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Growing Your Own Mushrooms In Leftover Coffee Grounds Is Easier Than You Think

yngveleyn - Pixabay / H. Krisp - Wikimedia

Growing your own produce at home is a fun and easy way to save money.

Depending on how green your thumb is, you could grow a few herbs indoors or plant a backyard veggie garden.

And while mushrooms are a little tricky, if you know how, it's not too hard to grow tasty varieties like oyster mushrooms at home.

Some mushroom growing methods can take years, but starting from leftover coffee grounds can grow full-sized fungi in just a month.

Oyster Mushrooms
Mushrooms are not a popular grow-it-yourself food, but they're not so hard.Dominic Alves - Flickr

Here's how:

A note about how mushrooms grow...

While we all know what plants and vegetables need to grow (soil, water, sun, plant food), mushrooms have different needs.

Mushrooms grow outwards from tiny spores - which are harvested from full-sized mushrooms.

Coffee grounds mushrooms
Mycelium from mushroom spores grows on coffee grounds.Tobi Kellner - Wikimedia

Spores spread out thread-like mycelium over the area where they will grow, and once they've fully colonized the space mushrooms will sprout up (to spread more spores).

This is why used coffee grounds are a cheap but effective way to grow mushrooms: they are full of nutrients for the mushroom, and after the coffee is brewed the grounds are pasteurized, meaning there are no bacteria on the grounds to compete with the spores.

If you think this sounds a little complicated, don't worry. Unlike houseplants, growing mushrooms only takes two things: patience, and the right materials.

Let's Get Growing

Note: Wash your hands any time you touch the coffee grounds without gloves. Spreading microorganisms to the coffee could ruin your batch of mushrooms.

Start by collecting about a gallon of used coffee grounds.

Coffee grounds
You can collect your own coffee grounds, or borrow some from a local cafe.Shanegenziuk - Wikimedia

You can get them all at once from a local cafe, or collect your own leftover grounds until you have enough.

But make sure to keep the grounds in a sealed container in your fridge or freezer until they're ready to use.

Move your coffee grounds into a two-gallon container or bucket. As long as the container is clean, you don't need to be picky. In a pinch, even a large ice cream tub or freezer bag will work.

Mushroom experts will recommend a filter spawn bag as your container, since they're designed to let in oxygen while protecting the grounds from bacteria. But you don't need these bags.

Now, lightly spritz your coffee grounds with water from a spray bottle until they're moist (but not wet).

Mushroom spores
Mushroom spores are collected from the underside of mushroom caps - but you should leave this step to the professionals.amrvkoot - PXhere

This is the time to mix edible mushroom spore mixtures into the grounds.

You can buy these bags of mushroom spores and sawdust (which encourages the spores to grow) from a specialty garden store, or an online retailer. They can be ordered ahead of time and refrigerated until you need them.

Blend the spore mixture in with the grounds by hand through the top inch of the grounds.

(Pay attention to the size of your mushroom spore package: if it's meant for a larger container of substrate, you can split it up to suit the size of your grounds.)

Drill small holes around the edge of your container, about an inch or two above the grounds. These will allow carbon dioxide released by the fungi to flow out.

Finally, cover the top of the container in clear plastic wrap with a few holes punched in the top.

Turning Mush Into Mushrooms

Mycelium coffee grounds
Mycelium can be seen spreading over coffee grounds.ShadowShedding - Reddit

This container is now ready to grow mushrooms, and will need to be kept somewhere warm and dark for about three weeks.

If space is limited, storing the mushrooms under your bed or in a closet should work fine.

Be sure to moisten the grounds with your spray bottle twice a day while the mycelium is growing.

Note that patches of green or other colors on your grounds are mold, which should be killed to prevent it from competing with your spores - a sprinkle of salt on the mold should do the trick.

Once the grounds have turned completely white, and begin to sprout small mushrooms, you can move on to the next step.

Coffee grounds mushrooms
Small mushroom begin to sprout on the surface of coffee grounds - the entire surface is covered by mycelium.Tonie Walsh - Twitter

Move your container somewhere with fresh air and little more light, while continuing to water it each day.

In this final stage, full-sized mushrooms will grow very quickly, almost doubling their size each day.

You can encourage where they grow by snipping off a section of your container (if it's soft, like a plastic bag) or simply leaving the top open.

Mushrooms
The same container of grounds can grow several batches of mushrooms.Urban Oyster - Twitter

A month after you mixed in the spores, your mushrooms should be fully grown and ready to eat. You'll know they are ready for harvest when the mushroom's cap (the wide, flat top) turn up at their edges.

Trim the mushroom as close to the base of the stem as you can, and more mushrooms should sprout up from that container over time.

This was just a basic primer on growing mushrooms at home, but you can read full guides and buy supplies from GroCycle.

[H/T: SF Gate, GroCycle]

Are you going to try growing your own mushrooms now?

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