忌み枝とは──切る枝の見分け方と、あえて残す枝|樹木医が図解(Imi-eda: Branches Japanese Gardeners Remove)

English: Imi-eda — How Japanese Gardeners Identify the Branches to Remove, and the Ones to Keep

Imi-eda (忌み枝) is the Japanese gardener’s collective name for branches that spoil a tree’s form and cause crowding: water sprouts, downward- and inward-growing branches, crossing branches, parallel branches, whorled branches, weak interior branches, trunk sprouts and basal suckers. In this illustrated article, a Jumokui (tree doctor) explains how Japanese gardeners identify the branches to cut, and which ones they deliberately keep, with reference to Japanese public pruning standards and sources from abroad.

This is the third article in our series on the pruning techniques of Japanese gardeners (niwashi and uekiya). In the first article, on sukashi (thinning), I wrote that the branches removed in sukashi overlap with what gardeners call imi-eda. This article is about how to recognize them.

What imi-eda means: the gardener’s word and the official “unwanted branches”

The verb imu (忌む) means to dislike and avoid. Japanese gardeners call the branches that spoil a tree’s form or get in the way of other branches imi-eda, “branches to be avoided”, and these are the first thing they look for when pruning. The word is also used in the bonsai world for branches that should be cut (nippon.com, 2017).

The word imi-eda does not appear in the public pruning standards I have checked. They write fuyo-shi (不要枝, “unwanted branches”) instead. The Tokyo Metropolitan Government’s Standard Specification for Street Tree Maintenance (April 2013) lists, as branches unnecessary for form and growth, redundant branches, basal suckers, trunk sprouts, water sprouts, crossing branches, interior branches and upright branches, among others. The City of Yokohama’s Common Specification for Street Tree Maintenance Contracts (February 2026) illustrates twelve kinds of branch that are unnecessary for growth and obstruct ventilation and light within the crown, and the National Institute for Land and Infrastructure Management (NILIM) illustrates nine in its Guide to Preventing Street Tree Failure, 2nd edition (2019). The names differ, but the branches meant are almost the same.

The many names can be confusing, but the eye that sorts them works along three lines: the direction of a branch, the way branches overlap, and the vigor of a branch.

Reading direction: sakasa-eda and futokoro-eda

The natural habit of a branch is to grow outward from the trunk and obliquely upward. Branches that go against this flow are the imi-eda of direction.

Sakasa-eda (“reversed branch”, also sagari-eda, “hanging branch”) is, in the words of the Yokohama specification, a branch that grows downward or inward, against the tendency to grow outward. The NILIM guide likewise defines it as a branch growing downward or toward the inside. Because it heads into the interior of the crown, the longer it grows the more it collides with other branches.

Futokoro-eda (“bosom branch”) is a small, weak branch in the interior of the crown, close to the trunk. An appended table to a regulation of Kuki City, Saitama, defines it as a thin branch inside the crown with no prospect of growth. It receives little light and, left alone, becomes a dead branch.

Reading overlap: karami-eda, heiko-eda and kuruma-eda

Karami-eda (“entangling branch”, a crossing branch) is a branch that crosses another as if entwined with it. Crossing branches rub against each other as the wind blows and as they grow larger (Alabama Cooperative Extension System, 2020). Where they rub, the bark is worn away and a wound forms. From our experience in the field, wounds where large branches have rubbed together for years are sometimes the point where decay has entered.

Heiko-eda (“parallel branch”, also kasanari-eda, “overlapping branch”) is one of two branches growing in the same direction, one above the other. The upper one shades the lower, and the two compete for the same space. Which to keep is decided by the thickness of each branch, the angle of its attachment and the space around it. It is not a rule that the upper one is cut.

Kuruma-eda (“wheel branches”) are several branches arising like the spokes of a wheel from the same position on the stem (Kuki City regulation). The Yokohama specification describes them as branches of the same age radiating from the place where a cut was made, and they often form where a branch was headed back. From our experience in the field, if wheel branches are left to thicken, their bases crowd together at one point and swell like a knob, and the stem or branch beyond them stays thin. The well-directed branches are kept and the number reduced.

