Kim, I'm so glad I saw this thread because it got me to googling and reading about Ruellia and I believe that the Ruellia growing in my garden is more than likely Ruellia humilis rather than R. ciliosa, which I originally thought. This site says that R. ciliosa flowers are very pale, almost always white:
http://hawthornhillwildflowers...
I'm not sure why we don't have a database entry for R. humilis because according to the Catalogue of Life it is an accepted name. I did submit a proposal to have it added to the ATP database so I'll wait to see what happens and them move my photos over.
As others have suggested, I think R. humilis is probably the one you have growing on your property:
http://www.illinoiswildflowers...
Although MOBOT:
http://www.missouribotanicalga... shows it as zones 4 - 8, I believe that's an error. This USDA map shows it as native to the lower 48 with distribution in most of the central and eastern part of the U.S.:
http://plants.usda.gov/core/pr...
I live in Florida where there are so many invasive plants but I haven't found this Ruellia to be bad at all. It does pop up in beds here and there and I found it in a couple of container plants but it hasn't taken over or become a pest like some plants do down here. Don't get me started on the Cashmere Bouquet (Clerodendrum bungei) plant!! I mowed the lawn today and mowed a lot of that down ... a few months ago we yanked and dug so much of it out but it travels by runners beneath the soil and pops up fifteen and twenty feet or more away from the original planting.
For comparison, this is the Ruellia I have:
