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Growing Mushrooms (Part 4)

Grow Mushrooms at home like a BOSS!

Learn to grow mushrooms (part 4 of 4)

Part 4 will cover: Woman holding king oyster mushrooms

  • The ideal fruiting space
  • How to fruit your mushrooms
  • How to harvest and store your mushrooms

Growing Mushrooms Guide:
Growing Mushrooms Part 1
Growing Mushrooms Part 2

Growing Mushrooms Part 3


Indoor Fruiting Space

Indoor fruiting spaces can vary widely, depending on how much area is available and how many mushrooms are desired.  They can be as small as a single quart sized jar or as large as entire buildings.  We recommend starting with a tote if it's your first time growing mushrooms.  If you desire more mushrooms, upgrade to a small grow tent.  There are many different sizes of grow tents that work well.  These are usually constructed out of a metal or plastic frame covered with heavy fabric.  The inside is usually covered in a reflective coating.  Another grow space option is a small greenhouse.  They can be purchased on Amazon for under $100 and are basically wire shelving with a plastic cover.  With a few modifications, they can work great.  Beyond this, entire rooms, your garage, an outbuilding, etc. can be converted into a mushroom fruiting space.

Totes are great for growing mushrooms, and are inexpensive to set up.  There are many YouTube videos about how to construct monotubs, which are essentially a big tote (30-120 quart size) with 2 inch holes drilled in the sides.  We usually drill 4 holes on the two long sides with 2 holes toward the top and 2 holes 6 inches from the bottom.  We also drill one on each end in the middle.  These holes can be taped over with 3M Micropore Tape™ or stuffed with poly fill to allow for gas exchange.  Poly fill is better because it allows for more gas exchange.  Either option will help keep humidity in and contaminants out.  An easy way to maintain humidity is by putting 4 inches of perlite on the bottom of the tote and hydrating it to holding capacity.  You want it to be completely saturated without puddles forming on the bottom of the tote.  The perlite will slowly allow the water to evaporate over several weeks, allowing your mushrooms to grow.  Pro tip:  Add hydrogen peroxide to the water you use to hydrate the perlite.  This will keep bacterial contamination to a minimum.  Mixing a 1:10 ratio of hydrogen peroxide to water in a spray bottle and using it to spray the top of the perlite just before placing your mushrooms inside the monotub, also helps keep contamination down.  Check our blog post specifically on making your own monotub mushroom growing setup at home.

The design of larger fruiting spaces should allow for the floor to be continuously wet.  Since the humidity is often approaching 98%, water will build up on the floor.  Design your fruiting room with a tubed bottom to retain water so you can remove it with a wet vacuum, or make sure it's close to a floor drain.  Building a fruiting space over carpeted areas isn't ideal, but if you choose to do this, take extra precautions so your carpet doesn't get ruined.  You’ll also need the ability to vent air into and out of your fruiting space.  For room-sized fruiting spaces, you need to allow the air to be exchanged many times per hour, either scheduled by a timer or activated by a CO2 sensor.  Ideally, you’ll be able to blow the heavy CO2 and spore laden air outside while bringing fresh oxygen rich air into the fruiting space.  Also, investing in a CO2 sensor is a good idea for managing your fruiting space and maintaining good air quality wherever you grow mushrooms.  Most mushroom species prefer CO2 levels between 400 ppm and 800 ppm.  Oyster mushrooms are particularly prone to becoming "leggy" in higher CO2 environments.  "Leggy" oyster mushrooms have long stems with small caps, and the stems tend to be tough, and not great for eating.

The majority of gourmet and medicinal mushroom species like to grow in temperatures ranging from 50° to 85° F.  For best results, know your mushroom species, and plan on fruiting them when you know that you can maintain the specific temperature in your fruiting space over a given period of time.  Keep in mind that some species need a couple of months to produce multiple flushes of mushrooms. 

Controlling and maintaining proper humidity is also key to getting your fungus to fruit.  Using humidifiers with ultrasonic humidifying discs, or building your own humidifier with a fan and an ultrasonic pond fogger can produce great results.  There are also mushroom fans designed to produce a fine mist which is blown into a space or even high-pressure misters that are typically used in commercial grows and can produce a lot of humidity in a fruiting space.  Controlling humidity with cheap humidity controllers doesn't work very well.  They tend to lag behind the actual humidity levels causing your space to "fog out" and drip everywhere, followed by drying out.  This will happen over and over again causing water problems, contamination problems, and poorly growing mushrooms.  You're better off using a cycle timer that can be adjusted as needed to maintain the proper humidity.  Cheap humidity sensors can be used to see if the timer needs an adjustment.  Just don't rely on the sensor to control the humidity directly.  If you want direct control, invest in a wet-bulb humidity sensor and controller.  They are pricey, but very accurate, and show relative humidity in real-time.  They will give you ultimate control over your fruiting space when it comes to humidity. 

Fruiting Your Mushrooms 

Once full colonization of your fruiting substrate is complete, your fruiting blocks can be stimulated to fruit by controlling 5 main variables; temperature, humidity, air exchanges, light, and timing. 

