Astragalus oreganus

Plants somewhat stout and leafy, 6–20(–25) cm, strigose; from deep, subterranean caudex, rhizomes horizontal or obliquely ascending, slender. Stems from rhizome buds, internodes short and strongly flexuous, decumbent, ascending distally, 3–10(–14) cm underground, strigose. Leaves (2.5–)5–15 cm; stipules bidentate, (2.5–)3.5–11 mm, papery, pallid; leaflets (7 or)9–15(–21), blades broadly obovate or suborbiculate-obcordate, 4–20 mm, apex obtuse or widely and shallowly notched, surfaces strigose, sometimes less densely so adaxially. Peduncles erect or divaricate, 1.5–5.5 cm. Racemes (15–)20–35-flowered, flowers nodding; axis 3–7.5 cm in fruit; bracts 2–5.5 mm. Pedicels 0.6–2.2 mm. Flowers 15.5–19 mm; calyx deeply campanulate or subcylindric, 6.5–10 mm, sparsely strigulose, tube 5.5–7.3 mm, lobes subulate, 1–3 mm; corolla ochroleucous, concolorous; keel 11.5–13.5 mm. Legumes erect or narrowly ascending, brown, ± straight or incurved through 0.25 spiral, oblong, slightly obcompressed, 1–1.5(–1.8) × (3–)4–6 mm, fleshy becoming leathery, sparsely strigulose; sessile. Seeds (17–)20–28.

Phenology: Flowering mid May–Aug.
Habitat: Barren bluffs, gullied knolls, swales, dunes, detritus under cliffs or buttes, on sandy or sandy-clay soils from weathered sandstone, on alkaline clay flats moist in spring.
Elevation: 1100–2100 m.

Mont., Wyo.

Discussion

Astragalus oreganus is a xeric badland species, probably a recent habitat-specialized derivative of A. canadensis var. brevidens (R. C. Barneby 1964); it occurs from south-central Wyoming to north-central and south-central Montana.

Selected References

None.

Lower Taxa