Mold on Plant Soil: How to Get Rid of Mold on Houseplant Soil

white mold on houseplant soil

White fuzzy mold appears on plant soil due to moisture issues. Over-watering, poor drainage, or poor light can cause mold to appear on houseplant soil. White fuzzy mold on plant soil spoils the appearance of your houseplants but it is less dangerous than it appears. The white mildew-type of fungus is usually harmless. It is also easy to get rid of mold on houseplant soil to help improve your plant’s appearance.

How to get rid of mold on plant soil: The best way to remove the white stuff on plant soil is to repot your plant in sterile soil. If the fungal growth isn’t too severe, you could transfer the plant to a warmer, sunnier location. Additionally, you could use a natural fungicide to kill the mold on houseplant soil.

Thankfully, the unsightly mold on plant soil and around the base of the stems doesn’t harm the plant. However, the appearance of white or gray fungus is a sign that there are issues with the plant care: over-watering, soggy soil, or poor lighting can all affect your houseplant’s growth.

So, it makes sense to get rid of the mold and then resolve the underlying problem to prevent soil mold returning.

In this article, you will learn about the best ways to get rid of mold on plant soil. At the end of the article, we’ll discuss ways to prevent white mildew growing on soil.

Why is there Mold on the Soil of My Plant?

The white fluffy stuff  on the plant soil is most likely a harmless saprophytic fungus. Too much water, poor soil drainage, contaminated potting soil, and a lack of sunlight can all cause fungal problems (mold) on the plant soil. The “perfect” environment for white mold on house plants to grow is dampness and low light.

The mold fungus is made up of tiny microscopic spores, and they start to grow and flourish in certain circumstances. Depending on the cause of potting soil contamination, the mold can vary in color. Here are some types of fungi that can affect your houseplants.

White fungus on soil

The Royal Horticultural Society says that white thread-like growths on dirt are saprophytic fungi. This white fungal growth—also called mycelium—is harmless, even if there’s lots of it. (1)

Yellow fungal mold

Yellow mold growth on plant soil is also a type of harmless saprophytic fungi. You can get rid of it by scraping it off or repotting the plant in sterile potting soil.

Gray mold on houseplant soil

Some types of gray mold can be a kind of fungus called Botrytis. This fuzzy growth is usually found near the soil surface or growing in dense foliage. Gray mold can harm the plant if left untreated.

Sooty mold

Patches of black or dark green soot-like substances could be a sign of scale. These tiny insects can suck the life out of your plant as they feed on the plant’s sap. The sooty mold isn’t harmful to the plant, but you need to get rid of scale insects quickly.

Powdery mildew

Houseplant fungal problems can look like a dusting of flour called powdery mildew. If this fungus problem gets too large, it can affect the plant’s photosynthesis and stunt its growth.

How to Get Rid of Mold on Plant Soil

Killing mold on plant soil requires physically eliminating the fungal growth and changing the potting medium to prevent mold from returning. Let’s look in detail at four ways to get rid of fungus in houseplant soil.

Repot Houseplants to Get Rid of Mold on Soil

It makes sense to repot houseplants if any kind of mold or fungal growth is on or in plant soil. Repotting plants to remove mold gives you a fresh start with your plant. Replacing contaminated soil with sterile soil will immediately get rid of the white stuff and help prevent it from returning.

Of course, you need to ensure that you don’t transfer fungus spores to the new pot. Before repotting, sterilize all equipment you plan to use—pruning shears, knives, or other implements. So how should you repot your indoor plant to eradicate soil mold? Here’s how:

  • Use a damp cloth to remove any signs of white fuzz that’s on plant leaves or stems.
  • Carefully remove the plant from its container and empty all the soil into a plastic bag.
  • Get rid of all the dirt from the roots by putting under running water.
  • Check the roots for any sign of disease and prune as necessary with sterile shears.
  • Take a sterile pot and fill it one-third full with the appropriate sterile potting soil.
  • Put the plant in the container and make sure it’s at the same growing height as before.
  • Fill the pot with the remaining soil and thoroughly water.
  • Water your plant again when the top 1” (2.5 cm) has dried out.

If you plan on using the same pot, it’s critical to sterilize it thoroughly before adding new potting soil. With plastic pots and ceramic pots, carefully wash the pot—inside and out—with hot soapy water. If you have a terracotta pot, it is probably best to discard it and get a new container.

Let Potting Soil Dry Out and Place in Sunlight to Get Rid of Soil Mold

If you don’t want the hassle of repotting a houseplant, you can let the plant soil completely dry out. Fungal growths and mold don’t survive well in dry environments. Also, the sun’s ultraviolet rays kill fungus spores.

To kill mold on plant soil, put your houseplant outside in a sunny location. The heat from the sun and the dry conditions will help to limit or kill off the growth of white mildew. The reason why this method works well for mold is that mold generally lives in the top layer of soil. So, the heat from the sun should dry out the soil quickly. So, you only have to wait until the top 2” (5 cm) has dried.

If white feathery residue remains, you can safely scoop this away with a sterile spoon.

Another way to dry out plant soil to remove mold is to spread out the soil and leave it in the sun. However, because you will have to repot your plant after, it is best just to discard the soil and repot using fresh a potting mix.

Clean Out the Mold

One of the easiest ways to eliminate white mold from plant soil is to remove it. White fuzzy mold only affects the top part of the potting mix. You can use a sterile spoon to remove 2 inches (5 cm) of soil carefully. Just don’t allow any infected soil to fall back into the pot otherwise you will contaminate more soil.

The next step is to remove any evidence of mold from the stems and leaves. Take a damp cloth and gently wipe down all parts of the plant. Cleaning the whole plant helps ensure you remove all spores and traces of white mold.

