Rachel BairdShiitake mushrooms (Lentinula edodes) are among the most popular edible mushrooms in the world, and you can grow them outdoors on logs. Also called “Black Forest Mushrooms” and “Oakwood Mushrooms,” shiitake take their name from the shii tree on which they grow in their native habitat. Native to Japan, Korea, and China, shiitake mushrooms have adapted to growing on a wide variety of hardwoods.
While waiting for the first flush of shiitake mushrooms takes some patience, they are among the easiest mushrooms to grow on logs. Depending on the size and quality of the log, one log can produce shiitake mushrooms for up to eight years. Learn how to grow shiitake mushrooms outdoors on logs for a regular supply of this super forest mushroom.
Why Grow Shiitake Outdoors on Logs?
While shiitake mushrooms are the second most widely cultivated mushrooms in the world (second only to Agaricus Bisporus), they are still difficult to source fresh in many regions. China is the world supplier of shiitake, producing over 80% of those commercially sold. Like many mushrooms, shiitake have a short shelf life, so it is more common to find dried shiitake. However, for those on a hunt to try fresh shiitake, your best bet is a local farmer’s market, an Asian market, or to grow them yourself.
Shiitake mushrooms are easy to grow outdoors, fruiting on oaks, maples, sweet gum, and most other hardwoods, in addition to their namesake Shii tree. Logs usually fruit within 6 to 12 months of inoculation and can continue producing for up to eight years (depending on the type and diameter of the tree used). Shiitake are capable of fruiting from spring through fall (depending on the strain), meaning you can grow enough mushrooms for the whole family in a small space. One log can produce up to 2 pounds of mushrooms yearly (productivity does decrease after 3 to 4 years).
A huge benefit to growing shiitake on logs outdoors is the quality of the mushroom. Log-grown mushrooms (versus those grown on a substrate) produce a higher-quality product. Mushrooms grown outdoors are also likely to contain higher levels of vitamin D due to exposure to sunlight.
How to Source Shiitake Mushroom Spawn
There are a variety of online suppliers of mushroom spawn. It is best to purchase mushroom spawn from a local distributor for a compatible strain, as well as to reduce the shipping distance. For our logs, we used Shiitake Plug Spawn (Cold Strain and Wide Temperature Strain) from Grow Mushrooms Canada. The plug spawn comes in two sizes, with either 100 or 500 wooden inoculated dowels. 100 plug spawn is enough to inoculate approximately two logs.
You can also inoculate logs with sawdust spawn, which is more economical than plug spawn for larger operations. In addition to a power drill, and mushroom log drill bit, you will also need an inoculation tool if using sawdust spawn.
Note: Cold-weather, warm-weather, and wide-range strains refer to the seasons/weather in which the mushrooms fruit, not the type of climate they are best suited for.
Selecting Logs for Inoculation
Logs should be harvested when trees are in their dormant stage. The best time of year to source your shiitake logs is late winter or early spring before the trees start to bud. This is the time when the sugar concentration is the highest in the wood, providing vital nutrients. Fall is another time you can source logs after ⅓ of the leaves have changed color.
Select live, healthy trees that don’t have any evidence of insect or disease damage.
Note: Moss and lichen commonly live on the bark of trees. This is normal and does not affect the quality of the wood or the ability to inoculate the logs. You can use a wire brush to carefully remove (do not damage the bark) some of the moss if it is making it difficult to inoculate the log, but this often isn’t necessary.
Best Species of Trees for Shiitake Mushrooms:
- Maple (hard maple: sugar maple and red maple are ideal)
- Oak (white oak is one of the best)
- Alder
- Sweetgum
- Beech
Note: Different strains of shiitake mushrooms have varying wood preferences.
If you don’t have any of these types of trees to harvest or sustainably cut down on your property, you may be able to source logs from an arborist, tree service, or local shiitake grower.
While you can inoculate a variety of sizes of logs, including tree stumps, logs 3 to 4 feet in length with a diameter of 4 to 6 inches is a good size to look for. Smaller sized logs will generally colonize faster and produce fewer flushes, whereas larger logs will take longer to colonize and produce more flushes of mushrooms. Since you may need to move the logs to stack or soak them, it’s best to select a size that is easy to lift.
