Honey fungus: making a spore print

Mushrooms and toadstools change as they age, so it can be difficult to identify them. Honey fungus can kill garden plants. Here’s how to check if a mushroom is likely to be honey fungus.

Honey fungus spore print with an ideal mushroom specimen

Honey fungus spore print with an ideal mushroom specimen

Quick facts

  • Mushrooms only appear in the autumn (and not every year)
  • Spores are pale in colour, as are the gills underneath the mushroom cap
  • Mushrooms grow in clumps, close to their food source
  • Species that affect gardens possess an annulus (ring of tissue) near the top of the stipe (stem), but this can be hard to see

Introduction

Fungi make multiple structures during their life cycles. Mushrooms or toadstools are their fruiting bodies. These carry spores (the fungal equivalent of seeds).

Taking a ‘spore print’ helps you identify different species as spore colours can be different. Making a spore print of a suspected honey fungus mushroom will help you distinguish it from the many other orange-brown mushrooms that may grow in the garden, but are harmless to living plants.

How to make a spore print

Equipment required:

  • Mushrooms
  • Scissors
  • Gloves
  • Black paper
  • White paper
  • Glass beaker
  1. Pick your mushroom
    Choose the freshest mushroom you can. Young mushrooms may be too immature to drop their spores, whereas old mushrooms may have already released all their spores. Young specimens of honey fungus look like button mushrooms, then uncurl as they age before turning dark and slimy once they are past their peak. Wear gloves when handling unknown mushrooms, or make sure to wash hands afterwards.
  2. Lay out the materials
    Cut the stipe (stem) off as close to the base of the cap as possible. Position the black and white paper on a flat surface where it can be left undisturbed for several hours. Place the mushroom, gills facing down, over both colours of paper (either cut the mushroom in half and place separately on the two sheets, or put the sheets side by side and place the mushroom so half rests over each colour).
  3. Incubate
    Cover the mushroom cap with a glass beaker and allow to rest for 3+ hours to allow as many spores as possible to fall from the mushroom’s gills.
  4. Check the results
    Carefully lift the beaker and cap from the paper. If the print has been successful there will be spores visible on the sheets below. Make a note or take a photograph of the colour observed.

Results

Honey fungus mushrooms release pale spores which are visible against a black background. In clumps of honey fungus mushrooms a white dusting on the tops of shorter mushrooms is caused by spore deposits from the caps above them. The precise colour of these spores can be white-cream, but spores darken as they dry.

There are other features of honey fungus infection that you can check for if you suspect it in your garden. These include white mycelium under the bark of roots and stem-bases as well as black rhizomorphs (aka bootlaces) on root surfaces and in the soil.

Seeking advice

If you are an RHS member and you still unsure if you have correctly identified a honey fungus infection in your garden, send samples or photographs to RHS Gardening Advice for confirmation. To ensure you provide enough information for a successful identification, please send us:

  • A photograph from the top, side and underside of the mushrooms
  • A photograph showing the location where the mushrooms are growing
  • Results of the spore print (by photography or description)

Please note, honey fungus mushrooms are not important for the spread of the disease within gardens. Removing the fruiting bodies will not help protect healthy plants in your garden from becoming infected.

The RHS helps members with pathogenic fungi only, ie those that cause plant disease. We are unable to help in the identification of saprophytic fungi (non-harmful, decay fungi), neither can we confirm if such fungi are edible.


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