If you’re serious about mushroom cultivation, using grain as substrate is the gold standard. Growing on brown rice flour (BRF) cakes makes for a fun project, but grain is the way to get worthwhile yields—and most gourmet species fare much better using this method. There are various types of substrates that fungi can grow on, including whole brown rice, wild bird seed, whole oats, popcorn, millet, rye, wheat berries, and more. The choice of grains often comes down to what is available to you and how much each costs.
Grain can be used in jars or plastic bags. There are pros and cons to each. Bags make it easier to “break and shake” when mixing the grain during the colonization process—you can squeeze, push, and pull through the malleable plastic, which is obviously not possible with a solid glass jar. Bags are also single use only, so there is no hassle of cleaning out the jars between grows. However, I prefer to use quart jars because the avoidance of disposable waste is more environmentally friendly. It is also more cost effective than having to buy bags continuously.
There are two main ways to inoculate grain: 1) directly with a multispore syringe (MSS) or 2) with mycelium that has been grown out on agar. The first method, so I have heard from others on the internet, doesn’t have a very good success rate compared to the second. This is because spore syringes are inherently dirty and contain a genetic lottery. By putting the MSS to agar instead, you can clean up any contamination that may be present and isolate the genetics before sending it to grain.
It’s also possible to grow mycelium from cloning tissue rather than using MSS. This is a great option because it goes faster (you don’t have to wait for the spores to germinate) and the genetics are already isolated. This was what I did here—I cloned a tissue sample of oysters onto three agar plates. I would also like to say that although the agar looks really dirty or dusty in the picture, it’s just the reflections on the outside. The agar itself was clean, I promise.
While cloning might sound like a “mad scientist”, high level, complex procedure (at least, that’s what cloning brings to my mind), it’s actually stupid simple. You just take a small piece of either mycelium or mushroom and lay it on some agar. That’s it—really. Of course, you want to be as sterile as possible, so it does take a bit of care in that respect. An effective way to ensure cleanliness is to gently tear the mushroom open instead of slicing directly into it, to prevent the knife or scalpel from picking up contaminants that could be sitting on the surface, then excising a piece from the clean inner flesh.
Oysters are very aggressive and grow quickly. Isn’t it incredible how fast the cloned tissue overtook the plates? The photos above are from days 0, 3, 4, and 6. By day 7 (see the photos further down of the agar going into the oats), it had reached the edges!
I am saving one plate for another project and using two plates for grain spawn.
I picked up some whole oats from the horse food section of Farm and Fleet, which was running a sale of 50 pounds for $12.89. That is insanely cheap for a big bag that will last a very long time. I measured out one jar’s worth of oats, which expands to twice the dry size after cooking, and boiled it for 20 minutes. Also note: some space should be left in each jar so that there is room to shake it up later. I don’t bother measuring how much water to use—there just needs to be at least twice as much water as oats. Excess water is not a problem because it’s all drained once it’s done boiling.
After I drained the oats, I spread them out on pans and a mesh screen (screens are the most efficient). The more surface area, the faster they dry. According to PGT, you want them to be mostly dry on the outside but wet on the inside. This took over an hour. At that point, I divvied the oats up into two jars and put the lids on upside down (so that it doesn’t seal and burst from the pressure) with the ring slightly unscrewed. I also put a square of foil over the top—same as with the BRF jars—before pressure cooking them for 90 minutes in the Instapot (6 quart). I can only fit one jar in at a time, unfortunately, and that’s not even standing upright, but laid at an angle.
After the jars had pressure cooked and cooled down to room temperature, I took the oyster plates and sliced them in a checkerboard pattern, then added the wedges to the oats. This is known as an agar-to-grain (a2g) transfer. I used one plate per quart jar, but you can use more (for faster colonization) or less (to get more end product out of your plate). This should all be done, by the way, in a still air box or possibly a flow hood, if you have access to one. Once the jars were inoculated, I closed the lids tightly, shook them up to distribute the agar, and slightly unscrewed the lids again to allow for fresh air exchange (see photo below, on the left).
Three days after inoculation, the mycelium had partially colonized the oats and, interestingly, sucked the blue-green food coloring out of the agar wedges. I shook the jars again so that the colonized grains would mix with the uncolonized grains and help the process along at a speedier rate. After shaking, the grain almost looks uncolonized again; this is normal, as the mycelium needs a bit of time to recover. Two days later (day 5 after inoculation), it was back to colonizing at full force (see photo below, on the right). The collective mixture of grain and mycelium is known as grain spawn.
By day 10, the jars were what I judged to be fully colonized (see photo below, on the left). At this point, I expanded the grain spawn from two jars to six (see photo below, on the right). This is done fairly easily by adding colonized grain to newly prepared grain and letting it all colonize again. This is known as a grain-to-grain (g2g) transfer. The downside is that each transfer introduces another possible point of contamination. The reward, however, is the generation of more end product.
On the left, see a close-up of oyster mycelium growing from the agar to the grain. On the right, see the view of a fully colonized oyster jar from above.
Isn’t it amazing to think about how two tiny pieces of mushroom tissue turned into six jars of grain spawn? Mushroom cultivation is such a cool and rewarding hobby!
Grain spawn is only one step in the cultivation process and can be used for fruiting blocks, monotubs, and more. I plan on having posts for these as I experiment further.
Spooky Mushrooms 