Condo Blues: What’s this Yellow Mold Doing in My Compost?

Monday, May 11, 2009

What’s this Yellow Mold Doing in My Compost?

As with most newly built homes, my developer sold off all of the wonderfully fertile topsoil in my neighborhood and built our homes on the clay subsoil residing underneath. Unfortunately the builder didn’t put any topsoil back into the planting areas. Ever try to grow anything in clay soil? It doesn’t work very well.


Before I can even consider turning this dirt patch into a raised garden bed I need to mix organic material into the clay soil – preferable compost. Fortunately, sneaky person that I am I have a big ol’ composter making some fertilizer for me by way of a garbage can I made into a compost bin that fully complies with my Homeowner’s Association Rules. My first batch of compost came out well. After feeding the Covert Urban Composter food scraps all winter it was time to check how much Gardner’s Gold I had to work with this spring.

I mosey on over to the compost bin in the backyard. I take a look. I see this.

I get grossed out.

After some research I discovered that this yellow spongy, foamy and phallic looking blob is a slime mold. Specifically, Dog Vomit Slime Mold .

Aptly named don’t you think?

Dog Vomit Slime mold (gosh you just don’t get to type that several times in one sitting do you?) usually develops in damp, shady areas where there is a lot of decaying organic matter like soggy flower beds that use bark mulch.

This makes perfect sense because we’ve had a very rainy Spring. When I took the lid off of the compost bin everything was water logged. There was slime mold all over the top and sides of my compost. And boy did it ever stink! Bad.

How Do You Get Rid of Dog Vomit Slime Mold?

Easy. You don’t.

First off Dog Vomit Slime mold is not harmful to people, plants, or pets. In fact, some people in Mexico eat slime mold.

No thanks, I’ll pass.

It’s lifecycle is very short. When slime mold first appears it’s usually bright yellow and can grow as it chows down on the decaying wet leaves and whatnot (legend has it that slime molds were the inspiration for the kitschy 1958 sci-fi movie The Blob.) Next, the slime mold turns light brown and finally dries into dark, powdery spores. The whole process can take a couple of hours or a couple of days.

If this slime mold grew in the mulch in my flower beds I could just leave it and it would go away on its own. In this case I was advised to throw the moldy compost out.

Oh and just to you gross you out a little further, when I emptied the bin I found a nice big family of maggots in my compost.


Once the compost bin was empty I was told to clean it with either bleach (no thanks) or hydrogen peroxide (yes, please.) I mixed up a solution of hydrogen peroxide based “oxygen” bleach and water and used that to clean the compost bin inside and out, including the lid. I let the clean bin dry in the sun.

I emailed Gardener's Supply Ask an Expert and asked them how I could prevent my compost from molding again. This is what they said.

If you're developing mold in your compost pile it certainly sounds like the materials are too wet most of the time. Drilling more aeration holes would definitely help the ability of the pile to receive more air and should keep the materials more dry. Too much moisture will drown the microorganisms, and too little will dehydrate them. A general rule of thumb is to keep the material in your compost pile as moist as a well-wrung sponge.

To do their work most efficiently, microorganisms require a lot of oxygen. When your pile is first assembled, there will probably be plenty of air between the layers of materials. But as the microorganisms begin to work, they will start consuming oxygen. Unless you turn or in some way aerate your compost pile, they will run out of oxygen and become sluggish.

When your pile is very wet, try adding materials to sock up some of the moisture, such as paper, dried leaves, sawdust, or straw. Keeping a good balance between these "brown" ingredients, and the "green" ingredients such as grass clippings and food waste is very important
To make sure that I didn’t have moldy, soggy, maggoty compost again, I drilled more aeration holes in the bottom and sides of the Covert Urban Compost Bin. This last batch of compost was mostly kitchen scraps so I’m going to concentrate on adding more paper from my paper shredder for "browns." I’m also going to ask the lawn service to leave the grass clippings on our lawn so I can rake them up and put them in my compost bin. Oh, and this time I’ll try to turn the compost more often because last time I didn’t mix my compost at all - oops.

