Homesteading, Gardening, and Off-Grid Living

Is Mold On Your Soil Good or Bad for Houseplants?

By: Zac Friedman

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If you spot some white, fuzzy-looking growth on the top of your houseplant soil, it’s probably mold. Mold can remove nutrients from the soil, slow plant growth, and even cause disease in your plants. It also doesn’t look very nice. 

There are different types of mold you can find in your houseplants. White mold is mostly harmless. Some types of mold, such as gray mold, can harm your plants. Regardless, it’s best to get rid of it.

In most cases, you can simply scrape the mold off the top of the soil and throw it away. If you have a bad mold problem, you can replace the soil or use a fungicide to get rid of the mold.

In this guide, I’ll explain how to get rid of mold on your indoor plants and prevent it from coming back in the future. Mold is a pretty common problem. Luckily, it’s easy to treat.

How to Get Rid of Mold on Houseplant Soil

How to Identify Mold On Your Houseplants

Mold usually grows on the top of your plant’s soil. It can also grow below the surface.

Mold can grow in different ways. Most commonly, it appears fuzzy in texture. It can also be slimy or powdery.

Usually, the mold found on houseplants is white. It can also grow in other colors including green, gray, pink, orange, or black. Mold can also produce a musty odor. 

If your plants are showing signs of stress, such as yellowing or wilting leaves, or if they just aren’t growing well, it may indicate that you have mold problems. It’s a good idea to inspect for mold in this case. 

How to Get Rid of Moldy Soil

houseplants in a window

1. Scrape it Off the Top

Mold usually forms on the surface layer of soil. To get rid of mold on the top of your soil, you can simply scrape the top layer of moldy soil off and throw it away outside. A spoon is a good tool to use.

This is the best solution if there is just a small amount of mold on the top of the soil. You only need to remove the affected soil. The rest is fine. 

While you’re scraping the mold away, consider wearing a mask so you don’t breathe the mold spores. Chances are, they won’t harm you but it’s a good idea to be cautious, just in case. Breathing mold could cause respiratory problems.

After you’re done, clean the spoon thoroughly. Add a bit of new soil if you need to. 

2. Replace the Potting Soil

If you have a more serious mold problem, the best solution is to replace the potting soil entirely with new, sterile soil. This may be the best choice if you find mold deeper into the soil below the surface. 

Remove your plant from its pot and shake as much soil off the plant roots as possible. Wash out the pot to kill the existing mold spores or use a new pot. Use some bleach or dishwashing soap to clean the pot. Be sure to rinse it out well.

Next, fill the clean pot with fresh soil and re-pot your plant. Use a potting mix that drains well or add some soil amendments to improve drainage. 

3. Use a Fungicide 

If you have a serious mold problem and you don’t want to replace the soil, you can apply a liquid fungicide.

Before applying a fungicide, do a test on a small area to see how it affects your plant. Some plants are sensitive to fungicides. It can be toxic. It can actually inhibit photosynthesis. For this reason, it’s best to try alternative methods before applying fungicide. 

There are some natural fungicides you can try including cinnamon, apple cider vinegar, or baking soda. 

How to Prevent Moldy Soil and Stop Mold From Coming Back

3 Houseplants

1. Improve Soil Drainage

The best way to prevent mold from coming back is to improve the soil drainage. Mold forms on damp soil.

Start by choosing the right container. Choose a pot that has drainage holes. Empty the saucer under the plant after watering. 

It’s also important to choose a potting soil that drains well. To improve soil drainage, you can mix in some vermiculite, peat moss, wool pellets, or another type of soil amendment.

These are porous materials. They allow water to more freely flow through the soil so the soil won’t stay wet for too long. They prevent the plant’s roots from sitting in water. 

2. Don’t Overwater

Only water your plants when the top 1-2 inches of soil feel dry. Mold needs moisture to grow. Excess water promotes mold growth. When the soil is dry, fungus can’t form.

To determine when it’s time to water, simply stick your finger in the soil to feel if it’s damp. When the top layer dries out, it’s time to water. Most plants are fine with this watering schedule. The soil deep in the pot will stay moist.

Another option is to bottom water your plants. Fill a saucer with water then place the pot in it. The plant will absorb water through the drainage holes. This keeps the top layer of the soil dry. For more info on bottom watering, check out this guide. 

3. Make Sure Your Plants Are Exposed to Sunlight

Moving your plants so they get enough sunlight will help prevent mold from growing. Sunlight helps the top layer of soil dry out between waterings. The heat from the sun makes the water evaporate faster.

In addition, UV radiation from the sun helps to inhibit the growth of some types of mold. Mold likes dark and humid areas with stagnant air. 

