Why do some fungi grow into mysterious “fairy rings”?

2025 Yan 26 Ri Report

“Fairy ring” is a natural arrangement of fungal (mushroom) populations forming a ring, appearing mysterious and having relevant legends in many cultures. But why do they grow in such a way?

According to a report on IFLScience website, when it comes to fungi, people often think of mushrooms, but these fruiting bodies actually only constitute a small part of the fungi. Beneath the surface and out of sight, fungi develop through a network of fine threads known as hyphae.

Hyphae sprout from the original fungal spores and continue to grow evenly in all directions, intertwining to form mycelium.

A single spore will produce a single-nucleus mycelium. Before merging with another mycelium to form a dual-nucleus mycelium, the single-nucleus mycelium cannot undergo sexual reproduction.

As the mycelium spreads, it will grow into mushroom-like fruiting bodies, forming a small circular ring known as the “fairy ring” that people see. As fungi age, these rings continue to expand.

“Fairy rings” mainly appear on grasslands but can also manifest in forests, symbiotically with trees. Fungi thrive in damp conditions, so the moist aftermath of autumn rain provides a favorable opportunity for the “fairy rings” to sprout from the ground.

Maurizio Zotti, a mycologist and soil community ecologist at the University of Naples Federico II in Italy, told National Geographic that “fairy rings” only form when the soil consumed by the mycelium is homogenous, meaning it has uniform components.

Regarding why “fairy rings” present in a circular shape, Zotti suggests that the round structure may help mycelium resist attacks from pathogens, increasing their chances of survival.

As the mycelium grows and spreads in the soil, it decomposes organic matter, crucial for soil health. The mycelium network aids in recycling leaf litter and providing food for various small soil-dwelling animals – the same applies to “fairy rings.”

However, the impact of “fairy rings” on other species is not always beneficial. A study published in 2020 found that the ripple-effect spread of “fairy rings” reduced the diversity of plants, fungi, and bacteria.

National Geographic notes that “fairy rings” exist worldwide, with almost every culture somehow connecting them to supernatural phenomena, resulting in associated legends.

Legends regarding “fairy rings” can be traced back centuries in Europe, Africa, and North America. They are also known as “fairy circles,” “witches’ rings,” or “sorcerer’s rings.”

In Japan, they are called “shiro,” meaning “white” and “castle,” referring to the color of the fungi and the underground palaces they are believed to construct. In some cultures, “fairy rings” are said to be formed by fairies or witches dancing in a circle, the most common legend. However, in some cultures, “fairy rings” are believed to be the places where devils place milk stirrers or dragons place fire tails.