Simple Mushroom Grain Spawn

Things you’ll need; 

Air Port Jar – Click here for instructions

Spawn Bags – Alternative to glass jars!

Pressure cooker – My recommendation is a good size presto from the USA. Cheap, reliable and has a great volume.  Make sure it has a gauge. 

Wheat Grain – Any pet shop will stock this. Don’t buy the stuff fit for human consumption it adds an unnecessary premium. 

Liquid Culture w/syringe – Either make your own or buy some from eBay, Etsy or in your local mushroom group! You could also use grain spawn to do a transfer or agar wedges! But those are a bit more complex teks! Alternatively you can buy grain spawn and expand it through transfers.  

Alcohol Wipes – You may have some lying about in the first aid kit, if not, get a bottle of Isopropyl Alcohol off eBay and just use some kitchen roll to apply it!

Disposable gloves – eBay is your cheapest bet, all supermarkets carry them though. Powder free is a must!

Mask – Again, eBay is the most reliable source. 

Lighter – Your local corner shop will have one! A blowtorch will work just as well but is a bit overkill for this method! 

Step 1 – Grain Prep

Fill your mason jar about half full with grain to measure out how much you’ll need. Grain will swell once hydrated so this should bring it up to 3/4 full by the time we are prepping it.

You don’t want your jars full as it will be impossible to shake as it colonises.

Once you’ve got your grain measured out pour it into a bucket/bowl and rinse with cold water. We want to clean the grain and remove debris to prevent the grains from sticking together and clumping, this would make it difficult to shake up, mix your spawn and remove from the jar. If you’re using a bag, cleaning the grain isn’t necessary as the bag is far easier to manipulate and break apart.

The water will get dirty, so you’ll need to strain and change it a few times. Once the water is clear leave it to soak for 24 hours. Make sure you have plenty of water covering the grain so they have enough room to swell. You may also add a tablespoon of gypsum or calcium carbonate at this time. This helps lower the PH and makes the grain less sticky.

After 24 hours strain your grain and simmer for 10 minutes in a pan with water covering them. If your grains look like they’re ‘popping’ or splitting, it’s time to remove them from the heat even if it’s before 10 minutes.

Strain your grains from the pan and spread them out on a towel or rack to steam dry. The aim is to hydrate the grains as much as possible without splitting them open. You will have a few split, as long as the majority are simply swollen you’ve been successful. Split grains aren’t a problem, but they will cause your grains to clump together making them difficult to shake up and get out of your jar, again, not such an issue if you’re using a bag.

Simmering the grain is a way of saturating the kernel with the most amount of moisture. In a more commercial environment, boiling the grain would not be practical so many people opt to miss this step out and simply hydrate the grain inside of a spawn bag with the approximate amount of water that it will absorb.

You can see the comparison of hydrated grain vs hydrated and simmered grain. You can see the grain on the right is more swollen with water and you’ll notice the bran of the grain is much softer. Both are perfectly adequate methods of making grain spawn so the choice is yours.

Fill your Air Port jars 3/4 and screw the lids down tight. Cover the lids with a sheet of tinfoil and load into your pressure cooker. Make sure you have a plate or metal grate at the bottom, you don’t want the jars directly on the bottom of the pressure cooker.

You can load your jars in any configuration inside your pressure cooker, just make sure the bottom layer is stood upright to prevent water from degrading your air filter and going into the jar. A good tip is to weigh your PC with a few litres of water in it and your jars. That way you can weigh part way through the cook to make sure there is still enough water is in your PC.

Pressure cook for 90 minutes at 15psi or if your PC doesn’t have a gauge, 90 minutes at the ‘loudest hissing noise’. This is 90 minutes from when it reaches the correct pressure/hissing noise and not from when you turn the pressure cooker on

If you suspect that the water has all boiled off, pause your timer and wait for the PC to naturally vent it’s pressure. Once it is safe to open add BOILING HOT water to the jars and return the pressure cooker to the hob. Do NOT add cold water as this will crack your jars. Once it has re-reached the correct pressure/noise resume the timer.

After the 90 minutes is up, allow the pressure cooker to cool on it’s own. Remove the jars when safe to do so and allow them to cool for 12 – 24 hours depending on the jar size. Mycelium is very sensitive, inoculating when the grain is too hot will kill or stunt the mycelium so it’s better to play it safe.

Step 2 – Inoculation 

Once adequately cooled. Place your jars/bags in front of a flow hood or inside a glove box. If you’re using liquid culture, a glove box isn’t strictly necessary.

Spray down all your surfaces including the jars and bags with 70% Isopropyl Alcohol or using alcohol based wipes. Make sure to clean your hands too and wear gloves. Note, i’m not wearing gloves because I ran out! I did frequently alcohol gel my hands throughout.

Break up the spawn you’re going to transfer into small grains of white. Shake up your liquid culture syringe too if using LC.

Open your bag with scissors either by cutting the cable tie or just below the heat seal.  Do this inside your glove box or as close as you can to the flow hood.

Pour in a small amount of grain spawn, you could in theory use 1 grain to inoculate the whole bag, this would however, take a long time to colonise and also increases the likelihood of contamination.  Make sure you pour the grain into the bag in-front of the flow of air, don’t come between the HEPA and the bag. I don’t tend to measure, I just divide my grain spawn evenly among as many bags as I have to do, aim for between 5% and 10% for a beginner.

Seal your bag up either with a cable tie or heat sealer, again, with the open bag facing into the filter with nothing blocking the flow of clean air. Always work behind!  See the poor diagram I drew below to understand better-ish. This isn’t important in a glove box as the working environment is sealed. Caution – When working inside a glove box. Be bloody careful with heat/fire or you may lose some eyebrows. 

Once sealed, pressure check the seal by squeezing the bag, it shouldn’t deflate but remain puffy. If it deflates, reseal the bag/tighten the tie. Then, mix the bag up so the grain is evenly distributed, make sure you get plenty to the bottom of the bag as this will always be the slowest part to colonise so the more grain that is there the quicker it will go.

Your liquid culture should come with a needle and syringe. Give the jars, syringe and needle (inside its case) a wipe down with alcohol wipes or isopropyl.

Attach your needle to your syringe by pushing it over the tip, it may also be a twist lock syringe/luer lock so this may require twisting in. Once on, remove the plastic cap and heat the needle until it glows.

Allow the needle to cool down for a few seconds before injecting through the port onto the grain. Again, split your needle between the amount of jars you have, though 2.5ml is pretty adequate for a jar of this size, again, there is no hard and fast rule for this but anything less than 1ml in a jar this size will be very slow to colonise, again exposing the same risks of contamination as with the spawn bags. 

Repeat this heating and cooling cycle for each jar. Once finished, recap your needle and safely dispose of it.

That’s it. Allow your grain to incubate in a warm environment, between 20c and 26c, an airing cupboard is ideal. Once the grain has half colonised, break it up by carefully tapping the jars on a flat wooden surface, break the bags up by hand and allow to continue colonising. Once fully colonise, break it up again the same way and use it to inoculate your substrate! Easy peasy, lemon squeezy! If you’ve got any questions, drop me a message in the contact form or comment below!