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Myths and Facts

Get to know some myths and curiosities about cork, the oak tree, the oak forest and cork stoppers. See also some interesting facts.

Search below by topic the myths and curiosities we have prepared.

The cork oak is an evergreen tree, of the Fagaceae family (Quercus suber), to which the chestnut and oak tree also belong. There are 465 species of Quercus, mainly found in temperate and subtropical regions of the Northern Hemisphere. Cork is harvested from the Quercus suber L species.

The cork oak may be sown, planted or propagate spontaneously, which is often the case in cork oak forests, thanks to the acorns that fall on the ground.

Despite being an evergreen tree, the cork oak does not develop evenly throughout the year. In winter, the tree enters a dormancy period, during which it produces neither wood nor cork, with its vegetal activity reduced to a minimum.

The cork tree grows simultaneously in two directions: vertically and horizontally, resulting in a robust tree of majestic size.

The cork oak is native to the Western Mediterranean Basin, where there are ideal growing conditions:

  • Sandy, chalk-free soils with low nitrogen and phosphorus, high potassium and a pH from 4.8 to 7.0;
  • Rainfall from 400-800 mm per year;
  • Temperature from -5 ºC to 40 ºC;
  • Altitude from 100-300 m.

A cork oak has an average lifespan of over 200 years.

The oldest and most productive cork oak in the world is the Whistler Tree, in Águas de Moura, in the Alentejo region (South of Portugal). The cork oak was planted in 1783, stands over 14 metres tall and the diameter of its trunk is 4.15 metres. In 2018, the Whistler Tree, representing Portugal, was voted European Tree of the Year. Its name comes from the noise made by the numerous songbirds that shelter among its branches. Since 1820, it has been harvested over twenty times. Its 1991 harvest produced 1200 kg of cork, more than most cork oaks yield in a lifetime. This single harvest produced over one hundred thousand cork stoppers.

Besides being a very resistant species with extraordinary resilience, the cork tree gives much more than it takes away. As Professor Joaquim Vieira Natividade wrote in 1950: "In the often-ungrateful soil conditions and climate of our Country, the cork oak is a precious tree ... No tree gives more while demanding so little.

Corticeira Amorim has invested significantly in partnerships with forestry producers, prestigious academic institutions and national and international scientists and local authorities, in order to reduce the first cycle of cork oak extraction. The Forestry Intervention Project, operational since 2013, aims to find answers and solutions to the main challenges faced by the cork oak forest. Through the development and implementation of improved irrigation systems it is possible to reduce the first cycle of cork extraction from 25 years to 8 years.

In each cork harvest, it is possible to extract an average of 40-60 kg of cork per cork oak tree.

Stripping is the ancient process of extracting the bark of the cork oak - the cork. Today, this work is still done by specialised professionals, with absolute precision, who use just a single tool: the axe.

This delicate operation takes place between May and August, when the tree is at its most active time of growth and it is easier to remove the bark from the trunk.

The first stripping, or «desboia», takes place when the cork oak is 25 years old and the trunk has reached a diameter of 70 centimetres, measured 1.3 metres from the ground. Subsequent stripping take place with an interval of at least nine years.

Over the course of its lifetime, the cork oak may be stripped around 17 times, at intervals of at least nine years, which means that the harvesting of the cork will last 150 years, on average.

The first stripping is called "desboia" from which the virgin cork is obtained, which has a highly irregular structure and hardness that make it difficult to process.

Nine years later, when the second stripping takes place, the cork, known as "secundeira", has a regular structure which is not as hard. 

The cork from these first two harvests is not fit for the manufacture of stoppers and thus used in other applications for insulation, flooring, decorative items, among others.

From the third and following  strippings the "amadia" or reproduction cork is obtained. Only this cork has a regular structure, with a flat front and back and the ideal characteristics for the production of natural, quality cork stoppers.

No. After stripping, the planks are stacked into piles in appropriate structures and shall remain outdoors for at least six months for the cork to stabilise. This process is governed by the strict compliance of the Code of Cork Manufacturer Practices.

No. Stripping is carried out manually and the trees are never cut down. After each stripping, the cork oak undergoes an original process of self-regeneration of the bark, which gives the activity of cork harvesting a uniquely sustainable nature.

Nothing is wasted from the cork oak, all its components have a useful ecological or economic purpose:

  • The acorn, which is the fruit of the cork oak, is used to propagate the species, as animal fodder and in the manufacture of cooking oils;
  • The leaves are used as fodder and a natural fertiliser;
  • The material from tree pruning and decrepit trees provide firewood and charcoal;
  • The tannins and natural acids contained within the wood from the tree are used in chemical and beauty products.

In Ancient Greece, cork oaks were revered as the symbol of Freedom and Honour. Thus, only priests had permission to cut them down.

Yes. Some scholars argue that the existence of cork oaks dates back over 60 million years. It has been scientifically proven that cork oaks survived the ice age in the Mediterranean Basin, over 25 million years ago. In Portugal, where the largest cork oak forest area in the world is found, a fossil fragment over ten million years old was discovered which is testament to the ancient existence of this tree in the country.

At the end of 2011, the cork oak was unanimously established as Portugal's National Tree. This classification is directly related to the economic, social and environmental performance that it represents to the country. Around 23% of Portugal's forest area is made up of cork oaks, which support the country's main industry, besides providing a fundamental contribution against social desertification and making an unparalleled contribution to the preservation of the biodiversity associated with the cork oak forest. 

The cork oak's importance in Portugal has been recognised since the 13th century, a time when the first laws arose for the protection of the species.

In Portugal the felling of cork oak trees is prohibited by law and each cork oak is individually identified, in order to ensure its absolute traceability.