Well established Fairy Ring with the 'toadstools' showing in dry summer conditions.
Fairy rings in lawns normally start to show up in late spring or mid-summer. They then carry on growing right through until the autumn – and usually into subsequent years. They are easily recognised by either of two – or both – trademarks. Once they have started, they will be visible throughout the year.
They are most commonly seen as dark green circles of lush grass in the lawn – usually after they are a half a metre or so across, though they are visible at first as a tuft of dark green grass.
The Fairy rings may also be first noticed as a group of toadstools manifest in mid-summer. (Sometimes without the dark green grass!) Not all toadstools in the lawn are as a result of Fairy Rings.
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!
Generally, the grass inside the circle is lighter green - if not brown, whilst the grass just outside the circumference of the circle is slightly darker. This a result of Nitrogen being released - or activated.
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. Thereafter the fungi take hold proper and leaves behind it, a weakened central are of the Fairy ring in your lawn. This is how the Fairy Ring becomes visible.
Sometimes the fairy rings are made up of two circles - 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. This is not a 'remedy' as such, but does have an affect upon the strength or weakness of the rings.
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. Do NOT over-feed, for this will eventually weaken the grass. But, a weak feed will darken the rest of the lawn to the same colour as the fairy rings! Not a cure, but one of the best ways to 'hide' the full effect of the lawn 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! This method - often recommended as a cure - is not foolproof, as you can never be certain that you have removed all the fungi. The feeding method will be favourite for most gardeners! If this is not a way out, then you will need to carry out extensive excavation - without a guaranteed success at the end of it!
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.