When to do itBC-02

When to Repot Bonsai: Months for 13 Species, How Often, Rootbound Signs and Aftercare

Published 2026-10-22 · By Bonsai Calendar editors

Your guide: KouKnows everything. Sometimes writes things that are wrong. Sorry in advance.Bonsai Calendar editors · Checked against bonsai writers, nurseries and garden product makers: 2026-10-22

Kou

The basic time to repot bonsai is spring, just before the buds start to move. Some species, such as needle juniper, chojubai and satsuki azalea, are repotted at other times.

In this article (16 sections)

In short: when should you repot bonsai?
How does the time to repot bonsai differ by group?
Why do you repot bonsai in spring?
Why are needle juniper, chojubai and satsuki azalea not repotted in spring?
Why do sources give different months for repotting bonsai?
How often should you repot bonsai?
What are the signs that a bonsai is rootbound and needs repotting?
What are the steps for repotting bonsai?
What should you not do in the year you repot a bonsai?
Where should you place a bonsai and how should you water it after repotting?
What should you do if repotting a bonsai goes wrong?
How do you shift the time to repot bonsai for your region?
What terms come up when repotting bonsai?
What else goes with repotting bonsai?
What are common questions about repotting bonsai?6
Sources

In short: when should you repot bonsai?

The basic time to repot bonsai is spring, just before the buds start to move. Some species differ: needle juniper waits until it warms up, chojubai is done in autumn, and satsuki azalea after flowering.

The Omiya Bonsai Art Museum gives the time when trees bud out as the best time to repot. If the tree is healthy, it grows new roots even after its roots are cut back hard.

The trouble is that trees bud out at different times depending on the species. This site turned the care data for 13 species into a table of repotting months.

What this article covers:

Repotting months for 13 species, and why some species are not repotted in spring
How often to repot
Signs of a rootbound tree, and the key steps of repotting
What not to do in the year you repot
Where to place the tree and how to water it after repotting, and what to do if it goes wrong

Repotting
	1	2	3	4	5	6	7	8	9	10	11	12
Japanese black pine
Japanese white pine
Shimpaku juniper
Needle juniper
Japanese maple
Trident maple
Japanese zelkova
Japanese apricot (ume)
Flowering cherry (e.g. Asahiyama)
Satsuki azalea
Chojubai (dwarf flowering quince)
Crabapple (hime-ringo)
Banyan fig (gajumaru)

Source (13)

The months in the table are a guide for lowland Kanto (the Tokyo area). In colder areas shift them later, and in warmer areas shift them earlier.

Here is the table above, grouped by type of tree.

Group	Species	How to think about repotting
Conifers (except needle juniper)	Japanese black pine, Japanese white pine, shimpaku juniper	Spring, when the buds start to move
Needle juniper (a conifer)	Needle juniper	Spring, but only after outdoor temperatures rise
Deciduous	Japanese maple, trident maple, Japanese zelkova	Spring, early, before the new buds extend
Flowering	Ume, flowering cherry, satsuki azalea, chojubai	Differs by species (after flowering or autumn for some)
Fruiting	Crabapple	Spring or autumn. Autumn for trees grown for their fruit
Indoor	Banyan fig	Once it warms up

The key point: the time to repot bonsai is decided by two things: "just before the buds move" and "that tree's weak point".

How does the time to repot bonsai differ by group?

Conifers and deciduous trees are repotted in spring, while flowering and fruiting trees may also be repotted in autumn or after flowering. Deciduous trees start moving early, so they come early even within spring.

