Mushroom Dowels

Growing mushrooms in wooden logs with mushroom dowels

Grow mushrooms in your garden or at your cottage! Inoculating wooden logs with our dowels is simple and requires little attention until the harvest. The first mushrooms may arrive in as little as six months after successful inoculation and the logs can continue giving harvests for many years. We offer various mushroom species suitable for different trees – check out the tree species table below on this page.

Quick start


Drill holes 10-15 cm apart in an evenly spaced “diamond” pattern.


Insert the dowels into the holes and gently tap them in.


Seal the dowels with some wax or put the log in a plastic bag.

Detailed instructions and tips

Choosing the wood

Use healthy wood that does not grow other fungi and whose bark is intact.

The best logs to grow mushrooms on are from trees cut in the autumn just before they drop their leaves. A tree cut during the winter dormancy period (i.e. between the fall of the leaves in autumn and the onset of buds in spring) is also very suitable.

Cut the logs that are 10-20 cm in diameter into pieces of 50 cm to 1 meter long to make them easier to handle. Store logs in a sheltered place away from soil and leaves. Inoculate or insert  the mycelium dowels into the logs according to our instructions, 2-12 weeks* after felling the tree. The fresher the wood you use is, the more likely you are to succeed. There is an increased risk of contamination and dehydration in logs that have been resting for more than 6 weeks.


Thick logs make great mushroom totems!

Logs with a diameter of more than 20 cm are perfect for making a mushroom totem. Instead of dowels, you need some spent substrate (from your Growkit or mushroom bed) and brown cardboard.

Saw a log about a meter into three parts, e.g. 40 cm, 40 cm and 20 cm. You can soak the pieces in water overnight if you have the possibility. Find a place sheltered from the wind and direct sunlight and place a piece of cardboard larger than the diameter of the log on the ground and water it. Spread the mycelium on the cardboard in a layer of about 1 cm thick and put the biggest log on top of it. Add another layer of mycelium and place the second largest piece on top. Put another layer of mycelium and place the smallest piece or ‘cap’ on top.

If you wish, you can place a plastic or paper bag loosely over the totem to prevent moisture from evaporating.

Choose a suitable mushroom

This table shows which tree species our different mushrooms prefer.

Note that the chaga mushroom is inoculated into a living tree. More specific growing instructions are available when ordering.


Improve the conditions for slow-growing species

Some mushrooms like Chicken-of-the-Woods, reishi, maitake or tender nesting polypore benefit greatly if you change the following steps in the basic method explained on this page. Cut the logs short enough (20-30 cm long) to fit in your largest pot. Drill the holes in the sawing surfaces of the log (max 10 cm apart) and then boil or steam the logs to clean the wood of possible contaminants. Pressure cook for 2 h, boil in a pot for 1 h or steam for 4-6 h and let the log cool down fully. Insert the dowels and incubate the logs in a clean plastic bag until they are fully colonised by the mycelium. Then bury them in the ground so that the top of the log remains 2-3 cm above the ground.

We warmly recommend to use the boiling-resistant incubation bag of our selection.

Read the detailed instructions below – just change the parts mentioned above.

Inoculating step-by-step

Equipment needed

Helsieni dowels available in our webstore
The appearance of the mushroom dowels may vary, as shown in the photo


9 mm drill bit available in our webstore


Mallet or hammer

Optional: Garden wax, beeswax, plastic film or big plastic bags


Soak the logs


Ensure a suitably moist growth environment for the mushroom mycelium by immersing the logs in water overnight before inserting the dowels. This is not mandatory, but gives a better chance of success. The mycelium colonizes moist wood faster.

In the picture, the logs to be soaked are held underwater by some buckets and previously inoculated logs.


Drill the holes

with a 9 mm drill

Helsieni dowels are 8 mm in diameter. Because we are dealing with moist wood, we recommend using a 9 mm drill bit for making the holes. A 10 mm drill makes the holes too wide and an 8 mm drill is too tight. The holes should be about 5 mm deeper than the length of the dowels. You can mark the appropriate depth of the holes on the drill with a piece of tape.

Drill holes 10-15 cm apart, forming a diamond pattern.


Insert the dowels and tag the logs

mark the date and the mushroom species on the log

Push the dowels completely into the log so that they do not stick out. If necessary, use a hammer or mallet. Fill each hole to prevent contaminants or spores from other fungi from entering.

Inoculate (i.e. plant) only one species of mushroom per log. Otherwise, different mushrooms will fight for living space and might not give a proper harvest.

Mark the species of mushroom and the year you inoculated the log with. Write the information with a permanent (UV resistant) marker on tag and nail it to the log. The best material is aluminum or another metal, for example a lid of a jar or can. Another option is polypropylene (PP) plastic, such as a lid from a yogurt bucket. Other plastics break into many small pieces and text written directly on wood soon becomes unreadable.


