Hi all. I am new to the bonsai hobby. I am interested in starting a Mimosa bonsai with this tree I dug up (pictured below). I cut off the very long branches and this left me with a very nice trunk and decent roots. Any advice as to where I could take it from here? The tree is at the desired thickness for me. Should I cut off the straight up trunk to make that side shoot the new leader? When should I put it in a bonsai pot? I am trying to achieve something similar to the second picture below. Thanks in advance. Also any general tops for mimosa bonsai would be appreciated.

I dont have experience with mimosa. But that tree seems to be totally depleated of fine fender roots. I am sorry, but I think you killed it.

The tree is not dead nor dying. The tree had no fine fender roots when I was digging it up, only large roots. Also, the tree has grown new green leaf buds since the roots have been cut. This is a relatively hardy tree, and actually considered invasive in my area and is hardy when it comes to heavy root pruning.

Please post a picture of the tree in full leaf in july.