Bonsai care calendar by species
Species	Type	Repotting
Japanese black pine	Conifer	Mar–Apr
Japanese white pine	Conifer	Mar–Apr
Shimpaku juniper	Conifer	Mar–Apr
Needle juniper	Conifer	May
Japanese maple	Deciduous	Mar
Trident maple	Deciduous	Feb–Mar
Japanese zelkova	Deciduous	Mar
Japanese apricot (ume)	Flowering	Mar
Flowering cherry (e.g. Asahiyama)	Flowering	Mar, Sep–Oct
Satsuki azalea	Flowering	Jun, Sep–Oct
Chojubai (dwarf flowering quince)	Flowering	Feb, Sep–Oct
Crabapple (hime-ringo)	Fruiting	Mar, Sep–Oct
Banyan fig (gajumaru)	Indoor	May–Jun

Source (13)

Each group has a different reason behind its timing.

Group	What sets the timing	Source
Conifers	Use the force of budding to push out new roots	Omiya Bonsai Art Museum, Kimi's Mini Bonsai Days
Deciduous	Roots grow fast, and the tree weakens if repotted after the new shoots extend	Kimi's Mini Bonsai Days (zelkova, maple)
Flowering	Avoid the flowering period and the season when root disease breaks out easily	Kimi's Mini Bonsai Days (satsuki, chojubai)
Fruiting	Repotting in spring can make the tree drop its fruit	Kimi's Mini Bonsai Days (crabapple)

Trident maple roots grow fast, and the tree easily becomes rootbound. Japanese zelkova weakens if it is repotted after the new shoots have extended.

For deciduous trees, remember "finish before the buds open," and you will rarely miss the timing.

Why do you repot bonsai in spring?

Bonsai are repotted in spring because, before the buds open, cut roots regrow quickly. Cutting the roots is also a technique for keeping the tree from growing large.

The Omiya Bonsai Art Museum names two purposes of repotting.

Purpose of repotting	The museum's explanation
Fix a rootbound tree	When the roots fill the pot, the tree can no longer take up water and nutrients
Keep the tree small	When the roots are cut back, the tree spends nutrients on growing roots again

A bonsai grows in a small container, so its roots have nowhere to go. This is where it differs from a tree in the ground or a garden tree in a large pot.

The same museum repots even a large Japanese black pine over 1 meter tall when it buds out. It explains that even when most of the roots are cut short, a healthy tree grows roots again.

Kou

On repotting day, look at the tips of the buds. When they start to swell, it is time to repot that tree.

The basic rule is to repot bonsai just before the buds move, and to do it on a healthy tree.

Why are needle juniper, chojubai and satsuki azalea not repotted in spring?

Needle juniper is weak to cold, chojubai easily gets a root disease in spring, and satsuki azalea is repotted after flowering. Each species has its own reason.

Repotting
	1	2	3	4	5	6	7	8	9	10	11	12
Needle juniper
Chojubai (dwarf flowering quince)
Satsuki azalea
Flowering cherry (e.g. Asahiyama)
Crabapple (hime-ringo)
Banyan fig (gajumaru)

Source (6)

Species	When to repot	Reason
Needle juniper	After outdoor temperatures rise	Weak to cold. Autumn is possible, but getting through winter is a worry
Chojubai	Autumn first. If in spring, early, before bud break	The bacteria that cause crown gall are active in warm weather
Satsuki azalea	After flowering, or in autumn	It can be done together with pruning after flowering
Flowering cherry	Spring and autumn	Bonsai sources give both spring and autumn
Crabapple	Spring and autumn. Autumn for trees grown for their fruit	Repotting in spring can make the tree drop its fruit
Banyan fig	Once it warms up	An indoor tree that is weak to cold

Crown gall is a disease in which bacteria enter through wounds on the roots and form galls at the base of the tree. Kimi's Mini Bonsai Days says there is currently no medicine that cures it.

The name chojubai contains the word for ume (Japanese apricot), but the tree is a relative of flowering quince. Take care not to repot it in spring as if it were an ume.

Some sources recommend autumn for satsuki azalea, saying that in the hot summers of recent years the roots may not grow out fully. Look after a satsuki repotted in autumn carefully through the winter.

