Why Are My Mushrooms Turning Blue? Bruising vs Contamination

Short answer: if your mushrooms or mycelium turn blue or blue-green, it is almost always oxidation, not contamination. When the tissue of a Psilocybe mushroom is bumped, cut or ages, psilocybin is converted into psilocin, and psilocin oxidises into blue pigments. That blue does not mean anything is wrong with your grow, and it does not mean the mushroom is more potent. What should worry you is an intense green, powdery mould that spreads on its own: that is contamination (usually Trichoderma).

In this article we explain why the blue colour appears, where it is normal to see it, how to tell it apart from contamination and how to reduce it.

Why mushrooms turn blue

Psilocybin-containing mushrooms have a chemical system that switches on when the tissue is damaged. A study by Lenz and colleagues, published in 2020 in Angewandte Chemie, described the process in two steps:

1. From psilocybin to psilocin. When the cells break, an enzyme (a phosphatase) removes the phosphate group from psilocybin and turns it into psilocin.
2. From psilocin to blue pigment. Another enzyme (a laccase) oxidises the psilocin, and the resulting molecules link together into blue-coloured chains (oligomers).

The formation of a blue product from these compounds had already been described in 1967 in the journal Nature. So what you are seeing is psilocin breaking down. We explain the difference between the two molecules in psilocybin vs psilocin.

Where and when blue is normal

• When you touch or cut the mushrooms: the stem and the edge of the cap mark within minutes wherever they have been squeezed.
• At harvest: the base of the stem, where it is cut, often turns blue.
• After knocks or rubbing: for example, if the mushrooms bump into each other or against the bag.
• On the mycelium: bluish patches in areas that have been pressed, after sudden temperature changes, or in grow bags that have already produced several flushes.
• When drying and storing: dried mushrooms can show dark blue or almost black areas where they were bruised or where drying was slow.

The shade ranges from light blue to blue-green, turquoise or almost black, depending on how much pigment there is and how much time has passed.

Blue bruising or contamination? How to tell the difference

The most common question is whether a blue-green patch is mould. These differences help you decide:

Feature	Oxidation (blue)	Green mould (Trichoderma)	Bacteria
Colour	Blue, blue-green or turquoise	Intense green, sometimes olive green	Grey, yellowish or brown
Texture	Same as the surrounding tissue, no powder	Powdery (spores); starts as a white patch	Wet, slimy or shiny
Where it appears	Exactly where there was a knock, cut or pressure	Anywhere on the substrate	Wet or waterlogged areas
Does it spread on its own?	No	Yes, it grows day by day	Yes
Smell	Normal, mushroomy	Mouldy	Sour or unpleasant
What to do	Nothing; handle more gently	Do not open the bag indoors	Do not open the bag indoors

If in doubt, take a photo in good light and compare it a few days later: oxidation does not progress, contamination does. More symptoms in mushroom growing problems and in how to prevent Trichoderma.

Blue patches on the mycelium of a grow bag

Seeing bluish areas on the mycelium of a grow bag is common and, on its own, not a bad sign. It is usually caused by pressure on the bag, knocks during transport, temperature changes or the mycelium ageing in the later flushes. If the patch does not grow, is not powdery and the rest of the mycelium is white, the grow is on track. With a MycoBag all-in-one grow bag, the advice is the same as always: do not open the bag until harvest. We explain this in the complete guide to growing with a MycoBag grow bag.

Does more blue mean more potent?

No. Blue means psilocin is breaking down, so a heavily blued mushroom has lost some of those compounds in the damaged areas. The intensity of the colour depends mainly on how much the mushroom has been handled, its age and how it was dried. The only way to know the actual alkaloid content is a laboratory analysis, such as MycoTest.

Blue does not identify mushrooms

Some mushrooms without psilocybin also turn blue when cut, such as several boletes, because of the oxidation of other compounds. And some psilocybin species barely change colour at all. That is why bluing should never be used to identify wild mushrooms: some toxic species look very similar to Psilocybe.

How to reduce bluing

• Touch as little as possible: hold the mushrooms by the base and avoid squeezing the cap.
• Cut, don’t pull: use clean scissors and cut at the base of the stem.
• Don’t move or squeeze the bag during the grow.
• Dry promptly: the longer they stay fresh, the more they oxidise.
• Store dried mushrooms properly: in an airtight, opaque container with a desiccant, in a cool, dark place. We explain this in how to dry and store magic mushrooms.

Frequently asked questions

Why are my mushrooms turning blue?

Because psilocin oxidises when the tissue is bumped, cut or ages. It is a natural process in Psilocybe mushrooms, not a disease of your grow.

Is it normal for mycelium to turn blue?

Yes, especially where there is pressure or knocks, after temperature changes and in the later flushes. If the patch does not grow and is not powdery, it is not contamination.

Are blue-green patches mould?

Usually not. Green mould is powdery, starts white and spreads day by day; oxidation appears where there was damage and does not progress.

Does the blue go away?

No. The pigment stays and over time can darken to a very deep blue or almost black.

Does a bluer mushroom have more psilocybin?

No. Blue means some of the psilocin in that area has broken down; it cannot be used to measure content.

Why do my dried mushrooms have bluish-black spots?

These are areas that oxidised before or during drying, from knocks or slow drying. Drying promptly and handling gently reduces them.

Sources

• Lenz, C. et al. (2020). Injury-triggered blueing reactions of Psilocybe “magic” mushrooms. Angewandte Chemie International Edition, 59(4), 1450-1454. doi:10.1002/anie.201910175
• Levine, W. G. (1967). Formation of blue oxidation product from psilocybin. Nature, 215, 1292-1293.
• Gotvaldová, K. et al. (2021). Stability of psilocybin and its four analogs in the biomass of the psychotropic mushroom Psilocybe cubensis. Drug Testing and Analysis, 13(2), 439-446. PubMed 33119971