Best Substrates for Mushroom Growing: A Comprehensive Guide

Mushroom cultivation is a fascinating and rewarding hobby or business. To grow mushrooms successfully, you need the right substrate – the material that provides nutrients and energy for the mycelium to grow and produce mushrooms. In this article, we’ll take a closer look at some of the best substrates for mushroom growing, cultivation methods, common problems and solutions, nutritional benefits of mushrooms, and recipes.

Substrates for Mushroom Growing

Straw Substrate

Straw is one of the most common substrates used for mushroom cultivation. It’s inexpensive, readily available, and easy to work with. Straw is a great substrate for many different types of mushrooms, including Oyster mushrooms, Enokitake, and Wine Cap mushrooms. To use straw as a substrate, soak it in water for several hours to hydrate it.

After draining the excess water, sterilize it in a pressure cooker or other sterilization method to kill any unwanted bacteria or fungi. Once sterilized, inoculate the straw with mushroom spawn and place it in a suitable growing container. Straw is an excellent substrate because it’s high in cellulose, which provides a great food source for the mycelium to grow.

How to Prepare Straw Substrate for Mushroom Growing

Straw has a low nutrient content, which makes it a suitable substrate for many species of mushrooms that require low-nutrient environments. Here’s how the straw is typically prepared for use as a substrate:

1. Collect and clean the straw: Clean straw is collected and then soaked in water to remove any dust, dirt, or other debris.
2. Chop the straw: After cleaning, the straw is chopped into smaller pieces to increase surface area and make it easier to handle.
3. Add nutrients: Various nutrients are added to the straw to provide the necessary food source for the mushrooms. The most common nutrient sources added are soybean meal, cottonseed meal, bran, and gypsum.
4. Moisturize the straw: Water is added to the straw to make it moist enough to support mushroom growth.
5. Sterilize the straw: To ensure that no unwanted microorganisms grow in the substrate, the straw must be sterilized. This is usually done using heat, either by steaming or autoclaving the substrate for several hours.
6. Inoculate the substrate: Once the straw has cooled down after sterilization, it is inoculated with mushroom spores or spawn. The inoculated straw is then placed in a suitable growing environment, such as a plastic bag or container.

Overall, preparing straw for mushroom cultivation involves a combination of chopping, nutrient addition, sterilization, and inoculation. The exact methods used will depend on the specific species of mushroom being grown and the resources available to the cultivator.

Choosing The Right Substrate Nutrients

Bran for Straw Substrates

Bran is a byproduct of milling cereal grains, such as wheat, rice, or oats. It is an excellent source of carbohydrates, which are an important nutrient for mushroom growth. Bran also contains proteins, vitamins, and minerals, making it a valuable supplement to the straw substrate. When adding bran to the straw, it is usually mixed in dry, with a ratio of around 5-10% by weight.

Soybean Meal for Straw Substrates

Soybean meal is another common nutrient source added to straw for mushroom cultivation. It is a byproduct of processing soybeans for oil, and is high in protein and amino acids. Soybean meal is usually added in small amounts, around 1-2% by weight, as too much can make the substrate too rich and lead to contamination.

Gypsum for Straw Substrates

Gypsum is a naturally occurring mineral that is often added to straw substrate to increase its calcium content. Calcium is important for mushroom growth and helps to maintain the pH of the substrate. Gypsum is typically added at a rate of 1-2% by weight, and is usually mixed with the straw before sterilization.

Adding Nutrients to Straw Substrate

Bran and soybean meal are mixed in dry, while gypsum is usually dissolved in water before being added to the straw. The goal is to create a nutrient-rich substrate that is also free of contaminants, so that the mushrooms can grow and thrive without competition from other microorganisms.

Adding these nutrients to the straw is an important step in preparing it for mushroom cultivation. By providing the necessary food source for the mushrooms, as well as other important nutrients like calcium, cultivators can help ensure a healthy and productive crop.

Sawdust Substrate

Sawdust is another commonly used substrate for mushroom growing. It’s easy to find and relatively inexpensive. Sawdust is a good substrate for many different types of mushrooms, including shiitake, lion’s mane, and many others.

Sawdust is typically mixed with other ingredients such as bran, gypsum, and water to create a substrate that’s suitable for mushroom growth. The mixture is then sterilized and inoculated with mushroom spawn. Sawdust is an excellent substrate because it’s high in lignin, which is broken down by the mycelium to provide nutrients for the mushrooms to grow.

