Ordinarily the beds are only 8 to 10 inches deep; that is, they are faced with 10-inch-wide hemlock boards, and are only the depth of this board. In such beds put a layer of fresh, moist, hot manure, and trample it down firm until it constitutes half the depth of the bed; then fill up with the prepared manure, which should be rather cool (100° to 115° F.) when used, and pack all firmly. If desired, the beds can be made up entirely of the prepared manure. Shelf beds are usually 9 inches deep; that is, the shelf is bottomed with 1-inch boards and faced with 10-inch-wide boards. This allows about 8 inches for manure, and 1 inch rising to 2 inches of loam on top. In filling the shelf beds the bottom half may be of fresh, moist or wettish, hot manure, packed down solid, and the top half of rather cool prepared manure, or it may be made up of all prepared manure. As the shelf beds can not be trodden and can not be beaten very firm with the back of the fork, a brick is used in addition to the fork.
The beds should be spawned after the heat in them has fallen below 100° F. The writer considers 90° F. about the best temperature for spawning. If the beds have been covered with hay, straw, litter or mats, these should be removed. Break each brick into twelve or fifteen pieces. The rows should be, say, 1 foot apart, the first one being 6 inches from the edge, and the pieces should be 9 inches apart in the row. Commencing with the first row, lift up each piece, raise 2 to 3 inches of the manure with the hand, and into this hole place the piece, covering over tightly with the manure. When the entire bed is spawned pack the surface all over. It is well to cover the beds again with straw, hay or mats, to keep the surface equally moist. The flake spawn is planted in the same way as the brick spawn, only not quite so deep.
At the end of eight or nine days the mulching should be removed and the beds covered with a layer of good loam 2 inches thick, so that the Mushrooms can come up in and through it. This gives them a firm hold, and to a large extent improves their quality and texture. Any fair loam will do. That from an ordinary field, wayside or garden is generally used, and it answers admirably. There exists an idea that garden soil surfeited with old manure is unfit for Mushroom beds because it is apt to produce spurious fungi. This, however, is not the case. In fact, it is the earth most commonly used. For molding the beds the loam should be rather fine, free and mellow, so that it can be easily and evenly spread and compacted firmly into the manure.