How to Grow Mushrooms on Logs Outside

Inspired by our shiitake log and curious how the process started, I spent some time online reading about growing mushrooms. The process typically starts by inoculating logs via sawdust or plugs. Plugs seemed to be the easiest way to do it on a small scale at slightly higher price than sawdust. Pure spores could also be used, but the other two have a higher success rate and a lower price. Mushrooms grown outside on logs are supposedly more flavorful than their indoor counterparts. 



Lots of the tasty varieties grow on logs. I found two sites online that were selling plug spawn: fungi perfecti and field & forest. We selected two types of oyster, one shiitake, and one turkey tail. Each of the above bags holds about 100 plugs which is enough to start two ideal logs. An ideal log is freshly cut and four to eight inches wide and three to four feet in length.



Thinking about drilling 50+ holes in each log was a bit overwhelming. A regular drill would take a long time. Field and Forest had an adapter to turn an angle grinder into a high-speed drill. I bought one with my plug spawn along with an 8.5mm high-speed bit. It made the process MUCH easier. I was able to drill a hole in about a second or maybe slightly less. It was impressively fast, and totally worth the small price of the adapter. Each hole was just over an inch deep which is slightly longer than the plugs.



I drilled the holes about six inches apart alternating each row to get a diamond pattern. Each of the holes would be the starting islands for the mycelium to spread out and colonize the log. Mycelium likes to connect to other mycelium, so the pattern gives the biggest mass and most coverage.



Next, we put the plug spawn into the holes. Plug spawn is essentially just wooden dowels colonized by mycelium. They usually have grooves for the mycelium to live in and survive being implanted into the logs. If they didn’t, the mycelium could be scrapped off when inserted. The mycelium is the white stuff on the dowel below. Wearing gloves is a good idea to avoid harming the mycelium due to antibacterial soap residue on your hands. An alternative to gloves is to rinse thoroughly.



A few gentle taps from a rubber mallet and the plugs are easily inserted.



We dabbed some soft wax over the holes to seal them up against the weather and insects. Mycelium are high in protein and apparently a tasty treat to roaming insects. They also dry out easily. We wanted to give them a chance to get established before having to worry about competition and weather.



A finished log ready to incubate. We were able to finish six logs in about 80 minutes including setup and cleanup. It would have gone faster, but the first two took a while as we figured out how it all worked. The grinder made a big difference in speed. 



Here is our incubation pile. This is a very shady spot in our backyard. The shade will help control moisture loss. The logs have been stacked so none are blocked from the rain by the log above. The six logs on top have been inoculated with plug spawn. In the upper left of the pile, you can see the metal tag we used to mark each log with date and strain. The bottom two logs have not been inoculated and are there just to keep the incubating logs off the ground. We want to give our mycelium a chance to get established before other competing with other varieties in the soil. Contact with the soil will cause the logs to decompose more quickly.

The incubation period is typically 9-12 months depending on how aggressive the strain is and the type of wood used. Each log should last several years hopefully fruiting several times each year. Next summer, we hope to get some mushrooms. Now we wait.

Tools Used:

• angle grinder
• rubber mallet
• gloves