How to Get Rid of the Yellow Foamy Fungus on Your Mulch

Don’t fret if a foamy fungus has sprung up in spots across your mulch. We’ll tell you what it is, what causes it, and what to do about it.

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The Question: A builder landscaped our new home, sodding the front lawn and planting various perennials and shrubs. The plants are surrounded by mulch. About a week ago, I saw two foamy yellow piles on the mulch. What is it, and how do I get rid of it?

It sounds as though you have a slime mold growing on your wood mulch. I'm guessing that the lawn and new plants have been heavily watered (probably to help the sod), because this slime mold generally develops when moisture is plentiful. There's not much you need to do except cut back on the moisture a bit.

Luckily, the fungus won't harm anything, and it will disappear on its own when the weather warms up and dries out. If it continues to appear as the weather gets drier and you have cut back on watering, it could be a sign that the area drains poorly. Keep that in mind, and water less often in those spots. In the meantime, you can break up the foamy yellow piles with a garden rake to make them less unsightly. Newly ground or chipped wood mulch is more likely to develop slime molds. It's best to allow the wood mulch to sit for a year or so before it's spread.

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