Cork Oak-Quercus suber

The Cork Oak,Quercus suber, is an evergreen tree that grows to about 20 metres high. It is native to the Mediterrranean region where it receives plenty of sunshine, low levels of rainfall and high levels of humidity.

The leaves are tough and leathery; dark green above, grey and downy beneath and toothed.

The tree has evolved its specialised bark to protect itself from the harsh conditions the forests of the area are exposed to; frequent droughts, temperature fluctuations and brush fires.

The cork bark is made up of water-resistant cells that separate the outer bark layer from the delicate interior bark. It has a unique set of properties that are not found in any other naturally existing material. It is lightweight, rot resistant, fire resistant, termite resistant, impermeable to gas and liquid, soft and buoyant and it is these properties that make it an ideal material for stopping wine bottles and for flooring.

The trees flower from April to May

The countries that produce the most cork include Portugal, Algeria, Spain, Morocco, France, Italy and Tunisia. Spain is the second largest producer, providing around 25% of the world supply, following Portugal.

Harvesting the bark

November - a tree stripped of its bark earlier in the year

Much of the cork oak woodland of Spain and Portugal survives because its bark has commercial value for its growers. There is much concern that the demand for the product for use as wine-bottle stoppers may dwindle as the practise for using other materials for the purpose increases. Growers may then clear trees to create open land on which to grow other more profitable crops. 

A tree must be at least 25 years old before its bark is harvested for the first time. Harvesting takes place during June, July and August when the cork is stripped off by hand using a long-handled hatchet to cut sections out of the bark. These sections are then pried away from the tree. It’s a skilled job as workers must be careful not to damage the inner layer of the bark, otherwise the bark won’t grow back. This layer slowly regenerates, therefore creating a sustainable crop. Areas are harvested every 9 to 12 years, often with little work carried out in between these times. A tree will be approximately 50 years old before its bark will be suitable for a wine stopper and may live to be 200 years old.

Traditionally the bark is stacked and left to mature outside for several months before being used for bottle stoppers

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