Growing mushrooms is often perceived to be an extremely complex and time-consuming task, but that doesn’t have to be the case! In this article we’ll show you how you can successfully cultivate oyster mushroom mycelium using coffee grounds – an economical and readily-available substrate.

Spent coffee grounds make an excellent resource for mushroom cultivation as they contain high levels of nutrients that have already been pasteurised during the coffee brewing process. Furthermore, they represent a valuable waste resource that would otherwise end up in landfill. Mushrooms tend to thrive on decomposing plant fibers and woody materials; using just some creativity and gardening skills we can transform this waste into delicious edible mushrooms!

This method can also help make use of excess coffee from local cafes and coffee shops that would otherwise go to waste, or tea bags or any other compostable plant material that you don’t like drinking yourself.

Let’s get going! Start by filling a large bucket with enough fresh, cool, and clean coffee grounds to cover about one third of its depth. Next, mix 50-100g of oyster mushroom spawn (or your own homemade slurry containing mycelium suspended in water) with coffee grounds using a spatula until everything is evenly mixed; and no gaps remain in the lid of your jar.

Once your jar has been inoculated with mycelium, cover it tightly and cover with vermiculite to preserve moisture levels and lower contamination risks while shielding mycelium from light that can break it down or produce fruiting bodies. This will also protect it from light damage that might lead to its breakdown or fruiting bodies forming prematurely.

Ideal results come from keeping the bag/jar in a warm dark environment until both coffee and mycelium have turned white. Any patches of green may indicate competing molds; should this happen repeatedly it may be best to separate this batch of spawn from its siblings and try again with an entirely new setup.

After approximately one week, you should start to see patches of cottony white growth on the coffee surface. This indicates mycelium colonising the substrate and creating a network that will support future fruiting. At this stage it is important to monitor for mold in your jar as well as use only clean tools in order to avoid contamination of your product.

Once your jar has become completely myceliated, it’s time to transfer it to a larger container – either 3-5L bucket or plastic bag will suffice – provided there are holes punched through for airflow and humidity regulation. Oyster mushroom strains that tolerate cold can go straight into the fridge while yellow and pink oyster mushroom strains require temperature drops for 12-24 hours as a cold shock in order to prevent fruiting on the surface of mycelium mycelia. Keep bag/bucket in dark humid environment ensuring daily misting sessions!