I keep reading that oyster mycelium, once it has grown some, will out-compete other organisms. To what degree is this true? Will it eventually push out green mold?

1 Answer 1


Oyster mushroom mycelium will definitely NOT out-compete green mold in anything but the most nitrogen poor substrates. Even then, it is usually just a race to get the mycelium to the point of fruiting before the mold starts to take hold. And although some molds are harmless, there is concern about consuming mushrooms from substrates that have begun to mold.

And once you start fortifying straw or sawdust with nitrogen (whether through molassas, alfalfa, or some other source), the chances of losing to the mold increases.

  • ahh.. How serious are these concerns about consuming from contaminated substrate ? Commented Jan 26, 2018 at 17:37
  • I will admit that I have eaten mushrooms from contaminated (moderately) substrate. But the literature advises against it and a friend who grows commercially is fanatical about avoiding contamination.
    – That Idiot
    Commented Jan 26, 2018 at 18:59
  • Mushrooms are used in remediation as they can uptake toxins. But a contaminated substrate probably just has penicillin molds or similar. Commented Jan 26, 2018 at 22:32
  • Well, I've eaten moldy food before and I'm still here. Thanks for the answers but I'll have to look around for a bit more detail. I suppose it depend on which mold you have too, there are several types. I'm experimenting with cardboard, and cardboard + coffee and so far the only problem is with the coffee. So I was thinking maybe throw in coffee grinds when mycelium is established on cardboard. Commented Jan 27, 2018 at 20:09
  • That is almost like saying, "well, I've eaten button mushrooms before, and I'm still here. So I'm sure it's ok to eat these mushrooms I found in the woods." Odds are that it won't kill you or even make you really sick, but why take the chance. Coffee grounds are NOTORIOUS for getting contaminated - even if they are pasteurized. The coffee grounds would give you higher yields for the same mass of substrate, though.
    – That Idiot
    Commented Jan 27, 2018 at 20:34

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