JARS v61n2 - Tips for Beginners: Propagation by Air Layering

Tips for Beginners: Propagation by Air Layering
Dr. Mark Konrad
Sewickley, Pennsylvania

The propagation of plants by layering dates back to ancient times, at least 2,000 years ago. This is easily understandable with the common experience of seeing branches strike roots when lying on the ground for a period of time.

Ground layering is still the method of choice with some plants, such as raspberries and others, but this has been supplanted largely by more advanced technology.

For a detailed list of the many layering methods the reader is referred to Plant Propagation, Principles and Practices , Hartman, Kester, Davies, Fifth Edition, 1990, Simon and Shuster Co.

This article will concentrate on air layering of rhododendrons by a simple method I have been working with experimentally.

David Leach in his book Rhododendrons of the World , Charles Scribners Sons, 1961, gives very detailed information about this method. The salient points covered for a successful outcome are as follows:

1. The optimum time for air layering is early spring. Late summer is a second choice.

2. Proper preparation of the stem is important. A deep upward slit is made in the stem and held open with a toothpick. The slit should be several inches long (see Fig. 1).

3. The use of a rooting hormone can be helpful.

4. Sphagnum moss is packed around the wounded stem and held in place with polyethylene sheeting or tubing (see Fig. 2). Aluminum foil is a second option.

5. Excessive moisture should be avoided. The upper and lower ends should be sealed off with waterproof tape to prevent water from seeping in.

6. Drying out of the sphagnum moss can be a problem. My solution for this is to supply additional water through the use of a hypodermic needle and syringe.

7. Quite often rooting does not take place until the second year.

8. The biggest problem for rooting has been excessive moisture and often not waiting until the second year for rooting to take place.

Recently, I have been experimenting with the use of small pots made of soft plastic (yogurt containers). These are easily slit and after a small hole is made in the bottom they are easily placed around the stem (see Fig. 3). The stem is wounded on both sides and a rooting hormone applied. The cups are filled with moistened sphagnum moss, and thereafter rainwater is free to enter since there is no covering. I have been giving this a trial, since many stems are too short to work with. One disadvantage has been the limited number of vertical stems strong enough to carry the weight without drooping.

Air layering can also be done on a larger scale (see Fig. 4). The bottom of the upper container has been removed.

Air layering offers a special niche in certain areas of propagation. One such case might be a difficult to root plant. Another case, perhaps, is to have a backup plant of a special clone in case of an inadvertent loss.

Reference
Konrad, Mark, 1983. Ground-air layering revisited, Journ. Amer. Rhod. Soc ., 37: 1: 29.

Dr. Konrad is president of the Great Lakes Chapter.