What Is Fusion In Bonsai?

Fusion bonsai is not very well understood, so I will try and explain what it is and how it works so that you can have a clearer understanding of what these trees are and maybe you will want to try it out yourself.

Fusion is basically when you get a couple of small trees and make them grow together, so that they turn in to one bigger tree.

It sounds pretty strange, maybe impossible, but it does work. It can be difficult to do well, which is probably why they are not really that common as bonsai.

What Is Tree Fusion?

Fusion is actually a naturally phenomenon called Inosculation and is a form of grafting. (Grafting is a technique that that gets a branch from one tree to grow on to another tree)

If you go out into nature you will notice that some branches grow into each and sort merge together and become connected …this is fusion.  

In bonsai we can use this phenomenon to our advantage. We can take a number of small trees and grow them next to each other and force them to graft together and become connected and sort of merge into one larger tree.

In nature it is just random where and when it happens, usually at the point where two branches grow next to each other, where as in bonsai we are actively trying to make it happen where we want, which is usually along the entire length of the trunk.

When we try and force the trunks to merge into one …we are creating a bigger tree. If you do this with multiple trunks, you can quickly turn a lot of small trees into one bigger tree.

So really fusion in bonsai is a technique we use to quickly create a tree with a thick trunk …we just do it by taking a lot of small trees and trying to merge them all into one thicker trunk.

How Does Fusion Work?

Fusion works in a very similar way to grafting, basically the two trees touch each other and as they grow they will start to rub up against one another, causing damage to the bark.

This damage causes the cambium layer underneath to be exposed and the trees will try and heal this area to stop it being exposed. This is where it is similar to grafting, as you now have two trees with exposed cambium layers that are touching.

Trees will always try and protect their cambium, so it will try and heal this area; however, as the trees are touching and also genetically very similar they sort of heal together and merge in one at this spot.

This now means the two trees are now fused and the cambium layer sort of becomes one and the bark on the outside starts to merge together too.

I will give you a weird example here, it’s kind of gross and wouldn’t actually happen, but it will hopefully help you understand the idea pretty clearly. 

I’m sure you’ve heard of that old tradition of becoming blood brothers. You cut your hand and I cut mine and we shake hands and mix the blood. (Please don’t do this). Now imagine we did this, but we just kept holding hands for a few days. Eventually our two cuts would start to clot over and heal… but because we didn’t move our hands, they would sort of clot together and we would sort of be stuck together.  Now imagine a few days later and our cuts have fully healed over, but our skin sort of merges together in our hand so now and blood can go back and forth between us like we are Siamese twins… that’s fusion …it’s just less weird when a tree does it.  

How Do You Fuse Trees?

Fusing trees is actually very easy, you just need to get them to grow next to each other and eventually they will touch and start rubbing against each other.

However, this isn’t every efficient and there is a chance that the tree will grow away from the other tree, rather than into it, so we can use some techniques to help direct it.

The most common way to fuse trees is to tie them together. This can be with wire, cable ties or even string.

Once the trees are tied together, they are sort of restricted …which means they can only grow in one direction, which is directly into each other.

Of course they will push out against the wire or cable tie, but really they can only go so far and this restriction causes them to push into each other and basically causes more pressure in that area, which will create friction… and therefore damage to the bark, exposing the cambium … so there is much higher chance of a fusion happening.

The fact that the tree will push up against the wire does mean it will start to grow around it, causing it to cut in, so you do actually run the risk of creating ugly scars in the process of getting the trees to fuse.

You have to balance everything, you want everything to be tight so it’s grows together, but you also don’t want it to be so tight that it causes wire marks too.

It is also common for people bundle a couple of trees together with something on the inside, such a piece of wood or a stone. It doesn’t really matter what it is, so long as it is solid. This just again limits where the expanding tree can do. It can’t go outwards due to the wire and it can’t go inwards due to the stone, so really it can only grow sideways, which means they are forced to grow into one another.

Should You Damage The Bark Before Trying To Fuse?

I’ve just had a thought while writing this, that maybe damaging the bark may be sensible. Normally you just plant the trees next to each other so they are touching and use some something to tie them together and eventually they will grow into each other and fuse.

