Why Is My Chinese Elm Bonsai Turning Yellow?

Chinese elms are a popular bonsai, especially for beginners. They are pretty tough and easy to care for, but you can still run into problems with them, one of the main ones being the leaves turning yellow.  

Sometimes yellow leaves are normal, but a lot of the time it means your Chinese elm is suffering from some sort of stress which will need to be addressed or it will only get worse and the tree might die.

(I have an other article that covers some of the same and similar topic areas that you may also find useful – Chinese Elm Bonsai Is Dying? – How To Save It)

You can also follow the development of my tree in my – Chinese Elm Bonsai Progression.

Why Do The Leaves On A Chinese Elm Bonsai Turn Yellow?

The leaves on a Chinese elm bonsai can turn yellow for many reasons, which I am going to discuss below.

Some of these are nothing to worry about and some the reasons are problems you will need to address. If you are noticing your leaves are turning yellow then you should use the information below to try and work out what might be causing it to happen and then work out if its normal, or not.

Chinese Elm Bonsai Can Turn Yellow In Autumn

Chinese elms are semi deciduous, which means they will lose their leaves in winter… but not always.

It really depends on the individual tree and the climate it is in, but you may find your tree does not lose any leaves, or only maybe a couple.

If it is autumn or winter and some or all of you leaves are turning yellow then this is totally normal. This is just nature doing its thing and you do not need to do anything.

You just have to wait until spring and you the new green leaves will appear.

Personally my tree holds on to a lot of its leaves at the start of winter. It may only drop a few in autumn, but by late winter they are all pretty much gone and there will be no new leaves until spring. 

Chinese Elm Bonsai Will Shed Old Leaves

If your bonsai doesn’t drop its leaves over winter, you may find that it will still shed the old leaves at some point throughout the year.

Leaves only have a certain lifespan, so you may find your tree gets rid of them once they are finished with them. This usually happens when there are fresh new leaves that will replace the older ones.

This means you may find some of the older leaves turning yellow and dropping off in spring or summer.

This isn’t anything to worry about. So long as you have plenty of fresh new growth then you tree is fine and it’s just regulating its self and getting rid of some its old leaves.

Inner Foliage Is Dying And Turning Yellow?

If you have a particularly bushy elm tree you may find some of the more inner leaves start to turn yellow.

This can be for two reasons; it can firstly be due to the shedding of old leaves, which I have just talked about above. The older leaves are going to be more towards the centre of the tree and are more likely to be the ones that tree does not want to keep.  

Secondly the problem can also occur from a lack of light. The inner leaves of your bonsai can have their access to sunlight blocked by the outer leaves and cause them to die off.

Usually it is a bit of both that causes this to happen on Chinese elms bonsais. This can be a problem, but it usually isn’t.

Those inner leaves are always going to turn yellow and fall off at some point, so it’s fine if they do. However, you still want light to be able to get light to this area, as there will be dormant buds in there that you will want to grow.

Once your bonsai tree is in the refinement stage, you just need to prune your tree often and this will allow the light to get into the inner structure and activate any buds that might be there.   

So long as you prune often, you have nothing to worry about, any yellow leaves will just be from old leaves shedding.

Chinese Elms Can Get Stressed And Turn Yellow

If your bonsai tree is stressed, then that is not a good thing and this will cause the yellowing of the leaves.

However, there are many things that can stress a Chinese elm and you need to work out what it is, you may also find it can be a combination of stressors, but I will go through all the possible stressors below so you can try and work out what might be happening with your tree.

You will know you have solved the problem when leaves stop turning yellow and new healthy growth is showing.

You will also find that once a leaf has gone yellow, it may be dead. This isn’t always the case, but the chances are that the leaf will fall off.

So long as you see new fresh growth starting to appear on your Chinese elm, then everything should be okay. 

Re-acclimatising Stress

If you have bought a new Chinese elm bonsai tree, especially online, you will find that your tree goes into re-acclimatisation shock. (You can read my experience of – Buying A Chinese Elm Bonsai On Amazon)

The bonsai tree is just panicking as its had a sudden change in environment, which is of course is pretty unnatural for a tree that is supposed to grow in the ground and never move.

A lot of the bonsai nurseries keep their Chinese elms in greenhouses so when they sudden get put in a box and shipped to you, then end up in your garden it’s quite the shock for them.

This usually causes some leaf yellowing, but the tree will quickly adapt and settle into its new home fairly quickly.

You can’t really avoid this, but there is also no real cure. You just have to be patient and care for you bonsai tree while it settles in. 

Watering Stress

Watering a bonsai can seem easy, but it’s not. If you mess this up your tree will eventually die. If the leaves are turning yellow it can be a sign that something is not right with your watering and your tree suffering.

(You can read my guide on how to water a bonsai properly)

Under Watering Your Bonsai

If you do not give your Chinese elm bonsai enough water this can be catastrophic. Your bonsai tree is going to die very quickly without water and the leaves turning yellow can be the first sign of this. The tree is trying to save itself, so it will drop its leaves in order to preserve its water supplies.

If you think you have under watered your Chinese elm (like if you have gone on holiday or forgot to water it for a few days) then you need to correct this quickly by watering your tree, and hopefully you can do this before it dies.  

Over Watering Your Bonsai

Over water takes longer to happen. A few heavy rain showers or just watering your Chinese elm bonsai a lot for one day isn’t going to be a problem.

