Donna Denton is an expert camellia grower and a Master Gardener who writes for Master Gardener newsletters. She is our guest writer this week.
From this article, learn how to make new plants. You can propagate just about any tree or shrub, like the Pineapple Guava or Hydrangea pictured on this page, by the simple process of air layering. Cuttings might be easiest, but air layering is a close second, both for ease and for successful propagation. Seeds might not give you a replica of the plant you want to copy but a branch of the plant will give you a clone, the exact flowers and foliage of the mother plant.
Layering is only one of many methods of plant propagation and has been done by gardeners for hundreds of years. Typically, the gardener would take a lower branch of a desirable plant, wound the bark slightly with a sharp knife or thumbnail, lay it on the ground, put a little dirt on top of the wounded area and secure it with any handy weight such as a brick or rock. Four to six weeks later, a quick peek under the rock or tug on the end of the branch may reveal new, adventitious root growth at the wound site.
You can then separate this newly rooted branch from the mother plant and then either pot it up or plant it directly into the ground.
There are several advantages of layering over other methods of propagation. Growing trees and shrubs from seed or cuttings may take years to produce a plant mature enough to flower or fruit. Layering, on the other hand, can be done on a stem or branch with considerable caliper size and length so that the resulting new plant could be large enough to produce fruit or to flower the next year. Camellias are a great example of this result.
Layering may be done at any time of the year but works best when the cambium layer is active and the ‘sap is rising’ as they say. Late March and April are the best months but you should check that the bark is slipping for best success.
Layering works easily and well with many plants and trees including Magnolia, gardenia, roses, fig and, surprisingly, many houseplants. Some plants, though, are extremely difficult to propagate by any method and layering may not be successful either. Native Azalea and Kalmia are two tough shrubs that quickly come to mind.
Air layering is simply an adaptation of the old timey layering technique. It allows layering in the upper levels of a plant or tree. If the mother plant is large enough and has enough limb structure, you can put multiple air layers on a single plant. Because the potential new plant remains attached to the mother until adventitious roots form, the mother continues to support the branch or limb with water and nutrients. In fact, if the layer is not successful, you could simply leave the limb on the mother plant or make another air layer at a different spot on that limb later. The limb will probably not die, or at least not as a cause of the unsuccessful air layer.
Select a limb or branch that (a) you would want to remove any way for pruning purposes or (b) would not leave the mother plant looking butchered. Choose a site for the air layer about 12-24 inches from the end of the branch. With a very sharp knife, make a cut around the limb, through the bark and cambium layer only. Then make a second, similar cut about an inch or two from the first cut. Finally make a cut from the first to the second girdling cuts and use your thumbnail or knife to remove the bark and cambium layer from this section.
Squeeze the excess water from a generous handful of presoaked sphagnum moss (do not use peat moss), sprinkle rooting hormone over the surface of that moss and wrap it around the exposed wound site on the branch. Wrap a doubled strip of clear plastic wrap (Saran Wrap or Handi Wrap) around the entire section of moss overlapping the end of the wrap over the beginning. Turn the wrapped moss so that the overlapping section faces the ground to prevent rainwater from getting into the wrap. Tightly secure each end of the plastic wrap with baggie ties. You could use aluminum foil for this wrap; however, unless you crimp the foil instead of overlapping, this tends to dry out more than the plastic wrap.
You can also cover the plastic wrap layer with foil but birds and squirrels tend to tear open these ‘baked potatoes’ more frequently than plastic wrapped air layers. Using green colored plastic wrap may diminish the attraction for critters.
Some literature indicates that air layers may show roots after 4-6 weeks. The real test is to check the air layers frequently both to insure critters have not torn the wrapping (which allows the potential root ball to dry out) and to see if roots have begun to form and appear through the moss. As roots grow, the moss ball will also begin to feel more firm when squeezed. Usually the roots will have formed an adequate root ball by the fall of the year and you can remove the air layer in September or October.
The most important lesson here is in the removal. When roots have filled the moss ball, you can remove the air layer from the mother plant and plant in the ground or pot it up. To remove the new plant properly, be certain that you cut below the newly formed roots (between the root ball and the mother plant) so that you are taking the root ball off attached to the branch.
Don’t laugh, it has happened that someone made the cut above the new root ball and took the branch off leaving the root ball on the mother plant. Well, if that happens, just make another cut beneath the root ball, pot it up and see what happens. It may surprise you and send out new growth. You know, plants just want to grow.
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Every year, I challenge myself as a gardener to grow something I've never grown before and this year was no exception. As a professional garden writer, I was privileged to be given several exciting new varieties to trial. Additionally, in my travels this year, I had the chance to evaluate many more new plants in trial gardens across the country. The following new annuals, which will be new at retail in Spring 2017, received top ratings in my book.
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