Last year was the first year I grew flowers for farmer's markets. I started with a friend mid June. We planted a few china asters, but they did not begin to flower until the end of September. They were hit by frost before they really took off. But, they were planted in cold zone 5.

Zinnias, cosmos and sunflowers were the bulk of our sales. Especially darker colored sunflowers--we grew autumn beauty.

Are the asters already started as plugs or seedlings?

We planted ours out Memorial Day weekend but they were started in our greenhouses in April about 6-8 weeks before transplanting. They usually start blooming in mid-August so you should be ok, depending on when they were started.