Pre-Mixed Grain Spawn Bags — Skip the Soak, Skip the Simmer
Making your own grain spawn is one of the most rewarding (and messiest) parts of mushroom cultivation — measuring, soaking, simmering, draining, and bagging before you've even started colonising. Our Pre-Mixed Grain Spawn Bags cut straight to the part that matters: just add your measured water, sterilise, and inoculate. No scales, no guesswork, no soaking pots tying up your kitchen for a day.
Each bag contains a pre-portioned amount of clean, Australian-grown grain — choose from Millet, Organic Wheat, or Organic Rye — filled to the exact dry weight needed to reach your chosen finish weight once hydrated. We add 3% by weight of calcium sulphate and calcium carbonate to assist with stopping clumping and raising pH levels. Available in 500g, 1KG, and 2KG finish weight bags, in heat-resistant, filter-patch grow bags ready straight for the pressure cooker or autoclave.
Choose Your Grain
Millet Best Value
Small, even-sized grain with a high surface-area-to-volume ratio — fast, vigorous colonisation and excellent spawn-to-grain ratios for bulk substrate.
Organic Wheat Classic Choice
Certified organic wheat berries — a long-standing favourite for grain spawn thanks to reliable hydration and consistent mycelial run.
Organic Rye Grower Favourite
Certified organic rye berries with a tougher hull — slower to break down, giving spawn a longer usable shelf life once colonised.
What You'll Notice
- No measuring — each bag is pre-portioned to the dry weight needed for your chosen finish weight
- Faster prep — go straight from bag to pressure cooker, no separate soaking or simmering pot required
- Consistent results — the same dry grain to water ratio every time, batch after batch
- Less mess — no draining colanders or grain spilled across the kitchen bench
- Ready for inoculation within hours of sterilising, once cooled
The Science: Grain spawn works because cereal grains are dense in starches and proteins that mycelium can rapidly metabolise, while their compact surface area allows colonisation to spread quickly between kernels. Hydration is critical — grain typically absorbs water to roughly 1.8–2x its dry weight during soaking and simmering. Too little water and the mycelium dries out before colonising fully; too much and excess surface moisture invites contamination. Each of our bags is filled to a dry weight calculated against this ratio, so the listed finish weight reflects what you'll have once your measured water is added and absorbed.
How To Use
| Finish Weight |
Dry Grain (approx.) |
Water To Add (approx.) |
Method |
| 500g |
~280g |
175mL |
Add boiling water, soak 15–20 min, shake and fold, pressure cook |
| 1KG |
~550g |
350mL |
Add boiling water, soak 15–20 min, shake and fold, pressure cook |
| 2KG |
~1110g |
690mL |
Add boiling water, soak 15–20 min, shake and fold, pressure cook
|
Water amounts are approximate and assume a standard soak-and-simmer prep. Adjust slightly depending on your altitude, grain freshness, and personal technique. Pressure cook at 15PSI for at least 90 minutes (or follow your usual sterilisation routine) before cooling to room temperature and inoculating.
Storage & Safety: Store bags in a cool, dry place away from direct sunlight and moisture. This is raw, unsterilised grain — it must be properly hydrated and sterilised (pressure cooked or autoclaved) before inoculation. Do not consume raw grain. Keep away from pets and children prior to preparation. Once sterilised and inoculated, follow standard sterile technique to avoid contamination.
Specifications
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Contents: 100% raw grain (Millet, Organic Wheat, or Organic Rye — no additives, fillers, or chemicals)
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Bag type: Heat-resistant polypropylene grow bag with breathable 0.2 micron filter patch, suitable for pressure cooking and autoclaving
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Finish weight options: 500g, 1KG, 2KG (after hydration)
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Origin: Australian Grown
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Certification: Wheat and Rye are sourced Certified Organic; Millet is conventionally grown
Hand-Prepared on Tamborine Mountain
Kai Kai Farm is a family-run, certified organic farm in Queensland's Scenic Rim, founded by Quintin and Amy. We portion and pack every grain spawn bag ourselves using the same grain we use to spawn our own farm's mushroom blocks. When you buy from us, you're supporting a small local business focused on accessible, science-backed mushroom cultivation.
