Wikipedia:Reference desk/Archives/Science/2020 June 22

= June 22 =

Fairy Circles
Please review the attached pictures, I have noted these in several places in the British Isles over many years and would like to know a number of things, firstly, what causes the grass to grow better in this circular pattern? Is this a known phenomena? Are these related to Fairy circle (arid grass formation) as seen in Namibia?


 * See fairy ring. PaleCloudedWhite (talk) 09:29, 22 June 2020 (UTC)


 * Did you actually take these pictures while lying on your side? :) ←Baseball Bugs What's up, Doc? carrots→ 11:42, 22 June 2020 (UTC)
 * Took the liberty of stuffing the images in a template so they don't blow out the page length. Revert if there's any issue. They're landing sites for really tiny aliens, obviously! --47.146.63.87 (talk) 17:59, 22 June 2020 (UTC)


 * Patterns in grass or crop growth, particularly when it is dry, are often evidence of some previous construction, foundation, or groundwork. This looks like a newbuild residential estate - many of which in the UK are built on formerly industrial sites. Housebuilders are quite content to put down a scandalously thin layer of soil and call it a garden (they happily sold my house with a piece of rebar sticking up out of the grass). So this may simply be the foundation of some old structure (perhaps a chimney, kiln, or furnace) or groundwork (a well or pit). It's a good idea to pull out an old OS map (you can find the 1913 OS map at the National Library of Scotland - but it's not just Scotland) and see what was there beforehand. -- Finlay McWalter··–·Talk 22:56, 22 June 2020 (UTC)


 * "What Causes Big Dark Green Circles in Your Lawn?
 * The appearance of big, dark green circles in your lawn indicates your turf is under attack by the fungal disease known as fairy rings. This annoying fungus can appear on all species of turf... The appearance of the fairy ring depends on the species of fungus infesting the lawn. The rings are semi-circular or circular and vary in size."
 * --Guy Macon (talk) 05:50, 23 June 2020 (UTC)
 * FairyRingSchoolField.jpg too think the Fairy ring theory (already pointed out in the first reply) is far more plausible; just look how similar this appears to some of the images in the article, one of which I have copied here. --Lambiam 06:33, 23 June 2020 (UTC)

Thanks All, I agree that these are most likely fairy circles as caused by fungus. This is not my garden, just by the way, its a local park. Can anyone tell me if there is any correlation to the Namibian fairy circles please? Thank you.


 * Probably not. The ones in Nambia are dry earth with no grass, and do not seem to be associated with fungus. Also, the Nambian circles have a negative correlation to rain, and the British Isles are not exactly deserts. --Guy Macon (talk) 12:24, 23 June 2020 (UTC)


 * I've just zoomed-in on the OP's images and they seem to have a circle of bare earth on the outside of the circle of green. I don't recall seeing that before in relation to a fungal fairy ring and wonder whether it might have been the imprint of a circular object of some kind? Perhaps like this? Alansplodge (talk) 15:45, 23 June 2020 (UTC)


 * Hmmm. Could be. One test would be to look carefully and see how circular the circle is. A man-made object would tend towards being a perfect circle, while anything biological would tend towards being at least somewhat irregular. --Guy Macon (talk) 19:42, 23 June 2020 (UTC)
 * It is definitely "somewhat irregular" (eventually, the fairies get dizzy dancing around in a circle). 107.15.157.44 (talk) 20:53, 23 June 2020 (UTC)

The suggestion that it is from something like this is not likely as this is a public park between houses...The Snail Park in Milton Keynes and is unlikely to have had a swimming pool erected in it. https://www.google.com/maps/place/Snail+Park,+Rockspray+Grove,+Walnut+Tree,+Milton+Keynes+MK7+7EP/@52.0191366,-0.6960534,17.65z/data=!4m5!3m4!1s0x4877ab4ac925800f:0x5d0fa8dacef9c62d!8m2!3d52.0199051!4d-0.6959125 — Preceding unsigned comment added by Anton.Brad (talk • contribs) 08:47, 24 June 2020 (UTC)
 * It is quite normal for a circle resulting from fungal growth to have a 'dead zone' - our article on fairy rings states, "One of the manifestations of fairy ring growth is a necrotic zone—an area in which grass or other plant life has withered or died". Though it may be more usual for the necrotic area to be on the inside of the ring - in Pests, Diseases and Disorders of Garden Plants by Stefan Buczacki and Keith Harris, it states that grass growth is diminished due to the fungal mycelium on the inside of the ring exhausting available nutrients, dying, and forming "an impervious layer which deprives the grass roots of moisture". PaleCloudedWhite (talk) 08:58, 24 June 2020 (UTC)
 * Splendid answer PaleCloudedWhite; the paddling pool hypothesis dies here. Alansplodge (talk) 17:40, 24 June 2020 (UTC)