Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
Habitat: Shores, seeps, damp ground, and ditches.
Flowers: June - September
Origin: Native
Growth Duration: Perennial
Conservation Status: Not of concern
Pollination: Wind
Tufted perennial, the stems 1.5-6 dm. tall.
Leaves only on the basal portion of the stem; leaf blades flattened, 0.5-1.5 mm. broad; leaf bases sheathing, the sheaths projecting upward into auricles that are either gristle-like and short or membranous and elongate.
Flowers few to numerous in a terminal, congested to open, cymose inflorescence, exceeded by the involucral bract; perianth 4-5 mm. long, the 6 segments greenish to tawny with a green midrib, the margins membranous, the tip acute or awl-like; stamens 6, the anthers shorter than the filaments.
Capsule firm, cylindric-ovoid, truncate, about equal to the perianth.
PNW Herbaria: Specimen records of Juncus tenuis in the Consortium of Pacific Northwest Herbaria database
WA Flora Checklist: Juncus tenuis checklist entry
OregonFlora: Juncus tenuis information
E-Flora BC: Juncus tenuis atlas page
CalPhotos: Juncus tenuis photos