Beginner-friendly definitions for home growers and small farms. Use this as a quick reference while you read grow guides, troubleshoot, or shop supplies.
Quick cross-reference for beginners
- Want the fastest path to growing? Liquid culture syringes → grain spawn → bulk or sawdust blocks
- Want the lowest-tech method? Outdoor logs or wood chip beds
- Most common failures? Contamination from poor sterile technique, overly wet substrate, and low fresh air during fruiting
A
Agar
A jelly-like medium (usually made with agar-agar) used in petri dishes or jars to grow and clean up mushroom cultures.
Agar Plate
A shallow dish containing agar. Used to start spores, transfer clean mycelium, and spot contamination early.
Agar Transfer
Moving a small, clean piece of mycelium from one agar plate to another to isolate healthy growth and leave contamination behind.
Air Exchange
Replacing stale air with fresh air in your grow space. Often discussed as FAE.
Aseptic Technique
Clean handling practices that reduce contamination. Examples: gloves, alcohol wipe-down, flame-sterilizing tools, working in a still-air box or in front of a flow hood.
Autoclave
A machine that sterilizes using pressurized steam. Many small growers use a pressure canner instead.
B
Bacteria (in grows)
Microscopic organisms that can cause sour smells, wet or slimy grain, and stalled colonization. Often appears as “wet spot” in grain.
Batch
A specific run of product or grow materials made at the same time (for example, one substrate mix and sterilization cycle). Used for tracking and quality control.
BE (Biological Efficiency)
A yield metric: fresh mushroom weight divided by dry substrate weight, expressed as a percent. Example: 1 lb fresh from 1 lb dry substrate equals 100% BE.
Block
A solid mass of colonized substrate, usually in a bag, that fruits mushrooms.
Blotch
A bacterial issue that can appear as spots on fruit bodies, often linked to overly wet conditions and poor airflow.
Bulk Substrate
A larger-volume fruiting substrate (often coir-based for some species, or sawdust-based for wood lovers) that grain spawn is mixed into.
C
Cap
The top part of many mushrooms. Lion’s Mane is different and forms spines instead of a cap.
Casing Layer
A top layer of moist material (often peat-based or coir-based depending on species) placed over colonized substrate to help initiate pinning for certain mushrooms.
Clean Culture
A culture with no visible contamination. Clean cultures are the foundation for reliable spawn.
Clone
Starting a culture from the inner tissue of a fresh mushroom. Clones preserve traits of that specific fruit.
Colonization
The phase where mycelium spreads through the grain or substrate until it is fully white and “taken over.”
Contamination
Unwanted organisms growing in your culture, grain, or substrate. Common contaminants include molds and bacteria.
CO2 (Carbon Dioxide)
A gas that builds up in enclosed grow spaces. High CO2 can cause long stems, deformed fruits, or blob growth. Fresh air lowers CO2.
Culture
A living sample of mushroom genetics growing on agar or in liquid culture.
D
Dehydrator
A device that dries mushrooms at low heat for long-term storage.
Dehydration
Drying mushrooms until they are cracker-dry. Helps preserve flavor and shelf life.
Dikaryotic
A stage of mushroom mycelium where cells contain two nuclei. Many cultivated mushrooms fruit from dikaryotic mycelium.
Disposable Sterile Supplies
Pre-sterilized items like syringes, petri dishes, and swabs that reduce contamination risk.
E
Extract
A concentrated product made by pulling compounds from mushrooms using water, alcohol, or both. Selling extracts may involve additional rules and labeling considerations.
F
FAE (Fresh Air Exchange)
How often fresh air replaces old air in your fruiting space. Low FAE often causes deformed growth.
Field Capacity
A hydration level where substrate holds the right amount of water without dripping. The “squeeze test” is a common way to estimate.
Filter Patch Bag
A grow bag with a filter that allows gas exchange while blocking many contaminants. Used for spawn and fruiting blocks.
Flow Hood (Laminar Flow Hood)
A HEPA-filtered workspace that blows clean air toward your work area, making sterile work easier.
Flush
A wave of mushrooms that fruits and is harvested around the same time. Many blocks produce multiple flushes.
Fruiting
The stage where the mycelium produces mushrooms.
Fruiting Chamber
A controlled space for fruiting, often with humidity, airflow, and light management.
G
Genetics
The traits of the mushroom strain you are growing. Genetics impact speed, yield, shape, and fruiting behavior.
Grain Spawn
Sterilized grain colonized by mycelium. Used to inoculate bulk substrates or sawdust blocks. Often called “mushroom grain spawn.”
Gypsum (Calcium Sulfate)
A common additive that helps prevent clumping in grain and can improve substrate structure. Sometimes helps stabilize pH.
H
HEPA Filter
A high-efficiency air filter used in flow hoods. Helps reduce airborne contaminants during sterile work.
Humidity (RH)
Moisture in the air. Mushrooms often need high humidity to pin and develop properly.
Hydration
Adding water to substrate to reach the right moisture content for colonization and fruiting.
I
Incubation
The colonization period after inoculation. Usually warmer, with minimal fresh air needs compared to fruiting.
Inoculation
Introducing mushroom genetics (LC, agar, or spawn) into sterile grain or substrate.
Inoculation Port
A self-healing rubber port on a jar lid or bag that allows sterile injection of liquid culture.
