Geneva official chestnut tree

The Geneva official chestnut tree is a horse chestnut tree planted in 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 living traditions in Switzerland. In 2022, the first leaf was observed on 10 March, in line with the observations made in recent years.

History

Between 1807 and 1817, Marc-Louis Rigaud regularly observed a chestnut tree located on the Promenade de la Treille in Geneva, and recorded the date of opening of the first bud on the tree. 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.

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, which died due to a fungus infection shortly after the last record, on 13 March 2015. A fourth tree was chosen in September 2005, just across the Tour Baudet, where the Council of State of Geneva sits.

Climate

The dates of opening of the first bud of the official chestnut tree, collected since 1818, form the oldest series of phenological records in Switzerland, and one of the oldest in the world. Researchers have thus been interested in it, as a witness to how a plant react to changing climatic conditions.

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, global warming plays a role in this change, and so do other factor linked to the urban environment which increase the quantity of heat in the city. Between 2005 and 2019, however, we can observe an inversion of this trend, with an opening that comes later. The reason for this inversion is not known, although it may be linked to the new tree that is used for the observations.

Images

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 ''sautier'', showing the official tree in 2009

References

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External links

The official chestnut tree
on the website of the Grand Council of Geneva.

The chestnut tree of la Treille
on the website of the city of Geneva.

Individual trees in Switzerland
Culture in Geneva