Growing houseplants is a rewarding experience, but it can also be frustrating when you run into issues that impact the health of your greenery. Beyond yellowing leaves and spider mites, one common issue that often plagues houseplants is moldy soil.
Though it's not always harmful, mold can remove nutrients, reduce growth, and leave your plants vulnerable to diseases. If you've noticed mold growth on your houseplants, don't worry. With some routine care you can get rid of the unwanted substance and prevent future infections.
3 Ways to Promote Better Soil Drainage in Your Houseplants, Which Is the Key to Healthier Greenery
How to Identify Mold on Soil
The first step to treating moldy soil is knowing what it looks like. The substance commonly lurks on the surface of the soil, but may also grow below it. "Mold can present itself in various colors and may appear fuzzy, slimy, or powdery," says Josh Brown, owner of Predatory Plants. If your plants are not thriving or are showing signs of stress, it could be a sign of mold soil. Pink, white, or light orange growth is typically a sign your plant has a fungus. Some forms of mold will produce a musty odor—another indicator your plant is infected.
Why Houseplant Soil Gets Moldy
There are a few different reasons mold forms on houseplant soil. "Mold and other fungi can form in soil after prolonged exposure to excessive moisture," says Brown. Although mold is a normal part of caring for houseplants, there are some living conditions that can lead to excessive and harmful growth.
Poor Soil Drainage
Ensuring water drains through your plant properly is essential to its health. "If your soil does not drain well or is not given time to dry out, it creates ideal conditions for mold to grow," says Brown. Poor soil drainage can also lead to root rot, which may cause the leaves to turn yellow or brown and even result in the death of your plant.
Overwatering
Feeding your plant too much water is one of the most common reasons mold forms. When the soil is wet for too long it creates the perfect breeding ground for fungus. "Very few plants require soil that is constantly wet enough to enable mold to grow," says Brown. Follow a watering schedule suitable to your plant's needs and generally wait until the top inch of soil is dry before providing further hydration.
High Humidity
Many tropical plants prefer a humid environment, but too much humidity causes the soil to stay consistently damp and can lead to mold growth. Ensure you're providing your plants with proper air circulation to reduce humidity. "Stagnant air allows humidity and mold spores to build up," Brown says.
Organic Matter
Mold and other types of fungi feed on decomposing organic matter, so it's important to regularly remove fallen leaves from plant soil. "Leaves or plant debris provide a source of nutrients for mold to grow," says Brown.
How Moldy Soil Affects Plant Health
Not all types of fungus are harmful to houseplants, but some strains can inhibit growth. "For most plants, especially carnivorous ones, moldy soil can take nutrients from the plant and end up being toxic to its growth," Brown says. A heavily infected plant is more susceptible to diseases and other stressors and in some severe cases, moldy soil can lead to the death of a plant.
Fungus build-up may also attract common houseplant pests. "The fungal and algae mats are also a food source for some insects like fungus gnats," says Melinda Myers, gardening expert and host of the Great Courses How to Grow Anything DVD series. "These are usually just an annoyance but when populations are high due to an abundance of food they can damage plant roots."
How to Get Rid of Moldy Soil
Luckily, getting rid of mold on soil is relatively easy. You can scrape mats of fungus off the soil surface and throw it away, or replace the soil entirely with fresh potting mix. Another common way gardeners choose to get rid of mold on houseplant soil is by improving soil drainage. "If soil is poorly drained, add peat moss, vermiculite, wool pellets, or other amendments to promote better drainage," says Myers.
If the infection is severe, a liquid fungicide may be necessary. "With fragile plants like butterworts, make sure to do a small test to make sure the fungicide is safe," says Brown. "Copper-based fungicides can be extremely toxic to certain plants."
How to Prevent Moldy Soil
There are a few preventative measures you can take to minimize the risk of future mold infections. Most methods involve ensuring the soil doesn't stay consistently wet, which can be achieved through improving soil drainage, improving air circulation, and exposing your plant to sunlight.
Improve Soil Drainage
The first and most important way to prevent mold in houseplants is to fix the soil drainage. "Empty saucers, choose containers that have drainage holes, and let plants dry in between waterings," says Brown. Additionally, you can add a porous material to your potting mix, like shredded bark or peat moss, which will help keep the roots from sitting in water.
Expose Soil to Sunlight
A lack of sunlight can also keep the soil from drying out between waterings. "It is important to ensure that your plants are getting ample sunlight because UV radiation from the sun helps inhibit mold growth," says Brown. Keep mold growth at bay by exposing the soil to sunlight during the day.
Improve Air Circulation
Another way to limit the risk of mold growth is by improving the air circulation in your home. "If the plant is on a windowsill, open the window if the temperatures aren't too extreme," says Brown. "If natural air circulation isn't practical, a small fan blowing across your pots will have the same effect." Spacing out clusters of plants will also improve air circulation and decrease humidity.
