Layering is a plant propagation method that involves encouraging roots to form on a stem of the parent plant and then removing and replanting the new growth once it has properly rooted. This “vegetative” propagation method produces plants identical to the parent plant. It is used for rare species and ones that cannot be propagated in any other way, and also to rejuvenate some indoor plants. In the latter case, the very easy air layering method is used.
Air layering is done on upright plants with stiff stems, like figs and dieffenbachias. Plants that have become too leggy or large can be kept going for many years thanks to air layering.
Because layering is done on the plant’s young tissues, the cut must be made less than 1 m from the tip of the stem. Choose a sturdy stem at least 2.5 cm in diameter. Anything less will be too weak.
Before making the incision, remove any leaves immediately above and below it. Note that you can air layer more than one stem on a plant at a time.
The following plants are easily propagated by air layering:
- Brassaia actinophylla
- Codiaeum variegatum (croton)
- Fatshedera lizei
- Ficus benjamina
- Ficus elastica
- Monstera deliciosa
Preparing the stem
There are various air-layering methods.
The most efficient method, especially for woody stems, is to remove a ring of bark around the stem. Make the incision under a node, with a very sharp knife. Make it one and a half times as wide as the diameter of the stem. Remove the bark and then scrape the green part (the cambium) until you can see some white or beige wood.
Another method involves making an upwardly slanting cut, under a node, one-third of the way into the stem. Hold the cut open with toothpicks, to prevent the wound from closing over. This method is not as reliable as the first one, however, because it is not as effective for all plants.
You can dust the top of the wound with rooting hormone to encourage roots to form more quickly.
Make an incision into the stem and apply powdered rooting hormone to the wound.
Preparing the sleeve
You will need to cover the stem section with a sleeve of damp sphagnum moss.
Use sturdy string to hold the moss in place on the stem. Cover the entire sleeve with clear plastic wrap and secure both ends of it firmly to the stem.
Cover the sleeve with aluminum foil (shiny side facing out) if the plant is in a sunny spot, to avoid overheating the roots. The wad of moss should be about 5 cm thick and 5 to 10 cm long.
Poke a few holes in the bottom of the sleeve to allow any excess moisture to evaporate.
In some cases, you may need to stake the layered stem or tie it to a sturdy adjacent stem for support.
Check the moss regularly and mist it to keep it damp. Roots will eventually appear on the stem. How long this takes will depend on the plant species and ambient conditions.
Place two handfuls of damp sphagnum moss around the stem, on the treated part.
Cover the sleeve with clear plastic wrap and secure it in place.
Once you can see a root ball, about 6 to 8 weeks after getting started, remove the plastic wrap and cut off the stem under the sleeve. Repot the newly rooted stem, using suitable potting mix.
Place the new plant in a spot with good humidity for the first few weeks. If the air is too dry, cover the plant with a clear plastic bag and poke a few holes in the bag.
You can also keep the parent plant if you wish, as new shoots will eventually appear.
Air layering can be done at any time, but roots will form more quickly in spring and summer.
Once the roots are visible, cut the stem underneath the new plant. Repot using suitable potting mix.
Illustrations: Espace pour la vie/Audrey Desaulniers