The appearance of a well-designed bonsai is subject to two competing factors – human perception and the natural unmodified form of a mature tree. While the natural tree exists indifferent to a persons approval or interest, a bonsai is a human-created caricature of the natural tree; colored by our perception of right and wrong, space, time, and peace – the tidbits of our consciousness. The bonsai is an arrogant but inevitable improvement of the natural tree to fit the ideal that we create inside our minds.
Visual flow is the concept of- and result of – the process of viewing a tree. The natural tendency of our inspection is to look at the base of the trunk and then follow it upward as it twists and turns and then pause in the mass of foliage at the apex. The eye then travels down the side of the apex and finds the key branch which completes the viewers journey by moving the eye away from the tree.
The role of the trunk. The direction of the visual flow starts with the lean of the trunk and continues with the changes in direction of the trunk. On a typical informal upright the trunk gently changes direction rather than twisting. On yamadori or exaggerated style trees the trunk can twist enough that the upper and lower sections of the trunk flow in opposite directions. On a good bonsai the trunk is the center of attention and the foliage acts like a picture frame. The trunk is normally the primary determining factor in the overall flow of the tree.
Understanding the apex. The apex of an upright tree is the part of the foliage near the front of the top of the tree. It should be generally leaning at least slightly toward the viewer. Similarly, the apex of a cascade or semi-cascade style is either the top of the tree or the bottom depending on the specifics of the style; it should still be inclined toward the viewer regardless of position. In multiple trunk arrangements the apex is typically the top of the tallest tree – the tops of the shorter trees frequently serve as the key branch or the side branching and back branching.
The flow of the apex is controlled by the direction that the base of the apex takes and by the relative mass to the left and right of the woody part of the upper trunk and apex. The shape of the apex can also determine the direction of flow – generally the longer and more gently-sloped side of the apex is the direction that the eye naturally travels when viewing. The branching of a poorly-formed apex will rob the tree of good flow. The branching should be even, small and generally slightly longer on the side that agrees with the overall flow of the trunk and key branch.
Understanding the Key Branch. The Key branch is usually the largest directional branch on the left or right side of the plant, the key branch is rarely (perhaps never) a back branch. Under-developed material will require that a key branch be developed to a larger size to improve the flow of the tree. Select a branch based on it’s position relative to the direction of the apex and the movement of the trunk. Typically the key branch is also the lowest branch, however this is not always true.
Strong, Weak, neutral, poor and cross flow. Whether the foliage or the trunk are a more powerful part of the overall composition determines their influence over the overall flow. Trees with foliage and trunk flowing in the same direction and the trunk slanting strongly have an overall flow that is strong. Trees with foliage and trunk flowing in the same direction but with little or no inclination in the trunk have weak (which is not the same as poor!) or neutral flow. Tress with trunk and foliage that flow in opposite directions have cross- flow. Trees with foliage masses in the key branch and apex that flow in different directions, regardless of the trunk flow, typically have poor design and poor flow.
Enhancing visual flow. To enhance the visual flow of a tree or correct cases of poor flow, make a plan to shorten some branches and simultaneously elongate sections of the key branch and apex over time. In Figure 1a the right low branch could be eliminated while also growing out the branch on the left in a fashion similar to figure 1c. Figure 3c could be corrected by reducing the right side of the apex while growing out the left side, the result being similar to 2a. The flow of figure 4d could be corrected by simply shortening the lower left branch and reducing the mass of the foliage so that the secondary trunk acts as the key branch instead. To correct problems with the flow within the apex consider wiring and/or removing any large branches that are headed opposite to the direction of the overall flow.