Moisture – The cuttings cannot be allowed to dry out.
Capable cuttings – Cuttings should be taken in September or October and from the lower branches on the shady side of the plant. Avoid thick, fat stems, rather chose thin stems.
Allow roots to emerge – Root initials are found in the cambium layer, a thin layer of cells directly under the bark and on top of the hard wood inner stem. Remove a one inch sliver of bark at opposite sides of the base of the cutting to expose the cambium layer. This is called a wound.
Hormone – Use the strongest hormone you can buy. I use a 2% IBA powdered hormone. Just dip the wounded base of the cutting in the hormone and tap to remove extra hormone. Many people use Woods Rooting Compound made by Earth Science Products Corp. It is a liquid and is 1% IBA.
Rooting Mix – A mixture of peat with sand, pearlite or vermiculate. 50 – 50. Mix should be moist but not sodden.
Take cuttings of current year’s growth, cutting just above the leaves from last year. Take cuttings in the early morning the day after rain or irrigating the plant. Immediately place cuttings in plastic bag and close bag to reduce water loss.
Wound cuttings by removing a one inch sliver of bark on both sides of the lower end of the cutting. I cut about 1/3 of leaves off to be able to get more cuttings in the bed. Do not let the leaves overlap a neighboring cutting as the covered leaf will abort. Dip in hormone and stick into rooting mix by first making a hole with a pencil or finger. Do not compress the mix around the cuttings, the roots want an airy mix in which to grow but gently fill the space between the cutting and the mix. The mix can be in any container. The container, mix and cuttings should be placed in a sealed plastic bag and placed in a very light area but no direct sunlight as sunlight will heat up the bag. Water is not necessary as the sealed plastic bag will prevent water loss. I root mine under 18 hour fluorescent lights.
The frame is 8′ x 4′ (the size of a standard piece of plywood) with 6″ high sides. There are 4, 2 bulb light flixtures over the frame which are on 18 hours a day. In May open the bag for a few days to acclimate the plants to the atmosphere. In June plant the little plants in a protected spot in the garden. Fertilize with water soluble fertilizer several times over the summer, stopping on August first. Do not let the little plants dry out.
Deciduous Azaleas: Rooting deciduous azaleas is similar to rooting evergreen rhododendrons in that the mix, the hormone and the lights are the same. The main difference is that the cuttings are taken July 4th in my garden. (I live on Long Island, a suburb of New York City.) The cuttings are very soft, but that is OK. A wound is not necessary. The cuttings root quite rapidly and by October 1st are ready to be removed from the propagation bench (to make room for rhododendrons!). THE ROOTED CUTTINGS MUST HAVE A FLUSH OF GROWTH BEFORE THEY GO DORMENT AND DROP THEIR LEAVES. If they don’t have a flush of growth they will not leaf out next spring. This is accomplished by putting the rooted cuttings under 24 hour lights. After the new growth is mature put them in a cool place with natural light and they will go dormant. Do not let them freeze. Next spring plant them out in a protected spot and away you go.
Commercially, mature plants are lifted in the late fall or early winter after they have dropped their leaves and have been dormant for a couple of months and placed in a warm greenhouse. This is usually December. By February they have done their spring thing: bloomed and produced new growth. Soft wood cuttings are taken and rooted. In May or June they are planted out. Over the summer they will have a flush of growth and are thus ready for the winter dormancy and will leaf out next spring. They should be placed in a cold frame for the first winter. Do not let them freeze.