Yellow Mushrooms: Causes and Solutions

Yellow Mushrooms: Causes and Solutions

Yellow mushrooms in your houseplants, garden, or yard usually indicate overly damp soil. The bright yellow fungi can appear overnight, seemingly from nowhere. These brightly colored yellow growths typically have rounded umbrella-like caps and yellow stems, and grow in clusters in damp potting soil. If you spot these yellow mushrooms in houseplants, you may wonder what they mean.

Bright yellow mushrooms in potted plants, flower beds, or lawns are not a cause for concern. Mushrooms typically only grow in rich, fertile soil. Therefore, the yellow fungi are a sign that the soil condition is good. However, the yellow mushrooms thrive in damp, soggy soil — not ideal for most houseplants.

Because the common cause of yellow mushrooms is overwatering, the health of your potted plants could be at risk. Many houseplants become weak and susceptible to disease when growing in overly wet soil. The classic signs of root rot are yellowing leaves, wilting stems, black spots on leaves, and stunted growth.

This article explores the various causes of yellow mushrooms growing in plants. You will also find tips on removing these unwanted yellow spongy mushrooms from your indoor plants.

What Are Yellow Mushrooms in Houseplants?

Yellow Houseplant Mushrooms

Yellow Leucocoprinus birnbaumii mushrooms growing in a houseplant pot

Bright yellow mushrooms are a type of fungus called Leucocoprinus birnbaumii in the family Agaricaceae. The yellow fruiting bodies appear in summer through fall outdoors, but indoors in houseplants and greenhouses throughout the year. The yellow gilled mushrooms are also called yellow parasols, plantpot dapperlings, yellow houseplant mushrooms, or flower pot parasols.

Yellow mushrooms Leucocoprinus birnbaumii typically grow outdoors in tropical or subtropical regions. The yellow variety of fungi thrives in damp conditions and begins to appear in summer. That is why yards in Florida often have these yellow mushrooms.

The common houseplant mushrooms may also grow in yards and lawns in warmer areas of temperate regions. In colder regions, the yellow mushrooms may start to fruit when indoor conditions are ideal. This usually happens when the spores in the wet soil start to fruit in warm temperatures.

Related reading: How to identify common lawn mushrooms.

The potted plant yellow mushrooms may look like pale yellow bumps on the soil surface. Then, very quickly, the round to conical caps emerge on cylindrical yellow stems (stipes). Finally, you’ll notice the bright yellow mushrooms tend to grow in clusters.

How to Identify Yellow Mushrooms

Leucocoprinus birnbaumii mushrooms in pot

A cluster of Leucocoprinus birnbaumii mushrooms in a pot

Leucocoprinus birnbaumii mushrooms are easy to identify due to their bright yellow color, conical or egg-shaped scaly caps, and bright yellow inner flesh. These yellow mushrooms are typically the only ones you’ll find in your houseplant soil. Under the rounded caps are tightly growing sulfur-yellow gills that don’t attach to the stems.

Yellow houseplant mushrooms have a bulbous bell-shaped lemon-yellow cap that tends to flatten with age. The caps can grow 0.78” to 3” (2 – 7.5 cm) wide and sit on stems 1” to 3.5” (2.5 – 9 cm) tall. In time, the brightly-colored lemon gills may darken to a brown color.

mushrooms in pot

Two day old Leucocoprinus birnbaumii mushrooms in a flower pot where they develop flat caps

Another way to identify these yellow mushrooms is to test the soil. Yellow flowerpot parasols typically only grow in wet, soggy soil. Therefore, if it is summertime and the potting soil is saturated, the yellow mushrooms will typically be the species of fungus called Leucocoprinus birnbaumii.

Why Do Yellow Mushrooms Grow in Houseplants?

yellow mushrooms in pot

Leucocoprinus birnbaumii mushrooms growing in potting soil

Yellow houseplant mushrooms grow in potting soil when conditions are ideal for fruiting. First, there must be spores in the soil or the plant for the yellow growths to sprout. Second, conditions for mushrooms to grow must be ideal — wet soil and warm temperatures produce an abundance of mushrooms. Third, the yellow fungi need organically-rich soil to fruit.

Therefore, it’s not uncommon for a yellow mushroom cluster to start growing at any time of year. However, they tend to grow more prolifically during the summer months.

Yellowish mushrooms seem to appear suddenly because of the length of time the mycelium takes to grow. These are the network-like fungus roots that attach themselves to plant roots. As soon as temperatures and soil moisture content rise, the fungus roots begin to fruit and grow, producing yellow growth visible above the soil.

Where Do Yellow Mushrooms Come From?

