Can You Use Moldy Potting Soil? (Expert Gardeners Comment)

Oh no!

You see some white mold in your bags of potting mix.

Is there a way to use this potting mix? Or will you have to throw it away?

Yes, moldy potting mix can be used for plants because the mold is a harmless fungus. You need to investigate the cause for the mold because it is a sign of overwatering. This happens when water is not draining out from the potting mix due to lack of drainage holes or poor potting mix.

Despite popular belief, moldy potting mix is not as big of an issue as it may seem to be. You can choose to ignore it and continue to use the potting mix you have, treat your potting mix for mold, or you can throw out the entire package and start over, whatever works best for you. Let’s talk about some ways you can deal with mold in your potting mix. 

Why is my potting mix moldy?

Your potting mix is moldy because it may have got too much moisture. An excess of water will not only lead to potentially moldy soil, but it could also lead to root rot which will slowly but steadily kill your plants.

If you are noticing mold in potting soil, adjust your watering schedule.

Potting soil can also get contaminated and moldy over time. If you’ve got a bag of soil that has been sitting in a warm, moist area for years upon years, it should come as no surprise that there is mold in potting soil bag.

If you resort to using the oldest bag of potting mix hanging around the house, you can probably count on having a fair amount of fungus coating it. 

What are the effects of mold on potting mix?

If we’re being honest, most mold that you will find on your potting mix is pretty harmless. Most of the mold you’ll find is white and dusty-looking, sometimes with brown or black splotches. This harmless fungus is called Saprophytic fungi. It usually results from the issues mentioned earlier, such as too much water, age, and more.

This mold is unnecessary to make a fuss over because, in reality, it won’t damage the plant. It is a likely indicator that your soil and plant aren’t getting all that they need to flourish, but it won’t pose an immediate threat.

Although the mouldy potting mix is not always harmful to your greens, it may compete with your plants for soil nutrition. Hence, it’s important to either discard the affected potting mix or try getting rid of mould with some organic neem cake. – Karan Mahajan, Co-Founder, All That Grows

Growth of mold is a sign that you are overwatering the plant. Or it is not getting the right amount of sunlight. Maybe the growth is causing humid conditions that are encouraging mold growth.

If nothing else, get rid of moldy potting mix for your own sake. It may not bother the plant right away or even ever, but if the mold gets, well, moldy enough, you will notice it giving off a mild yet unpleasant odor.

Those who have smelled mold wish never to smell it again. If your plant stinks, that is a sign to replace your potting mix. If you decide not to replace the stinky potting mix, treat it for mold growth at least.

How do I treat mold on potting mix?

The obvious next step is to get rid of that mold that you are finding in your potted plants. Don’t fret, because this is probably going to be a lot easier than you might think.

Use a mask and gloves because mold is the last thing you probably want getting all over your hands or up your nose! Be careful, since inhaling mold spores can get you sick as well.

The first thing you’ll need to do is move your plant to a more sunny area. Dark, moist areas allow mold to flourish and grow with absolutely no restraints. Moving it to the heat and the light will help keep all the mold under control, plus hopefully, the sunlight will make it easier for the plant to get all the nutrients it needs. 

You can also try sprinkling the surface of your soil with cinnamon. Cinnamaldehyde is what gives cinnamon its natural scent and flavor.

It acts as a natural fungicide that will keep mold and fungus from growing in your potting soil just as well as any other chemical you might find at the hardware store. Sprinkle it over your soil every so often and see if that works.

It is ok to use, since they don’t harm the plant. Although we cannot see, molds and fungi are present in gardening mixes. Also many gardeners believe that living soil is an ideal environment for growth and a sign of life, although it doesn’t look good to the eye. If it doesn’t seem right, one can scoop out the mold along with a little soil beneath it. – Vinayak Garg, Founder, Lazy Gardener

If you are not convinced that cinnamon will work, you can also try using fungicides at the store. Remember, store-bought fungicides may be more dangerous, especially for kids or pets who might try to get into your plants. Be careful about using these products, and there should not be a problem.

Finally, you adjust your watering schedule. Make a habit of touching the soil to see if the top couple of inches are dry. Water the plant only if the surface of the potting mix is dry else hold off on the watering.

Overwatering will, as mentioned earlier, cause mold and rot to grow pretty quickly. If you carefully regulate your watering, you shouldn’t face as many problems with mold as you might otherwise.