樹形の骨格とは──主幹・主枝・副主枝・側枝の見方と、切る前に木を読む庭師の目|樹木医が図解(Reading the Framework: Trunk, Scaffold and Lateral Branches)

English: Reading the Framework — Trunk, Scaffold and Lateral Branches in Japanese Pruning

A tree’s framework is the arrangement of branches that holds up its form, becoming thinner step by step from the trunk to the main scaffold branches, the secondary scaffolds and the laterals. Before making a single cut, Japanese gardeners read this framework and decide which branches to keep and which to remove. This illustrated article explains how to read the framework of deciduous trees, evergreens and pines, and how main branches should be arranged, with reference to Japanese public pruning standards and sources from abroad.

This is the seventh article in our series on the pruning techniques of Japanese gardeners (niwashi and uekiya). So far I have written about cuts: sukashi (thinning), eda-nuki (removal cuts), kirimodoshi (cutting back) and the three levels of sukashi. This time the subject comes before the cut: how to look at a tree.

Beneath the leaves lies the framework

In summer a tree is covered in masses of leaves and looks from outside like a rounded green shape. When the leaves fall in winter, the structure appears: the trunk dividing into thick branches, and thick branches into thin ones. Gardeners call this kokkaku (framework) or edaburi (branch habit), and pruning always begins by reading it.

Winter pruning of deciduous trees has building the framework of the tree form as its main purpose (Tokyo Metropolitan Government, Standard Specification for Street Tree Maintenance). Because the branch habit can be seen after leaf fall, this is the time when the arrangement of the framework branches can be made (NILIM, Guide to Preventing Street Tree Failure). Summer pruning is lighter work that adjusts the density of new growth, with a different purpose.

Thinning, removal cuts and cutting back are all tools used after the framework has been read. Which branches support the form of the tree, and which are replaced year by year? Without seeing that, the choice of branches to cut has no logic.

Trunk, main, secondary and lateral: the four tiers of the framework

Branches come in tiers. Thick branches from the trunk (shukan) are shushi, main branches; branches from the main branches are fukushushi, secondary scaffolds; and branches from the secondary scaffolds are sokushi, laterals (NILIM, citing the Japan Landscape Contractors Association’s Street Tree Pruning Handbook). Secondary scaffolds are also called a-shushi (City of Yokohama specification), and “lateral” sometimes means a branch grown from a side bud of a main branch.

The framework that decides the tree’s form is the main and secondary scaffolds. Laterals and the twigs beyond them are the parts removed or cut back and renewed in yearly care. Once a framework branch is cut it takes years to restore, so how it is handled changes what the tree will look like ten years from now.

There is also a way of dividing the crown by height. From the top, each third of the crown is called the upper, middle and lower branches (NILIM). Looking at branches with two measures, tier (thickness) and position (height), makes it clear where work is needed.

The framework differs by species

The structure of the framework differs from species to species. Zelkova (keyaki) divides low into several main branches that rise in a fan, a broom-like (hokijo) framework. Cherry has a thick, short trunk with heavy main branches spreading sideways into a wide umbrella. Even with the same intention to thin, in zelkova you look between the rising main branches, and in cherry you look along the tops of the spreading ones.

Evergreen broadleaf trees such as Japanese white oak (shirakashi) and camphor are covered in leaves all year, and their framework can hardly be seen from outside. From our experience in the field, before setting up a ladder on an evergreen we step under the tree, walk around the trunk looking up, and confirm the direction and number of the main branches through gaps in the leaves. We draw the structure inside the foliage in our heads, not the outline, before starting work.

A trained pine shows flat layers of needles stacked tier upon tier. Beneath each layer is a main branch growing horizontally from the trunk, alternating left and right, and the layer sits on top of it. Among Japanese gardeners, pine care is thought of less as tidying the needle layers than as checking, every year, the arrangement of the branches that support them (edakubari). Plucking old needles in winter momiage makes this arrangement easy to see.

Arranging the main branches: spread on all sides, spacing up the trunk

In a good framework the main branches spread evenly in all directions when seen from above, and attach at staggered heights when seen from the side. When main branches overlap in the same direction, they shade each other, weight shifts to one side, and a gap without branches opens on the other. American sources also say that branches on young trees should ideally be evenly spaced on the main stem (USDA Forest Service), with good radial placement (Purdue University).

A framework is easier to build the younger the tree is. A few years after planting, the main branches that will become the framework are arranged evenly throughout the crown (NILIM). Of branches growing in a bundle from the same height, one is kept, and branches nearly as thick as the trunk that compete with it (kyososhi, competing branches; City of Yokohama) are removed early.

There are guides for branch thickness too. A branch should be no more than one-half to three-quarters of the diameter of the stem at its attachment (USDA Forest Service), or kept smaller than half the trunk diameter (University of Florida). For vertical spacing between main branches on large-growing trees, figures of 18 to 24 inches (Oklahoma State University) and 24 to 36 inches (Iowa State University) are given. I could not find numerical guides in Japanese public documents; Japanese gardeners have decided these by eye and by the form of each species.

