National Mushroom Day

What the day is

National Mushroom Day is observed on October 15. It is an informal food observance that celebrates mushrooms in the kitchen, from the everyday white button mushroom to shiitake, oyster and portobello. The day has no clearly documented founder, and calendars that list it do not agree on where it started.

October suits it well. Autumn is the season when wild mushrooms appear in forests and when earthy, savory dishes are back on the table.

Origin and background

Mushrooms are not plants. They are the fruiting bodies of fungi, which feed on decaying matter rather than making their own food from sunlight. People have eaten them since prehistory, and several cultures, including Chinese, Roman and Mesoamerican, recorded them as food or medicine long ago.

Cultivation came later. Growers in France began raising mushrooms in the limestone quarries and caves under Paris in the seventeenth century, where the temperature and humidity stay steady. Today the most common cultivated mushroom in the United States is the white button mushroom, which is the same species as the brown cremini and the large portobello, picked at different stages of maturity. Chester County, Pennsylvania, around Kennett Square, calls itself the mushroom capital of the world because of its large farms.

Nutritionally, mushrooms are low in calories and provide B vitamins, selenium and potassium. Mushrooms exposed to ultraviolet light, either sunlight or a lamp at the farm, make vitamin D, which is rare in a non-animal food.

Wild mushrooms carry a serious warning. Many edible species have poisonous lookalikes, and some, such as the death cap, can cause fatal liver damage even in small amounts. Never eat a wild mushroom unless an experienced local expert has identified it in person. A phone app is not enough, and cooking does not make a poisonous one safe.

How to take part

• Cook mushrooms in a hot, dry pan without crowding them, so they brown instead of steaming, and salt them near the end.
• Wipe them with a damp cloth or give them a quick rinse rather than soaking them, since they absorb water.
• Try a variety you have not cooked before, such as oyster, maitake or king trumpet.
• Visit a farmers market and ask the grower how a particular mushroom is best cooked.
• Grow your own from a kit, which fruits on a kitchen counter in a couple of weeks.
• Join a local mycological society walk if you are curious about wild fungi, and let the experts do the identifying.