I have never been able to keep Rosemary growing very long in Tennessee.
I have a Rosemary plant in the front yard of the Arizona house it grows like crazy. All I have to do is trim it like a bush to keep it smaller and under control. It grows year round the 21 degrees winter weather we had did not hurt it at all. Bush is almost 5 feet diameter now.
Rosemary must like sandy well drained soil and hot dry weather?