I can't answer your question, but here is a link my son sent me about moving a large Acer. It looks like a lot of work!

Here is a link that might be useful: Moving a large Acer

Don't touch it until the day you are digging it to move it. Quite a few new roots would not be expected to form over the next 6 months. And if you cut any new roots that did form off during the final dig, the point of having cut the old roots back previously will have been lost - you are just molesting the specimen, making it grow replacement roots twice during the cycle instead of once.

The general pattern is for new roots to come out of cut root ends in spring, when opening winter buds send a chemical signal to the roots that causes them to make new growth.

The greatest amount of root activity for the whole year occurs when winter buds are matured, in fall. At that time hormones are sent from the buds to the roots that cause existing roots to extend significantly into surrounding soil.

Then the roots pretty much shut down until winter buds open in spring. That is why bare-rooted stock is not planted until spring. Most of the small roots of bare-rooted stock coming out of commercial systems have been killed by the process. No significant production, if any, of new roots will occur until the top activates the following spring.

Thankyou to both of you. That is a big tree they moved in the link. Dotty. Fortunately the split-leaf Japanese maple we have been given, while older, is much smaller - only about 6 feet tall.

What you say makes sense, bboy, but root-pruning in preparation for a move is something that I have been taught to do for years. I guess it makes me feel that I can do something to help ensure success...On the bright side, it now looks like I can take one big chore off of my 'to do' list for the next day or two!

Bob

I'm with Bboy, cut the roots once when you move it with the leaves off. I've moved hundreds of Japanese Maples successfully, but very few as big as that shown in the link. No matter what the size of the maple, don't cut the root ball any larger than you can comfortably handle. Too big is as bad as too small.
They are not as delicate as they might appear.
Mike

Roots liable to be Acer palmatum seedling. This will be tougher than the lace-leaved cultivar grafted onto it.

With trees and shrubs in general you want to choose bare-rooting over digging and moving with an intact soil ball when and if it comes down to having to cut most of the roots away in order to get a manageable size of soil ball. Different species vary widely in their tolerance of exposure of the roots to air. I would have a hose with a nozzle adjusted to a mist setting on hand for keeping roots moist of anything large I was in the process of bare-rooting anyway.