How Gourmet Mushrooms Are Grown

Gourmet mushrooms are commercially grown in three stages. The ability to control temperature, humidity, and fresh air exchange is key to any cultivator’s success, and proper infrastructure is required to meet the different parameters required in each stage of growth.  

Stage 1: Petri Dishes

Mushrooms live most of their lives in a vegetative state called mycelium. In nature, mycelium grows in soil or decaying wood where it absorbs vital nutrients. These nutrient-rich conditions can be replicated in a laboratory setting using a specially formulated gel, called agar, that can be customized for a particular mushroom species. The commercial mushroom growing process begins by placing a small bit of mushroom mycelium onto a petri dish, and within several weeks the mycelial tissue replicates itself and covers the entire surface of the petri dish—this is referred to as colonization. 

After a petri dish has been fully colonized by mycelium, cultivators can proceed in two directions: 

  1. Divide the agar into small pieces and transfer the pieces to new petri dishes, where the mycelium will continue to expand (one petri dish covered with mycelium can serve to start about 80 new petri dishes). These new petri dishes can then be used for further propagation, or they can be used for the second option: 
  2. Distribute the cut-up pieces of mycelium into receptacles of sterilized grains. 
Petri dishes at different stages of colonization

Step 2: Grains

After being introduced to sterilized grains (typically wheat, millet, and sorghum), the mycelium will begin to replicate and grow, metabolizing all available nutrients. This process typically takes several weeks so the mycelium can adjust to its new environment and nutrient availability. With these nutrients, however, comes the risk of contamination by other fungi and bacteria. Grains must be sterilized carefully prior to being inoculated with mycelium. Any lapse in attention during the inoculation process can lead to contamination and a lost grain bag (contamination can also go unnoticed, leading to problems later in the cultivation process). Once a grain bag is fully colonized with mycelium, the bag can be used for two purposes: 

  1. Propagating the myceliated grains into other sterilized grain bags, or: 
  2. Introducing the myceliated grains into bags of substrate suitable for growing the mycelium into its next stage—the production of fruiting bodies (mushrooms). 
Grain spawn during colonization

Step 3: Fruiting Substrate

There are many substrate options for growing mycelium out to its final stage, where it produces mushrooms. Commercial cultivators in the West typically use hardwood sawdust supplemented with agricultural waste products—this can include soybean hulls, wheat bran, rice bran, sugarcane bagasse, and coffee grounds. Cultivators prepare substrate bags by mixing the dry inputs with a specific volume of water and then placing them in an autoclave for sterilization. After the substrate bags have cooled, cultivators shake the grain bags to break them up and then distribute them in small amounts to the sterilized substrate bags. The inoculated substrate bags will then remain in a temperature-controlled room for several weeks; the mycelium moves from the grains throughout the substrate colonizing it completely during this time. After the substrate bags are completely colonized, the substrate bags move into the fruiting chamber, where cultivators cut them open and expose them to lower temperatures, high humidity, and fresh air. After several weeks, mushrooms will be fully formed and ready for harvest. Depending on the species, several harvests can be picked from each bag. After a bag has produced its mushrooms, the substrate can be composted or added to soil where it will continue to produce small quantities of mushrooms.

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How to Grow Mushrooms – 5 Steps to Success

Have you been considering growing your own gourmet mushrooms, but just don’t know where to start? Well, it’s time to ditch your mushroom grow kit, and let us show you how you can grow gourmet mushrooms on your own. But first, let’s cover a few basics.

 

Why should I grow mushrooms?

Even though mushrooms are on the Clean 15 list, that doesn’t mean that they are actually pesticide free! A study done by the FDA shows that 26% of imported mushrooms had more than the allowable amount of pesticides, even thiabendazole, a carcinogen, and a developmental and reproductive toxin.

Pesticides are not our only concern with commercial mushrooms. Gourmet mushrooms are expensive and can be hard to find at your local store, but don’t let that stop you from capitalizing on the many benefits mushrooms provide! 

 

Is it difficult to grow mushrooms? 

