Thank you for the suggestions but this doesn't answer my question because this flower/bush is taller than gentian and the flower is a cluster as you can see from the photos....
Looks like Liatris from the spicata family. Monarch Butterflies love them. after the flower dies there will be seeds that when resown will develop the bulb. I have these in my yard and in October the Monarchs are headed back to Mexico. They swarm these flowers. It's so beautiful.
gastache, hyssop for common name
http://tinyurl.com/yzyz4nd