Mushroom Basics and a Look at My Process

When I tell people that I run an indoor mushroom farm, I find that a lot of people have never heard of such a concept, they don’t know specifics on how indoor cultivation works, or they ask if I am growing ‘magic’ mushrooms. So for my inaugural blog post I am going to cover the basics of mushrooms in general and an overview of indoor commercial cultivation.

What Are Mushrooms?

Mushrooms are part of the fungal kingdom which consists of mold, yeast, and mushrooms, among other things. Mushrooms are the reproductive portion of the fungus, whereas the vegetative structure is called the mycelium. Mycelium consists of a network of white filaments, hyphae, that are responsible for nutrient uptake and the decomposition of materials. In comparison to a fruit tree, you can think of the mycelium as the roots, trunk, branches, leaves, the mushroom as the fruit, and the spores as the seeds. There are three main categories of mushrooms. 

The first is saprophytes. These mushrooms break down organic material and are an important player in soil creation and carbon cycling. Parasitic fungi use living organisms as a host in which they extract nutrients. The third main category of mushrooms are mycorrhizae fungi which pair with plant root systems to transfer nutrients, fix nitrogen, and send chemical signals. These are the most intriguing of mushrooms as they can take decades to become established thus being very difficult to cultivate. There is a fantastic TedTalk on mycorrhizae regarding the way trees communicate with each other in the forests of Canada.

Mushrooms release spores as they grow and mature. These spores are responsible for the reproduction of the organism. Mushrooms can reproduce sexually (with another individual) or asexually (with themselves). Mushroom spores are released on the magnitude of hundreds of millions.

Indoor Mushroom Cultivation

Growing mushrooms indoors can be a fun hobby or a full on business, either way there are ways for everyone to get started and it can be relatively easy. Hobbyists tend to grow on logs or in hydroponic tents. Logs are easy, low maintenance options but can take a long time to fruit compared to growing indoors on blocks. Hydroponic tents allow you to grow indoors, all year round on a small scale. Commercial production requires much more and I am going to give an overview of what that entails. 

Full scale commercial mushroom cultivation often contains all portions of the mushroom life cycle, many times from culture to compost. In this scenario, growers will often grow their own mushroom cultures in petri dishes filled with agar, a nutrient rich substrate that allows for vigorous mycelial growth. As the culture expands it can be transferred to a larger substrate to allow the mycelium to keep “running”, many times this substrate is some type of grain. This is known as spawn. As this expands and grows, cultivators will need to obtain, mix and sterilize bulk substrate. A very popular substrate mixture is 50:50 hardwood sawdust/fuel pellets and soybean hulls with 60% water. This was concocted by T.R. Davis of Earth Angel Mushrooms. Check out his YouTube channel as he is a wealth of knowledge. The substrate mixture is then bagged in autoclave bags with microporous filter patches. While this may seem straightforward, there is a plethora of information and requirements when doing this lab work. I suggest, Growing Gourmet and Medicinal Mushrooms by Paul Stamets as a good jumping off point. These bags are loaded into a steam sterilizer, autoclave, pressure cooker or other and sterilized to kill any bacteria of fungus that could contaminate the bag. After the bags cool, mushroom spawn is used to inoculate the substrate. The bags are put into a room where they are left to colonize the substrate to a suitable percentage until they are ready to fruit. At this time, the bags are brought into the grow room where they produce mushrooms. Sounds easy enough, right?

Substrate Mixing

A quick note about the rooms/separate spaces required for each of these processes. There needs to be a storage and mixing area. This area is inherently not going to be very clean, but that’s alright. This is where all the raw material is mixed and bagged, as well as various supplies can be stored. Auto baggers are commonplace in large scale commercial operations, but using a large tote/bucket and hand filling bags is fine when you’re just starting out. You should have water readily accessible in this portion because you will be going through a lot when making bags.

The Lab

Now, for the lab. The lab is going to be the cleanest room in the whole operation. Typically growers will do all lab work, agar plates, spawn production, substrate inoculation in front of a laminar flow hood. This is essentially a fan that is pushing air through an electrostatic HEPA filter. This ensures all work being done directly in front of the flow hood has a very low risk of contamination from airborne particles. These rooms are typically positive pressured by filtered air. 

Incubation Room

The next room is the incubation room. This is where the mycelium grows. These rooms need to be climate controlled and able to maintain a steady temperature. Typically this temperature is in the low 70s but it can differ between species. Maintaining a stable temperature is key as to make sure the core of the bags does not overheat, thus killing off mycelium and becoming a risk of contamination. The walls in this room should be non-porous, will not be able to harbor bacteria/mold, and able to be cleaned periodically.

Grow Room

Finally, we have the grow room which is responsible for the final product of this operation. Grow rooms vary as mushroom species have different requirements, but are typically cooler, 50-70 F, and have high humidity, 80-99%. Requirements for any grow room include; a floor drain, a floor that is made of a hard, non-porous material, and walls that are easy to clean and will not absorb water. The main factors to consider in the grow room are temperature, humidity, fresh air exchange/CO2 ppm, and light. These are all important factors to consider when building a grow room because it will ultimately determine your success. 

Caveats

There are other ways to grow mushrooms commercially such as logs, compost, straw and other substrates. However, for indoor commercial cultivation of gourmet mushrooms this seems to be the recipe that is most replicated, obviously with some degree of variation between operations. In terms of lab work, there are other ways to sterilize substrate. One way is to use very low percentage hydrogen peroxide (H2O2) and that can effectively sterilize substrate without impeding mycelial growth. This is broken down into water and oxygen quickly by the mycelium and produces a mushroom that is safe for consumption while sterilizing the substrate. This process is advantageous because it does not require thousands of dollars in equipment and hundreds, if not thousands, of additional square feet. 

Dislaminer: I am not a mycologist or an expert cultivator. I am sharing with you the knowledge that I have gained from books, tutorials, I and my own experiences.