I enjoy growing potted plants in my garden but found that a few of them are growing mold in the potting soil. I wanted to know why this is happening and what I can do about it.

Your potted plant is growing mold because of overwatering. The potting soil contains too much moisture that is encouraging mold growth on the plant. You need to ensure good drainage in the pot and only water the plant when the potting soil is completely dry.

Several other reasons may cause mold growth on your potted plant and I’ve listed them below. I’ve also written steps you can take to get rid of this mold and prevent it from growing in the future.

Why is my potted plant growing mold?

Overwatering

If the water in the potting soil remains for a long time, it will lead to overwatering where the roots are drowning in this excess water. One reason could be the lack of drainage holes in the pot.

Another reason could be the poor quality of potting soil. You may have used garden soil that is dense or contains clay. This will lead to water-logging and drowning the roots. The stress on the potted plant will lead to the invitation of mold on the leaves and foliage.

You need to give sufficient time for the potting soil to dry out between each watering. Otherwise, the humidity in the soil may lead to mold growth.

Too much fertilizer

If you are fertilizing your plant, it could be that the potting soil is over-fertilized and as a result has become acidic.

The excess acidity will encourage mold growth in the potted plant because of nutrients like nitrogen and phosphorus that feed the fungi.

Lack of sufficient light

If you have an indoor plant, you need to be careful with the amount of sunlight it can get especially during fall or winter.

The mold growth may be a result of low-light conditions that are conducive to fungal development.

Poor air circulation

This could be caused due to thick foliage that is blocking the air circulation among the leaves.

It could also happen if too many plants are growing in one pot. Or the potted plants are very close to each other.

Poor air circulation will create a humid environment that encourages the growth of mold on the potted plant.

Poor potting soil

It’s important to use potting soil for your potted plant and avoid using garden soil. This soil is too dense and it may also contain a lot of clay.

These materials don’t allow good drainage of the moisture from the soil which leads to moist conditions. This is the type of environment that encourages mold growth in the plant.

Unwanted debris in the pot

If leaves and debris are lying in your pot, they will start decomposing over time. This will create an environment that is conducive for mold to grow on the soil and the plant.

The decomposition process produces ammonia that encourages fungal growth.

Is mold on my potted plant dangerous?

The mold on the potted plant may harm the plant depending on the type of fungus that’s causing it. Some of them may cause the leaves to turn yellow or brown and fall off.

The mold may cause the leaves to not function as expected and they won’t be able to create nutrients with photosynthesis.

The spores of the mold could also be released in the air and cause allergies to humans and pets.

If you inhale a large quantity of the spores it can irritate your respiratory system. This is especially a problem for people who are already suffering from ailments like asthma, COPD, or other breathing issues.

Some types of molds could produce mycotoxins that are known to cause cancer, liver damage, and other health problems.

How to get rid of mold on the potted plant?

Identify the type of mold

It’s good to identify the type of mold so you can check the impact and how to get rid of it. If the mold is black, it may be a type of fungus called “Botrytis.” Botrytis can cause plants to wilt and die.

If you think this might have happened with your plant then remove all affected parts from around its base. Remove any dead leaves or flowers that are touching other vegetation for them not to spread spores.

Move the plant so it gets good sunlight

The easiest way to get rid of mold is to move the plant to a location that gets plenty of sunlight. The heat will dry up the mold and kill it.

If you’re growing potted plants indoors, it’s best to move them outside at least for a few days till the problem goes away.

Wipe the mold off the plant

If the mold is a type that is just cosmetic it will not affect the plant. It just looks bad on the foliage. You can use a cloth and wipe the mold from the leaves.

I would suggest soaking the cloth in a mixture of 1 part bleach and 9 parts water. This will act as a disinfectant and clean the mold. It will prevent any remaining spores from growing back again.

Cut off affected parts of the plant

If the mold is a type that is infecting the foliage and causing damage, you need to cut off the infected parts. The infected leaves and branches may have turned yellow, brown, or black due to the mold.

I suggest using a bypass pruner that is soaked in rubbing alcohol when you’re cutting the infected parts. This will prevent the spores from spreading to other parts or other plants.

Spray a natural fungicide on the plant

You can make a spray using materials like bleach, vinegar, hydrogen peroxide, or cinnamon. Mix 1 part of the material with 9 parts water and add it to a spraying bottle. Spray it on the affected foliage of the potted plant to get rid of the mold. 

You can also use already available fungicide sprays that contain neem oil or horticultural oil. Make sure to wear gloves and a mask when spraying the fungicide on the plant.

Repot the plant in fresh potting soil

If the mold has infected the potting soil as well, it’s best to get rid of it. You can transplant the plant into a fresh batch of potting soil.

You can reuse the pot after you have cleaned it up after removing the potting soil. Soak the pot in a mixture of 1 part bleach and 9 parts water that will help sterilize it. Keep it in this mixture for at least 1 hour.

Take the pot and rinse it well with water to remove all of the mixture. Now you can add fresh, sterile potting soil to the pot and transplant the plant into this.

How to prevent mold from growing on the potted plant?

Prevent overwatering of the plant

Make sure there are sufficient drainage holes at the bottom of the pot. This helps drain out any excess water and prevent overwatering.

If you are using a saucer under the plant, make sure to throw away the water that collects after watering the plant.

It may be good if you can keep the potted plant on a height by placing stones or gravel underneath. This will help improve the drainage.

Check the moisture in the potting soil before watering it. Stick your finger 1-2 inches in the soil and check the tip of your finger for moisture. Only water the potting soil if the tip of your finger comes out dry.

Prevent humidity near the plant

The major cause of fungus and mold is a humid condition on your potted plant. This happens when there is a lack of air circulation in the foliage.

You want to make sure the foliage is spaced apart to have good airflow. You can cut a few leaves if you feel this is a problem.

Make sure you’re not growing the potted plants very close to each other and give them sufficient space.

Another reason for the humidity is if there is water present in the foliage. Make sure to water only the potting soil. Avoid splashing water on the leaves.

Keep the potted plant clear from debris

Mold prefers to grow in damp places with decaying foliage. So keep the potted plant and soil clean. Remove any dead or fallen leaves and flowers from the pot.

You can be proactive and deadhead the potted plants before the parts fall into the potting soil. Deadhead the flowers and leaves by picking those that are weak or dying.

Ensure the potted plant gets good light

The simplest solution to prevent mold is to keep the potted plant in direct sunlight for several hours. The mold prefers damp, humid conditions that go away with good light.

If you’re growing plants indoors, you can move them outside for a few hours every day to keep mold away. If the potted plant is heavy, you can keep the pot on a moving tray so it’s easier to move around.

If you have a windowsill that gets plenty of sunlight, you can move the potted plant towards it.

Use a sterile potting soil

If the potting soil contains impurities, the mold may find it attractive for nutrients and start developing. So make sure you buy high-quality and sterile potting soil.

Avoid using garden soil for your potted plants as it may already contain fungal spores. And if you really have to, make sure to sterilize the soil before use.

The simplest way to do this is to bake the soil in an oven at 180 degrees for at least an hour to get rid of any fungal spores and impurities.