Growing gourmet or medicinal mushrooms (specialty forest mushrooms) as a component of a Forest Farming system can be a satisfying and profitable venture if your forest site has the appropriate conditions and you have the appropriate resources, including a market, to make a go of it. This module should help you determine if “specialty forest mushrooms” are a good option for forest farming under your particular circumstances. You should consider carefully both the pros and the cons of SFM production before you begin. This module will provide a discussion of the critical issues, a video illustrating the the log inoculation process, and other How-to resources for shiitake mushroom production, as well as a step by step guide (including video) for growing Shiitake mushrooms, and links to other resources about shiitake and other specialty forest mushroom production.
Our top recommendations for beginners who would like to learn how to grow specialty forest mushroom are shiitake, followed by oyster mushrooms. These two are the most reliable, predictable, and can be grown on natural substrates (wood) commonly available as byproducts of forest farming. Shiitake will take longer (6-18 months) to begin producing on a log of a given tree species but production of mushrooms is likely to last longer – 2 to 4 pounds of mushrooms from a single log over several (3-5) years is realistic with proper management. Oyster mushrooms can be grown on logs of a more limited range of tree species, especially poplar, on which they may begin fruiting with a single growing season (3-4 months. For both shiitake and oyster mushrooms there is a well developed market demand so that you can be assured of getting a reasonable financial return on the time, energy and investment that go into cultivating mushrooms in the woods.
More experienced mushroom growers, or beginners who are less risk averse than most of us, have a broader palette of mushroom species to choose from for forest production. These include Maitake (Griffola frondosa), Lion’s Mane (Hericium sp.), Reishi, and Stropharia. The first 3 can be grown on logs similar to the cultivation of shiitake and oyster mushrooms described in the next section, although cultivation of stumps is also a possibility. Stropharia on the other hand is grown on a ground bed of wood chips. All of these more exotic mushrooms usually take longer to begin fruiting than either shiitake or oyster mushrooms and are simply not as reliable. Even the experts experience failures with no readily apparent causes.
Robert L. Anderson, USDA Forest Service. www.forestryimages.org
The need for further research on the production of specialty forest mushrooms, other than shiitake, before it can be considered reliable has been emphasized by Johann N. Bruhn, a leading authority on specialty forest mushroom production at the University of Missouri (Colombia). In his book, What Do We Still Need to Know About Commercial Production of Forest-Grown Specialty Fungi?, he writes, “Although a great deal has already been learned and written about the cultivation of specialty fungi we are still clearly on the steep portion of the learning curve."
It should be pointed out that although mushroom production under forest farming conditions can be a satisfying and profitable experience, most of the species mentioned above including shiitake and oyster give substantially higher yields with greater profit potential when produced “commercially” under intensive, climate controlled, indoor conditions, on artificial, sterilize or pasteurized substrates such as sawdust blocks supplemented with nutrients. For example, the standard “commercial” method for producing oyster mushrooms involves growing spawn in large plastic bags filled with pasteurized straw (Adams. 2000) under controlled environment (warm, high humidity) conditions, rather than outdoors, and hence does not qualify as a forest farming venture.
By all means, we encourage you to experiment with production of other mushroom species, perhaps even from the beginning in addition to shiitake if you are are a risk taker. Once you have learned the basic skills involved in specialty forest mushroom cultivation you may wish to try your hand a production of a number of other, potentially even more profitable than shiitake. Here is a list of possibilities and some sources of information about their cultivation under forest conditions:
|Fungal Species||Production System||Notes|
|Logs or Stumps|
|Logs or Stumps|
|Morels||Potentially highly lucrative but highly risky as an economic venture.|
|Truffles||Potentially extremely lucrative but extremely risky. Not recommended.|
Additional Web Resources
These next sections will provide you with several resources to help you learn how to grow shiitake mushrooms using the traditional log production methods developed in Japan over a hundred years ago. The same or similar approach can be used for growing oyster mushrooms. The resources provided below include:
The information that follows is intended to give you a general introduction to the three main stages of shiitake production, but this is not intended to be a substitute for reading one or more of the excellent books that describe the in detail the factors and variables that can make the difference between success and failure. The video of John Boyle is intended to allow you to look in on an expert conducting a shiitake mushroom workshop to a group of beginners, but the video only covers the inoculation stage of a 3 stage process that includes inoculation, spawn run, and fruiting. We strongly recommend consulting one or more of the excellent books or pamphlets listed in the Additional Web Resourcessection.
Shiitake mushrooms are grown on hardwood logs, usually 4 to 6 inches in diameter, and 3 to 4 feet long. Many hardwood tree species can be used but oaks are considered best, if available. Cherry and ash should be avoided, as should all conifers. Logs must be relatively fresh, cut from live trees and used within several weeks to no more than several months of cutting. The best time to cut logs is while trees are dormant, either late fall or early spring. Since inoculation should be performed only when the temperature is well above freezing, logs cut early in the winter must be protected from excessive drying by shading and/or covering prior to inoculation in the spring. Maintaining relatively high moisture content is one of the most important considerations and many of the specific recommendations given below are based on maximizing log moisture content. Wood that has been allowed to dry below about 29% moisture is well on its way to becoming well seasoned firewood but it won’t grow mushrooms. Another reason to avoid older logs is because other fungi may have already colonized them, so that the shiitake fungus simply can’t compete.
There are many different configurations for stacking logs which varies depending on available space and optimal environmental conditions for the logs. “Dead stacking” like firewood, is not recommended since logs need aeration. Crib stacking [picture] is the most efficient use of space but can result in excessive drying of logs at the top of the stack. Stacking in an leaning A-frame [picture] or Lean-to configuration keeps logs adequately aerated, but drying is reduced compared to cribbing since they are lower to the ground, where humidity is higher during the summer and where snow cover can protect logs from drying during winter
The process of inoculation refers to, introducing into the log a pure culture of the vegetative mycellum of the shiitake fungus. This inoculum, which is also called spawn, is produced under laboratory conditions and is best left to the specialist. There are many commercial sources of high quality spawn, and several of these are listed in the Supplies section. Spawn may be purchased from a commercial suppliers in any one of several formuations but sawdust spawn and plug spawn (short hardwood dowels) are most common for log inoculation.
Spawn run is the period of time necessary for the fugal mycelium to completely colonize the inoculated logs. This occurs in a “laying yard”. As mentioned above, the most important consideration during this period is to prevent the logs from drying out. First and foremost this means to keep them out of direct sun. The shade provided by a dense, closed canopy of trees is ideal. If your forest or woodlot is more open than this you may consider hanging an artificial ceiling of greenhouse woven shade cloth (80% or higher light exclusion).
Fruiting refers to the period of actual mushroom formation and harvest, after the fungal mycellim has fully colonized the substrate log. This may occur in as little as 6 or as long as 18 months for shiitake on hardwood logs, or within as little 3 to 4 months for oyster mushrooms on poplar logs. Forced fruiting of shiitake logs can be achieved by soaking them in cool water for 24 to 48 hours. This allows for more control in scheduling harvests throughout the growing season.
One advantage of shiitake over oyster and other specialty forest mushrooms is that temperature sensitive strains of the fungus are available. These strains fruit at different temperatures so that fruiting can be spread out across the entire growing season. There are cool weather strains, warm weather strains and wide range of other strains.
Additional Web Resources
Additional Web Resources