California Orcutt Grass [Orcuttia californica Vasey]

California Orcutt Grass [Orcuttia californica Vasey]

Listing CNPS List 1B R-E-D Code 3-3-2

State/Federal. Status -- CE/FE POACEAE Apr.-Jun.

Global Rank G2 State Rank S2.1

Distribution: Riverside County, San Diego County; Baja California, Mexico

Habitat: Vernal Pools are the preferred habitat of this inconspicuous prostrate grass. Stockpen gravelly clay loam is mapped for the Dillon Road population while the Skunk Hollow site has Ramona sandy loam. At the few locales examined, vernal pool associates were not representative of the pool flora in the region, but limited to certain species. Psilocarphus brevissimus, Navarretia fossalis, and Myosurus minimus var. apus may be present. California Orcutt Grass tends to grow in wetter portions of the vernal pool basins, but this annual does not show much growth until the basins become somewhat desiccated.

Known Sites: California Orcutt Grass is common in a very few "J" series pools on Otay Mesa; it is particularly well developed at the south end of Dillon Road near Spring Canyon. This grass is reported near the Miramar Air Field runway. Data Base records for San Diego County note sites northeast of Brown Field on Otay Mesa 1 mile north northeast of the Alta School, 0.8 mile south southeast of the Alta School, adjacent to the west side of Highway 163 approximately 1 mile north of Clairemont Mesa Boulevard, approximately 0.25 mile southwest of a finger canyon north of the south rim of Otay Mesa, in Spring Canyon south of Dillon Road on the south rim of Otay Mesa, north of Wruck Canyon on southern Otay Mesa, and 1 mile east of San Ysidro at the E-4 1/2 Pond 0.5 mile east of the port of entry along the south side of the road. It is also reported from Skunk Hollow, a massive vernal pool in western Riverside County which very rarely ponds substantial water, and on the Santa Rosa Plateau. Vast, almost monotypic stands grow in the vernal pool complex on the corner of Stowe Road and California Road near Hemet. An old report from the junction of Western Avenue and Rosecrans Avenue in Los Angeles around the old municipal airport is apparently an extirpated site. Data Base records for Riverside County are for six pools on Mesa de Burro and three pools of the Mesa de Colorado of the Santa Rosa Plateau, and a site near Murrieta Hot Springs which may be extirpated.

Thirteen collections from Baja are found at the San Diego Herbarium; south to 30 56' North where collected by Moran 2 km northwest of Ejido Ruben Jaramillo.

Status: California Orcutt Grass is slowly declining throughout its range. Populations on southern Otay Mesa are regularly impacted by free ranging cattle and horses which are allowed to wallow in the few vernal pools left here. The border patrol heavily utilizes dirt roads adjacent to these pools, and the road shoulders continue to expand into the pool areas. Populations near Hemet are clearly endangered by urban expansion. One of the rarest plants in San Diego and Riverside counties; all populations should be protected. In some years of sporadic rainfall this grass may not germinate and appear to be absent or to occur in low numbers in pools where it is normally abundant.

Copyright May 1994 Craig H. Reiser.

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