Stumps as Elatforms for Growing Mushrooms

Stumps are especially suitable for growing gourmet mushrooms. There are few better, or more massive platforms, than the stump. Millions of stumps are all that remain of many forests of the world. In most cases, stumps are seen as having little or no econonr" potent' J. These lone tombstones of biodegradable wood fiber offer a unique, new opportunity for the mycologically astute. With selective logging being increasingly practiced, cultivating gour met and medicinal mushrooms on stumps will be the wave of the future.

The advantage of the stump is not only its sheer mass, but with roots intact, water is continuously being drawn via capillary action through the dead wood cells from the underlying soil base. Once mycelium has permeated through wood fiber, the stump's water carrying capacity is increased, thus further supporting mycelial growth. Candidates for stump culture must be carefully selected and matched with the appropriate species. A stump partially or fully shaded is obviously better than one in full sun light. Stumps in ravines are better candidates than those located in the center of a clear-cut. An uprooted stump is not as good a candidate as a well-rooted one. The presence of mosses, lichens, and/or terns is a good indicator that the microc':mate is conduc;ve to mushroom growth. However, the presence of competitor fungi generally disqualifies a stump as a good candidate. These are some of the many factors that determine the suitability of stumpage.

Cultivating mushrooms on stumps requires forethought. Stumps should be inoculated before the first season of wild mushrooms. With each mushroom season the air becomes laden with spores, seeking new habitats. The open face of a stump, essentially a wound, is highly susceptible to colonization by wild mushrooms. With the spore cast from wild competitors, the .ikelihood of introducing your species of choice is greatly reduced. If stumps are not inoculated within several months of being cut, the probability of success decreases Therefore, old stumps are poor candidates. Even so, years may pass after inoculation before mushrooms form on a stump.

Large diameter stumps can harbor many communities of mushrooms. On old-growth or second-growth Douglas fir stumps common to the forests of Washington state, findir g several species of mushrooms is not unusual.Th's natural example of'polyculture"—the simultaneous concurrence of more than one species in a single habitat—should encourage experimentally inclined cultivators. Mushroom landscapes of great complexity could be designed. However, the occurrence of poisonous mushrooms should be expected. Two notable, toxic mushrooms frequent stumps: Hypholoma fasciculare (=NaematoIoma fasciculare) which causes gastro-intestinal upset butusually not death and Galerina autumnalis, a mushroom that does kill. Because of the similarity in appearance between

Flammulina velutipes (Enoki) and Galerina autumnalis, I hesitate to recommend the cultivation of Enoki mushrooms on stumps unless the cultivator is adept at identification. (To learn how to identify mushrooms, please refer to the recommended mushroom field guides listed in

Appendix IV.)

Several polypores are especially good candidates for stump cultivation, particularly Grifola frondosa—Maitake, mdGanoderma lucidum— Reishi and its close relatives. As the anti-cancer properties of these mushrooms become better understood, new strategies for the cultivation of medicinal mushrooms will be developed. I envision the establishment of Maitake & Reishi mushroom tree farms wherein stumps are purposely created and selectively inoculated for maximum mushroom growth, interspersed amongst shade trees. Once these models are perfected, other species can be incorporated in creating a multi-canopy medicinal forest.

On a well-travelled trail in the Snoqualmie Forest of Washington State, hikers have been stepping upon the largest and oldest Polypore: Oxyporus nobilissmus, a conk that grows up to several feet in diameter and which can weigh hundreds of pounds ¡This species grows only on old growth Abies procera (California red fir) or on their stumps. Less than a dozen specimens have ever been collected. Known only from the old growth forests of the Pacific Northwest, the Noble Polypore's ability to produce a conk that lives for more than 25 years distinguishes it from any other mushroom. This fact- that it produces a fruiting body that survives for decades—sug gests that the Noble Polypore has unique anti-rotting properties from antibiotics or other compounds that could be useful medicinally. These examples from the fungal kingdom attract my attention in the search for candidates having potential for new medicines .With the loss of old-

growth forests, cultivator-mycologists can play an all-important role in saving the fungal genome from the old-growth forest, a potential treasure trove of new medicines.

