You’re a small-space gardener with a few potted plants. You love your plants - who doesn’t? - and you want to see them thrive.
There you are, minding your own business when BLAM! - you notice that there is some mold growing on the surface of your soil.
Next step is, obviously, googling what in the Sam Hill is wrong with your tiny garden.
Well, first thing to keep in mind: don’t panic! The mold you see growing there is not dangerous, not usually allergenic, and is actually a good thing for your plants and soil. If you require more convincing, read on!
Note: Experiencing other troubleshooting issues with your plants? Check out Epic Gardening's Plant Problems for some top tips!
What Type of Mold Is It?
Does the mold on the surface of your potted plant’s soil look something like this:
If so, then this is almost certainly something called saprophytic fungi (mold).
Saprophytic means: an organism which consumes decaying organic matter. When you see mold in your potted plants, this is essentially your plants going “wow, this soil is LIT!”
Saprophytic fungi are known as “litter transformers”. By eating dead organic material, they literally change the chemical composition of that material into something valuable for the soil.
Saprophytic microbes are therefore very important to composting, as they break down the organic material added to compost piles to turn it into rich soil. They essentially eat garbage and poop out gold.
Note: Not literal gold. Lol.
Compost fungi that result in mold are most often actinomycetes. Now, we’re not expecting you to remember that fancy word, but just know that these guys are naturally occurring in soil and that their presence is a GOOD THING.
Why Is There Mold On My Soil?
We’ve learned that the fungi which results in this type of mold (or “fruiting bodies” of fungi) is naturally-occuring. But not all soils have visible proof that these fungi are indeed present. Why, then, are you seeing mold?
Indoor plants are unfortunately (or fortunately, depending whether you’re looking at this scenario from the soil’s perspective) nearly a perfect environment for saprophytic fungi to develop fruiting bodies - mold.
The soil is closed-in, regularly dampened, and is not usually turned or aerated by either bugs, animals or gardeners.
1. Not Enough Aeration
There could be multiple reasons for seeing mold. Actinomycetes thrive in anaerobic (no air) conditions. If you’re seeing white mold on your soil, this could mean that there is an excess of anaerobic conditions - too little aeration - and actinomycetes are taking advantage.
2. Not Enough Sunlight
Not allowing your indoor plants to bask in the sun will limit the nutrients made available to these plants through photosynthesis. Insufficient natural light will also encourage the dark-and-damp conditions that mold loves so much.
3. Poor Drainage/Over-Watering
The same could be said for poor drainage in your soil. Fungi generate spores which float on any small air current and land nearby (for the most part). However, if the environment is not comfortable for them - lacking sufficient moisture - they will not propagate and develop into mold.
4. Organic Fertilizers
If you add an organic fertilizer to your soil just before planting or after you’ve already planted, you are increasing the risk of seeing that white mold on the top of your soil.
Fertilizer produced by an electric composter, or a material such as PittMoss, is a regular suspect for feeding the existing bacteria in your soil.
Because the powerful biomatter introduced into your soil is still in the process of decomposing, it is providing all the necessary nutrients for these bacteria (and your soil) to thrive.
Now, remember, this is a GOOD THING. You absolutely want to encourage the health and diversity of these bacteria and fungi.
However, just know that mold is often a symptom of this natural and positive phenomenon. Seeing mold from actinomycetes in your compost is fairly normal.
Once the compost has broken down into soil, it has been digested by fungi to such an extent that these bacteria are unlikely to produce mold after being added to your soil. However, it’s not impossible.
Because electric composters essenti