When you go out “trick or treating” this Halloween, not everything that glows in the dark will be a spectre, phantom, or ghost – or someone pretending to be one. By an incredible quirk of nature, one of the commonest of British fungi creates natural luminescence (Ramsbottom 1953). The Honey Tuft Fungus (Armillaria mellea) which grows on both living and decaying wood, has a vast hidden network of black fibres called hyphae that somehow or other make the wood glow in the dark.
This common fungus tends to grow most frequently on or near stumps of trees, with clusters of the fruiting bodies that can reach a metre across. The exact form that the Honey Tuft Fungus assumes can be extremely variable. It is the hidden parts of this fungus, the rhizomorph and mycelium, that are responsible for most of the luminous wood in Britain.
Luminous wood has been recognised since the time of Aristotle and Plato; and it may account for such phenomena as the burning bush that was not consumed by fire as seen by Moses in the Bible. Walter Raleigh in Elizabethan times is quoted as saying “Say to the Court it glowes and shines like rotten wood”. In 1667 Robert Boyle studied the luminescence of rotten wood – and that of decaying fish! However, the discovery of the fact that it was actually the infecting fungus in the rotten wood that was causing the luminescence was not established until the late 18th and early 19th centuries by people like Sowerby (1797), B. von Dershau (1822) and J F Heller (1843).
The fungus is known to widely infect wooden support structures in mines, and has been noted creeping across the floors of damp wine cellars. In the First World War soldiers placed small bits of luminous rotten wood on their gun sights and helmets to avoid collisions in the dark. In the Second World War the wood in a London timber yard is recorded as glowing so brightly on moonless nights that men on fire watch covered it with a tarpaulin in case it attracted enemy aircraft.
It makes me wonder whether many ghostly apparitions both indoors and out might be attributable to the hidden fibrous support networks of this common British fungus.
Ramsbottom, J 1953 Mushrooms and Toadstools, New Naturalist Series, Collins, London. Chapter 14 pp 154 -164, Sixth Impression 1972.