Bonsai Soil

You may have noticed that the soil used for bonsai trees is specifically referred to as bonsai soil. The reason for this is that the make up of bonsai soil is considerably different to normal houseplant soil. In the case of a normal house plant, we want to develop a root system that continues to grow, and we 'upsize' the pots as the plant grows larger and larger.

As you know, bonsai trees are trees that are kept in a miniature form and one of the ways that this is achieved is through the practice of keeping the tree in a small pot or tray, which keeps the root system shallow and hence, the tree, small. Because the root system is shallow, the soil needs to have a careful balance of both drainage and the ability to maintain moisture.

To achieve the porous nature of bonsai soil, to allow suitable drainage and air circulation, inorganic materials are used. These may include non-living, or inorganic, materials such as exploded clay, stone, pebbles and sand.

To allow the soil to retain moisture and nutrients, living, or organic, materials such as peat moss, pine bark and compost are used.

If bonsai soil does not have adequate drainage, the shallow roots can become compacted and airless. This can lead to diseases, such as rootrot, that can cause the bonsai tree to become unhealthy and possibly die.

Conversely, if the soil is too dry or porous, the tree will not be able to retain enough moisture and nutrients. These elements are necessary for the healthy growth of the bonsai tree and without them dehydration, starvation and death may occur. How much of a mix of organic and inorganic materials in bonsai soil is a debated topic, but the most important thing to be aware of as a beginner is that there does need to be a mix of the two and normal, houseplant soil should not be used.

Another thing to be aware of, is the area that you live in. If you are in a particularly dry, hot region, your bonsai soil may need to have a little more organic material in it to retain more moisture. If you live in an area that has a lot of rain over long periods, you may need soil that is a little more inorganic, to allow for more drainage and air circulation. Whether you intend to make up your own bonsai soil or simply purchase it from a nursery, it is important to be aware of all of the above components and take them into account when caring for a bonsai tree.
Christine Taylor is a bonsai enthusiast and author of Help! Someone Just Gave Me A Bonsai Tree! She is dedicated to helping the beginner bonsai tree owner.