Gourmet mushrooms such as oyster or shiitake mushrooms can be expensive to buy, but they are easy to grow. Most people use commercially available mushroom spawn for the kind of mushroom they wish to grow. They mix the spawn into a growing medium such as wood dust or sawdust and harvest the mushrooms a few weeks later. Going back a step and making the mushroom spawn is more difficult. A good source of spores and laboratory conditions for a sterile environment are needed. Once these initial conditions are in place, mushroom spawn can be made in large quantities and with excellent results.

Mushrooms are the fruits of the mycelium fungus, and the spores produced by the mushrooms are a kind of seed. Scattered spores often don't produce any fungus because they need ideal conditions to grow. To make mushroom spawn, the ideal conditions required by the spores have to be created in a controlled setting. Once the spores have generated a well-established growth of fungus, the fungus culture can be transferred to grains.

Placing mushroom spores onto a sterile medium to start the fungal growth and then transferring the culture to millet seeds is a good way to make oyster mushroom spawn. Gelatin with a small amount of sugar, boiled for sterilization and poured into small, sterile jars makes a good starting medium. Spores from the inside of the cap of an oyster mushroom placed on the gelatin with sterile tweezers will produce mycelium growth within about a week.

Once the mycelium culture is established in the jars, the culture can be cut into pieces with a sharp, sterile knife. Millet seeds have to be soaked overnight and then boiled for an hour to sterilize them. After they are cool, they are placed in sterile mason jars together with the pieces of the mycelium culture, and the jars are well-shaken to mix the seeds and the culture. Jars should be kept in the dark at room temperature for 10 to 20 days until the mycelium has completely penetrated the millet seeds. These seeds are the mushroom spawn seeds used for growing mushrooms in organic material.

The gelatin medium and the millet grains are very fertile environments for the growth of all kinds of fungi and bacteria. Contaminating spores and organisms from the surroundings in the home can easily come into contact with the spawn production materials. Mushroom spores will only grow in the absence of competing organisms so the maintenance of a sterile environment is essential.

For the production of mushroom spawn at home, the main methods for sterilizing tools and growth media are disinfectant, boiling and flames. Tools such as knives and tweezers can be sterilized by placing the tips or blades into the flame of a bunsen burner or a similar clean heat source. Jars and growth media can be boiled for at least an hour to sterilize them. The work environment can be cleaned with a 70 percent solution of ethanol to remove contaminants. When everything is clean and sterile, the mother culture prepared from spores and the mycelium in the millet grains will exhibit strong, healthy growth for a high-quality mushroom spawn.