Another Garden Tip: Propagating Rhodos by Layering
Reprinted and modified from the Fraser Valley January 2009 Newsletter

        Often, plants become lanky and top heavy with clusters of leaves at the ends of bare stocks. The stems can be pruned back, with the clippings discarded, or your rhododendron stock can often be increased easily and with minimal effort by different types of "layering." The most advantageous time of the year to undertake either activity is in the mid-spring after the frosts have gone, when growth is rapid. For "simple layering" which works best in situations where flexible branches can be brought close to the ground, choose a preferably young, healthy stem and wound it with a 3 cm (1") long slicing cut 12-36 cm (6-18") from the end farthest away from the parent plant. Be careful not to sever the stem from the parent. Remove any side shoots. Wedge the wound open with a sliver of wood. Bury the wounded stem in a 12 cm (6") hole filled with good potting soil mix and stake it or put a rock on it to prevent it lifting out of the hole. Check back in six months and with reasonable luck, you will have it rooted. Sever from the parent to create a new plant, pot up and treat it as you would any new tender shrub.
        If you can't find a suitable low level stem to reach ground level or have stems that are quite rigid and upright, where it is impossible to bring them near the ground, try "air layering." This is a little more tricky, and somewhat similar to the above. An ideal place is around 30 cm (12") down from the top, and about 13 cm (5") below a leaf. The stem should be sturdy and preferably young, as old, hard wood does not root as easily. Again, make a diagonal cut, being careful not to sever the stem and dust evenly with a suitable hardwood hormone rooting powder. A matchstick can be placed inside the cut to keep it open. Press moist (not wet) sphagnum moss around and in the cut area (moist coarse peat or even a peat-based compost can be substituted), wrap the moss in self-clinging kitchen plastic wrap, and secure top and bottom with twist ties so that it will not dry out. Overwrap the plastic with aluminum foil or some other light impervious material to keep it dark. Keep an eye on it, and if it seems to be drying out, loosen the top and add some water. Once a root ball has formed, usually in six-nine months, sever it from the parent and pot the new plant as above.