Growing Mushrooms (Part 3)

Grow Mushrooms at home like a BOSS!

Learn to grow mushrooms (part 3 of 4)

Part 3 will cover:

• How to make fruiting substrate for wood-loving species
• Inoculating fruiting substrate
• Incubating/colonizing fruiting substrate
  

Making Fruiting Substrate for Wood-Loving Species

Many gourmet mushroom species live on hardwood. To grow mushrooms indoors, we mimic this by using hardwood sawdust. 

• Sterilized fruiting substrate-  A great substrate mix to use is known as "masters mix," consisting of 50% soy hulls and 50% hardwood sawdust. Hydrate your chosen substrate to approximately 60% and place it in jars with filter patch lids, or autoclave-able filter patch bags.  Pressure sterilize at 15 psi for 3 hours to ensure full sterilization.  Now your fruiting substrate is ready to be inoculated by grain spawn!  Hard wood fuel pellets (HWFP) are often used as a source of sawdust.  Presoaking your HWFP helps to break it up evenly and turn it back into sawdust.  Here are four fruiting block recipes that work well.

• HWFP, wheat bran, and gypsum (wheat bran @ 20% dry weight of HWFP, gypsum @ 2% dry weight total)

• HWFP, soy hulls, and gypsum (50% HWFP & 50% soy hulls, gypsum @ 2% dry weight total)

• Hardwood sawdust, wheat bran, gypsum (wheat bran @ 20% dry weight of HWFP, gypsum @ 2% dry weight total)

• Hardwood sawdust, wood chips, wheat bran, gypsum  (wood chips @ 15% dry weight of hardwood sawdust, wheat bran @ 20% of combined wood chips and sawdust dry weight, gypsum at 2% dry weight total)

• Pasteurized fruiting substrate-  Pasteurizing substrates doesn't completely sterilize them, but provides a window of time for fast-colonizing mushroom cultures.  To pasteurize substrate, heat the substrate submerged in water to 160-180° F for 60 minutes.  Don't allow the temperature to rise above 180 degrees.  Doing this will kill the good bacteria and potentially allow the bad to thrive.  Pasteurizing works great for growing mushrooms outside, and takes less time, effort, and equipment than full sterilization.  We’ve had much success growing several species of mushrooms using pasteurized substrates, but oyster mushrooms and lion's mane are probably the easiest. 

Inoculating Fruiting Substrate

Inoculating your fruiting substrate is easy once you’ve determined a method to use and have learned the basics of sterile technique.  Generally, you need to get colonized grain mixed into your final fruiting material, such as masters mix.  This needs to be done in an extremely clean way, ending with a good seal of the final fruiting substrate container if you’re growing mushrooms indoors.  Make sure your lid or bag has a filter patch to allow your fungus to breathe.  Mix grain spawn into your fruiting material at 10 to 20% wet block weight.  Again, this needs to be done using a sterile technique method.  Here are a couple of ways you can do this.

• Laminar flow hood-  Inoculating in front of a laminar flow hood is the ideal method.  Flow hoods create a sterile, even, steady stream of air, preventing contaminants from settling on your cultures, grains, fruiting blocks, petri dishes, slants, spore prints, etc.  Follow sterile technique best practices when using a flow hood, for best results.  The downside is that building or buying a flow hood is costly; from $300 to $1,000 or more depending on the size of the HEPA filter.  Use 99.99% HEPA filters that filter down to 0.3 microns.

• Glove box/still air box-  Much success can be achieved with a simple glove box or still air box.  Glove boxes are a sealed environment and may have a positive pressure filtration system installed.  To use a glove box, you place your hands into gloves that are installed through holes in the side of the box.  This seals outside air from entering the box, but allows you to use your gloved hands to work with mushroom cultures.  The downside to using a glove box is that you sacrifice mobility and dexterity, which are important when working with mushroom cultures.  We prefer to use a still air box with open holes in the sides where you stick your hands through.  Wear nitrile gloves and sterilize the inside of the box and your gloves with a disinfectant spray (70% rubbing alcohol).  Also, adding a clear plastic flap right above the hand holes that covers the holes after your hands are removed is a nice addition.  It keeps contaminants from drifting into the box while you aren't using it, and while you are waiting for the disinfectant spray to settle inside the box.  You can easily make your own still air box by buying a clear tote and cutting 2 large holes in the sides that you can stick your hands and forearms through.  Use sterile technique to minimize contamination while using your still air box. 

• Flame method-  It’s possible to achieve a small sterile/mostly sterile space using a candle, torch, or other flame.  The heat of the flame creates an updraft, thus creating an umbrella shaped, mostly sterile space just below the height of the flame.  The updraft created by the flame prevents contaminants from settling on your work.  Much mushroom culture success can be had with this method, especially with fast colonizing species such as oyster mushrooms, but for the best results we recommend using a still air box or flow hood rather than this method.  The main advantage of this method is the low cost and ease of setup.

• Open air inoculations indoors or outdoors-  Believe it or not, indoor air, including the air in our homes, is much more "dirty" than outdoor air.  For this reason, inoculating pasteurized substrates can be done outside without worry and with great success.  If you choose to do any open-air inoculating in your home, turn off the HVAC system and spray a disinfectant in the air space twenty minutes prior to inoculating.  This will allow for suspended contamination-causing particles to settle and be cleaned by the spray.   We also follow this air cleaning practice when using a still air box or the flame method.  It’s not preferred over a laminar flow hood, but will increase your odds of success.

Incubation/Colonizing Fruiting Substrates

Maintaining humidity in your substrate colonizing space will help boost yields.  As your grain, sawdust, or other materials colonize in their containers, they slowly loose moisture through the filter patch or air exchange filter.  Generally, this isn’t a problem for grain spawn, but for longer colonizing species, or for over-colonized fruiting substrates, this can decrease mushroom yields.  Try to keep your colonizing area humidity level around 60 to 70%. 

Some mushroom growers like to shake up their fruiting blocks part way through colonization in an attempt to speed up the process.  We've found that fruiting blocks perform well by simply letting them colonize on their own after being inoculated by grain spawn.

Many gourmet mushroom species only take 1 to 3 weeks to colonize fruiting substrates. This is dependent on many variables including colonizing temperature, species, genetics, substrate formulas, humidity, and inoculation rate.

Part 4 will describe the ideal indoor fruiting space, how to fruit your mushrooms, and how to harvest and store your mushrooms.

Growing Mushrooms Guide:
Growing Mushrooms Part 4