Growing bonsai is challenging at first, especially learning how to thicken, shape, and taper the bonsai trunk. So, how do you build a bonsai trunk? 

Well, developing a trunk from scratch is a relatively long process. Each stage takes a few months to years. So, which is the best method for developing bonsai trunks? And what bonsai species are best suited for bonsai trunk development? Discover the answer by reading on!

Building a bonsai trunk 

Your bonsai tree’s trunk is essential for its health, wellbeing, and nutrient flow. They provide a lot of support to your tree. Hence, bonsai trunk development is important for bonsai owners.

The right bonsai trunk can give the impression of a natural tree. It can help make your bonsai look much older than it really is. Additionally, trunks with a thicker, more developed structure are typically more attractive and make great home decor pieces.

An ideal bonsai tree trunk will have three main characteristics: 

  • Thick trunks 
  • A nice shape with movement 
  • A gradual taper

However, in certain bonsai tree styles, not all 3 components will be present in equal amounts. For example, a larger sumo bonsai style will perform better if the trunk is wide and thick. Further, it tapers gradually instead of displaying lots of movement and shape.

For most trees, it’s vital to develop the trunk gradually, over time, for bonsai to thrive. As a result, to grow a bonsai trunk, we need to follow certain methods, such as

  • Ensure it’s the right time of the year to grow your bonsai,
  • Decide on your bonsai style, 
  • Decide on the bonsai species, 
  • Use a sacrifice branch to grow out the trunk thickness, 
  • Taper to the tree by trunk chopping, and 
  • Shape the trunk.

Now, let’s take a closer look at each of these.

Ensure it’s the right time of year 

Taking note of the season is essential before starting any bonsai trunk work. Bonsai trunk development is a little bit challenging, no matter what you do, whether you are trying to increase thickness, shape, or taper.

Moreover, you might have trouble healing your bonsai if you do them during the wrong time of year, such as during the winter months. Bonsai work in the winter can lead to dead branches, fungal infections, pest infestations, and even tree death.

Thus, developing bonsai trunks is best done early to mid-spring, between March and mid-April. You can also work on trunk development until early summer. However, in the fall, avoid any trunk development. 

For deciduous species, the best time to develop a bonsai trunk is early spring. Whereas coniferous species, such as junipers and Scots Pine, work well near the end of the summer when they are still sap-filled.

Decide on your style 

There are many different styles of bonsai trees, including,

Sumo
Moyogi
Cascade
Semi-cascade		Upright
Broom
Slating
Windswept

However, depending on the style you select, the trunk will vary in shape, taper, and size. For example, you can compare sumo bonsai styles with cascade bonsai styles.

Sumo style bonsai

By nature, Sumo bonsai trees have smaller and wider trunks. Hence, the thickening of the trunk will be more important than the shape or movement of the trunk.

Cascade style bonsai

Bonsai with a cascade trunk has a strong bend. Because of this, the shape and taper of the trunk will be far more important than its thickness. You will save a great deal of time if you know this before starting any trunk tapering. 

Also, the best way to design your bonsai is to write down exactly what style you want.

Decide on the bonsai species 

Once you have decided what style and design you want for your bonsai, the next step is to decide what species you want to use for the trunk.

If you are still unsure about what tree to buy, I would definitely suggest investing in a beginner-friendly species.

In my research, I discovered that conifers like elms, Ficus, and jade are the easiest trees to maintain. When developing bonsai trunks, you can make mistakes with these species without severely harming them. They can take a lot of damage without losing their shape.

In particular, jade bonsai holds a lot of water in its branches and leaves, making it easier to maneuver its trunk.

For a beginner, I recommend avoiding species with hardwood such as hickory, which is notoriously difficult to bend.

Store-bought or plating forms seedlings 

In addition, consider whether you will be using a store-bought tree or growing your bonsai from seedlings or cuttings. 

Rather than growing a bonsai from scratch, I recommend using a store-bought tree, as growing one from scratch takes a lot of time. 

Use a sacrifice branch to grow out trunk thickness 

Here’s where the fun begins!

I believe that the best place to begin bonsai trunk development is to grow out the thickness of the trunk first.

Fortunately, there are a number of different ways to cultivate a thick bonsai trunk, including:

  • Bonsai planting in the ground
  • Combining two bonsai trunks
  • Bonsai trunk splitting
  • Putting a tourniquet on nutrient flow

However, it is my opinion that growing sacrifice branches is the best approach.

The sacrifice branch of a bonsai tree is a branch that is left to grow out of either the side or back of your tree. Also, they are unpruned. Additionally, it is not a part of the main structure of the tree. 

With time, the size of the sacrifice branch increase as it is connected to the branch. Eventually, in turn, it causes the trunk of the tree to grow thick as well.

Add taper to the tree by trunk chopping 

A tree’s trunk should be thicker at its base than at its top; this is called tapering. While it is hard to improve irregularities in the thickness of a trunk (select trees carefully before purchasing), small changes can be made:

Thickening of the Bonsai trunk

  • Trees will grow thicker if the nutrient flow is allocated to the branches just above the thin part of the trunk.
  • Chopping can be done to allocate growth by excluding the branches above the thin parts. 
  • In this method, you will notice a change after two years.

Overall shape

One of the most eye-catching features of a tree is its trunk shape. The trunks of certain Bonsai are elegant, slender, and twisting; Juniper Bonsai is a good example. On the other hand, the classic Japanese black pine often reveals a thick, heavy trunk.

Also, it is important to take a trunk’s shape into account when buying it. Because it becomes almost impossible to bend once it reaches a certain thickness (until then, you can use a trunk-bender).

Conclusion 

It is not an easy task to build a bonsai trunk. However, the good news is that you can have a beautiful bonsai trunk by taking a few things into account. Initially, bonsai trunk development may seem difficult, but eventually, you will enjoy the process.

Make sure you keep in mind a few things such as the right time, the type of bonsai, and the species. Don’t forget, a great trunk is all you need for an excellent bonsai!

Please, let me know how your bonsai trunk turned out if you have followed all the instructions.

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