Cuttings of the stems of most evergreen azaleas can be rooted rather easily. Use new growth for the cuttings, at any time from June onwards, depending on the weather and the variety of azalea. The exact timing depends on the condition of the cutting wood, which should be somewhere between soft and brittle: it should not bend like rubber, and it should not snap like a matchstick. At the proper time, it will probably be putting out a new terminal bud.
Take cuttings from the short shoots that come from the ends of existing wood, not the strong thick shoots that come from the base of the plant. Cut them two to five inches long, preferably in the morning, and preferably from a well-watered plant in good condition.
Cut off all but the top cluster of leaves, or carefully strip them off without also removing the tender bark. If the terminal leaves are quite large, consider cutting them in half. If the cuttings will not be stuck immediately, moisten them, shake off the excess water, put them in a plastic bag and put the bag in a refrigerator. Some people think overnight refrigeration is preferable to sticking them immediately.
When you are ready to stick the cuttings, wound the bottom half inch or so of each cutting by scraping off the bark with a knife or thumbnail. You can optionally use a rooting hormone. With a liquid hormone such as Wood’s, use a 5% solution (mix 1 part of the hormone with 20 parts of water), and put the bottom inch of the cutting in the liquid for no more than 5 seconds. If the solution is stronger or the immersion is longer, you may burn the cutting and it will not root. A talc-based rooting powder such as Hormodin or Rootone is safer to use. Put the bottom inch of the cutting in the powder and shake off the excess. In general, evergreen azaleas root well without any hormone.
The most commonly used rooting medium is 50/50 peat and perlite, although various other mixtures of peat, coarse perlite, sand, fine pine bark and vermiculite are used. The goal is to provide both moisture and oxygen. The medium should be from four to six inches deep, and may be in a flat for large quantities, or a one gallon pot for up to a dozen or so cuttings. Prepare it a few days before you will use it, and water it several times to moisten it well. Leave the medium loose to promote drainage and aeration.
If planting in a flat, use a straight-edge to prepare each row. Lay the board on top of the medium and use a knife to cut a two- to three-inch deep line along the edge of the board. Insert the cuttings into the cut every two to four inches, depending on the size of the cuttings and how long you intend to leave them in the flat. Move the board, cut a new line, insert more cuttings, and so on. In a pot, use a large nail or a pencil to make a hole for each cutting. Use a consistent convention for labeling the cuttings, such as a pot label at the beginning of each row, or a pot label at the beginning of the cuttings for each different kind of azalea.
After sticking the cuttings into the medium, water them in to settle the medium around the cuttings, preferably without wetting the leaves. Then cover the flat or pot with plastic to seal in the moisture. A large zip-lock bag works well with a one gallon pot, and a plastic tent can be made for a flat. Finally, put the flat or pot where it will get as much light as possible, with no direct sunlight. While brief exposure to early morning or late afternoon sun is not harmful, strong daylight sun will heat the enclosure and burn up the cuttings.
The cuttings should root in four to eight weeks. Be patient. While a very gentle tug can indicate progress, it can also break off any initial roots before they get established. When the cuttings have rooted, the enclosure should be gradually opened a little to acclimate the cuttings, and opened entirely in a few more days. Finally, transplant the rooted cuttings to pots or flats of peat moss, sand and leaf mold and keep them from freezing temperatures in a greenhouse or cold frame for at least one year.
Cuttings of deciduous azaleas are more difficult to root. The first problem is rooting them at all, and the second problem is getting them to break into new growth after they have grown some roots. The general procedure is the same as for evergreen azaleas. The differences start with the cuttings, which should be taken earlier, while the wood is still quite soft and green, usually around late May. They will require the use of a rooting hormone. While a stronger rooting hormone will increase their chances of rooting, it makes it harder to get them to break dormancy and go into active growth.
The cuttings will do best in a greenhouse with bottom heat from electric heat cables at around 75 degrees F, and with a mist system during the day to ensure they get all the moisture they can use. However, they can also be rooted under plastic as described for evergreen azaleas.
As soon as they have rooted, the cuttings should be fertilized with half strength liquid fertilizer and given three to four hours of extra light through the summer to force them into active growth. Use 75 watt incandescent bulbs or a mix of incandescent and flourescent bulbs, as close as possible to the cuttings without burning them, which is about 6 inches away. In late September, stop the extra light to let the cuttings harden off for the winter. Do not disturb their roots until they begin to grow the following spring, at which time they may be potted up or moved to a bed in the garden.