Adding Nutrients to Sawdust Substrates

To create a nutrient-rich environment for the mushrooms to grow in, a variety of supplements can be added to the sawdust substrate. Some of the best nutrients to add to sawdust include:

1. Bran: Bran is a good source of carbohydrates, proteins, and vitamins, which can help stimulate mushroom growth. To add bran to sawdust, mix in approximately 20% bran by weight.
2. Gypsum: Gypsum is a source of calcium and sulfur, which can help improve the structure and stability of the substrate. It also helps to control pH levels. To add gypsum, mix in approximately 2% gypsum by weight.
3. Soybean Meal: Soybean meal is a source of nitrogen and other essential nutrients that can help stimulate mushroom growth. To add soybean meal, mix in approximately 5% soybean meal by weight.
4. Calcium Carbonate: Calcium carbonate is a source of calcium and can help to adjust pH levels. To add calcium carbonate, mix in approximately 2% calcium carbonate by weight.

To sterilize the substrate as a whole, follow these instructions:

1. Fill a large pot or pressure cooker with water and place a steaming rack at the bottom.
2. Put the sawdust substrate into a plastic bag or other suitable container, and seal the container tightly.
3. Place the container onto the steaming rack.
4. Cover the pot or pressure cooker with a lid and turn on the heat.
5. Steam the sawdust substrate for approximately 2 hours or until the internal temperature reaches at least 160°F (71°C).
6. Let the sawdust substrate cool before inoculating with mushroom spores or mycelium.

Adding supplements to sawdust substrate can help provide essential nutrients for mushroom growth. Sterilizing the substrate is necessary to prevent contamination and ensure successful mushroom cultivation.

Compost Substrate

Compost is an excellent substrate for many different types of mushrooms, including Warm Weather Button mushrooms, Hen of the Woods, and more. Composts are typically made from a mixture of organic materials such as manure, straw, leaves, and more.

Organic composts can be used as a growing medium for mushrooms because it provides the necessary nutrients, moisture, and structure for mushroom growth. The compost should be prepared using specific ingredients and methods to ensure that it is suitable for growing mushrooms.

How to Prepare Compost for Substrate

Here are the general steps for preparing compost for growing mushrooms:

1. Select your compost ingredients: Mushrooms grow best in compost made from organic materials such as straw, sawdust, or corn cobs. Other organic materials such as coffee grounds, manure, or gypsum may also be used.
2. Mix your compost ingredients: Mix your compost ingredients thoroughly, taking care to ensure that they are evenly distributed. The ideal moisture content of the compost should be around 65-75%.
3. Pasteurize the compost: Pasteurization is a process of heating the compost to kill off any unwanted bacteria or fungi that may compete with your mushroom spawn. This can be done by heating the compost to a temperature of 140-160°F (60-71°C) for 2 hours.
4. Inoculate the compost: After pasteurizing the compost, it is ready for inoculation with mushroom spawn. The spawn is added to the compost and mixed thoroughly to ensure even distribution.
5. Incubate the compost: The inoculated compost is then placed in a dark, humid environment to allow the mushroom mycelium to colonize the compost.
6. Add a casing layer: Once the mycelium has colonized the compost, a layer of moist soil or coco coir is added on top to encourage mushroom fruiting.
7. Harvest the mushrooms: After a few weeks, the mushrooms will begin to grow through the casing layer. Harvest them when they reach maturity.

Prepare Compost Based on Mushroom Strain

The best way to prepare a compost for growing mushrooms may vary depending on the specific type of mushroom you are growing, as different types of mushrooms have different growing requirements. 

It is always a good idea to research the specific needs of the mushroom you plan to grow and follow a trusted recipe or guide. Additionally, it’s important to maintain good hygiene practices throughout the growing process to prevent contamination and ensure a successful harvest.

Hardwood Chips for Mushroom Substrate

Sometimes a mixture of sawdust and woodchips are the perfect environment for growing mushrooms. While sawdust alone can be used for many species, adding woodchips can improve the overall fruiting and performance of the mushrooms.

When growing mushrooms indoors, it’s important to use smaller woodchips, as they help the mycelium to hold the substrate together and provide it with more “staying power” over several flushes. Using large woodchips should be reserved for outdoor beds. According to research, adding woodchips to sawdust-based substrates can significantly improve the yield and quality of several mushroom species, including shiitake, oyster, and lion’s mane (1).

