Let me start by saying that despite its advertised simplicity, growing oyster mushrooms and other types of mushrooms on stumps and logs is not as easy as it may seem. It requires careful attention to detail and strict adherence to instructions.
Deviating from the recommendations below can lead to failure.
For example, if the log is not wet enough, the mycelium won’t have enough moisture and will die. But if the log is too soaked, it might not get enough air—and the result is the same.
I've seen advice suggesting that you can simply push small pieces of mature mushrooms into cracks or cuts in the bark.
Honestly, I’m skeptical that this method would work to inoculate a log with mycelium.
However, I haven’t tried it myself, so I can’t give a definitive answer.
If you’re curious, you could experiment with this method and share your experience and photos with me—I’d be glad to include a detailed description of your approach on my site!
You can purchase plug spawn (wooden dowels infused with mycelium) from spawn suppliers or garden centers. How can you tell if the spawn is healthy? Look for a fluffy white coating on the surface of the plugs—it should resemble soft velvet.
Avoid plugs with mold in colors like black, red-orange, green, or gray—these are signs the mushroom mycelium is already dead. If your shipment arrives in this condition, take photos and request a replacement from the supplier.
The color of healthy mycelium, whether for oyster mushrooms, shiitake, or Laetiporus (also known as chicken of the woods), should range from white to a creamy, flesh-toned shade.
Mycelium can only remain viable at 80–90% humidity.
Therefore, if the packaging is just paper, it’s a risk.
A plastic package is better, but if it lacks a clear window to inspect the contents, I wouldn’t recommend buying it.
Ideally, the packaging should contain a small silica gel packet to help regulate moisture.
You might think this is a good method—after all, in nature, mushrooms spread to trees through their spores, which settle into cracks in the bark.
However, spores germinate slowly, reducing the chances of thorough colonization by mycelium.
Meanwhile, mold spores, which thrive in harsh conditions, could take over, leading to colorful mold patches instead of mushrooms.
You can drill holes in the log and fill them with grain spawn. However, you’ll need more holes than the 20 I recommend in the instructions below—aim for 30–35 holes instead. Follow all other steps exactly as outlined, from step 1 to step 10. The only difference is that instead of inserting plugs, you’ll fill the holes with grain spawn.
It's best to buy grain spawn from a professional laboratory to ensure quality.
I haven’t worked with liquid cultures myself, so it’s better to ask for advice directly from the suppliers. However, my guess is that these cultures are too delicate for inoculating logs and stumps.
1. Choose freshly cut stumps or logs.
Fresh wood still has intact natural channels that conduct moisture. The mycelium uses these channels to send out hyphae, allowing it to act as a whole organism—drawing water and breaking down the wood to produce clusters of mushrooms.
2. If you're unsure when the trees were cut, use only logs with tightly attached bark that doesn’t peel away from the wood. The logs should be adequately moist, even slightly damp to the touch, but not so wet that water drips from them.
3. If the wood isn't moist enough, soak the logs in a container of water for 12 hours, then let the excess water
drain off.
4. Drilling holes in wet logs is not easy!
Don’t take on too many logs at once—start small to avoid getting overwhelmed.
5. Drill the holes using a drill bit that is 2-3 mm (about 1/8 inch) larger than the diameter of the dowels. Space the holes evenly across the log. It helps to mark the log with chalk first, arranging the holes in a staggered pattern. You should also drill 3-4 holes into each cut end of the log.
- For stumps, drill holes on the top and sides, ensuring they are evenly distributed.
6. For a log with a diameter of 20-30 cm (8-12 inches) and a length of 70-80 cm (28-32 inches), you need at least 20 dowels—this is usually one full pack. Avoid smaller packs with only 10 dowels.
- If you buy in bulk (e.g., a pack of 100 dowels), you’ll need to inoculate five logs in a single day. It’s best to drill all the holes the day before to streamline the process.
7. When inserting the dowels, wear gloves. Quickly place the dowel into the hole and immediately seal it with modeling clay or tree wound dressing.
