Resources for Mushroom Growers
Specialty Mushrooms

A Small-Scale Agriculture Alternative: Specialty Mushrooms

If you enjoy cultivating the unusual, specialty mushrooms offer many possibilities. The term "specialty" refers to any mushroom except the white button mushroom commonly found in supermarkets. Specialty mushrooms include shiitake, oyster, enoki, wine cap, maitake, and pompom among many others. Selling large quantities of any of these mushrooms may be a challenge unless you are near a large ethnic population (e.g., Asian American) that has enjoyed these delicacies for centuries. Smaller quantities can be sold locally in farmer's markets, as part of a pick-your-own fruit and vegetable operation, to gourmet restaurants, to health food stores, or to local grocery stores. While production of the common button mushroom is a possibility, it is already widely available in grocery stores, and new growers will be competing with large-scale producers in established markets. However, small-scale cultivation of specialty mushrooms could be a profitable addition to your farming enterprise.

About Mushrooms

A mushroom is neither a plant nor an animal, but has properties of each. Modern taxonomists give the fungi, including all mushrooms, a kingdom all their own. Most mushrooms have a "common" name and a "scientific" name. The latter identifies the genus, species, and sometimes the variety of mushroom for the experts. This eliminates confusion since one common name can apply to several different species. Scientific names usually appear in italics with the genus capitalized.

Like plants, mushrooms begin with a "seed", which is actually a microscopic spore. The gills or pores beneath the cap of a parent mushroom produce spores and a single mushroom produces thousands. The wind can easily transport a spore until it comes to rest in a suitable environment and then germinates and grows into a mat of root-like filaments called hyphae. The mat of hyphae is called the mushroom's mycelia. Unlike plants, this outgrowth of a single spore cannot produce a mushroom. Instead, like animals, a sexual union is necessary. In mushrooms, that union occurs when a hyphae from one spore contacts a hyphae of a compatible spore. After joining, the mycelia is capable of producing mushrooms, the fruit of the fungi.

Mushroom cultivators typically use already-growing mycelia called spawn, rather than growing their mushrooms from spores. The spawn can be purchased from several sources or produced in-house on grain. When the spawn is ready to use, each grain kernel has enough living mycelia to begin mushroom growth when introduced to the growing medium or "substrate".

Environmental conditions are the key to cultivating mushrooms. The hyphae may not grow if the substrate is not correct. If nutrients are not sufficient or the weather is not appropriate, healthy mycelia may not bear fruit. Some mushrooms will produce fruit under a wide range of conditions while others are very specific in their needs. Some even require a symbiotic relationship with specific tree species before they will fruit. Mushroom cultivators must understand the requirements of the species they want to grow. After identifying environmental needs, the grower determines whether to grow a particular species outdoors or in a controlled environment. Typically, investments in climate-controlled rooms will be much greater than investments in outdoor growing space. Mycologists are regularly discovering ways to cultivate new species. Let's look at the attributes of a few specialty mushrooms and their requirements.

Shiitake (Lentinula edodes)

Shiitake mushrooms are very popular in Japan. American production of shiitake has increased faster than any other specialty mushroom. Until recently, worldwide production of shiitake was second only to the common button mushroom. Shiitake grow best with certain hardwood species, especially ironwood and oak. Other substrates with a corncob or straw base and several additives can produce shiitake, but they so far haven't proven as good a substrate as the hardwood species. Depending upon the climate, shiitake may grow outdoors on logs. Indoor growers typically use a substrate composed of sawdust and several additives. Current wholesale market prices for shiitake range from $3.50 to $8 per pound, depending upon quality and size. Growers typically get from $4 to $6 per pound for their best mushrooms.

Oyster (Pleuratus spp.)

There are several species of oyster mushrooms that are widely cultivated internationally. Major production increases in China recently moved the oyster mushroom to second place in terms of worldwide production. Some of the more common species include the Indian oyster, tree oyster, golden oyster, pink oyster, and the abalone mushroom.

Unlike the shiitake mushroom, oyster mushrooms grow prolifically on a variety of substrates including most hardwoods, paper, cereal straws, coffee grounds, corn cobs and sugarcane bagasse, among many others. If you have an agricultural or wood waste product in your area, you can probably find a variety of oyster mushroom that will grow on it.

Oysters are most commonly grown indoors in specially constructed growing rooms, which sustain the necessary climatic conditions. They need high humidity and warm, not hot, temperatures. Many growers convert existing barns, stables, or sheds or buy an inexpensive greenhouse that can be insulated. Humidity is provided via misters or commercial-scale humidifiers. Heating comes from whatever inexpensive source is readily available. Most mushrooms, including oysters, require light during their life cycle and daylight florescent bulbs seem to work well.

