While mushrooms may grow on most organic matter, there are some particularly good substrates for growing mushrooms, and coffee grounds are one such substrate.

Coffee grounds are the leftovers that are produced when you make a pot of coffee. They offer a rich source of nitrogen and other nutrients that many kinds of fresh and dried mushrooms like oyster, shiitake, white button, and portabella can use - including more exotic specialty varieties.

Mushrooms have been grown in coffee grounds for decades and it remains a popular substrate today.

Why grow mushrooms on coffee grounds

There are a few reasons why growing mushrooms in coffee grounds is a good option. For those who want to experiment with growing their own mushrooms, coffee grounds can be a great option because:

• They're easy and economical to obtain.
  
  
• Coffee is one of the richest sources of nitrogen for growing mushrooms, which is why it's the most popular substrate for growing mushrooms. 
  
  
• Growing your own mushrooms in coffee grounds is eco-friendly; it reduces waste and saves you money in the long run.
  
  
• It's ideal for mushrooms species that grow very quickly and can produce a good-sized crop in only a few weeks.
  
  
• It's suitable for growing different varieties of mushrooms.

What kind of mushrooms can I grow?

There are also a few kinds of mushrooms that are particularly well-suited to growing in coffee grounds.  This includes oyster mushrooms, shiitake mushrooms, portobello, and white button mushrooms.

In addition, these mushrooms are easy to cultivate, don't require a high level of expertise, require sufficient amounts of nitrogen which coffee grounds are a rich source of, they give large yields over a short period of time and lastly they don't require a lot of space and can be grown indoors.

Step by step instructions for growing mushrooms on coffee grounds.

What you'll need:

• Coffee grounds (fresh or dried)
• A knife and/or scissors (for cutting out or punching holes in liners and mattings)  
• Parchment paper
• Compostable liner(s) for your mushroom growing container

Step 1 - Find your coffee grounds!

Gather your coffee grounds. Coffee grounds can be either fresh or dried. Choosing one over the other depends on your preference, but it's important that you don't choose grounds that have been left to stagnate for a while - they'll likely cause mould to grow instead of mushrooms! I keep mine in a sealed jam jar in the fridge once they've cooled down.

Step 2 - Sterilisation

Sterilise the coffee grounds by baking them in an oven at 400 degrees Fahrenheit for about 10 minutes. Make sure you use parchment paper to line the baking sheet so that you don't stick them on the pan after your coffee grounds are baked. Remove from oven and set aside for later use.

Step 3 - Setting the grow environment

Create the proper growing environment. For most kinds of fresh mushrooms, it's best to use a humidity level of around 85%. This can be done by simply misting the surface of your coffee ground-based mushroom farm with water from time to time.

However, you should also make sure that there is enough air in your container for good aeration because mushrooms need oxygen for proper development.

This is usually done with holes that you can punch out in your compostable bag, but if you're using something like a milk jug or plastic bin, you can simply cut out some air holes in the sides of your growing container.

Step 4 - Spreading your substrate

Use your substrate to create the shape of the surface on which your mushrooms will grow. To do this, simply dump out your substrate (coffee grounds) into the growing container and spread it evenly across the surface. You can opt for a very thick layer or a thin one depending on how much you want to harvest at once.

Step 5 - Add your spawn

Sow mushroom spawn onto the coffee ground-based mushroom farm. In other words, get your mushroom spawn ready and all set up so that you can sow them onto the surface of your coffee ground-based mushroom farm.

Remember to also sow a sufficient amount of spawn because it's important that there are enough spawn grains in the container for mushroom development.

Step 6 - Add the bag/lid - or cover

Place compostable liner(s) on the surface of your coffee ground farm. The compostable bag you're using should be placed directly onto the surface where your mushrooms are going to grow.


If it's a liner, make sure that there is at least 1 inch worth of space between its edge and the coffee ground-based mushroom farm so that excess water can drain down and outside the liner.



If it's a growing container, you can also choose to put a layer of perlite on the bottom before putting down the compostable bag so that excess spores and water have somewhere to go after they come in contact with the coffee ground-based mushroom farm.


However, make sure that whatever material you use for this step is not toxic to your mushroom culture, which is why it's good to use perlite instead of soil.

Step 7 - Cut holes for fresh air exchange (FAE)

After placing your liner or container on the surface of your coffee ground-based mushroom farm, cut out several holes in its bottom so that excess water and spores can drain down and away from the growing medium. This will prevent unwanted contamination.

Remember to be gentle with your knife or scissors since you don't want to damage the liner.

Step 8 - Keep it humid (but not wet!)

There has to be enough humidity for good mushroom development. You also need to make sure that the substrate is moist but not too wet.

Make sure you keep your coffee grounds-based mushroom farm moist but not too wet for optimal mushroom development. Remember that by keeping its substrate moist, you also run the risk of spore contamination.

This is why you need to fan the growing container with air at least 2 or 3 times a day in order to let in the fresh air and prevent the formation of excess spores around your mushrooms.

Step 9 - Sit and wait...

Wait for your mushrooms to grow. The time it takes for mushroom development depends on the kind of mushroom spore you have sewn onto your coffee ground-based mushroom farm, but in most cases, it should take anywhere around 8 to 10 days.

When you see your first flush, wait for it to mature fully before proceeding with the harvest.

Step 10 - Harvesting

Harvest your mushrooms once they are fully grown or have reached their full size. Staying organized is important here since you should place all harvested items in a clean container so that contamination does not occur.

Make sure you only use the kind of containers that are meant to preserve mushrooms, which you can easily get at your local grocery store.

Wash all mushroom varieties before cooking or consuming them.

You may also choose to dry your mushrooms instead of eating them fresh. This is usually done by simply hanging them up on strings or racks in a cool, dark area with good air circulation (not inside the house).

Make sure you dry them until they are completely dehydrated, which takes about 2 to 3 days.

Bonus Tips:

• Throw away or use coffee grounds from time to time because using them for too long may lead to a decrease in mushroom formation.
  

• You may also need to make some changes to your coffee ground-based mushroom farm every once in a while, but this all depends on how often you are able to keep it clean and free of contamination.
  

• Rinse your hands thoroughly before handling the mushrooms or touching their containers because chances are that they are still carrying spores with them.
  

• Space out the containers you have placed in your coffee ground-based mushroom farm so that their contents will be able to breathe well at all times. This way, they won't grow into one another and get crowded too soon.

Get started growing mushrooms with coffee grounds!

Growing mushrooms in coffee grounds is a great way to recycle and reuse old and unused materials like coffee grounds. It's also an inexpensive way to start your own mushroom farm.

All you need to do is follow the step-by-step guide above and watch your mushroom culture grow.

Have you grown mushrooms in coffee grounds before, what was your experience like? Let us know in the comments below. We'd love to hear from you!