According to the Utah State University Extension, mushrooms are "the fruiting bodies produced by some fungi." Mushrooms reproduce through spores instead of seeds. The spores, or basidia, spread naturally through the wind and grow under favorable conditions. Commercial mushroom producers use the spores to create mushroom spawn. Spawn is incubated spore that is attached to grain and can be spread throughout prepared bins to produce mushrooms. When making spores at home, the most important factor is a sterile work environment.
Fill the large pot with water and bring the water to a boil.
Place the Petri dishes, jars and tweezers into the boiling water and boil for 30 minutes to completely sterilize their surfaces.
Remove the items from the pot and place them face down on a sterile drying rack to cool and dry. Always handle the supplies with sterile gloves to avoid contamination.
Fill the jars with grain and seal them with their lids. Fill the Petri dishes with agar medium.
Slice the desired mushroom into pea-sized pieces and place a piece onto each Petri dish using the sterile tweezers.
Place the Petri dishes into the incubator and set it to the correct temperature for the desired mushroom. The average temperature for mushroom growth is 75 degrees F. If your spawn does not appear to be growing, verify your temperature with a mushroom production book such as "The Principles of Growing Mushrooms and Spawn Making" by Benjamin Minge Duggar. Leave them in the incubator until long strands form on the agar medium.
Transfer the mushroom spawn into the grain-filled jars and leave them in the incubator with their lids off. Keep the jars in the incubator until the spawn covers the grain with white filaments. This is your completed mushroom spawn.
Mix the mushroom spawn with straw, mulch or sawdust, depending upon your particular mushroom. Determine your particular mushroom's medium with a reference book such as "The Principles of Growing Mushrooms and Spawn Making" by Benjamin Minge Duggar. For example, portabella mushrooms grow best in straw. After four weeks, the mushrooms will be ready for cutting.