How To Prepare A Topnotch Grain Spawn For Cultivating Mushrooms At Home

Grain spawn is described as the oldest way of cultivating mushroom cultures. You get started with just 1 liter of grain that has already been decontaminated, then you add this to a cultured slice from a petri dish. You are free to expand the mushroom mycelium to get about 1000L of spawn.  A single jar can produce about 10 jars, and these can in turn give you 100 jars, then 1000 jars from 100 jars. All these can be possible within a very few weeks. You can imply from this that an immense amount of mushrooms can be reproduced from this number of grains. Provided that your grain is prepared most properly, and put under appropriate growing conditions, you can be sure that huge success of mycelial growth is what awaits you.


Several numbers of grain are available, and you’re free to pick any of your choices for spawning. From wheat to brown rice to rye to white rice, popcorn or even wild bird seed, the list is long. I can say beyond doubt that Rye is the most used grain for mushroom cultivation. There’s an explanation for this, and this is because rye has an excellent ability to absorb water. Also, its nutrient composition is superb, and many mushrooms seem to enjoy it.


Grain can be made through 4 easy steps. (Read on for a copious understanding of the instruction.)

Step 1: Gather, wash and clean the grains, soak them in water for 16-24 hours.

Step 2: Boil the grains in water for 20 minutes to allow them to absorb water.

Step 3: Drain excess moisture from the grains, till the outside appears very dry.

Step 4: Load up your mason jars with grains and sterilize for 2 hours at 15 PSI.



  • Cereal Grain (preferably rye)
  • Jars of mason with polyfill
  • Pressure sterilizer
  • 25 Liters Bucket or a container of similar size
  • Stove and large pot.
  • Strainer or screen.

Though the following method is a bit demanding, it remains a proven way to arrive at a perfect grain spawn any time any day.


Take accurate measurements of the grain you desire to use and remind yourself that the size becomes almost double the original size after you’ve soaked it in water  because your rye grain will absorb a sufficient amount of water. So fill up your jars to about ⅔ after they’re adequately sterilized. Then, measure a 1-quart jar of grain to be introduced into a 3-quart spawn. Feel free to add extras to get a good measure.

Your grains may contain dust and other things that are not wanted or that won’t do your mushrooms any good. With this in mind, thorough rinsing of your grain is required until you have it clean. After you’re satisfied with how clean your grain is, pour them into a container, and add water to it. A handful of coffee or even gypsum can be introduced to the mixture.

Adding these two ingredients has benefits, for example, gypsum prevents your mixture from sticking together while coffee presence in your mixture helps to raise the pH slightly, and in this way, the overall yield of the grains will step up. If you’re making  10 jars of grains, then about a tablespoon of gypsum is enough, and 2 handfuls of coffee.

Leave the grains in water for close to 1 day, this will make the grains take in a lot of water which is good for it. It would even allow for the sprouting of the contaminants. Soaking your grains in water also makes them more susceptible to drying out during sterilization.


Cooking is another way to further soften the grains, in the same way, cooking makes them take in more water. By cooking your grains for about 20 minutes, you end up having grains that will be easily digested by your mycelium. But avoid overcooking them if you don’t want them to start cracking open because that will make them vulnerable to contamination along the process of incubation.


When you cook them for a longer time, you end up drying them up. So this could also be another reason for cooking them. The process is simply called evaporation and is done by draining the water several times from the grains then drying them with a towel or over a screen. When you’re done, your grains shouldn’t contain any visible water on them. You must ensure you dry everything out.


After you’re sure that your grains are free from water, the best thing is to pour them inside your jars to about ⅔-¾ level in the jars. The jars need to have filters on them which will make it possible for air to move in and out of the jars during incubation. There are various ways by which that can be achieved, what I do is that I make a ¼ hole on the lid and pass a ensure a pillow stuffing goes through the hole. This filter serves many purposes, it effectively helps to shield the mycelium against contaminants and also allows breathing to occur. It also makes it possible for the jars to be inoculated introducing a culture syringe directly into the jar through the hole created in the lid.

You can also have access to the jars by drilling a couple of holes in the lid and putting a filter disc in between the lid and the screw cap.

The final thing to do in preparing your mycelial jars is to ensure that you cover the lids with tinfoil. This tinfoil helps a great deal in protecting your pressure cooker and the mycelium inside. It disallows water from gaining entry into the grain, and thereby maintains the moisture level of your grain.

Examine your grains to see whether there are moderate broken grains and also see to it that these grains do not glob together. If you check and you don’t have these grains globbed together, then you can now say that you’ve got perfect grain.

At the end, your grains are ready for inoculation with your mushroom culture!

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