Spawn: You can purchase spawn, which is much like a cheese or bread mold, from several catalog garden seed companies. Bottle spawn is the purest form of culture. Break it into pieces a little smaller than a golf ball and plant them eight to ten inches apart, about two inches deep.
To get a good run of spawn, keep the room as dark as possible and the temperature about 70 for the next 21 days. At the end of that time, the threadlike filaments (mycelium) from adjacent plantings should meet. The temperature should then be dropped to about 60o and the beds “eased” – covered with a oneinch layer of good garden soil. (Many home growers keep their beds near the heating plant for the sweating out and spawning periods, then move them to the 60o spot at casing time.
Water well with a gentle spray; the medium should be moist and crumbly, but not so moist that water can be readily squeezed out of it. Most mushroom diseases and pests – fogging off, sow bugs, and black spot – will never make their appearance if moisture and temperature conditions are carefully tended. Any snails and slugs can be trapped with lettuce or cabbage leaves. If the air in your cellar is on the dry side, a layer or two of moist burlap over the trays will maintain the proper humidity.
Water whenever the topsoil feels powdery.In approximately three weeks, tiny white dots will appear. You’ll find these clustered together in groups, called a “flush” or “break.”
In another ten days, the largest will be ready for picking, but don’t rush the harvest. Pick only those whose cap has split away from the stem. These ripe ones will taste much better than the “green,” immature ones commercial growers must ship to avoid bruising.