Plants tuft- or mat-forming, mounds 1–3 dm wide, acaules­cent or subacaulescent, 1–2.5 cm, ashen-strigulose, hairs mal­pighian; branched caudex with thatch of marcescent stipules and leaf bases. Stems obscured by stipules and leaf bases. Leaves 0.5–3 cm; stipules dis­tinct, 1.5–3 mm, submembranous becoming papery; leaf­lets (3 or)5–9, blades elliptic, oblanceolate, or obovate, 1.5–5 mm, apex obtuse or subacute, surfaces ashen-strigulose. Peduncles axillary, ascending, 0.2–0.6 cm. Racemes (1 or)2(or 3)-flowered, flowers ascending; axis 0.1–0.3(–0.4) cm in fruit, slightly elongating; bracts 0.7–2.2 mm; bracteoles 0. Pedicels 2.2–3.5 mm. Flow­ers 9–11.5 mm; calyx campanulate, 4–5.9 mm, silky-strigulose, tube 3.2–4.2 mm, lobes subulate, 0.8–1.8 mm; corolla pink-purple, wing tips whitish, keel maculate, or near-white; keel 7.5–8.7 mm, apex blunt. Legumes ascending or spreading, green, slightly incurved, obliquely-ovoid, laterally compressed, 5–7.5 × 2.8–3.8 mm, thinly fleshy becoming stiffly papery, densely strigulose. Seeds 8–10. 2n = 22.

Phenology: Flowering May–Jun.
Habitat: Rocky knolls on high rolling plains, arid grasslands, on granitic or calcareous sub­strates.
Elevation: 1800–2000 m.

Distribution

• Generated Map
• Legacy Map

N.Mex.

Discussion

Astragalus siliceus is a narrow endemic of Guadalupe, Santa Fe, and Torrance counties in central New Mexico, where it is locally common, especially on rocky areas exposed by disturbance years earlier. Hundreds of dense, mounded mats provide a spectacular spring display of various whitish to pink-lavender hues when covered by low, close flowers. The extent of the population recently discovered in Santa Fe County is not documented; the plants collected there have measurements in the small end of the range for A. siliceus.

Selected References

None.

Lower Taxa

None.