The mushroom variety Agraricus campestris is the only cultivated variety being used today, according to Kansas State University. Growing mushrooms at home saves money and prevents the possibility of poisoning from outdoor collection. There are a numerous mushroom varieties that are hard to identify by an amateur mycologist. Mushrooms grow on compost, requiring nothing more than a dark area and cool conditions. Mushroom spawn is available from some garden centers and possibly from online retailers.
Find an area in the home, such as a basement or cellar, and block off all light from the room. Seal all drafts and ensure the room is between 55 and 60 degrees F.
Wet horse manure outside and allow it to compost. Turn it every four or five days. Once the compost is turned four times it will appear a dark brown, meaning it is ready. Water the manure at each turn so that it is moist.
Place 100 pounds of corn fodder on the floor. Water it so that it is moist and allow it to sit for a three to four days.
Mix into the corn fodder pile 20 pounds of peat moss, 20 pounds of tankage and 20 pounds of greensand using a shovel, and another 30 pounds of sand to finish off the mixture. Tankage is the animal residue left after fat rendering in a slaughterhouse. Greensand is sandstone rock used as a fertilizer and found at gardening centers. Water the pile so that it is moist and allow it to sit for five to six days. You can reduce the size of the pile according to your growing needs or save it for later use.
Check the temperature of the compost pile. Place portions of it into the seed tray once it reaches a temperature of 75 degrees F. Use trays that are 14-by-18 inches, using as much compost as needed to fill the tray. Save the rest of the compost for another batch.
Shake your bottle of spawn to break it up into golf ball-sized pieces. Place the pieces of spawn 8 to 10 inches apart in the trays. Plant the spawn about 2 inches deep. Allow the spawn to sit in the trays for 21 days at 70 degrees F.
Drop the temperature of the room to 60 degrees F after 21 days. Water the medium using a spray bottle so that the surface is slightly moist, watering again once the compost feels dry.
Check the state of the topsoil in three weeks for white dots. These are the growing mushroom caps. Harvest after another 10 days, or when the caps split, by pulling the cap from the ground. Reuse the compost in the garden once plants begin to mature. Do not use the compost on young plants as this may cause issues, says the Oregon State University Extension.