Kou

If you repot chojubai in spring, disinfect your tools and the roots. If you can move the job to autumn, that is safer.

Do not repot every bonsai in spring. Learn the exception species first, and you will not be left wondering.

Why do sources give different months for repotting bonsai?

Repotting months vary with the region a source assumes, the stage of the tree, and whether it is written for garden trees or for bonsai. This site uses the months where bonsai sources overlap.

Here are examples of where the months differ.

Difference	What the sources say
Autumn repotting of Japanese black pine	One bonsai guide allows late summer to early autumn for a finished tree. A garden store guide also allows autumn for pine bonsai
Calendars for garden and potted trees	NHK's plant encyclopedia is written for garden and potted trees. Its repotting months for maple do not overlap with the bonsai sources
Region	Most bonsai guides use Kanto as the baseline

For Japanese black pine, the table shows only spring months. It can also be repotted in autumn, but the sources overlap more in spring.

How the months are chosen is explained in how this site sets its timings.

The months in the table are "the months the sources agree on." It does not mean that every month outside the table is wrong.

How often should you repot bonsai?

Repot young trees at shorter intervals and finished trees at longer intervals. The interval also changes with the species.

Here are the intervals given in the sources.

Species	Young or small trees	Finished or large trees	Source
Japanese black pine	Once every 3 to 4 years	Once every 4 to 5 years	Kimi's Mini Bonsai Days
Pine bonsai	Shorter for young trees	Once every 3 to 5 years	Komeri
Trident maple	Every year	Once every 2 years	Kimi's Mini Bonsai Days
Ume	Once every 1 to 2 years	Old trees once every 2 to 3 years	Kimi's Mini Bonsai Days
Satsuki azalea	Small trees every year	Large trees once every 2 to 3 years	Kimi's Mini Bonsai Days
Chojubai	Young trees once every 2 years	Mature trees once every 2 to 3 years	Kimi's Mini Bonsai Days
Crabapple	Young trees every year	Mature trees once every 1 to 2 years	Kimi's Mini Bonsai Days
Bonsai in general	Not stated	At least once every 3 years	All About (Seikoen)

Pine roots are slow to recover, sometimes taking more than a year. Kimi's Mini Bonsai Days recommends leaving a repotted pine alone for a while.

Deciduous, flowering and fruiting trees grow roots quickly, so their intervals are shorter. Decide the interval by both the guide in years and the rootbound signs in the next section.

What are the signs that a bonsai is rootbound and needs repotting?

The signs are water that is slow to soak into the soil, hard soil, and weakening branch tips. The roots have filled the pot, and water and air struggle to get in.

All About (Seikoen) describes how a tree becomes rootbound like this.

The roots fill the pot and the soil hardens
Water and air struggle to get into the soil
Healthy roots decrease and dead roots increase
Water and nutrients do not reach the branches, and the branches die

Here are the signs you can see from outside, as a table.

What you see	What is happening in the pot	How to check
Water pools on the surface when you water	Roots and packed soil keep the water out	When watering, watch how fast the water soaks in
Drainage was poor the previous year	The soil has broken down and clogged	The black pine guide treats this as the cue to repot
Branch tips die back, buds are weak	Fewer healthy roots are taking up water	At repotting time, take the tree out of the pot and look at the roots

Kou

If you notice a rootbound tree out of season, do not cut the roots; just water more carefully. Wait until the time in the table to cut roots.

The year when both the guide in years and the signs line up is the year to repot.

What are the steps for repotting bonsai?

Repotting a bonsai goes in this order: take it out of the pot, remove the old soil, cut the roots, plant it, and water it. How much root to cut depends on the species and the stage of the tree.

Here are the steps from the Omiya Bonsai Art Museum and All About (Seikoen), put together.

