Beech forests across Catalonia, including the Montseny massif and Alt Berguedà, have turned green significantly earlier than usual this year, a phenomenon likely accelerated by high April temperatures. This premature budding of the region's beech trees raises concerns about their vulnerability to late frosts.
The beech tree (Fagus sylvatica), a deciduous species typical of humid, mid-latitude regions, usually displays spectacular autumn colours between late October and mid-November in Catalonia. However, it also offers a range of highly photogenic green tones in spring. The timing of both leaf emergence and fall fluctuates annually based on various factors, including weather.
This year, leaf emergence began relatively early, around 10 April in lower areas of Montseny, and has since spread across all altitudes of the massif by Sant Jordi (23 April). In Ripollès and Alt Berguedà, beech trees also budded earlier than in recent years, with leaves visible before mid-April and now fully deployed.
Early Budding Across Catalonia
According to Marc Noguera, a phenological observer for Meteocat, leaf emergence in the Catllaràs massif (Alt Berguedà) occurred a week earlier than last year and 10 days earlier than in 2022. Historical data provided shows that by 18-20 April 2026, over 50% of new leaves were out, compared to 25-27 April in 2025 and 28-30 April in 2022.
Early leafing is not a beneficial strategy for beech trees, as it makes them highly susceptible to severe damage from late frosts. Beech trees are known for their particularly late budding because their new shoots and first leaves are extremely sensitive to sub-zero temperatures. While dormant winter buds can withstand intense frosts of -20 or -30 degrees Celsius, tender new shoots can barely tolerate slightly negative temperatures.
Just a few degrees below zero can cause significant damage to new leaves and stems, leading them to “burn” and die. The tree is then forced to attempt to bud again, which is not always feasible. This second budding attempt requires a substantial energy expenditure, weakening the tree and making it more prone to diseases or, in the worst-case scenario, death.
Widespread Presence and Monitoring Efforts
Beech trees are common in the Vall d'Aran and on the northern slopes of the Pyrenees. On the southern side of the mountain range, they are primarily found in Garrotxa, Alt Empordà (in Les Alberes), Ripollès, parts of Osona, and Alt Berguedà. More isolated occurrences are noted in Alta Ribagorça, Pallars Jussà, Solsonès, and Moianès.
Notably, small beech forests in the Ports de Tortosa massif, in the country's southern extreme, are considered the most southerly in Europe. Extensive beech forests also thrive in Montseny due to high rainfall and frequent low clouds and fog. Generally, beech trees typically grow above 800 or 1,000 metres, reaching altitudes of 1,600 or 1,700 metres. Exceptions include parts of the Vall d'Aran, where they can grow below 800 metres, and particularly in Garrotxa, such as the Fageda d'en Jordà, where they are found at just over 400 metres.
The timing of leaf emergence and fall, along with other phenological events like the arrival of swallows, provides crucial information on how climate change is altering the rhythms of plants and animals. Since 2013, the Catalan Meteorological Service (Servei Meteorològic de Catalunya) has operated the Catalonia Phenological Network (Fenocat), which collects systematic observations from 50 volunteers. These volunteers record the phenological states of 25 plant species, 14 bird species, and six butterfly species. Additionally, the CREAF research centre runs the 'Nature's Rhythm' project, gathering phenological data contributed by citizens. Continued monitoring is essential to understand and respond to these environmental shifts.
