Mycology Glossary

Agar is a gel-like substance derived from seaweed that is used as a solidifying agent for nutrient media in mushroom cultivation. When mixed with water and nutrients (typically malt extract, peptone, or potato dextrose) and sterilized, it creates a firm, transparent surface on which mycelium can be grown, observed, and isolated.

Common agar media in mushroom cultivation:

• MEA (Malt Extract Agar): The most common general-purpose medium
• PDA (Potato Dextrose Agar): Good for most species, slightly more nutritious
• LMEA (Light Malt Extract Agar): Lower nutrient for slower, cleaner growth

Agar work is the foundation of clean culture technique. It allows you to isolate clean mycelium from contaminated samples, clone productive mushrooms via tissue culture, germinate spores in a controlled environment, and store cultures long-term. Working with agar requires either a still air box (SAB) or a laminar flow hood to maintain sterility during transfers.

Colonization is the process by which mushroom mycelium grows through and takes over a substrate, consuming the available nutrients and establishing a dominant mycelial network. During colonization, the substrate transforms from its original state (grain, sawdust, straw, etc.) into a solid mass bound together by white mycelium.

Key aspects of colonization:

• Begins immediately after inoculation
• The mycelium secretes enzymes to break down and absorb nutrients from the substrate
• Full colonization means the mycelium has permeated the entire substrate — no uncolonized patches remain
• Typical colonization times range from 1-4 weeks depending on species, spawn rate, and temperature
• The substrate should be kept in a warm, dark, still environment during this stage

Colonization is a race against contamination. The faster your mycelium colonizes, the less opportunity competing organisms have to establish themselves. This is why spawn rate, temperature, and grain preparation all matter — they influence colonization speed.

Contamination refers to the unwanted introduction and growth of competing organisms — molds, bacteria, or yeasts — in your mushroom substrate, spawn, or cultures. It is the single most common cause of failed grows and the primary challenge in mushroom cultivation.

Common contaminants include:

• Trichoderma (green mold): The most common and aggressive contaminant in mushroom cultivation
• Cobweb mold (Dactylium): Fast-growing, wispy gray mold
• Bacillus and Pseudomonas bacteria: Cause wet spots, sour smells, and slimy grain
• Aspergillus (black mold): Black or dark green powdery contamination
• Penicillium (blue-green mold): Common environmental mold

Contamination enters through breaks in sterile technique — unfiltered air, non-sterile tools, insufficiently sterilized substrate, or working in dirty environments. Prevention is always better than treatment: proper sterilization, clean work areas, adequate air filtration, and good hygiene are the foundations of contamination-free cultivation.

FAE stands for Fresh Air Exchange — the introduction of fresh, oxygen-rich air to replace the stale, CO2-laden air around your mushrooms. It is one of the four critical fruiting parameters alongside humidity, temperature, and light.

Why FAE matters:

• Mushrooms consume oxygen and produce CO2 through respiration
• High CO2 levels during fruiting cause elongated stems and tiny caps as mushrooms stretch toward fresh air
• Adequate FAE also helps control surface moisture and prevent bacterial blotch
• During colonization, minimal FAE is needed (some CO2 buildup actually promotes mycelial growth)

Methods for providing FAE:

• Fanning the fruiting chamber several times daily
• Passive air exchange through holes covered with micropore tape or polyfill
• Computer fans on timers for automated setups
• Simply opening the lid of your monotub periodically

The goal during fruiting is to maintain CO2 below 800-1000 ppm for most species. You can tell FAE is insufficient when stems grow long and thin with undersized caps — the mushroom is literally reaching for fresh air.

Field capacity is the maximum amount of water that a substrate can hold while still allowing adequate air space for mycelial growth. It's the ideal moisture level for most mushroom substrates during colonization and is determined by a simple squeeze test.

The squeeze test:

• Take a handful of your prepared substrate and squeeze it firmly
• At field capacity, a few drops of water should drip out — roughly 2-3 drops
• If water streams out, it's too wet — add dry material
• If no water comes out, it's too dry — add water

Why field capacity matters:

• Too wet: anaerobic conditions develop, promoting bacterial contamination and suffocating mycelium
• Too dry: mycelium cannot grow efficiently and may stall
• Just right: the substrate holds enough water for mycelial growth while maintaining air pockets for oxygen exchange

Different substrates reach field capacity at different total moisture contents — coir is typically around 65-70% moisture, straw around 70-75%, and supplemented sawdust around 60-65%. The squeeze test works regardless of substrate type.

