If your bonsai has started dying or losing leaves after repotting, there might be a few reasons for that. In this post, we discuss all the causes of a dying bonsai after repotting, how to fix Bonsai after repotting, how often to repot Bonsai, replanting aftercare.
There are three main reasons of a bonsai dying after repotting. Those include disease or insect attacks, repotting aftercare issues, wrong soil or wire used, repotting mistakes.
Causes of Bonsai dying after repotting
1. Disease and pest attack
Some pests might live in the soil of your Bonsai, and you would only know when repotting, such as root aphids. Also, make sure to use sanitized scissors or a knife when repotting your Bonsai, to prevent spreading harmful microorganisms.
In general, repotting causes ‘shock’ in your plant, which can weaken its natural defense against diseases and pests. Start with inspecting your bonsai and its soil. Can you see any insects or results of their activity?
Insects can leave some bites, fluff, webs. Check roots, leaves, and stem for any damage, discoloration, and small bugs. The most common Bonsai pests are aphids, spider mites, caterpillars, root aphids, mealybugs.
If your Bonsai tree is getting weaker and you notice something wrong with leaves like discoloration, sudden falling off of immature leaves, and similar, make sure to act quickly. Some pests can be hard to get rid of, so you need to provide good conditions for your Bonsai to fight off disease/pests.
To get rid of insects and pests, use an insecticide like this one. If your notice any white patches on leaves, use a fungicide. Brown marks, or raised yellow spots with discoloration (rust), will also need a fungicide, such as this copper-based fungicide.
Below, you can find common diseases and pests that can affect Bonsai trees and what to do if you notice symptoms.
Leaves rapidly turn yellow and wilt, with discoloration of a stem which is extending from roots?
This condition is due fungal attack known as ‘root rot’. You will need to use a fungicide to overcome this situation. Make sure there is proper drainage available; Otherwise the problem will not go away. Repot your Bonsai into fresh soil with proper drainage.
Wilting of new shoots and branches die back?
Might be due to a fungal disease. A fungicide will be needed. Remove any affected leaves or shoots. Root rot might also cause your new Bonsai shoots to turn black and fall off.
White marks or patches on the upper surface of the leaf:
It is fungal growth on the surface of a leaf, called mildew. It will not only block the sunlight, but also weaken the plant.
This disease mostly attacks when leaves are too wet and the plant stands mostly in water. However, it can also happen with under watered Bonsai. Appropriate fungicide like this and reviewing growing conditions will be a way to go.
Appearance of brown circular marks on leaves and leaf drop:
It is either a bacterial or fungal disease. In this type of situation, remove the affected leaves and treat Bonsai with fungicide. If this condition is not treated, then it will lead to the death of the plant.
The leaves develop yellow or orange spots with discoloration:
This condition is known as ‘rust’. Remove any affected leaves as soon as possible and treat with a fungicide.
The seedling suddenly died without any apparent reason:
Could be due to waterlogged soil and humid conditions. Good soil drainage, good hygiene, and good ventilation will help solve this situation. Avoid overwatering.
An outgrowth on leaves or any part of the plant:
This condition is known as ‘’Galls”. To solve this issue, you have to cut off the affected portion with sanitized knife or scissors. Then spray the open area with a fungicide, to avoid the risk of other diseases.
If when pruning you made any cuts to a tree, or have wounds and cuts on Bonsai due to pests, cover them with a wound paste like this to prevent infection.
2. Improper watering
After repotting, it’s important not to let your Bonsai soil dry out. Mist your Bonsai regularly after repotting to boost growth and take your Bonsai out of shock.
Because of root pruning during repotting, Bonsai get stressed. With fewer roots, you need to make sure to water just enough to help your Bonsai get back to normal quickly.
3. Wrong placement of your Bonsai
Where you place your Bonsai, especially after repotting, is very important.
It is not advised to place the plant in direct sunlight, after repotting. Instead, place it in some shade until new roots develop. Allow some shade, but not total shade, as most Bonsai love to get lots of sunlight.
