Cultivation glossary

Mushroom cultivation has its own vocabulary. This glossary defines the terms you will meet in a grow log — spawn, substrate, flush, biological efficiency, fruiting body, colonization and more — in plain language, with a sentence of practical context for each.

Core concepts

Spawn: Spawn is mushroom mycelium growing on a carrier material, most often sterilised grain, used to inoculate a larger substrate.; Spawn is the starter culture. Grain spawn is the most common because individual grains give many inoculation points, which speeds up colonisation. Sawdust spawn is preferred for wood-loving species, and liquid culture is a mycelium suspension used to inoculate grain in the first place.
Fruiting body: The fruiting body is the visible, reproductive structure of a fungus — the part commonly called a mushroom, which produces spores.; The fruiting body is what growers harvest. It develops from primordia, the small pin-like structures that form when colonised substrate is exposed to fruiting triggers such as fresh air, light and a drop in temperature.

Substrate and preparation

Substrate: Substrate is the material mushroom mycelium digests and grows through, such as straw, coco coir, hardwood sawdust or supplemented pellets.; Substrate supplies both water and nutrition. A substrate that has been properly hydrated and pasteurised or sterilised gives the mycelium a head start against competitor organisms. Substrate weight is the denominator in biological efficiency calculations.
Hydration: Hydration is the amount of water in a substrate, usually expressed as a percentage of the dry ingredient weight.; A 70% hydration mix contains 70 g of water per 100 g of dry ingredients. Hydration is one of the strongest levers on yield and one of the easiest to change unintentionally, which is why recording water weight separately in a recipe is worthwhile.
Spawn rate: Spawn rate is the proportion of spawn to substrate in a batch, typically expressed as a percentage of the total wet substrate weight.; Higher spawn rates colonise faster and resist contamination better, at the cost of more spawn per batch. Many growers run between 10% and 25% by weight, depending on species and substrate.
Pasteurization: Pasteurization is heating a substrate to a moderate temperature to reduce competitor organisms while leaving beneficial microbes intact.; Pasteurisation is generally adequate for straw and coir substrates. Supplemented substrates with bran or soy hull typically need sterilisation instead, because the added nutrition raises the risk from heat-resistant contaminants.
Sterilization: Sterilization is heating a substrate or medium to a temperature that destroys all organisms present, usually with a pressure cooker or autoclave.; Sterilisation is used for grain spawn, supplemented sawdust blocks and agar work. It is distinct from pasteurisation, which only reduces competitor populations rather than eliminating them.

Growth and process

Flush: A flush is one distinct wave of mushroom fruiting from a single batch, harvested together before the substrate rests and produces the next wave.; Most species produce several flushes from one substrate. Flush number matters for analytics because yield typically declines with each successive flush, so comparing a first flush to a third flush without noting the difference is misleading.
Colonization: Colonization is the phase in which mycelium spreads through the substrate after inoculation, before fruiting conditions are introduced.; Colonisation is usually complete when the substrate surface is fully covered in white mycelium. Rushing this phase by introducing fruiting conditions early is a common cause of weak first flushes.
Primordia: Primordia are the small pin-like knots of mycelium that develop into fruiting bodies; growers usually call this stage pinning.; Pinning is triggered by a combination of full colonisation, fresh air exchange, light and often a modest temperature drop. Primordia that dry out or receive too little fresh air will abort rather than develop into mature mushrooms.
Monotub: A monotub is a single large modified plastic tub used to colonise and fruit a batch in one container, with holes for gas exchange.; Monotubs suit high-yield species such as oysters because the large substrate mass holds moisture and temperature more steadily than small containers. They also simplify humidity management.
Contamination: Contamination is the presence of an unwanted organism competing with or damaging the cultivated mycelium, such as trichoderma, bacteria, cobweb or yeast.; Contamination is measured as a rate: the share of containers affected across a batch. Recording the affected container count rather than just the batch is what makes the rate meaningful.
Trichoderma: Trichoderma is a fast-spreading green competitor mould and the most common contamination in home mushroom cultivation.; It typically appears as dense white growth that turns bright green as it sporulates. It is usually traced to incomplete substrate sterilisation, contaminated spawn, or inoculation carried out in open air.
Spawn run: Spawn run is the period immediately after inoculation during which the mycelium recovers and begins spreading through the substrate.; The spawn run is a recovery phase rather than a growth phase. Disturbing the substrate or introducing fresh air too early during spawn run can slow colonisation and leave an opening for competitors.
Cold shock: Cold shock is a deliberate drop in temperature used to trigger pinning in some species after colonisation is complete.; Not every species needs it. Oysters often pin readily with fresh air and light alone, while some wood-loving species respond more reliably to a temperature drop. It is a technique to test one variable at a time rather than a universal step.
Fresh air exchange (FAE): Fresh air exchange is the replacement of carbon dioxide-rich air inside a fruiting chamber with fresh air from outside it.; Fruiting bodies need oxygen. Insufficient fresh air exchange produces long, thin stems and small caps as mushrooms stretch toward the nearest air source. It is one of the most common causes of poor fruit quality.

Measurement and analytics

Biological efficiency (BE%): Biological efficiency is the fresh weight of harvested mushrooms divided by the dry weight of the substrate, expressed as a percentage.; A 1,000 g dry substrate that yields 700 g of fresh mushrooms has a biological efficiency of 70%. It is the standard measure for comparing yields between substrates of different sizes, and it is cumulative across all flushes of a batch.
Typical BE% ranges: Typical biological efficiency ranges describe the yields commonly reported for a species across a full flush cycle.; Oyster species commonly reach 50% to 120%. King oyster and pioppino typically land between 35% and 80%. Lion’s mane, shiitake and maitake on supplemented hardwood generally return 20% to 60%. These are guides rather than targets, and technique moves the number substantially.

Keep learning

The glossary pairs with the growing guides, which show these ideas applied to real records. If you want to run a projection straight away, the yield calculator needs no account.