Astragalus trichocalyx Nuttall. Phen: (Mar-) Apr-May (-Jun). Hab: Glades, barrens, woodlands, and prairies, often over calcareous substrates. Dist: IL south and west through MO, AR, and se. KS to nc. LA, ne. TX, and OK.
Origin/Endemic status: Native
Taxonomy Comments: Barneby (1964) describes this taxon (relative to the other taxa, almost all formerly species, he treats as varieties of A. crassicarpus) as "ordinarily very distinct" and states that it "differs (at least ideally) from var. crassicarpus in growth-habit, pubescence, and especially ecology, [and] might with reason be retained at specific level". The evidence supports its recognition as a species.
Synonymy: = Astragalus crassicarpus Nutt. var. trichocalyx – Ar, C, GrPl, Il, K3, K4, NcTx, SE3, Tx, Barneby (1964), Isely (1998); = Astragalus mexicanus A.DC. var. trichocalyx (Nutt.) Fernald – F