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Growing Mushrooms (Part 1)

Grow Mushrooms at home like a BOSS!

This 4 part growing guide is for beginners to mid-level mushroom growers.

Part 1 will cover:

  • Introduction to mushrooms
  • Preparing and sterilizing grain spawn
Growing Mushrooms Guide:
Growing Mushrooms Part 2

Growing Mushrooms Part 3

Growing Mushrooms Part 4


Generally speaking, the first step in growing mushrooms is to create grain spawn.  This can be done several ways, by adding tissue from a petri dish or slant to sterilized grain, or by squirting 2 to 6 ml of liquid culture onto sterilized grain.  You can even add spores to sterilized grain to start growing a unique strain of a particular culture.

Let's take one step back and understand some basics about mushrooms.  Mushrooms are classified as their own Kingdom, Kingdom Fungi.  Fungi “breathe” oxygen and "exhale" carbon dioxide similar to animals. Mushrooms are the fruiting bodies of a fungus.  The mushroom fruiting body is how some fungi reproduce.  The actual being of the mushroom consists of a network of tiny strands collectively called mycelium.  Mycelium of gourmet mushroom fungus tends to live in dead or dying hardwood trees.  There, the mycelium breaks down wood fibers into food, and grows until it encounters the boundary of its resources.  At this point, along with other factors such as temperature and humidity, the fungus will put energy into producing its fruiting bodies, mushrooms!  These mushrooms produce spores that will hopefully land on another food source, such as a freshly fallen tree, and start the entire cycle again. 

An analogy to understand the relationship between mycelium and mushrooms is as follows.  Imagine that an apple tree, including its roots, trunk, branches, and leaves all grow underground just below the soil surface, and when this apple tree produces an apple, it pops out of the ground just like a mushroom.  Its apple seeds are so small and light that they can float in the wind to more suitable locations, just like spores do to start a new network of mycelium.  Mycelium is the true body of the fungus and mushrooms are the reproductive structures that  produce and distribute spores.


Please note that sterile technique should be used whenever necessary.  This is extremely important for growing sterile cultures successfully.  Books such as Growing Gourmet and Medicinal Mushrooms by Paul Stamets, Radical Mycology by Peter McCoy, and Organic Mushroom Farming, and Mycoremediation by Tradd Cotter are excellent resources to learn sterile technique and much more.

Also, we use distilled or reverse osmosis filtered water in our pressure cooker, for hydrating grain, for simmering grain, and for hydrating fruiting substrates.  Note that when we mention using water, we are referring to non-chlorinated water.  Distilled water can be purchased at grocery and department stores.  Reverse osmosis filtering systems can be purchased online or in stores.  Tap water can be left out for 24 to 48 hours to allow the chlorine to dissipate, but we don’t recommend using tap water in pressure cookers.  The minerals can interact with the cooker and degrade it over time. 

Grain Spawn 101

The basic idea behind grain spawn is that you are creating "the seeds" to plant mushrooms into their fruiting substrate, such as hardwood sawdust.  The mushrooms will grow on the sawdust.  The easiest way to create grain spawn is by adding liquid culture to grain.  Below are some grain spawn recipes that work for us. 

Grain Spawn Jar Recipe (The Soak and Simmer Method)

The most reliable method of creating grain spawn is the "soak and simmer" method.  The first thing you need to do is hydrate your grain.  You'll want a quality grain, such as rye berries, to cultivate your mushroom fungus.  We soak our grain for 8 to 24 hours before draining, rinsing, and simmering on the stove for 10 to 20 min.

Here is what you do.  Start with pint or quart sized jars such as Ball Mason jars, and fill them with rye grain, 1/3 full. Repeat this step as needed to prepare the desired amount of grain.  For example, if your pressure cooker can fit 6 jars and you want to inoculate that much grain, repeat this step 6 times. 

Ultimately, when the grain is hydrated, it will expand to double its volume, so your jars will be 2/3 full. Pour the grain from the jars into one container and soak it in non-chlorinated water for 24 hours.  Make sure the water level is 3 or 4 inches higher than the dry grain so there is extra water for the grain to absorb; you don’t want to end up with dry grain at the top. If you soak the grain too long, the rye grain will begin to sprout.  Somewhat sprouted grain can still be used, but is undesirable due to the increased risk of contamination.  After the 8 to 24 hr. soaking, drain and strain your grain.  Also, rinse your grain until the water runs clear.  Put your clean soaked grain into a pot, and fill with water to a height of three inches above the grain.  Then simmer it for 10 to 20 minutes.  Ideally, you want your grain to swell to its full capacity without bursting.  If you start to see burst grain, take your grain off the stove immediately.  They will work fine at this point, but you cooked them a little too long.  The next time you prepare grain spawn, cook it for a few minutes less and you'll have perfect grain!  After you perform this step a few times, you’ll get good at knowing what fully hydrated grain looks like.  Easy peasy!

Now that your grain is simmered, take it off the stove and strain it while hot.  We spread our grain out in trays or on a table, so they can dry through evaporation.  Stir your grain around periodically until it is fairly dry on the outside.  Pick up a handful when you think your grain is dry enough and drop it.  It shouldn't leave very much water behind, if any and all the grain should fall from your hand without sticking.

At this point, your grain is almost ready!  The final step before sterilizing your grain is to add some gypsum powder and mix it in thoroughly.  Add 1 teaspoon per quart jar of grain spawn, or 2-8% gypsum by dry weight of grain.  Mix the gypsum in thoroughly so the grain is covered evenly.  Gypsum adds minerals (calcium sulfate) that help your fungus grow, and keeps your grain from sticking together after sterilizing it.

Load your grain into pint or quart sized jars a little over halfway full.  Screw on a cultivation lid that has a built-in air filter or a lid with an air filter and injection port.  Cover the lid with tinfoil to protect your grain from excess moisture that can penetrate through the air filter during sterilization.  Too much water is not good for growing fungus.  Extra water tends to pool on the bottom of jars and create an anaerobic space where fungus can't colonize, but contamination such as bacteria can.  Put your jars on a rack in a pressure cooker and add a couple inches of distilled water to the bottom.  Cook your grain jars for 3 hrs at 15 psi, typically 250° F.  A three hour cook time is a little longer than absolutely necessary, but we like to be 100% sure our grain is sterile.  After your grain has cooled to room temperature, or at least under 95° F in the center of your cooled grain, you can inoculate your grain with mushroom liquid culture, colonized agar (petri dish or slant tissue), or spores from a spore print.

Luckily Cloud Culture Mushrooms provides liquid cultures, petri dish cultures, slant cultures, and spore prints.  Check out our inventory at

Part 2 will cover gas exchange lids, how to inoculate grain spawn with mushroom culture, and incubating grain spawn.

Growing Mushrooms Guide
Growing Mushrooms Part 2

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