Astragalus osterhoutii

Astragalus osterhoutii is a rare species of milkvetch known by the common name Osterhout milkvetch. It is endemic to Grand County, Colorado, where it is known from a few populations in Middle Park, a mountain basin.[1] There are five or six occurrences.[2] It is a federally listed endangered species.

Astragalus osterhoutii

Critically Imperiled  (NatureServe)
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Genus: Astragalus
Species:
A. osterhoutii
Binomial name
Astragalus osterhoutii

The plant grows on sagebrush badlands on soils originating from the Niobrara Formation and the Pierre Shale. The gray-brown shale and siltstone clay soils are high in selenium, which the plant concentrates, causing it to develop a foul odor.[3]

This is a perennial herb producing many slender, erect, green stems up to a meter tall. The leaves are made up of several narrow linear leaflets up to 3 centimeters long. The inflorescence bears cream-colored, pealike flowers each over 2 centimeters long. The fruit is a flattened legume pod up to 4 centimeters long.

Threats to the species include flooding and reservoir creation, which have eliminated at least one occurrence.[2][3] All-terrain vehicle use and oil and gas exploration activities damage the habitat occupied by the plant.[2][3] The species was named after botanist George Everett Osterhout.

References
  1. USFWS. Final rule to determine Astragalus osterhoutii and Penstemon penlandii to be endangered species. Federal Register July 13, 1989.
  2. The Nature Conservancy
  3. Center for Plant Conservation Archived December 15, 2010, at the Wayback Machine


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