Growing mushrooms on logs is a fun way to enjoy fresh mushrooms at home. Log-grown mushrooms are satisfying even if you only have a small back yard!
Any hardwood-loving mushroom species can be grown on logs. That includes shiitake, various oyster varieties, reishi, and lion’s mane. Although log cultivation doesn't have the same predictability as indoor grown mushrooms, the process to grow them is much simpler. It involves first inoculating hardwood logs with mushroom mycelium, and then allowing the log to colonize naturally over a period of six-to-nine months. When the logs are fully colonized, and the weather conditions are right, the mushrooms will emerge from the log and can be harvested and enjoyed.
What is plug spawn?
Mushroom plug spawn, also known as dowel spawn or mushroom plugs, are hardwood dowels that have been inoculated and colonized with mushroom mycelium. The plugs are used to inoculate hardwood logs and stumps for the purpose of growing mushrooms outside.
Although typically used for growing shiitake on logs, mushroom plugs can also be used to inoculate any hardwood loving species, including lion's mane, reishi, oyster, and others.
Why Use Mushroom Plugs?
There are many different ways to inoculate logs for growing mushrooms, all with varying levels of difficulty and predictability.
These methods include everything from sandwiching sawdust spawn between layers in tree stumps, to cutting wounds into a log or stump with a chainsaw blade covered in "spore oil." Using properly-made mushroom plugs is both easy to do and relatively reliable. Once you have plug spawn, the process of log cultivation is actually pretty straightforward.
What You'll Need
- Hardwood Logs: Many types of hardwood will work, including aspen, birch, poplar, oak, maple, etc. In general, avoid softwoods (spruce, pine, fir) and fruit trees. Different species of tree will work better for different species of mushrooms.
- Plug Spawn: 3/8" dowel spawn works best.
- Adequately Sized Bit: Any power drill with a suitably sized wood bit. You want a tight fit between the dowel and the log.
- Hammer: This is for pounding in the dowels. They will be too tight to push in by hand.
- Paraffin Wax (or Beeswax): Wax is needed to protect the inoculation points from drying out before the mycelium gets a chance to grow.
Step 1: Harvest or Gather Logs
First, you’ll need to find a log suitable for the mushroom species you want to grow.
Good choices for mushroom logs are hardwoods like Aspen, Maple, Beech, Oak, Poplar or Birch, and what is best for you will depend on what grows naturally in your area.
Look for logs between 4-8” thick, and chop them to between 3 and 4 ft long.
The logs can be harvested anytime, although it is often recommended to harvest the log in the fall or spring, when temperatures are below freezing at night and above freezing in the day. Logs plugged under these conditions can produce mushrooms in four to five months. However, you can have success plugging logs all year just as long as logs are recently cut (within the month) from a disease-free tree.
Step 2: Soak Logs
This is not completely necessary, but it does seem to help. The logs should be soaked in water for a week or so in order to become more suitable for colonization.
You can do this by floating the logs in a lake or pond, or by staking them in the yard and soaking them with a hose. You can wrap them in burlap to ensure they do not dry out too fast.
Step 3: Drill Holes
Drill holes all over the log, approximately 4 inches apart. Some people form different stacking patterns with the logs, but the pattern doesn’t really matter, as long as there is a suitable number of holes.
Use a drill bit that is nearly the same size as your dowel, so that you’ll get a nice tight fit with the mushroom plug. Holes should be about 1-¼” deep, or just deep enough to fully take in the plug. Do as best you can to clear the remaining sawdust from the holes to make room for the plugs. This can be time consuming, and much more comfortable if you can get some sawhorses or a table to keep the logs off the ground.
Step 4: Inoculate the Log
Inoculate the log by pounding the dowels into the holes. They should be too tight to push in by hand, but can be gently pounded in with a hammer or mallet.
Step 5: Wax Over Plugs
In order to keep the plugs from drying out, you need to cover the freshly inoculated holes with wax.
Paraffin wax or beeswax both work great. Heat the wax until it is malleable enough to spread, and then place some over the hole. Use a spreading tool so not to burn your fingers!
Some growers also like to cover the top and bottom of the log with wax to prevent moisture loss, but this is not necessary.
Step 6: Wait For Mushrooms
Once inoculated, place the logs in a shady spot so they can colonize. Shade cloth works well for this, but if you have a suitable location, feel free to just lay them down in the forest. You can even dig a small hole in the ground and stand your logs up.
The important part is that they are not inundated with direct sunlight, and that they stay relatively moist. Check your logs often, and don’t be afraid to set the sprinkler on them every once and awhile. Alternatively, you can also just stack them up and cover them in burlap as they colonize.
How long until the mushrooms show up?
If your logs were properly inoculated with plugs from a trusted source, then it is relatively unlikely that another species will grow in its place.
That said, it is definitely possible that another type of mushroom could fruit instead.
Make sure you can safely identify any mushrooms before eating!
With careful management, each log should produce around two pounds of mushrooms over its lifetime. Many variables can affect overall production. Expect mushrooms within one year; the total productive life of a log can be 4 to 6 years.