Mine are all in pretty big pots - half whiskey barrel sized or just a little smaller. Plenty of room to grow. I've been using regular potting soil with a quarter cup of cottonseed meal down under the roots, and another quarter cup mixed in at the top. I've been advised that I'll need to renew that quarter cup at the top each year to keep the soil acidity level where they like it. So far no complaints from the plants! And none from me, either, because this way I get blueberries that are (a) not flown in from another hemisphere, and (b) not sprayed with pesticides, so we don't have to wash them.