Other mushrooms require a sterilized substrate. A boiler and autoclave large enough to sterilize commercial quantities of substrate are quite expensive. Oyster mushrooms are so prolific that the mycelia outgrows most contaminants. Thus, pasteurization is generally sufficient. For a chopped straw substrate, pasteurization can be accomplished in a hot (160 degree F) water bath for a couple of hours. After cooling, the spawn is mixed with the straw. One technique for growing oysters uses plastic bags from a roll of tubing usually 8 to 14 inches in diameter. The grower cuts a length of tubing, ties a knot in one end and stuffs the inoculated straw into the bag. When the bag is nearly full, a knot is tied in the other end and the bag is hung in the growing room. Holes are punched in the bag to allow the mycelia to breathe and to provide a place for the mushrooms to pop out.

Oyster mushrooms have several advantages and only a few drawbacks. They are easy to grow using agricultural waste as a substrate. If straw is used as a substrate, the remaining composted material can be used as a feed for cattle or hogs or as a soil amendment after the mushrooms are harvested. On the cautionary side, oysters produce numerous spores which trigger allergies in many people. Usually a respirator is required for lengthy stays in the growing room. Marketing opportunities may be limited since oysters have a relatively short shelf life of approximately one week. Finally, they attract mushroom gnats more than most other species. Current wholesale prices range from $2 to $4 per pound.

King Stropharia or Wine Cap (Stropharia rugoso-annulata)

This mushroom is good for outdoor growing. It can be easily cultivated in a shady bed of hardwood chips and/or straw. Some gardeners use beds in cold frames to produce crops from summer to fall. These mushrooms grow to enormous size, weighing five pounds and more. Unfortunately, these huge specimens are usually filled with fly larvae and unsuitable for human consumption. However, the larvae infested mushrooms do make great fish food! Obviously, the younger mushrooms are the desired edible for people.

Since these mushrooms have not been widely commercialized there is no established market. However, there is the opportunity to combine stropharia with other products of a small farm for sale at a farmer's market or vegetable stand. Expect prices in the $5 per pound range. They also have the advantage of turning your waste woodchips or sawdust into a rich compost while providing mushrooms for several years.

Shaggy Mane (Coprinus comatus)

This mushroom is not typically produced on a commercial basis as it becomes an undesirable mass of black ink within a few hours of harvesting if it is not cooked immediately. Inclusion in a pick-your-own operation may be profitable if customers are carefully taught how to handle this species.

The main advantage is that it is easy to grow and you may already have some growing wild on your farm. It even shows up as a contaminant for growers of other mushrooms, like the oysters. To encourage its growth, you need only inoculate a bed made up of a soil/sawdust, manure/sawdust, or straw/manure mixture and keep it wet. Research from China indicates that this mushroom may suppress the growth of certain types of cancers.

Maitake (Grifola frondosa)

The maitake -- or hen-of-the-woods -- is different. It comes from a group called the polypores. Rather than distinct individuals, this mushroom produces a large clump of interwoven "leaves". It grows wild on dead or dying hardwood trees or stumps in the Northeastern and Mid-Atlantic States. Growth can be induced by inoculating a suitable log or stump with its mycelia. An advantage is that the Maitake can recycle old stumps into forest soil. The major disadvantage is the 3 years it may take to produce any fruit.

More Information

This factsheet only hints at the possibilities of growing specialty mushrooms. You may already have delicious species, like some of those mentioned above or common meadow mushrooms or even giant horse mushrooms already growing on your farm. The details needed for cultivation have not previously been well understood or easily available to the public. Continuing experimentation has led to more accessible information. In addition to the publications that specifically address shiitake cultivation, as noted in the factsheet entitled Shiitake Mushrooms from the Office for Small-Scale Agriculture (OSSA), the following selections may be helpful:

For a quick overview of several species: Organic Gardening Magazine - November 1993

For a more detailed discussion on growing many mushroom species outdoors: Mushrooms in the Garden by Hellmut Steineck. A 152 page book published by Mad River Press. ISBN: 3-8001-6122-2.

For details on both outdoor and indoor cultivation: The Mushroom Cultivator - A Practical Guide to Growing Mushrooms at Home by Paul Stamets and J.S. Chilton. A 415-page book published by Agarikon Press. ISBN: 0-9610798-0-0.

For more details on more species: Growing Gourmet and Medicinal Mushrooms, by Paul Stamets. A 552-page book published by Ten Speed Press. ISBN: 0-89815-608-4.

For a comprehensive mushroom guide with over 1,000 color photographs: Mushrooms of North America by Roger Phillips. A 319-page book published by Little, Brown and Company. ISBN: 0-316-70612-4.

For a monthly update on prices, marketing information, and production techniques: The Mushroom Growers' Newsletter, P.O. Box 5065, Klamath Falls, OR 97601,Published monthly, 8 to 10 pages, $35 annually.

By Jerry Haugen, P.O. Box 5065, Klamath Falls, OR 97601 and George B. Holcomb (Retired), Office of Communications, U.S. Department of Agriculture, for USDA's Office for Small-Scale Agriculture (OSSA); Howard W. "Bud" Kerr, Jr., Program Director. OSSA's address: Ag Box 2244, Washington, DC 20250-2244. Telephone: 202-401-1805; Fax: 202-401-1804.

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July 1994