Symphyotrichum oolentangiense, Sky Blue Aster
Sky blue is one of my favorite asters. It has an airy spray of more widely dispersed light blue-lavender flowers. This is an aster that isn't as dense as some of its cousins, doesn't push into its neighbors, instead poking up from the crowd late in the season. You'll love it.
Blooms: pale blue-lavender, August to October
Height: 3 feet
Conditions: sun to pt shade, medium to medium dry soils