Mushrooms are not plants, and require different conditions for optimal
growth. Plants develop through photosynthesis, a process that converts
atmospheric carbon dioxide into carbohydrates, especially cellulose.
While sunlight provides an energy source for plants, mushrooms derive
all of their energy and growth materials from their growth medium,
through biochemical decomposition processes. This does not mean that
light is an unnecessary requirement, since some fungi use light as a
signal for fruiting .
However, all the materials for growth
must already be present in the growth medium. Mushrooms grow well at
relative humidity levels of around 95-100%, and substrate moisture
levels of 50 to 75%. 
Instead of seeds, mushrooms reproduce sexually during underground
growth, and asexually through spores. Either of these can be
contaminated with airborne microorganisms, which will interfere with
mushroom growth and prevent a healthy crop.
or actively growing
mushroom culture, is placed on growth substrate to seed or introduce
to grow on a substrate. This is also known as inoculation, spawning or
spawn. Its main advantages are to reduce chances of contamination while
mushrooms a firm beginning. Spores
are another inoculation option, but are less developed than established
Since they are also contaminated easily, they are only manipulated in
laboratory conditions with laminar flow cabinet.
All mushroom growing techniques require the
correct combination of humidity, temperature, substrate (growth medium)
and inoculum (spawn or starter culture). Wild harvests, outdoor
log inoculation and indoor trays all provide these elements.
Due to its climate, the Pacific Northwest produces commercially
valuable mushrooms. Valued species include :
Mushroom gatherers have the fewest requirements to begin business.
Gatherers only need to supply funds for possible park fees, knowledge
for identifying mushrooms and gathering time.
There are significant disadvantages to relying on natural mushroom
production. These sales may be unregulated, placing buyers at risk for
buying toxic or inedible mushrooms. By honest error, harvests may
include toxic or inedible species. No controls exist to regulate the
quality or frequency of harvests, since gatherers rely on favorable
natural conditions and weather to produce fruiting. Conflicts may arise
between competing gatherers trying to harvest from the same location.
State parks in the Pacific Northwest or elsewhere may charge fees for
mushroom gathering permits . Appalachia also produces edible
wild mushrooms, including chanterelles and morels
. Pickers may
sell directly to distributors, restaurants, or sell their harvest
through roadside stands wherever a natural supply of mushrooms is
While there may be concern that harvesting wild mushrooms may exploit
or damage a natural environment, harvesting wild mushrooms is different
from harvesting wild plants, fishing or hunting animals. In these last
three cases, removing individuals decreases the ability of a wild
population to reproduce, since fewer adults remain. Removing adults
leaves fewer individuals capable of reproducing and reduces genetic
Harvesting wild mushrooms
removes only fruiting
bodies and their attached spores.
However, the fruiting bodies (mushrooms) have likely dropped spores
harvest time. While truffles
also represent the fruiting body of a larger underground network, they
exception, since they rely on animal spore dispersion.
and propagation can still occur by propagation of the parent mycelium. Harvesting
none of the parent mycelium, which remains intact underground.
Additionally, reproduction and
propagation can still occur by propagation of the parent mycelium.
Harvesting removes none of the parent mycelium, which remains intact
Mushrooms can be grown on logs placed outdoors in stacks or piles, as
has been done for hundreds of years
. Sterilization is not
performed in this method.
Since production may be unpredictable and seasonal, less than 5% of
commercially sold mushrooms are produced this way 
. Here, tree logs
inoculated with spawn, then allowed to grow as they would in wild
Fruiting, or pinning, is triggered by seasonal changes, or by briefly
the logs in cool water .Shiitake and oyster mushrooms have traditionally been produced using the outdoor log
technique, although controlled techniques such as indoor tray growing
or artificial logs made of compressed substrate have been substituted. 
Indoor growing provides the ability to tightly regulate temperature and
humidity while excluding contaminants and pests. This allows consistent
production, regulated by spawning cycles.
Indoor tray growing is the most common commercial technique followed by
containerized growing. The tray technique provides the advantages of
scalability and easier harvesting. Unlike wild harvests, indoor
techniques provide tight control over growing substrate composition and
growing conditions. Indoor harvests are much more predictable.
"[Indoor m]ushroom farming consists of six steps, and although the
divisions are somewhat arbitrary, these steps identify what is needed
to form a production system. The six steps are phase I composting,
phase II composting, spawning, casing, pinning, and cropping."
Earliest formation of recognizable mushrooms
Adjusting temperature, humidity and CO2 will
also affect the number of pins, and mushroom size [1, p. 14]
Repeated over 7-10 day cycles [1, p. 14]
Complete sterilization is not always required or performed during
composting. In some cases, a pasteurization step is not included to
allow some beneficial microorganisms to remain in the growth substrate
Specific time spans and temperatures required during stages 3-6 will
vary respective to species and variety. Substrate composition and the
geometry of growth substrate will also effect the ideal times and
Pinning is the trickiest
part for a mushroom grower, since a combination of CO2 concentration,
temperature, light, and humidity triggers mushrooms towards fruiting
. Up until the point when rhizomorphs or
appear, the mycelium is an amorphous mass spread throughout the growth
substrate, unrecognizable as a mushroom.
CO2 concentration becomes elevated during the vegetative growth phase,
when mycelium is sealed in a gas-resistant plastic barrier or bag which
traps gases produced by the growing mycelium. To induce pinning, this
barrier is opened or ruptured. CO2 concentration then decreases from
about 0.08% to 0.04%, the ambient atmospheric level 
converts raw natural ingredients into the cell walls of
most notably the carbohydrate chitin.
An ideal substrate will
contain enough nitrogen
mushroom growth. Common bulk substrates include :
in their substrate into glucose,
which is then transported through the mycelium as needed for growth and
While it is used as a main energy source, its concentration in the
medium should not exceed 2%. For ideal fruiting, closer to 1% is ideal.
Pests and Diseases
insects, bacteria and other fungi all pose risks to indoor production.
The sciarid fly
or phorid fly may
lay eggs in
growth medium, which hatch into worms and damage developing mushrooms
all growth stages. Bacterial blotch caused by Pseudomonas bacteria or
of Trichoderma green mold also pose a risks during the fruiting stage.
and sanitizing agents are available to use against these infestations .Biological
controls for insect sciarid and phorid flies have also been proposed
A recent epidemic of
Trichoderma green mold has significantly affected mushroom production:
1994-96, crop losses in Pennsylvania ranged from 30 to 100%" .
is the top-producing mushroom state in the USA, and celebrates
September as "mushroom month."
The borough of Kennett
is a historical and present leader in mushroom production. It currently
of Agaricus-type mushrooms,
followed by California, Florida and
Cultivating mushrooms in natural logs. Global Village Institute (1998, 2001).
Hill, Deborah B.. Introduction to Shiitake: The "Forest" Mushroom. Kentucky Shiitake Production Workbook..
Davis, Jeanine M.. [Http://Www.Ces.Ncsu.Edu/Nreos/Forest/Woodland/Won-20.Html Producing Shiitake Mushrooms: A Guide For
Small-Scale Outdoor Cultivation On Logs.]. North Carolina Cooperative
Shiitake and Oyster Mushrooms.. University of Kentucky College of
Agriculture New Crop Opportunities Center.