Astragalus monumentalis

Plants dwarf, acaulescent or subacaulescent, 3–18 cm, strigulose, hairs basifixed or shortly malpighian; from branching caudex, often with thatch of marcescent leaf bases. Stems obsolete, ascending, 0.5–6 cm, internodes usually concealed by stipules, strigulose. Leaves 1.5–8(–11) cm; stipules distinct throughout, 2–4 mm, membranous becoming papery, stramineous; leaflets (5–)9–17(–21), blades oval to obovate or oblanceolate, 2–9 mm, apex obtuse, acute, or emarginate, surfaces strigulose abaxially, glabrous or glabrate adaxially. Peduncles ascending, 1–12 cm. Racemes 3–9-flowered, flowers ascending; axis 0.5–7 cm in fruit; bracts 1.5–5 mm; bracteoles 0. Pedicels 0.8–2.2 mm. Flowers 7–10.5 mm; calyx purplish, campanulate, 3.6–4.5 mm, strigose, tube 3–3.5(–4.5) mm, lobes subulate, 0.5–1.4 mm; corolla pink-purple; keel 7.8–12.4 mm. Legumes separating from receptacle at maturity, ascending (humistrate), green, often purple-mottled, becoming stramineous, straight or incurved, narrowly oblong to lanceoloid, 3-sided compressed, 12–17(–21) × 2–3 mm, ± bilocular, thinly fleshy becoming papery, strigose; sessile or subsessile. Seeds 16–30.

Phenology: Flowering Apr–Jun.
Habitat: Rimrock and other slickrock in mixed desert shrub and pinyon-juniper communities.
Elevation: 1200–1900 m.

Utah.

Discussion

Astragalus monumentalis, A. cottamii, and A. deterior are exploiters of crevices in sandstone rimrock. They are allopatric except for confluence of the first two in the vicinity of Natural Bridges National Monument, San Juan County, Utah. The three differ from each other to about the same degree. Astragalus monumentalis is restricted to Garfield and San Juan counties.

Selected References

None.

Lower Taxa