Food Facts: All About Mushrooms


How do mushrooms grow? 

    Mushrooms are fungi so they grow from microscopic spores instead of seeds. A mature mushroom will drop as many as 16 billion spores. Spores are 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, crimini, and portabella mushrooms get all their nutrients from the compost that they're grown in. This compost is specifically made for growing mushrooms and can take one to two weeks to prepare. Once the compost is ready, its pasteurized, placed in large trays and the spawn is worked in.

    The trays of spawn are kept in specially constructed buildings with strict temperature and humidity controls. In two to three weeks, the compost fills with the root structure of the mushroom, a network of lacy white filaments called mycelium. A layer of pasteurized peat moss is then spread over the compost. Tiny white protrusions, called pins, form on the mycelium and push up through the peat moss. The pins continue to grow, becoming the mushroom caps. The caps are actually the fruit of the mushroom, 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.

    Mushrooms are harvested over a period of several weeks and then the building is emptied and steam-sterilized before the process begins again. New compost is used each time and the old compost is used for potting soil.