We show which soil is best suited for bonsai and why normal substrate is not an option. After all, the small tree has special requirements.
Bonsais grow in a small pot that has a big task. With its rather sparse content, it must provide the basis of life for the tree. Because the plants draw their water and nutrients from the soil in the bowl and find support. Not that less soil requires less labor or accuracy. On the contrary - due to the small volume of soil there is hardly any room for mistakes. This is not only reflected in the care of the miniature trees, but also in the choice of the right substrate for your bonsai.
You should consider this before buying bonsai soil
Without the right choice of soil, you will have little success in keeping your bonsai he althy for years to come. Bonsai soil should have certain properties: the irrigation water must drain well to avoid waterlogging. Nevertheless, water should be able to be stored well. The organic matter content should not be too high so that the structure remains stable for years and the roots get enough oxygen. In addition, the garden art of bonsai is not limited to just one plant species. Many different species with different demands on soil conditions can be trained to be bonsai. Depending on the bonsai species, a small variation of the bonsai soil may be necessary. With this article we will help you to choose a suitable soil for your botanical artwork.
Why do bonsai need special soil?
In order to speak of a bonsai, the miniature trees must be cultivated in a suitable pot. This means that the roots of the plants - unlike in their natural environment - only have a very limited space available. This spatial limitation ensures the strong growth brake, which is what makes the miniatures possible in the first place. By choosing the right coarse-grained, structurally stable bonsai soil, you ensure adequate root ventilation and the right thing, even with years of pot cultureBalance between water storage and runoff.
This is what the perfect bonsai soil looks like
Because of the culture in the pot, you should attach great importance to the right soil for your bonsai. The requirements of different bonsai species vary. In general, however, the substrate used should have the following properties:
- Good nutrient storage
- Quick drying of the surface
- Well ventilated due to coarse grain
- Sufficient water storage despite good water drainage
- Good structural stability, which prevents the substrate from collapsing
- High buffering capacity against fluctuating pH values
- Low Organic Content
In order to have these properties, bonsai soils contain ingredients such as pumice, lava grit, zeolite, expanded clay and sand and only a small amount of bark humus or peat. Akadama earth, dried volcanic ash clay from Japan, is also often included because of its beneficial properties. Special bonsai soils for plants that prefer a low pH level contain Japanese kanuma, a granulate also of volcanic origin, but lighter and more acidic than akadama. Also from Japan comes the Kiryu earth, which is extremely dimensionally stable and stores water very well. It is mainly used for juniper and pine bonsai. Compost can also be contained in small amounts as a nutrient store, but more so in the production of the bonsai and less in further cultivation. Below are some possible ingredients and their properties.
| Ingredient | Features |
|---|---|
| Akadama Earth | Structural Stability, Water Storage, Ventilation |
| Pumice gravel | Mineral, volcanic powder, water and nutrient storage, structurally stable |
| Blähton | Water storage, drainage, ventilation, structural stability |
| Humus | Nutrient storage, not structurally stable, variable pH |
| Fine Gravel | Drainage and Ventilation, Structural Stability |
| Perlite | Drainage and Ventilation, Structural Stability |
| Sand | Fast drying, structurally stable, drainage |
| Kanuma | Structural Stability, Aeration, Low pH |
| Kiryu | Structurally stable, water storage, very good ventilation |
| Gravel | Drainage, structurally stable |
| Tone | Nutrient store, water store |
| clay | Mixture of clay and sand |
| peat | Water storage, aeration, low pH value, not quite structurally stable |
| Coconut substrate | Depending on the fineness for ventilation or as water storage, not quite structurally stable |
| Zeolite | Nutrient and water storage, structurally stable |
In the right combination, the above substances can be used as a substrate for your bonsai. The exact composition depends on the species you want to grow into a bonsai. Plants from tropical areas with high humidity, such as fig species (Ficus) or fukien tea (Carmona microphylla), prefer to embed themselves in soil with good water-storing properties. Species that are sensitive to waterlogging enjoy particularly good drainage.
The condition and age of the plant also have an influence on the correct composition. Sick or young plants need a coarser grain than slow-growing and older plants, because the roots can spread faster in the loose structure. The suitable soils for bonsai can be derived very roughly by dividing them into needle-bearing and leaf-bearing types. In addition, you should also consider whether you are dealing with an indoor or an outdoor bonsai. However, since this is only a rough classification, there is plenty of room for arguments about the most suitable mix.
A good choice for many beginners bonsai is a basic bonsai soil. These high quality mixes are well suited for many types of bonsai or can be optimized by mixing in other ingredients.
Bonsai soil" mix yourself
Here are a few promising recipes for the gardener who wants to put together his own bonsai soil.
The following mixtures are recommended for conifers:
- 2:2:1 sand, clay and peat
- 1:1:1 Akadama, pumice and lava granules
- 1:1:2 Kiryu Earth, Pumice, and Akadama
For deciduous trees or indoor bonsai, a high water storage capacity is important, but the trees are usually satisfied with low drainage. For example, the proportion of sand goes down and the proportion of clay goes up.
Good mixes for deciduous trees are forExample this:
- 2:2:1 peat, loam and sand
- 2:1:1 Akadama, Pumice and Lava
- 1:1:1 Akadama, Kanuma and Pumice
Mixtures like these are suitable for bonsai on the windowsill:
- 2:1:1 Akadama, hummus and fine gravel
- 1:1:1 soil, peat and pumice gravel
If you want to plant your bonsai in a substrate that is precisely adapted to the species, you should first deal with the needs of the plant and then adjust the mixing ratio appropriately or add other components. You can find suggestions for substrate selection for the most popular indoor and garden bonsai here.
Buy bonsai soil
An easier way to find the right substrate is to use universal basic bonsai soils, which can be adjusted with a few additives if necessary. Mixing in other ingredients will not always be necessary if less special bonsai are grown. However, if you dare to try some trickier bonsai species, you should find out more about their soil requirements.
Starting with such basic bonsai soil, perlite, gravel, sand or expanded clay can be used, for example, to improve ventilation, which, however, also reduces the water storage capacity. The water storage can be increased with clay, fine coconut fibre, peat or bark humus. Clay and mature compost can be mixed in to store nutrients - but be careful: compost does not remain structurally stable for long, so the substrate will sag and aeration will deteriorate.
Tip: The best substrate is of no use to your bonsai if the pH value in the pot is not right. Therefore, pay particular attention to acid-loving bonsai species such as the azalea and just test the pH of your mix before use. The pH can be corrected up or down with acidic kanuma, peat or lime - and subsequent fertilization and watering should also maintain the appropriate pH.
In this article you will find out how to water your bonsai correctly.
Many thanks to Floragard for the support!