Plants dwarf, clump-forming, acaulescent or subacaulescent, 3–9 cm, silky-strigose to strigu­lose, hairs malpighian, lustrous; from superficial caudex. Stems obsolete, ascending, or pros­trate, radiating from root-crown, to 3 cm, internodes mostly obscured by leaf bases, silky-strigose to strigulose. Leaves (1.5–)2.5–10 cm; stipules 3–7 mm, submembranous; leaflets 7–13, blades obovate-cuneate or elliptic-oblanceolate, 3–12 mm, apex obtuse or subacute, surfaces strigulose. Peduncles ascending, 0.5–3(–5) cm. Racemes 2–10-flowered, flowers ascending; axis 0.1–1.5 cm in fruit; bracts 1.5–5.5 mm; bracteoles 0(–2), exceptionally conspicuous. Flowers (14.5–)15–18.5 mm; calyx cylindric or vase-shaped, 6–10.5 mm, strigulose, hairs black or white, tube 6.5–8 mm, lobes subulate, 1.3–2.5 mm; corolla white, whitish, or ochroleucous; banner recurved through 40°; keel 8.3–14.3 mm. Legumes spreading-ascending (humistrate), green or purplish becoming brownish or stramineous, scarcely to moderately incurved, obliquely ovoid, lanceolate-ovoid, or lunately ellipsoid, obcompressed becoming laterally compressed distally, 9–20(–22) × 4–8 mm, unilocular, distinctly beaked, leathery, walls much less than 1 mm thick, densely strigulose. Seeds 18–33.

Phenology: Flowering May–early Jul.
Habitat: Gentle slopes and flats in ponderosa pine and pinyon-juniper forests, rarely in oak woodlands, in dry stony soils of basaltic or, rarely, calcareous substrates.
Elevation: (1800–)1900–2500 m.

Distribution

• Generated Map
• Legacy Map

Ariz., Utah.

Discussion

Astragalus castaneiformis is a species of the Kaibab and Mogollon plateaus, Coconino County, Arizona, extending southeastward to the Natanes Plateau, in Gila County. To the north, it just enters Kane County, Utah, in the Buckskin Mountains.

Selected References

None.

Lower Taxa

None.