Homesteading, Gardening, and Off-Grid Living

How to Get Rid of Yellow Mold or Fungus on Soil

By: Zac Friedman

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There are many different types of yellow mold and fungus that you could find growing in your houseplants or in your garden. Most types of mold are harmless. Still, if you spot some yellow mold growing on your soil, it’s best to get rid of it. Some molds can remove nutrients from the soil, slow plant growth, and even kill your plants. Mold can also be harmful to pets and people in your home. Of course, it also doesn’t look very nice.

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 use a fungicide to get rid of the mold. If the mold is in houseplant soil, you can replace the soil and re-pot the plant.  

In this guide, I’ll explain how to get rid of yellow mold or fungus on your soil and prevent it from coming back in the future. Yellow mold is a pretty common problem. Luckily, it’s fairly easy to treat.

How to Get Rid of Yellow Mold on Plant Soil

What is Yellow Mold?

There are many different types of yellow mold. Some of most common types of mold you’re likely to find is are slime molds. These tend to be yellowish in color. One common variety is called Fuligo septica. This is sometimes referred to as ‘dog vomit slime mold’.

Mold can grow in different ways. It can appear fuzzy, slimy, or powdery in texture. Yellow mold is often slimy. It usually grows on the top layer of soil. It is generally harmless and usually goes away on its own when the conditions change. 

A yellow slime mold

There are also some yellow types of mushrooms that can grow on your soil. One variety is Leucocoprinus birnbaumii (also known as Lepiota lutea). These are a type of yellow mushrooms that are commonly found growing on houseplants. In fact, they’re sometimes referred to as the ‘yellow houseplant mushroom.’ These are usually around 3-8 cm tall. They have a bell or oval shape, depending on their age. The yellow color often fades as these mushrooms age. 

Mold and mushrooms grow best on soil that is moist, dark, and lacking oxygen. These are common on soil that has mulch that hasn’t been composted. Particularly bark, wood chips, and leaves. 

In most cases, yellow mold or fungus on the soil of your houseplants or in your garden is harmless. It can actually be beneficial for your plants. Some fungus helps break down dead organic matter. Some types of fungus can actually draw nutrients down into the soil.

Of course, there are also some harmful types of fungi. Yellow mold also doesn’t look very attractive. You may want to remove it, even if it isn’t harming your plants. 

How to Get Rid of Yellow Mold on Soil

Scrape the Mold Off the Top of Your Soil

Yellow mold usually forms on the surface layer of the soil. It doesn’t grow too deep. You can simply scrape the top layer of moldy soil off, put it in a bag, and throw it away. A hand trowel is a good tool to use. This is the best way to deal with mold if there is just a small patch on the top of the soil. 

While you’re scraping the mold away, it’s a good idea to wear 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. Also, don’t put the moldy soil in another part of your yard because it could spread mold spores and cause more mold to grow.

There is a chance that the mold will come back if you don’t find out what is causing it. This is more of a temporary fix. You will want to modify the soil conditions to make sure the mold doesn’t return. 

Replace the Potting Soil

re-potting a plant

If you have a serious mold problem that won’t go away, the best solution is to replace the potting soil with new, sterile soil. This is the best choice if mold keeps coming back after you scrape it off the top. Replacing the plant’s soil should get rid of the fungus. 

Start by removing your plant from its pot and shaking as much soil off the roots as possible. Next, use water to wash as much soil off the roots as you can. There could be spores on the plant itself. If there are any moldy spots on the plant itself, cut them off. It’s also a good idea to apply a fungicide to the plant to help kill the spores. Also, be sure to bag the old potting soil and throw it away. You don’t want it re-contaminating your indoor plants. 

Next, wash out the pot to kill any mold spores. Use some bleach or dishwashing soap to clean the pot. Be sure to rinse it out well. Of course, you could also use a completely new pot.

Finally, 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. 

Apply a Fungicide

If you have a serious mold problem, you can apply a liquid fungicide. Every garden center carries fungicide that can be used to treat yellow mold. One popular option is called liquid copper. It will kill yellow mold. It will also kill potentially dangerous fungi such as Cladosporium and mucor. 

