Mushroom spawn is actually mushroom mycelium grown on various substances. Mycelium is mushroom spores that have been sprouted. Mushroom spawn is used instead of mushroom spores to grow mushrooms because the spores are not always reliable, but the germinated spores have a limited storage life. When you purchase mushroom spawn, you should plan to use all of it. However, if you have some left over, you can store it to lengthen its shelf life a little.
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Note the date on your batch of mushroom spawn. Commercially produced mushroom spawn should bear the date of when the mycelium was mixed with the substrate. Because mushroom spawn is living, it is also prone to bacteria, mold and the waste produced by the mycelium.
Attempt to use most or all of your mushroom spawn after you receive it. The sooner you use it, the more mushrooms you will reap. The longer you keep it, the more it degrades.
Keep unused mushroom spawn in its original bag. Do not move the spawn into a different container. The original bag it came in was specifically made for the purpose of holding mushroom spawn.
Store the unused mushroom spawn in a refrigerator programmed to between 32 and 35 degrees Fahrenheit. Your mushroom spawn should last 2 months stored this way. Because it is alive, it will not last forever.
Use all your mushroom spawn as soon as possible before the spawn dies completely.