However, causing some damage to the outer bark, where the two trees are touching could speed things up. You would be exposing the cambium and getting the two trees cambiums to touch straight away, which should speed things up.

I’ve not seen this done with a fusion, but it should work. If you were doing a graph, this is exactly what you would do. You would remove the bark and expose the cambium for the two parts of the tree you want to join. You would then press them together and tightly seal it with graphing tape.

I think I need to try this on my current fusion project as I think this may actually speed things up and will mean the trees should have started to mesh together before they start pushing out against the wire that is holding them together. 

Can You Fuse Any Tree?

I don’t want to say yes …but I think for the vast majority of trees, this will work in one way or another. I am sure there will be an exception, but I think you can fuse most trees.

You can pretty much graph any tree, so in theory you should be able to fuse any tree.

Of course you can only fuse trees of the same species together you can’t make some weird hybrid species, that would be impossible.

You will find in nature that the trees that fuse a lot are the ones with thinner bark. The bark is easily damaged by them rubbing together, making it easier to expose the cambiums, so you will probably find thinner bark tress are more suited for it.

However, as I just mentioned above, maybe removing, or at least damaging the bark would help, especially with the thicker barked trees. I think this is something that really needs more experimentation.  

Are There Any Downsides To Creating Fusions?

While I may have made fusion trees sound amazing, they are usually quite troublesome and a lot of people find them to be more effort than they are worth.

The biggest issue is that you will struggle to avoid scars. In order to restrict the tree you need to apply pressure in some way, and most people use cable ties or wire which are going to produce scars when the tree starts to push up against it.

You will also have scars where the tree fuses, these scars are not a bad and usually grow out, but you can normally see the seam where they have joined which can be unsightly and is a dead giveaway that the tree is a fusion and is why a lot of people do not like them.

You also have the problem of failure. Both from the fusion not happening for some reason, or one of the trees you are trying to fuse dies.

We usually use small young trees, so they can easily die and I guess being squished up against another tree can cause it to be dominated by its neighbours and it struggles to survive. It’s pretty hard to fuse trees if they are dead and if you are trying to fuse a large number it is common for a few to die.

You can of course replace these the following season, but it’s still not ideal and more importantly shows that fusion is not a quick process. Many people try it as it seems like a shortcut …just place these 10 small trees next to each other and you will soon have one big tree …it can happen, but I don’t think it really saves you any time.

You would probably get the same result in the same length of time by trying other techniques such as growing a tree in the ground and allowing it to thicken. I actually think doing this would both be easier and quicker than messing round with a bunch of small trees and trying to get them to fuse.

Are Fusion Bonsai Trees Respected?

When it comes to bonsai …I don’t think fusions are respected.

However, I asked my youtube subscribers their opinion on this and I was surprised by the result:

The majority of people actually seem to like them. This is a small sample size, but it is still good to see the most people are in favour of these types of trees.

You are of course always going to have the purists that see Japanese bonsai as the only way, so it’s only natural they don’t respect it.

I do think there is a problem that there are no really high quality examples of fusion trees, which is why I added that question. There are some okay examples, but you can very clearly see where the trees have fused, or the tree itself is not overly impressive …but that didn’t seem to put people off. I guess they can see the future potential in the trees.

A lot of the fusion trees are like my own example, where I fused 3 small ficus trees together. While it worked well, the final tree is still pretty small and something you could have easily achieved in the same time with a large pot.

Most fusions seem to be weird experiments people try and they don’t quite work out as planned …but people still like them.

I think they are great, but I do think they are more on the experimental side, so I understand why some people don’t like them

(You can read more about my Ficus, which is 3 trees fused into 1 – Ficus Benjamina Progression (2018 – Now))

Conclusion

As you can see the science behind fusions is simple, grow some trees next to each other and they will merge into one tree.

However, it usually doesn’t go to plan, some trees can die or the fusion does not take very well and generally leaves an ugly tree that just looks like some smaller trees that have been welded together.

I think they are a fun experiment and if you have the time and space, along with plenty of young trees, then you should give it a go. It is quite interesting to see how they merge …but if you actually just want a thicker trunk, you would be better off planting a tree in the ground and letting it thicken naturally.   

(You can read more about – How To Get A Thicker Trunk On A Bonsai?)