However, if you are constantly over watering your bonsai tree and it is basically just sat in water all the time, it’s going to start causing it problems. The roots are going to start to rot and then the tree will not be able to take up any water. This means the tree will start to act like it is being under watered, since it can’t actually “drink” anything and of course the leaves are going to go yellow.

If this is happening you need to cut back on the water and try to keep the soil moist, and stop it from being soaking wet.  

Bad Soil Can Affect Watering

Chinese elm bonsai like well draining soil. You need to use good bonsai soil that it is well draining or you will end up in trouble and start seeing yellow leaves.

If you have good bonsai soil the tree will have the right balance of oxygen and water and will be healthy. If the soil is bad, it is probably going to hold too much water, meaning it’s too wet.

bad soil can exasperate the problem of over watering. You may think you are watering an acceptable amount, but if the soil is just holding on to the water, you are going to start seeing yellow leaves from over watering.

If your soil is bad, which it often is with Chinese elm bonsai bought online, then you need to manage this problem until spring. A lot of Chinese elm bonsai are sold in some sort of coco peat soil and this holds too much water.

If you buy your tree in spring you can repot it right away. If it’s not spring you will just have to be very careful and really try and manage your watering and try to keep the soil from not being too wet until you can repot.  

(You can read more about – A General Guide To Bonsai Soil)

Root Problems Can Make A Chinese Elm Bonsai Turn Yellow

Root problems can make the leaves on your Chinese elm bonsai turn yellow.

However, most root problems are cause by the issues I’ve already talked about – too much water and bad soil.

You need to see your bonsai as a whole tree. Everything is interconnected and one problem can actually cause a chain reaction, which is why I said that you might have a combination of stressors that are affecting your Chinese elm.

Problems down in the pot will show themselves through yellow leaves. If you think the main root problem is root rot, you need to either change the soil, or fix the water levels. If it is not spring, then controlling the water is your best option until it is safe to repot the tree

Over Pruning The Roots Can Cause Yellow Leaves

Chinese elms can get pretty gnarly roots and when it comes to repotting it’s very easy to get a little excited. They can take a lot of pruning, but every root you remove will weaken the tree.

This weakness that you have caused can manifest itself in the leaves turning yellow. Basically the tree hasn’t got enough roots to support itself, which makes sense if you have just hacked them all off. This can cause the leaves to go yellow and drop.

So long as you give good aftercare to your tree, it should bounce back and you should see new fresh growth soon. 

(You can read more about – Repotting Aftercare Advice For Your Bonsai)

A Pot Bound Chinese Elm Can Get Yellow Leaves

If you have not repotted your Chinese elm bonsai in a while the pot will probably be totally filled with roots. This means that it can be hard for water to get into the pot. This basically results in the tree being under watered and therefore the leaves turn yellow.

You need to repot your tree in spring so you can actually get oxygen and water into the pot and to the roots.

Until then you need to just manage your watering and basically make sure the root ball is really soaked and just try and get as much water in to the pot as possible.    

Lack Of Light Can Make A Chinese Elm Bonsai Turn Yellow

Chinese elm bonsai need light to grow. If they do not have enough light, they will start to turn yellow and then eventually die.

If you are keeping your tree outside then this should not be a problem. The natural daylight and sunshine will be more than enough to keep your tree healthy.

If you are keeping your bonsai tree inside, then you may find some yellowing.

The only way to correct this is to give it more light. This means a better window, a grow light, or preferably putting it outside.

Too Much Light?

This is rare, but it is possible. Chinese elms love the sun, so too much light should not be an issue, especially if you are watering correctly.

However, they can still get sunburnt leaves, but these usually are more of a brown colour, rather than yellow.  

Pests and Disease Can Turn A Chinese Elm Bonsai Yellow

Chinese elms are pretty tough, but they can still be affected by pests and disease.

This problem will usually manifest themselves in other ways first, but ultimately pests and disease will stress the tree and can cause the leaves to turn yellow.

You just need to check your bonsai trees regularly for signs of trouble and then act accordingly. Don’t ignore it, pests and disease will not go away on its own.

Most things can be treated fairly easily and your tree will recover. If your leaves are turning yellow, you need to act fast as it means the pests must be really upsetting the tree quite a lot.  

Does A Lack Of Nutrients Turn A Chinese Elm Bonsai Yellow?

If you are finding you Chinese elm bonsai is turning yellow it could be form a lack of nutrients.

However, this is very unlikely.

Most people fertilise their trees too much and the fact that we repot trees often and replace the soil, usually means the tree has enough nutrients to keep it healthy.

It is still a possibility though, especially if the tree is has not been repotted in a while and is in a very non-organic soil mix. If you think this is the issue, then adding some fertiliser should fix the problem pretty quickly.

I would make sure it is not another issue first. If you fertilise a sick tree you can overwhelm it and make its problems worse.

If you have only recently bought your Chinese elm bonsai and it arrived very green, but is now turning yellow …This is not from a lack of nutrition. It can take a long time for this type of issue to show and if your tree was green pretty recently, then you have a different issue.

Conclusion

As you can now see, there are a lot of reasons why your leaves can turn yellow on a Chinese elm bonsai. Most times it is going to be harmless, but you still need to check everything to make sure it’s not an issue.

If you notice leaves going yellow then just work your way through the list of potential problems in this article until you think you have worked out what might be causing it, then try and correct things from there.  

If you can keep everything balanced and happy you should not really have any problems. Chinese elms are great trees and they are very easy to care for (You can read my Chinese Elm Care Guide)

(You can also read more about their suitability for bonsai – Is A  Chinese Elm A Good Tree For Bonsai?)