Ruellia humilis

Wild petunia is a perennial native to thickets and open woodlands in Central and Eastern U.S. It can handle a range of site conditions and will bloom in the heat of summer. Although it's not related to true petunias, Ruellia humilis has lovely petunia-esque flowers that are lilac-blue in color.

Wild petunias attract long-tongued bees and butterflies. Try it out in a naturalized area as it may reseed readily.