Answer: This is a difficult question, partly because I am unable to see the tree. If you look at a mature mimosa, you will notice that the trunks are very long and arching and often the tree will have more than one; the branches usually start rather high on the tree. So to some extent what you have is normal. If you cut it back (do not do it now, wait until spring) you may cause it to send out additional growth from the roots resulting in multiple trunks. You might trim off the low growing side branch if it is at an odd angle or at an unhealthy angle. Or, you might tip back the taller branch to allow the lower one to catch up. This should also cause the taller one to fork. Or, you could leave it alone. So you do have choices. Keep in mind also that it should continue to grow quickly as it did this year. I would suggest you take a photo of it and consult with your county extension or your professional nursery staff and see what they suggest. Good luck with your tree!
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