Hi, Dr. Hill,
This is another Fall Line plant, but it was growing in sand (no visible clay) in full sun on a private, back woods road. It had two main branches, each arched in a graceful curve. The small leaflets are a dull green and slightly lighter dull green on the bottom side. There are small hairs on the upper leaf surfaces and each leaflet has a tiny pinpoint at the tip. It reminds me of Amorpha app. Tiny vertical spikes of legumes (about 1/2-inch when measuring the main body of the legume) grew alongside the leaf base on the stem.
this is a very nice native plant, a subshrub, called Indigofera caroliniana, the Carolina indigo. It is closely related to the commercial Indigo once grown in the Carolinas as a crop. The image shown here shows the fruits which are quite distinctive, especially because they are on an axis that stands straight up.
Steve Hill, Ph.D., Botanist, SCNPS