The large-leaved rhododendrons, popular, evergreen ornamentals in the mild and semi-rigorous regions of the country, are hard to propagate.
However, moisture-proof plastic wrapping is a technique that uses and increases the number of successful rootings with a simple use of modern material.
This common material, polyethylene, is used to provide proper conditions for air-layering, a means of getting roots started on stem cuttings before the cuttings have actually been cut off the parent plant.
Air-layering, developed by plant propagators long ago from the more or less natural method of soil or mound layering, has been a greenhouse technique for conservatory plants, usually tropical.
Propagating Rhododendrons
Rhododendrons have been propagated commercially by grafting in the greenhouse. The wrapping makes field propagation feasible and easy for the amateur in their yard.
In air-layering, as practiced in the greenhouse, the stems are wrapped in tied-on balls of moss that must be watered daily.
Without a moisture-proof cover, it would be impractical to keep these handfuls of moss damp outdoors.
To root Rhododendrons using the air-layer method, try starting in early May out in the open.
The last season’s wood was slit, and a small quantity of indole-butyric acid (one of the hormone-like plant growth substances) was put in the cut.
Wrapping Moist Sphagnum Moss
The moist sphagnum moss was squeezed as dry as possible and wrapped around the treated part.
Then wrapped in turn with a sheet of plastic made tight to the stem at the top and bottom with rubber grafting bands (aluminum foil will also work).
In August, about three months later, when the stems should have a ball of roots ready for cutting and setting in pots, the moss should still be moist, although no water had been added after wrapping.
This procedure is great in the propagation of Rhododendrons and a great gain in rooting many others.
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