- Mushroom grain spawn is vital for mushroom growing to be successful, giving a firm starting point for mycelium to spread.
- Even though a sterile setting is helpful, do-it-yourself methods allow home growers to make grain spawn without fancy lab tools.
- Right amount of water, sterilization, and keeping it at the right temperature are important steps to make sure grain spawn is free from contamination.
- Best conditions for colonization are temperatures between 70–75°F with very little light.
- One jar that is fully colonized can be used to make many more by moving grain to grain, growing your mushroom growing projects.
Mushroom Grain Spawn: Can it be This Simple?
Grain spawn for mushrooms is really important when you grow mushrooms at your house. It's like the starting point where the mycelium can begin to spread and take over a bigger substrate. Lots of people think you need a fancy lab to make good grain spawn, but actually, you can do it at home with regular stuff. You don't even need a special air filter hood. If you prep right, sterilize carefully, and inoculate correctly, you can make mushroom grain spawn right in your kitchen and not worry too much about it getting contaminated. This guide will take you through each step to make your own grain spawn and get started growing mushrooms.
Step 1: Selecting and Soaking the Grain
The kind of grain you pick for mushroom grain spawn really affects how fast it colonizes and how well it works overall. Organic rye berries are usually seen as the best because they hold water just right. But there are other options too, such as
- Wheat berries – They're a bit smaller than rye but work just as well.
- Millet – This is good if you want colonization to happen quicker because the grains are smaller, which lets the mycelium spread fast.
- Brown rice – It can be used, but it's not as good as rye or millet.
- Oats or corn – Sometimes people use these, but there's a greater chance of contamination.
Hydration Process
Getting the hydration right makes sure the grains have enough water for the mycelium to grow well. Here's what to do
- Put the dry grain into a big bucket or bowl.
- Add enough water so the grain can get bigger but the water doesn't overflow.
- Let it soak for 12 to 24 hours. Don't leave it longer than 24 hours, because it might start to sprout, and that's not good.
- After soaking, the grains should be about three times bigger.
A simple tip: If you start with one cup of dry rye berries, you'll get about three cups of grain that's hydrated. If you're making ten quart jars, start with around three jars of dry grain.
Step 2: Getting Jars and Lids Ready
For growing mushrooms in jars, you need to change the lids a bit so it's easy to put the mycelium in and also keep out any bad stuff.
How to Ready the Lids
- Make two holes in each lid, whether it's metal or plastic
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- Drill a 1/4-inch hole in the middle so air can get in and out through a filter.
- Drill a 1/8-inch hole near the side to inject the mycelium.
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Make a port that seals itself after injection
- Put high-heat silicone sealant (like RTV silicone) over the smaller hole.
- This way, when you stick the syringe in, the hole closes up afterwards, so nothing bad can get in.
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Put in a filter
- Use polypill or synthetic filter disks over the bigger hole. This lets the mycelium get air but stops germs from getting in.
With these special lids, you don't need a pricey air filter hood. The self-sealing port and air filter help keep mold and bacteria out of the jar.
Step 3: Cooking, Draining, and Drying the Grain
After soaking, the grains need to take in a bit more water by being simmered. This makes sure they have just the right amount of water for the mycelium to grow well.
Steps for Cooking and Draining the Grain
- Move the soaked grains to a pot of water and bring it to a gentle boil for 10 to 15 minutes.
- Watch them carefully. If you cook them too much, they can get too soft and mushy, which makes it hard for the mycelium to colonize.
- Drain the grains right away using a strainer or mesh screen.
- Spread the grains out on a clean towel or rack to dry in the air for 1 to 2 hours. The outside should feel dry so there's not too much water in the jars.
Once they are dry enough, fill each jar about two-thirds full, leaving some space to shake the grains later so they colonize evenly.
Step 4: Making the Grain Sterile
Sterilizing gets rid of bacteria, mold spores, and other bad things that could fight with the mycelium and stop it from growing.