Inoculation Loop
A tool used in microbiology and mycology to transfer cultures, often for agar work.
Inoculum
The material used to start growth in a new medium. Examples: agar wedge, liquid culture, grain spawn.
J
Jar (Spawn Jar)
A glass container used for grain spawn. Often fitted with a filter lid and injection port.
K
Kernel Spawn
Spawn grown on grains or seed-like materials. Often used as a general term for grain-based spawn.
L
LC (Liquid Culture)
Mycelium growing in a sterile nutrient liquid. Often sold as “liquid culture syringes.”
Liquid Culture Syringe
A syringe filled with liquid culture for easy inoculation of grain jars, grain bags, or agar.
Lignin
A tough component of wood. Many gourmet mushrooms break down lignin and cellulose.
M
Master’s Mix
A popular high-yield wood-loving mushroom substrate, usually hardwood sawdust and soy hulls. Typically requires sterilization.
Mycelium
The white, thread-like fungal body that colonizes substrate and produces mushrooms.
Mycology
The study of fungi.
Monotub
A large plastic tub used as a fruiting chamber, often for bulk substrate grows.
N
Nutrients (Supplementation)
Extra food added to substrate (bran, soy hulls, etc.) to boost yield. More nutrients often means higher contamination risk without proper sterilization.
O
Overlay
A thick, matted mycelium layer that can reduce pinning. Often caused by poor surface conditions or stale air.
P
Pasteurization
Heating substrate enough to reduce harmful organisms while leaving some microbes alive. Often used for lower-nutrient substrates.
pH
A measure of acidity or alkalinity. Some substrates are adjusted to discourage contaminants or better match a species’ preference.
Pinning
The stage where tiny mushrooms begin to form. Pins develop from primordia.
Pins
Small baby mushrooms that grow into mature fruit bodies.
Primordia
The earliest visible formation of mushroom tissue, before pins fully develop.
Pressure Canner (Pressure Cooker)
A vessel that reaches 15 PSI for sterilizing grain and supplemented substrates. Not all “pressure cookers” reach sterilization pressure.
PSI
Pressure measurement used in sterilization. Standard sterilization is commonly done at 15 PSI.
Q
Quarantine (in grows)
Separating questionable jars or bags from your main area to prevent potential contamination spread.
R
RH (Relative Humidity)
A percentage that describes moisture in the air. High RH supports pinning and fruit development.
Rot
Breakdown of substrate by unwanted organisms. Can cause bad smells and failure to fruit.
S
Saprotroph
A fungus that feeds on dead organic matter, like wood. Lion’s Mane and shiitake are saprotrophic wood decomposers.
Sawdust Spawn
Mycelium grown on sterilized sawdust. Often used to inoculate logs, wood chips, or sawdust-based substrates.
Sawdust Substrate
A wood-based growing medium, often hardwood sawdust or pellets, sometimes supplemented.
Seal (Impulse Sealer)
A tool used to seal grow bags after filling or after sterilization, depending on workflow.
Shaking (Grain Spawn)
Mixing grain jars or bags during colonization to redistribute mycelium. Over-shaking can stress some species.
Shelf Life
How long a product remains usable. Applies to cultures, spawn, and harvested mushrooms.
Shotgun Fruiting Chamber (SGFC)
A simple fruiting box with many holes for passive airflow, often used by beginners.
SOP (Standard Operating Procedure)
A step-by-step routine used to keep processes consistent, especially for farms.
Spore
A reproductive cell produced by mushrooms. Spores can start new genetics, but are typically slower and less predictable than liquid culture.
Spore Print
A deposit of spores collected from a mushroom cap. Used for microscopy or to start cultures.
Sterile
Free from living organisms. Sterile grain and substrates reduce contamination risk.
Sterilization
Using pressurized steam heat long enough to kill microbes and spores. Required for nutrient-rich substrates and grain.
Still-Air Box (SAB)
A clear tote with arm holes that reduces air movement, helping sterile work by limiting airborne contaminants.
Strain
A specific genetic line of a species. Strains differ in speed, yield, and behavior.
Substrate
The material the mushroom grows on, such as sawdust, straw, wood chips, or compost.
Supplement
A nutrient additive used to increase yields, such as bran or soy hulls.
Syringe Filter (Gas Exchange Filter)
A small filter that allows air exchange while blocking particles. Used on jar lids or certain LC setups.
T
Tek
Slang for “technique” or method. Example: “bucket tek” for pasteurizing straw.
Tissue Culture
Starting a culture from mushroom tissue rather than spores.
Trichoderma
A common green mold contamination. Often called “green mold.”
U
UV (Ultraviolet) Exposure
Light that can increase vitamin D2 in some mushrooms post-harvest by converting ergosterol.
V
Vegetative Stage
The growth phase where mycelium expands through substrate before fruiting.
Vent
An opening that allows airflow in a fruiting chamber or tent.
W
Wet Spot (Bacterial Contamination)
A bacterial issue in grain that causes slimy kernels and sour smells. Often stalls colonization.
Wood-Loving Species
Mushrooms that primarily grow on wood-based substrates, like shiitake, Lion’s Mane, and many oysters.
Y
Yield
The amount of mushrooms harvested. Often measured per block, per pound of substrate, or by BE.