All About The Shiitake Mushroom (Lentinula edodes)

Intoduction

Shiitake mushrooms (pronounced shee ta’ kay) are a traditional delicacy in Japan, Korea, and China. For at least a thousand years, Shiitake mushrooms have been grown on logs, outdoors, in the temperate mountainous regions of Asia. To this day, Shiitakes figure as the most popular of all the gourmet mushrooms. Only in the past several decades have techniques evolved for its rapid cycle cultivation indoors, on supplemented, heat-treated, sawdust-based substrates.

Fig. 01: The Shiitake Mushroom

Cultivation of this mushroom is a centerpiece of Asian culture, having employed thousands of people for centuries. We may never know who first cultivated Shiitake. The first written record of Shiitake cultivation can be traced to Wu Sang Kwuang who was born in China during the Sung Dynasty (A.D. 960–1127). He observed that, by cutting logs from trees that harbored this mushroom, more mushrooms grew when the logs were “soaked and striked.” In 1904, the Japanese researcher Dr. Shozaburo Mimura published the first studies of inoculating logs with cultured mycelium (Mimura, 1904, 1915). Once inoculated, logs produce 6 months to a year later. With the modern methods described here, the time period from inoculation to fruiting is reduced to only a few weeks.

Log culture, although traditional in Asia, has yet to become highly profitable in North America—despite the hopes of many woodlot owners. However, log culture does generate modest supplementary income and fits well within the emerging concept of mycopermaculture.

Common Names:

• Black Forest Mushroom
• Black Mushroom
• Chinese Mushroom
• Donku
• Golden Oak Mushroom
• Oakwood Mushroom
• Pasania
• Shiangu-gu or Shiang Ku (Chinese for "Fragrant Myshroom")
• Shiitake (Japanese for "Shii Mushroom)

Description

The cap size of Shiitake mushroom is 5-25 cm broad with hemispheric and expanding to convex which becomes plane at maturity. The cap color may vary from the developmental stages i.e. darker brown to nearly black at first, becoming lighter brown in age, or upon drying. Cap margin even to irregular, inrolled at first, then incurved, flattening with maturity and often undulating with age. Gills white, even at first, becoming serrated or irregular with age6, white, bruising brown when damaged. Stem fibrous, centrally to eccentrically attached, fibrous, and tough in texture. Flesh bruises brownish.

Natural Habitat:

This mushroom grows naturally on dead or dying broadleaf trees, particularly the Shii tree (Castanopsis cuspidata), Pasania spp., Quercus spp., and other Asian oaks and beeches. Although occasionally found on dying trees, Shiitake is a true saprophyte exploiting only necrotic tissue.

Microscopic Features:

Spores white 5–6.5 (7) × 3–3.5 µ, ovoid to oblong ellipsoid. Basidia four-spored. Hyphal system monomitic. Pleurocystidia absent. Clamp connections and cheilocystidia present.

Mycelial Characters

Mushroom mycelium white at first, becoming longitudinally linear and cottony-aerial in age, rarely, if ever truly rhizomorphic. In age, or in response to damage, the mycelium becomes dark brown. Some strains develop hyphal aggregates—soft, cottony ball-like structures—that may or may not develop into primordia. Many mycologists classify this species as a white rot fungus for the appearance of the wood after colonization. However, the mycelium of Shiitake is initially white, soon becoming chocolate brown with maturity, leaving a white-pulped wood.

Methods of Cultivation

On hardwood logs, especially oak, sweetgum, poplar, cottonwood, eucalyptus, alder, ironwood, beech, birch, willow, and many other non-aromatic, broadleaf woods. The denser hardwoods produce for as long as 6 years. The more rapidly decomposing hardwoods have approximately half the life span, or about 3 years. The fruitwoods are notoriously poor for growing Shiitake. Although Shiitake naturally occurs on oaks and beeches, the purposeful cultivation of this mushroom on hardwood stumps in North America has had poor success thus far.

