Both the Latin and common names of oyster mushrooms (Pleurotus ostreatus) refer to the shape of the fruiting body. The Latin pleurotus (sideways) refers to the sideways growth of the stem with respect to the cap, while the Latin ostreatus (and the English common name, oyster) refers to the shape of the cap, which resembles the bivalve mollusk of the same name. Many people also think they taste a bit like oysters. Oyster mushrooms are also known as oyster cap mushrooms, elephant ear mushrooms, tree mushrooms, pleurottes, and shimeji. Other species known as oyster mushrooms include Pleurotus pulmonarius, Pleurotus nebrodensis, and Pleurotus eryngii, the latter two of which are gaining market share in Asia because these thick-fleshed and short-gilled mushrooms have a shelf life that exceeds most species by several weeks.

Oyster mushrooms grow on both deciduous and coniferous trees in forests around the world, where they fruit in both spring and fall. Gardeners and farmers can grow them on dead wood, straw, grasses, cotton, cacti, Scotch broom, hemp, coffee wastes, paper products, and practically any other dried cellulose material.

Oyster mushrooms have a long history in traditional Chinese medicine, where they have been used for over 3,000 years.

They were described scientifically in 1775 by Dutch naturalist Nikolaus Joseph Freiherr von Jacquin (1727–1817), who named them Agaricus ostreatus, because at the time, most of the gilled mushrooms were included in the genus Agaricus.

In 1871 German mycologist Paul Kummer transferred the oyster mushroom to the genus Pleurotus (a new genus that Kummer himself had defined), giving it its currently accepted scientific name.

Oyster mushrooms were cultivated in Germany as a subsistence measure during World War I. In 1950, one of the first antibiotics isolated from mushrooms, pleuromutilin, was discovered after observing that Pleurotus ostreatus inhibited a wide range of Gram-negative bacteria, including Salmonella and Pseudomonas.

People who grow crimini mushrooms have an exasperating time fighting nematodes, tiny roundworms that feed on living plant and fungi. But nematodes do not infest oyster mushrooms, which led to the 1986 discovery that oyster mushroom mycelium is carnivorous:  it eats nematodes. The mycelium produces toxins that stun the nematode, and then the fungus invades the nematode’s body through its orifices. Gardeners and farmers may soon be able to control nematodes without using toxic pesticides.

Oyster mushrooms are rich in protein (up to 30 percent by dry weight), plentiful in B vitamins, and have no cholesterol.

Mushrooms contain ergosterol, a substance that turns into vitamin D as it’s exposed to ultraviolet light. Your body can’t absorb calcium without vitamin D. It also regulates genes that influence cell growth and enzymes in the immune system. Vitamin D helps protect your heart by lowering blood pressure. The amount of vitamin D varies depending on the length of exposure to ultraviolet light. Oyster mushrooms may have as much as 103 international units in 100 grams, which is a little less than 1 cup. But the USDA Nutrient Data Laboratory reports 25 international units in 1 cup, which is 4 percent of the Daily Value.

Oyster mushrooms can:

