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How To Thicken Bonsai Trunk – A 6 Methods Guide

One of the goals of cultivating the bonsai tree is to have a robust tree trunk. The trunk of a bonsai has two functions.

To begin with, the trunk protects the whole tree from the weather. Second, the stem distributes carbohydrates to the roots from the leaves and transports water and nutrients to the foliage.

A robust trunk ensures the lifespan of this tree. Therefore, in this article, we’ll discuss how to thicken Bonsai trunk.

How To Thicken Bonsai Trunk
Tips for thickening the trunk – via Reddit

A Guide on How To Thicken Bonsai Trunk

Bonsai enthusiasts often strive to create the illusion of a large, sturdy tree. One way to achieve this is by thickening the trunk of your bonsai. This can be done in several ways, depending on the tree species and your level of experience.

To thicken the bonsai trunk, the plant must develop rapidly. Therefore, the tree should be moved out of its shallow pot to foster rapid development. Let’s see how to thicken Bonsai trunk.

Growing in the Yard Soil

Bonsai trees are miniaturized versions of full-size dwelling plants confined to small pots for aesthetic purposes.

Yanking it out of the pot and planting it in the ground will eventually increase the size; however, many gardeners find themselves eager to let their roots go as they watch this occur because once trunk thickness has been reached after several years pass by – which can be sooner depending on the care taken with regards how often one removes them during growth period–the tree must again return back into the shallow pot it was taken from or else it will continue to grow.

Sacrificial Branches

Sacrificial branches are terminal bonsai tree branches that can grow unchecked to increase trunk girth. It grows around the trunk’s base and provides it with many nutrients to promote the thickening. While the tree remainder is pruned and controlled, the side branch will grow out.

Once the branch has been allowed to grow freely for a while and achieved the expected thickness, it is then cut back (usually to the thickness of the desired trunk diameter) and wired into place.

This approach eliminates the need to grow the bonsai tree in the ground, making it an excellent choice for gardeners having certain space constraints. This process is repeated every year until the desired thickness is achieved.

Any side branch could be a sacrificial branch and will be hefty and create a noticeable scar. Gardeners have been working on closing the bark wound for several years. Plan to develop the sacrificial branch toward the tree’s back if you’re using this method to reduce the scar’s cosmetic impact.

You’ll need to wire a sacrificial branch to keep it straight while it grows. Pick a branch that’s about midway up the trunk. The trunk under the connection point will gain girth as the branch grows.

Above the sacrificial branch, nothing will grow thicker. Hence, it is an excellent approach to achieve a tapered trunk.

To achieve trunk’s smoother tapering, many gardeners develop several branches. Choose taller branches first, then lower branches as time goes on for a better taper.

How To Thicken Bonsai Trunk 2
How can I get a thicker trunk? – via Reddit

Cut Back the Trunk

One of the most effective ways to achieve a thick, tapering bonsai trunk is to cut the trunk back. When the tree is growing in the ground, this strategy works well. Then, you’ll trim down the tree’s trunk to stimulate it to become tapered and thicker.

The first significant cut will be made whenever you observe a trunk section that has achieved the proper thickness. It’ll be around one-third of the bonsai tree’s desired height.

Before making the first cut, the tree might be relatively tall, up to ten feet tall in some cases. The trunk will be trimmed down to a few inches in length. The tree will then be allowed again to grow out.

Keep the tree in the ground after the first cut and let the branches grow. To induce additional thickness at the lowest trunk’s region, try to employ the sacrificial branch strategy.

As your trunk gets thicker, you’ll need to create more massive incisions. At least three large cuts are required for a natural appearance. As a result, you’ll have a robust, tapering trunk.

Trimming back the leaves of the trunk may produce large scars on the bonsai that will take years to repair. In addition, using this design, establishing a broom-style or formal upright shape can be difficult.

Trunk Merging

A rapid approach to growing a thick bonsai trunk is to merge the trunks. This approach, also known as trunk fusion, is not going to work on an existent bonsai tree.

Rather, you will need to tie numerous seedling trees together so that they can eventually combine and appear to be one tree. Fast-growing tree species, such as Chinese Elm or Ficus, are ideal for trunk merging.

Trunk merging may not be a traditional method of thickening the bonsai trunk; many gardeners prefer it since it is quick. After a few months of being linked together, the saplings may merge.

Gardeners that use the trunk merging approach have more influence over the tree’s design. For example, they can estimate the size and start tapering as soon as possible.

Split The Trunk

The fastest way to accomplish Bonsai trunk thickness is to split it. First, you’ll turn the bonsai upside down after removing it from the shallow pot.

Then, divide the trunk along the middle with a rotary tool or a saw until you achieve the midway point. Use wood wedges or wires to hold the two trunk portions apart as it recovers with this procedure.

To hasten the healing process, it’s ideal to repot the tree in an enormous container. This will instantly give the bonsai tree an appearance of a thicker trunk. The trunk will take years to mend fully.

The results of splitting the trunk are virtually instantaneous. It should only be applied to trees that can withstand it. This technique should be used at the start of the growing season. 

Bend The Trunk

Bending the bonsai trunk is a fantastic way to thicken it without leaving huge scars. Using wires, bend the main trunk downwards while also bending the lateral branches upwards near the conclusion of the growing season.

The lateral branches will bulk up slower as compared to the main trunk throughout time, giving the tree a lovely tapering appearance. The focus of this approach is on tree movement and fluidity.

It is best for trees that have many side branches. Since it’s difficult to bend a thick trunk, it’s preferable, to begin with, a young tree.

Final Remarks

A bonsai tree’s attractiveness requires the development of a robust trunk. The trunk of a healthy bonsai should be thick, tapering, and aged. The gardener can employ a variety of strategies to obtain a thick trunk.

Most techniques take years to complete, and others will leave significant scarring. There are numerous factors to consider when deciding which approach is best for the bonsai tree. Any gardener could comprehend how to thicken Bonsai trunk with the right amount of devotion, patience, and practice.