Reading vigor: tocho-shi, dobuki and hikobae

Tocho-shi (water sprout) is a branch that grows abnormally longer than the others and whose tissue is often soft (NILIM guide). Gardeners also call it tobi or tobi-eda, “leaping branch”. It often stands straight up from the back of a large branch, and so overlaps with tachi-eda (“upright branch”), a branch growing upward parallel to the trunk. It shoots through the crown and breaks up the form.

Dobuki (trunk sprouts) are small shoots arising directly from the trunk; hikobae (also yago; basal suckers) are small shoots arising from the base of the tree or from roots near it.

Before they are a matter of form, these three are signals from the tree. The NILIM guide states that heavy pruning produces numerous adventitious shoots, water sprouts and trunk sprouts, and that removing too much foliage in summer induces trunk sprouts. The glossary of Saitama Prefecture’s Street Tree Pruning Manual (December 2020) defines a trunk sprout as “a small branch arising from the trunk because of the decline of the tree”. They are shoots the tree has put out in haste to regain the foliage it has lost.

On a tree where water sprouts or trunk sprouts are conspicuous, we ask why they appeared before we cut. Was the last pruning too heavy? Is there something in the roots or the trunk that is weakening the tree?

Imi-eda, yet not all are cut

They are imi-eda, so cut every one you find: think that way, and you end up weakening the tree.

The Saitama manual, after stating that basal suckers, parallel branches and crossing branches are basically unnecessary, asks that water sprouts, interior branches, upright branches, reversed branches and trunk sprouts not all be removed without thought, because they are sometimes kept to be retrained as normal branches when a tree’s form is being restored. The Yokohama specification likewise says that trunk sprouts and interior branches that spread horizontally or are well directed are to be kept, with the balance of the tree’s vigor in mind, and that branches intended to replace a main or secondary branch in the future are not to be cut.

In the interior of an old branch that is dying back, a single well-directed twig has appeared. From our experience in the field, such a twig becomes the replacement branch a few years later. The name imi-eda is given to the shape of a branch; whether the tree needs that branch or not is decided by looking at the whole tree.

There is also a limit to the amount. The Tokyo Street Tree Maintenance Plan (December 2021) and the NILIM guide state that when evergreens are thinned while in leaf, no more than one third of the whole should be removed, and the USDA Forest Service guide “How to Prune Trees” states that, to avoid unnecessary stress and excessive production of epicormic sprouts, no more than one quarter of the living crown should be removed at a time. A tree on which removing every imi-eda would exceed this amount is worked on over several years. The cut is made at the branch’s origin, just outside the branch collar (see our article on where to cut).

Step back before you cut: the craftsman’s eye for reading branches

Knowing the names of the imi-eda is not enough to prune. Among Japanese gardeners, the work is held to begin, before the shears go in, with stepping back from the tree and walking around it to look at its branching: the line of the trunk, the spread of the main branches, the place in the garden from which the tree is viewed. Change where you stand, and the same branch that looked like an obstruction from one side looks, from another, like an important branch filling a space.

Among gardeners, the names of the imi-eda are taught on site, up in the tree, one at a time. “That one is a sakasa.” “That will turn into a kuruma.” Once a branch has a name, what had looked like a single tangle separates into individual branches. I think the words train the eye.

Sensibility shows in the cutting too. From our experience in the field, when a water sprout is removed at its origin, we choose an angle at which the cut surface cannot be seen from the front, and check that the line of the remaining branch flows naturally. The aim is not a tree from which the imi-eda have been removed, but a tree on which no one notices that work has been done. Sukashi that does not look pruned, described in the first article, rests on these branch-by-branch judgments. Not shearing uniformly by machine, but looking at each branch and removing it by hand: this slow handwork has made the form of Japanese garden trees.

How this corresponds to pruning abroad: for readers outside Japan

Arboriculture outside Japan has ideas that correspond to imi-eda. The International Society of Arboriculture (ISA) calls the removal of dead, dying, diseased, weakly attached and low-vigor branches from the crown “cleaning”. The USDA Forest Service guide lists the removal of crossing and rubbing branches under pruning for health. Tocho-shi and dobuki correspond to water sprouts, hikobae to suckers.

