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There are many types of soil particles which can make up a good bonsai soil or, if you will,
Always if you remember the primary characteristics of the soils and particles, you can create your own bonsai soil matrix out of many different particles. Just remember the soil characteristics which will provide the plants’ needs.
Think of a mix of particles with the consistency of miniature swiss cheese pieces. These particles’s air spaces will be so fine they will likely not allow the water to drain out from them but they will increase the amount of water in the mix without reducing the amount of air in the mix.
Almost all bonsai mixes include clay;
clay baked to a high enough temperature that they are “calcined”, that is, turned into a material that can’t turn back into mud. We can, of course, bake it to a high enough temperature that it will never turn back into mud at all; in other words, baked into a rock, or “vitrified” but it will not hold any water at all..
Of the processed clays available which have been baked, there are some best known brands. You may know them as “kitty litter” (which hasn’t been baked to any degree), and the calcined clays: turface, terragreen (and their best, highest baked variety, “Soil Conditioner red”). You can always test the degree of baking by putting some of the clay in a cup of water. If it begins to decay, it hasn’t been fired high enough. You generally can tell the degree of baking by the color, even without testing, of the finished product ; the darker and redder the color, the higher the bake.
There are many other products which result in the
Some diatomaceous earth clays are baked high enough to retain their shape. One sold in the UK is “Tesco” which gives favorable results. Another relatively inexpensive product is Haydite, an expanded gray shale (if you don’t mind the color). Then a relatively new product on the market is “Growstone”, made of expanded glass. This works well, for a while, but like some others it abrades and, as their own website explains, eventually turns back into sand.
Another product I used
which was wonderful and held together without decomposing was totally decomposed muck peat from the Florida swamps. Totally dried to a rock-hard consistency it would last for a couple of years before needing to be replaced and had all of the water holding capacity of the Japanese akadama and kanuma tsuchi soils. These have different characteristics, but always the primary needs are for air and water holding.
The last component
that needs mentioning is bark. The best kind of organic material is pine bark – and there are many kinds of bark as well. Most are too resinous. The least resinous are the Florida pines, especially the slash pine, not the longleaf pine. No other bark has the capacity to remain in granular form and not break down right away and is not too resinous.
Here’s another note of caution: don’t use composted pine bark. If you do, you’ll use something that all the value the critical mycorrhiza loving microorganisms will already have ingested. Raw bark is necessary.
Don’t use peat moss;
any peat moss, period. Remember what we said earlier in this series: all particles in the soil should be the same size, approximately. Again, the mind experiment which can prove it is to consider a container whose mix is of all same sized large particles. When you then add much smaller particles many of the new particles, peat for example, will fill in the larger original air pockets and, to a certain degree, no additional volume of soil will result. What will happen is that air pores will be taken up, resulting in reduced air in the mix.
There are, of course, soil particles with particular charactistics, as for example, crushed oyster shell, which will reduce the acidity in the soil which is occasionally necessary, as with buttonwoods.