A mushroom is described as the fruiting body of a fungus plant that typically appears above the ground and contains spores. It is this fleshy bracket (fruiting body) that is commonly eaten and which reproduces by dispersing spores in the same way that other plants disperse seeds. Instead of drawing nutrients through the roots, fungi are sustained by a network of fine, microscopic threads known collectively as the mycelium. This network can extend over vast distances, implanting into rotting wood, soil, or other preferred medium.
Fungi are more akin to molds and yeasts than to vegetable plants. Although mushrooms are technically part of the plant kingdom, they are very different organisms since they do not contain chlorophyll or have a root system. Mushrooms must also rely on organic material for their nutrition and do so in three ways:
- as saprophytes (living on dead wood or dead tissue of living trees or dung)
- as parasites (attacking living plant or animal tissue), or
- as mycorrhizae (having a symbiotic relationship with plants).
To separate some of the confusion as to what is a simple fungus and what is a mushroom, scientists now generally use the term ‘mushroom’ to encompass fungi of either the order Agaricales or the order Boletales.
Agaric is an old term once used for any mushroom but is hardly ever used anymore. It was derived from the classical Greek name for mushroom, “agarikon”, and named after the town of Agara, once famous for its mushrooms.
The scientific classification of Agaricales comprises all the families of mushroom-like fungi, especially those with caps having radiating gills and which grow on stems. Today, agarics are not restricted to “true” mushrooms (genus Agaricus), but also include cultivated mushrooms, or their numerous close relatives.
The ‘orange agaric’ includes both the edible and poisonous forms of Amanita, as well as the saffron milk cap (Lactarius deliciosus). At one time, edible mushrooms were distinguished from poisonous ones by labelling these as “toad stools”. Botanically, however, there is no simple distinction; and one should definitely not rely on that old method.
Boletes are a diverse group of fungi which consists of hundreds of different species which belong to about a dozen different genera. The most prominent are Suillus, Leccinum, Tylopilus, and, of course, Boletus. Boletes often appear the day after it rains and are very perishable, especially in the summer.
Boletes have three distinct features.
- Most of them have an umbrella shape as opposed to the flat, shelf-like shape of other mushrooms, although they can sometimes resemble Agarics.
- Another difference is that Boletes do not have gills. Instead, they have a spongy layer of tubules called pores from where the tiny spores are diseminated.
- Nearly all grow on the ground near trees and should not be confused with Polyspores which grow on the wood and are shelf-like. The trees provide them with food. In exchange, the Boletes provide the trees microscopic roots with water and minerals and sometimes even growth hormones.
Many of them are difficult to identify, even for professionals; but they are some of the best-tasting mushrooms you can find. A few – for example, Frosts Bolete (Boletus frostii) – can cause nasty gastrointestinal symptoms (vomiting, diarrhea); but none are deadly. The general rule of thumb is not to eat Boletes that have a red or orange pore surface or any version of these colors.
Some Boletes turn blue slowly when they are bruised, while others turn blue instantly. Certain ones, especially those of the genus Suillus, have a slimy layer on the cap that can cause diarrhea if it is not peeled away before being eaten.
Although edible fungi are mentioned by classical authors, their nature was not understood, nor did it improve over the next several hundred years. Dioscorides was one of the first to offer some fanciful speculations of the origins of such a “plant”. By the 16th century, one author even claimed that snails crept out of their shells and turned into toads, and, because they then had nothing to sit on, created “toadstools” for themselves.
Finally, in 1729 in Micheli’s Nova Plantarum Genera, some scientific reasoning began to emerge. Even Linnaeus, the great Swedish naturalist of the mid-18th century, failed to allot fungi to a classification system. Instead, he accommodated them in a genus called Chaos. Later, in his Genera Plantarum, he created a class that was better-suited for them, Cryptogamia. However, it was another Swede, Fries (1761-1878), who did the most to further the classification that is still used today.
To help identify an edible fungus, it is important to know the particular substrate on which it depends or the higher plant species with which it lives. For instance, certain fungi only grow only in the vicinity of such trees as birch or oak. Others grow on decaying substrates or live symbiotically with living plants. Some are edible, while others are poisonous, and, therefore, should not be gathered, except by the most knowledgeable.
Only a few of the many thousand types of fungi are amenable to cultivation. At best, it is is wildly unpredictable because the organism depends on precise temperatures and moisture to produce fruiting bodies. Many are also sensitive to such environmental changes as recent air pollution and high nitrate levels. Because of their erratic behaviour and the deadly toxins some develop, cultivation remains a risky business.
Mushroom cultivation has had a widely varied past. The Romans esteemed mushrooms as a delicacy, while the rich employed collectors to find the most desirable species. By the late 17th century, varieties of Agaricus began to be grown in underground caves in the Paris region, where giant heaps of manure were impregnated with soil taken from fields known to have horse mushrooms growing naturally.
For many centuries, cultivated mushrooms were a delicacy enjoyed only by the wealthy; and from the 18th century on, most stableyards had a shady corner where there was a mushroom bed. Some owners had outhouses converted to provide the ideal growing medium. George IV had a large mushroom house at Kensington Palace in London.
In the mid-17th century, melon-beds were found to be good for mushroom growing; and many farmers took advantage of the availablility of two crops growing at once. This led to growing mushrooms in caves and quarries, especially in the Paris region and the Loire Valley, where rock had been taken for building purposes. The quarries of the Loire Valley are still in use; but mushroom-growing in Paris has almost ceased, except in the form of the cultivated “champignons de Paris”, which are also cultivated all over the world.