Moisture Content

Moisture content is crucial when making a sawdust-woodchip substrate, especially when using sealed filter patch bags for colonization. Excess moisture can cause the mycelium to drown, leading to bacterial or mold contamination. To prevent this, it’s better to err on the side of too dry rather than too wet. It’s also important to ensure that the substrate is properly hydrated before the first flush of mushrooms. Studies have shown that water content can greatly affect the yield and nutritional composition of shiitake mushrooms (2).

To make the substrate mixture, we recommend using twice as much sawdust as woodchips, along with gypsum and wheat, rice, or oat bran. Woodchips can be soaked in water overnight or boiled for an hour to absorb moisture. The amount of water needed to hydrate the sawdust depends on its initial dryness. Fresh sawdust requires less water than aged sawdust that has been stored for a year or more in dry conditions. Researchers have found that using aged sawdust in substrate formulations can increase the yield of shiitake and oyster mushrooms (3).

It’s important to let the sawdust rest for at least 15 minutes after mixing and then check the moisture content again. If it’s too wet, dry sawdust can be added to the mixture. Proper moisture content can be determined by squeezing a handful of the mixture; no water should drip out when squeezed hard. Also, make sure there’s no standing water at the bottom of the container used to mix the substrate.

Making Fruiting Blocks with Hardwood Chips

Once the substrate mixture is at the right moisture content and the woodchips have been soaked and drained, it’s time to load the bags. We recommend using a 2:1 ratio of sawdust to woodchips. It’s not necessary to get the ratio exactly right. Clean off any sawdust stuck to the inside of the bag and insert a tyvek sleeve to allow steam to escape during sterilization. After sterilization, the vacuum that forms as the substrate cools will create the only path for air to enter, which is through the tyvek filter.

By following these guidelines, you can create a sawdust-woodchip substrate that’s perfect for growing mushrooms. Remember to pay attention to moisture content, use smaller woodchips, and add aged sawdust to improve yield. With some trial and error, you’ll be on your way to harvesting your own delicious and nutritious mushrooms in no time!

References:

1. Stamets, P. (2005). Mycelium running: How mushrooms can help save the world. Berkeley: Ten Speed Press.
2. Zhang, X., Shi, X., & Sun, J. (2016). Effect of water content on the yield and nutritional composition of shiitake mushroom. International Journal of Food Properties, 19(7),

Coco Coir for Mushroom Substrate

Coco coir is a popular substrate for growing mushrooms due to its ability to retain water and provide a porous structure for mycelium growth. It is made from the fibrous husk of coconut shells and is available in different grades, including fine and coarse.

Compared to other mushroom substrates, such as straw, sawdust, and manure, coco coir has several advantages. Firstly, it is easy to prepare and does not require extensive sterilization or pasteurization. It also has a low risk of contamination since it is naturally high in lignin, which is difficult for most contaminants to digest. Coco coir also has a high water holding capacity, which helps maintain a consistent level of moisture for the mushrooms to grow.

Disadvantages to Coco Coir

One disadvantage of using coco coir as a substrate is that it is relatively low in nutrients. Therefore, it may require supplementation with other ingredients, such as bran, to provide adequate nutrition for the mushrooms. Additionally, coco coir can be prone to compacting, which can restrict air circulation and impede mycelium growth.

Coco coir can also be used as a casing layer, which is a protective layer placed on top of the substrate to prevent it from drying out and provide a moist environment for fruiting. As a casing layer, coco coir can provide additional water retention and a porous structure for mushroom growth. However, it may also increase the risk of contamination and require careful monitoring of moisture levels.

Choosing The Best Substrate for Mushroom Growing

In conclusion, mushroom cultivation is a fascinating and rewarding hobby or business that requires the right substrate to grow successfully. Straw, sawdust, compost, hardwood chips, and coco coir are some of the most common substrates used for mushroom cultivation, each with its own advantages and disadvantages.

By adding nutrients, sterilizing the substrate, and inoculating it with mushroom spawn, cultivators can create a nutrient-rich environment for mushroom growth. However, it is important to pay attention to moisture levels and maintain good hygiene practices to prevent contamination and ensure a successful harvest.

With the right substrate and growing conditions, anyone can enjoy the nutritional benefits of delicious and healthy mushrooms!