Plants annual. Culms to 25 cm, glabrous. Blades 2.5-15 cm long, 1-4 mm wide, flat, soft. Panicles 5-15 cm, contracted; pedicels scabrous. Spikelets with 2-3 florets, lower floret in each spikelet a little longer than the upper floret. Glumes sub-equal, 3-4 mm, exceeding the florets, lanceolate, keels scabrous, margins scarious, apices acuminate; lemmas 1.5-2 mm, pilose, obtuse to acute. 2n = unknown.
Dissanthelium californicum is known only from Santa Catalina and San Clemente islands, California, and Guadalupe Island, Baja California, Mexico. It grows in coastal sage-scrub. Until its rediscovery on Santa Catalina Island in 2005, it was thought to be extinct in California, not having been reported from the state since 1903.