If you have more plants than places to put them, clay pots make attractive and relatively affordable containers for flowers, herbs, succulents, and more.
But in certain conditions, you might notice patches of white mold forming on these pots. This guide will explain how to remove mold on plant pots. Plus, it will cover a few tips for preventing mold growth in general.
What Causes White Spots on Terra Cotta Pots?
White spots on terra cotta pots are usually caused by one of three things: white mold, mildew, or mineral deposits.
White mold is a type of fungus that often forms on the outside of the pots. Like many other fungi, this mold thrives in warm, moist, and dark conditions.
Terra cotta pots are clay-based ceramics, meaning they are very porous once fired. You can purchase glazed or unglazed terra cotta pots. Unglazed terra cotta pots are the quintessential plant pot. Because their pores are exposed, unglazed clay pots are also the most likely to host mold growth.
Clay pots naturally absorb moisture. In the right conditions (i.e. warm temperatures, high humidity, and shade) white fuzzy mold forms on the outside of the pots.
Mold is not harmful to plants. However, inhaling mold spores may harm human health (particularly people who have asthma, allergies, or compromised immune systems). So if white mold starts to form on indoor pots, it might be time to break out the cleaning supplies.
Mold Growth Vs Mineral Deposits
Some basic sleuthing will help you determine if the white spots on your pots are mold growth or mineral deposits.
Mold is a slightly raised, fuzzy growth. It typically grows in small circles, the center of which has a more concentrated color. Efflorescence, the residue of mineral deposits, is flat and hard to the touch.
Put on a pair of gloves and scratch at the spot. Mold will scratch off. Mineral deposits will not.
Mineral deposits occur when terracotta absorbs salt, calcium, and other minerals from the water.
This natural buildup does not harm plants, pots, or humans.
If you have what looks like white mold on top of your houseplant soil, that is also mineral buildup. To avoid mineral buildup, use filtered water rather than tap water. Over-fertilizing can also increase mineral buildup.
A quick note on mildew:
Mildew is a member of the fungi family, closely related to mold. Many people use the terms interchangeably, but there are slight differences between mold and mildew¹.
Mildew tends to have a flat texture and a more powdery, dotted appearance than mold. Long-term mold exposure can cause more serious health issues than mildew.
Fortunately, you can prevent and treat both of these fungal growths in the same ways.
Removing the White Fuzz / Mold on Terracotta Pots: 3 Methods
The best way to remove mold on terracotta pots depends on when you notice the mold outbreak. The earlier you notice the mold, the easier it is to clean the pot without bothering the plant.
If you catch the mold in its early stages, try spot cleaning (Method 1). Spot cleaning does not require you to remove the plant from the pot. So it’s less work for you and less stressful for the plant.
But in cases of more widespread mold, follow Method 2 to deep clean the pot. It involves a little extra elbow grease and temporarily removing the plant. If you don’t completely eradicate mold spores, the pot will become moldy again very quickly.
Once you’ve scrubbed your way to a mold-free pot, give the pot an occasional maintenance clean (Method 3) to help prevent future mold growth.
Method 1: Hydrogen Peroxide Spot Clean
This method uses 3% hydrogen peroxide, the standard strength of the antiseptic when you buy it in pharmacies. If you don’t have hydrogen peroxide, you can also use a natural fungicide such as Neem Oil, adding 1 tablespoon per a half gallon of water.
To spot clean, pour the hydrogen peroxide into a spray bottle. Do not dilute it with water.
Spray the moldy area on the pot, shielding the plant from the undiluted liquid. When the hydrogen peroxide comes into contact with the mold, it should begin to bubble. This effervescent reaction means that the peroxide is still effective.
The bubbles occur as the peroxide releases oxygen on the surface of the mold. If you do not notice bubbles, the hydrogen peroxide has probably lost its effectiveness (usually from light exposure).
Wait for 10 minutes. Then, scrub the pot vigorously — but be careful not to disturb the plant as you do so. Rinse the pot with water to remove the mold.
Finally, place the pot somewhere with good airflow so that it will dry quickly.
Method 2: Bleach Deep Clean
This method involves temporarily removing the plant from its pot. You should avoid deep cleaning your pot unless necessary because transplanting plants can stress the plant’s root system. (Not to mention increasing the likelihood of you knocking off a precious orchid bud.)
