Solidago caesia /Aster Family
Goldenrods are notoriously difficult to identify, because there are so many of them and many of them are very similar. I'm going with the Blue-stem Goldenrod on this one because the flowers bloom in the leaf axils. I found this one blooming in the woods in Pickett State Park in early September.
Where seen: Pickett SP, Great Smoky Mountains NP