Coffee Grounds and Mould
Up until this weekend, I had a shed floor covered in used coffee grounds, with another lot sitting in a cardboard box. The idea was simply to see what happens with it, in a cold and dry environment.
Yes these are the sorts of things that I find interesting – things growing in coffee grounds. Let’s not dwell on it too long 🙂
Here we have some 4 month old grounds, covered over with fungi. I have seen this happen without fail to damp grounds regardless of whether they are in a plastic bag, a bucket, or piled in a heap on the garden or around plants. As you can see from the photos, it has spread through the entire pile. So to answer one of the questions I’m asked about all the time – will mold grow on used coffee grounds? The answer is yes (if they are kept damp).
Coffee Cake anyone?
Inside the cake -more coffee!
Even older – The box of 5 month old coffee grounds.
It seems that much of the fungi (which we also refer to as mould) drops off once the grounds are handled. Not having done a analysis of the type of fungus, I turned to the Internet, just like a do when I need to have a medical condition diagnosed.
Is there a Problem with Mould Growing on Coffee Grounds?
The general consensus among the gardening community is that no harm will come to you when handling the type of fungi that make use of coffee grounds, and that it is just a natural step in the process of decomposition. There is an interesting thread here about fungus on coffee grounds, another post here about fungus on coffee grounds, and many many more if you care to Google it.
What I find works is by using the grounds before they visibly mold, avoid keeping them in a pile when damp, or letting them dry out and then used at a more appropriate time. It is not always easy getting hold of freshly made used coffee grounds, and I have had my fair share of collecting bags of moldy coffee grounds. And at the end of the day, I’m not overly fussed what they look like, because they will end up the same, breaking down in one or another into the garden.
If moldy grounds are an issue for you, see if you can strike a deal to collect coffee grounds with a local coffee shop when they are fresh (same day or day after). The Ground to Ground Google map might be helpful in finding an appropriate cafe to collect from.
Like with anything else in the garden, take some simple precautions with gloves and a mask if things are dry and dusty. And wash your hands afterwards. There are billions of little creatures swimming around in those coffee grounds, like any other organic material.
If you have had an experience with coffee ground fungi growth, let us know in the comments below.
2011 Summer Update – Some more photos of mold on coffee grounds
This series of photos are from coffee pucks taken out of the worm farm – were sitting in there for several weeks. See the variety of green to blueish to white mold growing on them?
It is as it should be.
Ground to Ground 
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