Run a blade between the rim of the pot and the soil, and lift the tree out while loosening the roots
Remove the old, packed soil while loosening the roots
Cut back the long roots (on the bottom as well as the sides)
Fix the mesh over the drainage hole and lay coarse soil on the bottom
Set the tree in place and work soil into the gaps with a chopstick
Tie the tree to the pot with wire
Water thoroughly until clear water runs out of the bottom of the pot

All About says that if the soil is not worked in well enough, the tree can weaken within about 2 weeks. It is important to get soil in between the fine roots.

How much root to cut varies by species.

Species and stage	Guide to root work	Source
Young Japanese black pine	Loosen up to about half of the root ball	Kimi's Mini Bonsai Days
Finished Japanese black pine	Up to about a third. Cutting too much loses the look of age	Kimi's Mini Bonsai Days
Trident maple	Half to two thirds. Roots grow back well even after deep cuts	Kimi's Mini Bonsai Days
Chojubai	Cutting half to two thirds is fine	Kimi's Mini Bonsai Days
Old ume	Keep about two thirds of the soil. Deep cuts make flower buds less likely to form	Kimi's Mini Bonsai Days
Needle juniper	Just tidy the outside and replace the old soil	Kimi's Mini Bonsai Days

For most species the soil is mainly akadama (a granular Japanese clay). For satsuki azalea, the soil is mainly kanuma, which is acidic.

Remember "go easy on pines and needle juniper, cut more on deciduous trees," and you will grasp the difference between species.

What should you not do in the year you repot a bonsai?

In the year you repot, hold off on candle cutting for black pine and on stacking heavy pruning or wiring on top. Also wait to fertilize right after repotting until the roots recover.

What not to do	Species	Reason and source
Candle cutting	Japanese black pine	Skip it in a repotting year or on a weak tree (Kimi's Mini Bonsai Days)
Stacking heavy pruning or wiring on top	Shimpaku juniper	Doing them in the same year tends to bring out juvenile needle foliage (Kimi's Mini Bonsai Days)
Fertilizer right after repotting	All species	The roots are damaged. Wait 2 to 3 weeks and start with a small amount (Kimi's Mini Bonsai Days, Hyponex)
Root cutting after the buds have moved	Crabapple, Japanese zelkova	New shoots wilt, and the tree weakens (Kimi's Mini Bonsai Days)

Juvenile needle foliage is the sharp, needle-like young form of leaf that can appear on shimpaku juniper. It spoils the look, so it is a change you want to avoid on shimpaku.

Candle cutting is a technique of cutting off the new shoots of a black pine so that the second flush of buds evens out the needles. It uses the tree's strength, so do it only on vigorous trees.

Kou

Do not do repotting and candle cutting in the same year. For a black pine, choose one of them for each year.

How to start fertilizing is covered in detail in when to fertilize bonsai. Think of a repotting year not as a year to thicken the tree but as a year to bring the roots back.

Where should you place a bonsai and how should you water it after repotting?

After repotting, keep the bonsai in the shade for a few days and do not let it dry out. Protect weak or small trees in a spot such as under the eaves.

Here are the places and watering given in the sources for after repotting.

Species or situation	Place	Water	Source
Needle juniper	Rest it in the shade for a few days	It dries out easily, so do not let it run dry	Kimi's Mini Bonsai Days
Weak or small Japanese black pine	Under the eaves or in a cold frame	When the inside of the pot is dry. Normally morning and evening	Kimi's Mini Bonsai Days
Chojubai with damaged roots	Under the bench	After the soil dries. Mist the leaves to keep the humidity up	Kimi's Mini Bonsai Days
Crabapple	Keep it out of frost in winter	Not stated	Kimi's Mini Bonsai Days
Satsuki azalea repotted in autumn	In winter, wait longer before putting it outside	Not stated	Kimi's Mini Bonsai Days
All species (right after repotting)	Not stated	Until clear water runs out of the bottom of the pot	All About (Seikoen)

A cold frame (muro) is an enclosure that protects bonsai from winter cold and dry wind.