In seasons when wild or cultivated crops were plentiful, surplus mushrooms were conserved in the form of sauces, and ketchups and only recently has the role of the mushroom sauce been usurped by the tomato sauce.
There are about one hundred poisonous mushrooms, but they vary in their degree of toxicity. The Amanita genus of mushrooms is by far the most infamous. There are edible ones (mainly Amanita muscaria) in this genus, but most are risky at best. Two of the Amanita species, in particular, are responsible for many poisonings: Destroying Angel (A. ocreata) and Death Cap (A. phalloides). Then there is the False Death Cap (A. citrina), which is not as deadly but which looks so much like the Death Cap that it should also be left alone.
Amanita poisoning has a fatality rate of about 50% and is particularly dangerous because symptoms are delayed. When they do finally appear, anywhere from 6 to 24 hours later, there is little that can be done to reverse the effects.
There are some mushrooms that contain psychoactive chemicals that cause certain nerve receptors in the brain to misfire. This creates a euphoric sensation and a highly altered sense of reality, culminating in hallucinations. Such mushrooms have been used for thousands of years in religious and shamanic ceremonies, including during “sacred quests”. Abuse of these hallucinogenic mushrooms is one of the major causes of poisoning. Another is misidentification.
Most countries gather mushrooms with incredible enthusiasm, except for Britain, Holland, and most Arab nations. British woods and fields have plenty of varied and delicious fungi; but only the easily recognized field mushrooms are gathered, while all others are shunned as toadstools. This tendency is even more noticeable in Ireland, where large crops of precious morels go unharvested. By contrast, Russians, Scandinavians, and the Swiss all favor gathering wild mushrooms, forming crowds in the woods every autumn.
Certain kinds of mushrooms are favored, depending on the area. An expensive delicacy in China and other Asian countries is the Chinese straw mushroom (Volvariella volvaceae), also called paddy or padi straw. Grown on composted rice straw, it has a grey-brown cap, often marked with black and a dull brown stem. In Europe, the King Stropharia (Stropharia rugosoannulata) is a brown-capped fungus with violet gills. It is commonly cultivated in Eastern Europe, where it is claimed it can grow in the average vegetable garden. It should be acquired from reputable sources, however, as it has lookalikes from the deadly Cortinarius species.
Cultivated Agaricus species have remained popular in northern Europe and the English-speaking world, but elsewhere other types are more commonly found. In Japan, velvet shank, nameko, oyster, and shiitake mushrooms are well-established as cultivated types. They are slowly becoming more popular in other countries as people learn that mushrooms are more nutritious with some having decided medicinal value.
Another species, Hypholoma capnoides or Nematoloma capnoides, is a gilled fungus found growing in clusters on conifer stumps. Caps can be about two inches in diameter and are a pale ochre with a buff-coloured margin. Check identity carefully as a Hypholoma species look-alike is suspect. Lobster mushrooms are not really a mushroom, but a parasitic fungus. The Americas also have an unusual “delicacy” in the form of corn smut. (See corn.)
The nutritional value of edible mushrooms compares favorably to that of most vegetables. Generally, they are rich in the B vitamins, including choline, which acts as a protective agent for the liver in case of mushroom poisoning. Some are also high in vitamins A, D, and K; but only a few contain any vitamin C. Other nutrients include potasium, linoleic acid, folate, copper, and iron, as well as other trace elements. Cultivated mushrooms, especially the grocery store white buttons, contain very few nutrients.
Depending on the species, mushrooms can contain up to 3% useful proteins. Some types are actually quite high in protein, especially Agaricus, Lepiota, and Calvatia species. On a dried weight basis, the King Bolete (Boletus edulis), contains more protein than any common vegetable, except soybeans. However, much of it is indigestible so should not be used in place of other proteins.
Mushrooms are low in calories, until they are fried in butter. They are about 90% water, low in fat, and have most of their carbohydrates in the form of indigestible chitin. Chitin is a polysaccharide composed of the essential sugar, Glucosamine. Supplements are often derived from shells of crustaceans (shrimps, crabs, krill).
Mushrooms should always be cooked, but never overcooked. Cooking does increase their nutritive value by increasing their digestibility, but overcooking decreases this value. Mushrooms should not be washed, but rather wiped free of dirt and debris. However, certain ones do require soaking to remove the dirt and insects imbedded in their deep crevices. Few rarely need peeling, and some have stems that should not be eaten. Again, ALWAYS have a knowledgeable person confirm the species before any mushrooms are eaten as there are look-alike species which can be lethal.
(See also Essential Sugars Dictionary.)
Medicinal fungi contain many unique and powerful substances, including the essential sugars which help boost the immune system. Penicillin is but one component that was first discovered in bread mold. Many mushrooms contain natural antibiotic substances while some are valued for other healthful benefits.
Maitake, shiitake, and reishi mushrooms have overlapping properties; and all have high essential sugar content that boosts the immune system, supports cardiovascular health, and are being extensively studied for their cancer-reducing properties. More specifically, though, Maitake mushrooms are used for stomach and intestine ailments as well as to stabalize blood sugar levels. Shiitake is used to treat nutritional deficiencies and liver ailments; and Reishi is used to restore respiratory health.