剪定の時期はいつ──落葉樹・常緑樹・針葉樹と花木、植木職人が木の一年で決める手入れの季節|樹木医が図解(Timing: When Japanese Gardeners Prune Deciduous, Evergreen and Conifer Trees)

English: Timing — When Japanese Gardeners Prune Deciduous, Evergreen and Conifer Trees

When to prune depends on where a tree is in its year. Deciduous trees have their framework shaped in winter after the leaves fall; broadleaf evergreens are pruned away from the cold, once their new shoots have hardened; pines are worked twice, with candle pinching in spring and momiage (needle plucking) in winter. Flowering trees are pruned with an eye to when their flower buds form. This illustrated article explains the timing with reference to Japanese public pruning standards and sources from abroad.

This is the eighth article in our series on the pruning techniques of Japanese gardeners (niwashi and uekiya). So far I have written about how to cut, from sukashi (thinning) to eda-nuki (removal cuts). This time the question is when to cut. The same cut, made at the wrong time, can place a very different burden on the tree.

The Timing of Pruning Is Set by the Tree’s Year

Through the year a tree repeats a cycle: opening buds and spreading leaves, making and storing food in those leaves, then dropping its leaves and resting. Because pruning removes branches and leaves, the damage it causes depends entirely on which stage the tree is in.

The basic rule is to prune in the dormant season, when growth has stopped, or when growth is slow (NILIM, Guide to Preventing Street Tree Failure). The guide divides pruning times into three: winter, summer and unscheduled. Unscheduled work covers dead or broken branches and branches obstructing traffic, which are removed without waiting for a season. Dead branches can be removed at any time of year (USDA Forest Service).

Calendar months are only a guide. Even in December, a tree on the Kanto plain is in a different state from one in a colder region, and bud movement shifts with the warmth of the year. I give the months as the sources state them, but the final decision is made by looking at the tree.

Deciduous Trees: Shape the Framework in Winter, Prune Lightly in Summer

The main pruning of deciduous trees is done in winter. Pruning that forms the framework of the whole tree is called basic pruning, or winter pruning, and is carried out in the dormant season (late autumn to early spring) to keep damage to a minimum (Tokyo Metropolitan Government, Street Tree Maintenance Plan). Yokohama’s specification applies winter pruning to trees that have lost more than half their crown’s leaves and sets the period at roughly November to February. For Tokyo’s street trees, zelkova and Somei-yoshino cherry are pruned from about December to February.

Sources abroad explain the advantages of winter in the same way. The USDA Forest Service guide recommends pruning hardwoods not grown for flowers in the dormant season, because the structure is easy to see, wounds close best with the following season’s growth, disease is less likely to spread, and sap flow is minimised. For the gardener, the absence of leaves also makes it easier to decide which branches to remove in large and medium sukashi.

There are exceptions. Maples begin to draw up water from about February, so they are pruned before the end of the year (Tokyo’s maintenance plan). Cut in late winter, they keep dripping sap from the wound; a US university likewise notes that maples and birches can be pruned in midsummer or late autumn to avoid sap bleeding (Purdue Extension).

Summer pruning has a different purpose. Summer pruning (light pruning) is a light treatment carried out only when necessary — when overextended branches disturb the crown, when the crown is too dense, or to reduce wind load before typhoons (Tokyo, Standard Specification). It is done from around the rainy season until before autumn, avoiding the hottest weeks, and heavy pruning is not done (Tokyo’s maintenance plan). Yokohama’s specification treats summer as a poor time that places a large burden on the tree and, in principle, does not prune then except when unavoidable.

Pruned hard in summer, a tree tries to replace the lost leaves by sending out a second flush of shoots and epicormic sprouts from the trunk (NILIM). In summer we leave the outline almost unchanged and only remove a few conspicuous water sprouts or crowded branches.

Flowering Trees: Prune According to When Flower Buds Form

For trees grown for their flowers, the timing is set by when their buds form. Cherries, dogwoods and kobushi magnolias form next year’s flower buds around summer and carry them through the winter, so winter pruning is limited to light thinning and the flower buds are kept (Tokyo’s maintenance plan). Crape myrtle, which flowers on the current year’s shoots, can be pruned in winter.

