Which Mushrooms Can You Grow on Coffee Grounds
Oyster mushrooms and shittake are by far the most popular mushrooms to grow on coffee grounds and they’re also two of the easiest for beginners. Best of all, they’re both pretty nutritious.
Pearl and elm oyster mushrooms should both do equally well, and their taste is close enough to one another that they could be used interchangeably. Other related species should have similar levels of performance.
You could also grow cubensis from used grounds, though this is going to be a little more challenging than an oyster mushroom would be. Black poplar mushrooms are sometimes grown by enthusiasts, but again these would be quite challenging for most beginners.
Can You Grow Cubensis on Coffee Grounds?
While you can grow cubensis on coffee grounds, you’ll want to make sure that the clear plastic bag you used to do so is completely sterilized. These mushrooms tend to be even more sensitive to bacteria than most other culinary grade ones that you might want to grow, so they take special care to grow properly.
Use a bag that’s truly clear as opposed to a translucent color. Dyes used to color bags can actually change the pH level of the coffee ground and substrate mixture.
This isn’t usually enough to cause much of a problem, but it can be for mushrooms of this caliber.
Can You Grow Lion’s Mane in Coffee Grounds?
In theory, you could grow Lion’s Mane coffee grounds, but it’s relatively difficult. Biologists from the University of Arizona have gotten these valuable gourmet mushrooms to grow on coffee grounds as well as grass clippings.
They’ve even found that they could grow on a combination of used pizza boxes and damp straw. However, all of these tests were conducted under laboratory conditions.
Lion’s Mane has a tendency to be finicky, which is why it’s worth so much to chefs. If you wanted to try growing them this way, then you might want to find an area that has just the right temperature and humidity level to do so.
How Do You Sterilize Coffee Grounds?
Place the coffee grounds into an oven bag inside of a pot of boiling water on a regular kitchen stove. To sterilize them, you need to reach a temperature of around 250°F for at least a half hour.
Some mushroom enthusiasts recommend boiling them for a longer period of time, especially if you plan on growing cubensis or lion’s mane in your coffee grounds. Others recommend a 161°F temperature for 15 seconds in order to pasteurize them, which is useful for growing less sensitive mushrooms.
How Do I Know if Mycelium Is Growing?
Mycelium particles attached to mushroom fungus can lie dormant for a long period of time, which makes it hard toknow if they’re growing or not. Check to see if there are any white hairs starting to form through the coffee grounds.
Don’t expose your bag or container to too much light if you don’t have to, but you’ll want to perform a complete inspection. These fibers should be visible if the mycelium has started to grow.
Eventually, these will begin to sprout full-sized mushroom caps, which is a clear sign that your colony has reached a relatively mature stage of development.
How Do I Prevent Contamination?
Inadequate sterilization is the biggest cause of contamination. Treat all of your equipment, work surfaces and the growing area itself with alcohol before you start working.
Use a pressure cooker or other kitchen device to sterilize your substrate. This will make sure that no bacteria gets into the final mixture.
You’ll also need to make sure that the coffee grounds themselves are boiled until they’re sterilized as well. Check the pressure on any pressure cooker that you might be using to ensure that your substrate and grounds are being cooked to just the right level to ensure cleanliness.
How Do I Know if it Gets Contaminated and What Do I Do?
Bacteria will often produce biological slime or discolor the substrate itself. These are your biggest clues that something has gone wrong.
Use sterilize tools to remove at least some portion of the affected area and make sure that all future substrate or coffee grounds added to the mix has been treated following the best growing practices possible.
Make sure to clean your hands before performing this kind of work, because there’s a risk that you could actually introduce additional bacteria cells into the mixture from your hands. Pressure cook any material that you add to a mushroom growing container to reduce the risk of cross-contaimination.
How to Grow Mushrooms on Coffee Grounds
First, you’ll want to make sure you have enough grounds for the weight you’re working with. Consider using a mixture of 70 percent grounds, 20 percent sawdust pellets or straw and 10 percent mushroom spawn.
Try following these steps to build a successful mushroom garden:
- Disinfect the growing area to prevent the spread of bacteria
- Boil your straw or sawdust at 170°F to kill any organisms in it, then use a salad strainer to get the loose water out
- Mix coffee grounds with straw, sawdust or other substrate
- Pull out any clumps
- Break up your mushroom spawn and add it
- Dump the mixture into a cleaned container
- Seal it with a twist tie after burping out all the air
- Poke a few holes in the bottom for air
- Place the container in a humid area around 65-75°F
- Periodically increase the size of the holes
- Move the container into an area with a slight bit of light once the mushrooms start to grow
- Sprinkle them with moisture occasionally, but never use enough to cause mold to grow
Most people will want to use a dedicated clean plastic bag as a container.