What the Japanese have been doing differently in log cultivation for eighty years

Anyone tapping our plugs into a log is doing something that has been done in exactly the same way in Japan for eighty years. The wooden plug as a carrier of mycelium, tanekoma in Japanese, was developed there in the 1940s and turned shiitake growing from a gamble into a craft. Before that, shiitake was grown by laying logs in the forest and hoping the right spores would drift by. Afterwards anyone could do it, controlled and repeatable. Over the decades that craft has produced a set of habits that we, with our gardens and dead hedges, can still learn from. Five of them.

1. The wood is "killed" first

Japanese growers fell their oaks in winter and then leave the logs for a month to six weeks before inoculating. That period is literally called letting the wood die. The idea: straight after felling the tree is still alive and its cells are full of defensive compounds; after a few weeks those are gone and the moisture content has dropped to the level mycelium likes. We call it "leave for two to six weeks", as in the cutting calendar. The Japanese have a word for it, which says something about how seriously they take it.

2. Logs are stacked, and the pattern changes with the season

A Japanese shiitake farm is a field of thousands of logs that are not just lying around. In the first phase, when the mycelium has to conquer the wood, they lie in low, dense criss-cross stacks, covered against sun and wind. That way the logs keep each other moist. Once colonised, they stand upright or lean against long rails in open rows where light and air can reach them. The lesson for the garden: in its first year a log wants mass and shelter, after that it wants space. Anyone who stands their logs up singly right after inoculation is doing the opposite of what works.

3. They do not wait for rain, they make rain

Shocking a colonised log, a day submerged in cold water to trigger a flush, is not a trick in Japan but the standard method. There are farms with basins the logs go into on fixed days, and growers who log the water temperature because colder water gives a stronger response. Afterwards the logs go into a humid, cool space and the mushrooms appear within a week or two, all at once. We described the method in our piece on logs doing nothing. What the Japanese add: do it at fixed moments, not whenever it happens to occur to you, and let a log rest at least two months after a flush.

4. The wood is sacred

Japanese shiitake growing runs on two oaks, konara and kunugi, and those trees are grown for the purpose. Woods are coppiced every twenty years, after which the stumps resprout and the new stems reach exactly the right thickness again: ten to fifteen centimetres. So the wood is not a by-product but a crop. We have no konara, but we do have native oak and beech, and the lesson stands: the quality of the harvest is largely decided before a single plug enters the wood. See which tree for which mushroom.

5. The sun does the final work

Dried shiitake is a product in its own right in Japan, with quality grades and prices far above fresh. The best are dried in the sun, not only to lose moisture but because sunlight drives up the vitamin D content and deepens the flavour. The thick, cracked donko that only forms in cold, dry weather is the top grade there. How to do it at home is in our drying piece. The Japanese addition: the sun is not an afterthought, it is the last step of cultivation.

What we do not adopt

The scale. A Japanese farm works with thousands of logs and a calendar planned to the day. For a garden with four logs that is overkill, and it does not need to be. But anyone who takes on the "letting die", the stacking, the shocking at fixed moments, the wood and the sun is growing shiitake in a way a Japanese grower would recognise. And eighty years after the first plug, that is a pleasant thought to have while drilling.