Brent - the only way I can root prune at this time of year in zone 7 is to
place the newly pruned material in my unheated garage after the operation. If I
leave it out in 20F temp., I lose it every time. BRBR

That doesn't surprise me. I try not to let my sunporch go below 25 F. I have
this wonderful little thermostat which is set between 35 and 45. If the weather
forecast is for temps below 10, I plug a little heater into the thermostat, &
set it on low heat on the other side of the porch. The area where the trees are
goes down to about freezing.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"A tree never hits an automobile except in self defense." - Woody Allen