Bonsai Mold: What is the White Growth on the Plant Soil

  • By: Josh Koop
  • Date: February 28, 2022
  • Time to read: 6 min.

Bonsai trees are one of the easiest plants to take care of. Not to mention that they bring a sense of aesthetic to your home without doing much. Yet, sometimes that look can be tainted a bit by the white spots growing on the bonsai trees and their soil. You might be wondering what exactly that white stuff is. 

The white stuff on your bonsai tree is white mold. It is a sort of fungus that is sustained in the soil of your bonsai tree. They grow when the soil is left damp all the time. 

You might be wondering how much of a threat bonsai mold is to your bonsai tree. In this article, I am going to highlight that along with a few more details as to how to get rid of it. I would recommend reading the whole article so that you are best enabled to take care of your bonsai trees. 

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What Are The White Spots On Your Bonsai Tree?

As mentioned earlier, the white stuff or spots on your bonsai trees are caused by a fungal infection known as bonsai mold or white mold. If you have been taking care of bonsai plants for a long time, sooner or later, you will come across infestations on your bonsai tree. 

The white spots usually start to grow on the tops of the leaves of the bonsai trees. If not fixed, they then spread to the underside of the bonsai trees, to the stems, and then to the roots.

Such spots mostly appear on young bonsai trees, meaning indoor bonsai plants are comparatively more vulnerable to them. 

Understanding If Your Bonsai Has Mold

You might have questions about whether the powdery substance is mold or something else. Sometimes, the white spots on your bonsai plants can also be mineral deposits from the water.

Fertilizers can also crystallize into white spots as the water evaporates. Hence, below are a few common symptoms that bonsai trees exhibit when exposed to mold. 

  • Branches are drooping or wilting 
  • Leaves falling down even though the season does not call for it 
  • Yellow leaves 
  • Leaves are dry or start to fall 
  • The growth of the plant has slowed down 
  • Distorted or discolored leaves or flowers 

Causes Of White Mold On Your Bonsai Trees

Overwatering is the primary reason for white mold on your bonsai trees and soil. They also grow in humid conditions at times. When a healthy bonsai plant receives a lot of water, there is a sense of suffocation in the soil of the bonsai.

This is because the oxygenated spaces, or air pockets, are being overtaken by the excess water molecules. The roots start to die due to the lack of oxygen in the soil. 

In addition, if you sometimes leave out pruned foliage on the bonsai soil instead of taking it out right away, the pruned foliage is prone to infection by mold. This will also contribute to the spread of the mold. 

How Bad Is White Mold For Your Bonsai Tree?

You might feel better knowing that white mold growing on the soil of your bonsai tree is not particularly harmful. It is a very common feat and can be treated quite easily, as you have read above. However, it can be harmful if the plant tissue under the mold is soft. 

A “soft mold” means the mold is inside the bonsai plant instead of being in just the soil. Additionally, if left unattended for too long, the white mold can cause a lot of damage to your bonsai plants. As the mold is the result of overwatering, the surplus of water in the soil can clog the oxygen pockets in the soil. 

The roots of your bonsai plant will weaken and gradually be broken down by the mold. Initially, they turn black and grow soft. In extreme cases, the leaves of your bonsai tree might turn yellow or brownish. They will dry up and fall off. 

In case you are looking for a more insightful demonstration, you can check this video out. 

How To Get Rid Of White Mold From Your Bonsai Tree? 

In most cases, when you see white spots on the soil of your bonsai trees, just scraping off the white powdery substance does the trick. Yet, sometimes you have to go the extra mile when the mold spreads a bit too much. So, below I have provided the instructions on how to get rid of the white mold on your bonsai tree. 

Step 1: Place your infected bonsai plant away from all the other plants and keep it secluded. This will prevent the spread of the infection and cross-contamination. 

Step 2: Remove the bonsai plant from its pot to assess the extent of the damage caused to the root system. 

Step 3: Any fungus-infected branch or root that you see, prune it off. Make sure you have sterilized the tools for pruning, if any, before starting the procedure. Removing them straight from the tree is an extremely effective way of getting rid of the fungus. Also, wipe down any white spots you see on the leaves or the soil.  

Step 4: After the pruning is finished, place the plant in a new pot with a new bonsai soil mix. 

Step 5: Wear a pair of gloves and use a fungicide spray to spray over the leaves. Aim it directly over all the parts of the leaves so that the spray is evenly distributed. The fungicide spray will kill off any remaining bacteria that were not already killed during the pruning process. 

Step 6: Place the bonsai tree in a properly ventilated area with good lighting. 

Step 7: After 24 hours have passed, repeat the process. 

Doing this for 2 weeks consistently can effectively get rid of the white mold. Even if that does not work, you should take your bonsai tree to a specialist or local nursery and enable them to fix the problem. They can also offer expert advice, which can help you in the future. 

Ensuring The Mold Does Not Appear Again

The most essential part of having a healthy bonsai plant is to monitor it regularly. When you do so, the signs of problems are observed earlier. Hence, to prevent white mold from forming again, come up with a routine for your plant and religiously stick to it.

Water the plants once a day but do not overdo it. If you feel that the soil is still a bit wet, skip watering for that moment and wait till the soil is dry again. 

Also, it is important that you spray your bonsai plant with fungicide spray once a week. If you are confused as to which fungicide spray to use, below is a list of some of the best ones. Do read the instruction manual before applying them. 

  • Bayer Insecticide Fungicide Miticide 3-in-1 Insect, Disease and Mite Control, 24 oz 
  • RoseClear Ultra! Gun 2 
  • Mancozeb 

As mentioned, sometimes humid conditions can also lead to mold. As dead leaves and debris surround the plant, the atmosphere around the plant gets humid and moist. This is not ideal for your bonsai as it can lead to various bacteria and mold. Below are a few precautions that you can take. 

  • Use a fan so there is more air movement around the bonsai plant 
  • While spraying or misting, angle them away from the branches or foliage. 
  • It is better to keep branches and foliage as dry as possible because moisture can easily build up in these areas. 

If you have further questions about bonsai plants and fungus infections, you can take a look here.

Conclusion

After reading this article, you should now know exactly what the white stuff on your bonsai tree is. Bonsai plants require extra care and attention at times, but it is all worth it in the end. You will see it is not a particularly difficult task, just one that requires patience. 

I wish you and your bonsai a healthy life ahead!

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