Plants cushion- or mat-forming, 1.5–9 dm wide, caulescent, 1–8 cm, silvery-pilose; from branched caudex, branches with thatch of persistent petioles; taproot stout. Stems prostrate, silvery-pilose. Leaves 1–4 cm; stipules 2–8 mm, hyaline, densely pilose abaxially; leaflets usually 3, rarely 5, blades narrowly to broadly oblanceolate or obovate-cuneate, 3–13 mm, apex subacute, surfaces silvery-pilose. Peduncles 0.5–2.5 cm. Racemes (2 or)3–5-flowered; axis to 1 cm in fruit; bracts 1–2.5 mm. Pedicels 1–3.5 mm. Flowers 5–6.2(–8) mm; calyx cam­panulate, 2.4–4.2 mm, densely pilose, tube 2–3 mm, lobes triangular-subulate, 1–1.2 mm; corolla pink-purple or white, often drying yellowish; banner recurved through 90°; keel 4–4.5 mm, apex bluntly deltate. Legumes ascending or recurved, ovoid-ellipsoid, slightly compressed, 3–4.5 × 2 mm, papery, densely silky-strigose or silky-pilose. Seeds 6–10.

Phenology: Flowering late May–Jul.
Habitat: Barren ridges, knolls, hill­tops, on gravelly clay, shale outcrops in higher prairies.
Elevation: 1100–1700 m.

Distribution

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Colo., Kans., Nebr., N.Mex., Wyo.

Discussion

Astragalus sericoleucus occurs on Niobrara Shale out­crops from southeastern Wyoming to western Nebraska, northwestern Kansas, and northeastern Colorado, with a disjunct population in Union County in northeastern New Mexico.

Selected References

None.

Lower Taxa

None.