Well developed desert dunes are the preferred habitat of this short-lived perennial. The dearth of this habitat on the San Diego County deserts probably accounts for its rarity there. Much better habitat is found on the dune systems east of El Centro in Imperial County. Biological survey reports note a site approximately 8 miles north of the Superstition Hills, as well as north of the New Coachella Canal and north of Highway 78. Shreve and Wiggins report this species in Arizona from the vicinity of Yuma.
Astragalus magdalenae var.
The status of Peirson's Milk Vetch in San Diego County is unknown. Until more cumulative population and range information is available, all populations should be protected. Copyright May 1994 Craig H. Reiser.