Fruit the block

A colonized block fruits when its conditions change: the bag is cut, fresh air reaches the mycelium and the air stays moist. Oysters, lion's mane and chestnut fruit from an X or slit cut in the side of the bag. King oyster and reishi fruit from the top, inside a collar of bag. Shiitake blocks come out of the bag altogether.

Three things then have to hold. Temperature inside the range for the species; the chart has each one. Humidity of about 85 to 95 percent at the block, from misting a few times a day, a loose plastic tent with holes, or a growing tent with a humidifier. And fresh air: mushrooms give off carbon dioxide, and when it builds up, stems stretch and caps stay small.

Pins, the first tiny mushrooms, usually appear one to three weeks after opening and can double in size daily after that. If nothing happens, or the pins dry up, the cause is nearly always dry air, stale air or the wrong temperature; why a kit is not growing goes through each symptom.

Ready to move on when: The mushrooms show the harvest sign for the species: oyster caps flattening with the edge still curled under, lion's mane spines about a quarter inch long.