Grow Mushrooms in your Garden

Last week we went to Lohja to visit Eric Puro and his new outdoor mushroom farm called Gifts from Metsä. This spring he has been inoculating over 1000 logs with different strains of Shiitake, Oyster, Nameko, Elm Oyster and Reishi. Eric has been farming Shiitake in Kentucky (USA) for many years and now he is starting to do this here in Finland. The local climate conditions in Southern Finland are very different from hot & humid Kentucky. This is why he has made a big variety of trials and he will be meticulously monitoring his logs’ humidity and mushroom output. He will also try different watering methods, to figure out what practises work best in the dry & cold Finnish climate. In this article we will focus on the different methods of inoculation and we will explain the considerations that come with each method.

STEP 1: Choose Your Growing Substrate

Logs may be cut at any time during the year. However, for best results, we recommend cutting your logs when the tree is dormant (late winter/early spring) and before tree buds sprout. Cut the logs in 1 m pieces. The mushroom mycelium will feed on the sap and moisture during the colonization period. It is recommended to let freshly cut logs rest at least 2 weeks before inoculation. Stumps are also usable, but they can get a lot of sun and might dry out or start to sprout before the mycelium ‘takes’. Select stumps that are well shaded, don’t sprout and are not more than 3 months old. Don’t let the wood dry out. If you see large cracks in the wood (you can slide a euro into the largest cracks), consider soaking the logs 24-36 hours and letting them dry a day before inoculation.

Oak, Birch, Maple, Alder and other hardwoods are recommended. Avoid using any coniferous tree species (Havupuut: mänty, kuusi, etc.) for growing mushrooms as they contain many anti-fungal resins. Your logs and stumps should be clean, healthy, and free of any other fungi. Moss or lichens will not interfere with your mushrooms. The logs or stumps should also have their bark intact.

STEP 2. Choose your mushroom

The table below shows a list of common Finnish tree species and which mushrooms Eric has inoculated them with.

Mushroom Species Tree Species
Shiitake (Lentinula edodes) oak (tammi), birch (koivu), black alder (terva leppa)
Oyster (Pleurotus Ostreatus) aspen (haapa), willow (paju)
Nameko (Pholiota microspora) alder (leppa), birch (koivu), aspen (haapa)
Reishi / Lakkakääpä (Ganoderma Lucidum) oak (tammi), birch (koivu)
Elm oyster (Hypsizygus ulmarius) aspen (metsähaapa)
Chaga / Pakuri (Inonotus obliquus) Living birch (koivu)

Since there is not much data on what species of mushrooms work well with what tree species here in Finland, the above list is Eric’s educated guess of what might work. Please try your own experiments, and we would love to hear from you what worked, but also what didn’t work.

STEP 3: Inoculation

Below we list three different inoculation methods, all are relatively simple procedures but some require more specific tools and equipment. Eric uses sawdust spawn, but since this is harder to come by, it is easiest to start with the dowel method. Dowel spawn can be stored at room temperature for up to 1 month. You can store dowel spawn in your refrigerator for up to 6 months.

Setting up your workstation

Eric’s workstation consisted of 3 log holders, a small table with an electric stove with molten wax and some bar stools for putting on the bags of spawn.  Eric uses a double boiler for the wax which has water in the bottom and beeswax in the top and keeps the wax at 70-80C which prevents it from burning or sticking to the pan. He has 3 log holders is so that he can do each process step in batches of 3. By the time he is done waxing the 3rd log, the wax of the first log has dried. If there are more people helping out 1 person fetches the logs, drill holes, labels ready logs and stacks them on piles, 2 people inoculate the holes (the bottleneck process which takes the most time), 1 person waxes the inoculated holes.

Inoculation Methods

Dowel Spawn

This method is requires the least amount of equipment and is perfect for beginners. However it is not the fastest method.


  • Dowel spawn
  • 8.5mm or 9 mm drill with duct tape at 35 mm to create a stop, or a special mushroom drill bit.
  • High speed drill. Generally the wired ones have a higher rpm than the battery-powered ones.
  • Rubber or wooden mallet.
  • Beeswax, garden wax, cling film or duct-tape for sealing your logs or stumps.
  • A brush or spatula to apply the wax.

Drill holes no more than 10 cm apart, and in an evenly spaced “diamond” pattern around the log. 4 rows of holes per log is enough, unless you have very large logs. If inoculating stumps, the holes should be drilled along the circumference of the face of the stump, in the area between the bark and heartwood (called the sapwood).
With clean hands, take one dowel from the bag put it in the hole. If it is a bit tight, grab your mallet and gently pound the plug into the hole. The top of the dowel should not stick out of the bark and be flush or slightly sunk into the wood. Do not leave any drilled holes empty.
Seal the holes with wax, cling film or tape. This step will help retain moisture and prevent the invasion of parasites and competitive fungi.

Hensley Chainsaw / Duct tape Method

Eric also showed us this supercool method which he learned in Kentucky from Mr. Hensley himself.


  • Sawdust spawn
  • A Chainsaw (preferably a light / electric one. Eric uses vegetable oil on the chain, to minimize the chances of contamination).
  • Duct tape.


About 5 cm from each end of the log, cut a 1cm wide groove, about 3/4ths around the log, until the beginning of the heartwood, a few cm into the log. If you are inoculating a stump, simply cut a cross in the face of the stump.Press the sawdust spawn into the groove.Seal the groove with wax or duct tape.

Japanese Method

This method is the most commonly used one for outdoor shiitake cultivators around the world, and is the one Eric used to inoculate most of his logs.


  • Sawdust Spawn
  • A lightweight angle grinder with a steel adapter and a 12 mm mushroom bit.
  • A sawdust spawn filler tool.
  • Beeswax and a thick brush for applying it.
  • Metal / Plastic Labels and a waterproof marker for marking the logs. Eric used old window blinds and cut them in 10cm pieces.

Drill 4 rows of holes along the length of the log. The holes should be around 10 cm apart and make a ‘diamond’ pattern.
Fill the holes with sawdust spawn. The hole does not need to be fully filled with spawn, as the wax will hold better if there is about 5mm of space left in the hole.

Apply the hot wax generously on and into the holes and let it cool and harden. If you want you can also apply some to damaged parts of bark and cut off branches.
Label the log with the mushroom species & strain, type of wood and year.
Stack the logs in squares of about 5 logs x 5 logs in 3 levels. Don’t stack them too high as they might collapse in winter with heavy snow, and the humidity tends to be higher lower to the ground. He uses 2 coniferous (pine) branches/logs to prevent the bottom layer of logs from touching the ground, as this might invite other fungi to start eating them.

Optional: Monitor the moisture content of the logs periodically. If it falls below 30% they need to be watered. This can be either by soaking them or spraying water on them. Using some kind of breathing tarp to cover the logs helps keep the moisture high. Do not use plastic to cover your logs as this will encourage mold or bacteria to form on your logs.


The logs stumps will require 6–12+ months for the mycelium to fully colonize the wood. The length of time needed for colonization depends on the species of mushroom, wood type, and the size of the log. Smaller diameter logs (4–6 inches) will colonize more quickly compared to larger (8+ inch) logs.

Good luck with your cultivation projects!

In the future we will post updates on how the different methods, substrates and strains are performing and we want to build and share the knowledge of what works in Finland regarding outdoor mushroom cultivation. So please get in touch , join the Myco Hacklab Finland group, or contact Eric via email. You can order dowels and other tools from Helsieni’s online store.

Resources / Further reading

Myco Hacklab Finland

Cornell University research on log cultivation

Erkki Pöytäniemi’s Blog: Iso-Orvokkiniitty