07/17/2026
What's That Bright Yellow Stuff in Your Mulch? If you've spotted a bright yellow patch in your mulch, there's no need to worry. It's most likely slime mold—a naturally occurring organism that appears as mulch begins to decompose.
Here's what you should know:
• It's harmless to people, pets, plants, and your landscape.
• It's temporary and usually disappears on its own during warm, dry weather.
• It's a sign that natural decomposition is taking place.
If you'd rather remove it, gently cover it with fresh mulch or carefully shovel it out. Avoid raking it, as that can spread the spores. Healthy mulch is always changing, and sometimes nature puts that process on full display.
Have you ever found slime mold in your mulch?