Small-diameter stumps rot faster and produce crops of mushrooms sooner than bigger stumps. However, the smaller stump has a shorter mushroom-producing life span than the older stump. Often times with large diameter stumps, mushroom formation is triggered when competitors are encountered and/or coupled with wet weather conditions.The fastest I know of a stump producing from inoculation is 8 weeks. In this case, an oak stump was inoculated with plug spawn of Qiicken-of-lhe-Woods,Laetiporus(Polyporus) sulphureus. Notably, the stump face was checkered—with multiple fissures running vertically through the innermost regions of the wood. These fissures trapped water from rainfall and promoted fast mycelial growth. As with the growing of any mushrooms, the speed of colonization is a determining factor in the eventual success or failure of any cultivation project.

For foresters and ecologists, actively inoculating and rotting stumps has several obvious advantages. Rather than allowing a stump to be randomly decomposed, species of economic or ecological significance can be introduced. For instance, a number of Honey mushrooms, be • longing to the genus Armillaria, can operate as both saprophytes orparasites Should clear-cuts become colonized with these deadly, root-rotting species, satellite colonies can be spread to adjacent, living trees. Now that burning is increasingly restricted because of air pollution concerns, disease vectors coming from stump-age could present a new, as yet unmeasured, threat to the forest ecosystem.

The advantages of growing on stumps canbe summarized as:

I) Developing a new, environmentally

Growing Oyster Mushrooms Logs
Figure 20. Drilling and inoculating a stump with plug spawn.

friendly wood products-based industry.

2) Recycling wood debris of little or no economic value.

3) Prevention of disease vectors from parasitic fungi.

4) Rapidly returning organic nutrients ;nto the food chain, benefitting other citizens of the forest community and invigorating the ecosystem. Few studies have been published on recycling stumps with mushrooms. One notable work from eastern Europe, published by Pagony (1973), describes che cultivation of Oyster mushrooms (Pleurotus ostreatus) on large diameter poplars with a 100% success rate. Inoculations occurred in the spring for fruitings which began in the ensuing fall, and continued for several years hence. An average of four pounds of Oyster mushrooms were harvested over four years (i. e. 1 lb. /year/stump), rr-7-. .- ■■■ .j -rr.— . mr ■■ -- "

Hilber ( 1982) also reported on the utility of using natural wood (logs & stumps) for growing Oyster mushrooms, and that per cubic meter of elm wood, the yield from one season averaged 17-22 kilograms.A study in France byAnselmi & Deandrea (1979) where poplar and willow stumps were inoculated with spawn of the Oyster mushroom showed that this mushroom favored wood from newly felled trees, zones which received speckled sunlight. This study confirmed that Pleurotus ostreatus only attacked dead wood and never became parasitic. Their study supports my opinion (Stamets (1990)) that the purposeful inoculation of stumps can forestall the invasion by parasites like Honey Mushrooms of the Armillaria mellea complex. Mushrooms of this group first kill their host and then continue to live saprophytically. A stump with Honey Mushrooms can later destroy neighboring living trees. In Washington State, one colony of Honey Mushrooms is blamed for destroying hundreds of acres of conifers.

