Propagating Mushrooms

Mushrooms are hardy organisms. The mycelium of a mushroom producing fungus is capable of living for hundreds of years, perhaps more. For example, there is a patch of Armillaria mushrooms in Oregon that is believed to be over 2,000 years old. However, most of these magnificent organisms rarely live more than a few years. This is because of fungus’s way of eating. It grows into its food source and lives there until the food is gone. Unless it has another nearby source of food to grow into, it will starve to death and die. The art of propagating mushrooms is primarily the art of transferring the mycelium from one food source to another to keep it going as long as possible.

There are several ways to propagate mushrooms. In commercial production, they work under sterile conditions and take a sample of mycelium, either from the center of a fresh mushroom or a stored mycelium, and grow it onto agar in a petri dish. Then they transfer it onto sterilized rye grains (sometimes more than once) and then transfer it to pasteurized straw or wood chips for the final production of mushrooms*. However, in most people’s homes, mine included, sterile conditions are a bit hard to come by. So I will talk a bit about methods you can use that don’t require sterile conditions.

What we are going to be making is called spawn. Spawn is a growing medium for mushrooms that is used to expand a sample taken from living mycelium in preparation for making something larger for producing mushrooms. There are many kinds of mushroom spawn, and selection of such depends on what you have on hand and what you are hoping to transfer mushrooms onto. For example, mushrooms that are going to be transferred onto a log might be cultivated in a different form than mushrooms that are going to be transferred to a wood chip bed. Below are some common kinds of mushroom spawn out there and a brief description. I will cover some of them in detail later in individual posts.

Plug spawn – Plug spawn is made from wooden dowels that are grown through with mushrooms and then hammered into logs.

Coffee ground spawn – Coffee ground spawn takes advantage of the fact that coffee grounds are small, easily colonized and pre-sterilized.

Cardboard spawn – Cardboard spawn makes a nice surface to sandwich between two layers and makes an ideal growth medium for mushrooms.

Bunker spawn – A large mass of myceliated material covered in a protective cloth coating is good for helping mushrooms leap off in less-than-ideal conditions.

Wood chip spawn – Wood chips give an easy medium on which to grow and expand mushrooms.

*Note that this is how most gourmet mushrooms, such as oyster and shiitake, are grown. Button mushrooms have different requirements and are grown on composted, pasteurized steer manure.