Q.Best Time to Transplant Deciduous Trees
We have a deciduous tree which self-seeded itself in our garden about 4 years ago and has grown vigorously. We are moving this summer and wonder if we should dig it up. When is it dormant this winter? Should we keep it in a 500L bag, wait until we move?

It would be helpful to know the type of tree that you are transplanting.
Generally moving and planting trees is best when they are dormant.
https://www.clemson.edu/extension/hgic/videos_posters/posters/tree_planting.pdf