When watering, watch out both for letting it get too dry and for giving too much. Right after repotting there are few roots, and the tree's ability to take up water is low.

Everyday watering is covered in watering bonsai, and where to keep trees in winter in bonsai winter care. After repotting, the basic rule is to place the tree where its roots are protected from sun and drying out.

What should you do if repotting a bonsai goes wrong?

If repotting goes wrong, move the tree into the shade, water only after the soil dries, and remove the fertilizer. Do not repot it again right away; wait for the roots to recover.

Symptom	Likely cause	What to do
Leaves or new shoots wilt	The roots were cut too hard, or the soil was not worked in enough	Move it under the bench or into the shade, and mist the leaves to keep the humidity up
The tree wobbles	The tree is not tied firmly to the pot	Tie it to the pot again with wire
The leaf color gets worse	The roots are damaged, and the fertilizer is irritating them	Remove the fertilizer for now
Needle juniper suddenly dies back	The roots were cut too hard	Next time, only tidy the outside

Kimi's Mini Bonsai Days also describes resting a chojubai with damaged roots in a covered seedling bed. Keeping the humidity up helps it recover.

The same source says that most sudden die-back in needle juniper comes from forcing the root work. Pine roots are also slow to recover, sometimes taking more than a year.

The basic remedy is to wait, without adding any work that puts more strain on the roots.

How do you shift the time to repot bonsai for your region?

Shift the time later in cold regions and earlier in warm regions. The months in the table are a guide for lowland Kanto (the Tokyo area).

Region	How to shift	What to watch
Lowland Kanto (the Tokyo area)	As in the table	The months in the table
Cold regions and high ground	Shift later	Whether the buds have started to swell
Warm regions	Shift earlier	Whether you can finish before the buds move

Bud movement also shifts with each year's temperatures. Do not decide by the month alone; look at the buds on your own tree.

You can also check which jobs to do this month with the tool where you pick a month and a species.

The month table is the starting point, and the buds on the tree make the final call. This way of thinking works in any region.

What terms come up when repotting bonsai?

Term	Meaning
Repotting	Taking the tree out of the pot, removing the old soil, trimming the roots and planting it again
Rootbound	A state where the roots fill the pot and water and air no longer pass through
Root ball	The mass of roots and soil when the tree comes out of the pot
Bonsai soil	The soil put in the pot. For bonsai it is mainly akadama
Crown gall	A disease in which bacteria enter through root wounds and form galls at the base of the tree
Candle cutting	A technique of cutting the new shoots of a black pine so the second buds even out the needle length
Juvenile needle foliage	The sharp, needle-like young form of leaf that can appear on shimpaku juniper
Cold frame	An enclosure that protects bonsai from winter cold and dry wind
Conifers and deciduous trees	Evergreen conifers such as pines and shimpaku, and deciduous trees such as maples and zelkova

What else goes with repotting bonsai?

Repotting bonsai is tied to the timing of fertilizer, pruning and watering. Go on to the next article for whichever job you want to know more about.

How to start fertilizer after repotting: when to fertilize bonsai
Pruning you should not stack with repotting: when to prune bonsai
Water after repotting: watering bonsai
All the jobs for 13 species in one place: bonsai year calendar

Year calendarHow to Care for Bonsai: A Yearly Calendar for 13 Species, Seasonal Care, and 3 Basics for BeginnersHow to care for bonsai with a yearly calendar for 13 species, from black pine to maple and satsuki. Repotting, pruning and feeding by group, and fixes.

When to do itWhen to Fertilize Bonsai: Months for 12 Species, Why Stop in Midsummer and Winter, Solid vs Liquid, and Fertilizer BurnWhen to fertilize bonsai, by month for each species. Feed in spring and autumn, stop in midsummer and winter. After repotting, solid vs liquid, fertilizer burn.