A flush is a single wave or crop of mushrooms that fruits from a colonized substrate. Most substrates produce multiple flushes over time, with the first flush typically being the largest and most productive.

Flush characteristics:

• First flush: Usually the largest, producing 40-60% of total yield
• Second flush: Typically 20-30% of total yield, sometimes with larger individual mushrooms
• Third flush and beyond: Diminishing returns, smaller mushrooms, increasing contamination risk
• Most home cultivators get 2-3 productive flushes before the substrate is exhausted

Between flushes, the substrate needs a rest period during which the mycelium recovers and accumulates energy for the next fruiting. Many cultivators dunk (soak) their substrate blocks or cakes in water between flushes to rehydrate them, as the previous fruiting depleted significant moisture. The time between flushes varies by species — typically 1-2 weeks.

A fruiting body is the visible, spore-producing reproductive structure of a fungus — what we commonly call a mushroom. It is produced by the underground or substrate-dwelling mycelium when environmental conditions signal that it's time to reproduce.

Fruiting body development stages in cultivation:

• Primordia (pins): The earliest visible stage — tiny bumps or knots of hyphal tissue forming on the substrate surface
• Buttons: Small, immature mushrooms with their features beginning to differentiate
• Development: The cap expands, the stem elongates, and the veil (if present) stretches
• Maturity: The cap fully opens, gills or pores are exposed, and spore production begins
• Harvest window: Ideally just before or just as the veil breaks (for veiled species) or before the cap edges flatten or curl upward

In cultivation, we manipulate environmental conditions to trigger fruiting body formation — lowering temperature, increasing humidity, providing fresh air exchange, and introducing light. The mycelium interprets these signals as "you've reached the surface" and responds by producing fruiting bodies to disperse spores into the air.

Fruiting conditions are the specific environmental parameters that trigger and support mushroom development after the substrate has been fully colonized. Shifting from colonization conditions to fruiting conditions is one of the most critical steps in the cultivation process.

The four key fruiting parameters:

• Temperature: Typically lowered 5-10°C from colonization temps (species-dependent)
• Humidity: Maintained at 85-95% relative humidity
• Fresh air exchange (FAE): Significantly increased to reduce CO2 levels
• Light: Indirect ambient light or a 12/12 light cycle (mushrooms need light to orient their growth but don't photosynthesize)

Each species has its own ideal fruiting parameters. For example:

• Blue oyster: 10-18°C, 85-95% RH, high FAE
• Shiitake: 15-21°C, 80-90% RH, moderate FAE
• Lion's mane: 18-24°C, 85-95% RH, high FAE

Getting these parameters right is essential for healthy development, good yields, and proper mushroom morphology. Incorrect conditions lead to aborted pins, malformed mushrooms, or no fruiting at all.

G2G stands for Grain-to-Grain transfer — a technique for multiplying grain spawn by transferring colonized grain from one jar into fresh, sterilized grain jars. It's the most efficient method for scaling up your spawn supply without needing additional liquid culture or agar work.

The G2G process:

• Start with a fully colonized jar of grain spawn
• Shake the jar to break up the colonized grain into individual kernels
• Under sterile conditions (SAB or flow hood), distribute a portion of colonized grain into each fresh jar
• Each colonized kernel acts as an inoculation point in the new jar

G2G ratios typically range from 1:5 to 1:10 — one colonized jar can inoculate 5-10 fresh jars. Each new jar colonizes in roughly 7-14 days, and the process can be repeated for 3-5 generations before mycelial vigor may decline (senescence).

G2G is valued because it's faster than inoculating from liquid culture (more inoculation points) and more economical than buying new spawn for each grow.

Hyphae (singular: hypha) are the microscopic, thread-like filaments that make up the body of a fungus. They are the building blocks of mycelium — what you see as white growth in your jars and substrate is actually millions of hyphae woven together.

In mushroom cultivation, you'll encounter two growth forms:

• Rhizomorphic growth: Hyphae bundled into visible rope-like strands that extend rapidly through the substrate. This is generally considered a sign of vigor and is preferred for spawn production
• Tomentose growth: Hyphae spreading as a uniform, fluffy, cotton-like mat. This is normal for many species and not necessarily a sign of weakness

Hyphae perform all the essential functions of the fungus:

• Exploration: Growing tips push through substrate, branching to maximize coverage
• Digestion: Secreting enzymes to break down complex organic molecules
• Absorption: Taking in simple nutrients through their cell walls
• Transport: Moving water and nutrients through the network

Healthy hyphae appear bright white in most cultivated species. Discoloration (yellow, brown, or gray) may indicate stress, contamination, or metabolite production.

