Colusa grass is an annual plant, so it germinates during the rainy season and then dies at the end of the following summer after dropping its seeds.

Flowering begins approximately 3 to 4 weeks after germination, typically in the early summer. The species is primarily wind pollinated, but pollen is probably not carried long distances between populations. Local seed dispersal is by water, which breaks up the inflorescences.

Colusa grass is endemic to vernal pools. The seeds germinate underwater after being immersed for prolonged periods during the rainy season. The seeds can take approximately 3 months to germinate after an initial rain event, which is longer than other related species. Thus, germination typically happens in late spring when little standing water remains in the pool, and flowering begins approximately 3 to 4 weeks later. Colusa grass is an annual plant, so it dies at the end of the summer after dropping its seeds.

Colusa grass has a pith-filled stem, lacks distinct leaf sheaths and excretes a sticky substance.

Colusa grass is an annual plant that can be found in vernal pool habitat in the Sacramento and San Joaquin valleys. Colusa grass is found on the rim of alkaline basins in the Sacramento and San Joaquin valleys with 43 presumed occurrences in Yolo, Solano, Merced and Stanislaus counties. The vast majority of these occurrences are in Stanislaus County, with 15 occurrences noted, and 22 noted in Merced County. Population sizes vary from year to year.