Overview
Colusa grass is an annual plant that can be found in vernal pool habitat in the Sacramento and San Joaquin valleys. Colusa grass requires its seeds to be covered by water for approximately three months before seed germination will occur, so it is found more often in deeper pools and stock ponds that hold seasonal water for longer periods of time. Colusa grass has a pith-filled stem, lacks distinct leaf sheaths and excretes a sticky substance.
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. Most of these occurrences are in Stanislaus County, with 15 noted, and 22 noted in Merced County. Population sizes vary from year to year.
Colusa grass was listed as threatened on March 26, 1997. Critical habitat was designated on August 6, 2003. Colusa grass continues to be threatened by habitat loss and fragmentation.
Scientific Name
Identification Numbers
Characteristics
Life Cycle
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.
Similar Species
Physical Characteristics
Colusa grass has a pith-filled stem, lacks distinct leaf sheaths and excretes a sticky substance.
Habitat
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.
Land on which the natural dominant plant forms are grasses and forbs.
Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.
Timeline
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