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Geo-Joint: the Circular Reasoning of Fairies

Posted on March 26 2019

Lawns are generally not complicated things. Give them some water, rake up the leaves, run the lawnmower when it gets shaggy, and watch for dandelions and crabgrass. But sometimes strange and mysterious things appear there, and no, it’s not what the neighbor’s dog leaves behind. After a good rain, you may notice that little white heads are poking up through the green blades. Mushrooms, of course, and while some will be here and there at random, occasionally they will come up in a circular pattern a number of inches or a few feet in diameter. Where did they come from? Why are they in a circle? Of course there are good biological reasons for these things, but nothing in nature that puzzles fails to get a folk interpretation, so these mushroom displays have come to be known as fairy circles, or fairy rings. Various cultures have folktales regarding their origin, such as them being the paths of dragon’s tails that prohibit all other growth, as told in Austria. Germans call them Hexenringe, or witches’ rings, and the Dutch say the devil churns his milk within them. The English and the Celts mark them as the dancefloors of elves and fairies,  whose magic oughtn’t be trifled with. Whether they act as charming reminders that mischevious imps are about in the garden, or as tiny stools upon which to sit during fairy board meetings, the supernatural explanations have probably caused more than one lawn owner to spare the display out of bemused respect for the little sprites.

Caution: Fairies at Work

Meaning no disrespect to Tinkerbell, the mushrooms you see pop up in the lawn or out in the woods are really only the fruiting bodies of an organism that lives underground. It all begins with a spore (from a mushroom) that finds some old, dead, buried organic material such as a stump, log, or roots to feed upon. As the mycelia, or fiber-like form of the fungus grow unseen in the soil, they spread tubular hyphae out radially, at an even pace. After this has gone on a while, the fungus sends mushrooms up to the surface, and they appear in a ring. As long as the mycelia have material to decompose, they keep growing and spreading underground, looking for new food. As the living mycelia expand their diameter, so does the fairy ring, for years of growth cycles. Most are about 2 to 15 feet across, but they can be smaller, or much larger—some irregularly shaped rings can be 1,200 feet across. A French record-breaker had a diameter of 2,000 feet, and is thought to be 700 years old!

Looks like the fairies added some nutrients to this lawn before they left.

Interestingly, they neither grow back inwards nor cross each other should two of them meet—within each ring the food source has been used up. The decomposition of woody material releases nitrogen, so the grass associated with a fairy ring may green up nicely, happy to have the extra nutrient available. On the other hand, some fungi draw water from grass roots, or create a waterproof mass that inhibits moisture flow to grass. The fungus can also diminish other soil nutrients, or produce hydrogen cyanide, which doesn’t sound healthy for anything. So fairy circles may also plague your lawn with a ring of dead grass. Thanks a bunch, you troublemaking fairies!

Fairy circle areas, shown in purple, are found in a number of locations in western Namibia.

Strange rings on the ground are not limited to the grassy spaces of suburbia. The country of Namibia, in southwest Africa, features some mighty strange circles of its own, and there is no green lawn in sight. There, in the very remote scrubland desert, low-growing vegetation covers all but a pattern of round, bareground patches that they call fairy circles. These circles appear by the thousands, covering vast amounts of the terrain, persisting for periods of a couple of decades to three-quarters of a century, depending upon their size. Like mushroom fairy rings, sizes range from a few feet in diameter to more than 80. And similar to the more domestic variety, locals there claim they are the footprints left by the gods, or places where a foul-breathed dragon left the ground unfit for growth. Researchers though, leaned more toward the work of termites. Nibbling as they do the roots of plants, it was thought that a given termite nest might denude a patch of ground and then move outward until it encountered another nest. That termite group might be battled and defeated if smaller, or retreated from if bigger. In time, the termites would establish boundaries and stick to their own circle. This explanation works fairly well in some cases, but with many fairy circles there was a problem—no termites to be found.

A Namibian fairy circle. Seen by itself, it’s not too remarkable.

This led other researchers to come up with the idea that the plants themselves were working out a roughly hexagonal pattern of growing and barren areas. Plants that grow in close association can benefit from the shade, and protection from drying winds, provided by their near neighbors. Conversely, plants that extend roots far away from their location can diminish the water supply of plants living at a distance. These help/hinder strategies can give rise to patterned growth arrangements, and help explain the taller plant growth around the perimeter of each circle. Lending weight to this theory is the diminishment and outright disappearance of the circles in heavy-rain years, and their subsequent reappearance and expansion during drought years. The answers were still not conclusive. Finding neither the termites nor the battling plant theories sufficient on their own, scientists ran computer modeling experiments that showed, big surprise, a combination of both processes was contributing to the strange landscape. Other teams of researchers have documented the role that grazing animals might play in keeping the circles cleared of vegetation. More variables could still be awaiting discovery.

The fairy circles come in great quantity, and cover broad areas of terrain.

Dry conditions and competition for water favor the development of fairy circles.

The Namibian fairy circles are a curiosity, but they have been found not to be unique. In the Pilbara region of the Western Australia’s Outback, a similarly odd pattern in spinifex grasslands has been studied to unravel its explanation as well. With termite influence at a minimum or non-existant, the mechanism in Australia has almost exclusively to do with rainwater movement due to soil conditions and plant competition. What these researchers conclude is that on flat, water-hungry terrain, generally hexagonal patterns of fairy circles will develop as something of a universal self-organizing function of nature. That hexagonal shape is found from honeycombs to snowflakes to the scutes on a turtle and expresses itself as an economical arrangement reflective of the efficiency of nature. The mathematical science behind the scientists’ thought process is complex enough to give a fairy a headache, but it makes the craziness of patterns in the desert a little more rational. The fairies continue to have the upper hand, though. The final verdict still isn’t in, and given the difficulty of running experiments in remote Namibia, it may be a while yet.

It doesn’t show fairy circle locations, but this vintage 1962 National Geographic wall map of Southern Africa reflects the past, including Namibia’s former name: South-West Africa. See what Zambia, Malawi, and others were once called, on this historic map available from



caption: Caution: Fairies at Work
source: Wikimedia Commons: User: Mrs skippy (Public domain)

caption: Looks like the fairies added some nutrients to this lawn before they left.
source:  Wikimedia Commons:  Kelisi (Public domain)

caption: A Namibian fairy circle. Seen by itself, it’s not too remarkable.
source: Wikimedia Commons: Thorsten Becker (CC by SA 2.0)

caption: The fairy circles come in great quantity, and cover broad areas of terrain.
source: Wikimedia Commons: Stephan Getzin (via Beavis729) (CC by SA 3.0 Unported)

caption: Dry conditions and competition for water favor the development of fairy circles.
source: Wikmedia Commons: Olga Ernst and Hp. Baumeler (CC by SA 4.0 International)

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