Why You Need a Pressure Cooker
- Just boiling water (at 100°C) isn't hot enough to kill everything. Some bacteria spores can still live.
- Using high pressure at 15 PSI (about 121°C) for 90 minutes really makes the grain spawn sterile.
- A good, cheaper option is the Presto Pressure Canner (it can hold up to ten jars).
How to Sterilize
- Put aluminum foil over each jar lid so water doesn't get into the grain.
- Put the jars in the pressure cooker, making sure they aren't touching the sides.
- Set it to 15 PSI for 90 minutes. Start timing when it reaches full pressure.
- Turn off the heat and leave the jars to cool down all night before you touch them.
Not sterilizing properly is one of the main reasons why mushroom growing gets contaminated.
Step 5: Adding Mycelium with Liquid Culture
After the jars are cool, it's time to put the mycelium into the grain using a syringe with liquid culture.
How to Add Mycelium
- Clean the jar lid area with 70% isopropyl alcohol to sanitize it.
- Put a sterile needle on the liquid culture syringe.
- Stick the needle into the self-healing injection port and inject 1 to 2 CC into each jar. If you put in too much, it can make too much moisture, which can cause contamination.
- Sterilize the needle with flame between jars if you're doing more than one.
You can buy liquid culture syringes online from places like Mycelium Emporium.
Step 6: Keeping Warm and Growing Mycelium
Once you've added the mycelium, keep the jars in good conditions to help the mycelium grow and colonize well.
Best Conditions for Colonization
- Temperature: For most kinds of mushrooms, keep it at 70–75°F (21–24°C).
- Light: Not much light, or light that's not direct. It doesn't have to be totally dark, but darkness can make colonization slower.
- Humidity: The jars already have enough moisture inside, so you don't need to add more humidity.
Checking on Growth
- When colonization is healthy, it looks bright white and like a web.
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Signs that something is contaminated
- Bacterial infection → Wet, slippery spots that smell sour.
- Mold → Green or black fuzzy stuff growing.
- When about 30% of the jar is colonized, shake it up to spread the mycelium around so it grows faster.
For most types of mushrooms, it takes 2 to 3 weeks for a jar to fully colonize if the conditions are right.
Usual Mistakes and How Not to Make Them
- Cooking the grain too much → It gets mushy and you can't use it. ⟶ Just simmer for 10–15 minutes.
- Not sterilizing → Big chance of contamination. ⟶ Always pressure sterilize at 15 PSI.
- Using too much liquid culture → Too much water can bring bacteria. ⟶ Don't put in more than 2 CC per jar.
- Conditions not good for colonization → Growth is slow or doesn't happen. ⟶ Keep it at 70–75°F and make sure there's some air flow.
What to Do After? Growing More and Using Your Grain Spawn
Once the jars are fully colonized, you can use them to grow mushrooms in different ways
- Putting spawn into bulk substrates – Mix the spawn with coco coir, sawdust, or straw to get bigger harvests.
- Monotubs and fruiting chambers – These are great for mushrooms like oyster and psilocybe.
- Grain-to-Grain Transfers (G2G) – You can use one jar that's colonized to start ten more. This way, you can make a lot more spawn.
Making mushroom grain spawn is a simple but effective way for people at home to grow mushrooms. With basic tools and good sterilization, anyone can successfully grow mushrooms at home—you don't need a fancy lab!
For cheap sterilized stuff and liquid cultures, take a look at Zombie Mushrooms. Happy growing!
References
- Stamets, P. (2000). Growing yummy and healing mushrooms. Ten Speed Press.
- Moore, D., Robson, G. D., & Trinci, A. P. J. (2011). 21st Century Guidebook about Fungi. Cambridge University Press.
- Smith, J. E., & Sullivan, R. (2017). "Sterilization Ways for Mycology: A Review." Microbiology Research Journal, 25(3), 150-165.
