There are a wide variety of substrates that growers can use, including straw, soil, coconut coir and vermiculite, coffee grounds, logs, and manure; however, some mushroom species are more selective than others and respond best to certain substrates. For example, Hericium erinaceus, Ganoderma lucidum, and Maitake (also known as Cocktail Mushroom) - all of which grow naturally in forested areas - are best grown in wood substrates such as elm, beech, or ash.

While there are a wide variety of substrates to choose from, they all have some things in common. A good mushroom substrate must be:

● Rich in lignocellulosic material such as lignin, cellulose, and hemicellulose
● Contain 1% to 2% nitrogen
● Contain small amounts of magnesium, potassium, calcium, sulfur, and phosphorus
● Slightly acidic, with a pH of about 5-6.5 (although some mushrooms, such as oyster mushrooms, can tolerate higher pH values)
● Have a structure that allows for air exchange
● Contain 50%–70% water content
● Free of microorganisms, mold, and bacteria
The last one is especially important, because any microorganisms, mold, or bacteria remaining in the substrate will compete for available water, nutrients, and energy—preventing spore germination, mycelium development, and mushroom growth. To completely remove contaminants from the substrate, growers must first prepare the substrate using one of two preparation methods: pasteurization or sterilization.

Pasteurization involves exposing a substrate to mild dry or steam heat — usually less than 100° C (212° F) — for a brief period of time to kill off pathogens. Pasteurization is popular with smaller growing facilities because it does not require any special equipment — just a reliable heat source — and with larger facilities because it is easy to use and highly scalable.

That said, pasteurization does not completely eradicate all microorganisms, only pathogenic bacteria. That means that any substrate prepared using pasteurization could still contain other microbes (albeit in a weakened state), including fungi, viruses, mold spores, and other forms of bacteria, which could prevent mushroom spores from taking root and growing. It’s also worth noting that certain substrates, particularly supplemented substrates, cannot be prepared through pasteurization.


Sterilization is another popular method of substrate preparation, one that totally eliminates all bacteria, microorganisms, and other contaminants from your preferred substrate. There are quite a few sterilization techniques growers can use, including exposure to ultraviolet light or chemicals and hot water immersion, but steam sterilization is the most effective.