Bonsai’s soil is crucial to the health of the tree. Soil needs to supply the tree with nutrients, drain water properly, provide good aeration, and retain water. Bonsai tree soil is different from regular gardening soil. Using the right kind of soil is very important. In this article we will be talking about the qualities of a bonsai soil, the difference between organic and inorganic soil, and the components of a bonsai soil.

Qualities Of A Good Bonsai Soil

bonsai soil

Bonsai soil needs to do a number of things in order to qualify to be a good soil. This includes having good water retention, drainage, and aeration. Your soil needs to be able to hold a certain amount of water so that your tree receives a good amount of moisture. Additionally, the soil you choose needs to be able to drain any excess water from the pot immediately. Water build up will kill you tree because of a build up of salts or root rot. The soil should allow for little air gaps in order for the tree’s roots to get oxygen.

Organic vs Inorganic Soil


There are two kinds of soil, organic and inorganic. Organic soil mixtures are made of dead plant matter such as bark, peat, and leaf-litter. This kind of soil is not recommended for bonsai trees. Organic mixtures break down and reduce drainage quality. Potting composts do not absorb water well. You may think you are watering the tree, but the water is just running out of the pot before it has a chance to be absorbed. Inorganic soil contains no organic matter. Instead, it contains fired or calcite clays or volcanic lava. While these absorb less water and nutrients, they provide amazing aeration and drainage.

Bonsai Soil Components


Components commonly found in bonsai soils are Akadama, Pumice, Lava rock, gravel, and organic potting soil. As mentioned before, pure organic potting soil is not recommended for bonsai trees. It can be used in small quantities in bonsai mixtures, but this is not necessary.


Akadama is specially made for bonsai soils. It is a Japanese, hard baked clay that is available in all bonsai stores. This clay must be sifted before use. Every two years you need to replace the Akadama because it breaks down and reduces aeration. Akadama is a bit on the pricey side, so some prefer to substitute this clay with other baked or fired clays.


Pumice is a nutrient and water absorbent volcanic product. In bonsai soil mixes, it is used to aid root ramification and water retention. Lava rock is a product that provides good water retention and structure in bonsai mixes. Roots are unable to grow into these rocks.


Fine gravel provides the soil mixture with good drainage and aeration. This is typically used as the bottom layer of soils to enhance the soil’s drainage. While you can use this in your soil mixture, most experts no longer use gravel.


Organic potting compost is made of sand, perlite, and peat moss. As part of a soil mixture, this can be used just fine, but this should never be used on its own for bonsai trees. Organic soil does not allow for good aeration or drainage.

Soil Mixture Recommendations


Every tree species needs a different kind of soil mixture. There are, however, two common mixtures you can use for bonsai trees. One of the mixtures is for deciduous trees, and the other for coniferous. Both of these mixtures contain Akadama, Pumice, and Lava rock, but in different ratios.
These mixtures can be adjusted to fit your circumstances. For instance, if you are unable to check on your trees several times a day, you can add more Akadama into your mixture to increase its water retention. Additionally, if your climate is particularly wet, you can more lava rock to outdoor tree’s soil to increase drainage.


Deciduous bonsai tree soil mixture: Akadama, Pumice, Lava rock at ½, ¼, ¼.
Coniferous bonsai tree soil mixture: Akadama, Pumice, Lava rock at 1/3, 1/3, 1/3.

A bonsai tree’s soil should be well draining, provide good aeration, and be water retentive. Soil mixtures should contain Akadama, Pumice, and Lava rock with ratios varying depending on tree species and climate. Never use organic potting soil on its own as it does not provide any of the qualities you need in a soil. Happy growing!