Colusa Grass

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Colusa Grass

Neostapfia colusana

ListedMarch 26, 1997
FamilyPoaceae (Grass)
DescriptionRobust, tufted annual; inflorescences resemble small ears of corn.
HabitatVernal pools.
ThreatsLoss of habitat resulting from land converted to agricultural and urban development.


Joseph Burtt-Davy collected and first described Neostapfia colusana (Colusa grass) as a member of the genus Stapfia in 1898; he then renamed this genus Neostapfia the following year. Later in 1899, Frank Scribner submerged Neostapfia within the genus Anthochloa. Robert Hoover finally placed this species in the resurrected monotypic genus Neostapfia in 1940.

Colusa grass, N. colusana, is a robust, tufted annual that grows 3-12 in (7-30 cm) in height. The stems are decumbent toward the base with the upper portion erect and terminating in spike-like inflorescences that are cylindrical, dense, and resemble small ears of corn. Because of this unique inflorescence, this distinctive plant is not easily confused with any others.


The Colusa grass grows in vernal pools. This habitat is wet during the winter to early summer, and then progressively dries during the summer.


Colusa grass has been extirpated from its type locality in Colusa County. Seven populations of Colusa grass in Colusa, Merced, and Stanislaus counties have been lost. Three populations in Merced County and one occurrence in Stanislaus County have not been seen in many years and are considered to possibly be extirpated. The 40 remaining populations in the San Joaquin Valley are concentrated along a 98 mi (200 km) stretch of the eastern edge of the San Joaquin Valley in Stanislaus and Merced counties. Additionally, two separate populations occur in Solano County in the Sacramento Valley and another two populations are found in Yolo County. All populations exist on private lands, except for one population found on Castle Air Force Base in Merced County and one population found on McClellan Air Force Base in Yolo County, both discovered in 1993. In addition to the population on the Nature Conservancy's (TNC) Jepson Prairie Preserve in Solano County, this plant is afforded some protection via a 2,400 acre (970 hectare) conservation easement purchased by TNC at the Flying M Ranch in Merced County.


Colusa grass is threatened by loss of habitat resulting from land converted to agricultural and urban development. Ten populations of Colusa grass are lost or suspected of being lost due to conversion of habitat; of the 44 remaining populations, 22 are threatened, damaged, or declining due to agricultural land conversion, discing, a flood control project, a proposed Federal prison, herbicide-contaminated runoff, and competition with non-native plants.

The conversion of land to agricultural use within the last 20 years is known to have eliminated five populations of Colusa grass in Stanislaus County, one in Colusa County, and one in Merced County. Agricultural land conversion now threatens 14 populations of this plant in southeastern Stanislaus County. Livestock pond construction has inundated one population of Colusa grass in Merced County. Discing also has destroyed one population of this taxon in Tulare County. Pond construction for recreational waterfowl hunting in Colusa County has presumably eliminated one population of Colusa grass. Increases in agricultural field runoff are responsible for possibly extirpating one population of this plant in Merced County and one in Stanislaus County.

The Merced County Stream Channel Project of the U.S. Army Corps of Engineers threatens four populations of Colusa grass in Merced County within the San Joaquin Valley. The Merced County Landfill will destroy vernal pools containing this taxon. One population of Colusa grass in Merced County is threatened by a proposed Federal prison on part of the former Castle Air Force Base.

Another population of Colusa grass on TNC's Jepson Prairie Preserve is threatened by competitive exclusion from the invasive alien Phyla nodiflora var. nodiflora. Initial results from on-going research regarding controlling or eradicating Phyla nodiflora var. nodiflora at the Jepson Prairie Preserve have indicated that either islikely to be very difficult.

A population of Colusa grass on the McClellan U.S. Air Force Base radio transmitter site in Yolo County is severely degraded due to herbicide runoff from the antenna pads and to discing of firebreaks.

Conservation and Recovery

The Colusa grass occurs on the Jepson Prairie Preserve of TNC, a private conservation organization. However, that population is threatened by competition from invasive alien plants, which must be controlled. The rare plant also occurs on a 2,400 acre (970 hectare) easement owned by TNC at the Flying M Ranch in Merced County. The only populations on public lands are on the Castle Air Force Base and the McClellan Air Force Base. These critical habitats must be protected and managed in favor of the rare grass. All other critical habitats of the Colusa grass are on private land. The largest of these should be protected. This could be done by acquiring the habitat and designating ecological reserves, or by negotiating conservation easements with the landowners. The known populations of the Colusa grass should be monitored, and research undertaken into its biology, habitat needs, and management practices to maintain and enhance its populations.


U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
Federal Building
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121


U.S. Fish and Wildlife Service. 26 March 1997. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Three Plants and Threatened Status for Five Plants From Vernal Pools in the Central Valley of California." Federal Register 62 (58): 14338-14352.

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Colusa Grass

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