Juncus tenuis - slender rush

Family: Juncaceae
Wetland Indictor Status: FACW-

General Species Description

Juncus tenuis is a rush that typically grows to about 15-70 cm tall, and blooms from June to September. Some distinguishing features are that the involucral bracts are longer than the inflorescence, and the lower of the bracts is often percieved to be a continuation of the stem. It is a tufted perennial with fibrous roots and rounded, slender, bright green stems.


The leaves of Juncus tenuis are vestigial, inconspicuous, and flat. They tend to be about 1-3 mm wide, and only occur on the lower 1/5 of the stem. There are no leaf blades.


The inflorescence of the slender rush are branched, terminal, and grow to about 1-7 cm long, each being made up of 10-50 singly borne flowers. The slender rush has two long involucral bracts that are longer than the inflorescence, and the tepals are longer than the capsules. Blooms from June to September.


The slender rush has capsules that are cylindrical to egg shaped and rounded and dimpled at the top. The seeds are small and elliptical with a ridge along the entire length of both sides.


The slender rush is often found in areas that are saturated freshwater sites during winter and dry during summer months. It is also able to grow in more disturbed areas including shaded roads, meadows, springs and ditches.


Though the slender rush is not very evenly distributed in the Northwest, it can be found from Alaska to Mexico, and east across Canada and the United States.

Similar Species

Juncus tenuis is most often confused with other members of the Juncus genus including j. gerardii, j. oxymeris, j. nevadensis, and j. articulatus. The easiest way to distinguish j. tenuis is that the tepals are longer than the capsules.

Ecological Value

Rushes are often used for nesting materials, food, and shelter by a variety of animals. They are also valuble for removing excess nutrients and heavy metals from urban storm water, and slow surface water flows allowing sediments to settle.

Human Value

Native Americans used rushes for weaving and sewing as decoration, and they are still used today in basketry.


Cooke, S. S. 1997. A Field Guide to the Common Wetland Plants of Western Washington & Northwestern Oregon. Seattle Audubon Society, Seattle WA, p. 256 Guard, B. J. 1995. Wetland Plants of Oregon and Washington. Lone Star Publishing, Richmond WA, p. 169 Hitchcock, C.L. and A. Cronquist. 1973. Flora of the Pacific Northwest. University of Washington Press, Seattle WA, p. 575 Pojar, J. and A. MacKinnon. 1994. Plants of the Pacific Northwest Coast, Washington, Oregon,British Columbia, and Alaska . Lone Star Publishing,Richmond WA p. 413

This page was created by: Maya O'Neil, August 1998

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