This site is supported by our readers. We may earn a commission, at no cost to you, if you purchase through links.
You can get rid of mold on top of plant soil by physically removing the mold, repotting the plant, adding a thin layer of cinnamon on the top soil, flushing with neem oil or placing the plant outside. Which method is most effective will depend on how severe the mold situation is.
An even better approach is to prevent mold from growing on potted plant soil. It is an easy plant problem to avoid if you know what to pay attention to.
Read on to learn more about mold on plant soil, how to prevent it from growing on your houseplants and how to get rid of it.
Table Of Contents
- Why Is There Mold On Top of My Plant Soil?
- Is Mold Bad for Plants?
- How to Prevent Mold from Growing on Potted Plant Soil
- How to Get Rid of Mold in Potted Plants
- Frequently Asked Questions:
Why Is There Mold On Top of My Plant Soil?
Mold in plant soil is relatively common and there are many different kinds of mold that can grow on plant soil. The most common type looks like a white fuzzy layer, similar to a thick spider web. This is not a Halloween decoration, it is most likely Saprohytic Fungus.
Saprophytic fungus is a type of fungi that feeds on decaying organic material. Plant soil often contains a lot of decaying debris which is why this fungi may show up on your potted plants.
This fungi is actually quite common in soil but often remains unnoticed. Saprophytic sungus becomes noticeable when there is a lot of dead matter in the soil along with its ideal humid conditions.
Other Types of Mold Growing on Plant Soil
- Botrytis: a grayish blue mold that appears on damaged plants and decaying plant soil
- Sooty Mold: dark gray fungal disease caused by insects secreting honeydew
Is Mold Bad for Plants?
In the case of saprophytic fungus, mold is not necessarily bad for the plant. However, if you notice a lot of the fuzzy white mold on your plant it is an indication that your plant is not healthy.
Saprophytic fungus is a sign that the soil is too moist and the plant is not receiving enough sunlight. Most fungi thrive in humid and low light conditions.
The good news is that the mold is not necessarily harmful to the plant itself. This is because it only feeds on the decaying matter found in the soil.
On the other hand, overly moist soil can lead to root rot so you do have to take action in time to save your plant. Fortunately, getting rid of mold on plants is not too difficult.
How to Prevent Mold from Growing on Potted Plant Soil
Preventing mold from growing on potted plant soil is simple: prevent overly moist soil and provide sufficient sunlight. The key elements here are water and sunlight.
Here are five simple ways you can prevent mold from growing on potted plant soil.
1. Water Plants According to Soil Moisture
As creatures of habit, many of us have a routine for when we water our plants. Although there are good rules of thumb, checking the actual soil moisture is more reliable.
For example, watering plants every week could lead to overwatering if the plant has a slower absorption rate. The more accurate option is to check how moist the potted soil is.
In this case, the rule of thumb is only watering when 1/5 of the soil is dry which generally amounts to the top 1 – 2 inches of potted plant soil. To make things simpler, do not water your plants when the top layer still feels moist – wait until it has become drier.
2. Provide Enough Drainage
Excess water should flush through the soil which is why pots with drainage holes are so important for potten plants. Make sure that these holes are not blocked by anything other than soil.
Most potted plants are placed on top of a drip tray to catch excess water. Make sure you throw away the excess water regularly to avoid creating more humid conditions.
If you are watering your plant by filling up the drip tray, you still need to remove the excess water. Generally, plants are able to absorb enough water after just 30 minutes in a filled drip tray.
3. Offer Enough Ventilation
Well ventilated rooms are less likely to be humid. So, if you keep a plant in a more humid room, like the bathroom for example, it is worth it to move the plant to a more airy space.
This doesn’t mean that the plant can never be in the more humid room. It means that you will have to give it a few hours or even a day in a space with better ventilation, every once in a while.
4. Place in Enough Sunlight
Fungus thrives in low light conditions. Dark rooms or even dark corners are generally not the ideal spot for a houseplant.
If you notice mold on your potting soil this is often an indication that the plant does not receive enough sunlight. The solution is simple, move the plant to a brighter spot.
5. Remove Debris
A few leaves falling off your plant is no reason to panic, for some plants it is even natural. The problem is that once this debris starts to decay, you are risking the growth of mold.
