i think bass is testing for cold hardyness,
i dont have any of my trees coverd eather as the past few winters have been mild. we had snow on the ground for about a week so far this year and thats it. i lookt at my trees daily and they still look great and asleep. not seeing any sign of damage eather. but i am also testing for cold tolerance in trees for zone 6.
now some of the trees i will be planting in spring like RdB, VdB, ect will have some winter protection for next year (just to be safe, dont want to lose any of those ones)