Akadama bonsai soil: good drainage, air permeability, pH buffer, no root rot
Akadama bonsai soil
Repotting Bonsai with Akadama: Proven and Safe
Akadama (Akadamatsuchi) is a bonsai substrate that is indispensable when repotting bonsai. It is a clay granulate with a, as the name already says (Japanese 赤玉土 = red earth), red to reddish brown colour.
Akadama occurs naturally on the island Honshu (mountain Akayi - near Tokyo), is mined there in the open-cast mining and is exported into all world. Akadama is of volcanic origin.
Akadama qualities: Double line and single line brand or Hard / Soft Quality
Akadama is very dimensionally stable, hardly compacts and decomposes only slowly. Depending on the quality of the substrate used, it should be replaced after 2-4 years. During this time Akadama slowly loses its coarseness, the air permeability decreases, the salt content increases and consequently the humidity in the soil increases. Thus the essential advantages are lost - an exchange becomes necessary.
- Akadama Hard Quality, Double line brand (Japanese 硬質, Kōshitsu): Is longer structurally stable (4-5 years). Akadama Hard Quality should be taken if the bonsai remains longer than 3 years without repotting in the bowl. This is especially true for older bonsai as well as for most coniferous bonsai.
- Akadama Soft Quality, Single line brand (Japanese 上質, Jōshitsu): Up to 3 years structural stability. Can be used for bonsai that are often repotted (especially young, root-strong deciduous trees, but also other plants such as flowers).
Akadama and bonsai earth mixtures:
Akadama is mostly used purely, i.e. to 100%. Sometimes, however, it is also added more or less strongly as a component of an earth mixture. This depends essentially on the type of plant and the age of the bonsai. By combining the advantages of clay with very good water permeability, it is possible to reduce the proportion of sand and gravel in an earth mixture.
If a slightly acidic pH value is required (e. g. for buffering when using harder pouring water), a little peat (30%) can be added.
It is difficult to give a general recipe for the use of Akadama in bonsai blends. In general it can be said that older plants have a higher proportion of Akadama than young plants.
Some tree species seem to tolerate pure Akadama badly (e.g. Larix - larch).
Properties of Akadama:
- Ensures sufficient to good stability of the tree
- Very good air permeability
- Hardly any tendency to soil compaction
- Excellent drainage properties (very good against root rot)
- High ability to retain nutrients in soil once they have been ingested
- Good buffering capacity against pH-value fluctuations
Akadama and watering:
Akadama can store water, but due to its good water permeability it can be watered more often than usual, depending on the proportion of Akadama. If it is used pure, this can mean that in summer it has to be poured more than once a day.
In Japan, where many bonsai are drawn in pure Akadama, watering is much more frequent than in Germany. However, with this substrate overpouring and the resulting waterlogging is almost impossible.
Depending on water absorption, the colour changes from a light reddish brown (dry) to almost brown (moist). This colour change makes it easy to see when it is time to water.
Important: Since Akadama is delivered dry, it is important to water well immediately after stewing. Otherwise root damage may occur.
Akadama and fertilization:
The higher the proportion of Akadama in the soil mixture (similar to other mineral substrates - e.g. expanded shale), the more attention must be paid to fertilization.
Mineral fertilizers dissolved in water are quickly washed out and are therefore no longer available to the plant. If mineral fertilizers are to be used, a small dosage is recommended for frequent applications.
The use of organic fertilizers (Biogold Bonsai fertilizer, Horn shavings) has proved its worth well. Due to the slow release process of nutrients, bonsai are adequately and above all evenly supplied over a long period of time. There is hardly any overfertilisation or salinisation of the soil.
pH of Akadama:
pH value 6.5-6.9, ie. slightly acidic. Due to the high buffer capacity of this earth, the pH value hardly rises.
Akadama grain sizes:
Akadama is available in various grain sizes (fine 1-5mm, medium 5-10mm and coarse 10-20mm) from specialist bonsai retailers.
The coarse-grained mixtures are used to improve drainage in the lower part of the bonsai substat, the fine-grained mixtures as top layer. Many bonsai designers sieves Akadama before use to remove the fine ingredients (dust) and further increase water and air permeability.