cold is irrelevant ... in your z6 ... the key is keeping pots out of winter sun .. which can bring them in and out of dormancy in sun .. in winter ...

the shed is even better than an attached garage ...

late in fall ... better if they freeze solid ... you can stack them on top of each other.. or lay them on their sides and stack them ...

just bring them out into the late cold winter.. and then let them come out of dormancy out of the shed ...

bottom line.. the shed i no different than garage.. proceed as before ..

ken

Did not see this thread when I asked myy question about digging to move south. Here is the link to that thread

Here is a link that might be useful: Digging hostas for move south...thread