Inoculation is the act of introducing mushroom mycelium or spores into a prepared substrate to begin colonization. It's the starting point of every mushroom grow — the moment your culture meets its food source.

Common inoculation methods:

• Spore syringe to grain: Injecting a spore suspension through a self-healing injection port into sterilized grain
• Liquid culture to grain: Injecting established mycelium in nutrient broth into grain jars or bags
• Agar to grain: Transferring a wedge of colonized agar into sterilized grain
• Grain to grain (G2G): Transferring colonized grain into fresh sterilized grain
• Grain to bulk substrate: Mixing colonized grain spawn into a prepared bulk substrate (spawning to bulk)

The critical requirement during inoculation is sterility. Any break in technique — unsterilized tools, contaminated air, exposed substrate — risks introducing competing organisms. Work in a still air box (SAB) or in front of a laminar flow hood, flame-sterilize tools, and minimize the time containers are open.

LC stands for Liquid Culture — a suspension of actively growing mushroom mycelium in a sterilized nutrient broth. The broth is typically a simple sugar solution (honey water, light malt extract, or dextrose) that feeds the mycelium as it multiplies in the liquid.

Advantages of liquid culture:

• Fast inoculation: LC colonizes grain faster than spore syringes because you're adding established mycelium, not ungerminated spores
• Multiplied supply: A small piece of agar or grain can be expanded into hundreds of milliliters of LC
• Known genetics: Unlike spore syringes, LC contains a single dikaryotic strain with known characteristics
• Long shelf life: Properly stored LC can remain viable for months in the refrigerator

LC is typically grown in jars or bottles with modified lids that include an injection port and a filter for gas exchange. The mycelium is visible as wispy clouds or clumps suspended in the clear or slightly cloudy broth. LC should be tested on agar before use to confirm it's contaminant-free.

A monotub is a large, modified plastic storage tote used as a fruiting chamber for bulk mushroom cultivation. It's the most popular home cultivation method for species that grow on bulk substrate (oysters, shiitake, and especially cubensis-type species).

Monotub design:

• A clear or translucent 50-100+ liter plastic tote with a latching lid
• Holes drilled in the sides (typically 2-3 per long side) at substrate level and above, stuffed with polyfill or covered with micropore tape for filtered air exchange
• Substrate is prepared and spawned directly in the tub
• The lid is kept closed during colonization and cracked or flipped during fruiting

Why monotubs are popular:

• Simple and inexpensive to build ($10-20 in materials)
• Self-regulating humidity when properly sealed
• Large surface area for good yields
• Minimal daily maintenance compared to shotgun fruiting chambers

The key to monotub success is proper substrate preparation and spawn rate. Once spawned and sealed, the tub largely takes care of itself during colonization, requiring only periodic observation until the surface is fully colonized and ready for fruiting conditions.

Mycelium is the vegetative, feeding body of a fungus — a vast network of microscopic filaments (hyphae) that grows through and digests substrate material. In mushroom cultivation, establishing healthy, vigorous mycelium throughout your substrate is the primary goal during colonization.

What healthy mycelium looks like:

• Bright white color in most cultivated species
• Dense, even coverage spreading outward from inoculation points
• Rhizomorphic (ropy, strand-like) or tomentose (fluffy, even) growth patterns
• Clean, fresh mushroom or earthy smell

What unhealthy or contaminated mycelium looks like:

• Yellow, gray, or brown discoloration (may indicate bacterial contamination or stress metabolites)
• Patchy or stalled growth
• Off-colors (green, pink, black) indicating mold contamination
• Sour or sweet off-odors

Mycelium is the actual organism — the mushroom you harvest is just its temporary reproductive structure. A healthy mycelial network is essential for strong fruiting: vigorous, fully colonized substrate produces faster pin sets, higher yields, and better resistance to contamination during the vulnerable fruiting stage.

Pasteurization is a heat treatment that reduces — but does not eliminate — the microbial population in a substrate. Unlike sterilization, which kills everything, pasteurization selectively kills most harmful competitors while leaving beneficial microorganisms alive. These surviving beneficials help protect against recontamination.

Common pasteurization methods:

• Hot water bath: Submerge substrate in 65-80°C (150-175°F) water for 1-2 hours
• Steam pasteurization: Expose substrate to steam at 60-80°C for several hours
• Cold water lime bath: Soak substrate in hydrated lime solution (pH 12+) for 16-24 hours
• Cold fermentation: Submerge substrate in cold water for 5-7 days

Pasteurization is used for substrates that don't contain supplementation (added nutrients like bran or soy hull) — primarily straw, coir, and plain hardwood. These low-nutrient substrates can withstand partial sterilization because there isn't enough nutrition to fuel aggressive contaminant growth. Supplemented substrates require full sterilization because the added nutrients make them vulnerable.

