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AIR LAYERING IN BONSAI
One process of removing a large branch or section of
the trunk of a tree to create another tree is known as Air layering
. Before the branch is removed it is girdled, wrapped with peat moss and
then sealed with plastic or other media, and the girdled section is
allowed to root. After rooting the branch is removed from the tree. This
is a very common practice in bonsai to obtain another tree from an
unwanted branch or to save a thick trunk section that was going to be
removed anyway.
During the process of air layering, it is necessary
to remove the bark, the cambium, and the phloem layer cutting away about a
1-inch wide ring of these tissues from around the circumference of the
tree. The layer just under the bark is a layer of actively dividing cells
called the cambium, the next layer of cells called the phloem it is
responsible for the transportation carbohydrates and other photosynthates
down from the leaves to the lower parts of the plant. The layer beneath
phloem is called the xylem; it transports water and mineral nutrients from
the roots and soil up to the leafy parts of the tree. Removing the bark,
cambium, and phloem prevents carbohydrates and photosynthates from flowing
down the trunk. It still allows water and mineral nutrients to flow upward
to the leaves via the channels in the xylem, thus keeping the leafy
portions of the tree from drying out and maintaining them with an adequate
supply of nutrients. Removing the cambium layer prevents the regeneration
of phloem and healing over of the wound, the carbohydrates and
photosynthates flow down the trunk and collect at the girdling site. The
presence of this excess of carbohydrates and photosynthates at the
girdling site, plus the presence of the water in the sphagnum moss, causes
dormant adventitious buds in the area to grow into roots.
THE PROCESS of AIR LAYERING
Materials needed to perform air
layering include a sharp instrument, fresh sphagnum moss, root tone, clear
plastic (saran wrap, etc), wire for tying the plastic (garbage bag ties),
gloves to protect cuts on your hands from varying types of fungus that
have been found in some mosses.The moss must be soaked in water for about
20-30 minutes before using.
Utilizing a sharp blade the area must be cut
(ringed) continuously around the limb or trunk and then repeated
approximately (1) one inch above or below the original cut, the larger the
branch the greater the distance between the cuts,
The area between the cuts must then be removed by cutting or scraping,
taking care to NOT go to deep and cut into the xylem.
Taking the sphagnum moss that has been soaking in water, squeeze out
minimal water and form a square pad 2-3 inches wide. Sprinkle the rooting
hormone on the pad liberally and form the pad around the branch or trunk.
Wrap the entire pad with the plastic.
The top and bottom of the plastic must be tied
securely with the bag-ties or wire to help hold in place and retain
moisture. Be careful that no moss is exposed, this will act as a wick and
cause maximum evaporation. Ensure that the upper tie is in a position that
can be removed to inspect occasionally and add water as needed. Place the
tin foil with the glossy side in over the entire air layer, forming it
tightly to resemble a baked potato, this will help to ensure contact and
prevent over-heating.
Depending on the species of tree, roots should
normally start to show in 4-6 weeks, although many take longer and some
shorter. By removing the tin foil and checking while you water you can
observe the development. They will start, as little white nodules on the
branch or trunk, be careful they are very fragile at this stage.
Once the roots have developed enough the rooted
air-layer can be separated from the original. Caution is once again
required, cut the branch or trunk long if you are not sure about hurting
roots, they can be recut at subsequent repotting.