A simple tip is to check for debris each time you water the plant. Either throw it in the garden waste bin or add it to your compost pile.
How to Get Rid of Mold in Potted Plants
Sometimes it is too late for prevention and we have to deal with potting soil that is already moldy. Again, this is no reason to panic – it is relatively easy to get rid of mold growing on soil.
Here are ways to remove mold from the top layer of your houseplant soil.
1. Place the Plant Outside
When you only see the beginnings of mold, no drastic measures are necessary. All you have to do is place your plant in a spot that is the opposite of ideal for mold: outside in bright sunlight with wind.
After a few days, the mold will probably have died off making it safe to place inside again. Just remember to put it in a ventilated, non-humid and sunny spot.
2. Physically Remove the Mold
Often, mold only affects the top layer of the soil. In theory, it is possible to simply remove the top layer of soil and replace it with fresh new soil.
Most mold variations growing on plant soil are not harmful to humans but they can still be irritating. That is why it is best practice to wear gloves when removing the mold, avoid contact with the eyes and thoroughly wash your hands and tools after.
3. Repot the Plant
If you want to be completely sure that there is no mold left in the soil you will have to repot your plant. This can be quite an undertaking, especially for the more sensitive plants so think it through.
Make sure to properly sterilize the plant pot, even if you are moving the plant to a different container. There might still be traces of spores left which could affect the next plant you place inside.
4. Add a Layer of Cinnamon Dust
Cinnamon is naturally anti-fungal and could actually help eradicate mold from plant soil. All you have to is spread an even layer of cinnamon powder on the top soil.
5. Flush with Neem Oil
Neem oil seems to be the new miracle liquid that cures a wide range of household issues, including mold on potted soil. In this case, the neem oil is diluted in water to create an anti-fungal flush.
Add approximately two teaspoons of neem oil to half a gallon of water. Water your plant as you regularly would with the neem solution.
It is important that you leave enough time for the neem oil to drain through the soil. Do not overwater in the hope it will work faster, wait until the top layer is dry before watering with the neem solution again.
Frequently Asked Questions:
Does Cinnamon Kill Mold in Soil?
Yes, cinnamon has the potential to kill mold growing on plant soil. Cinnamon contains cinnamaldehyde which has natural anti-fungal properties.
Sprinkling a thin layer of cinnamon powder on potted plant soil can help kill any mold that might be growing on it. The cinnamon powder will not harm the plant.
Does Vinegar Kill Mold?
Vinegar does kill mold. In fact, it can tackle over 80 different species of mold, including most that grown on plant soil.
However, vinegar is also highly acidic. Spraying vinegar on a plant can cause burning of the leaves and flowers and it can make the soil too acidic.
Even though vinegar is effective in treating mold, it is not the best solution for treating mold on houseplants. There are safer natural ways that won’t cause harm to plants.
Does Baking Soda Kill Mold on Plants?
Baking soda does kill mold on plants but it is not a good option for treating mold that is growing on top of plant soil. This is because baking soda affects the pH level of the plant soil, causing a change in essential nutrients or even stunted plant growth.
The only time it is safe to use baking soda to kill mold on plants is if the mold is on the plant itself – the leaves, stems or flowers. In that case, you can make a very diluted spray using 1 teaspoon of baking soda for 1 quart of water.
Even then, spray sparingly so that the baking soda solution does not seep into the soil.
Mold is a more commonly present on potting soil that you might think. Often, plant owners don’t even notice the mold because it might only be present in very small quantities.
Mold becomes more noticeable when the plant is not as healthy as it should be. Fungi tends to grow in humid, poorly ventilated and dark spaces which is the opposite of ideal conditions for most plants.
So, the first step in dealing with mold on plant soil is placing the plant in a more suitable spot. If there is already a lot of mold, repotting may be necessary.
Other solutions for mold on plant soil are placing the plant outside or using natural substances with anti-fungal properties like cinnamon and neem oil. When testing these methods, make sure to also avoid overwatering.
Although it is relatively easy to remove mold, it is even easier to prevent it. The most important things to remember is to make sure the plant soil is not overly moist and that the plant receives enough sunlight.
With these preventative methods and solutions to mold on plant soil, your plants can survive the presence of fungi. Keep the plant healthy and mold will not be a problem.