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Growing Mushrooms (Part 2)

Grow Mushrooms at home like a BOSS!

Learn to grow mushrooms (part 2 of 4)

Part 2 will cover:

  • Gas exchange lids
  • How to inoculate grain spawn with mushroom culture
  • Incubating grain spawn
Growing Mushrooms Guide:
Growing Mushrooms Part 1
Growing Mushrooms Part 3

Growing Mushrooms Part 4


Gas Exchange Lids

Mushrooms, like humans, “breathe” oxygen and "exhale" carbon dioxide.  It's important for mycelium health to grow in a sterile environment that allows gas exchange.  The sterile environment enables mycelium to colonize the substrate quickly without competition, and the gas exchange port allows the mycelium to breathe.

  • Gas exchange lid for liquid culture- We build, use, and sell wide-mouth liquid culture lids that have been designed with super heavy-duty injection ports and syringe filters for gas exchange.  It's by far the best option for making liquid culture.  The injection port allows for clean and easy inoculation with a syringe and can withstand several hundred injections.  Mushrooms breathe, so the syringe filter allows just the right amount of air exchange to keep fungi happy.  Check out our Liquid Culture Lids.
  • Gas exchange lid for grain spawn-  The cheapest and most effective grain spawn lid can be made at home easily. Gather a Mason jar lid, a trim nail, and a hammer. Pound two holes in the lid, spaced out toward the edges.  Hammer down any sharp edges.  Now you will need 105 g Tyvek sheets, which are easy to find on   Cut out squares that are an inch wider than the top your jar.  The Tyvek acts as an air filter.  After your prepped grain is in the jar, put your Tyvek square over the top of the jar. Put the lid with 2 holes on top of the Tyvek, gasket down, and press down to seat the Tyvek and lid.  Then add the Mason jar ring and screw it down.  Having Tyvek underneath the lid makes shaking the grain much easier after sterilization by preventing the grain from sticking to the bottom-side of the lid.  Sterilize your grain/substrate as described in Part 1 of Growing Mushrooms before inoculating it with mushroom culture.  Not interested in making your own grain spawn lids?  We have you covered.  Check out our Grain Culture Lids. 

How to Inoculate Grain Spawn with Mushroom Culture

  • Liquid culture inoculation of grain spawn-  If you are using a lid with an injection port, inoculations can be done in open air, but we always recommend using a still air box or laminar flow hood whenever possible.  If that last sentence didn't make sense, learn sterile technique!  Shake up the liquid culture syringe to get the mycelium pieces floating around in the liquid.  Spray the injection port of the grain spawn jar and spray the liquid culture syringe with 70% rubbing alcohol, before attaching a sterile needle.  Let it clean any potential contaminants for a minute or so.  Push the needle through the injection port on the sterilized grain jar and inject 2 to 6 ml of liquid culture onto the grain.  It helps to squirt some on grain next to the glass so its easy to see colonizing. If you are using a lid without an injection port, you can simply twist off the grain jar lid and squirt a few ml of liquid culture onto the grain.  Be extra clean and follow sterile technique if you are taking the lid off your grain spawn jars.  Contaminants like to eat grain too.  Typically, it will take 2 to 4 weeks for your grain to be fully colonized by mycelium, but this is dependent on which mushroom species you are growing.  When the grain is about 1/3 colonized, you can shake the jar to break up the colonized grain and redistribute it evenly throughout the jar.  This will speed up colonization significantly for most species.  Be careful not to break your jar!  We smack our jars against dual density foam designed for car seats.  It has the perfect balance of rigidity and give for mixing grain jars.  It’s also very helpful to break up the colonized grain in your jars before inoculating fruiting substrates.  We’ll add more on this in part 3 of Growing Mushrooms.
  • Agar inoculation of grain spawn- Agar inoculations from a petri dish to grain requires a still air box or laminar flow hood to have consistent high levels of success.  In front of a flow hood, grain spawn jar lids can be taken off, and pieces of colonized agar from a petri dish can be placed on the grain to inoculate it.  Sterile technique should be followed during the procedure.
  • Spore inoculation of grain spawn- Spores are the true “seeds” of mushrooms and can be used by placing a small amount directly on sterilized grain.  This should be done in a sterile environment.  Grain is highly nutritious and can contaminate easily if not handled using sterile technique.  When inoculating grain with spores, you’ll produce unique strains of the fungus that have very young genetics.  This is important because young genetics are necessary for colonizing fast, producing great mushrooms, and helping prevent contamination.  This assumes you mate a good set of spores.  Mating spores on grain is like mushrooms having children.  The “kids” are genetically different from the parent(s), but can be very similar too.  One disadvantage of using spores is you may have several unique fungal “kids” growing in the same grain jar, competing for resources.  Ideally, you would isolate one strain to continue propagating, so you aren’t growing multiple strains together.  Growing an isolated strain will produce much better mushroom yields since there won't be direct competition.  Isolating a strain can be as easy as taking a small tissue sample from an area of mycelium that appears uniform and healthy.  Put this tissue sample on a petri dish or in another grain jar to let it continue growing.  As it grows, check for contamination and see if it's growing uniformly.  Take a small sample from an area with uniform mycelium and transfer it to another petri dish/grain jar.  If it looks like its growing as expected for that species of mushroom, take a new sample to start growing your isolated strain on grain.  With some luck, you'll discover a new, high yielding strain with favorable characteristics.

Incubation/Colonizing Grain spawn

You've made grain spawn!  Now all you need to do is wait for it to colonize.  This can take one week to several depending on the species you are growing, and the incubating conditions.  Optimal colonizing conditions for many gourmet and medicinal mushrooms species is 70°-75° F and 60-70% humidity.  Temperature is more important than humidity at this stage, for fast colonization.  Shake your jars to evenly distribute the colonized grain when you can see that the mycelium has colonized 1/3 of it.  This will accelerate colonizing significantly. 

Your grain spawn will be ready when it's fully colonized.  Over-colonized grain can be extremely difficult to break up, so don't let your grain jars sit too long before using them.  Immediately before using your grain spawn to inoculate fruiting substrate, shake and break up all the grain one final time to create as many inoculation points as possible.  This grain will be mixed in with fruiting substrate or used to make more grain spawn. It also adds nutrition to the final fruiting block allowing the mycelium to quickly colonize the substrate.

Want to start growing mushrooms?  Check out our mushroom growing supplies.

Part 3 will cover how to make fruiting substrate for wood loving species, inoculating fruiting substrate, and incubating/colonizing fruiting substrates.

Growing Mushrooms Guide
Growing Mushrooms Part 3

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