Wild Bird Seed (WBS) - Grain Spawn
Wild Bird Seed (WBS) is one of the cheapest and most widely available grains for mushroom cultivation. Typically found in the pet or outdoor sections of grocery stores, big box stores, home improvement stores, and pet shops. However, my local grocery store hides it on the bottom shelves of the produce section of all places. You can also find it online; this is the brand I purchase on Amazon:
There are many types of wild bird seed, and only specific varieties will work for mushroom cultivation. You want wild bird seed that mostly consists of millet and milo; this type usually contains sunflower seeds and cracked corn in addition to the millet and milo. The sunflower seeds are easy to remove, and the crack corn isn't an issue.
Wild bird seed is an excellent choice for grain spawn because of the many inoculation points. Meaning the mycelium can colonize it faster, and it will mix more evenly in a bulk substrate. WBS isn't perfect; you'll need to clean it, removing sunflower seeds, larger corn kernels, and debris like twigs, stones, etc. The sunflower seeds could cause a contamination issue if not removed.
Don't throw away the sunflower seeds
My neighborhood birds have mush-love for the discarded sunflower seeds and cracked corn. A family of cardinals and song sparrows visit my house regularly for the discarded grain. Instead of throwing away the excess, try leaving them outside for the birds; you'll have a fair amount of excess after each batch of spawn.
Preparing Wild Bird Seed Grain Spawn
Measure Dry Grains
Measure the amount of grain you would like to use and place it in a large pot. A mason jar (1-Quart) of dry grain usually yields around 2 jars of spawn. The measurement isn't an exact science as we will need to remove the sunflower seeds.
In a sink, add water to the pot and begin scooping out anything that floats; this will mostly consist of sunflower seeds. Tip: I use a small mesh strainer that works excellent to collect floaters.
After removing the floaters, run your hands through the grains a few times to release any trapped sunflower seeds. Continue this process until you are left with murky water.
Dump the dirty water through a colander or mesh strainer to catch any grain. Then refill the pot with clean water. Run your hands through the grain to shake dirt loose. Rinse and repeat until the water looks crystal clear.
While cleaning the grains, discard any large corn kernels, sticks, pebbles, and other debris. You do not need to be very thorough; just remove the larger debris.
Once the water is cleaned, fill the pot until the water is about 1 inch above the grains.
To prevent the grains from sticking together, add a scoop (tablespoon) of gypsum. Increase the nitrogen (pH) by adding a cup of mild coffee to the grain.
Cover the pot and allow it to soak for 12+ hours. I typically let the grains hydrate overnight.
Cook Grains Simmer
Heat the pot until it comes to a simmer (just before boiling). It is crucial that you don't let it boil, or else the grain will break apart into a sludgy mess. Cooking will soften the grains, making it easier for the mycelium to consume.
Strain & Air Dry
Strain the grains and let the outer surface area air-dry. Usually, this takes 45-60 minutes. The grains are ready when they don't leave a puddle when placed on a paper towel.
Fill Mason Jars
Fill your jars about 2/3 of the way full. The extra space is needed to break up the colonized grain later and it also helps for conducting grain to grain transfers.
Jar Lids & Foil
All jar lids should contain a filtered gas exchange. Without it, the mycelium could suffocate and die. Simply punch a hold in the lid and cover it with a filter patch, micropore tape, or stuff with polyfill. If you plan on to inoculate the grain with a syringe, add an injection port. Once your lid is on, cover the top of the jars with foil to prevent moisture from entering the gas exchange.
Prepare your pressure cooker to sterilize the grain spawn. You'll want to cook the grain spawn for 90-minutes once the pressure cooker reaches 15-PSI. Tip: Instructions for operating a pressure cooker: Pressure Cooker Tutorial
Allow the pressure cooker to come down in pressure and cool overnight. You'll want the grains to be at room temperature before inoculation. If the internal temp of the spawn is too warm, it could kill the mycelium.