Fieldwork: Cork Harvesting in the Dehesa of Extremadura

The cork extraction in Extremadura It is a traditional trade associated with the maintenance of the pastureland and the population in rural environments. This work in the field It is a whole ritual in the Dehesa of Extremadura and it is called “cork extraction”.

Cork is obtained from the cork oak (Quecus suber). It is a magnificent thermal and fire insulator; and it is the natural defense these trees have developed to endure over the centuries. Cork is the evolutionary response to periodic fires and the extreme heat of some summers in the Mediterranean basin; when it burned, it left the tree safe, and the plant detached itself from it, producing new cork. This regenerative property is what gave rise to its exploitation, also allowing the cork oak to survive after its removal.

At first, it was used for containers, thermoses, and, to a lesser extent, stoppers. Until the advent of plastics, it was the best insulator available to the industry. Today, however, it is primarily used in the wine industry, for the production of stoppers, and, to a lesser extent, as insulation in construction or decorative materials. The cork oak is a emblematic tree of the Extremadura pastureland, which grows throughout the Mediterranean basin: mainly in Spain and Portugal, to a lesser extent in southern France, the west coast of Italy, Corsica and Sardinia and in North Africa (Algeria, Tunisia and Morocco).

Cork harvesting in the Extremaduran pastureland is a highly specialized craft with a distinctly seasonal character, from early June to late August, and is primarily passed down from parents to children. It involves the work of true artisans, purely manual, where the skill and expertise of the cork puller play a fundamental role. Field work requires highly specialized personnel since poor handling could cause irreversible damage to the tree.

When is cork extracted in the Extremadura dehesa?

The period for the cork extraction in the Extremadura pastureland It runs from early June to late August, provided that optimal conditions exist for the cork to separate easily from the tree without causing any damage.

When there is excessive humidity or insufficient temperature, the cork sticks to the rest of the bark and the tree trunk, and removing it could cause wounds in the cork oak. Similarly, if the environment is very hot and dry (like this summer of 2020), the tree has little water, and extracting it would also be impossible, since attempting to extract it would cause wounds (the cork is completely stuck to the trunk) and also cause a loss of water to the tree, which it struggles to replenish under these circumstances. When any of these conditions occur within the optimal period for cork extraction (from June to August), it would be necessary to wait until the following year to proceed with the extraction, peeling, or sacking. The latter two are the common terms for this process in Extremadura.

The cork extraction process in the Extremadura pastureland

The work in the field for the extraction of cork is a completely manual and artisanal process.

The first time the cork is removed from a cork oak is when it is 25-30 years old and it is called bornizoBefore harvesting, cork strippers must assess whether the tree is ready for harvesting, or whether it's preferable to wait another nine years, the period between harvesting. To make this decision, the perimeter of the cork oak is measured. Only when the tree's circumference measures more than 60 cm will extraction be possible. The cork extracted from a "virgin tree" will be of mediocre quality, unsuitable for making stoppers, but it can be used for decoration (it's the typical cork used in Nativity scenes) or as a byproduct for making fireproof or insulating material.

As previously indicated, subsequent extractions will be carried out at intervals of 9-10 years. The overall qualities of the ore will determine the time required to reach the appropriate commercial caliber; this will depend on the quality of the soil, rainfall, and average temperature in the area. That is, the second cork extraction will take place when the tree is approximately 30-40 years old (9 years after the first extraction). In this case, it is called "secondary cork," which will also have a reduced commercial value and is used in lower-quality corks or crushed to make agglomerated corks.

It is not until the third extraction that we can obtain a suitable commercial cork, called "amadia," for the production of quality corks. Thus, for a cork oak to offer a quality cork It must be more than half a century old. Generally, when a landowner decides to plant cork oaks, they know that their children or grandchildren will be the ones who will see the results of their efforts…

When extracting cork, the cork stripper must have exceptional skill to make small, precise cuts without damaging the tree. When handling an old cork oak, the cracks left over from previous harvesting can be used to avoid creating new indentations. The axe handle is inserted through these cuts or cracks to pry the cork away from the rest of the bark. Under suitable conditions, the cork is easily separated without risk to the cork oak. The process usually begins before sunrise, when the sun begins to lighten at dawn, and ends around midday; this ensures the best possible temperature so that this difficult work is not so arduous for the cork strippers. The cork strippers always work in pairs (called collars (in Extremadura) to be able to climb trees and be accompanied so they can help each other if necessary. Furthermore, during this time of day, there is higher relative humidity, and the cork separates more easily from the tree.

