What it Means and What to Do

A flourishing indoor garden can create a wonderful sense of fulfillment and satisfaction. Houseplants have more to offer than mere decoration. They also create a healthier environment by purifying the air in your home. Considering the benefits, It’s perfectly reasonable to feel concerned when an issue like white mold shows up in your soil.

If you’ve recently identified this phenomenon in your own home, you’re not alone. It’s a common problem that many of us deal with. However, when we see mold forming in any space, it can be concerning. I consider it to be a negative thing when I see it growing anywhere indoors. 

The good news is that this particular issue isn’t always to the detriment of your leafy friends. If you’re worried about how this could negatively impact your plants, I’ve got the lowdown on this common concern. Let’s dive in and find out what we are looking at and what causes this issue to pop up. 

What is It?

What we are referring to as mold is a specific type of fungus. Specifically, it’s a saprophytic fungus. These fungi play an important and highly valuable role in nature. They are responsible for breaking down organic matter and turning them into valuable nutrients. Without these organisms, the world would be full of dead animal and plant material with nothing to recycle it.

Sometimes referred to with the term saprotrophic, these organisms feed on dead and decaying matter. They convert this matter into useful nutrient-rich soil that new plants use to grow. As you can imagine, these fungi play a vital role in many ecosystems. The question is, how do they affect your houseplants when they turn up in your potting mix?

Some types of fungus can be highly detrimental to our bodies, so it’s natural to assume that they have similar effects on plants. The reality is, this fungus—and other types that may pop up—are not necessarily harmful to your plants. 

That said, this fungus can be an indication that something else in the environment is not ideal. While the organisms themselves can be beneficial, the reasons for their proliferation can be less so. Let’s talk about what causes it to grow in your potting mix. 

How Does White Mold Occur?

Most types of fungus grow best with the influence of specific environmental factors. The blanket answer to what causes it to grow is, essentially, warmth and moisture. It is also influenced by the availability of matter for it to feed on. Without the right type of food, the organisms will starve rather than proliferate.

Since it is a combination of warm moisture, and the presence of food that cause it, we should look to these things to understand its overall effects. To get to the root of it, we need to determine where the excess moisture is coming from. Excessive moisture can be the result of different factors, some more obvious than others. 

Overwatering

The most obvious cause of excessive moisture is overwatering. If the plant cannot absorb all the water you’re giving it, it will stay in the soil and create the right environment for fungus. Similarly, if your container has poor or no drainage, you can easily end up with a soggy potting medium.

While this particular type of fungus won’t harm your plant, there are other concerns. Overwatering and poor drainage are a recipe for root rot. Other types of fungi don’t have the same symbiotic relationship with plants. For this reason, it’s good to pay attention to the mold because it could indicate other, more serious issues. 

High Humidity

High humidity is not the most common issue for indoor gardens. In fact, it’s usually the opposite, and you’ll have plants that need more humidity than is naturally present indoors. As a result, we use supplemental humidity for our tropicals. 

This added moisture in the air can be a culprit of facilitating the growth of fungus. In this case, there is little concern for root rot. Humidity in the air won’t keep your soil wet beneath the surface. It may cause the top to stay damp, though. 

High humidity may be good for your plants, but it can cause other issues in the home. If you’re creating enough moisture in the air to grow mold on this surface, there’s a good chance it’s causing mold to grow in other places. 

‘Consider adjusting the amount of humidity you are intentionally introducing. A pebble tray is a good way to give your foliage moisture without increasing the ambient humidity in the surrounding area. 

Poor Air Circulation

Another cause of white mold is a lack of proper air circulation. This includes both the location and the potting mix. Compacted soil doesn’t allow air to circulate, which can keep it damp for a longer period. 

A lack of air circulation in the surrounding space can also slow the pace at which your potting mix dries out. For most indoor plants, you want to allow the surface to dry between waterings. If there is a lack of circulation, this might take much longer than it should, facilitating the growth of fungus.  

Lack of Sunlight

I’m sure you’ve noticed that your plants that need more sun tend to dry out faster than those in low light. This is true indoors and out. There is a higher probability of this mold forming with plants that get less sun exposure. 

If your plant prefers lower light, there is not much harm in giving it those conditions. Again, this won’t harm the plant, so it’s not necessarily something you need to fix. You can simply scrape the fungus off the surface if it bothers you. 

Organic Fertilizers

Fertilizer is another potential culprit of this issue. Organic fertilizers will feed the existing beneficial fungi in the soil. You may notice it grows faster for those plants that like frequent fertilization. This won’t typically be the sole cause. Usually, this works in conjunction with moisture-related issues.        

Is It Harming My Plants?

The short answer is: no. White mold formed by saprophytic fungi will not harm your plants. In fact, it can be an indication that your soil is healthy. As these organisms break down the decaying matter, they convert it into nutrients that are beneficial, making it easier for your plants to absorb them. 

Think about this in terms of composting. These organisms improve soil health by breaking down matter that is otherwise not making much difference. The resulting effect is an improvement in structure, health, and fertility.  This can all encourage faster, and healthier growth. 

If you’re watering too frequently, fixing this is easy. Something to keep in mind is that most plants have growing and dormant cycles. When they are dormant, they naturally take in less water. Make sure to adjust your watering habits accordingly. 

Humidity issues often go hand in hand with air circulation problems. If you increase the airflow, humidity will typically be less of an issue. I keep a lot of plants in my bathroom because it’s more humid there, which is great for my tropicals. I find that I often need to keep the vent fan on to keep the air moving. 

If your soil composition is the issue—because it’s too dense and doesn’t allow air to circulate—amending is your best bet. When you re-pot, mix some perlite or pumice in with your potting mix for added aeration. 

Treatment 

Treatment and prevention methods are similar. If you’re bothered by it, you can simply scrape it off the surface with a spoon. You can also apply a fungicide to the surface. Neem oil or a solution of baking soda and water are usually effective, though repeated applications may be necessary.