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Mycological Background

Mushrooms are the reproductive bodies formed by certain fungi. Just like the apple on a tree, mushrooms are the “fruits” of these fungi. The actual organism that produces the mushrooms is called MYCELIUM,  a strand like mass of white cells found in the growing substrate, which may be a dead tree stump, a live tree or in the ground. Under the right conditions the mycelium will produce mushrooms which release millions of spores into the environment for further propagation of the species. Many of these mushrooms are edible and some can be easily cultivated.

 Mushrooms are classified into three types according to their growing characteristics.

PARASITIC mushrooms normally attack a living tree and eventually kill the host. They may also be found growing on dead trees, but they probably started growing while the tree was alive 

Why grow your own?

Some people are avid mushroom hunters and may belong to various mycological clubs. These people go out on forays and at the right time of the season may bring home morels, chanterelles and other edible species. Most of us however have to resort to the grocery store for our mushroom,  and unfortunately the average North American  supermarket is seriously lacking in quality and variety. This is getting better, we regularly have white button mushrooms, oyster, and more often now shiitake, brown Agaricus and Portobello .  Unfortunately the quality of the oyster and shiitake is usually poor due to improper storage conditions and slow turnover from consumer unfamiliarity with these species. In Japan for example the following varieties are available even in most small grocery stores, Shiitake, Shiimeji, Nameko, Maitake ( Hen of the Woods), Auricula auricularia. white & brown . By growing your own you can get a good quality product at the peak of freshness, free of chemical additives, and you can experiment with many varieties that are not commercially available.

So, how do you start growing mushrooms?

The simplest way is to buy a kit or a inoculated log from a reputable supplier, follow the instructions and  enjoy a few crops of mushrooms. Typical kits available are Shiitake, and various Oyster species. The selection of species in kit form is  limited so if you are interested in some of the more exotic mushrooms the only solution is to make your own. 

The procedures for cultivating mushrooms are as follows (The examples used will be the more common mushroom species, which have a high, proven success rate. The techniques however apply to all SAPROPHYTIC mushrooms, variations for success of different types are developed from experimentation.). The basic concept in cultivation is to start with a bit of mycelium and to expand that mycelial mass to the point that it has enough volume and stored up energy to support the final phase of the mushroom reproductive cycle, which is the formation of fruiting bodies or mushrooms. To do this you need either spores from a spore print,  a fresh mushroom, or a culture bought from a culture bank or other source. Growing out the spores is the sexual reproductive cycle and requires the combination of two spores to produce a new individual fungus. Reproduction from a culture or a fresh mushroom involves asexual reproduction, you basically clone the original organism . The spores or a small piece of the mushroom or culture are placed on agar medium in petri dishes and the mycelium is grown out. After the mycelium has colonized the petri dishes, usually about 2 weeks, it is transferred onto sterilized grain (rye, wheat, millet). It will then completely colonize the grain ( about 2-4 weeks). This grain spawn, as it is now called, can then be used to inoculate more grain, for a larger quantity of grain spawn, or can be used to make sawdust spawn, kits, or to inoculate outdoor beds in orchards, gardens or bush. Sawdust spawn, which is used to make wooden dowel plug spawn or to inoculate logs directly, and to inoculate outdoor beds,  is made by transferring grain spawn to previously sterilized hardwood sawdust. The mycelium will run through the sawdust in about 3-4 weeks, at which point it will be ready to use. Plug spawn is made by transferring some sawdust spawn onto sterilized wood dowels and letting the mycelium permeate the dowels. The above procedures should be carried out in a sterile environment otherwise there will be a large percentage of contamination due to molds and bacteria. Also the substrates used ie agar, grain, sawdust must be sterilized beforehand to give a competition free environment for the mycelium to grow. Therefore if you want to do it all from scratch, you must invest in some basic equipment.  A clean room such as a closet, or small washroom are suitable. A sterilizer is a must, a High Efficiency Particulate Filter (HEPA) to work in front of is almost essential also, home made glove boxes can be used but will be awkward when handling jars of spawn.  A detailed description of sterile laboratory techniques are found in two excellent books:  The Mushroom Cultivator, and Growing Gourmet and Medicinal Mushrooms by Paul Stamets.