Also, don’t move your Bonsai around too much. That’s especially true after repotting your Bonsai. Most Bonsai react very negatively to being moved around, even by just a little. Many Bonsai drop leaves when you move them around.
4. Improper fertilization
In the first month of repotting your Bonsai, fertilizer application is forbidden. The fertilizers provide instant nutrition and in the first month of repotting, the plant is still in the stress phase. The roots are developing and adjusting in the pot, so don’t burn the bonsai with fertilizer.
If you have applied enough fertilizer and the plant is suffering, then pour enough water one time so the nutrients will leach out. This trick may help you lessen the effects of a fertilizer.
Organic fertilizer like this is preferred after repotting, as it will be slow-releasing. The development of positive microorganisms in the soil will help your Bonsai grow better as a growth season approaches.
You might also decide to choose a higher nitrogen fertilizer in the beginning to promote foliage growth, but it’s not crucial.
5. Unsuitable soil mixture
The soil mix must provide good drainage and aeration. If soil has poor drainage, then the water will stand in the roots. This leads to the rotting of roots and other diseases.
What is more, you also have to sterilize the soil mixture before repotting. This will help prevent any diseases and pests in the soil.
Each Bonsai tree will need a specific soil mixture. But in general, you will need to use Akadama (more of it required for deciduous trees), pumice like this and lava rock.
6. Wiring issues
An important thing to remember is that you need to do all the wiring before you replant your Bonsai. Bonsai become weaker after repotting, and wiring after repotting will harm your Bonsai and shift its roots.
Wire your pot first, and then you can replant your Bonsai. Wiring after your repot your Bonsai might cause it to weaken and start dying.
7. Environment
Placing your Bonsai in the correct environment is important after repotting. You might need to move your Bonsai somewhere else if it’s not responding well after repotting.
- Place your Bonsai in a suitable environment that is not very hot or cold.
- Avoid any frost or harsh wind. Wind is not good for a freshly repotted bonsai.
- Allow some shade after repotting
8. Mistakes in repotting
Be careful about repotting in the wrong season. This can easily lead to a dying bonsai after repotting.
Repot the bonsai towards the end of the dormant period, in early spring, when it’s only starting to grow. After repotting, keep your Bonsai in comfortable temperatures until it strengthens again and starts to show growth.
Never repot your Bonsai during its growth phase. This might cause leaves to fall out. That’s why the best time to repot is when your Bonsai doesn’t have many leaves.
Make sure it’s early spring, and that temperatures are at around 10 C (50 F) before repotting. Keep your Bonsai at around 20 C (68 F) after repotting while it’s recovering, and starts growing again.
Note on pruning frequency for Bonsai trees
Make sure to be careful with pruning roots when repotting your Bonsai. Pruning too many roots can kill your Bonsai quickly after repotting.
How to know when to repot a Bonsai?
You will need to repot your Bonsai when it becomes root-bound. You will know that your Bonsai needs repotting and is root-bound when you notice poor drainage, rootball coming out of the pot and roots coming out of the drainage holes.
If you notice that your Bonsai is root-bound, don’t repot until spring arrives. This will minimize any further damage to your Bonsai.
How often to repot bonsai?
Repotting of mature Bonsai can be done every 4-5 years. For immature Bonsai which are less than 15 years old – repotting once in 2-3 years on average is optimal.
A slow-growing Bonsai plant can go longer without repotting, as opposed to a fast-growing one. March-April is the best time to repot Bonsai.
