Mushroom Substrates 101: In-Depth Guide to Mushroom Substrates (2024)

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Mushroom substrates are a fundamental part of mushroom cultivation. They are the food and habitat for your fungal mycelium. They must be well-chosen and prepared for a successful yield.

In this article, we will cover everything you need to know about mushroom substrates. What you need to know, to start growing your own mushrooms!

Food For Thought

Mushrooms are not plants. They have to eat. In this sense, they’re no different from us. In other ways, they are magnificently unique organisms.

The peculiar thing about mushrooms is that they not only consume their food, but they also live within it! They colonize their food source, breaking it down with digestive enzymes. Thus their food source needs to be nutritious and also conducive for healthy growth.

Related: What do Mushrooms eat?

Mushroom Substrate = Mushroom Food and Habitat

Mushroom substrates are the most important materials used for cultivating mushrooms. They serve as your mushroom’s growth medium, food source, and habitat. They’re made from a wide quantity of different materials.

Mushroom Substrates must Provide:

  • A Food Source
    Mushroom substrates are the food for your mushroom. They must provide all the minerals, nutrients, and energy-rich compounds needed for growth.
  • Environmental Conditions
    Substrates also provide the living environment for mushroom mycellium. They should provide have the right physical and chemical properties needed for growth. Physical structure promotes the porosity, moisture level, and air exchange needed for growth. Chemical properties include pH and compounds that may interfere with growth.
  • Clean Growing Environment
    Substrates need to be free of harmful microorganisms. These will contaminate and affect your mycellium. For this reason, substrates are usually pasteurized or sterilized.

Most common Mushroom Substrates

  • Straw
  • Hay
  • Wood Chips
  • Wood Shavings
  • Wood Burning Pellets
  • Coffee
  • Saw Dust
  • Agricultural waste

Choosing the RIGHT Substrate

Choosing the right substrate may seem difficult at first. There are hundreds of different resources you can use. In reality, the best substrate largely depends on two things. The mushroom you are growing and what type of resources you have readily available in the area.

Your Substrate should be:

  • Adequate For The Mushroom Variety You Are Growing
  • Affordable
  • Free or Toxins or Pollution
  • Easily Available
  • Easy to Work With
  • Require Minimal Processing

Best Substrate for different Mushroom Varieties

Different types of mushrooms need different types of substrates for growth. Some mushrooms, like the famous Oyster Mushroom, can eat almost anything you feed them! Some require very specific diets.

Mushroom Substrates 101: In-Depth Guide to Mushroom Substrates (1)

Growing Mushrooms on Straw

Straw is one of the most used substrates for mushroom cultivation. It is affordable, easy to handle, and accessible. There are many types of straw, so it is important to consider when purchasing.

Straw Substrate works for:

  • Common Oyster
  • Pink Oyster
  • King Oyster
  • Other varieties of Oyster Mushrooms

Pros and Cons of Straw Substrate


  • Cheap
  • Accessible
  • Low Environmental Foot Print
  • Works well with all oyster varieties
  • Stores well under proper conditions


  • Requires processing
  • It may not be organic
  • A bit messy
  • May vary in quality
  • Difficult to transport

Things to consider with Straw Substrates

  • Different Types of Straw – There are many types of straw to choose from. Wheat and Oat are the most recommended. Rice straw is also a good option. Nutrient-dense straws such as pea straw are less recommended. Avoid hay.
  • Finding Organic Straw – Straw is not always organic. If you worry about pesticides and agrochemicals look for organic straws.
  • Cleaning Your Straw – Straw is often dirty. Most growers don’t do it, but if your experiencing troubles, consider rinsing your straw.
  • Chopping Your Straw – You want your straw to be in pieces about 3” in length. While you can do this by hand with a machete or other hand tools, it is easily done with a weed whacker. An easy way to do this is by placing your straw in a large barrel and running your weed whacker inside it!
  • Straw Gets Everywhere – It can be messy! So be ready to prepare your workspace adequately!
  • Unsupplemented Straw Doesn’t Need Sterilization – It only requires pasteurization.

Growing Mushrooms on Wood Substrate

  • Hardwood is one of the most prized materials in mushroom cultivation. You can practically grow most gourmet edible and medicinal mushrooms on hardwood substrates. Hardwood substrates come in many forms.
  • Sawdust is an incredible substrate. It is useful for many types of mushrooms.
  • Wood shavings are not as good as sawdust. Some growers age this material until it is more broken down.
  • Wood chips are not the best material. They are too large. Growers may age these until they become well decomposed.

Wood Pellets are sawdust compressed into pellets. These are available for wood-burning stoves and standardized. They are not very expensive, but usually more than a direct source of sawdust. Look for pellets with no glues or chemicals.