The investment to set up a simple “laboratory”,  can run into a couple of thousand dollars.  If this is beyond the scope of your interest in cultivation,  the next best alternative is to purchase spawn from a supplier and inoculate your own logs,  make your own kits, or  set up growing beds outdoors. Spawn is usually available in grain, dowel, and sawdust form from the same people who make kits. Again the variety will be limited to a few species, so if you want to grow your favourite wild species you will usually have to do it from scratch unless you can find someone that has a “laboratory” set-up to custom make spawn for you. If you can custom make your spawn, then a much larger selection of mushrooms is available for you to experiment with. Most wild Agaricus sp. can be cultivated, Blueits are actually cultivated commercially in Europe, Chicken of the woods, Shaggy manes are just some of the types that you can grow. Mushrooms in The Garden by Hellmut Steinbeck lists a few pages of mushroom species that can be cultivated. Whether you purchase spawn or make your own, the next step is to inoculate the final substrate that will eventually produce mushrooms.  This substrate can be logs, stumps, sawdust/wood chip mixtures, straw, cardboard, compost etc. The main thing to remember is that you want to introduce your fungus into a medium that is relatively free of other fungi.  The competition between fungi is fierce so you want to give yours a head start, once it has colonized the substrate it can fight off the competition.  If you are growing on logs or stumps, these must be freshly cut, preferably winter cut so that the sugar content in the wood is high, giving an initial boost to the mycelium. If growing indoors on  sawdust/wood chips or straw the type of mushroom will determine the amount of processing of the substrate. Shiitake, Maitake, Enoki (Flammulina velutipes), which are grown on sawdust, for example require sterilization of the medium, because at the beginning they do not compete well with molds or bacteria. Oyster sp. and Stropharia  only require the medium  to be pasteurized because they actually consume the other organisms in their life cycle. Simply sterilization, means steam sterilization in an autoclave at 15 psi for a few hours or at atmospheric pressure for  at least 12 hrs. Pasteurization means boiling the medium in water. 

Outdoor log cultivation

Almost any type of hardwood logs can be used for mushrooms. Commercially the most common species grown on logs is shiitake. This is due to the fact that log cultivation is usually more expensive than sawdust cultivation and shiitake give a higher financial return than other types of mushrooms. Also for commercial cultivation  oak is the preferred hardwood because it has a longer bark retention period than other species such as maple, alder, beech etc. The bark keeps the moisture in the log and keeps out competitor fungi. Once the bark has fallen off the log usually becomes useless. Typically oak logs last an average of 1 year per inch of diameter, in other words a five inch diameter by four foot log should last five years. Maple on the other hand will debark much more quickly. For home mushroom cultivation this is not usually  a major factor. 

Freshly winter cut logs are preferred due to the large quantity of sugars in the wood. Logs that have been laying in the bush for some time are probably being attached by a whole series of fungi and inoculation of these logs will not be successful. Logs are inoculated by drilling a series of holes 1.5″ deep  spaced about 5″ apart in a series of rows about 4″  apart. The holes are then filled with either dowel plug spawn or sawdust spawn, sawdust spawn works faster than plugs. Plugs can be placed in the holes by hand and tapped in with a hammer, sawdust spawn requires an applicator. The holes are then sealed with molten wax. The wax prevents the spawn from drying out and dying.  A newer method is sawdust plug spawn with a styrofoam backing. The plugs are inserted manually into the pre-drilled holes , no wax is necessary as the styrofoam acts as a vapour an contamination  barrier.   The logs are then stacked in the bush  under some artificial shade until the mycelium takes over the whole log, this is called the spawn run. In  North America this period varies from 6 months to a year. After the spawn run the logs are ready to fruit, they are now stood up and leaned against a wire between two trees or posts, this is done so the mushrooms do not come in contact with dirt.  A good spring rain will usually induce the logs to produce, to force them you can use a sprinkler or soak them in a water tank. The water is the stimulus needed by the mycelium to start the reproductive cycle. After fruiting the logs are rested for a couple of months and the watered again to produce another crop. An excellent book on log cultivation is Growing Shiitake in a Continental Climate by Mary Ellen Kozak and Joe Krawczyk. The Shiitake Growers Handbook by Paul Przybylowicz and John Donoghue is also very good but it also covers indoor cultivation of Shiitake on sawdust blocks.

