The substrate is the term for the material you grow your mushrooms on.
One of the first things for potential mushroom growers to learn about is how significant mushroom substrates are. It is very important to choose the right substrate recipe in order to achieve a good crop of mushrooms.
The correct substrate recipe depends on a variety of factors including which variety of mushrooms you want to grow, the environment where they will be grown, and your budget, as well as which materials you are able to get.
If you are new to mushroom farming, take a look at the following tips and advice about which substrate to choose for which mushroom variety. If you have some experience under your belt already, why not try a new substrate? Part of the fun of growing your own mushrooms is experimentation, and combining different substrates and trying different supplements can result in some really high yields and great quality mushrooms!
Why Mushrooms Need a Substrate
To answer this, let’s take a look at what makes mushroom growing special and so different from growing plants. A mushroom is of course not a plant but a fungus. All mushrooms are fungi but not all fungi are mushrooms. Think of a mushroom like a fruiting body to ensure reproduction.
Plants have roots to reach their food source while mushrooms have mycelium, which is the vegetative part of the fungus that produces mushrooms. Mushrooms grow from mushroom spores released when the cap opens.
These spores then develop into living mycelium in the right conditions, and this will look like a network of white threads over the substrate. When they are mature they release their spores, and the process starts over again.
The mushroom growing process is similar to plant growing in some ways, but you can see how there are differences. You can grow a plant in a pot of soil but mushrooms require a special mushroom substrate or food source, since they don’t have roots like a plant to get food from the soil.
Substrates are a Vital Source of Nutrients
This is where substrates come into play! Mushroom substrates provide the food in order for your mushrooms to grow. These substrates provide various nutrients. Different types of mushrooms require different growing substrates.
The 3 main components found in plant cell walls are cellulose, lignin and hemicellulose. Those are what mushrooms like to feed on. They also like small amounts of minerals, nitrogen, and a pH level between 4 and 7 depending on the mushroom variety. Mushrooms also like between 50 and 70% water content in the growing substrate.
However, read on and discover some very different substrate ideas. You will see that there are more types than you perhaps realized!
Examples of Good Substrate Materials
A substrate can be any material where mycelium is able to grow. Remember, the substrate will be the organic host while the mycelium is the part of the fungi that will produce your mushrooms.
Substrate options include logs, grains such as organic rye berries, chopped wheat straw, coffee granules and manure based mushroom substrates. If you are on a budget or do not have access to those things, you can even make a substrate from cardboard! That is a feasible low-cost alternative.
Why Substrate Sterilization is Not Optional!
The developing mycelium is vulnerable to contamination, which means it is critical to sterilize the substrate before using it, and later inoculate in a sterile environment.
If you skip the sterilization part, the substrate will probably have a high level of contamination resulting in a low mushroom yield. In the worst case scenario, the contamination will be too high for any mycelium to grow - which would mean no mushrooms at all!
As a mushroom grower, you will find there are plenty of options for substrates, and you can find ideas online about how to make your own mixtures.
Experimenting with different kinds is also a good idea, as you discover works best for your mushroom farm. Let’s now take a look at some different mushroom growing substrates, and discover which ones work best for which type of mushrooms.
To make a 5-pound block of this, you will need:
- 5 cups hardwood pellets
- 1¼ cups oat or wheat bran
- 6 cups water
Add the ingredients to a pressure cooker and sterilize them. Although wood pellets are already sterilized, using bran means you need to repeat the process. This substrate works for nearly all types of mushrooms but is especially good for ones which naturally grow on dead logs and trees.
Psilocybe Fanaticus Technique (PF-Tek)
Combine the following in a half pint mason jar, then put them in a pressure cooker for 45 minutes at 15 PSI.
- 1/6 cup brown rice flour
- ½ cup vermiculite
- ¼ cup water
This is a good substrate for growing a small amount of mushrooms, and works with most varieties. However it is not designed to grow big mushrooms and you will get small to medium sized ones only. Many mushroom growing beginners choose this substrate because it is easy to work with, and gives good all-round results.