The next step to get rid of houseplant soil fungus is to treat the plant with an antifungal treatment. Of course, there are many fungicidal sprays you can use. However, rather than fill your home with chemicals, it’s best to use natural fungicide solutions.

Use Natural Fungicide to Eradicate Mold from Plant Soil

Many natural ingredients are naturally antifungal and can help kill white fungus on the soil. The best natural fungicides for killing mold in houseplants are neem oil, apple cider vinegar, cinnamon powder, or baking soda. These can be just as effective at eradicating houseplant soil mold as their chemical counterparts.

Here is how to use natural fungicides on plant soil mold:

Cinnamon—Sprinkle cinnamon powder on the houseplant soil to kill the fungus. You can also work cinnamon into the top layer of soil to tackle your white fungus problem. Some studies show that cinnamon has antifungal, insecticidal, and larvicidal properties. (2)

Neem oil antifungal soil flush—You can use a neem oil solution to flush the soil and help kill off mold in the soil. Mix two teaspoons of neem oil, one teaspoon of dish soap, and half a gallon (2 l) of water. Use to water your contaminated plant thoroughly. Wait until the soil dries before watering again. If necessary, flush with neem oil once a month to prevent fungus growth. Research shows that neem oil has antifungal activity. (3)

The benefit of neem oil is that it helps get rid of fungus gnats on houseplants as well as other insects.

Baking soda—Baking soda can help get rid of fungus when mixed with water and sprayed on soil, leaves, and stems. Mix four teaspoons of baking sold with a gallon (3.7 l) of water. For an even more effective method, use potassium bicarbonate instead of baking soda.

Apple cider vinegar (ACV)—A weak solution of apple cider vinegar and water could help rid your houseplant of fungus. Mix three tablespoons of ACV with one gallon (3.7 l) of water. Spray on plants to help zap fungus spores.

How to Prevent Mold in Plant Soil

The best way to deal with any mold contamination in houseplant soil is to prevent it in the first place. Most types of white furry fungus on houseplant soil are preventable with proper watering techniques and enough sunlight. Even growing plants under artificial lights can help kill plant mold.

Let’s look at the best ways to prevent mold from causing ugly white fuzz on your houseplants.

Water plants properly to prevent plant soil mold

To avoid mold in plant soil, you must water houseplants only when needed. As a general rule, water indoor plants when the top 1” to 2” (2.5 – 5 cm) of soil has dried out. With most types of houseplants, it is better to under-water rather than over-water.

Proper watering is essential because it prevents soil from becoming too soggy. Overly damp soil is usually the cause of white fungus and—more seriously—root rot.

Another tip to prevent white mold fluff is to water thoroughly. This means pouring plenty of water in the pot until it drains out the bottom. Occasional deep watering is more effective than frequent shallow watering. All shallow watering does is to create the perfect environment for the white mold to grow.

Ensure proper soil drainage

Another way to prevent mold on houseplant soil is to make sure water drains properly. Fungus thrives in damp, dark conditions. So, if you have houseplants that sit in waterlogged soil and have dense foliage hanging over the pot, you are bound to get fungal problems.

How can you ensure proper soil drainage to prevent mold from developing? Here is a checklist for white fungus prevention:

  • Make sure pots have drainage holes in the bottom.
  • Never let pots sit in a tray of water.
  • Use the appropriate type of soil for your plant.
  • Work perlite or sand into the potting mix to increase airflow.
  • Let water completely drain from the pot after watering.

Keep houseplants in bright light to avoid white stuff on plant soil

You can help prevent mold growth on houseplant soil by keeping plants in bright, indirect sunlight. Adequate sunlight helps the top part of the soil to dry out and also prevents mold. Light is necessary for photosynthesis, which keeps plants healthy and resistant to disease.

Even though many houseplants grow well in low light, they are more prone to mold problems. So, if you have low-light plants indoors, be extra careful with watering them. Also, the humid atmosphere of bathrooms means that some “shower plants” are susceptible to mold.

Use the proper potting mix

The right potting mix allows excess water to drain away, thus preventing fungal spores from multiplying. Houseplant soil should drain well. To achieve the correct type of soil, use sand, perlite, or orchid substrate mixed through it to create a lighter mix. This type of potting medium doesn’t hold too much moisture.

If you notice that water drains slowly or not at all, you should lighten up the potting mix. This way, you can avoid problems with root rot, mold, and houseplant pests.

Good air circulation helps keep houseplants free from mold

The right potting mix also helps with another mold prevention method—good air circulation. Water that drains well also allows enough oxygen in the soil. However, adequate air circulation is also necessary for the plant itself.

One reason why indoor plants are more prone to fungus than outdoor plants is air circulation. So, it helps to open windows during summertime or have an oscillating fan near houseplants to improve air circulation. However, it’s important to remember that most indoor plants don’t like drafts. So, make sure that they are well away from open windows or doors.

You can help improve plant pot drainage and air circulation by putting a layer of pebbles on the bottom of the pot.

Repot houseplants

Repotting indoor plants helps to get rid of, and prevent plant soil mold. There are several reasons why most houseplants require repotting. These reasons include:

  • Preventing plants from becoming rootbound.
  • Refreshing potting mix with fertile, nutrient-rich soil.
  • Getting rid of contaminated soil and replacing it with sterile soil.
  • Checking roots for signs of disease or rot.
  • Encouraging healthy growth by giving roots more room to grow.

Remove debris from potting soil to prevent mold

Mold on houseplant soil also forms when dead leaves and other organic material is left to rot on it. These decaying bits of plants increase moisture levels in the top layer of your soil. This creates the optimal setting for white mold to grow.

When checking your houseplants to see if they need watering, remove any debris from the soil. This way, you can help to avoid white fuzz from growing around the base of your plants.

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