Growing Mushrooms

How do mushrooms grow?

Mushrooms are fungi that do not require roots, leaves, flowers or seeds to grow. They are a special type of living organism that grows from microscopic spores. These spores are too small to handle so they are collected and grown onto grain in a sterile laboratory type of environment. The inoculated grain is known as mushroom spawn and is like a “mushroom seed” to produce cultivated mushroom.

Unlike plants, mushrooms have no chlorophyll and they must get all of their nutrients and energy from their growing medium. Cultivated mushrooms are grown in a rich organic medium known as compost. Compost is carefully formulated from various materials such as wheat straw, gypsum and nitrogen supplements. A rich dark compost is made to imitate the ideal growing conditions as would be found in wild mushroom production.

Preparation of compost and growing mushrooms requires specialized steps. The stages of mushroom growing involve:

  • composting,
  • pasteurization,
  • spawning,
  • growing,
  • cropping and
  • competition of harvest.

The composting process involves mixing and blending of organic material and takes place in specialized composting facilities. This compost is then pasteurised to ensure that all harmful microbes and pests are destroyed while maintaining beneficial organisms that favour mushroom production.

The growing of mushrooms takes place in specially constructed mushroom houses. Growers purchase compost and spawn. The spawn grain is worked into the compost and the mushroom mycelium that is growing on the surface of the grain steadily colonises this compost. Mushroom farmers must carefully maintain the temperature of the compost and the humidity of the growing rooms in order for the mycelium to fully develop. Next, a casing layer of peat moss is spread over top of the compost. Soon after tiny white structures appear on the surface. This growth stage is called pinning. The pins continue to grow to become mushrooms caps, which is also the fruiting structure of the fungus.

In BC three flushes of mushrooms are carefully harvested by hand over a period of a few weeks. The harvested mushrooms are sorted by size and quickly refrigerated on the farm to maintain freshness and quality. The mushrooms are then shipped to packers daily from the farms where they are packaged and shipped quickly to supermarkets, food processors and restaurants.

Mushroom growers in BC produce fresh mushrooms year round. The entire process from the time preparing the compost until the mushrooms are harvested and shipped to market takes about four months. Once a mushroom harvest is completed the mushroom houses are steam-sterilized and emptied before the process begins again. The remaining compost is often recycled as an organic matter for home gardening and agricultural uses.