Frequently Asked Questions About – Air Layering For Bonsai

I get asked a lot of questions about air layers, and I will go though some of the most common ones below.

If you haven’t already, you should read – What Is Air Layering For Bonsai?

and also – How To Air Layer For Bonsai

These two articles pretty much cover everything you need to know, but there are still plenty of good questions below.

They are in no real order, but hopefully they help you out and if you are unsure about anything, or have a different question, just ask.

Can Any Tree Be Used For Air Layering?

If you want to air layer a tree, it will depend on the species. It will not work for every tree, but I would say that it does work for the vast majority.

You can either look up the species and see if it is possible, or just try it yourself on a random branch as an experiment. (then if it works, do it on the branch you want).

Most trees are going to form roots and really it’s only a few conifers, like pines that you are going to have trouble with.

You also can’t air layer succulents, and I guess any other plant that isn’t a tree that you might be using for bonsai. You need the plant to have an outer woody bark, so long as it has that, it is probably possible to air layer it. 

How Long Does It Take For An Air Layer to Develop Roots?

How long it takes for roots to grow really depends on a lot of different factors. The time of year and the climate will play a role and of course the tree its self is very important.

The species, size of the tree and its health will all determine how quickly it roots, along with how well you actually created the air layer. If you have not cut the sap flow properly, then the tree will never make new roots.

Can Air Layering Be Done in Any Season?

This question can also be asked as “When Is the Best Time to Air Layer a Bonsai?”

Ideally you want to start your air layers in late spring. You want the leaves to have opened up and hardened off and the tree to be actively growing. This is going to mean that the new roots pretty much start forming straight away as energy is going to be getting sent down the branch by the leaves …and of course it will be blocked by your cut. This is going to allow the build up of resources in this area, which will turn into roots.

I have actually started air layers before this point, both in early spring, when the buds are swelling (so the point you would be repotting) and even in late winter, just before the buds have started swelling.

I still had success with these air layers, but these where on species that are very aggressive root growers, so I had a bit of leeweay. I would still recommend you do it in late spring to make sure you get the best results. 

What Are The Risks Associated With Air Layering?

There are two main risks when it comes to air layering. The first is that you mess up the application of the air layer, and nothing happens. This will result in you just basically putting a large scar on the branch you are trying to remove. This isn’t too bad, you could always retry again and actually do it properly.

The other risk is that branch dies, this is more likely to happen on a tree that will not really air layer, but it could really happen for any number of reasons… which isn’t great since it was that section you where wanting to keep and use for future bonsai.

However, when it comes to the whole tree, there isn’t much risk. You may kill a section of the tree, but the tree in general should be fine. You are only really removing a branch, it’s just that you are doing this in a very slow and particular way, rather than just chopping it straight off.

Is It Possible to Air Layer More Than One Section of a Bonsai at a Time?

You can certainly add more than one air layer to a tree, but how you do this needs to be thought through.

You can only air layer one branch at a time, so if you tree has two branches you want to air layer, you can do both of these at the same time.

If there is one branch… that you want to do two air layers on, this isn’t going to work. You can still do this, but you need to stagger things.

You can start by removing the top of the branch, then come back and do a second air layer and remove the lower section. You could also start by removing the lower section, and take this away and pot it up …then do an air layer on this tree and remove the top from it.

Either way you cannot do two air layers on the same branch at the same time.

When you cut the bark and create your ring, you are stopping the flow of sap to that area below, which is why roots form. If you did this, then tried to do it again below, the sap flow in that region would not be very strong and roots would struggle to grow.

You could argue that if there was a lot of foliage in between the two air layers it would work …and I kind of agree, but most trees we do this on …do not have this luxury, so I would just avoid it. 

Should I Apply Rooting Hormone During Air Layering?

Rooting hormone can certainly help your air layers, and if you are using a tree that is slow to root, or is just generally difficult to air layer, then some hormone could give you a helping hand.

I have used it in the past, but really I didn’t use it much. Most trees I air layered are extremely aggressive root growers, so it just wasn’t needed.

You can air layer a tree just fine without it. If you have some use it, but don’t panic if you don’t.

What Type of Soil Should Be Used for Air Layering?

When it comes to “soil” for air layers … I wouldn’t use soil. Use sphagnum moss.

You can use either fresh or dried sphagnum, either works fine and while you can use soil, I would always recommend using sphagnum. This is going to hold the right amount of moisture and give the air layer the best environment to produce roots. The moss its self can help promote healing and rooting, which soil cannot. 

If for some reason you don’t have access to sphagnum …buy some, but if you can’t, then I would use bonsai soil.

I would use very bonsai fine soil …although you would also have to basically tie a plastic pot to the tree and fill it up. You wouldn’t be able to use the normal plastic wrap method if you use bonsai soil, so you are just making life harder for yourself by using soil.

You also have higher risk of the soil drying out and any new roots dying …so just use sphagnum moss.

How Often Should the Air Layer Be Watered?

You shouldn’t really worry about watering your air layer. Just look after your tree and the air layer will look after its self.

The sphagnum moss will hold moisture much longer than your soil, and it will also be wrapped in plastic, basically trapping the water, so it can take a long time for an air layer to dry out.

However, that doesn’t mean you should just totally ignore it. All you have to do is just spray your hose on it every time you water the tree. You should be checking your tree daily and watering if it needs it. You should also be doing this from above, which means using a hose or watering can to soak the soil surface.

Any time you do this, just give the branch a quick spray with the water too and that should be fine.

The outer plastic will of course block a lot of the water, but some will creep in through the holes you made and also at the edges where it meets the branch. This little extra amount should be more than enough to keep the moisture levels totally fine throughout it is time on the tree.

