Air layering is one of the ways of producing identical trees from a mother plant. Also known as marcotting, this type of plant reproduction has several advantages over other methods. Of course, seeds are the easiest reproduction method; however, usually the resulting plant is not truly identical to the originating tree. Grafting produces an identical tree but takes much longer as you need to have rootstock plants ready to take the graft and usually a grafted (or budded) tree will be a year or two behind its air-layered counterpart in size. Tissue culture is not a viable option for the average grower who is not set up to do it. Resulting plants from tissue culture will definitely be several years behind air layered ones. There are several disadvantages that should be noted. Air layered plants do not have the taproot of a plant grown from seed. Rather, the root system tends to be shallower in nature, i.e., susceptible to hurricane or other high wind damage. Additionally, you’ll need to have a fairly mature plant to be able to air layer it.
Wet the sphagnum moss only to the point that when you squeeze a wad of it in the hand a drop or two of water comes out—no more water is needed. Mix in about 10%–15% of sponge rock by volume. Hand fill the poly bags to about 3/4 full with this mix. Tie the top of each bag with the sisal twine, leaving a tail of twine about 6 inches or so in length.
Choose nice, straight branches on your tree to air layer. Branches selected should be from 3/8 to 3/4 inch diameter—about 1/2 inch is ideal. Clip off side branches in the area where the bag will be placed so you have at least 12 inches to work with. With the sharp knife, carefully make an upper cut completely around the branch (figure 1).
Then 3 to 4 inches below that cut, make another cut (figure 2).
With the pliers, grip the branch just below the upper cut and twist off the bark (figure 3).
Do the same just above the lower cut (figure 4).
Continue to twist the pliers to remove all bark until clean. Then scrape the cleaned wood to make certain that no bark remains (figure 5).
If any bark is left, the tree might be able to repair itself and then will not produce roots where they are wanted. Nick the upper bark area once or twice (figure 6) about 1/4 inch.
With the dauber, wet the upper branch near the nicked area with the Dip ’N Gro® hormone (figure 7). We use undiluted Dip ’N Gro, but dilution will be the subject of a study next year.
Cut the poly bag in half lengthwise as shown (figures 8 and 9) and place it around the upper portion of the selected branch (figure 10).
While centering the bag onto the branch, be sure to lift both sides of the cut poly bag so the ends overlap. The bottom of the cleaned stem should not be within the bag. This helps prevent the branch from reattaching to the main plant.
Now begin to tie the twine around the poly bag and then finish by tying both ends of the twine together (figure 11).
Finally, wrap the entire poly bag with aluminum foil so that the bag inside is entirely darkened (figure 12). At this point you have a finished air layer. The bagging is now complete unless you have birds that love to see themselves in the foil. If you do, you’ll need to wrap everything in some type of bird-proof cloth material (see figures 13 and 14). Then You Have to Wait for Roots!
Now comes the hard part—keeping your hands off the air layer for at least two or three months so that the roots can adequately form in darkness. In some cases with temperamental plants (macadamia, for instance), you’ll need to wait up to nine months for roots to appear. When you just can’t wait any longer, carefully remove the cloth and the foil. Roots should fill the inside of the bag completely and be easily seen. If not, redo the foil and the cloth to give the plant additional time. You will easily see when enough roots have formed. When that has happened, clip the branch just under the bag and let the branch, with the plastic still intact, soak in a bucket of water for an hour or so. Prepare a 3–5 gallon pot with a good planter mix. With scissors, carefully clip the twine and then clip the plastic bag away from the root ball. Then plant, stake, and water in well. The plant will then take about 6 weeks in warm weather to grow out its roots entirely within the pot.
Unfortunately, not all plants will successfully air layer.
We’ve found that the following can be reproduced in this manner: Lychee and Longan, Guava, true Sapotes such as Green Sapote, White Sapote, but not Black Sapote, Syzygiums such as Wax Jambu, Malay Apple or Mountain Apple, and Rose Apple, Eugenias such as Surinam Cherry and Cherry of the Rio Grande, Macadamia (but slowly), Peanut Butter Tree, Allspice.
My air-layering failures so far are: Cherimoya, Avocado, Citrus, Jaboticaba (but it has been done!)
Current air-layering trials in progress: Lucuma, Kwai Muk, Mango, Chico Sapote.
Finally, don’t be discouraged by thinking that this procedure takes a long time; it doesn’t. With some practice, we can do one plant in roughly 3½ to 4 minutes, not including the time required to prepare and fill the poly bags. California is generally too cool in the winter to begin air layering. You should wait until the weather begins to warm before trying it. That means that by Spring you can begin. Good luck!
Roger and Shirley Meyer are longtime California Rare Fruit Grower members
They own and operate a rare fruit nursery in Fountain Valley, Calif. and welcome you anytime.