Growing mushrooms indoors: Adding spawn

Welcome back to our series on growing mushrooms indoors. The first article described the setup and process for making the mushroom substrate. To summarize, there are bags. We put mushroom food in them. We sterilize them.

Although wild fungi grow in an unsterilized environment, growing mushrooms indoors requires as little competition as possible so we can maximize the number of grow kits and mushrooms for you.

The major theme is being careful, so the mushroom yields turn out scrumptious, sizeable, and safe. When mixing the ingredients before sterilizing them, the block cannot be packed tight. There needs to be enough air in the block so the steam and heat can properly travel and do their job.

Once the sterilizers finish, the bags are moved to a disinfected metal counter with a laminar flow hood. This homemade flow hood has a pre-filter and a main six-inch filter to catch the particles nobody wants near their sterilized mushroom substrate. It gives just enough circulation so the bags can cool down to room temperature and reduce any chance for outside contaminants to settle. No loitering here!

The bags are pressed together to keep the tops folded down as well – reducing the risk for contamination and trying to prevent creases in the plastic.

Time for the spores. Clear, polypropylene bags with mushroom grain spawn go from the cooler to the counter. This spawn is when mycelium grows on a grain, such as millet, to act like seeds when added to the mushroom blocks. Just like the grow mix, the spores are prone to contamination.

Tucked into the left pocket of the room, we sit with a grain spawn bag, a bottle of isopropyl alcohol disinfectant spray, and a bag sealer in the only counter space remaining. We wear gloves, spray them with the disinfectant and rub our hands together as well as the top of the spore bag before opening it carefully with a precision knife. We always try to minimize contact with the bags and we especially avoid touching inside them with our hands.

We pull the sides of the block bag to have enough opening for the spawn bag to fit inside when pouring the grains. The spawn bag is set aside and we press the mushroom block like a stress ball to break up any clusters. We lay the bags onto the sealer where we press usually between two and four times to make up for any creases and gaps in the plastic. Once the bag is sealed, we treat the mix like Shake ‘N Bake to ensure the spores spread throughout the block.

Sealing the bag after adding mushroom spawn.

The grow bags are packed tightly, awaiting mushroom grain spawn before going on the cart. Our own John Bakker breaks up clumps in a block before sealing it.

The bags fill up a mobile rack to our right, enclosing us in the left end of the room. The rack will eventually fill up and be ready to move to the incubation room where the feast begins for the mycelium.

Overall, this process takes patience and precision to reduce contamination and leave more high-quality mushroom products for you to buy! Check out what we offer on our shop page.

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