The techniques describes above for shiitake mushrooms can also be used to cultivate Tree Oyster, Monkey head or pom pom mushroom (Hericium erinaceum), Chestnut mushroom, and many other primary decomposer species.

Log Management

Indoor sawdust/wood chip blocks cultivation

Most of the primary wood decomposers can be grown indoors on a block made up of sawdust, wood chips and bran. The ingredients are mixed together and placed in autoclavable polypropylene bags that have a breathable patch ( a filter that allows the exchange of gases). The bags are then sterilised to kill all bacteria and competitor fungi. After sterilisation and cool down grain spawn is mixed into the sawdust in a sterile environment and the bags sealed. The mycelium will run through this mixture in 3-4 weeks at 75 F (25C). After full colonisation the “blocks” are removed to a growing room where the bag is removed. The growing room is kept at a constant temperature and high humidity thereby promoting the fruiting of the mushrooms. After the mushrooms are picked the blocks are rested for 2 weeks and the cycle is begun again by soaking them in water. See The Mushroom Cultivator, and Growing Gourmet and Medicinal Mushrooms by Paul Stamets and The Shiitake Growers Handbook by Paul Przybylowicz and John Donoghue for excellent instruction on growing by this method.

Indoor straw block cultivation

Oyster mushrooms are very aggressive colonisers and can compete successfully with some bacteria. They grow very well on pasteurised straw (any cereal straw is usually suitable as well as many other substrates). Pasteurisation only requires the substrate to be heated to 160F for about an hour, which can be accomplished by boiling in water. Grain spawn is then mixed into the cooled down straw in a clean area and the mixture is bagged. The mycelium will run through the straw in a couple of  weeks and then the bags can be placed in a growing room and fruited. The Mushroom Cultivator, and Growing Gourmet and Medicinal Mushrooms by Paul Stamets is a good reference.

 Many species of mushrooms require stimuli which are only available outdoors to produce fruiting bodies. It may be the bacteria in the soil, the pH of the soil, the varying temperatures, whatever it is they will not do as well indoors in a controlled environment. Shaggy manes, Stropharia rugoso-annulata and Morels are some of these. One outdoor growing technique involves digging a trench or making a raised bed in a suitable spot, which may be under your bushes, in your garden between the rows of vegetables or in your  bush. This trench is then filled with wood chips or  straw or both. It is then inoculated with grain spawn or sawdust spawn, covered with topsoil and watered. If kept moist the mycelium will take over the substrate and a couple of months later will produce mushrooms. A good reference is Mushrooms in The Garden by Hellmut Steinbeck.

Home cultivation

Any of the methods described above are suitable for home cultivation. Sawdust or straw based kits are easily available and can be grown successfully in a small area of your kitchen using a plastic tent to provide the necessary micro climate suitable to mushrooms. Logs can be placed under your flowering bushes in the back yard and will provide you with crops for a few years with little work. Bed cultivation is an easy step for the person with a “green thumb”

Mushrooms are a tasty addition to your diet and are a good source of protein, minerals and some vitamins. They are good for your garden as well because they break down organic matter and make the nutrients available to your plants. As well as many edible species, medicinal mushrooms such as Reishi or Ling Zhi can easily be grown in kits. The usefulness of mushrooms in the fight against cancer and AIDS is just becoming known as more research is being done, especially in Japan. Medicinal Mushrooms by Christopher Hobbs details the medicinal properties of many wild and cultivated species.

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