Mushrooms should be grown in a cellar or shed, away from frosts and rains. Light is unnecessary. The method is this. Fresh manure is placed in a heap, and about every fourth day it is turned over. During this time the manure should remain moist, and a little tepid water should be used if needed. At the end of three weeks, or longer if the manure contains shavings or sawdust, the heap will be ready to make up into a bed. It should have lost its disagreeable odour by this time, and the temperature should have dropped to about 120 degrees centigrade.
The bed can be flat, 10 in. deep, or built to a ridge shape. When the temperature has dropped to about 70 degrees centigrade, pieces of mushroom spawn about 2 in. square are pushed in so that they are covered by about an inch of manure. The surface should be beaten firmly after the spawning, and a layer of soil an inch or two deep should then be added all over the heap. Tepid water may be needed to prevent the beds drying out, but this is not usually required.
When the first small buttons are seen, gather them and immediately dress the whole bed with a little more sifted soil. More mushrooms will appear, for perhaps several months, the supply being dependent on the weather and other conditions. It is possible, in a frost proof shelter, to grow mushrooms continuously all the year round, and fresh beds can be made up in succession so that the supply is maintained. When a bed has ceased to bear, the manure is no longer valuable in the mushroom house, but is very useful for making up beds for vegetable marrows or for other garden manure.
Mushrooms can be grown in sheds, outhouses, cellars, mine workings, frames and greenhouses if darkened, and outdoors. Outdoor beds are unreliable, as an even temperature and cool, damp atmosphere are essential for success. Fresh horse manure. or straw or chaff treated with special proprietary preparations are necessary for making the compost. If manure is used it should be strawy and free from shavings and must be obtained from horses that are in good health. Remove twigs or other refuse and make into a stack 3 ft. high Cover with 1 in. of soil. After a week shake and mix thoroughly ; water any parts that appear dry and stack again but without soil. Continue in this manner every four or five days for about three weeks. By this time the manure and straw should have rotted to an even texture and dark brown colour and should smell sweet, without trace of ammonia. Place in boxes 9-12 in. deep or build into beds 8-10 in. deep, 2-3 ft. wide, and any convenient length. For outdoor cultivation, ridge beds 3 ft. wide and 2 ½ ft. in height are to be preferred. In either method the manure should be trodden down firmly little by little as the bed is filled. Place a thermometer in the bed and wait till the temperature falls to between 70° and 75°F. Then break up purchased spawn into pieces the size of a walnut and place one every 9 in., 1 in. beneath the surface. Cover with a layer of straw 6 in. thick under cover, 1 ft. outdoors. Ten days to a fortnight later examine the bed to discover whether the spawn is running i.e. producing white filaments of mycelium. If so, remove the straw and case the bed with peat or good soil to a thickness of 11 in. for ridge beds, 1 in. for flat beds. Re-cover outdoor beds with straw or matting. Under cover, if temperature can be controlled, maintain at about 65° until mushrooms appear, when it may fall to 55°-60°. Maintain a damp atmosphere throughout. Water if beds become dry, but avoid watering over much. Indoor beds can be made at any time; outdoor beds are best made in July.
If proprietary preparations are used to convert straw or chaff into mushroom compost, obtain manufacturers’ directions for use and follow these closely.
Maggots are the principal foes.