Cultivating Bonsai Nebari (Roots)

There are three methods you can use to encourage root growth (nebari): simple cutting, air layering, or grafting.

Cutting. Cutting off the undesirable parts means removing the bark, cambium, and phloem. The cambium is the fast-developing growth tissue located just beneath the bark, and the phloem transfers nutrients to the roots. Do not cut the deeper structure of the root. After cutting off the areas where new root growth is desired, leave the plant alone to let the roots grow.

Air layering. This also removes the bark, cambium, and phloem, but instead of leaving the open roots exposed you wrap them with something to retain moisture — the most common material is moistened sphagnum moss. New roots develop on the covered surface. It is the best method for root development because it is quicker and more successful than simply removing undesirable parts; the main disadvantage is that it is hard to maintain.

Grafting. This can be done alone or together with the other methods. Grafting attaches a tree of the same species to your mature tree in the area where you want to encourage root growth; the young plant will take root in the desired area.