Mushroom spawn is simply any substance that has been inoculated with mycelium, the vegetative growth of a fungus. Mycelium, a thread-like collection of cells, is to a mushroom like an apple tree is to an apple. You need to have one as the base for producing the other.

The spawn is used to transfer mycelium onto any material from which mushrooms will grow, called a substrate. Lets take a look at the types of spawn.


Grain spawn is sterilized grain that has been inoculated with spores or a sterile culture of mycelium. Many types of grain can be used with rye and millet being some of the most common. Other choices are corn, wheat, and different cereal grains.

Grain spawn can be used to create sawdust spawn, more grain spawn, or inoculate all sorts of pasteurized substrates such as straw.

A big advantage of using grain is that it’s much more nutritious than sawdust, making it ideal to create more spawn or to inoculate indoor substrates.

A disadvantage is that it’s not as good a choice for inoculating outdoor beds.


250 ml Flasks
50 ml beaker level full of rye grain
1/2 tsp. Calcium Carbonate, powder (lime)
1/4 tsp. Calcium Sulfate (gypsum)
60 ml warm water

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