He cork sector in Spain It is very traditional and uses a unit of weight called “Castilian quintal” which is equivalent to 46 kg, 100 pounds or 4 @.

To finish off a few interesting facts about the cork oak and its cork removal, the tree trunk, once stripped of its cork slabs, is left an earthy white; after a week, it takes on a pinkish-yellowish color due to the oxidation of the sap and other tannins in the bark. At the end of summer, it turns orange-ochre. After the first summer, the trunk may have a dark carmine color; over time, it oxidizes even further, taking on a dark wine color with grayish tones. A wonderful range of colors that contrasts with the intense green of the cork oak leaves and the gray of the sap on the upper branches (an area that is never removed during the tree's life).

How is the quality of cork from the dehesa measured?

He quality cork It is extracted from the cork oak after its third harvest, but only if the tree is healthy and free of any insect attacks or infestations. When assessing cork quality, the following variables are analyzed:

• The caliberThe larger the caliber (thicker), the better the cork. The caliber can vary from one estate to another, depending on the time between extractions. If a estate has a low cork yield, it's preferable to extend the interval to 9 years to improve quality.
• Porosity: The greater the porosity, the poorer the cork quality. A tighter cork offers better quality, as the pores allow air to pass through and it loses its insulating quality, which is detrimental to wine stoppers, for example. This is closely related to the following variable.
• The quality of the landWhen the soil is poor, for example sandy soil, the tree has greater difficulty growing, and the cork is more dense. When the tree is more leafy, has very fertile soil, and grows in good conditions, it tends to develop a lot of pores. It's a very curious natural paradox: the highest quality cork is found on farms with the worst soil, what technicians call poorer soil characteristics.

Fieldwork for the sustainability of the Extremadura dehesa

The profitability of cork makes it possible for many farms to sustain themselves solely on the basis of its extraction and marketing. However, what is usual in the pastureland of Extremadura is that cork oaks coexist with holm oaks, so the extraction of cork is a further complement when exploiting the natural land, which must be combined with other traditional activities and trades such as cattle, sheep and livestock breeding especially from acorn-fed Iberian pork.

The price of cork varies greatly from year to year. Approximately 20% of the value of cork is the cost of the skilled labor dedicated to its extraction. This generates significant wages at a time when there is little work in the Extremadura countryside. ensures the population in rural areas most in need. Furthermore, throughout the cork oak's life, the trees must be pruned, the shoots that will replace the dying trees must be planted and protected, and they must be protected from pests.

However, it is necessary to highlight that cork extraction directly affects the quality of the acornThe year the cork is harvested, and also the following year, that cork oak will have a lower acorn production due to the stress caused by the peeling.

But although the cork oak (Quecus suber) is of the same genus as the oak (Quercus Rotundifolia either Quercus Ilex  according to authors) has a different behavior: the cork oak's growth is much faster and more vigorous. While a holm oak takes about 40 years to reach a height of 10 meters, the cork oak could reach it in a third of that time. Regarding acorn production, both trees also behave very differently. The holm oak normally produces the same amount of acorns each year, although there may be some variation in the rainiest years compared to the driest. However, the cork oak is very alternate-bearing (like the olive grove), meaning it does not flower the same way each year, so its production varies greatly from year to year. That's why farms with many cork oaks enjoy an exceptionally good montanera some years, and exceptionally poor ones others. The 2019-2020 montanera was much better in the holm oak forests than in the cork oak forests.However, in the upcoming 2020-2021 campaign, acorn production is expected in the cork oaks due to the large number of acorns they have on their branches.

Cork extraction is one of the most exciting jobs in the field, along with Iberian pig breeding in the Dehesa de ExtremaduraThese types of traditional crafts allow us to connect with nature and our ancestors in a unique way.