Astragalus nudisiliquus

Plants mat-forming, caulescent, (2–)5–25(–30) cm, white-tomentose, hairs basifixed; from root-crown; taproot loosely forked. Stems diffuse or prostrate, radiating from root-crown, white-tomentose, white-felted. Leaves 3–11 cm; stipules (1.5–)3–7 mm, thinly herbaceous becoming membranous; leaflets (7–)11–17, blades broadly obovate, obovate-cuneate, or broadly oblanceolate, 4–17 mm, apex usually obtuse, sometimes subacute or subretuse, surfaces tomentose. Peduncles incurved-ascending, 1–7 cm. Racemes (2–)4–8-flowered, flowers ascending; axis 0.5–2.5 cm in fruit; bracts (1.5–)3–6 mm; bracteoles 0–2. Pedicels 1.4–3.4 mm. Flowers 19–25.5 mm; calyx cylindric, 12–17(–19) mm, sparsely villosulous, tube (11.3–)12–13.8 mm, lobes subulate-setaceous, (2–)3–5 mm; corolla pink-purple, banner with white or pale eye-spot, this with pink-purple lines; banner recurved through 40°; keel 17.4–21.3 mm. Legumes ascending (humistrate), brown or stramineous, strongly incurved, obliquely ovoid or oblong-ellipsoid, strongly obcompressed, (15–)20–40(–45) × (8–)9–13 mm, unilocular, fleshy becoming stiffly leathery, sparsely villous-hirsute, hairs 1+ mm. Seeds 30–41.

Phenology: Flowering late Apr–early Jul.
Habitat: Summits and gullied slopes of river bluffs and terraces, on sand, sandy clay, or cobblestone alluvia.
Elevation: 600–1100 m.

Idaho, Oreg.

Discussion

Astragalus nudisiliquus occurs in east-central Oregon and southwestern Idaho as far east as Cassia County, with greatest abundance along the Snake River and its tributaries.

The specific epithet nudisiliquus is a misnomer, although the hairs on the fruit of Astragalus nudisiliquus are spaced sufficiently apart that the surface is evident. It may be easily confused, especially when in flower, with two varieties of A. purshii in the same region; var. ophiogenes is ecologically congruent but has much smaller flowers, and var. glareosus is usually at higher elevations and has mostly 2–5-flowered racemes.

Selected References

None.

Lower Taxa