The term nebari describes the lower trunk and exposed roots of the bonsai above the soil surface.
Nebari are important features in the bonsai aesthetic and are essential to a well-defined display. Nebari add balance to a bonsai tree. A bonsai with well-developed nebari appears well-grounded, and appears closer in form to that of a mature tree.
Nebari are part of the allure of bonsai and although they can look impressive, the techniques to produce it are relatively straightforward.
This article has details on three different techniques for how to develop bonsai nebari.
Bonsai nebari techniques
A few different techniques can be used to produce a nebari.
1. Root pruning
Pruning the roots to remove any large vertically-growing roots will cause the horizontal-growing surface roots to grow thicker.
If you do this every time you report your bonsai it will develop natural-looking nebari.
2. Lifting with a stone
The field growing technique of placing a flat stone, tile or brick under the roots can also build nebari by forcing the roots to grow sideways.
This technique can be used to lift roots individually, or can be used to send the roots splaying-out in all directions in a large container.
3. Air layering
It is possible to build a nebari on a healthy bonsai tree relatively quickly by promoting more root growth higher on the plant using air layering.
Air layering is a process used to propagate new plants from an existing one. Because air layering requires an interruption in the plant’s trunk, it should only be done on healthy plants that can withstand this extra burden.
When the new roots are well established on the trunk at the point of the air layer, the old trunk and root system is removed and the plant is repotted using this new base as the nebari.
4. Cinching/ tourniquet
Another common method of creating better nebari is a derivative of the air layering technique where a cinch (essentially a tourniquet) is used. The tourniquet is applied to the trunk slightly above the soil line where the new nebari is desired.
The squeezing pressure creates the trunk to thicken, and new roots will form below that level.
After these new roots are established, and the new trunk has thickened to an appropriate size, the old trunk and roots should be removed, and the tree replanted.