Read the framework, then cut: the order of pruning

Once the framework is read, the order of cutting follows: from sorting out thick branches toward thin ones. The City of Yokohama’s specification shows a diagram in which work proceeds from limb removal, to removal cuts, to cutting back to a lateral, to heading back. In height, work moves from the upper to the middle and lower branches of the crown, cutting the top more strongly and the bottom more lightly (NILIM; Tokyo Metropolitan Government).

When a framework branch must be shortened, it is not cut off midway but cut back to the fork of a smaller branch that can take over its role (Tokyo Metropolitan Government; kirimodoshi). The cut is made just outside the swelling at the branch base (the branch collar).

From our experience, if you clip from the branch tips without reading the framework, the outline may look tidy, but thick branches stay crowded inside, and the next year fine shoots sprout densely where you clipped. Sorting the framework first and then moving to the tips means fewer branches need to be cut at all.

Time standing before the tree: the craftsman’s eye

Among Japanese gardeners, time spent looking at a tree is valued as much as time spent working on it. On arriving at a site, you do not set up the ladder at once. You step back, walk once around the tree, and follow it with your eyes from trunk to main branches, from main branches to secondary scaffolds. Tracing branches as if with a finger, you decide in your head which to keep and which to remove, and only then pick up a tool.

Once up the ladder, the hands begin to tell you more. From our experience, the thickness and firmness of a branch in your grip tells you whether it is part of the framework connected to a main branch or one that will be replaced within a few years. Reading the framework with the eyes and confirming it with the hands while cutting: this back-and-forth leads to a finish that does not look cut.

Caring for Japanese garden trees means watching the same tree for years, sometimes decades. You see how the branches you left last year have grown, and read this year’s framework again. The leafless branch habit in winter is when you can check that year’s answers. I believe the eye for reading a framework grows through a long relationship with each tree.

Structural pruning abroad: for readers outside Japan

In English, pruning that builds the framework of young trees is called structural pruning. Among the objectives of pruning in ANSI A300 is “Develop structure”, to improve branch and trunk architecture (TCIA summary). Shushi corresponds roughly to scaffold branches, the main trunk to the central leader or trunk, and kyososhi to codominant stems.

The difference lies in how it is expressed. American sources give numbers for branch-to-trunk ratios and vertical spacing. Japanese gardeners have read the framework by eye and hand, with each species’ form as the model, and arranged the branches accordingly. The shared idea is to decide the framework early, so that large branches do not have to be cut later.

Frequently Asked Questions (Q&A)

Q1. What is a tree’s framework?

A. It is the arrangement of branches that holds up the tree’s form, becoming thinner step by step from the trunk to the main, secondary and lateral branches. The framework that decides the form is the main and secondary scaffolds; laterals and twigs are renewed in yearly care.

Q2. What is the difference between main, secondary and lateral branches?

A. Thick branches from the trunk are main branches, branches from main branches are secondary scaffolds, and branches from secondary scaffolds are laterals. Secondary scaffolds are also called a-shushi, and “lateral” sometimes means a branch grown from a side bud of a main branch.

Q3. When is the best time to look at the framework?

A. For deciduous trees, winter, when the leaves have fallen and the branch habit can be seen. Winter pruning has building the framework as its main purpose. Evergreens are in leaf all year, so you step under the tree and walk around the trunk looking up to confirm the direction of the main branches.

Q4. Can thick framework branches be cut?

A. A framework branch takes years to restore once cut, so it is kept wherever possible. When it must be shortened, it is not cut off midway but cut back to the fork of a smaller branch that can take over its role.

Q5. What should be done while a tree is young?

A. Select the main branches that will become the framework and arrange them evenly throughout the crown. Of branches growing in a bundle from the same height, keep one, and remove early any branch nearly as thick as the trunk that competes with it.

Sources

– National Institute for Land and Infrastructure Management (NILIM). Guide to Preventing Street Tree Failure, 2nd edition. Technical Note No. 1059, 2019 (citing the Japan Landscape Contractors Association, Street Tree Pruning Handbook).
– Tokyo Metropolitan Government, Bureau of Construction. Street Tree Maintenance Plan. December 2021.
– Tokyo Metropolitan Government, Bureau of Construction. Standard Specification for Street Tree Maintenance (Green Space Management). April 2013.
– City of Yokohama, Road and Highway Bureau. Common Specification for Street Tree Maintenance Contracts. February 2026.
– Tree Care Industry Association. ANSI A300 Part 1: Pruning (summary).
– Bedker, P.J., O’Brien, J.G., Mielke, M.E. How to Prune Trees. USDA Forest Service, NA-FR-01-95, 1995 (revised 2012).
– Gilman, E.F. Pruning Shade Trees in Landscapes. University of Florida IFAS Extension, EP276.
– Hillock, D., Schnelle, M. Pruning Ornamental Trees, Shrubs and Vines. Oklahoma State University Extension, HLA-6415.
– Iowa State University Extension. Pruning Young Trees.
– Lerner, B.R., Daniel, K., Purcell, L. Pruning Ornamental Trees, Shrubs, and Vines. Purdue Extension, HO-4-W.

Masatoshi Nakamura
Jumokui (Tree Doctor), Toshi Landscape Co., Ltd., Tokyo