Close to 600 trees were planted last winter, with almost half of them in the streets, to extend the urban canopy

Between November 2022 and April 2023, the Parks and Gardens Service (SEVE) planted some 585 trees. With 197 isolated specimens managed by the SEVE having had to be felled the previous year, the City has achieved its objective of tripling the number of trees planted compared to the number of trees cut down. Since the beginning of the Parliamentary term in 2020, a total of 2,030 trees have been planted compared to between 450 and 600 in previous terms. “This massive planting effort, which represents one of the tools for addressing the climate emergency and making the city cooler, will be pursued in order to contribute to increasing tree coverage from 21% in 2020 to at least 25% of the municipal territory in 2030,” states Alfonso Gomez, Mayor of the City of Geneva responsible for the environment.

Trees planted at the heart of the neighbourhoods

Almost half the trees have been planted in the streets (264). New plants have been added to embankments, such as the 10 young trees and 80 shrubs (not included in the calculation) planted on Rue Louis-Favre and inspired by the “Ostryaie buissonnante” of the southern Alps, which involves bringing together trees, shrubs and perennials present in Switzerland which can live successfully in dry, limestone environments. School yards (Hugo-de-Senger, Trembley), Saint-Georges cemetery and Parc des Bastions are just some of the locations that have been chosen. Fifteen trees have been planted in partnership with the association OneAction, which has been tasked with identifying private plots of land and acting as a relay between the owners and the City, which covers 50% of the costs. Finally, with an average increase in leaf surface of 250% giving rise to greater shade, the reduction in cat’s head pruning has continued with 129 new trees earmarked for conversion this winter, in particular in Rue Hoffmann, Rue de la Terrassière and Place des Bergues. 

The diversity of the species selected – totalling one hundred – serves to protect against disease and meets the climate change resistance or biodiversity promotion criteria. Half of the trees are indigenous species, including linden, maple, alder and hop hornbeam. Ornamental or botanical species, such as the Japanese pagoda tree and the Chinese quince, also account for a large number of the trees planted. Forty fruit trees, primarily ancient varieties recommended by Pro specie rara (botzi pear tree, Fellenberg tree, etc.), complete the selection.  

An objective of 480 trees next year

The period from June 2022 to May 2023 witnessed a slight decrease in the number of trees felled, in particular due to a fall in the number of storms. A total of 161 trees managed by the Parks and Gardens Service had to be cut down, with each tree first subject to a meticulous inspection, calling on outside expertise if a specimen displayed a high dendrological value or if the diagnostic was uncertain. Half of them were dead and 35% were either dangerous or in decline, while the remainder were suffering the effects of extreme weather episodes. The species most frequently affected include elms, increasingly the victims of Dutch elm disease which is probably on the rise due to global warming, and maple trees, particularly affected by the “sooty bark disease”. Next winter, some 480 trees are scheduled to be replanted in order to meet the 3-to1 ratio. It should be noted that after 3 seasons of intensive planting, fewer areas are now available. The Parks and Gardens Service is exploring other options, in particular on private plots belonging to the City, and is continuing to study alternative planting methods, such as micro-forests, to extend shaded areas and increase biodiversity. 

Heat placing a strain on trees

Despite the care provided, the successive heatwaves and periods of extreme heat experienced in 2022 placed a particular strain on trees, in particular young specimens which had not been able to develop a sufficiently robust root system. To mitigate this impact, the teams are making every effort to monitor the 2,030 trees planted over the past 3 years for a period of 3 to 5 years (watering, stake control, etc.). Tensiometric monitoring makes it possible to measure the trees’ water needs and white paint is applied to the trunks to protect them against the sun.