What’s a Substrate? The Best Growing Mediums for Potent Mushrooms

The world of mycology has its own vernacular, terms which can seem quite confusing. What’s a mushroom substrate, for example? Or mycelium? Even the word “mycology” itself can be considered jargon, as it’s often used among mushroom growers. To the average person, however, the term may sound like a pseudoscientific designation—or just complete gibberish. 

The confusion around nomenclature is perhaps most prominent in the psychedelic mushroom space, likely due to the influx of new growers wanting to learn how to grow magic mushrooms. Many of these individuals are hobbyists, not formally educated in biology or mycology. That being said, formal education is by no means necessary to grow magic mushrooms. Yet, having a solid grasp on industry terminology will certainly streamline your growing process, allow you to better understand the science behind the process, and perhaps even save you from making costly mistakes. 

As someone who has been cultivating magic mushrooms in Canada for just over a decade for spores, there are a few terms that stick out as the most commonly misused and misunderstood.  The term “substrate” perhaps offers the best example. The Oxford definition of substrate is as follows:

… the surface or material on or from which an organism lives, grows, or obtains its nourishment.

Based on this definition, a “substrate” is any medium that a mushroom culture will grow upon. But, the word takes on slightly different meanings in the world of cultivation. Mushrooms need different substrates at different points in their life cycle. In addition, different mushroom species require different substrates to grow. Some mushroom species grow on decaying wood, for example, while others thrive on manure or decaying grass.

Mushroom Growing Substrates for Each Life Stage

Mushrooms need different nutrients during each stage of their life cycle. There are two main life stages for mushrooms: spawning and fruiting. Plant-lovers may find this concept familiar—plants require different nutrients in their vegetative stage than they do in their blooming stage. The vegetative stage for plants is similar to the spawning stage for mushrooms.

During spawning, all of the organism’s energy is put towards growth. No energy is devoted to reproduction. This tendency changes in the fruiting phase. During the fruiting stage, some of the fungi’s energy is put towards growth, but most energy is devoted to reproduction. The fruiting stage for mushrooms is comparable to the blooming state for plants. Mushrooms are the primary reproductive organs of fungi, just like flowers are the primary reproductive organs of plants.

The Spawning Stage  

Spawning is the first portion of the mushroom life cycle. During this life stage, fungal spores develop into mycelium, the web-like structure that exists underground in the wild. Mycelium is composed of many thin, threadlike tendrils, each one cell thick, called hyphae. These hyphae grow out in all directions from the initial point of inoculation in the spawn medium. Once they have spread throughout the spawn medium, the medium is considered “colonized” by the fungus. (Colonized is another vernacular term often used in mushroom cultivation).

The Fruiting Stage

After colonization, the fruiting stage can begin. The mycelium will start to form thick knots of hyphae if the spawn medium is given the correct environmental conditions. These hyphal knots develop into mushroom fruiting bodies over a period of 7 to 10 days—in the case of psilocybe mushrooms, at least. Other species can take much longer to fruit.

You can increase the yield of your mushrooms by amending your substrate after the mycelium has colonized its initial growing medium. The process of adding a fruiting substrate to your spawn medium serves numerous functions, the most prominent of which are: 

• Increasing the surface area on which the mushroom fruiting bodies can form, a process referred to as “bulking with substrate”
• Increasing the water retention capacity of the mixed medium
• Increasing the nutrient content and microbial content of the mixed medium

Adding fruiting substrate to your spawn is not completely necessary. Your mushroom culture will fruit right out of a spawning medium if given the correct environmental conditions. Yet, you will see a drastic difference in yield if you skip the fruiting substrate. You will also see slight differences in the concentration and ratio of psychoactive compounds based on the mediums you use for spawning and fruiting substrates. Nutrients are more bioavailable to the mushroom in some substrates over others. The mushroom culture uses these nutrients to synthesize these active compounds.

Best Spawning Substrates (Spawning Mediums)

The correct term for a spawn material is “spawning medium.” A spawning medium consists of just one ingredient—some kind of grain or flour. In contrast, a fruiting substrate is typically a mix of three to five ingredients. As such, choosing a spawning medium is notably easier than choosing or building a fruiting substrate. Yet, there are a few important things to remember when selecting a spawn medium, such as its nutrient profile, pH, water retention capacity, and whether or not the medium was treated with fungicide as it grew. Some of the most common mediums used to spawn magic mushrooms are: 

• Rye grain
• Oats
• Wheat grain
• Bird seed
• Popcorn
• Brown rice flour

We at Spores Lab exclusively use rye grain as a spawning medium. Rye grain can hold more moisture than any other grain, which translates to greater yield in fruiting. However, many growers prefer oats or popcorn as these two mediums have a lower density than rye. A lower density makes mediums like oats and popcorn easier to sterilize—they take less time in the pressure cooker. This quality makes these mediums less susceptible to contamination.

