Winter Storage Above Ground

I will not have enough ground in which to put my trees for the winter, so 1 or 2 will have to be on a patio against a wall.

My 9" burning bush is in a 12" diameter, 4" high pot. How big of a container or box would I need to put this potted bush to best ensure the tree will survive? I believe avoiding freeze thaw cycles and early budding are the dangers?

Thanks.

(zone 6)

If it is out of the wind and against a heated building, they would probably be ok.
Burning bushes are very rugged and should be fine in that size of pot.

Japanese maples are much more prone to cold damage at both ends (foliage and roots).

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