Updated: Jan 7
Its becoming more and more of a debated topic in the world of Bonsai if Akadama is actually a good choice of substrate for you or not. Recently i have seen some argue that a $5 bag of regular potting mix will get you the same results as Akadama... Is this True? Let Find Out.
I think the biggest road block for most people when it comes to Akadama is simply the lack of education around the substrate, Mix this with the higher price per bag and people tend to go with the cheap stuff and convince themselves that it is all the same. Unfortunately this couldn't be further from the truth. In my time i have tried a few different mix's before Akadama was readily available here in Australia and with all these mix's they were all trying to achieve 1 thing and that was to replicate Akadama.
So whats all the confusion about then?
First we need to understand why we use akadama. To put it plain and simple we use Akadama in the refinement stage of Bonsai as the root growth we get by using akadama is very fine and bifurcates in the process. We know in Bonsai that what ever is happening in the root system is happening on top of the tree so subsequently by growing in Akadama paired with proper technique we are getting fine ramified branches on our trees. Akadama is one of the only inorganic materials that also has a cation exchange Capacity ( CEC ) which is the ability to hold onto important nutrients. Most other inorganics dont do this meaning that your nutrients are washed out of the pot as quick as they go in. Akadama also has a good moisture retention while also having a great ability to drain excess water out of the pot meaning the tree will have the moisture it needs to survive and wont have excess water build up causing root rot. Another bonus of Akadama ( and most inorganic materials ) is that they are manufactured and are broken up into particle sizes meaning we can layer our soil mix inside the bonsai pot. This allows us to have a larger drainage layer, A medium size particle for our body mix and a finer layer on top for moisture retention. Organic material don't allow for this.
So what dont we use Akadama for? This is easy, We don't develop trees in Akadama. We reserve Akadama for the Bonsai Pot and for refinement. When developing a tree we want to use organic materials because not only are they a lot more dense which makes the tree growing bigger thicker roots ( remember bigger thicker roots = bigger thicker tree ) but organic materials also hold a lot more nutrients and moisture which will make the tree grow a lot faster.
Now there is an important aspect to Akadama that we must acknowledge and keep in mind when using the substrate and that is the fact that it breaks down. Akadama will break down over a period of around 18 months, This can be dependant on how hard the Akdama is that you have bought, You can buy both soft and hard Akadama. Softer Akadama will break down quicker and if you live somewhere that gets frost this will speed up that process. The breaking down of Akadama is not a bad thing though, We just need to understand how to handle it and how to plan for it. You have probably heard that most inorganic mixs have either 1 or 2 other substrates mixed in as well which are most commonly lava rock and pumice, but this can also be zeolite, scoria or many other substrates. Generally the purpose of these other substrates is to stop the mix from completely breaking down. If we let a plant sit in 100% Akadama for 18 months we will need to repot that plant soon after because as the particles break down getting smaller and smaller in size they start to hold more water and occupies the space that once had oxygen in them, we know that we need to keep a balance of water and oxygen in our bonsai pot and after 18 months of straight Akadama there is not much oxygen to speak of. By mixing in substrates that dont break down this helps us always keep a level of oxygen in the soil system, This is important for trees like junipers and pines which should remain in a Bonsai pot for at least 5 years before repotting, Other trees like maples and out Australian Natives this is not as important. In fact i personally use 100% Akadama for all my natives and maples because i can repot them every 2 years with no issues and because Akadama holds moisture really well those particular species love it!.
There is another important aspect to akadama that you just wont get with regular old potting mix and that is bifurcation of the root system. What's bifurcation? its a fancy word for ramification or simply turning 1 root into 2 which then turns into 4 then 8 then 16 and so on.
Akadama has tiny little pockets in which the roots can grow into seeking out moisture and nutrients, during this time the root can grow through the particle and bifurcate in the process, Given that Akadama breaks down this wont be an issue as the particle will eventually fall apart but leave with with a ramified root system. Mix this with the coarse nature of inorganic substrate and you now have a root system that is not only growing finer, but its bifurcating and you have a lot more control of what and how much nutrients the tree is receiving giving you complete control of the refinement process. Compare this to a regular bag of garden soil in a bonsai pot which is going to give you very little oxygen, the roots will grow thick and wont bifurcate and the soil will hold a tonne of nutrients which for your tree is going to mean big thick growth, the exact opposite of what we want with a tree in refinement.
I hope this has helped clear the air somewhat for you when it comes to Akadama. As you can see that if you use regular potting mix in a bonsai pot you wont get very good results, Sure your tree will survive and stay healthy but you wont get the results that you should be getting in the refinement stage of Bonsai.
You can purchase Akadama here
Until Next Time Enjoy Your Bonsai Journey.