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Why Bonsai Soil Is Different?
Bonsai soil is not your everyday garden or house plant soil. When one grows a bonsai plant, often a miniature tree, in a very small container, it becomes critical that the soil the plant is growing in meets its needs for water and nutrition. Ordinary soils are generally not good for a bonsai plant’s health. Not only is it necessary to understand what goes into the makeup of basic bonsai soil, but one needs to take into account the type of plant involved, which can rapidly make things complex.
In general, there are two types of soil, organic bonsai soil, and inorganic bonsai soil. If you were to ask a room full of people (who knew little about caring for a bonsai plant) which type of soil is best, chances are most would respond “organic soil of course”. That would seem to make sense, but in reality, is not really the case. Both types of bonsai soil have there pluses and minuses, but overall, an inorganic soil appears to be the most advantageous and is usually the soil of choice for advanced bonsai hobbyists. There are two fundamental requirements a bonsai plant has.
It requires adequate nutrition, and it requires an adequate, but not excessive, amount of water. It is the water factor that tilts things towards inorganic soils as a better choice.
Organic Bonsai Soils
Most bonsai plants require a soil that will retain a certain amount of water but will at the same time allow an excess of water to drain away. This means the soil must have the proper structure, light, and full of air pockets as opposed to being heavy and compacted. The trick is to find the proper mix of materials that will yield a light, structured, easily drained soil that still retains sufficient water for the plant’s needs. For many plants, peat moss is ideal. However as far as bonsai is concerned, peat moss has a tendency to hold too much water once it is moistened, and insufficient water if it is allowed to dry out, without reaching a happy medium. Composted bark is considered to be about the best organic growing media one can find. A mix of bark, peat, sand, and perhaps one of two other materials may do, but getting things just right may be a challenge. Since different plants do best in different soils, there is no “best” bonsai soil.
Fired Clay And Diatomaceous Earth
Where inorganic soil shines lies in the fact that, if the right medium is chosen, it will not break down and will provide both water retention and adequate drainage over a long period of time. There are two important factors to take into account. First, the medium must not break down easily, especially when exposed to moisture, and all the “fines”, or small particles, need to be removed so they won’t eventually clog up the open spaces or pores in the soil, causing its drainage capability to degrade. A good choice is fired clay, which generally holds its structure well. Another good choice is diatomaceous earth. Diatomaceous earth is made up of fossils of algae, and is readily obtainable, having many uses beyond that of potting soil. Other choices include perlite and vermiculite. Whatever the choice, the fines have to be shaken out. If you purchase a box of perlite or vermiculite you may find a significant percentage of the contents consists of fines.
An alternative to the above inorganic materials, which can be expensive, especially if one is repotting larger bonsai plants on an annual basis, is cat litter. A little research may be needed here, but cat litter is enjoying fairly wide usage as bonsai soil. One does need to purchase litter that consists of pellets made of either fired clay or diatomaceous earth. Many brands of cat litter contain both. Avoid cat litter made from paper products. Paper-based products will tend to break down when they become moist and create a very unhealthy environment for the bonsai plant.
Nutrition, A Secondary Factor
A few words should be added regarding nutrition. Most people, in the example given, would vote for organic soil, having nutrition in mind. A bonsai plant needs to be fed fairly frequently, and whether the soil is organic or inorganic really makes little difference. It’s really water retention and drainage that makes the case for using inorganic soils.
Choosing The Right Kind Of Bonsai Soil