Although it may seem tricky at first, once you understand the basics of growing mushrooms, the process is pretty simple! Take care to prevent contamination, monitor temperature and humidity, and you will be enjoying fresh, homegrown, gourmet mushrooms before you know it!

 

Is it dangerous to grow mushrooms?

Nope! Follow our guidelines below and wear a respirator when you are exposed to mushrooms that are in the fruiting phase – this is when they release spores. If you are going to be using a pressure cooker or autoclave, be sure to adhere to all of the manufacturer’s instructions.

 

Step 1: Prepare your substrate

When it comes to choosing a substrate, you have quite a few options. We have seen the best results using sawdust, soybean hulls, wheat bran, rice bran, peanut hulls, sugarcane bagasse, or straw. Although this is far from a comprehensive list, the options above are tried and tested and should provide you with great results!

  • Depending on the substrate, it may be beneficial to chop up your substrate before beginning the hydrating process — this will cut down on the time needed to hydrate and thoroughly mix your substrate.
  • The next part is to hydrate the substrate. The water to dry mix ratio will be specific to your chosen substrate, so be sure to add the correct volume of water. 
  • After you have finished prepping your substrate, divide it evenly into mushroom bags. Fold the opening of the bag over to seal the substrate so it is ready for the next step.

Step 2: Sterilization

Sterilization is a very important part of the process. If not done correctly, your substrate can become contaminated and the contamination will compete with your mushrooms for nutrients.

There are two main ways to sterilize substrate:

  • Atmospheric steam sterilization: This process involves keeping the bag of substrate immersed in steam for several hours until sterilization is reached. This method takes longer but is the safer option and the one we prefer.
  • Autoclave or pressure cooker: Using this method is faster, but it is essential to take proper precautions whenever using an autoclave or pressure cooker.

Don’t forget to let your sterilized substrate cool completely before inoculating! You can even let your substrate cool overnight, although we don’t recommend letting it sit for longer than 24 hours.

Step 3: Inoculate the substrate

Be careful not to contaminate your grain spawn or substrate bags during this step. Pay close attention to your work during this process, since it is easy to introduce contaminants during inoculation. Contamination can easily go unnoticed, leading to problems later in the cultivation process.

  • After cooling the substrate, it’s time to inoculate. We recommend inoculating in a cleanroom or under a HEPA flow cabinet. This ensures that no mold spores, yeast, or bacteria will enter the bag and contaminate it. If you don’t have access to a HEPA flow cabinet, consider building or buying a still air box.
  • Add the grain spawn to the substrate bag using a sterilized spoon or another sterilized tool. Try to put the same amount of grain spawn into each bag.
  • Seal the bag closed using an impulse sealer. Don’t force any air out of the bag before sealing — this not only allows for air exchange but also makes mixing much easier.
  • Thoroughly mix the substrate and grain spawn until you have a uniform mixture.

 

Step 4: Incubation

During incubation, the mycelium moves from the grains throughout the substrate colonizing it completely. Incubation time will vary depending on the species of mushrooms you are growing. 

  • Place the inoculated substrate bag in a room with the temperature set to the mid to low 70’s (Fahrenheit). 
  • Incubation usually takes between 2 and 3 weeks depending on species.

Step 5: Fruiting

After the substrate bags are completely colonized, the fruiting process can begin.

  • Take the colonized substrate bags to a room with high humidity with the temperature set to the low to mid 60’s. 
  • Cut the bag open, exposing the mycelium to oxygen. At this point, the temperature drop and high humidity will act as biological triggers telling the mycelium to begin forming mushrooms.
  • After about 2 weeks (just keep an eye on them), you will have mature mushrooms that are ready to be picked! Depending on the species, several harvests can be picked from each bag. After a bag has produced its mushrooms, the substrate can be composted or added to soil where it will continue to produce small quantities of mushrooms.

Not that hard, right? The ability to control temperature, humidity, and fresh air exchange is key to successfully growing mushrooms, and proper infrastructure is required to meet the varying needs of different mushroom species.

When you’re ready to take things to the next level, give us a call! Our Gourmet Mushroom Farms are equipped with everything you need to grow mushrooms on a large scale, and our amazing team is here to help you every step of the way.

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