Recommended Courses for Expansion of Mycelial

Mass to Achieve Fruiting

Modern methods use a hardwood-based substrate, amended with a nitrogen-rich supplement (rice bran, wheat bran, rye bran, oatmeal, wheat flour, etc.). The mixture is moistened and packed into heat-tolerant plastic bags, sterilized, and inoculated with either grain or sawdust spawn. The Shiitake bags or “blocks” as they are commonly called are then placed into indoor, controlled-environment growing rooms. The first flush is initiated by simply elevating humidity and watering. Subsequent flushes are initiated by submerging the blocks into cold water for 24 to 48 hours. The fruiting cycle usually spans no more than 3 months.

This species adapts well to liquid culture techniques. I prefer to use malt agar media supplemented with 3–5 grams of alder sawdust. Once the cultures are grown out, they are blended in a stirrer, subproportioned into Erlenmeyer flasks containing malt sugar, yeast, and alder (2%, .1%, .5%, respectively), fermented for 2 days, and injected into sterilized rye grain. These liquid-inoculated grain masters are then used to inoculate sawdust for the creation of sawdust spawn which can then be used to inoculate the fruiting substrate: sawdust/chips/bran. For further information on Shiitake under liquid culture conditions, see Raaska (1990), Yang and Jong (1987), and Leatham (1983).

Substrate for Fruiting

Broadleaf hardwoods such as oak, ironwood, sweetgum, beech, poplar, cottonwood, and alder.

This formula, utilizing sawdust, chips, rice, or rye bran, and buffered with gypsum is ideal for high-yield, indoor production. At makeup this substrate hovers around 5.5 to6.0. Prior to fruiting, the pH drops to 3.5 to 4.5. (The optimal range for fruiting, according to Chang and Miles, 1989, falls between 4.2 and 4.6.) Other recipes utilize a variety of supplements, including various grains. The cereal brans, most flours, tea leaves, yeast, molasses, etc., are widely used. For further information on formulating sawdust based media, consult Jong (1989), Royse and Bahler (1986), San Antonio (1981), and Ando (1974). The Forest Research Institute of New Zealand published one of the first studies exploring the usefulness of pines (Pinus radiata—the Monterey Pine), which produced satisfactorily yields when combined with a hardwood such as beech or poplar and supplemented with barley grain. (The ratio was 6 parts pine: 3 parts hardwood: 1 part grain.

Recommended Containers for Fruiting

Polypropylene, high-density, thermotolerant polyethylene bags, usually fitted with a microporous filter patch, or stuffed with a cotton plug. Bottle fruitings are impractical. Tray fruitings à la Button mushroom culture have been employed with some success in Europe. However, the advantage of bag culture is that contaminants can be isolated, limiting cross-contamination of adjoining substrates.

Yield Potential

1.5–3 pounds of fresh mushrooms from 6 pounds of sawdust/chip/bran. Biological efficiency rating of 100–200% using the methods described herein.

Harvest Hints

Humidity should be constantly fluctuated during fruitbody development and then lowered to 60% RH for 6 to 12 hours before the crop is harvested. This causes the cap’s leathery, outer skin to toughen, substantially extending shelf life. We prefer to pick the mushrooms when the margins are still inrolled, at a mid-adolescent stage. However, greater yields are realized if the fruitbodies are allowed to enlarge. For best results, the growing room manager must carefully balance the interests of quality vs. yield throughout the cropping process.

Flavor, Preparation, and Cooking

Shiitake can be enjoyed in a wide variety of dishes. A traditional Japanese soup recipe calls for slicing the mushrooms and placing them in a preheated chicken broth complemented with chopped green onions. The addition of miso (a vegetarian substitute for chicken) is also delicious. The Shiitake are steeped in this soup broth for a few minutes and served hot. The flavor and fragrance of slightly cooked Shiitake is tart and totally different than the flavor imparted from thorough cooking. Chinese restaurants usually rehydrate Shiitake and simmer them in the broth of stir-fries.

Published Date: Thursday August 29, 2019 

Topic:  The Shiitake Mushroom

Subject: Mushroom Cultivation

References: Stamets P. Growing gourmet and medicinal mushroom, Ten Speed Press (2000) , eISBN: 978-1-60774-138-1, 2000,