Table of contents
Bonsai Soil Mix Introduction
What is the best soil mix for bonsai? That is different answers for different people, different trees, and growing conditions.
Short Answer:
The three ingredients pictured above.
- Akadama
- Lava Rock (volcanic rock)
- Pumice
Typically these three ingredients in a equal ratio of 1/3 each is the most recommended bonsai soil mix to use. Mix thoroughly, do not layer.
BUT this is the short answer and is not the best in every situation. There are different ratios required and more substrates we can add and also substitute for if products are not available near you. Stay with me and I will explain the mix you may need for your situation.
Why is soil mix so important
Basically we are taking a tree that in nature could grow from 20-60 feet tall, and a root system could be half as deep as the tree is tall. And we are training these trees from a young age to grow into undersized shallow pots.
To have a happy, healthy tree and to make up for limited room in a bonsai pot. We need to do everything we can to ensure the tree gets everything it needs for survival.
Let’s Look at the Soil Mix
- Akadama
- The reason Akadama is used because it has good drainage but can absorb a lot of water for release throughout the day. It can also hold good amounts of nutrients from fertiliser for healthy tree and root system. Akadama has enough open pores for the finer roots to penetrate into it.
- One of the negative aspects of Akadama is it breaks down in composition fairly rapidly, especially in colder environments where it is exposed to freezing and thawing out.
- But this is also one of the best attributes of Akadama because the roots that penetrate can also break down the composition. And when this happens the roots will also split into 2 or 3 or more finer roots. These finer roots are the difference and the key, between a healthy thriving tree and one that is just surviving.
- It will need replacing every 2-3 years and fresh Akadama used.
- Lava Rock
- Is used purely for its draining qualities. But because the surface is so rough and can have holes it can also pool small amounts of water. Lava Rock can also hold nutrients from fertiliser, and the uneven surface will create air pockets.
- Good bacteria will grow in these air pockets and aid in turning fertiliser into food the tree roots can absorb and send to the trunk and foliage.
- Pumice
- Is mainly used for its draining abilities but pumice is porous and can absorb small amounts of water and nutrients for use during the day.
- Pumice is pH neutral and sterile, it also aids in the oxygen levels in the soil mix which will promote healthy roots.
Last Considerations
As mentioned in the introduction I named three variables. They were people (you), type of tree and growing conditions.
These three variables combined will dictate what bonsai soil mix is best suited for you.
We just went over the type of tree and growing conditions in the table above. Now let’s dive into the last consideration YOU.
You
The free time you have available will make a difference to your bonsai soil mix. Especially if you live in a hot climate.
If you are working full time and have a busy life or live in a hot climate. I would recommend that you use a soil mix that is more rich in Akadama and Pine bark mulch.
Keeping in mind that you will still need to keep a good balance of the lava rock and pumice for drainage.
If you are very busy and you also live in a hot climate, you may want to look into a automated watering system for those very hot days.
What’s needed for healthy roots
Water
Water is needed to hydrate the tree. But good drainage is required also for a healthy bonsai. If roots are left sitting in a pool of water for too long this will cause damage and a unhealthy root system.
So we need to find a balance of good drainage and enough water retention to hydrate the tree throughout the day.
Fertiliser
Fertiliser is required to feed the tree with nutrients for strong healthy growth for the trunks, branches, foliage and roots. A strong healthy tree will also provide essential nutrients back to the roots.
Because of the small amount of nutrients available in a good draining soil mix. Fertiliser will be required frequently either through a liquid fertiliser or a slow release fertiliser.
The advantage of using a liquid fertiliser is you have greater control of exactly how much fertiliser your tree receives.
Oxygen
Oxygen is vital for a healthy root system. The roots require oxygen and it is also essential for good bacteria growth. Good bacteria is essential to turning fertiliser into a food the roots can absorb. It also aids in keeping a healthy pH level in the soil.
Substitute Soil Mix
Not everyone has access to all of these ingredients. Unless you are lucky enough to have a Bonsai nursery close by, your probably going to have to compromise.
For a good bonsai soil mix we have learned we need good drainage for oxygen levels. We need a mix that can retain and deliver water and fertiliser.
It does not matter what part of the world you are from we can find substitutes that can still do the required job.
Let’s dive in
When looking for substitute materials don’t limit yourself to where you search. Some good places to find substitutes are Nurseries, Hardware stores, Landscape suppliers and even hydroponic supply stores are a great place to find what you want.
Akadama Substitutes
When substituting Akadama it is important to find out about the qualities of the substitute. Compare the two and adjust ratio in the mix to compensate.
- Pine bark Mulch: Is a good organic alternative.
- Hydro Clay: Has good water and nutrient retention.
- Coconut Coir: Holds lots of water and fertiliser.
Pumice Substitutes
- Perlite: Very common and does good at doing similar job to pumice.
- Vermiculite: My favourite it holds more water than perlite and pumice which is perfect for hotter climates.
Lava Rock Substitutes
- Fine Gravel: Any type, the best size is 4-6mm.
- Fine Granite: Same size as above is best.
Really Lava rock’s main job is drainage and aeration so any small stone or rock with rough edges is ok to use.
Summary
With all the information given above, you are now qualified to start making your own decisions on what is best for you.
Try things, experiment that is the best way to learn. There are so many variables that there is no 100% correct answer.
Go with what is available in your local area and in your budget. It’s fairly simple we just need good drainage but holds enough water and nutrients. It really is that easy.