small bonsai tree

The Fascinating Science Behind Keeping Bonsai Trees Small and Healthy

How Bonsai Plants Are Kept Small

This question is a common one among people who don’t practice the art or are just getting started. There is a mystery on how we get the trees to be so small but yet so old and mature. Today we will try to answer the question of How Bonsai Trees Are Kept Small.

What Bonsai Means

First of all lets quickly cover the meaning of Bonsai. Bon-Sai is simply Tray Planting. It can be translated to a few other things but no matter the translation it all means the same thing, a plant in a pot basically. But bonsai is a little more then just a tree in a pot, it is an art form and requires the marriage between art and horticulture. If this marriage breaks down the tree can suffer.

Where Do Bonsai Trees Come From

Bonsai trees are not a species or variety of tree, Bonsai can be made from any tree that gets a woody trunk and limbs. The tree is then styled and paired with a pot to create the composition of Bonsai. Bonsai can be made from popular species such as Japanese Maple, Black Pine or Junipers, But they can be also made from native materials in your country. Bonsai comes from the imagination and is created with horticulture and art.

How Do We Make Miniature Trees?

So getting back to the main topic of this article we look at how bonsai are kept so small. There are 3 main aspects here that each play a critical role which are the Bonsai Pot, Soil and Fertilizer. But there are also techniques that need to be performed leading up to a tree being a bonsai to ensure you end up with a quality tree. You can read about how to grow bonsai here.

The Bonsai Pot 

When we talk about keeping a bonsai small the bonsai pot plays a big role in this, by restricting the amount of room roots have to grow this restricts the size the tree can grow. If a tree doesn’t have a big root system it cant support a large tree, so the smaller the root ball the smaller the tree. A tree in nature can have roots that are as long as the trunk itself on the tree, that’s why the tree has grown big and tall. Having a small tree and root system though can come with some challenges such as pest and disease, watering requirements and temperature limitations. With such a small root ball the tree doesn’t have a big defence system so extra care needs to be taken to help protect the tree.



The next part of keeping a tree small is using the correct soil, when we grow trees we use organic soils which have a high ability to hold nutrients ( cation exchange capacity ) and are also dense. This allows us to grow a tree quick and with good results. But when we are ready to slow the tree down and make it a bonsai after the development phase we need to change our soil strategy. This is where we change over to In Organic soils. These soils have a higher amount of oxygen available and also promote smaller root growth. They also have a low cation exchange capacity allowing us to better control our fertilizer. Using in organics to grow smaller roots not only slows down and limits the type of growth the tree can have but it also allows us to fit a higher surface area of roots in a smaller pot which can increase the trees natural defence systems, it also gives it more surface area to move water which is crucial in a small pot environment.


Once we are in the refinement stage of bonsai where we are concentrating on building small intricate branching it is vital that we have a fertilizer strategy to help control our bonsai growth. If we used the wrong fertilizer and wrong soil we can actually begin to grow larger branches and leaves again which isn’t what we want. Usually in refinement we will fully change over to an organic fertilizer which will be low in nitrogen and we will apply it a certain times of the year to help control the vigor of growth. This usually means not applying any fertilizer just before a strong flush of growth to reduce its size. The fertilizer is then applied after the flush of growth just to maintain the health and colour of the plant.
As you can see all 3 of these things work with each other to achieve the result of a small tree and once you know how to use them to your advantage your trees will begin improving as you will have more control over them.
If you wish to learn more about the fundamentals of bonsai please consider joining our online bonsai beginners course. This course is cheap and can be done from the comfort of your own home.
bonsai artist with bonsai tree

Author : Joshua Hooson

Joshua Hooson is an author and enthusiast of the art of bonsai. He has built his knowledge and understanding of bonsai through a combination of self-experience, lessons learned through hands-on practice, and extensive research. His articles reflect his passion for the subject and offer insights gained through his own personal journey in the world of bonsai. All the information provided in his works is a result of his own experiences and the knowledge he has gained through his studies. He is dedicated to sharing his love of bonsai and helping others grow in their understanding and appreciation of this ancient and beautiful art form.

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