Depends on the plant and where you are in Tennessee. The average-last-freeze-date varies by over a month from one extreme to the other in different parts of the state.

Keep in mind that containers don't hold heat as well as ground soil. So as Brandon points out, a sensitive plant in a container will be toast long before the same type of plant in the ground.

Old timers watched walnut trees and the first appearance of mouse ear-sized walnut leaves meant no more plant killing freezes.

I laughed a couple of decades ago when an aged neighbor told this to me; but so far our walnuts are better predictors than our weathermen.