0yster
mushrooms are a delicious gourmet mushroom, relatively simple to grow in your
own home. There are many varieties, but the most commonly cultivated are Pleurotus
ostreatus and Pleurotus pulmonarius. They are primarily wood decomposers,
growing in forest situations, but for the home cultivator, straw makes an excellent
medium. In this class you will learn how to cultivate P. ostreatus on straw.
In the wild they are usually found growing on tree trunks and wood detritus.
However, they grow in all kinds of environments and temperatures. They grow
in a wide range of forest and agricultural waste products in areas where temperatures
range from 50° to 90° degrees, mostly in moist environments.
The
straw that remains after cultivation is excellent compost matter. Since it is
virtually pre-composted, it can be used directly out of the bags as either
mulch or compost.
Oyster
mushrooms are healthy. One-third of their dry weight is protein. They also
contain amino acids and enzymes that have been said to boost the immune system.
A recent medication advertised on TV for the prevention of Herpes outbreaks is
created from an extract of one of the Pleurotus family.
They can average
in size from about a dime to over 250 mm. across. They usually grow in clusters,
the entire cluster emerging from one small point. The stem tapers from the
small hole to the size of the fruit body. Gills run the full length of the stem
from the base all the way to the fringe. The stem attaches asymmetrically. The
cap may also be asymmetrical, mostly flat with a depression in the middle. They
are mature when the fringe turns down. Their color varies from light gray to
dark brown, usually getting lighter with age.
They
get their name from the fact that as they mature their color and shape
resembles an oyster shell. They have a distinctive flavor, smelling somewhat of
anise when freshly picked. Cooked, they reduce considerably as the water cooks
out and the stems are relatively woody.
They
have the ability to blend flavors, and are especially delicious stir fried or
baked with poultry.
What you will learn
By the end of this class, you will have created a growing
“block.” This is a small bag of inoculated straw. You will take one home with
you, and actually grow the mushroom in your home.
You will also learn how to prepare the straw, mix the
prepared straw with the spawn, pack and prepare your mushroom “block.” You will
also learn about mushroom spawn; the growing media (called the substrate); how
to prepare the substrate (straw) for the spawn; the care and feeding of
inoculated straw; spawn run or incubation; and the care and feeding of the
fruiting block.
Definitions
Substrate is the medium on which the cultivated
mycelium grows. Oyster mushrooms grow wild on a variety of broadleaf hardwoods
and especially in the west, on conifers. Home cultivation uses a small plastic
bag of prepared straw as a substitute tree trunk. The mycelium is the trunk.
The mycelium, introduced by the spawn, will completely infiltrate the straw.
This period is called the “spawn run.”
Mycelium is the true mushroom “plant.” The part you
eat is actually the fruit, often referred to as the fruit body. It is, in the
simplest terms, a compact form of the mycelium.
Spawn is grain on which the mycelium is growing. The
spawn used in this class is from a commercial spawn producer, and comes on rye
berries. Each berry already has the Pleurotus Mushroom mycelium growing in it.
Under the right conditions, the mycelium will grow from the rye berry into the
prepared straw. Each berry becomes a point of “inoculation.”
Inoculation is the mixing of the substrate with the
spawn. After the straw is cooled, the spawn is mixed into the prepared and
pasteurized straw.
Incubation is the period during which the spawn grows
out until it has completely filled the bag. At first you will see white fuzz
all around the grain kernels. Then the mycelium will reach out into the straw.
White patches will appear, and then there will be a white surface through out
the block.
Fruiting (the emergence of the mushroom) will occur after a
complete spawn run.
Preparing the Substrate
Straw is a fine substrate for the
commercial growth of many varieties of Oyster Mushroom, because it provides the
necessary cellulose base for fruiting. But it must be properly prepared for
mycelial growth.
The straw must first be chopped in order
to break down the straw body and break the waterproof coating on the straw.
This enables the straw to absorb water, providing a better medium for the
mycelium to grow.
You can chop your straw using various
tools. The tool most easily available is the lawn mower. The mower is placed on
flat, smooth surface and the straw fed into the side away from the exit blower.
Be very careful not to get your fingers under the mower body!!! Catch
the chopped straw into a corner or against a screen.
Other means to chop straw are: garden
chipper, mulching lawn mower, chain saw, and tub grinder. Small quantities can
also be chopped with a machete. Chopped straw can also be acquired commercially
from landscape and reclamation companies.
Pasteurize the Substrate
The prepared straw
must then be pasteurized
in hot water at 160° for 45 minutes. For small quantities, pack the chopped straw into a
five-gallon container, pour boiling water over the straw to cover, and let
sit for 45 minutes. Drain and cool to room temperature.
