tough one with the clay soil. and the heat. I would say that even though you want perennials I would plant annual seeds to start with. Cosmos-the yellow variety-are fast growing and will reseed for next year. Mine get about 4ft tall, sometimes taller. Plus a good fence makes a nice wind break for anything taller. Blackeyed Susans will come back and spread. Rose Campion will throw seeds and you'll have more every year. Day Lilies might work too and they are a perennial.