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This is Condo Blues’ submission for the May Green Moms Carnival where our topic is gardening. The Carnival will be held at Green and Clean Mom. Please check it out after May 18th!


Erika Jean said...

It looks kind of like a really nasty messed up cheese burger.

Lisa said...

That is nasty! I'm starting to get a little normal mold in my compost due to all the rain. I think I will put some cardboard or something in it tomorrow. It's not much so I think it's okay. Hoping it will heat up really well and dry out when we have some sun this week and go away. It doesn't really smell or anything.

Cheap Like Me said...

AAAAaaauuuuughhhh - that is disgusting. Thank you for showing me another reason to be happy to live in dry Colorado. On the plus side, what a wonderful biology experiment. Ew, ew, ew. The name is oh-so-apt. Good luck with your next batch of compost! I hope it works much better. Meanwhile, maybe some composted manure??

Contrariwise said...


We get those too, usually on top of our mulch. I always wondered what they were.

Cathy said...

wow--i've never seen that before--that's so gross! i can't believe some people eat it!

Sarah Eliza @ devastateboredom said...

Ewwwww that is freaking IMPRESSIVE. I love all that naturally occurring hideous weirdness... but sure wouldn't want to stumble across it one dark night LOL

Lisa Nelsen-Woods said...

Oh, yeah it was funky looking. Funny thing NONE of the dogs (mine or the neighbors) would go near it! And they are alwys sniffing around the compost bin!

My DIY pain for your enjoyment. Just one more service that I offer :)

Storm, The Psychotic Housewife said...

Ick ick ick!

Unknown said...

What in the world! I have never seen any thing that green and foamy like ever. Dog vomit, for real? That is just the nastiest thing ever and it grows......o no Lol

Jean Martha said...

Dog Vomit Slime?!?!? LOL Sorry,that made me giggle. Sorry to hear you're back to ground zero on making mulch.

Lidian said...

Oh, that is terrible! We have kitchen compost in a bin under the sink, not outside, the city has a program for this...and I used to think that got bad, sometimes. Never will i complain again.

hungryhungryrosa said...

Nice blog :) So do you use hydrogen peroxide instead of bleach for sanitizing everything? I can't stand the smell of bleach (plus it's kinda nasty stuff for the environment) but had trouble looking for a good alternative to use for cleaning...

JessTrev said...

Cmon, you made it up JUST so you could claim to be almost eating Dog Vomit Mold. Which, by the way, is the only thing that can make your maggots seem tame by comparison. If you are short on browns to balance out yr wet greens, remember you can always use newspaper and dryer lint (if you have either of those handy)! Good luck...

mother earth aka karen hanrahan said...

Truly interesting gardening phenomenon and really gross too!

Anna (Green Talk) said...

I get dog vomit in my mulch and absolutely hate it. As a tip this fall, collect bags of dry leaves and store them in your garage. I haul mine out every summer and this is my "brown" part of my compost. I find that paper takes too long to decompose.

I love Gardener Supply. I am always calling them to ask questions. I have one of their composter which has lots of air holes. My problem is my compost is never wet enough since it has a lid on it. I have lot of critters in my neighborhood!

Lisa Nelsen-Woods said...

Rosa – My research suggested either bleach or hydrogen peroxide because both will kill the mold spores in my compost bin. I don’t like to use bleach either for the same reasons, so I switched to hydrogen peroxide. It also works on cleaning icky stuff in the shower too. Who knew?

JessTrev – I am not making this up. In The Condo, DIY isn’t always as easy or perfect as it appears on TV!  And yes, the people who eat slime mold apparently fry it up like scrambled eggs. There’s no way I’d do that but it proves that slime molds just look disgusting but are harmless to you and yours.

Anna – Thanks for the tip. I was really impressed with Gardner’s Supply. They answered my questions quickly and I’m not even a customer! So, yeah, the next time I need something that I can’t buy locally I’m getting it from them. I have my eye on one of their tumbling composters, go fig? 

katyfarber said...

I too have been lusting after a compost tumbler, especially after our bin was hit by a slow plow. Let's just say it is far from pretty. Good job for sticking with it, dispite the serious drama.


mold inspections Manhattan said...

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