Today I am super excited to share with you my latest adventures: how to grow mushrooms in used coffee grounds and cardboard! It’s a very simple technique of growing mushrooms that requires no sterilization or special tools. And it can be done at home indoors or outdoors in any season.
I learned this method of growing mushrooms from an expert ( see more in resources at the end ). I love the simplicity of it, and how it allows everyone to grow delicious mushrooms at home using easily accessible and mostly free materials.
Below is a video of how fast these Oyster mushrooms grew in just 4 days!
Ready to come down the rabbit hole with me? ( Some of the helpful resources are affiliate links. Full disclosure here. )
Materials and tools to grow mushrooms at home:
( Some of the helpful resources are affiliate links. Full disclosure here. )
- coffee grounds and cardboard: a match made in mushroom heaven. Coffee grounds are rich in nutrients, but can contaminate easily. Corrugated cardboard is not as rich and delicious to competing molds and bacteria, and the corrugation allows room for air and for the mycelium (mushroom roots) to run.
- mushroom spawn: think of them as seedlings for you to grow mushrooms. This beautiful box of Elm Oyster spawn ( Not all kits are spawn! See tips at the end!) came from 100th Monkey Mushroom , a wonderful family run business with many great products and tutorials. Eventually you can learn to grow your own mushroom spawn from mushroom stem base! But you do need great quality spawn to get started! (more on that at the end)
- 13 gallon clear medium size trash bags like these will come in handy throughout the process
- 70% to 99% rubbing alcohol to keep everything clean and reduce contamination
Step 1: prepare cardboard and container to grow mushrooms
When you have all the materials you need to grow mushrooms, ask for a bag of hot-off-the-press coffee grounds from the fabulous people at Starbucks, and soak some cardboard in water 1-2 days prior. The coffee grounds should be used on the same day, and the long soaking of the cardboard helps to hydrate the material for growing mushrooms.
Take a one-gallon plastic container, cut 3 sides of the lid. Poke and cut 4 to 6 small 1/4″ size holes to allow air exchange and drainage on the bottom. Wipe the inside and outside of the container with 70% to 99% rubbing alcohol.
When you try to grow mushrooms at home, the biggest challenge is contamination. So keep the working area as clean as possible, and work fast!
Another fun growing project you may love – How to create a strawberry tower planter with built-in reservoir!
Step 2: layering mushroom spawn, coffee grounds, and cardboard
Break up 20% to 25% of the oyster mushroom spawn for each 1 gallon container.
Keep some paper towel dipped in alcohol handy, and wipe your work surface, hands, and anything that would come in contact with the spawn.
First put down 2-3 layers of cardboard. I put the Starbucks mermaid bag in there for fun, but it’s not required!
Sprinkle some spawn, then cover with a thin layer of coffee grounds. The coffee grounds can be warm or cool, but should not be too hot or freezing cold to the touch.
When in doubt, always use more spawn, because it will give competing fungus and bacteria less chance to establish.
Repeat the layers till the container is filled. Top with a layer of cardboard, and close the lid. Small air gaps are fine.
Loosely drape a plastic bag over the container to allow for air exchange, but keep in moisture. The saucer on the bottom is to catch excess liquid, if any, and to pour them out so the growing medium won’t get soggy on the bottom.
Put the container in a dark place for 2 weeks. Check every few days to make sure it’s not drying out. (OK, I checked many times a day, well, too excited! ) Spray water inside the bag or lid of the container if needed.
Within just 4 days, the mycelium (mushroom roots) started to grow happily! See photo above. Isn’t it exciting to grow mushrooms?!?
Then the magical day came in about 20 days, when the first baby mushrooms ( primordia ) were spotted!!!
Dr. Seuss little forest!! Can you see them? Continue to next page –