The low-down on “mushroom rings”

The following may interest those who hesitate at the idea of "mushroom rings" being evidence of UFO landings—or of fairy shindigs.

A single mushroom can release over a billion spores. For a mushroom spore to germinate it must alight in a field with a plentiful supply of nourishment and moisture. The spore sends out a thread which branches into further threads to form a network known as a mycelium. The mycelium radiates out in a circle which keeps expanding as long as there is adequate food and moisture and the temperature is suitable.! At the outer edges of the circle the mycelium develops knobs which as they grow appear above the surface as mushrooms.

The expanding mycelium produces an effect cursed by lawn enthusiasts and known as a "fairy ring". A common type of fairy ring has been described as two rings of enhanced grass growth separated by a zone of poor growth or even bare ground.

C.L. Duddington has explained it thus— "At the edge of the ring the advancing mycelium acts upon the organic matter in the soil. Proteins, in particular, are converted into simpler amino-acids, and these are further acted on by soil bacteria, forming salts of ammonia and finally nitrates. The grass benefits from this free dressing of nitrate, and the effect is seen in the increased luxuriance of its growth."

As the mycelium expands the central area begins to die off. The bacteria which breaks down the protein in the dead mycelium also encourages grass growth, so forming the second ring.

There is some uncertainty amongst botanists as to the cause of the bare patch between the two rings.

"The most likely theory at the moment is that this area of soil is filled with actively growing hyphae (threads) of the fungus, which clog the spaces between the soil particles so that both drainage and aeration are impaired. The grass roots are in a state known as physiological drought: though rain may turn the surface of the soil into a quagmire, none can penetrate to the grass roots... With the lack of water the bacteria in the soil are unable to do their work of breaking down organic matter, so that there is a shortage of minerals for the grass roots to absorb. The grass dies from drought and starvation."

1. Marteka, Vincent Mushrooms Wild & Edible, W.W. Norton, 1980 p7, and Encyclopaedia Britannica Micropaedia entry for "mushroom".
2. Duddington, C.L. Beginner's Guide to the Fungi, Drake, New York, 1972, p40.
3. Ibid.