Getting a Year-round Harvest from Japanese Forest Mushrooms

Getting a Year-round Harvest from Japanese Forest Mushrooms

by Albert Bates, Mushroompeople

The shiitake (pronounced she-eh-ta-kay) mushroom is one of the most popular foods in Japan and a major staple in China and other parts of the Pacific Rim. As a protein source, it has the combined attributes of being appetizing, nourishing, dietetic, and healthful. In Japan, it is often eaten three times per day.

• Shiitake contains all 8 essential amino acids in better proportion than soybeans
• Shiitake contains a good blend of vitamins and minerals, including vitamins A, C, and D, and Niacin
• As little as five grams of shiitake taken daily reduces serum cholesterol and blood pressure dramatically
• Shiitake produces interferon and interleukin compounds which strengthen the immune response to protect against cancer and virus infections
• Shiitake produces a fat-absorbing compound which aids in weight reduction

Although shiitake has been cultivated in Asia since at least the time of Christ, it is still relatively insignificant as a food crop in the West. One reason is the confusion of Dept. of Agriculture scientists who mistook shiitake's Latin name, Lentinus edodes (oak fungus), for the fungus that attacks railroad ties, Lentinus lepideus. USDA instituted a complete quarantine on shiitake imports that only ended when the mistake was officially recognized in 1972. Today, health conscious cooks are taking a cue from the handful of food gourmets who make shiitake a regular part of their diet.

Shiitake grows on hardwood logs under forest shade where cold running water is nearby. In Japan, the shiitake industry is responsible for the retention of at least 10 percent of the forest in that country. Without the money which the mushroom trade brings in, small farmers would have cut their forests or sold the land to developers long ago. With shiitake, they have kept their farms in productive forest and used mushroom revenues to support other traditional farming activity.

Deep Forestry

"Forestry" as the term is used most often today, literally fails to see the forest for the trees. Recently, a soil scientist in Oregon (David Perry at the Oregon State University, whose work is reported by Dan Wheeler in the Spring 1994 of Mushroom The Journal.) microscopically examined about a half a cubic foot of untrammelled ancient forest soil and discovered some 7,000 new species of life, including arthropods, mites, copepods, centipedes, millipedes, wireworms, psuedoscorpions and other organisms. He hopes to have them all described by the year 2005. This richness in healthy soils is entirely thanks to the workhorses of waste management--the forest fungi. Fungi make up 52 to 55 percent of forest biomass and about 95 percent of all plant life survives by virtue of symbiotic relationships with mycorrhizal fungi.

Forest management from a myco-optic perspective becomes a task of healthy soil replenishment by making available lots of woody wastes together with suitable micro-climates for the proliferation of the primary decomposers: bacteria and fungi. It involves continuous thinning, pruning and selective harvest--but it is aimed at maintaining a full canopy of rapidly-growing, healthy trees above and a depth of waste matter in various stages of decay below. In a young forest stand, this may require thinning up to 80 percent. In an older stand, perhaps only one or two trees can be removed in an acre of forest each decade.

Mushroompeople is a cottage industry of The Farm, an experimental village begun in 1971 by Stephen Gaskin and 320 hippies fleeing the Haight Ashbury. Our interest in mushrooms dates to that early period of our development, but in recent years we have grown increasing concerned about the future of Earth's forests and have discovered that mushrooms have something to contribute to forest preservation as well. The Farm manages more than 2 square miles of hardwood forest as part of our freehold, and we are interested in preserving its biological integrity.

One thing we have learned is that the nutritional value of shiitake as a protein source and its medicinal and dietetic benefits have made this mushroom very popular in Japan and China, encouraging small farmers to keep large areas of land forested. We fully expect that health-conscious consumers in North America and Europe will develop an interest in shiitake for much the same reason. Shiitake cultivation can then serve to protect North American stands of hardwoods in much the way it has saved trees in China and Japan.

Since shiitake is one of the easiest mushrooms to grow and the techniques developed for shiitake growing carry over to many other saprophytic species of mushrooms, learning to cultivate shiitake can lead to a good understanding of mushrooms in general. Many people are afraid to begin growing forest mushrooms because of early childhood associations of mushrooms as poison. When you cultivate particular mushrooms however, you know what to expect and are not likely to confuse what comes up with something else that is not good for you. Shiitake, with its cracked, fleshy top--deep brown in the center and lightly misted with white flecks at the edges--is difficult to confuse with other oak-dwelling mushrooms.

Getting Started

Shiitake prospers in sixty percent or better shade outdoors (not darkness) where ventilation is good. Running water is needed several times a year but not continuously (the bark should dry out between waterings to avoid destructive surface molds). Shiitake yards are usually in places one can easily visit daily, not too remote from other activities. Indoor production, often used for commercial operations where continuous fruiting is desirable, requires environments which approximate outdoor conditions, with variable temperature, lighting, humidity and ventilation. Many farmers have found converted poultry houses and tractor sheds make ideal growing barns.

