If you have houseplants, you may have occasionally seen small, yellow, or white mushrooms poking out of the soil next to your plant. Usually, when people keep plants, they don’t want an unsightly mushroom ruining the look. But what causes these mushrooms to grow on houseplants?
Mushrooms grow on houseplants because of overwatering, using contaminated potting soil, lack of sunlight, using regular garden soil, or heat and humidity. Spores are normally airborne and could have drifted into your house because of the wind or on your clothes.
In the rest of this article, I’ll explain why mushrooms grow on houseplants and which are the most common houseplant mushrooms. I’ll also give you tips on how to solve the root causes of mushrooms growing and prevent them from growing back.
1. There’s Too Much Water in Your Soil
The main cause of mushroom growth in your houseplant soil is excess water. Mushrooms use water to enlarge and grow bigger, so the bigger your mushrooms, the more moisture you have in the soil.
The excess moisture content in your potting soil could have two main causes:
- You’re watering your plants too much or too often.
- Your soil doesn’t have good drainage (meaning the water remains in the soil for longer instead of draining away).
Long-Term Overwatering Leads to Mushroom Growth
Giving your plants too much water by accident likely won’t cause them to grow mushrooms overnight. The problem arises when you overwater your plants frequently and keep the habit going for long periods until you run into a mushroom problem.
Chronic overwatering is a major problem that not only causes mushroom growth but also has the potential to kill your plant or cause significant damage to it.
Simply put, if you have a plant engulfed in water all the time, some harmless mushrooms would probably be the least of your concerns. In fact, overwatering can often cause more permanent damage than underwatering.
Most mushrooms that grow on indoor pots are actually harmless. They feed on the decomposing matter in the soil, so they don’t compete with your plant for nutrients. But they don’t feed on your plant or hurt it meaningfully.
It’s safe to leave them be, for the most part. Things are different if you have pets, as certain species of mushrooms may be poisonous to them.
If you see mushroom growth, how can you surely tell that it’s caused by overwatering? Here are a few signs and indicators to look for:
- Stunted growth: Overwatered plants with weakened roots cannot absorb moisture and nutrients from the soil.
- Root rot: Waterlogged soils cause roots to suffocate from a lack of oxygen. These roots will die and begin decomposing.
- Wilted or droopy leaves that don’t respond to watering: Decaying roots mean moisture can’t reach the rest of the plant, even when the soil is engulfed in water.
- Yellowing or browning leaves: The discoloration is often accompanied by water-soaked spots on the leaves.
If you see your plant suffering from one or more of these symptoms, dig your finger 2 inches (5 cm) deep into the soil and check the hydration levels.
Usually, a well-draining substrate should be dry enough at such depth 5-7 days after the last watering session. If it’s still wet, then the soil either has poor drainage or has excessive moisture-retaining potting mix ingredients.
You can also examine the roots directly to see whether or not they’re rotten.
Why Too Much Water in Soil Can Cause Root Rot
If you’re watering your plants too much and the water isn’t draining away, it can adversely affect your plants. So if you’ve got mushrooms growing next to your houseplants, check the plant to ensure it isn’t damaged.
Mushrooms aren’t harmful to plants but could indicate a deeper issue.
Root rot is one of the biggest problems caused by excess water in the soil, and it’s a condition where certain fungi species cause the plant’s root systems to fail. Too much water in the soil makes the fungi grow faster.
One way to identify root rot is if your plant’s leaves turn yellow or brown. If they’re wilted despite the plant being well-watered, it’s likely because of root rot and not mushrooms.
Even if your plant looks healthy from the top, mushrooms might still indicate too much water in the potting mix. Check your plant’s roots to see if they’re healthy, but if they’re soggy and dark brown or black, they’re infected with root rot.
How to Fix
There’ll be times when your plant looks healthy and the roots are still white even with mushrooms growing in the potting mix. In that case, you’ll just have to remove the mushrooms and make adjustments to your watering routine.
However, if the cause for the excess water in your soil is poor drainage, you’ll need to put in a little more effort to fix the problem, such as amending your potting soil.