Most fungicides will require multiple treatments. You may need to spray your plants and soil once per week for a month or so. Read the instructions on the label and follow them.

Generally, it’s a good idea to water before applying fungicide so you don’t wash it away. If you’re treating outside, it’s usually best to apply fungicide after it rains. With some types of fungicide, it doesn’t matter.

Before applying a fungicide, it’s a good idea to do a test with a small amount to see how it affects your plant. Some plants are sensitive to fungicides. It can inhibit photosynthesis. It’s also a good idea to wear a mask so you don’t breathe in the spray.

Apply a Natural Fungicide

Before applying a chemical fungicide, consider trying a natural antifungal. A few natural fungicides you can try include:

  • Cinnamon- After removing the mold, sprinkle some cinnamon on the soil’s surface. This will help prevent the mold from coming back. It won’t harm your plant. You will have to re-apply the cinnamon once in a while because it will wash away when you water. One benefit of cinnamon is that it has a pleasant odor.
  • Neem oil- This is a type of vegetable oil that comes from a tree. Neem oil is effective against most types of fungus. Mix a teaspoon or two with a gallon of water and use it to water your plant. It may take a couple of treatments but the mold should go away.
  • Baking soda- Mix 2 tablespoons of baking soda with a gallon of water. Put this mixture in a spray bottle. Spray your plants and soil every three days for a few weeks and the mold should go away. 
  • Vinegar- Mix one or two teaspoons of vinegar with a gallon of water and use this mixture to spray your plants and soil. You can use regular vinegar or apple cider vinegar. Spray every few days for a couple of weeks. 

The best type of natural fungicide depends on the type of mushroom or mold you’re dealing with. Before using these natural treatments, it’s a good idea to test them on one spot first to make sure they don’t affect your plant.

These treatments are generally harmless. Baking soda or vinegar could affect the pH of your soil. Baking soda could make it more alkaline. Vinegar could make it more acidic. You don’t want to apply too much. Some plants are sensitive to changes in soil pH. 

How to Prevent Yellow Mold

To prevent yellow mold from forming, you have to change the conditions. Mold prefers dark, humid, and warm environments. If you make the conditions less hospitable for mold, it will usually go away. In this section, I’ll outline the best ways to prevent fungal growth on your soil.

Yellow mushrooms

Don’t Overwater. Allow the Soil to Dry Out Between Waterings

Overwatering is one of the main causes of mold. If the top layer of soil is moist, mold can start to grow within 24 hours. Excess moisture can also cause root rot, which can eventually kill your plants. Most types of mold can’t survive on dry soil. 

Wait for the top 1-2 inches of soil to dry out before you water your plants. Mold needs moisture to grow. When the soil is dry, fungus can’t form as easily. When you do water, water deeply. Make sure the soil is good and moist. The soil near the plant’s roots will stay wet for a long time.

If you’re having trouble with yellow mold in house plants, you can also try bottom watering them. Fill a saucer with water then place the pot in it. The plant will absorb water through the drainage holes in the bottom. This keeps the top layer of the soil dry so mold is less likely to form. 

Improve the Soil Drainage

One of the best ways to prevent mold from growing is to improve the soil drainage. Mold forms in damp conditions. When there is poor drainage, the soil will stay wet for too long and it will eventually start to mold. 

Start by choosing the right container for your plants. Choose a pot that has plenty of drainage holes. Empty the saucer under the plant after watering so the soil doesn’t stay too moist for too long.

It’s also important to choose a potting soil that drains well. To improve the drainage of your soil, you can mix in some type of soil amendment like vermiculite, peat moss, or wool pellets. These materials allow water to flow through the soil more freely so the soil won’t stay wet for too long. 

If you’re experiencing mold outside in your flower beds, you may need to redirect rainwater so it doesn’t pool in your beds. You can also add a soil amendment to improve the drainage of the soil. 

