Air Layering - The In's and Outs of This Useful Tool in Bonsai
Air Layering is when you take a branch or section of the trunk; remove the bark, and place it in a medium to grow roots from that point. This can be used in a number of ways in bonsai, most often the tree is cut off from the point of the air layer creating a brand new tree (with it's own root system)
Air Layering a branch from a desirable tree or bonsai requires the removal of the bark from about an inch. This prevents carbohydrates from flowing down below the removed bark. However this still allows water, minerals and nutrients to flow upward to the leaves through the "xylem". As a result the tree will get the nutrients it needs and create a new root system where the bark was removed. Root hormone can be used in the process. In my experience though it's not necessary. Most likely root hormone will speed up the process, however this is debated inside the bonsai comunity.
Air layering allows us to create multiple bonsai from one mother plant. We can use the technique to correct flaws such as a reverse taper or find a desirable parts of what would otherwise be junk. Since a mature bonsai with a thick trunk and good taper take decades to produce naturally, air layering is one way to create the look of age in the art of Bonsai.
Should Hormones Be Used When I Air Layer?
In regards to the argument regarding if using root hormone increases the success of the air layer. In my experience patience is the most deciding factor on if the air layer is successful.
How to Air Layer
After removing the bark and reaching the cambium of the tree apply hormone if desired. Next secure the bottom with a plastic bag to hold in the growing medium. I typically use sphagnum moss. Let the new root system develop and you can remove by cutting it at the base of the new root system.
It usually takes the new tree six to nine weeks to develop a complete root system.
If you have specific questions regarding the technique of air layering you can start a thread on our forum Bonsai Artists of South Florida.
Air layering is in my opinion the fastest method to Start an Exhibition Level Bonsai Tree.
Remove the bark and the cambium from one inch of the trunk or branch
Secure the plastic wrap to create a base to place the growing substrate inside.
Pack the plastic with your sphagnum most or the substrate of your choice and secure the plastic.
Create tiny holes for drainage and make sure the top is slightly open so water can enter. Must keep the substrate moist throughout the process.
Wait! It will take 4 months to a year to create a strong root system with most species. Patience helps in this process.
Once you see roots fill up the substrate cut from that point and plant in appropriate size pot.
In the example below a Chinese Elm suffers from a reverse taper. By air layering the trunk from above that point we can create a more aesthetic trunk line.
It will usually take 90 days to 6 months to develop a strong root system. Once roots are established we cut below the new roots and plant this new bonsai. At this point you can begin developing your artwork into a finished bonsai through other traditional bonsai techniques.