Repotting shock is a common issue after transplanting bonsai trees. Symptoms include wilting, discolored leaves, and stunted growth. To prevent and mitigate the shock, repot in early spring, water properly, and avoid direct and strong wind.
Bonsai repotting shock defined
What is bonsai repotting shock?
Repotting shock refers to a set of stresses that a bonsai tree undergoes when it is transplanted into a new pot. These stresses include root damage/pruning, change in soil composition, and exposure to a different environment.
Repotting shock can result in a range of negative effects on the tree’s growth, including reduced vigor, leaf drop, and even death in severe cases.
Why does bonsai repotting shock happen?
Repotting shock occurs in recently transplanted trees due to a sudden change in the soil environment as well as damage to the roots. When bonsai trees are repotted, the roots need to be pruned to allow the root system to fit in a small pot and to promote the growth of new fine roots.
Root pruning is necessary for bonsai trees but the tree will be vulnerable to water stress when it has limited root systems to take water in. The lack of sufficient water can make it more susceptible to injury from external factors such as harsh weather, insects, or disease.
This is why repotting shock happens.
Symptoms of bonsai repotting shock
(It is important to note that not all of these symptoms may be present in every bonsai tree experiencing repotting shock.)
Some common symptoms of repotting shock in bonsai trees are as follows.
- Wilting or dropping leaves
- Discolored leaves or leaf scorch
- Canopy thinning
- Stunt growth
Wilting or dropping leaves
Wilting and dropping leaves are common symptoms of repotting shock. New leaves come out but they may start to wilt, which is a sign that the roots are not taking up enough water.
Bonsai trees may also lose some of their leaves after being repotted. This is because the plant is diverting its energy to the roots and is not able to support as many leaves as before. This is why you have to prune the upper part of the tree when you prune the root system.
Discolored leaves or leaf scorch
Leaf scorch is another common symptom of repotting shock for deciduous bonsai trees whose leaves may turn yellow or brown.
For needled coniferous trees, the first symptom of water stress is an overall grey-green discoloration of the foliage. With further water stress, the ends of the needles often turn a light tan color.
Canopy thinning
Trees’ foliage, including leaves, stems, and branches, may become thin and sparse from repotting shock, which leads to reduced overall canopy size.
Stunted growth
Repotting shock may cause overall growth to be reduced, with very short new growth or no growth at all.
How long repotting shock last
The duration of repotting shock in bonsai trees can vary depending on various factors such as how much energy they had before repotting, the extent of root pruning, and how well they are cared for after the repotting.
In general, the initial shock period can last for a few days to a few weeks, during which the tree may show signs of stress such as wilting or leaf drop.
With proper care, the tree should start to recover and show signs of healthy new growth within a few weeks. It is important to note that some trees may take longer to recover than others.
How to avoid repotting shock
While repotting is stressful for your bonsai trees, there are several steps you can take before and after repotting to avoid repotting shock and help their recovery.
Tips you can do before repotting
Here are some tips you can do before repotting to prevent repotting shock in bonsai trees.
Prepare the tree
When you are planning to repot your bonsai tree, make sure to fertilize your tree well to retain vigor the year before so that your tree can endure repotting stress. Unhealthy trees from existing stresses are more prone to repotting shock.
Choose the right timing
Choose the right time to repot your bonsai tree. Early spring, before the growing season starts, is the best time for repotting bonsai trees.
Choose the right soil
Make sure to use soil that is appropriate for your bonsai tree’s species and growth stage. A good bonsai soil needs good water retention, drainage, aeration, adequate soil pH (slightly acidic), and low in nutrition.
Mist the roots
Mist the roots from time to time while repotting to prevent roots from drying out. Roots that are dried out during repotting cause root damage as they are extremely sensitive to dryness.
Watering
Water your bonsai tree thoroughly a day or two before repotting, just in case. If you repot in early spring, your tree is still in the dormant stage and is not taking much water yet. But this will ensure that the tree is well-hydrated and better able to handle the shock of repotting.