Sealing the hole is crucial! It prevents mold spores from getting in and keeps moisture from evaporating.
8. Follow this rule: The larger the log's diameter, the shorter its length should be.
Remember, the mycelium needs to connect fully to produce a good harvest.
Mycelium spreads through hyphae, which are thread-like structures resembling tiny plant roots. The hyphae from neighboring holes must intertwine to form a unified network.
9. At air temperatures between 20-25°C (68-77°F), the mycelium typically colonizes the wood within 2-3 months.
Maintaining this temperature range is critical.
If the temperature drops, colonization will slow down significantly and may stop entirely below 12-13°C (53-55°F).
10. When inoculating stumps outdoors, spring is the best time—wait until nighttime temperatures consistently stay above 12°C (53°F).
If you inoculate in the fall, ensure at least a full month of temperatures above 12°C (53°F) to give the mycelium time to establish itself.
Look for a white, mold-like substance spreading from the drill holes—this is a sign the mycelium is thriving.
Mushrooms won’t necessarily pop out from the drill holes - they’ll emerge wherever they please.
Most often, they appear in the cracks of the bark, at the top of the cut wood, or right on the cut surface, as seen in the top photo.
Maintaining Humidity During Colonization
For the three months it takes for the mycelium to colonize the wood, you need to maintain a consistent humidity level - at least 80%, ideally 85-88%.
The easiest way to achieve this is to dedicate a special room where you can store the logs, regularly wet the floor, or use an ultrasonic humidifier.
Indoor spaces also make it simpler to control the temperature.
If your logs are stored outdoors, keeping the moisture level right is more challenging.
Some growers suggest wrapping logs in plastic wrap or placing them in large plastic bags (like garbage bags) with a wet cloth inside. You would then re-wet the cloth as needed.
However, it is crucial to provide airflow to prevent mold.
A better method is to wrap the log in breathable burlap fabric and regularly spray the fabric with water until it is well-moistened but not dripping.
1. In Summer:
- Protect the stump from direct sunlight and dry soil.
- Regularly water the ground around it. As the water evaporates, it will create a humid microclimate.
- To retain this moisture, you can create a makeshift tent using plastic film, leaving small ventilation windows for airflow.
2. In Winter:
- If the logs or stumps remain outdoors, insulate them well to prevent freezing.
- Start by covering them with thin branches to allow some air circulation. Then add layers of cut grass, straw, or even snow - if it lasts through winter in your area.
- For logs stored indoors (e.g., in basements or rooms), maintain the temperature above freezing and wait for spring.
When temperatures rise, move them to a cool, shaded spot and maintain at least 80% humidity.
- If you can create fruiting conditions indoors (11-15°C / 52-59°F and 85-87% humidity), you don’t have to wait for spring—mushrooms can appear every 5-6 weeks.
Most likely, nothing.
A healthy tree that isn’t stressed or drying out will naturally suppress the mycelium's growth.
Some gardeners worry that mushrooms appearing on their property could lead to fungal spores infecting healthy, fruit-bearing trees. However, this is highly unlikely.
The only mushroom with some parasitic traits (meaning it can grow on live trees) is the winter mushroom (Flammulina velutipes).
Even then, it usually targets weakened or diseased trees.
The chance of spores from cultivated mushroom clusters finding a crack in the bark and successfully germinating is very low.
No. Sawdust is not the same as intact wood from a stump or log.
In natural wood with its structure intact, there is enough moisture for mycelium growth, and when properly hydrated, water is absorbed through the wood's network of vessels.
In sawdust, this structure is disrupted, making it harder to maintain the right conditions for mycelium growth.
Suppose you filled a plastic bag with pre-boiled sawdust and then placed plug spawn inside, distributing them evenly throughout the bag.
Mycelium growth will only start from the inoculation points, which are too few in this setup.
By the time the mycelium reaches the center of the bag, mold spores and bacteria that survived pasteurization may already take over, spoiling the entire batch.
