The Q&A Archives: Fungus in Mulch

Question: It has been quite a wet spring here in eastern Wisconsin, I have several very large flower beds on hillsides and have used shredded red oak bark as a mulch. It is several inches thick, and has developed patches of thick yellow
foamy looking growths on the surface. After a day or two each patch (approx 5 inches X 10 inches) turns black on the surface and dries. They are very unsightly and I am uncertain if they will harm my perennials planted in these beds. How can I get rid of them, and can I do anything to prevent their growth?

Answer: Welcome to the wonderful world of slime molds! These goopy fungi (Myxomycetes) live on dead organic matter and thrive in moist conditions. You can rake it out and dump it in the trash; especially in the early stages before it spreads its spores. Increasing the air circulation and allowing the soil to dry out will help eliminate the stuff. To help stop the growth of slime mold, just rake any mulch on the soil surface to expose it to air and sunlight. It's perfectly harmless - just revolting to look at!

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