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With a life's experience of teaching field studies in the Forest of Dean, Brian Cave explores the ecology of rural France. More Info

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An English Naturalist in France

Why do some toadstools smell?

December 22, 2014

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For more than twenty years this toadstool (see top photo)  has avoided my attention.  Yesterday – the day of the winter solstice December 21st I found it.  Dozens of small whitish toadstools scattered in the grass of my pasture.  The  caps have a slightly yellow stain in the centre but are mostly white .   They average less than three centimetres in diameter, so they are not very big.  What is remarkable is the smell they carry.

Cuphophyllus (Hygrocybe) russocoricea

They exude a strong smell of cedar-wood!   WHY?   Does there have to be a reason?  Quite a few toadstools have remarkable odours.  I recall for example  Aniseed in Clitocybe odora, Cucumber in Macrocystidia cucumis, Almonds in Russula laurocerasi,  Curry in Lactarius camphoratus.   Various Hebeloma specis and also Mycena pura smell strongly of Radish.  The human sense of smell is poor, so there may well be odours which are either not noticeable to us  or are sensed in a different manner by other creatures.   The  fact that dogs and pigs can sense the smell of the black truffle buried a few inches in the ground is well known.  The Truffle fly which lays eggs on the truffle can be seen hovering over where they are growing.  Stink-horns (Phallus impudicus) have a powerful odour of rotting flesh which certainly Many toadstools attract flies which lay eggs on the fruiting body.   It is difficult to find ceps (Boletus edulis and others) which have not been fly food before you can collect it for the pot!

So all these smells may  be a a procedure to attract creatures which can aid their propagation by swallowing the spores and excreting them elsewhere. Or, quite contrarily the smells may be a way to repel creatures. 

The toadstool here with the intriguing smell of cedar wood – the smell of pencil wood- and sometimes also called ‘russian leather’  grows in old pastures of poor nutrients. Various species of  a sub- family of the Hygrophoraceae share this same environment.  The genera  are sometimes called Hygrocybe or Cuphophyllus or Camarophyllus.  That is confusing enough.  Perhaps the simplest term is the English ‘Wax-caps’.   They do all have a waxy appearance.  Many have descending lamellae which are fairly widely set apart.  All would seem to be obtaining nutriment from the decomposition of dead grass and herb stems. 

The snow white wax cap
Cuphophyllus virgineus

It happens that in my pasture close to, in fact adjacent to the crop of  the cedar-wood toadstool, also grows another related species – which I will name the Snow-white wax cap (Cuphophyllus virgineus – syn. Hygrocybe virginea).

It is rather larger than the cedar-wood smelling species.  I have found it in other places and found it often infested with the tiny insects called springtails (Ceratophysella species). These insects eat the spores.

Thinking perhaps that there might be a difference of infestation of these tiny creatures between these two species of wax caps, I went to collect specimens of both the wax caps to compare.  As they are growing  adjacent to each other it could just give an indication of the reason for the  smell;  i.e it repels the insects. I have to report that the analysis was inconclusive.  Though the cedar wood toadstool specimens carried no springtails, and the snow-white species had a few, it was nowhere near  a clear cut distinction.  Unfortunately the next night – last night – developed a frost of minus three degrees and I fear the examination was brought to an end.

Oh well – next year?

 

by Brian Cave. Find out more about Brian Cave here.

Categories: Fungi, Toadstools, Wax-caps