What’s growing in my bag of mulch or soil?

Spotting mold in soil you’re about to plant your heirloom tomatoes in, or finding fungus on mulch you plan to spread around the pansies by your front door may raise an alarm in your head. After all, mold and fungus just about anywhere else around your house may be a problem. But not all molds and fungi are harmful, and when it comes to gardening and landscaping, they can even play a helpful role in the ecosystem.

While it’s nothing to worry about, finding mold or fungus in your mulch or soil may raise some questions.

How does plant soil get moldy inside the bag? What about mulch?

Did you ever open a new bag of soil or mulch and find spots of white mold in it? Wonder how it got there? Well, mold or fungus can show up when there is moisture present around soils or organic matter. So if you find mold in your bag of soil or mulch, it’s due to the water content. Colored mulch, in particular, retains moisture from the dyeing process. Also, since soil and mulch bags typically aren’t waterproof, water can seep in after packaging occurs. 

Is mold in bags of soil or mulch harmful?

No, mold and fungus are natural components in healthy soil and mulch, and even contribute to a thriving garden. They won’t harm your plants, and they are safe for you and your pets to be around, though it’s still a good idea to wear gloves when handling soil and mulch.

What if I find mold on the outside of a bag of soil or mulch?

Mold that appears on the outside of a bag of growing media is bad. It indicates improper storage conditions and potential contamination. Do not buy it. 

So, you’re saying mold inside bags of soil or mulch is normal?

Yes, mold spores are naturally present in composted soils and mulches rich in organic matter. These spores thrive under moist conditions inside bags, helping decompose organic material and enrich soil. 

Mold and fungus in bags of soil and mulch can actually be beneficial? 

Fungi such as mold and mushrooms are important components that support a healthy soil ecosystem. These microorganisms help break down the organic material into nutrients your plants can absorb. This is why we don’t sterilize our growing media—we don’t want to kill off these beneficial microorganisms that play an important role in the ecosystem of your garden, enriching the soil and helping balance conditions that are good for your plants’ roots. 

What if there’s a lot of mold on my soil or mulch?

Sometimes, when soil or mulch is too wet, you’ll see an overgrowth of mold, which isn’t very attractive. While it’s not harmful to your plants, it should go away when the growing media is exposed to sunlight and air. So, if you want to reduce or eliminate the mold, for soil that hasn’t been used yet, you can let it dry out on sheets of newspaper before you use it. If the soil or mulch is already in your garden, allow your plants to dry out a bit between waterings. Again, it’s a good idea to use gloves when handling any growing media product.

Are some mulches less likely to have mold in the bag?

While mold and fungus in mulch and soil are normal, and not harmful to your plants, if you’re looking for a mulch that is less likely to have them, consider Miracle-Gro Organic™ All Natural Mulch. This product isn’t dyed, so there is less moisture in each bag, which means less mold.

Remember, not all molds and fungi are harmful. If you find some in your bags of soil or mulch, know that they are a natural occurrence and they play a helpful role in a healthy garden.