can Rhododendron be grown from cuttings? When is the best time in my zone to do so.
Most rhododendrons can be propagated from cuttings. The procedure varies a little depending upon the type a rhododendron.
Propagation of hybrid plants requires a form of cloning. These include cuttings, tissue culture and layering. Most rhododendron and evergreen azalea cuttings root fairly easily. Deciduous azaleas require special techniques to root.
Most evergreen rhododendrons and azaleas may be propagated from stem cuttings. Cuttings are usually taken in the early fall from new growth that is just beginning to harden off. Generally, softer wood roots more readily than harder wood, though the softer the wood, the more likely it is that problems will occur with fungus diseases. Cuttings are taken in the morning when full of moisture. The cuttings are usually terminal cuttings with one whirl of leaves with the leaves cut in half (to reduce the leaf area) and any flower buds removed. Wound the cutting with a cut on each side, about 1/2" to l", just deep enough to cut through the bark. Dipping the cutting in a rooting hormone containing indolebutyric acid will make rooting easier. The exact formula depends on the hardness of the cutting and the difficulty in rooting the cultivar you are tying to propagate. The cutting has the end cut off just before placing in hormone powder (containing a fungicide). Then the cuttings are placed in a flat of sterile media containing a mix of 50% peat moss, and 50% horticultural perlite or vermiculite. The flat is placed in a polyethylene bag with struts to keep bag away from the foliage and placed in a light area with no direct sunlight. The flat is rotated once or twice a week to compensate variations in light and temperature. Usually bottom warmth of 70-75F is used to encourage root growth. Rooting usually takes about 6 weeks for evergreen azaleas and 3 to 4 months for large-leaf rhododendron. Once the cuttings have rooted, pot or transplant them to flats containing a sterile mix of 60% peat moss and 40% perlite. Fertilize once a month with an acid-based azalea plant food like Peters. Removing terminal buds promotes sturdy well branched plants.
Deciduous rhododendrons are propagated by seed, grafting or cutting. Deciduous azaleas are very tricky to propagate from cuttings. Tissue culture is used to propagate varieties that are difficult to root. It is a laboratory technique that is very successful.
Take cuttings of deciduous azaleas when the new growth is soft and pliant. This is often coincident with time of bloom in early June. The ability to root decreases rapidly as new growth matures. Select cuttings daily for best results. Trim cuttings below a node (overall length of cuttings 3 to 5 inches) and dip in a root hormone containing fungicide. Insert in a medium of 60% peat moss and 40% horticultural perlite. Usually bottom warmth of 75Â°F is used to encourage root growth. In late August, transplant cuttings that are rooted and grow on in the greenhouse with supplementary light (14-hours a day) to prevent dormancy and induce new growth. In the fall after new growth has matured, transfer to a cool, frost-free cool (35Â°F to 41Â°F) environment to induce dormancy. As new growth develops in the spring, transfer plants to a shaded environment. [After "Rhododendrons and Azaleas" by J. Lounsbery, Horticultural Research Institute of Ontario, Canada]
Layering is the easiest form of propagation for the home gardener. A lower branch is held down on soil (not mulch) with a stone. A slit is cut in an area in contact with the soil and the cut is treated with a rooting hormone. Then the cut area will sprout roots. When the roots are developed enough to support the end of the branch, usually in 2 years, the branch is cut from the parent plant and, if desired, transplanted.
Thank you Rhodyman for such a nice reply.