Mushroom cultivators growing sclerotia producing species have traditionally used rye grass seed. However, due to its small kernel size, it makes an excellent grain spawn to use to inoculate bulk mushroom substrates, and is perfect for grain-to-grain transfers. Perhaps best of all, rye grass seed is generally available at lawn and garden centers everywhere. In most areas, you'll find a 'local mix' of several types of grass seed pre-mixed together. As long as it has the majority of seed listed as rye, it will work great. The rye grass seed I get locally is simply labeled, lawn grass seed, but when I look at the back of the bag, several varieties of rye grass seed are listed along with a few other types of grass seed mixed in.
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A simple recipe for preparing rye grass seed for growing mushrooms or sclerotia is to use twice as much grass seed by volume, as water. If using quart jars, use 1 1/4 cup of rye grass seed, and 5/8 cup water. The water can be weak coffee if desired. Coffee has shown to increase sclerotia production for an as yet unknown reason. If using coffee, make sure it's no more than 1/2 normal drinking strength. An easy method if you're a coffee drinker is to simply mix some of your morning coffee with an equal amount of plain water, and use this to hydrate your grass seed. If you're like me and drink coffee strong enough to curl your toes, mix it at 1 part coffee to 2 or 3 parts water.
My procedure is to place the grass seed in the jar, add a pinch between my thumb and forefinger of gypsum, mix well, and then add the water. Place a non-vented lid on the jar and shake well. This coats the seeds with water. Allow to sit for an hour or two to allow the seeds to absorb some of the water and then shake again before sterilizing. This 'resting' period is optional, but it hydrates the seeds slowly, which helps prevent bursting. Once the seeds, gypsum and water-coffee have been mixed well, put a vented lid with a filter on the jar, cover with aluminum foil, and pressure sterilize for an hour at 15 psi, which is 100 kpa if you're outside the US and use the metric system.
If you need information on methods of filtering grain jars, see our grain preparation video clip where 4 easy procedures for filtering are demonstrated.
When cool, the grass seed is ready to inoculate with the spores or mushroom culture of your choice.
Here you'll see a few short clips from the grass seed preparation chapter of "Let's Grow Mushrooms!".