When to do itWhen to Prune Bonsai: Months for 13 Species, Pinching vs Candle Cutting vs Defoliation, When Not to Cut, and WiringWhen to prune bonsai, by month for 13 species from black pine to satsuki. Pinching, candle cutting and defoliation, when not to cut, wiring and fixing mistakes.

Watering and seasonsHow Often to Water Bonsai: Seasonal Guide for 13 Species, plus Summer Evenings, Winter, Trips and Drying OutHow often to water bonsai, by season for 13 species. Pot size and spot, how much and when, summer evenings, winter, trips, and drying out vs root rot.

What are common questions about repotting bonsai?

What is the best time to repot bonsai?

For most species, spring just before the buds start to move. Needle juniper, chojubai, satsuki azalea and banyan fig differ, as shown in the table.

Check the months for each species in the table above.

Should you repot a bonsai right after you buy it?

Ideally, do not repot it right away; repot it at the first suitable time after you buy it. All About (Seikoen) recommends this.

Check the roots at that point by taking the tree out of the pot.

Can you repot bonsai in autumn?

It depends on the species. Chojubai, flowering cherry, crabapple and satsuki azalea have autumn months too, as shown in the table.

Some sources also allow autumn repotting for a finished Japanese black pine. Protect trees repotted in autumn from the winter cold.

When can you fertilize a repotted bonsai?

Do not feed it right after repotting; wait about 2 to 3 weeks and start with a small amount. This is because the roots are damaged.

This is covered in detail in when to fertilize bonsai.

How much root do you cut when repotting bonsai?

It depends on the species and the stage of the tree. A finished Japanese black pine can be trimmed by about a third, and a trident maple by half or more.

Go easy on pines and needle juniper.

Do you have to repot bonsai every year?

Yearly repotting is needed for trees such as young deciduous trees and small trees. For a finished Japanese black pine, once every 4 to 5 years is the guide.

Decide the interval together with the rootbound signs.

When to Repot Bonsai: Months for 13 Species, How Often, Rootbound Signs and Aftercare

In short: when should you repot bonsai?

How does the time to repot bonsai differ by group?

Why do you repot bonsai in spring?

Why are needle juniper, chojubai and satsuki azalea not repotted in spring?

Why do sources give different months for repotting bonsai?

How often should you repot bonsai?

What are the signs that a bonsai is rootbound and needs repotting?

What are the steps for repotting bonsai?

What should you not do in the year you repot a bonsai?

Where should you place a bonsai and how should you water it after repotting?

What should you do if repotting a bonsai goes wrong?

How do you shift the time to repot bonsai for your region?

What terms come up when repotting bonsai?

What else goes with repotting bonsai?

What are common questions about repotting bonsai?

What is the best time to repot bonsai?

Should you repot a bonsai right after you buy it?

Can you repot bonsai in autumn?

When can you fertilize a repotted bonsai?

How much root do you cut when repotting bonsai?

Do you have to repot bonsai every year?

Sources

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When to Repot Bonsai: Months for 13 Species, How Often, Rootbound Signs and Aftercare

In short: when should you repot bonsai?

How does the time to repot bonsai differ by group?

Why do you repot bonsai in spring?

Why are needle juniper, chojubai and satsuki azalea not repotted in spring?

Why do sources give different months for repotting bonsai?

How often should you repot bonsai?

What are the signs that a bonsai is rootbound and needs repotting?

What are the steps for repotting bonsai?

What should you not do in the year you repot a bonsai?

Where should you place a bonsai and how should you water it after repotting?

What should you do if repotting a bonsai goes wrong?

How do you shift the time to repot bonsai for your region?

What terms come up when repotting bonsai?

What else goes with repotting bonsai?

What are common questions about repotting bonsai?

What is the best time to repot bonsai?

Should you repot a bonsai right after you buy it?

Can you repot bonsai in autumn?

When can you fertilize a repotted bonsai?

How much root do you cut when repotting bonsai?

Do you have to repot bonsai every year?

Sources

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