Making Millet Spawn Bags for Mushroom Growing

Millet Spawn bags

Share This Post

Mushroom cultivation is both an art and a science, and one of the essential steps in the process is preparing the mushroom “spawn”. Millet is a popular choice for many cultivators because of its high nutritional content and suitability for various mushroom species. It is also cheaper than using rye berries and takes less time and effort. Here, we will guide you through creating your own millet spawn bags using 4T unicorn mushroom grow bags.

Materials Per Bag:


  1. Preparation:
    • Start by cleaning your workspace. Make sure it is free from dust and contaminants. Wipe down surfaces with isopropyl alcohol or another disinfectant.
    • Put on gloves to ensure your hands are clean throughout the process.
  2. Weighing Out Millet:
    • Grab one of the 4T unicorn bags and tare it out on a scale. The bags weigh around 12 grams for reference. Using a measuring cup or a scooper, scale out 1000 grams of millet into each bag.
    • Millet grain bags
  3. Filling the Bags With Water:
    • Using the measuring cup or syringe, measure out exactly 500 mL of water. If you are preparing multiple bags, do this step one at a time to avoid mix-ups.
    • If you’re using a funnel, place it in the opening of the bag.
    • Slowly pour or push the 500 mL of water into the bag. If you’re doing this without a funnel, be extra careful to prevent water from spilling.
    • Water Into Unicorn bag
  4. Sterilizing:
    • Next, sterilize the bags to kill off any potential contaminants. Place the bags in a pressure cooker or autoclave, fold them with the filter patch facing out and follow the manufacturer’s instructions.
    • Millet into Pressure Cooker
    • Pressure cook at 15 PSI for two and a half hours.
    • After sterilizing, let the bags cool down in a clean area. Make sure not to rush this step; introducing mycelium to a hot substrate can kill it.
    • Sterilized millet
  5. Inoculation:
    • Once your millet spawn bags have cooled, you can introduce mushroom mycelium via a grain-to-grain transfer or using a spore syringe or liquid culture.
    • If doing a grain-to-grain transfer, seal the bags with an impulse sealer after the transfer.
    • Using a spore syringe or liquid culture would require you to use a self healing injection port and the bags should be sealed prior to the inoculation.
    • Ensure you’re working in a sterile environment, such as a glove box or laminar flow hood.
    • After inoculation, seal the bags and store them in a warm, dark place.
    • Millet Spawn bags
  6. Incubation and Colonization:
    • Over the next few weeks, you’ll observe the mycelium colonizing the millet. Regularly check the bags and gently break up the grains once the mycelium starts to colonize. This helps in speeding up the colonization process.
    • Once the mycelium fully colonizes the millet, your spawn bags are ready to be used to inoculate bulk substrates or fruit directly, depending on your cultivation method.


Creating millet spawn bags for mushroom cultivation is a straightforward process. With patience and attention to detail, you can produce high-quality spawn that will serve as a solid foundation for your mushroom-growing endeavors. Happy cultivating!

Subscribe To Our Newsletter

Get updates and learn from the best

More To Explore

Do You Want To Learn More?

drop us a line and keep in touch