There is no single best method to grow stem cuttings. Evergreen azaleas usually root easily. Deciduous azaleas can be more difficult to get to root and live to grow on. Each propagator works out a method that works for her or him. The formula for the growing medium can vary but most contain perlite and fine pine bark. Some propagators use a fungicide and insecticide wash before sticking the cutting. Some use a mist method; others use some form of closed container or tent to keep the cuttings moist. It can be as simple as a white garbage bag. Some use florescent lighting; some use outdoor sunlight. Moisture, humidity, and light are key. Do not over fertilize. Cuttings should be taken when the growth is almost ripe. The stems should be crisp but flexible. Early morning cuttings are best because the moisture in the stems is high. Evergreen azalea cuttings are usually ready about a month or six weeks after deciduous azalea cuttings. The article below by Earl Sommerville explains his method for deciduous cuttings. Earl's method is excellent and works well, but there are less complex methods for the casual gardener that also work. The illustrations use evergreen azaleas and also show other techniques.
Over the past thirty years, I have sought to develop a reliable process for propagating native azaleas. For the first twenty of those years, my efforts were met with little or no success. The next five years showed marked improvement, and for the last five years I have been consistently rooting at the rate of eighty percent. After much trial and effort, I have learned that some plants simply will not root. Ironically, these are usually the very best plants. Although this may seem frustrating, do not give up. For instance, I dug a 'horizontal calendulaceum' in 1963 and for twenty-eight years it refused to root. After all that time, last year it produced two plants, and from those two plants, four were yielded this very year.
North Georgia contains a variety of native azalea species that have crossed naturally through the years to form natural hybrids or inter-species hybrid azaleas. This natural crossing may serve to aid the propagation process. While I have been successful in propagating particular plants in all species, I have also found individual plants that will not root in each of the species I have worked with. For years I have been told that you can't root native azaleas, but I have been quite pleased with the results. The following sections provide a detailed methodology I have developed over the years for propagating native azaleas.
The bench measures four feet wide, eight feet long, and twelve inches deep. On the bottom of the bench is a one-fourth inch hardware cloth topped by a three-fourth inch water pipe. Next is three inches of large pine bark, a heating cable or hot water pipe, and three inches of small pine bark.
Four daylight tubes, eight feet in length, are positioned two feet above the propagating bench. These tubes are controlled by a twenty-four hour clock with one hour trips (on at 7:00 PM, off at 11:00 PM).
Primary Mist System
The primary mist system consists of a filter, solenoid valves, and a twenty-four-hour clock with fifteen-minute trips that controls a six-minute clock with one-second trips. Flora Mist brand nozzles are used in conjunction with baffle wire and placed eighteen inches above the bench. The mist head spacing is not to exceed three feet six inches, and the operating pressure on these heads should be set to sixty psi. This system should be operated from 8:00 AM to 7:00 PM for two seconds every two minutes or for one second every one minute. By the first of July the primary mist system is phased out to allow the secondary mist system to take over.
Secondary Mist System
I use a Mist-A-Matic brand system made to operate around the clock. Although this system is billed to operate twenty-four hours a day, in actuality it operates from 7:00 PM to 8:00 AM or as needed.
The medium consists of two parts pine bark (screened through a one-fourth inch screen), one part peat moss and one part Perlite. It should be subjected to the mist for a period of seven days before it is ready to accommodate the cuttings.
Use tree seedling pots measuring ; 3" x 3" x 5 1/2" with an 'almost open' bottom.
The recommended hormones are Hormodin #3 and Roots, a liquid gel (Canadian product). Failure to use a hormone in the propagation process slightly lowers the success rate percentage, but if the cutting roots they will break into new growth sooner without the added hormones.
The fertilizer of choice is Peters 21-7-7 distributed in a Gewa injector with a 1-100 mixing valve. Issue the fertilizer at a ratio of two pounds per gallon (derived from the Gewa Constant Feeding Chart for a seven to ten day feeding). If watering by hand, mix one teaspoon of fertilizer per gallon. Plants should be fertilized beginning on the fifteenth day of June and every ten days thereafter. Moreover, make sure never to fertilize plants that are in winter dormancy.
Cuttings from the Garden
Here in Georgia I generally take cuttings from the 1st of May to the 20th of May but never after May 30th. The cutting should be taken “very early” in the season while it is “extremely soft” from a plant that has been well watered and fertilized with a well balanced mix the previous year. The plants also need to be in a stage of active growth. After taking the cuttings, put them in a plastic bag and place them in a refrigerator for twelve to forty-eight hours. It is very important that water not be added to the plastic bag prior to refrigeration.
Cuttings from the Mountain
If the cuttings are allowed to wilt, they will not root. Therefore, the cutting should be taken early in the morning, placed in an airtight plastic bag with a wet paper towel, and if at all possible, stored in a cooler with ice. The cooler will greatly increase the probability of successful propagation. I have even converted a backpack into a small cooler for this very purpose.
After removing the cutting from the refrigerator, remove the tip and all but four leaves. Next, cut off one-half of each of the remaining four leaves and dip the cutting into a Insecticide - Fungicide mix before placing it into the medium. By July the cutting will begin to show new growth, and by the first of October it will have grown an additional six to eight inches in length. In the middle of October, move the rooted cuttings to a cold frame covered with white polyethylene for the winter season.
The greenhouse should receive a full measure of sunlight from 8:30 AM to 7:00 PM, and no shade should be provided for the propagating bench. The temperature rises to a full 100 degrees Fahrenheit in the greenhouse while the medium temperature approached 85 degrees Fahrenheit under the mist. Experience has proven that providing this atmosphere to the cuttings increases the likelihood of success.
The rooted cutting should not be potted up until the following spring.
Conventional wisdom discourages the possibility of propagating native azaleas, but the formula I have developed after years of trial and effort has consistently provided a respectable level of success. While each of the steps involved in the process is important, there are three areas that require the most attention: the timing of taking cuttings, using the refrigerator, and fertilizing properly. Giving these three steps the utmost attention will greatly increase your chances of success.