Mushrooms seem to spring up over night in the yard.  However, how are mushrooms grown commercially?  Mushrooms are a delicacy.  When we buy mushrooms, we see them still covered in dirt on the shelf.  When we eat out, there is usually an expensive appetizer containing mushrooms on the menu.  But when we go back home, we see them growing in the yard, and we know we didn’t plant them there.  We pull it up, and it keeps coming back.  How hard can they be to grow?

There are 6 main steps to growing mushrooms.    Initial Composting, finished composting, spawning, casing, pinning and cropping.Mushrooms - Fungus and DelicacyCredit:

In the first step, preparing compost for the mushrooms is done.  This provides a mushroom substrate, or a surface that is receptive to the growing of the mushroom spores.  There are several ways. Straw and horse manure one group of compost starting materials.  The grower arranges the straw and manure in long rectangular piles, making sure the center is loose and the sides tight.  He will then use a turner to make sure it is all mixed together, adding water, gypsum and nitrogen to the mix.  he turns and mixes the pile about every 2 days during this process.  This step takes 7-14 days. 

The starting materials have now become compost.  But, at this stage, the mushroom substrate has a high ammonia content.  The ammonia will have to be removed from the compost.  If this was left in the compost, it would be deadly for the mushroom spawn in the next step.  There are two methods of removing the ammonia.  The two methods are high heat or low heat.    After either method, the temperature of the mushroom substrate is slowly lowered to 75-80 degrees, 1-2 degrees per day, before beginning planting.

In step three, the grower will spread the spawn of the mushrooms over the compost and mix it into the compost.  Spawn is some grain that the mushroom has already been growing on.  It is possible to grow mushrooms from the spores, but is it is more tricky.  What are spores?  Spores serve the same function as seeds in the growth of bacteria, algae, fungi and some plants.  

The grower will buy spawn from a distributor.  Spawn are from other mushrooms, like seeds are from tomatoes.  Because they are so small, the grower will need to take special care while propagate them to make sure they are not mixed with other fungi.  As the spawn grows, heat is generated, so the compost temperature will be kept under control.  The temperature is kept about 75 degrees.  If the temperature were to go too high the spawn would be killed, and if the temperature falls too much, the process slows down.

Step four is the applying of a casing to the top of the compost.  This helps as a water reservoir and as a spot for the mushrooms to spread into.  As the mushrooms spread, the temperature is allowed to lower.  The growers will add water slowly and carefully.

In step five, the mushrooms start to grow and pins emerge.  Pins grow bigger and become buttons, and these enlarge to become mushrooms.  In all, this takes 18-21 days from the time casing begins to become a harvestable mushroom.  Introduction of fresh air and water is tricky at this stage.  If improperly executed, the pins might form, or grow,  below the surface of the casing, and then when the mushrooms grow larger, they will start below the surface of the casing, resulting in dirty mushrooms as they push through the casing.

When harvesting, called cropping, in step six, the grower will still keep a close eye on water and temperature.  The mushrooms reach size in just a 3-5 day period.  They are then harvested.  Then there is a period of waiting, and then harvesting.  This cycle can go on for 30-150 days, depending on the grower.    Water and temperature are closely watched.  Lower temperature helps the mushrooms grow, and slows the growth of insects and other pathogens that might harm the mushrooms.

They are now ready for shipping to the store, and for you to buy mushrooms for your table.

We often hear about mushrooms being grown in the dark.  Mushrooms, don’t need light to Mushrooms - How They Are GrownCredit:, so it often easier just to let the workers carry light with them when entering the room, rather than light the entire room.

Knowing how are mushrooms grown can often be considered more of an art.  Controlling temperature and humidity takes a careful hand and detailed knowledge of the mushroom life cycle, to maximize yields to keep costs down.  The spontaneous sprouting in the yard is a far cry from the commercial growing of this special delicacy.

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