Plants 5–15 cm, strigulose; from shallow, subterranean caudex. Stems ascending and radiating, to 6(–9) cm underground, strig­ulose. Leaves 5–10 cm; stipules connate-sheathing at proximal nodes, distinct at distal nodes, (3–)5–11 mm, membranous; petiolate; leaflets 19–27, blades elliptic or elliptic-obovate, 7–16 mm, apex shallowly emarginate, surfaces sparsely strigose abaxially, gla­brous or glabrescent adaxially. Peduncles ascending, 4.5–7.5 cm. Racemes 10–16-flowered, flowers ascending to spreading; axis 1–2 cm in fruit; bracts 6–10 mm; bracteoles 2. Pedicels 2–2.5 mm. Flowers 17–19 mm; calyx purplish, short-cylindric, 9–10.5 mm, sparsely pilosulous, tube 7–8.5 mm, lobes subulate, 2 mm; corolla bright pink-purple; keel 13–14 mm. Legumes pale green or reddish becoming stramineous suffused with brown-purple, straight, globose to plumply oblong-ellipsoid, terete or slightly dorsiventrally compressed, 14–26 × 12–16 mm, bilocular, somewhat fleshy, gla­brous; valves differentiated into double envelope separated by air space 1.5–2 mm wide. Seeds 26–28.

Phenology: Flowering Jun–Jul.
Habitat: Limestone juniper glades, edges of shrub thickets.
Elevation: 200–300 m.

Distribution

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Tenn.

Discussion

Astragalus bibullatus, restricted to three sites in Rutherford County, is nearest to A. crassicarpus, but disjunct by approximately 750 km. A population from Davidson County was apparently extirpated by construction of the Percy Priest Reservoir. In comparison to A. crassicarpus, it has a reduced ovule number and specialized fruits, particularly the double-envelope of the valves upon which the taxon is based in large part.

Astragalus bibullatus is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Selected References

None.

Lower Taxa

None.