But a deep clean is sometimes the only way to eradicate a stubborn mold infestation (which could also lead to some nasty white fungus balls in your soil).
Once you have transplanted the plant to its temporary location, remove any excess soil or debris in the pot. Rinse the pot with water if necessary.
Then, grab your gloves and make a bleach solution, measuring one part bleach to nine parts of water. Soak the pot in this mixture for an hour, then scrub it until you have removed all visible mold.
Rinse the pot with water, then soak it in a bucket of clean water for another hour. At the end of this hour, scrub the pot with a clean brush and rinse again with water.
Terra cotta pots are very porous, so you’ll want to repeat the water-rinsing process several times. Remember to use a fresh bucket of water and a clean brush each time to avoid transferring resilient spores.
Let the pot dry completely before repotting the plant.
Method 3: Vinegar Maintenance Clean
Vinegar is an acidic liquid that contains antifungal and antibacterial properties. Although not completely effective at killing mold spores, it will kill over 80% of known molds.
Plus, it’s an effective way to hinder mold growth when combined with other preventative measures.
For best results, use white vinegar. White distilled vinegar usually contains 5% acidity. But you can sometimes find cleaning vinegar that contains 6% acidity. Either version will work.
First, dilute the vinegar with equal parts water. Pour this solution into a spray bottle and spray the plant. Again, try not to get any liquid on the plant. Diluted vinegar won’t harm foliage, but it can change the pH balance of the soil.
Once you’ve sprayed the pot, use a clean cloth to rub in the vinegar. No need to rinse the pot!
Method 4: Neem Oil & Dawn Dish Soap
To remove mold on terracotta plant pots using this method, you will need the following:
- Dawn dish soap or any antibacterial soap
- Neem oil concentrate
- Hot water
Here are the steps to follow:
- Fill a container with hot water and add Dawn dish or antibacterial soap.
- Add neem oil concentrate to the mixture.
- Dip a sponge into the mix and scrub the mold off the terracotta pot.
- For stubborn mold growth, put some neem oil concentrate on the sponge before scrubbing the plant pot.
- Once the mold has been removed, rinse the pot thoroughly with clean water.
The neem oil concentrate removes the mold and helps protect the plant from future mold growth and pests².
What’s fantastic about this solution is the mixture will seep through the pot into the soil and work both ways.
How To Prevent Mold on Terracotta Plant Pots
Mold spores can travel through air, water, and from surface to surface. So once you have a white or black mold infestation, it’s difficult to remove the fungi permanently.
Here are a few ways to prevent pot mold from forming in the first place:
- Avoid overwatering the plant. Let the soil dry between waterings, particularly with houseplants.
- Use a pot with several drainage holes. Poor drainage also causes moisture buildup.
- Lower the humidity levels. Remove any pebble trays or excess water standing in the pot’s saucer.
- Position the pot in direct sunlight. Fungi cannot survive exposure to direct sun. Just remember to check your plant’s light requirements first; not all plants like full sun.
- Make sure the plant receives good airflow. Using a fan is an easy way to promote air circulation around indoor plants. Outdoors, avoid placing pots in corners, and maintain space between plant pots.
- Remove excess organic matter from the pot. Fungi feed on organic matter to survive. Removing dead leaves and other organic debris around the pot will help remove the fungi’s food source.
- Remember to clean gardening tools, including gloves, after use. This step prevents the spread of mold spores. Reusing infected soil will also spread the spores. So dispose of or sanitize infected soil before reusing it.
If you’re concerned about mold growth, another way to prevent it is to use a less-porous type of pot.
Clay pots are excellent containers for a variety of plants. They are attractive and friendly to both budget and environment. Best of all, their permeable material allows for side evaporation.
However, because of their porous nature, terra cotta pots are often moist — making it easy for mold to grow.
Mold can grow on many surfaces. But it will do so less swiftly on a plastic or tin container than a clay pot.
1: Mildew | Definition & Description. (n.d.). Encyclopedia Britannica. https://www.britannica.com/science/mildew
2: Houseplants Proper Care and Management of Pest Problems. (n.d.). Retrieved March 3, 2023, from http://library.nd.gov/statedocs/NDSUExtensionService/pp74420100503.pdf
Davin is a jack-of-all-trades but has professional training and experience in various home and garden subjects. He leans on other experts when needed and edits and fact-checks all articles.