1. Fight free radicals. Oyster mushrooms are an excellent source of riboflavin, which helps protect your cells from oxygen damage. The copper in oyster mushrooms helps form superoxide dismutase (SOD), anantioxidant enzyme, along with other antioxidant enzymes. Oyster mushrooms are one of the best sources of ergothioneine, a unique antioxidant exclusively produced by fungi. A 3 oz. serving of oyster mushrooms contains 13 milligrams of ergothioneine, and cooking the mushrooms does not reduce this level. Ergothioneine also fights chronic inflammation, and may prevent the buildup of plaque in the arteries that leads to cardiovascular disease.
2. Fight cancer. Extracts of oyster mushrooms inhibit the growth of colon and breast cancer cells without significant effect on normal cells, and they out-performed similarly prepared extracts from crimini, shiitake, and enoki mushrooms. Additionally, the beta glucan and glycoprotein complexes oyster mushrooms alert your immune system’s natural killer and cytotoxic T cells, improving your body’s natural anti-cancer responses.
3. Fight pathogens. Oyster mushrooms have significant antibacterial activity against a wide range of Gram-negative bacteria, including Salmonella and Pseudomonas. The active compound benzaldehyde reduces bacterial levels. It may form on the mushroom as a reaction to stress. Oyster mushroom mycelium is one of the most adept fungi at consuming bacteria (Pseudomonas and Agrobacterium) in order to get nitrogen and protein. Exudates from oyster mushroom mycelium strongly inhibit E. coli and Staphylococcus aureus.
4. Fight anemia. The copper in oyster mushrooms works together with iron to form hemoglobin and red blood cells.
5. Control hypertension, obesity and diabetes. Oyster mushrooms are high in niacin, which stabilizes your blood sugar, and helps your body process fats. Potassium in oyster mushrooms lowers blood pressure by counteracting the detrimental effects of sodium and regulating fluid balance. The copper in oyster mushrooms plays a role in the conversion of dopamine to norepinephrine, which is involved in regulating blood pressure. Oyster mushrooms are also low in sodium, carbohydrates, fat, and calories.
6. Relieve constipation. Oyster mushrooms have beneficial high fiber content.
7. Reduce cholesterol. The niacin in oyster mushrooms helps lower cholesterol levels, stabilizes your blood sugar, supports genetic processes in your cells, and helps your body process fats. Oyster mushroom naturally contain 0.4%-2.7% of lovastatin, commonly used in cholesterol lowering drugs.
8. Bolster immunity. Oyster mushrooms contain contain compounds that help enhance immune function. Oyster mushrooms are being studied as a possible defense against HIV.
9. Improve your response to stress. Pantothenic acid in oyster mushrooms improves your ability to respond to stress by supporting your adrenal glands. The copper in oyster mushrooms plays a role in the conversion of dopamine to norepinephrine, which affects your body’s biological response to stress.
10. Give you energy. Riboflavin supports cellular energy production. Pantothenic acid helps turn carbohydrates and fats into usable energy. Potassium stores carbohydrates for muscles to use as fuel. Phosphorus helps you use carbohydrates and fats and synthesize protein. You also use it to make adenosine triphosphate (ATP), a molecule that stores energy in your cells. The copper in oyster mushrooms helps your mitochondria produce energy.

Oyster mushrooms are available year round. Fresh oyster mushrooms are available in many markets in a wide variety of colors and sizes, but must be used quickly. Dried varieties are available in many markets too and are a perfectly acceptable substitute for fresh.

Good-quality oyster mushrooms are dry and have smooth, firm caps with firm plump white stems. Avoid oyster mushrooms that are wet, dark-brown, bruised or have spots of mold.

Store oyster mushrooms in closed paper bags inside your refrigerator for up to two weeks. You can extend your mushroom’s storage life by placing a dry paper towel in with the mushrooms to help absorb any extra moisture.

Dried oyster mushrooms don’t require reconstitution; they can be added directly to a dish. In fact, you should add them toward the end of recipes with long cooking times as they need little cooking time themselves.

*That said, it’s extremely important that you always cook oyster mushrooms. They contain ostreolysin, a hemolytic protein that can be toxic unless the mushrooms are cooked at temperatures exceeding 140 degrees Fahrenheit. In fact, all mushrooms, with the exception of truffles, should be cooked to best take advantage of their beneficial nutritional properties while deactivating heat-sensitive toxins.

Try oyster mushrooms as a substitute for actual seafood in these recipes:

• Oyster Mushrooms Rockefeller
• Oyster Mushroom Tacos with Sweet Mango Salsa
• Oyster Mushroom Scampi
• Oyster Mushroom Po’ Boy
• Crab Free Crab Cakes
• Vegan Crab Cakes