A few months after I got my tree a Chinese Elm, the leaves on the bonsai tree turned yellow. It can be pretty disheartening for new enthusiasts and the majority will just assume the bonsai tree is dying, so they stop putting effort in.
When bonsai tree leaves turn yellow, it’s not always due to a health problem. In the colder months, a lot of bonsais, including the Chinese Elm, will have leaves turning yellow and dropping, which is to be expected and within 6 weeks your tree should start re-growing healthy buds. Let’s find out what causes your bonsai trees leaves to turn yellow.
The Time Of Year
The Chinese Elm Bonsai is subtropical, meaning that during the coldest periods in the year it should drop the leaves and enter a dormant period. It’s perfectly normal that when dropping the leaves, they will turn yellow before they fall off. This dormant period should start happening when temperatures are around 15 degrees Celsius. At this point you should be bringing the Chinese Elm inside for the next 6 weeks roughly.
A lot of beginners in bonsai treat watering a bonsai tree like watering a cactus – they just don’t do it. Subtropical bonsai trees such as the Chinese Elm require a lot of attention when it comes to water. If your bonsai is too dry, that would be why your leaves are turning yellow. So, how do you make sure it’s not underwatered?
Push your finger 1 inch down into the soil. If it feels dry, you need to water the bonsai.
Keep a constant check on your Chinese Elm, every day during the periods. When I first started taking my tree seriously it did take a few weeks to really get into the routine of watering properly but once you’re there, you can keep your Chinese Elm healthy without much effort. This is most likely a big reason as to why your bonsai leaves are turning yellow. I have actually put together a full watering guide to ensure you can keep your bonsai tree perfectly watered and the steps you need to follow daily!
Hard Pruning And Wiring
If you undertake a huge amount of pruning or some very structural changes to the tree, sometimes the leaves on the Chinese Elm will yellow in colour. Like plants, a bonsai tree can get stressed by these changes, leading to leaves turning yellow and most likely dropping off.
Don’t prune your Chinese Elm if the tree is unhealthy, only healthy, thriving trees should be pruned back. I would recommend washing your pruning scissors before you start the pruning, to ensure that you don’t spread disease around the tree. It’s also recommended not to prune your tree just after repotting, just let the bonsai have enough time to settle in – keep it watered and getting a lot of light for a short while before you think about pruning. If you’re looking for a good pair of pruning scissors, here is the pair I recently picked up from Bonsai Boy of New York.
There are plenty of pruning tutorials online and video tutorials on YouTube to ensure you prune using a correct technique. I have put together a step by step guide on pruning a bonsai tree, which you may find extremely useful.
When wiring a bonsai, it’s advised to do it in the growing period of the tree and remove the wiring in the same growing season. If you don’t remove the wire, there’s a chance that it will break through the bark and it can lead to your Chinese Elm getting a number of detrimental infections. After any wiring, keep a check on the moisture levels and try to avoid stressing your bonsai tree anymore for a few weeks.
Below I’ve listed a few types of wire to use on your bonsai tree ranging in thickness:
Again, there are a lot of amazing video tutorials on YouTube to guide you in shaping and wiring your Chinese Elm. I have a fairly comprehensive guide to wiring a bonsai tree safely, which is definitely worth a read if you’re struggling with this process.
If you’re trying to grow a Chinese Elm indoors, chances are that the tree isn’t healthy. It’s extremely hard to grow a subtropical bonsai tree indoors as a beginner – unless you’re able to create the perfect growing conditions.
Any plant or bonsai tree can be grown indoors or outdoors, it really makes no difference as long as you’re able to give them exactly what they need to grow and survive. Growing a Chinese Elm indoors would require you to carefully monitor the temperature, humidity and light, which beginners in bonsai would find expensive and difficult to do.
I would highly recommend growing your Chinese Elm outdoors the majority of the year. Since I moved my bonsai outdoors, not once the leaves turned yellow. The majority of problems that could cause your Chinese Elm leaves to turn yellow can be cured by letting your tree live outside. If in doubt about where you should be growing your bonsai tree, have a quick read of my article detailing the perfect placement for a bonsai tree.
Lack Of Light
The Chinese Elm is a very resilient bonsai tree, which is why it is so popular with beginners. One of the hardest things to maintain to keep the bonsai tree healthy is the light.
As Chinese Elm bonsais are subtropical plants, so by nature they’re accustomed to a high level of light. The light required to keep the tree healthy usually can’t be obtained by just placing the tree next to a window or something similar.
Maintaining the light in hot months:
If the temperature is above 15 degrees Celsius your Chinese Elm should be living outdoors, in natural light. Too much direct sunlight isn’t the best for your tree but if you’re monitoring the soil moisture and misting the foliage daily, it’s not a problem. You really shouldn’t have any problems with light levels in the hot months having your bonsai outside – if your Chinese Elm leaves are turning yellow in summer, it’s most likely not due to the lack of light.
Maintaining the light in cold months:
In colder months, it’s obviously a good idea to bring your Chinese Elm inside, as they aren’t used to such cold temperatures and they need time to rest. When you bring a tree indoors, it’s highly recommended to place a fluorescent grow light around 5-10 inches about the Chinese Elm. This additional light will keep the bonsai healthy and will help the bonsai come back to it’s healthy state after the dormant period.
It’s really important to know that the leaves of your bonsai tree turning yellow isn’t always a problem with the health of the tree. In subtropical bonsai trees like the Chinese Elm, it’s very normal to expect the seasonal drop off of leaves. I would recommend doing some research if the tree doesn’t start re-growing after roughly 6 weeks as this could indicate that the bonsai tree has a health issue.
In conclusion then, there are a variety of reasons surrounding why the leaves on your Chinese Elm might be turning yellow. Whilst you’re unable to control the time of year, make sure you’re keeping on top of factors like pruning and watering to ensure your bonsai is in the best health it can possibly be! Whilst some yellowing can’t be helped, most of the time it is completely preventable.