Juncus patans - grooved rush
Wetland Indictor Status: FACW
General Species Description
The grooved rush is a perennial, native, emergent plant growing to a height
of 30-90 cm. This species has creeping rhizomes and grows in strong tufts.
Grooved rush has lateral inflorescence (involucral bract appears to be
a continuation of the stem). The involucral bract is generally one third
as long as the stem and end in a sharp point. The stem is blue-green
and round, bearing brownish, loose, pointed sheaths.
The leaves of the Juncus patans are reduced and bristle-like, if
they are present at all.
Grooved rush appears to have lateral inflorescences because the involucral
bract, which is round and erect, appears to be a continuation of the stem.
The inflorescence is 2.5-9 cm in length and are open with more than 20
flowers. Individual flowers have tepals (2-3.5 mm) which are greenish
or brown, needle-like, stiff, with transparent margins spreading away from
the the capsule. The capsule is almost as long as the tepals and appears
enlarged and round. This species usually has 6 stamens. Blooms June
The seeds are an oval shape and have a distinctive ridge along the entire
Juncus patans can be found primarily in saturated soils on the westside
of the Cascades in Oregon.
You can find this member of the Juncaceae family in the Willamette
Valley and Cascade Mountains, and south from there to Santa Barbara County
Soft Rush (Juncus effusus) is similar and also has round stems with
an apparent lateral inflorescence and is strongly tufted as well.
However this plant tends to be more robust with stout, sharp stems, and
flowers that have only three stamen. Baltic rush (Juncus balticus) can
be distinguished by its more delicate form and flowers with 6 stamens and
tepals that are 3.5-5 mm long. The baltic rush is also primarily found
in coastal areas.
Grooved rush can be used by muskrats and nutria as a food source and as
shelter by various wading birds. The strong tufts make it a good for erosion
Erosion control and ecological balance.
Cooke, S. S., ed. 1997. A Field Guide to the Common Wetland Plants of
Western Washington & Northwest Oregon. Seattle Audubon Society
and Washington Native Plant Society. Seattle Audubon Society, Seattle WA,
This page was created by: Mike
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