While it's dormant, so from now on unless the ground is frozen. Prepare the planting site and then dig round the Acer. Get as much of the rootball out as you can and plant it imediately. Don't forget to water it in dry periods!

Just to add, Japanese maples are notoriously fickle when it comes to transplanting, If you have very sandy soil and can't lift as a root-ball, i would forget it, or at least prepare to loose it.

the 2 best times for moving are at the beginning of there doremancy or the end . i prefer the latter as they start growing soon after and dont sit there damaged all winter ow and ofcourse water well for at least the first year till its established .

Hello ... I successfully transplanted two acers from pots to garden earlier this spring. They had a mild set-back with a late sudden frost that burnt off a lot of the new shoots, which could have happened in the pots anyway, but they fully recovered. I watered them often during the summer and planted in with them lots of leaf mould compost I had. Agree with the advice above ... if you can transplant quickly then it won't register shock long enough for it to have an effect. Nerrines are the same!

spot on avkq47 thanx .

Remember to water it for the whole of next spring and summer, with rainwater if possible.

my bonseifriend blatently pulls the leaves of of his acers which makes them produce smaller leaves so lots of things are possible .