Inoculating stumps with strains cloned from native mushrooms is favored over the use of exotic fungi. Spring inoculations give the mycelium the longest possible growing season. Stumps can be inoculated by one of several simple procedures. Plug spawn can be inserted into the open face of each stump. If the stumps are checkered through with cracks, the plugs are best inserted directly into tne fissures. Another method is known as the wedge or disc inoculation technique. Using a chain saw, a wedge is cut or a shallow disc is sliced from the open face of the stump. The newly cut faces are packed with sawdust spawn. The cut disc is then replaced. By hammering a few nails into the stump, you can assure firm contact between the cut faces

The broad-leaf hardwoods are easier to saprophytize with the gourmet and medicinal mushroom species described in this book than the softwood pines. And within the hardwood group, the rapidly growing specks such as the alders and poplars decompose more rapidly— and hence give an earlier crop—than the denser hardwoods such as the oaks, etc. However, the denser and more massive stumps sustain colonies of mushrooms for many more years :han the quick-to rot, smaller diameter tree species. In a Colonial graveyard in New York state, a four foot diameter oak has consistently produced clusters of Mauake mushrooms sometimes weighing up to 100 lbs. apiece, for more than 20 years!

Stump cultivation has tremendous potential. This unexploited resource—stumpage— can become production s:fes of gourmet and medicinal mushrooms. Although more studies are needed to ascertain the proper matching of species to the wood types, I encourage you to experiment. Only a few minutes are required to a inoculate a stump or dead tree. The potential rewards could span a lifetime.

Log culture was developed in Japan and China more than a millennium ago. Even today, thousands of small-scale Shiitake growers in Asia use log culture to provide the majority of mushrooms sold to markets. In their backyards and along hillsides, inoculated logs are stacked like cordwood or in fence-like rows. These growers supply local markets, generating a secondary income for their families. Attempts to reproduce this model of Shiitake cultivation in North America and Europe has met with modest success.

The advantage of log culture is that it is a simple and natural method. The disadvantage

Are White Mushroom Maitake Mushroom
Figures 21 and 22. Inoculating a stump with the wedge and the spawn disc tech^que.

is that the process is labor-intensive, and slow in comparison to growing mushrooms on sterilized sawdust. Besides Shiitake, many other mushrooms can be grown on logs, including Nameko (Pholiota nameko). all the Oyster-like mushrooms (Pleurotus and Hypsizygus spp.), Lion's Mane (Hericium erinaceus), Wood Ears (Auricularia species), Clustered Wood Lovers (.Hypholoma capnc:ies md H. sublateritium) and Reishi (Ganoderma luc'dum) S' ice log culture is not technically demanding, anyone can do it. In contrast growing on sterilized substrates requires specialized skills and involves tr lining in laboratory techniques

Logs are usually cut in the w,riter or early spang before leafing, when the sapwood is rl^h i i sugars, to a meter in length and 4-10 inches in diameter. Cultivators generally favor logs which have a 1 igher ratio of sapwood to heart wood. (These logs come from fast-growing tree species like alder, poplar or cottonwood.) Once inoculated with sawdust orplug spawn, the logs (or "billets" ) are stacked in ricks and, after 612 months are initiated by heavy watering or soaking. After soaking, the logs are lined ud in fence-like rows. Japanese growers have long favored the "soak and strike" method for initiating mushroom formation. (See Figures 24 and 25.) Before the advent of plug and sawdust spawn, newly cut logs would be placed near to logs already producing Shiitake so that the spores would be broadcasted onto them. This method, although not scientific, succeeded for centuries, and still is a pretty good method. After a year, logs showing no growth, or the growth of competitor fungi, are removed from the production rows.

A wide variety of broad-leaf hardwoods are suitable for log culture. Oaks, and similar dense hardwoods with thick outer barks, are preferred

Shiitake Mushroom Log Inoculation
Figure 23. Plug spawn of Shiitake. Spirally grooved wooden dowels help the mycelium survive Trom the concussion of inoculation.
Oyster Large Log Inoculation Methods
Figure 24. The "soak and strike" method for initiating Shiitake.

Figure 25. Natural Cdture of Shiitake in the mountains of Japan. (Photographs, both from f imura, circa 1915, Japan.)

Figuie 27. Inoculated logs are stacked and covered with a tarp.

