Grain spawn is typically what most home mushroom growers start with. Either they’ve purchased it online or received their first patch from a friend. If you’re going to be more serious about growing mushrooms, or you just can’t find grain spawn for the variety you like, you’ll you have to learn how to make it from scratch. Luckily grain spawn can be made simply in your own home.

Making Grain Spawn, Two Methods

We’re going to cover two methods today, both step by step. The first method will be using a spore syringe or liquid culture. The second will be using a agar culture. The methods are similar, but they’re worth noting individually.

Additionally, I have written this guide to use grow bottles/jars for our grain spawn. This is solely preference. Grow bottles are reusable, but most bags are not. I think as a home gardener of any kind you should seek to cut down on plastic waste. If you do decide to use any other type of container the method varies only slightly and is nearly identical.

Method 1: Making Grain Spawn from a Spore Syringe


Step By Step Instructions:

  1. Soak your rye berries for 24 hours in cool water.
  2. After soaking for 24 hours, boil the grain for 10-15 minutes.
  3. Drain the remaining water and let the rye stand until most excess moisture has evaporated (15-30 minutes).
  4. Load your grow bottles with the rye. Leave about a half inch head space in the bottle. Secure the bottle lids finger tight.
  5. Sterilize your grain in your pressure cooker for 90 minutes at 15psi.
  6. Once cooled, move your growing bottles to your work area. Be sure to spray down all your equipment with alcohol and let evaporate completely before working. Additionally bring your syringe into you work area and clean the outside with alcohol.
  7. In your flow hood or glovebox open your grain and syringe. Apply the desired amount of liquid to your grain and then recap seal. Repeat this process until all jars are inoculated. You can do several jars with a single liquid culture or spore syringe, but you can also use the entire syringe on one. As long as you use aseptic technique you should yield good results.
  8. Move your inoculated jar to a dry warm place to incubate outside of direct UV light. You can warm your jars to their ideal temperature, which dependent upon the species, but this will at most speed up the colonization process by a day or two.
  9. Watch your jars carefully over the next days to make sure the mycelium is spreading and to ensure there is no contamination.
  10. Once the jars are fully colonized and mycelium covers all visible grain, the grain spawn is ready for use to grow mushrooms or make additional batches of grain spawn.

Method 2: Making Grain Spawn from a Agar Culture

Material Changes:

The materials are the same as method one except for the following:

  • An agar mycelium culture instead of liquid culture or syringe
  • A scalpel

Step By Step Instructions:

  1. Follow method one for steps 1-6, being sure to also sterilize your scalpel in your pressure cooker.
  2. In your glovebox or flow hood, remove the seal from your agar dish and set aside. Open your grain and using the back end of your sterile scalpel make a small well in the middle of the grain, 1-2 inches deep.
  3. Next open your agar dish and cut a small square chunk of colonized mycelium out of the agar. Using the tip of the blade only lift and transfer the chunk to the well you made in your grain. Using your scalpel push grain over the mycelium chunk and then reseal the both the jar and the agar dish. Be sure to re-seal your agar dish with paraffin before removing it from your work area.
  4. Follow steps 8-10 from method one above.

Propagating your Grain Spawn

While you can use your grain spawn in the normal way, moving small amount to growth medium to produce mushrooms, it may also be beneficial to propagate it as well. In propagation to simply follow method 2 above, except you are transferring grain spawn into fresh grain instead of an agar culture. You can make a nearly limitless amount of grain spawn this way (though cloning like this has limits).

If you’re getting ready to grow a lot of mushrooms, this is a great idea. It gives you a ton of material to work with and helps you avoid contamination failures by creating multiple back ups. In a larger growth setup it is always a good idea to attempt to propagate your spawn so you never run out of ready to grow material.

The Take Away

If you’re getting serious about growing mushrooms, you’ll want to start making your own grain spawn. The cost savings alone will be worth it in the long run. The methods above a simple and easy enough for anyone to do, so long as you keep your spawn clean. Once you get the hang of this you’ll be able to keep growing mushrooms from your very own stock of ready to grow spawn.