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Substrates for mushroom cultivation

Growing mushrooms on grainThe material which mushrooms are grown on is known as the substrate.  Although some species are very picky, others (like the oyster mushroom) can be grown on almost anything that started life as a plant.  We'll provide sterilization instructions for all of these substrates tomorrow.  For now, here are recipes for turning your plant matter into growing media.

When commercial growers start their mycelium in a petri dish, they often expand it into jars of sterilized grain.  Millet, rye, and wheat are most often used, but Paul Stamets reports that any grain will do.  To fill a one quart jar, mix 200 grams of grain, 220 mL of water, and 1 gram of gypsum (to keep the kernels separated and provide calcium and sulfur.)

Later, mycelia can be expanded onto a mixed wood substrate made up of different sizes of chips and sawdust.  The fungus will quickly colonize the smallest sawdust grains, while the larger chips provide for air flow and allow the fungus to form rhizomorphs that lead to big mushroms.  Paul Stamets recommends using only one species of tree at a time, if possible, and sticking to fast-growing and -decomposing species like alder.  These trees have more sapwood, which is easy for your mycelium to colonize quickly.  His recipe for sawdust spawn is very simple --- moisten the sawdust to 60 to 70% water, sterilize, and innoculate.

Growing mushrooms on wood chipsSawdust and wood chips are a bit hard for your mushrooms to digest quickly, so if you want to boost your yields you may choose to supplement them with some source of protein.  Lots of homestead and farm waste products fit the bill, including rice, wheat, or oat bran; ground corn; grape pumice from wineries; spent barley from breweries; vegetable oil; and stale bread.  Enriching your substrate, though, is a double-edged sword --- the extra nutrients also help contaminants grow quickly, so you'll need to double your sterilization time.  Paul Stamets' recipe for enriched sawdust is as follows: 100 pounds of sawdust, 50 pounds of one half to four inch wood chips, 40 pounds of bran, and 5 to 7 pounds of gypsum, moistened to 60 to 65% water and then sterilized. 

The last widely used mushroom substrate is straw --- this is Paul Stamets' favorite for economical oyster mushroom production.  He chops wheat, rye, oat, or rice straw into 1 to 4 inch lengths, then pasteurizes it and inoculates.

Although grain, wood chips, and straw are the main substrates used in commercial mushroom production, you shouldn't stop there!  Growing Gourmet and Medicinal Mushrooms teased me with notes that mushrooms can be grown on newspaper, cardboard, books, corncobs, corntalks, peanut shells, tea leaves, coffee grounds, and much more.  I hope that by this time next year I'll have information on the best ways to turn these waste products into mushrooms!



This post is part of our Growing Gourmet Mushrooms lunchtime series.  Read all of the entries:





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