Felling

Oak logs are usually used, but many other hardwoods can also produce shiitake. Young, living, healthy trees are selected from stands needing to be thinned. Care is taken to avoid damaged bark, sections with bark less than 1/8" thick (too fragile!), logs over 7" thick (too heavy!), deadfalls, and logs of uncertain age or origin. Among commercial growers, a standard width is 4", cut 30" to 48" long. Pines and other conifers will not produce shiitake.

The "perfect" time to fell trees is the fall and winter; felling in summer produces lots more contamination as well as lowered yield. Winter-felled trees may be kept until spring if the internal moisture content remains above 35%, but it is recommended to inoculate within 3 weeks of felling, if possible.

Optimal moisture content for spawning is 35 to 45 percent. This is not bark moisture, which can be affected by spraying or rainfall, but core moisture, which can only be affected by soaking or moisture conservation after cutting.

Strain Selection

There are three basic strain categories:

1) year round fruiting (wide-range);

2) winter to spring (warm);

2) fall, winter, and spring (cold).

The best types for most uses are the year-round, wide-range strains. These produce quickly and easily, so logs turn over more rapidly and less growing area is required. Warm weather types are usually grown for dried mushroom production, and often require two to three summers after inoculation until the first flush. The cold weather types generally fruit two summers after inoculation although there are some varieties which will produce mushrooms the first fall after spring inoculation. Cold weather strains are most likely to produce the highest grade, or what the Japanese call "donko" (flower-petal) mushrooms.

All strains need one full summer before they will produce. Generally, the more spawn you put into a log, the sooner it will produce its first crop when environmental conditions are right.

Inoculation

Commercial sources supply spawn in three forms: on wooden plugs (dowels), in sawdust, and in grain. Plugs are inoculated by pre-drilling the logs. Sawdust is inoculated by either predrilling and using a special pressure inoculation tool, or by making a saw-cut and packing the cut with spawn. Grain spawn is used to produce mushrooms in a greenhouse, on sawdust or wood chips. The standard methods of inoculation are quite simple, so that two workers can put up 300 logs in a day.

Wooden-plug spawn (easiest method)

1. Drill. Use a 5/16" (8.5 mm) drill bit. Beginning two or three inches from the end of the log, drill close-spaced rows (2-4" between holes), 11/4" deep. Move down the log, drilling rows every 6 to 8 inches until you get 2 or 3 inches from the other end.

2. Hammer. Tap wooden plugs flush with a hammer, leaving air space below.

3. Wax. Apply hot melted wax to seal in moisture and protect spawn.

Sawdust spawn (commercial technique)

1. Drill. Use a 3/8" to 5/8" drill bit (7/16 is best), to drill rows of holes on 2 to 4-inch centers, 3/4" deep, 6" apart.

2. Fill. Pack spawn firmly to rim of hole. No air space is necessary.

3. Wax. Seal with hot wax.

Spawn Run

After inoculating, it takes 4 to 10 months before the log is completely colonized by the fungus. Freshly inoculated logs are temporarily stacked in square criss-cross tight piles (crib stack) in the shade and covered with canvas or polyvinyl for about 2 months. Some growers cover them with shade cloth or burlap and after each rainfall uncover the logs to allow the bark to dry, to prevent growth of unwelcome fungi.

Cold temperatures cannot hurt the spawn, although growth will diminish when temperatures are below 43!F. Snow cover does not hurt the logs. Spawn can die above 100!F, so in the Southern tier, growers protect their logs from overheating by watering them and keeping them well-shaded and ventilated.

After 2 months, the logs are restacked in a loose crib stack or a lean-to stack. The slant angle is determined by the sunlight, with the objective being to keep as little of the log exposed to direct sun as possible (unless air temperature is always below 43!F and some solar warming is desirable). The spawn run is nearly complete when fuzzy white blotches appear at log ends or mushrooms sprout after a rainfall. To reduce the chances of contamination by wild fungi, some growers rotate spawn yards each year, moving logs to the "permanent" laying yard after shiitake mushrooms have appeared.

Fruiting

Once the spawn run is complete, mushrooms can be forced to appear by soaking. To get optimum, more or less continuous, production, commercial producers "cycle" about 1/7 of their producing logs each week as follows:

1. Logs are soaked for 6-36 hours, depending on temperatures, usually in a 55-gallon drum, tub or stock tank. If air is warm and water is cool, the soak can be 6-12 hrs. If air is cool and water is cool, longer soaking is recommended. If bubbles no longer appear on the surface of the logs, they are totally saturated and are removed.

2. Many growers "thump" them into position for fruiting. Some Asian growers use mechanical vibrators or electric shock. Many recommend "cold shock" (very cold water) as the most effective way to force fruiting.

