Most people have probably heard that a bonsai will die if its new growth doesn’t have a chance to harden off before a frost. This Japanese Maple was trunk-chopped in very late summer, and was given a hefty dose of full-strength, nitrogen-rich fertilizer in the autumn. The leaves were about 1/8″ when they got hit by frost, and the tree went dormant. It was heated to around 25F over the winter. Today it has lots of back-budding in preparation of spring, including where the late-season growth had been.
While we wouldn’t recommend pruning just before dormancy, don’t panic if you make a mistake. Trees tend to be much hardier than we give them credit for. It can probably be considered wasting the energy that the tree used trying to produce new leaves, but it should hardly be considered a fatal error. Also, don’t believe everything you hear about caring for bonsai. Not all of the conventional wisdom is rooted in horticulture.