Yet, regardless of what medium you choose, you must ensure that it was not treated with fungicide at any point in its life cycle. Many farmers apply fungicides to their crops, and trying to spawn on grain that has had a fungicide will not work very well, for obvious reasons. The best way you can ensure that your spawn medium has not had a fungicide applied is to purchase a certified organic medium.

Read: Mushroom Spores and the Wild Ways They Work

Best Substrate for Mushrooms

Due to the non-discriminatory nature of the internet—anyone with an internet connection can post their recipe—there are now thousands of different substrate recipes available at the click of a mouse. Many of these recipes can provide your shrooms with the ideal conditions to promote large, healthy, and potent fruiting bodies. Unfortunately, I don’t have the time to cover all of them in depth in this brief article. So, I’ll limit myself to the three of the most commonly used recipes for fruiting substrates:

Coco Coir Mushroom Substrate with Vermiculite and Gypsum (CVG)

A substrate mix of coco coir, vermiculite, gypsum (CVG) is probably the most widely used fruiting medium for growing psilocybin mushrooms. This substrate recipe will work excellently for any Psilocybe mushroom variety, and is the recipe we would recommend for beginners as it actually contains few nutrients—but, don’t worry. There will be enough nutrients in the spawning medium for the culture to produce multiple flushes of potent fruiting bodies. This recipe is considered better for beginners since having high nutrient levels raises the chances of contamination developing; competitor molds and fungi also love the same nutrients that magic mushrooms do. 

The basic process of making a CVG substrate is mixing coco and vermiculite at a 50/50 ratio. Then, you add gypsum at a ratio of approximately five percent by volume. Finally, you add water until field capacity is reached. “Field capacity” is a term used to describe a medium’s maximum saturation capacity. An excellent field capacity test that you can use when making a fruiting substrate is to pick up a handful of substrate and lightly squeeze. If the medium is at field capacity, you should get a steady stream of water dripping when you squeeze.

After field capacity is reached you are ready to bag the substrate into an autoclavable bag or container and then sterilize or pasteurize the medium. After sterilization or pasteurization, be sure to let the medium cool sufficiently, and then mix it with your spawn medium within 24 hours.

CVG with Horse Manure Substrate

This fruiting substrate recipe is a modification of the CVG recipe that will provide not only more nutrients but also beneficial microorganisms, which form a symbiotic relationship with your mushroom culture. The addition of microorganisms from manure allows the mushroom culture to more effectively uptake nutrients, which increases the overall health of the culture. Many growers also report that mushrooms grown using manure-amended substrates are higher potency, but this is purely anecdotal. These claims are not able to be backed by test results—yet. 

This recipe involves making a CVG mix, then adding horse or steer manure (not chicken manure, as it’s too high in nitrogen). You must be cognizant of how much manure you add, however. Too much manure will result in high nitrogen levels which cause the formation of ammonium, creating an environment that is toxic to mushrooms. Ideally, you want to have the mixture be approximately five percent manure.

An important note if following this recipe is that the medium should be pasteurized, not sterilized. If you sterilize the medium you will negate most of the benefits provided by the microorganisms in manure, as these will be killed during sterilization. Pasteurization will still kill contaminants, but allow most of the microorganisms to survive.

MYCO-PRO™️

Finally, I’ll mention the substrate we’ve developed ourselves at Spores Lab. We formulated our MYCO-PRO™️ fruiting substrate recipe using more than a decade of experimentation. We laboratory tested our recipe both prior to being mixed with spawn, and again after harvesting four flushes of mushrooms. Perhaps needless to say, we are extremely pleased with the results. Even after harvesting four flushes, the substrate still contained ample amounts of all important nutrients and was still within an acceptable pH range.

We developed our MYCO-PRO™️ Fruiting substrate as a modification of the CVG and horse manure substrate that provides greater consistency. It consists of coconut coir, vermiculite, peat moss, calcium carbonate (which serves a similar function to gypsum), and worm castings (which serve a similar function to horse manure).

While manure is a great addition due to the nutrients it provides and its microbial content, it can be difficult to procure manure that is consistent. Numerous variables, such as age, storage conditions, and whether or not the manure is aerobic or anaerobic,  can have a notable effect on your growing results. This is why we have substituted manure for worm castings in the MYCO-PRO recipe, as worm castings have much greater consistency in nutrient and microbial content. We have also substituted gypsum for calcium carbonate, as both can serve as an anti-binding agent. Calcium carbonate, however, also serves to raise pH. Raising pH slightly is necessary, as the addition of peat moss to the recipe lowers pH, making the substrate more acidic. 

Read: Why You Should Grow Your Own Mushrooms

Regardless of what medium you use, however, you must either sterilize or pasteurize your fruiting substrate. Whether you sterilize or pasteurize will depend on which recipe you follow. This process is necessary to kill any competitor molds or fungi living in the input ingredients.

In conclusion, there are many different mediums and recipes that can be used to grow shrooms, and as such there is a significant deal of confusion surrounding this topic. I hope that after reading this article you will not only be able to discern what the best spawn and fruiting substrates for your application are but also have a better grasp on some terminology that can definitely be confusing for a beginner grower.