Inoculating logs with mushroom spawn is similar to starting seeds indoors for planting outdoors when danger of frost is over. Both require procuring growing media, tending nursery beds of growing organisms until they are ready to take off on their own, and lots of watering. This year we are trying a more challenging variety than oyster mushrooms that we've grown successfully for a few years. Oyster mushrooms grow in a much wider variety of soft hardwoods, including trees that commonly grow around here: popular, ash, willow and many "weed" varieties. This fungus aggressively colonizes these woods and out competes fungi that are commonly found in these logs. This year we will use a large ash-leaved maple for producing golden oysters. For growing the more difficult to grow shiitake mushrooms, a friend brought us a pickup truck full of red oak logs, the best medium for growing this hardwood loving variety.
Although we placed our popular logs on corrugated cardboard to prevent soil organisms from competing with the oyster mushroom spawn we used, two years later there are shelf fungi emerging from many of the logs. To prevent this from happening this year, we are placing our logs on old two inch thick solar panels that have an aluminum skin to keep them elevated above the ground. We have kept the bark very clean, minimizing any contact with soil. Within a few days of harvest, the cut ends of the logs and limb nubs have been coated with latex paint both to conserve moisture and to prevent airborne fungi spores from colonizing these wounds.
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| Red Oak and Ash-leaved Maple Logs Ready for Inoculation |
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| Shelf Fungi Competing with Oyster Mushrooms in Two Year Old Popular Logs |
We cut our mushroom logs to lengths that are readily handled. Since we did not have the luxury of ordering uniform logs that optimize the amount of sapwood available, three to eight inches, for mushroom mycelium to colonize, our diameters from only three trees vary from four inches to well over a foot. We ordered 5.5 pounds of each variety of mushroom spawn growing in sawdust that will colonize about 30 logs each. The process starts with drilling 7/16" diameter holes evenly spaced about 6" apart along and around each log. The tool I use pulls itself into the log and automatically stops at an inch deep. A fixture with four wheels makes it easy to rotate a log so that it takes only a minute or two to make the 25 to 40 holes required. These holes are then filled with the sawdust impregnated with mycelium using an injection tool that compresses the mixture so the top is just below the surface of the log bark. This depression is then sealed with hot cheese wax that we've saved from two years of fancy cheeses. The completed logs then look like they have a bad case of chicken pox!
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| Drilling Holes in a Log on a Fixture That Facilitates Rotating the Log |
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| Sealing Injected Mushroom Spawn with Molten Cheese Wax |
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| Wax Both Seals in Moisture and Prevents Competing Organisms From Entering the Wound |
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| Completed Red Oak Logs with Shiitake Spawn Sealed In |
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| Closeup of Logs with a Bad Case of Cheese Pox |
Once the logs have been inoculated and sealed, they are stacked close together on the north side of a building so they are always in shade to prevent them from drying out. They are also under the eaves so that they are directly watered every time it rains. When it doesn't rain for a few days, I'll spray them with water. I'll place boards on the east and west sides of the piles to keep early morning sun from shining on them and minimize wind from drying them.
If we're lucky, we'll be getting the first blush of mushrooms from these logs this fall, but real production won't occur until next year. Then, with any luck, we'll get up to seven more years of mushrooms in diminishing harvests.
