ShiitakeLentinula edodes

Shiitake (Lentinula edodes), also sold as black forest mushroom or oakwood mushroom, is an edible wood mushroom from East Asia. It doesn't grow wild in Britain or anywhere else in Europe: every shiitake you see in a supermarket, at a market stall or on a log in someone's garden was grown by people. So this page isn't about foraging. It's about recognising shiitake, cooking it safely and growing it yourself.

What does shiitake look like? The cap is brown, from pale tan to deep chocolate, 5–20 cm across, though shop mushrooms are mostly 5–10 cm. Around the inrolled edge there are small white scales and fibres, the remains of a veil that covered the gills of the young mushroom. The gills are white or cream, turn brownish with age and develop ragged, saw-toothed edges. The stem is short, tough and fibrous, often slightly off-centre. The spore print is white. Shiitake smells pleasantly mushroomy, and dried shiitake even more so.

Does shiitake grow wild in the UK? No. Its native home is Japan, China, Korea, South East Asia and the Russian Far East, where it grows in clusters on dead broadleaf trunks such as oak, chestnut, hornbeam, beech and maple. British records are almost all of cultivated mushrooms: supermarket specimens and inoculated logs in gardens, with a single London find noted as apparently naturalised. It has occasionally escaped from garden logs in the Netherlands too, but these are isolated cases. If you find a brown mushroom on a stump in a wood, it isn't shiitake, and it needs identifying as a wild mushroom.

Can you eat shiitake raw? No. Raw or undercooked shiitake can cause shiitake dermatitis. A day or two after the meal, rarely up to a week later, itchy red streaks that look like whip marks appear on the trunk, arms and legs, sometimes with a fever or an upset stomach. The rash clears by itself, usually within one to two weeks, occasionally lasting more than a month, and the bigger the helping, the longer it tends to last. Anti-itch treatments ease it but don't reliably shorten it. French poison centres recorded 59 cases between 2014 and 2019, nearly all after raw or undercooked mushrooms from a wok, a soup or a pizza. The likely trigger is lentinan, a polysaccharide in the mushroom's cell walls. So cook shiitake until it is soft all the way through, and don't add it raw to salads. If you get the rash, see your GP. If your face or throat swells or you struggle to breathe, call 112 (999 in the UK).

How do you cook shiitake? Fry, braise or add fresh shiitake to soups and stews; the stems stay tough, so they're best used for stock. Soak dried shiitake in water until the caps are soft, then cook them like fresh ones. Dried shiitake has the stronger aroma, which is why many cooks prefer it.

How do you grow shiitake at home? There are two ways. On logs: freshly cut oak, hornbeam or maple is inoculated with spawn within a few days of felling, the holes are sealed with food-grade wax, and the logs rest in the shade. The first crop takes about a year. After that you can soak a log in cold water for 12 to 24 hours, and pins appear three to five days later. Give each log six to eight weeks' rest between soakings; it will keep producing for three to four years. Outdoors, logs fruit naturally in spring and autumn, and in summer after soaking. The second way, sawdust blocks or grow kits, is faster and suits indoor growing. If you grow a lot of shiitake in a closed room, keep it ventilated: in a few reported cases shiitake spores caused an allergic lung inflammation in growers, with a cough and breathlessness. If you develop that kind of cough, tell your doctor you grow mushrooms.

Shiitake benefits: what is actually known? It's a delicious mushroom with deep umami flavour, which is reason enough to eat it. Lentinan extracted from shiitake is given by injection in Japan and China alongside chemotherapy for stomach cancer, but that is a purified prescription medicine, not a meal. Ordinary shiitake, powders and capsules don't treat any disease, and most other claimed benefits have only been tested in the lab.

What can be confused with shiitake? The only risky situation is your own growing log, because wild fungi can appear on it too, including the deadly funeral bell (Galerina marginata). It is brown and looks a little like shiitake, but it's much smaller, with a honey to rusty brown cap 1–4 cm across, a thin ring on the stem and a rusty brown spore print. Eat only mushrooms you are sure about, and if in doubt take a spore print: shiitake's is white. The scaly sawgill is another tough mushroom with a scaly cap and saw-toothed gills, but it grows on conifer wood, old railway sleepers and posts, has a whitish cap with brown scales and smells of aniseed. Oyster mushrooms are often mixed up with shiitake by name only: they have fan-shaped caps on a short side stem, gills running far down it, and no scales.