Button/Portobello (Agaricus bisporus)
Agaricus bisporus has a different name for each stage of its development. They can be harvested when they are small button or leave them only another 2-3 days and they will turn into a much larger Portobello. Other names are common mushroom, button mushroom, white mushroom, cultivated mushroom, table mushroom, and champignon mushroom, Swiss brown mushroom, Roman brown mushroom, Italian brown, Italian mushroom, cremini or crimini mushroom, brown cap mushroom, or chestnut.
Agaricus bisporus can be grown on many substrates horse manure, wheat straw chicken manure, corn cobs. In a lot of commercial operations chicken manure and wheat straw is used. The mixture is composted by heat tolerant bacteria. This process not only breaks down the ingredients into a mushroom rich food substrate and the heat generated helps to kill off unwanted organisms.Once composting is complete the temperature drops back down and the grain spawn is added. A casing layer is put on top of the substrate once it is fully colonised by the mycelium. For Agaricus bisporus the casing layer is essential, for reasons not really understood without the casing layer the mycelium will not produce mushrooms. The casing layer helps to hold moisture and is generally nutrient poor.