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Can You Use Moldy Mulch? (Quick Answers)

Do you want to use moldy mulch for your plants? Are you wondering whether or not any negative consequences can happen from the usage of moldy mulch in the soil? Does the usage of moldy mulch affect humans negatively?

Using moldy mulch 

There is nothing wrong with using moldy mulch for your garden plants but it is better not to use one. This is because although plants aren’t really harmed by moldy mulch, humans are definitely severely affected by the spreading of mold spores from mulch around the garden.

There isn’t anything wrong with using moldy mulch in your plants as mold growth is a very common and natural phenomenon.

It is the moisture, humidity, and temperature of the mulch that attract mold to grow on mulch and the growth of mold on mulch is also a way of decomposing the organic elements that are found in mulch.

Therefore, this natural process shouldn’t be a matter of concern for gardeners rather maintaining the mulch properly may help you in controlling the mold growth.

Moldy mulch isn’t the best appealing look for your garden but the moldy mulch will not severely damage the integrity of mulch.

Therefore, moldy mulch will still be able to provide water retention, weed prevention, insulation, temperature balance, and so on. However, the effect may not be the same as the fresh mulch. 

Moreover, there are several types of molds that can grow on mulch such as brown, yellow, green, black, white, and so on.

While some varieties of mold may result to be damaging, most of them aren’t really harmful to your plants.

However, the problem comes when mold spores from the mulch are spread with water, animals, insect, wind, and so on.

This spreading of mold spores will definitely be harmful in this situation as several health damages can be caused by the spreading.

This is why it is usually better to prevent mold spores from developing in mulch and to do that, you need to alter the pH level of the soil, use vinegar or sulfur, root out the mold spores, dry out the moisture from the mulch, and so on.

Is it safe for humans?

Moldy mulch may not be that much harmful to plants but it is not at all safe for humans. While gardening, if you happen to inhale mold spores, you risk having several long-term lung-related diseases.

In addition, you may also develop different types of allergic reactions to the inhalation of mold spores from mulch which are as follows runny nose, itching, difficulty breathing, fatigue, sneezing, headache, and so on.

Moreover, you may also get skin rash, infection, and asthma which can cause you to end up in the emergency room.

In addition, the mycotoxins and irritants in the mold spores are responsible for causing such intense reactions in humans which is why it is better to discard moldy mulch and use new ones.

Should I remove moldy mulch?

It is not necessary to remove moldy mulch because normally, it is not damaging to plants. However, some mold can be harmful to plants, for instance, white mold but in most cases, moldy mulch is not destructive to plants.

Accordingly, mulch mixed with the soil works as a source of natural nutrients for it, so removing moldy mulch will not be a wise decision because it will be a waste of physical energy and money. 

Therefore, you need to first analyze the damage moldy mulch has caused to your plants and you need to act accordingly to that.

So, if you see the mold spores from the mulch have taken over most of the mulch of the garden, then you need to either use vinegar or lessen the moisture intake to remedy the situation as soon as possible.

What can I do with old moldy mulch?

Gardening supplies aren’t really cheap and the same goes for mulch. Therefore, if your garden mulch is infested with mold, you may reuse it in several other ways instead of discarding it completely. 


One of the best ways to reuse your old moldy mulch is to use it as a fertilizer. Although this will not be one of the best fertilizers, it will still get the work done to a minimal level.

This is because the organic matter (wood, leaves, or cover crops) that is present in mulch will add nutrients and beneficial microorganisms which will cause less disease and damage to plants.

Use for compost:

Because old moldy mulch has already gone through the processes of decomposition, you can therefore throw it in your compost basket to work as a soil amendment instead of tossing old moldy mulch away.

Soil cover:

You can still use old moldy mulch as a soil cover so that weeds cannot grow, moisture can be retained, and proper temperature can be maintained for the betterment of plants.

Therefore, all you need to do is to spread old moldy mulch about three to four inches high on top of the soil to work as a good soil cover.

How to remove mold spores from mulch? 

Mold spores found in mulch aren’t always a bad thing for the soil or the plants. Rather several beneficial attributes can be derived from the development of mold spores in mulch.

However, you definitely should be aware of the processes that you need to follow to remove mold spores from mulch so that you can act effectively when the situation arises.

Use vinegar:

One of the best things you can do to remove mold spores from mulch is through the usage of vinegar as almost 82% of mold spores can get eradicated by the usage of vinegar on mulch.

In addition, you can use either pure vinegar or diluted vinegar to get the job done. To make the diluted vinegar, you need to use one cup of vinegar and one cup of water and you need to mix it, and then pour it into a spray bottle.

After you are done making the vinegar solution, you need to spray that vinegar solution onto the mold spores on the mulch.

You need to make sure you do this several times as a single treatment with vinegar won’t do much. Rather the constant usage of vinegar solution will definitely weaken the structure of the mold spores and thus will definitely eradicate them for good.

This is because the acidity level of the vinegar doesn’t really sit well with mold structure which is why the mold will start to deteriorate.

Remove from the root:

There can be times when vinegar solution may not work and thus you need to adopt a process that requires you to remove, relocate and replace the mold spores from the mulch.

Accordingly, to do this, you need to dig out all the mold-infested mulch from the soil completely. You then need to relocate it meaning you need to throw the affected mulch away.

After that, you need to replace your old mulch with new mulch so that proper nutrients and minerals can be provided to your plants and the soil.

In addition, while digging out mulch, you need to make sure you wear gloves and masks so that you don’t breathe in any mold particles or spores which can cause serious allergies or asthma.

Let the mold dry:

One of the things that you can do is to dry the mold out properly so that mold spores can be eradicated from mulch.

In addition, this method will not work in conditions where there is high humidity or heavy rain probability.

To make this process work, you need to make sure that moisture which is the main source of mold growth is not always soaking the mulch fully.

While watering, you need to make sure to notice the condition of the mulch to see whether it is dry or wet and act accordingly to that situation otherwise you will risk overwatering.

This is why you can use a drip irrigation system instead of a sprinkler to water your plants or you can use a watering can to control the water intake properly so that excess moisture can’t cause mold spores in the mulch.

Adjust the pH level:

Another step you can follow if the above-mentioned processes don’t work is related to the raising or lowering of the pH level of the soil. Soil that is too acidic or too alkaline offers a very unfavorable environment for mold spores.

Therefore, you can use sulfur to lower the PH level and calcium carbonate to raise the pH level of the soil so that mold spores are eliminated efficiently from mulch.

Final Thoughts

It is more than common to have mulch develop mold over time as perfect humidity, temperature, and moisture of mulch attract mold structure. Therefore, mold growth on mulch is natural and it still can be used on the soil to provide water retention and weed prevention.