How Portabella Mushrooms Grow
Making the Growing Medium (weeks 1 - 4)
To produce mushrooms a growing medium is needed. Mushrooms have no chlorophyll so they must get all their nutrients from the organic matter in their growing medium. Compost is made with straw, dried poultry litter, canola meal, gypsum and water. The ingredients are blended together and placed into “tunnels” where air is forced through the material. Temperatures and oxygen levels are closely managed until the compost is ready for pasteurizing. The use of tunnels to prepare compost is new technology in North America.
Pasteurizing the compost is also done in tunnels at Ostrom's. This is a process of managing temperature, oxygen and time to convert ammonia into a useable form of nitrogen which the mushroom needs for it to grow. Compost Preparation and pasteurization is a four week process, and is followed by introducing mushroom spawn to the compost.
Spawning the Compost (weeks 5 - 6)
Mushroom spawn is grain that has been colonized with a pure culture of mushroom fungus. The spawn is mixed into the compost. Over the next two weeks, under carefully managed conditions of temperature, humidity and carbon dioxide, the thread-like mushroom fungus, called mycelium, begins to grow through the compost.
After the mycelium has completely colonized the compost, a layer of soil is applied to the surface of the compost in each growing tray. This layer is a moisture-rich growing soil consisting of peat moss, sugar beet lime and water, and provides a water reservoir for the growing mushrooms.
Formation of Mushrooms (weeks 7 - 9)
At a commercial mushroom farm mushrooms must be induced to grow in order to produce a high yielding and high quality crop. This is called “pinning”, and is accomplished by making adjustments to the oxygen, carbon dioxide, humidity and temperature levels in the growing room. After approximately eight days tiny “pinhead” mushrooms are visible on the surface of the layer of soil and by day twelve the mushrooms are mature enough to pick. The mushrooms almost double in size every 24 hours.
Picking and Packing (weeks 10 - 12)
Picking mushrooms is done by hand every day of the year. The best quality is accomplished by trained pickers who select the mushrooms, cut the root structure from the stem and place them directly into the shipping boxes. This direct-picking technique is used to minimize over-handling the mushrooms. Each room will produce three “breaks” of mushrooms over a three week period before the room is removed from the production cycle.