Stems clustered on a stout taproot and caudex, 1-6 dm, decumbent with ascending tip, strigose; stipules 3-10 mm; lfls 15-29, oblanceolate to elliptic, 8-15 mm, appressed-hairy on both sides or glabrous above; fls 17-25 mm; cal-tube 6-8 mm; fr subglobose, abruptly pointed, indehiscent, glabrous, bilocular, the walls 2-5 mm thick at maturity;
2n=22. Prairies and plains; Apr., May. Var. crassicarpus, with purple fls, with the pubescence of the cal appressed or ascending, partly or wholly of black hairs, and with the fr 1.5-2.5 cm, occurs from Wis. to Alta., s. to n. Mo., Okla., Tex., and N.M. (Geoprumnon c.; Astragalus caryocarpus) Var. trichocalyx (Nutt.) Barneby, with ochroleucous fls (sometimes purple-tipped), with the cal densely villous- tomentulose, and with frs 2.5-3 cm, occurs from c. Ill. to Mo., Ark., Okla., and Tex. (Geoprumnon t.; Astragalus mexicanus, misapplied) Three other vars. are more western.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.