Remove Mushrooms Caused by Overwatering
If you’re seeing mushrooms grow on an indoor plant, you probably don’t have a case of severe overwatering, you’ve probably just been a little too generous with your watering routines.
I’d recommend repotting your houseplant in sterile soil, but the process, admittedly, can be troublesome. Some plants also don’t respond well to being repotted too soon and may die from transplant shock. So it’s also possible to simply remove the mushrooms, especially if your plant is looking healthy.
The mushrooms that have established themselves on the soil can be removed manually:
- Remove any and all mushroom heads from the pot while wearing gloves.
- Scrape off the top 1 to 2 inches (2.5 to 5 cm) of the soil. Be careful not to damage shallow-rooted houseplants.
- Refill the pot with a fresh and sterile potting mix.
There’s no guarantee that the mushrooms won’t grow back, especially if the mycelia (root-like structure) have grown deep into your potting mix. But with improved watering practices and indoor conditions, the fungi won’t be able to produce fruiting bodies (mushrooms).
Adjust Your Watering Schedule
Reduce the amount of water you use for your plants or the number of times you water them. Make it a habit to check the potting soil for moisture before watering your plants.
You might be surprised to learn that most plants can get by comfortably with weekly watering. You’ll want to go with less frequent but thorough waterings. Plants that are watered deeply but less frequently respond by digging their roots deeper into the soil in search of water.
If your home’s light, humidity, and temperature and the potting soil quality match your plant’s growth requirements, you can go by the following watering tips:
- Moisture-loving plants: Water when the top 1-2 inches (2.5-5 cm) are dry.
- Drought-tolerant plants: Wait until the top half or 2-3 inches (5-7.6 cm) of the soil is dry.
Amend the Potting Mix with Porous Materials
I’d recommend a potting mix that contains around 25% perlite, which is the perfect material to improve soil drainage. It provides a good drainage level to prevent root rot but not so much that it’ll dehydrate your plants.
Pumice, perlite, or bark are perfect for improving potting soil drainage. You can buy pumice or perlite and mix it into your potting soil as needed.
Use Pots With Drainage Holes
It’s also crucial to have pots with drainage holes since you’re much more likely to overwater a plant and end up with mushrooms without proper drainage.
I discussed this topic in great depth in this article: Should All Indoor Plant Pots Have Drainage Holes?
To further improve drainage, aim for breathable pots like unglazed clay. The material will wick moisture away from the roots to prevent waterlogging. This will greatly reduce the likelihood of mushrooms or potentially harmful fungi growing in the soil. It also has remarkable benefits for the health of your plant.
2. Your Potting Medium Is Contaminated With Spores
You may have done everything right, yet you still have mushrooms growing next to your houseplants. So, where did they come from? The answer is spores that come into your house through the air, your clothes, or even the potting mix.
But before I get into how you can get rid of mushrooms and reduce their growth, let’s talk about what spores are.
What Are Spores?
Mushrooms reproduce through spores, which are airborne, microscopic cells that disperse through the air and land on other surfaces where they might form a new fungus growth. The mushroom is the reproductive part of a fungus.
So, in the same way that fruits produce seeds that grow into new plants and trees, mushrooms produce spores that form new fungi.
Spores Come From Regular Garden Soil
You can introduce fungi and a lot of other unpleasant microorganisms to your indoors by using regular garden soil as a potting mix. This is one of the major reasons you should always use specialized, commercial potting mix for your indoor houseplants.
However, even store-bought potting mixes can harbor fungi, especially ones that haven’t been sterilized properly. It’s worth spending a few extra bucks to get a high-quality potting mix so that you don’t run into problems like these.
The long-term benefit you get is also hard to overstate.
How to Prevent Spores From Growing New Mushrooms
Unfortunately, there isn’t anything you can do to prevent spores from landing in your soil mix. Spores are incredibly tiny and are completely invisible to the naked eye. A single mushroom could produce millions of spores, so there are far too many to guard against.
