Harwood's Milk Vetch [Astragalus insularis Kell. var. harwoodii Munz & McBurn.]

Harwood's Milk Vetch [Astragalus insularis Kell. var. harwoodii Munz & McBurn.]

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

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

Global Rank G5T3 State Rank S?

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

Habitat: Sonoran Desert Scrub with sandy washes or dunes is the preferred habitat of this annual. Near Ocotillo, the perennial vegetation was extremely open with substantial annual growth interspersed following good rainfall. Psorothamnus spinosa may grow nearby.

Known Sites: Harwood's Milk Vetch was reported in sandy washes near Elephant Tree Nature Trail south of Ocotillo Wells. No other sites are known for this species in San Diego County. An old report by Gander for 2 miles southwest of Carrizo Station has not been rediscovered. Herbarium collections were examined for Imperial County at Ogilby Road; as well as locales 3 miles west of Blythe, the Pinto Basin, and Chuckwalla Valley in Riverside County. It is reported by Felger in the Gran Desierto of Sonora, Mexico. Barneby reports it in Yuma County, Arizona south to the Colorado Delta in northeastern Baja California; to the head of the Gulf of California, northern Sonora, the San Lorenzo Islands, Angel de la Guardia, and the Desierto de San Julian.

Eight herbarium specimens from Baja California are deposited at the San Diego Natural History Museum, south to 15 miles west of Los Angeles Bay where collected by Harbison (SD 41763). Also collected on Angel De la Guardia Island in the Gulf of California. Subspecies insularis is more widely collected in the Baja deserts.

Status: The Harwood's Milk Vetch populations on the southern deserts, while apparently quite uncommon, are presumed stable, based on the limited impacts to their potential desert habitat. More information is needed on the desert range and cumulative population size of this species, and its tolerance for various microhabitats. Until such information is gathered, known sites should be protected.

Copyright May 1994 Craig H. Reiser.

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