Why Does My Potting Soil Have Mold? (And How To Fix It)

Last updated on October 23rd, 2023 at 08:34 pm

For amateur gardeners, this sight is a horror: As if from nowhere, mold sprouts on the potting soil of beloved houseplants. Unfortunately, some plants can no longer be saved after this infestation and they die, but usually you can ensure with a few means that they recover quickly. We reveal the best way to deal with potting soil mold in pots – and how to make sure it doesn’t get that far in the first place.

What can I do if potting soil becomes moldy?

First, it’s best to move the flower pot outside so that mold spores can’t spread further into your home. Also, investigate whether other plants in the immediate vicinity are also affected and remove them as well. In addition, avoid skin contact with the fungus and also do not go too far with your face to avoid inhaling the spores. It is best to work with gloves and possibly even a mouth guard.

Why Does My Potting Soil Have Mold? (And How To Fix It)

Then remove the infested soil by completely loosening it from the root ball of the plant and pour it into a garbage bag. Pack it well and dispose of it in the household waste. Then clean the roots thoroughly under running water.

Your little plant should then not only get fresh soil, but also a new pot to be on the safe side.

Home remedies for particularly stubborn mold infestation.
Unfortunately, it can happen that the once infested potting soil relapses and molds again and again. So that you do not have to cope with a big repotting action every time, you can then also help yourself with the following home remedies:

  • Tea tree oil as a fungus fighter: mix it into the watering water or place cloths soaked with it on the potting soil – this can put the mold in its place.
  • Proceed with activated charcoal: Grind some up and sprinkle it on the soil. This fights acute outbreaks and can prevent more.
  • Cinnamon as an effective remedy: Just like activated charcoal, sprinkling the soil with cinnamon can also kill the spores.
  • Liverwort extract as an anti-fungal: Mix the extract with water in a ratio of one to ten and spray it on the affected areas of soil.
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Also, in case of hardship, it may be helpful to take a closer look at the soil in question or the plant’s environment: Are there possibly other sources of mold nearby? Is the watering can perhaps contaminated? Or was the soil already infested in the packaging? All these can be reasons for repeated mold growth on your plant.

In addition, ventilate the entire apartment daily with open windows and doors and avoid room temperatures below 18 degrees and humidity levels above 60 percent. It is also best to avoid excessive temperature fluctuations between individual rooms.

Prevention tips: How do I prevent mold on potting soil?

To prevent mold spores from forming in the future, keep the following tips in mind while planting your pots:

Add a so-called soil activator to the potting soil, which will keep your substrate healthy.
Alternatively, you can loosen the soil with coconut fiber substrate or coco humus – it has a mild fungicidal effect, i.e. it kills fungi.

Adding bird sand as the top layer of growing medium also acts as a mold barrier.
In general, pay attention to the quality of your soil and invest in products without peat – these do not mold as quickly.

Make sure you have adequate ventilation indoors and enough light in your plant location.
Rather than watering infrequently and generously, water more frequently in small amounts.
Avoid waterlogging and make sure that water can drain away, for example, through a layer of clay shards in the pot.

Loosen the soil and thereby allow better aeration of the substrate.

How dangerous is moldy potting soil for health?

Not only for houseplants, but also for your own health, contact with fungal spores can be harmful in the long run. If people or animals regularly come into contact with it, gastrointestinal complaints, headaches, fever, respiratory diseases or allergies can be favored by it. While it usually takes more than a single, infested flower pot, the spores can quickly spread further – in addition, people who suffer from asthma or a weak immune system may experience symptoms of illness more quickly. Therefore, avoid a mold outbreak not only for the sake of your plants.

Perhaps also interesting: how to fight mildew on roses naturally and prevent it.

How can I tell if it is mold spores?

Not everything that looks like mold actually is: lime deposits, for example, look similar and should not be confused with it. They too are whitish and rather unsightly, but not harmful. Unlike fungal spores, they are comparatively dry and crumbly and also do not smell unpleasant. Mold, on the other hand, can also have green or brownish spots, in addition to appearing fluffy and smelling musty-musty. However, don’t get too close to it to check the smell, because you might inhale its spores.

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Potting Soil Mold How The Fungal Infestation Occurs And What You Can Do About It

Potting Soil Molds: What you can do now: While watering your flowers, you discover that a white coating is covering the soil of your staghorn fern. The next day, the potting soil of your green lily also shows clear white traces. Mold alert! If potting soil becomes moldy, immediate action is called for, because mold spores lead to numerous diseases.

Why Does My Potting Soil Have Mold? (And How To Fix It)

Fungal spores are everywhere. Potting soil is an organic material that is an ideal breeding ground for fungi. However, when a coating of mold covers the soil in your flower pots, alarm bells start ringing. This coating releases millions of spores into the air you breathe. People develop allergies and respiratory problems in rooms contaminated with mold spores. The spores settle in damp corners and lead to mold in the walls.

It’s best not to let it get that far in the first place. As a precautionary measure against mold, you should consider the following points:

  • Clay pots prevent mold growth because moisture can evaporate through the porous wall.
  • Loosen the top layer of soil on your houseplants once a week with a fork.
  • Mix commercial potting soil with some sand to prevent moisture buildup.
  • A thin layer of sand over the potting soil will prevent wet surfaces.

Why does the soil in the flower pot mold?

Mushrooms need two things to multiply:

  • Heat
  • Humidity

A warm home is the perfect temperature for mold. When moisture builds up in flower pots, molds quickly multiply en masse. They can appear overnight and spread in a flash.

Remove moldy potting soil immediately

The only measure against moldy potting soil is repotting. Before you start this action, it is recommended to test. Is the coating actually mold? Sometimes drying fertilizer or lime in the irrigation water leaves white edges on the soil. Rub a piece of the coating between your fingers. If you feel small crystals, the white coating is not mold.

To repot your flowers if the soil is moldy

Before repotting, please get high-quality potting soil and possibly new flower pots. You can also mix potting soil yourself. If possible, move the affected plants outdoors. Lift the root ball out of the pot and remove the soil. To be safe, you can rinse the root ball to remove any remaining contaminated soil. If you don’t have a garden hose, a large tub will do the trick.

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Install drainage in the flower pot.

You can reuse the old pot. However, thorough scrubbing and a vinegar rinse are necessary to prevent new fungus. Install a drainage system in the flower pot to prevent waterlogging. Cover the drainage hole with a piece of clay. Over it, add a layer of porous material, such as expanded clay, gravel or coarse sand. Following this, place your clean plant over the drainage and fill the flower pot with new soil. Do not press the soil too tightly into the pot so that the roots can breathe.

Potting soil: differences in quality

Cheap potting soil is more susceptible to fungal attack than expensive goods. The reason: it consists largely of compost, an exceedingly organic product. Black peat in these products is usually finely ground. In a flower pot, this causes the soil to compact. Under these conditions, accumulated moisture promotes mold growth. High-quality potting soil contains small pieces of bark and wood fibers that provide a loose consistency. If you want to know exactly what is in your potting soil, mix the soil yourself.

Important: Even if the soil doesn’t mold, you should repot your houseplants regularly, replacing the soil as you go.

Water houseplants sparingly more often

After you have eliminated the mold, it is recommended that you critically rethink your watering technique. Experts say that in Europe many houseplants drown. Water according to the motto: less is more. Gardeners advise watering plants a little more often than putting the flower pot under water once a week. Before you water, check each plant to see if the surface of the soil is moist. If it is, do not water.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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