University of Vermont Extension
Late Winter/Spring News
Department of Plant and Soil Science
GROWING SHIITAKE MUSHROOMS
Dr. Leonard Perry,
University of Vermont
You may have seen shiitake mushrooms
in stores or on restaurant menus, as they are becoming increasingly
and not just in gourmet cuisine. One
reason is for their flavor, meaty and buttery fresh, and smoky when
dried. They’re low in calories but high in protein, B
vitamins, vitamin D, minerals, and dietary fiber. They provide
healthful flavonoid compounds,
comparable to apple peels (the healthiest part of apples). With a
few logs in a
shady spot, and buying some of the “starter plugs”, you can grow
mushrooms easily at home.
Shiitake mushrooms have been grown
for thousands of years in Asia, originally found growing in the wild
mountainous regions. Today, it is the
second most grown mushroom in the world, next to the common button
mushroom. They are good in soups, stews, Asian and
pasta dishes, with seafood or poultry.
The stems—tough to eat—are good in broths.
The shiitake has a lightly convex
“cap” or top, 3 to 6 inches across when mature.
It is light to dark brown, with white “gills” underneath. The caps
are on top of a 2 to 4-inch, light
brown stem. If you see such mushrooms
naturally in the woods, make sure they are shiitake and not another
species that may be toxic. If you aren’t
positive, check with a local mushroom expert or “mycologist”, often
college or university.
Unlike many mushrooms which grow on
compost or manure-based potting media, shiitake mushrooms grow on
logs. You’ll need to obtain or cut logs (“bolts”) about
3 to 6-inches across, and 3 to 4 feet long.
For ease of handling, consider the 3-foot lengths for the thicker
logs. The best logs are from hardwood
trees (“shii” is “from hardwood trees” in Japanese), particularly
and sugar maple. Avoid fruit wood such as apples, ash, soft
hardwoods such as aspen, or evergreens such as pine or spruce.
Since this mushroom (as all
mushrooms, this one is a fungus) doesn’t compete well with other
logs should be freshly cut within one day to three weeks of use—the
better. Late winter and early spring is
the best time to cut logs, but if you’re too busy then, you can cut
winter and store until spring. If
storing, keep them off the ground so they get less contamination
from rot and
organisms, and keep them in shade or under a cover.
Once you have the logs, they need to
be “inoculated” with the fungus. Most
find it easiest to order “plugs” of the inoculum. You can easily
find sources online by
searching for “shiitake mushroom supplies”.
Since you’ll want to inoculate soon after cutting logs, you’ll want
order these plugs ahead of time. You can
store them in the refrigerator if needed.
plugs are just that, which you insert into holes drilled into the
logs. The plugs consist of sawdust, the fungal
inoculum (usually called spores, but correctly they are fungal
“hyphae”), and some grain material for nutrients for the fungus.
Figure on a minimum 30 to 40 plugs per log,
so a packet of 100 would be good for a couple logs.
Drill holes the size of the plug in
the log, making holes about 3 inches apart, and in staggered rows.
You may figure on one row for each inch log
diameter, so a 5-inch wide log might have 5 rows of plugs. Then
insert the plugs
in the holes, and seal the holes so competing fungi won’t enter.
Seal the holes with cheese wax
(available from cheese companies or online suppliers), or bees wax
crack at very low temperatures), or paraffin.
While sealing the holes, also seal any areas missing or with damaged
bark. These areas can allow other fungi to enter.
As when storing logs, keep these
inoculated ones off the ground, and in 80 percent to full shade.
The north side of a building can provide
this, as can a burlap cover. Don’t use
cover such as plastic, which keeps out air and rain.
Direct sun and wind can damage the
early fungal growth or “spawn”, and can dry out the logs. The fungus
moisture from the wood to grow. Ideally,
moisture content of the wood should be above 35 percent. During
you should wet the logs down well, as with a garden hose or under a
for a couple of hours.
So once you have the logs, and they
are inoculated and sealed, they need a period (“spawn run”) of 8 to
for the fungus to “colonize” or grow through the log. This is
usually done laying four logs
horizontally, then another four on top in the other direction, and
The shiitake fungus should
eventually “fruit” or produce mushrooms on its own, but this is
unique in that
more production can be forced sooner and around the same time by
“shocking”. This is simply done by
soaking the logs in cold water for 12 to 24 hours, during the warmer
night temperatures are generally above 50 degrees. A pond or stream
of cold water is ideal, but
any large container will work such as a cattle trough, even a small
Once logs are shocked or forced,
stack them in an A-frame arrangement, or simply leaning up at an
a structure or side of a building. If
they don’t fruit in a few weeks, you may need to shock again. Or, if
fruited, allow them to rest for 6 to 8 weeks before shocking again.
A few days to week from shocking the
logs, you should see small white dots or bumps the size of a pencil
eraser. These are called “pins” and this
process of early mushroom growth is called “pinning”. From this
point until harvest, cover the logs
with a white woven frost blanket (available from complete garden
online), or even a sheet if cold or frost is predicted. Cover logs
and the growing mushrooms with a
canopy or plastic cloth when rain is forecast.
Rain will cause soggy, waterlogged mushrooms.
Covering logs with a white,
lightweight cloth as used for row covers with vegetables, can
protection from the few insects that may bother the developing
well as squirrels and chipmunks. The
most common problem is slugs. There are
many less toxic controls than poison slug baits, including rolls of
newspaper (which slugs hide in by day and you can discard), saucers
(which attracts them, and they drown), or simply gravel under the
keeps the area less moist and so less attractive to slugs.
Shiitake mushrooms may be ready for
harvest in 7 to 10 days from shocking, longer if cool weather. Most
yield is in the second and third years,
with one quarter to one half pound per log typical. Harvest when
the “gills” underneath are
visible, and the outer edge is slightly curled under. If the edge
is flattened out, the mushroom is
overripe but still edible. Either twist
off, or make a clean cut with knife to lessen bark damage. Merely
brush off dirt, but don’t wash. They
should go into refrigeration within an hour of picking.
Mushrooms can be used fresh, frozen,
or dried. If kept cool (41 degrees F),
dry, and dark, they can remain fresh for several weeks. Use a paper
bag, not a plastic bag nor
airtight container. For freezing, first
soak in a solution of one teaspoon lemon juice to a pint of water,
minutes. This reduces darkening. Then steam slices or quarters for
whole for a little longer. Cool, drain,
and place in freezer storage bags or containers.
For drying, remove stems, then place
them on trays, bottoms (gills) up. In a
dehydrator, they should be dried until they are light but still
flexible. In the oven, they will need to dry on low
heat (200 degrees F, with the door ajar). Once dried and cooled,
plastic bags in a cool, dark place. Reconstitute
dried mushrooms by soaking in hot water for 20 minutes.