While a 1,100-year-old tree recently made headlines in Germany, Portugal quietly harbours hundreds of olive trees that have stood for more than two millennia. Researchers at the University of Trás-os-Montes and Alto Douro (UTAD) have developed a patented method to estimate the age of these ancient specimens, and their findings are rewriting the country's natural history.
For years, the so-called "Oliveira do Mouchão" in Abrantes was considered Portugal's oldest olive tree. In 2018, UTAD announced it was already 3,350 years old—a living contemporary of the Phoenicians, Celtiberians, and Romans. Despite a trunk hollowed by time, it continues to produce olives "as if in the flower of youth," according to the university. It even competed in the 2022 European Tree of the Year contest, finishing fifth nationally.
But newer assessments have pushed the record further south. On the Herdade do Peso estate in Vidigueira, in the Alentejo region, an olive tree known as "Oliveira do Peso" is believed to be over 3,700 years old, based on a 2021 analysis. The estate describes it as the oldest of a group whose combined ages exceed 7,000 years. It placed third in Portugal's Tree of the Year 2024 competition.
A method rooted in mathematics
The dating technique, developed by UTAD researcher José Luís Louzada and his team, uses a mathematical model that correlates a tree's age with trunk characteristics such as diameter, height, and circumference. The method has been applied in collaboration with the company Oliveiras Milenares since 2007, certifying ancient trees both in Portugal and abroad.
Beyond Vidigueira, other notable specimens include a 2,850-year-old olive tree in Santa Iria de Azóia, near Lisbon, and several in Monsaraz, Évora district, one of which is around 2,450 years old. The trees are scattered across the country, from Estremoz and Montemor-o-Novo to Lagoa, Beja, Vilamoura, and even Serralves Park in Porto.
UTAD's expertise has also been sought internationally. The team has dated olive trees in Spain and France, including in Bordeaux, Girona, Málaga, and on Menorca, where one tree was certified at over 2,300 years old.
Why do olive trees live so long?
Louzada attributes their longevity to an extraordinary capacity for rejuvenation. "A piece of trunk, no matter how old it is, has the capacity to sprout again," he explains, allowing the tree to keep producing olives. The species is also "very well adapted to our Mediterranean climate," which enables remarkable longevity.
In Portugal, these ancient olive trees are found mainly south of the Mondego River. In theory, Louzada says, they could live "for eternity," outlasting generations of human history. Their survival is a testament to resilience—both of the trees and of the landscapes they anchor.
As Europe grapples with heatwaves and wildfires, these ancient trees stand as silent witnesses to centuries of climate variability. They also offer a cultural link to the Mediterranean's deep agricultural roots, much like Greece's ancient sites open to the public this summer.
For Portugal, the certification of these trees is not just a scientific exercise—it is a matter of heritage. The Herdade do Peso estate, for instance, highlights the "heritage significance" of its olive grove, which draws visitors and researchers alike. As the country looks to balance conservation with development, these ancient trees remain a living archive of the past.
