 15-flowered; perianth 3-4 mm. long, the 6 segments sub-equal, greenish, lanceolate; stamens 6, the anthers shorter than the filaments.


Capsule ovoid to obovoid, firm, slightly shorter than the perianth.

Accepted Name:
Juncus filiformis L.
Publication: Sp. Pl. 1: 326. 1753.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Juncus filiformis in the Consortium of Pacific Northwest Herbaria database

WA Flora Checklist: Juncus filiformis checklist entry

OregonFlora: Juncus filiformis information

E-Flora BC: Juncus filiformis atlas page

CalPhotos: Juncus filiformis photos

16 photographs:
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