Bonsai trees need good, loose, airy soil that drains well and will allow oxygen to flow over their roots.
So, it’s crucial to provide more than just ordinary potting compost.
Planting a bonsai into straight compost may compact around its roots and eventually kill the tree.
Bonsai soil is usually a mix of pumice, akadama, compost, grit, and lava rock.
This combination provides nutrients, drainage, water retention, air circulation, and everything else the bonsai needs to survive and grow.
This article will examine what bonsai soil is, why bonsais need this soil, and how to make your own bonsai soil.
What Is in Bonsai Soil?
Bonsai soil is a mixture of several different ingredients.
It usually includes at least some drainage material, such as grit.
Bonsai soil also generally has an organic material rich in nutrients, like potting compost.
Each of the materials in bonsai soil serves an essential purpose, so let’s look at them individually.
Pumice is a soft rock good at absorbing nutrients and water.
This material will trap water and keep it available to your tree for longer than other kinds of rocks.
Akadama is a kind of Japanese clay perfect for bonsai soil.
Manufacturers specifically produce akadama for bonsai trees, so you can usually find it in bonsai stores.
Overall, akadama maximizes the aeration in the pot and ensures your bonsai tree gets enough oxygen.
Unfortunately, though, akadama doesn’t last forever, so you’ll need to replace it every couple of years.
Otherwise, it will break down, and your tree will start to suffer from oxygen deprivation.
Also, remember that akadama is quite expensive.
But, you can sometimes replace it with other alternatives that will help with aeration, such as another clay.
Compost ensures that the bonsai gets enough nutrients and retains water.
However, compost must only make up a small proportion of the overall mix.
If you plant your bonsai in pure compost, it will likely get root rot and die quickly because the compost will hold on to too much water.
Grit will help to ensure that the bonsai’s container drains well and the tree does not get waterlogged.
You can use a layer of grit in the bottom of the bonsai tree’s pot to encourage water to flow out and ensure the tree is not standing in water.
Lava rock will help soak up moisture and release it back to the tree gradually.
And like the akadama clay, lava rock adds structure to stop the soil from getting compacted and smothering the bonsai tree’s roots.
Why Do Bonsai Trees Need Special Soil?
Bonsai trees need unique soil because they are in such cramped conditions.
They are also so small that compost will weigh heavily on their tiny roots and stop them from growing or getting enough air.
Yet, if you try to raise a bonsai tree in ordinary soil, it will probably grow, but it will struggle more than if you planted it in the correct growing medium.
Your plant will also be more vulnerable to under-watering and over-watering.
Thus, bonsais planted in regular potting soil are more likely to get root rot because the soil will stay wet for longer.
But, if you are going to use standard soil for a bonsai tree, you should at least make sure you mix in some fine gravel or sand to improve the drainage.
Mixing in these materials will not solve all of the issues associated with pure compost, but it should be better than nothing and may help keep your tree healthier.
Do All Bonsai Trees Need Special Soil?
All bonsai trees will struggle if you put them in pure compost, but some will find it harder to survive than others.
Also, not all will like the mix described above, so you may wish to alter it depending on the kind of tree you are trying to grow.
Most deciduous trees should cope well with the mix mentioned above.
They also like to have a high percentage of akadama in their containers.
However, conifer bonsai trees will thrive better if you give them equal amounts of pumice, lava rock, and akadama.
Additionally, you should consider your own watering routine when choosing your soil mix.
If you water your tree infrequently, it will need more potting compost or akadama to hold onto the water and keep the tree damp.
Conversely, if you water the tree regularly or live in a more humid environment (or the tree is outside and will get a lot of rain), increase the drainage materials to ensure the soil doesn’t stay sodden and drown the roots.
Can I Make Bonsai Soil?
Yes, you can mix your own bonsai soil at home, and doing so will give you greater control over what nutrients your tree gets.
How to Make Bonsai Soil for Deciduous Trees
First off, you will need to sift some akadama to get it ready for the mixture.
Typically, for deciduous trees, your mix should be 50 percent akadama.
Then, create a mixture of half pumice and lava rock.
The pumice and lava rock concoction should be equal to the akadama mixture so that your final result is half akadama, ¼ pumice, and ¼ lava rock.
Making Bonsai Soil for Coniferous Trees
You will again need to begin by sifting your akadama clay.
Next, just simply mix equal parts akadama, pumice, and lava rock.
Fixing Your Bonsai Soil Mixture
After you have mixed the soil and potted your tree, you need to keep an eye on how well your mix is draining and whether it is getting too dry or staying too wet.
If you feel you haven’t got the proportions quite right, tip the tree out of its container so that you can adjust the growing medium.
Generally, if your soil is too wet, you can add some grit to help it drain.
Conversely, if your soil drys out very quickly, mix in a bit of compost since it retains water.
Bonsai trees do need special soil if they are going to grow well.
Thus, make sure you either buy a ready-mixed growing medium or make one yourself.
Additionally, remember that it is fairly easy to make or adjust bonsai soil by altering the proportions of the ingredients.
So, take the time to get the soil combination right, and your tree will be happier.
Table of Contents