Grifola frondosa

A large, fleshy polypore, dark grey/brown when young, becoming lighter gray in age. (Some varieties fade to a light yellow at maturity). Fruit body is composed of multiple, overlapping caps, 2-10 cm. in diameter, arising from branching stems, eccentrically attached, and sharing a common base. Young fruitbodies are adorned with fine grey fibrils. The pores on the underside of the caps are white.

Mycelial Characteristics: White, longitudinally linear, eventually thickly cottony on enriched agar media, non-rhizomorphic. The mycelium grows out unevenly, not forming the circular colonies typical of mort mushrooms. Regions of the mycelium surge while other regions abate in their rate of growth. This pattern of growth seems characteristic of the species, as some have seen it in the majority of the many strains of G. frondosa. Often times, the mycelium develops light tawny brown tones along the outside peripheral edges in aging. At maturity, the dense mycelial mat can be peeled directly off the agar media. Once on sawdust, many strains have mycelia which develop strong yellowish to orangish brown mottled wones, exuding a yellowish orange metabolite. Sawdust spawn, when young, is white. As the spawn matures, rust colors prevail.

Mycrospic Features: This mushroom produces white spores.

Suggested Agar Culture Media: Malt Yeast Agar (MYA), Malt Yeast Peptone Agar (MYPA), Potato Dextrose Yeast Agar (PDYA), or Dog Food Agar (DFA).

Spawn Media: Grain-to-grain expansions. The final spawn medium can be another generation of grain spawn, or alternatively sawdust. The sawdust spawn can be used to inoculate supplemented sawdust (i.e. sawdust/chips/bran) or plugs for outdoor cultivation in stumps or partially buried, vertically positioned, large diameter hardwood logs. Considering the long incubation period, cultivators are well advised to weigh the advantages of creating another generation of sawdust spawn. The advantage of the grain spawn-inoculated bags is that they produce several weeks earlier than do the sawdust-inoculated blocks. However, the quality of colonization is better provided by spawn made of sawdust than from grain.

Substrates for Fruiting: Supplemented hardwood sawdust, particularly oak, poplar, cottonwood, elm, willow, and alder. Alder and poplar stumps are less likely to support outdoor fruitings, given the hold competitors like Pleurotus ostreatus and allies have on that niche. For indoor cultivation, yields vary substantially between various wood types. Oak is generally preferred, although strains growing on conifers are being developed.

Yield Potentials: 1/2 to 2 lbs. mushroom per 5-7 lbs. or sterilized, enriched hardwood sawdust.

---Growth Parameters---

Spawn Run:

• Incubation Temperature: 70-75* F (21-24* C)
• Relative Humidity: 95-100%
• Duration: 14-30 days, the dormant for 30 days
• CO2: 20,000-40,000 ppm
• Fresh Air Exchange: 0-1
• Light Requirements: n/a

• Initiation Temperature: 50-60* F (10-15.6* C)
• Relative Humidity: 95%
• Duration: 5-10 days CO2: 2000-5000 ppm
• Fresh Air Exchanges: 4-8 per day
• Light Requirements: 100-500 lux

• Temperature: 50-60* F (10-15.6* C)
• Relative Humidity: 95%
• Duration: 10-14 days
• Co2: 2000-5000 ppm
• Fresh Air Exchanges: 4-8 per hour
• Light Requirements: 100-500 lux.

• Temperature: 55-60* (65*) F (13-16* (18*) C)
• Relative Humidity: 85-90%
• Duration: 14-21 days
• Co2: <1000 ppm
• Fresh Air Exchanges: 4-8 per hour
• Light Requirements: 500-1000 lux.

• Every 3-4 weeks, for a maximum of two flushes.

Comments: This species is delicious and much sought-after. Specimens weighing up to 100 lbs. have been collected at the base of tewws, snags, or stumps. Although primarily a saprophyte, G. frondosa behaves facultatively as a parasite, attacking trees dying from other causes, especially elms and oaks.

According to Paul Stamets, only a few strains isolated from the wild perform under artificial conditions. Those which do fruit, mature best if the environment is held constant between 55-60* F (13-16* C). Substantial fluctuation beyond this temperature range arrests fruit body development. The best fruitings are those which form slowly and are localized from one or two sites of primordia formation. When Maitake is incubated outside the ideal temperature range, the fruitbody initials fail to further differentiate. Should the entire surface of the block be encouraged to form primordia, an aborted plateau of short folds results.

Fruitbody development passes through four distinct phases. During initiation, the mycelium first undergoes a rapid discoloration from white undifferentiated mycelium to a dark grey amorphous mass on teh exposed surface of the fully colonized block. During the second phase, the surface topography soon becomes contoured with dark gre/black mounds which differentiate into ball-like structures. the third phase begins when portions of this primordia ball shoot out multiple stems topped with globular structures. Each globular structure further differentiates with vertically oriented ridges or folds. The fourth and final phase begins when, from this primordial mass, a protion of the folds elongate into the petal-like sporulating fronds or "leaflets". With some strains and under some conditions, the third phase is skipped.

The strategy for the successful cultivation of Maitake is in diametric opposition to the cultivation of Oyster mushrooms. If Maitake is exposed to substantial and prolonged light during the primordia formation period, the spore-producing hymenophore is triggered into production. This results in dome shaped primorial masses, devoid of stems. If, however, minimal light is given, and carbon dioxide levels remain above 5000 ppm, stem formation is encouraged. (Elongated stem formation with Oyster cultivation is generally considered undesirable). Once the stems have branched and elongated to two or more inches, carbon dioxide levels are lowered, light levels are increased, signaling Maitake to produce the sporulating, petal-shaped caps. Humidity must be fluctuated between 80-95%. Maitake, being a polypore, enjoys less humid environments than the fleshier, gilled mushrooms.

If growing in polypropylend bags, the bags should be opened narrowly at the top so that a forking bouquet is elicited. Stripping off all the plastic increases evaporation from the exposed surfaces of the block, jeopardizing the moisture bank needed for successful fruit body development. Given good environmental controls an dmanagement, successful attempts at growing Maitake by fully exposing the upper surface of the mycelium once the grey primordial mounds have formed 45-60 days after inoculation. Leave the remainder of the plastic around the block to amerliorate the loss of water. Holes are punched in the bottom of the bags for drainage.

As the mushrooms develop, less watering is needed in comparison to that needed by, for instance, Oyster mushrooms. Furthermore, cultivators should note that if too much base nutrition of the substrate is allocated to stem formation, the caps often abort. If the sawdust is over-supplemented, bacteria blotch is triggered by the slightest exposure to excessive watering or humidity. Every strain behaves differently in this regard. Maitake cultivation requires greater attention to detail than most other mushrooms. Because of its unique environmental requirements, this mushroom can not share the same growing room as many of the fleshier gourmet and medicinal mushrooms.

Once the production blocks cease producing, they can be buried outside in hardwood sawdust and or soil. In outdoor environments, the subterranean block becomes a platform for more fruitings, maximizing yield. Blocks planted in the spring often give rice to fruitings in the fall. The autoclavable, plastic should be removed, unless made of cellulose or other biodegradable material. By scratching the outer surfaces of the blocks, the internal mycelium comes into direct contact with the sawdust bedding, stimulating leap-off.

(Information taken from Growing Gourmet and Medicinal Mushrooms, Paul Stamets)