Grain spawn is the center of mushroom cultivation. A good clean technique here is essential to good harvests. Making mushroom grain spawn is pretty simple. Starting with a liquid culture is the easiest and most cost-effective way to set up grain spawn.
I have outlined the steps below.
1-pint mason type jar
175 ml of while millet with hulls (about 3/4 of a cup)
(See below for an update on using millet)
75 ml water (about 2 1/2 ounces, or 1/3 cup) distilled water is preferred.
Put the millet in the pint jar and add water.
Shake to mix in the jar, seal.
Sterilize at 15 psi for 90 minutes in a pressure cooker. (I tried an Instapot and it didn’t work well.)
Let the jars cool completely. Any temperatures over 106 degrees will kill the mushroom mycelium.
Shake the jar vigorously several times to separate the grains.
This can be quite a vigorous shake. It takes a lot to break them apart.
If the grains are not separated the chance of mold is much higher.
Once the grains are separated inject with liquid culture. I typically put in about 10cc per jar. It is probably more than is needed, but it helps to overcome any bacteria that might still be in the grain.
Set the jar in a dark cool place for one week. Check it for mycelium. If you don’t see any leave it for another week.
When the mycelium starts to grow and takes up about 1/3 of the jar, shake it vigorously again. You want to spread the inoculated grain to the rest of the jar.
Set it in a dark cool place again. It can take up to 3 weeks to fully colonize.
I usually shake mine a couple of times as it grows.
Once the jar is fully colonized you are ready to move to the next step.
This image is the white millet I use. The hulls are important so be sure to get millet with hulls.
The links above will take you to Amazon where I purchased mine. They had the best price I could find.
Mushroom grain spawn is at the heart of growing mushrooms successfully. It is imperative that you practice clean technique so you don’t get contamination. Having contamination at this stage is heartbreaking and can discourage even the most ardent of growers. Make sure your mushroom grain spawn is clean and uncontaminated from start to finish. It will make your mushroom growing much easier.
I have gotten tired of how difficult it is to break apart the millet so I have switched to wheat berries for my grain spawn. The link is to Amazon where I have bought them. They have a nice product and it is convenient to purchase them online. When doing larger quantities I have bought them locally. Many health food stores carry wheat berries in the bulk section. It is cheaper to buy them locally, but if like me, you aren’t close to a large urban center, online works well.
The recipe is essentially the same. I measure out the berries in the container I want to use them in to get the amount. Then I pour them out and soak them for 24 hours. Once they have soaked, I rinse them well. Then I put them in a pan and cook them for about 10 minutes. This step isn’t necessary but it does seem to help colonization. Then sterilize at 15psi for 90 minutes.