Borrego Milk Vetch [Astragalus lentiginosus Dougl. var. borreganus Jones]

Borrego Milk Vetch [Astragalus lentiginosus Dougl. var. borreganus Jones]

Listing CNPS List 4 R-E-D Code 1-1-1

State/Federal. Status -- None FABACEAE Feb.-May

Global Rank G5T3T4 State Rank S?

Distribution: San Diego County, Riverside County, San Bernardino County, Imperial County; Arizona; Baja California and Sonora, Mexico

Habitat: Very open desert scrub in sandy locales and semi-stabilized dunes is favored by this herbaceous perennial. Blowing sands (Carrizo soils) may create some instability of habitat which enables the Borrego Milk Vetch to out-compete normally hardier desert species. Helianthus niveus ssp. canescens may grow in association with this milk vetch.

Known Sites: The Borrego Milk Vetch grows on sand dunes near Font's Point in the Anza-Borrego Desert. The population probably fluctuates dramatically depending upon precipitation. It is occasional near Borrego north of Henderson Canyon Road in very sandy locales. It is reported from a wash near Thimble Trail and east of Palo Verde wash in Anza-Borrego State Park. Herbarium specimens are from the south end of Clark Valley, in Coyote Creek, on the east side of Ogilby Road in Imperial County, and on the Kelso Sand Dunes in San Bernardino County. Old biological survey reports note sites near Palo Verde Boulevard and the Riverside/Imperial County line, as well as north of the New Coachella Canal and north of Highway 78. Reported by Barneby from extreme southwestern Arizona and adjoining northwestern Sonora, Mexico.

Status: County populations of Borrego Milk Vetch are apparently stable, given the limited impacts to its desert habitat. This species is potentially impacted by ORV use in Borrego Valley, as well as by people gathering wildflowers during the occasionally high seasonal influx of tourists to the valley. Until more range and cumulative population size information is available, all populations should be protected. Specimens of Astragalus lentiginosus annotated by Barneby as variety coulteri from Font's Point Wash are deposited at the San Diego Natural History Museum. A second annotated specimen for this entity is recorded from between Holtville and Yuma in Imperial County. This related variety appears to be poorly known in California. Astragalus lentiginosus is a notoriously variable taxon.

Copyright May 1994 Craig H. Reiser.

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