What is Growing on my Mulch?

What is this growing on my mulch?

Wind River Tumbled Edging Garden

Mulch serves some incredibly valuable benefits for your plant beds—not only making them look great but also protecting your plants’ roots from wind and heat and suppressing weeds. When you invest in top-quality mulch, you are looking for optimal performance and if installed properly, that’s exactly what you’ll get. However, even with a proper installation and a high-quality mulch, you can still end up finding some icky and unattractive growth atop your mulch. With this, you must ask yourself “What is this growing on my mulch?”

You might be wondering what this growth is and more importantly, whether it can harm your plants. We’re digging into the details to help set you up for success.

Identifying What’s Growing on Your Mulch

First, let’s cut straight to the chase. The growth that you may have spotted in your mulch is fungus. There are several types of fungal growths that occur in mulch, which we’ll dive into next. Although unpleasant, fungal growth in mulch is normal. Many types of fungi assist in the natural breakdown of mulch. This mulch decomposition process is actually beneficial to your plant beds as it improves soil fertility by making nutrients more readily available to your plants. Decomposed mulch also increases the soil’s capability of retaining water.

Now that you know why you might be seeing growth—and that it is no reason to panic—let’s look into the types of fungus that can be present in mulch.

Slime Mold

To be candid, slime mold looks a lot like something thrown up in your plant beds—so much so, that it has earned the common moniker “Dog Vomit.” The scientific name for this species of mold is Fuligo Septica.

This type of mold begins as a bright yellow, slimy foam that really does look a lot like a dog got sick. Over time, the slime begins to dry and turn brown—and then, in the last stage, turns to a white powdery color. This type of fungus thrives in warm, moist areas of the plant bed, particularly in shady spots. Slime mold will feed on bacteria in the mulch for a while until it begins to eventually dissolve and disappear on its own. That means you can just leave it be—allowing the natural decomposition process to take place. But if it really bothers you, it won’t hurt to scoop it up with a shovel and dispose of it.

Bird’s Nest Fungus

Another fungus named for its appearance, bird’s nest fungus resembles tiny egg-filled birds’ nests. The scientific name for this growth is Nidulariaceae. The “eggs” are actually spore masses. Again, these are naturally occurring fungi that are helping in the decomposition process and will not cause any harm. However, if it is bothering you, can you rake the areas of fungus to disrupt the fruiting bodies and break up the growth?

Artillery Fungus

This type of fungus also has an egg-like look. It resembles a tiny cup with one black egg inside. However, unlike the other fungus types, artillery fungus can actually become a problem—but not to your plants.

Although this fungus grows in mulch, it can shoot its spores onto light-colored surfaces such as house siding or even your car where it will leave black specks that are hard to remove. As you might expect, artillery fungus gets its name from its shooting ability. Spores can be shot as far as 20 feet! Try and prevent this fungal growth in the first place by keeping mulch beds well-raked to remain dry and aerated.


Finally, we would be remiss if we didn’t also mention mushrooms, which can also commonly grow in mulch. Mushrooms can pop up in a variety of colors and sizes. Though a lot of homeowners think of mushrooms as a nuisance, they aren’t generally a problem and won’t do any harm to your plants. However, it must be mentioned that mushrooms can be very dangerous—even deadly—if consumed. If you have children or pets, always be cautious of any mushroom growth that might occur in your plant beds and dispose of them safely.

We are Here to Help!

Hopefully, this helped to answer some of your mulch growth questions. However, if you have more questions or think you see something else growing in your plant beds that wasn’t covered here, we at Nature's Mulch are always available to help. Feel free to reach out or stop in at any time. We’re committed to helping set you up for success!

Back to Posts Back to Posts
Contact Us for Order and Delivery