Answer: Japanese maples require very little, if any, pruning. The main reason to prune would be to remove dead or damaged or diseased wood; this can be done at any time preferably as soon as possible once the problem is noticed.
If you need to prune for shape or size control, do so very cautiously. Prune in early summer. Step back often to check your work, and do not remove more than ten percent of the branches in one year.
These trees have a lovely natural shape and over-pruning will ruin the natural look of the tree. If you have an older tree that seems to need quite a bit of pruning I would strongly suggest you work with a professionally trained and certified arborist who has extensive experience with ornamental trees rather than try to prune it yourself. Enjoy your Japanese maple!
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