Paul Nickerson

Archive for July, 2011|Monthly archive page

Air Layering: Arborvitae

In Propagation on July 21, 2011 at 4:59 pm

Air layering is an effective means of propagating many species of trees and shrubs. By adding an air layer to a host plant, one can root a stem clipping prior to removing it from the parent plant, allowing it to grow a strong root system while still being supported. For most plants, air layering should be done in the early spring, before new growth. For some shrubs, such as Rhododendron, propagation can be done after the blooms have fallen from the bush, as the bush will begin to develop new growth at that point.

The process of air layering is very simple. For demonstration I photographed an air layer I recently did on an Arborvitae. In this case, I placed an air layer on every healthy branch, as we are planning on removing that tree altogether. Typically, it is best to select a healthy branch that will not ruin the look of the parent plant when removed.

Scored Pattern

Once you have selected the desired branch, find an internode that is about four inches long. If this is not possible, it may be necessary to prune some small branches to get a workable area.

Bark Removed

Using a knife, score around the branch in two places, about three inches from each other. Some people prefer to have these lines closer together, as to reduce the amount of bark removed, but it is important to realize that the tree will develop scare tissue around the edges of the cuts, and can close up the wound, restricting the development of roots. After making a long score from one cut to the next, peel the bark back from the hardwood of the branch. the goal is to only remove the bark, trying hard not to damage the wooded portion of the branch.

Plastic Wrap Attatched

Using zip-ties or twist-ties, attached the bottom end of an 12×12 inch square of plastic to the branch. For this I used a piece of a black garbage bag. It is best to use colored plastic as light will disturb root growth. You can also use clear plastic, then cover the wrap with foil.

Completed Wrap

Creating a pocket with the plastic, fill it with sphagnum moss. Be sure the branch has moss on all side, and that the moss is densely packed into the wrap. When the moss is in place, spray the moss with root hormone. It is important that the humidity is high inside the wrap, so don’t worry about over-watering. When the wrap is thoroughly moistened, secure the top of the wrap to the branch. Depending on the weather during the season, it may be necessary to remoisten the wrap periodically.

The wrap should be left on the branch for a few months. When it is ready to be removed, prune the branch just below the new roots and plant. Once the new cutting is in the ground, treat it as a new plant, being sure to water it often until it develops a larger root system.

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