3. "Pinning" occurs as the primordia push through the bark. Careful management during pinning can result in higher yields. Optimal conditions call for maintaining the logs between 55 and 65% moisture at 55 to 65!F until small bumps form under the bark.

4. There is at least a 30 day wait after a harvest before soaking again. This "rest period" is essential to allow the mycelia to store more nutrients.

Some growers use clear poly covers reaching to the ground to control moisture loss for several days after soaking. Some use poly to keep rain off the logs during the rest period, or during the harvest period (wet shiitake doesn't keep as well). Special felt blankets are often used on the West Coast and Northern Plains, where excessive drying is a problem.

Harvesting

The mushrooms are harvested after the veil breaks while the caps still have curled edges and are less than 4 inches in diameter. During cool weather, the mushrooms are left on the logs for many days. When it's warm, growers harvest early and often, to minimize bug damage and discoloration from spore discharge.

Fresh shiitake will keep for 2-3 weeks in the refrigerator, but should be marketed within 4 to 5 days from picking. They usually reach market in small (strawberry) baskets, cloth or paper bags, or in perforated cardboard boxes (unsealed). Shiitake which can't be sold fresh locally can be dried and shipped to commercial packagers. One packager, Hardscrabble Enterprises of Cherry Grove, West Virginia, offers a standard price of $15 per pound, dry weight.

It is possible to fruit shiitake at any time of year. Therefore the production can be scheduled to coincide with labor availability and to keep a constant supply in the market. Continuous production encourages consistently high prices, typically $3 to $9 per pound, fresh weight. Fresh weight is about 7 times more than dry weight, so growers usually try to sell shiitake fresh whenever there is a local market.

Left to nature, a log will fruit for as many years as its diameter in inches. Forced fruiting speeds crop production but also shortens the productive life, since each log has a fixed available quantity of nutrients, which, once exhausted, are gone.

Calculating Production Rates

A one person farm (less than 5000 logs) can produce 45-65 pounds per day (at 0.25 to 0.33 lb/flush/log). A two person farm (5,000-10,000 logs) can produce about 110 pounds per day. A four person farm (20,000-30,000 logs) can produce about 220 pounds per day. Labor is needed for soaking the logs, harvesting the mushrooms, packaging them, and then selling them. A small farm with perhaps a father and his son and hired help in season, inoculating 4,000 logs/yr will generate $20,000 to $30,000 pre-tax annual income or about $10 per hour of labor, assuming an average sale price of $4 per pound. If a steady buyer at $8 per pound can be found, returns go up dramatically. For this reason, many shiitake farmers devote as much time to marketing as to production, driving long distances to service gourmet restaurants and halth food stores.

Shiitake has adequate nutritional qualities to serve as a main dish. It's oriental mystique gives it an easy entr into the vegetarian/health food/gourmet circles. As the baby boomers begin to age (the leading edge is now 45 and the back edge is 25), they will demand foods that are filling without being fattening. Endowed with blood-pressure lowering qualities and a demonstrated anti-viral property, shiitake sales could take off quickly as this flavorful mushroom becomes for America what it has already become in Japan: a popular all-around food.

Returns for Raising Shiitake Mushrooms on One Cord of Wood

All figures are approximate. No cost is assigned to logs or to labor. Logs per cord: 300 (4" diameter, 42" long). Inoculation holes per log: 25. Mushroom drying ratio: 7 pounds fresh produces 1 pound dry.

Inoculation Costs Per Cord Per Log

Using plug spawn:

1000 dowels/bag, 10 bags @ $35 $350 $1.16

(easier & faster, fewer contaminated logs)

Using sawdust spawn

15 bags spawn @ $19 $285 $.95

Less expensive, produces mushrooms sooner)

Expected returns over four years - at wholesale prices

All sold fresh: 2.25 pounds/log

x 300 logs x $4/pound $2700 $9.00

All sold dried: .325 lbs/log

x 300 logs x $13/pound $1267 $4.22

70% sold fresh, 30% sold dried: $2270 $7.57

>From 1988 to 1991, some 230 U.S. shiitake growers increased production from 3.7 to 4.1 million pounds and earned from $22 to 22.4 million/year in gross sales, about $4.17 per pound. Local wholesale rates vary from $3 to $9 per pound.

For more information about growing shiitake, we recommend Growing Shiitake Commercially by Bob Harris ($13.50), which is available post-paid from Mushroompeople (P.O. Box 220 Summertown TN 38483-0220). Mushroompeople, which is the oldest shiitake spawn company in North America, also offers a free catalog with a wide selection of shiitake spawn, tools and equipment. A starter kit for beginners, with everything you need to inoculate ten logs for your home kitchen, sells for $19.

Mushroompeople PO Box 220 / 560 Farm Rd. Summertown TN 38483-0220 Email: NATLAW@igc.apc.org Int'l Voice/Fax: (int. code +) 615-964-2200 U.S. Fax: 1-800-MYCOFAX

Copyright 1994 The Second Foundation

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