Blue Mt. milkvetch is an upright, many-stemmed perennial wildflower with the clusters of stems arising to a height of 4-18 cm. The stems and leaves are nearly glabrous but may bear some long, soft, straight hairs. The numerous leaves are held nearly erect and measure from 7-30 cm long, with 21-41 leaflets which are linear to oblong-oblanceolate in shape, and measure 3-25 mm long and 1-4 mm wide. Individual leaves often have the margins folded upwards with the dorsal surface largely glabrous and the ventral surface covered with crinkled hairs.
The fairly stout flower stems are equal to or exceed the upper leaves. The racemes contain 6-35 flowers which may droop slightly or also be erect or spreading. Individual flowers are creamy or slightly yellow-tinged in color and 13-23 mm long. The banner is often well reflexed upward, and the wing petals are about 2-4 mm longer than the keel. The bell-shaped calyx is 7.5-10 mm long (but occasionally to 15 mm long) and is covered with whitish to blackish, appressed hairs. The calyx teeth are narrowly awl-shaped that are about one-half as long as the calyx tube. The pods are held erect and are smooth-skinned (glabrous), green at first, and 7-10 mm thick and up to 30 mm long. The pod may be straight to slightly arched.
Idaho Milk-vetch: Astragalus conjunctus - Calyx cylindrical, 6-15 mm long, about 2 times as long as thick. Calyx teeth 1.5-3 mm long. Corolla white or with purplish tip to keel and banner. Leaflets 13-31. Pod glabrous. Found from Wasco County, northcentral Oregon east to the Blue Mts. and south to the the Steens Mt. and east to southwestern Idaho.
Hood River Milk-vetch: Astragalus hoodianus - Calyx bell-shaped, 11-15 mm long, about 1.5 times as long as thick. Calyx teeth 4.5-7.5 mm long. Leaflets 17-37. Pod pubescent. Found near the Columbia River Gorge in Wasco and Hood River Counties in Oregon and Klickitat County in Washington.
Yakima Milk-vetch: Astragalus reventiformis - Calyx bell-shaped, 8-12 mm long, about 1.5 times as long as thick. Calyx teeth 2.5-5 mm long. Leaflets 17-37. Pod pubescent. Found from Kittitas County in Washington near Ellensburg south to Klickitat County, Washington and south into Sherman County of Oregon.
Blue Mt. Milk-vetch: Astragalus reventus - Calyx bell-shaped, typically 8-10 mm long. Leaflets 21-41. Pod glabrous. Found in the Blue Mts. of northeastern Oregon near the headwaters of the Umatilla and Grande Ronde Rivers into southeastern Washington.
Sheldon's Milkvetch: Astragalus sheldonii - Leaflets 23-41. Pod usually pubescent. Found from southern Asotin County in southeastern Washington south into Wallowa County, northeastern Oregon and into Lewis and Nez Perce Counties in Idaho.
Blue Mt. milkvetch is found on dry rocky slopes and grassy openings in the ponderosa pine forest.
Blue Mt. milkvetch is primarily found in the Blue Mts of southeastern Washington and northeastern Oregon, generally north of the headwaters of the Grande Ronde River. It is evidently found in western Idaho in the Hells Canyon area.
Blue Mt. milkvetch blooming on the east-facing slopes of Sourdough Ridge, Asotin Wildlife Area, Asotin County, WA.........June 3, 2017