Glossary

Words you will see on the box

We try to keep our packaging plain, but a few terms show up in our instructions and in the wider world of growing. Here is what they mean.

The growth cycle

Substrate

The material the fungus grows through. Ours is a pasteurised blend of hardwood sawdust and wheat straw. Substrate is to a mushroom what soil is to a plant - it is the growing medium, and its quality determines how well the fungus can feed.

Spawn

Grain that has been colonised with a specific strain of fungus. It is the "seed" of the whole process. We use rye grain because it colonises quickly and holds moisture well.

Mycelium

The fungal root network. On a colonised block it is the white, web-like growth filling the substrate. Mycelium is the living body of the mushroom; the mushroom itself is just the fruiting structure that grows out of it.

Colonisation

The point at which the mycelium has fully consumed the substrate. Our blocks ship already colonised, so you skip this stage entirely. A well-colonised block is uniform white, firm, and springs back when squeezed.

Incubation

The warm, dark period where colonisation happens. Held at 72-75°F. Because our blocks are pre-colonised, incubation is a manufacturing step for us, not one for you.

Pinning / primordia

The tiny white bumps that signal a block is about to fruit. This is the moment beginners most often mistake for mould, and it is the moment that tells you everything is going right.

Fruiting body

The mushroom itself - the cap, gills and stem you eventually eat. Technically the fruiting body is the reproductive structure of the fungus, the part that releases spores.

Flush

A wave of mushrooms from the same block. Most blocks give two flushes. The first is the big one, usually 60-70% of total yield; the second comes about a week later and is smaller but often just as good.

Sporulation

The release of spores from mature gills. You will see a faint dusty mist under a mature cap. This is normal, though it means the mushroom is slightly past its best texture. It is not a health risk for an edible species at normal exposure.

Yield

The total weight of mushrooms a block produces across all flushes. A good Pink Oyster block gives roughly 250-350g of caps across two flushes from a 500g block.

Conditions

Relative humidity (RH)

The amount of water in the air as a percentage of what the air could hold. Mushrooms want 80-95% RH. Below about 70% the caps crack and dry out; above 95% with no airflow you get bacterial issues.

Fresh air exchange (FAE)

The rate at which fresh, CO₂-depleted air replaces the air a fruiting room has used up. Too little and you get long stems and small caps. Too much and the block dries out. It is the balance point that separates a good grow from a great one.

CO₂

Carbon dioxide. Mushrooms respire, so a dense cluster of mushrooms in a sealed tub raises the CO₂ around itself. That is what makes stems stretch. A fan or a daily bag opening is all you need to keep it moving.

Substrate pasteurisation

Heating a substrate to around 68°C for two hours. It kills most bacteria and mould without destroying the structure the fungus needs. Pasteurised is not the same as sterile - a sterile substrate needs pressure and about 121°C, and it is only necessary for grain spawn.

When something goes wrong

Contamination

Any other organism getting into the block. Bacterial contamination usually shows as yellow, orange or pink wet patches. Fungal contamination shows as coloured mould. Both are more common in a wet, still, unventilated environment.

Trichoderma

A green mould that is extremely aggressive and will take over a block within a couple of days. It is extremely common in home grows and is almost always caused by contamination handling rather than the block itself. Isolate it, do not open it indoors, and wash your hands.

Botrytis

Also called grey mould. It causes fuzzy grey patches on caps and stems and thrives in cool, humid, stagnant air. It is not dangerous to handle but the affected mushrooms are not edible.

Blanching

A pale, washed-out cap colour caused by too much CO₂ or not enough light. The mushroom is still perfectly good to eat; it just does not look as appealing.

Stunting

Mushrooms that stay small. Usually a combination of low CO₂, low humidity and crowding. Often the caps are fine and it is mostly a yield loss.

Decontamination

Cleaning and sterilising a grow space between runs. Even with a home setup, wiping down surfaces with a diluted bleach solution between grows meaningfully reduces contamination risk.