Many spring-flowering trees are pruned within a month after flowering, before next year’s flower buds form (NILIM; Saitama Prefecture, Street Tree Pruning Manual). The US guide takes the same view: trees that flower in early spring are pruned immediately after flowering (USDA Forest Service).

Cherries need care. Decay fungi enter easily through the wounds, so cutting large branches and heavy pruning are avoided as far as possible (Tokyo’s maintenance plan). The Flower Association of Japan sets the pruning period at November to early March, after leaf fall, and recommends removing branches likely to become a problem while they are still thin enough to cut with secateurs. At our company too, cherries are pruned mainly after leaf fall (cherry pruning time and wound treatment, in Japanese).

Broadleaf Evergreens: Avoid the Cold and Wait for New Shoots to Harden

Broadleaf evergreens such as Japanese white oak (shirakashi), camphor and Machilus keep their leaves and stay active through the winter. Warm-climate species in particular run a high risk of dieback when the wounds are exposed to cold if they are cut in the depth of winter (Saitama manual; NILIM). The period when spring leaves are opening is also avoided. The tree is spending a great deal of energy to unfold its young leaves, and cutting then forces it to produce buds all over again (Saitama manual).

The sources give a range of periods. For Tokyo’s street trees, camphor and Machilus are pruned around June to September, and shirakashi oak around February to March, avoiding the coldest weeks and before new buds break. Yokohama sets the best period for evergreens in early autumn (September–October), with the rainy season (June–July) also acceptable. The Saitama manual says that heavy framework pruning is best done as new buds begin to swell (early to mid April, taking Tokyo as the standard), and that July to September should be limited to light heading and thinning. What all the sources share is avoiding severe cold and the time when young leaves are opening. Even in summer thinning, no more than one third of the whole is removed (Tokyo’s maintenance plan).

Heavy heading cuts after autumn begins are avoided, because the young shoots that grow afterwards often fail to mature before winter and die back in the cold (Saitama manual).

Conifers and Pines: Each in Its Own Way

For cold-hardy evergreen conifers, winter is the right time for thinning and light heading (NILIM). Yokohama likewise sets the same period for conifers as for deciduous trees. The US guide, which says conifers may be pruned at any time, notes that pruning in the dormant season minimises sap and resin flow (USDA Forest Service). Large conifers such as Himalayan cedar have branches removed at their base in winter to tidy overlapping tiers.

Pines have two clearly separate seasons of care. In spring (April–May) the new shoots, called midori (candles), are pinched to balance vigour and the number of branches. In winter, old needles are plucked by hand in momiage. On our sites, momiage is done from November into the new year.

Candle pinching is done before the needles open. A US university also advises removing one half to two thirds of the candles before the needles expand, and warns against cutting pines back to older growth (University of Wisconsin–Madison). Pine buds form only at the tips of the shoots, so a branch cut back to bare old wood will not sprout again.

On a trained pine, the strong central candle is not the only one removed: the two side candles that are kept are also snapped partway so that their lengths match (MLIT Noshiro road maintenance office; Yamanashi Prefecture). Pinching partway shortens the distance between nodes and makes the branch structure finer (Kyoto University, Kamigamo Experimental Station). In my experience, the stronger the candle, the shorter it is left, and weak candles are left longer, so that the vigour of each branch evens out.

Times to Avoid: Spring Bud Break and Early Autumn

The NILIM guide lists four times to avoid: the period when spring leaves open, heavy pruning in summer, pruning in early autumn, and the coldest weeks for warm-climate broadleaf evergreens.

When spring leaves are opening, the tree is using the food it stored over winter to spread them. Cut then, it must produce leaves again from adventitious buds, and if this is repeated the tree may even die (Saitama manual). In the United States too, heavy pruning is discouraged while leaves expand in April and May, when energy reserves are low (Missouri Department of Conservation).

Cut in early autumn, the tree cannot store the food its summer leaves have made, and young leaves pushed out in autumn go into winter and die (Saitama manual). A US university advises against pruning within ten weeks of the first hard frost (Clemson Extension), and autumn wounds give fungi a foothold (UNH Extension).

