I have apple, plum, cherry, pear and apricot trees all growing in pots. Totally agree with valmarg on both points but for me the only one I will overwinter in the greenhouse is the Apricot because its early flowers can be killed by frost. I'm undecided how I am going to treat the other trees as although they are on dwarfing rootstock there is not enough room in my greenhouse for them.
This leaves me with two options as far as I can see, either I lag the pots for winter or I dig a hole somewhere and bury the pots up to ground level?
Interested to know what other dwarf fruit tree growers do for winter?