Cultivation: Inoculating Grain Bags

Feeling a little nervous about inoculating grain for the first time? Not to worry - we're here to help you through it! This blog will provide step-by-step mushroom cultivation tips to help you successfully create a mushroom spawn bag. Let's get started!

There are many ways to inoculate your grains. You could use an agar culture, liquid culture, liquid inoculant, spore syringe or spawn. Let's walk through a few of these methods before we begin.


You could classify the grain inoculation methods into two types:

1. Injection

This method of inoculation poses a much lower risk of contamination when you do not have access to a laminar flow hood. The inoculants that are injected into grain bags are: liquid culture, spore syringe, and liquid inoculant


Please make sure that you test your culture on agar to ensure that the inoculant is not contaminated before using it to inoculate your grain bag.


2. Incision

The Myterra Difference

This method of inoculation has the lowest risk of contamination when performed in front of a laminar flow hood, but can be performed in a large still air box. The inoculants that are put into the bag after cutting off the top of the grain bag are: Agar culture and colonized spawn. Colonized spawn cultures can be expanded by adding them to grain, but you should only do this once or twice to avoid putting your culture into dormancy.





Here are a list of tools you are going to need to successfully inoculate your grain bag with a syringe:

  • Syringe filled with with your culture
  • Needle 
  • Adhesive injection port (included with Myterra Labs Grains)
  • Spray bottle with 70% isopropyl alcohol
  • Loop sterilizer or a lighter or alcohol burner
  • Gloves are good practice, but not strictly necessary



The last thing any mushroom grower wants is to put in the time and effort to get to this stage of cultivation, only to lose your new spawn bags to contamination. This is why it is extremely important to clean all work surfaces and tools. Spray your work surfaces with 70% isopropyl alcohol before placing any bags or tools on the surface. Spray all tools with 70% isopropyl alcohol and allow the alcohol to evaporate before placing them on your clean work surface.



All Myterra Labs substrates are sealed and packaged in a HEPA-filtered clean room. Myterra Labs grain bags are sealed inside of a protective white bag to prevent dehydration of the substrate and denaturing of the chemical composition of the substrate. You will need to remove the white outer packaging before inoculation. 

BE CAREFUL when removing the outer packaging to avoid puncturing the unicorn bag inside. Hold one of the corner flaps of the white bag and use your scalpel/knife to make a cut underneath the seal of the bag. You will be able to peek inside of the white bag to see the inner unicorn bag and can continue cutting the bag whilst making sure not to puncture the inner bag.



Spray the outside of the unicorn bag, focusing on the area between the filter patch and the surface of the grain. Wait for the alcohol to dry before removing the backing on the injection port and stick the port onto the bag about an inch below the filter patch, above the surface of the grain. Once attached, spray the black rubber of the injection port with alcohol and allow it to dry.



Spray your hands/gloves with alcohol and wipe the alcohol over all surfaces of your hands. Remove the needle from its sterile packaging and attach it to your syringe. If you are not using a new/sterile needle you will need to spray the needle with alcohol and hold it under a flame until the needle is red hot and allow it to cool before use.



The best method that works for us with a liquid type of inoculant is to spray the surface of the grains with the inoculant. Use your needle to pierce the injection port, face the needle towards the surface of the grains and slowly depress the syringe plunger. While depressing, move the tip of the needle so that you are able to spray all over the top surface of the grains. You can use as little as 5cc of inoculant, but be aware that the colonization process will be slower with smaller amounts of inoculant. We find that 10-20cc of inoculant has the fastest colonization time. Remove the needle once you have added your inoculant. DO NOT shake the bag.

As a precautionary measure, tape over the injection port with a piece of packing tape. This will prevent the injection port from possibly falling off when the bag is shaken at a later stage.



Leave the bag unshaken until you see thick white mycelium form on the top of the grain. You can shake the bag once you see that the mycelium is growing well. Shaking the bag ensures that the mycelium is spread throughout the bag. You will need to shake the bag again once the bag is about 50-60% colonized.