Plants clump-forming, slender, 30–60 cm, strigulose, hairs basi­fixed; from superficial caudex. Stems erect to ascending, strigu­lose. Leaves 5–21 cm; stipules 2.5–6 mm, papery at proximal nodes, subherbaceous at distal nodes; leaflets (15–)19–27(or 29), blades oblong, oblong-oblanceolate, or linear-oblong to linear, 5–25 mm, apex truncate to retuse or apiculate, surfaces strigulose abaxially, glabrous adaxially. Peduncles erect, 8–20(–25) cm. Racemes 10–20(–25)-flowered, flowers nodding; axis (3–)5–27 cm in fruit; bracts 1–3.5 mm; bracteoles 0–2. Pedicels 0.7–4 mm, little, if any, clavate thickening in fruit. Flowers 13–15.5 mm; calyx cam­panulate, 5.1–6.6 mm, strigulose-pilosulous, tube 3.8–4.9 mm, lobes subulate, 1–1.9 mm; corolla white or cream, drying ochroleucous, immaculate; banner recurved through 45–90°; keel 10.2–11.8(–12.5) mm. Legumes erect, greenish stramineous, straight, linear-oblong or narrowly oblong-ellipsoid, obtusely 3-sided, lateral face convex, dorsal face scarcely narrower, grooved or not, 14–24(–28) × 2.7–4.5 mm, ± bilocular, firm and scarcely fleshy becoming leathery, glabrous or strigulose; septum 0.8–1.7 mm wide; stipe (2.5–)3–6 mm. Seeds 20–29. 2n = 22.

Phenology: Flowering May–Jul.
Habitat: Grass and sagebrush-grass com­munities.
Elevation: 300–2500 m.

Distribution

• Generated Map
• Legacy Map

Idaho, Mont.

Discussion

Astragalus atropubescens occurs in Custer, Idaho, and Lemhi counties in Idaho, and adjacent Beaverhead, Lewis and Clark, and Silver Bow counties in western Montana.

The combination of typically widely spaced, mod­erately sized, white (drying ochroleucous) flowers with immaculate keel followed by erect or erect-ascending, stipitate, subcylindrical (obtusely three-sided) legumes is diagnostic for Astragalus atropubescens. The legume bodies and shorter stipes borne in the same plane (or nearly so) distinguish this species from the closely geo­graphically adjacent A. scaphoides.

Selected References

None.

Lower Taxa

None.