Endangered Species
Mountain-Prairie Region


Holmgren milk-vetch
(Astragalus holmgreniorum)
Shivwits milk-vetch
(Astragalus ampullarioides)

Species Description:  Both Astragalus holmgreniorum (Holmgren milk-vetch) and A. ampullarioides (Shivwits milk-vetch) are members of the pea family (Fabaceae or Leguminosae).  Holmgren milk-vetch is a shortlived perennial; few plants live past three years, with 4 years being the oldest documented lifespan.  The best time to detect the species is while it is producing flowers (typically between March and April) and fruit (the majority of plants set fruits by the end of April).  The population consists of approximately 500 to 10,000 plants depending on yearly conditions.  Shivwits milk-vetch is a perennial herb.  Its lifespan is unknown, but available data indicate a lifespan of at least 9 years.  Flowering occurs between March and late May.  Shivwits milk-vetch popoulations numbers less than 2,000 plants.

Location:  Holmgren milk-vetch is found in both Washington County, Utah (UT), and Mohave County, Arizona (AZ), while Shivwits milk-vetch is only found in Washington County, UT.  Both species are narrowly distributed Mojave Desert endemics. Three populations of Holmgren milk-vetch and five populations of Shivwits milk-vetch are known to exist.  Holmgren milk-vetch grows on the shallow, sparsely vegetated soils derived primarily from the Virgin limestone member of the Moenkopi Formation.  Shivwits milk-vetch grows only on purple clay soils derived from the Petrified Forest member of the Chinle geological formation.

Recent Actions: On September 28, 2001, the U.S. Fish and Wildlife Service (Service) listed Holmgren and Shivwits milk-vetches (66 FR 49560) as endangered under the Endangered Species Act of 1973, as amended. 

On September 29, 2006, the Service published the final recovery plan in the Federal Register.

The Service announced on December 26, 2006 a final rule designating approximately 6,289 acres as critical habitat for the Holmgren milk-vetch in Mohave County, Arizona and Washington County, Utah; and approximately 2,151 acres as critical habitat for the Shivwits milk-vetch in Washington County, Utah.

In April 2007, the Service completed a 5-year review of the status of the Holmgren and Shivwits milk-vetch. This status review conclued non change in its listed status under the Endangered Species Act was necessary.

More information about the Holmgren milk-vetch and the Shivwits milk-vetch can be found through the Service's ECOS webpage


Last updated: May 7, 2010