Mushroom Plug Spawn Log Inoculation Instructions: Grow Mushrooms on Logs & Stumps
All of these Mushroom Plug strains are bred to grow and produce mushrooms in a wide range of temperatures.  They grow and produce mushrooms well in warm, as well as cold climates.

Mushroom Plug Spawn Log cultivation is usually done with logs 4 – 6 inches in diameter with a length of 3 to 4 feet. Oak is particularly good for the cultivation of most mushrooms though many other species work well also: poplar, aspen, sugar maple, willow, alder and birch, among others.  Approximately 100 plugs are needed to inoculate 3 – 4 logs.  Mushroom Plug Spawn may be used immediately or can stay viable for up to 6 months in a refrigerator.  Tree species to avoid include many of the conifers, eucalyptus, hackberry, beech and dogwood. For certain mushroom species such as  Reishi, hemlock, fir, and spruce can be used.

The best times for cutting the logs are either in the winter months for spring inoculation or after July 15 for mid-summer or fall inoculation. When inoculating logs in the summer, it is best to do the inoculation in the morning in a shady place. When selecting logs for mushroom cultivation, choose healthy, living trees without signs of decay or mushrooms growing on it. If the tree is dead, it will certainly already have other, competing fungi growing in the wood.  Sapwood and cambium are sources of nutrition for mushrooms (Sapwood contains living cells and is located next to the cambium; sapwood size varies by species and where the tree is growing.); the larger the sapwood area, the more productive the log will be.

Using logs from a dead or unhealthy tree will either lower your yields or prevent production altogether. It is best to inoculate logs in early spring if they have been cut during the winter. You can usually begin to inoculate logs one month before the average last frost date as long as day-time temperatures are above 40o F.

Log Preparation

If you cut logs during summer, it is best to inoculate them within 3 weeks after they have been cut so that the logs will still have an adequate moisture content. After inoculation, the logs are just placed in a shady place out of the wind.  The logs must be maintained in an environment above 40 percent moisture and kept fully shaded in the summer. Under natural conditions, mushrooms fruit in the spring and fall when temperatures are cool.

Logs generally begin producing 6 months to 1 year after inoculation; after which, they usually continue to fruit once or twice a year for up to 4 years producing 1-2 lbs. per year. Mushroom production depends on the depth of the cambium and sapwood and environmental conditions.  The timing of mushroom production in nature depends on both temperature and the timing of rain. Once a log has “flushed” (produced a crop of mushrooms), it should be allowed to “rest” for at least 10 to 12 weeks. This provides the mycelium (roots) time to replenish the energy required for fruiting.  Each log usually produces 2.5 lb – 4 lb over its lifetime. For inoculation, you will need a drill with a 5/16-inch drill bit, a hammer, and cheese wax.

Step 1:

Drill 1 ¼ – 1 ½ in. deep holes into the log spacing the holes about 3 – 4 in. apart within a row. Leave approximately 3 to 4 in. between the rows and offset the holes so that they will create a diamond pattern that evenly covers the log and allows the mycelium to spread along the grain of the wood.

A 4 in. diameter log will need 6 rows; a 5 in. diameter log will need 7, and a 6 in. diameter log will need 9 rows.  A 4 in. log usually is given about 40 – 50 plugs. The more plugs you use per log, the faster the wood will be colonized with mushroom mycelium.  A large stump usually requires 100 holes arranged in a similar hexagonal / diamond fashion around the trunk and with holes on the top of the stump, as well. All mushrooms are inoculated into logs in the same way.

Step 2:

Hammer the plugs into the holes.

Step 3:

Cover the plugs with the Organic Cheese Wax.  To do this, melt the wax in a pan which can be maintained at 300F. An electric frying pan with a thermostat control works well for this.  If inoculating away from electricity, using a camp stove, make sure that the wax is hot when you apply it. Otherwise, the wax will not create a tight seal and can easily fall off. The wax can be applied with a foam paint brush or cotton dauber.

Mushrooms can also easily be grown on a small scale for home consumption in a highly productive backyard mushroom garden with just a few logs.  By inoculating just 10 logs each year, one can harvest up to 25 pounds of fresh mushrooms each year. The total number of mushrooms you can expect to get on each log or stump will vary from log to log, from season to season, and from year to year.  Approximately 100 plugs are needed to inoculate 3 – 4 logs.

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For Details on Log Cultivation, See:

Growing Shiitake Mushrooms in an Agroforestry Practice (PDF)


A Guide to Outdoor Mushroom Log Cultivation: Highlighting shiitake, reishi, and tree oyster mushrooms (PDF)