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.
TL;DR (Too Long; Didn't Read)
Mushroom spawn seeds for growing mushrooms can be made under sterile conditions with grain seeds as a substrate. Mushroom spores, obtained from the inside of a mushroom cap, are initially grown in small dishes on gelatin. The dishes and the growth media have to be sterilized and kept in a sterile environment. When the spores have produced mycelial growth, pieces of this culture are placed in sterilized jars with boiled grain seeds such as millet, rye or wheat. The fungal mushroom culture penetrates the seeds completely after a few weeks. The seeds can then be used as mushroom spawn and mixed in with sawdust or other organic material to produce mushrooms.
Making Oyster Mushroom Grain Spawn at Home
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.
Sterilization Methods for Grain Spawn Production
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.
- Spread the spawn around other, more-porous mediums like compost or straw in order to get the most mushroom production per grain of spawn. The mycelium in the spawn usually take about two to four weeks to run through the medium, at which point it is ready to be fruited for mushrooms.
- Different mushroom species require different spawn growing conditions and techniques. Research the variety you want to grow before you begin.
- If the desired end result of your project is to grow mushrooms, you'll find it easier to accomplish if you use store-bought spawn.
About the Author
Bert Markgraf is a freelance writer with a strong science and engineering background. He has written for scientific publications such as the HVDC Newsletter and the Energy and Automation Journal. Online he has written extensively on science-related topics in math, physics, chemistry and biology and has been published on sites such as Digital Landing and Reference.com He holds a Bachelor of Science degree from McGill University.