Mushroom Growing Terms, Explained Simply

The mushrooms we harvest are temporary fruiting bodies. The mycelium is the longer-lived organism producing them.

On our farm, most of the mycelium is hidden inside hardwood logs. We may not see much happening from the outside for months, but the fungus is gradually moving through the wood and using it as food.

The fruiting body is what we ordinarily call a mushroom.

Its job is reproduction. Under suitable conditions, the mycelium forms mushrooms that produce and release spores. For a grower, this is also the part that ends up in the harvest basket.

Thinking of a mushroom as the fruit of a much larger hidden organism helps make sense of the entire growing process.

Spores are the fungal equivalent of seeds, although they work differently biologically.

A mature mushroom can release an enormous number of microscopic spores. Those spores may germinate and eventually form new mycelium when conditions are favorable.

Most home growers do not begin with spores. Starting with established mycelium is faster and more predictable.

A culture is a living sample of a particular fungus.

It may be growing on agar in a dish, suspended in a liquid culture, or maintained in another controlled form. Cultures allow growers to preserve and reproduce a specific mushroom strain.

For a beginner, it is usually enough to know that the culture comes before the spawn in the production process.

Spawn is a material that has already been colonized by mushroom mycelium and is used to start a new grow.

Depending on the method, spawn might be made from grain, sawdust, or wooden plugs. We primarily use sawdust spawn when inoculating logs.

Spawn is not mushroom seed, even though it serves a similar practical purpose.

A hardwood log is a substrate. So are straw, hardwood sawdust, wood chips, and many prepared growing blocks.

Different mushroom species prefer different substrates. Shiitake is strongly associated with hardwood, while oyster mushrooms can grow on a wider range of plant-based materials.

Inoculation simply means introducing mushroom spawn or culture into a new substrate.

When we inoculate a log, we drill holes, place sawdust spawn into them, and seal the holes with wax. With a bucket grow, inoculation may mean mixing or layering spawn with prepared straw or another substrate.

This is the point when the grow officially begins.

During this stage, there may be little to see from the outside. Inside the log, bucket, or bag, however, the fungus is claiming the available material and building enough strength to fruit later.

A fully colonized substrate has been thoroughly occupied by the intended mushroom mycelium. How long that takes depends on the species, substrate, temperature, moisture, and growing method.

Fruiting conditions are the environmental signals that encourage colonized mycelium to produce mushrooms.

The exact combination varies by species, but moisture, fresh air, temperature, and some light commonly play a role.

Outdoor logs largely take their cues from the weather. Rain, temperature changes, humidity, and the season can all influence when mushrooms appear. That is one reason naturally fruited log growing is less predictable than a tightly controlled indoor grow.

Pins are the tiny beginnings of mushrooms.

They often appear as small bumps or clusters before developing recognizable caps and stems. When pins form, the grow has entered a sensitive stage. Dry air or a sudden loss of moisture can cause them to stall or dry out.

Fruiting is the stage when the mycelium produces mushrooms.

For indoor growers, this usually means providing the humidity, airflow, light, and temperature the species needs. For naturally fruited outdoor logs, it often means watching the weather and checking the log yard after favorable conditions.

A bucket, block, or log may give several flushes rather than producing everything at once. The first flush is often the largest, but later flushes can continue as long as the mycelium has enough moisture and usable material remaining.

That might be mold, bacteria, yeast, or another fungus. Sour smells, unusual slime, or rapidly spreading green, black, or brightly colored growth can all be warning signs.

Not every strange-looking patch is automatically contamination, and healthy mycelium can vary in appearance. Learning what normal growth looks and smells like is part of becoming a better grower.

Pasteurization uses heat to reduce the number of competing organisms in a substrate without making it completely sterile.

Straw used for oyster mushroom buckets is commonly pasteurized. The goal is to give the mushroom mycelium a strong head start while keeping the process practical for a small grower.

Sterilization is a more intensive process intended to eliminate nearly all living organisms and resistant spores from a material.

It is commonly used for nutrient-rich substrates that would otherwise contaminate easily. Sterilization generally requires higher temperatures and pressure, not simply boiling water.

Pasteurization and sterilization are not interchangeable terms. Which one is appropriate depends on the substrate and growing method.