1. Pot length
The size of the pot is probably the easiest aspect to approach.
It is usually governed by two simple rules. The first states that a pot should be about two thirds of the dominant
dimension of the tree — height or width, depending on which is visually dominant.
If your tree measures 30 cm in width, the pot should be around 20 cm long (two thirds of 30 cm).
This is a useful guideline… but not a law.
And to help you, I’ve created a pot size calculator tool, which will give you an idea of the ideal size for your tree, based on classic rules.
In composition — whether in sculpture, painting, architecture, or bonsai (because the tree–pot association is a form of artistic composition) — there are a few key principles, one of which is the concept of the “tangent.”
In art, tangents are avoided whenever possible. These are lines or shapes that almost touch. The human brain dislikes forms that merely brush against each other. A line grazing a circle, one shape barely touching another — these situations rarely feel visually elegant.
Either the forms clearly intersect, merge, or they stay clearly apart.
The same applies to a tree in its pot: tangents should be avoided. This is why one tries at all costs to avoid a pot that is exactly the same width as the tree.
This principle already allows us to bend the two-thirds rule. A pot can be larger than the tree if it serves a coherent compositional intention. Sometimes a tree is placed in a very large pot to evoke an open landscape — a solitary tree standing in a wide plain.
2 – With a two-thirds pot, the composition feels balanced and harmonious.
3 – With a pot the same width as the tree, the alignment between foliage and pot feels disturbing and lifeless.
Ultimately, the two-thirds rule is a compromise: it produces a coherent overall impression while avoiding tangents and extreme disproportions between pot and tree.
2. Pot height
The second commonly mentioned rule is that the height of the pot should correspond to the width of the nebari.
But this is merely a simple way of conveying a fundamental idea:
The pot should be neither too dominant nor too discreet.
➜ The pot must not outweigh the tree,
➜ and the tree must not overwhelm the pot.
If your tree’s nebari measures 5 cm, then a 5 cm tall pot is a good starting point. But this guideline truly applies to mature trees whose root systems have been refined over many years.
2 – A shallower pot to add lightness to an airy tree.
3 – A deeper pot suited to cultivation needs, climate, or tree health.
Beyond aesthetics, the most important criterion is the health of the tree.
Depending on the root system or your local climate, choosing a deeper pot may be wise.
This is a matter of visual balance — but sometimes also of basic horticulture.
For a light deciduous tree, a slightly shallower pot enhances elegance and airiness. For a massive conifer, a taller pot can help anchor the composition visually.
3. Special cases
The two-thirds rule works in the vast majority of cases. But some bonsai styles were designed specifically to move beyond it.
These trees play with emptiness, imbalance, tension, or landscape. Their logic is no longer that of a “grounded” tree, but of a strong artistic intention. Applying the rule mechanically often results in pots that are too large, too long, or simply incoherent.
Tall, slender trees and literati (bunjin)
Literati bonsai are about verticality and emptiness. They are often very tall with minimal width.
Applying the classic rule leads to a pot that feels oversized compared to the actual mass of the tree.
In this style, the width of the composition is a far more relevant reference than height.
The pot is deliberately smaller than the rule would suggest, reinforcing lightness and vertical tension.
Here, emptiness is an integral part of the composition.
Wide canopies and forests
Some compositions are strongly horizontal: spreading trees, forest plantings, landscapes.
In these cases, width clearly dominates visual perception.
A longer-than-average pot is often necessary to provide stability and allow the composition to breathe.
The two-thirds rule remains a starting point, but is often expanded to serve the landscape rather than the individual tree.
Cascade and semi-cascade
Cascades and semi-cascades are very specific cases.
The dominant dimension (height or width) is often misleading.
In these styles, pot length does not compensate for the downward movement.
That balance is achieved instead through pot depth and height, which provide visual anchoring.
Pot length is often determined by the tree’s most compact dimension, not its most dramatic one.
Small formats (mame, shohin)
At very small scales, rules naturally become more flexible.
The eye tolerates deviations more easily, and the relationship between tree and pot becomes more intuitive than mathematical.
Proportions still matter, but they are less restrictive.
The rule mainly helps avoid major mistakes, not to freeze the choice.
• These are traditional aesthetic conventions, not cultivation rules.
• Avoid a pot that is exactly the same width as the tree.
• Pot height is judged by balance of masses, not by centimeters.
• The pot should be neither too dominant nor too discreet.
• These are guidelines to inform your choice — and can be freely adapted.
• Above all: the health of your tree always comes first.