Using the right soil mixture for your Bonsai trees is crucial. Soil is important to supply your trees with nutrients, but it also needs to drain properly, provide enough aeration and retain water. While there is much debate and discussion regarding recipes for the “perfect” Bonsai mix, most experts and hobbyists alike will agree on a few basic tenets:
A good soil mix must have good water retention. The soil needs to be able to hold and retain sufficient quantities of water to supply moisture to the bonsai between each watering.
A good soil mix must have good drainage. Excess water must be able to drain immediately from the pot. Soils lacking good drainage are too water retentive, lack aeration and are liable to a build-up of salts. Too much water retention will also cause the roots to rot, killing the tree.
A good soil mix must have good aeration. The particles used in a bonsai mix should be of sufficient size to allow tiny gaps or air pockets between each particle. It is important to the health of the roots that they have access to oxygen.
A good soil mix will contain a combination of organic material and inorganic/aggregate material. The organic material provides the water retention qualities while the inorganic/aggregate material ensures drainage consistency.
A good soil mix will have a pH that complements the specific tree being grown. Most bonsais prefer soil that is neutral to slightly acidic.