Tips you can do after repotting
Here are some tips you can do after repotting to prevent repotting shock in bonsai trees.
Watering
Watering is the single most important thing you can do for preventing repotting shock.
Repotting shock is often caused by the disturbance of a tree’s roots during repotting, which will inevitably occur because you have to prune roots. While your bonsai tree definitely needs water, it does not have the ability to take in much water before its root system has regenerated. That means overwatering and underwatering can be a big problem.
After repotting, give abundant water so that the new soil is saturated with moisture. Then, check the soil moisture level regularly and give water when the soil is half dry. You can put your finger in the soil around the rim of the pot and feel the moisture level. Be careful not to touch the roots when doing this.
At each watering, give abundant water, letting it drain out of drainage holes, and then allow the soil to half dry between watering. Avoid frequent light watering.
When the roots are regrown, you may notice that the soil will dry out sooner than before.
Light and wind
Avoid strong wind as well as direct sunlight for a week after repotting. Place your bonsai tree in a location where it can receive an appropriate amount of but not too strong sunlight. Strong wind is also stressful so put a windshield if necessary.
Refrain from fertilizing
Do not fertilize your bonsai tree immediately after repotting. Wait for at least 2 to 4 weeks before it takes root.
Giving fertilizer can further stress your tree, in addition to repotting stress. Besides, it does not have many roots to take in nutrients. Also, fertilization may result in the growth of more leaves than limited root systems can support.
Trees often do better when they are allowed to recover from the initial shock of transplanting before fertilization. The point here is to wait until the root system recovers and not to facilitate leaf growth or risk further root damage.
How to recover from repotting shock
Repotting is a stressful experience for your bonsai tree and it is not uncommon for the tree to exhibit signs of stress or shock after the procedure.
It may take a few weeks to recover from repotting shock but if you notice your tree isn’t doing well, here are some tips to help your bonsai tree recover from stress and shock after repotting.
Check for root damage and repot again
Gently make a small hole in the soil and check the roots for any signs of damage or bad smell. If the roots are black or smell rotten, the root system is not regenerating as expected.
You can either;
- take out the damaged parts and repot in the same pot or
- leave the root system as it is and repot in a bigger pot,
depending on the season and species.
If it is before summer, carefully prune the damaged roots off and repot the bonsai tree in the same pot using fresh soil. Your tree is undergoing a lot of stress already so be very gentle and do not overdo it.
If it is already summer, it is better to repot the tree in a bigger pot with fresh soil around the roots. This is true when your tree is coniferous species or old. The roots of these trees grow slower and root regeneration takes more time.
I should say that there might be some cases where it is better to leave the tree and wait to see if it recovers. If the damage is too severe, doing nothing is better because the tree can use all its energy to recover from the repotting shock. Adding another repotting shock can kill the tree instead of saving it.
Prune back damaged leaves and branches
If your bonsai tree has damaged branches (die back, etc.), prune them back to reduce the amount of energy the tree needs to put into those areas. Take the yellowing or browning leaves as well. When leaves lose their color, they rarely turn green again and come back to life. These energies are better used to reestablish the tree.
Adjust watering
You may have to adjust the watering schedule. It can be either too much or too little. Make sure you water abundantly and let the soil half dry before you water again.
Provide proper care
Make sure your bonsai tree receives the appropriate amount of light and water and avoid stressing it by limiting its exposure to direct sunlight, strong winds, and extreme temperatures.
It may take several weeks or even months for it to fully recover from the repotting shock.
How to tell recovery from repotting shock
You can tell if your bonsai tree is recovering from transplant shock by observing its growth and overall health.
Signs of recovery include the growth of new leaves, shoots, and roots. The tree should also start to look healthier, with more vibrant color and improved vigor. Another way to tell is by checking the soil moisture. If the soil gets dry faster than before, besides the weather getting warmer, it is a sign the root system is developing nicely.
Again, it is important to be patient and take good care of your bonsai tree until it recovers from the repotting shock, which might take several weeks.
