Because sterile conditions are required to begin the life of a cultivated mushroom, the entire operation begins in a laboratory. The spores, or natural seeds of the mushroom, are so minuscule that the mushroom grower cannot handle them. Laboratory personnel inoculate sterile cereal grains with the spores and incubate them until a viable product is developed. These grains become "spawn" which can then be sown like seed.

At the farm, the grower carefully prepares the substrate, the basic growing medium for mushroom production. Two types of starting material are generally used for mushroom substrate: synthetic compost consisting of wheat or rye straw, hay and/or crushed corn cobs or manure-based compost made from stable bedding from local race tracks and horse stables. Both types of substrate require the addition of other supplements.

The substrate is produced outdoors on a concrete slab, commonly referred to as a composting wharf. The ingredients are thoroughly mixed, wetted, and placed in large piles to initiate the composting process. As the starting materials degrade, the substrate continues to be mixed, watered and supplemented for about 15-25 days. The outdoor process is followed by an indoor pasteurization cycle to kill any pests that are present in the substrate.

Inside the growing houses, the pasteurized substrate is placed in stacked, wooden trays or beds, the spawn is mixed in and a top layer (usually of peat moss) is applied. From this point, it takes about a month to produce the first mushrooms for harvest. Throughout the growing period, temperature and humidity are carefully controlled.

Mushrooms mature at varying times, so picking by hand is continuous for six to ten weeks. The tray or bed is then completely emptied and the entire growing area is pasteurized with steam before a new crop is started.

Mushrooms are one of the most difficult commodities to grow. Intensive labor is required to produce a consistent, high-quality crop. Also, mushroom farms today are highly technical operations, complete with extensive computerized systems to monitor each point in production.