It isn’t only plants that we get from the forest garden – it produces a regular supply of mushrooms too. I’ve experimented with growing a wide range of fungi over the years, but for me one really stands out from the others as providing a good supply of produce for the work you put in, and that’s shiitake (Lentinula edodes), which has one secret power that the others don’t.
Shiitake is a wood-rotting fungus that is grown on logs: in Britain beech, oak and birch are particularly suitable. Its advantages over other such fungi include that it is a strong grower, quickly colonising its logs and outcompeting the other, less useful, fungi that inevitably turn up and make a bid for complete log domination. It also helps that it is a tasty, nutritious mushroom that is easy to preserve.
Since I work as a forester, I get occasional supplies of the freshly cut logs that are needed for growing shiitake. I quickly order some mushroom spawn (the fungus grown on bran or on softwood dowels) from Ann Miller’s Speciality Mushrooms, which happens to be just up the road but which is behind most suppliers of mushroom spawn in the UK. The spawn is put into holes drilled in the log and sealed with wax (there’s an excellent how-to video about the process at on YouTube).
As the fungus colonises the log, I see wedges of white colour appear at the end of the logs as the mycelium works its way up and down the vessels in the wood. After a while these fill in with a chocolatey brown colour which indicates that it is ready to fruit. It also develops a wonderful mushroomy smell. It’s at this point that you can use the trick that makes shiitake so useful. Most wood-rotting mushrooms fruit all at once, giving you a famine followed by an unmanageable glut. This was my experience with oyster mushroom: I would have one week a year eating oyster mushrooms with everything, then back to nothing. In addition, since mushrooms give little notice of when they are going to come out, it is quite possible that you will be away for a few crucial days and come back to find nothing but a rotting mess and feasting slugs. The difference with shiitake is that you can reliably induce individual logs to fruit, as and when you want them.
The process for this is known as ‘shocking’, as you are basically trying to give the fungus a fright. First the log is given a sharp rap at either end with a lump hammer, then the whole thing is plunged into cold water for two days or so. Many internet sites will tell you to use iced water but this seems rather wasteful to me as they always fruit quite reliably after being dunked in my (very small) frog pond. Theories abound as to why this treatment actually works. The way it was explained to me was that you are messing with the mushroom’s mind, trying to make it think that its log has fallen out of the tree in an autumn storm and that it needs to reproduce quickly.
Whatever the reason, soon after you take it out of the water you will notice little ‘initials’ appearing through the bark. Over the course of a week or so these swell up into the full-size fruiting bodies. The challenge during this time is to keep it in a cool, moist place away from slugs and snails, which will travel for three days without carrying water at the merest sniff of a shiitake mushroom. I used to swaddle mine in horticultural fleece, which kept the humidity up and the slugs out, but it was awkward and not entirely reliable. Nowadays I put them in my shed, stood up in a plant saucer with a little water in the bottom. This creates a defensive moat and at the same time helps to keep the log wet as fruiting will stop if it dries out. So far this method has been completely reliable. For once I have managed to get on a regular schedule with shocking my logs, doing one a week, and we have had a continual supply of them since May.
Shiitake are a versatile and delicious mushroom that can be used in all sorts of ways, so I’ll just share my one favourite way of cooking them with you. If you cut them into thin strips (just a few millimetres thick) and fry them, they develop a texture and even a taste reminiscent of crispy bacon. Instead of putting them in dishes like pasta where the flavour can get a bit lost, I will often cook them this way and put them over the top instead.
Finally, another of shiitake’s super-powers comes into play with any that don’t get eaten in the first few days. Shiitake self-dry incredibly easily if left in any reasonably well ventilated place. They will then store for years but rehydrate very nicely when water is added. I particularly like them in miso soup, where the soaking water can be added to the stock.
Of course, you don’t need a forest garden to grow shiitake, but it is a very good match as there are plenty of damp, shady places where you can leave the logs between fruitings. They can usually be refruited after two months rest and are said to last for two or three years, but some of my big beech logs have been going for eight, so I suspect it depends a lot on the size and species of the log.