Temperature- Most mushrooms fruit within a specific temperature range.  Knowing this range allows the grower to manipulate the temperature in their fruiting space to produce mushrooms.  Simply, maintaining the temperature in the middle of your mushroom's ideal fruiting temperature range can yield great results, but different species may prefer variations in temperature over time for best results.  Some species even require a cold shock in order to fruit to their full potential.  Learn what works for the specific mushroom species you’re growing.

Humidity- Many mushroom species need high humidity (95-98%) to begin fruiting.  When small mushroom fruit bodies start to form (pinning) and grow larger, humidity can be decreased steadily until it's time to harvest.   Harvesting at a lower humidity level (75-90%) helps mushrooms stay fresh longer in the refrigerator, plus they will have better texture, and cook more easily.  Also, like temperature, many species prefer variations in humidity at different times.  Shiitake are known for this, preferring daily oscillations. 

Air exchange- CO2 concentrations in your fruiting space will change the way your mushrooms look, and how many mushrooms you are able to grow.  Again, this is species specific, so know your mushroom species and adjust air exchanges accordingly.  As mentioned above, oyster mushrooms notoriously need more fresh air compared to other gourmet or medicinal species.  We exchange the air for our oyster mushrooms 8 times per hour to grow short-stemmed and large-capped oysters that are the desired form.  Try and keep your CO2 levels between 400 & 800 ppm for most mushroom species.

Light- Light is necessary for growing the majority of gourmet and medicinal mushrooms species.  The exact light requirements are species specific.  Most mushrooms grow well with simple LED rope lights that produce 6000k light.  Put your lights on a timer with at least several hours of light per day.  Fruiting spaces that are too dim tend to under-produce mushrooms, so have enough lights to make it bright while the lights are on.  

Timing- Timing makes a big difference when fruiting your mushrooms.  Letting your colonized fruiting blocks sit too long can cause them to dry out, which usually decreases your mushroom yields.  If you put them into your fruiting space too early, they will continue colonizing the substrate until full colonization takes place, delaying when mushrooms will start to fruit.  This can lead to contamination if uncolonized substrate is exposed, or if the mycelium is exposed for a long time before starting to fruit.

Now that you have a space where you can control these factors, it’s time to fruit your mushrooms.  Put your fruiting blocks in the fruiting room or monotub, and cut the plastic to expose the mushroom tissue to the appropriate humidity, fresh air, light, and temperature.  Allowing more of the fruiting block to be exposed, leads to more, but smaller mushrooms.  It can also lead to the fruiting substrate drying out too quickly.  Experiment with different shaped cuts and locations to determine what will work the best for your mushroom culture and fruiting space conditions. 

A simple 6’’ x cut across the front of an oyster mushroom fruiting block usually does the trick. A diagonal 6’’ cut with a 3 inch cut going diagonally the other way from the top corner to the original cut (3/4 of an x cut) works very well too, and helps maintain humidity.  1-to-2-inch diameter circular cuts are ideal for lion's mane and make it easy to harvest.  With lion's mane we've noticed that taking a pair of scissors and cutting at the base of the mushroom, leaving a 1/4-to-1/2-inch nub still attached to the block will allow the lion's mane mushroom to re-grow twice as fast.  It's truly amazing!  Oyster mushrooms can be harvested by grabbing the whole bouquet and lifting, plus twisting to remove the entire cluster at once.  Shiitake require you to pick up the block and cut off the mushrooms close to the block with scissors.  Between those 3 harvesting techniques, you'll be able to harvest most gourmet and medicinal species.  One last trick we've discovered recently for super clean cuts is to use an electric carving knife.  We've used them for years for cutting meat and close-celled foam, but had an epiphany recently that many species of mushrooms have mycelium with the consistency of close-celled foam.  We tried harvesting and cutting up mushrooms with an electric knife, and it works very well.  

Store harvested mushrooms in a paper bag in the refrigerator.  Heat is the enemy for freshly harvested mushrooms.  You want to get them in the refrigerator as fast as possible.  Also, the mushrooms still need to breathe after harvesting, so using paper containers works much better than plastic for longer storage.  If you decide to store your mushrooms in plastic containers, make sure there is air exchange with holes, or the lid is cracked so the mushrooms stay fresh.  Lining the bottom of plastic containers with pink butcher paper will help your mushrooms breathe better too.   Usually where the mushrooms touch the plastic is where they will start to go bad first.  How long will fresh mushrooms stay good in your refrigerator?  It's species specific, but generally you'll have a week or more to enjoy your mushrooms.  Also, mushrooms don't really go "bad" if they have air exchange, they just get drier and drier to the point that they aren't great for cooking, assuming your recipe is calling for fresh mushrooms.  If they dry out too much, they can be dehydrated and used to make powders, or used in soups and stews.  Dried mushrooms can be re-hydrated for recipes that call for fresh mushrooms, but in our experience, they aren't as good as when they were freshly harvested.

We've made it from start to finish in our growing mushrooms guide.  Enjoy the fruits of your labor!  Want an easy way to start?  Try our Home Grow Kit.

"Always grow culture."


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