How To Grow Mushrooms With Grain Spawn Bags

Supplies/Materials

• Grain spawn bag (rye, millet or milo)
• Spore syringe or liquid culture syringe
• Bulk substrate (CVG or Coco Coir)
• Micropore tape or poly-fil

Tools

• Monotub
• Alcohol swabs (included with every bag)
• Nitrile gloves (included with every bag)

Instructions

1. 1.

   Choose Your Grain Spawn Bag: Rye, Millet or Milo

   
   Before you start, decide which mushroom grain bag fits your goal. The bags are identical in setup and handling. The only difference is the grain inside, and it affects how fast your mycelium colonises and how big your harvest will be once you spawn it to substrate.
   

   
   

   Rye: best for high yield

   Rye is the classic choice if you want the biggest harvest. Colonisation is a little slower, but rye holds a lot of nutrition, which pays off in the final yield. Get our rye mushroom grain bags.

   
   

   Millet: fastest colonisation

   Millet colonises the quickest of the three. The small grains give the mycelium many starting points, so you will see white growth early. It is a great pick if you are impatient or want your spawn ready fast. Try our millet mushroom grain bags.

   
   

   Milo: the balanced option

   Milo sits right between the other two. It colonises faster than rye and still gives a solid yield. If you cannot decide, milo is the safe choice. Pick our milo mushroom grain bags.

   
   

   Each grain is available in 1 kg, 1.5 kg and 2 kg bags. Pick the 1 kg bag to try the method, or the 2 kg bag if you want more spawn for a bigger grow.
2. 2.

   Set Up a Clean Workspace

   
   Before you do anything, get your workspace ready. Contamination almost always comes from the environment rather than the bag itself, so a clean setup makes a real difference.

   
   

   If you have a still air box (SAB), use it. If not, work in the cleanest, least drafty spot you can find. Wipe down your work surface with 70% isopropyl alcohol and let it dry completely before you start.

   
   

   Take a moment to inspect your grain bag before you inoculate it. Hold it up to a light source and look for signs of contamination. Green, black or pink patches, slimy grain or a sour smell are bad signs. The bag itself should be fully intact, with no tears or holes, and the filter patch should be dry and clean.

   
   

   If anything looks off before inoculation, we replace contaminated bags at no extra cost. Just keep in mind that we can only guarantee sterility up to that point, so make sure you are working with clean liquid culture or spore syringes.
3. 3.

   Wipe Down the Injection Port

   
   Your grain bag has a self-healing injection port, a small rubber square on the outside of the bag. This is where your syringe goes in.

   
   

   Decide whether you want to use a spore syringe or a liquid culture syringe. From experience, liquid cultures have a much higher success rates. Spores injected directly onto grain still need to germinate first, which can take 1 to 2 weeks before colonisation even starts. Liquid culture contains already-active mycelium, so it gets going within just a few days.

   
   

   Every bag comes with a pair of gloves and 2 alcohol swabs (70% isopropyl). Put on the gloves, then wipe the injection port thoroughly with one of the swabs and let it dry for about 30 seconds. This one step removes most of the surface bacteria that could otherwise hitch a ride into your bag on the needle.
4. 4.

   Inject Your Spores or Liquid Culture

   
   Shake your spore syringe or liquid culture syringe for about 10 seconds to distribute the contents evenly, then push the needle through the injection port at a slight angle.

   
   

   Inject 2 to 6 ml per bag. More is not always better. Here is how much you should use for each bag size:

   
   

   • 1 kg (2.2 lb): 2 to 3 ml
     
   • 1.5 kg (3.3 lb): 3 to 4 ml
     
   • 2 kg (4.4 lb): 5 to 6 ml
     

   
   

   Spread the liquid across a few different spots in the grain rather than putting it all in one place. The more starting points you give the mycelium, the faster the bag colonises.

   
   

   If you are inoculating more than one bag, sterilise your needle between each bag. Either use a new needle, or hold a lighter flame to the needle for about 15 seconds and then wait 30 seconds for it to cool down completely before moving on. This prevents cross-contamination, and one bad bag can ruin the rest if you skip this.
5. 5.

   Let Your Grain Spawn Bag Colonise

   
   Find a spot where the bag can sit undisturbed at room temperature. Mushroom mycelium grows best between 21 and 27°C (70 and 80°F). 

