Plants slender, delicate, wiry, caulescent, 15–40 cm, strigu­lose, hairs basifixed; from super­ficial to slightly subterranean branched caudex. Stems decum­bent to ascending, strigulose. Leaves (2.5–)4–10 cm; stipules 1.5–2.5 mm, papery at proximal nodes, herbaceous or with her­baceous tips at distal nodes; leaflets (5 or)7–13, blades broadly oblong-elliptic to lanceolate-oblong or linear-elliptic, 2–10(–15) mm, apex obtuse to truncate, shal­lowly retuse, or subacute, surfaces strigulose abaxially, sparsely strigulose or glabrous adaxially. Peduncles straight, sometimes incurved-ascending, 3–15 cm. Racemes (3–)6–14-flowered, flowers ascending; axis (1–)2–8 cm in fruit; bracts 0.8–2.5 mm; bracteoles 0–2. Pedicels 0.5–2.2 mm. Flowers 7–10.5 mm; calyx short-cylindric, (3.1–)3.6–5.5 mm, strigulose, tube (2.3–)2.8–4 mm, lobes triangular to subulate, 0.4–1.6 mm; corolla ochroleucous or whitish suffused with lilac; banner recurved through 45°; keel (6.3–)7–10 mm, apex tri­angular and beaklike. Legumes persistent on receptacle until well after maturity, falling while still attached to pedicel, erect, stramineous, straight, linear-oblong, obtusely 3-sided compressed, 10–25 × 2.4–3.3 mm, ± bilocular, thinly fleshy becoming leathery, strigulose; septum 1–1.4 mm wide; sessile or subsessile. Seeds 14–23.

Phenology: Flowering May–Jul.
Habitat: Sandy to fine-textured substrates or gravelly slopes, with juniper, sagebrush, bitterbrush, or rabbitbrush.
Elevation: 900–2300 m.

Distribution

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Calif., Idaho, Nev., Oreg.

Discussion

Astragalus obscurus occurs in northern and north-central California, southwestern Idaho, northern and western Nevada, and southeastern Oregon.

R. C. Barneby (1964) discussed variation in Astragalus obscurus, including one morphologically differentiated outlier from the northern foothills of Mount Shasta in Siskiyou County, which may represent a distinct variety.

Selected References

None.

Lower Taxa

None.