Orange Mold Growing on Indoor Plant Soil? (Kinds & Causes!)

Orange mold isn’t the prettiest thing in the world and can startle any gardener once it’s seen on indoor plant soil. Unless you’re really familiar with them, it’ll likely be difficult to identify which orange mold you have in your indoor plant soil. Luckily, these things aren’t as terrible as they look. These slimy molds can easily be controlled too!

The 4 most common orange molds that grow on indoor plant soil are 1) Fuligo septica, 2) Lycogala epidendrum, 3) Trichia decipiens, and 4) Trichia varia. They can be prevented and removed by 1) physical removal, 2) organic treatment, 3) increased drainage, 4) improved airflow, and 5) use of clean potting mixes.

It can be confusing—trying to understand why this mold appeared in the first place. Unlike other molds, however, these orange molds aren’t dangerous. Let’s keep going and you’ll learn how this interesting lifeform breaks the mold!

1. Scrambled Egg Slime (Fuligo septica)

Fuligo septica is a common orange slime mold that can appear overnight in damp soil. It is generally not harmful but can be a health risk for people with asthma. Let it harden before manually removing it from indoor plant soil.

Toxicity to Animals and Humans: None

Commonly Found in: Damp soils

This is the most common slime mold to appear on houseplants. As gross as it looks, this is an organic life form often called “dog vomit” due to its orange and unpleasant appearance.

Once it matures, it forms a dry and flat crust. In its early stages, it can be bright yellow and look similar to scrambled eggs—giving its other nickname.

It certainly looks disgusting. But the Fuligo septica, or dog vomit slime mold, is harmless. Typically appearing in damp soils, it feeds off of bacteria in soil and is not harmful to humans or plants.

However, this slime mold can be harmful to those with delicate immune systems once it’s inhaled. You’ll need to be extra careful when trying to get rid of it if you have asthma as it can trigger asthma attacks.

Wait for it to harden before you pick it up. This shouldn’t take more than a few days. But avoid splashing or pouring water on it in the meantime, as this can cause it to release its spores.

2. Wolf’s Milk Slime (Lycogala epidendrum)

Resembling red and orange puffballs, the Lycogala epidendrum is a common slime mold seen growing in groups on rotting wood chips indoors. Commonly called wolf’s milk slime, it will release an orange ooze when popped.

Toxicity to Animals and Humans: None

Commonly Found in: Old and decaying wood and mulch

Lycogala epidendrum, also known as wolf’s milk slime, is a common slime mold that can look very similar to a mushroom. However, it is not part of the fungi kingdom.

This slime mold usually only grows in the woods, but it can also be seen indoors growing on decaying wood chips. When still young, it can be red, brown, or orange. You can identify this mold by its tendency to ooze a bright orange liquid out once popped.

Don’t worry about this though, as it is non-toxic. Simply put, it doesn’t pose any danger to plants or humans. It can even make an interesting addition to your potted plants!

However, it does have a bitter putrid smell. so it’s up to you to decide if you’d like to get rid of them. Keep reading to find out how to effectively remove and prevent these slime molds!

3. Eggs of Salmon (Trichia decipiens)

Trichia decipiens is a bright orange slime mold that looks similar to fish eggs and is normally found on damp indoor plant soil. This slime mold is not harmful and feasts on bacteria in rotting plant material.

Toxicity to Animals and Humans: None

Commonly Found in: Old and decaying wood and mulch

Another orange slime mold that is readily found is eggs of salmon. Not to be mixed up with the succulent Tylecodon decipiens, this slime mold is much smaller. Compared to wolf’s milk slime, it often has a glossier appearance.

Trichia decipiens can be identified by their similarity to fish eggs—in particular, orange salmon eggs.

Eggs of salmon slime mold is found all over the world and can be found in moist soils with high humidity. It likes to feed off of microorganisms in rotting organic material and is not dangerous to plants, animals, or humans.

Because of this, it usually grows on mulches of wood chips and can even be found on dead conifer trees!

You can leave this slime mold alone to eat bacteria or remove it on sight.

4. Varia Slime Mold (Trichia varia)

Trichia varia is a white and orange slime mold that commonly grows in moist indoor potting soil. It is non-toxic and does not have any health risks. It can, however, feed off of soil nutrients. Unwanted varia slime mold can easily be removed.

Toxicity to Animals and Humans: None

Commonly Found in: Damp soils

Although it might look like discolored perlite at first, this slime mold is much smaller than that.

Indoor houseplants with consistently damp soil offer the best environments for Trichia varia to grow. Initially, the slime mold will look like white insect eggs before it becomes a dull yellow-orange.

This slime mold poses no risk to animals or humans, but it is rather unsightly. More importantly, the varia slime mold might feed off of soil nutrients that your plants need to grow well.

Unless you’re growing carnivorous plants that need nutrient-poor soil, you might want to remove this mold from the soils of your indoor plants. This slime mold tends to grow and spread quickly, so remove it as soon as you can!

How to Prevent and Remove Orange Mold in Indoor Plants

Orange mold can be removed and prevented from spreading with physical removal, organic treatment, increased drainage, improved airflow, and clean potting mediums.

These curious amoeba-like organisms aren’t toxic. But if you plan to get rid of them permanently, there are some factors you’ll need to consider.

1. Physical Removal

The best way to eliminate orange slime mold is by physically removing them from the soil and disposing of them. Most slime molds on indoor plant soil can be quickly removed with a shovel, except for Fuligo septica, which is easier to remove when dry.

