Stage 2 of the process
Add the spawn
Spawn is grain, sawdust or wooden plugs already grown through with a named species. Mix it into cooled substrate at about 5 to 10 percent of the wet weight, a little more for straw, and close the container.
- Spawn for straw
- 5 to 15% of the wet weight
- Spawn for sterilized sawdust
- about 4 to 10% of the wet weight
Spawn comes in three forms. Grain spawn is the usual choice indoors for straw and sawdust blocks. Sawdust spawn goes into logs and garden beds, and plug spawn into logs only; grain vs sawdust vs plug spawn sets them side by side. Buy spawn of a named species from a supplier, keep it refrigerated and use it within the period on the label, usually a few months.
The amount is a share of the wet substrate weight. For straw, suppliers give 5 to 10 percent, and 10 percent or more for a first try, because more spawn means faster cover and less room for mold. Sterilized sawdust needs less, about 4 to 10 percent. Wash your hands, wipe the work surface, break the spawn up inside its bag and mix or layer it through the substrate.
For a bucket of straw, alternate a couple of inches of straw with a sprinkle of spawn until the bucket is full, then put the lid on; growing oysters at home has the full steps. For a sawdust block, the spawn is shaken through the bag, the top is folded or sealed, and the filter patch is left clear so the block can breathe.
Ready to move on when: Spawn is spread evenly through the substrate and the bag or bucket is closed.
Common mistakes at this stage
- Using too little spawn on straw, which gives mold a head start.
- Using grain spawn in logs, or leaving it exposed outdoors where animals find it.
- Mixing spawn into substrate that is still hot from pasteurizing or sterilizing.