San Joaquin Valley Orcutt Grass

views updated

San Joaquin Valley Orcutt Grass

Orcuttia inaequalis

ListedMarch 26, 1997
FamilyPoaceae (Grass)
DescriptionA tufted annual grass.
HabitatVernal pools.
ThreatsHabitat destruction through agricultural and urban development and associated disturbances.


San Joaquin Valley orcutt grass, Orcuttia inaequalis, is a tufted annual that reaches 2-6 in (5-15 cm) in height. The grayish, pilose (bearing soft, straight hairs) plants have several spreading to erect stems, each terminating in a spike-like inflorescence. The spikelets of the plant are aggregated at maturity into a dense, hat-shaped cluster, which separates them from other members of the genus Orcuttia. The lemmas-lower bracts enclosing the grass floretare also deeply cleft into five prominent teeth which may be sharp-pointed or have awns that are 0.2 in (5 mm) long. The middle tooth is conspicuously longer than the four laterals. Orcuttia inaequalis does not occur with any other species of Orcuttia. The species most closely resembles O. californica and O. viscida. The former does not have the long central lemma tooth and lacks the grayish appearance, whereas the spikelets of the latter are more congested toward the apex of the inflorescence, although not as much as in O. inaequalis. Orcuttia inaequalis has also smaller lemmas, noncurving lemma teeth, and smaller seeds. Orcuttia inaequalis grows with Neostapfia colusana at five sites in the San Joaquin Valley.


The San Joaquin Valley orcutt grass occurs in vernal pools, which are wetlands that have standing water in the winter and early spring, and then progressively dry in the later spring and summer.


Sixteen populations of San Joaquin Valley orcutt grass have been lost in Fresno, Madera, Merced, and Stanislaus counties, while three additional populations have not been seen in some years of surveying and are considered possibly extirpated. The remaining 23 populations, discontinuously scattered over a 36 mi (57 km) range, are mostly in the southeastern San Joaquin Valley in Fresno, Merced, and Madera counties. Twenty-one populations are found on private lands and two on Federal land, one population managed by the Bureau of Land Management and one transplanted population by the Bureau of Reclamation. Three populations of O. inaequalis are protected by a conservation easement with the Nature Conservancy at the Flying M Ranch in Merced County.


The major threat to San Joaquin Valley orcutt grass is habitat lost to land converted to agricultural purposes and urban development.

Sixteen populations of San Joaquin Valley orcutt grass have been lost and three other populations are possibly extirpated; of the remaining 23 native extant populations, 11 are variously threatened by urbanization, agricultural land conversion, and competition with non-native weeds. Conversion of land to agricultural use within the last 20 years is known to have eliminated five populations of San Joaquin Valley Orcutt grass in Stanislaus County, four in Madera County, three in Merced County, and one in Fresno County. Irrigated agriculture and associated runoff have likely eliminated one population in Madera County.

Overgrazing and hay production likely have destroyed one population of this plant in Tehama County. Hydrological modifications have destroyed two Merced County and one Fresno County population. The Merced County Stream Channel Project of the U.S. Army Corps of Engineers threatens three populations within the San Joaquin Valley.

Urbanization has extirpated one population in Fresno County. Three proposed gravel and aggregate mining projects, two in Sacramento County and one in Fresno County, threaten to destroy vernal pool habitat containing San Joaquin Valley Orcutt grass. The Merced County Landfill will destroy vernal pools containing this plant. Two populations are threatened by proposed expansion of State Highway 41 in Madera County.

Non-native annual grasses such as Hordeum geniculatum, Phalaris paradoxa, Polypogon monospeliensis, and Lolium multiflorum and soil disturbance associated with cattle grazing appear to result in low vigor and low seed production of two populations of O. inaequalis in Merced County. Sida hederacea, a non-native perennial herb, appears to threaten another population at a heavily grazed site in Merced County.

Conservation and Recovery

The San Joaquin Valley orcutt grass only occurs in about 23 surviving populations scattered over a 36 mi (58 km) range. Only two populations are on Federal land, one managed by the Bureau of Land Management and one transplanted population by the Bureau of Reclamation. Three populations at the Flying M Ranch are protected by conservation easement owned by the Nature Conservancy, a private environmental organization. All other populations are on non-conserved private land and are threatened by development and other disturbances. These critical habitats should be protected. This could be done by acquiring the habitats and designating them as ecological reserves, or by negotiating conservation easements with the landowners. The populations of the San Bernardino bluegrass should be monitored, and research undertaken into its basic biology and ecological requirements.


U.S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
Federal Building
2800 Cottage Way, Room W-2605
Sacramento, California 95821-1846
Telephone: (916) 414-6600
Fax: (916) 480-4619


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.

About this article

San Joaquin Valley Orcutt Grass

Updated About content Print Article


San Joaquin Valley Orcutt Grass