How to Get Rid of Mold on Plant Soil: Prevention and Treatment Tips


Mold on  houseplant soil.

Mold on the plant-soil usually appears due to high humidity. If you have this problem then you need to take immediate action. Almost every beginner grower sooner or later faces a similar problem. 

No worries you can get rid of this problem easily and I will tell you how. 

How to get rid of mold on plant soil:

  1. Remove the infected topsoil at the early stage
  2. Water potting soil with citric acid/lemon juice
  3. Transplanting in a new pot with new soil mix
  4. Disinfect the soil in direct sunlight or oven drying
  5. Add natural antifungal agent like charcoal your plant soil
  6. Spray your houseplant and soil with fungicide
  7. Use baking soda mixed with antifungal agents
  8. Sprinkle coal grind on the moldy soil surface

So, it is important to know why mold appears in the soil of a plant pot, how to get rid of it, and how to prevent its new appearance. Keep reading, I have all the answers and solutions to this problem.

Why Mold Appears in The Plant Soil?

Before getting rid of mold in the plant soil, it is necessary to find out why it appeared there. Only after that, you can create such conditions in which the fungus does not even think to reappear.

So, the most common causes of mold:

  1. Poor Ventilation

Insufficient ventilation and high humidity favor mold growth on plant soil. It is most often seen in spring and autumn. This is due to the fact that the room is cold enough, which causes the moisture to evaporate slowly. 

Poor air and water circulation are ideal conditions for fungal growth.

  1. Excessive Soil Moisture

It is normal for a gardener to be afraid of drying out their plant. Therefore they water too often and more importantly incorrectly.  

The main reason for mold in plant soil is excessive watering.

When you overwater your plant, it does not always have time to absorb it in time. Next comes another watering, more and more.

As a result, the constant accumulation of excessive moisture, insufficient drainage, and blockage of the drainage holes in the pot leads to mold development. 

So the mentioned situation creates a favorable microclimate for the development of mold.

Now, Let’s know the influencing factors of growing mold in plant soil:

  • Improper watering of the plant. It causes accumulation of water and increased soil moisture. 
  • The low temperature in the room where the plant grows. 
  • Poor functioning of the drainage system: the holes must match to the size of the tank, otherwise they will clog and the water will stagnate in the soil.
  • Watering with cold water.
  • Poor quality soil.

You can fix this problem as follows:

  • You should water the plant so that water passes through the substrate and does not stay in it. This requires the creation of a quality drainage layer, through which the excess liquid after each watering will go down.
  • Dry air indoors, as well as excessive humidity, is not a favorable condition for indoor plants. It leads to intense evaporation of moisture, which causes salts to reach the ground surface more quickly. Gradually, the ground becomes saline and the plants begin to hurt. To prevent this from happening, keep an eye on the moisture level – it has to be optimal.

 (Source: Bean Production Problems in the Tropics)

Types of Mold

Before knowing the ways to get rid of mold, you have to learn the types of mold. Without identifying the correct types of mold you can not take action to get rid of it. There are quite a few different types of mold:

Black mold

Black mold may appear due to excess moisture in the pots. It may vary in various shades. It is considered the most dangerous species. Therefore, when it appears,  you should take immediate measures to get rid of it. Spores of this mold cause allergies and lead to disruption of the normal functioning of the lungs.

White mold

This is the most common type of mold, which most often appears on the indoor plant soil. You may get confused that mold stains resemble salt patches but differ in their structure. While salt stains have a crystalline structure, the mold has a soft texture that can be easily rubbed with your fingers.

White mold is dangerous to humans and animals. It may cause allergic reactions and a serious infectious disease called mucormycosis.

Efflorescence

As a result of chemical reactions, spots of various shades may form on the plant-soil surface. This has nothing to do with mold and they are called efflorescence. The efflorescences have a negative effect on all soil layers if they penetrate deep into the soil.

Blue Mold

The blue mold is especially dangerous for trees. It has a blue color. And if you are engaged in growing bonsai, it can cause the death of the tree. Since spores can penetrate into the wood and destroy it from the inside.