Over 900 slime mold species exist. Most of them are harmless. In other words, you can leave them alone so that they can naturally complete their life cycle and consume fungi and microorganisms.

If you’d like to remove them, however, the best way to do it is by manually removing them. Simply use a spoon or shovel to scoop them up from the soil and discard them.

Just be sure to sterilize your removal tools afterward to prevent spores from lingering.

Identifying Slime Mold

Slime molds can be removed on sight, but it’s best to eliminate them while they’re young and unable to produce spores.

An exception to this would be Fuligo septica. It’s easier to pick this up after it has hardened completely. Throw the slime mold away in a sealed plastic bag, and you’re all set!

2. Organic Treatment

Spray a solution of 1 tbsp baking soda with 2 L of water onto the soil to prevent orange slime mold from growing on indoor plants. 1 tbsp cinnamon powder can also be used to combat any remaining spores from growing into slime mold.

Another way to prevent and remove slime molds is with organic treatments. These organisms are not a high enough threat to necessitate the use of harsh fungicides or chemical treatments. Plus, they’re not even fungi!

While they are found in similar environments, slime molds belong to the Protista kingdom. The Protista kingdom is a collection of lifeforms that do not conform to the characteristics of fungi, plants, or animals. So buying fungicides to remove them would be useless.

However, as an added measure, you can mix 1 tablespoon of baking soda with 2 liters of water. Mix this and spray the solution on the surface. This won’t have much of an effect on your plant, so don’t worry!

Many gardeners also sprinkle a tablespoon of cinnamon powder on top of their soil. This is another great way to help keep slime molds away. But this is best done with the other prevention methods—which I’ll be discussing below.

3. Increase Drainage

Orange slime mold can be prevented by using well-draining potting soil and increasing overall drainage. Without any damp soil to live in, slime mold is less likely to grow indoors. Use cactus soil or ingredients like pumice to increase soil drainage.

Oftentimes, slime molds appear in our indoor plants when we’re overwatering them. Aside from breaking the habit of overwatering, one change to make is to increase drainage. By doing so, you’ll be able to minimize the chances of mold growth.

This can be done in multiple ways. Use a potting medium with more drainage, like cactus soil. Make sure the pot’s drainage holes aren’t blocked as well.

Generally, the goal is to ensure the soil isn’t left soggy and invites slime molds.

Pro Tip: With a clean wooden stick or a skewer, you can poke holes into your soil before watering to promote drainage.

Terracotta pots are excellent at wicking away excess moisture and keeping plants dry. Growing mediums like pumice, perlite, or lava rock are frequently mixed in potting soils to add drainage.

Stay away from any wood chips or bark, however, as slime molds love to shelter in the cracks of these wood pieces and feed off of their bacteria!

Discover the Best 13 Perlite Substances in Gardening (and the Worst). 

4. Improved Airflow

Good ventilation and airflow can help prevent orange slime molds from growing on indoor plant soil. Leave nearby windows open or place a fan near indoor plants to ensure the soil dries out faster, preventing slime mold growth.

If your plants need consistently moist soils or already have well-draining soil, consider increasing the ventilation.

By adding this one simple thing, you’ll be able to help keep the topsoil of your indoor plants dry and less likely to harbor slime molds. This is especially important if you live in a humid area.

Our plants are much more sensitive to moisture than we are. An open window in the room or a running fan makes a world of difference in preventing slime molds from growing.

Pro Tip: Position the fan so it blows directly on the leaves or at the top of its pot to ensure proper airflow.

5. Use Clean Potting Mediums

Potting mediums can sometimes contain slime mold spores and must be cleaned before use. To prevent the spread of orange mold in indoor plants, use only clean potting soil or replace the first 2 inches of infected soil with a new potting mix.

Sometimes, the growth of slime molds isn’t your fault. It’s also possible that the slime molds are naturally growing because of all the organic material in the soil.

Bagged ready-to-use potting soil can sometimes go bad and harbor unwanted lifeforms, so be sure to inspect your potting mediums regularly. Make sure to store them well.

Learn more in Does Potting Soil Go Bad? (Plus 3 Signs That It Has) 

If you can’t replace the potting soil for your indoor plant, scrape up the top 2 inches of soil and replace it with clean soil.

Once you’ve confirmed that your potting medium is the source, don’t worry! It’s also possible to sterilize the soil with hot water.

These are all small but easy and actionable tips which can help prevent your houseplants from growing orange slime mold.

Again, these slime molds aren’t harmful and can help eat fungi and bacteria!

So if it’s too much trouble trying to remove them, they can always be left as a unique and harmless addition to your garden.

FAQs

Summary of Orange Mold on Indoor Plant Soil

Fuligo septica, Lycogala epidendrum, Trichia decipiens, and Trichia varia can all appear in excessively damp indoor plant soil. These orange molds are not toxic and typically grow when potted plants are overwatered.

Orange mold can be prevented and removed by physically removing them from the soil, treating them with organic solutions, increasing overall drainage and airflow, and using clean potting mediums to ensure the mold does not grow again.

Sources

• “Harmless orange slime mold found in gardens” by Bonnie A. Coblentz in Mississippi State University
• “Slime Molds” by Ann Joy and Brian Hudelson in University of Wisconsin-Madison
• “Slime mold” by Dr. Kevin Ong in Texas A&M University
• “Wolf’s-Milk Slime (Toothpaste Slime)” by n/a in Missouri Department of Conservation