Astragalus proimanthus

Plants tuft- or cushion-forming, 0.5–2(–3+) dm wide, acau­lescent, silvery-hirsute; from branched caudex, branches with thatch of marcescent stipules and petioles. Stems obscured by stipules and marcescent leaf bases. Leaves unifoliolate or palmately trifoliolate, 1–3.5 cm; stipules sometimes ruptured in age, 7–12 mm, hyaline; leaflet blades spatulate to elliptic, (3–)5–9 mm, apex acute to subacute, surfaces silvery-pilosulous. Peduncles subobsolete. Racemes 1- or 2-flowered, cap­itate; axis obsolete or very short; bracts sometimes tri­dentate, 3–6 mm; bracteoles 2. Pedicels subobsolete. Flowers 12.3–17 mm; calyx 8.3–10.5 mm, loosely villous, tube 5.9–6.5 mm, lobes linear to narrowly subulate, 2.4–4.2 mm; corolla whitish to ochroleucous, petals glabrous abaxially; banner differentiated into blade and claw, with shoulderlike projections at middle; keel 11.1–12.8 mm. Legumes green, straight or slightly decurved, narrowly ellipsoid, 7–10 × 2.5–3 mm, fleshy becoming leathery, densely strigose-hirsutulous. Seeds 11–14.

Phenology: Flowering late Apr–mid Jun.
Habitat: Barren, white shale hills, ridges of shale bluffs, with Cryptantha and wheatgrass.
Elevation: 1900–2200 m.

Distribution

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Wyo.

Discussion

Astragalus proimanthus is restricted to the valley of Henry’s Fork in southern Sweetwater County. Plants appear as miniature A. gilviflorus, being smaller in all parts.

Selected References

None.

Lower Taxa

None.