Photo © Robert K. Moseley
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Astragalus jejunus S. Wats. var. jejunus

Starveling milkvetch

Fabaceae (Pea; Legume family)

General Description: A dwarfed, densely tufted, multi-stemmed perennial herb from a taproot having minute foliage with short, appressed, straight hairs. Leaves are pinnately compound and 1-6 cm long. The 9-15 linear leaflets are less than 5 mm long and 1.5 mm wide, and have the terminal leaflet continuous with the leaf stalk. The old, stiffly erect or recurving leaf stalks persist after the leaflets have been shed. The raceme inflorescence has 3-7 purplish flowers. The calyx is 1.7-3 mm long with white or partly black appressed hairs. Fruit pods are inflated, papery, ovoid or roundish in outline, 10-17 mm long, essentially beakless, and brightly mottled with red or purple.

Photo © Roger Rosentreter
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Illustration.

Field Identification Tips: Starveling milkvetch's low-growing, densely tufted, multi-stemmed habit, tiny leaflets, stiff, persistent leaf stalks, small purplish flowers, and papery, inflated, roundish, red-mottled pods distinguish it in the field.

Phenology: Flowers late May and June, to July at higher elevations.

Similar Species: None in southeastern Idaho.

Habitat: Dry barren ridges, bluffs or river terraces, on shale, tuff, clay, sandstone and cobblestone. In Idaho, starveling milkvetch occurs on knolls, ridges, and other exposures of raw, loose, sparsely vegetated, light-colored shale. It seems to be restricted to calcareous shale having a fine to stone size texture. These bright outcrops stand out visually on the landscape. Starveling milkvetch is found on all aspects, usually on gentle to moderately steep slope areas. Associated species in Idaho include Artemisia longiloba, Artemisia tridentata, Eriogonum brevicaule var. laxifolium, Mahonia repens, Stenotus acaulis, Cryptantha breviflora, Ivesia gordonii, Phlox hoodii, Pseudoroegneria spicata, and Achnatherum hymenoides.

Global Distribution: Basins of the Green and Bear rivers in southwestern Wyoming, and immediately adjacent Utah, Idaho, and northwestern Colorado. Disjunct populations are known from White Pine and northeastern Elko counties, Nevada.

Idaho Distribution: The southeastern corner of the state, in the southern Preuss Range, Sheep Creek Hills, and Bear Lake Plateau, all in Bear Lake County.

References:

Barneby, R. C. 1989. Intermountain Flora. Vascular plants of the Intermountain West, U.S.A. Vol. 3, Part B, Fabales. The New York Botanical Garden, Bronx, NY. 279 pp.

Mancuso, M., and R. K. Moseley. 1990. Field investigation of Astragalus jejunus (starveling milkvetch), Cryptantha breviflora (Uinta Basin cryptanth), and Eriogonum brevicaule var. laxifolium (varying buckwheat) in the Caribou National Forest. Unpublished report prepared by the Idaho Department of Fish and Game, Conservation Data Center, Boise, ID. 25 pp. plus appendices.

Wyoming Rare Plant Technical Committee. 1994. Wyoming rare plant field guide. USDI Bureau of Land Management; National Park Service; Fish and Wildlife Service; USDA Forest Service, Intermountain Region and Rocky Mountain Region; Wyoming Game and Fish Department; and The Nature Conservancy, Wyoming Natural Diversity Database.