Straw Mushroom

Common names

• Paddy Straw Mushroom
• Straw Mushroom

Straw mushrooms are a traditional ingredient of many Asian cuisines and widely cultivated for this purpose all around East and Southeast Asia. In this area, they can be easily found fresh, while in other parts of the world they are only usually available in dried or canned form. The aspect is very similar to the one of toxic death caps. However, death caps have a white spore print, while the one of straw mushrooms is pink. In addition, they are rarely found growing in the same area because their native distribution is different. However, many cases of poisoning in Australia or California are due to Southeast Asian immigrants confusing death caps to these edible mushrooms from their homeland. The species is usually cultivated on rice straw, which gives it the common name. For the same reason, it is also known as the paddy straw mushroom. They grow in the specific hot climate of Southeast Asia. They are the third most consumed mushroom in the world, after the common store mushroom (Agaricus bisporus) and shiitake (Lentinus edodes). This is due to their popularity in Asia, especially in China where they have been eaten for thousands of years, while they are a rarity in the USA. The species grows in clusters or gregariously and is a saprobic mushroom. It naturally colonizes places like greenhouses, gardens, compost piles or wood chips. It is the most common outdoors during the summer but can also grow during the whole year. It has become widespread on the North American continent, especially in areas east of the Great Plains. The cap of young straw mushrooms is shaped like an egg; it turns convex or conic later and finally becomes almost flat at maturity. It is between 5 and 16 cm in diameter, with a surface that is streaked with radial hairs and dries on touch. It has a dark color when young and can be brown or black, it later turns grey or brown. The edges have a paler color and split when the mushroom becomes old. The gills do not touch the stem and evolve from white to pink. They are very densely packed and are usually close. The stem has a diameter of up to 2 cm and a length between 4 and 14 cm. They tend to be thicker at the base, which is protected by a volva similar to a sack, almost black on top and white on the lower part. The stem itself has a silky surface, with a color that can be white or brown. Straw mushrooms are sold fresh in baskets in the markets of south China and other Asian states. They are usually harvested before the caps emerge from the universal veils, so they look like quail eggs with a tan color. They are popularly known as unpeeled straw mushrooms when sold at this stage. However, the wisdom of this tradition has been validated by modern scientific research. Scientists have discovered that unpeeled caps have a better nutritional combination of amino acids than the opened ones. They are rarely available in the mature form because the young caps supply more of the proteins that are missing from typical Asian diets. Straw mushrooms are also available in the United States, usually dried or canned. Cans of these mushrooms are often sold by Asian specialty stores. The labels should specify if the contents are peeled or unpeeled, since this can be quite important. Unpeeled mushrooms are not only more nutritious but also have a more powerful taste. However, the shapes and sizes of the canned products vary from one vendor to another. Chinese herbal stores also offer dried straw mushrooms, which have a richer flavour than the canned varieties.

Uses

Straw mushrooms provide many important nutrients, in particular B-complex vitamins, proteins, copper, potassium, selenium and zinc. They are low in both types of fats, saturated or not, but very rich in dietary fibers. All of the B-complex vitamins play vital roles in the body. Vitamin B1 (thiamine) is needed for the health of nerves and the heart but especially because the body can't break down sugars without it. Vitamin B6 has a major role in the activity of the immune system. It also keeps the lymph nodes healthy and is involved in the metabolism of carbohydrates, fats and amino acids. It plays a key role in the management of diabetes because it maintains a healthy level of glucose in the blood. Vitamin B9 (folate) is required for a healthy liver function. Vitamin B12 is a part of the DNA synthesis process and also needed for healthy blood cells. In addition, it is involved in the neurological function and the nervous system mechanism must be supplied with it. Straw mushrooms are rich in dietary fibers, which improve peristalsis and digestion. With a good supply of fibers, the risk of constipation and other digestive issues is very low. One of the main minerals needed by the body is potassium. It plays a major role in the balance of fluids, heart health and the production of proteins. A high level of potassium reduces the risk of strokes, improves bone structure and balances blood pressure. Zinc is a mineral with multiple uses that can be traced to the immune system, the balance of blood sugar levels, energy management and proper digestion. Copper is especially important during growth but also helps with a healthy heartbeat, solid connective tissues and for proper enzyme reactions. Consuming straw mushroom is known to reduce hypertension and high levels of cholesterol, so it is advised for people who have these problems. They can be used in the treatment of diabetes and cancer as a support therapy.

Habitat and cultivation

Just like the name suggests, straw mushrooms are cultivated on rice straws. They are typically harvested early, while the veil is still intact and they are in the button or egg stage. They require subtropical climates with high yearly rainfall and grow quickly, maturing in just 4-5 days. Straw mushrooms are a prized ingredient of Asian cuisine and are widely cultivated in the area. They are available in fresh, dried and canned forms in most local markets. They are eaten in large amounts and also exported. Outside of Asia, straw mushrooms are available from imports and can be found in very large stores, as well as Asian specialty ones. They are easily to prepare, the dried varieties must be first drained and rinsed, while boiling water can be used to rehydrate dried mushrooms. Straw mushrooms are available fresh during the entire year in Asia because they can be easily cultivated indoors. Their preferred habitat is the straw that remains after harvesting rice, also known as paddy straw, which gives the species its popular name. Many other types of vegetal matter can also be used for cultivation instead. The most common examples include grass or other straw varieties, cut dry plantain leaves, wood debris or compost. In cultivation for commercial purposes, a mix of paddy straw and cotton fiber is used as a base. The straw mushrooms can be harvested as soon as they reach the size of a thumb, when they develop a white spore print and pale pink gills.

Side effects and cautions

Besides its original native range in Asia, the species has been spotted in the wild in Eastern Europe as well. It has not been detected in North America so far. Many Asian immigrants who are used to collect this mushroom confuse it with various members of the amanita genus, which are often deadly. Inexperienced mushroom harvesters can easily be confused by the superficial resemblance between them, especially since amanitas also have a veil and a bulbous base when young.