I am growing oyster mushrooms. I am a beginner. My first batch. It has been something like 10-11ish days now since I started the batch. It is almost three quarters colonized. Suddenly some brown-red spots appeared.

I used woodchips and oat bran as substrate,

Here are the photos of the spots

enter image description here

enter image description here

enter image description here

I looked at some forums and stuff. Is it like a sign that it is drying out? Can I save it if it is drying out? Is it a contamination? Help!?

I don't want to mist it now because it hasn't colonized yet?

Check out my two other questions about this batch for further info ( Very heavy smell while growing oyster mushrooms

Growing Oyster mushroom: Is my spawn growing healthily? )

  • all you can do is let it do its thing. I think perhaps you are overly concerned you messed up. You may have messed up, but its too early to tell. I mentioned before the method used for sterilising the medium was not effective. But that doesnt mean their is a problem. You have a culture that is growing. It is going to make weird smells and look strange at times, because it's brewing. Perhaps in a good or bad way. There is nothing you can do about it at this point.
    – GardenGems
    Commented Dec 31, 2019 at 14:36
  • 1
    @GardenGems OK, I 'll let it colonize fully and then I ll start misting. Thanks.
    – user27663
    Commented Dec 31, 2019 at 15:19

2 Answers 2


Those are metabolites because the mushrooms are unfortunately contaminated. Oyster mushrooms should not have a heavy mushroom smell, in fact they smell like sweet aniseed or liquorice when they are colonizing.

Your spawn looks too wet aswell, may I suggest you don't add bran (supplementation) to your grows until you understand proper substrate hydration and have a few non supplemented grows under your belt as these are far easier.

  • Welcome to the site, and thank you for all your contributions already! :)
    – MackM
    Commented Oct 20, 2023 at 12:11

The orange liquid is a metabolite that the mycelium produce, typically in response to some stress.

How did you sterilize the substrate? If using bran as a supplement, you really should be sterilizing rather than pasteurizing (which is just fine with un-supplemented substrate like chips or straw). A bacterial contaminant would cause the mycelium to produce this orange liquid.

I think the moisture content looks good - there's moisture on the walls, but no pooling at the bottom.

What is the temperature? Remember that the core of this will be up to 5 deg F or more higher than the outside. High temps could cause a stress.

That said, I've grown oysters many times, seen the metabolite in many grows, and have had most of them turn out just fine. I wouldn't worry about it.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.