Many long-time plant owners are familiar with the feeling of finding an unpleasant surprise like mold in their soil. Mold is the result of the perfect storm of growing conditions, and sometimes it sneaks up on you. This article discusses the conditions that lead to mold in houseplants, how to get rid of it, and how to avoid it in the future.
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What Causes Houseplants to Mold?
When you find mold in the soil of one of your indoor plants, it’s time to evaluate the growing conditions you’ve created for them. Here are some of the many factors that can lead to mold growth in indoor plants:
- Overwatering: Mold grows easily in moist, humid conditions. Watering too often without giving your plants enough time to dry out makes them susceptible to mold.
- Lack of Drainage: Without holes for excess water to drain, any water that the roots don’t absorb sits in the pot, creating a host of potential issues – including mold.
- Poor Air Circulation: If your home doesn’t have some degree of air moving around, soil takes a long time to dry out, which contributes to ideal conditions for mold to grow. Many plant owners experience this in the winter when the windows are closed.
- Decaying Plant Matter: Many types of mold thrive in soil with an abundance of decomposing plant matter, such as dead leaves.
- Damaged Leaves: Some mold can enter through wounds on the foliage and spread through the rest of the plant.
Will Mold Kill My Houseplants?
There are several kinds of mold that can grow on houseplants. You will need to identify the type of mold to find out whether it is harmful to your plants.
Here are some of the standard mold varieties that grow in plants:
This mold grows on the surface of the soil, and is white and fuzzy in appearance. It looks similar to the mold you find on food that’s been in the fridge or pantry for too long.
White mold in small amounts is relatively harmless to the health of your indoor plants. However, the conditions that promoted the mold growth need to be addressed, such as constant moisture with little air flow.
White mold could be a problem for humans, though. It has been known to cause respiratory issues for those with allergies or asthma, and is generally something you don’t want to have in your home.
Like the name indicates, sooty mold causes grayish black soot-like patches to appear near the base of the plant, and on the soil’s surface. Since this mold is caused by fungi that feed on honeydew secretions left by insects, it usually indicates a pest infestation.
In addition to the potential for insect damage, sooty mold can interfere with the process of photosynthesis, which would eventually lead to the death of the plant.
Powdery mildew is recognizable by small white spores on the foliage of your plant which make it look dusty. It begins on the leaves, but can quickly spread to the rest of the plant, as well as other plants nearby via lightweight spores.
Quick intervention is necessary with powdery mildew, since it can cause long-term damage to all plants that are affected.
Also known as Bortrytis blight, gray mold starts with large grayish, tan spots on older leaves or flowers. It primarily attacks dead or damaged tissue, and the infected areas can spread rapidly.
Although gray mold doesn’t usually attack healthy plant tissue, the spores can enter growing leaves through wounds, causing the infection to spread.
How Do You Get Rid of Mold in Houseplant Soil?
Your plan of attack will vary based on the type of mold you’re battling. Here’s how to treat the mold, based on the species:
- White Mold: If you have a small amount of white mold growing on the surface of the soil, you should be able to remove it by replacing the top couple of inches of potting mix. If the mold grows back after that, you can try repotting the plant altogether, making sure to clean the pot before you return the plant.
- Sooty Mold: Since sooty mold feeds on insect secretions, you will need to tackle whichever pest has invaded your plant. Treatment will depend on the type of insect, so you should identify the culprit first.
- Gray Mold: Remove all of the infected parts of the plant, and address the conditions that promote gray mold growth. These include high humidity, moisture on the leaves, and low air circulation. Although these steps should be enough, you can also deploy a registered fungicide that is safe for use in the home.
- Powdery Mildew: Remove and destroy any infected leaves, and isolate the affected plants to ensure that it doesn’t spread to your other houseplants. Increase the airflow and reduce the humidity to prevent reoccurrence. Depending on the severity of the infection, you can use a registered fungicide. If you’re having issues with powdery mildew in your outdoor garden, this video has some helpful information, including homemade remedies:
How To Prevent Mold in Indoor Plants
Once you have the mold under control, you will need to take the appropriate steps to avoid it from coming back. Here’s how you can prevent mold from coming back:
Address Watering Issues
Overwatering is a common mistake that leads to many different illnesses in houseplants, including mold. Since the roots can only absorb a certain amount of water at a time, watering too often can cause them to stay wet constantly, leading to a lack of oxygen.
Roots that sit in more water than they can absorb and don’t get enough oxygen will essentially suffocate and die off. So even if you get rid of the mold in your soil, your plant will not remain healthy unless you correct any watering issues you may have.
Most plants need at least the top 1-2 inches of their soil to dry out before another watering. Since the amount of time it takes a plant to dry out varies greatly depending on its environment and growing conditions, it’s important to water plants only when they need it versus following a schedule.
Ensure Proper Airflow
Plants in their natural environment have wind to give them adequate air circulation. It’s important to provide some type of airflow in the home to prevent mold, pests, and other issues.
When the weather is warm enough, open the windows regularly to allow the breeze to give your plants a taste of their natural environment. Otherwise, you can emulate this by running a fan near your plants.
Remove Dead Plant Matter
Make it part of your plant care routine to remove any leaves that have died or fallen off of your plant. Many organisms, including fungi and insects, love to feed on dead plant materials.
Minimize Foliage Wounds
Plants incur damage many different ways, like during transport or accidents at home, etc. These things happen – it’s part of life.
While a torn leaf here and there will rarely lead to an issue, a large amount of damage on a single plant can leave it vulnerable to illness and infection. This is partly why gardening experts recommend that you only trim back about ⅓ of your plant while pruning.
If other conditions exist in its living environment that cause mold to form, a leaf with a fresh wound can put the plant at risk.
Although it can be stressful to find mold growing with your houseplant, the treatment process is often straightforward and effective – especially when you catch it early.
As long as you keep up with your regular houseplant care tasks and pay attention to their growing conditions, you should be safe from any reoccurrences. And if you want more plant care advice, here is our guide on plants and fruit flies.