The mushroom is the fruiting body of a subterranean network of long root-like cells (hyphae) which thread themselves through the soil like neurons in a human brain. Called the mycelium, this network of cells can grow for long periods without fruiting and cover large areas. A single mycelium found in Michigan is said to cover around 40 acres and is thought to be a few centuries old.

Mushrooms are 90% water and virtually calorie free. They are high in vitamin D, vitamin B6, protein, magnesium, iron, potassium and many other important minerals. They lack chlorophyll and so can’t manufacture food using the sun’s energy. They obtain their energy by decomposing dead vegetable matter (saphrophytes) or associating with the roots of living plants (mychorrhizals).  Whites, browns, oyster mushrooms and shiitake are all saphrophytes. Chanterelles and morels are mychorrhizals.

Mychorrizal mushrooms have co-evolved with trees. The mushroom breaks down organic molecules and minerals in the soil and feeds it through the tree’s roots. In return, the tree provides sugars synthesized by the plants leaves. The mycelium extends a tree’s root structure and is also thought to help protect the tree from bacterial and fungal diseases. Without mushrooms to break things down, the earth would long ago have suffocated beneath a blanket of organic matter created by plants and living things would run out of things to eat. This makes them indispensable, not only to trees but to all life on earth. If the soil is the earth’s stomach, mushrooms supply its digestive enzymes.

Saphrophytes are cultivated by allowing the mycelium to colonise a compost block. Compost blocks are made from materials such as wheat straw, poultry manure, sugar cane bargasse, gypsum and water, heated in huge ovens, to eliminate pathogens, competitor moulds or nematode infestations. When the compost cools, the mycelium is added and allowed to grow by ingesting molecules present in the compost.

The compost is then covered by peat moss. The mycelium is allowed to colonise the peat moss for around 18 days, then is triggered to produce its fruit (the mushrooms) using a regime of high humidity and higher than normal air temperature. The mycelium will produce large numbers of mushrooms when it considers the temperature is ideal for reproduction.

The large scale production of mushrooms by the mycelium is called a ‘flush’. The mycelium then lies dormant for about a week and flushes again. After three to four flushes, the compost blocks (with the peat moss) are sold to gardeners.

Not all mushrooms can be cultivated and many wild mushrooms, though full of flavour, can be poisonous or hallucinogenic. When eating wild mushrooms, always be sure you know what you are eating. If in doubt, eat something else.