Brown and white speckled mushrooms growing out of a brown medium
(Image credit: Erica Hilario - EIGHTHREE MEDIA)

Mushroom lovers can now grow their own fungi. There are kits available containing the growing medium and spawn, or the gardener can make their own substrate. One easy way to source the substrate is from your local coffee shop. Have the shop save their grounds and then bring them home to start a mushroom colony. When you grow mushrooms in coffee grounds it helps reduce waste while providing a perfect medium for the fungi to form.

Gardeners are always looking for ways to reduce waste. We compost our food scraps, save our grass clippings, and constantly look at ways to give back to our soil. Coffee grounds are a natural byproduct of enjoying a cup of Joe, but they don't need to be garbage. Growing mushrooms with coffee grounds provides the pasteurized substrate that spawn need to colonize and grow mycelium, which will eventually fruit.

Coffee Grounds Mushrooms

Mushrooms grown in coffee grounds experience a couple of benefits. Used grounds are pasteurized when the scalding water passes through them. This means there are no competitive fungi, bacteria, or other items in the material.

The second benefit is more for the planet than the fungi. When a cup of coffee is brewed, less than 1% of the biomass is used, so the rest is discarded. Using this resource prevents adding to landfills. The remaining 99% is still loaded with nutrients that mushrooms can use. Probably the easiest mushrooms to grow using coffee grounds are oyster mushrooms. There are several varieties from which to choose. Use a reputable supplier of spawn to ensure a good crop.

Tips on Growing Mushrooms

When growing oyster mushrooms, coffee grounds should be fresh. Use the grounds as fresh as possible, because over time, the grounds will repopulate with unwanted organisms. The grounds should be collected on the same day and used, or frozen for later use.

You may purchase a grow bag or make your own growing container. A large bucket or tub, sterilized, and with holes drilled into the sides is also an excellent DIY solution. Fill the container 2/3rds full of a mixture of spawn and coffee grounds. Mix the spawn evenly into the coffee substrate. Cover the container or fold the bag down to seal in moisture. Keep the container where the temperature hovers around 68 degrees Fahrenheit (20 C.) in a dark location. Expect cottony growth in around 7 days. Mist the holes daily and wait for fruiting.

More Benefits of Using Coffee Grounds

As mentioned, the coffee should be fresh so it is free of other organisms. It should also ideally be organic. Coffee that is not organic many have been through chemical exposure or processes that can reduce the health of the grounds.

In addition to using up the extra biomass, using grounds removes the need to sterilize a substrate. Many mushrooms are grown on straw or sawdust which needs to be pasteurized with boiling water or steam. The process is messy and unwieldy in the home growing situation.

Coffee grounds are free, easy to source, and a quick way to get into mushroom growing. Growing your own mushrooms also reduces the carbon footprint necessary to get our food to the market and our tables. The process will turn you into an eco-warrior while providing delicious food for your family.

Bonnie L. Grant

Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping.