Astragalus yoder-williamsii, commonly known as the Osgood Mountains milkvetch, or mud-flat milkvetch, is a species of flowering plant in the family Fabaceae. It is a subshrub with leaflets, white flowers, and pod fruits. The species is native to the western United States.
Astragalus yoder-williamsii was described in 1980, and is considered Vulnerable by NatureServe.
Taxonomy The species was described by Rupert Charles Barneby in 1980.
Distribution Astragalus yoder-williamsii is native to the temperate biome of Idaho and Nevada, United States. It has been reported from Oregon, but this may be a false report. The species' overall range is .
Astragalus yoder-williamsii grows in shrublands and chaparral, at elevations of . It is found on dry ridge crests, stony flats, and disturbed roads. The species is associated with Artemisia arbuscula and Artemisia tridentata.
Description Astragalus yoder-williamsii is a small perennial subshrub. It is densely tufted, and has a taproot. The stems are long.
The leaflets are long. The leaflets are arranged oppositely, or are scattered.
The inflorescence is a raceme with two to eight flowers. The stem of the inflorescence is long. The calyx is long. The calyx tube is bell-shaped, long, and wide. The tube has long teeth. The petals are whitish.
The fruit is a pod, which is pendulous, or confined among the leaf stems. The pod is elliptical, long, and wide. The fruit stalk is long. The seeds are long, and ochre to pale green in colour.
Conservation NatureServe lists Astragalus yoder-williamsii as Critically Imperiled in both Idaho and Nevada, but as Vulnerable overall. The population consists of 1000 to 2500 individuals. The species is threatened by mining, and the use of off-road vehicles.
In 1981, the species received an emergency listing of Endangered. This listing has expired.
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