Astragalus solitarius
Plants 20–45 cm, strigulose-cinereous; from shallow, subterranean caudex. Stems erect, strigulose-cinereous. Leaves 2–7 cm; stipules 1–3 mm, papery at proximal nodes, herbaceous at distal nodes; leaflets 5–9, blades linear to linear-oblong, 3–15 mm, apex obtuse to subacute, surfaces strigose, sometimes glabrescent adaxially. Peduncles divaricate and incurved-ascending, (3–)5–15 cm. Racemes (3–)7–30-flowered; axis (1.5–)4–25 cm in fruit; bracts 0.6–1.5 mm; bracteoles 0. Pedicels 1–2 mm. Flowers 6.3–8 mm; calyx 2.6–3.2 mm, strigose, tube 2.3–2.8 mm, lobes deltate or subulate, 0.3–0.8 mm; corolla ochroleucous, concolorous; keel 6.3–7.4 mm. Legumes pendulous, pale green, often faintly purple-mottled, becoming stramineous, straight or falcately decurved, narrowly oblong or lanceoloid-oblong, 12–25 × 3–4(–5) mm, papery, strigulose; stipe 4–8 mm. Seeds (6–)8–14.
Phenology: Flowering May–early Jul.
Habitat: Sandy clay soils, almost always under low sagebrush.
Elevation: 900–1500 m.
Distribution
Nev., Oreg.
Discussion
Astragalus solitarius is a narrow endemic of southern Harney and Malheur counties, Oregon, and adjacent Nevada. Plants are usually intertangled with low sagebrush and may establish only with protection (R. C. Barneby 1964). It is closely related to A. alvordensis, and the ranges of the two overlap along the Owyhee River, near Rome, Oregon, but there they are ecologically separate. Astragalus solitarius occurs on stiff clays of valley floors and mesas, whereas A. alvordensis grows on bluffs and knolls where the soil is deep, soft, and porous, and plants often form colonies in the open.
Selected References
None.