Luckily, there are ways in which you can remove the mushrooms and try to reduce their growth:
- Remove mushroom heads as soon as they sprout to prevent them from producing spores. This won’t eliminate the fungus already present, but it will prevent more mushrooms from coming up in other places.
- Use homemade or commercial fungicides. Regular applications of homemade fungicides like neem oil sprays can kill off the mushroom spores and mycelia. However, it can also kill off some beneficial soil microbes and insects.
- Use a new and sterile potting mix.
3. You Live in a Warm, Humid Climate
The most common mushroom that grows with houseplants is the Leucocoprinus birnbaumii, colloquially known as the plantpot dapperling or flowerpot parasol. This mushroom, and most houseplant mushrooms, love warmth and humidity.
Humidity measures the amount of water vapor in the air, and more humidity means the air carries more water. As the humidity approaches 100%, it gets increasingly harder for the air to hold more water, making it harder for water to escape into the air. Evaporation slows down considerably at this point.
The plus side is that you won’t have to water your plants as frequently, while the drawback is that any moisture in the soil will stay there for longer, increasing the odds of fungal growth. That said, you may want to temporarily lower the local humidity while dealing with a mushroom problem.
Poor Ventilation Raises Humidity
Poor ventilation can drastically increase the humidity levels in a room. Although mushrooms prefer fresh air, the increased humidity is enough of a reason for them to grow in poorly ventilated rooms.
The growth of mold, another fungus, is yet another indication of poor ventilation. You may also experience negative health effects in poorly ventilated rooms, so it’s best to get the problem sorted out as soon as possible.
Of course, you’ll want to open the windows and doors to let the air run through. Examine the air vents and ducts too.
It’s important to note that high humidity is probably not the sole reason your indoor plants are growing mushrooms. Usually, it’s a contributing factor, and the primary cause is something more pronounced, such as overwatering or a lack of sunlight.
How to Cool Down Your Room
Warmth and humidity are climatic conditions, so we can’t control that. However, you can do a few things to reduce the heat and humidity inside your house.
Here are some of the most effective ways to reduce heat and humidity in your house:
- Use a dehumidifier or air conditioner as needed, as they take the water vapor out of the air, lowering humidity.
- Use exhaust fans in places where humidity increases, like the kitchen or bathroom.
- Fix leaks or areas where water seeps into your house, like leaky pipes or drains. Identify and fix any indoor water leaks that may be causing your humidity to rise via evaporation.
- Keep the afflicted plant(s) out of high-humidity rooms. Bathrooms and kitchens are typically the most humid rooms in the house. Keep mushroom-harboring plants out of these rooms.
- Pause misting. It’s a common practice to mist an indoor plant collection regularly for extra hydration. You should stop misting afflicted plants until you get rid of the mushrooms.
4. There Isn’t Enough Sunlight Near Your Plants
Sunlight doesn’t negatively impact mushroom growth, but there are some indications that mushrooms grow faster without sunlight. So if your houseplants are in a darker section of the room, that might inhibit their own growth and encourage the growth of mushrooms.
Plants Have Varying Sunlight Requirements
Plants vary in their daily sunlight requirements, but almost all plants need at least a few hours of sun every day.
We can break down plant sunlight requirements into three broad categories:
Full Sun
Full-sun plants need more than 6 hours of direct sunlight daily and are almost always grown in outdoor gardens. Some popular houseplants, such as daisies and roses, need the full sun.
Partial Sun
Partial sun plants need 3 to 6 hours of indirect sunlight daily. Plants are sensitive to burn damage, so they’re best kept out of intense sunlight. Most common houseplants fall into this category.
Full Shade
Full-shade plants can be kept in shady areas and need less than 3 hours of sun daily. But most still need to see the sun every now and then.
As you can see, even the gloomiest plants need a few hours of sunlight, as they need this exposure to carry out photosynthesis. Photosynthesis is the process that allows plants to convert nutrients into energy.
