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.
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 Trunk
* 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.
Preparation
* 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.
Removal
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.
This article was last updated on: June 5, 2003