This section is from the book "Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc.", by George Francis Atkinson. Also available from Amazon: Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc..
The beds for growing the mushrooms having been made up, the spawn having been selected, the beds are ready for planting whenever the temperature has been sufficiently reduced and the material is properly cured. It is quite easy to determine the temperature of the beds, but it is a more difficult problem for the inexperienced to determine the best stage in the curing of the material for the reception of the spawn. Some growers rely more on the state of curing of the manure than they do upon the temperature. They would prefer to spawn it at quite a low temperature, rather than to spawn at what is usually considered an optimum temperature, if the material is not properly cured. The temperature at which different treatises and growers recommend that the bed should be spawned varies from 70° to 90o F. Ninety degrees F. is considered by many rather high, while 70° F. is considered by others to be rather low; 8o° to 850 is considered by many to be the most favorable temperature, provided of course the other conditions of the bed are congenial. But some, so far as temperature is concerned, would prefer to spawn the bed at 750 F. rather than at 900, while many recommend spawning at 700 to 750. In some cases, I have known the growers to allow the temperature of the beds to fall as low as 6o° before spawning, because the material was not, until that time, at the proper state of curing. Yet an experienced grower, who understands the kind of spawn to plant in such a bed, can allow the temperature to go down to 6o° without any very great risk. Fresh spawn in an active state, that is, spawn which is in a growing condition, as may be obtained by tearing up a bed, or a portion of one, through which the spawn has run, is better to plant in a bed of such low temperature. Or, a bed of such low temperature, after spawning, might be "warmed up," by piling fresh horse manure over it loosely for a week or ten days, sufficient to raise the temperature to 8o° or 90°.
When the brick spawn is used, the method of planting varies, of course, with the methods of different operators. Some break the bricks into the desired size and plant the pieces directly in the bed, without any special preparation. The brick is broken into pieces about two or three inches in diameter. Some recommend breaking the brick of the ordinary size into about twelve pieces, some into nine pieces, so the custom varies with different operators. These pieces are planted from seven to nine inches apart in the bed. For example, if they are to be planted nine inches apart in the bed, holes are made, either with the hand or with some instrument, by pressing the material to one side sufficiently to admit of the piece of spawn being pressed in tightly. These openings are made, say, the first row on one side of the bed, about four and one-half inches from the side, and nine inches apart in the row. The second row is made nine inches from the first row, and so on. The pieces of spawn are inserted in the opening in the bed, and at a slight distance, two to three inches, below the surface. Some, however, insert the piece of spawn just at the level of the bed, the opening being such that the piece of spawn pressed into the opening is crowded below in place, and the surrounding material fits snugly on the sides. Thus, when the bed is spawned, the pieces may be a slight distance below the top of the bed when they can be covered by some material, or in other cases, where the operator varies the method, they would lie just at the surface of the bed.
Pieces of brick spawn ready to plant.
The bed is now firmed down according to the custom of the operator, either tamped down with some instrument very firmly, or by others, with the back of the fork or other similar instrument, the bed is made firm, but not quite so hard. The object in firming it down after spawning is to make the surface of the bed level, and also to bring the material in the bed very closely in touch on all sides with the spawn with which it is impregnated.
Some growers follow the method of giving the spawn some little preparation before putting it into the bed. This preparation varies with different operators. Its object, however, is to slightly moisten " Flakes" many generations old, "running out." the dry spawn, and perhaps, also, to very slightly start the growth. To accomplish this, some will cover the bricks, before breaking them, with fresh horse manure, and allow this to remain several days, so that the warmth and moisture generated here penetrate the material and soften somewhat the brick. Some pile it in a room or compartment where there is little moisture, until the bricks are permeated to some extent with the moisture, so that they are a little easier broken. They should not, under any circumstances, be wet or soft in the sense of having absorbed an excess of water, nor should they be stored for any length of time where they will be damp. Still others break the bricks into the desired pieces and place these directly on the top of the bed, at the place where they wish to plant the piece of spawn. They are left here for two or three days on the surface of the beds. These pieces absorb some moisture and take up some warmth from the bed. Then they are planted in the ordinary way.
Piece of French Spawn.
Figure 236. Piece of Natural Spawn.