Botanical name is Symphyotrichum oblongifolius (or Aster oblongifolius). Fall blooming, September to November, but sometimes blooms out of season also. I notice that Sally Wasowski lists it at one foot tall, but one of mine is over two feet tall right now. I wonder. Anyway, they are lovely and cold-hardy and a bit drought tolerant. I have divided clumps in the past to propagate it.