Fresh Locally Grown White Mushrooms

White Mushrooms

Monterey Mushrooms® white mushrooms are probably the most popular mushroom in the U.S. They are an excellent source of B vitamins including vitamin B2, niacin and pantothenic acid. In addition, white mushrooms are a very good source of potassium, zinc, vitamin B1 and manganese.

How Mushrooms Grow

White mushrooms, like all mushrooms, grow from microscopic spores, not seeds. Plants growing from spores are called fungi. A mature mushroom will drop as many as 16 billion spores. Spores must be collected in the nearly sterile environment of a laboratory and then used to inoculate grains or seeds to produce a product called spawn (the mushroom farmer’s equivalent of seed).

White Mushrooms


Because mushrooms have no chlorophyll, they must get all their nutrients from organic matter in their growing medium. The medium, called compost, is scientifically formulated of various materials such as straw, corn cobs, cotton seed and cocoa seed hulls, gypsum and nitrogen supplements. Preparing the compost takes one to two weeks. Then it’s pasteurized and placed in large trays or beds. Next the spawn is worked into the compost and the growing takes place in specially constructed houses where the farmers can regulate the crucial aspects of heat and humidity.

In two to three weeks, the compost becomes filled with the root structure of the mushroom, a network of lacy white filaments called mycelium. At that point, a layer of pasteurized peat moss is spread over the compost. The temperature of the compost and the humidity of the room must be carefully controlled for the mycelium to develop fully. Eventually, tiny white protrusions form on the mycelium and push up through the peat moss. Farmers call this pinning. The pins continue to grow, becoming the mushroom caps, which are the fruit of the plant, just as a tomato is the fruit of a tomato plant. It takes 17 to 25 days to produce mature mushrooms after the peat moss is applied. Size is no indication of maturity in mushrooms. Perfectly ripe mushrooms vary in size from small buttons to large caps.

Each crop is harvested over a period of several weeks and then the house is emptied and steam-sterilized before the process begins again. The remaining compost is recycled for potting soil. The harvested mushrooms are set in carts, refrigerated and then packaged and shipped to supermarkets, food processors and restaurants. The entire process from the time the farmer starts preparing the compost until the mushrooms are harvested and shipped to market is about four months.

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