By Dan Burden, content specialist, AgMRC, Iowa State University, djburden@iastate.edu.

Revised May 2009 by Diane Huntrods, AgMRC, Iowa State University.


Overview
Although over 2,000 varieties of mushrooms are edible, only a handful have become important in the American diet. The mushrooms most familiar to U.S. buyers are the "whites" or common button agaricus. Other varieties of agaricus, the criminis and portabellas, are known as the “browns.” Shiitake (shee tah kay), oyster, wood ear and enoki (e nok e) mushrooms are also popular. Particularly in the Pacific Northwest and the northeastern United States, seasonal species such as morels, oysters and chanterelles are gathered in the wild and sold at farmers' markets and through retail stores. U.S. consumers continue to purchase increasing amounts of fresh, canned and dried mushrooms, both domestic and imported.

Production
Overall mushroom production continues to decrease even as the value of mushroom sales increases. During the 2007-08 season, 809 million pounds of U.S. mushrooms were produced, down 2 percent from the 2006-07 season. The total value of the crop was $964 million, with little change from the previous season. The number of commercial mushroom growers is up by six, reaching 286. The average price for U.S. mushrooms was $1.19 per pound, up 3 cents from last season.

Agaricus
Most commercially produced mushrooms are agaricus species. During the 2007-08 season, the sale of agaricus mushrooms totaled $914 million, down slightly from last season. Of the 793 million pounds of agaricus produced that season, the majority, or 675 million pounds, were grown for the fresh market and 118 million pounds were processed.  Brown mushrooms (portobello and crimini varieties) accounted for 13 percent, or 105 million pounds, of the agaricus mushrooms sold. The value of the brown mushroom crop for 2007-08 was $143 million, or 16 percent of total agaricus sales.

Pennsylvania is the leading state producing agaricus mushrooms. The state supplies 63 percent of the nation’s production, with California second at around 14 percent of U.S. production. Farms that produce Pennsylvania's 497 million pounds of mushrooms per year are concentrated in the southeastern portion of the state. The value of the crop totaled over $453 million.

Specialty
The sales of specialty mushrooms, such as shiitake, oyster and similar unusual mushrooms, remains strong. In the United States, sales for commercially grown specialty mushrooms in 2007-08 was $50 million, up 9 percent from the last season. The average price per pound received by growers, at $3.08, is down 16 cents.

Organic
While only representing two percent of total 2007-08 sales, mushrooms that are certified organic are an area of increasing interest. Growers sold 39.8 million pounds of certified organic mushrooms during the 2007-08 growing season, nine percent more than in 2006-07. Agaricus mushrooms accounted for 84 percent of the certified organic mushrooms sold, while all specialty mushrooms made up the remainder. The number of certified organic growers now totals 42 and represents 15 percent of all mushroom producers (NASS 2008).

Cultivation
Most hobbyists or small-scale growers should begin by cultivating such easy-to-produce specialty mushrooms as shiitakis and oyster mushrooms. The criminis and other agarics that are commercially grown by large-scale operations are labor- and technology-intensive species, and it is not cost effective to try to compete with large-scale production systems. Likewise, some of the other high-value species (morrels, truffles) also are very labor or technology intensive.

Small-scale mushroom production represents an opportunity for farmers interested in an additional enterprise and is a specialty option for farmers without much land. Many small-scale production systems are well suited to market gardeners who wish to incorporate mushrooms into their vegetable production systems and for those individuals interested in using mushroom cultivation as a way to add value from the material derived from thinning woodlots and similar “waste” materials. Mushroom production can play an important role in managing farm organic wastes, encouraging the production of value-added bedding materials from agricultural and food processing by-products.

All commercial mushroom production involves the purchase or production of substrate (bedding-compost) material. This is an intensive aspect of production for large-scale producers; however, it can be quite manageable for small-scale producers and hobbyists. The substrate or compost must be “spawned” with mushroom mycelium that must then be allowed to develop in the compost mixture. This usually is done under relatively aseptic conditions. At some point, after the mycelium has fully colonized the substrate, the “cast” is exposed to air, and perhaps soil and water, to promote formation of marketable fruiting bodies.

