Fairy rings start growing from a central point, then gradually radiate
outwards in circular shapes. There may be several fairy rings in the lawn at the
same time – sometimes overlapping ending up not unlike the interconnected
Olympic flag symbol!

Well established Fairy Ring with the 'toadstools' showing in dry summer
conditions.
The lush dark green grass is a result of nitrogen being released by the
fungal activity as the ring spreads outwards. As the fungi (toadstools) spread
outwards they feed on decayed matter (dead grass roots and other decaying
matter) and release Nitrogen into the soil behind them. The live grass in the
area feeds upon this Nitrogen, which in turns it a dark green. This is how the
Fairy Ring becomes visible.
Sometimes the fairy rings are made up of an outer and inner circle, with dead
grass between. This is normally bought about in highly compacted soils, when the
rainwater cannot penetrate down to the grass roots. At the first sign of fairy
rings, aerate the area with a fork, to about 15cm (6in) deep, and drench the
area with water, thereby allowing the moisture to penetrate into the affected
area of soil.
Disguising Fairy Rings in Lawns
Fairy rings are rarely fatal to lawns, which is satisfying to know, as there
are no chemical remedies for use in UK gardens. The best method of dealing with
Fairy rings in your lawn is to water the area well, then lightly feed the lawn
with a general lawn fertilizer. This will darken the rest of the lawn to the
same colour as the fairy rings!
The other option is to dig out the soil where the fairy ring is growing – to
a depth of up to 90cms, and refill with sterilized loam! The feeding method will
be favourite for most gardeners!
The dark green grass in the area of the fairy ring will also be taller than
the rest of the lawn, so close mowing of the Fairy ring area will help to
disguise it, as well as mowing off the toadstools – just in case you are
throwing a garden party!
There are several thoughts as to how Fairy rings first invade lawns – non
conclusive. There is no doubt that Fairy Rings first start as a central tuft of
dark green grass – rarely noticed in well kept lawns, until well into the
growth cycle.