Mulch Fungus: Why it Forms and How to Deal with It.

Slime mold Dog Vomit (Fuligo septica) on shreds of woodIt’s gross. It’s ugly. It’s ruining your beautiful landscape. And no, it’s not the neighbor’s Pekingese.

It’s mulch fungus—an unattractive and unwelcome sight for many homeowners this spring. Known colloquially as “slime mold” and “dog vomit” due to its lumpy, often brightly colored appearance, mulch fungus can strike just about anywhere you spread mulch, and it’s common to Indiana.

The formation of mulch fungus happens in damp conditions as bacteria starts to feed on mulch. This is a microscopic process, but once fungi can feed on bacteria, they grow and create spores that eventually turn into clearly visible patches. While these patches are often yellow, they can be black, brown, white, orange, or even bright pink in certain cases.

Luckily, mulch fungus is not a serious problem. It poses little threat to plants since it feeds on bacteria, and it’s usually limited to small areas of your landscape. But it’s quite unsightly—and if you see it pop up in your mulch beds, you should get rid of it. It’s safe to touch, but you’ll probably want to get a shovel to dig it out. Make sure you scoop a few inches around the patch to eliminate unseen spores which can lead to a recurrence. Discard the fungus in a compost pile or in the trash—just make sure it’s far away from any mulch as spores can easily travel through the air.

Preventing mulch fungus is tricky, especially during wet spring months. But your best chance is to make sure your beds aren’t overwatered, and to water as closely to plant roots as possible. Letting a sprinkler water your entire flower bed all day creates an ideal environment for mulch fungus, so it’s better to use a hose or watering can to water plants individually when possible.

Another helpful tip is to give plants a significant watering once or twice per week (depending on precipitation) instead of watering them every day. A heavy watering will penetrate through mulch and get to roots more easily, while a light watering leaves much of the moisture stuck in the mulch—a perfect environment for mulch fungus. You might also want to rake your mulch at least a couple of times a month—especially during periods of heavy rain—to break apart fungus colonies.

If you’re having trouble with mulch fungus this year—or just need help improving your landscape with lighting, hardscaping, or beautiful plants—our team at Engledow would love to help. Contact us today to see what we can do for you.

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20 thoughts on “Mulch Fungus: Why it Forms and How to Deal with It.

  1. Thanks I was grossed out to see this, and glad it won’t harm my new bed. It is really ugly , yellow cream , dark brown, what a variety of colors.
    Again thank you

  2. Does mulch fungus get real hard almost like cement and very heavy?
    If not do you know what we have growing in a mulchy dirt area ?

    • Yes, over time it can get very hard like cement. Remove the fungus, along with a small area around it, in order to prevent it from spreading.

  3. Can it harm humans when discarding it? I cleaned some up today and wore gloves.
    But when I threw it in trash there were dust clouds.

    • The “dust” was simply the spores of the plant. It shouldn’t harm you, especially if you were wearing gloves.

    • Unfortunatly not. The easiest way to limit it is to remove it, thus removing the spores and potential for spread.

  4. I’ve just noticed this to pop up over the last week or so as I’ve noticed that my sensor on my Hunter Sprinkler unit wasn’t functioning properly. My system had been watering the grass after we’ve had downpours, so it’s apparent that my mulch beds had been overwatered.

    • We are unsure about its affect on dogs. To be safe, we would recommend removing it quickly to avoid potential exposure.

    • It is in the spores. Like all fungus, this type launches its very, very tiny spores out into the air with the hopes that some of them will survive. This is why it spreads so easily and is tough to keep under control.

  5. When I sprayed with the water hose, it form a brown fine dense cloud, dust like. iIs it dangerous to breath that dust? Also spread everywhere !

    • Those were the spores of the fungus. While I am unsure about breathing them in, I am sure that the human body will no be too negatively affected by the spores.

  6. This stuff is nasty. Looks like and has the texture of mustard mixed w/ mayo. I see it growing on the base of my trees. Will it harm them?

  7. Thank you! It was amazing getting to know if it was safe to touch and what it was! I was terrified when I saw it under my mint 🌱 plants! We Live in Arizona, never saw anything like this before, thank you.

  8. thanks for the great information,I was going to dig my mulch all up and not put any more down, but it does keep the weeds for filling in so fast.

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