Many hobbyist kits and other small-scale production systems use a similar strategy to produce spawn under relatively aseptic conditions. In these systems, the spawn is mixed into a sawdust-based substrate watered and stimulated to fruit. For other species like the oyster mushrooms, the substrate is chopped wheat straw or cottonseed hulls or some mixture of the two, but production is similar. Many kit manufacturers and supply houses market “ready for production” pre-spawned sealed bags of spawned substrate. This, in itself, has become a value-added business for many specialty mushroom growers.

Most U.S. specialty growers use some sort of “synthetic log” production system. Sawdust is the most popular ingredient used in synthetic substrate formulations for shiitake and many other high-value species. Sometimes sawdust is substituted for straw or corncobs. Usually a starch-based supplement, wheat bran, rice bran, millet, rye, corn and so on, is added at a 10 percent to 40 percent dry weight ratio. The starch-based material serves as an additional nutrient source for optimum growth. Many small-scale production systems are simple and inexpensive to establish, with information and materials being readily available from on-line sources and mail order suppliers.

Additionally, there are numerous spawn suppliers throughout the United States and Canada. Besides experimenting with different strains, commercial growers are encouraged to purchase spawn from more than one spawn supplier. Mixing inoculum and spawn sources ensures that different strains can be merged to produce the best mushroom under the specific growing conditions of the operation. Individual strains vary from one to the other. In some cases, strain variability may be extreme. In a Minnesota research study, it was demonstrated that an eleven-fold difference in yield existed across several shiitake varieties. Many spawn suppliers also sell equipment and supplies related to mushroom growing; product catalogs are often available from them upon request.

With respect to the log production of shiitakes, many hobbyists as well as commercial producers use locally sourced logs or other wood material. For instance, the hardwood tree family most recommended in the United States for shiitake cultivation is the oak genus of the beech family. All oak trees can be used with the possible exception of live oak. The thicker bark oaks such as white and chestnut oak are often preferred over the thinner bark oaks such as red, scarlet and pin oak. Beech, birch, chestnut, chink-a-pin, alder, maple, cottonwood, willow, aspen, poplar, elm and hop-hornbeam also may be suitable. As a rule, the thin-bark, low-density species provide relatively quick mushroom production but only for a short time period. Locust, walnut and all conifers are not suitable for shiitake cultivation.

In Ireland, mushroom production is a rapidly expanding new segment of agricultural production that builds on the greenhouse-production model. These new Irish mushroom farms are family-managed units where the production system consists of three to five “polythene tunnels” similar to U.S. hoop buildings. The Irish industry is based on a satellite grower system, whereby growers are linked into central compost companies that supply spawned compost. These companies then collect, grade and market the finished product. More than 70 percent of growers have contracts with central marketing groups.

Value-added Products
Mushroom pastes, pates and creamy sauces are popular in Europe, while mushroom-based snacks, cakes, teas and beverages are often consumed in Asia. Jerky-like meat-flavored snacks, extruded "puffy" snacks, even mushroom jellies and cakes are popular in China. Mushroom wine is common in Korea, as are alcoholic drinks with mushroom extract in Japan. Patented products include mushroom and fish paste, mushroom-flavored coffee and soy sauce flavored with mushroom juice.

Many people are intrigued by mushrooms' nutritional properties in addition to their culinary appeal. Mushrooms are the only non-animal source of Vitamin D. In addition, mushrooms contain some unsaturated fatty acids and provide several B vitamins. Some even contain significant vitamin C, as well as potassium, phosphorus, calcium and magnesium. Mushrooms contain many essential amino acids; white agaricus mushrooms, for example, contain more protein than kidney beans. Shiitake mushrooms are less nutritious but are still a good source of protein. Some mushrooms could be a viable and economical source of antioxidants in the diet. Numerous mushroom-based products have been marketed to promote weight loss.

Mushrooms have been used to treat or prevent diseases for centuries. Asian traditions maintain that some mushrooms are natural pharmaceuticals and promote good health. Researchers have confirmed that mushrooms contain substances that may reduce the risk of cancer, boost the immune system and reduce the risk of coronary heart disease. Other therapeutic applications of mushrooms include wound-healing covers, antibacterial mushroom extracts and liver function preparations. At its clinical trials Web site, the National Institutes of Health lists studies involving oyster mushrooms, agaricus mushrooms and shiitake mushrooms. 

