Juncus patens is a perennial herb forming narrow, erect bunches of stems. It grows up to 3 feet (0.91 m) in height by 1–2 feet (0.30–0.61 m) in width.[3][4] It spreads by rhizomes, which can increase a colonies width substantially.
The stems are thin, gray-green, often somewhat waxy, and grooved, and grow 30–90 centimetres (12–35 in) in height.
The inflorescence sprouts from the side of the stem, rather than its tip. It holds many flowers, each of which has short, narrow, pointed tepals and six stamens. It flowers in the summer.
The fruit is a spherical red or brown capsule which fills and bulges from the dried flower remnants when mature. The seeds attract birds.
^Harlow, Nora and Kristin Jakob; Wild Lilies, Irises, and Grasses: Gardening with California Monocots; Berkeley and Los Angeles, CA; University of California Press; 2003.
^Bornstein, Carol, David Fross, and Bart O'Brien; California Native Plants for the Garden; Los Olivos, CA; Cachuma Press; 2005.