   
   

   If your place runs cooler than 19°C (66°F), you can use a heating mat. But don’t put the bag directly on the mat, because it will dry out the grain. Place something between the mat and the bag instead. A kitchen rack works perfectly fine.

   
   

   Light is not really important. Just keep the bag out of direct sunlight, which can heat the bag unevenly. If you are running more than one bag, leave a little space between them and keep the filter patch uncovered, so the bags get fresh air and don’t build up heat.

   
   

   Now comes the part that trips up most beginners: waiting. You should see the first white mycelium after a few days, and a full bag takes about 4 weeks. Until then there is not much to do.

   
   

   Take a quick look every few days, and leave the bag alone otherwise. Once about 30-40% of the grain is white, it’s time for the next step: break and shake.
6. 6.

   Time to Break and Shake

   
   After roughly 1 to 2 weeks, the grain should be around 30 to 40% covered in white mycelium. Depending on temperature, strain and genetics this can take a bit longer, so don’t worry if it’s not there yet.

   
   

   Once you hit that point, it’s time to break and shake. Wash your hands first and don’t touch the filter patch. Hold the bag with both hands and gently squeeze and break up any clumps of grain through the bag, then shake it so the colonised grain spreads evenly through the uncolonised grain. If the grain has formed a solid block, lay the bag flat and press it apart with your fingers.

   
   

   Put the bag back where it was before. Growth speeds up a lot after this step, because every piece of colonised grain is now a new starting point. A second break and shake when the bag is about 60 to 75% white helps if some areas are lagging behind, but it isn’t required.

   
   

   Take a quick look every few days. If nothing seems to be happening, just keep waiting. It’s almost always slower than you expect, and patience pays off.
7. 7.

   How to Tell When Your Grain Is Fully Colonised

   
   Once the whole bag is covered in white mycelium, the grain is ready to spawn to bulk substrate. It should look solid white, with the grain easy to separate when you shake the bag. A few yellow droplets (mycelium “pee”) are normal, but if you see any green, black or pink patches, don’t use it.

   
   

   A fully colonised bag can be stored in a cool, dark environment for several weeks, but should best be used within 4 weeks.
8. 8.

   Mix Your Spawn into the Bulk Substrate

   
   Prepare your bulk substrate first, for example CVG or manure in a monotub, and let it cool to room temperature.

   
   

   Wipe your hands, scissors and work surface with 70% isopropyl alcohol. Give the bag a final shake to loosen the grain, then cut it open with the clean scissors and tip the spawn into the substrate.
   

   
   

   A common starting ratio is 1 part colonised grain to 3 parts substrate by weight. A higher share of spawn colonises faster and lowers the risk of contamination. Mix everything together evenly with clean, gloved hands, then level the surface and close the monotub.

   
   

   Use the spawn within a few days of opening the bag, because it keeps colonising and slowly gets old. If you can’t use it right away, keep the bag closed and store it in the fridge until you’re ready.
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   Check out our CVG substrate guide!
9. 9.

   Give the Monotub Time to Colonise

   
   Over the next 2-3 weeks, the spawn will colonise the substrate. You’ll see white mycelium spreading outwards from the grain until it covers the whole surface. 

   
   

   Keep the tub somewhere warm and undisturbed during this time. Once most of the surface is covered in white mycelium, it’s time to switch to fruiting conditions.
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   Full Video: How to Grow Mushrooms in Monotub
10. 10.

    Switch to Fruiting Conditions with Micropore Tape

    
    To trigger fruiting, the mycelium needs fresh air. During colonisation, CO₂ builds up inside the sealed tub, and mushrooms only start to form once it drops again.

    
    

    So now we open the tub up for airflow while still keeping contaminants out. Remove all the plugs covering the small holes and cover each hole with micropore tape.

    
    

    The tape works like a filter: fresh air gets in and CO₂ gets out, but most contaminants stay outside. You can also use poly-fil or filter patches on the holes instead of micropore tape.
11. 11.

    Harvest Your Mushrooms

    
    Once fresh air flows through the tub, the pins you saw will start to grow into mushrooms. This happens fast, and they can double in size every day. Leave the lid closed unless the surface starts to dry out.

    
    

    Harvest when the caps are fully grown but before they flatten out or drop spores. Twist and pull each mushroom gently from the base. After harvesting, the tub often gives a second flush within 1-2 weeks, so leave it in place and keep the same conditions.

Conclusion