Reading the Tree, Not the Calendar — The Craftsman’s Sense of Season

Among Japanese craftsmen, the time to prune is not decided by the calendar alone but checked by touching the tree. On a deciduous tree in winter, the gardener pinches the winter buds at the branch tips between the fingers to feel whether they are still tight and firm or beginning to swell. In my experience, once the buds start to move, the way the branches flex changes too. When that happens, heavy pruning is put off until the next winter.

Caring for a garden cannot be planned around a single tree. Pines have their momiage season, deciduous trees wait for their leaves to fall, and each flowering tree has its own time after flowering — every tree in the garden has a different moment. Among craftsmen it has long been the normal way of working to plan a year’s sequence of care tree by tree, and to visit the same garden several times in different seasons.

Flowering time, the movement of buds, the firmness of leaves: the eye that reads where a tree is in its year grows over years of returning to the same trees. Keeping to the right time for pruning is the first consideration we owe a tree, before any question of how skilfully we cut.

Frequently Asked Questions

Q1. When is the best time to prune?

A. It depends on the kind of tree. As a rule: deciduous trees in the dormant season after leaf fall (late autumn to early spring); broadleaf evergreens outside the coldest weeks and the time of young leaves; pines with candle pinching in spring and momiage in winter; spring-flowering trees within a month after flowering.

Q2. Can I prune in summer?

A. Light care is possible. Limit it to removing a few crowded branches or water sprouts, and avoid heavy cuts. Pruned hard in summer, a tree sends out a second flush of shoots and epicormic sprouts, which increases the burden on it.

Q3. When should cherries be pruned?

A. After leaf fall. Cherries form next year’s flower buds around summer, so winter pruning is limited to light thinning. Because decay fungi enter easily through wounds, large branches and heavy pruning are avoided as far as possible, and branches are removed while still thin.

Q4. Why shouldn’t evergreens be cut in winter?

A. Broadleaf evergreens keep their leaves and stay active in winter, so cutting them in the coldest weeks exposes the wounds to cold and risks dieback. Warm-climate species such as camphor and Machilus in particular are not pruned in severe cold.

Q5. What happens if I prune in autumn?

A. Cut in early autumn, the tree cannot store the food made by its summer leaves, and shoots or buds that grow in autumn may fail to mature before winter and die. Autumn wounds also give fungi a foothold, so heavy pruning is avoided.

Sources

– National Institute for Land and Infrastructure Management (NILIM). Guide to Preventing Street Tree Failure, 2nd edition. Technical Note No. 1059, 2019.
– 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.
– Saitama Prefecture, Road Environment Division. Street Tree Pruning Manual. December 2020.
– City of Yokohama, Road and Highway Bureau. Common Specification for Street Tree Maintenance Contracts. February 2026.
– The Flower Association of Japan. Training and Pruning; FAQ on Cherry Trees.
– Bedker, P.J., O’Brien, J.G., Mielke, M.E. How to Prune Trees. USDA Forest Service, NA-FR-01-95, 1995 (revised 2012).
– Clemson Cooperative Extension. Principles & Practices for Pruning Trees. HGIC 1003, revised 2019.
– Missouri Department of Conservation. Basic Pruning Guidelines.
– Lerner, R. Late Winter Recommended for Pruning Chores. Purdue Extension, 2005.
– Russavage, J. To Prune or Not to Prune. UNH Extension, 2025.
– Jull, L. Pruning Evergreens. University of Wisconsin–Madison Extension, XHT1013, revised 2012.
– Ministry of Land, Infrastructure, Transport and Tourism, Tohoku Regional Bureau, Noshiro Road Maintenance Office. R7 Noshiro, No. 96. 12 June 2018 (illustrated guide to candle pinching).
– Yamanashi Prefecture. Greening Consultation (Jumokui Q&A): How to Prune Pines.
– Kyoto University, Field Science Education and Research Center, Kamigamo Experimental Station. Research Forest and Station Report, FY2011 (candle pinching and partial pinching).

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