When to Inoculate Shiitake Logs
Once the logs are cut, they should sit for about two weeks before inoculating. Don’t let the logs sit for longer than two months, or they could start to dry out. If you leave the logs too long other fungi may also start to grow, which will compete with the shiitake mycelium. Another way to deter competing fungi is to keep them up off the ground on a pallet or in the garage when you store them.
The best time to inoculate shiitake logs is in the spring or fall months. Shiitake mycelium can survive the cold winter weather, so they are safe to leave outdoors over winter. Once inoculated, you can expect to see shiitake fruit within 6 to 12 months. However, in some cases, it can take up to 2 years to see the first fruit.
How to Inoculate Shiitake Logs
Once you have your recently harvested logs, you’ll need a few additional supplies, including:
- Shiitake plug spawn or sawdust spawn
- Power drill
- 8.5 or 12mm Drill bit
- Angle grinder / adapter (optional)
- Soy wax
- Double boiler or pot and metal bowl
- Heating source (to melt wax)
- Wax dauber
Step One: Drill the Holes
Drill 1-inch deep holes into the logs using a power drill and drill bit. Space the holes about 3 to 4 inches apart in a diamond pattern. You will need about 50 plugs for a 3 to 4-foot log.
Many suppliers sell specialized drill bits that stop at the proper depth. You can also use an angle grinder with an adapter to speed up the process.
Step Two: Insert the Spawn
Press the plug spawn into the holes. If needed, tap them into the holes with a hammer or mallet. If using sawdust spawn, use an inoculation tool to insert the spawn.
Step Three: Melt the Wax
Using a double boiler or a pot and metal bowl, bring water to a boil and melt the soy wax. To keep the soy wax melted while you apply it, use an outdoor camp stove, fire, or hot plate.
Note: It doesn’t take long to melt the wax, so it’s best to wait until you are finished with steps one and two before melting the wax. However, if you have enough people and an assembly-line set-up, you may want to heat the wax earlier.
Step Four: Seal up the Holes
Using the dauber, cover the plug spawn holes with melted wax. In addition, it’s a good practice to cover the ends of the logs with wax as well as any areas where there is damage or the bark is missing. This helps to keep the moisture in and keep other fungi and critters out.
Caring for Shiitake Logs
Once you have inoculated your logs, they are best stored in a shaded location outdoors. Shiitake can handle some filtered light, especially in the winter and spring months, but the hot summer sun will dry out the logs. If you don’t have a natural location on your property, you can create one with shade cloth.
While the logs are colonizing, store them up off the ground on a pallet. During this time, the logs can be stacked together to retain moisture. To reduce drying, you may even cover your logs with burlap or other porous materials. However, once they are ready to fruit, raise and space out the logs. There are many options of configurations, including A-frame stacking, lean-to stacking, and crib stacking. Consider both air flow and ease of harvest when choosing the right configuration for your logs.
If you live in a region with cold winters, stack the logs low to the ground to protect them from the wind and prevent them from drying out. It is not necessary to cover them as the snow provides the ideal insulation as well as much-needed precipitation.
Water
For proper colonization and a successful harvest, it’s important to keep the moisture level up in the logs. Water your shiitake logs once a week throughout the fruiting season during periods with no rainfall.
Once your logs are fully colonized, you may want to shock them into fruiting. Signs of colonization include white mycelium on the log ends and a spongy bark. To shock the logs, submerge them underwater in a large stock tank for about 24 hours. If the shock was successful, you should see fruiting in about one week.
Many growers aim to shock every eight weeks, but this isn’t required. You can also just let nature take over, and the logs will fruit when they are ready. While forced fruiting is popular among commercial growers to time harvest, it can reduce the overall life of the logs.
Grow Shiitake Mushrooms Outdoors on Logs
Growing shiitake mushrooms on logs requires a bit of patience, but the reward is well worth the wait. Shiitake mushrooms are among the easiest mushrooms to grow on logs and can provide your family with a bountiful supply of a prized and pricey delicacy. Adding shiitake mushrooms to your diet also has many health benefits, as they are high in B vitamins, copper, selenium, manganese, and iron.
Have you tried growing shiitake mushrooms on logs? Tell us about it in the comments!
Sources:
Cornell University and University of Vermont: Best Management Practices for Log-based Shiitake Cultivation
Fungi Perfecti: FAQ About Log and Stump Cultivation
Grow Mushrooms Canada: Guide to Growing Mushrooms on Logs
Ohio State University: Shiitake Mushroom Production