Can Air Layering Be Done on a Bonsai with Weak Roots?

I would only air layer a tree that is healthy. If your tree is not healthy, it is weak … doing any sort of work to it is probably going to make it weaker …which is probably going to kill it.

A tree with weak roots is going to have weak top growth, and really the success of your air layer really depends on having strong top growth. You want this growth to be going crazy and pushing down energy into the roots …which of course it can’t, since you made a layer, where the new roots will form.

If you have weak roots, the tree is not going to be supporting this vigorous top growth you need, so your air layer is either going to take a very long time, or just isn’t really going to work too well.

I would focus on getting the tree strong and healthy, then do your air layer.

Can Air Layering Be Done on a Dwarf Bonsai?

So long as the species you are using is a tree that can be air layered, then it should not matter if it is a dwarf variety.

The only issues you will have is firstly finding a decent section to air layer, and then actually applying it.

If the tree is very small, it may not really have any sections that are worth using for bonsai, although if you are just trying to make more plants and are not really worried about the shape/size of the branch you are removing, then this doesn’t matter.

You may also find it tricky to get apply the air layer if the branch is small, it can still be done, but it is certainly easier if the branch has a bit more size to it.

Can Air Layering Be Done on a Bonsai with a Curved Trunk?

An air layer can be done on a trunk of any size and thickness. It doesn’t matter what shape the trunk is …so long as you can cut a ring around it …that is all that matters.

How you cut the ring is actually more important than the trunk itself. You can cut the trunk at any angle, so your tree may be growing perfectly upright …if you make the cut around the tree at a 45 degree angle, well that is where you new roots are going to be. Once you remove that branch, and plant it up,  you are going to have to tilt the tree 45 degrees to get the root plan horizontal …you have now taken a straight tree and made it slant to one side.

Of course you can do the opposite of this and an unlimited amount of options in between.  

Just look at what you are starting with and think about where you want to make your cut, as this will be where the roots are, so you can really play around with things and end up with whatever angle you want.

How Can I Tell If An Air Layer Is Ready to Be Removed?

You will know an air layer is ready to be removed because you can see the roots.

Too many people cut their air layer off too early and then they die. You need to wait until you can see the roots. They will grow in the sphagnum and then when that gets full, they will start to poke out.

The fact that we use clear plastic is exactly for this reason, we can see the roots poking out and filling the moss ball and we can see that there is now enough to support the branch and we can remove it.

If you cut your branch off before you see all these roots …your air layer is likely not going to have enough to support itself.  

How Long Does It Take for an Air Layer to Form a New Tree?

An air layer will take as long as it takes. There is no real way to answer this. Every species is going to be slightly different and even every individual tree will be slightly different.

You need to just start your air layer with the mindset “it will take as long as it takes”.

I can sit here and try and give estimates or examples, but it doesn’t matter, your tree may respond differently and all you can do is wait until you see roots. So long as you have applied the air layer properly and made your cuts in the right way (and so long as the species can be air layered) you will see results eventually.

Even if you have to wait all season long and wait until the next season …so be it. It really will just take as long as it takes.

Are There Any Specific Precautions That I Should Take When Air Layering a Bonsai?

The two biggest precaution I would suggest you take are to make sure you cut the tree properly when you apply and air layer and to also make sure the moss is touching the wound properly. These are usually the two biggest failing points.

You need to make sure that you have properly cut the trunk and cut the connection, otherwise new roots are never going to form. The energy will just continue down the trunk and to the roots and your air layer will fail.

It is also important to make sure that the sphagnum moss is properly touching the wound. You really need to squeeze it on there. Too many people do not do this properly and there ends up being a little gap between the tree and the moss …and the new roots can die in here. You will have greater success if these new roots are in constant contact with the moss.

Of course I would recommend that you take precautions to do everything properly, but I would pay extra attention to these two things since it is where most people mess up.

Can Air Layering Be Done on a Bonsai with a Fungus Disease?

As I have already mentioned, you need your tree to be healthy to do an air layer. You need the leaves to be strong and vigorous so that they can send energy down into the tree to create new roots.

If your tree is suffering from some sort of disease, it is going to be weak. You need to deal with this first and get things back to full health, then do the air layer.

You will see stronger and faster results if your tree is healthy. There is a chance that it will still work when the tree is sick, but it will be harder for the tree and it will take longer. You are more likely to further stress the tree out, so it may not end well and it will certain be slower, so I would focus on getting the tree healthy again first.

How Should I Care for the Air Layer After It Has Developed Roots?

Once your air layer has developed roots and you can see them filling the moss ball, it is time to remove the branch and plant it up as its own tree.

The air layer should have enough roots to support its self, but it is going to be weak and delicate so you will need to be careful. It is best to not disturb the roots. Just cut the branch off, remove the plastic and plant the whole root ball.

Do not try and mess with the roots or touch the moss, just leave it alone and plant it up. Put it in a pot and cover the lot with bonsai soil.

After this, just pay attention to the tree. It may need some more care than other trees and may need sheltered from wind and really strong wind. You should be watering it like any other tree, where you just check daily to see what it needs and then give it water, or not depending on what you are seeing.

After a few weeks the tree should have fully acclimatised from being removed from the main tree and happy to support itself with its new roots and you can just treat it like any other tree you own.

Conclusion

Hopefully that clears some things up and of course if you need more information about how it all works, or how to actually perform an air layer, then read the two articles I mentioned right at the start.

They should cover everything else, including the basics and if you think I have left something out, just ask me and I will add it.