JARS v38n2 - Rooting Evergreen and Deciduous Azaleas

Rooting Evergreen and Deciduous Azaleas
Mark Konrad, M.D., Sewickley, PA

In the dawning age of the meristematic tissue culture process which has begun to revolutionize plant production, it may seem redundant to describe another variation of propagation. Despite the inexorable march of science, however, there may always be the need to multiply plants on a simple level, if for no other reason than for the fun and challenge it can afford. The advantage of being easy and economical is also quite helpful when a few additional plants are desired.
It has been a common experience that rooting evergreen and deciduous azaleas can be difficult without exacting conditions. This is obviously true for the amateur who does not have enough time or equipment. With the method about to be described, much of the difficulty can be circumvented.
Clean plastic flats measuring 16 x 20 x 2 inches are used. Approx. 1 inches of media consisting of equal parts of Canadian peat and perlite are placed in the flat, leaving a 1 inch air space. The mix is then pre-wetted and firmed into place. Next, the cuttings are inserted at a 15 degree angle so that the tips are superficially embedded. Finally, the flat is then covered with thin plastic and secured with string to avoid any unnecessary air loss (See Figure 1.). The cuttings should be kept in a shaded area until rooted. Because the plastic is in contact with the foliage and the narrow air space is highly humid, the conditions are very close to misting. The flats can be lifted weekly to estimate the moisture by weight and the plastic removed to allow for a fresh supply of air and a chance to check for disease or insects.

Rhododendron propagation photo.
Figure 1.
Photo by Mark Konrad

Considering the high humidity and the high degree of aeration around the superficially inserted stems, conditions are ideal for rooting. Hormone treatment is necessary with deciduous but not evergreen azaleas. The evergreen cuttings need not be wounded. Additional use of either a fungicide or pesticide might best be judged on the basis of a particular need. I have on occasion, added a pinch of powered sulfur to the sprinkling bottle when replacement moisture becomes necessary. Additional aeration can be applied by placing a wire mesh in the bottom of the flat.
The proper time to take cuttings is vital. This may range from early to mid summer. For some propagators the proper snap of the wood might be the best indicator of early maturity. The earlier the better with the deciduous azaleas.
Evergreen cuttings need nothing special following rooting except gradual acclimatization. The rooted deciduous azaleas, however, need an increased photoperiod immediately following rooting to avoid early bud dormancy.
This method is applicable to any plant needing high humidity for rooting and could be ideal for rhododendron, although using more space. The rooting success has proven well over 90% with evergreen azaleas.