In Knoxville you should be able to to use the Northern type
Blueberries. They do need an acidic soil. Lots of limestine in East
Tennesee, so that may be a problem. You may have to acidify your soil
each year. In a climate where the ground freezes, I prefer to plant in
the fall. However if you use potted plants, Spring planting is ok, but
you have to baby them the first year.
http://www.uri.edu/ce/factsheets/sheets/blueberry.html
http://www.uga.edu/fruit/bluberi.htm