(Source: University of Illinois Extension

What is the danger of white mold?

In any case, you need to get rid of mold on the soil of a plant pot. However, many beginner indoor gardeners do not fully understand the dangers of plant damage due to mold.

Therefore, you can not allow it to actively fill the space in the pot, and here’s why:

  1. The plant is sick, because mold blocks the access of nutrients to the stems, leaves and flowers.
  2. Oxygen is also blocked to the root system.
  3. Mold can provoke the appearance of various diseases.
  4. Since soil moisture is above normal, the roots of the plant can simply rot.

If you do not take necessary action in time, then the  plant will simply die.

Nevertheless, the old plants can be almost harmless of white mold. If it occurs on the young green plant soil, then you should worry about this. Take action immediately or your plant will simply wither.

Now, lets find out whether houseplant soil mold is harmful or not. Here is a quick useful video:

Mold or fungal infestation changes the metabolic process in the soil. As a result, the plant will not get the required number of nutrients and die in fact from a kind of hunger. In addition, fungus spores can even physically affect the young roots, which causes the withering of the whole plant.

(Source: University of Massachusetts Amherst)

How to Get Rid of Mold in Plant Soil

If the soil in the pot smells of rot and is covered with plaque, change the watering schedule of the plant. You have to reduce the volume of water and also the frequency of watering. 

Some plants do not need frequent watering and feel good in slightly moist soil. Overwatering of such plants will cause their roots to rot due to mold/fungal infection.

If you water the flowers less frequently but abundantly, you will have to loosen the soil. Do this deep enough, but be careful not to damage the roots.

You can get rid of the mold in pot soil without damaging the plant as follows:

  1. Remove the topsoil (if this is not done, the infection will penetrate deeper, the roots will rot and the plant will die).
  2. Dilute citric acid/ lemon juice in a glass of water. Moisten the lower layers of the soil with the prepared liquid (the acidic medium prevents the mold from multiplying).
  3. Replace the removed topsoil with a new one. Add fungal agents to it. It is recommended to add crushed sphagnum (a genus of moss growing in swamps from which peat is produced) and pieces of charcoal to the soil. Their additional property is to filter components for incoming moisture.
  4. Disinfect the soil drying it out in direct sunlight. You can also try oven drying to disinfect the soil. Oven drying is quick and effective.
  5. Mix 8 ml of Liquid Copper Fungicide to 1L water. (A fungicide that effectively fights against diseases of indoor and garden plants). Treat the infected soil with the prepared solution. If the infection has spread to the plant, carefully treat it with the same solution.
  6. To ensure the result of the treatment, loosen the topsoil from time to time (so that the liquid does not stagnate and distribute evenly).

Pro Tips

If the soil in the pot is again covered with white mold, dissolve half a teaspoon of citric acid/lemon juice in a glass of water.  Then water the plant with this mixture at least 2 times a month.

Besides the above mentioned quick steps. Now lets learn about the effective and comprehensive methods to get rid of mold in flower pots.

Backfilling With Moisture-intensive Material

Before the start of “rescue operation” it is necessary to eliminate the main centers of defeat. To do this, you have to remove  the top layer of the ground infected  with the main mold.

If spores have not penetrated deep into the pot, stop panicking and take care of preventing new fungi.

Bulk materials are great for combating mold and preventing fungal reproduction. Perlite, vermiculite, fine expanded clay, river sand have two excellent qualities: moisture retaining capacity and permeability. 

They are able to absorb the excess moisture and contribute to better  aeration of the ground in the pot. It helps prevent stagnation of water, which is a favorable condition for mold to grow.

Cover the surface of the affected pot with one of the bulk materials. For best results, add about 30% pearlite or river sand to the soil at the next transplant. 

Moss sphagnum also has the ability to absorb excess moisture. Place  Pieces of moss on the soil surface to restore the water and acid balance.

Transplanting plants

Transplanting is a quick and efficient way to get rid of mold in plant soil. This is a drastic measure to keep your plant healthy. If you want to free your mind from doubt then go for comprehensive transplanting your plant. 