The handling corresponds as well. University of New Hampshire Extension (2021) explains that water sprouts and suckers are a response to stress such as storm damage, root loss or over-pruning, and that if too many are cut off at once they will grow back. This is the same view as the Japanese public standards that say not to remove them all without thought.

There is a difference too. As I understand it, standards abroad select branches mainly for the health and structural strength of the tree. Japanese gardeners lay a further measure over that: the beauty of the branching, the flow of the branches. Reversed branches and parallel branches are disliked for the sake of the tree and, at the same time, for the sake of its form.

One pillar of GREEN MANAGEMENT, the approach of our company, is the integration of scientific knowledge (arboriculture) and field experience. Reading branches through the workings of the tree, and choosing them with the gardener’s eye: I believe that identifying imi-eda is a skill that needs both.

Frequently asked questions

Q1. What are imi-eda?

A. It is the collective name Japanese gardeners use for branches that spoil a tree’s form, get in the way of other branches or cause crowding. They include water sprouts, upright branches, reversed branches, crossing branches, parallel branches, wheel branches, interior branches, trunk sprouts and basal suckers. Public pruning standards call them “unwanted branches” (fuyo-shi); the kinds are shown in the Tokyo and Yokohama specifications and in the NILIM guide.

Q2. Should all imi-eda be cut?

A. Not necessarily. Saitama Prefecture’s Street Tree Pruning Manual asks that water sprouts, interior branches, upright branches, reversed branches and trunk sprouts not all be removed without thought, because they are sometimes kept to be retrained when a tree’s form is being restored. The Yokohama specification also says that well-directed trunk sprouts and interior branches are to be kept.

Q3. Why do water sprouts and trunk sprouts appear?

A. They often appear as a response to heavy pruning or declining vigor. The NILIM guide states that heavy pruning produces numerous adventitious shoots, water sprouts and trunk sprouts. The Saitama manual defines a trunk sprout as a small branch arising from the trunk because of the decline of the tree. Before cutting, we ask why they appeared.

Q4. Why are crossing branches (karami-eda) cut?

A. Because crossing branches rub against each other as they sway in the wind and thicken, and the bark is worn away into a wound. The USDA Forest Service guide also lists the removal of crossing and rubbing branches under pruning for health. A crossing branch is removed at its origin.

Q5. How much can be removed at one time?

A. The Tokyo Street Tree Maintenance Plan and the NILIM guide state that when evergreens are thinned while in leaf, no more than one third of the whole should be removed. The USDA Forest Service guide states that no more than one quarter of the living crown should be removed at a time. On a tree with many imi-eda, they are removed over several years.

Sources

– Tokyo Metropolitan Government, Bureau of Construction. Standard Specification for Street Tree Maintenance (Green Space Management). April 2013.
– Tokyo Metropolitan Government, Bureau of Construction. Street Tree Maintenance Plan. December 2021.
– City of Yokohama, Road and Highway Bureau. Common Specification for Street Tree Maintenance Contracts. February 2026.
– National Institute for Land and Infrastructure Management (NILIM). Guide to Preventing Street Tree Failure, 2nd edition. Technical Note No. 1059, 2019.
– Saitama Prefecture, Road Environment Division. Street Tree Pruning Manual. December 2020.
– Kuki City. Enforcement Regulations for the Ordinance on the Management and Selection of Street Trees, appended table. 2010.
– nippon.com. “Listening to the voices of trees: the world of bonsai artist Kawabe Takeo” (Japanese edition). 24 March 2017.
– Bedker, P.J., O’Brien, J.G., Mielke, M.E. How to Prune Trees. USDA Forest Service, NA-FR-01-95, 1995 (revised 2012).
– International Society of Arboriculture. “Pruning Trees.” TreesAreGood.org.
– University of New Hampshire Extension. “Can water sprouts and suckers be prevented on trees?” 26 February 2021.
– East, C. “Pruning Ornamental Trees.” Alabama Cooperative Extension System, 19 November 2020.

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