Plants annual; somewhat fleshy. Culms to 25 cm, glabrous, bases geniculate. 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 florets in each spikelet a little longer than the upper floret. Glumes subequal, 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 considered to have been endemic to the Santa Catalina and San Clements islands, California, and Guadalupe Island, Baja California, Mexico. It grew in coastal sage-scrub. It was considered to be extinct in California, not having been reported from the state since 1903. On March 30, 2005, it was discovered on Santa Catalina Island, growing in an area that had been burned two years earlier. This is the only extant population known from the Flora region.