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Inoculation of Tree Logs and Stumps

Wood species suitable for mushroom cultivation are oak (suitable for shiitake), maple, hornbeam, poplar, alder, beech, birch, willow, etc.

Coniferous and fruit trees are NOT suitable.

In general, on harder wood species (e.g., oak tree) mushroom yields are higher, while spawn growth is faster on softer wood species (e.g., poplar tree). Wood obtained by cutting down trees during the dormant season contains the highest amount of sugars and other nutrients, which makes it the most suitable for mushroom cultivation, as it provides the highest yields. In addition, wood with high portion of sapwood is highly suitable, because mycelium can overgrow and decompose it more easily.

The surface of fresh tree logs with diameters of 6 – 21 cm should be cleaned of lichens and other dirt. Trunks should be fresh, healthy and not decayed or rotten, with bark still intact. Moreover, tree stumps can also be used for mushroom cultivation.

Inoculating logs with plug spawn
Holes are drilled over the entire surface of the log in a zigzag pattern (Picture 1, Sketch 1). Holes are drilled more densely on both ends of the branches, where side branches grew and around possible bark damage. Holes should be about 0.5 mm to 1.0 mm wider than the plugs of 6.5 mm to 7 mm width. Then plug spawn is inserted into the holes (Picture 2, Sketch 1).

gojenje_gob-knjiznica-20Picture 1

gojenje_gob-knjiznica-21Picture 2

gojenje_gob-knjiznica-22Sketch 1: Inoculation of a tree log with plug spawn

Plugs are inserted into the holes completely. A number of plugs required is shown in Table 1. Plugged holes are then coated with melted paraffin or beeswax (Picture 3) but not with grafting wax! Moreover, the ends of logs are also coated in order to prevent contamination and the ingress of dirt as well as evaporation of tree sap (Picture 4).

gojenje_gob-knjiznica-23Picture 3

gojenje_gob-knjiznica-24Picture 4

Table 1: Number of rows and holes for plug spawn using a log of 1 m length

Trunk diameter

6 cm

8 cm

10 cm

12 cm

15 cm

18 cm

21 cm

No. of rows








No. of holes/trunk









Inoculating logs with grain spawn
Logs are cut transversely into smaller sections (Picture 5). Between them a layer of grain spawn and a layer of fresh sawdust, obtained from sawing the logs, are placed (Picture 6, Picture 7, Sketch 2). The layers are then protected from drying by using a cling film (Picture 8) and the ends of logs are coated with beeswax or paraffin (Picture 4).

gojenje_gob-knjiznica-25Picture 5

gojenje_gob-knjiznica-26Picture 6

gojenje_gob-knjiznica-27Picture 7

gojenje_gob-knjiznica-28Picture 8

gojenje_gob-knjiznica-29Sketch 2: Inoculation of a tree log with grain spawn

Alternatively, a V-shaped notch can be cut into the log, where grain spawn is placed and then the cut-out piece of the log reinserted (Picture 9). If necessary, the cut-out piece can be fixed with a nail or screw and protected from drying using a cling film or plastic sheeting (Picture 10, Sketch 3).

gojenje_gob-knjiznica-30Picture 9

gojenje_gob-knjiznica-31Picture 10

gojenje_gob-knjiznica-32Sketch 3: Inoculation of a V-shaped cut log with grain spawn

Plug spawn or grain spawn-inoculated logs are then placed in a shade, where they get wet by rain. It is important that the logs do not dry up, still they must not be soaked, therefore places with a lot of water or strong wind should be avoided. One has to take care that water does not accumulate in the sections containing spawn, as it may rot. If water is collecting under the plastic film, a few holes should be made. In addition, places with extremely variable humidity due to the strong sun, wind and rain should be avoided, since bark starts detaching from the logs quicker in such conditions (Picture 11), which enables unwanted organisms to access the wood, resulting in a lower mushroom yield.

gojenje_gob-knjiznica-33Picture 11

Shaded areas without direct sunlight in the garden are suitable and sand base is ideal. For the first six months, logs should be about 1 cm above the ground in order to prevent unwanted organisms from entering. Afterwards, when mycelium has overgrown the logs, it is recommended that they are in contact with the soil so they can draw water from it during dry seasons. In the case of severe drought, outdoor logs should be regularly splashed with water.

For the mycelium-growing phase, damp basements with temperature above 10°C or rooms with temperature and humidity fluctuations lower than outside, are the most suitable (Picture 12, Picture 13). Such places enable spawn growth even during the winter. If mould appears on the logs, the humidity is too high; therefore it is recommended to increase the ventilation or temperature in the room. On the other hand, logs should be sprayed with water when the room is too dry (Picture 14).

gojenje_gob-knjiznica-34Picture 12

gojenje_gob-knjiznica-35Picture 13

gojenje_gob-knjiznica-36Picture 14

The substrate colonisation process lasts between 9 and 18 months, and even longer with shiitake mushrooms. In general, the longer the substrate colonisation, the better for the mushrooms and the higher the yields.

Besides logs, tree stumps can also be inoculated with mycelium for mushroom cultivation. Stumps of deciduous trees are the most suitable for inoculation, however they must not leak tree sap that can cause the mycelium to rot. In this case, it is best to wait for the stumps to dry and then inoculate them. Two inoculation methods are the most effective:

Inoculating stumps with plug spawn
Over the entire surface of a stump, holes are drilled (Sketch 4), then plug spawn is inserted and protected from drying. It is best to use as many plugs as possible.

Inoculating stumps with grain spawn
The stump is cut transversely and grain spawn is spread over the top surface of the cut stump. It is recommended to add a layer of fresh sawdust and on top, the remaining cut-off disc of the stump is placed (Sketch 5).

gojenje_gob-knjiznica-40Sketch 4: Inoculation of a tree stump with plug spawn

gojenje_gob-knjiznica-39Sketch 5: Inoculation of a tree stump with grain spawn

Finally, to protect inoculated stumps from excessive sunlight and drying, they should be covered with cling film or plastic sheeting and, in addition, with soil, leaves, straw or sand (Picture 15, Picture 16). Plastic sheeting and soil can be removed after a few months, when the stump is overgrown by mycelium, however this is not recommended in dry periods.

gojenje_gob-knjiznica-37Picture 15

gojenje_gob-knjiznica-38Picture 16