4. Improve the Air Circulation Around Your Plants

Avoid placing your plants in areas with poor ventilation. Mold doesn’t grow as well in areas where air is circulating. You could open a window near the plant if it’s not too hot or cold outside. You could also mount a small fan near your plants and let it blow across them. Alternatively, you could also use your ceiling fan if you have one. The air doesn’t need to move fast. 

It also helps to space out your plants. Don’t keep them all bunched together with the leaves touching. Good air circulation and spacing out your plants will also help to get rid of excess humidity around them. 

5. Apply a Natural Fungicide

There are some home natural household goods that can act as a fungicide.

Cinnamon is one of the best options. After removing the mold from the surface of the soil, sprinkle some cinnamon on top of the soil. This won’t harm your potted plant at all. As an added bonus, it will smell nice. You will have to re-apply the cinnamon once in a while because it will wash away when you water. 

There are some other natural fungicides you can use including baking soda, dish soap, or apple cider vinegar. These can prevent fungal growth.

You should mix these with water before applying them. 2-3 tablespoons per gallon of water is a good ratio. 

To be safe, you should test these natural products on a small area to make sure they don’t harm your plant. Some plants are more sensitive than others. 

For more info on natural fungicides, check out this great guide.

Houseplants near a window

Why Does Soil Get Moldy 

Mold grows in moist environments. It also grows best on surfaces that aren’t disturbed. It likes areas with poor air circulation. Soil can get moldy for a number of reasons including:

  • Overwatering- One of the most common reasons for mold to form in indoor plants is too much water. When you overwater, the soil stays wet for too long. This creates ideal conditions for mold to grow. Excess moisture will cause mold. Most pants do not require the soil to be wet at all times. Ideally, you should wait until the top inch of the soil is completely dry before you water. 
  • Poor drainage- Mold is more likely to develop if the soil doesn’t drain well because the soil will remain moist for longer. Wet soil is a breeding ground for fungus. Poor water drainage can also lead to root rot. This condition can cause your plant’s leaves to turn yellow or brown. Eventually, it can kill your plant. Proper drainage will reduce the likelihood of mold growth. 
  • High humidity and poor air circulation- Many plants prefer humid environments. This is particularly true of tropical plants. The problem is that excessive humidity can cause the soil to stay moist for too long. When the air stays stagnant, mold spores can also build up. This is the perfect environment for mold growth. Having proper air circulation reduces humidity, which can reduce mold growth. 
  • Organic matter on the soil- Mold feeds on organic material, such as dead leaves that fall from your plants. Removing the fallen leaves from the soil surface can remove a source of food for mold. This can help to reduce mold growth.

Which Type of Fungus Should You Worry About?

The two most common types of mold infestation to find on houseplants are white mold and grey mold. Generally, white fuzzy mold is harmless. It can use up some of your plant’s resources but it probably won’t harm your plant. 

Gray mold can harm your plant. It usually grows on the plant itself, not on the soil. It can give your plant a wrinkly appearance. Gray mold usually has a dusty look. 

Black mold can be a cause for concern if you see it. It can be dangerous. You will want to remove it if you spot it. 

Grey mold and black mold are pretty uncommon on houseplants. White mold is the most common type of mold. 

How to Get Rid of Grey Mold

If you do find grey mold, you need to get rid of it. Over time it will kill your plant if it’s left untreated. To get rid of grey mold: 

  1. Isolate the plant. You don’t want the mold to spread to your other houseplants. Mold contamination is possible. 
  2. Cut off the moldy parts of the plant and throw them away. You want to get rid of all leaf mold. Wash your hands afterward. Be careful not to spread it to your other plants. 
  3. Move the plant someplace dry, well-lit, and with good air movement. It should not be in direct sunlight. These conditions make it hard for mold to grow. 
  4. Use a fungicide. Follow the instructions on the bottle. Test a little area first to make sure it doesn’t harm your plant. Some plants are sensitive. 
  5. Monitor your plant closely over the next week or so to make sure the grey mold doesn’t come back. 

Final Thoughts

Mold can be bad for houseplants. It can use up resources such as nutrients from the soil and water. It can slow plant growth. Some types of mold can harm your plants and even kill them over time. If you spot mold, you should get rid of it. In most cases, you can simply scoop it out of the soil.

Moist, humid, and stagnant environments are the perfect breeding ground for mold. Make sure you avoid overwatering, improve ventilation, and give your plants enough light to avoid mold. 

Mold can also form on an outdoor plant but it’s less common because outdoor plants are exposed to more sunlight and airflow is better. 

Have you experienced mold in your houseplants? How did you get rid of it? Share your experience in the comments below!

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How to Get Rid of Mold on Houseplant Soil

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