This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
For these rather different treatment is required. The usual size of winter beds is 3 ft. high and 3 ft. wide. The manure is trodden down very firmly in 6-in. layers, the sides being dressed down to the necessary width, leaving the top about 6 to 8 in. across. As a rule, the temperature will be found to run up rapidly, sometimes to 120° or 130°. Holes 1 ft. apart and about 2 in. wide should be bored from the top nearly to the bottom with a crowbar. These will quickly reduce the temperature, but the base of the ridge will be soonest ready for spawning. Each layer should be spawned when ready. There may be a difference of a week between the start and the finish. The spawn should be inserted rather closer than in a flat bed, 8 in. each way being a suitable distance, and the pieces should be inserted in an upright position. The holes can be filled up with the rakings off the side, and all made firm.
Fig. 480. - Mushrooms (Agaricus campestris).
The soil for casing must be considerably wetter than that used for flat beds, as it must adhere to the bed - 2 to 2 1/2 in. at the base and 2 in. at the top will be none too much. It must be beaten very firm, men working from either side with flat spades and beating together against each other. The soil shrinks in drying, so it must not be too wet. Each crack lets out heat and moisture, and the temperature must be maintained. The beds should be placed 9 ft. apart, centre to centre, allowing plenty of room for litter and for moving between them. From 18 in. to 2 ft. of litter may be necessary in the coldest weather to maintain the heat.
In picking, a man should work each side of the bed, uncovering as little as possible at a time, carefully throwing out rotten litter, and damping the bed with warm water if necessary. Each picking should be started from either end of the bed alternately; the litter comes off easier that way. Mats, old sacks, or oiled canvas should be placed on the tops to shoot off the rain, and gullies dug between them to drain the water away.
It is always advisable to grade the Mushrooms well. The chief growers make several sizes of both cups and opens, and overweight is given, as shrinkage by evaporation always occurs.