Making Grain Spawn Step by Step
grain spawnsterile techniquebeginner friendly
Grain spawn carries mycelium from a culture into bulk substrate. A step-by-step guide to cooking, sterilising, inoculating, and colonising grain.
What grain spawn is
Grain spawn is cooked, sterilised grain fully colonised by mushroom mycelium. It carries vigorous mycelium and a little nutrition from a culture into bulk substrate such as straw or sawdust.
Preparing the grain
- Rinse and simmer grain such as rye, wheat, sorghum, or millet until just hydrated, not split.
- Drain well and let the surface dry so the grain is at about 45 to 55% moisture.
- Load jars or filter-patch bags, leaving headroom, and pressure sterilise at 15 psi for 90 to 120 minutes.
- Let everything cool fully without opening the cooker.
Inoculating and colonising
Inject 2 to 5 ml of liquid culture per jar, or add a piece of colonised grain, working in a still air box with flamed tools. Incubate at 21 to 24°C in the dark. Once you see healthy white growth, shake the jar to spread the mycelium and speed things up.
When it is ready
Fully colonised spawn is evenly white and smells faintly of fresh mushroom. Use it promptly, mixing 1 part spawn into 2 to 5 parts bulk substrate.
