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Bonsai Soil Information and How-to: What is Bonsai Soil Made Up Of

A couple of bonsai trees planted on rectangular pots.

Knowing and choosing the right kind of soil is critical to the development of your plant, especially if you are trying to grow a bonsai tree. Bonsai plants are a miniature of a tree. They are confined in a limited space or container. They are different from other plants that you have in your backyard.

Bonsai trees require a different form of care and nurturing. If you want them to grow and remain healthy, find a soil that can provide enough water and nutrients to your bonsai.

If you are just a beginner when it comes to gardening or growing bonsai trees, you should know that there are different kinds of soil. However, not all of them are suitable for your bonsai tree.

Of all the different types and kinds of soil, which one is best for your tree? How is it different from the normal soil you usually use in your other plant? Understanding these will make it easier for you to gauge your plant’s needs. This blog will tell you everything you need to know about the soil, its composition, and how it is prepared.

What is the Soil of Your Bonsai Made of: An Introduction and Information About Bonsai Soil

A close look at a bonsai tree with bonsai soil being watered.

 There are two main types or categories of soil in growing plants: organic and inorganic soil. In the past years, it has been a constant argument of which among these two is better than the other. However, you cannot easily say that one is better than the other in providing nutrients to your plants because each has its pros and cons.

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Also, plants have different nutrient requirements, so the “best” bonsai soil may depend on your type of plant. Before choosing the soil mix to use, you have to remember that an excellent soil mix should have these three qualities.

Good Drainage

Moisture and humid are important to your bonsai tree. However, it is not good that the excess water stays in the bonsai soil for too long. A good soil mix should drain the excess water immediately.

Too much water retention can cause salt build-up, which limits and reduces the movement of air and water in your soil. It can also lead to rotting of the plant roots that can eventually kill your bonsai tree.

Good Water-retention

The bonsai soil should be able to hold a sufficient amount of water to can provide enough moisture to your bonsai tree between watering intervals.

Good Aeration

The root system of your bonsai needs oxygen for greater survival. The soil should have enough space for air pockets. It should neither be too compact nor too loose. Aside from that, good bacteria should also have some space to thrive in for better nutrient and water absorption of your tree.

Organic Soil Mixes and Components

You must know the components of the soil and its properties. Eventually, you’ll learn and be aware of which of these components is best and suitable for your bonsai.

Bonsai soil spilling out of a terracotta pot.

Peat Moss or Humus

The peat moss will serve as the binder of all the components that you mixed in your organic bonsai soil. Peat moss is important so that all components will remain fixed in their place. It will prevent them from shifting once the root system starts growing. The humus can also hold water, which can keep the soil moist.

Aside from its water holding capacity, nutrients can also retain or stick in the humus. It includes ammonium, which is a good source of nitrogen, phosphorus, and calcium. Humus or peat moss also prevents water from washing those nutrients away.

However, there are also some disadvantages to using this component. It can hold or retain an excessive amount of water. Without proper drainage, it may hold a large amount of water for a long time.

Water retention is essential to your soil, but too much water retentiveness is not beneficial to your bonsai tree. Therefore, you should use it moderately as much as possible.

Conifer Bark

Aside from the fact that conifer bark is inexpensive and accessible from your local garden center, surprisingly, it’s multifunctional as well. It can retain water just enough to keep the moisture in the soil. However, it can also help in preventing wet feet by draining and blocking excess water.

Decomposing Plant Matter

This serves as a fertilizer, food, or an additional nutrient to your bonsai tree. Since it is organic, it is also an environment-friendly substance. Start adding in a small amount and just gradually increase it depending on your bonsai tree’s needs.

Potting Soil

Potting soil is added as a bulking and binding agent that will make your bonsai soil compact. It is also water-retentive, so just be aware of the amount of potting soil you are adding.

Adding this could be optional, but if you want to include this, apply only a small amount. It could be 1/5 to the rest of the other ingredient, but you can add less than that as well.