Pros and Cons of Wood Substrates


  • Grow almost any gourmet and medicinal mushroom variety.
  • Produces good yield improved via supplementation
  • Usually organic
  • Requires little processing


  • May be hard to get pure hardwood.
  • Mixed results with different types of hardwood.
  • Avoid contaminated substrates with oil from saw/machinery.

Things to consider with Wood Substrates

  • Always make sure you get pure hardwood materials. This includes oak, beech, maple, sycamore, alder, apple, almond, and other orchard trees. Coniferous trees like pine, spruce, cypress, and fir DO NOT perform well.
  • For best results, you want to use sawdust or a decomposed aged woody material.
  • Large chips may work for oysters and other vigorous varieties.
  • Supplement your sawdust to increase yield. It is usually supplemented with bran or soil hull. Supplemented substrates will need sterilization.

Supplementing Saw Dust

Some of the most used and esteemed substrate recipes are from supplemented sawdust. This is a nutrient-rich material that is added to the substrate to increase the yield.

  • One of the most common recipes is adding about 5-10% bran to your substrate.
  • The “Masters Mix” for Oysters includes 50% soy hulls and 50% hardwood sawdust.

The downside about supplementation is that the excess nutrients mean it requires sterilization!

Growing on Manure Substrates

Nature wastes nothing. One animal’s waste is another organism’s feast. Certain mushrooms in particular love growing on animal feces. This includes the button mushroom and portobello. Magic mushrooms are also cultivated on animal dung.

Consideration when using Manure Substrates

There are many different types of manure. They can originate from different animals with different diets. They can also be at different stages in decomposition.

  • Composted Manure is your best bet.
  • Fresh Manure is not ideal but work. Horse manure and those with less nitrogen are best. Chicken manure and other nitrogen-rich substrates are not suitable without composting. If you don’t want to compost it, drying it in the sun will make it easier to work with.
  • Manure is only useful for growing Agaricus and Psilocybe species.
  • Bedding from works after composting. Avoid materials with cigarette butts or other garbage.
  • You may have mixed results with the same type of manure depending on what the animal has been consuming!
  • Agaricus species need a casing layer. This consists of 50% vermiculite and 50% coco coir.

Pros and Cons of Manure Substrates


  • The best option for Button Mushrooms and other Agaricus species
  • Works for Psilocybe species
  • Can be inexpensive or free


  • Doesn’t work for most gourmet and medicinal mushrooms.
  • Can be messy
  • Usually requires composting
  • Needs caution when handling
  • May need other materials

Other locally available Substrates

Some of the most common forms of substrate used by growers are byproducts. Usually from the agricultural, woodworking, and food processing industries. These may be cheap or even free!

Using Waste Resource

  • Wood Waste – Ask a local carpenter about wood shaving or sawdust they may have. Most people are willing to give it away for free as long as your pack it out! Make sure to ask the type of wood they are using.
  • Agricultural Waste – Corn stalks, peanut shells, and other waste products are excellent substrates. Tough woody materials are best.
  • Food Waste – Coffee grounds, spent brewery grain, and food waste can work.
  • Garden Waste – Tree trimming companies often produce large quantities of wood chips. If they don’t already have someone who asked them for it, they may be happy to drop it off at your home!

Pasteurization vs Sterilisation

Once you’ve figured out your substrate of choice you now need to make it suitable for fungal growth. To do this, you will have to remove most or all microorganisms living on your substrate. This is what pasteurization and sterilization are for. These are processes that remove microscopic life from your substrate.

Why do you need to Pasteurize or Sterilise Mushroom Substrate?

  1. Microorganisms will compete with your mycellium for the substrate. They may produce anti-fungal compounds and make the substrate inaccessible.
  2. Microorganisms can contaminate and infect your mushroom mycellium. Specific antagonists like Trichoderma and Pennicilum are common reasons cultivation fails.

What’s the difference between Pasteurisation and Sterilisation?

Pasteurization aims to remove most microscopic life. Sterilization aims to remove ALL microscopic life.

Differences between Pasteurisation and Sterilisation


  • Less intensive
  • Only removes MOST of all microorganisms on the substrate.
  • Work well with unsupplemented substrates.
  • Is done with hot water baths, lime baths, and many other ways.
  • Particularly useful for the cultivation of Oysters on straw
  • Doesn’t work with the supplemented substrate
  • Doesn’t work with pickier mushroom species
  • Is done by submerging in water at 160-170 degrees F for 1 hour.


  • More intensive
  • Needs high heat and pressure
  • Aims to remove ALL microscopic life
  • Done within pressure cookers or autoclaves
  • Necessary for supplemented and nutrient-rich substrates
  • Requires grow bags, jars, or vessels that can withstand high heat and pressure.
  • Needed for the production of spawn, liquid cultures, and Petri dishes.
  • Requires around 90 minutes at 15 psi inside a pressure cooker.
Mushroom Substrates 101: In-Depth Guide to Mushroom Substrates (2024)


How deep should the substrate be for a cubensis monotub? ›

You want to have 3-5 inches of substrate. One 3lb injection port bag should readily inoculate one or two moderate sized tubs. Again, this is a great time to make use of your still air box. You want to start by sprinkling about one inch of bulk substrate into your sterilized monotub, or in the liner if you're using one.

