Air-layering is a technique of reproduction of trees and shrubs, by means of which the emission by roots in a branch is caused, to cut it later and to separate it of the plant mother, giving rise this way to new  independent identical tree to her.  In order to improve the success of this technique it is advisable, although nonessential, to cover with an opaque tape the piece with crust with the small branch that we want to lean, to cause his transformation in crust without chloroplasts, more similar to the crust by the roots, which is called ETIOLATION.  This way they increase the probabilities of success, since the etiolated crust emits roots with facility, even in trees of very difficult rooting. 


I put the example of an aerial layer in a Litchi sinensis:


SPRING:  to cover with opaque tape a piece with crust.


SPRING OF THE FOLLOWING YEAR:  to retire the opaque tape and to verify that the crust already is etiolated, transformed into crust of root without chloroplasts.

With two parallel and clean cuts to clear a ring of crust of a centimeter.  In order to facilitate the emission by roots still more hormones of rooting in the ring and the rest of the etiolated crust can be put, although it is not essential.

Next we take a piece of plastic transparency, surrounded with him the small branch to lean and we tied it with a cord in its inferior part, staying as a glass.

Soon we come to fill up it with crowd, vegetal earth or sphagnum and we tied it in its superior part .

We strongly tied the layer with a cord, so that the earth, disturbs or sphagnum contacts perfectly with the ring of the crust.

Next we injected water with a syringe to dampen the earth, disturbs or sphagnum and we repeated the injections every 2 or 3 weeks.

Next we covered the layer with paper with newspaper or one laminates of aluminum paper, to isolate it of the sun and the light.

FOUR MONTHS AFTER:  In an inspection of the layers it is verified if already they have taken root and, in affirmative case, is come to clear the paper of newspaper.

Another taken root layer.

Next the layer taken root is cut with a clean cut.

Layers already cut fence sights.

And only lack to already clear the plastic wrapper to them with taken care of much of not breaking the set of earth and roots and transplanting them in flowerpots with vegetal earth.  They are watered abundantly and they are placed in a place with much light, but without direct sun.  Normally they lose the old leaves and immediately they appear, which means that already we have new tree, identical to the plant mother.