You should carry out this procedure according to the following rules:

  • Choose a new pot so that it matches the size of the plant.
  • Correctly select the soil, taking into account the type and characteristics of a houseplant.
  • Free the plant from the old soil.
  • Fill a new pot with drainage holes.
  • Make holes in the bottom if none are available.
  • Rinse the roots in a weak solution of potassium permanganate.

If it is not possible to buy or collect new soil, you can disinfect the old one. To do this, you need to remove it from the plant pot. 

And pour it over with steep boiling water. Then warm well in the oven. Wait until the earth cools down, then again plant in a pre-processed pot.

So, you need to move the plant to a new pot. Also, completely remove the old soil and add fresh soil. Select the fresh new soil keeping the goal in mind. 

This selection will depend on type of plant, transplantation rules and more. Before transplanting, find out in advance which humidity level is best for each plant.

Here is a helpful video on how you should transplant houseplants:

After transplantation, you must:

  • Keep an eye on the plant. And, at the first sign of wilting, treat the soil and the aerial parts with bio-fungicides. Check the latest price of bio fungicide here.
  • Fertilize your plant regularly. Because fungus and transplants weakened the plant;
  • Loosen the soil so that the lower layers receive enough oxygen and water does not stagnate.

The use of baking soda

Another very effective and inexpensive way to combat mold in plant pots is normal baking soda. It is better to use it in combination with other antifungal agents.  Since the action of soda is targeted more to the plant itself than to the soil.

Soda solution can help a plant that has already been affected by mold. To do this, add a tablespoon of baking soda and a little detergent or liquid soap to a liter of warm water. Soap promotes the degreasing of leaves and plant stalk, which allows the solution to better stick to the affected areas.

With this mixture, you need to wipe the plant every couple of days. If the result is positive then continue it once every couple of weeks for prevention.

Use Coal As Disinfectant

Coal has not only an absorbent but also a disinfecting element. You have to sprinkle the surface of moldy soil with charcoal.

It will be effective if you grind coal, because the smaller the grinding, the better. You can sprinkle the root neck and the base of the potted plant.

Coal will kill the mold spore and have a beneficial effect on soil conditions. It is useful to add it to the soil not only when mold occurs, but also for prevention.

When you are using coal to eliminate mold, there are several important rules to follow:

  • You must change the coal layer every few days. Absorbing pathogenic spores, it becomes an excellent medium for the reproduction of bacteria and new colonies of fungi.
  • If you use activated charcoal pellets, in no case you  should put them in the pot as a whole. Actively absorbing moisture, the pellet also becomes a breeding ground for mold growth.

Watering The Soil with Special Agents

You can find a lot of antifungal agents in any plant shop or amazon. But in some cases their effectiveness is very questionable.

I have experience in working with farmers and gardeners. From my experience, I can say that potassium permanganate works very effectively to get rid of mold from pot soil. 

Besides perfectly killing various types of spores, it provides necessary potassium to the plants. Potassium is especially needed by young and immature plants. 

Remove Mold from Infected Plant Soil

You have mold in the potting soil of the plant. So, you are looking for a way to remove it completely.

No worries! There is a solution to this problem. And the best part is it’s very easy. I’ll walk you through this step by step process.

  • To do this, you need good-quality soil, a plant container, filtered water, oxalic acid or lemon juice, a colander, and saucepan.
  • Now what to do if you still have the problem in spite of following the water frequency? Well, in this case, you should try replacing the topsoil. I have seen results doing this. You should do this so that the disease does not take root and penetrate plant tissue. 
  • You have to rinse the plant pot with watering. Rinsing it with normal water is not enough. You need to use boiling water to disinfect it completely. Then let the pot dry in the direct sunlight. 
  • Make sure to have a good drainage system in the pot. Clean the drainage hole at the bottom of the pot. Use brick chips or gravels at the bottom to ensure good drainage through the holes. 
  • Now,  you must calcine the new soil on a stove or in an oven. Even purchased soil mix is often infected with mold. It is better if you steam it before using it in the pot. For steaming, pour soil into a colander and place it over a boiling pan. 