Sun-Deprived Plants Are More Susceptible to Fungal Growth
Plants that aren’t exposed to the sun for long enough end up malnourished and weak.
This is important because it affects the plant’s ability to protect itself from:
- Pathogens
- Insects
- Pests
- Fungi
It’s only natural that a healthy plant with a strong immune system will be better able to protect itself from threats than a spindly plant with impaired immune function.
The good news is that most of the fungi that cause mushrooms to grow on indoor soil tend not to be harmful to plants. But many species of fungi do indeed feed on plants, such as plant roots, to be more specific.
Unwanted fungal growth is damaging in itself but can also lead to an infestation by fungus gnats.
Fungi Prefer the Dark
Fungi prefer growing in darker conditions. The UV radiation in sunlight is harmful to them and can kill susceptible fungi within a matter of hours if exposure is direct and the sun’s rays are intense.
Unfortunately, the same cannot be said for mushrooms that have already grown. Mushrooms can tolerate moderate-intensity sunlight reasonably well, so it likely won’t cut them off entirely.
If you want to rid your plant of the mushrooms, remove the top 2 inches (5 cm) of the soil along with the mushrooms.
You can then relocate your plant to a more sunny spot in your house to kill off the exposed fungi and discourage any new mushrooms from growing. The added heat can also dry out the soil more quickly, making it twice more effective in preventing mushroom growth.
Balconies, porches, and windowsills are perfect candidates for such a spot. They receive sunlight throughout the day, and you can conveniently control the duration of exposure with the help of curtains.
Avoid Using LED Lights on Mushroom-Infested Plants
Indoor gardeners who live in a place with little access to sunlight often use an LED light to provide artificial light for their plants. According to the University of Missouri, LED lights provide the best source of red and blue light for plants.
Unfortunately, LED lights rich in blue light can also promote the growth of mushrooms or fungal fruiting bodies.
You’ll want to move your plants near the windows or doors where they get enough natural sunlight.
5. There Is Decaying Organic Matter in the Plants
Mushrooms love nutrient-rich soil. In fact, many people see mushroom growth as a good sign because it can indicate good soil health.
The main macronutrients that mushrooms need are:
- Carbon (C)
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
- Magnesium (Mg)
Most of these are produced by decaying organic matter, like dead wood, animal waste, or compost.
If your plant looks healthy and you’ve ruled out the other causes listed above, then you can easily address this issue.
- Remove the mushrooms by scraping the soil surface (as instructed above).
- Improve the air circulation and lighting intensity around your plant.
- Reduce the humidity to the lowest possible level tolerated by your plant species.
- Remove dead plant matter like fallen leaves from the soil.
With improved environmental conditions around your plant, the mushroom problem can go away on its own.
6. There Is a Lot of Organic Matter in the Pot
Unlike plants, mushrooms don’t acquire nutrients from the soil, but rather, they feed on decaying and decomposing organic matter. Mushrooms grow particularly well in soil rich in organic matter, which means that mushroom growth can indicate fertile soil.
Modern-day gardeners have realized the importance of organic matter in growing media. As such, many potting mixes today contain organic materials, so it makes sense that they’d made a good habitat for mushrooms.
Mulch and compost, two of the most popular homemade organic fertilizers, are also almost entirely composed of organic matter. Using these fertilizers frequently can increase the organic content in the soil enough for it to be inviting to mushrooms.
So if you see mushrooms in your soil, you can at least be assured that you’ve got high-quality, fertile soil perfect for plant growth.
It doesn’t make much sense to refrain from fertilizing your plants just because it might increase the likelihood that mushrooms will grow. This is, again, a case where the benefits of using organic fertilizer appropriately far outweigh the cons.
How to Reduce Organic Waste
If your plant is shedding leaves or you’re trimming parts of it, ensure that none of it is getting mixed into the potting soil. You might also need to change your compost or stop using it until the mushrooms disappear.
Avoid using tree bark as mulch because mushrooms love growing on them. You can more easily regulate growth conditions when growing plants indoors, so there’s often no need to use mulching materials in pots.
