Cultivation of Shiitake on Natural and Synthetic Logs

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Shiitake have been enjoyed for centuries in Asia because of their health-promoting properties. Now consumers in Western countries endear shiitake because of their unique culinary characteristics. Shiitake can be found on supermarket shelves nationwide. Shiitake are an excellent source of selenium, a very good source of iron, and are good sources of vitamin C, protein, and dietary fiber.
The shiitake, Lentinula edodes, begins life as an invisible network of pale, spidery threads that burrow through the dead tissue of various hardwoods—oak, beech, chestnut, or the shii tree (from which the mushroom derives its name). The threads, or mycelia, digest the wood and convert it into fungal tissue. When the wood has deteriorated sufficiently, the fungus produces fruit. In the wild, the mushrooms that pop out of the wood from spores, which the wind blows to new logs, starting a new life cycle.
In China, shiitake have been cultivated on notched logs stacked in evergreen forests since as early as 1100 ad. It is believed that Chinese growers introduced shiitake cultivation techniques to Japanese farmers, who named the mushroom and were later responsible for its spread eastward. Centuries later, in 1972, the U.S. Department of Agriculture lifted a ban on importing live shiitake cultures, and the U.S. shiitake industry took off. Between 1986 and 2008, total U.S. production of shiitake increase from less than 1 to 10.2 million pounds, while the price dropped from $5.40 to $2.81 per pound.
Recent trends suggest that, in the future, most shiitake will be cultivated on synthetic logs. This is especially true for the United States. The major advantages of producing shiitake on synthetic logs compared with producing shiitake on natural logs are as follows: consistent market supply through year-round production, increased yields, and decreased time required to complete a crop cycle. These advantages far outweigh the major disadvantages of a relatively high initial investment cost to start a synthetic log manufacturing and production facility.
Natural and synthetic log production of shiitake are described in their normally occurring sequences. The explanations emphasize the salient features within each production step. First, let’s examine natural log cultivation to see how shiitake have been grown for nearly a thousand years. Then, let’s look a synthetic log production, or how most shiitake are produced.
Total commercial mushroom production worldwide has increased more than twelvefold in the last twenty-five years from about 1,060,000 t (one metric t = 2,205 lb) in 1978 to about 14,274,000 t in 2003. The bulk of this increase has occurred during the last fifteen years. A considerable shift has occurred in the composite of genera that constitute the mushroom supply. During the 1979 production year, the button mushroom, Agaricus bisporus (A. brunnescens Peck) accounted for over 70 percent of the world’s supply. By 2003, only 30 percent of world production was A. bisporus. The People’s Republic of China is the major producer (10,387,000 t, or about 73 percent of the total) of edible mushrooms. In 2003, China produced 2,227.6 t of shiitake, or about 91 percent of the total worldwide production. Much of China’s production is exported either fresh or dried. The United States, Canada, and Mexico combined produced 10,560 t (about 0.2 percent of the world supply) of shiitake in 2003. Annual increases for shiitake production in the United States have averaged about 10 percent since 1987.

Daniel J. Royse
The Pennsylvania State University