Inorganic Soil Mixes and Component

Unlike inorganic material, organic components change their properties over time. Organic soil mixes become compacted due to breakdown, which results in poor aeration and drainage. This is the main reason most cultivators choose to invest in a non-organic soil mix.

A look at Akadama Japanese soil for Bonsai Trees and cactus and cucculents plants.


This clay is produced from Japan specifically for bonsai growing. It is even considered as an essential component in the soil mix. Akadama comes in different grades and sizes. This component is great for water retention. It also absorbs and holds nutrients, then gradually releases it for your bonsai tree to absorb as well.

However, it can be expensive. For this reason, other cultivators use similarly baked or fired clay as a substitute. The only disadvantage of akadama is that it breaks down after two years. This breakdown will result in reduced aeration in the soil. Hence, repotting is necessary.


This may look similar to Akadama, but this one has different properties. It is primarily used in the underline of golf courses and baseball playgrounds. It is excellent in providing aeration to the soil as well.

The grasses that thrive in the baseball field are often healthy and strong. It’s because air can easily flow and penetrate the soil. It will do the same wonders to your bonsai tree.

Lava Rock

Unlike akadama, this component takes a longer time to break down because it is coarse. Most cultivators and growers are using this as a cover in the top surface of the soil in their garden.

However, for your bonsai soil, it is used as an aggregate. It has tiny holes that absorb water and then gradually release it to the plant.


This kind of volcanic material is capable of absorbing water and nutrients. It helps retain water in the soil, and it can ramify the roots as well.

Diatomaceous Earth

This is a substitute that you can use if ever you cannot find the other recommended components mentioned above for your bonsai mix. The diatomaceous earth or the Oil Sorb is excellent in absorbing oils.

That’s why mechanics often use it for oil spills on the floor or ground. This same absorbing property will work wonders on your bonsai tree. The only difference is that it is for water retention in bonsai. It will hold and soak up water for moisturizing. Since it has a coarse shape, roots can grow around it.

How to Make and Mix Bonsai Soil

A bonsai soil mix containing sterilized soil, peat, pumice, grit, akadama, and other ingredients.

1. Aside from the components that you need, the most important tool or equipment you should have in mixing is the soil sifter. Since materials may come with impurities like dust and grass, you need to remove them. You will also need it for the granules of the components to be finer since they will be placed in smaller pots.

2. After preparing the materials, you have to decide about the ratio of each of the components. The different species of bonsai tree requires different soil mixtures as well. There are four different bonsai mix recipes with a balanced ratio of organic to inorganic mix.

  • Basic Bonsai Mix- 50% should be Akadama or Turface, 25% should be rock lava or diatomaceous earth, and the remaining 25% should be organic compost
  • Tropical Bonsai Mix- 40% is Akadama or Turface, 25% is rock lava or diatomaceous earth, and 35% is organic compost
  • Deciduous Bonsai Mix- 50% should be Akadama or Turface, 30% should be rock lava or diatomaceous earth, and the remaining 2% should be organic compost
  • Coniferous Bonsai Mix- 60% is Akadama or Turface, 30% is rock lava or diatomaceous earth, and 10% is organic compost

Please note that you can adjust this according to your climate or other environmental conditions.

3. After finalizing the ratios, the next thing to do is to sift your components. Remove the dust to make sure that the bonsai soil is airy and can drain well. If you will use pumice, sifting is not necessary. If your lava rock is dusty, you can sift it before adding to the mixture.

4. After sifting and cleaning the components, you can now start adding soil layers in your pot. You can test your bonsai soil mix through a clump test by squeezing a big clump of the mix in your hand. If it ends up dense and hard, then your mix is filled mostly with organic matter.

This kind of mix will hold a lot of moisture and may result in different problems like rotting of roots. But if the mix falls away after releasing them from your palms, it means that it has good drainage. If it’s too compact or too loose, you can simply adjust or increase the amount of the organic matter or the grit in your mixture.

NOTE: Did you know that many there are only a few bonsai tree that can be kept indoors? Check out our article “5 Species that Make Great Indoor Bonsai”