Slender, but stiff and wiry, with a woody taproot and at length knotty caudex, densely gray-pubescent throughout, the herbage villous with mixed sinuous and straighter ascending hairs up to 1-1.3 mm. long, the stems subappressed-pilose, the lowest 3-4 abbreviated internodes white-tomentose; stems numerous, erect and ascending, (1) 1.5-3 dm. long, simple or bearing a few subbasal spurs and an occasional branchlet from the axil next below the first peduncle; stipules (2) 3-8 mm. long, early becoming pallid and scarious, the lowest and median ones connate through half their length or more into a tightly amplexicaul (sometimes tardily ruptured) sheath, the upper ones progressively less connate, the uppermost sometimes united by a stipular line or free; leaves 3.5-9 (10.5) cm. long, petioled or the uppermost subsessile, with stiff rachis and 11-19 (23) narrowly elliptic, lance- elliptic, or narrowly oblong, sharply acute, or in some leaves oval, subobtuse or merely mucronulate, flat or loosely folded, at length deciduous leaflets (3) 5-15 (18) mm. long; peduncles erect from the 3-5 upper axils, 0.5-5 (7) cm. long, mostly much shorter than the leaf; racemes loosely (5) 10-25-flowered, the flowers at first ascending, early spreading and then declined, the fruiting axis (1.5) 3-10.5 cm. long; bracts submembranous, subulate or setaceous, 1-2.5 mm. long; pedicels at anthesis mostly obconic and 0.4-0.9 mm. long, in fruit divaricate or recurved, 0.6-1.3 (1.5) mm. long, tardily disjointing; bracteoles 0; calyx 3.5-5.5 mm. long, densely villous-villosulous with white or mixed black and white hairs, the subsymmetric disc 0.2-0.5 mm. deep, the obconic-campanulate tube 2-2.5 (2.8) mm. long, 1.7-2.2 mm. in diameter, the subulate-setaceous teeth (1.3) 1.5-3 mm. long; petals whitish tinged with grayish-lavender, yellowish when dry, commonly marcescent; banner recurved through ± 50° flabellate-obcordate or broadly obovate-cuneate, 4.5-6 (7) mm. long, 3.4-5.2 mm. wide; wings 4.5-6.1 mm. long, the claws (1.4) 1.7-2.2 mm., the obliquely obovate, obtuse, strongly incurved blades 3-4.3 mm. long, (1.3) 1.8-2.1 mm. wide, the left one concave and folded over the keel; keel (3.6) 4-5 mm. long, the claws (1.6) 1.8-2.3 mm., the halfcircular blades 2.3-2.8 mm. long, 1.4—1.8 mm. wide, abruptly incurved through 110-130° to the bluntly deltoid, sometimes obscurely porrect apex; anthers 0.3-0.45 mm. long; pod reflexed, sessile, tardily disjointing (after falling), subsymmetrically lance-ellipsoid or ellipsoid, 6-8.5 mm. long, 2-2.7 (3) mm. in diameter, rounded or cuneate at base, gradually contracted distally and cuspidate at apex, somewhat laterally and triquetrously compressed, with flat or low-concave lateral faces, keeled ventrally by the prominent suture, narrowly sulcate dorsally (the groove sometimes almost closed), the papery, finely reticulate, canescently tomentulose valves inflexed as a complete or nearly complete septum 0.6—1.3 mm. wide produced into the pod’s apex; dehiscence not seen; ovules 6-8; seeds olivaceous, purple-speckled, smooth but dull, 2.3-2.8 mm. long.—Collections: 22 (i); representative: Maguire & Holmgren 26,252, 26,259 (NY, RSA, WS); Peck 25,928 (CAS, RSA, WILLU, WS); Nelson & Macbride 1713 (ID, NY, RM, WTU); Ripley & Barneby 6471 (CAS, NY, RSA); Cronquist 6583 (ID, NY, OKLA, SMU, TEX, WS).
Gullied bluffs, barren hillsides, and fallow fields, commonly in sandy soil or on wind-blown dunes derived from basalt substrata, occasionally on shaley clays or stiff loams, locally plentiful, 2400—4300 feet, along the Snake River and immediate tributaries from the lower Raft River in Cassia County, Idaho, downstream to northern Owyhee County and extending just into eastern Malheur County, Oregon; also disjunctly, at 700—1250 feet, along the Columbia and lower Yakima Rivers in Benton, Grant, and Yakima Counties, Washington.—Map No. 156.— May to July.
Astragalus caricinus (Jones) Barneby in Amer. Midl. Nat. 55: 502. 1956, based on A. Lyalli var. caricinus (sedgelike, the pod likened to a "buckwheat or Car ex grain") Jones, Rev. Astrag. 174, Pl. 41. 1923.—" ... on sand dunes at Glenn’s Ferry, Idaho."—Holotypus, collected June 17, 1911, by M. E. Jones, POM! isotypi, CAS, NY!
Along the Snake River in Idaho the buckwheat milk-vetch, A. caricinus, is easily recognized by its gray-villous herbage and basally tomentose stems combined with tiny, loosely racemose flowers and small, reflexed, bilocular pods. One must be careful in eastern Washington to distinguish the superficially similar A. Lyalli, under the heading of which the differential characters and other matters of interest concerning A. caricinus are discussed.
The earliest-known collection of A. caricinus dates back to the Northwestern Expedition of 1883 (Canby, or possibly Brandegee, 717, GH). It was one of many interesting plants from the Columbia Valley which Canby distributed under the vague label of "Walla Walla region." According to this label the plants were eaten greedily by stock.