Non-technical Description: Sodaville milkvetch is a short-lived perennial forb with multiple, spreading to weakly erect, leafy, glabrate to grayish appressed-hairy stems 10-30 cm long.  Leaves are 4-11 cm long, once-pinnately compound with 11-19 obovate leaflets, and have few basally-attached hairs.  Stipules at the base of the leaf stalk are not united into a tube.  The inflorescence is a raceme 1.5-9 cm long with 10-30 blossoms.  The pea-like flowers are whitish or cream colored with a faint blush of purple and have keels 6-9.5 mm long and a calyx 4-6.5 mm long.  Fruits are green, bladdery, 2-celled pods 14-35 mm long that taper gradually to the tip and become glabrate, papery-textured, and somewhat translucent at maturity. Flowering and Fruiting from May to early July. (Barneby 1964, 1989; Dorn 2001; Fertig 2012).

Similar Species: Astragalus lentiginosus var. chartaceus has larger flowers with keels 10-15 mm long, a calyx 7-12.5 mm long, and somewhat firmer-textured fruits (without flowers, var. chartaceus and var. salinus are difficult to distinguish).  Astragalus tenellus has erect, reddish stems, narrow leaflets, and dark-banded stipules that are prominently fused into a tube (Dorn 2001).

Habitat: Sodaville milkvetch is reported from slopes, valley bottoms, playas, and sagebrush plains on sandy or clay (often alkaline) soils (Barneby 1989).  In Fossil Butte National Monument, Wyoming, populations are mostly associated with old roadbeds, gravel quarries, and trails at the edge of sagebrush stands (Fertig 2012).

References: Barneby, R.C.  1964.  Atlas of North American Astragalus. Memoirs of the New York Botanical Garden 13(II):1-1188.  Barneby, R,C,  1989. Volume 3, Part B. Fabales.  In: Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren, eds.  Intermountain Flora, Vascular Plants of the Intermountain West, USA. New York Botanical Garden, Bronx, NY. 279 pp.Dorn, R.D. 2001. Vascular Plants of Wyoming, second edition. Mountain West Publishing, Cheyenne, WY.  Fertig, W. 2012. Rare plants of Fossil Butte National Monument.  Wyoming Natural Diversity Database, Laramie, WY. 76 pp.

Author: Walter Fertig, Moenave Botanical Consulting, Kanab, UT. April 2017