Answer: Mimosa trees should be pruned in the early spring, taking the branches back to 5-6 buds. If there are only a few very long branches on your tree, you can clip them back now, but for general pruning, it's best to wait until early spring.
It's difficult to predict just how each branch will develop new shoots, so some summertime pruning may be necessary for the first few years.
Best wishes with your mimosa!
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