This way you can get rid of the fungus or mold from your potting mix soil. The good thing about this method is that the soil will be free from mold in the future. 

Important!

There are some rules to follow when watering your indoor plants. You should not water your plants more frequently. Let the potting soil dry and then water with small quantities. 

Keep the normal water for 1-2 days to let it settle down a bit. Then you use the topwater for your plant leaving the sediment. Now you know how to get rid of the mold in plant soil. 

Soil Disinfection

To rid the earth of infection and mold smell, disinfect it completely. Here’s how to it step by step: 

  1. Separate the infected soil from the roots of the plant.
  2. Move the soil from the plant pot to another container.
  3. Pour boiled water over the soil.
  4. Place the soil on a baking tray and calculate it in the oven.
  5. Wait until the substrate cools down.
  6. Treat the pot with disinfectants (you can also burn it with open fire).
  7. Fill the soil and plant back into the pot.

Chemical treatment

You can also get rid of molds with the help of chemical agents. These chemical agents are available in plant stores and amazon. Before you go for the purchase, you should find out:

  • soil type;
  • How often you watered the plant
  • the characteristics of the plant;
  • the degree of mold development and its characteristics;
  • whether fertilizers were used and which ones.

These facts are very important in the selection of fungicides. Because if it is wrong, the result will be opposite.

The plant may die from an overdose of chemical compounds. Nevertheless, you should prefer organic based antifungal components. 

Such agents make the soil unfavorable for the development of fungal spores. The most common is fundazole. This tool is safe for indoor plants, so they can handle the leaves and trunk.

Be careful!

Using the wrong product can have the opposite effect. In some cases, you can use chemicals to eliminate mold.

You should give preference to organic means that affect the soil in such a way that it becomes not the best place for the fungus to grow.

(Source: University of Minnesota)

Preventing Mold in Houseplant Soil

Mold on the ground can occur for many reasons. Most often, you will find a white variety of mold in houseplant soil.

White mold appears on the surface of the soil if the room is cool enough. For example, you could often see such mold appear in basements or cellars where it is cold and damp. 

The development of the colony begins after the spores get into the ground or on the plant itself. If your room air is highly humid then it will favor fungal growth. Besides, the accumulation or stagnation of water in the pot can be another reason for the mold in the soil.  

A small drainage system in the pot can cause the holes to get blocked. As a result, excess moisture will remain in the root system of the plant. The soil will remain dump and cold which is an ideal condition for mold growth.

Note

White mold is more likely to appear in the soil if it is sufficiently acidic or has many heavy elements in its composition. White mold may appear regardless of the variety of potted plants. For the same reasons, mold may appear on the soil surface in vegetable gardens. 

Here is a helpful video for preventing mold in plant soil. 

In order not to fight against mold in pots, you can prevent its appearance. Here’s how to do this:

  • Clean all the drainage holes at the bottom of the pot; 
  • Installing good drainage using brick chips, gravel, expanded clay; 
  • Instead of frequent small watering carry out watering when the soil gets dry out. 
  • Use filtered water  (tap water is a big NO!); 
  • Carry out regular watering of plants with a weak solution of manganese.

If you do not have access to filtered water, then you can preserve the water for 1-2 days into a jar. At the end of this period, you can water the plants with this water.

Once in month water with 1-2 drops of lemon juice per liter. Instead of lemon, you can use oxalic acid.

Your indoor environment should not be very wet, not too dry. Because dryness also contributes to the formation of mold in a plant pot. But the question is how you can monitor humidity? Get a hygrometer or indoor humidity monitor.

Conclusion

Finding the mold in plant soil in time is the first step to success. It depends on whether the spores have time to penetrate into the earth. To save the flower, use all possible methods I described above. The beauty and health of a houseplant will depend only on proper care.

So, which method are you going to apply to get rid of mold from your houseplant pot? Let me know your thoughts by dropping a comment below.

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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