From Flora of Indiana (1940) by Charles C. Deam

Infrequent but locally common in the unglaciated area, and northward either absent or very rare and, I think, introduced. It prefers dry, sandy or sterile soil and in the south it is usually found in open woodland on the crests or slopes of ridges, along roadsides, and in fallow fields. I found … [variety leiocarpa] in two places in Brown County and Friesner has also found it in Brown County. All the specimens found at the various places have both the stem and legume glabrous except one that has the stem densely pubescent as in the typical form.