What is incubation?

Incubation matters because it's a race: the mycelium has to claim the substrate before contaminants do. Anything that slows it gives them time. When a Fungi Ally crew top-spawned half its bags, those took 24 days to colonize instead of 14, and Cornell notes that "the extra time also left more opportunity for contaminants to take hold" (Cornell). Steady conditions and leaving containers alone do most of the work. How to tell when it's done is on the colonization page.

Incubation needs steady warmth, no light and still but not stagnant air.

• Temperature. Cornell keeps incubation under 80°F (27°C), ideally around 70°F (21°C). It can drop as low as 50°F (10°C), but incubation takes longer. Cornell also warns that the core of a 5- or 10-pound sawdust bag can run 10–15°F warmer than the room (Cornell). The Cornell Small Farms and Fungi Ally farm guide keeps its incubation room at 65–75°F (18–24°C). It puts bags 7 or 8°F warmer than the room, so in a room in the 80s they approach the 90s, which "can cause suffocation and contamination to grow" (Cornell Small Farms and Fungi Ally).
• Light. "During incubation, lighting is not required," the farm guide says. UF/IFAS incubates oyster grain spawn at 73°F (23°C) in darkness (UF/IFAS).
• Air. Colonizing mycelium tolerates CO2. UC Cooperative Extension gives the oyster spawn run 20,000 ppm CO2 and no fresh air exchanges (UC Cooperative Extension). The farm guide says incubation air "does not need to be actively exchanged with the outdoors", uses oscillating fans to keep it from going stagnant, and spaces bags a palm's width apart so they don't overheat. Our CO2 guide explains why fresh air waits until fruiting.

Incubation in bags takes from about 10 days to 12 weeks, depending on species and substrate; logs take months. Cornell's figures (Cornell):

Species and substrate	Incubation
Oyster on sawdust	10–20 days
Oyster on straw	14–28 days
Most specialty species on sawdust	21 days
Shiitake on sawdust	42–84 days
Shiitake logs	6–18 months

Grain spawn comes first and takes 2 to 3 weeks to colonize (GroCycle). Our grow timeline guide adds the stages before and after, by species.

• Moving blocks by the calendar. A block is ready when it looks fully colonized, not when a date passes. Shiitake stays in until about 75% of the block has turned brown (Cornell).
• Packing bags tight on a warm shelf, which traps their heat.
• Not counting losses. Our grow log guide shows how to work out incubation loss apart from fruiting loss.

Hypha sets reminders for each block from typical timings: break and shake for grain spawn and all-in-one bags, and a move into fruiting for bulk blocks. You can adjust them for each block.