Researchers from the University of Trás-os-Montes and Alto Douro (UTAD) have been working to identify and date these trees, many of which can be found in central and southern Portugal.

One of the best-known examples is the Oliveira do Mouchão, in Mouriscas, in the municipality of Abrantes. The tree is estimated to be around 3,350 years old and, despite its age and hollowed trunk, continues to produce olives.

Innovative method

UTAD researchers calculated the age using a method they developed and patented. Rather than relying on traditional tree-ring dating, which can be difficult with very old olive trees, the method uses characteristics such as the diameter, height and circumference of the trunk to estimate its age.

For some time, the Oliveira do Mouchão was considered the oldest known tree in Portugal. However, another olive tree in the Alentejo may be even older.

The Oliveira do Peso is located at Herdade do Peso in Vidigueira, in the Beja district. An assessment carried out in 2021 estimated that the tree could be more than 3,700 years old. It was later nominated for Portugal's Tree of the Year competition in 2024, where it finished in third place.

It is not the only ancient tree on the estate. The area is home to a group of old olive trees whose combined ages are estimated to exceed 7,000 years.

Other examples can be found around the country. In Santa Iria de Azóia, in Loures, one olive tree has been estimated at around 2,850 years old, while Monsaraz has several ancient olive trees, including one thought to be approximately 2,450 years old.

Regeneration abilities

UTAD has also identified old olive trees in places including Estremoz, Montemor-o-Novo, Beja, Évora, Lagoa and Vilamoura in the Algarve, as well as Serralves Park in Porto.

The remarkable lifespan of olive trees is partly linked to their ability to regenerate. José Luís Louzada, the UTAD researcher who developed the dating method, explained to Euronews that even very old sections of an olive tree can produce new shoots, allowing the tree to continue growing and producing fruit.

Their ability to adapt to the Mediterranean climate also plays an important role in their longevity.

Portugal's ancient olive trees are particularly common south of the Mondego River, and their survival means that some trees standing today were already growing thousands of years before Portugal itself existed as a country.

UTAD's work has also gone beyond Portugal, with researchers invited to date olive trees in Spain and France. One tree studied on the Spanish island of Menorca was estimated to be more than 2,300 years old.