By Bill Mee and Krystal Folino
An air layer is a way to create a new mature lychee tree from the branch of an existing one while it is still attached to the parent tree. Since this process occurs in the foliar branches, suspended in air above the ground, it is referred to as “air” layering. The resulting tree is the same species and cultivar as the parent, rather than a hybrid with questionable fruit and growing characteristics.
When new trees are propagated in this fashion the resulting fruit is identical in taste, color, texture and maturing characteristics as the parent tree. This is especially important because the fruit of trees grown from seed often have widely varying characteristics.
Check out the video we created about air layering:
When you find a tree with a desirable fruit or other feature it is highly advantageous to recreate this tree within a short time frame rather than the 10 – 15 years typical of the seed to fruit time span documented for Lychees.
An air layered tree is, in actuality, a fully mature tree that will begin bearing fruit immediately. For practical reasons though, small air layered trees should be kept from bearing fruit until they gain some reasonable size.
How do you make an air layer and what is the best practice. (how to select a branch, the optimal time of year, the rooting mix and rooting hormones)
- Selection of branch
- Bifurcated or trifurcated
- Short trunk for grove
- Long trunk for decorative
- ½ to 1 inch in diameter
Creating an air layer is a relatively easy process that can result in a well proportioned, healthy new tree, if performed correctly.
Selection of the branch that will become the air layer is very important and must be done with consideration for what you want to achieve in the future tree. An air layer with a main trunk of 6 to 12 inches below a bifurcation or trifurcation should have a trunk ½” to 1″ in diameter.
- Remove bark & cambium layer to expose xylem
- Rooting hormone (optional)
- Sphagnum moss or other growing mix
- Aluminum foil or plastic sheet
- Container to create optimal root mass
- Springtime best time of year
To prepare the air layer you first must remove the bark around a complete circular section of the branch and fully expose the xylem layer. The section removed can be about 1″ wide. The bark must not only be stripped off, but the vascular layer of plant tissue just below the bark known as the cambium, must also be removed. This can easily be accomplished by scraping the exposed area just below the bark with a knife or pliars with serrated jaws.
Rooting hormone (Rootone – Indole-acetic acid) may be used, although this is not necessary. The rooting hormone may be applied directly to the exposed cambium or diluted in aqueous solution and mixed with the rooting material. Cambium, which is the vascular layer that conveys nutrients from the leaves to the plant root system, will differentiate into roots. Remember that with hormones, more is not always better. Excess hormone will actually have a suppressing affect so follow the directions suggested on the hormone preparation you decide to use.
The exposed strip must be encased in a growing medium. Generally, sphagnum moss is the preferred rooting medium. We like to use a 50-50 mix Pro-Mix with sphagnum moss; however, just about any loose, well drained growing medium will work. The growing medium should be pre-mixed and moistened with water. A section of heavy duty aluminum foil or plastic sheet approximately 12″ x 12″ should have a large handful of growing medium placed in a swath at the center of the foil segment, almost like a band-aid. The foil/growing medium combination should be wrapped around the exposed xylem and twisted at the top and bottom end to form a seal around the branch. If you are producing a large air layer then duct tape should be applied at both ends to prevent ants from entering into and nesting in the air layer. If carpenter ants make a nest in your air layer they will eat all of the growing medium away from the forming roots.
If your objective is to create a larger tree you can split a plastic growing container down the middle to the circular hole in the center and wrap this around the tree branch, filling it with growing medium and sealing it with foil and duct tape. Taking the extra time and effort to do it this away assures a larger root mass and a more vigorously growing tree whose chances of survival, post removal, are greater.
- 8-12 weeks
- Squeeze or tap air layer / remove when tight like a drum
- Saw off at about ½ to 1 inch below root mass
- Strip or prune at least 50% (or more depending on the size of the root mass) of the leaves
- Soak in water for a few hours & wet down the remaining foliage
Now ready to plant in the ground, plant in a container or ship to lychee growers & enthusiasts.
If the air layers are applied in early Spring it will take approximately 8 – 12 weeks to produce a sufficient root mass. The rate of root growth is a function of temperature and humidity so that the overall process is shortened as the weather warms up. You know that the air layer is ready to remove when the mass contained within the foil or plastic is full of roots. You can see the roots when clear plastic is used. In the case of foil, readiness is indicated when the foil becomes tight like a drum.
The air layer should be either clipped or sawed 1 to 2 inches below the root mass. After removing the foil or plastic approximately 50% or more of the foliage should be either stripped or pruned away from the air layer. This is a good time to shape the soon to become a new tree. The root mass of the air layer should be soaked for a while (until fully saturated) in water and the remaining foliage wetted.
At this juncture you can either plant the air layer directly into the ground, a container or you can ship it to lychee growers and enthusiasts.