Astragalus osterhoutii

Astragalus osterhoutii

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

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. 1 2 3 The Nature Conservancy
  3. 1 2 3 Center for Plant Conservation Archived December 15, 2010, at the Wayback Machine.


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