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Choose a well-lit spot where you can observe and mist the bag. Light, ventilation, and humidity matter more than temperature; the block will fruit in a wide range of temperatures. With a clean knife make a 1 inch X-shaped cut through one of the smaller sides of the bag (don’t worry about hurting the mycelium). Don’t fold back the flaps of the opening; the slits will provide enough air flow. Fold the tented top portion of the bag over, squeeze all the air out, and tape it down over the side, to cut off the air through the filter patch.

Shade all but the open end of the bag. For example, cover it with a bag, box, or cloth to block light. Make sure the open end gets light and fresh air.

Mist or sprinkle the opening with fresh water 3 – 4 times a day, enough to wet it thoroughly, and watch for pinheads to form. They usually appear after 10 –14 days of spawn run. Have your camera ready — they’re too cute to miss! Keep misting them as they grow. Depending on temperature, they will mature in 3–10 days.

If you have dry air—a common problem during the winter heating season—consider making a humidity tent out of clear plastic to cover the opening between mistings. If you do, make sure not to seal off the kit entirely; it needs ventilation, especially near the bottom, where carbon dioxide—which is heavier than air—can collect. 



Your block is preparing to form pinheads when the mycelium thickens into solid masses that start to thicken on the surface of the substrate. This image shows small white lumps forming, indicating it’s time to cut an opening!