Lou,
I have had pretty good luck bare-rooting trees, even when not dormant. If you are concerned about the weight, you can remove "most" of the growing medium (maybe leave about 4" diameter and 4" tall or so). Wrap the remaining growing medium and any exposed roots in damp newspaper followed by a plastic bag or foil. Watering the tree a couple of days before you strip the extra growing mix will allow it to have some moisture without extra water weight. I've also found that moist soil comes off the roots easier than if it were dry.
The file attached shows a pomegranate tree partially bare-rooted while still in leaf.
~james


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