Spring has arrived. The maples are pushing young growth, making this a perfect time for air layering. I have a few young grafted Japanese maples. I bought these some three years ago to grow out for bonsai. But I will need to get rid of the grafted rootstock!
Why layer bonsai?
If you have a nice tree but you need to remove a large branch or the trunk needs to be shortened, you can of course cut the section off and throw it away. However in some cases you have a special species. Or you just want to have another three. Then it is an option to use layering techniques. Take a look at the step by step manual for air layering bonsai.
Another good reason to layer a tree it to get rid of a graft join. Some cultivars of Japanese maples are mainly traded grafted on the wild form of Japanese maple. This is the case for these A. palmatum ‘shin-deshojo’ and ‘Arakawa’ that I bought some 2 years ago. Now that the plants have grown a little bit, the trunks are big enough for air layering.
Air layering of Japanese maples
Just like described in the step by step manual I removed a ring of bark from the trunks. Then I left the sites to dry out for an hour. This helps to kill of any leftover cambium cells. Meanwhile I cut open two small pots and removed a small section of the bottom of the pots to fit around the stems. After tying the pots in place, I filled them with substrate, taking care to place some sphagnum against the bark just above the cut area.
Why does the top of a bonsai not die during layering?
Some of these pictures were placed online, and resulted in the question.. Why does this work and why does the top not die? So a somewhat longer explanation on the physiology of layering.
Simplified, a plant has 2 types of sap transport. There is the transport from the roots towards the leaves, bringing water, hormones and fertilizer components into the tree. This takes place in the wood of the tree, called Phloem. The second type takes the assimilates (Sugars) and hormones from the leaves to the roots. This takes place in the bark of the tree, called Xylem.
By interrupting the movement of water from the leaves to the roots (Cutting away the bark) the hormones from the leaves to the roots accumulate just above the areas where we removed the bark. Normally, these hormones signal to the roots: Th leaves are growing, and need more water and nutrients. Roots, you have to grow too! Now that these hormones accumulate in the bark, and -by adding moist substrate against the bark- we have good growing conditions for roots, most plants will grow roots.
To avoid the tree repairing the gap we created in the bark, not only the bark but also the vascular cambium is removed. This is a thin layer of cells that are still actively replicating. This is where the wood and bark are formed, so this layer is able to bridge the gap
How long does layering take?
With young trees like this, in early spring, with good weather I would expect to have roots in some 6 weeks time.