How to Choose Soil Mixes for Bonsai

When ten bonsai people get together to discuss soil mixes, you end up with ten different recipes for ideal mix. Thus the subject of potting mix can become complicated and confusing, but there is no need to let that happen.

What is the Function of Soil


Potting soil should support your tree in two ways. First, the soil should have enough texture to stabilize the tree in the container. Second, the soil should be a mixture that stimulates the feeding roots that supply nutrients to the tree.
soil mixes for bonsai
Soil Mixes for Bonsai

A basic soil mix should be easily understandable and ready available, and should allow you to grow all types of bonsai, with minor adjustments for different species of trees. The mix should drain fast, so most water passes through and does not sit in the container. However, some water retention should occur. Texture is an important element, for the roots need something to hold onto to provide stability for the tree. Nutrients are another important element in the basic mix. The soil you use should also be clean and insect-free.

In most outdoor areas the soil down where the roots are growing looks dark and rich, has texture from decaying matter, and lots of small stones and grit from erosion. View this as a basic soil mix.

Roots develop in a quick draining soil, one that allow the ongoing exchange of moisture and air. When root tips sense dryness (air), they begin to move, seeking moisture. As they rub against sharp objects like small stones, they divide and go around them. Roots surrounded by water do not have to move to find a water source, but instead of increasing, they begin to rot away. All water and lack of air amounts to suffocation.

The basic mix of equal parts of loam, humus peat moss, and coarse sand meets the needs of most trees. The loam provides nutrition. The humus peat moss retains moisture and supplies various stages of decaying matter as texture for roots to hold onto. The most important ingredient is a sand, which must be coarse, with lots of little stones and grit. Do not use fine sand, as it will make the soil unusable. Poultry grit or aquarium gravel can be used in place of sharp sand. Do not use beach sand or anything else suspected of containing salt.

The basic soil mix can be adjusted for climate and type of plants. In very warm, dry climates, peat moss provides more moisture retention. In cold, damp climates, additional sand allows the soil to dry more quickly. For bonsai like pines that require more dryness between waterings, increasing the sand allows for quicker drainage. Bonsai maples, which suffer leaf burn during hot spells when planted in shallow container, benefit from extra peat moss in the mix.



Soil Mixes Varieties

There are many soil mixes various individual ingredients, but the ingredients described here – loam, humus peat moss, and coarse sand – are familiar, inexpensive, and readily available.

In most areas soil mixes are offered already bagged and sterilized, and are available under many trade names. Usually they do not list their ingredients. Many contain mostly water-retaining components that permit slow drainage.

Soil varies from place to place, and an article like this one cannot begin to describe the differences. Search out information about local soil conditions, and rely on advice from your garden center.

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