Now the Yangs are looking for some relief from the summer sun that beats down on their 15 acres of long beans and cherry tomatoes. Mushrooms, which grow indoors at room temperature, might be the answer.

Half of the edible fungi enjoyed by Americans are the white button variety, commonly seen on pizzas, in salad bars and in canned cream of mushroom soup. However, consumers are now seeking out the unique flavors of specialty mushrooms, such as shiitake, oyster and portobello, opening up a market for mushrooms grown on a much smaller scale.

UC Cooperative Extension (UCCE) researchers are studying the best and most economical ways for small-scale producers to break into the burgeoning mushroom business and sharing the information with those who might like to give it a try.

Certain specialty mushrooms, like truffles, porcini, chanterelles and morels, grow only on living organisms. To date, nobody knows how to effectively cultivate them.

“If you figure this out, you’ll be a millionaire overnight,” said UCCE plant pathologist Mike Davis at a recent mushroom meeting at the UC Kearney Research and Extension Center near Parlier.

Fortunately, poisonous mushrooms fall into this category. Farmers need not fear accidentally growing the notorious “death cap” or “destroying angel” on their farms. A good species for inexperienced farmers to start with are oyster mushrooms, according to Davis.

“Oysters are the weeds of the mushroom world,” he said.

Besides, oyster mushrooms have good flaor, firm texture and can be used in a wide variety of gourmet dishes. Or, they may be simply sautéed in olive oil or butter and seasoned with garlic, salt and pepper to top grilled meat or cooked pasta or to be eaten on their own.

Oyster mushrooms grow on dead organic matter, and almost any kind will do – coffee grounds, straw, sawdust, shredded newspaper, cardboard, leaves and other yard trimmings. The substrate must be sterilized or pasteurized so edible fungi can colonize it without competition from other organisms generally present in the environment.

UCCE Fresno County small-scale farm advisor Richard Molinar and his assistant Michael Yang have adapted a system of oyster mushroom production that, they believe, was first developed by Chinese producers. The researchers purchased inexpensive cotton seed hulls from a local cotton gin. After the substrate is boiled in a vat of water and allowed to cool, a commercial oyster mushroom “inoculum” is mixed in. The blend is packed into plastic bags about 24 inches long and 20 inches around that are open at both ends. At each end, the bag is threaded through a small collar of PVC irrigation pipe. The opening is covered with a small piece of newspaper held in place with a rubber band.

Once prepared, the bags may be stacked in a ventilated greenhouse, insulated barn or out-building where the temperature can be kept at 70 to 80 degrees (Fahrenheit) as the fungi grow rapidly to colonize the material in the bag. When the fungi run out of room inside the bag – in three to four weeks – a bouquet of mushrooms breaks out through the newspaper (see photo). At this point, high humidity – about 95 percent – is necessary to prevent the mushrooms from dehydration as they grow to a marketable size.

Santa Clara County farm advisor Maria de la Fuente has researched the use of composted municipal yard trimmings – called “greenwaste” – for mushroom production. California produces more than 10 million tons of grass clippings, tree leaves, limbs and twigs, vegetable cuttings and other greenwaste every year. Working with the city of San Jose, which is interested in finding alternative uses for greenwaste, de la Fuente made arrangements to study three substrate formulas based on greenwaste San Jose residents placed in their recycling bins. De la Fuente’s aim was demonstrating inexpensive mushroom production as a way for farmers to diversify their operations and boost the bottom line while reducing municipal waste.

De la Fuente modified a storage shed with insulation, inexpensive plastic shelves and a misting system for humidity. She packed composted greenwaste in bags and spread the sealed bags in the sun so heat generated by “free” solar energy pasteurized the substrate, a process called “solarization.” Commercial oyster mushroom inoculum was later added, the bags were perforated and placed on shelves in the shed, where a few weeks later, oyster mushrooms were ready for harvest.

“We grew food from garbage,” de la Fuente said triumphantly.

Because mushroom growing is rather simple, there is room for improvisation and creativity. For sterilizing substrate, Davis commissioned a stainless steel drum from a welder and made a basket out of screen purchased at a hardware store. A common propane burner completes the system. Molinar suggested the Central Valley’s high summer heat makes the substrate solarization tested by de la Fuente a particularly promising option for growers. A readily available patio misting kit, he said, could provide the humid environment.

Heulong Siong, a strawberry farmer of Hmong descent who also attended the mushroom cultivation training program, said he felt confident about producing mushrooms, but is concerned about marketing.

“Strawberries, they buy,” he said. “Mushrooms, I don’t know who will buy.”

Regardless, he may give it a shot.

For more information on mushroom cultivation, contact:

Mike Davis, (530) 752-0303, rmdavis@ucdavis.edu

Richard Molinar, (559) 456-7555, rhmolinar@ucdavis.edu

Michael Yang, (559) 456-7189, myang@ucdavis.edu

Maria de la Fuente, (408) 282-3131, medelafuente@ucdavis.edu

click for high resolution image

Bright yellow oyster mushrooms.