El trunk of a bonsai It is one of the most distinctive and attractive features of this ancient art. The structure, shape, and thickness of the trunk determine not only the visual appearance, but also the impression of the tree's age, strength, and stability. In this article, we explain How to shape a bonsai trunk, delving into key concepts such as nebari, taper, thickening, shaping techniques, and essential care.
Nebari: the base of the trunk and its importance in bonsai
El nebari is the Japanese term that refers to the set of superficial roots and the base of the trunk. This characteristic gives a sense of groundedness and stability, providing visual balance and enhancing the impression that the bonsai is a robust tree established on the ground. To better understand how to enhance this characteristic, you can consult our guide on How to choose the best bonsai species according to the climate.
- A well-developed nebari is usually the result of careful work in the initial stages of cultivation.
- To enhance nebari, the tree can be planted on a board or slab, forcing the roots to grow horizontally.
- Roots that grow vertically (tap roots) should be removed to promote radial development.
An attractive nebari is essential for any quality bonsai, and its early formation ensures a solid foundation for later trunk and crown work.
Taper: How to achieve a naturally shaped trunk
La taper It is the progressive transition in thickness of the trunk, from greater at the base to lesser at the top. This characteristic is crucial for simulating the maturity of trees in nature. For other tips on suitable species for your bonsai, we recommend visiting How to choose trees for bonsai.
- The trunk must avoid the reverse taper, that is, the top part is thicker than the base, as this looks unnatural and breaks the visual balance.
- If irregularities are detected, it is possible to thicken specific areas by allowing branches to grow just above the desired area and pruning the rest.
- To achieve taper, it is advisable to purchase specimens that already have a certain shape, since subsequent corrections are slow and limited.
The use of sacrificial branches and strategic pruning can help shape taper, although they require patience and long-term planning.
How to thicken a bonsai trunk: effective techniques
A thick and vigorous trunk conveys longevity and robustness. Thickening is, therefore, one of the main objectives in the first years: if you want to delve deeper into the correct care of the Ficus bonsai or in other species, these techniques will be useful to you.
- Sacrificial branches: Allowing one or more branches to grow without pruning accelerates trunk widening by taking advantage of the abundant sap flow. It's important to remove these branches before their size creates unsightly scars or complicates future design.
- Growing in soil or sieves: Planting bonsai in open soil or in sieves promotes accelerated root development and, therefore, the trunk, due to hyperoxygenation and good drainage.
- Cut&grow technique: This involves letting the tree grow freely in a large container. When it reaches the desired thickness, it is cut to the planned height, stimulating sprouting at the base. From there, the process is repeated according to the taper and height requirements.
- Fusion of cuttings or seedlings: Especially effective with species like Ficus, braiding or grouping several seedlings and holding them together until they merge allows you to obtain thick trunks in less time. For more details, visit our section on fusion of cuttings in bonsai.
- Layers and stakes: Obtaining thick trunk material by layering or planting thick cuttings simplifies the subsequent training of the bonsai, since it starts from a solid base.
Whichever method you choose, the key is not to be impatient: trunk thickening requires time, care, and planning.
Global trunk formation: styles and modeling
La overall shape of the trunk and the style chosen determine the character and personality of the bonsai. It is essential to define this in the early stages of the work, since modifying the curvature of a mature trunk is complex and risky. For more information on bonsai styles, you can consult The most beautiful trees at the World Bonsai Convention.
- Wiring the trunk: In young, flexible trees, copper or aluminum wire can be used to guide the trunk's curve, creating movement, waves, and character. It's essential not to force the wire to avoid breakage or deep wounds.
- Pruning and selecting shootsRemoving poorly positioned or unwanted branches helps direct growth and shape the style. Strategic pruning in the early years is key to defining the final silhouette.
- Advanced techniques: In more advanced stages, techniques such as: jin o Shari (simulation of dead wood) to give an old appearance, although they require experience and skill.
In all cases, the choice of style responds to both the species and the natural form of the material at hand.
Recommended proportions and visual balance
To achieve a harmonious design, there are classic recommendations on proportions:
- El trunk diameter The maximum recommended height of the bonsai is usually determined at the base, usually between 6 and 12 times that diameter.
- La main cup It usually starts around the first third of the height.
- The primary branches They should not exceed one third of the thickness of the trunk at their insertion point.
- Avoiding crossing branches and branches towards the interior improves the aesthetics and balance of the canopy.
Care and maintenance during trunk formation
Success in trunk formation relies on a series of essential care measures:
- Quality substrate: A well-drained and aerated substrate favors root development and, therefore, trunk vigor.
- Balanced fertilizer: Using solid organic fertilizers allows for vigorous and constant growth, without excessive stress.
- Adequate wateringAdjust watering frequency according to the species and climate. Tropical trees prefer constant humidity; others, such as olive trees and conifers, appreciate dry periods.
- Exposure to the sun: Direct sunlight stimulates robust growth and reduces internodal distance, resulting in smaller leaves and a compact appearance.
- Control of pests and diseases: Regularly check the condition of the trunk and base to detect any problems and act quickly.
Tools needed to work on a bonsai trunk
To shape and care for your bonsai trunk accurately, you will need some specialized tools:
- Pruning shears: For clean cuts on young branches or shoots.
- Wire cutters: Essential to remove the wire without damaging the bark.
- Aluminum or copper wire: To model the position of the trunk and branches.
- Protective tape or raffia: Protects the bark by wiring thick areas.
- sealing paste: Accelerates healing and reduces the risk of infection after large cuts.
If you're just starting out, invest in quality scissors, some wire, and a small amount of sealing paste. You can gradually add the rest of the tools as you progress in training and caring for your bonsai.
