During the air layering method of propagation, a girdle is created by removing a ring of bark, phloem and the cambium. The removal of the cambium will prevent the healing of the wounds. But the ring of xylem will remain intact so that the uptake of water and nutrients to the leaves take place. But the photosynthate produced get collected at the girdled site and the presence of the moisture breaks the dormant adventitious buds in the area so that the root emerges out. Then the shoot is cut off and planted individually in a pot.
