Growing Mushrooms

Mushroom production is completely different from growing green plants. Mushrooms do not contain chlorophyll and therefore depend on other plant material (the "substrate") for their food. The part of the organism that we see and call a mushroom is really just the fruiting body. Unseen is the mycelium—tiny threads that grow throughout the substrate and collect nutrients by breaking down the organic material. This is the main body of the mushroom. Generally, each mushroom species prefers a particular growing medium, although some species can grow on a wide range of materials.

If you are considering mushroom production, become thoroughly familiar with the life cycles of fungi. A very general description is included below. A plant pathology textbook is a good resource for learning more about these complex life cycles.

Once you are familiar with the various fungi life cycles, learn the growth requirements of each of the species you are considering. Two basic references are The Mushroom Cultivator, by Stamets and Chilton, and the aforementioned Growing Gourmet and Medicinal Mushrooms by Stamets (See Resources).

Growing mushrooms outdoors as a part of a market garden involves little effort after you have inoculated the logs or other substrate with the mushroom spawn. Your duties are mainly to maintain humidity and monitor for fruiting. When mushrooms appear, you add them to your other garden products and sell them. (See Mushrooms on the Farm and in the Garden, Below)

Most available markets, however, require more mushrooms than occasional fruiting provides. Indoor production can fill the gaps when outside fruiting lags. The entire operation can also be conducted inside. However, indoor mushroom production demands a much higher level of knowledge, continuous monitoring, and timely manipulation of environmental conditions.

These are the steps in mushroom production—a cycle that takes about 15 weeks (time varies by species) from start to finish.

• Choosing a growing medium
• Pasteurizing or sterilizing the medium
• Seeding the beds with spawn (material from mature mushrooms grown on sterile media)
• Maintaining optimal temperature, moisture, and other conditions for mycelium growth and the conditions that favor fruiting (This is the most challenging step.)
• Harvesting, packaging, and selling the mushrooms
• Cleaning the facility and beginning again

The substrate on which the mushrooms will fruit must be sterilized or pasteurized in order to destroy any fungal and/or bacterial competitors. Low-tech substrate preparation methods are described in the books by Paul Stamets and by Peter Oei (See Resources).

To produce spawn, you inoculate a pasteurized medium, usually grain, with the sterile culture of a particular mushroom species. After the culture has grown throughout the medium, it is called spawn. Producing spawn requires exacting laboratory procedures. Terri Marie Beauséjour, cultivation chair for the Mycological Society of San Francisco, has written an excellent article that can help the beginner who is put off by the technical aspects of mushroom cultivation. Titled "Getting Started with Mushroom Cultivation: The Wisdom of Simplicity," it is available on the Web at www.mykoweb.com/articles/cultivation.html.

Many mushroom suppliers sell several kinds of spawn, and the beginning mushroom farmer should take advantage of this selection in early trials to determine which species grow best on available materials. Eventually, learning to produce spawn might reduce your cost of production. Evaluate this possibility only after you have mastered the later stages of cultivation.

While the mycelium is growing—and until it fully occupies the substrate—the mushroom farmer typically manipulates the growing environment to favor mycelial growth. The atmospheric conditions are then changed to initiate "pinheads," and then to complete fruiting. For example, in oyster mushroom production under closely controlled conditions, the grower lowers the temperature and the CO2 in the grow room to initiate fruiting. Each species has specific requirements for its stages of development. The Mushroom Cultivator provides detailed information on the requirements for 16 species.

When you can cut the time between harvests, annual production increases. Short cycles are what the large-scale commercial producers aim for, constantly looking for ways to increase efficiency. This is the competition you face if you plan to sell your product on the wholesale market.

Paul Stamets of Fungi Perfecti, an educational and mushroom supply company
(See Recources), has spent most of his life studying the growth and cultivation of fungi. His book Growing Gourmet & Medicinal Mushrooms (See Recources) is an invaluable resource for anyone considering the cultivation of any mushroom species. He describes several alternative methods of producing mushrooms, including growing them outdoors on logs, on stumps, and in the garden, as well as indoors in bags or on columns.

Peter Oei, in Manual on Mushroom Cultivation (See Recources), describes in some detail how alternative mushroom production systems have been used successfully in developing countries. Many ideas for low-input systems are included. In practice, it is unlikely that the beginner can successfully compete in the wholesale market against highly capitalized and efficient mushroom companies. A better choice for the beginner is to develop a niche market for high-quality fresh mushrooms, then sell them at retail, or to produce a value-added mushroom product, such as a soup mix or sauce.
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