All of it is going to be moot until next spring just before buds open... that's the time to prune deciduous trees.

If the tree is in good health you can pretty much prune anytime from when it's dormant (or nearly dormant) until before the onset of fall/frost. You should stop a month or two before the onset of frost to give the new growth time to harden off.

Most of us wait until dormancy to make large trunk reduction cuts but those too can be done during the growing season with no problem.

Bob

I appreciate the input. I guess what i was wondering is if it would be safe to remove the majority of the canopy. pretty much cutting it back to a trunk and main branches....then begin training with new growth next spring. if i did this heavy pruning now is it safe to assume it would put out new growth this season? this particular cultivar is densely branching and from what ive read, back-buds with ease. Decisions,decisions. Some Japanese maple enthusiasts insist you should never remove more than 1/3 of the toatal tree to lessen stress/shock but others seem to think these trees are much hardier than we make them out to be.

If the tree is healthy it's normally not a problem to cut a lot. Yes, it will back-bud profusely, most will turn into a little fluff-ball after a hard pruning. One thing you should do is stop working it a month or two before first frost and allow the new growth to harden off.

Bob