Accelerate mycelial growth

The mycelium grows faster in warm and humid conditions. If you want to get your harvest sooner you can pre-grow them according to these instructions at least over winter.

Place the inoculated logs in plastic bags with 1-3 logs per bag. You can also saw the logs in shorter pieces and put them in regular shopping sized plastic bags if you do not have big ones. Close them loosely, but not completely airtight. Store them in a dark and warm place (10-20°C is ideal) until the white mycelium is visible at the ends of the log on the sawing surface. The logs can then be removed from the bags and taken out to their final location.

Fungal varieties grow at different rates: for example, this method of incubation takes about 3-6 months for oyster mushrooms and about 6-12 months for shiitake.

This step is optional, meaning you can also take the logs straight outside without pre-growing in a plastic bag. In this case, it may take longer to get the first harvest. However, make sure that the logs do not dry out, for example with dry winter winds.


Seal the holes

If you are not going to incubate the mushroom logs indoors, we advise to seal the holes. Sealing protects the wood from other spores and contaminants. It also prevents the mycelium on the dowels from drying out.

Cover the holes with garden wax, Vaseline, tape, plastic film, or beeswax. Garden wax or Vaseline should be applied with clean fingers to cover the hole and the dowel. Tape or plastic film does not need to be airtight as long as the hole and its immediate surroundings are covered. If you use beeswax, be careful not to overheat it. Hot wax may kill or dry the mycelium.

Sealing holes is not mandatory, but it can help your mushroom to grow successfully.


This is how the mycelium grows

The growth of mycelium can be difficult to see as it occurs mainly inside the log. It may appear at the ends of the log (i.e. on the sawing surfaces of the wood) as white, yellowish or reddish spots. The picture shows an example of a log that is well colonized with shiitake mycelium. 

After the mycelium has colonized the whole log and when the conditions are favorable: high humidity, colder nights you can expect your harvest.


Choosing a place for your logs

Shaded and protected from wind

A good place for mushroom logs is damp, shady and sheltered from wind. You should choose a place where the logs can be left for several years. Place the logs slightly above the ground and leaves, for example on a few smaller branches or rocks. Pre-grown logs can be in direct contact with the soil. As long as the rain can wet the logs naturally, they do not need extra care.

Some species like Chicken-of-the-Woods, reishi, maitake or tender nesting polypore should be buried in the ground so that the top of the log remains 2-3 cm above the ground. The chaga mushroom, on the other hand, is inoculated into a living tree and more detailed growing instructions are available when ordering.



Wait patiently and be ready

The mushrooms begin to grow when the mycelium has completely taken over the log and when the conditions are favorable for the fungi. It can take from six months to a few years from the inoculation of the log until the first harvest. The fastest growing mushrooms are oyster mushrooms and turkey tail. After the first harvest the log produces mushrooms for several years, so leave the logs until they have completely disintegrated.

During the late summer and autumn you should check your logs regularly. When the mushrooms emerge, they mature in days. The summer cottage forest is a great place to grow mushrooms but if the cottage is visited infrequently during the autumn, the mushrooms may have gotten old before you get a chance to harvest them.

New here in the Nordic region

Outdoor mushroom cultivation is still a relatively new thing in Finland and our climate is somewhat different from Japan and North America, where it has been practised for a longer time. Please share your good and bad experiences with us. We want to improve the instructions and help all those who grow mushrooms for fun or professionally to succeed!

Send your photos and share your experiences about mushroom logs to

Different inoculation methods in video

Questions & answers

Can I grow mushrooms in a stump instead of a log?

You can try inoculating stumps, but we cannot guarantee success. Success can be challenging, as a stump lives longer than a log and may even start to sprout again. In this case, the tree’s defense mechanism is also active and fights the fungal mycelium. On the other hand, the stump gets water through its roots and keeps the wood moist, which is also a good thing for mycelium.

You might want the stump to rest for several weeks prior to inoculation and instead of the dowels use the totem method: saw 5-10 cm piece off the top of the stump, put a half-centimeter layer of spent substrate, insert the off-cut disc back as a lid and cover the stump loosely in plastic or paper bag.

Please, share your successful and unsuccessful experiments with us at

Can I make mushroom logs from the wood I felled today? What if the tree was felled more than 12 weeks ago?

You may be able to grow mushrooms in a tree felled and inoculated on the same day. However, the tree defense mechanism that fights fungi may still be active. It slows down or, in the worst case, prevents the fungal mycelium from spreading to the log. For this reason, it is usually recommended to wait a week or two before inoculating the mycelium into the log. However, the holes should always be drilled on the day of inoculation and not before.

A log more than three months old can still be inoculated if it looks completely healthy. However, it must be remembered that another fungi may have gained a foothold in the log. In this case, the mushroom you grow may lose the fight or it may not get enough food, giving a smaller harvest.

We do not recommend using logs over six months old as a medium for growing mushrooms.