Large
quantities can be pasteurized
in a 55-gallon steel drum. First, pack the straw into a large burlap bag or
a wire mesh basket made from hardware cloth. Then heat the water in the drum
to 160° -170°.
A
simple heat source for the drum can be easily made using a propane weed burner
focused on the bottom of the barrel (we place the barrel up on blocks, then
blend the weed burner pipe at 90° and
place it facing the bottom of the barrel).
Cast
iron camp stoves can be used to quickly heat a 55-gallon drum. The marketplace
now has large burners being sold as “turkey cookers.” They are excellent.
Or you can use a wood fire. After the water has reached 160° to 170°,
place the bag or basket in the water. After about 15 minutes, turn off the
heat. Leave immersed for about 30 minutes more, then remove and drain
for 10 to 15 minutes.
Place
the pasteurized straw into a mixing container to finish cooling. (For large
amounts, we have found that a child’s wading pool is just the right size for
one large burlap
bag of straw.) Allow to cool.
This
is the fun part. To accelerate cooling, toss the straw in the mixing tub into
the air, until the straw is only slightly warm to the touch. Part of the fun is
to get your hands into it.
Inoculate the Substrate
Now mix
the spawn into the cooled
straw. If you calculate the dry weight of the substrate,
and add 10% of that weight in spawn,
you should have a proper mix. The commercial spawn we use comes in bags weighing
about 6.5 lbs. For a 55-gallon drum fairly full, use about one-third of a
bag of spawn. The straw in a 5-gallon bucket will weigh about 2lbs., so you
would only want to use a little less than a half-pound of spawn.
Mix
the spawn into the substrate until evenly distributed. Pack the inoculated
straw tightly into clear plastic bags (or tubes for larger quantities). Be sure
to pack it tightly, then tie the top off with a wire tie, or fold the top over
and use packing tape to create a seal. It doesn’t have to be air tight, as the
bag should be no smaller than about the size of a gallon jar. Tubes can be
created using plastic tubing up to 16 inches in diameter and 8 feet long. The
next step is very important. Using a 16d nail, punch holes into the bag, spacing
them about 6 inches apart.
(NOTE:
IT IS IMPORTANT TO PUNCH THE HOLES IN THE FILLED BAG. FAILURE TO DO SO WILL
KILL THE SPAWN.)
The
mixture must breath. If it can’t, it will go anaerobic and the spawn will die
and the straw will go sour. It also should not get too hot. While taking it
home, make sure it doesn’t sit in a hot trunk or in direct sunlight in your
car. The opposite is true, however, of cold. The spawn is unharmed in
temperatures down to and including freezing. Nominal temperature is between 70
and 80.
Care and Feeding of Your Take-Home Block
Incubation
You should incubate
in the dark at an optimum temperature of 70° until the straw is fully colonized.
The mycelium will be clearly visible. It should take about 10 days to colonize
at this optimum temperature. Temperature ranges of between 65° and 80° will
not harm the growing mycelium. After the block is fully colonized, cold-shock
the mycelium to start the fruiting cycle. To do this, place the smaller bags
in a refrigerator for 1 day. For commercial cultivation other means are used.
Remove from the cold and place in an area with an average temperature of about
65° to 75°.
Care of the Fruiting Bag
Prepare for the
fruiting
in advance. The fruiting
block will need to be in a relatively high humidity during the whole
fruiting cycle. Take a clear plastic bag, such as a dry cleaning bag, and
prepare a “tent” to place over the fruit block. You can use a coat hanger
to support the plastic bag. Place the bag in a warm area under this “tent.”
In only a few days it will start to show signs of the mushrooms growing. Keep
the humidity high. Spray (mist) several times a day. If the developing mushroom starts turning brown,
more humidity is required. Do not
remove the straw from the plastic bag unless necessary.
The
mushroom will form through the nail holes. (Believe it or not!!). When the mushroom gets to a dollar size or
larger, they can be picked. They can
get as large as 18mm across.
The
first fruiting will be the largest.
After all the mushrooms have been picked, leave the block under the hold
and continue to mist. There will be
another “flush.” With patience, the
block will fruit three, maybe four times.
After that, take the block outside and place in a shady moist area,
among plants you water often. Check it
out now and then. You may get even
more.
Congratulations!! You have become a mushroom cultivator.
Bon appetit!
**Please look at the following images of sucessful fruiting blocks produced
at one of John Corbin's mushroom workshops at the Telluride
Mushroom Festival 2000.**