Yellow mushrooms in houseplants typically appear because the fungus spores or roots are already in the soil. These microscopic spores can lay dormant for many months or years until conditions are ideal for fruiting. Even in soilless potting mixes, the spores are difficult to eradicate.

Seeing clusters of bright yellow mushrooms for the first time will cause you to wonder where they came from. Sometimes, the yellow fungi can appear without warning, even though you haven’t changed the growing conditions. However, the good news is that yellow mushrooms can benefit the soil without harming plants.

Do Yellow Mushrooms Benefit Houseplants?

Yellow mushrooms have a beneficial role in the soil ecosystem. The plantpot dapperlings improve the soil quality by breaking down decaying organic matter, increasing aeration, and helping plants absorb essential nutrients. In addition, some houseplant owners enjoy seeing wild mushrooms in plant pots.

One of the benefits of mushrooms to potting soil is that they increase beneficial nutrients. As the fungus roots work, they increase phosphate and nitrogen levels and lower pH levels. These elements combine to create a healthy growing environment.

Are Yellow Mushrooms Harmful to Potted Plants?

Yellow mushrooms are harmless to houseplants and plants growing outdoors in your yard. Because they improve the soil quality, there is no risk of them causing damage to plants. In addition, they are not a parasitic type of fungi; therefore, they don’t suck nutrients from the plants. In fact, they exchange nutrients with plants.

It’s good to remember that, although a type of fungus, yellow mushrooms are not the same as mold growths or fungal diseases. Therefore, confusing yellow mushrooms with dangerous mold growth would be a mistake.

However, seeing yellow mushrooms in potting soil could signify that your plant’s health is at risk. Of course, not from the fungal growths but from the growing conditions that allow yellow fungi to grow. Therefore, it may be time to change the growing conditions if you see yellow mushrooms in your potted plants.

Most houseplants — including tropical houseplants — require a loose potting soil mix that drains well. Ideally, the plant roots should always be slightly moist, but the top layer of soil must dry out between waterings.

Yellow mushrooms could signal that any of the potentially damaging conditions:

  • You are overwatering the plant or watering it too often.
  • Soil drainage is not adequate.
  • The plant has become root-bound, causing excessive soil moisture.

Watering less frequently or repotting the plant with an aerated potting mix can help prevent yellow mushroom growth. However, yellow mushrooms can safely grow in plant pots without damaging plants, people, or pets.

Are Yellow Mushrooms Harmful to People?

mushrooms in pot

Don’t ingest Leucocoprinus birnbaumii mushrooms as they are poisonous to humans and pets

Yellow mushrooms are harmless to humans unless you ingest them. They are safe to handle, and unlike mold growths, their microscopic spores are not harmful. Therefore, you can simply remove them with your hands if you don’t want them to grow in your houseplants.

However, it’s good to note that yellow mushrooms Leucocoprinus birnbaumii are considered poisonous mushrooms. Therefore, you should not consume them. Researchers at Michigan State University say these yellow mushrooms can be toxic in large amounts. So despite its cute appearance, the colorful mushroom isn’t among the list of edible mushrooms safe to eat.

Reports suggest that eating yellow mushrooms cannot kill you. However, ingesting the bright fungi can cause gastrointestinal upset, including nausea, cramping, diarrhea, and vomiting.

Do Yellow Mushrooms Harm Pets?

One reason to remove yellow mushrooms from potted houseplants is that they can be harmful to animals. Cats and dogs that consume Leucocoprinus birnbaumii may also suffer from digestive issues like vomiting, gastrointestinal pain, and diarrhea.

The Causes of Yellow Mushrooms

The reasons for yellow mushrooms growing in houseplants are always because fungus spores are present in the soil. However, the spores can blow in from outside or get transported indoors on plants. Then humidity, warm temperatures, and overwatering cause the yellow mushrooms to start fruiting.

Therefore, bright yellow growths can suddenly appear in summer or at other times of the year. All they need to start growing is for the conditions to become ideal.

Here are six reasons for having clusters of small yellow mushrooms:

1. Yellow mushroom spores already in potting soil or on the plant

The most common reason yellow mushrooms grow indoors is that the spores are already contaminating the soil. Commercial potting soil mixes contain a mixture of beneficial microbes and nutrients to improve plant health. Therefore, it’s not uncommon for the soil to contain Leucocoprinus birnbaumii spores.

2. Yellow mushrooms can grow because the houseplant soil has poor drainage

Potting soil that drains poorly is a reason why yellow mushrooms seem to appear from nowhere. Of course, the spores must already be in the soil before they start fruiting. But compacted soil, rootbound plants, or a lack of amendments can mean that the soil starts retaining excess moisture.