Are you a coffee drinker? Don’t throw those grounds away! If not, the nearest coffee shop probably won’t mind giving you some of theirs. You need to sterilize coffee grounds not used within 24 hours.
Nearly all mushrooms like used coffee grounds as a growing substrate, but you might also need to add supplements for better growth.
Most mushroom growers prefer to use the coffee grounds as a supplement to other types of substrates. Oyster mushrooms and shiitakes especially like coffee grounds.
Use a weed whacker in a 55-gallon barrel to cut straw into 3-4 inch lengths, then pasteurize it with hot water or lime.
For hot water, keep it between 149 and 175 degrees F for an hour or 2, then use a mesh bag to soak the straw, before letting it drain for 20 minutes. To keep the water hot, you can put some cinder blocks and a fire under the barrel, or put an electric drum heating belt around it.
For lime, use 175g of hydrated lime for every 100 liters of water, and soak the straw for 12-18 hours in a mesh bag, before letting it drain for an hour.
Most mushrooms will grow on straw, although some will need additional supplements. Oyster mushrooms especially like a straw substrate.
This mixture produces huge first flushes for most mushrooms, and can be used if you want to grow extra-large ones. Don’t use masters mix with shiitake. To make it, you need to combine the following in a pressure cooker for 2½ hours at 15 PSI.
- 1 pound hardwood sawdust
- 1 pound soy bean hulls
- 5.9 cups water
Letting the soy bean hulls soak overnight in boiled water makes them much easier to break apart. Use 700ml of water for each 2½ cups of pelletized soy hulls so the sawdust comes apart more easily.
Try combining 2 parts of sun-dried horse manure with 1 part of coir (which comes from coconuts). Next add water to make it ‘field capacity’ which means adding as much water as you can without having a pool underneath. You should be able to get a couple drops of water out if squeezing hard but none if you squeeze gently.
This mixture needs to be sterilized for 2½ hours at 15 PSI. If you don’t want to make your own, you can buy manure mushroom substrate bags which are ready for inoculation. Button mushrooms or psilocybe cubensis like to grow on this substrate.
Soak rye grains in water with a tablespoon of gypsum (and preferable also a cup of coffee for better mushroom yields) for 12-24 hours.
Bring the mixture to a boil and simmer it for 15 minutes, before transferring into jars or bags. Finally sterilize them in a pressure cooker at 15 PSI for 1½ hours.
You can also buy readymade rye grain substrate bags. This substrate is often used to make mushroom spawn to inoculate a bulk substrate later. Nearly any type of mushroom spawn will grow on rye grain.
Straw with Coffee Grounds
You can mix the ingredients together by hand or using a compost tumbler, then layer the mushroom spawn in so there is some spawn in every inch of the substrate. To make a straw with coffee grounds substrate, you will need:
- 60% hydrated, pasteurized wheat straw
- 30% used coffee grounds (no older than 24 hours)
- 10% mushroom grain spawn
Grain spawn can be bought premade or you can make your own. Most mushrooms will grow well on this mixture although some will need supplements. This is a good substrate for oyster mushrooms.
Straw with Sawdust and Coffee Grounds
This is similar to the straw with coffee grounds recipe above, but with the addition of sawdust pellets. You need to mix the following together with a compost tumbler or by hand:
- 40% hydrated, pasteurized wheat straw
- 30% used coffee grounds (no older than 24 hours)
- 20% hydrated sawdust pellets
- 10% mushroom grain spawn
Most mushroom varieties will do well on this substrate, although you might need to add in nutritional supplements for some types. Shiitake mushrooms in particular like this mixture.
A 3-4 feet long hardwood log with a 4-6 inch diameter is a good choice for several mushroom varieties. Bear in mind, the wider the log, the larger the mushrooms tend to grow.
