Attila

Hi Donna,

You could trunk-chop after the leaves are fallen (you don't want to disturb the roots until springtime) and it is most likely that the tree will come out fine next year. However, there is small danger of the maple dying during winter due to pathogens entering the tree. The tree is most defenseless during this time.

Severe pruning can also cause die-back during this time.

So the safest time is Spring, when the buds start swelling.

If you are planning a small bonsai (shohin, mame) with short internodes, you can do the chop a few weeks after the first leaves appear, so the new growth won't be as strong and coarse.

If you want a large trunk, do the chop before the first leaves come out.

Japanese maples belong to what some bonsaist call the "weaker" type of trees, so I wouldn't disturb the roots when trunk-chop is done. You could do it if you have a nice compact rootball, with lots of fine roots close to the base, but we don't know how your roots look like, so better to be cautious.

Regards,
Attila