Step 4: Incubation Store your grow bag in a room-temperature environment where it will not be moved around. Keep it out of direct sunlight and away from heat sources. Preferably, store the bag in a dark place. After a few days, you will begin to see white spots forming throughout the bag. It will spread rapidly. This is the mycelium forming. Be very careful not to open the bag until the substrate is fully colonized, as there is a high risk of contamination.
