People have harvested mushrooms from the wild for thousands of years for food and medicines. Of the estimated 1.5 million species of fungi, about 10,000 produce the fruiting bodies we call mushrooms. While commercial harvesting of wild mushrooms continues today, most of the world’s supply comes from commercial mushroom growers.
The Chinese first cultivated shiitake (Lentinula edodes) mushrooms around 1100 AD, with domestication efforts beginning centuries earlier. White button mushrooms (Agaricus spp.), most familiar to Ameri-cans and Europeans, were first domesticated in France in 1650. Commercial production began in the United States in the 1880s. Agaricus is the leading mushroom crop worldwide and accounted for 99 percent of the 1997 United States’ mushroom production.
Oyster mushrooms (Pleurotus spp.) were more recently domesticated, and now rank second in world production. Shiitake mushrooms, which are very popular in Asian cultures, rank third. Many other edible mushrooms, such as
straw and wood ear mushrooms, are gaining in popularity.
Roughly 300 mushroom species are edible, but only 30 have been domesticated and 10 are grown commercially. Button, oyster, and shiitake mushrooms make up about 70 percent of the world’s production . During the past 30 years, mushroom production worldwide increased twenty-fold, with much of that increase occurring in the 1980s and 1990s. Increased demand for
specialty mushrooms (everything besides Agaricus) has been particularly strong. Asian countries continue to dominate world production and
consumption, however, consumption in the United States has increased sharply in recent years, providing potential opportunities for mushroom growers.
Mushroom production in the United States has traditionally centered in Pennsylvania, which produces nearly half the nation’s button mushrooms. California and Florida are the second and third leading producers, with limited production in 27 other states. Large-scale growers with established, year-round markets dominate commercial mushroom production. In 1997, 7 percent of United States mushroom farms supplied 20 million pounds or more each, or 38 percent percent of total U.S. production. In contrast, 36 percent of mushroom farms produced less than one million pounds per year.
Even established growers are challenged with recent imports of canned Agaricus from China, Chile, India, and Indonesia. In the face of this competition, the prospects for new Agaricus growers are poor. The number of button mushroom growers in the United States has decreased steadily, from 357 in 1987 to 153 in 1997
The specialty mushroom market in the United States is growing. These mushrooms include oyster, shiitake, maitake, and lion’s mane. Shiitake and oyster mushroom production is a viable choice for small-scale production. These do not require the amount of equipment and facilities of some of the other mushrooms produced in the United States.
The shiitake mushroom is used in food and can be found in health food stores. This mushroom is growing in popularity in the United States due to its flavor and consistency. Production of these mushrooms in the U.S. began in the 1980’s. Shiitakes grow on rotting hardwood; in commercial production, the moisture and temperature of logs used for growing must be carefully controlled. Although large-scale commercial production requires a large commitment in terms of time and money, small scale production or hobby farming can provide supplemental income. Farmers should carefully consider the risks and benefits associated with growing specialty mushrooms before entering in to the venture.
Oyster mushrooms are grown on a sterilized cereal grain substrate and grown in bags or bottles. As with shiitake production, moisture, air movement, light, and temperature must be controlled for best production. These edible mushrooms are relatively easy to produce on a small scale.
Mushrooms lend themselves to many different growing systems from simple and inexpensive to highly sophisticated and expensive.
Shiitake has long been grown on sections of logs about 3ft in length. Oak is the preferred species, although beech, chestnut, and other hardwoods have been used in the United States. Gambel or scrub oak (Quercus gambelii) is found
in parts of the Intermountain West and can be used for shiitake production. Other oak species suitable for growing shiitake are native to Oregon and California. For outdoor production, log sections are inoculated with spawn (a starter mix of fungal mycelium and sawdust or grain) and set aside to allow the fungi to develop. Shade cloth is often used to protect logs stored outdoors from excessive drying caused by direct sunlight. The development period is called the spawn run and last 6 to 18 months, depending on the log species, diameter, moisture, and temperature. At the end of the spawn run, the logs are transferred to a cool, moist raising yard where the mushrooms develop and are harvested.
In outdoor systems, most shiitake production occurs in the spring and
fall. Greenhouses and converted farm buildings are used to produce winter crops. A single log may bear five crops of mushrooms. Some other mush-
room species can also be grown in basic, non-mechanical facilities.
Much of the increase in mushroom production is due to the development of high-yield systems that depend on precise environmental controls.
In 1988, shiitake production in the United States was equally divided between
natural logs and synthetic logs made from sawdust, straw, corncobs, and various amendments. Eight years later, synthetic log production doubled
and now makes up more than 80 percent of thetotal. By using synthetic logs, growers can harvest shiitake mushrooms year-round and produce three to four times the yield in one tenth the time natural logs require.
High yields and rapid production cycles with most mushroom species require specialized facilities. Substrates (materials the mushrooms grow in) are blended and packaged into special plastic bags or jars. Typical substrates include sawdust, grain, straw, corn cobs, bagasse, chaff, other agricultural byproducts.
Containers and substrate are then either pasteurized or sterilized to remove contaminating microorganisms. Hot water baths can be used for pasteurization, but steril- ization may require a commercial steam sterilizer. Some growers compost substrates outdoors and then sterilize them inside heated sheds.
After being pasteurized or sterilized, the substrate-filled containers are inoculated with the desired fungi and placed into spawn run rooms where temperature, humidity, light, and sometimes atmospheric gases are carefully controlled. When the spawn run is complete, the substrate may need additional treatments before mushrooms develop.
Many mushroom species require changes in temperature, moisture, substrate, and/ or light to begin fruiting. Large-scale, highly technical facilities are expensive to construct and operate. Whether you use a basic or sophisticated
production system, growing mushrooms is labour intensive.
A third option for mushroom production is to harvest mushrooms from the wild.