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Mushroom Grain Bags

Grain bags mushrooms sold at Rootlab

At Rootlab, we offer two types of sterile, ready-to-use grains: rye and millet.

We also sell these grains unprepared for you to make your own grain at home

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Mushroom Grain Bags

Mushroom Grain Bags are specialised mushroom bags filled with sterile grains. These grain bags serve as an essential intermediary step in the cultivation of mushrooms. The process involves inoculating the spores or mycelium, suspended in a liquid culture or spore syringe, into these grain bags through a self-healing silicone injection port. After inoculation, the injection port seals itself, preventing contamination from entering and jeopardising your hard work.

Sterile grain bags mushrooms

In addition to the injection port, our mushroom grain bags are equipped with a 0.2-micron air vent filter, effectively filtering out any airborne contaminants. This ensures a sterile environment inside the bag, as all spores and organisms are larger than 0.2 microns and cannot pass through the filter.

These bags also serve another purpose: if you have a colonised agar plate you’d like to introduce to the bag, you can do so by carefully cutting the bag in a sterile workspace, ideally in front of a flowhood or inside a still air box (Sab). You can then introduce small agar wedges into the bag and reseal it.

We often receive questions about which grain bag is better, and we have provided detailed information in our learning centre to guide you.

Once the grain bags for mushrooms are fully colonised, they are referred to as spawn bags, as they serve as the basis for mushroom spawn. These mushroom grain spawn bags are carefully inspected for visible contamination. If clear, they are broken down within the bag, and the contents are poured into a substrate.

The amount of spawn introduced to a substrate is known as the spawn-to-substrate ratio, which can range from 10% to 50%, depending on various factors such as mycelium growth speed, substrate nutrition, cultivation method, and the type of substrate (sterilised or pasteurised).

All grain bags offered by Rootlab undergo sterilisation in autoclaves and are infused with gypsum and calcium carbonate. This infusion not only eases the separation of grains once colonised by mycelium but also provides essential calcium supplements to support robust fruiting body development.

Think of grain bags for mushrooms as a kind of fuel. While colonising the substrate can take several months, mycelium can colonise the grains in just 15-20 days as it’s a quick and easy food source that’s easily digestible and then it can be spread into the substrate for even and fast colonisation.


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