Answer: Autumn is not a good time to prune. Pruning encourages new growth which will be frost tender and will die out in the winter. Wait until the trees are dormant to prune them (February is a good time). The only exception to this rule are spring flowering trees. If you prune them now or in the winter, you'll be pruning off next spring's floral display. Wait until these types of trees have finshed blooming and then prune them.
Enjoy your garden!
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