Contamination Court: the archive
Is it contamination or colonisation? Real jars and tubs submitted by growers, named and ruled on by the writers. When in doubt, it is contamination, and when it is contamination, it goes.
Green: Trichoderma
Green is the one everyone meets first. Trichoderma starts as a patch of white mycelium that looks almost normal, then, over a day or two, the centre turns a flat forest green as it spores. By the time it is green it has already been growing invisibly, which is why it feels like it appeared overnight. It is fast, it is aggressive, and it will take a whole jar or tub if you let it.
There is no saving a Trichoderma grow. Do not open it indoors to inspect it, and do not try to cut it out. Seal the container, take it outside or straight into a bag, and clean the area it sat in. The lesson is upstream: green is a sterile-technique failure in the grain, the air, or your hands, not bad luck, and the fix is in how you work next time, not in rescuing this one.
Grey and wispy: cobweb mould
Cobweb looks exactly like its name: a fine, grey, wispy web that spreads across the surface much faster than mushroom mycelium, with no defined edge. It is easy to mistake for fluffy mycelium, but mycelium advances as a firmer, whiter front and does not look like spun grey candyfloss. Cobweb can double overnight.
Caught very early and very small, some growers spot-treat it, but for a beginner the honest advice is the same as for green: if it is spreading, seal it and start again. Cobweb thrives on stagnant, over-wet, poorly exchanged air, so the real fix is more fresh-air exchange and a surface that is damp, not wet. You are changing the conditions, not fighting the mould.
Wet, slimy, and sour: bacteria
Not everything that goes wrong is a mould. Bacterial contamination shows up as wet, slimy, sometimes yellow or grey patches, and above all as a smell: sour, like old socks or bad cheese. Healthy grain and substrate smell clean and faintly of mushroom. If you open a jar and recoil, trust your nose. Wet spot in grain is the classic version, a sign of too much moisture and, again, technique.
Bacteria cannot be cleaned out of a grow. As with the others, seal and dispose, then look back at moisture and sterility. The through-line of this whole book is that almost every failure is a condition you set earlier, not a verdict on your luck. That is good news, because conditions are the one thing you control.
The verdict: save it or bin it
The rule that keeps beginners safe is simple: when in doubt, it is contamination, and when it is contamination, it goes. The cost of binning a jar is a few pounds and some time. The cost of nursing a contaminated grow is spores through your home and, at worst, mould you should not be breathing. There is no harvest worth that.
Healthy mycelium is white, sometimes bruising a faint blue where handled, and it smells clean. Anything green, grey and wispy, wet, slimy, coloured, or foul is not mushroom. Seal it, remove it, clean the space, and change the habit that let it in. Do that consistently and contamination stops being bad luck and becomes something you simply prevent.
Run the triage: from what you see to what to do · Reading your grow