Figure 29. The Oysier mushroom (Pleurotus ostreaius) fruiting on alder logs that were inoculating via the wedge technique-

Figurr* 28. Gymnopilus spectabiiis, the Big Laughing Mushroom, fruiting from log inoculated with sawdust spawn via the wedge technique.

Figure 29. The Oysier mushroom (Pleurotus ostreaius) fruiting on alder logs that were inoculating via the wedge technique-

Figure 30. Oyster mushroom fruiting from alder logs inoculated via the spawn disc technique.

Figurr* 28. Gymnopilus spectabiiis, the Big Laughing Mushroom, fruiting from log inoculated with sawdust spawn via the wedge technique.

over the rapidly decomposing hardwoods with their paper thin bark layers. The rap'dly decomposing hardwoods like alder and birch are easily damaged by weather fluctuations, especially humidity. Should the bark layer fa" from the log, the mycelium has difficulty supporting good mush room flushes.

Logs are generally cut from trees in the spring, prior to leafing, when the sap wood still retains ample sugars. The logs, once felled, should be kept off the ground. Ideally inoculations should occur within 2 months of felling. (In temperate North America. February and March are ideal.)

Numerous methods can be used for inoculating the spawn into the log. Logs are usually pegged, i. el drilled with holes and inoculated with plug or sawdust spawn. Most logs receive 30-50 plugs, which are inserted into evenly spaced holes (4-6 inches apart) arranged longi-

Figure 30. Oyster mushroom fruiting from alder logs inoculated via the spawn disc technique.

tudinally down the axis of the logs in a diamond pattern. By off-centering the rows of holes, ;n a diamond pattern, the mycelium grows out to become one interconnected, macro-oiganism, after which synchron-ous fruitings can occur. Once inserted by hand, the plugs are pounded in wi 'h a rubber mallet' or hammer. The plugged hole is covered with cheese-wax, usually painted on, to protect the mycelium from insect or weather damage.

Another method calls for the inoculation of logs by packing sawdust spawn into cuts made with a chain saw. A common technique is to cut a "V" shaped wedge from a log, pack the wound full of sawdust spawn, and press the wedge of wood back into place. Naiihg the wedge back into position assures direct and firm contact. Another variation is to cut logs into 16 to 24 inch sections and sandwich spawn in between.

Sawdust spawn can be usea in other ways. Newly cut ends of the logs can be packed with sawdust spawn and then capped with aluminum foil, or a "sock" to hold the mycelium in place. (San Antonio (1983) named this technique the spawn disk method.) Some prefer cutting wedges from the logs, and then repacking the cut wedge back into the log with mycelium sandwiched in between. Others cut the logs in sections, two feet in length and pack the sawdust spawn in between the two sections, which are reattached by any means possible.

For anyone growing outdoors in climates with severe dry spells, or where watering is a problem, logs should be buried 1/3 to 1/4 of their length into the ground. The ground moisture will constantly replenish water lost through evaporation, lessening the effect of humidity fluctuation .This method is especially useful for the cultivation of Lion's Mane, Nameko, Oyster and Reishi. It is widely used by growers in China. Many cultivators protect their logs from

Mushroom Log Cultivation
Figure 31. By burying the logs into the ground, subsurface moisture is drawn up into the log, encouraging mushroom formation.

the sun by either locating them under a forest canopy or by rigging up a shade cloth.

Most log cultivators develop their own, unique techniques, dictated by successes and failures. Many books on log cultivation have been written, too numerous to 1 : t here. Two books on Shiitake log cultivation that I highly recommend for those who wish to study these techniques further are Growing Shiitake Mushrooms in a Continental Climate (2 ed.) by Mary Kozak & Joe Krawczyk and Shiitake Grower's Handbook by Paul Przybylowicz and John Donoghue. The methods described in these books can be extrapolated for the cultivation of other gourmet and medicinal mushrooms on logs.


Figure 32. The Stametsian Model for Permaculture with a Mycological Twist


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