I live in Kansas City and have a cabin at Lake of the Ozarks. There is a large area by the road that I'd like to grow wildflowers that flower for the summer and self seed. The soil is terrible - very hard clay with a lot of rock (typical for this area). Because it is a get a way, there are periods that are very dry. To get things started, I can arrange to have watering done somewhat regularly. Oh, did I mention the somewhat steep grade. I am willing to bring in some good dirt, but would like to stay natural. Whacha think?
Black-eyed susans, coneflowers, phlox, sunflowers, daisies. Or just od what we did and go to Wal*Mart and buy a wildflower mix. Aster, bachelor buttons. Might also try sage and lavender. I'll think of more later but that should get you started.
Also if you cut some of them down at the end of summer they will start growing again. We cut down all but a few and they are growing and blooming again. But it's not a necessity to cut them down.
Tuckerm------You might be surprised what you can grow in that stuff. The problems are going to be digging and keeping it watered. I am a hosta collector and not much into wildflowers. However If your on the West Side of the lake there is a award winning garden club there called the Lake Bloomers. Maybe I can find someone in the area of your cabin that would come by and help you out in your planning. Several people in the club are certified master gardners.
No one has mentioned lemon balm or the various mints. They are not wildflowers but have a wide range of leaf colors from dark green to variegated green and white and have a wonderful fragrance. They will survive and thrive just about anywhere.