3. Overwatering houseplants can cause yellow mushrooms to grow

Giving houseplants too much water or watering too often causes colorful yellow mushrooms to appear. These yellow growths often appear in summer when you don’t allow the top layer of soil to dry between waterings. The warmth and moisture activate mycelium in the soil, and yellow mushrooms appear overnight.

Of course, yellow mushrooms are harmless to houseplants. So why should you be worried? Too much moisture in the soil can cause root decay, killing your plant. In addition, the mushy roots prevent plants from absorbing nutrients. This results in potted plants with stunted growth, yellowing leaves, and wilting stems.

Therefore, if you notice yellow mushrooms, you should check your watering technique and the soil for signs of overwatering.

4. Yellow mushrooms are growing because the potting soil is rich and fertile

Yellow mushrooms in houseplants are a sign that the soil is healthy. Most varieties of mushrooms require plenty of organic matter to thrive. The mushrooms help break down this decaying material, releasing vital nutrients into the soil. Therefore, some houseplant owners leave yellow mushrooms in pots to help improve soil health.

5. Yellow mushroom spores blow in from outside

It is not uncommon for microscopic spores to blow in through open windows and land on plants and leaf surfaces. For example, yellow mushrooms in houseplants in Texas can occur because the spores can live a long time in warm outdoor temperatures. However, this type of “spore spread” can happen in most warm climates.

6. Using garden soil for houseplants can cause yellow mushrooms to grow

It’s not advisable to use garden soil for houseplants for several reasons. For example, soil from the garden is rich with fungal spores, as well as friendly and harmful microbes. Therefore, you could transmit various plant diseases to your houseplants if you pot plants indoors with soil from flower beds.

Related reading: How to make a homemade potting mix.

How to Get Rid of Yellow Mushrooms

The easiest way to eradicate yellow mushrooms is to handpick them as soon as they appear. This prevents them from releasing spores. However, repotting the plant with fresh soil, changing your watering technique, and keeping moderate temperature and humidity can help stop yellow mushrooms from growing.

Let’s look in detail at how to get rid of yellow mushrooms from your houseplants.

Handpick yellow mushrooms from potted plants

The easiest way to eliminate a yellow mushroom infestation is to remove them by hand from the roots. To do this, use a small trowel to dig a few inches around the base of the yellow cluster of mushrooms. Then, put the unwanted fungal growth in a bag, seal it to prevent spore dispersal, and put it in the garbage.

Alternatively, you could put the yellow mushrooms on the compost heap. They may take root there and help the compost to decompose.

Change the top layer of the soil

Another way to get rid of yellow mushrooms in potted plants is to replace the top layer of soil. This can help to remove most of the mushroom roots and prevent further growth.

To replace the soil layer, remove 2” (5 cm) of soil and replace it with fresh, uncontaminated soil.

It’s good to note that this method doesn’t guarantee 100 percent results. The microscopic spores are difficult to eradicate and often remain in the root system. However, if you water your plant correctly, you can minimize the risk of the mushrooms returning.

Repot the plant to eliminate yellow mushrooms

Repotting houseplants that have yellow mushrooms growing can help to eliminate unwanted yellow visitors. In any case, repotting your plants is a good idea to replenish soil nutrients, and putting rootbound plants into larger pots encourages healthy growth.

To repot houseplants, remove the root ball from the pot and dispose of any signs of yellow mushrooms. Additionally, check the roots for a whitish cotton wool-like substance. Try to remove these fungus roots if possible. Next, half-fill a pot with fresh soil, put the plant in, and fill to the top with a fresh potting mix.

It is also a good idea to amend potting soil with perlite. This natural substance improves poor soil aeration and improves drainage.

Change your watering schedule

You can prevent yellow mushrooms from growing by watering houseplants correctly. Yellow mushrooms cannot start to grow unless they have ideal conditions — typically, overly moist soil. Therefore, only water houseplants when the top 2” (5 cm) of soil is completely dry.

When watering houseplants, it is better to water them less frequently and saturate the soil rather than watering frequently and only a little.  Always remember to allow excess water to drip from the drainage holes and never allow houseplants to stand in a saucer of water for an extended period.

Even if yellow mushroom spores are in the soil, a lack of adequate moisture prevents them from fruiting. As a result, you will probably never see yellow mushrooms again.

How to Prevent Yellow Mushrooms

The best way to stop yellow mushrooms from returning is by correctly watering your plants. The fruiting bodies have trouble growing in dry soil. Therefore, keep soil on the drier side rather than wetter to ensure healthy soil and plants. This way, you should avoid seeing bright yellow growths in potting soil

You can also put a layer of fine gravel mulch over the soil surface. This can prevent fungus growths from taking hold.

Suppose small yellow growths start to appear. In that case, remove them before their caps open and they release spores.

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