@ omotm...Steve, I use a razor knife on smaller root balls until I can work them by hand, and on larger plants like 10gal., 15gal., and above, I use a machete(no big swings, just wrist action) until I take off enough material to work the roots manually...at first I was concerned that I would damage the tree, but then I realized that if I did not free up the roots, the tree was eventually going to die from strangulation anyway...about two weeks after the root work and repotting, the tree took off and started to grow vigorously.