There should be no hard rules in bonsai. Every tree is distinctly different from another hence different rules should apply.
In competitions, one judge may favor one entry but another may disagree with him.
In fact, strict adherence to rules will likely hamper the imagination of the artist, limit his creativity, and prevent him from creating a unique masterpiece which carries with it his own brand of originality.
Worst, his collection may just be miserable imitations from books or with formulaic look as if mass produced with a moulding machine.
But a beginner ought to familiarize with and apply some basic rules before he can make any major modifications.
First be bookish then experiment to improvise, so to speak.
Also, the rules become important in the selection of potential materials and make decision as to their final design.
Furthermore, bonsai entries in competitions are judged according to or at least partially based on internationally accepted standards.
The Bonsai Rules
The following bonsai rules and characteristics provided me the basic guidance:
1. A good bonsai must have an impressive and characterful trunk. It should taper gradually as it rises from the pot towards the apex.
There are no abrupt or artificial changes.
The color and texture of the bark characterize that of an old tree.
Approximately the bottom or lowermost third of the trunk is clearly visible and the second third is partially visible.
2. The main branches are arranged left, back (rear), and right (or right-back-left) in ascending order starting from the bottom portion of the trunk approximately one-third of the height of the tree.
The thickness of the main branches should be proportionate to the size of the trunk and separated vertically at equal or nearly equal distances.
The first branches to the left and right of the tree should be slightly forward as if the tree wishes to embrace the viewer.
Viewed from the top, the tips of the three main branches should form a triangle with unequal sides (scalene) when connected by lines.
The first back branch should be arranged slightly to the right or left so that it is partly visible to the viewer.
This triangular arrangement of the branches continues as the tree rises to create a spiral of higher, shorter, and thinner branches.
If the trunk is curved, as, in the informal upright style, the branches should emerge from outside of the curve.
The apex should be treated as a small bonsai (for pines and most gymnosperm trees).
There should be slightly fewer branches at the front than at the back so that the viewer will have a good impression of depth and perspective.
No branch crosses another, nor points to the viewer (we call such branch “eye-poker”).
The branches should likewise taper gradually towards the tip with a texture proportionate to that of the trunk.
The heavier branches should drop toward the horizontal just like those of old trees because of their heavy load and the pull of gravity.
The extent of drop differs with species.
Note: A negative space or “gap”, that part of the trunk without a branch when it should have one, maybe considered positively as a gift and incorporated into the design of the tree to give it a natural effect.
It will be as if the tree itself made the decision.
3. Secondary branches or twigs emerging from the sides of branches are arranged in an alternate pattern.
It minimizes symmetry and allows gradual taper of the branch.
Opposite twigs (or bar branches) tend to constrict the development of the branch.
Bark, texture, and sizes of twigs should also be proportionate with branches.
4. The tree must have surface roots radiating from the base of the trunk. This is also important in the slanting style.
No roots are crossed one over the other, nor are any overexposed or appear in an unnatural manner unless this is consistent with the style of the tree. Buttress roots are desirable.
There may be no visible roots, but the base of the trunk should be large.
5. The foliage should be healthy and free from damage caused by pests and diseases.
There are no visible mechanical damage nor scorches left by strong wind or severe sunlight.
No precipitates from heavy water or foliar spray are visible.
As a whole, the entire tree should appear to be in prime health with miniaturized leaves.
6. The height of the tree and its canopy should be proportionate to the size of the trunk.
In general, its height may be six times that of the thickness of the trunk at its base.
7. The size of the fruits and flowers, if any, should be proportionate to the dwarf stature and the miniaturized leaves of the tree.
Large fruits and flowers are considered as fault although they may appear attractive and arouse curiosity among viewers.
8. There is no evidence of cuts or stubs left from pruning or marks from wires, weights, or other props used in training.
A “finished” bonsai has no wires. Shari and jin should look natural.
9. The container is of a style, shape, and color which complements the style and character of the tree.
It should not divert but instead enhance the viewer’s attention to the tree.
The depth of the pot should match the thickness of the tree’s trunk at its base.
Likewise, the diameter or length of the pot depends on the height of the tree.
Generally, a 1:1 ratio is the basis for selecting the depth of the pot in relation to the thickness of the base of the trunk while its diameter or length is about two-thirds of the height of the tree.
The trunk is positioned off-center or otherwise in an aesthetically satisfying spot for its particular style.
10. To simulate green undergrowth or a grassy field, the ground should be properly landscaped with live moss.
The moss cover must be healthy and free from weeds. Remove any mound of earthworm castings.