View source for Biology:Geneva official chestnut tree

{{Short description|Monitored tree in Geneva, Switzerland}}
{{Infobox tree
| name          = Geneva official chestnut tree
| image         = Geneve Vieille-ville 2011-09-09 12 57 16 PICT4528.JPG
| image_size    = 230px
| alt           = 
| image_caption = The Geneva official chestnut tree in 2011
| native_name   = 
| species       = Horse chestnut
| binomial      = ''[[Biology:Aesculus hippocastanum|Aesculus hippocastanum]]''
| location      = [[Place:Geneva|Geneva]], Switzerland
| coordinates   = {{Coord|46|12|02|N|06|08|47|E|display=inline,title}}
| seeded        = 
| felled        = <!-- {{End date|YYYY|MM|DD|df=y}} -->
| custodian     = 
| website       = 
| map           = Canton of Geneva
| map_size      = 230px
}}

The '''Geneva official chestnut tree''' is a [[Biology:Aesculus hippocastanum|horse chestnut]] tree planted in [[Place:Geneva|Geneva]], Switzerland. Every year, the tree is observed by the secretary of the Grand Council of Geneva (the local parliament), and the opening of the first leaf is recorded and announced publicly as indicating the beginning of the spring.

The series of records started in 1818; it forms the oldest set of records of phenological events in Switzerland and is one of the {{ill|living traditions in Switzerland|fr|Liste des traditions vivantes de Suisse|de|Liste der lebendigen Traditionen in der Schweiz}}.<ref name="livingtraditions">{{cite web |title=Botany in Geneva and the 'marronnier de la Treille' |publisher=Living traditions in Switzerland, Federal Office of Culture |url=https://www.lebendige-traditionen.ch/tradition/en/home/traditions/botany-in-geneva-and-the--marronnier-de-la-treille-.html |access-date=11 December 2022}}</ref> In 2023, the first leaf was observed on 9 March, in line with the observations made in recent years (in 2022, it was observed on 10 March<ref name="tdg2022">{{cite web |language=fr |first1=Marc |last1=Bretton |title=Sur la Treille, le bourgeon est de sortie |publisher=Tribune de Genève |date=10 March 2022 |access-date=11 December 2022 |url=https://www.tdg.ch/sur-la-treille-le-bourgeon-est-de-sortie-448895385580}}</ref>)

== History ==
Between 1808 and 1831, Marc-Louis Rigaud regularly observed a chestnut tree located on the {{ill|Promenade de la Treille|fr|Promenade de la Treille}} in Geneva, and recorded the date of opening of the first bud on the tree.<ref name="miege1967">Miège and Hainard, 1967</ref><ref>Stoller and Beer, 1994</ref> In 1818, an official tree was chosen, and the ''sautier'' (the secretary of the Grand Council of Geneva, the Parliament of the Canton of Geneva) is in charge of regularly observing the tree, and of recording the date of the opening on an official register. This event is then announced to the press and to the general public, indicating the beginning of the spring.<ref name="livingtraditions"/>

The tree chosen in 1818 died at the beginning of the 20th century, and a new tree was chosen in 1905. After its death in 1929, a third tree was chosen,<ref>{{Cite web |title=Marronnier de la Treille |url=https://www.geneve.ch/fr/marronnier-treille |access-date=7 January 2023 |website=geneve.ch |language=fr}}</ref> which died due to a fungus infection shortly after the last record, on 13 March 2015. A fourth tree was chosen in September 2015,<ref>{{cite web |title=Marronnier de la Treille |publisher=Republic and Canton of Geneva |date=September 2015 |url=https://ge.ch/grandconseil/data/communiques/marronnier_presse.pdf |archiveurl=https://web.archive.org/web/20151001002008/https://ge.ch/grandconseil/data/communiques/marronnier_presse.pdf |archivedate=1 October 2015}}</ref> just across the Tour Baudet de l’Hôtel de Ville, the seat of government in Geneva since 1488.<ref>{{Cite web |title=Marronnier de la Treille {{!}} 1818 – 2018 Genève |url=https://ge.ch/grandconseil/data/divers_publication_pdf/marronnier_officiel.pdf |access-date=7 January 2023}}</ref>

== Climate ==
[[File:Dates d'éclosion du marronnier officiel de Genève.svg|frame|center|Dates of opening of the first bud of the official chestnut tree, between 1818 and 2023.]]

The dates of opening of the first bud of these chestnut trees, collected since 1808, form the oldest series of phenological records in Switzerland, and one of the oldest in the world.<ref name="meteosuisse">{{cite web |title=Long-term series of phenological observations |publisher=MeteoSwiss |access-date=11 December 2022 |url=https://www.meteoswiss.admin.ch/climate/climate-change/vegetation-development/long-term-series-of-phenological-observations.html}}</ref> Researchers have thus been interested in it, as a witness to how a plant reacts to changing climatic conditions.<ref name="miege1967"/><ref>Miège and Wuest, 1983</ref>

Despite the large year-to-year variability of the data, data show a trend during the 20th century towards an opening that happens earlier and earlier, with a record in "spring 2003," during which the opening took place on 29 December 2002. According to MeteoSwiss, the Swiss Federal Office of Meteorology and Climatology, [[Earth:Global warming|global warming]] plays a role in this change, and so do other factors linked to the urban environment which increase the quantity of heat in the city. As of 2022, however, an inversion of this trend had been observed, with an opening occurring later over the previous few years. The reason for this inversion is not known, although it may be linked to the new tree that is used for the observations.<ref name="meteosuisse" />

== Images ==
<gallery>
Marronnier officiel Genève 2009 2.jpg|The plate indicating the third official tree in 2009
Marronnier officiel Genève 2009 7.jpg|Register recording the opening of the first bud, between 1818 and 1829
Marronnier officiel Genève 2009 6.jpg|Register recording the opening of the first bud, between 1982 and 2009
Marronnier officiel Genève 2009 1.jpg|Opening of the first bud on 6 March 2009
Marronnier officiel Genève 2009 5.jpg|Maria Anna Hutter, the ''sautière'', showing the official tree in 2009
</gallery>

== References ==
{{reflist}}

== Sources ==
* {{cite journal|author1=Jacques Miège|author2=Pierre Hainard|title=Un témoin genevois de l'évolution climatique récente|journal=Archives des sciences|publisher=Société de physique et d'histoire naturelle de Genève|volume=20|number=1|year=1967|doi=10.5169/seals-739384|pages=109–121}}
* {{cite journal|author1=Jacques Miège|author2=Marie-Claude Wuest|title=Le marronnier de la Treille: Un indicateur de l'évolution du climat genevois depuis 175 ans|journal=Archives des sciences|publisher=Société de physique et d'histoire naturelle de Genève|volume=36|number=1|year=1983|doi=10.5169/seals-740211|pages=147–161}}
* {{cite book|author1=Pierre Stoller|author2=Roger Beer|title=La première feuille du marronnier de la Treille|location=Geneva|editor=Service des espaces verts et de l’environnement (SEVE)|year=1994|oclc=715717865}}

== External links ==
*[https://ge.ch/grandconseil/secretariat/marronnier/ The official chestnut tree], on the website of the Grand Council of Geneva.
*[https://www.geneve.ch/fr/marronnier-treille The chestnut tree of la Treille], on the website of the city of [[Place:Geneva|Geneva]].

[[Category:Aesculus|+]]

{{Sourceattribution|Geneva official chestnut tree}}