Hi JoeR,
Search for the 80liters trashcan technique. It it a post from me.
To make a long story short, you need to protect the base of the tree. So remove the bottom of a big dark trashcan, and put it over a tree.
Fill the trashcan with dirt from the nurseries. That will be like a pullover protecting the bottom of your tree.
The dirt will avoid the rodents to settle in and act as a heatsink. That's how I do in my Zone7.
This year, I just put the trashcans around the trees and left them empty. Some I put them near the trees. Those containers being dark they still attract some heat from the sun, and cut the windchill.
I planted small bushes around to cut the windblow too ( currants, ... ).
My figtrees already started to leaf out. I lost some stems, but some terminal buds are alive, and figlets (brebas) have appeared and some new keep on appearing.
I may have lost some potted backup trees... Still too soon to know !