Nature on our doorsteps: Mushrooms, fungi and fairy rings

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

Mushrooms and fungi are plentiful in autumn, particularly after mild and damp weather.

Mushrooms are the fruiting cap of fungi. They produce the microscopic spores which float away to start a new colony elsewhere.

The fungus itself is a mass of tiny white root-like threads called a mycelium which lives underground in the soil or within rotting leaves and wood.

Sometimes we can see the effects of an underground soil fungus long before the visible mushroom appears.

These are the ‘fairy rings’ that are often seen in grassy lawns.

They look like large rings of dark, lush green grass that remain even when the grass is cut.

These rings represent the visible growth of an underground fungus.

When its spores first land in the grass and form a new colony, it grows outwards in a circle. As the fungus grows, it breaks down nutrients along its growing point at the edge of the ring. These nutrients cause the grass at the edge of the ring to grow lush and tall. In autumn, mushrooms will appear along this growing edge.

A different type of a fairy ring occurs in woodlands where they appear as curving lines of mushrooms around the base of trees.

These mushrooms are the visible part of the complex mat of underground fungi that work in partnership with the trees.

Woodland trees need certain nutrients from the soil for their growth. The mat of underground fungus breaks down these nutrients and passes them directly to the roots of the trees.

In return, the trees pass sugars that they have made for themselves on to the fungus.

Because they look so unusual, fairy rings were once said to be places where the fairies danced and feasted at night.

It was said that if you stepped into a ring on the night of a full moon, the fairies would hold on to you and not let you go.