What is Air Layering?

TreeBay

These are some brief notes on how to propagate a plant by a process called "air layering." You can find more information on Air Layering in bonsaiTALK Links under Techniques->Propagation->Layering

REASONS FOR LAYERING
Layering is performed to propagate material, to take advantage of interesting or pleasing forms, or to improve the rootage of a tree. Layering is an easy way to create "perfect rootage" on a tree with a one-sided or unattractive root system.

HISTORY OF LAYERING and GROUND LAYERING:
Layering is a process used to induce roots to grow on a mature branch. The process of layering was probably developed in conjunction with hedging. Hedges of boxwood, privet or thorns were a convenient way to designate property boundaries, particularly in the absence of good material for fences.

"Ground" layering was performed by making a cut approximately 1/2 way through a low branch, wedging it open with a stone and pushing the wound area into the ground a foot or two away from the plant. The branch produced roots at the wound site and so extended the length of the hedge by a couple of feet. In this way, a few plants spaced at regular intervals could serve as hosts to create a wide perimeter hedge over a number of seasons.

AIR LAYERING AND BONSAI
Air layering is a technique based on the same principles as ground layering, but the technique has been refined in such a way that it can be applied to branches in any position on the host tree. Some trees like wisteria and elm layer readily. Others like pine and cedar are much slower at developing roots.

MATERIALS REQUIRED
In addition to a suitable host tree, you will need the following materials:

• Sharp knife
• Narrow bladed saw
• Canadian Sphagnum Moss
• Polyethelene sheeting, thick (clear plastic)
• twine
• bonsai wire]
• marking chalk
• rooting hormone

HOW TO CREATE A LAYER
To make an air layer, first determine an appropriate site. Layer sites can be based on points of convenience or interest. There is no physical limit to the size of a branch that can be layered successfully. Branches up to 12" have been successfully layered.

Convenient sites are those that will be pruned away eventually anyway - to redesign the host tree or reduce its size, perhaps the top 1/3 of the tree is intended to be pruned away. This may make a great small bonsai if it is instead layered.

Interesting sites might be areas on a bonsai, or even a yard or garden tree that has unique characteristics, such as:

• fast taper
• interesting curves
• unique species
• interesting forked branch arrangement, etc.

MARK THE SITE OF THE LAYER
Using a piece of chalk, mark a line around the circumference of the branch. This will define the new "soil line" from which roots will emerge. Roots sometimes emerge slightly higher than this point, so take this into consideration.

Mark a second line below the first, completely around the trunk. This line should be positioned at a distance approximately equal to the width of the branch being layered. This line defines the lower portion of the layer. The bark between the two lines will be removed as follows:

• Using a sharp knife (Our folding grafting JR-0190 is ideal) scribe a 1/8" deep cut around the upper chalkline. The idea is to completely penetrate the bark down to bare wood. This is usually around 1/8" deep, but on thick- or rough barked trees like elm or pine it can be substantially deeper.
• Cut a second line around the lower chalkline.
• Using the knife, peel away the bark between the two chalklines. Remove it all the way down to the bare wood, which will be evident by its whitish color. Remove anything greenish between the cuts

PREPARE THE SITE

• Make sure that the wound near the upper chalkline is cut cleanly. It may be necessary to clean up the cut with the grafting knife. This is particularly important, because this is the point at which the roots should be developing.
• You may twist a thick piece of bonsai wire tightly around the circumference of the upper chalkline, just beneath the newly cut edge. This helps to ensure that the tree generates roots rather than simply healing over the wound. It also helps ensure a balanced root system by defining the edge at which the roots will develop.
• Swab the area with a liquid rooting hormone or paint on a slurry of powdered rooting hormone mixed with a bit of water.
• Drench a handful of moss in water. This should be the long, threaded Canadian variety of moss used in planter baskets, not the chopped fine sphagnum.
• Pack the region with sphagnum moss and tie it in place with twine or bonsai wire applied lightly.
• Add more moss to the region. You want enough moss to enable a rootball large enough to sustain the layered branch. This requires some judgement, but it would be approximately the size of an appropriate bonsai pot for a "tree" of equivalent size.
• Wrap the moss with clear polyethylene sheeting. This will preserve the moisture while allowing you to assess the condition of the layer. Tie the bottom of the sheeting below the lower chalkline. The upper end may be left partially open to facilitate watering the layer if you are in a moderate climate. If it is very dry, you may need to seal the top edge of the bag as well and open it occasionally to water.
• Mark the plant with a tag indicating the date of the layering operation

LAYERING

• After some weeks you should observe the development of white roots issuing forth into the moss
• Do not disturb the layer during this period. The roots need to harden-off into a darker, more mature form.
• Rotate the plant occasionally to ensure that the entire layer receives the sun's warmth.
• As necessary, water the layer area to keep moisture in the moss. It should be damp at all times, but should not remain sopping wet for long.
• The period of time required to create the layer varies with the season and the species. During the growing season a wisteria might fill the bag with roots in just a few weeks and be ready to separate in just a couple of months. A pine on the other hand might grow much more slowly, requiring up to 2 years for sufficient root to develop.

TIMING THE REMOVAL

• By the time the layer is ready to separate, the bag should be filled with roots that have matured from a pure whitish color to a darker appearance. The branch itself should have grown somewhat, indicating that the roots are functioning properly.
• The ideal time to separate the layer is the same as repotting; early fall through late winter

REMOVING THE LAYER
In removing the air layer from the host plant, caution should be taken not to disturb the roots, which are extremely brittle at this time.

• Using a pruner, cut back the extremities of the foliage on the layer. This will reduce the load on the new roots.
• Using a thin-bladed saw such as our JR-0111 Keyhole Saw, remove the entire branch and bag, leaving a generous stub
• Open the bag and remove the poly.
• Fluff the rootball just a bit, and plant it in a well draining bonsai soil. Do not disturb the roots very much or they will break. Do not try to go straight into a bonsai container on the first transplanting. Be very gentle with the plant at this stage.
• Tie the plant securely into the growing container.
• Update your tag with a record of the date of first transplant.
• Next year, when the tree is repotted, the stub may be entirely removed and the roots can be refined to create a more even, pleasing appearance. At this time the tree may be planted in a bonsai container.

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Adam

Matt, I just found this,and it is very helpful to me. Thanks for putting it up.

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[Adam]
"Cass Bonsai Gardens"
"Bonsai Knowledge"
"DaGhostCrew"

TreeBay

No problem. A new faq is in the works. I am just working at making it searchable.

Regards,

Matt

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Jerry Meislik

Matt,
nice job on summarizing the layering process.

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Jerry Meislik
Whitefish Montana USA
Zone 4-5
http://www.bonsaihunk.us/

bmor

once searchable it'll be a great --at your fingertips resource.

keep up the good work matt

conor

You said wisteria layers readily. I was wondering if I layered my wisteria that flowers, will the layering flower?

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-Conor