Pinning (also called primordia formation) is the earliest visible stage of mushroom fruiting — the point at which tiny bumps or dots appear on the colonized substrate surface. These pins are the embryonic mushrooms that will develop into mature fruiting bodies over the following days.

What triggers pinning:

• Drop in temperature from colonization temps
• Increased fresh air exchange (lower CO2)
• High humidity (85-95%)
• Exposure to light (even indirect ambient light)
• Full colonization of the substrate surface

What pins look like:

• Tiny white or colored bumps, 1-5 mm, emerging from the substrate surface
• Often appear in clusters
• Species-dependent in appearance — oyster pins look different from shiitake pins

Not all pins will develop into mature mushrooms. Some will abort (stop growing and turn brown or yellow) due to insufficient humidity, poor air exchange, or the mycelium's inability to support all the pins. This natural thinning is normal. Maintaining consistent fruiting conditions during the pinning stage is critical — fluctuations cause aborts.

Rhizomorphic describes a growth pattern where hyphae bundle together into visible, root-like or rope-like strands that extend rapidly through the substrate. It is contrasted with tomentose growth, which is fluffy and even. Rhizomorphic growth is generally considered a sign of a healthy, vigorous culture.

Characteristics of rhizomorphic growth:

• Visible strand-like or root-like growth patterns
• Faster substrate colonization compared to tomentose growth
• Often radiates outward from inoculation points like spokes on a wheel
• Considered desirable in spawn production because it indicates vigor and typically correlates with faster colonization and stronger fruiting

However, growth morphology is influenced by:

• Genetics (some strains are naturally more rhizomorphic)
• Substrate type and nutrition
• Temperature and environmental conditions
• Culture age and generational number

Tomentose growth is not necessarily bad — many productive strains grow in a tomentose pattern, and some species rarely show rhizomorphic growth. Don't discard a culture just because it's tomentose, especially if it's colonizing at a normal rate for the species.

SAB stands for Still Air Box — a simple, inexpensive enclosure used to create a low-airflow environment for sterile work such as agar transfers, inoculation, and grain-to-grain transfers. It's the beginner-friendly alternative to a laminar flow hood.

Building a basic SAB:

• Large clear plastic tote (60+ liters) with a lid
• Two arm-holes cut in one side (typically 10-12 cm diameter)
• Edges of holes smoothed or padded to prevent cuts
• That's it — no fans, no filters

How to use a SAB:

• Wipe the interior with isopropyl alcohol and let it settle for several minutes
• Place all materials inside (pre-sterilized jars, agar plates, scalpel, lighter)
• Close the lid and work through the arm holes
• Move slowly to avoid creating air currents
• Flame-sterilize tools between transfers

The SAB works because still air allows contaminant particles to settle to the bottom rather than floating around and landing on your work. It's surprisingly effective when used properly — many experienced cultivators use SABs exclusively and achieve low contamination rates.

Spawn is a carrier material that has been fully colonized by mushroom mycelium and is used to inoculate the final fruiting substrate. It functions like a seed in agriculture — you mix it into your substrate to introduce the mushroom culture and begin colonization.

Common spawn types:

• Grain spawn: Sterilized cereal grains (rye, wheat, millet, oats) colonized by mycelium — the most common and versatile type
• Sawdust spawn: Sterilized hardwood sawdust colonized by mycelium — preferred for log inoculation and wood-based substrates
• Plug spawn: Small hardwood dowels colonized by mycelium — designed specifically for log cultivation

The spawn production chain typically follows this path:

• Agar culture → liquid culture → grain spawn → bulk substrate
• Or: agar culture → grain spawn → grain-to-grain transfer → bulk substrate

Spawn quality directly determines grow success. Clean, vigorous, fully colonized spawn colonizes the substrate quickly, outcompeting potential contaminants. Contaminated, weak, or partially colonized spawn leads to slow colonization and high failure rates.

A spore print is a deposit of mushroom spores collected on a surface (usually paper, foil, or glass) by placing a mature mushroom cap gill-side down and allowing spores to fall naturally. In cultivation, spore prints are used as a starting point for growing new cultures. In foraging, they are an essential identification tool.

