Plants somewhat slender, (10–)15–40 cm, gray-villous; from superficial caudex; taproot woody. Stems decumbent to ascending, gray-villous. Leaves (3–)4–11 cm; stipules distinct, 3–8 mm, submembranous; leaf­lets 11–19, blades elliptic to linear-elliptic or oblanceolate, 6–16 mm, apex acute, surfaces villous. Peduncles erect or narrowly ascending, 1.5–6.5 cm. Racemes (7–)10–21-flowered, flowers spreading, later declined or nodding; axis (2–)3.5–9(–11) cm in fruit; bracts 1.5–4.5 mm; bracteoles 0 or 1. Pedicels 0.5–1.8 mm. Flowers 5.3–7.4 mm; calyx campanulate or turbinate, 3.8–5.6 mm, densely villous, tube 1.6–2.5 × 1.8–2.6 mm, lobes setaceous, 1.7–3.4 mm, not accrescent and covering 1/2 of mature legume; corolla whitish and lilac-tinged, banner veins purple; banner recurved through 50°; keel 3.8–4.9 mm, apex obtuse. Legumes declined or deflexed, stramineous, straight, subsymmetrically ellipsoid or ovoid-ellipsoid, 3-sided compressed, 5–8 × (2–)2.5–3.5 mm, papery, villous-tomentulose, hairs 1+ mm; stipe (0.1–)0.3–0.5 mm. Seeds 4–8.

Phenology: Flowering May–early Jul.
Habitat: Low hills and rolling plains, on sandy or loamy basaltic soils, with sagebrush.
Elevation: 100–700 m.

Distribution

• Generated Map
• Legacy Map

Wash.

Discussion

Astragalus lyallii occurs in central and southeastern Washington. R. C. Barneby (1964) called this a species of great theoretical interest because of its presumed close relationship to two species, A. caricinus and A. spaldingii, which are not closely related to each other. He postulated that it was more similar to the latter in its diffuse growth-habit and distinct stipules, and similar to the former in its loosely racemose, nodding flowers and declining, exserted fruits. He proposed a hybrid origin for A. lyallii involving these two species, followed by generations of selection, an argument supported by morphological intermediacy and the geographical dis­tribution of the species.

Selected References

None.

Lower Taxa

None.