The grow kit takes up relatively little space, colonizes quickly, and is an excellent choice for those who want to grow mushrooms for their own purpose. (Although we are talking about grow kits here the method is the same if you want to use a monotub.)

Once the brown rice is fully colonized – which takes about 2-3 weeks – you can mix it with your prepared substrate.

It is important to add the mycelium to the substrate as soon as possible after it has colonized the rice grains. The longer you leave the mycelium to sit, the weaker the results you will get.

Tools:

– isopropyl alcohol and paper towels for sterilization

– a larger container for mixing

– plastic boxs

– a spoon for loosening the rice grain spawn

– scissors

– rice grain spawn and substrate.

Sterilization:

Sterility is also very important at this stage. Although the colonized grain is no longer really susceptible to mold or bacteria, you still need to protect your substrate, especially if it is sterilized, from competitors. Pasteurized mixtures are less susceptible to infection, but in this case, it is still important to create sterile environmental factors.

Clean the table surface, the boxes and the lids with isopropyl alcohol, as well as the channel of course. Once the alcohol has completely evaporated from the walls of the mixing bowl, start mixing.

Open the top of the mason jar, use a spoon to crush the rice grains enough to be able to remove them from the mason jar. Pour into the mixing bowl and close it.

Mixing:

Then, sterilize the substrate bag surface and scissors with alcohol, then quickly open the bag. In case you want to use a mulch layer to cover the mixture, set aside a little of the substrate in one of the boxes.

Pour the contents of the bag into the mixing bowl. Next, mix the grain with the substrate by hand, while carefully separating any grains that have stuck together. The more homogeneous your mixture, the more even and faster the colonization will be.

The mixing ratio will affect both the colonization time and the yield.

For example, if you add 1 part grain to 1 part substrate, you will achieve a fast colonization time, but a lower yield.

In the case of 1 part grain and 2 parts substrate, slower colonization and higher yields will occur, as your mixture will contain more nutrients and water.

Example: If we mix 350 gram brown rice sprouts – that is, a mason jar – with 500 gram Grey booster substrate, which we divide into smaller boxes, we can harvest approximately 400-500 gram of fresh mushrooms, by including 3-4 flushings.

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Typical grain spawn to bulk substrate ratios range from 1:1 to 1:4 (spawn:substrate)

by volume, with 1:2 or 1:3 being the most common for balanced speed and yield.

Higher spawn ratios (1:1) speed up colonization and reduce contamination risk, while

lower ratios (1:4 or 1:5) are more economical for experienced growers.

Common Ratios & Applications

1:1 (High Density): 1 part spawn to 1 part substrate. Ideal for maximum speed and lower contamination risk.

1:2 (Standard/Balanced): 1 part spawn to 2 parts substrate. Considered the “sweet spot” for many, offering a balance of speed and efficiency.

1:3 to 1:4 (Economical): 1 part spawn to 3-4 parts substrate. Used to maximize substrate usage, resulting in slower colonization.

Fill the boxes:

Next, fill the boxes with the mixture. You have two options here. You can either fill the boxes almost completely – leaving room for the optional mulch – or you can only fill them to a depth of about 4-5 cm. I recommend the latter, as a mixture that is too thick may not give a satisfactory yield in some cases. In both cases, it is important to compact your mixture gently, but be careful. Soil that is too compact will have a harder time or will not be woven through at all by the mycelium.

If you decide to apply a mulch, spread it thinly over the surface of the mixture. As I mentioned, this is optional and should not be confused with the casing layer applied before harvest. This is used to provide a little extra protection for the grains. However, you should know that the mixture will colonize perfectly without it.

Once you are done with all this, close the boxes.

Colonization:

Place them in a shady spot out of direct sunlight, but don’t keep them in complete darkness. Minimal light is good for mycelium development. Colonization will require a stable temperature, which can vary depending on the mushroom species. The easiest way to find out what temperature your species prefers is to look up the temperature range, but in general, the ideal temperature is between 20 and 24 C. Too low a temperature slows down, while too high a temperature can stop the colonization.

If you have done everything correctly, within a few days the rice grains will start to fluff up, which means the mycelium growth has started. Within a few weeks your mixture will reach 90-95% colonization, which is the ideal time to start the fruiting. This time can vary depending on the species, temperature and the mixing ratio you have chosen, but it ranges from 2 to 5 weeks. Keep the blocks under constant control to monitor their development.

If you see signs of infection, select the infected boxes. As you approach 90% colonization, you can remove the lid of the box for half a minute every few days to remove any accumulated gases. Do not leave it open for long to avoid infections and to maintain the moisture content of the mixture.