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RESEARCH UNCOVERS ANSWER TO STUMPS THAT GLOW IN THE DARK
The question was one of the more unusual I've been asked in 11 years of fielding horticultural phone calls: "Can you explain why the stumps in my backyard glow at night when I walk out to put a trash bag in the garbage?"
My first impulse was to ask whether the caller had been hitting the gin a little too heavily before bed.
Fortunately, I went with my second impulse, which was to explain that I couldn't explain the phenomenon but I would find out and call him back.
A little internet searching led to a fascinating discussion of -- and you may know if by any one of these names -- bioluminescence, foxfire, will-o'-the-wisp, faerie fire or honey fungus.
Each of the names refers to a soft glow or light coming from leaf-covered ground or dead wood. Luminous wood, most commonly called foxfire, has been known for centuries among people living near forests. Foxfire is a curiosity, an educational toy for children, and part of folk tales and cultural myths concerning elves, ghosts, and supernatural "cold" fires. Mark Twain makes reference to it in Adventures of Huckleberry Finn.
What causes a stump to glow in the dark? Is it fungal, algal or extraterrestrial?
Despite all the romance and myth surrounding foxfire, its source is fungi rotting wood, explains Kim Coder, a forestry professor at the University of Georgia. The most common luminous fungi in a forest is a tree root rot and wood decayer. The glow of foxfire comes from rapidly growing and healthy fungal cells (rhizomorphs) consuming wood.
Around 40 species of fungi and certain bacteria are capable of carrying out chemical reactions that give out light, sometimes causing the wood or leaves they attack to become luminous. One of the most common species growing on rotten stumps capable of luminescence is honey fungus (Armillaria mellea).
The technical name for foxfire is bioluminescence -- the emission of light from living things (i.e., fungus). Bioluminescence is produced by the sudden decay of a high-energy molecule to a lower energy form. One way to understand bioluminescence, Codor says, is by comparison to photosynthesis. Bioluminescence is the reverse of photosynthesis. In photosynthesis, a living organism captures light and carbon dioxide to make organic materials and release oxygen. In bioluminescence, light and carbon dioxide are released by breaking apart organic materials using oxygen.
Nature provides instances of bioluminescence in other creatures, including bacteria, animals, fish and insects, including fireflies. Some mystery remains attached to foxfire, however, since researchers are unable to ascertain any survival advantage for fungi emitting this strange glow.
I found an interesting website (http://www.stumps.biz/honeyfungus.htm) for a stump-removal company in northern England. A page of their website is devoted to honey fungus and offers the following facts:
Aristotle noted honey fungus 2000 years ago.
In medieval times people lit hay barns with clusters of rhizomorphs, and roots covered with rhizomorphs were considered to have medical power. These were the original magic wands.
Soldiers in WWI put pieces of decaying wood on their helmets; the glow helped them avoid comrades in nighttime trenches.
In WWII fire wardens covered timber stacks to prevent enemy aircraft spotting them.
Honey fungus is the woodlands' hyenas, jackals and vultures rolled into one. It is a scavenger. It cleans up woodland whether it wants it or not. It reduces the lignum and cellulose to glucose, which insects can digest. Without honey fungus the surface of the world would be piled high with the corpses of dead trees.
The greatest interest in foxfire and honey fungus appears to be in the UK. I even discovered a website by an organization called the North West Fungus Group. NWFG was established in 1994 as a regional umbrella group to promote an interest in fungi in the Northwest of England and Wales, UK. What do you suppose a typical NWFG monthly meeting consists of?
Setting out to see foxfire can be difficult, especially where there is light pollution. Coder says that foxfire is a very low-energy light. He suggests picking overcast or moonless nights without surrounding artificial lights. Your eyes will need to be fully dark-adjusted for 20-30 minutes. Leave flashlights off and get away from any other types of light reflectance other than starlight. Forget flashlights, fires, candles, watch lights, or other light sources. Passive photo-multiplier binoculars (night scopes) can be helpful. Finally, Coder suggests, beware the other denizens of the nighttime forest.
Given all the interest in foxfire, perhaps I should suggest to the Scott County caller that he charge admission for guided tours of his luminescent backyard stumps.
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