Mushroom Growing Terminology: The Beginner’s Guide

Plenty of terms involved with mushroom growing can be confusing to beginners. For this reason, we’ve created a list of frequently used terms and their definitions to help you learn the basics.

Agar – Agar is a dried seaweed extract. Mushroom cultivators use this medium to observe mycelium and grow cultures on. To prepare the medium, the agar is dissolved in hot water, then pressure-sterilised and poured into petri dishes where it solidifies into a gelatinous substance. You can take a spore swab and rub it over the surface in a zigzag pattern.


Blue Bruising  – Blue bruising in the mycelium is not always a sign of contamination. It can happen if mycelium-covered grains press against glass jars and plastic bags or tubs. To determine if you have a contamination or bruised mycelium, gently wipe a Q-tip over the discoloration. Mould will colour the swab while bruising will not.

Cake – A block of substrate where mushroom spores are injected and grown.

Carbon Dioxide  – Much like humans, mushrooms exhale Carbon Dioxide and inhale Oxygen. Monitoring CO2 in addition to temperature and humidity is important to maximizing mushroom growth.

Casing Layer – A casing is a layer of material added on top of a colonised substrate to help keep moisture in. Common casing materials are Peat, Coco Coir and Vermiculite.

Colonisation – This is the stage of the mushroom life cycle where the mycelium is growing but no mushrooms are present.

Contamination – Contamination is anything unwanted in your substrate or mycelium that can cause long-term problems with your mushroom culture. They can spread very quickly so it is important to get rid of the contaminated cultures and separate them from the non-contaminated ones.

Contaminations can be easily identified – discolouration being one of the most obvious signs. If you spot green, blue, grey, or black patches, your culture is most likely contaminated. However, keep in mind that blue stains on the mycelium may just be bruising and not mould. Slime on your substrate or mycelium can also be a sign of contamination, which signifies excess moisture and presence of bacteria.

Flush – Each crop or harvest of mushroom is called a flush.

Fruiting – Once the substrate has been fully colonised by the spawn, it is time for the mushrooms to start fruiting. The medium is exposed to fresh air and light which triggers the mycelium to start producing mushrooms.

Fruiting Body – The fruiting body is the most recognizable part of a mushroom. Fruiting bodies contain spores which are dispersed for reproduction. A mature fruiting body can have various structures and it may contain a cap, stalk, ring, volva, and gills. The cap normally houses the spores but in some types of mushrooms, the spore-producing cells could be found in the gills, tubes or inside the cap.

Fruiting Chamber – A mushroom fruiting chamber is an enclosed space that growers use to imitate natural mushroom growing conditions.

Grain Spawn – Grain spawn is mushroom mycelium grown into sterilized grain. Once the mycelium has fully colonised the grain, it can be broken up and mixed into bulk substrate where it can continue to spread and eventually colonise the substrate.

Harvesting – This is the time to pick the mushrooms when the veil starts to break.

Hyphae – The hyphae are long and branching filamentous structures of a fungus and as a group is called the mycelium. The hyphae release enzymes and absorb nutrients from the environment and transport them into different parts of the fungus’ body.

Incubation – The step after inoculation and before the mycelium has fully colonised the substrate. It is the process of gently warming a culture to steady temperature and humidity to promote rapid growth. This is also the stage where the substrate is most susceptible to contamination.

Inoculation – The process of introducing spores into a sterile substrate to initiate its growth and development. Inoculation should be done in a sanitary environment to avoid contaminating the substrate.

Liquid Culture – A mushroom liquid culture is typically a mixture of sterilized water, sugar solution such as Dextrose, Corn Syrup, Maltose, or Honey and living mycelia cells. It is used to inoculate sterilized grains or substrates for spawn production.

Microscopy – The examination of minute objects not visible to the naked eye by the use of a microscope.

Misting – Spraying water as a very fine mist to allow the environment to stay humid during the fruiting stage.

Mycelium – The mycelium is the root system of the mushroom and an essential part of the life support system for the fungus. It is composed of a dense mass of fine, thread-like filaments that naturally extend into the soil, plant matter, wood and other materials to pick up water and nutrients.

The mycelium excretes enzymes to break down the substrate around them into digestible size so they can be absorbed through the mycelium’s cell wall which can then travel up to the fruiting body.

Mycology – A branch of biology concerned with the study of fungi.

Pins – These are baby mushrooms that will grow and develop into mature mushroom fruiting bodies over the next few days during fruiting stage.

Psilocybin and Psilocin – These are compounds found in mushrooms of the genus Psilocybe also known as magic mushrooms. Growing magic mushrooms are illegal in the UK but spores can be legally used for microscopy.

Spawning – This is the process of placing a spawn into another substrate to spread out bits of mycelium into its final habitat where it can grow, colonize and fruit.

Spore Swab – A spore swab is a medical sterile cotton stick swabbed on spore production site of the fruiting body to manually collect spores. These are commonly used on Agar petri dishes in microbiology labs to grow cultures on.

Spore Syringe – A spore syringe contains spores suspended in sterilized and distilled water solution. Spore syringes are commonly sold for the purpose of microscopy & mushroom cultivation.

Spores – Fungal spores are very similar to the seeds of a plant. They contain all the genetic material required to grow the next generation of a fungus. A single mushroom cap can release billions of spores, which are dispersed via wind into the surrounding environment.

If a single spore is lucky enough to find itself in a nutrient rich environment, i.e. its substrate (food), and the conditions are just right, it will germinate.

Substrate – Using substrate to grow mushrooms is like using soil to grow plants. A mushroom substrate is a material that the mushroom mycelium can grow itself in. It provides nutrients, moisture and energy needed for the mushroom to grow and fruit.

A substrate has to be prepared first before it can be inoculated with mushroom spores. Water will be added to the substrate and may also be amended with extra nutrients. Then, it needs to be sterilized or pasteurized to kill off competing mould or bacteria and gives the mushroom the best chance at taking hold.

Trichoderma – Also known as green mould, it Is one of the most common types of contamination in mushroom cultivation. It can be influenced by high humidity and poor ventilation on casing surfaces and accidental introduction of spores from the outside. The mould grows incredibly fast, taking away large amounts of nutrients and leaving the mushrooms with too little. Because it grows quickly, it is very important to isolate contaminated kits from your healthy mushrooms right away.

Veil – The veil covers the mushroom as they develop. When a mushroom is growing, the edges of the cap are connected to the stem. As it grows larger, the cap spreads and the edges tear away, leaving a very thin veil hanging from the stem.

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