Air-layering technique

Spring temperatures will be arriving soon here in Florida, and when that happens then it’s time for air-layering. What does that mean? Air layering is probably the least stressful way to propagate trees. Most trees with woody trunks are good candidates for this technique, however, fast growing tropicals such as Ficus (benjamina, green island, retusa, etc.), and Bougainvillea are more easily propagated by cuttings. Some species of succulents used in tropical region such as Portulacaria afra or Jade plant (not considered a true bonsai but commonly used to resemble a bonsai tree) does not have a woody trunk so this species is also best to propagate by cuttings. Air layering is not just a propagating technique, it is also a technique used to correct an undesired portion of a tree. For example; a tree that developed a reverse taper. Reverse taper means that instead of the tree trunk tapering from a wide flare near the bottom and thinner near the top of the tree, the taper progression from wide to thin is interrupted by a thickening of the trunk at any point in the trunk usually on the nodes rather than on the inter-node. This thickening usually happens if the tree has had unbalance pruning. To correct this problem, the air layer technique is used. If you haven’t done air-layering before then take a moment to jot down the materials that you will need.
  1. Aluminum foil
  2. Sharp grafting knife
  3. Rooting hormone
  4. Sphagnum moss

Step 1. Add some moss into a container with a light dusting of rooting hormone and combine with water. (I normally don’t use rooting hormone because the active ingredient only forms about 0.01% of the total volume in the bottle, but in this case I want to give it the best chances of rooting and I figure it can’t hurt.) Step 2. Choose a segment of a branch that is woody. You don’t want a tender shoot because It is not mature enough to support this technique. With a very sharp grafting knife score the trunk twice about 1.5 inches apart, one line above another. Make sure that your score line goes around completely and not in segmented lines. These score lines must be cut deep through the cambium layer down to the heartwood. By doing these score lines you are cutting off the food and water source to the branch that you are going to air layer. Note: For slower growing trees, leaving a sliver of cambium connecting the 2 lines is recommended. Step 3. Remove the bark and cambium layer between the score lines. Clean the area. Remove all growth layers down to the heartwood. Step 4. Now you need to provide moisture and protection to this air layer. Wrap the previously prepared moss around the air-layer. Use foil to hold and seal the wet moss from the elements. The moss should be wet. Make sure that the foil is tight around the top and bottom so that the moss does not dry out. The moss is not a usual Ideal growing medium because it tends to stay moist for far too much time and tends to rot rather than promote growth. However, in this case that same quality of the moss, is needed so to provide moisture and prevent the new tender roots from drying out.

Now it will need a couple of months to develop roots. Once the roots develop you can go ahead and cut it off the branch from the tree and pot it. With this technique you usually won’t need to water the moss inside. The moss being wet already will hold a large amount of water and won’t dry out. However, if the foil is opened by birds or critters, re-wet the moss and cover it again. Step 5. After 2 months or so, new roots should have formed. Removing the foil needs to be gentle so that you don’t damage the tender roots. Using a very sharp arbor saw, cut off the air layer just below the new roots. Once the new tree cutting has been made all you need to do is to put it into a nursery container with fresh soil-less bonsai mix. In this case, I do not recommend using potting soil or any soil that contains organic material. Potting soil remains too wet for too long and rots the new roots. It is also tricky to know when to water potting soil. While the top layer may look dry, the bottom of the pot remains wet and like mud hindering growth. It is very important that you do not let the new cutting dry out until the roots have had a chance to be established. At this point, I treat new cuttings in soil-less mix as a usual bonsai tree as far as watering is concerned. In soil-less mix, no matter how much watering I do, the soil will release all unnecessary water; all that is remaining is the right amount of water. So here is my rule of thumb for watering; my climate here in Florida is mostly hot (up to 98o F during the summer months with an average humidity of above 60%). Bonsai trees here can suffer a lot just because of the heat alone, so I want to keep them cool under the scorching sun. I water once in the morning (only the root ball), then during the hottest part of the day, which can be between 2 p.m. and 5 p.m., I water again the root ball and mist the leaves. If the day is windy, no matter the day temp., I water one more time. I have the luxury of having and automatic, micro spraying watering system, but if you don’t have a sophisticated system, make sure that you water thoroughly in the morning and making sure that the tree or in this case the new cutting is shaded from the hottest part of the day. You can do this by observing how the shadows from the sun against the building or your home move. Look at where the shadows fall around the 2 to 5 p.m. hours, then places your new cutting there.  You may also want to water in the afternoon.  

Step 6. Once your new cutting becomes established (This may take some time. It can take up to several years depending on the tree species so it is important to be patient. Some tropical tree species in tropical regions however, can become established in less than a year. {A tree or new cutting is considered established when it has enough roots and has strength of growth to withstand a re-potting}), then you may start it on the journey to becoming a bonsai tree. I must recommend that before you attempt this technique on a tree you really like, please practice on a tree you don’t like. I personally started to practice on a full sized tree branch. Once I was comfortable and confident with my technique, I attempted it on a tree I loved. You will have set backs with this technique, but don’t get discouraged. Practice, practice, practice.

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