Can You Use Regular Soil for Bonsai Trees?


Roots are the foundation of plants, and the substrates these roots live in determine whether the plant has access to water, air, and nutrients. Without the proper substrates, plants will die. So, is regular soil a good option for these tiny trees?

You can use regular soil for young bonsai trees, but it is not the best option for mature trees. Bonsai soil, made of akadama, lava rock, and pumice, is the best option for bonsai trees because it provides the water retention, drainage, airflow, and nutrients necessary for their health.

This article will look at how to use regular soil for your Bonsai trees and the benefits of using bonsai tree soil. We will also discuss the characteristics of a healthy bonsai tree substrate and look at how regular soil and bonsai tree soil compare.

Using Regular Soil for Bonsai Trees

When it comes to substrates, traditional soil is not the only option for plants. In fact, regular soil is not the best option for any bonsai. However, young bonsai trees can survive in regular or potting soil. 

When bonsai trees are young, they start growing like any other tree, so they can survive in regular soil. However, once you begin to slow the tree’s growth, turning it into a bonsai, it will have different needs, and regular soil will no longer be the best option.  

If you are growing bonsai trees from seeds or cuttings, it is best to start out in regular soil, which provides more support for roots to grow. Without a root system, trees do not have the structural support to keep them upright. Regular soil provides more of this support than bonsai soil, which is much more granular. 

Once the root system is established, you should transfer your bonsai into bonsai tree soil.

Bonsai Tree Soil Is the Best Option

While it’s referred to as soil, bonsai tree soil does not contain regular soil but is made up of many different materials. Bonsai soil will have various materials based on the type of tree you are growing and the climate you live in.

Most of the materials, or substrates, in bonsai tree soil are large-grained, with the exception of additional organic materials. 

The majority of bonsai tree soil is a mixture of the three most common substrates namely:

  • Akadama, a reddish dried clay found in Japan. The neat characteristic of akadama is that bonsai roots can grow right through the middle of the clay balls. While it does not contain any nutrients, akadama can store nutrients from lava rocks or supplemental minerals. It does degrade over time, so you will have to replace it every few years.
  • Lava rock, or bits of cooled lava. This is essential for bonsai health because it is full of minerals. It is also very durable and does not degrade over time. If you live in a wet climate, adding lava rock to your bonsai soil mix is important because it has excellent drainage.
  • Pumice. This is a white volcanic rock that provides good drainage for bonsai roots. It also helps prevent fungus from developing around the roots. If you live in a colder climate, adding pumice to your bonsai soil mix is crucial because it does not freeze.

A bonsai tree soil mixture for tropical plants may benefit from a small amount of organic material. Adding pine bark or peat moss will slightly increase water retention, mimicking the tropical climate the trees are accustomed to.

Bonsai Tree Needs

Substrates have several functions when it comes to bonsai trees. The material you plant a bonsai in will determine the amount of water available to the tree, the amount of airflow around the roots, and the variety and amounts of nutrients available.

Since different species of trees have slightly different needs, the best mix for one type of bonsai may be a little different from another. However, every bonsai has the same basic needs.

Balance of Water Retention and Drainage

The balance of water retention and drainage can be tricky to get right for most plants, and bonsais are not an exception. While there are all kinds of bonsai species, most bonsais require moist soil

Having slightly wet soil decreases the frequency you need to water the tree. Most bonsais should be watered every 5 to 7 days, so their substrates can provide water access for about a week. However, too much water will hurt the plant.

When a substrate does not provide enough drainage, water pools around the bonsai roots. This pooling cuts off the roots’ access to air and does not allow the tree to absorb nutrients, both of which are unhealthy for the trees. It can also lead to root rot, which in turn causes mold to grow around the roots. 

Any of these problems alone or in combination can lead to the death of your bonsai and are often irreversible.

Regarding water retention, bonsai soil has much better drainage than regular soil and slightly less retention. This means that bonsai soil can maintain a moist environment better than regular soil, which easily becomes too damp. You can alter the mix of bonsai soil to meet each climate’s water retention and drainage needs.

Good Airflow

While you often think about plants taking in oxygen through photosynthesis, the roots also need oxygen. Oxygen gives roots the energy they need to absorb water and nutrients and helps them grow faster. Airflow also helps protect the roots from root rot by preventing water from surrounding the roots entirely. On the other hand, too much airflow can dry out the roots.

Since the substrates in bonsai soil are larger pieces, there is more space in between to allow air to travel through the soil and, most importantly, around the bonsai roots. Regular soil without a high clay content does allow for moderate airflow around plant roots. Without soil analysis, it is difficult to determine your soil’s makeup and, by extension, aeration. 

The great thing about bonsai soil is that you create the mixture, so you are guaranteed to have good aeration. Bonsai tree soil also has good water retention to balance the airflow, so the roots will not dry out.

One factor that has a significant impact on airflow is compaction.

Compaction Resistance

When you think of soil compaction, large farm equipment usually comes to mind. In fact, many things can cause compaction, including rain, manual compaction, and settling over time. Compaction is dangerous for bonsai trees because it can crush the roots or cut off the airflow to the roots. 

Bonsai soil is much more resistant to compaction than regular soil. In addition to the airflow provided by the large, hard material that makes up bonsai tree soil, it also helps resist compaction. Akadama will degrade over time, so replacing it every year or two is important in resisting compaction.

Regular soil is typically more susceptible to compaction. However, the degree of compassion risk depends on the soil makeup. For example, clay soil generally compacts very quickly and even faster in the rain.

Adequate Nutrients 

Like most plants, bonsai trees take in nutrients through their roots. Therefore, their access to nutrients is determined by the soil or substrate in which they are planted. While you can always add fertilizer or supplemental nutrients to the pot, it is always best if bonsais can take nutrients naturally.

The nutrients in bonsai tree soil come from the lava rock. If your bonsai needs more nutrients, you can add more lava rock to the bonsai soil mixture.

Like the other factors we have discussed, a big concern with regular soil is that you just can’t tell its nutrient content without running many tests. Furthermore, the nutrient content of regular soil varies significantly based on the soil’s makeup.

For instance, soil high in silt will have more nutrients than other types of soil. On the other hand, soil high in sand or clay will not have many nutrients and may be unable to support the bonsai tree.               

Conclusion

The best option for substrates for your bonsai tree is bonsai tree soil. Bonsai tree soil is a mixture of:

  • Adakama
  • Lava rock
  • Pumice

This mixture meets all the needs of a bonsai, including:

  • Water retention
  • Drainage
  • Airflow
  • Compaction resistance
  • Nutrients

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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