Limestone Wild Petunia
There are three species of Wild Petunia's in Indiana. This one might more commonly be known as Smooth Wild Petunia, but that's a boring name, so the folks at the Plants Database are going with Limestone Wild Petunia.
For those of you interested in native plants, this petunia is native, as opposed to the Petunia petunia, so it might be a good choice for your garden. Does anybody have any experience planting this?