Prices
Prices for fresh mushrooms are considerably higher in winter than during the rest of the year. Some growers in temperate regions use greenhouses for winter mushroom production in an attempt to expand into the winter market. In many of the greenhouse production systems, water-soaked logs or flats of wood waste are inoculated with spawn and allowed to decompose and fruit. Following the first harvest, the logs are allowed to continue to incubate (up to three months), and the process is repeated (usually up to five times).

Marketing
Some parts of the country support mushroom-marketing cooperatives. These groups may be an important asset for developing a new business and may purchase wild-harvested mushrooms and those grown by hobbyists and small commercial producers.

Marketing of specialty mushrooms in the United States is a relatively new enterprise. For most individuals, growing shiitake mushrooms will be easier than selling them. Many growers invest time and money in production and devote little effort toward marketing. Even though shiitake is becoming more popular throughout the United States, growers must be excellent marketers as well as producers to succeed financially.

In recent years, the trend for specialty mushroom sales has been toward the retail market. This trend is driven partly by an increased interest in specialty mushrooms and by the convenience packaged products offered to the consumer. In some retail markets, only 10 percent of the customers buy 90 percent of the specialty types.

Exports
The value of fresh mushroom exports increased 13 percent to $36.9 million in 2008. Canada remained the top buyer of fresh mushrooms, purchasing $22.7 million, a 30 percent increase from 2007. Likewise, Japan remained a major importer of U.S. fresh mushrooms as did France.

Imports
In 2008 the United States imported dried mushrooms valued at $25.6 million, a drop of 13 percent. On the other hand, the value of imported canned mushrooms increased 11 percent to $163.1 million. China remained the top source of both dried and canned mushrooms. However, Italy and France were also major sources of imported dried mushrooms, while Indonesia and India were also major sources of canned mushrooms.

Future Trends
Production and consumption of specialty mushrooms in the United States and other western countries is expected to increase at an accelerated rate in the years to come. As production technology is improved through interdisciplinary efforts, the retail price for specialty mushrooms should decrease. As economies improve in Latin America, production of specialty mushrooms could increase at an even faster rate than in the United States. The culinary advantages offered by specialty mushrooms bode well for the continued growth and development of the specialty mushroom industry worldwide. Specialty mushrooms are sold fresh, dried or processed in Japan and China, so there is room for U.S. exports to address these markets.

Case Study
There are many case studies for successful operations. For nine years, Nicola MacPherson and her husband, Daniel Hellmuth, have grown shiitakes in the Missouri Ozarks on three acres. The mushrooms are grown on oak logs and marketed under the label Ozark Forest Mushrooms. The label carries a USDA organic seal. To sell their mushrooms, the couple has relied on a variety of nontraditional marketing approaches. "To promote sales, you must be prepared to tirelessly promote your product," MacPherson says. Their principal markets are up-scale restaurants, catering companies and gift catalogs. Regional customers who demand organic produce, such as community-supported agriculture subscribers, also provide a reliable market.

MacPherson urges beginners to start modestly, learn the process thoroughly, and develop a small, reliable customer base—say a half-dozen regular customers—as a foundation. At times they have offered free samples to help establish local markets. She cautions new growers not to create a market demand that they cannot meet. Selling to supermarkets, for instance, can be fraught with problems, including the challenge of ensuring product freshness and the recurring need for educating new produce department employees.

Producing associated products such as pasta sauces, pickled mushrooms and canned mushroom may require investment in a commercial kitchen or other specialized equipment. Some products, like sauces, can use frozen mushrooms. Freezing the fresh mushrooms allows the producer or group of producers to regulate their supplies for the value-added product line. This strategy may help to maintain better prices, since in some parts of the country there are gluts of some species at peaks of natural production in the spring or fall. Commercial growers may have peak production periods when the ambient temperature of their facilities is favorable for fruiting (summer). Freezing or drying also is a strategy for converting unsold fresh inventory into a salable product.


Profile created October 2004 and revised May 2009.