Questions often arise concerning air layering of plants. This is a method of reproducing a plant in order to create another exactly like the original. It has been used successfully as an alternative means of propagating some plants difficult to root, i.e. plants where grafting or cuttings have not been successful or where seeds do not come true to type. Another advantage to air layering is that these plants have the ability to bear fruit much sooner than a seedling. Some fruit trees may take 10 years to fruit from seed. Plants such as citrus, figs, lychee, longan, mountain apples, camellias, azaleas, croton and dieffenbachia are frequently propagated by air layering and bear fruit (where applicable) in less time than seedlings.
How to Proceed
After selecting the branch you want, come down about a foot from the tip. Here you will remove a one inch wide ring of bark by making two parallel cuts (1 inch apart) around the circumference of the shoot. This will leave the branch with a “naked” or barkless band. Don’t cut through the branch, just cut deep enough so the outside bark peels off. This is known as girdling.
Then wrap the wound with moist, unmilled sphagnum moss. You may need to tie some twine around it to keep it in place. Cover the moss with plastic wrap to form an airtight pouch. Alternatively, you may want to place the moss first, then wrap both moss and plastic around the wound at the same time. Make sure the moss is moist – not wet. Some gardeners will place a final wrapping of aluminum foil to shade the area from the hot sun. Also, some add a little rooting hormone to the wound to speed up the rooting process - a light dusting will do. For many trees, this is not necessary.
Tie the bundle at each end, secure enough to prevent moisture loss. Later, when roots are visible, all around the bundle, cut the branch just below the developing roots, remove plastic and plant the newly rooted branch in a pot. Keep it in the shade until the plant develops more roots. Rooting time will vary depending on the type of plant and the season. Some plants will begin to show roots in 4-6 weeks, others may take up to 2 years.
In the process of air layering, the removal of the bark (girdling) prevents carbohydrates from flowing down past this point, but still allows water and mineral nutrients to flow upward to the leaves. This keeps the leaves of the shoot from drying out, but the presence of the carbohydrates and the water in the sphagnum moss, will cause dormant buds in the area to grow into roots.
For optimum rooting, make air layers in the spring on shoots produced during the previous season, or in mid-summer on mature shoots from the current season's growth. On woody plants, stems of pencil size or larger are best.
East Hawaii Residents: Master Gardeners' Annual Plant Sale is Saturday, April 25, at 8:00am-Noon at the Komohana Agricultural Center. Nick will be there to answer questions.