Plants slender, forming bushy clumps, 2–16(–26) cm, strigu­lose; from superficial caudex. Stems erect or ascending, strigu­lose. Leaves (4–)5–14 cm; stip­ules 2–6(–7) mm, thinly her­baceous becoming papery; leaf­lets (15–)19–25(or 27), blades elliptic, linear-elliptic, or oblan­ceolate, 2–14 mm, apex obtuse to subacute, truncate-apiculate, or shallowly retuse, surfaces strigulose abaxially, glabrous adaxially. Peduncles ascending, often incurved, (7–)10–18(–20) cm. Racemes (5–)8–20-flowered; axis (2.5–)5–15 cm in fruit; bracts 1.5–3.5 mm; bracteoles 0. Pedicels 1–4 mm. Flowers 11.7–15.2 mm; calyx 6.6–8.8 mm, strigose, tube 4.5–6 mm, lobes lanceolate-subulate, 1.8–3.5 mm; corolla ochro­leucous, immaculate; banner recurved through 50–85°; keel (9.5–)10–11.7 mm. Legumes pendulous, stramin­eous, straight or gently incurved, linear-ellipsoid, 3-sided and laterally com­pressed, lateral face flat, dorsal face grooved, (25–)30–45 × 2.5–3.3 mm, length mostly 10 times width, papery, finely strigulose; septum 1.6–2.3 mm wide; stipe 6–15 mm. Seeds (16–)18–30. 2n = 24.

Phenology: Flowering mid Apr–Jun.
Habitat: Grassy hills, meadows, basaltic soils.
Elevation: 200–900 m.

Distribution

• Generated Map
• Legacy Map

Idaho, Oreg., Wash.

Discussion

The main area of dispersal of Astragalus arthurii does not exceed 80 km; it is restricted to the Snake River and its tributaries in extreme southeastern Washington and contiguous Idaho and northeastern Oregon.

Selected References

None.

Lower Taxa

None.