Tygh Valley milk-vetch is a perennial wildflower with closely clustered, spreading to erect stems from 20-30 cm high. As seen in the photo below, individual plants may form a broad clump up to a meter in diameter and up to half a meter high. The stout, deeply grooved stems are densely covered with whitish, long, spreading hairs as are the leaves. The pinnately compound leaves are 7-10 cm long with 15-25 marrow to widely elliptic or elliptic-oblong leaflets. The individual leaflets are 8-12 mm long and have rounded or acute tips, or the tips end with a short, sharp, abrupt point.
The stout flower stems are equal to or longer than the leaves. The flowers form dense, short racemes that only elongate slightly in fruit. The cylindrical calyx is about 8 mm long with narrow awl-shaped teeth nearly equal to the length of the tube. The calyx is also covered with long, white, spreading hairs which makes the inflorescence sparkle in the sun (See photo at right.) The corolla is light yellow in color and measures 9-12 mm long. The back of the banner and the outer surface of the wings are both covered with long, spreading hairs. The pods are obliquely ovate in shape, somewhat compressed and heart-shaped in cross-section. The pods measure 5-7 mm long and are densely covered with whitish, long, spreading hairs.
Spalding's Milk-vetch: Astragalus spaldingii - Flowers white tinged with lilac and glabrous on the outer surfaces. Calyx covered with whitish, long spreading hairs. Leaflets covered with shorter, gray or whitish hairs, so not as shaggy in appearance as those of Tygh Valley milk-vetch. Plants of grasslands and the sagebrush desert from Douglas and Lincoln Counties in north-central Washington south to Yakima and Benton Counties in south-central Washington. Found eastward to the Clearwater Valley in westernnn Idaho and southward to Umatilla County and central Baker County in northern and northeastern Oregon.
Tygh Valley milk-vetch may be found on dry grassy hillsides or in dry, forest clearings.
Tygh Valley milk-vetch is endemic to Tygh Valley and the White River of central Wasco County in north-central Oregon.
This plant which is growing amongst basalt boulders in a forest clearing full of cheatgrass has formed a clump about a meter in diameter.