The chart on how often to repot various species of Bonsai trees
| Bonsai Plant Species | How often to repot? |
| Trident Maple (Acer buergerianum) | three to five years |
| Japanese Maple (Acer palmatum) | three to five years |
| Amur Maple (Acer ginnala) | three to five years |
| Cotoneaster (Cotoneaster horizontalis) | two to four years |
| Temple Cedar (Cryptomeria japonica) | two to four years |
| Maidenhair Tree (Ginkgo biloba) | one to four years |
| Chinese Juniper (Juniperus chinensis var. sargentii) (Shimpaku) | three to five years |
| Needle Juniper (Juniperus rigida) | three or four years |
| Crab Apple (Malus spp.) | two or three years |
| Japanese White Pine (Pinus parviflora) | three or five years |
| Japanese Black Pine (Pinus thunbergii) | three to five years |
| Satsuki Azalea (Rhododendron indicum) | every tree years |
| Stewartia (Stuartia) (Stewartia) monodelpha | two to three years |
| Chinese Elm (Ulmus parvifolia) | every year or two years |
| Chinese Elm (Wisteria spp.) | two to four years |
| Japanese Grey-Bark Elm/Zelkova (Zelkova serrata) | two to three years |
| Fukien Tea (Carmona microphylla) (Ehretia buxifolia) | two to three years |
| Chinese Hackberry (Celtis sinensis) | every year or two |
| Figs (Ficus spp.) | every two years |
| Privet (Ligustrum sinensis) | every two years |
| Myrtle (Myrtus) | Two years |
| Olive (Olea spp.) | three or four years |
| Pistachio (Pistacia terebinthus) | two or three years |
| Chinese Yew (Podocarpus macrophyllus) | three or four years |
| Pomegranate (Punica granatum) | Early spring |
| Sageretia (Sageretia theezans) | two to three years |
| Serissa (Serissa foetida) | two to three years |
| European Larch (Larix decidua) | four to five years |
| Japanese Larch (Larix kaempferi) | four to five years |
| Sabina Juniper (Juniperus Sabina) | four to five years |
| Bougainvillea (Bougainvillea) | three to five years |
| Australian Pine (Casuarina equisetifolia) | three to five years |
| European Hornbeam (Carpinus betulus) | three to five years |
| Japanese Quince (Chaenomeles japonica) | three to five years |
How to prevent any issues with Bonsai when repotting?
- Use an appropriate amount of water to avoid the waterlogging and compacting of soil, especially in winter
- Check pH levels of the soil and water and correct it if needed. Very acidic or very alkaline soil will harm the bonsai. The water should be within neutral pH and soil should be healthy
- Avoid placing your Bonsai in excessively humid areas, excessive shade, direct sunlight, and spot with too much wind
- Clean the pot and remove any fallen leaves, branches, or debris. They can promote fungal growth and attract insects.
Is my bonsai dying or recovering after repotting?
After repotting, a Bonsai needs around three weeks to recover and adjust itself in its new pot.
However, if your Bonsai shows some abnormal signs like discoloration, red spots, or frequent drying, then you can start looking into it.
Often, if you damage your Bonsai roots when repotting and pruning, your Bonsai can decline even within a few days and might be beyond repair.
Bonsai repot aftercare
After you repot your Bonsai, please note that it will be stressed and is likely to start dropping leaves. That’s especially true for sensitive trees such as Ficus. Because roots are pruned before repotting, your Bonsai might drop leaves at such speed.
After repotting, put your Bonsai in a room with temperatures around 64 F (18 Celsius) and allow it to bounce back and start growing.
Put it somewhere with moderate lighting, but also partial shade, and avoid direct light for a few weeks. Key is not to change its environment too much either.
Don’t worry too much about dropping leaves. With longer daylight hours, more sunlight, your Bonsai will grow new leaves.
Don’t fertilize your Bonsai straight after repotting, wait at least 3-4 weeks to do it. After a few weeks, you can add some organic fertilizer (better for slow release), like this one. Organic fertilizer will help grow beneficial microorganisms in the soil and boost growth.
Another important repot after-care is to make sure that soil doesn’t dry out. Make sure to check water levels regularly. Also, a great help is to mist your Bonsai leaves, this will help it stabilize faster.
Conclusion
Dying of a bonsai after repotting is quite common, especially if you prune roots too heavily and use wrong soil mix. After-care of a freshly repotted Bonsai is also important.
Keep it in a partial shade and make sure to water enough, but never overwater due to freshly pruned roots. Avoid fertilizing for a month and don’t move it around too much.