ESSENTIAL CONDITIONS.—Mushrooms can be grown in any climate and in any season where the essential conditions may be found, obtained or controlled. These conditions are, first, a temperature ranging from 53° to 60° F., with extremes of 50° to 63°; second, an atmosphere saturated (but not dripping) with moisture; third, proper ventilation; fourth, a suitable medium or bed; fifth, good spawn. It may be seen that in the open air, these conditions are rarely found together for any length of time. It is therefore necessary, in order to grow mushrooms on a commercial basis, that one or more of these elements be artificially supplied or controlled. This is usually done in cellars, caves, mines, greenhouses, or specially constructed mushroom houses. A convenient disposition of the shelves in a cellar is shown in Figure 498. A large installation for commercial purposes is shown in Figure 500, and a specially constructed cellar is shown in Figure 499. Where abandoned mines, natural or artificial caves are available, the required atmospheric conditions are often found combined and may be uniformly maintained throughout the year.
Figure 499.—Specially Constructed Mushroom Houses.
Figure 500.—Mushroom Houses, Flat Beds.
TEMPERATURE.—Within the limits prescribed, the temperature should be uniform throughout the growth of the crop. When too cold, the development of the spawn will be retarded or arrested. A high temperature will favor the development of molds and bacteria which will soon destroy the spawn or the growing crop. The cultivation of the mushroom, as a summer crop, is therefore greatly restricted. As a fall, winter or spring crop it may be grown wherever means are at hand to raise the temperature to about 58° F. Many florists are utilizing the waste space under the benches for that purpose; they have the advantage of being able to use the expended material of mushroom beds in growing flowers.
MOISTURE.—Moisture is an important factor in the cultivation of the mushroom, and demands intelligent application. The mushroom requires an atmosphere nearly saturated with moisture, and yet the direct application of water on the beds is more or less injurious to the growing crop. It is therefore essential that the beds, when made, contain the requisite amount of moisture, and that this moisture be not lost by excessive evaporation. They should be protected from a dry atmosphere or strong draughts. Where watering becomes necessary, it should be applied in a fine spray around the beds with a view of restoring the moisture to the atmosphere, and on the beds after the mushrooms have been gathered.
VENTILATION.—Pure air is essential to a healthy crop. Provision should therefore be made for a gradual renewal of the air in the mushroom house. However, draughts must be avoided as tending to a too rapid evaporation and cooling of the beds, an unfortunate condition which cannot thereafter be entirely remedied.