How to Cultivate Mushrooms in Natural Logs

© 2013 Mushroompeople
Select healthy trees with medium-thick bark. Oaks are best, but hornbeam, ironwood, hard maple, and sweet gum also work well. The lighter hardwoods give faster results but don’t last as long as the denser hardwoods like the oaks.  Do not use softwoods like fir, pine, or cedar because they contain fungicidal resins.

Harvest your trees and cut your logs in the Fall, Winter or Spring. For best mushroom yields, trees should be cut after the leaves turn brown, when the sap and sugar migrate down to the branches and trunk to act as antifreeze. Good sources of logs include firewood suppliers, tree-trimmers, and  farmers. The ideal logs are 3″ to 6″ in diameter and cut 40″ long. Avoid damaging the bark by rough handling. Loosely stack the logs in dappled shade with some space between them, or cover them with 80% shade cloth.

Inoculate the logs within 3 weeks or less after cutting them to size.
Downed or cut whole trees can stay fresh for one or two months.
If you’ve experienced a recent drought, soak the logs by immersing in clean water for 24 hours, but let the bark dry before inoculating.
Place the logs on two 2”x6”s between sawhorses. You will need a drill and bits. For plug spawn, use a 5/16” bit and drill to 1” depth. For sawdust spawn, use a 7/16” bit, and drill to 1/2” depth below the bark. Start about 2” from the end of the log, and drill the holes in a grid pattern, spaced about 6” apart along its length, and  2 1/2” around its perimeter.
Inoculate each log immediately after drilling the holes. If you are using plug spawn, tap a plug into each hole with a hammer until the plug is flush with the bottom of the bark. For sawdust spawn, jab the end of the inoculating tool into the open bag of spawn to pick up some spawn, place the end of the inoculation tool over a hole, and push the handle down with your thumb, squeezing the sawdust spawn down into the hole. Knock off any excess spawn with your finger.

Waxing  Check that all the holes in a log are inoculated. Dab a thin coat of melted, hot cheese wax over each inoculated site, using a bristle brush or a wax dauber. Don’t let the wax get too hot, or it can flash into a fire. The wax protects the spawn against drying and insects.

Tagging  Use a ballpoint pen or a PaintStick to write the date and the mushroom strain on an aluminum tag or a plastic tag cut from a milk carton . Staple or nail the tag to the end of each log.

Stacking  Stack your logs in a year ‘round shady spot, a shaded greenhouse, an open shed, or under evergreen trees. The logs can also be covered with 60-80% shade cloth, which discourages hungry deer. Place your stack within the pattern of a water sprinkler, or next to a soaking tank. We recommend the Lean-To Stacking method shown below.

Soaking   After inoculation, the big task is to keep the logs from dehydrating.   The most common cause of failed crops is dried up logs. During the nine-month spawn-run (incubation period), soak your logs by sprinkling them for 2-3 hours once or twice a week, or by immersing them in water for 8-12 hours every two weeks or more often depending on the weather. You can use a clean trash can for 8 hours, then flip the logs end-over-end and soak them for another 8 hours.  The idea is to maintain a 45-60% internal log moisture content. It’s best to do infrequent deep soakings, but frequent light ones may be needed when it’s hot and dry.
It is very important to ALLOW THE BARK TO DRY BETWEEN SOAKINGS in order to discourage weed fungi. Logs should always be stacked spaced about a log-width apart. Stack the logs off the ground to reduce direct contact with dirt. Bricks, concrete blocks or a 3″ layer of gravel work well, and helps keep bugs away.

Fruiting   The spawn-run (incubation) period requires at least one warm season. If you  inoculate some logs every year, this is a one-time wait.   The mycelium produces mushrooms in response to stress, for example a rapid increase in moisture and a sudden drop in temperature. The first harvest occurs naturally after cool Fall or Spring rains. Once fruiting has begun, keeping optimal temperatures and high air humidity will produce higher yields and uniform quality. Fruiting is close when white splotches of mycelium appear at the ends of the logs. You can choose to let the logs fruit naturally while keeping them from drying out with an occasional deep soaking during hot, dry weather. This “natural” fruiting method yields lots of mushrooms in the Spring and Fall, but few or none in the Summer and Winter. The other method is forced fruiting.

Forced Fruiting  Immersing mature logs in cool water for 24 hours simulates Spring and Fall fruiting conditions. Within 3-4 days, buds (primordia) emerge from the log and grow to mature mushrooms in 5-7 days. You can let the mushrooms grow to any size up to 7″ diameter, but the larger the mushrooms, the fewer are  produced by the log. Four inches or less is a nice (and sellable) size.  To harvest, cut the stems flush with the bark using a sharp knife. Place the mushrooms in a paper or plastic bag, and store at 34-41ºF for up to a month. After fruiting for 7-10 days, each forced fruiting tapers off, and now the mycelium requires 6-8 weeks to digest more wood for the next fruiting. During this “resting” stage, the logs may be crib-stacked in a sheltered place (see figure), and covered to allow slow drying. Excessive drying of a log can kill the mycelium; but allowing rain to soak resting logs will cause premature fruiting, smaller harvests after the next soaking, and thus wasted labor.

 COMMERCIAL OPERATION:  Forced Fruiting for Year-Round Daily Harvests: Separate and label your logs into 5 or 6 stacks. Soak a stack every week (a few logs a day), by immersing the logs for 24 hours in cool, clean water. Each stack is rotated through the soaking tank every 6-8 weeks. A basement room or a greenhouse that is cool and humid will allow year-round production. Logs to be fruited in Winter and Spring should be rested indoors between soakings because mycelium stops digesting the wood once the average temperature drops below 50º. To reduce any heating/cooling costs, force-fruit the wide-range and cold strains in the cold months, and the wide-range and warm strains in warm months. An average-sized log yields 1/4 lb per fruiting, or 3-4 lbs. over the lifetime of the log. The best mushroom prices go for high-quality mushrooms and reliable deliveries to restaurants, produce, and health-food stores year ‘round.

Inoculating during freezing weather  Freezing the freshly-inoculated young mycelium can delay the log fruiting for months. Keep your logs indoors for 2 months, loosely wrapped in plastic to prevent excessive drying. After 2-3 months the logs can be taken outside. They can survive minus 50ºF and go dormant until Spring. Logs benefit from deep soakings from rain and snow.

WHAT ARE THE COMMERCIAL RETURNS FROM GROWING SHIITAKE?

Growing Shiitake on One Cord of Wood
No cost is assigned to logs or to labor.  Logs are 4″ diam x 40″ long, with 300 logs per cord. Seven lbs. of fresh mushrooms dry down to 1 lb.
Inoculation Cost:                                                Per cord       Per log
Plug spawn: 10 bags @ 1000 plugs/bag,                $350           $1.17
Sawdust spawn:  15 bags @ 1 Kg/bag                   $285           $0.95
Returns over logs’ 2-3 yr lifetime, at the lowest wholesale price of $4/lb delivered:
Sold fresh: 2.25 lb/log x 300 logs x $4/lb               $2700          $9.00
Sold dried: 0.321 lbs/log x 300 logs x $13/lb         $1252          $4.17
70% sold fresh, 30% sold dried:                         $2266          $7.55
Wholesale delivered prices vary from $4 to $9 /lb. The best prices are paid for reliable deliveries made to produce managers and restaurant chefs every week.