One of the most interesting characteristics of plants, I think, is the ability to reproduce asexually. For example, a stem cutting of a philodendron can be placed in soil and, given the right environment, will amazingly become a whole new plant.
There are many methods for asexual propagation in addition to stem cuttings, including other types of cuttings, grafting and budding, and division. Layering is another method and is a good choice for propagating plants with soft, supple branches like forsythia, azalea, rhododendron, holly and magnolia.
When plants are propagated by layering, the part of the plant that will hopefully become a new plant is still attached to and protected by the mother plant. Layering is often considered easier and more reliable than grafting.
Layering can be done in a few different ways. Layering is really about contact of the plant stem with soil and water that stimulates growth of plant roots. Plants’ ability to differentiate plant cells in this way is one means of survival.
Ground layering or simple layering is the easiest. Using a young, flexible stem that is close to the ground, press the stem to the soil surface until you hear the stem crack. This wounds the plant and encourages cell growth. Pin the stem to the ground or weight it with a rock and pile a bit of soil onto the wounded part of the stem. Root formation will occur over a period of several months.
Air layering is best when stems are too far from the ground for simple layering or when soil is dry, poor quality, and/or compacted. Again, choose a young, flexible stem, ideally about the same diameter as a pencil. Wound the chosen branch by slicing into it vertically, or carefully remove a small strip of bark.
After wounding the plant, brush the exposed plant tissue with rooting hormone. Rooting hormone is available at most garden centers and is made from a naturally occurring plant hormone. Use of rooting hormone helps to speed root formation.
Tuck moistened sphagnum peat moss into the wound or wrap it around the wound. The moistened peat moss will provide moisture without promoting decay. Wrap the branch and peat moss in plastic wrap and secure the wrap on both ends with rubber bands or plant tape. Cover the plastic wrap with aluminum foil or black plastic to protect it and encourage root growth.
Air layering, like ground layering, takes several months to a year. Carefully peel back the foil occasionally to check for moisture and formation of plant roots. Peat moss should be moist but not saturated.
Once the air or ground layered branch forms sufficient roots, remove it from the original plant. Give the new plant a good home in an ideal location.
Although plants can be air or ground layered in several places at once, each layering only works to create one new plant.
Not all plants can be layered. If you have a plant you want to propagate and are unsure how, there are many references available to direct you to the best method for each plant genus.
Also, before propagating any plant, note that new varieties of plants are protected by patents for 20 years. That means you cannot propagate your Knock Out™ rose and sell the new plants. You can, however, propagate your no-name forsythia. Plant patents are meant to protect plant breeders just as any other inventor is able to protect his or her work.