So last year, the cold weather caught me with air-layers still on the trees. All of the limbs the air-layers were on had severe cold damage even below the layer (the layers are completely cut off from good wood). Yesterday, I was pruning the dead limbs off an LSU Purple, I decided to cut open the air-layer. While I found all the dead/wilted roots which had grown before the cold, there was also new roots and to (white) limbs growing from within the plastic wrapping. I cut off the dead wood above and below the layer and potted it up. We'll see if it has enough oomph to be viable.