Plants annual or biennial, slen­der, 5–15 cm, strigulose; from superficial root-crown; taproot slender. Stems usually 3–10, decumbent to ascending, strigu­lose. Leaves 2–5(–6) cm; stipules distinct, 1.5–4 mm, papery at proximal nodes, herbaceous or submembranous at distal nodes; leaflets (5 or)7–13, blades oblong-obovate, -ovate, or obovate-cuneate, (2–)3–12 mm, apex obtuse, truncate, or retuse, surfaces glabrous. Peduncles divar­icate, 1–4(–5.5) cm. Racemes (3–)7–15-flowered, flow­ers ascending becoming spreading, later declined; axis (0.4–)1–3.5(–4.5) cm in fruit; bracts 0.8–1.8 mm; brac­teoles 0. Pedicels 0.6–1.8 mm (in fruit). Flowers 6.7–9.1 mm; calyx campanulate, 3.5–4.5 mm, strigulose, tube 2–2.6 mm, lobes lanceolate-subulate, 1.3–1.9 mm; corolla whitish, banner with lavender veins; banner incurved through 45°; keel 4.1–5.7 mm, apex obtuse, sometimes obscurely beaklike. Legumes deflexed or declined, purplish green becoming stramineous then brownish, lunately incurved, usually obliquely linear-oblong, oblanceoloid, or semi-ellipsoid, rarely semi-ovoid, somewhat inflated, almost bladdery, usually ± 3-sided compressed, (10–)15–28 × 3–9 mm, unilocular or subunilocular, thin becoming papery-membranous, translucent, sparsely and minutely strigulose, hairs straight, appressed; seed-bearing flange to 2.5 mm wide, septum 0.5–1 mm. Seeds (6–)8–14. 2n = 28.

Phenology: Flowering Apr–Jun.
Habitat: Gravelly soils overlying basalt, sandbars, sandy banks.
Elevation: 50–600 m.

Distribution

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Oreg.

Discussion

Astragalus diaphanus occurs along the John Day River from near Dayville in Grant County, Oregon, westward along the Columbia River to slightly south of The Dalles, but is considered extirpated in Washington. R. C. Barneby (1964) discussed variation in this species in detail and compared it with A. wetherillii, a species disjunct by hundreds of kilometers in west-central Colorado.

Selected References

None.

Lower Taxa

None.