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Bonsai Leaves Turning Yellow: 5 Reasons Why This Happens

Bonsai Leaves Turning Yellow: 5 Reasons Why This Happens

The term Bonsai literally translates to “planted in a container”. The ultimate goal of this type of plant is to grow a perfect miniature version of any tree.

They are not genetically dwarfed plants. Any type of tree can be used to make a Bonsai. They are created by specific pruning and wiring branches to limit and restrict growth. 


What does it mean when your Bonsai leaves turn yellow?

Bonsai leaves turn yellow if the tree is deciduous. This is the same as any full-sized tree in the autumn. If it is not autumn or it is an evergreen, yellow Bonsai leaves could be related to a care issue. It can be related to nutrition deficiencies, overwatering, cold air, trimming, or stress. There are a few simple ways to determine which one it is. 


1. Natural Yellowing of a Bonsai Tree

If a tree is deciduous, it will turn yellow and shed some of its leaves in the autumn. If your tree is looking yellow and dry in the leaves, determine the time of year.

Is it autumn? If so, it might be going through its natural seasonal change. Caring for these miniature trees is the same as caring for their larger counterparts. They will experience the same changes and a lot of the same stressors. 

Although most evergreen trees do not lose their leaves in the autumn, they do still shed older leaves. These leaves turn yellow and fall off.

If there are just a few leaves turning, then it is likely just the tree going through its natural shedding. If there are many leaves turning yellow, including new shoots, then it is most likely a Bonsai care issue


Common Mistakes When Caring for a Bonsai

There are many possible factors that could affect the leaves of your Bonsai Tree.


Underwatering or Overwatering

The first thing to determine is if you are underwatering your Bonsai Tree. This is the most common reason for their leaves to turn yellow. Bonsai trees need their roots to be soaked but not stagnant to thrive.

Check your Bonsai soil daily to make sure it is getting enough water. Stick your finger in the soil. If it is dry on top, it needs to be watered.

To do this, first, soak the top layer of the soil to make sure that the soil absorbs enough of the water to get to the roots. Then pour water liberally in the entire pot, allowing it to soak in before pouring more.

Too often the water ends up draining from the sides of the pot and missing the roots entirely since the soil is looser there. I always water it until water is coming liberally out of the holes in the bottom.

I check my Bonsai twice a day for moisture. Many Bonsai trees require multiple waterings per day sometimes, depending on the environment and time of year. 

I always use a soil designed specifically for Bonsai trees in a pot with draining holes to ensure proper drainage. If the roots sit in stagnant water, they will rot and are a magnet for parasites. Without proper drainage, it is impossible to tell if you are overwatering until it is too late. 


2. Sunlight

The second biggest reason for Bonsai trees leaves to turn yellow is a lack of sunlight. Like any tree, a Bonsai needs a large amount of sunlight to thrive.

The chlorophyll in the leaves is what makes them green. This is produced by sunlight. A Bonsai needs at least 5 hours of direct or indirect sunlight per day.

Each species is different though, so it is a good idea to know the specifics of the one you are growing. Some trees prefer indirect light while others love bright, direct light. One thing is certain though, any Bonsai without adequate light will struggle to survive. 


3. Trimming or Wiring 

Sometimes when a Bonsai tree is being over-trimmed this will cause stress on the tree and cause it to yellow.

Similarly, if you are using wire on your tree at the time of growth, it may break into the bark and leave the tree susceptible to infection and disease.  Try to make sure that the wire is removed in the same season it is put on to prevent this. 


How do I trim my Bonsai to prevent yellow leaves?

Always trim it when the tree is in perfect health. Prune them only when they are in the dormant stage and use sterile shears.

Don’t prune a Bonsai tree right after an environmental change or when it is newly repotted. If the leaves are turning yellow, hold off trimming it further until the leaves are green and healthy. 



Bonsai trees need to be in an environment that mimics their natural one. If the full-sized version of your tree needs direct sunlight and 70% humidity, then so does the miniature version.

It is really that simple. I find that too often the biggest environmental culprit for Bonsai owners is that they let their trees get too cold. Drafts from vents and air conditioners can impact its vitality as well. 


4. Imbalance of Minerals

Bonsai trees need to be fertilized during the growing season, but it is possible to have too much of one mineral or nutrient in the soil. For example, if the potassium levels are high, calcium will be low.

This can be checked with a soil testing kit. They are available at most gardening stores. I find that when I use a balanced fertilizer specifically designed for a Bonsai tree I have very few issues with it. 


How often should I fertilize my Bonsai to keep it from turning yellow?

The best rule of thumb it to fertilize every 7-10 days in the growing season and once a month in the dormant one. Use a fertilizer specific to Bonsai trees. 


5. Stress

Like most plants, a change in environment or being repotted can cause stress. This situation is usually temporary with the right amount of care.

Whenever you are repotting, make sure to use new soil and a pot that is big enough for the root system. Similarly, if you must change the environment your plant is in, it is a good idea to do it in stages to harden it if possible. 



Bonsai trees are easy to care for with a few simple tricks. It is always a good idea to know the care and environment of larger version of your Bonsai tree to ensure that you are giving it the proper environment for it to thrive. 

Author Bio

Daniel Iseli

Taking care of houseplants and gardening are my greatest passions. I am transforming my apartment into an urban jungle and am growing veggies in my indoor and outdoor garden year-round.

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