Coprinus and the compost bin

Fungi can be placed into one of three rough groups based on their temperate tolerance. These groups are rough in that they overlap and there is no agreement on their boundaries. They are the psychrophile, mesophile and thermophiles.

Psychrophiles can grow below 5°C but may still have a high optimum temperature similar to a mesophile. Many fungi that cause food spoilage in cold stores belong in this group.

Mesophiles do not grow at low temperatures or at high temperatures above 45°C. Their optimum growth is usually between 25° and 37°C. The great majority of fungi fall into this group.

Thermophiles can grow at high temperatures (45°C to 75°C) with an optimum between 55°C and 65°C and little growth below 40°C. True thermophiles are unable to grow at temperatures below 20°C.

Schizophyllum commune (Photo Don Horne)

Amongst the mesophiles, there are species which border being thermophiles and can live in the higher temperatures of decomposing compost and hay bales. Ones such fungus is usually a wood decay fungus, Schizophyllum commune, but which also grows in decomposing, plastic wrapped hay bales. Below is a temperature graph for S. commune with an optimum growing temperature in the mid-30s.

Composting bins can create high temperatures that are favoured by these borderline thermophiles. Here are two of my bins, at the end of last winter (September 2011), which I had filled with mulched perennial cuttings.

Compost bins (Photo Geoff Ridley)

Several weeks after filling the bins they were hot from the decay process and white with fungal hyphae. One morning, 4 September, I lifted the lid on one of the bins and found young expanding caps of what I think is Coprinus macrocephalus. Roger Phillips records it growing on dung-heaps and rotting straw. Coprinus fruitbodies are short-lived typically expanding rapidly in the morning and having collapsed by the evening of a single day.

Photo 1 – 9.24am: Stipes have elongated but the cap is yet to expand.

Coprinus macrocephalus (Photo Geoff Ridley)

Photo 2 – 11.45am: The caps are beginning to open, some radial splitting, and in the tallest one the margin is beginning to roll upwards.

Coprinus macrocephalus (Photo Geoff Ridley)

Photo 3 – 1.34pm: Caps are fully open, with a lot of radial splitting and the margin rolling back.

Coprinus macrocephalus (Photo Geoff Ridley)

Photo 4 – 4.23pm: Where near the end as the caps are beginning to autodigest and liquefy. The caps soon dissolve away and the stipes collapse.

Coprinus macrocephalus (Photo Geoff Ridley)

Why do they autodigest? One suggestion is that the gills bearing the spores are tightly packed so as they begin to liquify and roll back the distance between the gills increases allowing the spores to drop out and be carried away by the wind. There is also the possibility the liquefied tissue, which is black because it is a suspension of spores, adheres to insects that walk through it, and feed upon it, and they can carry the spores away. Read more about this process written by Lepp and  Landsman.

Lepp H 2011. Spore discharge and dispersal in mushrooms. Australian Fungi Website, Australian National Botanic Gardens, Australian National Herbarium.

Landsman J 2009. The dish on deliquescence in Coprinus species. Cornell Mushroom Blog.




  1. Hi, I found these mushrooms in my compost bin and I wonder if you can tell me what does this mean for the compost? Is it still useful for gardening? does it mean that the heap is reaching high temperatures? etc.

    Also, are these mushrooms edible?



    1. Hi. First up these fungi are part of the composting process breaking down plant material. So, yes it is still perfect for the garden. And yes, the heap is probably reaching a good temperature. But I can’t tell you whether they are edible.


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