Wild mushrooms have been collected by people for food since before recorded history. Once is it was figured out which ones were the best to eat, it made sense to try to grow them to have a more reliable supply. It is difficult to trace the origin of mushroom cultivation but some species have been grown in Asia for many centuries.
Mushroom growing techniques have been developed to a high degree of technical efficiency. Proven methods exist for growing many kinds of edible or medicinal species. Mushroom growing kits can be purchased ready to be set up in an appropriate environment to produce mushrooms. Commercial quantities of mushrooms are grown using large scale production methods.
Mushroom Spawn Production
Before mushrooms of any kind can be grown, a quantity of starting material called “spawn” must be produced. Spawn is a mass of the white fuzzy mycelium of a fungus grown in a form suitable for inoculating a large quantity of substrate on which the mushrooms will be produced.
Grain spawn is prepared by inoculating sterilized rye grain in jars, with a pure mushroom culture. The mycelium grows throughout the grain and the spawn is expanded to any desired quantity by using the colonized grain to inoculate still other jars of grain. This type of spawn is convenient for starting mushrooms that grow on compost.
Dowel spawn is produced by inoculating bags of sterilized wooden dowels. When fully colonized, the dowels are driven into holes drilled in logs, or the dowels can be added to bags of wood chips or sawdust. Dowel spawn is used to culture wood-inhabiting species.
Growing Mushrooms in Compost
The classic commercial button mushroom (Agaricus bisporus) and the larger portabello (which is the same species allowed to get well past the button stage) is grown in tremendous quantities on mushroom farms around the world. Since the natural habitat of its wild predecessors was in pastures, this species is grown on a substrate of horse manure compost. Other species grown on compost include Coprinus comatus (shaggy mane) and Lepista nuda (blewit).
A number of variations on preparing mushroom compost exist, but two basic formulas are (1) horse manure, cotton seed hulls and gypsum, and (2) chicken manure, wheat straw and gypsum. The compost is inoculated with spawn and the spawn is allowed to completely colonize the substrate. Production of mushrooms is initiated after a peat-based casing layer is spread on top of the colonized compost.
Growing Mushrooms on Logs
Reishi mushrooms (Ganoderma lucidum), shiitakes (Lentinula edodes), hen of the woods (Grifola frondosa), lion’s mane (Hericium eriniceus), and oyster mushrooms (Pleurotus spp.) are all wood-decomposing fungi suitable for log cultivation.
Most species prefer hardwoods such as oak, maple, elm, cottonwood and alder, although a few species do well on conifer wood. The logs are best cut just before winter when their sap content is highest. Logs should be allowed to age for a month or two, but should be used before they dry out. Any size of log should work, but if the logs are big and heavy they take longer to colonize and are difficult to transport and handle. A length of about a meter and a diameter of 10-30 cm is good.
Dowel spawn is driven into holes drilled into the logs. The holes are sealed with wax to keep the inoculum from drying out before the fungus can become established in the wood. Under the best of circumstances, the logs will not be ready to produce mushrooms for six months, with a year or more being more typical. When the logs begin to show mycelia on their cut ends, they are close to being ready for fruiting.
Fruiting is initiated by soaking the logs in cold water for twenty-four hours followed by further incubation in high humidity with fresh air. Logs can produce flushes of mushrooms periodically for several years.
Growing Mushrooms in Sawdust and Wood Chips
Mushroom species that do well in logs can also be grown in bag culture using the same kinds of woods. Dowel inoculum, liquid spawn, or grain spawn is added to bags of sawdust and/or wood chips and thoroughly shaken. After two or three weeks, once the mycelia have grown throughout the wood, the bags are shaken again and incubated an additional couple of weeks until the substrate is fully colonized.
Then the bags are usually slit open and soaked in cold water for a day and incubated in high humidity with fresh air exchanges. Mushrooms are produced in as little as five weeks with this method and two or three flushes, with rest periods in between, can be achieved before the nutrients are used up in the wood.
Many mushroom growing kits come with a substrate of sawdust and/or wood chips. These kits are easy to set up since they come ready to produce mushrooms in a relatively short time once the correct conditions are established.
Other methods of mushroom growing exist for research or laboratory purposes, but the methods outlined above are the ones usually used by both commercial and hobby mushroom growers.
Stamets, Paul, and Chilton, J. S., 1983, The Mushroom Cultivator, Agarikon Press, Olympia, WA
Stamets, Paul, 1993, Growing Gourmet and Medicinal Mushrooms, Ten Speed Press, Olympia, WA
Note: This article was originally published at Suite101.com.