You need to drill 1-inch deep holes 4-6 inches apart in a row. Make new rows 2-3 inches apart in a staggered formation (like a diamond shape). You can either use an angle grinder with a 12mm bit or a drill with a 5/16th drill bit to make these holes.
Hardwood log examples include alder, oak, beech, birch, polar, maple, aspen, willow, elm, and balsam.
If you are cutting your own trees, do this between midsummer and late fall, and never ones that are budding out during the late spring. It is best to wait a month before using the wood, so any natural fungi on the tree can die off before you use it as a substrate.
Mushrooms that naturally grow on dying or dead hardwood trees will grow well on a log substrate.
Coco Coir and Vermiculite
Also known as coconut fiber, coco coir is a fibrous material that comes from between the outer husk and the hard inner shell of the coconut.
You can either combine equal parts of coco coir and vermiculite, then pasteurize it and add your spawn, or else add the following to a bucket:
- 1.4 lbs coco coir
- 8 cups dry vermiculite
- 4 quarts boiling water
Put a lid on the bucket and let the mixture soak for 40 minutes, then remove the lid and give it a good stir. Put the lid back on and let it cool for 4 hours.
Most mushrooms will grow on this type of substrate, although some might require additional supplements for better growth. This coco coir and vermiculite mixture is often used as a manure substitute since manure is not always available (and this usually smells better).
Bring a pot of water to a boil, then let it cool down and soak some cardboard with it. You can mix in some coffee grounds too. This is an easy and economical substrate to make.
When layering, it is best to layer cardboard, then grain spawn, then more cardboard, then more grain spawn, and so on. Oyster mushrooms do well on a cardboard substrate.
You can use this method to make your own grain spawn instead of using rye grain. It works for any type of mushroom which like a rye grain substrate.
You need to rinse popcorn and put it in a pressure cooker. Add enough water for the popcorn to absorb, then turn the heat up to high.
Let the pressure cooker steam for 10 minutes to get rid of excess air, then put the weight on and build the pressure to 15 PSI. Cook the corn for 30 minutes, then drain it in a sieve for 10 minutes. Lay it on paper towels and pat dry, then put it in mason jars.
Drill a hole in the top of each jar and fill it with poly stuffing then aluminum foil. Once that is done, add the filled mason jars to the pressure cooker and give them 90 minutes at 15 PSI.
Can You Sterilize without a Pressure Cooker?
Alternatives to using a pressure cooker include composting, cold water pasteurization, chemical, scalding (hot water immersion), Tyndallization and pasteurization. Each of these has pros and cons.
Another alternative is to purchase substrate ingredients which have already been sterilized, so you can go ahead and make the mixture without having to sterilize them again.
For the best value though, it might be worth investing in a pressure cooker if you are planning to grow a good amount of mushrooms. You will save money over time making your own substrates.
What Comes Next?
After you have decided which substrate to use depending on which variety of mushrooms you are going to grow, you need to choose a suitable environment for the substrate so you can start growing the mushrooms.
The choices include making a ‘humidity dome’, using bottles, making a monotub for the substrate to divide it out for maximum growth, buying or making sealed plastic bags, or using lay-flat tubing.
After that, you will inoculate the mushroom substrate, incubate and finally see some delicious mushrooms growing! But all of that comes later. For now though, you can get started deciding on and preparing your substrate!
Some Final Tips
Picking out the best substrate for your mushrooms is largely a question of finding out where that mushroom variety grows naturally and what it prefers to feed on. Mushrooms that grow in the wild in dead trees, for example, will likely grow well on logs.
You can pick one of the above substrate recipes or combine a couple together. You could even experiment and come up with your own!
Choose a substrate recipe which uses resources you can get easily. If you live rural, for example, you might have plenty of straw around to use but not have access to large quantities of fresh coffee grounds.
Another option is to buy a ready-made substrate and use that instead. This can save tons of time and trouble since getting the mix right often takes some practice. Easy mushroom grow kits with everything included are a great starter option.