Astragalus lonchocarpus

Plants often densely clump-forming, slender, (22–)30–85(–90) cm, strigulose; from shallow, subterranean caudex. Stems erect, 1–8 cm underground, strigulose. Leaves 2–13 cm; stipules distinct throughout, 1–9(–10) mm, stiff-papery at proximal nodes, herbaceous becoming papery at distal nodes; leaflets (1 or)3–9(or 11), blades linear to narrowly oblanceolate, 2–36 × 0.5–4 mm, apex obtuse to acute, surfaces usually strigose, sometimes glabrous adaxially; terminal leaflet decurrent distally, not jointed to rachis. Peduncles erect or incurved-ascending, 6–24 cm. Racemes 7–40+-flowered, flowers spreading-declined; axis 3.5–45 cm in fruit; bracts 0.8–2.5 mm; bracteoles 0. Pedicels 1.3–4.5 mm. Flowers 13–20 mm; calyx brown, cylindric-gibbous, 5.8–10.3 mm, strigose, tube 5–8 mm, lobes subulate, 0.6–2.5 mm; corolla ochroleucous to nearly white, concolorous; banner recurved through 50°; keel 10.5–14 mm, apex bluntly or sharply deltate. Legumes pendulous, often brownish, straight or slightly curved, ellipsoid to oblong, dorsiventrally compressed, convex, 22–50 × 3.3–6.2(–7.5) mm, stiffly papery, faces smooth or cross-reticulate, strigose or glabrous; stipe 3–15 mm. Seeds 12–26. 2n = 22.

Phenology: Flowering May–Jul.
Habitat: Salt desert shrub, blackbrush, and pinyon-juniper communities, often on low-quality substrates such as saline shale and clay.
Elevation: 1100–2600 m.

Ariz., Colo., Nev., N.Mex., Utah.

Discussion

The main center of distribution of Astragalus lonchocarpus, a relatively tall, handsome, pale-flowered species, is in the Colorado Plateau. The species is sporadic and widely dispersed in the Great Basin as if recently introduced, perhaps by livestock. G. W. Smith et al. (1992) reported the indolizidine alkaloid swainsonine in this species, but there is little evidence that the plant is grazed by livestock. J. D. Karron (1989) reported the species to be self-compatible, and no inbreeding depression was detected in seedling produced by self-fertilization.

Selected References

None.

Lower Taxa