A raised garden bed
One great way to improve drainage outside is to plant in raised beds

Remove Organic Debris From the Soil

Yellow mold tends to develop on organic matter on the soil. This could be dead leaves, compost, mulch, grass clippings, and other dead organic material. Mold feeds on the organic matter. Removing this debris from the soil surface removes a food source for the mold. This can help to reduce fungal growth.

If you have stones, shells, or any other kind of decorative objects on the soil, you should remove those too. They can be contaminated with fungal spores that can spread back to the soil. You can reuse them if you sanitize them. 

Make Sure the Plants are Exposed to Sunlight 

Sunlight helps prevent mold from growing in a couple of ways. Most importantly, it helps the top layer of soil dry out between waterings. The heat from the sun speeds up the evaporation process. When the top layer of soil is dry, mold is unlikely to grow. 

In addition, UV radiation from the sun helps to prevent mold growth. Mold likes dark and humid areas with stagnant air. It doesn’t grow well in direct sunlight. In some cases, the sunlight can kill the mold.

If you can’t move your plants to the sun, you could install a grow light. This will also help prevent mold. 

Improve the Air Circulation Around Your Plants

Avoid placing your plants in areas with poor air circulation. Mold grows best in a humid environment. It won’t grow as well when there is a lot of airflow.

To improve airflow, you could open a window near the plant if the weather is nice. You could also mount a small fan near your plants or turn on the ceiling fan if you have one. The air doesn’t need to move fast. 

If the plants are outside, it helps to space out your plants. Don’t keep them all bunched together with the leaves touching. Some types of plants can be trimmed back. This allows more air to pass between them. 

Proper air circulation will also help to get rid of excess humidity around your plants. This will reduce the likelihood of mold growing. 

Potted plants in a windowsill

Clean Your Tools After Dealing With Mold

Your garden tools could get contaminated with mold spores. If you use them in another part of your garden, you could spread the mold. Mold contamination is a risk. After working with moldy soil, be sure to clean off your tools thoroughly. It’s also a good idea to wash your garden gloves after dealing with mold.

Make Sure You’re Not Using Contaminated Soil, Mulch, or Fertilizer

Soil, mulch, and fertilizer like compost can be contaminated with mold spores from yellow slime mold and other types of yellow mold. When you use them, the mold can start growing fruiting bodies in the right conditions. Mold spores can stay dormant for a long time. Even if the soil has been sitting around for a long time, it could contain spores. 

To avoid this, you should buy quality soil from a trusted seller. You could also buy sterilized soil or sterilize your own soil. It is also possible to sterilize mulch and compost to kill most harmful fungi and bacteria. To sterilize, you will need to increase the temperature to at least 140 degrees Fahrenheit. Check out this guide to sterilizing soil for more info. 

My Experience

A couple of years ago, I started noticing some type of yellow mold growing on the soil in my backyard. After some research, I identified it as some type of slime mold. At first, I just scraped it off with a shovel and threw it away. It ended up coming back. In the end, I used a fungicide to get rid of it. I also changed my watering habits. I may have been overwatering in a shady part of my yard. 

Yellow mold in your soil usually isn’t a big deal. You can just leave it if you choose. It’s generally harmless. If you have pets or kids, it may be a good idea to get rid of it so they don’t try to touch it or eat it. There are also some types of yellow fungus that can be harmful to your plants. Some types of mold can use up resources which can slow plant growth. 

You can get rid of the mold by changing the conditions. The ideal conditions for mold are moist, warm, and humid environments with stagnant air. Make sure you avoid overwatering, improve the soil’s drainage, and improve ventilation around your plants. This will help to prevent mold.

If you spot some mold, you can scrape it off and throw it away. If that doesn’t work, you may need to replace the soil or use a fungicide. These treatments will work for pretty much every type of fungus including yellow mold, white mold, and grey mold as well as mushrooms. It doesn’t really matter which type of mold you’re treating. 

Have you dealt with yellow mold on your soil? How did you get rid of it? Share your experience in the comments below!

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How to Get Rid of Yellow Mold on Plant Soil

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