I have some strange looking substance growing on top of our mulch! It has gone from yellow to brown and looks foamy. What is that?
Give me the right moisture levels, humidity levels and some organic matter breaking down, and I’ll show you some pretty funky looking things growing in the mulch. Whenever organic matter breaks down or is decomposing, you have bacteria and fungus helping out. You don’t see the bacteria, but the fungus can show up in many ways, including mushrooms. But there are a couple different things you’ll find in the mulch besides mushrooms. Birds Nest Fungus is one, and if you look closely, the fungus actually looks like a cup or birds nest, and looking even closer, you’ll see the ‘eggs’ in the middle. The fungus spores are actually in the ‘eggs’. When a rain drop lands in the nest, it forces the spores to jump out and land somewhere else in the mulch, to start the process all over again. You’ll also find what you’re describing. It’s called Dog Barf or Dog Vomit Fungus. Shows up over night, and looks like someone, or the dog, threw up in the mulch. This actually is not a fungus, but a slime mold, again developing as the mulch decomposes, and can slime its way up on foundations and plants. It starts out yellow or orange and slimy, then begins to dry, turns beige to brown and gets crusty on top – which eventually cracks open, and the spores fly away with the wind and the process starts all over again. Neither one of these are harmful to pets, kids or plants – they just look weird in the mulch – and there’s no control besides fluffing up the mulch, or scooping them up and throwing them away.