Maybe this link will help you as of why your Mimosa tree is not blooming:
If it's a new tree it may be too young to flower. Otherwise, be sure it's in full sun, getting enough water, and not too much fertilizer. Here's a link with more information:
I planted a "TWIG" that someone gave me & it is grown now, A MIMOSA twig & I did nothing to make it bloom, Only "SUN"...BEAUIFUL, & needs triming in the fall..."NO EXTRA CARE"~
Hello. This link might be helpful. Best wishes happy gardening
This may be helpful: https://www.atozflowers.com/flower/mimosa/
Hi Helen. If your Mimosa is getting full sun, adequate water, and not too much fertilizer, it should bloom each Spring. If your Mimosa has never bloomed yet, it might be too young to flower. It should be at least ten feet tall (approx) for it to support blossoms. Good luck with your Mimosa, Helen.
Hi Helen, sorry to hear your momosa is not blooming. Hope this will help you.
www.cleveland.com › insideout › 2011/08 › how_to_c...
Aug 3, 2011 - You need to give the little fellows a little more time to mature. I have read stories from some gardeners who had to wait until their Mimosa trees were 10 feet tall before they had blooms. Fertilize your mimosa trees in early spring, when you see the first signs of new growth.
Here you go https://homeguides.sfgate.com/old-mimosa-tree-before-blooms-68679.html
Here is a video with tips on how to grow and take care of a mimosa tree: https://www.youtube.com/watch?v=Vm5fXT8xFi4
Hi Helen, If your Mimosa is getting full sunshine, adequate water, and not too much fertilizer, it should bloom each spring. If it has never bloomed but otherwise looks healthy, it may be too young to flower. Some trees and shrubs take quite a while to mature to the point where they can support flowers yet continue to grow. Good luck!
We had a beautiful Mimosa tree in our yard growing up and lots of little sprouts around it. The sprouts never bloomed, just the large tree, but it was over 10 feet and in full sun.