Making a spore print for cultivation:

• Select a healthy, mature mushroom and remove the stem
• Place the cap gill-side down on a piece of sterile aluminum foil inside a still air box
• Cover with a clean glass or bowl
• Wait 12-24 hours for a heavy deposit
• Fold the foil over the print and seal in a ziplock bag
• Store in a cool, dark place — spore prints can remain viable for years when properly stored

Using spore prints:

• Scrape spores into sterile water to make a spore syringe
• Drop spores onto agar plates for germination
• Spore prints are the most genetically diverse starting point — each spore is genetically unique, so growing from spores produces variable results compared to cloned cultures

Sterilization is the complete elimination of all living organisms — bacteria, molds, yeasts, and their spores — from a substrate or piece of equipment. In mushroom cultivation, this is achieved using a pressure cooker or autoclave at 15 PSI (121°C / 250°F).

When sterilization is required:

• Grain spawn: Always sterilized (15 PSI for 90 minutes)
• Supplemented sawdust: Always sterilized (15 PSI for 2.5 hours)
• Agar media: Always sterilized (15 PSI for 20-45 minutes)
• Liquid culture: Always sterilized (15 PSI for 20-30 minutes)

When sterilization is NOT required (pasteurization is sufficient):

• Plain straw
• Coir or CVG
• Unsupplemented hardwood

The key difference from pasteurization: sterilization kills everything, creating a completely blank slate. This means the substrate is equally vulnerable to contamination as to your mushroom culture — only your sterile technique and the vigor of your spawn protect it. Supplemented substrates must be sterilized because the added nutrients (bran, soy hull) would fuel explosive contaminant growth if any survived.

Substrate is the material that serves as the food source and growing medium for mushroom mycelium. Different mushroom species have evolved to digest different types of organic matter, so matching the right substrate to your species is essential for successful cultivation.

Common substrates:

• Straw: Chopped wheat, oat, or barley straw — popular for oyster mushrooms
• Hardwood sawdust/pellets: Oak, maple, beech — used for shiitake, lion's mane, and many gourmet species
• Coir/vermiculite/gypsum (CVG): A hydrated mix — popular for bulk monotub grows
• Masters Mix: 50/50 hardwood pellets and soy hull pellets — a high-yield supplemented substrate
• Brown rice flour (BRF): Used in PF Tek jars
• Logs: Freshly cut hardwood logs for outdoor cultivation

Substrate preparation is the foundation of successful growing. The substrate must be properly hydrated to field capacity, either pasteurized or sterilized depending on its composition, and free of contaminants before inoculation. The substrate's nutrition, moisture content, and particle size all affect colonization speed and final yield.

Tek is mushroom cultivation slang for technique — a specific, step-by-step method or protocol for accomplishing a particular cultivation task. The term originated in online mushroom growing communities and has become standard terminology.

Common teks in mushroom cultivation:

• PF Tek: The classic beginner method using brown rice flour cakes in half-pint jars
• Monotub Tek: Bulk cultivation in modified plastic totes
• Bucket Tek: Growing oyster mushrooms in 5-gallon buckets filled with pasteurized straw
• Broke Boi Tek: Sterilizing grain without a pressure cooker using extended steam baths
• Uncle Ben's Tek: Using pre-cooked rice bags as a no-pressure-cooker grain spawn method
• Agar Tek: Protocols for working with agar cultures
• Shoebox Tek: A smaller version of the monotub using shoebox-sized containers

Each tek has trade-offs in terms of cost, complexity, equipment needed, contamination risk, and yield potential. Beginners typically start with PF Tek (simplest) or monotub tek (best yield-to-effort ratio) and expand their repertoire as they gain experience and equipment.

Tomentose describes a fluffy, cotton-like mycelial growth pattern where hyphae spread evenly across the substrate in a soft, wispy mat rather than forming defined strands. It is the opposite of rhizomorphic growth, which appears as rope-like or root-like strands.

Characteristics of tomentose growth:

• Even, fluffy coverage that looks like cotton or fine wool
• Slower colonization speed compared to rhizomorphic growth
• No visible directional strand formation
• Often described as "wispy" or "cottony"

Is tomentose growth a problem?

- Not necessarily — many species naturally grow tomentose, and some highly productive strains show this pattern - Tomentose growth can indicate: - Normal growth for the species or strain - A culture that's lost some vigor through many transfers - Suboptimal temperature or nutrition - Younger or less established mycelium that may become more rhizomorphic as it matures

Don't panic if you see tomentose growth. Evaluate the overall health of the culture — if it's colonizing at a reasonable rate, smells clean, and is bright white, it's likely fine. Some of the most productive commercial strains are tomentose growers.