How much mycelium is enough? ›

The common standard of spawning is 8-10 liters, or 5-6 kilograms of mycelium per ton of phase 2 compost.

What are the steps in mushroom substrate? ›

Preparation of Mushroom Growing Substrates
  1. Straw.
  2. Preparation of Straw Substrate.
  3. Stove Top Straw Pasteurization.
  4. Outdoor Pasteurization of Straw.
  5. Lime Bath Treatment of Straw Substrate.
  6. Peroxide Treatment of Straw Substrate.
  7. Cold Fermentation of Straw Substrate.

How many times can I use mushroom substrate? ›

Yes, you can most definitely reuse mushroom grow kits! Mushroom grow kits are generally designed to give you more than one harvest depending on the species of mushroom inside your growing kit. There is enough water nutrition available in the substrate to give you multiple harvests over a period of 2-10 weeks.

What is the best size Monotub cubensis? ›

Too small of a tub and your harvest won't be as successful as it could be—your fungi will be essentially competiting with itself for resources, and you'll ultimately get less pinning and fruiting. A monotub should be 54 quarts, more or less.

What is the best ratio for mushroom substrate? ›

The recommended spawn to substrate ratio for growing mushrooms, such as cubensis, b plus mushrooms, or oyster mushrooms, is around 1:2 to 1:4. This means that for the psilocybe cubensis substrate recipe, one part of grain spawn should be used for every two to four parts of mushroom substrate.

How deep does mycelium go? ›

Mycelium can extend for hundreds or even thousands of miles if they are stretched end to end. But since they are so compactly connected, you might find 200 kilometers or more in a single kilogram (2.2 pounds) of soil! The mycelial network is a shared economy, where ecosystems flourish without greed.

What does healthy mycelium look like? ›

Spend time getting to know what your mycelium is supposed to look like so you can better identify unhealthy or contaminated patches. While mycelium is typically white and filamentous, contamination generally takes the form of green, blue, gray, or black patches or discolorations in your substrate.

What happens if you add too much substrate? ›

Initially, a higher substrate concentration will increase enzyme activity, but when the enzymes become saturated, there is no further increase in processing activity no matter how much substrate is present.

What is the easiest mushroom substrate? ›

Pretty much every mushroom growing resource I could find says that oyster mushrooms are the easiest variety for first time-growers, as they grow fast and can easily thrive in substrates made of things like coffee grounds and straw, making them relatively low maintenance.

How wet should mushroom substrate be? ›

Your substrate should be slightly acidic, with a PH between 5 and 6.5. (Some mushrooms, such as oyster mushrooms, can withstand a PH of up to 8.) A minimum moisture content of 50-70% is essential for your substrate.

What is the best substrate for mycelium growth? ›

Using Hardwood Sawdust and Chips

The fine sawdust is typically mixed with wood chips, which seems to allow for faster colonization of the substrate and provide a better structure for the mycelium to take hold. Commonly used hardwoods are oak, maple, beech, and hickory- or a mix of multiple species.

What can I do with old mushroom substrate? ›

You may use spent substrate weathered for 6 months or longer in all gardens and with most plants. Obtaining spent substrate in the fall and winter, allowing it to weather, will make it ready to use in a garden the following spring. Spring and summer are the best time to use weathered material as a mulch.

What happens if mushroom substrate is too wet? ›

If you have insufficient moisture, as stated earlier, your mycelium growth will be stunted. However, if you have too much moisture, your mycelium will also be stunted, as it will suffocate. With too much moisture, your substrate will also have a higher risk of contamination from other organisms.

What happens if mushroom substrate is too dry? ›

However, excessive moisture can cause the substrate to become very wet, increasing mold growth. On the other hand, low humidity can cause the substrate to dry out, leading to poor mushroom spore and fruiting development.

How deep should substrate be for mushroom tub? ›

Follow by sprinkling a thin layer of fully colonized spawn over the base of sterile substrate. Then add another inch of substrate, and top with another thin layer of spawn. Keep repeating this process until you have reached the desired substrate depth, usually around three to five inches deep throughout the tub.

What is a bulk substrate for cubensis? ›


Manure is the aged, dried excrement of horses, cows, elephants, etc. It is one of the most effective bulk substrates for dung loving species like psilocybe cubensis, panaeolus cyanescens and agaricus bisporus (Portobello). It is usually cheap or free if it can be located.

What is the best humidity for cubensis mycelium growth? ›

Badham (1983) found that high relative humidities (> 90% RH) and low wind speeds ( < 100 mm/sec) favored the growth of Psilocybe cubensis (Earle) Sing. in the laboratory and natural environment.

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