Hi,
Well, I'm in Zone 7 and planted one this last Monday. This was a cutting in March this year.
I don't have a garage to protect them - but even if I had a garage, why get the garage messy during the winter ?
so planting in ground is my best option to protect the roots.
If your final plan is to go in ground why wait ? If rodents or cold are to hit the tree ...
The tree will get the blast this year or the next one, so, let's hope - and for sure protect them efficiently !
I plant most of my trees in big pots with bottom removed to protect against rodents - and so far so good .
Are you planting in your Zone6 or your Zone7 location ?
In Zone7 ... I would just do it now in ground .
My main problem at Spring time is that I often get really rainy weather and thus muddy dirt ... Go plant a tree in those conditions ...